| A reinforced concrete(RC)frame with masonry infilled walls is a kind of composite structure that uses masonry to fill the RC frame.It has become the most widely used architecture systems because of its simple construction technology and flexible layout.When subjected to an in-plane earthquake load,the masonry can lead to the damage of RC structure,when subjected to out-of-plane earthquake load,the masonry is prone to collapse.Therefore,it is very important to study the influence factors of in-plane and out-of-plane seismic performance of a reinforced concrete frame with masonry infilled wall.In this paper,the mechanical properties of the modified cement mortar are obtained through experiments,a refined model of the reinforced concrete frame with masonry infilled walls has been established by using ABAQUS.The characteristics of the structures with different cement mortar under the action of in-plane low circumferential complex load and out of plane unidirectional load are simulated.The main research contents and achievements are as follows:(1)The 28d strength tests of cement mortar is carried out,including flexural strength,compressive strength,tensile bonding strength and shear strength of masonry along the mortar joint.The influence of nano-SiO2 solution,styrene acrylate polymer(SA)emulsion and polypropylene fiber on mechanical properties of cement mortar is analyzed,and the improvement mechanism is explained.Four kinds of mortar with the best mechanical properties are selected:the flexural strength of PPF5 mortar is 6.51 MPa,improved by 11.6%;the compressive strength of PPF7 mortar is 26.9MPa,improved by 4.64%;the tensile bonding strength of SA1 mortar is 0.32MPa,improved by 95.52%;the masonry shear strength of NS1 mortar is 0.45MPa,improved by 60.28%.(2)The compression-flexure ratio,flexural fracture energy,tensile bonding stiffness and fracture energy of cement mortar,as well as the shear stiffness and fracture energy of masonry along the mortar joint are analyzed qualitatively and quantitatively.Four kinds of mortar with the best mechanical properties are selected:the compression-flexural ratio and flexural fracture energy of PPF7 mortar is 0.262 and 1.32MPa·mm respectively,improved by 21.6%and 7.3%respectively;the tensile bonding stiffness and shear stiffness of masonry along the mortar joint is 0.265MPa and 0.449MPa,improved by 86.1%and 72.4%respectively;the tensile bonding fracture energy of SA1 mortar is 34.6Pa·m,improved by 122.4%;the shear fracture energy of NS1 mortar is 140.6Pa·m,improved by 49%.(3)A refined finite element model is established by using ABAQUS,and the characteristics of the structures with different mortar under in-plane loads are analyzed,the experimental group with the best performance are as follow:the initial stiffness of infilled RC frame with NS1 mortar is 45.52kN/mm,improved by 8.45%,also the stiffness of infilled RC frame decreases the fastest;the ultimate bearing capacity and yield load of infilled RC frame with NS 1 mortar is 190.61 kN and 166.9kN respectively,improved by 9.4%and 11.4%respectively;the yield displacement of infilled RC frame with PPF9 mortar is 6.24mm,improved by 2.9%;the energy dissipation capacity of infilled RC frame with N1 mortar is the best at the early stage,the total energy consumption after the seventh hysteresis loop is 1484J,improved by 24.9%,after 10 cycles of loading,the cumulative energy dissipation of infilled RC frame structure with SA05 mortar is 3717J,improved by 3.3%.(4)The initial stiffness,stiffness degradation,ultimate bearing capacity,yield displacement,yield load and cumulative energy consumption curve of infilled wall RC frame structure under out of plane load are analyzed.The experimental group with the best performance are as follow:the initial stiffness,maximum bearing capacity,yield displacement and energy dissipated of infilled RC frame with NS1 mortar is 28.2kN/mm,69.4kN,2.3mm and 329.5J respectively,improved by 13.3%,5%,6.4%and 10.4%respectively;the yield load of infilled RC frame with SA3 mortar is 7.22kN,improved by 2.4%.(5)The in-plane main failure mode of infilled wall RC frame structure is mortar crushing and masonry shear failure,and the out of plane failure mode is masonry pulling off.In order to improve the seismic performance of infilled wall RC frame structure,it is necessary to select materials similar to nano-SiO2 that can promote cement hydration reaction to modify mortar.The improvement of mortar mechanical properties is important for the early seismic performance of the structure. |
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