Research On Mechanical Properties Of Variable Cross-Section Hybrid Truss Bridge

As a new type of steel-concrete composite bridge,the prestressed concrete composite girder bridge with steel truss webs,also known as hybrid truss bridge,has serval advantages including light weight,beautiful appearance,good visual transparency and convenient segmental construction.It is especially suitable in medium-span and large-span bridges and is more and more widely used nowadays.Until now,studies on the hybrid truss bridge are mainly based on equal-section girders.However,there are few researches on the mechanical properties of variable cross-section hybrid tuss bridge.In this paper,the Shuinianbao bridge which is under construction has been taken as an example to study the mechanical properties of variable crosssection hybrid tuss bridge,a series of studies have been conducted.The main tasks and conclusions are as follows:(1)Based on Shuinianbao bridge,a variable cross-section hybrid truss bridge,the corresponding finite element model is established and a simple calculation is performed.The corresponding finite element model of the variable-height and equal-height variable crosssection hybrid truss bridge are established to analyse the mechanical properties of variable cross-section hybrid truss bridge under deadweight and deadweight plus prestress load.(2)Study the web shear ratio of variable-section variable cross-section hybrid truss bridge under deadweight and deadweight plus prestress load.Serval section parameters that could affect the web shear ratio are analyzed,and the thickness of concrete floor,the supporting height and the height of the box girder are taken into consideration.and the variation law of the web shear ratio is obtained.(3)Combining the characteristics of hybrid truss bridge,its eccentric coefficient is subdivided into normal stress increase coefficient,equivalent shear stress increase coefficient and displacement increase coefficient.The eccentric load effect of variable cross-section hybrid truss bridge under lane load is analyzed.The results show that the eccentric load effect of variable cross-section hybrid truss bridge under lane load is significant,and its influence needs to be considered in the design and calculation of the bridge.The proposed values for the various coefficient coefficients along the longitudinal bridge are given.The parametric analysis of the effect of the ratio of width to span ratio,ratio of suspension to wing,ratio of high span on eccentric coefficient at each section along the longitudinal bridge is conduted.The results show that the width-span ratio and the wing-span ratio have significant influence on the eccentric coefficient of the variable cross-section hybrid truss bridges,while the high-span ratio has few effects.