Tensile Surface Structures: A Practical Guide to Cable and Membrane Construction

Andres Labarca

Tensile Surface Structures: A Practical Guide to Cable and Membrane Construction

Abstract

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Figures (486)

Fig. 1: Flexible load-bearing elements in wide-span surface structures The dimensions of the surface elements are exceptionally two-dimensional. Linear load-bearing ele ments are used to transfer loading though the edge. The mechanical material properties of both types of load-bearing e able the load transfer from the multiply cu exclusively through high tension forces. Th used normally have high elongation stiffn ement have to en- rved surface forms e types of material ess and negligible bending stiffness. The mechanical behaviour of the materials in buckling and plate buckling is, dependi ng on the loading, relatively flexible in comparison with the s ructural system. embrane surfaces installed in form-active structures are composed of load-bearing elements of varying materi- als, types of construction and geometry. Normally these are arge jointed surface elements and linear edge elements. Both types of element can only bear loading in a particular shape (curved), and have to fulfil certain technical criteria. n addition to keeping the weather out, they have to be re- sistant against chemical and biological attack and must be

dles (strand bundles). Bundles are mainly used as suspen- sion cables of bridges. On the construction site, parallel wire bundles are bound at intervals with soft iron round wire or clamped with clamps to hold the bundle together. to their shape into round strands, shaped strands and com- pacted strands. Parallel single members as ropes or bundles, combined to form larger units, can also be called cables (rope bundles). Cables are mostly used in building for larger spans, for example the perimeter rope bundle of a spoked wheel roof construction.

Single parallel members of wires or strands, combined to form larger units, are called bundles. These can be cate- gorised into parallel wire bundles and parallel strand bun-

Fig. 7: Lay type and direction Ropes with Lang's lay are exceptionally hardwearing and more flexible than regular laid ropes. Ropes with regular lay have less tendency to twist and spring, are less susceptible to damage by dirt and deformation and less flexible than ropes with Lang's lay.

Fig. 10: Stranding basket of a planetary stranding machine

Fig. 12: /eft: transfer sheave; middle: planetary stranding machine; right: model of a stranding mechanism

Fig. 11: Tubular wire rope stranding machine

Fig. 13: above: Schematic diagram of alignment rollers; below: Schematic diagram of reel alignment mechanism

Fig. 15: Length alteration and stress relaxation in deflected ropes

Fig. 20: Jeft: Splice; right: Splicing frame

Fig. 21: above left: Heuer-Hammer clamping system; above right: Rope clip according to DIN 1142; below: End-to-end connection with rope clips

End-to-end connection with wedged socket Fig. 22: High-strength end-to-end connections

Fig. 25: Production of a cylindrical cast socket An alternative to metal filling of the rope sockets is plastic filling. This is a very reliable rope end connection which, if made correctly, can achieve higher loads in destructive tests

After ordinary lay ropes have been swaged together, the out- er wires lie alongside each other (c in Fig. 28). After Lang's lay For the production of swaged socket end connections in the construction industry, the most commonly used methods are pressing and rolling of fittings. In addition to pressed and rolled fittings, versions with adjustable turnbuckle are also available for rope diameters up to 20 mm, which can be used

ropes have been swaged, the outer wires are crossing and can notch each other; this normally leads to no great reduc- tion of the breaking load. he end of the rope (a, b, c in Fig. 27). The size of the swag- ing sleeve is chosen according to the rope diameter, the rope construction and the filling factor. After the rope has been cut to length, the end is inserted through the swag- ing sleeve, bent to form a loop, fitted into a thimble and back hrough the swaging sleeve. Then the sleeve containing the “live” (load-bearing) end and the “dead” rope strands is laid in a hydraulic or pneumatic press, aligned in the pressing direc- ion and pressed in one pass until the sides of the die close ogether (b in Fig. 28). This process is called swaging. Project- ing wire ends are filed off.!

Fig. 30: Swaging a socket a Terminal rolling machine

For the tension anchorage into the subsoil, a combination of reinforced anchor block and piles can be used. The piles need to have a stiff connection at their heads. The ground

Fig. 34: eft: Crosshead with threaded tie bars; middle: Tolerance adjustment for highly loaded cables; right: Tensioning equipmen

Cylindrical speltered socket internally threaded with screwed-in tie bar Fig. 36: Connection to other building elements

Fig. 35: Construction of elevated anchors for stay ropes

Fig. 38: top: Weaving system with simultaneous weft insertion bottom: Needle weaving machine

Fig. 37: Polyamide and polyester webbing

Fig. 39: Webbing fixing to corner fitting

compensation, cut to length and sewed under tension to the membrane edge, ensuring shear-resistance.

Fig. 41: eft: Corner detail with belt tensioners; right: tensioning the edge webbing

Fig. 40: Hole and flat triangle as intermediate link After weaving, the webbing is delivered for fabrication on reels, where it is pre-stretched according to the specified The arrangement of belt tensioners (Fig. 41) is useful during erection, particularly for precise tensioning or detensioning of heavy fabrics.

Fig. 43: Welded-in keder in a PES/PVC fabric type 5

Fig. 42: Butt joint with one and two-part keder rails

Textile fabric composition Fig. 44: Diagrammatical section through a planar element

Fig. 45: Diagram — left: Spinning process; middle: Stretching; right: Crystalline structure of PET polymer chains

Fig. 46: Diagram of the weave of the main weave types with warp and weft section

Fig. 48: left: Automatic rapier loom; right: Rapier clamp with weft thread Fabrics are woven in widths of up to approx. 5 m. In Aus- tria, fabrics can be made at a maximum 3.2 m wide. The nor- mal roll widths are 2.05 and 2.50 m. Depending on the fabric width and the area weight of the raw fabric, roll lengths of a maximum of 2,200 running m are usual, with increasing sur- face weight underneath. Textile fabrics are subject to numerous factors influencing the ageing process and thus dition to load-dependant infl uences he quality requirements. In ad- ike alternating loads, extent of loading and creep, other factors and above all load- independent effects like agei pheric effects caused by po account with textile fabrics. Textile fab dertaking structural function non-flammable. uences ng, natural climatic and atmos- utants have to be taken into ics, in addition to un- s, have to be resistant against chemical and biological inf and also be almost

Fig. 47: Diagram showing section of weave with differing amplitude displacements in warp (K) and weft (S) section:

Fig. 49: Internal construction of a polyester fabric coated on both sides and with topcoating

Fig. 50: Polyester fabric exposed through breakdown of the coating This surface treatment also hinders the growth of sedimenta- tion and the formation of microbes with the resulting impair- ment of the optical properties.

One criterion for the long-term preservation of t cal properties of polyester/PVC fabri ness on the thread ridge. The fabric p rotection is portional to the coating thickness: “The higher t of the covering, the better the pro The usual coating thickness is from For fabric type 1 (plain weave) with of 500 g/m’, 200 g/m? are applied 0.08 mm o the fabri he mechani- cs is the coating thick- directly pro- he thickness ection of the thread.” o 0.25 mm. a total coating weight c underside

Fig. 52: Top coat with roller knife Some manufactures possess a “4-coat” coating plant, where the PVC coating is applied to both sides of the fabric in one production pass. The first three layers are applied by vertical coating equipment and the last coat, normally the top coat of the upper side, is applied with a horizontal roller knife.

Fig. 54: Separation of coating from a polyester/PVC fabric caused by fungal attack

Fig. 53: Wicking effect on polyester/PVC fabrics

Fig. 55: top: Glass fibre, glass fabric and coated fabric; bottom: Internal construction of fabric

Fig. 58: top: Clear and printed pattern on an ETFE foil bottom: Tetrafluoroethylene / ethylene copolymer (E/TFE)

Fig. 57: /eft: Linear (a) and branched (b) chain molecules; middle: Amorphous (unarranged) condition; right: Partially crystalline

Fig. 59: Jeft: ETFE granulate pellets (100-200 mm); right: Granulate particle The process stages required for the manufacture of a plastic forming mass suitable for processing from the raw polymer is described as preparation. These processes contain the break- ing up (milling, granulating) and the mixing in solid and plas- tic form?

Fig. 62: /eft top: Wide slot tool; left bottom; Blowing head; right: Diagram of a worm extruder homogeneity in the long and cross directions and thick- ness tolerance, while blown films have advantages regarding strength in both directions and the simple alteration of the foil width, enabled by variation of the blowing conditions.' A considerable disadvantage of blown films is the risk of crack- ing at the fold. One of the most important devices in thermoplastic process- ing is the extruder. This continuously melts the pellets and conveys them to the outlets (Fig. 62). Then the melted mass is extruded from the extruder through a shaped die In flat film extrusion, only wide-slot dies are used, which form the homogenised melted mass into a flat shape.

