Assessment of Old Railway Bridges Under the Pardis High-Speed Train

Abstract

There are numerous old arch bridges in Iran that have been used as railway bridges for more than eighty years. In Iran's railway network, there are about 3,700 bridges which all of these have been designed based on service load in that time (low-speed trains) and are still serving for trains at maximum speed of 100 km/h. Using of high-speed trains has been spread all over the world in the last two decades. In recent years, the use of high-speed trains is necessary in the Iran. It is not possible at all to replace old masonry arch bridges due to field and economic constraints, so it is necessary to evaluate the dynamic behaviour of these bridges under the high-speed trains. To evaluate complex behavior of these bridges, results of field tests are required. Since it is not possible to perform field tests for all arch bridges, these structures should be simulated correctly by computers for structural assessment. The present study investigates two plain concrete arch bridge which are located in kilometer 23 and 24 of the old Tehran-Qom railway. The numerical model of the bridge is established in accordance with detailed geometrical properties of the bridges. The numerical model has been validated based on the existing experimental results. In the model updating procedure, the vertical deflection at the crown under static loading and the movement of the six-axle train by 60 and 80 km/h, as well as the first three modes of the bridges were selected as a calibration criterion. In the second step, different geometrical of Pardis high-speed train are used and totally 13 geometrical models have been detected and investigated. By using the finite element method and the macro-modelling approach, the km-23 and km-24 bridges were simulated and totally 26-time history dynamic analyses have been conducted. Dynamic behaviour of the bridge under moving load model of Pardis trains at speeds of 150km/h have been assessed. Finally, deflection and acceleration responses for all 26 dynamic analyses at the crown of the bridges have been extracted and compared. These analyses are conducted to the aim of finding opportunities and constraints in using railway masonry arch bridges in the Iran as it is necessary to use existing rail lines on the rail network, due to the high cost of the construction of new ones and the need to know the existing structures such as bridges and their properties under the impact of high-speed trains. A realistic prediction of the structure's response helps a rational operation of the bridges in the service, that’s why the correct understanding of the dynamic behaviour of railway bridges is essential. The results of present study indicate that these bridges have good behaviour under high-speed trains.

Keywords

• masonry arch bridge
• finite element modeling
• geometrical properties of high-speed trains
• pardis train
• dynamic assessment