Rehabilitation of Masonry Walls Using Unobtrusive FRP Techniques for Enhanced Out-of-plane Seismic Resistance [microform] PDF Download
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Author: Yasser Korany
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780494042465
Category : Buildings
Languages : en
Pages : 341
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Book Description
The implementation of these techniques could have a significant economic impact in addition to the cultural and social impacts of conservation of the architectural heritage. Since the developed techniques are applicable to existing masonry buildings in general, it is anticipated that they will contribute to the Canadian economy through upgrading existing masonry buildings and extending their service life.
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Author: Yasser Korany
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780494042465
Category : Buildings
Languages : en
Pages : 341
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Book Description
The implementation of these techniques could have a significant economic impact in addition to the cultural and social impacts of conservation of the architectural heritage. Since the developed techniques are applicable to existing masonry buildings in general, it is anticipated that they will contribute to the Canadian economy through upgrading existing masonry buildings and extending their service life.
Author: Ji Yang
Publisher:
ISBN:
Category : Brick walls
Languages : en
Pages : 207
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Book Description
Author: Hyunchul Jung
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
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.
Author: Zuhair Al-Jaberi
Publisher:
ISBN:
Category :
Languages : en
Pages : 264
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Book Description
"A number of researchers have conducted experimental tests on unreinforced masonry walls (URM) strengthened with advanced composite materials. Consequently, the strengthening design guidelines are limited in their scope to URM. This research aimed to investigate the behavior of reinforced masonry walls strengthened with advanced composite and subjected to out-of-plane pseudo-static cyclic load. Experimental and analytical studies were conducted to evaluate the performance of different techniques such as near surface mounted (NSM) and externally bonded (EB) fiber reinforced polymer (FRP) with epoxy resin, in addition to NSM with cementitious adhesive and fiber reinforced cementitious material (FRCM). The experimental part included three phases. In the first phase, a series of 42 reinforced masonry walls were tested to study the effectiveness of advanced composites in enhancing out-of-plane flexural capacity. The effect of long-term environmental exposure on strengthening systems was investigated in the second phase of study by testing 10 reinforced masonry walls. The third phase focused on bond behavior between the advanced composite and the concrete masonry unit at different temperatures; 56 specimens were used for this purpose. The results indicated that the non-arching strengthened reinforced masonry wall's behavior was significantly dependent on the type of fiber and fiber reinforcement ratio. The specimens strengthened with glass under combined environmental cycles exhibited an insignificant change in terms of ultimate strength as compared to laboratory conditioned specimens. The theoretical part included the investigation of bond reduction factors, seismic performance, and the nonlinear analysis of strengthened reinforced masonry wall using moment-curvature analysis. As a result of this study, the proposed model for predicting debonding strain and the moment-curvature relation presented an excellent prediction compared to the experimental results"--Abstract, page iv.
Author: Jeremy Keith Wallace
Publisher:
ISBN:
Category :
Languages : en
Pages : 314
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Book Description
During recent years, near surface mounted (NSM) fiber reinforced polymer (FRP) bars have displayed exceptional results when used to retrofit un-reinforced masonry walls for flexural out-of-plane strengthening. This process involves cutting a shallow groove into the masonry wall, which is less than the thickness of the face shell. FRP bars are then placed into the groove and embedded in an epoxy paste, which transfers stresses from the masonry wall to the reinforcing bar. Although this retrofitting technique is advantageous for most structural applications, the nature of the bar location introduces an inherent restriction. By locating the bar at a depth no greater than the thickness of the face shell, the flexural strength is only increased in one direction. This limitation introduced an opportunity to develop a novel approach to flexural out-of-plane strengthening of masonry walls for cyclic loading, which was the overall objective of this research project. The retrofitting technique is similar to that of NSM rods; but the FRP bars are placed at the centerline of the wall analogous to traditional steel rebars for two directional reinforcing. Test results confirmed that FRP bars can be used to drastically increase flexural capacity of masonry walls subjected to cyclic loading, while remaining practical and beneficial in terms of field construction. Standard working stress equations were also used to conservatively predict the structural responses of the masonry walls within 9 to 15.8 percent.
Author: Robert A. Crist
Publisher:
ISBN:
Category : Building
Languages : en
Pages : 380
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 197
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Book Description
Unreinforced masonry bearing and shear walls common in the Tennessee Valley Authority's (TVA's) switch-house structures have been found to be vulnerable to earthquakes. One technique to reduce the seismic vulnerability of these structures is to retrofit the masonry walls using the Hexcel-Fyfe TYFO(TM) system. This system consists of a glass fiber fabric combined with special epoxies to create a high strength, lightweight structural laminate. Hexcel-Fyfe TYFO(TM) can be designed to work in conjunction with existing walls to increase both the in-plane and out-of-plane seismic strength of the unreinforced masonry walls. To ensure that this technique will perform its intended purpose, the U.S. Army Construction Engineering Research Laboratories (USACERL) and TVA conducted seismic analysis and shake-table seismic testing using USACERL's Triaxial Earthquake and Shock Simulator. The results of seismic testing documented in this report show that applying the overlay material to one side of the unreinforced masonry wall will enhance its seismic resistance.
