Research On Optimization Design Of Concretebeam Bridges For Engineering

Aiming at the problem that the optimal design function of reinforced concrete bridge is single at present,it is not closely combined with the design code.Combined with bridge design code,durability limit state theory and reliability theory,a practical,modular and integrated T-beam design optimization model is established.Based on this,the structural design optimization program of ordinary reinforced concrete and prestressed reinforced concrete T-beams is worked out,and the robust optimization design is preliminarily carried out,which is verified by an example.The main work and conclusions are as follows:(1)The optimization program for the design of reinforced concrete and prestressed concrete T-beams is established.The program structure is simple and clear,modular processing,easy to edit,has its practicability.Three optimal design modules including structural safety durability and reliability which can be distributed and used are constructed and compared with the standard diagram to verify the effectiveness of the optimization design module.And with the continuous addition of the module,the optimization scheme is more reasonable and perfect.The compilation of constraint conditions follows the order of design specification,which can effectively improve efficiency and avoid the absence of constraint conditions.(2)The structural constraints between flange thickness and web height indirectly limit the increase of beam height and limit the traditional design experience of reducing the cost of beam height.Compared with the warm and humid south,the regional differentiations of durability optimization design of T-beam structure in low temperature and dry north provinces are more obvious.The shear capacity reliability of T-beam structure mainly under bending is lower than that of bending reliability,and the spacing of reinforced stirrups can improve the reliability index of the main beam.(3)The prestressed steel bar in prestressed structure has a positive effect on the reduction of structure cost,and the prestressed steel bar is not sensitive to carbonization.It is suggested that when the unit price of ordinary rebar is less than that of prestressed rebar,prestressed rebar should be used as far as possible in structural design.(4)The structural robustness optimization design is based on taguchi method.When the concrete mark increases,the cost increases gradually.When the main reinforcement is changed from HRB400 to HRB500,the optimized design cost shows an obvious downward trend.When the stirrup reinforcement is taken as HPB300 and HRB400 respectively,thecost increase of optimal design is weak.Compared with the sensitivity method,taguchi method requires less model and is more practical.