Simulating the effects of remote tsunami waves induced by earthquake on transmission tower: A real case study

• Main Author: G. Nelvindran S. Govindasamy
• Format: text
• Language: English
• Published: 2023
• Subjects: earthquake; tsunami

The Manila Trench subduction zone is an active convergent plate margin between the South China Sea and northern Philippines. In recent events, Manila subduction zone has been distinguished as a high hazardous tsunamigenic earthquake source region within the South China Sea where no earthquake larger than Mw = 7.6 has been recorded in the past 100 years. However, there are probability for larger earthquakes in the future anticipated to affect neighbouring countries such as Malaysia as historical data are not reliable. These large earthquakes could potentially trigger the generation of tsunami that will propagate towards South China Sea and reach East Coast of Peninsular Malaysia. Hence, this study investigates the severity of tsunami and its impact on power plant structure located near the coastal areas, which in this case a transmission tower. The potential disastrous impact of tsunami waves on a power plant causes loss of lives, damage to assets, and loss of electricity for the coastal communities similar to year 2011 Tohoku tsunami in Japan. Therefore, application of shallow water equation (SWE) in tsunami modelling namely generation and propagation phase and nonlinear shallow water equation (NSWE) for run-up and inundation phase of a tsunami event are pertinent in simulating various scenarios of tsunami. In this study, simulations were carried out at earthquake intensities of moment magnitude Mw 7.0, Mw 8.0, and Mw 9.3. These ranges of earthquake intensities were chosen to illustrate the significant difference in the capacity of earthquake induce tsunami investigated in this study. The worst-case scenario of Mw = 9.3 was found to cause the state of Terengganu to experience a wave height ranging at 0.51m-1.54m with arrival time of 9-12hrs. Meanwhile, the inundation depth at power plant in Paka, Terengganu was found to reach up to 1.25m and resulted to tsunami force of 164.81kN as lateral load. This lateral load is then applied to a 275-kV transmission tower using Linear Static Analysis, where the maximum lateral force, Fx was determined. Based on the modelled transmission tower, beam number 395 and node number 274 exhibited the maximum value of Fx = 6442.28kN was obtained which produced a factor of safety for compression capacity of 4.61 that can be concluded as unsafe for compressive design. Hence, an additional member is recommended to be added at this critical beam and node in order to improve its compression and tension capacities and withstand lateral load from tsunami event. Gusset plate capacity and bolt resistance of critical members were, however, found to be able to withstand effects from tsunami force at Mw 9.3. Thus, this study has established that tsunami inundation depth and waves velocity were the parameters found to highly influence the stability of affected transmission tower.