Roberto Márcio da Silva

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.

Mortar Plaster and Reinforcement Use to Repair and Stiff Brazil Historical Constructions

Many Brazilian historical constructions built using the techniques of daub, paving clay or adobe have presented many pathologies and sometimes even ruptures risk of walls. In order to recover such pathologies, or to reinforce such walls, it is suggested to use cement-rich mortar plaster or reinforced mortar plaster with welded steel mesh, applied to the wall with non-structural blocks. With this, it is gained net area, resulting in a greater strength and inertia. For this purpose, nine walls were tested for compression, being three walls of non-structural blocks without mortar plaster, three walls with mortar plaster and three walls with mortar plaster reinforced with welded steel mesh. Three specimens had the dimensions of 1.20 m by 2.60 m and the other six, called small walls, had dimensions of 0.90 m by 1.04 m. In these tests, simple compression loads capacity were obtained and it can be concluded that the application of the mortar plaster substantially increased the walls load capacity, as compared to the walls without mortar plaster. An increase of up to eight times in the rupture load was observed. The tests performed with the walls containing welded steel mesh inserted in the mortar plaster were not conclusive, although comparing them with the walls without mortar plaster, there was also gain of significant mechanical resistance.

Análise do desempenho térmico de envoltórias em concreto no Brasil

The construction market started to adopt faster and serial systems to reduce the Brazilian housing deficit. However, so the same constructive systems are used similarly throughout the country, regardless the local climate. This paper aims to diagnose the thermal performance envelopment of a multifamily dwelling for the Brazilian Bioclimatic zones. For this, it considers a building prototype on concrete, tested using the prescriptive methods of Brazilian standards. The requirements of NBR 15.220, NBR 15.575, RTQ R and Blue House Label, about thermal performance and building efficiency for summer and winter for the RTQ -R were considered. It was selected a building with walls and slabs on concrete and fiber cement roof. It also analyzed projects variations on insulation for the roof and ventilation opening areas. Results showed that the limit values are different for each standard, which highlights the necessity of uniform the requirements. Furthermore, all the prescriptions indicated that is necessary thermal insulation for the concrete wall. There is no needing insulate light colors roofs. For RTQ -R, it can be inferred that the improvement of roof transmittance was enough to increase the envelope efficiency in the summer, except for zone 2. In sum, the concrete wall is a growing system in Brazil that requires verification of the thermal impact of its serial adoption. This study aims, collaborate with this demand.