No description available.

No description available.

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.

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.

Pseudo-dynamic testing was employed to observe the seismic performance of three different retrofit methods on two story three bay reinforced concrete frame structures. The three test frames have hollow clay tile (HCT) infills in the central bay. All of the test frames represent the seismic deficiencies of the Turkish construction practice such as use of plain reinforcing bars, low strength concrete and insufficient confining steel. Two non-invasive and occupant friendly retrofit schemes suggested in the Turkish Earthquake Code, namely use of Fiber Reinforced Polymers and precast concrete panels integrated on the HCT infills and traditional approach of adding concrete infill wall were employed. Specimens were subjected to three different scale levels of North-South component of Duzce ground motion. Reference specimen experienced severe damage at 100% scale level and reached collapse stage due to the loss of integrity of the infill wall and significant damage on the boundary columns. The retrofitted test structures were able to survive the highest level 140% Duzce ground motion. Test results confirmed the success of the retrofit methods for simulated earthquake loads.

There is an excessive demand for the rehabilitation of frame type reinforced concrete (RC) buildings which do not satisfy current earthquake code provisions. Therefore, it is imperative to develop user-friendly seismic strengthening methodologies which do not necessitate the evacuation of building during rehabilitation period. In this study, it was aimed to strengthen the brick infill walls by means of diagonal Carbon Fiber-Reinforced Polymer (CFRP) fabrics and to integrate them with the existing structural frame in order to form a new lateral load resisting system. The possible effects of height to width (aspect) ratio of the infill walls and scale of the frame test specimens on the overall behavior attained by the developed rehabilitation methodology were investigated. The experimental part of the study was carried out in two steps. In the first step, ten individual panel specimens were tested in order to understand the behavior of strengthened/non-strengthened masonry walls under diagonal earthquake loads. And in the second step, the tests of eight 1/3 and four 1/2 scaled one-bay, two-story RC frames having two different aspect ratios were performed to determine design details. The experimental results were revealed in terms of lateral stiffness, strength, drift and energy dissipation characteristics of the specimens. In the analytical part, an equivalent strut and tie approach was used for modeling the strengthened/non-strengthened infill walls of the frames. The predicted pushover responses of the frame models were compared with the test results. The design criteria required for the aforementioned strengthening methodology was developed referring these analytical results.

Materially non-linear analysis of reinforced concrete frame structures with infill walls requires appropriate mathematical models to be adopted for the beams and the columns as well as the infill walls. This study presents a mathematical model for frame elements based on a 3D Hermitian beam/column finite element and an equivalent strut model for the infill walls. The spread-of-plasticity approach is employed to model the material nonlinearity of the frame elements. The cross-section of the frame element is divided into triangular sub regions to evaluate the stiffness properties and the response of the element cross-section. By the help of the triangles spread over the actual area of the section, the bi-axial bending and the axial deformations are coupled in the inelastic range. A frame super-element is also formed by combining a number of frame finite elements. Two identical compression-only diagonal struts are used for modeling the infill. The equivalent geometric and material properties of the struts are determined from the geometry of the infill and the strength of the masonry units A computer code is developed using the object-oriented design paradigm and the models are implemented into this code. Efficiency and the effectiveness of the models are investigated for various cases by comparing the numerical response predictions produced by the program with those obtained from experimental studies.

The importance of seismic rehabilitation became evident with 1992 Erzincan Earthquake, after which a large number of reinforced concrete buildings damaged in recent earthquakes required strengthening as well as repair. In the studies related to rehabilitation, it has been realized that inadequate lateral stiffness is one of the major causes of damage in reinforced concrete buildings. Recently, economical, structurally effective and practically applicable seismic retrofitting techniques are being developed in METU Structural Mechanics Laboratory to overcome these kinds of problems. The strengthening technique proposed in this thesis is on the basis of the principle of strengthening the existing hollow brick infill walls by using high strength precast concrete panels such that they act as cast-in-place concrete infills improving the lateral stiffness. Also, the technique would not require evacuation of the building and would be applicable without causing too much disturbance to the occupant. For this purpose, after two preliminary tests to verify the proper functioning of the newly developed test set-up, a total of fourteen one-bay two story reinforced concrete frames with hollow brick infill wall, two being unstrengthened reference frames, were tested under reversed cyclic lateral loading simulating earthquake loading. The specimens were strengthened by using six different types of precast concrete panels. Strength, stiffness, energy dissipation and story drift characteristics of the specimens were examined by evaluating the test results. Test results indicated that the proposed seismic strengthening technique can be very effective in improving the seismic performance of the reinforced concrete framed building structures commonly used in Turkey. In the analytical part of the study, hollow brick infill walls strengthened by using high strength precast concrete panels were modelled once by means of equivalent diagonal struts and once as monolithic walls having an equivalent thickness. The experimental results were compared with the analytical results of the two approaches mentioned. On the basis of the analytical work, practical recommendations were made for the design of such strengthening intervention to be executed in actual practice.

