On the Physically Nonlinear Analysis of Composite Structures under Quasi-Static Long-Term Loading

On the Physically Nonlinear Analysis of Composite Structures under Quasi-Static Long-Term Loading

AbstractSoftware for designing structural frameworks in civil engineering is getting more and more complex. By offering reliable and efficient calculation methods, economic goals can be reached as well as the civil engineer's demands. Furthermore, opportunities for special developments are created and acceptance of new building systems is increased.The work presented here introduces a method for the physically nonlinear analysis of different composite beam designs for building and bridge structures which are subjected mainly to bending stresses under quasi-static, long-term loading. In addition, the utilization of these methods, including materials and modelling concepts, are shown in a newly developed software package. Present developments for composite construction and civil engineering requirements are the basis for the materials and modelling possibilities discussed.Particular attention is given to a realistic description of time and load dependent variables characterizing the state of the composite structures and their interactions. The selection of material models is based on experimental results. The main points of interest are concrete properties like creep, shrinkage, effluent hydration heat, cracking and boundary behaviour between different materials. Material behaviour under load and reload conditions was taken into account as well.The static solution is based on the incremental iterative application of the deformation method. Each iteration starts with the numerical integration of the beam system of differential equations. Based on the effects at the beam boundaries, the consideration of load and system modifications, as well as time dependent and independent constraint processes, is shown.An essential extension of the composite beam structure model is obtained using the system of differential equations for the flexible bond. Several detailed models are linked to a time dependent simulation for the entire system, which has been incorporated into a software package visualizing the time dependent variables.Finally, some practical application examples are presented. The validation of the implemented approach is demonstrated by correlating the calculated results with real life measurements.