Fig. 61: /eft: Flat film extrusion; right: Blown film extrusion

Fig. 63: Process stages — flat film extrusion according to Bogaerts

Fig. 65: Categories of long and short-term effects on PVC-coated fabric according to Durr Complex demands are placed on the materials in flexible structural elements in the various fields of application. In he construction of wide-span lightweight structures, this means, in addition to the linear elements like wire ropes and webbing, above all the textile sheeting, which not only has o undertake a structural function but is also subject to load- independent effects like the ageing process and has to re- sist natural, climatic and atmospheric influences. They have O protect against the weather, be resistant against chemi- cal and biological influences and be almost inflammable in case of fire. Various production measures serve to ensure he resistance of the material against load-independent ef- fects. The most important measures for linear and surface el- ements were described in section 2.2.2. For structures loaded in tension, because the load is trans- ferred by axial forces, it is possible to utilise the materials more efficiently and construct lightweight structures, which eflect the force transfer. For the load-bearing elements of such a structure, a certain extent of yielding under load is very advantageous for the structure. From the structural point of view, the structures are designed so that loading 2.3.1 Mechanical properties

Fig. 66: /eft: Geometrical non-linearity; middle: Strains under repeated loading; right: Loading and unloading curves

Fig. 67: Dependance of fabric behaviour on strip orientation

With the conventionally woven fabrics used in textile archi: tecture, the warp thread is less curved than the weft thread on account of the weaving manufacturing process (Fig. 69 a b).? The differences of thread geometry of the warp and weft threads have the effect that less curved threads under ten: sion loading curve less than strongly curved ones. The con:

Fig. 69: Schematic layout model of the fabric threads in undeformed (left) and uniaxially tensioned (right) condition

Fig. 70: Sketch of the transverse strain produced by axial strain for fabrics with dissimilar stretching properties

Fig. 71: /eft: Uniaxial tension test; right: Biaxial machine at Stuttgart University, Germany

Fig. 72: Jeft: Sketch of a biaxial test rig; right: Stress-strain diagram of a Glass/PTFE fabric

Fig. 73: Loading diagram for a Glass/PTFE fabric

Fig. 74: Axial and transverse loading of the seam 2.3.1.3 Strength and stiffness of the seam

Fig. 76: Diagram of the interaction of coating and fabric at a welded seam Fig. 75: Slanting of a welded overlap (left) and a sewn double seam (right) under transverse loading Welded seam

seam width for the distribution of the shear stress can be tested in uniaxial and biaxial short-term tests (Fig. 77). The results of these tests are also temperature-dependant. With increasing temperature, the coating tends to soften and the adhesion effect and mechanical linking are reduced in their effectiveness.' The data from the test, produced on the basis of the seam requirements from the structural design, is used for the structural calculation.

The adhesion strength of the coating on the fabric, the speci- fication of the optimal welding parameters and the optimal lf wider seams are used in order to improve the stiffness re- lationship between membrane and seam, then care must be taken that the seam can also conform to any deformations of the element, which may be necessary for a reverse cur-

Fig. 79: Biaxial test on a laced connection

Fig. 80: /eft: Test of tear propagation for the membrane roofing of the Sony centre in Berlin, Germany; right: Diagram of a uniaxial te 2.3.1.4 Tear propagation behaviour vature. In order to avoid unclear stress conditions, the direc tion of the strips in the surface should be kept parallel if pos sible. If this cannot be organised, then different forces will ac along the joints where the warp direction meets the weft di rection. This should be considered in the calculation of the patterning.

Fig. 82: Thermoplastic behaviour under loading over time, diagram of principle

Fig. 83: Thermal condition zones for amorphous (left) and partially crystalline thermoplastics (right)

Fig. 84: Creep behaviour of membrane joints at room temperature according to Minte

The extent of the angle of rotation is mainly dependant on he weave type and the coating. Tests and calculations are performed to determine the relationship between force and shear deformation and evaluate the influence of the de- formation between warp and weft threads. Different fabric materials permit different angles of deformation. The shear modulus as a physical value is of the greatest importance for the production of fabrics (see section 2.3.1.5). Geometrical surfaces can only be mathematically developed into two-dimensional surfaces when their Gaussian curva- ture at every point is zero. Curved structures, which have found their own form, always have a negative Gaussian cur- vature and so cannot be developed. So to produce the two-

Fig. 86: Membrane strips compensated in warp and weft direction before anchoring to fixed points

Fig. 88: Layout of strips, cut-out strips, intended geometry

Fig. 90: Stiffness distribution / layout of the strips in main direction of curvature The calculation of the patterning depends primarily on the shape of the surface to be created. Before the fabric can be

2.4.3.1 Topological and structural criteria cut to size in strips, the main anistropy direction of the fabric relative to the main direction of curvature must be deter- mined on the basis of calculations. Stiffness distribution — layout of the strips

The stresses, which arise in the membrane surface and its edges, and the resulting strains in the fabric determine the choice of strip layout. If the membrane surface, which is to be created, corresponds to the smallest surface, in which the stresses are equal in all directions, and fabric is used with the same strain in both thread directions, then the layout of the strips can be chosen at will. The material is then utilised opti- mally and local overstress is mostly avoided.

Fig. 92: Possible strip layouts for highpoint membranes

Fig. 91: Strip layouts with warp in the main bearing direction In the practice, this is actually very seldom the case; mem- brane surfaces normally consist of materials, whose main stresses vary from each other. The tion fabr esu nthe main bearing direction, because | main bearing direction of a membrane surface is the direc- of the greatest strain. Because the warp thread in woven ics has a higher E modulus than the we t that the material has a higher tensile strength in the long direction of the fabric than in the weft direction, care is taken in the determination of the strip layout that aid i then be expected under loading. Another ft thread, with the the warp is mostly ess deflection can advantage of this strip layout is that the weaker seams do no highest possible stress in the transverse direction. have to bear the

Fig. 93: Main stresses and strip layout for a swimming pool roofing in Malaysia

Fig. 94: Possible strip divisions for arched membranes with flat and strong curvature

Fig. 95: Diagonally arranged uplift ropes underneath an awning surface Because the length differences from the compensation can only be absorbed in the corners of the cut-out strips, the When deciding the strip layout for less curved surfaces, attention should be paid to possible changes of load trans-

Fig.97: Alteration of the main direction of curvature of a four-point awning through variation of the edge rope radius and edge rope force

Fig. 96: Load singularities depending on the width of cut pieces

Fig. 98: Diagram of idealised tensioning procedure with limitation of transverse strain The use of fabrics with dissimilar stretch properties can be very advantageous for the erection of geometries with dif- ferent lengths in warp and weft directions. When using such fabrics, the ideal case is to arrange the larger part of the com- pensation in the weaker weft direction. The strain in the stiff- er warp is very slight, and is therefore little compensated. If possible, the s ing all the crite rip layout will be arranged so that after test- ria stated above, the desired biaxial pretension will be produced solely by tensioning in the weft direction. In order to bui Id up enough stress in the warp direction by The cost of implementing a tensioning procedure is de mined mai Apart from the optical appearance of the seams and t structural conditions in a membrane surface, all erecti measures, sioning eq nly by the arrangement of the individual pan ike the dimensioning and installation of the ten- uipment, measures to stabilise the primary con- struction and the arrangement of scaffolding, depend on orientation of the strips. the

Fig. 99: Tensioning direction and sequence of arched membranes depending on the direction of cutting out

Fig. 100: Pulling in and tensioning the membrane for the stand roofing at stadium Volkswagen Arena Wolfsburg, Germany If the surface has to be tensioned between two arches, as is often the case with sports stadium roofs, the membrane can be unrolled parallel or perpendicular to an arch-shaped truss. Depending on the material, arch curvature, edge geometry and edge detail, the direction of the strips makes a large dif- ference for the tensioning process and the related measures. According to information from erection companies, there is a considerable scope for saving erection costs here, consider- ing the space taken up by erection equipment.

