Download or read book Concrete Masonry Unit Walls Retrofitted with Elastomeric Systems for Blast Loads written by and published by . This book was released on 2004 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concrete masonry units (CMU), commonly referred to as concrete blocks, are the most common construction material utilized throughout the United States and the world for exterior walls of conventional structures. While masonry provides adequate strength for conventional design loads, it does not meet the minimum design standards mandated for blast protection of new and renovated government facilities. One of the most dangerous aspects of blast response is debris hazard, defined as high-velocity fragments originating from walls, windows, light fixtures, equipment, and furniture. Retrofits for conventional structures have evolved over the years from blast hardening through the addition of mass using concrete or steel, to the application of lighter, more resilient and ductile materials. Research at ERDC has focused on the use of elastomeric materials to mitigate debris hazards resulting from blast events. A series of sub-scale and full-scale experiments was conducted by ERDC to investigate the potential benefit of elastomeric retrofit systems when applied to hollow, unreinforced, CMU walls subjected to an explosive event. This study discusses both the 1/4-scale static and dynamic experiments and the full-scale dynamic CMU wall experiments conducted over the past few years. The CMU wall response to static loading was characterized by resistance functions, and normalized pressure and impulse diagrams were used to characterize the dynamic loading.
Download or read book Concrete Masonry Wall Retrofit Systems for Blast Protection written by Carol Faye Johnson and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The increased threat against government and public facilities in the United States and abroad has highlighted the need to provide an economic and efficient method to retrofit existing conventional structures. Hollow, unreinforced, concrete masonry unit (CMU) infill walls, commonly used in reinforced concrete or steel framed structures, are particularly vulnerable to blast loads. Facilities that incorporate CMU walls must either be hardened or retrofitted for explosive events. Conventional retrofit techniques that focus on increasing the overall strength of the structure by adding steel or concrete are difficult to implement, time consuming, expensive, and in some cases, increase the debris hazard. The current research presents an alternative retrofit system for CMU walls that involves the application of an elastomeric material applied to the interior surface of the wall to prevent secondary debris in the form of CMU fragments from entering the structure when it is exposed to blast loads. The experimental program used to evaluate the alternative retrofit systems was divided into three phases. In Phase one, resistance functions for seven different retrofit systems were developed in 24 subscale static experiments. In Phase two, the structural response of the retrofit systems subjected to blast loads was evaluated in 25 subscale experiments. The final phase of the experimental program consisted of 18 full-scale high-explosive (HE) experiments used to validate the structural response observed in the subscale dynamic experiments. Data generated from the experimental program were used to develop a single-degree-of-freedom (SDOF) model to predict the mid-span deflection of the retrofitted CMU walls subjected to blast loads. The subscale resistance functions from Phase one were scaled and used in the SDOF model. The full-scale experimental results and the predicted results from the model were compared and the retrofit systems were ranked according to the qualitative and quantitative results obtained from the experimental and analytical research. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151905
Download or read book Blast Retrofit of Unreinforced Masonry Walls Using ECC Shotcrete written by Jordan Gandia and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Blast loads on buildings can originate from accidental explosions or from targeted attacks. Design against blast loads has become an increasingly important topic due to the current political climate. Unfortunately, many older buildings are constructed with unreinforced masonry (URM) walls which are particularly susceptible to out of plane failures caused by blast loads. One solution to increase the safety of these buildings is to retrofit them with advanced materials that can increase their out-of-plane stiffness and resistance. This thesis investigates the potential of using a high-performance shotcrete as a retrofit system for URM walls against blast effects. The shotcrete used in this study is made from Engineered Cementitious Composite (ECC), a special type of fiber-reinforced cementitious material, with high ductility and high energy-absorption capacity. The ECC shotcrete replaces aggregates with synthetic microfibers to increase tensile strength and ductility. A welded