Books by David Cormie
MCEER 14-0006, Oct 30, 2014
The effects of detonations of high explosives are the focus of this report. Analyses are performe... more The effects of detonations of high explosives are the focus of this report. Analyses are performed using computational fluid dynamics (CFD) and finite element codes, theoretical formulations and empirical data.
The effects of detonations of high explosives are characterized in terms of incident and reflected overpressures and impulses. Calculations are performed to verify and validate a CFD code in 1D and 2D; estimate blast effects using 1D models; predict incident overpressures and impulses; provide guidance on the use of reflecting and transmitting boundaries in 2D and 3D models, and provide recommendations on cell size for CFD analysis. The complex wave field in the Mach stem region is studied.
Air-blast parameters, including incident and reflected peak overpressures and impulses, and shock-front arrival times, are typically estimated for protective design using charts developed by Kingery and Bulmash. The charts underpredict incident and normally reflected peak overpressures and incident impulse near the face of the charge. Numerical analyses of detonations of spherical charges of TNT in free air are performed to understand the shortcomings of current approaches and to provide data for the development of new equations and design charts for incident and normally reflected overpressures and impulses and for shock-front arrival time.
Reflection coefficients are often used to transform incident to reflected peak overpressures for varying angles of incidence. Values for the reflection coefficient are available in textbooks and technical manuals but these values vary by document, especially in the region of Mach reflection. Numerical studies are presented to resolve differences between the documents. The corresponding reflected scaled impulses are also evaluated. Recommendations for design practice are provided.
Material erosion is often used for simulations of extreme damage to structural components, and elements are eroded from a finite element mesh based on user-specified criteria. Single element simulations of concrete are performed to establish reliable values of concrete erosion strain as a function of strain rate, compressive strength, element size and loading condition. Numerical simulations of a sample reinforced concrete column subjected to blast loadings are undertaken to demonstrate the utility of the proposed erosion criteria and to characterize, for a single case, the importance of concrete compressive strength, transverse reinforcement, and axial load on estimations of damage.
Blast effects on buildings, 2009
Blast effects on buildings, 2009
Blast effects on buildings, 2009
Blast effects on buildings, 2009
Blast effects on buildings, 2009
Journal papers by David Cormie
International Journal of Protective Structures, 2015
Equivalency is often used to enable calculations of overpressures and impulses for explosives oth... more Equivalency is often used to enable calculations of overpressures and impulses for explosives other than TNT. Equivalent mass factors are available for far field detonations but none are available for near field detonations. These reported factors are associated with incident overpressure and impulse and assumed appropriate for reflected overpressure and impulse. Numerical studies of TNT-equivalent mass factors for four high explosives (PETN, Composition B, Pentolite and Tetryl) for incident and normally reflected peak overpressure and impulse are presented for a wide range of scaled distance 0.06 ≤ Z ≤ 40 m/kg 1/3 . Emphasis is placed on near-field detonations for which no reliable factors are currently available.
Composite Structures, 2015
Several blast trials on laminated glass windows have been performed in the past, using both full ... more Several blast trials on laminated glass windows have been performed in the past, using both full field 3D Digital Image Correlation and strain gauges located on the supporting structure to collect information on the glass pane behaviour. The data obtained during three blast experiments were employed here to calculate reaction forces throughout the perimeter supports both before and after the fracture of the glass layers. The pre-crack experimental data were combined with finite element modelling results to achieve this, whilst solely experimental results were employed for post-cracked reactions. The results for the three blast experiments were compared to identify eventual similarities in their behaviour. It is intended that the results can be used to improve the existing spring-mass systems used for the design of blast resistant windows.
International Journal of Protective Structures
Equivalency is often used to enable calculations of overpressures and impulses for explosives oth... more Equivalency is often used to enable calculations of overpressures and impulses for explosives other than TNT. Equivalent mass factors are available for far field detonations but none are available for near field detonations. These reported factors are associated with incident overpressure and impulse and assumed appropriate for reflected overpressure and impulse. Numerical studies of TNT-equivalent mass factors for four high explosives (PETN, Composition B, Pentolite and Tetryl) for incident and normally reflected peak overpressure and impulse are presented for a wide range of scaled distance 0.06 ≤ Z ≤ 40 m/kg 1/3. Emphasis is placed on near-field detonations for which no reliable factors are currently available.
