Numerical Study of Blast Load Acting on Typical Precast Segmental Reinforced Concrete Piers in Near-Field Explosions

Experimental and numerical investigation of charge shape effect on blast load induced by near-field explosions

Many buildings located in industrial and petrochemical facilities require protection from accidental external explosions. Due to the difference in basic characteristics of the two loading types, design of these buildings to resist external explosions or blast loading poses significant challenges when the facility is located in in a region with high seismicity. Seismic loads are cyclic, inertial loads with long durations, whereas blast loads are short duration impulse loads. Seismic loads are defined by ground acceleration response spectra while blast loads are specified by blast overpressures and durations. In blast-resistant design, building owners determine hazard return periods and acceptable performance and damage levels based on risk evaluation of personnel safety and property loss. Current seismic code provisions have been developed with the intent of achieving performance through prevention of building collapse and protection of life safety. Next-generation, performance-based seismic design will be based on performance and damage levels similar to those used in blast resistant building design. For purposes of demonstrating an optimized design process for both seismic and blast loading using performance-based design philosophy, this paper presents a blast-resistant design of a reinforced concrete building in a petrochemical facility located in a region with high seismicity. Selection of effective structural systems, performance levels, acceptable damage levels, structural modeling, structural analysis methods and ductile design and detailing of structural components are discussed in this paper.

Blast-resistant design approach for RC bridge piers

Experimental investigation of polymer gravel slab under air contact and near-field explosions

Blast resistant and anti-terrorism design is essential in order to save the civil infrastructure and human lives. In the design of structures, a consideration for energy absorbing capabilities to resist the effects of blast loading or other severe dynamic loads it is vital, and structural provision of elements with large plastic deformation capacities is desirable. Structures need to be designed for ductile response in order to prevent partial or total collapse due to locally failed elements. The work in this paper considers theoretical studies to resist the structure against blast loading to understand the basic concept of explosion phenomena, parameters of blast loading, and different types of blast waves. The analysis focuses on the estimation of blast loading on structures and their response to explosions. Design of blast resistant structures requires thorough understanding of the structural dynamics, behaviour of materials under high strain rate of loading, and blast analysis. This paper concludes with an explanation of findings by different researchers using different country codes to simplify the design process for calculating blast load. Keywords: Blast Resistant Design, Blast Load, Explosion, ETABS.

Corrosion characteristics of tapered sleeve locking-type splicing reinforcement in precast segmental bridge piers

Numerical simulations of blast loads and structural deformation from near-field explosions in air

Structural reliability analyses are commonly applied to estimation of probabilities of structural damage to static and dynamic loads such as earthquake, wind and wave loads. Although blast loadings acting on structures from accidental explosions or hostile bombings are very difficult to be accurately predicted owing to many uncertain parameters that influence explosion shock wave propagation and shock wave interaction with structures, reliability analyses of structural failure to blast loadings with consideration of uncertainties in blast loading and structural parameters are very limited. Instead, a large safety factor is usually used to account for uncertain variations in blast loading and structural parameters in blast-resistant design and analysis. This may lead to an inaccurate design of structures to resist blast loads, and an inaccurate assessment of structure performance in a given explosion scenario. In this study, reliability analyses of three example RC columns to randomly varying blast loads are carried out. The column dimensions, reinforcement ratios and material strengths are assumed to be normally distributed with the respective design parameters as the mean values. The mean value and standard deviation of the peak reflected pressure and duration of the blast load at various scaled distances are derived from available empirical formulae, and are used in this study to model the blast pressure variations. Failure probabilities of the example RC columns subjected to blast loads of different scaled distances are estimated. Numerical results are compared with those obtained with the deterministic blast loading or deterministic column property assumptions. The importance of considering the random variations of structural properties and blast loadings in assessing the blast load effects on RC columns is discussed.

Residual axial capacity of seismically designed RC bridge pier after near-range explosion of vehicle bombs

This paper covers the development of the design blast loads for buildings in petroleum refineries and petrochemical plants as reported by the ASCE Task Committee on Blast Resistant Design. It briefly discusses the overall design process for such buildings and the considerations and methods for predicting the blast loading from vapor cloud explosions. The main focus is on determining the building component loads once the incident blast overpressure is defined.

Post-tensioned box girder bridges are considered one of the most structurally efficient bridge systems and are widely used in the U.S. This study investigates numerical results of progressive collapse for post-tensioned box girder bridges under blast loads. Limited data is published on this topic; however there is available literature on the analysis of the progressive collapse of cable-stayed bridges under blast loads. Accidental detonations are assumed to take place under the bridge deck. Numerical simulation is conducted using the Applied Element Method implemented in Extreme Loading for Structures software. The numerical model of the bridge structure and simulation results of the main bridge components, piers, and main span deck are investigated. The parameter studied was in terms of the weight of the explosion at two different locations simulating a large vehicle bomb (LVB) placed underneath the bridge. The progressive collapse analyses of the bridge structure after damage in either one of the two main bridge components are investigated. Damage mechanism and severity in the bridge pier, and deck are examined. Numerical results presented in this study could help departments of transportation and engineers and owners of similar bridges to determine appropriate measures for bridge protection against possible explosion threats.

SHCC-strengthened RC panels under near-field explosions

Explosion effects on structures have been an area of active research over the past decades. This is due to the increasing number of terrorists’ action against infrastructures. Although significant amount of work is continuing on the effects of explosions on infrastructures, experimental work involving live explosion testing is limited. Moreover, experimental testing of reinforced concrete (RC) columns subjected to near-field explosions is scant. This paper presents results of an experimental program designed to investigate the effects of near-field explosions on RC columns with different tie spacing and at different scaled distances. The results show that the response of columns is strongly dependent on scaled distance. As the scaled distance increased the severity of damage reduced; seismic columns showed better response. The effect of axial loading was also observed to increase the level of damage on reinforced concrete columns at the axial load level and blast loads considered in the test program.

Damage assessment of normal reinforced concrete panels strengthened with polyurea after explosion

Recently, polyurea has been applied to improve the anti-blast performance of metal plates, masonry walls, and concrete structures. However, the strengthening effectiveness of polyurea on ultra-high performance concrete (UHPC) slabs with an overall response is still unclear. Hence, this paper examined the strengthening effectiveness of polyurea on the anti-blast performance of UHPC slabs under near-field explosion by the finite element (FE) method. First, a benchmark finite element model for UHPC and polyurea-UHPC (PUHPC) slabs under blast loading was established and validated by field blast tests, with scaled distances ranging from 0.4 m/kg1/3 to 0.8 m/kg1/3. After that, parametric analysis was conducted to fully understand the strengthening effectiveness of polyurea on the anti-blast performance of the UHPC slab. Factors including the scaled distance, polyurea thickness, span-to-depth ratio of the slab, and longitudinal reinforcement ratio were considered. The results showed that (1) spraying polyurea on the rear face of the UHPC slab can reduce the width of cracks and mitigate the damage of specimens; (2) the strengthening effectiveness of polyurea on the UHPC slab became prominent when the UHPC slab suffered a larger maximum deflection; (3) in terms of the deflection and energy absorption capacity of PUHPC slabs, the optimum thickness of sprayed polyurea was determined to be 8 mm to 12 mm; and (4) by adopting the multiple nonlinear regression method, a prediction formula was developed to quickly obtain the end rotation of the UHPC slab strengthened with polyurea under near-field explosions.