Safety Research On High Concrete Frame-Core Tube Structure During Construction

At least two-thirds of the project collapses occurred during the construction stage according to the statistics data. To reduce the probability of the accidents during the construction of the concrete structures of highrise buildings, a safety control system for it must be established on the basis of the research for the performance of the concrete structure of highrise buildings during the construction.Concrete frame-corewall structure, as an important structure form of the highrise buildings and super highrise buildings, is widely used in our country in recent years. However, security incidents continuing to occur during the construction stage are still challenging to the country’s engineering sector and academia.Since the material properties of the concrete structure during the construction are unstable, the construction loads are various and complex and the stress is great and varied, the structure properties of the concrete are time-varying. Therefore, study on the performance of concrete structures during the construction becomes more complex and difficult.Based on the time-varying characteristics of the concrete structure during the construction stage, we conducted experimental studies and theoretical studies on the basic mechanical properties of the concrete structure of the highrise building, the mechanism of interaction between the concrete structure and the temporary template support system, the load measurement of the vertical members of the concrete frame-corewall structure of the highrise building as well as the reliability of the concrete structure. Main contents of this paper include:Based on the concrete strength characteristics of highrise building, we carried out experimental studies on the time-varying characteristics of the compressive strength and elastic modulus of the concrete which are changing with standard curing age. Through the experiments, a function with the age growth of the concrete compressive strength and elastic modulus are indicated. In addition, parameters of the fitted equations are determined by using the nonlinear least-squares algorithm.According to the properties of the HPC material widely used in the structure of the highrise building, experimental studies on the time-varying characteristics of the compressive strength and elastic modulus of the concrete of different grades with different water-cement ratios, different fly ash contents and different admixture contents were performed. Apparently, these characteristics change with the curing period. Moreover, the influencing rule of the water-cement ratio, admixture content and fly ash content on time-varying characteristics of HPC was obtained.Taking Chongqing China New City Project as a background and based on the actual construction condition of different supporting layers on the site, the simulation calculation model created with the finite element software was used to analyze the structural properties of the time-varying structure. The simulation result indicates that the form removal stage is a critical stage of the safety control for the concrete structure during the construction phase.Two-store single-span reinforced concrete frame test models were produced in the laboratory. We put loads on the frame model of different ages and analyzed the impact of the construction period and the concrete age on the interaction between the concrete structure and the temporary template supporting system. The test indicates that when the applied load is less than the cracking load, the temporary template supporting system constituted by the concrete frame structure at the early age and the template supporting system can have a common effect.Taking Zhongshan International Financial Centre project as a background, reasonable testing measures were taken to monitor loads of the vertical members of the concrete frame-corewall structure in the highrise building on the site and determine the development law of loads.Taking the two-store frame model test and the typical structure of Chongqing China New City Project as the background and based on the structure reliability analysis of the dynamic model, the structure characteristics of the concrete during the construction and the probabilistic model of the resisting force and the load effect of the structural members are combined to analyze the reliability of the concrete structure during the construction using Monte Carlo stochastic algorithm. The concrete cracking and punching shear failure are regarded as the failure mode in the analysis mentioned above. Additionally, suggestions on the construction of the concrete structure during the construction are made according to calculation results.