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Experimental study on masonry infill walls under blast loading

Pereira, João M.; Campos, José; Lourenço, Paulo B.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em /07/2014 ENG
Relevância na Pesquisa
66.66%
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 was experimentally investigated in this work. Confined underwater blast wave generators (WBWG) allows applying an extremely high rate conversion of the explosive detonation energy into the kinetic energy of a thick water confinement, which, in turn, allows a surface area distribution avoiding the generation of high velocity fragments and reducing atmospheric sound wave. In the present study water plastic containers, having in its centre a detonator inside a cylindrical explosive charge, were used. Tests were performed in unreinforced walls with 1.7 by 3.5 m, which are 1:1.5 scaled. Besides the usage of pressure and displacement transducers, pictures were recorded with high-speed video cameras to process the deflections and identify failure modes.

Masonry infill walls under blast loading using confined underwater blast wave generators (WBWG)

Pereira, João M.; Campos, José; Lourenço, Paulo B.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em /06/2014 ENG
Relevância na Pesquisa
66.75%
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 was experimentally investigated in this work. Using confined underwater blast wave generators (WBWG), applying the extremely high rate conversion of the explosive detonation energy into the kinetic energy of a thick water confinement, allowed a surface area distribution avoiding also the generation of high velocity fragments and reducing atmospheric sound wave. In the present study water plastic containers, having in its centre a detonator inside a cylindrical explosive charge, were used. Studies were performed in both unreinforced and reinforced walls with 1.7 by 3.5 meters. Bed joint reinforcement and grid reinforcement were used to strengthen the infill walls. Besides the usage of pressure and displacement transducers, pictures with high-speed video cameras were recorded to enable processing of the deflections and identification of failure modes. Two different strengthening solutions were studied under blast loading and the results are presented and compared.

Security evaluation and design of structures subjected to blast loading

Pereira, João Miguel
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 27/06/2014 ENG
Relevância na Pesquisa
66.88%
Tese de doutoramento em Engenharia Civil; 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...

A numerical simulation of metallic cylindrical sandwich shells subjected to air blast loading

Jing,Lin; Yang,Fei; Wang,Zhihua; Zhao,Longmao
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2013 EN
Relevância na Pesquisa
66.5%
The dynamic response of cylindrical sandwich shells with aluminum foam cores subjected to air blast loading was investigated numerically in this paper. According to KNR theory, the nonlinear compressibility of the air and finite shock conditions were taken into account in the finite element model. Numerical simulation results show that the compression strain, which plays a key role on energy absorption, increases approximately linearly with normalized impulse, and reduces with increasing relative density or the ratio of face-sheet thickness and core thickness. An increase of the impulse will delay the equalization of top and bottom face-sheet velocities of sandwich shell, but there is a maximum value in the studied bound. A limited study of weight optimization was carried out for sandwich shells with respect to the respective geometric parameters, including face-sheet thickness, core thickness and core relative density. These numerical results are of worth to theoretical prediction and engineering application of cellular metal sandwich structures.

Numerical dynamic analysis of stiffened plates under blast loading

Tavakoli,H.R.; Kiakojouri,F.
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2014 EN
Relevância na Pesquisa
66.62%
Using the general purpose finite element package Abaqus, an investigation has been carried out to examine the dynamic response of steel stiffened plates subjected to uniform blast loading. The main objective of this study is to determine the dynamic response of the stiffened plates considering the effect of stiffener configurations. Several parameters, such as boundary conditions, mesh dependency and strain rate, have been considered in this study. Special emphasis is focused on the evaluation of midpoint displacements and energy of models. The modeling techniques were described in details. The numerical results provide better insight into the effect of stiffener configurations on the nonlinear dynamic response of the stiffened plates subjected to uniform blast loading.

