Analysis Of Residual Stress And Deformation Of Welded I-Girders With Corrugated Steel Webs

The I-girder with corrugated steel webs is connected to the upper and lower base plates by welding,so there are irregularly distributed residual welding stresses and welding deformation inside the girder body after cooling and forming.In the service process of the girder welding residual stress as the initial stress and the applied load superimposed on each other,so that its internal stress redistribution,resulting in its structural stiffness is reduced,but also seriously affect its fatigue performance,so that the girder premature yielding phenomenon.This paper uses a combination of experimental and numerical simulations to study the experimental aspects of the proposed resistance strain gauge method to nondestructively measure the welding residual stress in the girder.Thermocouple and infrared thermometer are also used to measure the temperature field on the surface of the girder.In the numerical simulation to test the I-girder welding parameters based on the establishment of threedimensional thermoelastic finite element model.The two data are compared,thus verifying the correctness of the modeling approach.Specific analysis of the temperature changes during the welding process of the waveform steel web I-girder,as well as the distribution of residual stress and deformation law.In addition,a finite element model of a flat web I-girder was established to compare the stresses and deformations of the two different webs to obtain the effects of changing the flat web to a waveform steel web on the residual stresses and deformations.The specific study contents and results are as follows:(1)Selection of test bands in I-girder for measurement point arrangement.The resistance strain gauge is arranged at the stress measurement point,and the welding residual stress is obtained after measurement.Place thermocouples at temperature measurement points and measure thermal cycling curves.At the same time,infrared thermometer is used to collect the surface temperature of the girder at fixed time and interval.ABAQUS software is used to establish a three-dimensional thermoelastic finite element model,extract the residual stress and temperature values of the corresponding measurement points,and conduct comparative analysis.Comparison of the results show that the numerical simulation results of the welding residual stress and temperature field match well with the measured results,effectively verifying the correctness of the finite element model established using the relevant methods.(2)The finite element model extracts multiple temperature clouds at different moments in the two stages of the welding and cooling process,and the thermal cycling curves of each measurement point at different heights from the weld in the span position.The results show that the welding stage heat source center stable temperature up to 1401 ℃Away from the center of the heat source temperature rapidly decreases,when the distance from the center of the heat source is greater than 250 mm when the temperature has converged to room temperature,the temperature at the cooling stage of the weld rapidly decreases to 100℃.Girder surface welding temperature field distribution varies with time,and heat is transferred from the heat source to the web and bottom plate during the welding process.In the cooling process on the girder without heat input temperature transfer from the high temperature to the low temperature plate,while dissipating heat into the air,the temperature gradually converges to 0.(3)Extract the stress cloud in the release phase in the finite element model,and arrange 8paths at different directions in the model for the extraction of residual stress values.At the same time,a total of nine paths were created in the finite element model centered on the weld seam at the web,base plate,and the fusion position of both,and the numerical magnitude of the deformation was studied by the paths parallel to the weld seam.The results indicate that the weld residual stress on the waveform steel web I-girder is dominated by longitudinal stress,and is mainly distributed within 200 mm from the weld.The longitudinal residual stress on the surface of the web at 5mm from the weld is 351 MPa higher than the yield strength of the material,while the transverse residual stress on the surface of the web is relatively small with a maximum value of 48.5MPa.(4)The stress cloud,stress at each path,stress at each path and displacement values of the waveform steel web and flat web I-girder are extracted and compared for analysis.The analysis results show that the maximum values of longitudinal residual stresses in waveform steel webs and flat web I-girders are 410 MPa and 451 MPa,respectively.In the whole structure of the former due to welding residual stress is less than the latter.In addition,because the former welding curve is wavy,there is a large residual stress distribution at the bottom plate in front of its crest,while the latter residual stress is symmetrically distributed on both sides of the web.The maximum deformation of corrugated steel web I-girder is 1.32 mm at the base plate y+5.3mm on the right side of the weld,and the maximum deformation of flat web I-girder is1.02 mm at the web surface z+5.3mm,both of which are smaller than the displacement of the weld at the fusion position of the web and base plate.At the same time,the displacement curve of the former measurement point has a wave shape while the latter is more gentle with a clear hierarchy between the paths.