Experimental Study On Constructionally Optimized Long-span Continuous Composite Bridges With Corrugated Steel Webs

Several critical issues including inconvenient construction,cracking of the concrete upper flange when using cantilever construction method and insufficient longitudinal shear capacity may occur when prestressed concrete composite beams with corrugated steel webs using PC bottom flanges are applied to long-span continuous girder bridges.In order to address these problems,an optimized scheme which takes steel bottom flange as an alternate of the traditional PC bottom flange at the sagging moment region is proposed to reduce the self-weight of the structure and then reduce the negative bending moment at the support is proposed.Meanwhile,concrete inner-lining combined with the corrugated webs in the segments near the middle support which are under hogging moment may be used to improve the shear capacity.The behavior of the optimized-section beams are studied mainly by means of experiments and by FEM and theoretical analysis as well.The main works and results are as follows:1.Static bending experiments of two beams under sagging moment are carried out.One of the two specimens has steel bottom flange instead of the traditional concrete bottom flange while the other is a traditional one.The flexural capacity,the flexural stiffness,the distribution of normal strain on the cross-section,the distribution of shear force and the internal force of prestressed reinforcements of the speciments are studied and compared and conclusions are as follows: the distribution of normal strain on the section of the beam with steel bottom flange obeys the famous “Quasi Plane Assumption”.The corrugated steel webs carry about 90 percent of the shear force.It is more satisfactory to put the section with steel bottom flange instead of the traditional section in use in the mid-span segments under sagging moment because of its better self-weight and flexural capacity and easier construction.2.Static bending experiments of two beams under hogging moment are carried out.One of the two specimens has concrete inner-lining combined with its corrugatred steel webs while the other doesn’t.The corrugated webs of the beams gain greater axial rigidity when combined with the concrete inner-lining and may participate in the bending resistance of the section.The distribution of normal strain on the section of the beam with concrete inner-lining obeys the plane assumption approximately.The pre-stress in the concrete flange reduces when concrete inner-lining is used.The corrugated webs take much less shear force after combined with the concrete inner-lining,ranging from 20% to 50% of the total shear force from the beginning to the end of the test.The beam without concrete inner-lining presents a connection failure mode while the one with concrete inner-lining,connection between the webs and the flanges strengthened,presents a typical flexural failure mode with much more satisfactory bearing capacity.3.FEM models of the specimens are built and the experiments are simulated in MSC.Marc 2010.Parameters which have important influence on the carrying capacity of the beams are analysed as well,showing that the pre-stressed reinforcements are more efficient than the steel bottom flange in increasing the bending capacity of the positive-moment beam,and that the bending capacity and the post-cracking flexural rigidity of the negative-moment beams can be raised by increasing the thickness and the ratio of reinforcement of the concrete inner-lining.4.The longitudinal shear capacity on the interface between the concrete inner-lining and the concrete flanges and the ultimate flexural bearing capacity of the steel-bottm-flange beams are analyzed based on the results of the experiments on the hogging moment beams and a calculation method is proposed.