Experimental Study And Analysis On Mechanical Properties Of Bending And Torsion Of Prestressed Concrete Composite Box-girder With Corrugated Steel Webs

In order to explore the performances of restrained torsion and distortion of composite box girder with corrugated steel webs under complex torsion-bending force, the second Umanski torsion theory is introduced to establish control differential equation of restrained torsion and were solved according to initial parameter method. By the way, the control differential equations of distortion of composite box girder with corrugated steel webs is established by using plate element method, primary beam theory and theory of thin plate, and it is solved by analogous ground beam method. Key parameters of torsion and distortion are obtained from the solution of equation those two equations. Also this problem has been deeply studied through the static load test of indoor model beam and finite element numerical simulation as well, then the results of three kinds of methods are compared and analyzed. Meanwhile the diaphragms which are known as key impact structure to the torsional performance of box girders are studied and the reasonable maximum space between diaphragms and suitable thickness of diaphragms are given.The main research conclusions are as follows:1)When the composite box girder with corrugated steel webs is under eccentric loads, there generates a rigid torsion which will bring additional deflection and curl stress, and this part of curl stress accounts for a large proportion of bending stress. The result is verified by theoretical calculations, model tests and finite element numerical simulations.2)The maximum curl stress occurs in the concrete slab, and the curl stress of distortion is larger than that of torsion. However, the proportion of the two occupied in the coupling effects remains to be studied.3)Corrugated steel webs are less sensitive to longitudinal warpings, including torsional warpings and warpings caused by distortion. But the value of additional vertical shear stress in corrugated steel webs under eccentric loads is large, which can not be ignored in the shear design of corrugated steel webs.4)The comparison results of the three calculation methods show that the accuracy of the finite element calculation is higher than that of theoretical calculation and the measured values. Theories introduced in this paper are with certain accuracies and likely to be safe when they are used to calculated the torsion and distortion of composite box girders with corrugated steel webs.5) Setting diaphragms can significantly reduce deformations caused by the distortion,whereas it not have much effect on properties of bending and torsion of composite box girders with corrugated steel webs.The findings of this paper are expected to provide references for design and construction monitoring of this kind of bridges and similar experimental tests.