Thesis (M.S. in civil engineering)--Washington State University, May 2010. / Title from PDF title page (viewed on July 14, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 72-73).

Thesis (Ph.D.)--Drexel University, 2009. / Includes abstract and vita. Includes bibliographical references (leaves 363-370).

Thesis (M.S. in civil engineering)--Washington State University, December 2005. / Includes bibliographical references.

The most common form of dwellings in rural and semi-urban areas of India and other developing countries around the globe are one/two storey unreinforced masonry (URM) buildings. It is well known that such masonry buildings are most vulnerable during earthquakes. Out-of-plane flexural failures of walls are primarily responsible for collapse of URM buildings during an earthquake. The seismic performance of such buildings can be improved by reinforcing masonry walls in the horizontal and vertical directions with materials like steel, bamboo or fiber reinforced polymers (FRP). It is fairly easy to reinforce masonry in the horizontal direction by embedding the reinforcement in the bed joints of masonry construction. However, in the vertical direction, the reinforcement is generally provided in the cavities of hollow masonry units, which are grouted after placing the reinforcement. Even though the in-plane performance of masonry walls is enhanced with such a reinforcing technique, it still falls short in resisting out-of-plane lateral loads, as the vertical reinforcement is located close to neutral axis of bending. Hence, a novel technique of reinforcing masonry in the vertical direction on both the faces of the wall called containment reinforcement is proposed recently. Containment reinforcement improves ductility, energy dissipation and prevents overturning failure due to out-of-plane loading. The present study examines the role of containment reinforcement in improving out-of-plane / in-plane behavior of masonry. The research program consisted of characterizing the physical properties of the constituent materials of reinforced masonry, namely stabilized earth blocks, cement-soil-sand (1:1:6) mortar and steel and FRP reinforcement. The strength and elastic properties of masonry assemblages under compression, flexure and shear have been determined. The flexural behavior of three types of reinforced masonry assemblages namely; stretcher bond, English bond and rat-trap bond masonry beams under monotonic and reversed cyclic loading test protocols have been examined. The beams were reinforced with steel, Glass FRP (GFRP) and Carbon FRP (CFRP) materials. In the monotonic test protocol the moment-curvature relationships and ductility for each type of masonry beams were obtained. In the cyclic test protocols, the hysteretic behavior, energy dissipation and equivalent viscous damping characteristics were obtained. The shear behavior of unreinforced and reinforced masonry panels under diagonal tension (shear) was examined through monotonic and cyclic loading test protocols. A simple and cost effective device for producing horizontal to and fro motion to imitate earthquake ground motions, called shock table test facility, has been designed. The table platform is mounted on four wheels and moves on rails. The table is put into the motion through pendulum impacts. The table motion characteristics have been obtained using the parameters used to describe the earthquake ground motions like amplitude, frequency content, duration of the motion and mixed parameters. The parameters of the shock table motion have been compared with few of the recorded earthquake ground motions to evaluate the effectiveness of shock table testing protocol for examining the dynamic performance of scaled masonry building models. The performance of two half scaled containment reinforced masonry building models subjected to base motions provided through shock table and conventional shaking table was evaluated. The dynamic properties of masonry, responses and failure patterns were obtained. A non-linear finite element (FE) model was developed and calibrated using the experimental data generated in the flexural and shear testing of reinforced and unreinforced masonry beams and panels. The FE model was further used for analysis of half scale masonry building model tested on shock table and recalibrated by comparing responses of numerical model with experimentally measured responses. Furthermore, the finite element model was used to assess the performance of two storey unreinforced and containment reinforced symmetric/asymmetric masonry buildings subjected to a series of earthquake ground motions of increasing severity. The studies conducted conclude that the masonry with containment reinforcement was effective in mitigating seismic risks of masonry buildings in moderate to severe seismic regions. The provision of containment reinforcement significantly improved equivalent hysteretic damping at design displacement and offered excellent ductility to masonry elements. The existing construction practice can easily accommodate the provision of containment reinforcement with little modification to the construction sequence. The extra effort in construction does commensurate with the enhancement in the seismic performance of the masonry buildings.

