| The long-term fatigue load influences regular service of reinforced concrete structural member,or even endangers life and property of the people.The damage of reinforced concrete structural members under effect of fatigue load is an extremely complicated accumulation of damage.High piled slab-beam wharf has been applied to harbor engineering for many a long day,also serves as one of the most principal wharf structure forms.The fatigue load on portal crane track stringer exposed in natural environment does not only contain portal crane load,but also has temperature load,etc.The coaction of the two fatigue loads makes fatigue damage accumulate gradually in portal crane track stringer until damage occurs.Thus it is very necessary to research the fatigue performance of portal crane track stringer under coaction of portal crane and temperature loads to accurately recognize the dangerous positions,extent of damage and predict the fatigue life.A high piled slab-beam wharf under construction in Huanggang is taken for example to research the dynamic response of portal crane track stringer of this wharf under coupling of portal crane and temperature loads,and combine the existing life function of steel bar and concrete to predict fatigue life of portal crane track stringer.The main content and conclusions are as follows:(1)Compare and analyze the existing prediction models for fatigue life of steel bar and concrete to select a model fit for fatigue life prediction of portal crane track stringer from these models.Lastly predict fatigue life of concrete in compressive region and steel bar in tensile region respectively.The rule of influence of temperature,portal crane load,etc.on the fatigue life of portal crane track stringer is further discussed.(2)Conduct numerical simulation to delve into fatigue performance of portal crane track stringer under coaction of portal crane and temperature loads,finding the coupling stress under action of portal crane and temperature loads is not simply linear superposition of the two.To be concrete: with portal crane load of 350KN/wheel unchanged,when temperature difference between upper and lower surfaces of beam is smaller than 10℃,the coupling stress is smaller than the stress produced by sole portal crane.At this moment,the stress produced by temperature load is favorable for prolonging fatigue life of portal crane track stringer.When temperature difference is greater than 10℃,the coupling stress gradually becomes greater than the stress produced solely by portal crane,yet is smaller than the linearly superposed stresses respectively produced solely by portal crane load and temperature load.At this moment,the stress produced by temperature will shorten fatigue life of portal crane track stringer.(3)To cope with possible fatigue damage to portal crane track stringer in construction and operation,manifold measures to prolong fatigue life of portal crane track stringer are suggested,including blending steel fibre into reinforced concrete structural members,which is of far reaching significance to guarantee general security of high piled slab-beam wharf and improve economic benefit. |
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