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In light steel framing, the compression resistance of the walls may be improved by the stabilising effect of plasterboard attached to one or both sides of the wall. This paper presents the results of 28 load tests on 2·4 m high walls using 75, 100 and 150 mm deep C-sections in 1·2 to 1·6 mm thick steel with various types of board. The results were compared to the methodology in the standards BS EN 1993-1-3 and BS 5950-5, taking account of restraint to minor axis buckling. The test results showed that the lateral restraint provided by 12 or 15 mm thick fire-resistant or moisture-resistant plasterboard fixed to one flange is equivalent to an effective length reduction factor of 0·7 in the minor axis direction for a 100 mm × 1·6 mm C-section in a 2·4 m high wall. A theory is developed based on distortional buckling of the C-sections, which allows the test results to be extended to other wall heights and section sizes. The failure loads were predicted by finite-element modelling by considering initial imperfections in the C-sections and the torsional restraint due to the boards.

This paper explores the concept of the optimum span to depth ratio of reusable composite beams with demountable bolted shear connectors so that the beams may be designed most efficiently in terms of their weight and the shear connector distribution along the span. Three patterns of shear connectors were evaluated by a simple pseudo-plastic model and calibrated by finite element modules in terms of their effect on the overall composite beam stiffness in the range of 9 to 15 m span. The optimum span to depth ratio of symmetrical and asymmetrical beams was determined and compared to equivalent beams with welded shear connectors. It was found that the optimum span to depth ratio of uniformly loaded unpropped composite beams with demountable bolted shear connectors may be taken as 22 which allows for a utilisation factor of 0.7 at the ultimate limit state to ensure that plasticity does not occur in the first use cycle. It was found that the effect of asymmetry on the optimum span to depth ratio is small. For propped beams with demountable shear connectors, the optimum span to depth ratio may be increased to 24.

A new form of light steel composite beam has been developed that uses C sections acting in tension with shear connectors in the form of screws or bolts or perforations in the web of the C section. The shear and bending resistance is also increased by using side C sections to the beams. Bending tests on point-loaded beams of 0.8, 1.1 and 1.7 m span showed that for the short span beams, the longitudinal shear bond strength of the base C sections is 1.4 N/mm2 for plain C sections and 2.3 N/mm2 for perforated C sections when expressed over the horizontal plane. Plain side C sections added 80% and perforated side Cs added 130% to the load-bearing capacity of the composite beams with base Cs. The theory is extended to cover elastic design taking account of partial shear connection in which the shear stiffness of the perforated web of the C section is approximately 10 N/mm3 (per unit web area) and that of the plain web is approximately 3 N/mm3.

The deflection of steel beams with circular openings is dependent on the loss of bending stiffness and shear area of the web, which adds to the deflection of the solid web beam. The additional deflection is a function of the ratio of opening diameter, ho, to section depth, h, and also of the spacing of the openings. This paper presents derived formulae for the additional deflection of beams with circular web openings that are expressed as a function of the pure bending deflection of the unperforated beam. The formulae are calibrated against finite element models and against short span beam tests with opening diameters, ho, of 0.6 h and 0.72 h, in which the additional defection is mainly due to the effects of shear. Further simplified design formulae for additional deflection are also presented which are shown to be accurate for C-section beams with a span: depth ratio exceeding 15. It is also shown that circular openings may be represented for analysis purposes as an equivalent rectangle of width x depth equal to 0.75 ho x ho.

This paper presents the basis for the design of steel and composite beams with large web openings. The main design requirements are the transfer of shear by Vierendeel bending and the control of web buckling next to and between the openings. Cellular beams with regular circular openings are a common example of highly perforated beams and their flange areas are often highly asymmetric. For these beams, web-post moments may be generated to develop the full shear resistance of the cross-section. Tests on beams with circular, elongated circular and rectangular openings are presented which are used to verify the design methodology. In addition, the openings cause local displacements due to shear and bending, which add to the overall deflection of perforated beams. Simplified formulae are presented to determine the additional deflection relative to the equivalent solid-web beams.