An experimental program was performed for qualitative and quantitative comparison of the maximum tensile resistance of contact and non-contact lap spliced bars in reinforced concrete block masonry using double pullout and wall splice specimens. A total of 32 specimens were tested, consisting of an equal number of double pullout specimens and full-scale wall splice specimens. Both specimen types had the identical cross-section. Eight replicate specimens for each specimen type were constructed with both contact and non-contact lap splice arrangements. Grade 400 deformed reinforcing bars with a 300 mm lap splice length were provided in all specimens. The double pullout specimens were tested applying direct tension to the lapped reinforcing bars. The splice resistance and displacement were recorded during testing. All double pullout specimens with contact lap splices developed, as a minimum, the yield strength of the reinforcing bars and generally displayed evidence of a yield plateau. In contrast, the double pullout specimens with non-contact lap splices failed when only 46.1% of the theoretical yield strength of the reinforcing bars was recorded as the maximum splice resistance. The difference between the average value of the tensile resistance in the contact and non-contact spliced bars was identified as being statistically significant at the 95% confidence level. Wall splice specimens were tested under a four-point loading arrangement with the lapped bars located in the constant moment region. The applied load and specimen deflection were recorded until failure occurred. A numerical analysis was then performed to calculate the maximum resistance of the spliced bars. The specimens with contact lap splices developed the theoretical yield capacity of the reinforcing bars. In contrast, the wall splice specimens with non-contact lap splices developed an average tensile resistance of 78% of the theoretical yield capacity. The difference between the average tensile resistances of the lapped bars in the two splice arrangements was identified as being statistically significant at the 95% confidence level. On average, the contact and non-contact lap spliced bars in the double pullout specimens developed 8.47% and 41.2% less tensile resistance, respectively, as compared to the wall splice specimens with the identical splice arrangement. Both differences were identified as being statistically significant at the 95% confidence level. Bond loss between the reinforcing bars and the surrounding grout was identified as the failure mode for both the double pullout and wall splice specimens with contact lap splices. In contrast, bond loss at the masonry block/grout interface was observed along the non-contact lapped bars in both specimen types, as identified by visual observations upon removal of the face shell and the surrounding grout. Based on the test results of the wall splice specimens with non-contact lap splices, a correction factor of 1.5 is suggested when calculating the effective splice length for the non-contact splice arrangement as tested.

An experimental program was performed for qualitative and quantitative comparison of the maximum tensile resistance of contact and non-contact lap spliced bars in reinforced concrete block masonry using double pullout and wall splice specimens. A total of 32 specimens were tested, consisting of an equal number of double pullout specimens and full-scale wall splice specimens. Both specimen types had the identical cross-section. Eight replicate specimens for each specimen type were constructed with both contact and non-contact lap splice arrangements. Grade 400 deformed reinforcing bars with a 300 mm lap splice length were provided in all specimens. The double pullout specimens were tested applying direct tension to the lapped reinforcing bars. The splice resistance and displacement were recorded during testing. All double pullout specimens with contact lap splices developed, as a minimum, the yield strength of the reinforcing bars and generally displayed evidence of a yield plateau. In contrast, the double pullout specimens with non-contact lap splices failed when only 46.1% of the theoretical yield strength of the reinforcing bars was recorded as the maximum splice resistance. The difference between the average value of the tensile resistance in the contact and non-contact spliced bars was identified as being statistically significant at the 95% confidence level. Wall splice specimens were tested under a four-point loading arrangement with the lapped bars located in the constant moment region. The applied load and specimen deflection were recorded until failure occurred. A numerical analysis was then performed to calculate the maximum resistance of the spliced bars. The specimens with contact lap splices developed the theoretical yield capacity of the reinforcing bars. In contrast, the wall splice specimens with non-contact lap splices developed an average tensile resistance of 78% of the theoretical yield capacity. The difference between the average tensile resistances of the lapped bars in the two splice arrangements was identified as being statistically significant at the 95% confidence level. On average, the contact and non-contact lap spliced bars in the double pullout specimens developed 8.47% and 41.2% less tensile resistance, respectively, as compared to the wall splice specimens with the identical splice arrangement. Both differences were identified as being statistically significant at the 95% confidence level. Bond loss between the reinforcing bars and the surrounding grout was identified as the failure mode for both the double pullout and wall splice specimens with contact lap splices. In contrast, bond loss at the masonry block/grout interface was observed along the non-contact lapped bars in both specimen types, as identified by visual observations upon removal of the face shell and the surrounding grout. Based on the test results of the wall splice specimens with non-contact lap splices, a correction factor of 1.5 is suggested when calculating the effective splice length for the non-contact splice arrangement as tested.

Thesis (M.S.)--University of Alabama at Birmingham, 2004. / Printout. Includes bibliographical references (leaves 264-266). Also available online.

