Study On Seismic Performance Of Rigid Frame Bridge With Long Spans And High Piers

Rigid frame bridge with high piers and long spans has been widely used in southwest China especially mountainous areas with complex geological conditions due to its appealing design, convenient construction and great crossover capability of ravines. Because of its statically indeterminate structure, rigid frame bridge has high redundancy, so the rigid frame bridge has the great seismic capacity when it is affected by the earthquake load. However, at present because of the lack of earthquake damages about this type of the bridge at home and abroad, the designers relatively know the seismic capacity inadequately. This study is aimed to enhance the understanding of the seismic resistance capacity of this kind of bridge based on Niu lanjiang bridge in Yunnan Province through pseudo-dynamic test. The following work has been done:Firstly, introduce the reasons of the bridge seismic damage. And the bridge seismic damage mainly includes bridge upper structure damage, bridge bearing damage and bridge foundation structure damage. Several typical representative bridges in Wenchuan Earthquake have been chosen and their damage have been introduced in detail, in order to provide abundant data of samples for the mountainous bridge seismic fortification in future.Secondly, introduce the pseudo dynamic testing method. The basic thought and components of the pseudo dynamic testing are introduced in detail.Thirdly, design and make the Niu lanjiang bridge model. Because of the limitation of the area location and reaction walls in the laboratory, calculate the thickness of bridge piers reinforcement with the requirement that the top of south pier has the same displacement as the top of north pier. And then the experiment scheme is decided.Fourthly, the data analysis and experiment phenomena of the Pseudo-dynamic test indicate that:The bottom of piers is the seismic weak link of this bridge model; And the piers shows nonlinear behavior under the El Centro earthquake motion which of PGA is1200gal. The piers show concrete cracking, which contain horizontal circular cracks. This belongs to flexural failure mode; and the reinforced maximum strain shows the strains haven’t yielded. The result demonstrates that this kind of bridge possesses a high level of extreme seismic resistance capacity.