Minimum mesh design criteria for blast wave development and structural response - MMALE method

Trajkovski,Jovan; Kunc,Robert; Perenda,Jasenko; Prebil,Ivan
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
Relevância na Pesquisa
56.64%
The Multi Material Arbitrary Lagrange Euler (MMALE) method is widely used method for numerical investigation of structural response under blast loading. However the method is very demanding for use at the other hand. In this paper are presented the results of the detailed numerical investigation in order to simplify some decisions contributing to the accuracy and efficiency of this model. The influence of mesh properties (particularly mesh size, its biasing and distance of the boundary (DoB) conditions from the deforming structure) on blast wave loading parameters and structural response is investigated in detail and based on the results minimum mesh design criteria is proposed. The results obtained are presented as a function of the scaled distance and additionally related to the radius of the charge. Validation studies were also done successfully.

Continuum modeling of neuronal cell under blast loading

Jérusalem, Antoine; Dao, Ming
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.75%
Traumatic brain injuries have recently been put under the spotlight as one of the most important causes of accidental brain dysfunctions. Significant experimental and modeling efforts are thus ongoing to study the associated biological, mechanical and physical mechanisms. In the field of cell mechanics, progresses are also being made at the experimental and modeling levels to better characterize many of the cell functions such as differentiation, growth, migration and death, among others. The work presented here aims at bridging both efforts by proposing a continuum model of neuronal cell submitted to blast loading. In this approach, cytoplasm, nucleus and membrane (plus cortex) are differentiated in a representative cell geometry, and different material constitutive models are adequately chosen for each one. The material parameters are calibrated against published experimental work of cell nanoindentation at multiple rates. The final cell model is ultimately subjected to blast loading within a complete fluid-structure interaction computational framework. The results are compared to the nanoindentation simulation and the specific effects of the blast wave on the pressure and shear levels at the interfaces are identified. As a conclusion...

Dynamic Response and Optimal Design of Curved Metallic Sandwich Panels under Blast Loading

Qi, Chang; Yang, Shu; Yang, Li-Jun; Han, Shou-Hong; Lu, Zhen-Hua
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.64%
It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA) steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a “soft” outer face and a “hard” inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD) and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA) and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN) metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances.

Numerical simulation of strengthened unreinforced masonry (URM) walls by new retrofitting technologies for blast loading.

Su, Yu
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2009
Relevância na Pesquisa
56.83%
Terrorism has become a serious threat in the world, with bomb attacks carried out both inside and outside buildings. There are already many unreinforced masonry buildings in existence, and some of them are historical buildings. However, they do not perform well under blast loading. Aiming on protecting masonry buildings, retrofitting techniques were developed. Some experimental work on studying the effect of retrofitted URM walls has been done in recent years; however, these tests usually cost a significant amount of time and funds. Because of this, numerical simulation has become a good alternative, and can be used to study the behaviour of masonry structures, and predict the outcomes of experimental tests. This project was carried out to find efficient retrofitting technique under blast loading by developing numerical material models. It was based on experimental research of strengthening URM walls by using retrofitting technologies under out-of-plane loading at the University of Adelaide. The numerical models can be applied to study large-scaled structures under static loading, and the research work is then extended to the field of blast loading. Aiming on deriving efficient material models, homogenization technology was introduced to this research. Fifty cases of numerical analysis on masonry basic cell were conducted to derive equivalent orthotropic material properties. To study the increasing capability in strength and ductility of retrofitted URM walls...

Layered Blast Capacity Analysis of FRP Retrofitted RC Member

Wu, C.; Oehlers, D.; Day, I.
Fonte: Multi-science Publishing Co. Ltd. Publicador: Multi-science Publishing Co. Ltd.
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
56.68%
Fibre reinforced polymer (FRP) retrofitting of RC structures against blast loading is an emerging research area of major significance. Currently, several guidelines are available for the FRP retrofitting of RC structures against monotonic and seismic loads. However, no advice is provided from these guidelines for the retrofit RC structures against blast loading. This paper formulates a layered model that allows for both FRP strengthening and the consideration of strain rate effects on the blast resistant capacity of flexural structural members. The layered model is incorporated into a single degree of freedom model for dynamic analyses and it is validated with blast tests. The validated model is then used in a parametric study which investigates the changes in strength, ductility and energy absorption capacities of flexural FRP strengthened members under blast loads. It is found that the capacity of a flexural member to resist a blast load can be increased greatly with the use of compressive face plating with the ductility of the flexural member being the key factor.; Chengqing Wu, Deric John Oehlers and Ian Day

