Research On The Bridges Mechanics Performance Under The Standard Energy Impact Load

Currently the common methods for detecting bridge structure can be divided into staticload test method and dynamic load test method. The static load test method develops earlier,its theory and technology is relatively mature, however t he static load test method hasshortcomings of high cost, long time-consuming and needing traffic interruption. What’smore, the difficulty of the static load test is unthinkable under the special geographicalconditions. The dynamic load test method, which is low-cost, short time-consuming andwithout traffic interruption, can analyze the mechanical properties of the bridge quickly andaccurately. But the dynamic load test method develops later and parts of its theory and testingtechnology are immature. How to use the dynamic load test method to analyze the bridgestructure quickly and accurately is becoming a hot spot in current bridge detection.Under the support of HeBei traffic science fund project, The PERA China and Thenational supercomputing center in Tianjin (NSCC), researching on the rapid evaluationmethod of bridge’s bearing capacity by dynamic load test. Based on the bridge bearingcapacity evaluation method with calibration coefficient under static load test, putting forwardto a way that calculating static displacement use dynamic load test displacement and thebridge structure impact coefficient, so as to achieve the bridge structure calibrationcoefficient by dynamic load experiment and evaluate the bearing capacity rapidly.Dynamic displacement measurement can be obtained by using high precision sensors,But there are many factors that affect the structure impact coefficient and the relationships arecomplex. There has carried on detailed analysis of the bridge impact coefficient underdynamic response and studied the influence of the vehicle speed, the bridge deck flatness,bridge structure stiffness and the bridge structure form for impact coefficient.For the bridge deck flatness is a random variable of extreme uncertainty which isdifficult to measure accurately and the effect of the bridge deck unfairness on the impactfactor can’t be ignored, the method that standard energy impulsive experiment is raised,which makes the standard load vehicle to jump in the mid-span when traveling on the bridge.The results show that bumping test can effectively suppress the deck flatness influence on impact coefficient and obtain the relationship between impact coefficient and structurestiffness, bridge structure form.The bumping test uses the large impact caused by the jumping to suppress the smallimpact caused by the bridge deck unfairness. The bumping test makes severe vibration to thebridge structure, so the value of impact coefficient is big. Under the bumping test thatsleeper’s height is5-15cm, the FEM’s impact coefficient is2-3times of the normal condition.To solve this problem, a lot of indoor and field bumping tests were done with the test resultproving the above analysis is right.Above all, using the result equation of impact coefficient, the bridge structural staticdeflection can be calculated by testing the structural first natural frequency and dynamicdisplacement, from which the bridge’s static defection can be calculated quickly. So itprovides a new way to evaluate the structural bearing capacity.