Experimental Study And Numerical Analysis On Seismic Performance Of Reinforced Concrete Bridge Columns

Bridges are integral components of transportation networks,it is important to characterize the performance of bridges during earthquakes. Loss of bridge function can cause severe consequences when bridges are critical links in lifelines to emergency facilities, which are particularly important after the earthquakes. Although damage to other elements can have economic and life-safety impacts, reinforced concrete columns are often the most vulnerable elements in a bridge, and column failure can have catastrophic consequences.Investigations of recent earthquake disasters develop bridge seismic technologies,and the main bridge seismic designe codes in the world have adopted ductility design method. Performance-based bridge seismic design method is current research focus,of which understanding of nonlinear seismic response and damage mechanism of bridge column is the key component.In this thesis, a systematic and intensive study of seismic performance and ductility failure mechanism on reinforced concrete bridge columns under seismic load has been done. All the works aim to provide an essential theoretical basis and experimental foundation for safety seismic design of bridge, and offer an important support to compile the bridge seismic code in China. Firstly, based on an extensive literature review, the factors affecting the columns'ductility performance have been determined. Secondly, using orthogonal pseudo-static test, these factors have been examined and analyzed, after that, the effect of plastic hinge length and effective stiffness have been highlighted and the factors in them were determined. Thirdly, considering the reinforcement conditions in China, researched on the experimental studies and test data from the database of the USA and Japan, a formula for calculating plastic hinge length and effective stiffness of piers has been defined by regressive analysis. Finally, a numerical model has been built with OpenSees to validate the accuracy of the achieved formulas. The main topics and conclusions in this thesis listed as following:(1) Based on literature review, the factors influencing the ductility of columns have been summarized from four aspects,which are: geometrical characteristics, reinforcement assembly, material behaviors and load applications.(2) The orthogonal pseudo-static tests of four factors at three different levels (column height: L, the ratio of axial compression: P/Agfc', the diameter of longitudinal reinforcement: db, the stirrup ratio:ρh) have been designed and tested;(3) A evaluate has been done for the test results in terms of the strength and ductility of columns, after that the effects of ratio of axial compression, ratio of shear to span, and reinforcement ratio on the performance-based seismic and ductility failure mechanism of bridges have been researched systematically;(4) Based on the analysis of impact factors, the plastic-hinge length and effective stiffness formulas for reinforced concrete bridge columns have been proposed, then a evaluate has been done through comparing new formulas with existing ones;(5) An OpenSees fiber element model has been built effectively which verified the reliability of formulas in calculating plastic-hinge length and effective stiffness of reinforced concrete columns proposed in this thesis.