A large inventory of low rise masonry buildings in Canada and elsewhere in the world were built using unreinforced or partially reinforced load bearing wall. The majority of existing masonry structures is deficient in resisting seismic force demands specified in current building codes. Therefore, they pose significant risk to life safety and economic wellbeing of any major metropolitan centre. Because it is not economically feasible to replace the existing substandard buildings with new and improved structures, seismic retrofitting remains to be an economically viable option. The effectiveness of surface bonded carbon fiber-reinforced polymer (CFRP) sheets in retrofitting low-rise load bearing masonry walls was investigated in the current research project. The retrofit technique included the enhancements in wall capacity in shear and flexure, as well as anchoring the walls to the supporting elements through appropriate anchorage systems. Both FRP fan type anchors and steel sheet anchors were investigated for elastic and inelastic wall response. One partially reinforced masonry (PRM) wall and one unreinforced masonry (URM) wall were built, instrumented and tested under simulated seismic loading to develop the retrofit technique. The walls were retrofitted with CFRP sheets applied only on one side to represent a frequently encountered constraint in practice. FRP fan anchors and stainless steel sheet anchors were used to connect the vertical FRP sheets to the wall foundation. The walls were tested under constant gravity load and incrementally increasing in-plane deformation reversals. The lateral load capacities of both walls were enhanced significantly. The steel sheet anchors also resulted in some ductility. In addition, some small-scale tests were performed to select appropriate anchor materials. It was concluded that ductile stainless steel sheet anchors would be the best option for brittle URM walls. Analytical research was conducted to assess the applicability of truss analogy to retrofitted walls. An analytical model was developed and load displacement relationships were generated for the two walls that were retrofitted. The analytical results were compared with those obtained experimentally, indicating good agreement in force resistance for use as a design tool.

A large inventory of low rise masonry buildings in Canada and elsewhere in the world were built using unreinforced or partially reinforced load bearing wall. The majority of existing masonry structures is deficient in resisting seismic force demands specified in current building codes. Therefore, they pose significant risk to life safety and economic wellbeing of any major metropolitan centre. Because it is not economically feasible to replace the existing substandard buildings with new and improved structures, seismic retrofitting remains to be an economically viable option. The effectiveness of surface bonded carbon fiber-reinforced polymer (CFRP) sheets in retrofitting low-rise load bearing masonry walls was investigated in the current research project. The retrofit technique included the enhancements in wall capacity in shear and flexure, as well as anchoring the walls to the supporting elements through appropriate anchorage systems. Both FRP fan type anchors and steel sheet anchors were investigated for elastic and inelastic wall response. One partially reinforced masonry (PRM) wall and one unreinforced masonry (URM) wall were built, instrumented and tested under simulated seismic loading to develop the retrofit technique. The walls were retrofitted with CFRP sheets applied only on one side to represent a frequently encountered constraint in practice. FRP fan anchors and stainless steel sheet anchors were used to connect the vertical FRP sheets to the wall foundation. The walls were tested under constant gravity load and incrementally increasing in-plane deformation reversals. The lateral load capacities of both walls were enhanced significantly. The steel sheet anchors also resulted in some ductility. In addition, some small-scale tests were performed to select appropriate anchor materials. It was concluded that ductile stainless steel sheet anchors would be the best option for brittle URM walls. Analytical research was conducted to assess the applicability of truss analogy to retrofitted walls. An analytical model was developed and load displacement relationships were generated for the two walls that were retrofitted. The analytical results were compared with those obtained experimentally, indicating good agreement in force resistance for use as a design tool.

Within the past few decades a new technology has emerged using Fiber Reinforced Polymers (FRP) to rehabilitate and retrofit reinforced concrete (RC) structures. In FRP shear strengthening applications it is largely recognized that debonding is the prevailing failure mode. FRP debonding typically occurs prematurely as a brittle failure mode that limits the efficiency of the strengthening technique. No systematic tests have been conducted to investigate the capacity gained by anchoring FRP laminates to RC elements in shear applications. The objective of this research program was to study the effects of anchoring FRP laminates to RC members with FRP anchors thereby delaying or potentially eliminating debonding of FRP sheets from the concrete surface. FRP anchors used in this research were made from fibers used as part of FRP sheets that get bundled into a roll with a fanned upper end of the anchor allowing the fibers to be splayed over the FRP sheet. A single shear pull test experiment was developed to study the effects of anchoring FRP laminates using FRP anchors with varying anchor diameters, lengths, and patterning. The results of the experimental portion of this research project were used in combination with finite element analyses to develop models for anchored FRP sheets that can be used in design of shear strengthening applications.