Journal of Structural Engineering, 2014
Air-blast parameters, including incident and reflected peak overpressures and impulses, and shock... more Air-blast parameters, including incident and reflected peak overpressures and impulses, and shock-front arrival times, are typically estimated for protective design using charts developed by Kingery and Bulmash. The charts underpredict incident and normally reflected peak overpressures and incident impulse near the face of the charge. Numerical analyses of detonations of spherical charges of trinitrotoluene in free air are performed using a verified and validated computational fluid dynamics (CFD) code to understand the shortcomings of current approaches for calculating incident and normally reflected overpressures and impulses, and for shock-front arrival time. New equations and design charts are proposed based on CFD calculations.
Engineering Structures, 2014
The effects of close-in detonations of high explosives are characterized in terms of incident and... more The effects of close-in detonations of high explosives are characterized in terms of incident and reflected overpressures and impulses. Studies are performed using a verified (1D) and validated (2D) CFD code. Calculations are performed to verify the code in 1D, estimate blast effects using 1D models, predict incident overpressures and impulses in the near field, provide guidance on the use of reflecting and transmitting boundaries in 2D and 3D models, provide recommendations on cell size, and predict reflected overpressures on a rigid reflecting surface for close-in detonations. Contact detonations and their effects are not modeled. The complex wave field in the Mach stem region is studied.
Proceedings of the ICE - Engineering and Computational Mechanics, 2013
Proceedings of the ICE - Civil Engineering, 2012
ABSTRACT In recent years high-profile terrorist attacks, industrial accidents and natural disaste... more ABSTRACT In recent years high-profile terrorist attacks, industrial accidents and natural disasters have highlighted the importance of resilient infrastructure. This paper discusses the concepts and considerations associated with designing resilient physical infrastructure: the case for resilience is stated, providing a high-level overview of why it is important, the consequences of its absence and the significance of the concepts of risk and tolerance. To form the basis of design, resilience will be defined, exploring the significance of scale and understanding of the hazards. The challenges faced by the designer will be emphasised and, finally, guidance will be provided on how to incorporate better resilience into infrastructure design.
Journal of Performance of Constructed Facilities, 2013
ABSTRACT This paper investigates the contribution of unreinforced masonry infill panels to the ro... more ABSTRACT This paper investigates the contribution of unreinforced masonry infill panels to the robustness of composite steel framed buildings subject to sudden column loss. A previously developed multilevel robustness assessment approach is extended and used to establish the system pseudostatic capacity, which determines the level of gravity loading that could be sustained under sudden column loss without exceeding the system ductility limit. The infill panels are modeled according to the ultimate failure mode and confinement caused by the frame, where a simplified approach is proposed based on extracting the infill panel contribution in isolation of the surrounding frame. The developed modeling approach is applied to a 7-story building, where it is shown that accounting for infill panels can increase the structural resistance to sudden column loss significantly, thus avoiding disproportionate collapse in most cases.
Conference papers by David Cormie
The modeling of close-in detonations using computational fluid dynamics is common practice in the... more The modeling of close-in detonations using computational fluid dynamics is common practice in the design of civil structures against blast effects; however in the near field little is known about the accuracy of such modeling techniques. Attacks targeting vulnerabilities in structural systems are a recognized modus operandi in the threat, vulnerability and risk assessments for the design of critical infrastructure assets, and consequently the ability to analyse and design against such attacks is clear. The need to accurately quantify the load acting on the structural element is obvious, particularly where the element is critical to the stability of the structural system. However, it is impossible to directly validate the results of CFD analysis for close-in detonations against experimental data because the incident and reflected overpressures are too high to permit direct measurement using pressure transducers.
The protective design of civilian engineering structures requires the prediction of air-blast loa... more The protective design of civilian engineering structures requires the prediction of air-blast loadings. The scaled-distance charts developed by Kingery and Bulmash, as implemented in US government manuals such as UFC 3-340-02, are typically used to estimate values of incident and reflected overpressures and impulses for design. The Kingery-Bulmash charts reasonably predict these design parameters in the far field but not in the near field, close to the face of the charge. This paper derives predictive equations and scaled-distance charts for incident and reflected overpressures and impulses, and arrival time, based on numerical studies of free-air detonations of spherical charges of TNT.
