Study On Crack Control Of Super-long Concrete Frame Structures Considering The Temperature And Shrinkage Effects

Super-long concrete frame structure is a special type of structure for the largepublic buildings, commercial centers and industrial buildings. Tensile stress generatedin the super-long concrete frame structure under the thermal action and shrinkage ofconcrete is easy to cause cracking of the structure, thereby becoming a content that mustbe considered in the design, and crack control measures need to be taken in the projects.Currently, a unified and comprehensive computational design method of the super-longconcrete frame structure has not yet been formed. A lot of urgent problems, such as theselection of parameters to calculate, the choice of analysis model, difference of themodel and the interface of sturcture design between the thermal action and commnloads, still exist in the design of super-long concrete frame structure.Firstly, the characteristics and various parameters of temperature and shrinkgewere ananyzed in this paper. Secondly, an applicable analysis calculation model hasbeen elected by comparison between the SAP2000frame-shell element model andANSYS solid element, and also characterastics of the thermal force and deformation thesingle-layer long concrete frame structure and multi-layer super-long concrete framestructure were summed up. Then, based on the current crack control measures, asolution for the super-long concrete frame structure within200meters was proposed toachieve the goal of once pouring of the post poured strips and two batches of pretressing.Finally, the crack control solution proposed was used in the example model, and itsmechanical characteristics were analyzed at all stages of the situation, andreinforcement and width of crack of some elements of the super-long concrete framestructure have been calculated. According to the preliminary test and analysis results,some conclusions and recommendations are as the follows:①Models established with frame-shell elements in SAP2000can simulate thedeformation and forces of the super-long structure under thermal action accurately,but acorrection factor of1.25was recommended.②Temperature stress of floor should be represented by the local temperature stressat tops of the columns and the average temperature stress, which is a morecomprehensive and reasonable description. When taking crack control measures, thesetwo aspects of stress should be considered at the same time. Temperature deformationand internal force in the multi-layer super-long structure were mainly distributed in the lower floors. If other conditions were the same, the thermal stress in the single-layersuper-long frame structure was smaller than the stress in first layer of the foursuper-long concrete frame structure slightly. The single-layer super-long structurereflected the main effects of the multi-layer suepr-long structure under the influence oftemperature. Multi-layer super-long concrete frame structure can be simplified to a oneor two layer super-long concrete frame structure.③Setting post poured strips and batches of pretressing in the super-long concreteframe structures were effective measures to control cracks. Situations of forces ofsuper-long concrete frame structures in the various stages of the construction and usewere different, phased simulation was very important and necessary.④A solution, to achieve the goal of once pouring of the post poured strips and twobatches of pretressing, for the symmetrical rectangular super-long concrete framestructure was proposed. Analysis results of structure models used this solution, andreinforcement and width of cracks of some compponents of a modified structure modelinitially proved that this solution proposed is feasible for the symmetrical rectangularsuper-long concrete frame structures within200meters long.