wire mesh was embedded in the shotcrete to provide ductile behavior. The testing program includes a total of six large-scale unreinforced masonry wall specimens. Two walls were constructed using concrete masonry unit (CMU) blocks to be retrofitted. The first specimen was built as an infill wall, experiencing no axial load, while the second specimen was built as a load bearing wall, with 10% axial load. Four more walls were built out of stone blocks. Two of the stone walls were controls: one infill and one load bearing (4% axial load). The other two stone walls were retrofit with the shotcrete system: one infill and one load bearing (4% axial load). The blast loads were simulated using the University of Ottawa's Shock Tube. The walls were restrained at the top and bottom with a shear restraint to induce one way bending. Pressure, displacement and strain data were acquired with the use of pressure gauges, LVDT's, strain gauges and cameras. The specimens were subjected to gradually increasing blast pressures until failure. The performance of the specimens was observed by analyzing the displacement, crack widths, fragmentation and failure mode. The results indicate the benefits of using ECC shotcrete as a retrofit system. The displacements of the retrofit walls were very small compared to the control walls, and fragments were limited. The specimens with axial load were found to have increased resistance. While the failure mode was brittle for the retrofit walls, this can be avoided with the use of a mesh with a larger area of steel. A SDOF analysis was performed to predict the blast response of the test walls. The analysis was done by generating resistance functions for the walls through analytical models. The analysis was found to agree reasonably well with the experimental data.
Download or read book Handbook for Blast Resistant Design of Buildings written by Donald O. Dusenberry and published by John Wiley & Sons. This book was released on 2010-01-26 with total page 513 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unique single reference supports functional and cost-efficient designs of blast resistant buildings Now there's a single reference to which architects, designers, and engineers can turn for guidance on all the key elements of the design of blast resistant buildings that satisfy the new ASCE Standard for Blast Protection of Buildings as well as other ASCE, ACI, and AISC codes. The Handbook for Blast Resistant Design of Buildings features contributions from some of the most knowledgeable and experienced consultants and researchers in blast resistant design. This handbook is organized into four parts: Part 1, Design Considerations, sets forth basic principles, examining general considerations in the design process; risk analysis and reduction; criteria for acceptable performance; materials performance under the extraordinary blast environment; and performance verification for technologies and solution methodologies. Part 2, Blast Phenomena and Loading, describes the explosion environment, loading functions needed for blast response analysis, and fragmentation and associated methods for effects analysis. Part 3, System Analysis and Design, explains the analysis and design considerations for structural, building envelope, component space, site perimeter, and building system designs. Part 4, Blast Resistant Detailing, addresses the use of concrete, steel, and masonry in new designs as well as retrofitting existing structures. As the demand for blast resistant buildings continues to grow, readers can turn to the Handbook for Blast Resistant Design of Buildings, a unique single source of information, to support competent, functional, and cost-efficient designs.
Download or read book Resistance of Membrane Retrofit Masonry Walls to Lateral Pressure written by Lee Moradi and published by LAP Lambert Academic Publishing. This book was released on 2009-05-18 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mitigation techniques are currently being sought to ensure public safety in the event of intentional or accidental explosions. Building material fragmentation is a major cause of human injury during such events. One of the most common methods of construction in buildings is the use of masonry walls however; these walls are extremely vulnerable to blast pressure resulting in collapse, fragmentation, and severe injury to occupants. Blast tests and computational finite element models have shown significant improvement in the behavior of these walls when retrofitted with polymer or metallic membranes. But the cost of blast tests and high fidelity computational models make them impractical for day-to-day design. The research presented in this book developed resistance functions for three different scenarios of membrane retrofit unreinforced concrete masonry walls to lateral pressure. These functions were further coupled with single degree of freedom systems to predict the wall response to blast loads. This book provides a practical tool for the design of membrane retrofit masonry walls exposed to lateral pressures such as wind and blast.
