Space Frames: Application. Multistorey Structures

The MERO space frame developed by Mengeringhausen consists of joints and members (1) - (3). The underlying principle is that joints and members are selected from the frame systems as are appropriate for the loads which are to be carried. In the MERO structural elements, the joint/member links do not act as 'ideal pin-joints', but are able to transmit flexural moments in addition to the normal forces in the members (4) – (7). This three-dimensional format permits a free selection of a basic grid unit, then, with the factors √2 and √3 to size the lengths of the members, to develop a structure to provide the required load-bearing surfaces – (12) – (14).

The unlimited flexibility is expressed in the fact that curved space frames are also possible. The Globe Arena in Stockholm – (13) is, at present, the largest hemispherical building in the world. The assembly methods involve elements of prefabrication, sectional installation or the slab-lift method. All the components are hot galvanised for corrosion protection. As a consequence of the high level of static redundancy of space frames, the failure of a single member as a result of fire will not lead to the collapse of the structure. Starting from spherical joints, that allow 18 different points of attachment for tubular members, a large variety of other joint systems between nodes and members have been developed so as to optimise the solution to load-bearing and spanning requirements (8) – (11).

The Krupp-Montal® space frame was developed by E. Rüter, Dortmund-Hörde. The members are bolted to the forged steel sphere with bolts inside the tubes. The bolts have hexagonal recesses in their heads and are inserted into a guide tube through a hole in the tubing of the structural member. In general, all members are hot galvanised. A coloured coating may also be applied to them. On the Krupp-Montal® System, the bolts can be examined without being removed from the frame members; if required, it is possible to replace framework members without destroying the framework. The Krupp-Montal® System is illustrated in – (1) – (5) points of detail in - (6)- (8).

The KEBA tube and joint connection has been designed for the transmission of tensile and compressive forces. It does not require bolts and can be dismantled without problems - (9) – (13). The KEBA joint consists of the jaw fitting, the interlocking flange, the tapered wedge and the caging ring with locking pin.

The Scane space frame has been developed by Kaj Thomsen. Bolts provide the means of connection, which are inserted in the ends of the members using a special method and are then screwed into the threaded bores of the spherical joint fittings – (14) – (15).

In the case of all space frames, an unsupported span of at least 80-100m is possible.

Multistorey Structures. The main choice is of in situ or prefabricated manufacture in the form of slab or frame construction. The selection of the materials is according to type of construction and local conditions.

As in all areas of building construction, the number of storeys is limited by the load-bearing capacity and weight of the building materials. Construction consists of a vertical, space enclosing supporting structure made from structural materials with or without tensile strength. Vertical and lateral stiffening is necessary through connected transverse walls and ceiling structures. Frame construction, as a non-space enclosing supporting structure, permits an open planform and choice of outer wall formation (cantilevered or suspended construction). A large number of floor levels is possible with various types of prefabrication.

Structural frame materials: reinforced concrete - which provides a choice of in situ and prefabricated, steel, aluminium and timber.

Types of structure: frames with main beams on hinged joints, or rigid frame units in longitudinal and/or transverse directions. Construction systems: columns and main beams (uprights and ties) determine the frame structure with rigid or articulated joints (connecting points of columns and beams). Fully stiffened frames: columns and beams with rigid joints are connected to rigid frame units. Articulated frame units one above the other: columns and beams are rigidly connected into rigid frame units and arranged one above the other with articulated joints. Pure articulated frames: nodal points are designed to articulate, with diagonal bracing structures (struts and trusses) and solid diaphragms (intermediate walls, gable walls, stairwell walls); mixed systems are possible. Rigid joints are easily achieved with in situ and prefabricated reinforced concrete; however, prefabricated components are usually designed with articulated joints and braced by rigid building cores.

Construction. Framed structures with continuous vertical supports – (1) - (2); ties beams rest on visible brackets or conceal bearings. Skeleton structures with sectional vertical supports - (3) - (5); the height of the verticals can possibly extend over more than two storeys; the supporting brackets can be staggered from frame to frame; hinged supports with stiffened building cores.

Framed structures with frame units – (6) – (8): H-shaped frame units, if required, with suspended ties at the centre connection (articulated storey height frames); U-shaped frame units, with separate ties in the centre, or with ties rigidly connected to frames (articulated storey height frames). Flat head mushroom unit frame construction (9): columns with four-sided cantilevered slabs (slabs and columns rigidly connected together, articulated connection of the cantilevered slab edges). Floor support structures directly accept the vertical loads and transmits them horizontally onto the points of support; concrete floor slabs of solid, hollow, ribbed or coffered construction are very heavy if the span is large, and prove difficult in service installation; use of the lift-slab method is possible, suitable principally for rectangular planforms – (10) –(12).