A design method for continuous profiled decking based on post-elastic moment re-distribution is presented. This method is based on that permitted in EN 1993-1-3: Eurocode 3, and in this paper, its application to highly stiffened composite deck profiles is explored. The new aspect is the way in which the residual negative bending moment is established at high rotations using a non-linear moment–rotation stiffness relationship. Tests on three modern deck profiles of 80 mm depths are presented. It was found that the degree of redistribution of negative moment can be high, and so the stiffness coefficient used for deflection calculations should also reflect the degree of redistribution of moment that occurs at the serviceability limit state.

Modular construction is widely used in Europe for multi-story residential buildings. A review of modular technologies is presented, which shows how the basic cellular approach in modular construction may be applied to a wide range of building forms and heights. Case studies on 12-, 17-, and 25-story modular buildings give design and constructional information for these relatively tall buildings. The case studies also show how the structural action of modular systems affects the architectural design concept of the building. The combination of modules with steel or concrete frames increases the range of design opportunities, particularly for mixed-use commercial and residential buildings. An overview of the sustainability benefits and economics of modular construction is presented based on these case studies. © 2012 American Society of Civil Engineers.

The elasto-plastic analysis of composite beams is important when considering the increase in bending resistance of the beam and the end slip between the steel and concrete at higher strains. This paper provides a simplified method of elasto-plastic analysis by considering equilibrium of the composite cross-section as a function of its strain profile. A parabolic–rectangular stress block for concrete is used in this model with a declining concrete strength at strains exceeding 0.0035. The bending resistance of the composite beam is expressed as a function of the bottom flange strain, and is compared to fully plastic design to EN 1994-1-1: Eurocode 4 and the AISC LRFD Code. The effect of various parameters on the development of the plastic bending resistance of composite beams is investigated, such as asymmetry of the section, the steel strength, the influence of propped or un-propped construction, strain hardening in the steel and reducing concrete strength at high strains, interface slip, and the effect of openings in the web of the beams. It was found that a moment of 95% of the plastic bending resistance of a composite beam (0.95 M pl ) is reached at a flange strain of 2 to 4 × yield strain for propped beams and 5 to 10 × yield strain for un-propped beams. When strain hardening in the steel is included in the analysis, bottom flange strains at a moment of 0.95 M pl are reduced by up to 30% relative to the case without strain hardening.

This paper addresses the design of stainless steel sections with large circular openings subject to shear and bending. A total of nine tests on pairs of C sections using 2 and 3 mm thick stainless steel in austenitic 1.4301 and lean duplex 1.4162 grades was performed. The tests showed that the shear resistance at an opening is controlled by local compression at a radial cross-section at approximately 25° to the vertical. For closely spaced openings, the angle of highest stress increases to about 65° to the vertical. The shear resistance of a Class 4 web is also affected by local buckling around the opening, which is a function of its diameter to steel thickness ratio. An equilibrium model is presented which predicts the normal stress on the radial planes around an opening. A simplified formula for the local buckling strength around circular web openings is also presented, which agrees well with the test results.

The design of hot-rolled steel portal frames can be sensitive to serviceability deflection limits. In such cases, in order to reduce frame deflections, practitioners increase the size of the eaves haunch and / or the sizes of the steel sections used for the column and rafter members of the frame. This paper investigates the effect of such deflection limits using a real-coded niching genetic algorithm (RC-NGA) that optimizes frame weight, taking into account both ultimate as well as serviceability limit states. The results show that the proposed GA is efficient and reliable. Two different sets of serviceability deflection limits are then considered: deflection limits recommended by the Steel Construction Institute (SCI), which is based on control of differential deflections, and other deflection limits based on suggestions by industry. Parametric studies are carried out on frames with spans ranging between 15 m to 50 m and column heights between 5 m to 10 m. It is demonstrated that for a 50 m span frame, use of the SCI recommended deflection limits can lead to frame weights that are around twice as heavy as compared to designs without these limits.

This paper reviews the design criteria for composite slabs at the fire limit state in accordance with Eurocode 4 Part 1.2 and with other modern Codes. A review of fire test data is presented and an assessment is made of the requirements of EC 4 Part 1.2 relative to these tests. Simplified fire design tables are presented.