The structural damage after the Christchurch earthquake (2011) led to extensively damaged facilities that did not collapse but did require demolition, representing more than 70% of the building stock in the central business district. These severe economic losses that result from conventional seismic design clearly show the importance of moving towards resilience-based design approaches of structures. For instance, special reinforced masonry shear walls (SRMWs), which are fixed-base walls, are typically designed to dissipate energy through the yielding of bonded reinforcement while special detailing is maintained to fulfill ductility requirements. This comes at the expense of accepting residual drifts and permanent damage in potential plastic hinge zones. This design process hinders the overall resilience of such walls because of the costs and time associated with the loss of operation and service shutdown. In controlled rocking systems, an elastic gap opening mechanism (i.e., rocking joint) replaces the typical yielding of the main reinforcement in conventional fixed-base walls, hence reducing wall lateral stiffness without excessive yielding damage. Consequently, controlled rocking wall systems with limited damage and self-centering behavior under the control of unbonded post-tensioning (PT) are considered favorable for modern resilient cities because of the costs associated with service shutdown (i.e., for structural repairs or replacement) are minimized. However, the difficulty of PT implementation during construction is challenging in practical masonry applications. In addition, PT losses due to PT yielding and early strength degradation of masonry reduce the self-centering ability of controlled rocking masonry walls with unbonded post-tensioning (PT-CRMWs). Such challenges demonstrate the importance of considering an alternative source of self-centering. In this regard, the current study initially evaluates the seismic performance of PT-CRMWs compared to SRMWs. Next, a new controlled rocking system for masonry walls is proposed, namely Energy Dissipation-Controlled Rocking Masonry Walls (ED-CRMWs), which are designed to self-center through vertical gravity loads only, without the use of PT tendons. To control the rocking response, supplemental energy dissipation (ED) devices are included. This proposed system is evaluated experimentally in two phases. In Phase I of the experimental program, the focus is to ensure that the intended behavior of ED-CRMWs is achieved. This is followed by design guidance, validated through collapse risk analysis of a series of 20 ED-CRMW archetypes. Finally, Phase II of the experimental program evaluates a more resilient ED-CRMW is evaluated, which incorporates a readily replaceable externally mounted flexural arm ED device. Design guidance is also provided for ED-CRMWs incorporating such devices. / Thesis / Doctor of Philosophy (PhD)

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Title from PDF title page (viewed Feb. 4, 2010). Additional advisors: James S. Davidson, Robert J. Dinan, Alan E. Eberhardt, Jason T. Kirby, Talat Salama, Houssam A. Toutanji. Includes bibliographical references (p. 139-146).

Emendas por traspasse são criadas pela justaposição de barras de aço em um determinado comprimento, assegurando que elas se manterão em posição. Assim como em outros sistemas estruturais, a alvenaria estrutural de blocos de concreto utiliza barras de aço como reforço dos elementos quanto à resistência à tração, mais proeminentes em edifícios altos devido à ação dos ventos. As armaduras são projetadas para serem alocados no interior dos blocos, e a prática construtiva no Brasil é posicionar as armaduras de aço antes dos blocos serem assentados. Devido à essa prática, as paredes precisam ser construídas em pelo menos duas etapas, para considerar a altura limite imposta pela armadura posicionada ao operário na elevação dos blocos. Para aumentar a eficiência na elevação das paredes de alvenaria, hélices circulares são propostas como componentes de confinamento do graute que envolve a emenda, permitindo a elevação da parede em etapa única. A armadura é colocada dentro da seção transversal da espiral após a parede de alvenaria ser completamente elevada. O objetivo desta investigação é avaliar a eficiência da emenda por traspasse, com hélice circular atuando como componente do confinamento do graute que envolve a emenda. Quatro configurações de emenda distintas foram ensaiadas: a primeira, referência, foi justaposta e amarrada com arame; a segunda foi espaçada, porém sem a presença de um componente de confinamento; a terceira foi espaçada e continha uma hélice circular com passo de 3,5 cm; e a quarta foi espaçada e continha uma hélice circular com passo de 8,0 cm. Os ensaios permitiram concluir que a hélice de traspasse é um componente eficiente no confinamento das emendas por traspasse em alvenaria estrutural de blocos de concreto. Análises estatísticas dos resultados demonstram que emendas por a emenda com hélice circular de 3,5 cm não só é equivalente à emenda por referência do ponto de vista da resistência à tração, como também contribui para a redução de fissuras. / Lap slices are created by the overlapping of reinforcement bars over a specified length and reassuring that they stay in place. As with other structural systems, concrete block masonry uses reinforcing steel to carry the tensile loads which are more prominent on tall buildings due to the effect of wind. Reinforcing bars are designed to be placed inside block cells. The construction practice in Brazil is to place the reinforcing steel before the block units are laid. With this practice, walls need to be built in at least two lifts to account for the height limits imposed by the mason having to lift each block over the reinforcing bars. To increase the efficiency of wall construction, spirals are proposed as confinement components of the grout surrounding the lap splices, allowing a single-lift wall construction. The vertical reinforcement is then placed inside the cross-section of the spiral after the laying of blocks is complete. The objective of this investigation is to evaluate the efficiency of lap splices with spirals as confinement components of grout. Four types of single-bar splice specimens were prepared during the test program consisting of: first, contact lap splices tied by steel lock wires; second, non-contact lap splices without any confinement components; third, non-contact lap splices with the surrounding grout confined by spirals with 35 mm pitch; fourth, non-contact lap splices with the surrounding grout confined by spirals with 80 mm pitch. The results of the experimental program show that spirals are efficient confinement components of non-contact lap splices in concrete block masonry. Statistical analysis of results demonstrate that non-contact lap splices confined by spirals with 35 mm pitch are not only equivalent with contact lap splices regarding their ultimate tensile resistance, but also contribute to the reduction of cracks.