Study On Seismic Performance Of Prefabricated Shear Wall With Rabbet-unbonded Horizontal Connection

Prefabricated shear wall structure is an important structure form in the architecture industrialization process of our country,reliability of whose connection is the key to ensure the seismic performance.To improve the seismic performance of prefabricated shear wall,the author puts forward a new prefabricated shear wall connetion form:rabbet-unbonded horizontal connection,rabbets are used to improve the connection shear capacity,unbonded ordinary steels are used to improve the ductility and energy dissipation ability of shear wall.The new connection has a relatively clear damage mechanism,which can improve the steel stress concentration at connection.What’s more,the new connection’s construction is convenient and cost is low.Therefore,by the new connection form,we can obtain higher seismic performance through a relatively simpler operation and lower cost.In view of this,the author studies the seismic performance of prefabricated shear wall with rabbet-unbonded horizontal connection through experiment study,numerical simulation and theoretical analysis and finally evaluates the seismic performance.The main research contents and achievements are as follows:1.The quasi static tests of prefabricated shear walls with rabbet-unbonded horizontal connection are carried out with the axial compression ratio and unbonded degree as parameters.The results show that the ultimate failure pattern is that the edge steels yield,and then the concrete at the bottom of wall is crushed.There is no stiding at the connection in the loading process because of the rabbets,which states that the connection is reliable.Unbonded steels can obviously improve ductility and energy dissipation capacity of precast shear wall and have less effect on the bearing capacity of wall.2.The seismic performance of shear wall with rabbet-unbonded connection,shear wall with flat interface connection and cast-in-place shear wall are compared.The results show that the cracking load,yield load and peak load of three walls are almost equivalent.The rabbets make the connection no stiding.The final failure pattern of three walls is edge steels yield,and then the concrete at the bottom of wall is crushed.Compared with the shear wall with flat interface connection and cast-in-place shear wall,hysteresis loop of shear wall with rabbet-unbonded connection is relatively full,whose ductility increases by 25%and energy dissipation capacity increases by 57%.3.The author establishes shear wall with rabbet-unbonded connection model using the finite element software ABAQUS and puts forward the simulation method of connection.The simulation result is validated by test results.Then,the wall failure pattern,concrete compression damage,concrete cracks distribution and steel stress distribution are analyzed.Finally,the effects of unbonded length,unbonded degree and axial compression ratio on seismic performance of precast shear wall with rabbet-unbonded connection are analyzed.4.According to the shear friction theory of concrete interface,considering the grouting material,axial compression ratio and the shear effect of steel,the author puts forward the shear bearing capacity calculation formula of rabbet-unbonded horizontal connection,which is validated by numerical simulation results.After that,the effect of rabbet number on different shear bearing capacity parts of rabbet-unbonded horizontal connection is analyzed.The results show that that the shear bearing capacity of oblique compression bar increases with the increase of rabbet number.However,the shear friction of the sliding surface and the shear bearing capacity of the connecting steels decrease with the increase of rabbet number.Finally,the shear bearing capacities between shear wall with rabbet-unbonded connection and shear wall with flat interface connection are compared.The results show that shear bearing capacity of shear wall with rabbet-unbonded connection increases by 22%.Finally,the design suggestions at horizontal connection are put forward.5.The "strain lag"of unbonded steel causes the changes of tensile steel strain and the relative boundary compressive height.Introduce the changes into the axial force-moment capacity calculation formula in specification.And the theoretical value of flexural bearing capacity can be obtained,which is compared with the test value,and the result shows that difference of both values is very small,which states that the formula and assumptions are feasible.Then,the effect of unbonded length on axial force-moment capacity of shear wall with rabbet-unbonded connection is analyzed,which is compared with that of cast-in-place shear wall.The results show that the bearing capacity of shear wall with rabbet-unbonded connection and cast-in-place shear wall is roughly equal.What’s more,the effect of unbonded degree on axial force-moment capacity of shear wall with rabbet-unbonded connection is analyzed.The results show that for large eccentric compression,the axial force-moment capacities in different unbonded degrees are slightly different.However,for small eccentric compression,the axial force-moment capacity increases with the decrease of unbonded degree.6.Considering the effect of unbonded steel and edge constraint component on shear wall ductility,the calculation formula of curvature ductility is derived.To calculate the displacement ductility,assumed that the total displacement is approximatly made up of two parts:(1)the displacement which is produced by the wall itself when the connecting steels are bonded;(2)the displacement which is produced by free elongation of unbonded steel when the connecting steels are unbonded.The yield displacement and ultimate displacement are calculated and compared with the test values.Finally,the contribution of unbonded steel to yield displacement and ultimate displacement is analyzed.The results show that the unbonded steel’s contribution to ultimate displacement is greater than that to yield displacement.7.The seismic performance of shear wall with rabbet-unbonded connection is evaluated.The results show that the structure achieves seismic performance of cast-in-place shear wall structure and achieves "small earthquake not bad,moderate earthquake repairable,great earthquake not collapse" seismic fortification goal.The floor lateral,interlayer displacement angle,the compression damage distribution at the bottom wall and structural stiffness degradation in performance point are analyzed.Then,the effects of unbonded length and degree on seismic performance of shear wall with rabbet-unbonded connection are analyzed.Finally,the design suggestions are put forward.