The Research Of Fatigue Test Evaluation And Strengthening For Industrial Steel Buildings

The mutational fatigue damages generally have greater hazards to the safety of asteel structure. There are more accident probability in industrial buildings due theirseveral environments and also the fact that they must carry large loads and repeateddynamic loads； particularly there are some engineering cases in the industrial factorybuildings, where the cracks or even fractures have often occurred on steel cranebeams whose service lives are not up to their designed ones；and also fatigue damagesoccurred on those members, such as crane limb heads etc that carry dynamic loadsindirect or in which tensile stresses should not occur theoretically, all these have greatimpacts on the structural security of industrial buildings.Taking the linear cumulative damage principles as the theoretical basis, and alsoregarding the raw material bay, receiving bay and mechanical hydraulic pressworkshop of a steel making plant as the project backgrounds, the underload equivalentcoefficients of the crane beams in different workshops were tested and analyzed,putting emphasis on the inspection of structure damages dynamic&static testings andstructural FEA, etc for the upper flange-web connections of solid web crane beams,the ends of tapered crane beams, as well as the crane limb heads, etc. the reasons offatigue cracking were analyzed, the uses of different fatigue evaluation methods wereexplored and different strengthening methods and their optimizations were alsoresearched, thus forming complete sets of practical technologies for the fatigueassessment and reinforcement of steel structures of industrial buildings.1. The fatigue census and classification of the crane workshops with d ifferentproductions were carried out； and it was researched specially that the upperflange-web connection of the solid web crane beams, the ends of the tapered cranebeams, and also the crane limb heads, etc according to the dangerous degrees ofdifferent sorts of fatigues.2. For11steelmaking raw material bays and receiving bays, as well as18cranebeams of the mechanical hydraulic press building, the stress tests were conducted toestimate the underload equivalent coefficients of the crane beams bas ed on the fatiguestrength of2×106cycles. These estimated values were all larger than thoserecommended by China’s code, and the suggestions on regulating the values of the underload equivalent coefficient in the code were given.3. The fatigues close to the upper flange of the solid web crane beam wereresearched, and FEA of the track–crane beam combinations was also carried out tosimulate the track-crane beam interactions, which could show the complicated stressstate of a position under the track eccentricity. The result of FEA were used to assessthe fatigue near upper flange on the basis of shear and normal stresses in accordancewith the German specifications for the first time.4. The cracking causes of the crane limb heads were analyzed by combing fieldtesting with linear and nonlinear FEAs, for the strengthening of the crane limb headsmany schemes were proposed and optimized, whose fatigue reliabilities were alsoevaluated according to the measured data for the dust time.5. The behaviors of the fatigues at the ends of different types of right-anglemutational carne beams were studied, whose locations and degrees of stressconcentration were determined by FEA, and their behaviors were also assessed andcompared using the theory of crack driving energy, which has been advancedaccording to the theory of Verity at first, to verify the superiority of the angle plateright-angle mutational crane beam over the vertical plate crane beam, according towhich several strengthening schemes were presented, whose effects were verified aswell.