高原大桥桥台地震破坏机理与抗震措施分析

Analysis of seismic failure mechanism and earthquake resistant measures for the abutments of Gaoyuan bridge

通过现场震害调查和有限元分析,研究了汶川大地震高原大桥桥台的地震破坏机理和提高桥台抗主梁撞击能力的工程措施。研究表明,基于pushover静力分析技术可较好地模拟桥台在主梁撞击下的破坏形态。对不同的有限元模型假定,高原大桥虹口侧桥台可表现出"上弱下强"、"上下等强"和"下弱上强"等3种不同的破坏模式,且桥台胸墙、前墙、前墙与翼墙交界面是抗震薄弱点,在主梁撞击下易发生脆性开裂;而高原侧桥台的破坏则基本为自胸墙开始,沿45°夹角向斜下方扩展,最终导致桥台胸墙撞碎、后侧翼墙脱落倒塌。素混凝土桥台在主梁撞击下表现出明显的脆性,提高桥台混凝土强度可有效增大桥台抗撞击的强度,而在桥台混凝土中配置一定量的分布钢筋则可有效延缓桥台破坏过程。

The seismic damage mechanism and the engineering measures to prevent collision damage of the abut- ments of Gaoyuan bridge damaged during the Wenchuan earthquake were analyzed by post-earthquake observations and finite element analysis. It is found that the pushover static analysis can be used to simulate the failure modes of the bridge abutments under collision effect of the girder. Three types of failure modes in the abutments of the Hongkou side are obtained by using different finite element models, such as ＂week top and strong bottom＂, ＂equal strength from top to bottom＂, ＂week bottom and strong top＂ failure modes. Also, the breastwall, the frontwall, and the surface between the frontwall and wingwall are vulnerable to the collision effect of the girder. The damage to the abutment of the Gaoyuan side initiated from the breastwall, and propagated toward the base with an angle about 45~. Finally, the breastwall crushed and the wingwall dropped from the abutment. It is found that the plain concrete in the abutment showed brittle failure mode under the collision effect of the girder, and it is effective to in- crease the strength of the abutment by using concrete with higher strength. It is also found that the damage progress of the abutment will be delayed by using concrete with reinforcements.