The Factor Analysis Of Brittle Fracture In The Welded Flange-Bolted Wed Connection

Steel structure with light weight, good seismic performance advantages comparedto other forms of structure, it is widely used in the field of industrial production andhigh-rise buildings. The Japanese earthquake of2011show that the seismicperformance of steel structure is superior to other systems, however, in the Northridgeearthquake and Kobe earthquake, a large number of brittle fracture phenomenon ishappened in the Welded Flange-Bolted Wed Connection of steel structure. Brittlefracture of welded steel structures occur frequently in the area of welding defects andstress concentration interaction, especially in the Welded Flange-Bolted WedConnection. Plate present in the beam flange flat groove welds, so that the beam flangeweld root fusion is not good and the formation of artificial crack.According to thefracture theory in the connections were research by Scholars both at home and abroad,the loading rate and initial crack length has a great influence on the fracture toughnessof the Welded Flange-Bolted Wed Connection. Three-dimensional finite elementmodel is established by the ABAQUS software, to calculate stress intensity factor andJ integral in the beam flange weld root artificial crack tip to study the fractureproperties of the artificial crack at the beams bolt welding node beam flange weldroot.1. Calculation the stress intensity factor at the artificial crack in the weld root ofbeam flange, distribution of stress intensity factor in the width direction of the beamflange section is researched, the results show that the stress intensity factor along thewidth of the beam flange into a curve, least in the one-tenth of the width of the beamflange, and largest in the middle of beam flange. Show that the middle of beam flangewill fracture earlier than the edge.2. The calculation of stress intensity factor both at the beam top flange and thebottom beam flange. Starting from the point of view of numerical simulation tocompare the possibility of brittle fracture in the beam bottom flange and beam topflange. with the same initial crack length, the stress intensity factor value in the weldroot of beam bottom flange was significantly greater than the weld root of the beam topflange, the beam bottom flange of brittle fracture more easily than the beam top flange.3. The variation of stress intensity factor at the artificial crack in the beam flangeweld root is analyzed, the stress intensity factor K_Ⅰwith the increase of the initial flawlength nearly linear increase. 4. When using different loading rates (0.1mm/s,50mm/s,150mm/s), Study theinfluence of loading rate on brittle fracture of the weld root in the beam flange, theresults proved that the greater the loading rate, material to the brittleness development,so that brittle fracture of the weld root in the beam flange are more likely to fracturefailure.5. Calculation of stress distribution along the beam flange width direction of theweld root in the beam flange, the results show that the value ofσ_yin the beam flangeweld root along the direction of beam flange length is the largest, while both the valueofσ_xand the value ofσ_zare the smallest.The greater the loading rate, the higher thestress triaxiality Ratio of artificial in the weld root crack of beam flange. The stressstate in the weld root of the Welded Flange-Bolted Wed Connection are somewhat intension. Weld defects isⅠcrack.