Quasinormal modes of a black hole with a cloud of strings in Einstein-Gauss-Bonnet gravity

The quasinormal modes for a scalar field in the background spacetime corresponding to a black hole, with a cloud of strings, in Einstein-Gauss-Bonnet gravity, and the tensor quasinormal modes corresponding to perturbations in such spacetime, were both calculated using the WKB approximation. In the obtained results we emphasize the role played by the parameter associated with the string cloud, comparing them with the results already obtained for the Boulware-Deser metric. We also study how the Gauss-Bonnet correction to general relativity affects the results for the quasinormal modes, comparing them with the same background in general relativity.Comment: 15 pages, 7 figures; To appear in IJMP

The design and performance of high-performance perforated fired masonry bricks

Fire perforated clay masonry units have been extensively used through years in masonry structures, particularly in masonry walls both for loadbearing and non-loadbearing purposes (partition walls and enclosures). The location of the masonry walls as external enclosure brings some physical requirements, which together with mechanical requirements are the basis of the design of hollow clay bricks. This chapter provides an overview of the design requirements and design concepts of hollow clay bricks, together with some recent trends arising in the framework of obtaining more sustainable constructive materials. It discusses the main issues related to the mechanical performance of the units and of the masonry assemblages under distinct loading conditions. As often the unreinforced hollow clay masonry is built in seismic prone regions, an emphasis is given to the seismic behavior of hollow clay brick masonry under combined vertical and lateral in-plane loading, being discussed the main seismic performance parameters

Evaluation of the in-plane seismic performance of stone masonry walls

Although traditional historic masonry walls can be viewed as unsuitable structures to undergo seismic actions, they, in fact, exist and frequently represent the major structural elements of ancient buildings. Brick unreinforced masonry walls have been widely studied both from experimental and numerical point of view, but scarce experimental information is available for stone masonry walls. Therefore, the present work aims at increasing the insight about the behavior of typical ancient masonry walls under cyclic loading. Besides the strength and stiffness characterization, information about nonlinear deformation capacity is provided in terms of ductility factor and lateral drifts, which represent a step forward for the new concepts of performance based design

Modern masonry structures and earthquakes : reinforced or unreinforced?

The evolution of structural masonry is briefly reviewed, from old thrust line behavior to modern global behavior using shear walls. For modern structural masonry, the use of unreinforced, confined and reinforced masonry is addressed in seismic areas. A first focus is given to recent approaches towards the safety assessment of unreinforced masonry buildings and their performance in shaking table tests. Subsequently, building systems for modern masonry structures recently developed and tested at University of Minho are presented, one based on lightweight concrete blocks and another based on normal concrete blocks. The experimental and numerical work carried out is discussed and conclusions on the performance of the systems are given

Análise experimental do comportamento de paredes de alvenaria de pedra não reforçada sob acções cíclicas no plano

Com o presente trabalho pretende-se efectuar a avaliação experimental do comportamento de paredes de alvenaria de pedra não reforçada, com diferente aparelho das pedras em alçado, submetidas a acções horizontais cíclicas no plano. A análise dos resultados experimentais abrange a caracterização dos mecanismos de rotura, padrões de fendilhação, e a determinação da resistência última das paredes a acções horizontais cíclicas. Adicionalmente, realiza-se a discussão da resposta em termos de diagramas força-deslocamento, bem como o estudo comparativo da resistência e rigidez lateral para os dois tipos de paredes ensaiadas.Empresa Augusto Ferreira. Bettor MBT

Assessment of the in-plane shear strength of stone masonry walls by simplified models

The present work intends to represent a further step in the knowledge of ancient stone masonry walls through an experimental approach, from which only few information is available. The main results of an experimental program based on in-plane static cyclic tests conduct on masonry wall panels with distinct masonry bond are presented. It is also revealed that simplified models, often used to predict the lateral shear strength of brick masonry walls submitted to static in-plane lateral loading, are also valid for stone masonry walls. Besides, the prediction of the lateral strength by means of a novel equilibrium model is also pointed out