Download or read book Advances in Civil Engineering Structural Seismic Resistance Monitoring and Detection written by Mohd Johari Mohd Yusof and published by CRC Press. This book was released on 2022-10-21 with total page 787 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Civil Engineering: Structural Seismic Resistance, Monitoring and Detection is a collection of papers resulting from the conference on Structural Seismic Resistance, Monitoring and Detection (SSRMD 2022), Harbin, China, 21–23 January, 2022. According to the development of many new seismic theories, technologies and products, the primary goal of this conference is to promote research and developmental activities in structural seismic resistance, monitoring and detection. Moreover, another goal is to promote scientific information interchange between scholars from the top universities, business associations, research centers and high-tech enterprises working all around the world. The conference conducted in-depth exchanges and discussions on relevant topics such as structural seismic resistance, monitoring and detection, aiming to provide an academic and technical communication platform for scholars and engineers engaged in scientific research and engineering practice in the field of civil engineering, seismic resistance and engineering entity structure testing. By sharing the research status of scientific research achievements and cutting-edge technologies, it helps scholars and engineers all over the world to comprehend the academic development trend and broaden research ideas. So as to strengthen international academic research, academic topics exchange and discussion, and promoting the industrialization cooperation of academic achievements.
Download or read book Incorporating Sustainable Practice in Mechanics and Structures of Materials written by Sam Fragomeni and published by CRC Press. This book was released on 2010-11-18 with total page 956 pages. Available in PDF, EPUB and Kindle. Book excerpt: Incorporating Sustainable Practice in Mechanics of Structures and Materials is a collection of peer-reviewed papers presented at the 21st Australasian Conference on the Mechanics of Structures and Materials (ACMSM21, Victoria, University, Melbourne, Australia, 7th 10th of December 2010). The contributions from academics, researchers and practisin
Download or read book Performance of Polyurea Retrofitted Unreinforced Concrete Masonry Walls Under Blast Loading written by Laura Ciornei and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Unreinforced masonry walls subjected to blast loading are vulnerable to collapse and fragmentation. The objective of this thesis is to conduct experimental and analytical research for developing a blast retrofit methodology that utilizes polyurea. A total of four unreinforced masonry walls were constructed and tested under various shock tube induced blast pressures at the University of Ottawa Shock Tube Testing Facility. Two of the retrofitted walls had surface-sprayed polyurea. The results indicate that the use of polyurea effectively controlled fragmentation while significantly increased the load capacity and stiffness of masonry walls. Polyurea proved to be an excellent retrofit material for dissipating blast induced energy by providing ductility to the system and changing the failure mode from brittle to ductile. Single degree of freedom (SDOF) dynamic analyses were conducted as part of the analytical investigation. The results show that the analytical model provides reasonably accurate predictions of the specimen response.
Download or read book Blast Retrofit of Unreinforced Masonry Walls Using Fabric Reinforced Cementitious Matrix FRCM Composites written by Hyunchul Jung and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Unreinforced masonry (URM) walls are commonly found in existing and heritage buildings in Canada, either as infill or load-bearing walls. Such walls are vulnerable to sudden and brittle failure under blast loads due to their insufficient out-of-plane strength. The failure of such walls under blast pressures can also result in fragmentation and wall debris which can injure building occupants. Over the years, researchers have conducted experimental tests to evaluate the structural behaviour of unreinforced masonry walls under out-of-plane loading. Various strengthening methods have been proposed, including the use of concrete overlays, polyurea coatings and advanced fiber-reinforced polymer (FRP) composites. Fabric-reinforced cementitious matrix (FRCM) is an emerging material which can also be used to strengthen and remove the deficiencies in unreinforced masonry walls. This composite material consists of a sequence of one or multiple layers of cement-based mortar reinforced with an open mesh of dry fibers (fabric). This thesis presents an experimental and analytical study which investigates the effectiveness of using FRCM composites to improve the out-of-plane resistance of URM walls when subjected to blast loading. As part of the experimental program, two large-scale URM masonry walls were constructed and strengthened with the 3-plies of unidirectional carbon FRCM retrofit. The specimens included one infill concrete masonry (CMU) wall, and one load-bearing stone wall. The University of Ottawa Shock Tube was used to test the walls under gradually increasing blast pressures until failure, and the results were compared to those of control (un-retrofitted) walls tested in previous research. Overall, the FRCM strengthening method was found to be a promising retrofit technique to increase the blast resistance of unreinforced masonry walls. In particular, the retrofit was effective in increasing the out-of-plane strength, stiffness and ultimate blast capacity of the walls, while delaying brittle failure and reducing fragmentation. As part of the analytical research, Single Degree of Freedom (SDOF) analysis was performed to predict the blast behaviour of the stone load-bearing retrofit wall. This was done by computing wall flexural strength using Plane Section Analysis, and developing an idealized resistance curve for use in the SDOF analysis. Overall, the dynamic analysis results were found to be in reasonable agreement with the experimental maximum displacements.
