Yudai KOGAWA
Safety Assessment of Ohkouzu Canal Gate Trestle Bridge
Takeshi MIYASHITA
Completion since 1931, Ohkouzu Canal Gate has been playing important function in regulation of water flow and flood prevention of Echigo Plain. Its gate trestle bridge was determined as aging in 2003. It is also reported that the gate trestle bridge has served almost 80 years in 2012. The safety assessment, including the seismic performance, became an emergency work for this gate trestle bridge.
In this study, a seismic analysis was carried out both by finite element model and vibration test to assessment the structural safety. First, vibration measurement was carried on site to identify eigen frequency and eigen vibration mode of real structure. Then, a finite element model was made from designed drawings. Members were assumed un-corroded in numerical model. Some secondary members were ignored to simplify model. The ground motions L1 and L2 with type 1 and type 2 were introduced into finite element model in both longitudinal direction (X-axis) and transverse direction (Y-axis). Member stress was calculated then compared to allowable stresses. Dynamic response from finite element model was compared to dynamic response measured in vibration test. The following results can be obtained:
1) The mode shape in finite element model agreed with the mode shape result in the vibration test on site. However, their eigen frequencies are different.
2) When ground motion L1 was applied either in longitudinal direction or transverse direction in finite element model, no member exceeded allowable stress. Hence, the gate trestle bridge is safety.
3) When ground motion L2 was applied, some members such as the lower lateral bracings, the diagonal bracings of lower lateral bracings, the diagonal bracings and the vertical members exceeded allowable stress in both type 1 and 2. In type 2, some other horizontal members also exceeded allowable stress.
Please use "previous botton" to return the previous page