Fig. 101: Pulling in and tensioning the membrane for the stand roofing at Estadio Intermunicipal Faro, Portugal

Fig. 102: Seam loading during tensioning

Fig. 103: Tensioning of high point surfaces with different strip layouts

Fig. 104: Tensioning of high point surfaces with different strip layouts

Fig. 105: Schematic cutting-out diagram of an anticlastic membrane surface

Fig. 106: Marking for the edges of the strip

Fig. 108: /eft, centre: Mechanical cutting machine with round cutter; right: Manual vertical knife machine When there are a a number of strips to be cut with the same geometry, pre-cut templates made of thicker material can be used. The strips can be cut out singly or in piles according to the geometry and other requirements. The finished dimen- sions (cut lengths) must be checked in any case.

the shape of the press, the processing temperature and the welding speed. The average weld seam width is between 50 - 80 mm. A wider seam can increase the strength of the weld for heavier fabrics. When making such wide seams, there can be a problem with the coating “swimming out" from the welding area. This can be avoided through the use of a knurled welding electrode (b in Fig. 111). Full-surface welding in the entire area of the seam can be achieved with a flat electrode (a in Fig. 111). Special electrodes can be used to make intentional breaks in the surface of the seam, which makes the seams more controllable.’

Fig. 110: /eft; centre: Diagram of HF welding; right: HF welding plant

Torn seam Fig. 113: Seam tests called thermal crumple, is compensated during the welding process either by pretensioning the fabric (Fig. 114) or it has to be compensated in a calculation and pulled out of the fabric during erection. The thermal shrinkage must always be taken into account when cutting out. The heat development during welding produces shrinkage of the weld seam in the long direction. This shrinkage, also

Fig. 115: PTFE heat welding press with a heating beam length of 2m anda maximum pressure of 7 bar

Fig. 117: /eft: Manual welding device; right: Mobile magnetic welding device

Fig. 119: /eft: PES/PVC fabric corners of a circus tent reinforced with sewn seams; right: Sewing the edge area of a Glass/PTFE fabric provide weather protection and stop light passing through, the sewn seam can be welded over with a foil and sealed. This is normally done on the construction site by welding a prefabricated cover flap over the sewn seam.

2.5.1.2 Sewn seams Sewn seams, which are the traditional means of joining fabric in tent building, make possible a direct connection of fabric thread to fabric thread to transfer force. In the con- struction of lightweight structures, however, sewn seams to join two sheets are rather the exception today, particularly as the perforation of the membrane by the sewing needle dam- ages the waterproofing and has to be waterproofed later.

Fig. 122: /eft: Assembly of a clamping plate but joint; right: Stretching the membrane in a keder rail Fig. 121: Clamping plate butt joint

Fig. 125: /eft: Laced connection of the large pillow of the arena in Nimes, France; right: Loop joint of a circus tent

Fig. 124: /eft: Keder rail for fabric membrane; right: Clamping plate for ETFE cushion joint

Fig. 123: Prestretched erection joint in an arched surface

The membrane stress (SM) increases with increasing force in the edge element (SS). The relationship of edge rope force to membrane stress determines the edge geometry. An in- crease of edging radius (R) produces a reduction of the sur- face curvature, which means that increasing curvature radius leads to increased forces in the edge elements (Fig. 127). In order not to exceed the maximum stress in the edge element, the dimensions of the edge element have to be designed for forces.

Fig. 128: Form-fit, friction and bonded connection at a membrane plate

capability of resisting tangential forces resulting from trans- lational and rotational deflections under loading. This applies especially during erection, when the change from loose to tensioned condition causes large changes of form.

Fig. 129: Forces acting on the edge element f the edge element and the surface element consist of the same material, then the weight ratio of surface to edge element with changing radius can be used to derive a rela- ionship to the corresponding stretching of the two materi- als.' Deformation requirements on the detailed design and choice of materials for the edges and their anchorages result from the conditions of surface and edge geometry for the A further aspect in the design of edge and corner connec- tions is their dimension. If a structure is meant to be built as light and slender as possible, then the details should al-

Fig. 132: Rope edge with sewn-on webbing Fig. 131: Hem sleeve with rope as edge element

Fig. 133: Edge detail with sheet metal loops

Fig. 134: /eft: Erection of valley for the roof over the Sony Center in Berlin, Germany; right: Valley detail at the Gottlieb Daimler Stadion in Stuttgart, Germany

Fig. 135: Tensionable edge detail of the Grande Bigo hall in Genoa, Italy

It consists of polyester (PETP) fibres woven together with a total breaking load of about 1,000 kN and can be connect- ed with the membrane fabric using conventional fabrication methods. The connecting fabric transfers radial and tangen- tial forces into the thicker section part of the edge element, which has a load-bearing function. After a prototype had been made, tests were commissioned on possible anchorag- es for the textile edge element. These were sliding mandrel and a cast plastic anchorages.| Because of the difficulties involved in coordinating the strain stiffness of the membrane and edge reinforcement to each other, Hans Gropper and Werner Sobek have proposed as a

Fig. 139: Clamping plate edge and corner detail for the roofing of the Main Station in Dresden, Germany The length of the clamping plates is according to the rule of thumb: the less the curvature of the membrane, the longer the plates can be. The stretching of the membrane in the long direction should not be obstructed by the clamped connection. The nuts of the clamping plates are tightened with a defined torque setting. When the erection takes place at low tem- peratures, the level of tensioning force should be checked to avoid brittle fractures of the metal plates. The torque of

Fig. 142: Detail of an aluminium clamping profile Fig. 141: /eft: Corner connection and edge detail to the roof over the entrance to the Federal Chancellor's Office in Berlin, Germany; right: Detail photo of clamping profile

the clamping bolts has no influence on the strength of the connection if the assembly is correct. The spacing of the bolts does, however, have an influence on the strength of the joint (b in Fig. 138). The spacing should be hardly more than 200 mm.' The clamping plate dimensions should be designed so that when the membrane is strongly curved, the plates cannot come into contact (c in Fig. 138).

Fig. 145: /eft: Webbing corners with continuous and butted webbing; right: Rope corner with tangential webbing The edge detail and its anchorage at the membrane plate in- fluence the load-bearing behaviour of membranes consider- For membrane edge details, the extent and direction of the forces to be resisted are also dependant on the geometry of the corner, the angle in the membrane plate area of the mem- brane surface. The edge element in the membrane plate area runs almost parallel to the main curvature of the membrane surface. The membrane stresses, which near the edge run axi- ally to the edge rope tangent, are introduced in the mem- brane plate almost parallel to it. The more acute the angle of the corner is, the more important is the capability of resisting

Fig. 143: Schematic illustration of the possible course of forces

Fig. 146: /eft: Rope corner with lattice membrane; middle: Rope corner with webbing reinforcement; right: Rope corner with tangential webbinc

If the corner area is exceptionally acutely angled, then the limiting angle, at which the resistance to this rotation in- creases, becomes smaller and the geometrical stiffness in the fabric increases. This has the result that higher forces must be introduced in the membrane plate area during pretension- ing than into obtusely angled corners.

Fig. 147: Edge fitting with continuous rope

Fig. 149: Stiff corner details These factors make it clear that the cutting out and the seam length play an important role for the membrane plate area and make careful consideration of the design of these details necessary. The corner area of stiff edges is mostly detailed as an alteration of direction in the stiff edge element. These nor- mally consist of standard clamping plate elements (Fig. 149). For stiff edging, the strain stiffness of the edge element re- sults in a relationship with the direction of the planned strip layout during the pretensioning process. It is not possible to tension the entire edge uniformly here because of the move- ment of the corner fitting. The introduction of the pretension

is done by pulling the corner element in stages. The cutting- out direction arriving in the corner area does, however, not correspond to the axis of the pretensioning force to be intro- duced. The introduction of higher forces in the main aniso- tropy direction also makes tensioning considerably harder if the corner detail is stiff in bending, particularly at acutely angled corners (Fig. 148).

Fig. 150: Assembly operations — chain of processes

Fig. 151: Tasks in construction management

Fig. 152: Rolled fork fitting with general type approval under building regulations about 8-12 weeks. Apart from the availability of the wires, the weight and the unit weight (loading and transport), the delivery time for wire ropes can be influenced particularly by material and construction of the rope, considering the ca- pacity of the production machinery. The capacity to pro- duce larger weights and diameters is not available in every country. When small quantities are to be ordered, attention must be paid to the minimum production quantities for each diameter. Further factors, which can influence the delivery time, are the type and size of the end fittings. To avoid pro- gramme delays, wire ropes, anchorages and pins should be specified with general type approval, in order to avoid the need for extensive testing.?

Fig. 153: Possible schedule for a project with a membrane area of approx. 500-1,000 m?

