Experimental Study And Theoretical Research On Flexural Performance Of Composite Beam-Slab Structure On The Roof Of Underground Caisson

With the development of society,people’s utilization of above-ground space has gradually become saturated,and people have gradually turned their attention to underground space.How to ensure the construction feasibility and use safety of underground structures has become the main research direction of scholars in the engineering field.one.Steel-concrete composite structure is a new type of structure developed on the basis of steel structure and concrete structure.Because of its good mechanical properties,it is widely used in the history of modern human architecture.Experts and scholars have been researching steel-concrete composite structures for a long time,and have achieved rich research results,and their application development has become increasingly mature.Therefore,the rational application of steel-concrete composite structures in the field of underground structures enables the underground structures to meet the bearing capacity performance requirements,while the construction organization is safer and faster,and to obtain better economic benefits is the future research direction and development goal.In this paper,based on the actual situation of the caisson project,taking the caisson roof steel-concrete composite beam and slab used in the project as the research object,two kinds of model specimens of the underground caisson roof steel-concrete beam and slab composite structure are designed and produced.According to the steel framework and concrete Whether shear connectors are set between the plates,the two model specimens are divided into a non-shear model with beam-slab spot welding connection and a beam-slab integral cast with shear model.Through the three-point bending uniaxial static loading test on two specimens,the flexural bearing capacity of the composite structure is obtained,and its mid-span load-deflection curve and load-strain curve are drawn,and the stress conditions of the two are analyzed.Destruction characteristics.Perform theoretical model establishment and calculation on the non-shear model of beam-slab spot welding connection and the shear-resistant model of beam-slab integral pouring,and the theoretical calculation value is connected with the beam-slab spot welded non-shear model,beam-slab integral pouring The test values ??of the specimens with the shear model are compared and analyzed,and the bending moment of the composite beam is inversely calculated with the data of the measured stress and deflection of the test,and the bending moment is compared with the theoretical calculation to verify the feasibility of the theoretical model and the calculation formula.Provide method for calculation of bearing capacity of engineering steel-concrete composite structure.The test results show that,compared with the non-shear connection scheme of spot welding connection,the integrally poured shear connection scheme can greatly increase the cross-sectional bearing capacity of the composite beam and slab,delay the cracking time of the concrete slab,and slow down the development trend of cracks;The construction process of the non-shear-resistant model of spot welding connection is simple and the structure has good waterproof performance;the construction process of the integrally poured shear-resistant model is cumbersome,and the time and labor cost during the installation process is high,but there is no obvious feature before damage,which is not conducive to Prevent and eliminate potential safety hazards in actual shaft engineering.Through the comparison between the measured bending moment and the theoretical bending moment of each section,it can be concluded that the theoretical calculation method proposed in this paper is correct,simple and applicable.