Optimal Design Research For PC Continuous Box Girder Bridge

Abstract:The traditional design procedure of PC continuous beam bridge is:designers originally set the structural dimensions, calculate the internal forces, estimate and arrange the prestress tendon based on the span, width and construction method of the bridge. Then they recalculate and check the structure according to the standards related to it. Designers cannot calculate the loss of prestress and the secondary internal force caused by prestress accurately, neither can they consider the eccentric position of prestress precisely. So the estimation of tendon is very rough, and adjusting the original parameters, even modifying the sectional dimensions of the bridge, is needed to get satisfactory results. It is difficult for the designers to make the design reasonable and economical, because of many design parameters and control conditions are involved. After some limited times of trials and adjustments, the design is feasible, but not optimal.To make up for the shortcomings of the traditional design, this paper presents a new optimization design method for the PC continuous box girder bridge on the basis of the former researches:an optimal design based on the optimization theory, which combines the estimation and arrangement of tendon with completion stage, considering coupling and compatible relationship between parameters. The main contents are as follows:(1) MINLPB is used to do the optimization calculation. The validity and reliability of MINLPB to solve the optimization model of PC continuous bridge is verified by examination questions.(2) Mathematical model of optimization of the three stages is established by choosing the structural dimension, the number of tendon, the tendon layout and configuration as the variables.(3) In order to verify the accuracy of the method in this paper, Leishui Brige which has been opened to traffic operation is used to do the optimal design.The optimal design method for PC continuous box girder proposed in this paper not only overcomes the shortcomings of traditional design, but also makes up for the deficiency of the previous optimization design. With this design, the configuration between the sectional dimensions and the number of tendon can be optimized, and the elevation of tendon can be drew automatically, and the PC continuous box girder bridge can be preliminarily designed, making it valuable practically and theoretically.