The Theoretical And Experimental Research On The Shear-lag Effect In The Continuous Box-Girder With Corrugated Steel Webs

As all kinds of new types of bridges coming into people’s view, the shear lag effect increasingly attracts the attention domestically and abroad along with the development of communication. PC composite box beam bridge with corrugated steel webs is one of this new structure. The traditional concrete webs are instead by corrugated steel webs, which assume most shear, and top and bottom concrete flanges assume most bending moment. This type of structure reduced loss of prestress effectively and can be more economical and lighter.This paper adopts model test, finite element analysis and energy variation method to study shear lag effect of two span PC composite box uniform beam bridge with corrugated steel webs systematically. There are the main conclusions:(1) Two span uniform model beam (3+3) m with corrugated steel webs is designed, and the results show shear lag phenomenon exists in the beam under loads. And shear lag effect under concentrated load is more obvious than it under uniform load. In order to describe normal strain appeared larger in top and bottom plate and next to zero in webs, assumption of plane cross-section is brought in, which provides new deflection compatibility condition for design and calculation of corrugated steel webs.(2) ANSYS finite element calculation model of test beam is set up, and the results are close to test values, which confirmed the conclusion obtained in test and proved the correctness of finite element model.(3) The shear lag calculation formulas of PC composite box beam with corrugated steel webs are derived from energy variation method, which provide solution of free beam and continuous beam with corrugated steel webs shear lag in detail. The results show that the formulas, which have been derived from energy variation method in the paper, apply to the shear lag effect of the composite continuos box girder with corrugated steel webs under the uniform distributed loads. What’s more, the calculation results are more secure, while they are not fit to the case under the concentrated load.(4) Through study longitudinal distribution of shear lag, the shear lag coefficients of full-span can be instead by the coefficients of top and bottom plate. Because of the coefficients of bottom plate is a little bit smaller than top plate, the coefficients of top plate at mid-span can be regard as full-span’s for simplification.(5) The influence to shear lag of structure geometric parameters (wide high ratio, wide span ratio, flange plate ratio, wave height and longitudinal prestress must be considered in order to obtain shear lag calculation empirical formulas with a view of wide span ratio. The study shows the ratio effects much to the beam, which should be paid more attention, and other parameters can be ignored. In addition, longitudinal prestress almost doesn’t effect it.