Research On Seismic Behavior Of Continuous Rigid Frame Concrete Bridge With High Piers And Long Spans

The continuous rigid frame concrete bridges with high piers and long spans has many advantages, such as beautiful outline, higher span capacity, easy to construct, low cost of construction and so on, therefore, they are widely used in mountain regions these years in the southwest and northwest regions of China which is characterized by high mountains and deep valleys. Because of its short history, there is no earthquake damage lesson for this kind of bridge except Zipingpu Bridge which is damaged in Wenchuan earthquake in 2008. The high-pier and long-span continuous rigid frame concrete bridge is usually used as the backbone bridge of the trunk transport line, and its seismic damage would have a great influence on the transport of the whole area and the earthquake relief effort, so it is of great engineering significance to research the seismic performance of the continuous rigid frame concrete bridge with high pier and long span and know its earthquake damage mechanism and ultimate earthquake-resistant capability.The earthquake-resistant capability of the continuous rigid frame concrete bridges with high piers and long spans is researched by the integrated means of field investigation and analysis, field modal test on the real bridge, pseudo dynamic test on the bridge model, shaking table test on the bridge model, and numerical simulation, and the research findings are as follows:The earthquake damage of bridges is summarized based on some factors such as material, constitution, and earthquake effect. The seismic damage mechanism of all types of bridges is elaborated, the seismic weakness of these bridges is discussed, and on the basis of them, improved design advice is proposed.Taking Niulanjiang Bridge in Yunnan province, a continuous rigid frame concrete bridge with high piers and long spans, whose height is 140m, and main span is 170m as an example, a modal test is conducted on it. The horizontal, longitudinal, and vertical modal parameters are obtained which provide a strong basis for the subsequent model design and finite element analysis.Based on the modal test result on the real bridge, and combining the analysis of structural constitution, it is confirmed that the weak direction of the bridge is the horizontal direction. A high-pier and long-span continuous rigid frame concrete bridge model with a ratio of 1/12 whose height is 12m, length is 24m is designed. This bridge has 4 piers and 3 spans. A pseudo dynamic test is conducted on the model to research its ultimate seismic capability and failure mode. The test result shows that the continuous rigid frame concrete bridge with high piers and long spans designed in accordance with the present code has strong seismic capability, and its failure mode is bending failure in the horizontal direction of the pier which has better ductility, and the plastic hinge is near the bottom of the pier.The effect of the high order mode on the earthquake response of the high and flexible structure is studied by shaking table test. It is found that the high order mode contributes differently to different physical quantities of the high and flexible structure's earthquake response: the top displacement is controlled by the fundamental frequency, the strain of the bottom and middle of the system is affected more obviously by the higher order mode, and the contribution of the higher order mode to the strain of the middle of the system is greater than to that of the bottom of the system.On the basis of the field measurement and model test result, the seismic capability of Niulanjiang Bridge is researched comprehensively by the finite element analysis software, ABAQUS, and result which coincides well with the test is gotten.