Study On Assessment Of Safety Capability For Highway Steel Truss Bridges

From the end of 19 century to the middle period of 20th century, many steel truss bridges were built and even used today. However as a result of great runoff traffic load, fatigue cracks in steel members appeared. How to know the remaining reliability and fatigue life of a working steel truss bridge becomes a very important problem.On the basis of researches from many countries and the analysis of fatigue problems, the evaluation method of safety capability and fatigue life is researched systemically. The finite-element software ANSYS is applied in simulation of the work of the highway steel truss bridge, taking the Nenjiang steel bridge for example. The plane fracture toughness K IC is introduced, the fatigue life is calculated and the safety capability is evaluated of highway steel truss bridges based on the method of fracture mechanics. In details, the following aspects are investigated:1. The actual model is established by the finite-element software ANSYS based on the existing cracks, taking the Nenjiang steel truss bridge for example. Based on the comparison of calculated value and tested value, the veracity of the actual model is confirmed. Furthermore, static destroy of the bridge is simulated to determine the critical members.2. In the evaluation of highway steel truss bridges based on the method of fracture mechanics, the plane fracture toughness K IC must be detected firstly. So the method and steps of the testing for the plane fracture toughness K IC are explained. The plane fracture toughness is confirmed by Nondestructive tests, and K IC is calculated.3. The critical members are judged based on the method of fracture mechanics. The crack extension is simulated, and the stress distribution of the tip of cracks is determined. Furthermore, the size of critical cracks is calculated, the fatigue life is calculated and the safety capability is evaluated.