Tsunami Force Acting on Bridge Girders

Abstract

This paper deals with how tsunami force acted on bridge girders when the Great East Japan Earthquake broke out on March 11, 2011. First of all, almost all data of bridge girders in the inundation area were collected. Satellite images in internet websites were introduced to make a quick survey on how many bridges were in the inundation area and how many of them were damaged. Detailed data on the bridges, such as dimensions and types, were obtained from authorities that have maintained those bridges. For damage analysis of bridge girders, Prof. Kosa's method was introduced to see whether bridges were washed away or not by tsunami. Motion pictures of the tsunami taken by residents when it happened were examined to evaluate the velocity and height of the tsunami. In order to examine how bridge girders were washed away, an experimental investigation was conducted using a big water channel. Hydrodynamic analysis was conducted to evaluate the test results. In addition, a new numerical simulation technique was developed to follow the movement of a bridge girder during the tsunami.

Deciphering the Tsunami Wave Impact and Associated Connection Forces in Open-Girder Coastal Bridges

“…Their research study argued that although the maximum horizontal load and maximum uplift load applied on the bridge deck might not occur at the same time, it would be conservative to apply them simultaneously at the center of gravity (CG) of the deck. Other research studies [21] assumed that the hydrodynamic component of the tsunami loading is uniformly applied on the face of the bridge, meaning that in this case the resultant horizontal load would be applied at the mid-height of the bridge. This approach seems to be consistent with FEMA P-646 [38], which suggests that the hydrodynamic loading applied on the face of a building is uniform with height and the resultant force is applied at the mid-height.…”

“…In the 2004 Indian Ocean Tsunami, 81 bridges located on the coast of Sumatra were washed away [1]. In the 2011 Great East Japan Earthquake in Japan, many bridges were able to withstand the strong shaking; however, 252 bridges were washed away or moved by the tsunami [2]. The most severe and common type of failure in these bridges was the breaking of the connections between the superstructure and the substructure, which resulted in the unseating and wash out of the bridge deck by the tsunami waves ( Figure 1).…”

“…Some of the experimental studies investigated tsunami loads on flat slabs [8], decks with girders [6,9,20,21] and box-shaped decks [7,22,23]. Several studies simulated the tsunami waves via unbroken but transformed solitary waves, while others via turbulent bores.…”

Role of Trapped Air on the Tsunami-Induced Transient Loads and Response of Coastal Bridges

“…Recent tsunami events; however, demonstrated that such structures are vulnerable to the tsunami-induced loading. In fact, the 2004 Indian Ocean Tsunami washed away 81 bridges on the coast of Sumatra [1], while the tsunami generated by the 2011 Great East Japan earthquake damaged 252 bridges [2]. The most severe and common type of failure in these bridges was the breaking of the connections between the superstructure and the substructure, which resulted in the unseating and wash out of the bridge deck by the tsunami waves.…”

“…These studies included (i) on-site surveys and damage analysis [3][4][5], (ii) small-scale wave flume experiments [6][7][8][9][10], and (iii) numerical simulations [11][12][13][14][15][16]. Several studies focused on the tsunami loads on flat slabs [8], while other studies examined more complex geometries such as decks with girders [2,7,17]. Most of the experimental studies were conducted at small to medium scales, ranging from 1:100 to 1:20, and the bridge models consisted of acrylic or wood decks supported rigidly, either from the top or the bottom of the deck, without considering the actual flexibility or inertia of the bridge.…”