Download or read book Blast Simulator Wall Tests written by Michael G. Oesterle and published by . This book was released on 2009 with total page 655 pages. Available in PDF, EPUB and Kindle. Book excerpt: Loads generated in explosions that result from terrorist attacks and industrial accidents create devastating hazards for buildings and their occupants. The objective of this dissertation is to develop design guidelines and methodologies for protective/hardening strategies used to mitigate blast hazards in reinforced concrete and concrete masonry walls. Commonly, guidelines and methodologies are developed from experimental data. Field testing with live explosive is a reliable experimental method for demonstrating the performance of blast resistant concepts, but it is expensive, time consuming, and often produces low quality data. Static testing is another experimental method that allows researchers to clearly observe behavior and failure modes of structural components; however this too is limited because it cannot account for the rate effects associated with blast loads. The UCSD Blast Simulator was developed to offers an alternative method for testing structures to loads generated in an explosion without the difficulties and limitations associated with field and static testing. For this dissertation, tests were conducted with the blast simulator to study reinforced concrete walls protected with frangible panels, concrete masonry walls strengthened with carbon fiber reinforced polymer composite, and unreinforced masonry walls retrofitted with polyurea catcher systems. The objective of the dissertation was achieved through a succession of tasks that included; the development of a test protocol, validation and implementation of numerical models to predict loads delivered to specimens during blast simulator tests, development of method to correlate blast simulator loads to air blast loads, generation of high quality data on specimens with mitigation strategies for validation of numerical models to predict response of hardened/protected reinforced concrete and concrete masonry walls, and investigation of design variables with parametric studies. The investigation of concrete masonry walls demonstrated that the addition of carbon fiber reinforced polymers can increase the resistance to blast loads, but may result in a brittle failure mode. The study of reinforced concrete walls showed that frangible panels can improve the response by adding mass to the system. Finally, the research performed on unreinforced masonry walls with polyurea catcher emphasized the need for proper connection detailing.
Download or read book Evolution of Elastomeric Retrofits for Concrete Masonry Unit Walls for Enhanced Blast Resistance at the Engineer Research and Development Center written by Carol F. Johnson and published by . This book was released on 2011 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Boundary Connection Behavior and Connection Design for Retrofitted Unreinforced Masonry Walls Subjected to Blast Loads Preprint written by and published by . This book was released on 2010 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past decade, extensive experimental and analytical research has been conducted on the behavior and resistance of unreinforced masonry (URM) walls retrofitted with methods for increasing ductility. This includes numerous experiments conducted by the Airbase Technologies Division of the Air Force Research Laboratory (AFRL). These retrofit materials varied from soft elastomeric coatings to very stiff composites and metal sheets. Some retrofit materials were strongly bonded to the masonry wall, which resulted in an integrated system response, while others were not bonded to the masonry and the membrane simply acted as a barrier that prevented secondary fragmentation from entering the occupied space. Previous research programs by AFRL and others have focused on the development of the retrofit materials, with the predominant exploratory measure focusing on the maximum inward transverse displacement. However, little emphasis was placed on the real behavior of the boundaries of these systems and the proper and efficient design of connections. This paper discusses an appropriate analytical methodology for the design of retrofit connections to resist impulse loads due to blast. In addition, typical support conditions for URM walls, and the shear, flexure and friction interaction of blast-impulse-loaded retrofitted URM walls at their support boundaries are discussed. The ideas and conclusions presented herein are based on component-level static testing, full scale explosion arena testing, and high fidelity finite element modeling.