Fig. 154: Erection model for the roofing of the arena at Nimes, France: laying out the pillow

Fig. 155: Laying out the lower and upper membranes for the roofing of the Arena in Nimes, France The sequence in Figure 154 shows the simulation of the un- folding process of the lower and upper parts of the pillow Figure 155 shows the actual unfolding operation on the con- struction site. The erection of this project is documented ir section 3.5.2.2.

Figure 157 shows a model in scale 1:24 for the erection of a star-shaped stadium roofing in Riyadh (Saudi-Arabia). The pulling-in of an internal ridge and valley panel of approx. 1.700 m* was simulated with an erection model in a ware- house in Buffalo. This method of erection was tried for the first time for this project? 2 Philipp Holzmann — construction documentation (1988)

Erectio n models are only suitable tions to a limited extent. For the sys it is possible using catenary models to determine at which points vestiga in the system hinges should e or simulate the load-beari elements or structural systems is no ometrical models. To build such a model, it is necessary to observe rules of model similarity an nesses for structural investiga- em of supporting ropes, be assumed, but to in- ng capacity of individual possible using such ge- into account.! d take the relevant stiff-

Fig. 158: Areas of influence and responsibility of construction management in the design and construction process of flexible structural elements

Fig. 159: Manufacture of characteristic connections in membrane construction In addition to the manual work of preassembly, where assem- bly joints and membrane edges are prepared for lifting, hang- ing and pre ensioning, the app ication of lifting and preten- sioning devices also needs to be taken into account in the design of the connections. Loadi introduction manageabili ng during erection from load points, which alter during the erection proce- dure, cannot be allowed to affect the structural function and y of the connection . It must be possible to allevi- ate deviations from tolerances through appropriate details. The manufacture of sheeting connections is normally done by the fabricator in the works. All stages of the erection should be discussed with him. The edge connection, with the exception of webbing belts, is assembled on the site

Fig. 161: Exploded drawing of two membrane corner fittings

Fig. 160: Specification requirements for the detailing of membrane connections It is important that there is adequate room for erection in the detailing of assembly joints, edges and corners. In order to reduce the risk of accidents during erection, all connection locations should be easily accessible.

Fig. 163: /eft: Bottom-turning tower crane with luffing jib; right: Transport condition of a Liebherr mobile tower crane room for turning gear and ballast on the ground. When they are equipped with a jack-up mechanism, they can be exten- ded higher without having to use another crane (right in Fig. 164). Tower cranes with high-level turntable mostly have a nomi- nal load range of up to 120 mt. The ballast and the lifting winch are situated at the end of the opposing part of the jib, an advantage where space is restricted and there is no

Fig. 164: /eft: Tower crane with trolley jib and high-level turntable; right: Climbing system for a tower crane with high-level turntable

Fig. 166: Liebherr truck crane in working and driving configuration

Fig. 167: Load transfer devices and load suspension devices according to power

Fig. 168: Load suspension and load transfer devices for lifting a rolled membrane As shown in Figure 167, load suspension devices can be differentiated from load transfer devices by the method of force applied to the load.

When lifting with load transfer devices, these are laid round the load and hung on the lifting device directly or with an end connection. End fittings are available in many types, strengths and versions.

Fig. 170: /eft: Longer and shorter advantage tackle with fixed and loose pulleys; right: 600 kN tackle

Fig. 172: /eft: Tensioning set-up for a stay rope; right: Tensioning set-up for a group of ropes The most commonly used tensioning devices are hydraulic tension and compression presses. They consist of two cylin- ders of different cross-sectional areas connected to each oth- er, which are both closed by a piston. Coupled as a system with a liquid cylinder and a pump, they act on the of confined fluids. Enlargement of the piston area leads to an increase of the force acting on the piston. Tensioni hydraulic presses is very precise; with press tensionin ment, a thread play of only a few millimetres is prac other advantage of tensioning with presses is that be coupled to each other and individual press circui tensioned under central control and monitoring. principle ng with g equip- ical. An- they can scan be In order to be able to tension single wire ropes and groups of wire ropes with hydraulic presses, temporary construction like press tables or tensioning equipment has to be used, which make it possible to guide the tensioning forces safely.

Fig. 171: /eft: Press graph; right: Hollow piston press

Fig. 173: Equipment for tensioning a free rope length (left) and at a foundation (right) with hydraulic presses

Fig. 174: Equipment for tensioning a stay rope The technical effort to manufacture a tensioning mechanism and the amount of time and work to assemble it can be very considerable. The assembly and hangi ng of a tensioni ng sys- tem for a rope bundle can last many days, but the tensioning itself only lasts a few hours. If it is assumed that the amount of time and work to assemble a tens ioning system i s often many times that of the actual tensioning process, then it is clearly advantageous to tension with sible. Attention needs to be paid to as few presses he space requ as pos- ired for The picture in Figure 174 shows the setup to pretension a stay rope for a pylon of the membrane roofing in Bad Velbert.

Fig. 176: VSL strand tensioning device and the application for the installation of the cable stays in the construction of the Waldstadion in Frankfurt/M., German) One single rope is normally pulled by 1 or 2 devices, seldom by 4. Up to 20 devices can be controlled simultaneously. Fig. 175: Strand tensioning system

Fig. 179: Football stadium at Braga, Portugal after the roof erection Fig. 177: /eft: Installation of the rope clamp and the deflection system; right: Installation of the guide traverse and hanging the rope

Fig. 180: /eft: Mechanical griphoist; right: Tensioning a rope with a griphoist

Both tensioning devices need care to be taken during ten- sioning, because they can relatively easily be overloaded and damaged by too much strength. Fabrics and ropes can also be loaded to breaking load and damaged by incorrect use. It is therefore important to read the tension force from a meas- uring device during tensioning and observe the stated loads for the devices.

Fig. 181: /eft: Ratchet lever hoist; right: Moving a corner fitting using a lever hoist Griphoists (tirfors) are manually operated winches, which are mainly used for pulling, tensioning, lifting and lashing loads without limit to the rope length. They work on the princi- ple of an eccentric clamp grip. A wire rope of any length is drawn through the device using gripping jaws. The pairs of jaws are operated by pulling a lever backwards and forwards. The changeover from pulling to releasing can be done by changing the location of the operating lever, even under oad. The load in this case is held safe by automatic closing of both pairs of jaws. A shear pin safety device on the feed ever protects from overloading. By using a deflecting block, he load can be distributed over many ropes, allowing a dou- bling of the tension loading.

Fig. 182: Tensioning a stay rope with ratchet lever hoists and butterfly plates

Fig. 186: Tensioning a stiff membrane edge using a lashing strap system Examples of the most important tools for pulling in and tensioning membrane sheets are described in the following section and their function explained. To apply the force to a membrane sheet, it must be held, pulled with a defined force and fixed. Various tools are used for this process, depending on the material, the tensioning travel and the type of edging. These are normally electrical, hydraulic or mechanical tensioning devices and tensioning aids gripping the membrane edge.

Fig. 185: /eft: Lashing strap system; right: Ratchet tie-down 3.3.3 Tensioning devices and aids for membrane sheets Stiff membrane edges can be easily tensioned using lashing strap systems, such as are mostly used as tie-downs for se- curing loads (Fig. 185). Low-stretch, woven polyester straps equipped with lever ratchet tensioners are a tensioning sys- tem, which can apply permissible loading of up to approx. 200 kN. The advantage of tensioning with lashing straps is their manageability and low weight. Tie-downs can easily be installed in restricted spaces. As with all tensioning devices, they do need adequate anchorage (Fig. 186).

If higher forces need to be applied to the membrane edge, hydraulic presses can be used. If the tensioning involves long travel distances, then rope winches can also be used.

