装配式T梁桥汽车荷载效应的空间分布特征

为探讨汽车荷载作用下跨径、桥宽对装配式预应力混凝土简支T梁桥汽车荷载效应的影响,以交通部2008年T梁桥通用设计图为背景,利用实体有限元模型对比分析了25m、30m、35m三种跨径和9.0m、11.25m、13.5m、15.75m和18m五种桥宽下的竖/横向位移、竖/横向弯矩、纵向应力和扭转角,并与T梁桥实用空间解析解进行了对比分析。通过分析发现：汽车荷载作用下装配式T梁会同时出现竖向和横向挠曲变形,竖向荷载效应随桥梁宽度的增加而近似线性减小,但其横向形变效应会受桥梁跨径、宽度、布载形式等多种因素影响；当装配式T梁桥的所有T梁均使用边梁的设计活载效应时,T梁最大应力的解析结果能包络T梁的活载横向挠曲效应,但当跨径超过30m后中梁活载应力最大值可能会超过刚性横梁法的计算结果；T梁的侧向弯曲会显著增加截面中性轴附近的拉应力,且随着跨径的增大梁体侧向弯曲引起的中性轴位置处应力越大,T梁腹板外侧的分布钢筋最好能按照T梁腹板承受的横向弯矩大小设计为受力钢筋,并减小钢筋间距以更好地防止T梁腹板的竖向开裂。

Spatial Distribution Characteristics of Vehicle Load Effect of Prefabricated T-Girder Bridges

In order to investigate the influence of span length and width on vehicle load effects of simple supported T-shape girder, finite element models with different span length and width were established based on the 2008 T-girder bridge general design drawing of the Ministry of Communications. The numerical results of vehicle load effects, such as, vertical and horizontal displacement, moment, stress and torsional angle of T-shape girder with different span length and width were also discussed, and compared with the practical space analytical solution of T-girder bridge. Through analysis, it is found that the vertical and lateral flexural deformation occurs simultaneously in the assembled T-shape girder under the vehicle load. The vertical load effect decreases linearly with the increase of the bridge width, but the lateral deformation effect will be affected by the various factors ,such as the span and width of the bridge, the form of loading; when all the T-girders of the fabricated T-girder bridge are designed based on live load effect of the side beam, the analytical result of the maximum stress of the T-girder can cover the lateral deflection effect of the live load. However, when the span exceeds 30m, the maximum live load stress of the middle beam may exceed the calculation result of the rigid beam method; the lateral bending of the T-girder significantly increases the tensile stress near the neutral axis of the section, and increases with the span. the distribution of the steel outside the T-girder web is preferably designed as the stressed steel bar according to the transverse bending moment of the T-girder web, and the spacing of the steel bars should be reduced. to better prevent vertical cracking of the T-girder web.