下承式密布横梁体系钢桁结合梁桥受力性能分析

Mechanical Behavior Analysis for Through Bridge of Steel Truss Composite Girder with Multi-transverse Beams System

下承式钢桁结合梁桥通过桥面板与主桁结构的连接形成稳定的空间结构,使得桥梁的刚度,特别是面外抗弯刚度得到了有效提高。密布横梁体系的下承式钢桁结合梁桥则取消了纵梁,增加了节间横梁,改善了桥梁结构主桁的受力情况。本文以跨度64 m的密布横梁式钢桁结合梁桥为例,通过静、动载试验和有限元分析,研究了该结构体系的受力特性。研究结果表明:该桥一阶横向自振频率满足规范要求;且由于桥面板与下弦杆形成的整体共同承受外部荷载,在30 t轴重荷载作用下弦杆与横梁受力较小,最大应力分别为26.39,30.73 MPa,并有效减小了下弦杆挠度,实测挠跨比远小于限值;混凝土桥面板以受拉为主,顺桥向最大应力为3.53 MPa。该桥动力性能良好,跨中横、竖向振动特性均满足规范要求,满足30 t轴重重载运输要求。

A through bridge of steel truss composite girder forms a stable space structure by the connection between the bridge decks and the main trusses. So its stiffness,especially the out-of-plane bending stiffness is improved effectively. A through bridge of steel truss composite girder with multi-transverse beams system is cancelled the stringers and added cross beams between panels. So the stress condition of the main truss is improved and more reasonable. In this paper,aiming at a 64 m span through bridge of steel truss composite girder with multi-transverse beams system,its mechanical characteristics were analyzed by static and dynamic load tests and finite element analysis. The results showthat the first order transverse natural frequency meets the requirements of specifications.Since that the bridge decks and the bottom chord bars as an unity structure bear loads,the stresses of the bottom chord bars were small under the 30 t axle load,the maximum stresses respectively is 26. 39 and 30. 73 MPa,and the deflection of the bottom chord bar was effectively reduced,the measurement deflection to span ratio was far smaller than the specification limit. The concrete bridge decks mainly bear tensile force,its maximum longitudinal stress is3. 53 MPa. The static and dynamic behaviors of this bridge are good. The transverse and vertical vibration characteristics of the middle span section meet specification requirements. The bridge meets the requirements of 30 t axle load heavy haul transportation.