Over the past three decades the use of externally bonded fiber reinforced polymer (FRP) materials for structural strengthening applications has become an accepted and widely used method. A primary concern of FRP structural strengthening systems is that the FRP often debonds from the concrete well before the load capacity of the FRP material is reached. In addition, debonding failures are often brittle and occur with little warning. Past research concluded that fastening FRP sheets with FRP anchors is an effective method for delaying or preventing debonding failures. However, there is a clear lack of research pertaining to fastening FRP sheets with FRP anchors, and a corresponding lack of design guidance. The primary objective of this research program was to better understand the behavior of bonded FRP sheets that are secured with FRP anchors to aid in future development of design recommendations of this anchorage system. This thesis deals with carbon fiber unidirectional sheets applied using the wet layup system. Design parameters that were investigated include: manufacturer of the FRP materials, unanchored and anchored sheets, number of anchor rows and spacing between rows, number of sheet plies (single or double), and length of bonded sheet behind the anchors. A total of sixteen specimens were tested. Experimental results show that FRP anchorage systems are very effective in increasing load capacity by delaying debonding. Finite element models were also developed of anchored and unanchored bonded FRP sheets.

yes / This paper presents an analytical procedure based on the stiffness matrix method for deflection prediction of concrete structures reinforced with fiber reinforced polymer (FRP) bars. The variation of flexural stiffness of cracked FRP reinforced concrete members has been evaluated using various available models for the effective moment of inertia. A reduced shear stiffness model was also employed to account for the variation of shear stiffness in cracked regions. Comparisons between results obtained from the proposed analytical procedure and experiments of simply and continuously supported FRP reinforced concrete beams show good agreement. Bottom FRP reinforcement at midspan section has a significant effect on the reduction of FRP reinforced concrete beam deflections. The shear deformation effect was found to be more influential in continuous FRP reinforced concrete beams than simply supported beams. The proposed analytical procedure forms the basis for the analysis of concrete frames reinforced with FRP concrete members.

No description available.

Reinforced Concrete (RC) bridge piers, RC columns along exterior of buildings or those located in parking garages are designed to support large compressive axial loads but are vulnerable to transverse out-of-plane loadings, such as those arising from impacts or explosions. To address a lack of understanding regarding blast and impact response of RC members and the need for retrofit techniques to address deficiencies in existing structures, a multi-disciplinary team including various institutes of the National Research Council and the University of Ottawa has initiated work towards developing a fibre reinforced polymer composite protection system for RC columns subjected to extreme shocks. This thesis will focus on the impact program of the aforementioned project. An extensive literature review was conducted to gain a better understanding of: impact loading and associated dynamic effects; experimental testing of RC members subjected to impact; experimental testing of axially loaded members; and retrofit methods for the protection of RC under impact loading. Five half-scale RC columns were constructed and tested using a drop-weight impact machine and two additional specimens were tested under static loading. Deflections, strain distributions within the columns, impact loads and reaction loads were measured during the testing of the built RC members. Comparisons of experimental datum were established between members with differing levels of axial load and between a retrofitted and a non-retrofitted member. Single-degree-of-freedom analysis was used to obtain the predicted response of certain columns under impact loading allowing for comparisons with experimental data.

