Experimental Study On Mechanical Behavior Of Prefabricated Prestressed Concrete Box-girder Bridge With Corrugated Steel Webs In Construction Stage

Prestressed concrete box-girder with corrugated steel webs is a new type of steelconcrete composite girder,which is suitable for small and medium span bridges.This kind of girder is composed of concrete flange plate,corrugated steel webs and prestressed tendons.A new prefabricated splicing technology of prestressed concrete box-girder bridge with corrugated steel webs was described in detail based on an engineering practice.Mechanical properties and deformation behavior of the composite beam was studied in the process of adopting twice tensioning internal prestressed tendon technique.Then field static loading test was carried out on the bridge.Through literature research and study on existing bridges in China and abroad,the normal stress and deformation in test beam was studied by present methods while tensioning the prestressed tendons.Simulate the process of twice tensioning internal prestress with finite element analysis software MIDAS/FEA.Theoretical analysis and finite element analysis were proved by field tension tests.The tests included first tensioning internal prestressed tendons at the bottom of PC I-girder with corrugated steel webs and second tensioning tendons of box-girder after assembly by using wetjoints between I-girders.Through theoretical analysis,finite element and field test,the transmission mechanism of prestressed concrete composite girder with corrugated steel webs was obtained,and the conclusions are as follows:(1)The corrugated steel webs of test beam did not bear axial force and positive bending moments after prestressed.Part of prestressing force transferred from the bottom flange to the top flange because of the deformation compatibility of webs.Therefore,the test beam was under overall compression.That means,prestress can be effectively applied to the top and bottom concrete flanges.(2)Cast-in-situ part and prefabricated part of the top-and-bottom of assembled box-girder could work together effectively.Loads could be efficiently transferred between different precast plates.(3)The deflection of the test beam conformed to the characteristics of the flexural deformation of a simply-supported beam while tensioning the prestressed tendons.(4)The results of theoretical analysis and finite element analysis were proved to be in good agreement with the experimental data,and the feasibility of formula of theoretic calculation was proved.After the completion of the bridge,the static load model calculation of MIDAS/FEA and field static load test under seven working conditions were carried out.Mechanical response of prestressed concrete box-girder with corrugated steel webs under the action of static loads was studied,and mechanical property of this kind of bridge was revealed.The results indicated that cast-in-situ part of the beam was formed integrally within prefabricated part to work together.The longitudinal normal deformation of both the top and bottom plates of each section satisfied the "quasi plane section assumption" in the elastic stage.The section deflection of the test beam was small and the deflection of the whole bridge was smooth.The results of finite element analysis were proved to be in good agreement with the experimental data.It was proved that the mechanical properties of the bridge met the design requirements.