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The Structural Engineer

A method for selecting the optimum design parameters in the design of reinforced concrete slabs is presented. The optimum is selected from within the feasible region in the design space defined by the limit state requirements of CP110. Cost of material is treated as the objective function and is optimised subject to the behaviour and side constraints imposed by the limit state requirements. Initially, the optimum solution for a section is obtained considering only the ultimate limit state requirement. This is then modified, if required, to ensure that it lies within the feasible region defined by the serviceability limit state requirements for the member. From this result, the optimum design parameters for members having uniform, triangular or parabolic moment, distributions are obtained. Curves for selecting optimum design parameters are also given. D.J. Gunaratnam and N.S. Sivakumaran

The Structural Engineer

The present paper is based on well-known theoretical and experimental results which have established and verified the interaction of the two basic components of light steel buildings subject to static load, namely portal frames and panels of sheeting. The favourable effect of the above interaction is particularly evident in the case of horizontal load which in this type of building is represented by wind. Wind, however, may exert dynamic effects as well, and therefore full-scale tests were performed with the following aims: 1. to determine whether it is necessary to take the dynamic effect of the wind load into consideration, 2. to determine whether sheet panels and especially their fasteners are able to transfer possible dynamic load. Ing. M. Strnad and Doc. ing. M. Pirner

The Structural Engineer

Details are given of a numerical study of the elastic longitudinal bending behaviour of composite box girder bridges in which the use of flexible shear connectors results in incomplete interaction between the slab and girder components. The results of the study provided background for the formulation of design rules included in the draft Unified Bridge Code, and the rules are discussed in the light of these results. K.R. Moffatt and P.J. Dowling