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High-resolution simulation of blast effects on structural components has become feasible during the last decade because of the availability of high-performance computing hardware and software. These methods utilize computer programs called hydrocodes, such as LS-DYNA (Hallquist 2006) and AUTODYN (ANSYS 2009).loads on reinforced concrete structures and observed that a detailed modeling of rebars is important for the simulation of blast load effects on concrete structures. McDonald (2005) has developed the capability to model linear-shaped charge jet formation and target penetration using the commercially available nonlinear dynamics version of LS-DYNA. Luccioni et al. (2006) has investigated pressures and impulses of blast load to carry out computational dynamic analysis over a congested urban environment that corresponds to the opposite rows of buildings on a block on the same street. Luccioni and Araoz (2011) have presented erosion criteria for frictional materials under blast load. Yi (2009) has carried out an extensive investigation on blast load effects on a three-span reinforced concrete highway bridge and has identified all dominant failure modes during blast loads. Tang and Hao (2010) have performed numerical simulations of dynamic responses of a large cable-stayed bridge under explosive loadings from a 1,000-kg TNT-equivalent explosion at 0.5mfrom the bridge tower and pier and 1.0mabove the deck to investigate the damage mechanism and severity of the damage to the tower, piers, and deck of the bridge. Hao and Tang (2010) have presented numerical simulation results of the four bridge components to blast loads of different scaled distances and have performed progressive collapse analyses of the bridge structure after damage in either one of the four main bridge components has occurred. It has been observed that the failure of vertical load-carrying components leads to catastrophic bridge collapse, whereas an above-deck explosion causes severe instability of the bridge. Williams and Williamson (2012) have proposed a simplified procedure for predicting blast loads acting against bridge columns by focusing on slender structural components in which the effects of cross-sectional geometry, engulfment of blast pressures, and clearing effects strongly influence loading history. Ibarhim et al. (2012) have investigated progressive collapse of posttensioned box girder bridges under blast loads. Pan et al. (2012) have investigated blast load effects on reinforced concrete slab-on-girder girder bridges. They have established the dynamic performance and damage mechanisms of the whole bridge and have identified the critical blast event for this typical slabon-girder bridge.
The objectives of the research presented in this paper are focused on an effective approach for the application of blast loads on structural components, verification of reliability of finite-element models in LSDYNA in simulating blast load effects, and a detailed investigation of the behavior of various bridge components during blast loads. To develop a unified approach for multihazard design, the companion paper (Yi et al. 2013) presents the correlation of failure modes of the bridge under both seismic and blast loads. This information can be used for cost-effective retrofit of structures to resist both seismic and blast loads.
Blast Load Generation Method
Traditionally, blast loads can be generated and applied on structures by the pressure load or detonation simulation methods. In this paper, a new approach, named the hybrid blast load (HBL) method, is proposed, which overcomes the limitations of these two approaches to generate and apply blast loads on structural surfaces. Fig. 1 shows a visual comparison of the three approaches.
Pressure Load Method
The ConWep computer program is based on a collection of conventional weapon effects calculations in TM 5-855-1 [U.S. Dept. Of the Army 1998; Hyde 2005; United States Army Corps of Engineers Engineer Research and Development Center (USACE EDC) 2005]. Krauthammer and Otani (1997) have investigated the effects of blastThe ConWep equations have also been programmed into LS-DYNA to calculate blast pressure magnitudes accurately (Randers-Pehrson