Study On Mechanical Properties Of New Beam-Plate Joint In Prefabricated Inspection Pit

In recent years,the government of country has introduced a series of new policies to bolster urban planning and construction,These initiatives,implemented since,have had a profound impact on the developmental trajectory of our construction industry within the country.Notably,prefabricated buildings have emerged as a pivotal driving force,characterized by their environmentally-friendly nature,streamlined construction processes,and exceptional load-bearing capacity.The inspection pit of a metro vehicle depot plays a crucial role as a supporting facility for urban subway construction,specifically in the maintenance and upkeep of subway vehicles.The structure of the inspection pit primarily comprises three components: columns,bottom beams,and bottom plates.Currently,the majority of inspection pits are constructed using the cast-in-place method,resulting in a laborintensive process,a high number of construction personnel,lengthy construction periods,and significant pollution.Additionally,challenges related to casting quality and construction accuracy often arise,leading to complications in the overall structural integrity and subsequent rail installation.To address these issues,this thesis proposes a novel beam-plate joint designed for prefabricated inspection pits and investigates the mechanical properties of this new joint and the structure as a whole.The key research objectives are as follows:(1)A new type of prefabricated beam-plate connection node for inspection pits is proposed.This design incorporates H-section steel and anchor bolts as its primary components.The H-section steel bore "waist" type hole,while the bolts are fastened to the section steel using two nuts—one above and one below.This configuration enables seamless horizontal and vertical displacement adjustment,significantly streamlining the installation of pit members and subsequent rail laying processes.Notably,to balance bearing capacity requirements and economic considerations,no special reinforcement is done for H-section steel,concrete is poured at the joint site.(2)Three prefabricated specimens were made for single pass compression test,aimed at determining the joint bearing capacity level and strain characteristics of the H-section steel.The introduction of the new connector is anticipated to significantly improve the overall bearing capacity of the specimens.Moreover,the strain measurements will exhibit greater magnitudes in the upper edge of the H-section steel surface web and the upper flange plate.(3)Through a comprehensive analysis of the mechanical properties of prefabricated inspection pit members and cast-in-place members under low cycle reciprocating load.The cast-in-place structure exhibited superior energy dissipation capacity,surpassing the prefabricated inspection pit member by approximately 9%.However,the prefabricated inspection pit demonstrated increased ductility,with a coefficient increase of approximately 15.6%.Furthermore,the prefabricated structure showcased improved ultimate bearing capacity,with a noticeable increase of approximately 12.5% compared to the cast-in-place member.The prefabricated inspection pit exhibited enhanced initial stiffness,with a notable increase of approximately 21.1%,residual stiffness increased by 14.4%.(4)Analyze the influence of single factor change on the mechanical properties of assembled components.The results show that with the increase of section steel size,the mechanical properties of the assembled members are enhanced.The ultimate bearing capacity of the members is increased by 5.9%,the ductility coefficient by 11.6%,the residual stiffness by 32% and the maximum energy dissipation coefficient by 17.8%.With the increase of web thickness,the bearing capacity of components increases by5.6%,the ductility of components decreases slightly by 6.2%,and the energy dissipation capacity of components decreases by 10.1%.With the increase of section steel strength,the bearing capacity and initial stiffness of the member increase by 7%and 10%,but the ductility and energy dissipation capacity of the structure are decreased.With the increase of bolt spacing,the bearing capacity of the member decreases slightly,and the stiffness and strength degradation accelerate in the failure stage.Ductility coefficient decreased and energy dissipation coefficient decreased by 5.6%.(5)The seismic performance of the whole prefabricated inspection pit was analyzed.Northridge seismic wave was selected to analyze the stress of the whole structure,the failure of concrete,the acceleration response and displacement response of the column top.The results show that the column structure of the prefabricated inspection pit is the weak part,and the failure of the structure occurred first.The bearing capacity and seismic performance of the column should be improved by increasing the grade of concrete and reinforcement and strengthening the reinforcement.This thesis has 91 figures,18 tables and 71 references.