Analysis of retrofitted RC beam with fixed end supports against blast loads

Wu, C.; Cheng, W.; Oehlers, D.
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
46.77%
Currently, there are adequate guidelines available for FRP retrofitting RC structures against static and seismic loads. However, there is still limited information on retrofitting RC structures against short-duration dynamic loading effects such as blast loading. Due to the increasing threat of terrorism in recent years, retrofitting of RC structures against blast loading is of paramount importance in structural engineering. In this paper, a dynamic model that is based on single-degree-of-freedom (SDOF) approach is developed for the analysis of the response of retrofitted fixed end supported RC slabs subjected to blast loads. A previously validated layered capacity analysis method is used to determine the yielded and ultimate blast resistant capacity of a cross-section of a RC slab which allows varying strain rates with time along the depth of the member. The corresponding deflections are determined by plastic hinge analysis. To simplify the calculation process, a tri-linear resistance-deflection function which consists of elastic, elasto-plastic and plastic region for fixed end supported RC slabs is converted to an equivalent bilinear function. This developed model can adequately predict the retrofitted members’ response to blast loading. It is then is used to conduct a parametric study to optimise the retrofitting of RC slabs subjected to blast loading by varying the quantity...

Characteristics of confined blast loading in unvented structures

Hu, Y.; Wu, C.; Lukaszewicz, M.; Dragos, J.; Ren, J.; Haskett, M.
Fonte: Multi-Science Publishing Co Ltd Publicador: Multi-Science Publishing Co Ltd
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
46.84%
Confined blast loading occurs in many scenarios and the effects of confined blast loading may result in more serious damage to buildings due to multiple shock reflections (Shi et al. 2009). However, spherical charges are assumed for all confined explosive-effects computations in modern standards for blast-resistant design such as UFC-3-340-02 (2008) and the soon-to-be published ASCE Standard for the Blast Protection of Buildings (ASCE forthcoming) without consideration of effects of charge shape on the distribution of reflected overpressure and impulse. As confinement is an aggravation factor of explosion effects, analysis and design of infrastructure under critical scenarios of confined blast loading should take the aggravation factor into consideration. This paper is to develop a numerical model for prediction of blast loads inside unvented structures as a result of variation of the charge shape, charge orientation, geometries and volumes of confined chambers. A finite element program, AUTODYN (Century Dynamics, 2003), is utilized extensively to generate a model which is capable of being calibrated with the experimental results conducted by Wu et al. (2010) in external conditions and by Zyskowski et al. (2004) in a confined small box. The calibrated AUTODYN model is then used to conduct parametric studies to analyze the effects of the variation of charge shape...

Research development on protection of structures against blast loading at University of Adelaide

Wu, C.
Fonte: Institution of Engineers Australia Publicador: Institution of Engineers Australia
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
66.77%
This paper presents a review of research into the protection of structural members against blast loading at The University of Adelaide, including experimental, analytical and numerical studies on characteristics of blast loading, blast resistance of structural members and mitigation of blasts effects on structural members using retrofitting techniques. Explosive blasts are investigated experimentally and numerically to study the distributions of peak overpressure and impulse generated from spherical charges and cylindrical charges with different orientations in unconfined and confined environments. A series of blast tests on reinforced concrete (RC) slabs, ultra-high performance concrete (UHPC) slabs, and aluminium foam protected RC slabs was conducted to investigate the performance of those slabs under blast loads. With the blast testing data numerical models including single degree of freedom model, finite difference model and final element model, have been developed and validated and those numerical models are then used to analyse the blast effects of RC, UHPC and foam protected RC slabs. Investigation of mitigation of blast effects on masonry structures is also addressed.; C Wu

