The main topic of the thesis is the role of timber in the seismic resilience of unreinforced masonry (URM) buildings. The research addressed both existing timber components that can be encountered in URM buildings and timber-based retrofit solutions. The work presented herein can be split into two main phases. In the first part of the research, the in-plane behavior of traditional wooden floors was analyzed by means of numerical static and dynamic simulations. Modelling strategies with different refinement levels were proposed and implemented to assess diaphragm in-plane strength and flexibility. Modelling was undertaken considering as-built diaphragms first and was then extended to diaphragms retrofitted by means of timber-based techniques. The influence of diaphragm construction details on their in-plane response was evaluated and timber-based retrofitting solutions were observed to be effective in mitigating in-plane diaphragm flexibility and in increasing in-plane diaphragm strength. The second part of the PhD work was dedicated to investigate new retrofit solutions for URM buildings based on the use of engineered timber panels mechanically connected to the masonry. The first step saw the experimental testing of different types of timber-to-masonry connections considering both screw-type fasteners and adhesive anchors. In the second stage, full-scale masonry walls were tested in the as-built, retrofitted and repaired configurations, highlighting the benefits of the proposed technique on the in-plane response of the masonry walls.

The research described here is part of a multi-university project on “Performance-based Design of New Masonry Structures.” Within the context of that project, the main objectives of this research was to study the inelastic seismic performance of low-rise concrete masonry structures with clay masonry veneer and veneer connectors; to develop analytical models for those structures and the elements comprising them; and to use the results of the research to propose refinements to current design provisions for concrete masonry with clay masonry veneer. The experimental work described here includes the design and testing of concrete masonry wall specimens with clay masonry veneer under quasi-static loading. Identical specimens were subjected to shake-table testing at another university. The experimental work described here also includes the design of a full-scale, one-story concrete masonry building specimen with clay masonry veneer. That building specimen was subjected to shake-table testing at another university. The analytical work of this research includes the development of nonlinear hysteretic models for concrete masonry walls, clay masonry veneer and veneer connectors. The analytical models for wall specimens were calibrated using the results of the quasi-static and shake-table tests of wall specimens. The analytical model for the building specimen was compared with and refined using shake-table test results for the building specimen. Finally, the calibrated and refined analytical model of the building specimen was used for parameter studies intended to supply general information about the behavior of low-rise reinforced concrete masonry structures with clay masonry veneer. Based on the these experimental and analytical results, basic concepts of the seismic response and design of low-rise concrete masonry buildings were reaffirmed; most design and construction requirements of the 2008 MSJC Code and Specification were reaffirmed; and several recommendations were made to improve those requirements. / text

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.

This research focused on designing a grout mixture using lightweight aggregate that achieves the minimum 28-day compressive strength required for normal-weight grout, 2000 psi. This research specifically studied the effects of aggregate proportion, slump, and aggregate soaking on the compressive strength of the mixture. The variable ranges investigated were 3-4.75 parts aggregate to cement volumetrically, 8-11 in. slump, and 0 and 2 cycles of soaking. The statistical model developed to analyze the significance of variable effects included a three-way interaction between the explanatory variables. All three explanatory variables had a statistically significant effect on the grout compressive strength, but the effect of soaking was minimal and decreased as aggregate proportion decreased. This research also showed that lightweight grout, when prepared using aggregate proportion and slumps within the ranges suggested in American Society for Testing and Materials C476, reaches the required minimum 28-day compressive strength with a factor of safety of at least 2.7.

The structural response of unreinforced masonry elements strengthened with hybrid elastomeric/fiber materials was investigated through material characterization and flexural experiments. Material characterization tests were performed on various unreinforced and reinforced elastomeric materials to identify those materials that were best suited for use as structural retrofits. After material characterization was completed, the three most promising material systems were selected for further investigation, including one unreinforced elastomer film and two reinforced elastomer films with fiber orientations at 0/90° and +/- 45° relative to the major axis of the masonry elements. A series of four-point bending tests were performed on the selected masonry and epoxy bonded elastomer/fiber hybrid retrofits to determine the structural response of the composite systems. The experimental load-deformation response was used, along with material characterization results, in the development of a semi-empirical model to predict the static moment capacity of the strengthened masonry system. This model will be used in the development of reliable design criteria for masonry walls strengthened with these advanced materials.

The research described here is part of a multi-university project on “Performance-based Seismic Design Methods and Tools for Reinforced Masonry Shear-Wall Structures.” Within the context of that project, the objective of the research described in this dissertation was to develop and validate a specific displacement-based seismic design methodology for masonry structures. Experimental work consisted of reversed cyclic loading tests of reinforced masonry wall segments with different boundary conditions, aspect ratios, axial loads, and reinforcement detailing. Analytical work consisted of developing analytical models for in-plane concrete masonry shear wall segments; calibrating those models using reversed cyclic test data; and using those models to successfully predict the nonlinear seismic response of two full-scale, multi-story reinforced masonry specimens tested on the shake-table at the University of California at San Diego. Design work consisted of the force-based and displacement based design of those specimens. Based on the results, provisions for displacement-based seismic design are proposed for inclusion in United States design codes. / text

