Study On The Reliability Appraisal And Reinforcement And Defact Analysis And Measure To Remedy Of Existing Heavy Factory Buildings

Based on practical project of inspecting, appraising and reinforcing a main heavy factory building, especially its steel crane girder system, of the Second Steel Mill belonging to Taiyuan Steel & Iron Corporation, whose technology renovation leads to increase tonnage of many heavy cranes and vertical load of frame-bent structure, First the structure and its members were investigated, inspected, calculated and analyzed, and their reliability was appraised respectively and the strengthening projects or the measures to remedy were given. Then, in accordance with the requirement to strengthen the girders under non-stop production, the feasibility of strengthening the crane girders by adding steel diagonal braces underneath the existing girders has been studied by inspecting and evaluating the strengthening effect of the crane girders and comparing with other reinforcing scheme. Dynamic test has been performed on three strengthened girders after they were being put into service. According to the measured data from the dynamic test and the calculated results of the proportion of the load distribution on steel diagonal braces and steel crane girders as well as the increased carrying capacity after strengthening in consideration of the principle of cooperative work between braces and crane girders, the feasibility, rationality, and economy of this strengthening scheme have been verified. This scheme can be applied extensively to strengthen crane girders system including concrete crane girders system hereafter. In addition to, the fatigue crack between web and upper flange of welded steel crane beam on heavy duty service was discussed, and based on long-term observation and research, the author classified fatigue crack into bearing type and middle type crack along the horizontal direction. The causation, distributive law and mechanism of the crack were analyzed, and the precautions to take and the measures to remedy crack were presented. The main defacts including damage, crack, erosion and aging in structures, especially in concrete structure were introduced; the defact mechanism was analyzed and the precautions to take were also given.