Fig. 189: Pulling in the membrane for the roofing over of the Gottlieb Daimler Stadion in Stuttgart, Germany When stiff clamping plate edge details with external keders are specified, sheet metal plates with welded-on lugs can be used for tensioning (Fig. 191). For the tensioning process, these are bolted directly to the upper part of the clamping plate. A tensioning device can be hooked up to the hole in the lug, which provides the necessary force to the edge. The drilled hole thus has to be sufficiently large. One tool used by many erection companies is the tempo- rary clamping plate. This can be used to pull in the mem- brane sheet and also for tensioning. It has lower and upper clamping plate halves and connections for flat steel, ropes or

Fig. 188: Temporary clamps for pulling in membranes

Fig. 190: Tensioning equipment for clamping plate edge

Fig. 191: Clamping plate edge detail for the roofing of the Main Station in Dresden, Germany

Fig. 193: Tensioning a keder rail edge at the control tower in Vienna airport, Austria

Fig. 194: Equipment for fixing tensioning devices and tensioning aids

Fig. 196: Articulated and telescoping platform in use for the erection of a pneumatic pillow and the erection of a four-point awninc¢ The use of lightweight system scaffolding is economical where the erection of the membrane is laid out axially. In order to encourage economical erection progress, there should be enough space available. Such scaffolding is nor- mally stationary or wheeled frame or tube scaffolding with working platforms of steel or aluminium panels. The advan- tage of the use of scaffolding systems is that they can be When choosing suitable working platforms, safety and er- gonomic working conditions during the erection have to

Fig. 195: Use of system scaffolding as working platforms for the installation of membrane surfaces

Fig. 198: Travelling platforms for the membrane erection of the Tropical Island in Brand and for the Forum roof in the Sony Center in Berlin

Fig. 199: Mobile working platform for membrane erection at Neuchatel, Switzerland

Fig. 201: /eft: Stabilising the primary structure during the erection of the roof over the carport at the Munich Waste Management Office; right: Stabilising the wire rope construction at the Millennium Dome in London, England The advantages of abseil working are high flexibility and low cost. Especially for projects with wire rope systems, which can be used as access routes, abseiling is a very efficient solution. To ensure safe working with ropes, it is, however, necessary that the erectors are fully trained in abseiling. Various methods and temporary works can be used to stabi- lise the primary structure or the elements of the substruc- ture during erection depending on the erection process. Structural components can be tensioned, stayed, or propped with equipment like wire ropes, lashing straps or adjustable props to enable the erection to proceed safely. There must be adequate anchorages available for their use.

3.3.4.2 Temporary construction for the stabilisation of the main structure Scaffolds require a not inconsiderable length of time to erect and mount to fixed construction elements. The use of scaffolding or cranes is often impossible on account of the geometry of the structure, the space available or unavailability.

Fig. 203: top: Ballasting a wire rope construction for glass panels with sandbags at the nodes; bottom: Ballasting two carrier ropes with water containers during the erection of the roof over the Gerhard Hanappi Stadion in Vienna, Austria ing the tension. Tensioning chair, press chair and the required presses have to be positioned in the rope axis and anchored. This can be provided by the erection of accessible erection platforms.

Fig. 204: Platforms for the strand tensioning devices during the construction of the roof over the Waldstadion in Frankfurt/M., Germany

Fig. 202: Temporary state during the erection of a high point roof

a) Installation in a stable umbrella structure

c) Erection of an arch membrane d) Erection of high point structures

Fig. 207: Membrane erection with unstable primary structure

In Figure 210, constructional measures for stabilisation are de- rived from the type of loading on the structure and compared.

f the membrane surface and the primary construction stabi- ise each other in the structure, then the tensioning sequence for the introduction of the pretension must be designed accor- ding to the forces and deformations in the whole structure. The deformations arising in the structure from the staged ensioning are calculated as an iterative process in the erec- ion planning. Fig. 208: Schematic diagram of a possible tensioning sequence

Fig. 211: Conditions on the construction site and resulting erection conditions

Fig. 213: Use of cranes in membrane construction; left: Truck crane with telescopic boom, lattice-boom crane; right: Tower crane These small lifting devices are normally only suited for use in restricted areas due to their limited lifting height. The eco- nomy of their use depends on the ratio of force applied and dead weight to the load-lifting capacity. The most commonly used heavy lifting devices in membrane construction are truck-mounted cranes with telescopic or

Fig. 212: Criteria for the selection of a suitable lifting device

Fig. 215: /eft: Apparatus for tensioning stay rope; middle: Apparatus for tensioning carrier rope; right: Apparatus for tensioning stay rop This makes it clear that the method of pulling the edge can be an economic question. The design of the edge detail and the tensioning concept should include discussions with the construction firm. Tensioning equipment for wire ropes can have consider- able weight and can then only be moved with a crane. The time taken to set up and relocate such an apparatus can be several days. This results in the following rule of thumb for tensioning wire ropes: the lower the number of tensioning

Fig. 214: Criteria for the selection of the correct tensioning tools

Fig. 216: /eft: Mast transport; middle: Unloading a folded package; right: Unloading and lifting rolls The delivery of material from the fabricator to the construc- tion site is the most important in the chain of erection pro- cesses. It is important that the material in this delivery is properly packed and protected from external influences. In addition to the packing, the method of erection is also significant. Rolled fabrics and foils are lifted and laid out in a

Fig. 217: Erection procedures for lifting columns into a vertical position

Fig. 219: Lifting the masts at the Millennium Dome in London, England Fig. 218: Preparatory work left: for pivoting; middle: for lifting; right: Pylon head with preassembled membrane

Fig. 221: Mast erection at the Millennium Dome

Fig. 223: Erection sequence and rope connections Afte tion, the opposite masts can be hinged up by synchronously connected winches (a, b, ¢ in mas ways. The vertical position can be finely adjus between the stay ropes (f in Fig. 223). The setting up of the pivoting the first pair of masts into the i ntended posi- using the two Fig. 223). The ts are supported by temporary stays against tipping side- ed with tirfors mas ts including all preparatory work can nor in less than 2 hours. mally be done

Fig. 222: Scheme of the mast erection of the 4-mast Chapiteau

Fig. 224: Scheme of the mast erection for the swimming pool membrane roof in Kuala Lumpur, Malaysia

Fig. 226: /eft: Foot point of the king truss with cable anchorage nodes; middle: Head part of the king truss; right: King truss section:

Fig. 225: Segmental erection from underneath for the swimming pool membrane roof in Kuala Lumpur, Malaysia

Fig. 228: /eft: View of a quarter of the steelwork with temporary construction; right: Steel construction around the reinforced concrete core An example for the erection of edge beams for membrane structures is the assembly of the compression ring for the Fo- rum roof described above. The structurally independent, pre- ensioned structure has an external compression ring con- structed as a three-chord space truss ring beam (Fig. 227), which is supported at 7 points on the neighbouring build- ings. It consists of 146 straight tubes for the chords and 36 ubes of various diameters for the struts. The tubes were de- ivered to the construction site singly and welded togethe here. Only the nodes with welded-on eye lugs and the ring beam bearing were made in the workshop. Because of its dimensions, it was not possible to manufacture the 520 t ring beams in sections in the workshop. Altogether 11 sections of The Glass/PTFE fabric membrane panels are tensioned be- tween 12 horizontal steel rings, which are connected by 8 spokes each to a central concrete shaft (right in Fig. 228). The total weight of the steelwork is about 200 t. The membrane span between the adjacent ring sections is about 4 m. The structure with a total surface of about 3.300 m’ is the largest membrane structure in Austria.2

Fig. 227: left, middle: Three-chord ring truss; right: Completed roof

Fig. 230: Atrium roofing at the Palais Rothschild in Vienna, Austria; left: Scheme of structural system; right: Interior view (Photo © Werner Kaligofsky

Fig. 229: left, middle: Erection of the first two steel rings; right: Completed membrane surface

Fig. 232: /eft: Hinged support on arch; middle: Connection of the diagonal struts to the longitudinal rope; right: Rope connection to the horizontal framing After the erection of the vertical and horizontal framing, the arches were lifted by a truck crane, bolted to the horizon- tal framing and stabilised with belts. After the installation and tensioning of the longitudinal wire ropes, the transverse ropes could be connected and the diagonal struts mounted on the ropes. The adjustment of the diagonal struts and the fine tensioning of the transverse ropes brought the structure into the final intended position. Pretensioned cable structures normally consist of many sin- gle wire ropes, which are coupled with free-hanging node points or with elements, which are stiff in compression or bending. The erection of these structures is basically similar to that of single ropes.

Fig. 233: Erection of a single wire rope The rope is first hung to a fixed point with large sag and then ed to the tensioning point with a light force (A in Fig. 233). This lifting process can, for example, be done with a tirfor or a ruck crane. The slack hanging rope can then be continuous- y tensioned by the appropriate tensioning tool until the in- ended tensioning travel (S in Fig. 233) has been reached and he intended rope geometry and force have been achieved. n principle, it should be noted that ropes are mostly short- ened at their end points. If this is not possible, then tension- ing is done in the free length.

the elastic deformation of the rope are small. On tensioning the rope, it is shortened further. In the initial phase, the geo- metrical change of length and the elastic deformation of the rope are approximately of the same order as those on lifting. In the final phase of the tensioning process, where the rope nears its intended length, the tensioning force multiplies many times. Predominantly elastic extension of the rope is caused. Tensioning devices must often be first re-equipped or connected during this phase.