Download or read book Concrete Solutions 2014 written by Michael Grantham and published by CRC Press. This book was released on 2014-08-18 with total page 838 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Concrete Solutions series of International Conferences on Concrete Repair began in 2003 with a conference held in St. Malo, France in association with INSA Rennes. Subsequent conferences have seen us partnering with the University of Padua in 2009 and with TU Dresden in 2011. This conference is being held for the first time in the UK, in association with Queen’s University Belfast and brings together delegates from 36 countries to discuss the latest advances and technologies in concrete repair. Earlier conferences were dominated by electrochemical repair, but there has been an interesting shift to more unusual methods, such as bacterial repair of concrete plus an increased focus on service life design aspects and modelling, with debate and discussion on the best techniques and the validity of existing methods. Repair of heritage structures is also growing in importance and a number of the papers have focused on the importance of getting this right, so that we may preserve our rich cultural heritage of historic structures. This book is an essential reference work for those working in the concrete repair field, from Engineers to Architects and from Students to Clients.
Download or read book Evaluation of Elastomeric Polymers for Retrofit of Unreinforced Masonry Walls Subjected to Blast written by James D. Connell and published by . This book was released on 2002 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Simulation of Strengthened Unreinforced Masonry URM Walls by New Retrofitting Technologies for Blast Loading written by Yu Su and published by . This book was released on 2008 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: "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. To study the increasing capability in strength and ductility of retrofitted URM walls, pull-tests were simulated using interface element model to investigate the bond-slip relationship of FRP plates bonded to masonry blocks. The interface element model was then used to simulate performance of retrofitted URM walls under static loads. The accuracy of the numerical results was verified by comparing with the experimental results from previous tests at the University of Adelaide by Griffith et al. (2007) on unreinforced masonry walls and by Yang (2007) on FRP retrofitted masonry walls. To study the de-bonding behaviours of retrofits bonded to masonry, and find appropriate solution to protect certain masonry walls against blast loading, various retrofitting technologies were examined. The simulation covers explosive impacts of a wide range of impulses. Based on this work, pressure-impulse diagrams for different types of retrofitted URM walls were developed as a design guideline for estimating the blast effect on retrofitted masonry walls." -- From abstract.
Download or read book Experimental Evaluation and Modeling of Concrete Masonry Unit Walls written by Brittany Anne Bell and published by . This book was released on 2011 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many military and government buildings in the US and abroad use frame structures with infill wall systems. Conventionally constructed infill wall systems do not exhibit the blast resistance necessary. To develop blast design guidelines for Concrete Masonry Unit (CMU) wall systems, it is necessary to develop analytical models for the static resistance function of these walls that are verified using the results of full-scale physical experiments. The existing analytical models currently used for blast design of CMU walls underestimate the static resistance of the walls. Improvements in the prediction models for the resistance functions are necessary and could lead to improvements in the dynamic prediction tools. Ultimately this may result in improved accuracy and cost reduction of the blast design. The objective of this thesis is to develop an analytical model to predict the static resistance function for typical CMU wall systems and verify analytical resistance with data from full-scale physical experiments. Six full-scale CMU walls were tested using a vacuum chamber and their pressure-deflection response was recorded until failure. The walls were fully- or partially- grouted and constructed with various materials. An analytical model was developed to predict the static resistance function of the CMU walls. Depending on wall type and desired blast response the analytical model predictions were within 5-30% of experimental wall behavior.
Download or read book 1991 Census written by Statistics Canada and published by . This book was released on 198? with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