Normalized pressure impulse diagrams for RC members under bilinear blast loading

Wu, C.
Fonte: Universiti Malaya; Malaysia Publicador: Universiti Malaya; Malaysia
Tipo: Conference paper
Publicado em //2012 EN
Relevância na Pesquisa
46.66%
Terrorist bombing attacks in urban environments generate fully-vented or partially-confined blasts and magnify the effects of explosions. The current guidelines such UFC-3-340-2 simplify these blasts in the urban environments as bilinear pressure time history. Thus development of a normalised P-I diagram for the generic assessment of structures to establish safe response limits for bilinear blast loading would contribute significantly to the preliminary design of structures against blasts in the urban environments. In this paper, a previously validated finite difference model, together with the advanced moment rotation model, was used to simulate the response to broad ranges of structural members of given types under by-linear blast loading. Based on the simulated results, a series of PI diagrams were produced. Using the simulated results a normalised P-I diagram was developed for a given type of structural member under bilinear blast loading. Use of the normalized P-I diagram during the design phase of structures would substantially reduce costs by eliminating much of the time and effort involved in the preliminary design and analysis of structural members against bilinear blast-loads.; C. Wu

Numerical modelling of concrete-filled double skin steel tubular/square columns under blast loading

Zhang, F.; Wu, C.; Zhao, X.L.; Li, Z.; Heidarpour, A.; Wang, H.
Fonte: CI-Premier pte ltd; Singapore Publicador: CI-Premier pte ltd; Singapore
Tipo: Conference paper
Publicado em //2013 EN
Relevância na Pesquisa
56.66%
Concrete-filled double skin steel tubes (CFDST) have widely been used in constructing high-rise buildings, arch bridges and factories. Much research has been done to study its behaviour under axial compression. However, limited information can be found on its performance under lateral impact loading, especially under blast loading. In this paper, numerical models are developed for CFDST with two different cross sections: one is with CHS (circular hollow section) outer and CHS (circular hollow section) inner, and the other one is with SHS (square hollow section) outer and SHS (square hollow section) inner. Conventional concrete is filled in double skin steel tubes. Different blast loadings are applied on the surface of these columns for dynamic analysis. In addition, different axial loads are also applied on the columns to simUlate the combined load condition. The displacement-time history obtained from each simulation is recorded and then compared. The key factors that determine the performance of CFDST columns under blast loading are discussed.; http://www.cipremier.com/page.php?671; Fangrui Zhangi, Chengqing Wu, Xiao-Ling Zhao, Zhong-Xian Li, Amin Heidarpour and Hongwei Wang

Prediction of clearing effects in far-field blast loading of finite targets

Tyas, A.; Warren, J.A.; Bennett, T.; Fay, S.
Fonte: Springer Verlag Publicador: Springer Verlag
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
66.66%
It is well known that when a blast wave strikes the face of a target, the duration of the loading, and hence the total impulse imparted to the target may be influenced by the propagation of a rarefaction, or “clearing” wave along the loaded face of the target adjacent to free edges. Simple methods of predicting the effect of clearing on reducing the blast loading impulse have been available for many years, but recent studies have questioned the accuracy and physical basis of these approaches. Consequently, several authors have used numerical modelling and/or experimental techniques to determine empirical predictive methods for the clearing effect. In fact, the problem had been addressed more than 50 years ago in a study which appears to have been since overlooked by the blast research fraternity. This article presents the results of that earlier study, and provides experimental validation. The analytical predictions are very simple to determine, and are shown to be in excellent agreement with experimental results.; A. Tyas, J. A.Warren, T. Bennett, S. Fay

Performance of Tunnel Lining Materials under Internal Blast Loading

CHAKRABORTY Tanusree; LARCHER Martin; GEBBEKEN Norbert
Fonte: Multi-Science Publishing Co. Ltd Publicador: Multi-Science Publishing Co. Ltd
Tipo: Articles in Journals Formato: Printed
ENG
Relevância na Pesquisa
46.7%
Performance of different tunnel lining materials under internal blast loading is compared in the present study through three-dimensional nonlinear finite element analyses. A tunnel in sandy soil has been considered for the analyses. The performance of single layered steel plate, plain concrete (PC) slab, steel fibre reinforced concrete (SFRC) slab, sandwich steel-dytherm foam-steel (SDS) panel and steel-polyurethane foam-steel (SPS) panel linings under blast loading have been examined. For material modelling, Drucker-Prager plasticity for soil, Johnson-Cook plasticity for steel, concrete damaged plasticity for concrete, SFRC and crushable-foam plasticity for foams have been used. Strain rate dependent material parameters have been used for all lining materials and soil. Internal blast loading of 10 kg TNT has been simulated using the pressure-time curve obtained through CFD-calculations. The resulting displacements at soil-lining interface have been evaluated. It is observed that SDS and SPS sandwich panel linings cause much less displacement in the soil under blast loading as compared to the PC and SFRC linings.; JRC.G.5-European laboratory for structural assessment

