Study On Bearing Performance Of Space Frame Structures With Corroded Welded Hollow Spherical Joints

With the continuous promotion and development of space frame structures,the service time of the structures continues and the risk of structural failure after corrosion is increasing.Therefore,the research of residual bearing capacity and safety assessment of space frame structures after corrosion become increasingly important.However,at present,there are few researches on the bearing performance and safety evaluation methods of space frame structures with welded hollow spherical joints.The systematic research results and perfect evaluation methods haven’t been formed.Therefore,from the three aspects of structural materials,connecting joints and the overall structures,the residual bearing performance and evaluation method of the corroded space frame structures with welded hollow spherical joints were studied systematically.The specific research contents and results are as follows:(1)Experimental study on the properties of structural materials after corrosionThree kinds of structural steel were placed in an acetic acid spray accelerated corrosion environment,the longest corrosion time was equivalent to Qingdao 60 years.The structural materials with different corrosion degrees were tested by weight-loss experiment,scanning electron microscopy,three-dimensional microscope and threedimensional laser scanning equipment.The time-varying models of corrosion development of the three materials were derived,the corrosion mechanisms were analyzed,the corrosion simplified models were built,and the corrosion spatial distribution models of common structural steel were proposed.Finally,uniaxial tensile test was conducted on three structural materials,the degradation rule of residual mechanical properties was summarized,the relationship between corrosion behavior and mechanical properties degradation was comprehensively analyzed,and the residual properties evaluation methods for different structural materials after corrosion were finally establish.(2)Experimental study on welded hollow spherical joints after corrosionThe welded hollow spherical joints were placed in an acetic acid spray accelerated corrosion environment,and the corrosion cycles were equivalent to Qingdao 15,20,25,30,40,50 years.The welded hollow spherical joints specimens were tested under axial tension,axial compression and eccentric compression.The influence of joint size,steel strength,corrosion time,eccentricity,rust removal method and pitting corrosion on mechanical properties of the joints was considered,the failure mode,load-displacement curve,yield load,ultimate load and strain distribution of the joints during the corrosion process were obtained and analyzed,and the reliability of the test results was demonstrated.(3)Numerical study and practical calculation method of corroded welded hollow spherical jointsBy the defined Python programs,a refined and two simplified corrosion simulation methods were proposed firstly.Then,based on the corrosion development mechanism,different corrosion simplified models of four types of welded hollow spherical joints connected by round steel tube,square steel tube,rectangular steel tube and H-section steel were established to study the influence of corrosion depth,corrosion mode,groove height,joint size and other parameters on the bearing capacity.The methods for calculating the reduction coefficient of residual bearing capacity of four types of welded hollow spherical joints were proposed.Finally,the welded hollow spherical joints after corrosion were analyzed theoretically.The practical calculation methods of ultimate bearing capacity of four kinds of welded hollow spherical joints with axial tension,axial compression and compressed bending(/ tensile bending)were proposed.(4)Study on the residual performance and safety assessment methods of corroded space frame structures with welded hollow spherical jointsA numerical simulation method about the space frame structure with welded hollow spherical joints during the corrosion process was proposed based on ABAQUS Python secondary development.The influence of corrosion degree,corrosion location,random corrosion,stiffness of welded hollow spherical joints,section size of members,structural rise-span ratio,and structural span on the stability of reticulated shell structures were analyzed.A simplified formula for calculating the elastic-plastic stability capacity of the typical space frame structure with corrosion damage was proposed.Finally,several methods for collecting and treating the corrosion damage of space frame structures were proposed,and the safety assessment methods of the space frame structures in service were established.