The protective design of civilian structures generally requires the prediction of air-blast loadi... more The protective design of civilian structures generally requires the prediction of air-blast loadings. The scaled-distance charts developed by Kingery and Bulmash, as implemented in US government manuals such as UFC 3-340-02, are typically used to estimate values of incident and reflected overpressures and impulses for protective design. The Kingery-Bulmash charts reasonably predict these design parameters in the far field but not in the near field, close to the face of the charge, and inside the fireball. This paper presents predictive equations and scaled-distance charts for incident and reflected overpressures and impulses, arrival time, and positive phase duration based on numerical studies of free-air detonations of spherical charges of TNT.
Structures Congress 2012, 2012
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Books by David Cormie
The effects of detonations of high explosives are characterized in terms of incident and reflected overpressures and impulses. Calculations are performed to verify and validate a CFD code in 1D and 2D; estimate blast effects using 1D models; predict incident overpressures and impulses; provide guidance on the use of reflecting and transmitting boundaries in 2D and 3D models, and provide recommendations on cell size for CFD analysis. The complex wave field in the Mach stem region is studied.
Air-blast parameters, including incident and reflected peak overpressures and impulses, and shock-front arrival times, are typically estimated for protective design using charts developed by Kingery and Bulmash. The charts underpredict incident and normally reflected peak overpressures and incident impulse near the face of the charge. Numerical analyses of detonations of spherical charges of TNT in free air are performed to understand the shortcomings of current approaches and to provide data for the development of new equations and design charts for incident and normally reflected overpressures and impulses and for shock-front arrival time.
Reflection coefficients are often used to transform incident to reflected peak overpressures for varying angles of incidence. Values for the reflection coefficient are available in textbooks and technical manuals but these values vary by document, especially in the region of Mach reflection. Numerical studies are presented to resolve differences between the documents. The corresponding reflected scaled impulses are also evaluated. Recommendations for design practice are provided.
Material erosion is often used for simulations of extreme damage to structural components, and elements are eroded from a finite element mesh based on user-specified criteria. Single element simulations of concrete are performed to establish reliable values of concrete erosion strain as a function of strain rate, compressive strength, element size and loading condition. Numerical simulations of a sample reinforced concrete column subjected to blast loadings are undertaken to demonstrate the utility of the proposed erosion criteria and to characterize, for a single case, the importance of concrete compressive strength, transverse reinforcement, and axial load on estimations of damage.
Journal papers by David Cormie
Conference papers by David Cormie
The effects of detonations of high explosives are characterized in terms of incident and reflected overpressures and impulses. Calculations are performed to verify and validate a CFD code in 1D and 2D; estimate blast effects using 1D models; predict incident overpressures and impulses; provide guidance on the use of reflecting and transmitting boundaries in 2D and 3D models, and provide recommendations on cell size for CFD analysis. The complex wave field in the Mach stem region is studied.
Air-blast parameters, including incident and reflected peak overpressures and impulses, and shock-front arrival times, are typically estimated for protective design using charts developed by Kingery and Bulmash. The charts underpredict incident and normally reflected peak overpressures and incident impulse near the face of the charge. Numerical analyses of detonations of spherical charges of TNT in free air are performed to understand the shortcomings of current approaches and to provide data for the development of new equations and design charts for incident and normally reflected overpressures and impulses and for shock-front arrival time.
Reflection coefficients are often used to transform incident to reflected peak overpressures for varying angles of incidence. Values for the reflection coefficient are available in textbooks and technical manuals but these values vary by document, especially in the region of Mach reflection. Numerical studies are presented to resolve differences between the documents. The corresponding reflected scaled impulses are also evaluated. Recommendations for design practice are provided.
Material erosion is often used for simulations of extreme damage to structural components, and elements are eroded from a finite element mesh based on user-specified criteria. Single element simulations of concrete are performed to establish reliable values of concrete erosion strain as a function of strain rate, compressive strength, element size and loading condition. Numerical simulations of a sample reinforced concrete column subjected to blast loadings are undertaken to demonstrate the utility of the proposed erosion criteria and to characterize, for a single case, the importance of concrete compressive strength, transverse reinforcement, and axial load on estimations of damage.