STUDY ON IMPACT COEFFICIENT OF FOREST BRIDGE LIVE LOADS
Xu Ri chang (Northeast Forestry University) Lu Chun he (Daxing'an ling District Constructing Commission)
Log-track is the main form of loads in forest bridges, the bridge dynamic actions caused by log-track are quite different from those caused by normal truck in highways bridges. For the design of forest bridges, the specifications of the ministry of transportation was applied indiscriminately in the past, because of the lower impact coefficient of live loads, the design reliability and the safety performance of forest bridges are influenced to some extent. viberation tests were conducted with more than 10 forestry bridges, analysed the dynamic action for simple supported concrete bridges of spans of 15, 20 and 25 meters carrying two kinds of log-truck. The impact coefficient formula and the empirical curve which relates to the impact coefficient 1+μ, speed V and bridges span L, which are suitable to the log-truck loads in the forest region of China. It fills in the gaps in the design theory for forest bridges. It is also benefit to the development of forest bridges. It is also benefit to the development of forest bridges construction, the increment of design reliability and safety performance.