Finite Element Research On The Mechanical Properties Of Bolting Connection In Sinking Precast RC Floor

The assembly floor system has the characteristics of standardized design,industrial production and assembly construction,which is in line with the future development direction of construction industry.The assembly floor system can be divided into untopped diaphragm and topped diaphragm.The untopped diaphragm is assembled from precast slab.There is joint between slab and slab of untopped diaphragm.The joint result in the in-plane stiffness discontinuity and low integrity of the floor.Therefore,in order to ensure the integrity of the untopped diaphragm,? Technical standard for assembled buildings with concrete structure ?(GB/T 51232-2016)stipulate: It is necessary to take effective measures to ensure the reliable connection between slab and slab.The sinking precast RC floor is A new type of untopped diaphragm.In order to solve the problem of the in-plane stiffness discontinuity,the connection between slab and slab are connected by the bolting connection.In addition,the floor can avoid field weld and improve the assembly efficiency.At present,there is no related research on the bolting connection.Bolting connection applied between slab and slab is taken as the study subject.The parameters studied include the diameter and strength of anchor bolt,the spacing and edge distance of anchor bolt,the thickness and anchorage length of steel plate,the width of slab joint,the depth of connection groove,the friction coefficient between steel plate and concrete.ABAQUS finite element software is used for numerical simulation analysis.The effects of detailed formations of the bolting connection on the strength and stiffness of the connection are studied,through numerical simulation analysis of it under in-plan shear force or tension force.The analysis results show that:(1)The increase of the diameter and strength of anchor bolt,the increase of the thickness of steel plate,and the increase of the friction coefficient between steel plate and concrete,all these increases can improve the shear strength,tensile strength and stiffness of the bolting connection.(2)The increase of anchorage length of steel plate has little effect on shear strength,tensile strength and stiffness of the bolting connection,but it is beneficial to increase the cracking load of the slab.The anchorage length of steel plate should not be less than 12 times the thickness of steel plate.(3)The depth of connection groove has little effect on shear strength,tensile strength and stiffness of the bolting connection,but it has great influence on the cracking load of the slab.When the depth of connection groove is 0.5 times the thickness of the slab,the cracking load of both sides of the slab can be guaranteed to get large values.(4)As the spacing of anchor bolt increases,shear strength,tensile strength and stiffness of the bolting connection first increase and then decrease.It is the maximum value when the spacing of anchor bolt is 3 times the diameter of anchor bolt.The change of edge distance of anchor bolt affects the yield load of the anchor bolt and the steel plate.When the edge distance of anchor bolt is 2~3 times of the diameter of anchor bolt,the yield load of anchor bolt and steel plate is higher.(5)The width of slab joint has little effect on the tensile properties of the bolting connection,but it can effect the shear strength and stiffness of the bolting connection.Under the action of in-plane shear force,the shear strength and stiffness of the bolting connection decreases gradually with the increase of the width of slab joint.The width of slab joint should not exceed 20 mm.