Study On Cylindrical Core Formwork Hollow Floor Based On Multi-scale Anologue Slab Method

The cast-in-place concrete hollow floor structure is a new structural system using cast-in-place concrete,which formed after the ordinary beam floor and beamless floor.It has the advantages of low cost,light weight,good seismic performance,remarkable energy-saving effect,convenient construction and so on.The box hollow beamless floor is mainly used in the formwork refers to the hollow part of the floor in the engineering application and research,and there is relatively little research on other internal formwork forms.Thus,the hollow floor with cylindrical internal formwork is studied and analyzed in this paper.At present,the research methods of internal force and deformation of hollow floor at home and abroad mainly focus on scale experment and numerical simulation,while the research on the traditional analogue slab method is relatively few.And it is mainly focused on coarse-scale research,and the practicability of fine-scale quasi slab method has not been systematically analyzed.In this paper,the coarse-scale equivalent elastic modulus of thin-walled box hollow floor is calculated by using the self-developed multi-scale analysis software(AHMP),which is completely different from the traditional analogue slab method.The influence of the small-scale characteristics of hollow floor on the equivalent elastic quantity of hollow floor is analyzed.The modulus calculated by multi-scale method is used in the calculation of quasi plate method,and the concept of multi-scale analog slab method(MASM)is formed;This paper also uses the direct modeling method to calculate the internal force and deformation of the hollow floor,and compares and analyzes the calculaton resuts with the MASM method to verify the applicability and accuracy of the MASM method in calculating the deflection and deformation of the hollow floor.The main work and conclusions are as follows:(1)The unit cell finite element models of hollow floor with cylindrical core formwork without chamfer and with chamfer radius of 25 mm and 50 mm under different void ratios are established respectively,and their elastic constants are solved by using AHM program to study the effects of void ratio,chamfer and chamfer radius on the unit cell elastic constants.Based on the elastic constants of single cells with a chamfer radius of 50 mm,the young’s modulus is further calculated and compared with the results of the traditional pseudo plate method.(2)The direct modeling method(DNS)and multi-scale analogue slab method(MASM)are used to analyze the structural mechanics of hollow floors with different hollow ratios under vertical uniformly distributed load.The calculation errors of the two results are within the allowable range,which proves the feasibility of using the multi-scale pseudo plate method to calculate the cylindrical core formwork hollow floor.The model is established by using the pseudo plate method considering the stiffness of the side beam and the pseudo plate method without considering the stiffness of the side beam,and the calculation results are compared and analyzed to explore the influence of the stiffness of the side beam on the internal force and deformation of the hollow floor with cylindrical core formwork.The direct modeling method(DNS)and multi-scale analogue slab method(MASM)are used to analyze the structural mechanics of hollow floors with cylindrical core formwork with different void ratios under vertical uniformly distributed load.The calculation errors of the two results are within the allowable range.It is proved that the multi-scale pseudo plate method is feasible and effective to calculate the mechanical behavior of hollow floor structure with cylindrical core formwork.(3)The finite element models of hollow floor with cylindrical core formwork without chamfer and with chamfer radius of 50 mm are established respectively,and the calculated stress and deformation results are compared.The results show that when other conditions are certain,the chamfer has a certain influence on the calculation results of macro stress-strain field,local deflection and stress concentration.