Contents lists available at ScienceDirect Coastal Engineering journal homepage: www.elsevier.com/locate/coastaleng SPH numerical simulation of tsunami wave forces impinged on bridge superstructures Mohammad Sarfaraz, Ali Pak ⁎ Civil Engineering Department, Sharif University of Technology, Iran ARTICLE INFO Keywords: Tsunami wave forces Coastal bridges Numerical modeling Smoothed particle hydrodynamics SPH ABSTRACT This paper addresses numerically-derived tsunami wave loads on bridge superstructures using smoothed particle hydrodynamics (SPH), which is a type of mesh-free methods. Although there exist some relationships for the case of impinged loads on bridges exerted by regular (sinusoidal) waves, for the case of solitary waves such as tsunamis, no relation has yet been proposed in the literature. This shortcoming is partly due to the lack of understanding the mechanism of wave action on the bridge superstructures. In this study, three water depths, three wave amplitudes and four submergence depths of the deck are considered for the process of numerical investigation of tsunami-induced loads on bridge superstructures. The bridge elevation is chosen such that its deck may become either completely emerged, partially submerged or completely submerged upon occurrence of the tsunami event. Comparison of the numerical results with the experiment recordings approves high level of accuracy of the SPH scheme. Based on the obtained results from the numerical modeling, the maximum applied horizontal and vertical forces, to the bridge superstructure are presented for each configuration of water depths, wave amplitudes, and deck elevations. In this way, the maximum clockwise/counterclockwise moments induced at the center of the structure are also determined. Simple non-dimensional equations are proposed for computing the tsunami-induced forces and moments to the bridge superstructures, which can be used for designing the bridge superstructures at the coastal areas. 1. Introduction Recent tsunamis in Indonesia (2004), Samoa (2009), Chile (2010), and Japan (2011) have imposed severe damages both on human lives and coastal structures. The 2011 Japan tsunami imposed heavy damages to lands located up to 7 miles from the coast and destroyed over 162,000 buildings, where the direct material damages were estimated around $300 billion [48]. The 1964 earthquake in Alaska, produced the last major tsunami in the United States. Geological records show that the coasts of Washington, Oregon, and California have experienced major tsunami events in the past, with a return period of 450 years [33]. Coastal bridges are major infrastructures that connect different parts of the coastal areas and/or islands together. In addition to the important role of the coastal bridges on local transportation, emer- gency access to the tsunami-hit locations, is provided by these structures. In the 2011 Japan tsunami, more than 300 bridges were destroyed [22]. Two failure modes for coastal bridges can be distinguished during a tsunami event. In the first mode, “a total collapse” happens for the bridge mainly due to failure of the pier-girder system. For the second mode, failure occurs at the deck superstructure only. The multi-span Otsuchi Railroad Bridge, experienced a total collapse (Fig. 1), in which hydrodynamic forces caused either the connection to fail at the girder- pier interface, or the pier to fail by flexure at the ground surface [8]. Study of the three-span Rikuzentakata Bridge, however, showed that its piers and abutments experienced no damage from the tsunami attack (Fig. 2). In this case, the simply-supported bridge deck was moved 40 m upland from the place of substructure [8]. Post tsunami field surveys have shown that even engineered buildings can be severely damaged due to the action of the extreme tsunami-induced hydrodynamic forces [40]. Despite these losses, a comprehensive literature review of the current design codes for bridges indicate that tsunami hydrodynamic forces are hardly taken into consideration [33]. The first design guides regarding tsunamis will likely be included in the 2016 edition of ASCE-7: “Minimum Design Loads for Buildings and Other Structures” [33]. Existing methods for estimating wave loads on the coastal bridges are explained by Douglass et al. [14], McPherson [31] and AASHTO [1]. These methods are suitable as a preliminary design guideline, http://dx.doi.org/10.1016/j.coastaleng.2016.12.005 Received 3 July 2016; Received in revised form 26 November 2016; Accepted 29 December 2016 ⁎ Corresponding author. E-mail addresses: sarfaraz_mohammad@mehr.sharif.edu (M. Sarfaraz), pak@sharif.edu (A. Pak). Coastal Engineering 121 (2017) 145–157 0378-3839/ © 2016 Published by Elsevier B.V. MARK