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IDENTIFYING OPTIMAL CONCRETE STRENGTH FOR
VARYING LEVELS OF BLAST LOADING
Tarek H. Kewaisy
Principal Associate | Louis Berger
1250 23rd St., NW, Washington, DC, 20037, USA
ABSTRACT
This paper reports on the findings of a comprehensive study that involved various numerical
simulations of blast-loaded Reinforced Concrete (RC) slabs of different strength classes. The study
investigated response characteristics associated with the application of bilinear shock loading of
varying intensity and energy levels to one-way RC slabs of various material strengths and
boundary conditions. Three strength classes of RC concrete were investigated; Normal Strength
(5,000 psi concrete and 60,000 psi rebar), Medium Strength (10,000 psi concrete and 75,000 psi
rebar), and High Strength (15,000 psi concrete and 100,000 psi rebar). Nine shock loading profiles
were considered by pairing various levels of peak pressure (30 psi for Low, 45 psi for Medium, 60
psi for High) and duration (10 ms for Short, 20 ms for Medium, 40 ms for Long). Two numerical
techniques were implemented to simulate strain-rate effects, materials nonlinearities, and damage
patterns and extents typically encountered in blast applications: Single Degree Of Freedom- SDOF
using RCBlast program and Finite Element Analysis- FEA using LS-DYNA Software. Primary
simulation parameters for various RC slab configurations were calibrated using response
measurements obtained from testing. The blast testing program was funded by the National
Science Foundation (NSF), administered by the University of Missouri – Kansas City (UMKC)
and completed at the Blast Loading Simulator (BLS) of the Engineering Research and
Development Center (ERDC) at Vicksburg, MS. The effects of considering different strength
classes of concrete and reinforcement on the blast response of RC slabs were evaluated. Valuable
insights were obtained, and useful conclusions were drawn regarding the appropriateness of use of
various material strengths to achieve optimized and enhanced performance of RC slabs subjected
to varying levels of blast loading.
INTRODUCTION
In recent years, the design of blast-resistant structures has expanded beyond the boundaries of
military and industrial applications into civilian realms including infrastructure, government,
public and private buildings. This was primarily driven by the need to protect these assets against
the ever growing threat of terrorist attacks using high explosives as the weapon of choice to impart
the maximum damage to these prominent targets. The economic impacts of considering such a
severe threat combined with the technical engineering challenges to prevent civilian facilities from
becoming fortification-like structures have generated strong incentives and considerable
motivation among business owners and construction professionals to minimize the impact of blast-
resistant design requirements through optimization. Reinforced Concrete (RC) has been the
primary construction material for blast hardening for decades, therefore understanding its blast
behavior and performance through testing and simulation techniques has been identified as the
most important aspect of an optimum blast-resistant design. The accelerated advancements in
computing have made numerical simulation techniques (both simplified and advanced) the
preferred approaches of: modeling explosives detonation phenomena, identifying blast effects, and
