José Carlos Lopes Ribeiro

Experimental Evaluation of the Influence of Mortar’s Mechanical Properties on the Behavior of Clay Masonry

This study aims to evaluate the influence of mortar’s mechanical properties on the behavior of clay masonry. Experimental studies were performed using prisms of clay blocks under axial compression. The clay units were produced with a clay from Tres Rios, Rio de Janeiro, Brazil and had compressive strength of 4.9 MPa. Two mortar compositions were used, which had compressive strength of 94.7 and 50.4% of the clay blocks’ net area compressive strength. It was noticed a slight increase on the prism’s compressive strength with the increase of the mortars’ compressive strength and stiffness. Prisms made with flexible mortars had a ductile failure and collapsed under lower compressive stresses, while prisms made with stiff mortars resisted higher compressive stresses, but had a brittle failure, crushing the blocks. A very strong mortar is not recommended. Using more flexible mortars does not compromise the strength and stiffness of the masonry and prevents an excessively brittle failure of the structure.

Numerical and experimental evaluation of masonry prisms by finite element method

Resumo This work developed experimental tests and numerical models able to represent the mechanical behavior of prisms made of ordinary and high strength concrete blocks. Experimental tests of prisms were performed and a detailed micro-modeling strategy was adopted for numerical analysis. In this modeling technique, each material (block and mortar) was represented by its own mechanical properties. The validation of numerical models was based on experimental results. It was found that the obtained numerical values of compressive strength and modulus of elasticity differ by 5% from the experimentally observed values. Moreover, mechanisms responsible for the rupture of the prisms were evaluated and compared to the behaviors observed in the tests and those described in the literature. Through experimental results it is possible to conclude that the numerical models have been able to represent both the mechanical properties and the failure mechanisms.

Experimental evaluation of the interaction between strength concrete block walls under vertical loads

Este trabalho tem como objetivo avaliar a interacao entre paredes de alvenaria estrutural de blocos de concreto de alta resistencia, sob acoes verticais. Foram ensaiadas duas series de paredes com flanges intertravadas, em formato “H” em escala real e com amarracao direta, sendo uma serie composta de tres especimes com a parede central (alma) apoiada e a outra serie de tres especimes sem apoio na alma. A carga foi aplicada na parede central e atraves de transdutores de deslocamento foram monitorados os deslocamentos verticais em dezoito pontos do conjunto de paredes. Os resultados mostram que os valores de carga estimados para os flanges das paredes com apoio central foram proximos daqueles suportados pelos flanges das paredes sem apoio central, nas quais ocorrem 100% de transferencia de carga para os mesmos. As taxas de transferencia medias, calculadas com base na relacao de deformacoes no trecho superior e inferior para o conjunto de paredes com apoio central, foram de 37,65% e 77,30%, respectivamente, mostrando que existe transferencia de carga da parede central (alma) para os flanges, particularmente no trecho inferior do conjunto de paredes. Assim, ha um indicativo de que a distribuicao de forcas verticais pode ser considerada em projetos de edificios para cargas de servico, como no metodo de grupo isolado de paredes. Com relacao ao comportamento ultimo das paredes com flanges com apoio na alma, a ruptura ocorre no topo da alma, local onde ainda nao ocorre transferencia de forcas verticais entre paredes adjacentes, neste caso o metodo de paredes isoladas para a estimativa da carga de ruptura seria adequado.

Determinação de fatores de empilhamento através do software Digitora

ABSTRACT - The objective of this study was to evaluate the use of the Digitora software to obtain piling factors.Thus, stacks of eucalyptus wood were piled up manually on the soil. After the analyses, it was verified that: a) theDigitora software provided precise piling factor estimates; b) there was a slight tendency towards overestimatingthe factors by Digitora; c) the operator training related to classification of the points on the photographs inDigitora is an essencial condition for obtaining precise piling factor estimates; d) the photographs should alwaysbe taken with activated flash and ZOOM.Key words: Piling factors, eucalyptus, digital photographs. 1. INTRODUCAO O volume solido de madeira empilhada pode serobtido pelo somatorio dos volumes das toras de madeirana pilha, pela aplicacao de expressoes aproximativas nacubagem rigorosa, ou atraves do uso do xilometro (Huschet al., 1972; Scolforo & Filho, 1992). Porem, este metodopossui inconvenientes quando as pilhas de madeira saomuito grandes ou quando as dimensoes das toras saograndes, acarretando grande dispendio de mao-de-obrae tempo para a execucao do trabalho. Alem destes meto-dos, o volume solido de madeira empilhada pode serobtido atraves de fatores de empilhamento, da pesagemdas pilhas de madeira e da utilizacao de equacoes deregressao (Couto & Bastos, 1988; Andrade & Leite,1998; Paula Neto & Rezende, 1992), que sao metodoscujas precisoes podem variar consideravelmente, depen-dendo de como forem utilizados.No Brasil, o uso de fatores de empilhamento epratica comum para conversao do volume de madeiraempilhada em volume solido de madeira. No entanto,caracteristicas como os diâmetros e comprimentos dastoras de madeira, a espessura da casca, a forma de empi-lhar, a especie, a idade das arvores, entre outros fatores,afetam o volume de madeira empilhada, de tal forma que

Simulação numérica do comportamento estrutural de vigas casteladas de aço com ênfase na flambagem do montante de alma.

Este trabalho apresenta um estudo numerico sobre o comportamento de vigas casteladas fabricadas a partir de perfis laminados, com enfase na instabilidade do montante de alma. As analises foram realizadas utilizando um modelo de elementos finitos, desenvolvido com o software ABAQUS, validado com resultados de quatro programas experimentais. O modelo considera a influencia de tensoes residuais e imperfeicoes iniciais e inclui analise de instabilidade e analise nao linear material e geometrica, simulando o comportamento da viga durante todo o carregamento, inclusive na fase pos-flambagem. Foram modeladas e analisadas algumas series de vigas casteladas, formadas a partir de perfis brasileiros, variando-se alguns parâmetros geometricos e de carregamento. Os resultados obtidos demonstram aspectos importantes do comportamento estrutural relacionados a diferentes padroes geometricos de vigas casteladas, considerando a variacao da esbeltez da alma do perfil e a presenca de chapa expansora. Palavras-chave: vigas casteladas, simulacao numerica, metodo dos elementos finitos, flambagem do montante de alma. ABSTRACT This paper presents a numerical study on the behavior of castellated beams made from hot rolled I-sections, emphasizing the instability of the web-post. The analyses were performed using a finite element model, developed with ABAQUS software, validated with results of four experimental programs. The model considers the influence of residual stresses and initial imperfections and includes instability analysis and nonlinear geometric and material analysis, simulating the behavior of the beam throughout the loading, including post-buckling stage. Some series of castellated beams formed from Brazilian steel sections were modeled and evaluated varying some geometric and loading parameters. The results demonstrate important aspects of structural behavior related to different geometric patterns of castellated beams, considering the variation of the web slenderness and the presence of spacer plate. Keywords: castellated beams, numerical simulation, finite element method, web-post buckling.