| Large amounts of domestic and foreign earthquake information shows that thebrittle failure of full welded beam-column moment connection mostly starts from theweld toe, and will diffuse to its surrounding. The cracking is related to the inherentdefects of weld. Such as welding speed, welding sequence, interpass temperature, heatsource power and heat input, as welding processes can cause toughness of weld andinfluence seismic behavior of the joints, considering the influence of weldingconditions to mechanical properties of steel beam-column connections not only has thenecessity, but also has the importance. In this thesis, the non-scallop steel beam-columnconnection is used as the research object and a refined FEM model of the connection isestablished. Based on this refined FEM model, a research on the influence of variouswelding conditions on connection mechanical properties is conducted and excellentwelding processes are determined. Finally, the method of establishing refined FEMmodel and the excellent welding processes are used in the stud y on mechanicalproperties of the local non-scallop connection of steel beam-column. The main contentsand achievements of this work are as follows:(1) Firstly, the research of refined FEM model is conducted. On the basis of takingfull account of the actual welding conditions, refining the simulation parameters andimproving the mesh, the FEM simulation of a more realistic welding temperature fieldwas achieved with the use of Live-die Unit technology and subroutine DFLUX of heatsource on the Abaqus platform, then the welding residual stress and strain are calculatedby the method of thermal-mechanical coupling. Based on the residual stress fields, thequasi-static FEM analysis is conducted through applying low-cycle loads. Forcomparing with the results of the quasi-static connection test and the FEM analysisunder the simplified model, it is defined that the method of refined FEM simulationshows accuracy and validity.(2) Based on the refined model, the welding simulation analysis is conducted byconsidering the influence of welding conditions. In order to establish the researchscheme on the welding conditions, the following research schemes are set up inaccordance with the specifications, they are6interpass temperature research schemes,3welding speed research schemes,3heat source power and heat input research schemes, 6welding sequence research schemes according to the principle of avoiding heatexcessive concentration at short time. It can be clear through comparative researchingthat lower welding residual stress and strain may be obtained with the premise ofensuring welding quality through the following measures; they are the controlling ofheat input unchanged, reducing the welding speed appropriately, controlling interpasstemperature at100℃, welding with the sequence from beginning to end and weldingweb after flange.(3)The improved effect analysis of non-scallop connection under optimizedwelding processes is conducted. The results show that the excellent welding processesdeterminated in this thesis can effectively improve the parameters like welding residualstress, deformation and fracture properties index.(4) Finally, the refined FEM welding simulation and the quasi-static analysis oflocal non-scallop beam-column connection are conducted by combining with theexcellent welding conditions. The comparison results of mechanical properties betweenlocal non-scallop connection and non-scallop connection show that the non-scallopconnection has advantages both in bearing capacity and energy dissipation. Due to noaccess hole, the heat affected relatively concentrated, so that the RI（Rupture Index）onelastic stage is higher, but it gets lower while it falls into the plastic state. At a certainextent in the loading to the local non-scallop connection, the strength degradationbegins to occur, the energy dissipation ability is relatively weak, however, the RuptureIndex are relatively low, and the Rupture Index around welding holes are lower thanother path.Therefore, as long as good control of welding residual stress, strain and ensurewelding quality, non-scallop connection is not easy to crack after loading, for that it isrecommended in cantilever beam-column connection for fabrication. Except weld holesof local non-scallop connection can influence the bearing capacity and energydissipation capacity of the late, the local non-scallop connection is not worse thannon-scallop connection, for that it is recommended in steel beam-column connection ofsite welding while ultimate angle is0.045rad. |
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