Research On Crack Control Of Ultra-Long Concrete Side Wall At Early Age With Induced Joint

With the further acceleration of urbanization,the number of extra-large and extra-long concrete side wall structures is increasing day by day.The frequent occurrence of groundwater leakage caused by the cracking of the side wall in the early stage seriously affects the durability and safety of major engineering structures,and brings many difficulties to the later repair and maintenance.As one of the methods to control cracks from the perspective of structural design,induced joints have been partially applied in subway stations and other structures since the 1990s,which have received certain effects in crack control and waterproof measures,and have rich engineering application value.However,there are not many systematic researches in the field of construction engineering at present.In view of the shortcomings of existing researches,this paper analyzes the stress and strain of the lower side wall of the induced joint through on-site monitoring and finite element analysis,taking the houcun station of xiamen metro line 3 and maluan west station of line 2 as the engineering background.The content of the article mainly includes:(1)On-site monitoring was carried out on the side walls of platform floor of maluan xi station of line 2 and houcun station of line 3 of xiamen metro,and the data of temperature,strain,crack morphology and distribution of the concrete side walls without induced joints and the side walls with induced joints were obtained.The field monitoring found that:after the installation of the induced joint,the temperature field of the side wall did not change significantly,and the parts of the side wall under continuous pressure increased.The induced joint position along the wall length showed strain accumulation due to the weakening of the section.The total number of cracks,the number of harmful cracks and the width of cracks in induced seam side walls were all reduced.(2)Considering the temperature and external constraints,the temperature-stress field of the side wall of the early age ultra-long concrete without induced joints and the temperature-stress field of the side wall of the early age ultra-long concrete without induced joints were established on the condition of the mechanical properties parameters of the early age concrete.According to the theory of temperature stress and the existing engineering examples,the parameters of the section stiffness and the spacing of the induced joints are analyzed.Several improvement schemes are discussed.It is found that the installation of the induced joint can release the longitudinal stress of the wall and lead to the generation of cracks at the section of the induced joint.The stiffness of induced joint section has limited influence on the stress of the side wall,and the spacing of induced joints has certain influence on the setting effect of induced joints.The comparison of different schemes of induced joints found that the two schemes with spacing 6m were better.(3)By using the extended finite element method,the crack propagation of the side wall of the early age super-long concrete under the setting of the induced joint was obtained,and the stiffness damage of the concrete and the steel bar interface under the condition of induced joint cracking was induced.Based on the relevant experience,it is found that the durability measures,mainly the waterproof design of the induced joint section,are very important.