Fig. 235: Pivoting the masts vertical by shortening the stay ropes

Fig. 236: Wire rope structure, Geiger system Ridge ropes arranged in rotational symmetry in this dome- shaped system span from an external compression ring to

The erection of spoked constructions is essentially deter- mined by the nature and the location of the forces applied. For the version with internal node point and spokes splayed outwards (A, al in Fig. 237) or inwards (a2 in Fig. 237), the planes of the ropes can be pushed against each other by centrally placed press equipment. For constructions with an inner ring, the loads are normally transferred through ten- sion connections mounted on the compression ring, i.e. peripherally (b1 in Fig. 237), in which case it is possible to tension synchronously and under central control with press- es arranged at the node points. One exception to this is a tensioning method where the pretension is introduced by he lowering of the inner ring (b2 in Fig. 237).

Fig. 237: Method and location of force introduction into bicycle wheel structures The chief characteristic of the constructional system of a spoked wheel is that an internal tension ring is braced to an external compression ring by spokes splayed either out- wards or inwards. The structural behaviour is determined by loads acting perpendicular to the plane of the wheel being resisted by diverted forces from the rings so that the sys- tem transfers no horizontal forces to the outside. It should be pointed out that asymmetrical loadings are problematic for spoked wheel constructions, because they can cause great deformations and the constructional principle can then be poorly exploited.’ Any variation form the circular form must

carrier cables with membrane panels spanned between them. No example of simultaneous application of the tensioning forces by increasing the circumference of the edge beam, as is the case with saddle rope net structures, is known to the author.

To tension the cable stru cture, the carrier cable was ten- sioned with a travel of 1.4 m. The press force in the curve truss increased at this stage from 450 kN to 2,300 kN (right in Fig. 240). The decisive point for the success of the lifting and tensioning of the cab e structure was the simultaneous tensioning of all trusses. 1 dure was accompanied by The lifting and tensioning proce- checks of force and geometry and could be completed within 3 weeks.

Fig. 241: Factors influencing the erection procedure

3.4.3.1 Erection of Awnings The erection of a four-point awning starts with setting out the foundation centres and bolting the masts. Then the stay ropes are attached to the mast heads.

Fig. 242: Erection procedure for four-point awning

Fig. 246: Erection procedure — high point surface

Pushing up the hanging columns in stages with hydraulic presses effects the force introduction into the membrane surface. The surface can then be fine tensioned panel by panel by shortening the stay ropes and tensioning the edge ropes.

Fig. 251: Pulling the membrane off the package from a temporary platform Fig. 252: Edge detail with clips and cast nodes for the ropes spanned underneath Fig. 248: View of the roof with high point surfaces Fig. 249: Single layer ropenet construction

Fig. 253: Application of the pretension Fig. 250: Lifting the last membrane panel

After the erection of the perimeter rope bundle and the rope net has been laid out and preassembled, the radial ropes were lifted with strand tensioners over many weeks and

Fig. 254: Erection procedure for a high point surface

Fig. 255: Erection of a high point surface with internal masts

High point surfaces, which are supported on internal masts, can also be erected very efficiently.

Fig. 256: Erection procedure for high point surface

Fig. 257: Erection of a hanging high point surface by pulling up the hanger rope system

Fig. 262: Erection of edge panels Fig. 261: Connecting a membrane panel Fig. 259: Preassembly of membrane panel Fig. 258: Rope net construction

To prepare for erection, the individual panels are laid out on he ground (Fig. 259), and fitted with temporary tensioning fittings at the edge and reinforcement at the corner cut-outs. Once this preparation work is complete, the panels are fixed 0 specially prepared hanging scaffolds, with which they can be lifted at any angle to the cast iron rope nodes using rope winches and pulleys. The arrangement of the hanging scaf- folds along the edges of the surface enables the membrane panels, which are at risk of kinking, to be lifted while almost fully extended (Fig. 260).

Fig. 265: Erection sequence — Arch membrane and detail of arch crown

Fig. 267: Tensioning sequence and tensioning direction

Fig. 270: Erection variant for arched construction

Fig. 272: Erection of the rope net Fig. 273: Installation of the polycarbonate boards This erection procedure was repeated for each of the 108 membrane panels. 5 experienced membrane specialists managed 6 erection crews with 70 workers each working in- dependently of each other, who, split up into working gangs, worked on six panels simultaneously in a rolling schedule

Fig. 271: Aerial view of the airport in Bangkok, Thailand After the installation of the textile hanging scaffolds as ac- cess to the connection points along the trusses, a textile belt net with PVC membrane covering was spanned for the erec-

Fig. 276: Welding the covering membrane Fig. 275: Tensioning the outer membrane

3.4.3.4 Erection of ridge and valley surfaces Membranes tensioned between ridge and valley can be implemented in radial or parallel versions.

After the edge elements had been mounted, the ridge ropes were hung. The tensioning of the valley rope against the compression ring introduced pretension into the entire panel (right in Fig. 278). Fig. 277: Erection sequence - ridge and valley surface

Fig. 280: Scheme of the roof erection of the stadium in Riyadh, Saudi Arabia

1 Final assembly of the 58 m high masts, stabilisation with temporary ropes.

Fig. 279: Roof erection at the stadium in Riyadh, Saudi Arabia

Fig. 283: Section through valley (rope nodes) Fig. 282: Section through pillow construction Fig. 281: Tropical Island, Brand, Germany After the production of many proposals from various bid- ders, the decision was made to rebuild the existing ridge and valley construction by installing 14 new diamond-shaped pillows with load-bearing function in each of the 4 central, 35 m wide truss fields (Fig. 282). The 17 x 20 m pillows with a thickness of about 3 m are supported at their outside and inside by form-giving bundles of aluminium-steel ropes. In he valley area at the centre of the field, the rope bundles connect with rope clamps to the existing valley rope, where he edges of the pillow are also held fast by aluminium clamping strips. A thermally insulated GRP rainwater gutte and a condensate gutter are also fixed to this construction Fig. 283). The fixing of the outer edges of the pillow is to the appropriate upper chord of the 8 m high arch truss of the primary structure? The 16 m long membrane packages, delivered by low-loader, were prepared on a scaffold platform, lifted with the rope trave ona prest lar ca mate stalla supp theg se tot prepre etched re bein ial at t ion of ied wit he appropri pared webbing ate net (Fig. 286). Eac at its relevant installation height, g paid to the in he weld seams he outer di roduction of force and pillow corners. agonal rope net, the pil h air. The welding of the cover me utter then completed the erection of a me ocation for erection and spread h pillow was with particu- into the ETFE After the in- ow could be mbrane over mbrane field.

Fig. 286: Installation of the foil pillow Fig. 285: Access unit and rope traverse Fig. 284: Installation of the GRP gutter

Fig. 287: Activities in the implementation of construction of the working processes on the construction site. The exe- cution of membrane construction is a sequence of erection procedures. They are central to the practicalities of erection and can be categorised as follows: In order to realistically estimate the problems of constructing a wide-span lightweight structure, it is necessary to possess, in addition to knowledge of the factors resulting from form, force relationships and material, a thorough understanding

Fig. 288: top: Special transport; bottom: Rope drums

Fig. 289: /eft: Rope coils; middle: Turning pay-off stand; right: Drum reel with horizontal axis

Fig. 291: Jeft: Laying out the carrier cable at the stadium in Braga, Portugal; middle, right: Preassembly of the cable structure at the Waldstadion in Frankfurt/M., German Fig. 290: Unrolling rope from a braked stand

Fig. 292: /eft: Preassembly of the ring cable at the Gottlieb Daimler stadium; right: Preassembly of the hanger ropes at the Waldstadion, Frankfurt/M., Germany

For unloading and moving the single packages, it is helpful if ropes, chains or slings can be connected. A folding plan supplied with each package should include details of the centre lines, shape and weight of the indivi- dual panels and fields, the description of the edges, seams

Fig. 294: /eft: Folded package — roofing of the amphitheatre in Nimes; right: Folded package — roofing of the Millennium Dome in London, England

Fig. 295: /eft: Roll preparation for the wrapping of the Reichstag; right: Roll packaging Another way of transporting membranes is to roll them at the works. The unrolling on the construction site can, however,

Fig. 296: Rolled membrane surface and unrolling mechanism

To lift and pull wire ropes into position for tensioning, equip- ment is needed like rope spreaders, pulley blocks, rope winches or strand tensioning devices. The permissible radi- us of bend should be observed in order not to kink the rope. Ropes should be protected from loading in bending where they come out of fittings. They often need to be protected from damage by twisting. In order to lift ropes into position often requires special clamps to be made. Measures also have to be taken on site to turn and anchor the pulling rope. In the construction of rope trusses, the spanning ropes can be moved and lifted by a remotely controlled trolley mount- ed on the carrier cable (left in Fig. 301). Another way of lifting and laying ropes at height is to lift the bobbins with a crane and unroll the rope from the bobbin (right in Fig. 301). 3.5.2.1 Lifting and pulling of ropes After the preassembly is complete, the actual erection of the flexible structural elements starts with the lifting pro- cess, the laying or hanging in the intended position. Safety precautions are required to ensure adequate stability of the structural elements and avoid overloading.

