International Concrete Abstracts Portal

This CD-ROM contains 15 papers that were presented at sessions sponsored by ACI Committees 447 and 370 at the ACI Fall 2010 Convention in Pittsburgh, PA. In this publication, engineers report on how they are approaching the challenging task of predicting the response of structures subjected to blast and impact loading. Both experimental and analytical efforts are represented, often in tandem. The analytical approaches taken include single-degree-of-freedom modeling, highly nonlinear transient dynamic finite element simulations, and coupled Lagrangian-Eulerian simulations. Papers in the publication cover the design and evaluation of new and existing structures, as well as techniques for strengthening existing structures. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-281

Since its initial publication in 1969, Unified Facilities Criteria (UFC) 3-340-02 (formerly Army Technical Manual 5-1300/Navy Publication NAVFAC-P397/Air Force Manual AFR 88-22) has provided uniquely practical and intuitively straightforward procedures for analyzing and designing blast resistant structures. With its unlimited distribution, UFC 340-02 is the blast design manual of choice of both government explosives safety experts and private A-E firms throughout the world. This paper summarizes updates to the blast design guidance in chapter 4, reinforced concrete design. Detailed data are presented on the revisions in three areas: dynamic increase factor, design of diagonal tension reinforcement in walls and slabs, and prediction of concrete spall and breach. The paper concludes with a brief discussion of future work.

Fiber reinforced concrete (FRC) is known to exhibit superior performance in its post-peak energy absorption capacity, (i.e., toughness) under flexural and tensile loading. However, the behavior of fiber reinforced concrete under compressive impact has not previously been investigated. In the present research, the strain rate response of fiber reinforced concrete under compressive impact was investigated over the full strain rate regime, from static loading to high strain rate loading, and finally to impact loading. FRC was found to have higher strengths under compressive impact loading than under static loading. The compressive toughness under impact loading increased due to the high peak load and the high strain capacity. FRC displays a much higher Dynamic Improvement Factor (DIF) under compressive impact and provides an overall higher performance under impact than under static loading. Finally, the existing CEB model for dynamic behavior of concrete was evaluated and a new constitutive model, the RCM modelis proposed to describe the DIF of the compressive strength of FRC. The model was found to match the test results for FRC at 50 MPa, 90 MPa, and 110 MPa (7250, 10,150 and 13,000 psi) at strain rate from 10-5 1/sec to the strain rate of 10 1/sec.

Carbon fiber anchors can serve to improve the performance of externally applied CFRP (Carbon Fiber Reinforced Polymer) strengthened concrete structures because they do not rely on the bond of the CFRP to the concrete to transfer stresses. This paper seeks to identify the residual strength of externally applied CFRP after damage has been delivered by an instrumented drop-weight impact testing device. The paper further investigates effectiveness of carbon fiber anchors (anchors inserted into predrilled holes and fanned out over the CFRP sheet) in impact damaged specimens. The paper reports the results from 14 impact damaged CFRP strengthened 1.42 m (56 in.) long beams with and without anchors. The research found that impacts from the testing device with a drop height greater than 1.83 m (6 ft) significantly reduced the tensile strength of the CFRP. However, with the use of anchors the same strength can be reached in a damaged CFRP specimen as in an undamaged unanchored specimen. The paper also reports on the effectiveness of the anchors when used to strengthen a reinforced concrete slabs subjected to blast loads and a reinforced concrete beam under impact loading and finds that the anchors are able to fully develop the tensile strength of the CFRP under dynamic loading.

This research investigated the performance of full scale reinforced concrete and hybrid barrier systems coated with plain or discrete fiber-reinforced polyurea during blast testing. The testing was conducted at the Air Force Research Laboratory (AFRL) test range at Tyndall Air Force Base in Florida. This study builds on previous work investigating concrete hybrid construction performance during reduced scale panel blast testing (Tinsley and Myers 2007), reduced scale projectile impact testing (Carey and Myers 2009), and prior vehicle barrier blast testing (Coughlin 2008). Six barriers were constructed and tested to evaluate the performance of conventional and hybrid systems including the use of polyurea coating technology to minimize overall structural damage and debris scatter. The addition of a polyurea coating improved barrier performance and decreased the mass lost after detonation. The addition of E-glass fibers to the elastomeric polyurea coating was evaluated as well, but it was found that it did not enhance the performance of the polyurea coating system significantly. After detonation, all the barriers maintained their integrity sufficiently to prevent vehicle breach through the barrier chain.