| The U-shaped steel-concrete composite hollow waffle(CHW)floor is an innovative long-span floor.The floor is made up of reinforced concrete(RC)slab and composite hollow beams.The U-shaped steel plates are placed at the side and bottom of the lower beams to enhance the tensile strength and delay the crack development of the concrete.Hence,the floor span is further enlarged.Additionally,the U-shaped steel plates act as formwork during construction.The CHW floors have the characteristics of light-weight,large-rigidity,high story height,convenient for the pipeline to pass through and good seismic performance,which have been widely used in the construction of the long-span floor.To construct a multi-story and long-span assembled monolithic building is an effective way to realize the industrialization of the building.The current regulations can not guide the separation and construction of the assembled monolithic U-shaped CHW floor;it’s still unknown whether the mechanical characteristics and deformation mechanism of the assembled monolithic CHW floor are consistent with the cast-in-place floor.The rising span induces a low fundamental frequency of the floor,yielding large vibrations under excitation.Thus,it is necessary to explore the dynamic behavior of CHW floors due to human activity.The paper research the mechanical characteristics and construction technology of the fabricated CHW floors base on the static and dynamic test and the construction of first domestic multi-story and long-span assembled CHW floor,which provides the promotion and application of the new fabricated U-shaped steel plate concrete composite hollow floor and the compilation of the specifications technical support.The main conclusions are as follows:(1)In this paper,the pseudo sandwich plate method considering shear deformation is used to analyze the continuity of CHW floor,the equivalent stiffness of the CHW floor is given,the basic differential equation of continuity is established,the internal force and displacement of the CHW floor are solved,the basic assumption and calculation process of the simplified calculation method of CHW floor is introduced;Through the comparative analysis of the calculation example by the quasi sandwich plate method,practical algorithm and finite element method,the accuracy of various algorithms used in the static calculation of U-shaped steel plate concrete composite hollow floor are evaluated.(2)To verify the accuracy of the finite element method in the static calculation of the floor,it is necessary to carry out the field elastic static load test of the two-layer assembled hollow composite floor,track the deformation characteristics of the floor under the vertical load,monitor the stress and strain distribution of the key component composite rib beam,shear key and the surface floor.Under the design load,the floor reinforcement area from the finite element method and the practical algorithm are compared,the problems of the practical algorithm are pointed out,and the modified opinions of the simplified calculation of the assembled CHW floor are given.(3)Based on the theory of anisotropic thin plate and the principle of energy conservation,the calculation formula of the natural frequencies of the CHW floor is derived.The damping ratioes,mode shapes and frequencies of the floor are obtained by the ambient vibration tests.The test results verify the accuracy of the calculation formula of the natural frequencies of the floor.It shows that the experimental CHW floor is a long-span floor with a low frequency and damping ratio.The vibration response of the floor under transient human-induced excitation(heel-drop,jumping)and intermittent human-induced excitation(walking and running)are studied;Meanwhile,the vibration performance of experimental CHW floor is evaluated by the frequency threshold and amplitude threshold according to the current codes.(4)The finite element model of the experimental CHW floor is established,the modal analysis and vibration response analysis under human excitation are conducted for the composite floor,and the feasibility and accuracy of the finite element analysis are verified by on-site tests.The influence of floor span,span-tp-height ratio,beam spacing,opening ratio,additional load,damping ratio,slab thickness and thickness of U-shaped steel plates on floor vibration are studied.The vibration performance of the CHW floors is evaluated,and the suggestions for floor vibration control are given.(5)The assembly integral construction technology is used to construct the multi-layer and long-span CHW floor in China for the first time.At the design level,according to the stress characteristics of the CHW floor,the key steps such as fabrication,transportation,installation and transportation are fully considered to split the prefabricated components;at the construction level,the selection of key technologies such as support system,installation method and joint connection is discussed in the construction process of the assembly of the integral CHW floor,which provides a reference for the similar assembly large-span floors. |