Fig. 303: /eft:"Threading in” the columns, right: Lifting the rope net for the roofing of the Rhon Clinic in Bad Neustadt, Germany

Fig. 304: Rope net erection in Radolfzell, Germany

Fig. 305: Lifting of membrane surfaces into position for erection

Fig. 306: Lifting and unfolding a folded package for the erection for the Airport Center in Munich, Germany The lifting of partial panels from the air into the stabilised struc- ture can be done by lifting folded packages, rolled or loose panels. In many cases membranes are also pulled up along the primary structure or along temporary ropes. Large pillows are mostly inflated at low level and then lifted. Depending to the size of the membrane surface and the weather conditions, the lifting can take many days. If the primary structure is stabi- In addition to taking wind forces into account, a safety con- cept has to be considered in case of rain loading. The loading from rainwater produces an increase of weight and can amount to many tonnes of additional loading. If the mem-

Fig. 308: Lifting of rolled membrane for the wrapping of the Reichstag in Berlin, Germany Fig. 307: Lifting of rolled membrane with (left) and without unrolling apparatus (right)

Fig. 309: /eft: Lifting a high point surface; middle, right: Lifting the segments for the Forum roof at the Sony Center in Berlin, Germany The practicality of lifting or pulling loose sheets depends strongly on the weather conditions. The loose membrane sheets act as sails and are especially at risk of damage. A good weather forecast is needed for the lifting operation. If the edge fittings are mounted on the partial sheets, then the Large areas, which are pulled up over many days, should always be pulled so that shapes are formed, which allow rain to drain off. If water puddles do form during the pulling ope- ration, they should be cut out or pumped out.

Fig. 311: /eft: Lifting a membrane premounted to arches; right: Lifting a transformable membrane surface Fig. 310: Pulling in the 11,000 m” partial area for the membrane roof over the EXPO grounds in Brisbane, Australia

Fig. 312: Aerial view, section and plan of the amphitheatre in Nimes, France

Fig. 313: /eft: Scheme for the lifting procedure of the upper and lower membranes; right: Sectional view

Fig. 314: /eft: Slide bridge; right: Erection procedure

Fig. 315: Temporary construction to pull the pillow along the masts The challenge of the initial erection was to lift the outer and inner layers of pillow and the rope net into position for ten- sioning without damaging the historic stands. The erection procedure finally used was to pull the suppor- ting rope network and the loose layers of pillow in stages along 30 steel slideways mounted on the masts, tension

Fig. 316: Pulling the pillow along the slideway bridges

Putting up and staying every second of the 30 columns.

Fig. 318: Distance beam, telescopic beam and lattice boom The erection procedure for lifting the pillow parts is summa rised in Fig. 319.

Fig. 320: Annual process of lifting the pillow

Fig. 322: Plan and section of the Arena in Vista Alegre, Spain

The opening struction is for ring, on which square 300 x 3 act as horizon are connected pillow has a p by 12 rope winches situated a rope wheels o lifted 10 m and can be parked in vari med by the paral tal bearings for t at the heads wit an area of 1,960 n the heads of th elog he pi ma the e col for the pillow in the fixed gridshell roof con- am-section compression 12 stayed 12 m high rocker columns stand. The 00 x 10 mm hollow pr ofile columns, which also low under wind loading, h ring ropes (Fig. 324). The 60 t nd is raised and lowered foot of the columns over umns (Fig. 321). It can be ous positions.!

Fig. 326: Lifting the pillow To lift the pillow into its final position, it has to be raised 30 m in height. The play was only a few millimetres. This require- ment meant that the columns had to be aligned exactly through the rope stays, in order that the pillow guide would not jam on the steel columns.!

Fig. 329: Jeft: Section through the upper ring; right: Box-section beam with cantilevers Because of the dimensions of the three large pillows, which cover an area of 3,500, 4,000 and 9,000 m? respectively, the PES/PVC membranes had to be made in 2 pieces for the Galets No. 2 and No. 3 and in 4 pieces for the Galet No. 1 and joined together on site with assembly joints. The welded strip widths of the panels were between 1.8 m and 2.3 m.

n order to enable a flat underside, the pillows were built with- out supporting rope nets. To achieve this, the internal pres- sure had to be limited to about 0.25-0.4 kN/m? according to the weather situation in order to avoid damage to the fabric. Because the design loads could not be resisted with such a ow internal pressure, the Galets had to be equipped with a gas-fired heating system in order to combat excessive snow oading with warm compressed air. The heating mounted on the compression ring of the Galets was controlled auto-

Fig. 327: /eft: Plan of Galets No. 1-3; right: Section of Galet No. 1; Neuchatel, Switzerland

Fig. 328: Galets on the Arteplage in Neuchatel, Switzerland

Fig. 330: /eft: Preassembled compression ring; middle: Lifting the columns; right: Preassembled pillow

Fig. 331: Assembly joints Galet No. 1 Then the columns were lowered though the 1.2 m x 1.2m openings in the compression ring one after another by a ruck crane. After being marked, the membrane panels were rolled out, unfolded and prepared for assembly. The connec- ion of the clamping plate joints from the middle outwards, he individual panels of the lower and upper membranes were joined to each other. Then first the upper and then the ower membranes were clamped to the perimeter compres- sion ring from the panel joints outwards (Fig. 331). To do his for Galet No.1 required about 150 tirfors, which were dis- ributed around the ring.

Simultaneous erection of primary structure and membrane If the primary structure is to be lifted complete with the membrane panels attached to it, then the capability of the membrane corners to resist this loading case should be checked (left in Fig. 333). It is also important to avoid kinking of the edge rope and the foot of the column jamming in the joint. Temporary situations should be controlled with rigging ropes, which can be removed rapidly. The erection should take place when there is no wind.

Fig. 334: Erection of the roof over the marketplace in Zeltweg, Austria Extensive preparatory works are needed before this can be done. The membrane must be attached to the stiff load- bearing elements of the primary structure so that the fabric material and the ropes are kept free of damage at every stage of the process. The freedom of movement must be checked in every direction.

When the structure is pivoted up into position, the stiff struc- tural elements have to be positioned in their starting posi- tion so that they can be pivoted exactly into the bearing plane. Eye plates mounted on the foot of the mast should not be deformed. If masts are to be stood up by pivoting, they should be restrained against sideways movement. The exam- ple shown in Fig. 334 shows the process for the erection of a Glass/PTFE fabric for a market roof at Zeltweg, Austria. An awning was erected there by diagonally staggered pivoting.

Fig. 335: Equilibrium models: Increasing resistance to loading through alterations of the angle of the system axes to each other

Fig. 336: Criteria for the selection of tensioning procedure The known methods of pretensioning for flexible load-bear- ing elements are the mechanical pretensioning of ropes, webbing, fabrics and foils and the pneumatic pretensioning of fabrics and foils. Another way of achieving form stability is pretensioning through loading, as is the case with hang- ing roofs under ballast, where the weight is higher than the wind uplift to be expected. Pretensioning with dynamic for- The most important tensioning procedures for introducing the tensioning forces into flexible structural elements are illustrated and described in the following section.

Fig. 337: Scheme of the elasticity behaviour of membrane materials with similar and dissimilar stretch properties

The following section illustrates various principles and pro- cedures for introducing the pretension in to membrane sur- faces, from directly pulling the edges or corners of the mem- brane element with tensioning aids to position or shape of the primary structu alteration of the e or the substruc- ture (Fig. 338). The diagrams are to be understood as sketch- es showing the principles. In the practice, many of the princi- ples explained are combined during erecti on. When the tensioning is done tangentially, the geometry and stiffness of the edge detail determine whether the loads are ap- plied linearly or at points. If the membrane has an edge, which

Fig. 340: Tensioning travel for different cutting pattern directions of an arch membrane with stiff edging

Fig. 341: Space requirements for the tensioning process It is advisable for many structural geometries to tension the weft direction over a longer travel distance with less force. The considerably stiffer warp direction should, on the other hand, be tensioned over as short a travel as possible. It can be sensible for the practicalities of installation not to com-

If the stiff edge is assembled without tensioning the fabric parallel to it, then the calculated compensation value can The calculated shortening of the considerably more strongly compensated weft direction can be pulled out of the mem- brane surface parallel or perpendicular to the stiff edge. If this is not possible and the membrane has to be tensioned in both weave directions in order to obtain an end result without wrinkles, then measures are taken to enable the membrane surface to span in the long direction. Depending

on the material, edge detail and strip layout, the surface will then be tensioned in the long direction simultaneously or after the transverse tensioning.

