Field measurement, analysis and protection for the vibration of an ancient ruin induced by railway

Increasingly ancient ruins are subjected to higher levels of vibrations induced by rail due to urbanization. In this way, to better understand and preserve ancient ruins against train-induced vibrations, vibration measurements and FE analysis were conducted on the Hangu Pass, Luoyang, China, located adjacent to the Longhai railway line. Firstly, damage descriptions of the Hangu Pass are conducted, and train-induced vibrations were recorded at several points on the ground and the ruin. Then, attenuation characteristics of vibration in the ground and on the ruin were examined. Secondly, based on the FE analysis, the stress distributions of the Hangu Pass are present when the train crossed the nearby railway line. The results showed that the maximum stress distribution from the result of the FE analysis is similar to crack distribution of the Hangu Pass, which confirmed that the train-induced vibration is a significant factor to deteriorate the Hangu Pass. Thirdly, in order to protect the Hangu Pass against train-induced vibrations, an anti-vibration system, isolation trench, is introduced. The FE model of the Hangu Pass with isolation trench is established. The effect of the trench’s width, depth, location and filling materials on decreasing the train-induced vibrations of the Hangu Pass are studied. The results showed that the set isolation trench can protect the ancient ruin against environmental vibration

Time variant natural frequencies of a roadway bridge under stochastic vehicle flow

A general framework for investigating the on-load frequencies of roadway bridges under stochastic traffic flows was developed. The cellular automaton (CA) model was adopted to develop the stochastic traffic flow. The on-load natural frequencies of the bridge are analyzed statistically. The results show that the on-load frequencies of bridge are less than the corresponding natural frequencies of the bridge. For higher or lower traffic occupancies, the fluctuation of on-load natural frequencies of the bridge becomes smaller than that under the middle range of traffic flow densities. A linear relationship exists between the mean frequency difference and the traffic flow density, with the mean slope of regression lines for the first four natural frequencies being 0.0844. There is a stronger linear relationship between the mean frequency difference and the total traffic weight, with the mean slope being 0.482. Based on traffic flow density or total traffic weight on the bridge, it is possible to make an estimate of the effect of traffic flows on the on-load frequency of a reinforced concrete continuous beam bridge using the regression relationships