Blast loading of masonry infills: testing and simulation

This work intends to present a newly developed test setup for dynamic out-of-plane loading using underWater Blast Wave Generators (WBWG) as loading source. Underwater blasting operations have been, during the last decades, subject of research and development of maritime blasting operations (including torpedo studies), aquarium tests for the measurement of blasting energy of industrial explosives and confined underwater blast wave generators. WBWG allow a wide range for the produced blast impulse and surface area distribution. It also avoids the generation of high velocity fragments and reduces atmospheric sound wave. A first objective of this work is to study the behavior of masonry infill walls subjected to blast loading. Three different masonry walls are to be studied, namely unreinforced masonry infill walls and two different reinforcement solutions. These solutions have been studied previously for seismic action mitigation. Subsequently, the walls will be simulated using an explicit finite element code for validation and parametric studies. Finally, a tool to help designers to make informed decisions on the use of infills under blast loading will be presented

Experimental study on masonry infill walls under blast loading

The vulnerability of the masonry envelop under blast loading is considered critical due to the risk of loss of lives. The dynamic behaviour of masonry infill walls subjected to dynamic out-of-plane loading was experimentally investigated in this work. Confined underwater blast wave generators (WBWG) allows applying an extremely high rate conversion of the explosive detonation energy into the kinetic energy of a thick water confinement, which, in turn, allows a surface area distribution avoiding the generation of high velocity fragments and reducing atmospheric sound wave. In the present study water plastic containers, having in its centre a detonator inside a cylindrical explosive charge, were used. Tests were performed in unreinforced walls with 1.7 by 3.5 m, which are 1:1.5 scaled. Besides the usage of pressure and displacement transducers, pictures were recorded with high-speed video cameras to process the deflections and identify failure modes

Masonry infill walls under blast loading using confined underwater blast wave generators (WBWG)

The vulnerability of the masonry envelop under blast loading is considered critical due to the risk of loss of lives. The dynamic behaviour of masonry infill walls subjected to dynamic out-of-plane loading was experimentally investigated in this work. Using confined underwater blast wave generators (WBWG), applying the extremely high rate conversion of the explosive detonation energy into the kinetic energy of a thick water confinement, allowed a surface area distribution avoiding also the generation of high velocity fragments and reducing atmospheric sound wave. In the present study water plastic containers, having in its centre a detonator inside a cylindrical explosive charge, were used. Studies were performed in both unreinforced and reinforced walls with 1.7 by 3.5 meters. Bed joint reinforcement and grid reinforcement were used to strengthen the infill walls. Besides the usage of pressure and displacement transducers, pictures with high-speed video cameras were recorded to enable processing of the deflections and identification of failure modes. Two different strengthening solutions were studied under blast loading and the results are presented and compared

Comportamento das paredes não estruturais a ações sísmicas

A análise dos resultados dos sismos recentes relativamente a edifícios de betão armado com paredes de enchimento em alvenaria é preocupante. As imagens de expulsões para fora do plano e dano excessivo no plano são recorrentes e são também testemunhos de práticas erradas, soluções inadequadas e / ou projeto deficiente. A normativa europeia, a aplicar num futuro muito próximo, responsabiliza o projetista de estruturas pelo desempenho dos elementos não estruturais e obrigará a alterações radicais na forma como construímos as paredes de alvenaria, impedindo a utilização de panos de preenchimento de alvenaria não armada em Portugal. A Universidade do Minho, em colaboração com o Laboratório Nacional de Engenharia Civil, desenvolveu recentemente um amplo programa de investigação que inclui ensaios estáticos e dinâmicos em pórticos de betão armado preenchidos com panos alvenaria armados e não armados. No presente artigo, apresentam-se, de forma breve, os resultados obtidos, bem como a normativa nacional aplicável e recomendações para projeto

Ensaios em mesa sísmica de edifícios de betão armado com paredes de alvenaria de enchimento

