| The well tower is one of the most important industrial building structures in mine ground engineering,which is the key of connecting the upper and lower channels of the mine.A prefabricated concrete filled steel tube(CFST)well tower structure system is proposed aiming at practical engineering problems.The system is composed of prefabricated CFST shear walls,steel tube concrete columns,steel beam and laminated floor slab.It has the advantages of good seismic performance,short time of occupying well head.A large number of horizontal and vertical joints are existed in prefabricated structure.The quality of joint connection is the key of popularizing this sturcture.The method of pipe-to-sleeve connection is proposed aiming at the connection problem of CFSTs.The connection bond and slip relation curves were obtained through the tests of 54 pipe-to-sleeve connection.The influence of grout material strength and joint length on the connection bearing capacity was discussed.And the distribution of bond stress on the contact surface was analyzed.The results show that the bond stress distribution is not uniform under axial tension and compression load.The stress of each shear key is not uniform,and the grout material at the shear key reaches ultimate compressive strength one by one as the constraint effect of the sleeve.The plastic strength of the grout material is enhanced and the internal force is redistributed.When the ultimate load is reached,all the grout materials at the shear key reach the ultimate strength.The failure pattern simulation test of 48 steel pipe sleeve grouting connections were carried out.The failure process and failure mode of pipe-to-sleeve connection were analyzed.The effects of grout material thickness,shear key number and circumferential restraint stress were studied.The results show that the inclined crack distribution is not uniform and the crack position is random for the sleeve grout joint without shear key.The crack first appears at the position of the shear resistance key at the bottom of the steel tube with shear key connection.The angle between the crack and the horizontal direction is about 30°,then there are oblique cracks at the position of the middle and upper shear keys of the steel pipe,respectively.A calculation model of ultimate bearing capacity of pipe-to-sleeve connection was established through the analyse of connection stress.The ultimate tensile strain of grout material reached its limit state along the inner circumferential tension strain of the sleeve,and the ultimate tensile strain was taken as the limit state through the sleeve circumferential strain.The deformation coordination relationship between the circumferential strain of steel pipe and the circumferential strain of grout material.The integral static equilibrium of grout material and the three-direction constitutive relation of grout material were derived to calculate the ultimate bearing capacity.Five prefabricated CFST shear walls,one cast-in-situ concrete filled steel tube shear wall and one cast-in-situ reinforced concrete shear wall specimen were designed.The failure mode and hysteretic performance of the shear walls were analyzed through reciprocating load tests.The influence of axial compression ratio and loading rate on the seismic behavior of CFST shear walls is discussed.The results show that the seismic behavior of precast concrete-filled steel tubular shear wall is not lower than that of castin-situ concrete filled steel tube shear wall and is higher than that of cast-in-place reinforced concrete shear wall. |
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