Study On Seismic Damage And Evaluation Method Of Prestressed Precast Segmental Piers

Precast segmental piers can shorten the construction period,improve construction quality,and have less impact on the surrounding environment,which is in line with the needs of Chinese rapid social development.Compared with cast-in-place monolithic reinforced concrete bridge piers,precast segmental piers have stronger deformability and self-resetting capability,but the research on the damage characteristics and damage mechanism is insufficient,and qualitative and quantitative assessment of damage performance of precast segmental piers under external loads is also a major issue in seismic performance design.In view of this,this paper has studied the seismic damage and evaluation methods of prestressed prefabricated piers.The main work is as follows:(1)Based on a review of a large number of related domestic and foreign literatures,a systematical review and summary of the research status of seismic performance and structural damage assessment methods for precast segmental piers has been made,and a total of six seismic damage assessment models for concrete structures were summarized,including based on stiffness degradation,energy-based method,Park-Ang damage assessment model and three modified Park-Ang models.(2)Based on the test results,the damage evolution and damage status of reinforced concrete piers,prestressed piers,and prestressed assembled piers under pseudo-static forces were compared.According to the damage characteristics during the damage development process of specimens,four performance levels of piers were defined: basically intact,slightly damaged,damaged in the middle,and severely damaged.The results show that under the same displacement amplitude,the damage of UBPC-1 is more serious than that of RC.The addition of prestress can reduce the width of cracks in integral piers,but at the same time,the number of cracks and the concrete spalling area of column foot Increase;In the case of prefabricated assembly piers that do not suffer shear failure,the crack width is small,the number of crack is small,column foot concrete spalling area is small and the damage situation is smaller than the integral pier.(3)Six types of concrete structures damage model were used to evaluate the damage of pier specimens,and the rationality and accuracy of each damage model were analyzed.The results show that the stiffness degradation damage model and the energy law damage model do not reflect the damage difference of each pier specimen.The Park-Ang damage model and its three improved models have good evaluation effect.But compared with others,the damage evaluation effect of the Park-Ang damage model improved by Wang Dongsheng on the integral pier and the precast segmental pier specimens is in line with the actual situation,more accurate,and less discrete.(4)Based on the numerical simulation of OpenSees,the damage evaluation of pier specimens was carried out and the sensitivity analysis of pier specimens' damage performance was performed using orthogonal test design.The results show that the Park-Ang damage model improved by Wang Dongsheng has the smallest deviation from the calculated results and the experimental results.The volume distribution ratio of the plastic hinge area(first section)is the main factor affecting the damage performance of the pier,and it increases with the increase of the volume distribution ratio.(5)Based on the finite element model of material damage and the damage performance grade of piers,the structural damage was quantitatively described from the material strain limit,and damage evaluation of the pier specimen was performed using the damage assessment model based on material damage and stiffness degradation.This model can accurately and effectively evaluate the damage of integral piers and prefabricated piers.