Study On Seismic Performance Of Precast Pier With UHPC/ECC Post Pouring Connection

With the rapid development of China ’s economy,prefabricated assembly technology has gradually become an important method of bridge construction,but there are still some problems in the traditional prefabricated pier connection.High construction accuracy requirements,difficult inspection of grouting quality,and complex structural measures lead to problems such as reduced construction efficiency and difficulty in ensuring construction quality.Ultra-high performance concrete(UHPC)and engineered cementitious composite(ECC)have the characteristics of high strength,high toughness,strain hardening,and high bond strength with steel bars.Through reasonable design,the connection performance between UHPC/ECC and steel bars can be guaranteed.The connection performance between UHPC/ECC and steel bars can be guaranteed by reasonable design.Based on the problems existing in the connection mode of traditional precast assembled piers and the advantages of UHPC/ECC,this thesis proposes a simple connection mode of precast assembled piers based on post-cast UHPC/ECC composites.The finite element simulation analysis of integral cast-in-place piers,grouting sleeve connection piers,UHPC postcast connection piers and ECC post-cast connection piers was carried out by Open Sees finite element software.The main research contents and research results of this thesis are as follows :(1)The research status of precast assembled pier column connection technology at home and abroad is summarized.The material properties of UHPC and ECC and their application in structural members and joint connections are comprehensively summarized.(2)In order to verify the accuracy of the numerical simulation method,combined with the quasi-static test of the existing integral cast-in-place pier column and the grouting sleeve connection pier column,the numerical modeling analysis was carried out using Open Sees software,and the numerical simulation results were compared with the test results.The validity of the model provides a basis for subsequent research.(3)In order to simulate the performance of UHPC/ECC post-pouring connection pier more accurately,the modeling method of post-pouring connection area is improved.It is pointed out that the bond-slip constitutive model of steel bar in postpouring connection area should be simulated by the bond-slip constitutive model of steel bar and concrete under the condition of steel bar overlap,which provides a reference for the modeling of the same type of pier column.(4)In order to compare and analyze the seismic performance of integral cast-inplace pier,grouting sleeve connection pier,UHPC post-pouring connection pier and ECC post-pouring connection pier,the numerical simulation results of four pier columns under the same parameters were compared and analyzed.The indexes such as hysteresis curve,skeleton curve and displacement ductility coefficient are evaluated respectively.The results show that the peak lateral bearing capacity of UHPC post-cast connection pier and ECC post-cast connection pier is slightly higher than that of the whole cast-in-place pier,which is increased by 7.26 % and 5.13 %respectively.The displacement ductility coefficient of UHPC post-cast connection pier and ECC post-cast connection pier is higher than that of the whole cast-in-place pier,which is increased by 104.51 % and 47.95 % respectively.The cumulative dissipated energy of UHPC post-pouring connection pier and ECC post-pouring connection pier is higher than that of overall cast-in-place pier and grouting sleeve connection pier.(5)In order to study the influence of parameters such as shear span ratio,axial compression ratio and post-pouring connection height of UHPC/ECC on the performance of post-pouring connection piers of UHPC/ECC,numerical analysis under different parameter changes was carried out based on Open Sees finite element software.The results show that the shear span ratio is the key factor affecting the bearing capacity,ductility and energy dissipation capacity of the UHPC/ECC postpouring connection pier.For every 0.5 increase in shear span ratio,the peak bearing capacity,displacement ductility coefficient and cumulative energy consumption of UHPC and ECC post-cast connection pier columns decrease by more than 10% on average.The axial compression ratio and post-cast connection height have no significant effect on the seismic performance of the pier.