Tese de doutoramento em
Engenharia Civil; A envolvente dos edifícios em Portugal é constituída quase exclusivamente por paredes de
alvenaria, que têm principalmente a função de vedação. Apesar de não terem função estrutural,
as paredes ao interagirem com a estrutura, condicionam o comportamento sísmico dos
edifícios, exigindo-se-lhe sob esta óptica, um desempenho adequado, evitando a ocorrência de
danos severos nas paredes no seu plano, que conduzam a perdas económicas graves, e o
colapso das paredes para fora do plano, que poderão colocar em perigo vidas humanas.
Os actuais regulamentos estruturais europeus, no que concerne à segurança sísmica das
estruturas exigem a verificação da segurança de elementos não estruturais quando o seu
colapso acarreta riscos para pessoas ou para a estrutura principal. Os Eurocódigos estruturais
quando entrarem na fase de implementação obrigatória irão impor novas exigências que
deverão ser cumpridas pelos edifícios ou pelas suas partes. Tal é o caso das alvenarias de
preenchimento, que deverão resistir ao movimento para fora do plano imposto pela acção dos
sismos, devendo ser tomadas medidas adequadas para evitar a rotura prematura e
desintegração das paredes de preenchimento...
Generally two methods are proposed for analyzing the infilled frames; Micro modelling approach which finite element method is used to take into account local effects in detail and Macro modelling approach which is a very simplified method that takes into account the global behavior of the structure by replacing the infill with diagonal strut.
In the present study a numerical analysis is carried out on a one bay one storey reinforced concrete frame with masonry infill under in-plane loading by using finite element modelling through the DIANA software. The numerical model was calibrated based on experimental results and then a parametric study was carried out, taking into account variation of material properties of infill and its height to length ratio. It is concluded that compressive strength and height to length ratio of the masonry infill has dominant role on the in-plane behavior of these types of masonry infilled frames. Increasing the compressive strength of the masonry enhances the lateral strength of the infilled frames while increasing the height to length ratio of the infill panel results in decrease of their lateral strength and initial stiffness.; Fundação para a Ciência e a Tecnologia (FCT)
Dissertação de mestrado integrado em Engenharia Civil (área de especialização em Perfil de Estruturas e Geotecnia); Toda a história humana encontra-se recheada de eventos sísmicos que fustigaram as
populações e a suas cidades de forma mais ou menos grave, dependendo da intensidade
do sismo e da preparação das estruturas para resistirem. Perderem-se nesta luta travada
contra a natureza e a sua implacável redundância um número bastante significativo de
vidas humanas e danos materiais. Portugal, ao longo dos tempos, já prestou o seu tributo
a esta triste causa e poderá no futuro encontrar-se novamente perante um evento sísmico
de grandes proporções. A grande preocupação perante esta eventualidade é claramente o
facto de o património edificado não estar a altura deste evento. Dentro dos edifícios
modernos a maior preocupação, desencadeada em grande parte por recentes sismos em
países vizinhos com resultados catastróficos, é a vulnerabilidade das paredes em
alvenaria, pelo facto de poderem ceder segundo vários tipos de mecanismos de colapso.
O objetivo deste trabalho é contribuir para o conhecimento da engenharia civil sobre o
funcionamento destes elementos em particular e a sua influência no comportamento
global das estruturas. Para tal...
The latest earthquake codes in Europe require the safety assessment of no-structural elements (parapets, masonry wall’s veneer, infill walls, etc.), as their collapse entails risks for people or for the main structure stability. This work made possible th e development of a design method, supported by previous experimental researches by applying cyclic out-of-plane loads to damaged masonry infill in RC frames. Panels tested reproduce Portuguese traditional RC structure construction system and two reinforced solutions were created as innovative solutions. The experimental campaign was carried out in order to determine: masonry properties; out-of-plane panel behaviour with previous in-plane damage; building behaviour subjected to dynamic tests
performed in shaking table. Using finite element method to reproduce experimental tests and to broaden the range of samples it was possible to figure out equations according to parametric analysis which was able to reproduce in-plane and out-plane behaviour leading to an estimated load bearing capacity of each model and to determine frame strength and its stiffness. Those equations permit to design or verify the masonry infill panels in RC frames subjected to seismic loads.
Reinforced concrete (RC) buildings in Nepal are constructed as RC frames with masonry infill panels.
These structures exhibit a highly non-linear inelastic behaviour resulting from the interaction between
the masonry infill panels and the surrounding frames. In this context, the paper presents an extensive
case study of existing RC-framed buildings in a high seismic risk area in Nepal. A sensitivity analysis
of the structures with masonry infill is performed. For this, the influence of different material
properties is studied, namely diagonal compressive stress, modulus of elasticity and tensile stress of
masonry infill panels. Result shows the influence on the structural behaviour particularly by variation
of the diagonal compressive strength of infill masonry panels.
The in-plane cyclic response of reinforced concrete frames with unreinforced masonry infill was studied. Four full-scale reinforced concrete frame assemblies with masonry infills were designed and tested under reversed cyclic loading. The effect of panel aspect ratio and the stiffness of the infill relative to the frame were studied in terms of stiffness, strength, energy dissipation and failure mode. Based on the test results, an equivalent diagonal compression strut model was developed to represent the behavior of masonry infill bounded by a reinforced concrete frame and a simplified method for the linear-elastic analysis of R/C frames with masonry infills proposed. Using the experimental load-deformation plots, the hysteretic parameters relating to stiffness degradation, strength deterioration and pinching of the hysteretic loops were identified. These may be used to define the behavior of confined infills for the non-linear analysis of the infilled frames.
Many existing flat-plate buildings are seismically deficient and pose a threat to life safety if subjected to ground motions of even low to moderate intensity. Failure in such structures is typically the result of punching failure at the slab-column connection. Because of this, performance-based retrofit procedures are needed to upgrade these non-ductile buildings. This investigation evaluated the use of lightweight pumice stone concrete (LWPSC) infill panels as a retrofit alternative for flat-plate buildings.
Six four-tenth-scale slab-column subassemblies were designed and detailed based on ACI 318-63 and current performance-based testing requirements. Except for one bare frame specimen, all the subassemblies were retrofitted with prefabricated LWPSC infill panels and subjected to quasi-static loading conforming to FEMA 273. The geometry of the individual units was governed by weight limitations for handling and erection. Among the variables studied were connections between the slabs and the infill wall and the addition of uniformly distributed perforations (circular and rectangular openings).
All of the retrofitted specimens had significant increases in both strength and stiffness over that of the bare frame. The behavior of the specimen with the infill panels not attached to the slabs was similar to that of a masonry wall without any connections to the frame. Although diagonal tension cracks formed within the recessed region...