| The modular prefabrication technology is applied in the floor system to meet the requirements of factory-made component to the greatest extent,which greatly promotes the industrial development of buildings.This paper proposes a fabricated steel trussconcrete composite floor system with modular prefabricated combination units,which is suitable for multi-rise high-density frame-column steel structure.However,the prefabricated floor system must be transported by vehicles from the factory to the construction site for assembly,which sets limitation on the size of floor.Therefore,the prefabricated floor with a slightly larger span is generally assembled by several floor units.The joints will be produced during the assembly process,which makes the prefabricated floor significantly different from the integral cast-in-place floor in terms of in-plane mechanical properties and rigid properties.The rigid performance and integrity of the floor system in the plane(horizontal direction)is of great significance to the analysis of the structure.The in-plane rigid floor greatly reduces degree of freedom of structural analysis because it only produces rigid placement and does not produce any relative deformation in the plane,thus simplifying the calculation analysis.However,the semi-rigid or flexible floor must consider the deformation in the plane of the floor itself during the analysis of the overall structure,which complicates the overall analysis of the structure.However,how to assess the rigidity of the floor system in the plane,there is no clear regulation based on China’s current standards,and the experimental research is the most direct and effective method for its analysis and evaluation.The experimental research and finite element analysis have been carried out on the joint-filled prefabricated steel truss-concrete composite floor system.The deformation,integrity and rigidity of the floor system of this type and the related factors affecting the in-plane rigidity of the floor system are discussed in detail,which provides a reference for the engineering application of this type of prefabricated composite floor system.Our work mainly includes:(1)The high-rise beam steel structure comprised of the prefabricated steel trussconcrete composite floor system proposed in this paper,the typical practical project(Xiao Tian Cheng)was introduced,and the structural composition and assembly method of this type of composite floor system were analyzed.(2)Considering the joint-filled condition of composite floor,filling materials and loading directions,etc.,reduced-scale model specimens of two-layer frame structure consisting of four different types(6 in total)of steel truss-concrete composite floors were designed and manufactured.Type I: prefabricated floor with structural glue filling joints(LGGJ-1,LGGJ-2),Type II: prefabricated floor with mortar filling(LGSJ-1),Type III: integral cast-in-place floor(LGXJ-1),Type IV: unfilled fully prefabricated floor(LGZP-1,LGZP-2).The unidirectional loading test was carried out on the plane of the second floor of the six test pieces.The second floor of each test model was used as the analysis object.The failure characteristics,equivalent shear stiffness,overall deformation performance and the column end shear of the adjacent anti-side frame were analyzed.The effects of strengthening measures such as filling the joints in the unfilled fully prefabricated floor and setting the concrete post-cast stripe between floor and frame beam on the mechanical performance of the floor were discussed.The experimental research shows that the cracking load,the in-plane equivalent shear stiffness and the integrity of the joint-filled floor were greatly improved compared with the unfilled floor.The elastic modulus of the filling material is a key factor affecting the in-plane mechanical properties and integrity of the floor.(3)The finite element software Midas Gen was utilized to analyze the tested composite floor system and verify its effectiveness.The finite element supplementary analysis was carried out on the untested specimens(LGSJ-2 and LGXJ-2)bearing forces along the vertical assembly direction,and the floor system specimens(GXLG-1 and GXLG-2)based on the rigidity assumption.In order to further investigate the influencing degree of the filling joints,the setting post-cast strip,the thickNess of the concrete slab at the upper part of the floor and the elastic modulus of the filling material on the in-plane mechanical properties and integrity of the floor,the parameter analysis was carried out on the prototype of the prefabricated composite floor.The results show that the two reinforcement measures including filling joints and setting the post-cast strip can improve the in-plane rigidity of the floor,and obtain the elastic modulus of the optimal filling material of the type of joint-filled prefabricated steel truss-concrete composite floor.(4)The in-plane stiffness performance of the prefabricated composite floor with dense frame columns is evaluated via the existing displacement ratio method,the overall deformation deviation method and the load-bearing performance deviation method.The results show that the displacement ratio method and the load-bearing performance deviation method are not suitable for the rigidity evaluation of this type of floor.The overall deformation deviation method is applicable to the rigidity evaluation of this type of floor,but its calculation is more complicated and does not reflect the influence of the elastic modulus on the rigidity of the floor.(5)A modified displacement ratio method for evaluating the stiffness performance of a composite floor with a dense column frame is proposed.The evaluation results are reasonable and realistic.The joint-filled steel truss-concrete composite floors studied in this paper all belong to the rigid floor,and the fully prefabricated steel truss-concrete composite floor with seams are all elastic floors.(6)The theoretical analysis method of the in-plane rigid performance of the jointfilled prefabricated floor is discussed,and the theoretical calculation formula of the modified displacement ratio method is obtained.The calculation result agrees well with the finite element analysis.This formula can be used to evaluate the stiffness performance of the joint-filled prefabricated floor.The recommended thickNess of the concrete panel that guarantees the rigidity of this type of floor system is given. |