Author: Yi-Wei Lin
Publisher:
ISBN:
Category : Brick walls
Languages : en
Pages : 279
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Book Description
This doctoral study investigated the use of Engineered Cementitious Composite (ECC) shotcrete, a sprayable fibre reinforced mortar that exhibits a strain-hardening characteristic, for the seismic strengthening of unreinforced masonry structures. Additionally, the feasibility of utilising ECC shotcrete as a chloride resistant cover concrete to improve the service life of reinforced concrete structures was examined. A series of laboratory tests quantified the ECC shotcrete tensile characteristic properties using a new technique, with the results adopted for the structural analysis and design of ECC strengthened walls. Subsequent laboratory testing defined the chloride diffusion coefficients of multiple ECC mix designs, indicating that increased fly ash content significantly improved the chloride resistance. Life cycle modelling showed that assuming an uncracked state throughout the structure service life, replacement of the investigated 40 MPa concrete with the best performing ECC shotcrete mix for steel reinforcement cover could provide a service life extension of up to 42 years. Testing of 25 clay brick wallettes subjected to in-plane loading showed that ECC application increased wall capacity by up to 5.1 times their as-built state. Masonry wall thickness and ECC overlay thickness were the key parameters affecting strengthened clay brick wall performance. Testing of 26 concrete block masonry wallettes determined the effect of ECC applicator skill and application method on wall performance, with strength reduction factors introduced to account for this effect. Using the experimental results, an in-plane masonry wall strengthening design procedure was proposed. Testing of five ECC strengthened clay brick masonry walls subjected to out-of-plane loading showed a 12.7 times strength increase when ECC overlay was applied to the wall tensile surface and a strength increase of 3.4 times when ECC overlay and near surface mounted steel reinforcement was applied to the wall compression surface. Strengthened wall capacity was predicted using existing concrete flexural design methodologies, and design procedures for out-of-plane strengthening of clay brick masonry walls were proposed. An ECC shotcrete based seismic strengthening design was developed for a 1917 two-storey in-service unreinforced masonry building utilising the material properties and design methodologies defined in this doctoral study. No significant application issues were identified during the implementation process, and the current results support the use of ECC as a seismic strengthening system for masonry buildings.
Author: Wojciech Mierzejewski
Publisher:
ISBN:
Category :
Languages : en
Pages : 232
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Book Description
Masonry walls subjected to out-of-plane loading, such as in a seismic event, require reinforcement to improve the ductility of the system. In current masonry construction practice, reinforcement is placed internally and fully grouted. For new construction this can make the wall unjustifiably heavy by not taking advantage of its light, hollow structure. For existing construction, it is difficult to retrofit using this technique. Additionally, the reinforcement is located close to the neutral axis which reduces its effectiveness. Fiber-Reinforced Polymer (FRP) bars, strips and sheets are becoming increasingly popular in construction applications due to their noncorrosive nature and ease of installation. Also, stainless steel bars are used where the structure is exposed to a corrosive environment but have not found wider application for masonry structures. This study is an experimental investigation of the structural performance of masonry walls reinforced with Near-Surface-Mounted (NSM) FRP and stainless steel reinforcement under out-of-plane bending. Additionally, walls with Externally Bonded (EB) FRP sheets were tested. The study simulates retrofitting applications and also proposes the NSM technique for new wall construction, using pre-grooved blocks, in lieu of the conventional method of internal reinforcing and grouting. To accommodate the NSM reinforcement, the grooves in the masonry blocks were aligned with ducts used to anchor the NSM reinforcement in the concrete footing. Seven wall specimens were tested, including walls reinforced with conventional and stainless steel bars, glass-fibre reinforced polymer (GFRP), and carbon-FRP (CFRP) reinforcement. The study demonstrated the feasibility and effectiveness of the NSM technique for new construction. Walls with NSM reinforcement showed a superior performance to those with EB reinforcement. It was shown that increasing the FRP reinforcement ratio may result in a change of failure mode, and as such, the increase in strength may not be proportional to the increase in reinforcement ratio. NSM steel-reinforced walls showed a superior performance in terms of strength, stiffness and the ductility associated with the formation of a plastic hinge at the base.
Author: George G. Penelis
Publisher: CRC Press
ISBN: 0429659334
Category : Architecture
Languages : en
Pages : 350
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Book Description
Historic structures need to be restored in line with international guidance and charters developed by architects and archaeologists, but technical understanding of structural engineering and materials is crucial, particularly with respect to response to earthquake loading. This guide to structural assessment and restoration of masonry monuments and historical buildings outlines the techniques, materials and design procedures used. It begins with principles, theory and practice and then presents case studies. The assessment focusses on Building materials and construction techniques used in the past The mechanics of masonry The structural behaviour of masonry monuments and historical buildings In-situ investigation and laboratory tests for existing and restoration materials. The restoration elaborates on Techniques and materials available for structural restoration Structural analysis and design Deciding on the restoration scheme Emergency measures and protective measures.
