Publicação
Security evaluation and design of structures subjected to blast loading
| Resumo: | The work presented in this thesis was developed at the Department of Civil Engineering of University of Minho. This work involves experimental and numerical campaigns and intends to give a contribution for a better understanding of the effect of explosions. Blast loading is a subject of much actuality and considerable lack of expertise. Europe has never been so rich and safe, where the violent years of the first half of the 20th century lead to an unprecedented period of peace and stability. Despite the terrorist decades, e.g. connected to ETA and IRA in Europe, the attacks of Madrid (2004), London (2005) and worldwide (New York, Oklahoma, Mumbai) had a major psychological effect in the societies. Clearly, the understanding about the effect of blast loading in structures and their subsystems saves lives and reduces damage in buildings. The Buncefield explosion (2005) resulted in tremendous damage to the outlying area and huge fires involving 23 large oil fuel tanks. Experimental and finite element analyses are carried out for the static and dynamic response of lightweight metal boxes that are similar to the steel junction boxes on the site of this explosion. During the Buncefield Explosion Mechanism Phase I research, the lightweight steel junction boxes on the site located within the area covered by the gas cloud are compared with similar boxes tested under a range of different loading conditions using hydrostatic pressure, gas explosions and high explosive charges. The residual plastic deformations for these boxes are recorded and used to validate a finite element based modelling approach. The predicted pressure-time history is in reasonably good agreement with the measurements. Further parametric studies are then conducted to produce iso-deformation curves which can be used in accident investigations to back track the blast loading from structure deformations. Investigation of the dynamic properties of construction materials is critical for structural engineering. The strain rate effect influences the properties on most constructions materials. This effect on materials such as concrete or steel has been intensively investigated. However, such studies on masonry materials such as clay bricks cannot be found in the open literature easily. Understanding the strain rate effect on masonry materials is important for proper modelling and design of masonry structures under high velocity impacts or blast loads. This work aims to study the behaviour of masonry and its individual components in compression at different strain rates. A Drop Weight Impact Machine is used at different heights and weights introducing different levels of strain rate. The strain rate effect on the compressive strength, Young’s modulus, strain at peak strength and compressive fracture energy is determined from the experimental results. Empirical relations of dynamic increase factors (DIF) for these material properties are also presented. The vulnerability of the masonry envelop under blast loading is considered critical due to the risk of loss of lives. The dynamic behaviour of masonry infill walls subjected to dynamic out-of-plane loading is experimentally investigated in this work. In the present study water plastic containers, having in its centre a detonator inside a cylindrical explosive charge, are used as confined underwater blast wave generators (WBWG). Tests are performed in unreinforced walls with 1.7 by 3.5 m, which are 1:1.5 scaled, and the results presented. These results are used to calibrate numerical models using ABAQUS Explicit dynamics, allowing a detailed study on this kind of masonry panels under dynamic out-of-plane loading in the form of parametric studies. Two different reinforcement solutions are studied in the numerical model and the results are presented. The results are used to create pressure-impulse (P-I) diagrams which can help the designer to estimate the response of these elements under different loading conditions. Protection is not an absolute concept and there is a level of protection where the cost of the protection provided with respect to the cost of potential loss is in balance. On one hand, protection cannot offer full guarantee of safety and, on the other hand, too much protection is a waste of resources with regard to what is expected to be saved. The purpose of protective construction is to improve the probability of survival of people and other contents in a given facility for a given threat, to an adequate level. In order to improve this probability, one must first understand the threat and accordingly analyse the facility. In this work risk assessment is addressed and applied to a large Public Transport Operator. This assessment allows identifying potentially critical infrastructure, which are studied and its structural security is evaluated for different scenarios regarding blast loading. |
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| Autores principais: | Pereira, João Miguel |