Made available in DSpace on 2016-06-02T20:09:16Z (GMT). No. of bitstreams: 1 4457.pdf: 18463450 bytes, checksum: c0a25a178fa3c9a6561abc7109472ddc (MD5) Previous issue date: 2012-03-30 / Financiadora de Estudos e Projetos / This work proposes to develop a study about frame structure behaviour filled with masonry panel, for the purposes of building bracing. It aims to consider the hardening of this filling masonry in the frame which deals with the horizontal loadings analysis such as wind strength. The work starts with the historical development, depicting the fact that who started this study. Then, variables which influence the frame rigidity are shown, like: wedging, the kind of link between panel- frame, panel openings, codes and design specification. These topics describe theoretical and experimental studies that have already been carried out about the theme and the main approaches considered by the researchers. For the purpose of checking the structure stiffening increase some case study were held. The first one comprehends a simple frame, theoretical, with data and results obtained from specialized literature. The second one compares a steal frame tested on a laboratory, with a computer program modeled frame, using the same features as the real stuff. Then, the portics were analysed with different filled floors. For doing so, different available calculation methods were applied, which employ equivalent diagonal concept to consider the masonry filling contribution as a structural constituent. Bearing in mind to verify the stiffening increase when the filling masonry are considered, a real building was modeled, in this particular case Helena Building, it has 22 floors, built in São Paulo using reinforced concrete, either considering or not the filling masonry. As the research bottom line, this text allows an updating about the possibility of including the filling masonry in building projects, an evaluation of the stiffening increase that the masonry might cause, an analysis to verify the compressed diagonal model and finally it shows design criteria. / O presente trabalho propõe realizar um estudo da arte sobre o comportamento de estruturas aporticadas preenchidas com painéis de alvenaria, para fim de contraventamento de edificações. Visa considerar o enrijecimento dessa alvenaria de preenchimento no pórtico para análise de ações horizontais, como a força do vento. O trabalho inicia-se com o desenvolvimento histórico, descrevendo o fato que originou o estudo. Em seguida, apresenta variáveis que influenciam na rigidez do pórtico, como: encunhamento, tipo de ligação entre pórtico-painel, abertura em painéis, normas e considerações para projeto. Esses tópicos descrevem estudos teóricos e experimentais já realizadas sobre o tema e os enfoques mais relevantes considerados pelos pesquisadores. A fim de verificar o aumento de rigidez da estrutura foram realizados alguns estudos de caso. O primeiro trata-se de um pórtico simples, teórico, com dados e resultados obtidos na literatura especializada. A segunda análise compara-se um pórtico metálico ensaiado em laboratório, com um pórtico modelado em programa computacional, adotando as mesmas características do real. Em seguida, analisam-se teoricamente pórticos com diferentes pavimentos preenchidos. Para isso, adotaram diferentes métodos de cálculo disponíveis, que empregam o conceito de diagonal equivalente para considerar a contribuição do enchimento de alvenaria como elemento estrutural. Com propósito de comprovar o acréscimo de rigidez quando for considerada a alvenaria no preenchimento, foi modelado um edifício real, o edifício Helena, de 22 pavimentos, executado em concreto armado na cidade de São Paulo, considerando ou não a alvenaria de preenchimento. Como resultado da pesquisa, este texto permite uma atualização sobre a possibilidade de inclusão da alvenaria de enchimento no projeto de edificações, avaliar o aumento de rigidez que a alvenaria pode proporcionar, averiguar o modelo de diagonais comprimidas e, finalmente, indicar critérios para projeto.