THE DYNAMIC RESPONSE OF CONCRETE FILLED FRP TUBES SUBJECTED TO BLAST AND IMPACT LOADING

Qasrawi, YAZAN
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
46.85%
Blasts and impacts are two of the severest loads a structure can experience. Blast experimenters, however, have observed that the load imparted to a circular member was lower than the predicted design load. Additionally, numerous investigations have established the superiority of concrete filled FRP tubes (CFFTs) over conventional reinforced concrete members. These observations indicated CFFTs’ potential to resist dynamic blast and impact loads. The experimental and numerical investigations presented in this thesis aimed to demonstrate the suitability of CFFTs to resist blast and impact loads, to determine the parameters that influence their behaviour under such loads, and to develop a design procedure for resisting these loads. The initial numerical investigation determined the reflected blast loading parameters experienced by a circular cross section. The experimental phase consisted of testing twelve full scale specimens, two monotonically, four under impact loading, and six under close-in blast loading. The monotonically tested specimens acted as controls for the entire program. The results of the impact testing investigation were used to develop and validate a non-linear single degree of freedom (SDOF) model. This impact phase also led to the development of relatively simple procedures for designing CFFTs under impact loading using either SDOF modeling or the conservation of energy. Analysis of the blast testing results led to the development of numerical procedures for obtaining an equivalent close-in blast loading for SDOF analysis of CFFTs and Pressure-Impulse diagrams. The use of SDOF modeling and conservation of energy in blast design were also discussed. Finally...

High strain rate constitutive modeling forhistorical structures subjected to blast loading

Rafsanjani, Seyedebrahim Hashemi
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 07/05/2015 ENG
Relevância na Pesquisa
66.89%
Doctoral Thesis Civil Engineering; The work presented here was accomplished at the Department of Civil Engineering of University of Minho. This work involves detailed numerical studies intended to better understand the blast response of masonry structures, develops strain dependent constitutive material plasticity model for masonry, and addresses iso-damage curves for typical masonry infill walls in Portugal under blast with different loading conditions, which can be adopted for practical use in the case of enclosures. A bomb explosion near a building, in addition to a great deal of casualties and losses, can cause serious effects on the building itself, such as noticeable damage on internal and external frames, collapsing walls or shutting down of critical life safety systems. Until Oklahoma City bombing in 1995, studies dealing with the blast behavior of structures were a field of limited interest in the civil engineering community. After this terrorist attack, a great deal of effort has been done to better understand the blast response of the structures and devise solutions to reduce destructive damages and casualties due to such devastative loads. Moreover, the studies on the influence of the high strain rate on mechanical characteristics of construction materials such as steel and concrete have been carried out intensively. Unfortunately...

Blast loading of masonry infills: testing and simulation

Pereira, João Miguel; Campos, José; Lourenço, Paulo B.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em /03/2015 ENG
Relevância na Pesquisa
66.8%
This work intends to present a newly developed test setup for dynamic out-of-plane loading using underWater Blast Wave Generators (WBWG) as loading source. Underwater blasting operations have been, during the last decades, subject of research and development of maritime blasting operations (including torpedo studies), aquarium tests for the measurement of blasting energy of industrial explosives and confined underwater blast wave generators. WBWG allow a wide range for the produced blast impulse and surface area distribution. It also avoids the generation of high velocity fragments and reduces atmospheric sound wave. A first objective of this work is to study the behavior of masonry infill walls subjected to blast loading. Three different masonry walls are to be studied, namely unreinforced masonry infill walls and two different reinforcement solutions. These solutions have been studied previously for seismic action mitigation. Subsequently, the walls will be simulated using an explicit finite element code for validation and parametric studies. Finally, a tool to help designers to make informed decisions on the use of infills under blast loading will be presented.