Direct Design of Reinforced Concrete Transfer Girders

[摘要] This thesis reports experimental and theoretical investigations into the in-plane behaviour of reinforced concrete transfer girders designed by the direct design method. The girders tested were either continuous over two spans or single span. The direct design technique investigated used an elastic stress field obtained from a linear-elastic finite element analysis using the uncracked properties of concrete in conjunction with Nielson's yield criterion given by: (sigmax* - sigmax) (sigmay* - sigmay) - tauxy2 = 0 where sigmax, sigmay and tauxy are the applied stresses at the ultimate load, and sigmax* and sigmay* are the ultimate capacities of the section. An averaging procedure was used to smear out reinforcement requirements and select final bar sizes. This proved more satisfactory than selecting bars based on maximum stresses. A finite element procedure for obtaining an elasto-plastic stress field was developed in order to design the reinforcement. This approach may be better in producing more economical distributions for design the reinforcement. However, this was not adequately evaluated in this research. The experimental study consisted of testing eleven large scale girders. The major parameters studied for the two span continuous girders were; span to depth (L/D) ratio, the influence of the web reinforcement, the effect of using skew reinforcement and the main reinforcement distributions according to either CIRIA Guide 2 or the direct design technique. For the single span girders, the main purpose was to examine the direct design technique for girders with web openings which interrupt the load path. Also, to find the best location of the opening in the girder. One solid single span girder was tested with the aim of justifying the theoretical calculated amount of steel at each point, so that structure must yield simultaneously. Also, to justify the maximum and averaging envelope procedures. The theoretical study consisted of using a nonlinear plane stress finite element analysis. The material properites of reinforced concrete were represented by fixed crack smeared cracking model in conjunction with steel yielding behaviour etc. The experimental measured behaviour and the behaviour predicted by finite element model showed good agreement and allowed a greater insight into the behaviour of the girders. The test results indicate that the direct design approach is satisfactory in both ultimate strength and serviceability behaviour as given by 0.3mm crack width.

[发布机构] University:University of Glasgow

[关键词] Civil engineering