Applying lateral confinement to concrete columns using fibre-reinforced polymer (FRP) composites is a very promising technique. FRP rupture is the typical failure mode of FRP wrapped columns under axial compression. numerous experiments have shown that the FRP rupture strain in an FRP wrapped circular column is significantly lower than the FRP ultimate rupture strain determined from flat coupon test of FRP. Despite a large number of studies on the application of FRP confined columns, the mechanisms and level of lower-than-apparent FRP rupture strain still remain unclear. This thesis presents theoretical, Numerical and experimental studies aiming at developing a deeper understanding of the fundamental mechanisms of this phenomenon. A comprehensive literature review was presented providing the background on FRP confined columns, material properties of FRP composites as well as some factors which may lead to premature FRP rupture. A FE analysis was conducted to investigate the FRP hoop strains in the split-disk test, explaining for the first time that the fundamental mechanism of the lower FRP rupture strain in the split-disk test than in the flat coupon test is because strain localisation due to geometric discontinuities at the ends of the FRP and bending of the FRP ring at the gap due to change of curvature caused by the relative moment of the two half disks, as the FRP (as a brittle material) ruptures once the maximum strain at one of these locations reaches the FRP rupture strain. A list of contributory factors affecting the apparent FRP rupture strain in FRP wrapped columns were next identified and classified. An analytical solution was developed to investigate the influence of the triaxial stress state on the FRP strain efficiency, this factor has been shown to have a potentially significant effect on the failure of the FRP wrap but considerable discrepancies exist between predictions using different failure criteria so further research has been identified in this area. FE models were developed to examine the effect of the geometrical discontinuities on the strain efficiency of FRP jackets in FRP wrapped concrete-filled circular steel tubes and FRP wrapped concrete columns. It is demonstrated that severe FRP hoop strain concentrations occur in very small zones near the ends of the FRP wrap in both types of FRP wrapped columns, leading to premature FRP rupture and thus lower strain efficiency. The combined effects of end constraint and FRP overlap on the behaviour of FRP wrapped concrete columns was investigated using a three dimensional FE model considering one half of the length of an FRP-wrapped concrete cylinder. The results have shown that the frication between both ends of a column and the loading platens provides constraints to the ends of the column, but this constraint has little effect on the strain concentration caused by the geometrical discontinuities of the FRP overlap, though the ultimate axial strain of the FRP wrapped columns can be significantly overestimated if the end constraints are not considered.

No description available.

Master of Science / Department of Civil Engineering / Hayder A. Rasheed / Fiber reinforced polymer has recently become a popular replacement for steel rebar, used to reinforce concrete. Therefore much research is taking place to help develop and propose methods for best approximating the response of FRP reinforced members, to make them comparable to steel reinforced members. With this popularity comes multiple approaches to FRP deflection calculations. However, this study is significant, because it investigates the cracking moment equation adopted by ACI 318, in conjunction with state of the art deflection calculation methods. Specifically this research compares four deflection calculation methods. The first approach is proposed by Bischoff and implemented by ACI 440 in its latest revision. The second deflection calculation method is proposed by Rasheed et al. The third calculation is also suggested by Bischoff, as it is specific to four point bending. The fourth calculation method is proposed by this specific research and seeks to find a median between both the Bischoff and Rasheed equations. This fourth technique will be referred to as the Rasheed-Jacobs method, proposed to create a more conservative and relevant method for investigating the effect of cracking moment on the deflection calculations. This research was done with the help of Dr. Shawn Gross, and the database he had previously built through his investigation on FRP reinforced beams. Gross’s database shows results for 106 samples tested using the actual experimental cracking moment as well as the ultimate moment capacity values. Of these 106 samples, 56 independent samples were used to investigate three different moment levels of 0.333Mn, 0.400Mn, and 0.467Mn. From this research, Gross’s database was used to calculate the cracking moment of FRP reinforced beams based on ACI 318-08. A program was developed that uses the Gross database samples to calculate the cracking moment and deflection with the Rasheed, Bischoff, and Bischoff2 models as well as the new Rasheed-Jacobs model. This program calculates the Rasheed-Jacobs results, and then graphs the findings against the deflection values from the Rasheed, Bischoff, Bischoff2 models. These graphs showed very similar patterns amongst all four models, with the Rasheed-Jacobs results mainly falling on the more conservative side. However, when looking at the predicted deflection verse the Gross experimental deflection, the best results came from the 0.467Mn moment level, which shows consistent correlation while the lower moment levels are being less predictable using the cracking moment based on the ACI equation. It can reasonably be said that the 0.467Mn shows the best correlation between the four methods and the experimental results, because it is farther away from the actual nominal cracking moment of the FRP reinforced concrete beams.