Study On Spatial And Temporal Characteristics Of Multi-storey Formwork Supports System And Load Transfer Model During Construction

In the process of construction,the formwork supports system erection failure or premature removal are likely to cause the support system collapse,floor cracking and other accidents.The reason is that the cast-in-place concrete structure and the multi-storey formwork supports system form a time-varying structure,which is complicated and variable.People are still lack of understanding of the temporal and spatial characteristics of the system.In the specification,the stability of the support system is calculated only by single shores of one slab.At the same time,the formwork project as a construction process investment accounted for the main construction costs of nearly one-third of the investment project.How to improve the efficiency of formwork support system based on the safety of construction.This is also the construction party urgently needed to solve the problem.Therefore,the study on the temporal and spatial characteristics of the multistorey formwork supports system and the model of load transfer are great significance to ensure the structural safety during construction.In this paper,the implified model(G&K model and D&C model)are introduced into the study on force of the support under the beam.Then,conbined with a project of Chongqing Raffles City,to get a lot of oringal base data.Coupled with the data collation,finite element analysis and D&C model to study time-varying characteristics of supports of different regional in framed-tube structure during construction.The main research results are as follows:(1)According to the laboratory test data,using the G&K improved model and the D&C model to calculate the supports load,the model will overestimate the load transferred by shores and underestimate the load of the beam.But the D&C model calculation error is smaller,the percentage error is less than 20%;After the removal of the bottom support,the calculated results of the model are in good agreement with the experimental values,and the percentage of errors is basically within 15%.The D&C model is proposed to study the load transfer law of the supports under the beam.(2)Experimental study on multi-storey formwork support system during construction of frame-tube structure.Research results: 1)From the pouring stage to the end of the test,the vertical support force values generally appear three peaks and two lower concave segments.2)pouring stage,this storey of support(near the shear wall)to bear the load of the total load of 73.9%~84.5%,this storey of support(floor center)to bear the load accounted for the total load of the 85.3%~90.8%,the support(near the outer frame beam)assumes the load of the total load of the 78.6%~86.7%;Lower support(near the shear wall)assumes the load of the total load of 9.2%~15.6%,the lower support(floor center)bear the load accounted for the total load of 24.4% ~31.2%,the lower support(near the outer frame beam)assumes the load of the total load of 18.9%~21.7%.3)The vertical support is constrained by horizontal poles.(3)Through the research of finite element simulation,the research results: 1)The space-time characteristic of multilayer formwork support system in frame-tube structure is feasible by finite element analysis.2)With the increase of concrete age,the load transfer path of the whole structure is changed.From the pouring stage,most of the load passes through the support vertical shores to the lower structure and gradually forms the load transfer mode of traditional mechanics.3)The axial force changes of vertical shores and the corresponding load transfer law in different construction stages of construction period of 7 days.4)The load transfer in the removel stage is more affected by the structural arrangement of each storey than the casting stage(including vertical structure).(4)The D&C model is used to calculate the pouring and removel phases of the measured engineering,and the results show that: 1)The D&C model is used to calculate the load of the vertical support under the middle of slabs and beams in the frame-tube structure.It is feasible and has certain accuracy.2)The D&C model is good for the load transfer law of the vertical support beneath the slab and the coincidence of the numerical simulation value is better than the vertical supports beneath the beam.3)Two kinds of D&C improved model are proposed.With the improved simplified model,the deviation ratio between the calculated values and the results of finite element simulation of axial force of the support beneath the beam is reduced by 29%~33%.