| Assunto: | Blast loading Dynamic response FE modelling LS-DYNA Masonry Impact Drop weight Strain rate DIF Infill walls Out-of-plane loading WBWG Risk assessment COUNTERACT Structural security ABAQUS Alvenaria Impacto Torre de queda FID Paredes de enchimento Carregamento fora do plano Avaliação de risco Segurança estrutural Explosões Resposta dinâmica Elementos finitos |
| Ano: | 2014 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | The work presented in this thesis was developed at the Department of Civil Engineering of University of Minho. This work involves experimental and numerical campaigns and intends to give a contribution for a better understanding of the effect of explosions. Blast loading is a subject of much actuality and considerable lack of expertise. Europe has never been so rich and safe, where the violent years of the first half of the 20th century lead to an unprecedented period of peace and stability. Despite the terrorist decades, e.g. connected to ETA and IRA in Europe, the attacks of Madrid (2004), London (2005) and worldwide (New York, Oklahoma, Mumbai) had a major psychological effect in the societies. Clearly, the understanding about the effect of blast loading in structures and their subsystems saves lives and reduces damage in buildings. The Buncefield explosion (2005) resulted in tremendous damage to the outlying area and huge fires involving 23 large oil fuel tanks. Experimental and finite element analyses are carried out for the static and dynamic response of lightweight metal boxes that are similar to the steel junction boxes on the site of this explosion. During the Buncefield Explosion Mechanism Phase I research, the lightweight steel junction boxes on the site located within the area covered by the gas cloud are compared with similar boxes tested under a range of different loading conditions using hydrostatic pressure, gas explosions and high explosive charges. The residual plastic deformations for these boxes are recorded and used to validate a finite element based modelling approach. The predicted pressure-time history is in reasonably good agreement with the measurements. Further parametric studies are then conducted to produce iso-deformation curves which can be used in accident investigations to back track the blast loading from structure deformations. Investigation of the dynamic properties of construction materials is critical for structural engineering. The strain rate effect influences the properties on most constructions materials. This effect on materials such as concrete or steel has been intensively investigated. However, such studies on masonry materials such as clay bricks cannot be found in the open literature easily. Understanding the strain rate effect on masonry materials is important for proper modelling and design of masonry structures under high velocity impacts or blast loads. This work aims to study the behaviour of masonry and its individual components in compression at different strain rates. A Drop Weight Impact Machine is used at different heights and weights introducing different levels of strain rate. The strain rate effect on the compressive strength, Young’s modulus, strain at peak strength and compressive fracture energy is determined from the experimental results. Empirical relations of dynamic increase factors (DIF) for these material properties are also presented. The vulnerability of the masonry envelop under blast loading is considered critical due to the risk of loss of lives. The dynamic behaviour of masonry infill walls subjected to dynamic out-of-plane loading is experimentally investigated in this work. In the present study water plastic containers, having in its centre a detonator inside a cylindrical explosive charge, are used as confined underwater blast wave generators (WBWG). Tests are performed in unreinforced walls with 1.7 by 3.5 m, which are 1:1.5 scaled, and the results presented. These results are used to calibrate numerical models using ABAQUS Explicit dynamics, allowing a detailed study on this kind of masonry panels under dynamic out-of-plane loading in the form of parametric studies. Two different reinforcement solutions are studied in the numerical model and the results are presented. The results are used to create pressure-impulse (P-I) diagrams which can help the designer to estimate the response of these elements under different loading conditions. Protection is not an absolute concept and there is a level of protection where the cost of the protection provided with respect to the cost of potential loss is in balance. On one hand, protection cannot offer full guarantee of safety and, on the other hand, too much protection is a waste of resources with regard to what is expected to be saved. The purpose of protective construction is to improve the probability of survival of people and other contents in a given facility for a given threat, to an adequate level. In order to improve this probability, one must first understand the threat and accordingly analyse the facility. In this work risk assessment is addressed and applied to a large Public Transport Operator. This assessment allows identifying potentially critical infrastructure, which are studied and its structural security is evaluated for different scenarios regarding blast loading. |
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