Fig. 345: Stiff edge detail at the Graz airport tower in Austria

Fig. 346: /eft: Tensioning a tube edge; right: Tube edge against standing bolts In a tube edge detail, a steel tube pushed through the sleeve functions as a keder. The load is introduced by even pulling

When tensioning clamping plate edges, which are mounted on the edge rope with sheet metal loops, the ability of these to move along the rope is a problem. Care should be taken that the sheet metal loops do not slew, jam or damage the rope when the load is introduced.

Fig. 349: Arch bearing at the stadium in Al Ain, Dubai, United Arab Emirates

Fig. 348: Introduction of tension by tilting the edge beam

Fig. 350: Erection of the stand roofing at the stadium in Al Ain, Dubai, United Arab Emirates ection and clamped to the arches (1 in Fig. 348). After pull- ing in and bolting the edge ropes, the arches can be pulled apart using rigging ropes or webbing slings with tirfors and fixed (2 in Fig. 348). The surface can be finely tensioned by shortening the edge rope (3 in Fig. 348). To tension a number of arch fields, each field is tensioned alone and secured with temporary construction. The introduction of linear edge loads into the membrane surface can also be achieved by changing the position of the stiff edge beam. One example of this is the tilting of arch- shaped edge beams. This is an efficient method of tension- ing, which is mostly used with many parallel rows of edge arches. The membrane surface is prestretched in the arch di-

Fig. 351: Pretensioning a fabric membrane by vertical movement of the arches

Fig. 352: Erection of the stand roofing at the Fenerbahce stadium in Istanbul, Turkey This is done by first prestretching the membrane edge in the direction of the arch and then clamping it to the arch (1 in Fig. 351). After pulling in and bolting the edge rope, the arches can be jacked up in stages by hydraulic presses, which pretensions the membrane (2 in Fig. 351). The edges can subsequently be finely tensioned by shortening the edge ropes (3 in Fig. 351). If a row of arch fields are arranged parallel to each other, the membrane is mostly laid over the arches without fixing to the crown of the arch.

Fig. 354: Tensioning a rope edge Tensioning by direct pulling or pushing is performed in many stages. After the edge rope has been pulled in and the corner fittings preassembled, these are displaced towards the fixed primary construction element (1 in Fig. 353). After an altera-

Fig. 355: Pretensioning a fabric membrane by displacing the corner fitting

3.5.3.2 Application of loads at points tion of position by distance y, or y, and with the reaching of the anchorage position (P in Fig. 353), the corner fittings can be hung from the primary structure. In the second stage, the edge ropes are finely tensioned to the corner (2 in Fig. 353). The rope edge has then moved a distance y, at its crown.

The tensioning is done in the sequence laid down in the erection planning and depends on local conditions, cutting To finely adjust the masts, the stay ropes are shortened with turnbuckles. The fine tensioning of the edges is done by shortening the edge ropes.

pattern direction and fabric material. The duration of tension- ing and the sequence are especially critical when tension- ing glass fibre fabrics, where delayed tensioning can enable the stress to distribute in the surface. The force level can be balanced by alternatively tensioning and relaxing.

Fig. 356: Tilting of masts by shortening the stay ropes

Fig. 358: Central tensioning of a high point supported by ropes from underneath by lengthening the shaft axis

Fig. 359: Central and peripheral tensioning of high point constructions To be able to lengthen the effective axial length, the column has to be made in more than one part. The column can ei- ther be connected through an intermediate member with One disadvantage of this tensioning method is that the entire pretension force is applied at one point. This means hat relatively high forces have to be used. Another way of pretensioning high point structures is to tension the mem- brane solely by peripheral pulling of the edges and corners b, d in Fig. 359). This requires less force to be applied and a better stress distribution in the surface can be expected, but the amount of work involved in installing equipment for stretching along the edges and at the corners can cause high costs.

Fig. 360: Erection of the compartmental high point surface at the Munich Waste Management Office, Germany An example for the central introduction of pretensioning orces in a high point structure supported from underneath by wires is the roofing over the vehicle park at the Munich Waste Management Office (left, right in Fig. 360). The Glass/ PTFE fabric for the roofing was prefabricated at the works in 10-12 m widths and 70 m long strips with seams in the sur- face of 60 mm. The strips were laid out in the transverse di- rection on site and welded to the adjacent strips (see sec- ion 2.5.1.1). In order to be able to compensate for errors, he weld seams were made on site with a width of 150 mm. During the welding work, the hats of the high points were urned inwards and fixed down against wind loads, and in order to avoid puddle formation through rain or snow (right in Fig. 361). An endless rope was fabricated into the membrane at the upper ring and secured with 3 pegs. This construction en- sures that when sideways movement occurs, no sharp edg- es can damage the fabric and the rope can roll of the ring under loading. There are no clamping plate connections be- tween the 10 x 12 m panels.

Fig. 361: Installation of hanging column at the Munich Waste Management Office, Germany

correspond to the correct form of the edge of the envelope under long-term stress. The factors, which determine the edge detail, are the stretch properties of the envelope mate- rial and the surface curvature in the edge area. 3.5.3.3 Application of surface loads

Fig. 363: Anchoring to water containers To maintain the air pressure in pneumatic structures, blower units are used, which can be regulated and controlled. These supply the membrane envelope though a duct system with Air supported halls have to be anchored around the peri- meter foundation. The form of the foundation line has to

Fig. 365: Fabric membrane during the inflation of an air-supported hall The erection of air-supported halls starts with the construc- tion of the foundations and the assembly of the inflation

Fig. 364: /eft: Inflation connections for an air-supported hall; right: Blower plant for a large pillow

The roof should periodically be inspected and checked in an optical control of the roof construction. The membrane should be checked for air-tightness, air pressure and mate- rial condition. The inlet filter in the switching cabinet and the drier filter should be cleaned or replaced. The pressure meas- urement hoses should be checked for condensate formation and blockage.

In this electrical measurement process, the resonance fre- quency of a string clamped into a holder is measured dur- ing alteration of length and converted. When a tension force is applied, the tension in the wire changes and thus its resonance frequency. The wire can be resonated by a piezo- electric or an electromagnetic component transverse to the

(area of the press cylinder). After the full pretension has been reached and the press compression has dropped off, the tensioning equipment can be removed. It is often necessary to readjust the rope length when using this process. Another way of determining the force in a rope is to mount the extensometer on the pretensioned rope and then to un- load the rope (b in Fig. 366). The force is determined analog- ously to the above example. This method can, however, only be used with suitable tensioning apparatus and is therefore restricted to relatively thin ropes and rope forces.

Fig. 370: Plate method Fig. 371: Ring force measuring devicer

Fig. 369: /eft: Arrangement of the accelerometer; right: Curve relationship with ray angle fined force. A plate-shaped device is used for this, which presses a plunger within a ring against the membrane surface (Fig. 370). The deflections and stresses arising in the membrane surface can then be calculated.

06 | Vehicle park roofing Waste Management Office, Munich / Germany

9 | Roofing of Fréttmaning station, Munich/ Germany

2 | Roofing of stand, Estadio Intermunicipal, Faro-Loulé / Portugal

5 | Stand roofing Sheikh Khalifa Bin Zayed Stadium/ United Arab Emirate:

Key takeaways

During erection, a steel rope is pushed through as edge element (Fig. 131).
This erection process can essentially be divided into the lifting and the tensioning of the rope.
After the erection of the perimeter rope bundle and the rope net has been laid out and preassembled, the radial ropes were lifted with strand tensioners over many weeks and bolted to the compression ring (Fig. 249).
4,000 m2 upper membrane 1 Habermann, K. J.;Schittich, C. (1994) The challenge of the initial erection was to lift the outer and inner layers of pillow and the rope net into position for tensioning without damaging the historic stands.
This tensioning process is frequently used for the erection of awnings, where the fabric is pretensioned by the tilting of the masts and the shortening of the stay and edge ropes (Fig. 356).

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