Analysis And Study Of Seismic Performance Of Curved Girder Bridges In High Intensity Areas Based On Probability

Due to the particularity of its geometry,curved girder bridges are widely used in highintensity areas to overcome significant terrain differences with their advantages.Due to the asymmetry of the upper main beam structure,the pier needs to bear the bidirectional bending moment and bidirectional horizontal force under the action of earthquake,in view of this situation,this paper proposes to evaluate the seismic performance of the plastic hinge area under the action of earthquake by elliptical envelope diagram method,and explore the seismic performance of the plastic hinge area of the pier under the two-way bending.On this basis,the key design parameters of the pier were studied based on the bidirectional bending bearing capacity and the energy dissipation of plastic hinge,and the sensitivity analysis of the pier was carried out based on the Tornado graphic method.Finally,on the basis of the previous article,the appropriate cross-section is selected,and the reliability analysis and study of the plastic hinge area of the pier is carried out on the basis of surpassing the failure criterion for the first time based on the FORM method.The main research work and conclusions of this paper are as follows:(1)The finite element model of the whole bridge of the curved girder bridge in a moderate section of the Sichuan Ya’an Expressway was established,and through the time history analysis method,it was found that when the curved girder bridge was excitation input,the most unfavorable input angle changed due to the bending radius,and the excitation input direction needed to be clarified.The seismic response analysis and seismic performance evaluation of the pier area at the most unfavorable input angle were carried out by the elliptical envelope method,and it was found that the curved beam pier had a significant bidirectional bending moment coupling effect under seismic excitation.Under the excitation of high-intensity earthquakes,the maximum lateral and longitudinal bending moments generated are located in the envelope diagram,which confirms that the plastic hinge area of the curved beam pier has good bending bearing capacity,and can make full use of the plastic hinge to dissipate seismic energy.(2)Based on the Tornado method,the influence law and sensitivity of design parameters such as section size,section height,section reinforcement ratio and other design parameters closely related to the seismic performance of curved girder bridge piers were explored,and it was found that the shorter the pier height was under the condition of meeting the terrain conditions,the most suitable section size was 3m,and the most suitable reinforcement ratio remained at 1.6%～2.4%.For different response standards,there are obvious differences in the degree of influence of various parameters of the structure,among which the height of the curved beam pier is the most comprehensive,which further indicates that the axial pressure of the pier has a great influence on its performance of bearing the bidirectional bending moment.(3)Aiming at the reliability of the plastic area of the pier,Open Sees was used to establish the numerical model of the pier,and the local analysis of the pier of the curved girder bridge was carried out,and the FORM method and the first failure criterion were combined to study the number of times each unit and part of the curved girder pier with plastic hinge exceeded its bearing limit under random excitation,so as to explore its reliability.After analysis,the overall failure probability of the pier is 0.00486,which has a low failure probability,which proves that the principle of first transcendence based on the FORM method can be practically applied to the seismic reliability analysis of the pier of curved girder bridge,and provides a new reference basis and idea for the dynamic reliability design of curved girder bridge.