常规桥梁设计理念及《规范》条文应用探讨

Study of Design Conception and Code Provision Application of Conventional Bridges

常规桥梁中简支T梁因采用连续桥面而设置伸缩缝处的桥面频频损坏,成为既有交通的最大干扰源,受弯构件因抗裂能力不足而开裂超限也是较为普遍的桥梁病害。为了避免上述病害,分析支座、桥墩及其组合刚度对简支梁体系的受力分配影响,考虑到主梁能够承受一定的纵向水平力,不做连续桥面还可大幅提高桥墩安全系数,T梁还是简支为好。探讨受弯构件实际的荷载加载过程、荷载总量、总量限值,构件及材料的工作原理,抗裂标准要求,亦可得到结论:构件材料只能被限制在弹性阶段工作,普通钢筋更为主要的功能是向构件提供抗拉刚度,满足抗裂要求则必然满足极限承载力要求。以上理念可以更好地把握《规范》条文在设计中的应用。

The decks at the expansion joints of the simply-supported T-beams of conventional bridges are frequently damaged because the continuous decks have almost always been used. The damage of the decks becomes the most notable source of interference to the present traffic on the bridges and besides, the cracking of the flexural components of the bridges due to the insufficient cracking resistance capacity is also a kind of the common deterioration. To avoid the damage and deterioration, the influences of the bearings, piers and the rigidity combination of the bearings and piers on the force distribution of the simply-supported beam system are analyzed. In consideration of the fact that the main beam of a simply-supported beam system can sustain a certain longitudinal horizontal force, the system, if not provided with the continuous deck, can greatly improve the safety coefficients of the piers and it is still better if the T-beams are just simply supported. From the study of the actual loading process, total load, total load limit, working principles of the components and materials and cracking resistance criterion requirements of the flexural components, it can be concluded that the materials of the components can be only restricted to work in the range of elasticity. The more principal function of the common reinforcement is to provide the components with the tensile rigidity. The satisfying of the cracking resistance requirement of the components will certainly satisfy the ultimate load carrying capacity requirement. With the aforesaid conception in mind, the relevant provisions in the codes can be better applied to the design of the bridges.