Behavior of portable fiber reinforced concrete vehicle barriers subject to blasts from contact charges A.M. Coughlin a, * , E.S. Musselman b , A.J. Schokker b , D.G. Linzell c a Hinman Consulting Engineers, One Bush St., Suite 510, San Francisco, CA 94104, United States b Department of Civil Engineering, University of Minnesota at Duluth, 1305 Ordean Court, Duluth, MN 55812, United States c Department of Civil and Environmental Engineering, Protective Technology Center, The Pennsylvania State University, 212 Sackett Building, University Park, PA 16802, United States article info Article history: Received 27 July 2009 Received in revised form 29 August 2009 Accepted 6 November 2009 Available online 3 December 2009 Keywords: Contact charge Blast Concrete barriers Fiber reinforced concrete LS-DYNA abstract Portable concrete barriers are commonly used to form a secure perimeter to prevent entry of terrorist vehicle borne improvised explosive devices (VBIEDs). Barrier effectiveness can be compromised when satchel charges are used to breach a protective perimeter and subsequently permit closer access to the intended target by VBIEDs. The behavior of five portable concrete vehicle barriers was tested under satchel sized contact charge explosives at the Air Force Research Labs (AFRL) test range at Tyndall Air Force Base, Florida. Four barriers representing different fiber reinforced concretes (FRCs) including two types of synthetic FRC, two steel-synthetic blend FRCs with different fiber volumes, and a traditional reinforced normal weight concrete which served as the control specimen. Each of the FRCs exhibited less material loss and surface damage compared to the control. The two steel synthetic blended concretes exhibited the least amount of damage of all barriers, with no visible difference in performance between the two fiber volumes. The control barrier had widespread spalling and limited concrete in the core of the specimen remained intact. A finite element model was created in LS-DYNA to model one FRC barrier and the control barrier to see if the models could predict the observed damage. Both models were deemed successful due to their ability to show similar patterns of damage as the tested barriers. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Modern terrorist threats are constantly evolving and so must the systems used to mitigate them. In many locations impact resistant (‘‘anti-ram’’) barriers are used to create a secure perimeter to prevent vehicle borne improvised explosive devices (VBIEDs) from deto- nating close to their intended targets. Increased standoff distance from a large explosion can prevent many casualties and loss of key assets since the magnitude of a blast decays rapidly as the distance from its center increases [1]. When a suitable anti-ram perimeter is in place, the size of explosive that can be detonated in close prox- imity to targets is limited. In certain cases, however, terrorist tech- niques have focused on first attacking a barrier with a hand carried explosive to breach it and allow a VBIED to detonate closer to the target, where the blast will have a more devastating effect. Though anti-ram perimeters can take a variety of forms, portable massive concrete barriers, such as the ones tested in this study, are commonly used because of their versatility, low cost, and ease of construction. They can be implemented rapidly in high risk locations and rearranged when perimeter protection needs change. Concrete is a common material used for blast resistance due to its high mass per unit cost. However, its brittle nature makes concrete prone to spalling and fragmentation. It is well known that steel reinforcement can give concrete ductile behavior, however blast loads, especially those from close-in charges, can cause both rein- forced and unreinforced areas to fail in a brittle manner. Close-in blasts are less understood than far range blasts and can cause different response in concrete members [2]. Compared to far range blasts, close-in blasts have higher pressures, shorter load durations, and more temperature and gas clearing effects. As the standoff distance from a charge to a concrete panel is decreased, the blast can cause the panel to exceed a spall threshold, where frag- ments are ejected from the back of the panel. An even closer charge can cause the panel to exceed its breach threshold, where the blast is able to perforate the panel. The spall and breach thresholds have been observed empirically and have been shown to be dependent on concrete thickness and strength, but not on reinforcing percentage [2]. The explanation for these close-in effects is the propagation of compression waves causing areas of tensile failure * Corresponding author. Tel.: þ1 415 621 4423; fax: þ1 415 621 4447. E-mail address: andy@hce.com (A.M. Coughlin). Contents lists available at ScienceDirect International Journal of Impact Engineering journal homepage: www.elsevier.com/locate/ijimpeng 0734-743X/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijimpeng.2009.11.004 International Journal of Impact Engineering 37 (2010) 521–529