| The prefabricated building structure has the characteristics of rapid construction,energy saving and emission reduction,green and low carbon,and stable component quality,which is in line with the strategic goal of sustainable development in China.It is also the key to promote the industrialization of construction and realize the modernization of the construction industry.Several earthquake disaster analysis reports represented by the Wenchuan earthquake pointed out that the core area of the frame joint and the joint connection section are the weak links of the prefabricated building structure,and it is easy to present the ’ strong beam weak column ’ layer yield mechanism contrary to the concept of ’ strong column weak beam ’.At present,most of the existing research on prefabricated joints in China is based on the concept of ’ equivalent cast-in-place ’ proposed in the code,and its failure mode is consistent with that of cast-in-place joints.The plastic hinge area of the beam end is first damaged,and then the damage gradually spreads to the core area of the joint.In addition,many scholars have proposed ’ dry ’ connection technology,but most of them have limited application due to their structure and design reasons.Therefore,in view of the shortcomings of the existing precast connection technology,it is of great significance to propose a new precast reinforced concrete connection node.This paper will focus on this aspect,the main research contents are as follows :(1)In view of the complexity of the connection technology of most prefabricated reinforced concrete joints and the difficulty of mastering the design method,a new type of ’cast-in-place ’ prefabricated joints is proposed.By introducing the concept of ’ damage controllable ’,a new type of ’ damage controllable ’ prefabricated beam-column joints is further designed to improve the repairability of post-earthquake damage of prefabricated buildings.(2)Based on the existing design specifications such as ’ Steel Structure Design Standard’,’ Concrete Structure Design Code ’ and ’ Steel Structure Connection Joint Design Manual ’,a set of design methods and design processes including ’ equivalent cast-in-place ’ beam-column joints,’ damage controllable ’ beam-column joints and ’ equivalent cast-in-place ’column-column joints are proposed.(3)The general modeling method of assembled joints based on ABAQUS finite element software is described in detail,and the seismic performance of new prefabricated concrete connection joints is studied.The stress of steel bar,equivalent plastic strain of concrete,hysteresis curve,skeleton curve,ductility,cumulative energy dissipation-displacement curve and joint failure mode are compared and analyzed.The analysis results show that the peak stress of the steel bar of the cast-in-place beam-column joint is equal to that of the ’ equivalent cast-in-place ’ beam-column joint.The maximum equivalent plastic strain of the concrete in the plastic hinge area of the beam end is 17 %different,the hysteresis curve is highly coincident,the bearing capacity is 3 % different,the average ductility coefficient is 27.3 % different,and the cumulative energy consumption is2 % different.Compared with cast-in-place beam-column joints,the ’ damage controllable ’beam-column joints can reduce the peak stress of steel bars by about 43 %,the equivalent plastic strain of concrete by about 99 %,and the cumulative energy consumption by about26.8 %.The peak stress of the steel bar of the ’ equivalent cast-in-place ’ column-column joint is equal to that of the cast-in-place column joint,the peak value of the equivalent plastic strain of the concrete is 11 %,the yield failure area of the joint is close,the hysteresis curve is highly coincident,the bearing capacity is 5 % different,the average ductility coefficient is17.93 % different,and the cumulative energy consumption is 2.1 % different.(4)The parameter analysis of damage controllable assembled beam-column joints is carried out,including the length of energy dissipation section,the weakening coefficient of yield section,the position of connection section and the axial compression ratio,and the variation law of seismic performance index of joints is revealed.The analysis results show that when the length of the energy dissipation section is 60 mm,the cumulative energy consumption of the node is 44.82 %,28.77 % and 42.81 % higher than that of 30 mm,90 mm and 120 mm respectively.The larger the yield section weakening coefficient(less than 1),the worse the ductility of the joint.When the weakening coefficient of the yield section is0.618,the equivalent plastic strain of the joint concrete is reduced by about 99 %,and the energy dissipation capacity is the strongest.The cumulative energy consumption of the joint is 90.05 % higher than 0.463,5.30 % higher than 0.772,and 20.78 % higher than 1.236.The farther the joint connection section is from the column,the higher the bearing capacity of the joint.The bearing capacity of 110 mm,150 mm and 200 mm away from the column is 5.17 %,8.23 % and 12.75 % higher than that of 0 mm away from the column,and the cumulative energy consumption is increased by 1.93 %,3.36 % and 5.02 % respectively.The hysteretic curves,skeleton curves and cumulative energy dissipation curves of ’ damage controllable ’beam-column joints with different axial compression ratios are basically coincident,and the difference is very small.The difference of ductility coefficient fluctuates within 3.31 %,which is within a reasonable error range.The ductility of the joints can be regarded as equivalent.(5)The seismic performance of prefabricated frame structure is studied based on ’damage controllable ’ beam-column joints and ’ equivalent cast-in-place ’ column-column joints.Through the numerical simulation test of prefabricated frame,the seismic performance and mechanical performance of the two are compared.The test results show that compared with the cast-in-place frame,the stress of the beam end of the prefabricated frame is reduced by 52 %,the equivalent plastic strain of the beam end concrete is reduced by 100 %,the bearing capacity difference is 9.05 %,the ductility is increased by 60.54 %,and the cumulative energy consumption is increased by 18.86 %.Through comparative analysis,there is no damage to the concrete in the plastic hinge area at the beam end of the prefabricated frame and the core area of the joint.The early failure of the connection section at the beam end of the prefabricated frame realizes the function of ’ damage control ’.The concrete and internal steel bars in the core area of the joint do not fully exert their mechanical properties,resulting in the bearing capacity of the prefabricated frame lower than that of the cast-in-place frame,but the overall energy dissipation capacity and ductility of the prefabricated frame are better than those of the cast-in-place frame. |
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