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Utilization of Existing Blast Analysis Software Packages for the Back-Calculation of Blast Loads
Abstract
Recent increases in the number of terrorist bombings and explosions have led to increased need for postblast investigators. Numerous advances have been made in the area of chemical analysis of explosive residues, but little work has been done to aid postblast investigators in the determination of explosive charge weight using postblast structural damage. This technical note discusses the results of a review of existing blast analysis software packages for their ability to be used as a forensic tool supporting postblast investigations. The recurring limitations of the software found in this review are discussed. It is determined that individually the software packages do not show much promise as such a tool, but that when used concurrently, they may have some value to the postblast investigator. However limited knowledge about the built-in safety factors as well as the ability to specify and modify boundary conditions in the software packages have left the authors to pursue other avenues.
... Despite the significant contributions of the aforementioned research studies and blast models, they are incapable of: (1) efficiently predicting the performance of all feasible blast wall and building material design alternatives due to the significant computational time and effort required by numerical blast assessment models to analyze each possible combination of blast wall type, building material and facility location Sorensen and McGill 2012); (2) quantifying the effectiveness of feasible frangible blast wall types including sand-filled, water-filled, and wood walls in reducing reflected pressure and impulse loading on facilities; and (3) visualizing the anticipated facility damage areas based upon blast charge weight, blast wall type, and building material combinations. To overcome these limitations, this paper presents the development of an innovative model that is capable of efficiently quantifying and visualizing blast effects on facilities behind blast walls of various materials in order to support designers in their critical task of identifying the most effective design for blast walls and facility hardening. ...
Explosive attacks on constructed facilities are a significant threat worldwide, producing devastating consequences including loss of life, property damages, and economic losses. This paper presents the development a blast effects assessment model (BEAM) capable of efficiently quantifying and visualizing blast effects on constructed facilities behind blast walls. The model provides novel and unique capabilities that enable designers to: (1) efficiently predict the blast damage level on facilities for a wide range of feasible design alternatives of blast charge weight, blast wall type, building material, and facility location; (2) quantify the effectiveness of feasible frangible blast wall types in reducing blast loading on facilities; and (3) generate visualizations of the anticipated facility damage areas based upon the blast charge weight, blast wall type, and building material combinations. These distinctive capabilities enable designers to accurately and efficiently evaluate all feasible design alternatives in order to select an optimal design solution that minimizes the risks to site personnel and facilities from the threat of explosive attacks.
Many trials have been made to numerically simulate the Alfred P. Murrah Building bombing event using Finite Element Method. These trials were based on removal of one of the main supporting columns to investigate the generated internal forces and the possible deformations in other elements. However, these trials could not simulate real bomb explosion and automatic detection of the failed columns and floor slabs. Furthermore, the finite element analysis could not continue to model separation of failed elements, collision between structural elements till complete collapse. In this paper, a new technique, Applied Element Method (AEM), is used to simulate the collapse process of the Murrah Building. The bomb weight and location are considered in the simulation. Free-Field blast wave was assumed. The building dimensions, reinforcement and material properties were taken into account. The simulation shows real time analysis of the building performance since the blast occurs, failure of one of the supporting columns, and the failure of the supporting transfer girder till partial collapse of the structure. Two more cases were studied; the bomb was moved to the corner of the building and increasing reinforcement of the transfer girder to check building performance during these events. Results indicate that design firms, engineers, and insurance companies now can judge the safety of existing structures when subjected to extreme loads and to study the safety of proposed structures prior to their construction.
In May 1995, the Federal Emergency Management Agency deployed a building performance assessment team composed of ASCE and federal government engineers to investigate damage caused by the malevolent bombing of the Alfred P. Murrah Federal Building. This paper describes the investigation of damage caused by the blast, the failure mechanism for the building, and engineering details of the building.
The truck bombing of the Murrah Building caused significant damage to this structure. From the characteristics of the bomb crater, it was determined that the explosion yielded energy comparable to that from the detonation of 1,814 kg (4,000 lbs) of trinitrotoluene (TNT). The blast directly removed a principal exterior column, and the associated airblast caused the failure of two others. The airblast also destroyed some of the floor slabs in the immediate vicinity. This paper describes the blast loading and its effect on the building.
A review of existing literature dealing with the behavior of often-used building materials subject to blast loading is presented. Our focus is on the types of structural damage that might be observed at a blast scene, and in particular how this evidence can be used to infer characteristics of the blast (e.g., size and position of the charge). We consider two simple questions: what does damage look like in the wake of a blast for different structural materials (i.e., “what damage is seen?”) and what must the blast pressure have been to cause this damage (i.e., “what does the damage mean?”). This review looks at reinforced concrete, masonry, steel, glass, and timber. We propose the following principle for interpreting observed damage at a blast scene: if damage is present, a limit state was exceeded. The results from this review will be of great interest to post-blast investigators that seek to understand the size and position of a blast.
Utilization of reliability analysis for the back calculation of an explosive load
- A Sorensen
- W Mcgill
Explosives report 1998-2001 detection and characterization of explosives and explosive residue: A review
- E Byall