A influência das paredes de alvenaria de enchimento nas estruturas porticadas de betão armado pode ser visto como algo já estudado exaustivamente, mas as atividade sísmicas recentes, como em 2009 em Itália, mais concretamente em Aquila, demonstraram que as soluções adotadas pelos projetistas ainda são ineficientes. Paredes de alvenaria de enchimento em edifícios construídos nas últimas duas décadas, com base em regulamentos modernos, tiveram um comportamento indesejado, colapsando para fora do plano do pórtico, não cumprindo por isso os estados limite de utilização. Com o acima descrito, e assumindo que a NP EN 1998-1 não fornece elementos suficientes ao projetista para um correto dimensionamento destes elementos não estruturais, realizou-se um programa experimental no Núcleo de Engenharia Sísmica e Dinâmica de Estruturas do Laboratório Nacional de Engenharia Civil, fruto de uma parceria com a Universidade do Minho, onde foram ensaiados na mesa sísmica três modelos à escala 1:1.5 de estruturas porticadas em betão armado preenchidas por diferentes soluções para paredes de alvenaria de tijolo exteriores, com e sem armadura. No presente trabalho são detalhadas as soluções construtivas utilizadas e apresentados os resultados dos ensaios experimentais, com base na observação do comportamento estrutural e padrão de dano, mais especificamente da influência da alvenaria no comportamento global da estrutura, das alterações na interação entre a alvenaria e o pórtico de betão armado mediante a presença ou não de armadura e os modos de colapso dos panos

Analysis of the vegetation area and heat spots in the Porto Seguro settlement in Marabá-PA / Análise da área de vegetação e manchas de calor no assentamento de Porto Seguro em Marabá-PA

Sustainable Development Projects (PDS) are settlements aimed at environmental conservation, through agricultural production activities associated with sustainability. However, many settlements suffer from anthropogenic activities (such as deforestation and burning) to prepare the soil. For this reason, this study aims to analyze the period from 2003 to 2018 at three-year intervals with the generation of thematic maps, which represent the variations of vegetation, anthropized areas and heat spots in relation to the occupation and management of the settlement area. For this, images from the Landsat 5/8 satellite from the INPE image catalog and data from BDQueimada were used, which were treated in the QGIS software using the Supervised Classification (SCP) method. Thus, resulting in the computation of 84 heat spots, 9.25 km2 of anthropized area in the studied period. It should also be noted that in the period from 2015 to 2018, the greatest number of heat spots was observed, even with the reduction in the evolution of anthropized areas. So, it is possible to detect with this study the evolution in the hotspots and reduction of vegetation, from the use of geotechnologies to detect these points that offer conservation risk to the vegetation of the settlement

Multidisciplinary Treatment of a Double First Mandibular Premolar

Gemination aka twinning and fusion, are rare occurrences in posterior mandibular teeth, often requiring endodontic and surgical treatment for functional, orthodontic or cosmetic reasons. The diagnosis and design of a precise treatment plan in cases involving double teeth are in most cases challenging. The purpose of this case report is to describe a successful multidisciplinary treatment protocol for a double tooth. Upon completion of the endodontic, restorative and orthodontic treatments, the clinical and radiographic three-year follow-up revealed that the rest of the transected premolar showed evidence of healing of the supporting tissues and satisfactory cosmetic result.Keywords: Double Tooth; Hemisection; Orthodontics; Root Canal Treatmen

Influence of different photoinitiators on the resistance of union in bovine dentin : experimental and microscopic study

To evaluate in vitro the influence of photoinitiators on the microtensile strength of adhesive systems and composite resins in bovine dentin. Forty dentin obtained from bovine teeth were randomly distributed in four groups (n = 10) according to the dif

Evaluation of caries risk in pre-school children using the CAMBRA protocol and CAST index / Avaliação do risco de cárie em crianças em idade pré-escolar utilizando o protocolo CAMBRA e o índice CAST

Objective: To evaluate the risk of caries and oral health condition in children, using the CAMBRA protocol of the American Academy of Pediatric Dentistry (AAPD) and the Species and Treatment Index for Caries Assessment (CAST) in preschoolers. Method: Method: It is characterized as a cross-sectional retrospective observational analytical study, with clinical examination procedures, questionnaires and oral hygiene analysis in children from 2 to 5 years old. 507 preschoolers aged 2 to 5 years were evaluated in public daycare centers in the city of São Gonçalo - Brazil. Results: The CAMBRA protocol has a moderate risk of 55.4%, while 44.6% has a high risk of caries, from 2 to 5 years. When considering the range of 2 to 3 years apart, 67.1% of children are at high risk. The CAST index showed 10.6% of lesions caused by caries, correlated between caries and the CAST index. Conclusion: It is necessary to implement preventive strategies to reduce caries in this studied group