Reinforced concrete frames, infilled with brick/concrete block masonry, are the most common type of structures found in multi-storeyed constructions, especially in developing countries. Usually, the infill walls are considered as non-structural elements even though they alter the lateral stiffness and strength of the frame significantly. Approximately 80% of the structural cost from earthquakes is attributable to damage of infill walls and to consequent damages of doors, windows and other installations. Despite the broad application and economical significance, the infill walls are not included in the analysis because of the design complexity and lack of suitable theory. But in seismic areas, ignoring the infill-frame interaction is not safe because the change in the stiffness and the consequent change in seismic demand of the composite structural system is not negligible. The relevant experimental findings shows a considerable reduction in the response of infilled frames under reverse cyclic loading. This behaviour is caused by the rapid degradation of stiffness, strength, and low energy dissipation capacity resulting from the brittle and sudden damage of the unreinforced masonry infill walls. Though various national/international codes of practice have incorporated some of the research outcomes as design guidelines, there is a need and scope for further refinement. In the initial part of this work, a numerical modelling and linear elastic analysis of masonry infilled RC frames has been done. A multi-storey multi-bay frame infilled with masonry panels, is considered for the study. Both macro modelling and micro modelling strategies are adopted. Seismic loading is considered and an equivalent static analysis as suggested in IS 1893, 2002 is done. The results show that the stiffness of the composite structure is increased due to the obvious confinement effects of infill panels on the bounding frame. A parametric study is conducted to investigate the influence of size and location of openings, presence/absence of infill panels in a particular storey and elevation irregularity in terms of floor height. The results show that the interaction of infill panel changes the seismic response of the composite structure significantly. Presence of openings further changes the seismic behaviour. Increase in openings increases the natural period and introduce newer failure mechanisms. Absence of infill in a particular storey (an elevation irregularity) makes it drift more compared to adjacent storeys. Since the structural irregularities influence the seismic behaviour of a building considerably, we should be cautious while construction and renovation of such buildings in order to take the advantage of increased strength and stiffness obtained by the presence of infill walls. A nonlinear dynamic analysis of masonry infilled RC frames is presented next. Material non linearity is considered for the finite element modelling of both masonry and concrete. Concrete damage plasticity model is employed to capture the degradation in stiffness under reverse cyclic loading. A parametric study by varying the same parameters as considered in the linear analysis is conducted. It is seen that the fundamental period calculation of infilled frames by conventional empirical formulae needs to be revisited for a better understanding of the real seismic behaviour of the infilled frames. Enhancement in the lateral stiffness due to the presence of infill panel attracts larger force and causes damage to the composite system during seismic loading. Elevation irregularities included absence of infill panels in a particular storey. Soft storey shows a tendency for the adjacent columns to fail in shear, due to the large drift compared to other storeys. The interstorey drift ratios of soft storeys are found to be larger than the limiting values. However this model could not capture the separation at the interfaces and related failure mechanisms. To improve the nonlinear model, a contact surface at the interface is considered for a qualitative analysis. A one bay one storey infilled frame is selected. The material characteristics were kept the same as those used in the nonlinear model. Contact surface at the interface was given hard contact property with pressure-overclosure relations and suitable values of friction at the interface. This model could simulate the compressive diagonal strut formation and the switching of this compressive strut to the opposite diagonal under reverse cyclic loading. It showed an indication of corner crushing and diagonal cracking failure modes. The frame with central opening showed stress accumulation near the corners of opening. Next, the micro modelling strategy for masonry suggested by Lourenco is studied. This interface element can be used at the masonry panel-concrete frame interface as well as at the expanded masonry block to block interface. Cap plasticity model (modified Drucker – Prager model for geological materials) can be used to describe the behaviour of masonry (in terms of interface cracking, slipping, shearing) under earthquake loading. The blocks can be defined as elastic material with a potential crack at the centre. However, further experimental investigation is needed to calibrate this model. It is required to make use of the beneficial effects and improve upon the ill-effects of the presence of infills. To conclude, infill panels are inevitable for functional aspects such as division of space and envelope for the building. Using the lateral stiffness, strength contribution and energy dissipation capacity, use of infill panels is proposed to be a wiser solution for reducing the seismic vulnerability of multi-storey buildings.