Study On Flexural Behavior Of The Multi-cavity Steel Reinforced Concrete Composite Structure

In recent years,the rational development of urban deep underground space has become an important solution to alleviate problems caused by urbanization.Due to the has high soil-water pressure and complex environment of deep underground space,the related deep underground enclosure structure are extremely important.The common deep foundation pit enclosure structure,including reinforced concrete diaphragm wall,has low economy,poor waterproof and crack resistance performance and low construction quality.Therefore,it is of great significance to develop a new enclosure structure with excellent mechanical properties and easy for construction.This paper proposes a new type of the multi-cavity steel reinforced concrete(MSRC)diaphragm wall which can be used as "two walls in one".Compared with the traditional reinforced concrete diaphragm wall structure,this structure is economic and has good mechanical properties.The new multi-cavity steel reinforced concrete composite structure was taken as the research object,and experimental and numerical studies of pure bending performance and load-resisting mechanism of this structure under concentrated load were carried out.The main research work and conclusions of this paper are as follows:(1)A new type of multi-cavity steel reinforced concrete underground diaphgram wall in the form of "two walls in one" was proposed.The wall was composed of multicavity steel and concrete,the multi-cavity steel was welded by H-shaped steel or coldformed C-shaped steel through the flange,and then the concrete was poured into the steel cavity.The steel cavity provided restraint to the concrete to avoid cracking and water seepage of the wall,and to prevent the soil collapse of the groove section during construction,which could result in poor construction quality;The concrete inside the cavity can prevent the local buckling of steel,and make the combined effect of steel and concrete to be fully realized,which can improve the mechanical performance of the structure.The side wall of multi-cavity steel reinforced concrete composite structure was designed based on a practical project.Compared with the traditional reinforced concrete diaphragm wall,this structure has obvious advantages in mechanical and economic performance.(2)The pure bending performance tests of two types of scaled three-cavity composite structures were carried out,and the data was recorded and analyzed.The test results showed that the discrepancy in the bearing capacity between H-MSRC and C-MSRC was slight.During the whole loading process,there was no obvious decline in bearing capacity,both specimens have good ductility and shown flexural failure.(3)The finite element analysis was carried out by ABAQUS software,and the accuracy of the models were verified by the test results.The parameter analysis shown that the flexural capacity of this structure was positively correlated with concrete strength,steel yield strength and steel content.To be specific,the influence of steel content was the greatest,while the influence of concrete strength can be ignored.In addition,the yield strength of steel was negatively correlated with the flexural stiffness of specimens.(4)Based on the experimental and simulated results,the two types of specimens were simplified to members with the same cross-sectional form,and three simplified methods of structure splitting for bearing capacity calculation were proposed.The results showed that the third simplified method was in good agreement with the experimental and simulated results.For structures with identical steel thickness of the flange,the middle standard section can be simplified into separated H-shaped steelconcrete composite structures to calculate the flexural capacity.