An experimental program was conducted to investigate some aspects of in-plane behaviour of masonry infilled steel frames. Eight concrete masonry infilled steel frames, consisting of three fully grouted and five partially grouted infills, were tested under combined lateral and axial loading. All specimens were constructed using one-third scale concrete masonry units. The in-plane lateral load was gradually increased at the frame top beam level until the failure of the specimen while an axial load was applied to the top beam and held constant. The parameters of the study included axial load, extent of grouting, opening, and aspect ratio of the infill. The experimental results were used, along with other test results from the literature, to evaluate the efficacy of stiffness and strength predictions by some theoretical methods with a focus on Canadian and American design codes. Cracking pattern, stiffness, failure mode, crack strength, and ultimate strength of the specimens were monitored and reported. Presence of axial load was found to increase the ultimate strength of the infilled frame but had no marked effect on its stiffness. Two specimens exhibited “splitting failure” due to axial load. Partially grouted specimens developed extensive diagonal cracking prior to failure whereas fully grouted specimens showed little or no cracking prior to failure. An increase in grouting increased the ultimate strength of the frame system but reduced its ductility. Presence of opening reduced the ultimate strength of the infilled frame and increased its ductility but its effect on the stiffness of the frame system was not significant. A review of current Canadian and American design codes showed that the Canadian code significantly overestimates the stiffness of infilled frames whereas the American code provides improved predictions for stiffness of these frame systems. Both design codes underestimate the strength of masonry infilled steel frames but grossly overestimate the strength of masonry infilled RC frames. / Masonry infilled steel frames tested under combined axial and lateral loading. Behaviour as affected by axial load, grouting, aspect ratio and openings discussed. Correlation between axial load level and the infill lateral resistance examined. Efficacy of the Canadian and American masonry standards on infill design was examined.

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.

Thesis (C.E.)--Lehigh University, 1888. / Manuscript. Also available online.

Submitted by Regina Correa (rehecorrea@gmail.com) on 2016-09-09T19:49:38Z No. of bitstreams: 1 DissRDP.pdf: 6790691 bytes, checksum: b888125fd30db642f17445cce46fe74c (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-13T14:55:38Z (GMT) No. of bitstreams: 1 DissRDP.pdf: 6790691 bytes, checksum: b888125fd30db642f17445cce46fe74c (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-13T14:56:11Z (GMT) No. of bitstreams: 1 DissRDP.pdf: 6790691 bytes, checksum: b888125fd30db642f17445cce46fe74c (MD5) / Made available in DSpace on 2016-09-13T14:56:58Z (GMT). No. of bitstreams: 1 DissRDP.pdf: 6790691 bytes, checksum: b888125fd30db642f17445cce46fe74c (MD5) Previous issue date: 2015-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / This study intends to analyze, in the construction system that is in ascendancy - the structural masonry, an element that demands a special attention comparing to other elements: the reinforced concrete masonry beam. The beams carry vertical loads, with flexure and shear forces. In the theoretical part, the literature review included national and international papers and codes. The assessed codes were the national (NBR15961-1/2011 and NBR 6118/2014) and international (ACI530-13, AS3700/2001, S304/2014 and Eurocode 6.1/2001). The experimental study includes testing of ten (10) concrete block masonry beams, designed to fail due to shear forces. As a conclusion, it can be pointed that concrete masonry beams failure in a similar behavior to concrete beams, except for some particularities such as prior joint cracking. Furthermore, the specification at Brazilian and European standards led to considerably higher results than the experimental results while the specifications at ACI530-13, AS3700/2001, S304/2014 and NBR6118/2014 yielded reasonable predicted values when compared to experimental results. / O presente trabalho busca analisar, dentro de um dos sistemas construtivos que está em ascendência, que é a alvenaria estrutural, um dos elementos estruturais que necessita de uma atenção maior quando comparado com os demais: a viga de alvenaria armada com blocos de concreto. Vigas apresentam carregamento vertical e são submetidas a flexão e cisalhamento, sendo esse último esforço o tema desta pesquisa. Na parte teórica, foram considerados trabalhos anteriores, tanto nacionais quanto internacionais, e as prescrições das normas brasileiras NBR15961-1/2011 e NBR 6118/2014, além das norte-americanas ACI530/2013 e ACI530/2013, a australiana AS3700/2001, a canadense S304.1/2014 e a europeia EuroCode 6.1/2001. Com intuito analisar e validar as especificações da literatura, foi realizado programa experimental de análise de dez vigas de alvenaria com blocos de concreto submetidas principalmente ao esforço cortante. Como conclusão, verificou-se semelhanças no comportamento último das vigas de alvenaria armada com a teoria proveniente das vigas de concreto armado, com algumas particularidades de fissuração na região das juntas de argamassa. Além disso, as especificações estabelecidas pelas normas brasileira e européia levaram a resultados consideravelmente maiores do que os resultados experimentais, enquanto que as presentes nas normas ACI530/2013, AS3700/2001, S304.1/2014 e NBR6118/2014 levam a resultados próximos aos obtidos experimentalmente.