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## Parametrical study of masonry walls subjected to in-plane loading through numerical modeling

HAACH, Vladimir G.; VASCONCELOS, Graca; LOURENCO, Paulo B.
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
75.62%
This paper deals with the numerical assessment of the influence of parameters such as pre-compression level, aspect ratio, vertical and horizontal reinforcement ratios and boundary conditions on the lateral strength of masonry walls under in-plane loading. The numerical study is performed through the software DIANA (R) based on the Finite Element Method. The validation of the numerical model is carried out from a database of available experimental results on masonry walls tested under cyclic lateral loading. Numerical results revealed that boundary conditions play a central role on the lateral behavior of masonry walls under in-plane loading and determine the influence of level of pre-compression as well as the reinforcement ratio on the wall strength. The lateral capacity of walls decreases with the increase of aspect ratio and with the decrease of pre-compression. Vertical steel bars appear to have almost no influence in the shear strength of masonry walls and horizontal reinforcement only increases the lateral strength of masonry walls if the shear response of the walls is determinant for failure, which is directly related to the boundary conditions. (C) 2011 Elsevier Ltd. All rights reserved.; European Commission[COOP-CT-2005-018120]; Programme Alssan...

## Fatigue apparatus for geometrically complex non-standardized specimens

Nascimento, Marcelino P.; Voorwald, Herman J.C.
Tipo: Artigo de Revista Científica Formato: 48-54
ENG
Relevância na Pesquisa
45.62%
Standard Test Methods (e.g. ASTM, DIN) for materials characterization in general, and for fatigue in particular, do not contemplate specimens with complex geometries, as well as the combination of axial and in-plane bending loads in their methodologies. The present study refers to some patents and the new configuration or configurations of specimens (non-standardized by the status quo of test methods) and a device developed to induce axial and bending combined forces resultants from axial loads applied by any one test equipment (dynamic or monotonic) which possesses such limitation, towards obtaining more realistic results on the fatigue behavior, or even basic mechanical properties, from geometrically complex structures. Motivated by a specific and geometrically complex aeronautic structure (motor-cradle), non-standardized welded tubular specimens made from AISI 4130 steel were fatigue-tested at room temperature, by using a constant amplitude sinusoidal load of 20 Hz frequency, load ratio R = 0.1 with and without the above referred auxiliary fatigue apparatus. The results showed the fatigue apparatus was efficient for introducing higher stress concentration factor at the welded specimen joints, consequently reducing the fatigue strength when compared to other conditions. From the obtained results it is possible to infer that with small modifications the proposed apparatus will be capable to test a great variety of specimen configurations such as: squared tubes and plates with welded or melted junctions...

## Effect of fiber orientation on the shear behavior of glass fiber/epoxy composites

Almeida, Jose Humberto S.; Angrizani, Clarissa C.; Botelho, Edson C.; Amico, Sandro C.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 789-795
ENG
Relevância na Pesquisa
55.52%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); This paper deals with the study of the influence of the lay-up configuration on interlaminar and in-plane shear properties of glass fiber reinforced epoxy composites. The following laminates were produced by resin transfer molding with vacuum assistance for this study: [0](5), [90](5), [0/90/0/90/0] and randomly oriented (mat). The composites, with similar overall fiber volume fraction, were evaluated based on four tests: double-notched shear, short beam shear, V-notched rail and Iosipescu shear tests. Besides, the dynamic shear modulus was measured with non-destructive testing based on free vibration method. The [0](5) laminate presented interlaminar shear strength almost twice that of [90](5), whereas the mat samples presented higher in-plane shear strength in both tests used due to its random fiber orientation. The dynamic shear modulus was higher for the composites [0](5), as expected due to the longitudinally oriented fibers. Among the shear test methods applied, double-notched and V-notched methods exhibited more auspicious features...

## Behavior of masonry infill panels in RC frames subjected to in plane and out of plane loads

Pereira, Manuel Fernando Paulo; Pereira, M. F. Neto; Ferreira, J. E. Dias; Lourenço, Paulo B.
Tipo: Conferência ou Objeto de Conferência
Relevância na Pesquisa
65.72%
The building envelope in Europe is usually made of masonry walls, with enclosure and infill functions. Masonry walls have a major economical importance and contribute significantly to the building performance. Even if infill walls have no load-bearing function, they contribute significantly to the seismic behavior of buildings. Therefore, their adequate structural performance is needed, avoiding the occurrence of severe in-plane damage, with very large economical losses, and the out-of-plane expulsion, which additionally represents a large risk for human life. Recent earthquake codes in Europe require the safety assessment of non-structural elements (parapets, veneer masonry walls, infill walls, etc.), when their collapse entails risks for people or for the main structure. The Eurocode standards, entering the mandatory stage now, incorporate new requirements to be fulfilled by buildings or their parts. Such is the case of masonry infilled RC frames whose panels, according to Eurocode 8, are explicitly required to withstand the out-of-plane movement induced by earthquakes. Appropriate measures should be taken to avoid brittle failure and premature disintegration of the infill walls, as well as the partial or total out-of-plane collapse of slender masonry panels. This paper presents the experimental work and results achieved by applying cyclic out-ofplane loads to damaged masonry infilled RC frames. The masonry panels were previously damaged by applying an in-plane cyclic load after which the cyclic out-of- plane loads were applied. The frames and panels tested follow the traditional Portuguese RC structure construction system to which different types of reinforcement have been introduced in the panels.

## Monte Carlo homogenized limit analysis model for randomly assembled blocks in-plane loaded

Milani, G.; Lourenço, Paulo B.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
65.57%
A simple rigid-plastic homogenization model for the limit analysis of masonry walls in-plane loaded and constituted by the random assemblage of blocks with variable dimensions is proposed. In the model, blocks constituting a masonry wall are supposed infinitely resistant with a Gaussian distribution of height and length, whereas joints are reduced to interfaces with frictional behavior and limited tensile and compressive strength. Block by block, a representative element of volume (REV) is considered, constituted by a central block interconnected with its neighbors by means of rigid-plastic interfaces. The model is characterized by a few material parameters, is numerically inexpensive and very stable. A sub-class of elementary deformation modes is a-priori chosen in the REV, mimicking typical failures due to joints cracking and crushing. Masonry strength domains are obtained equating the power dissipated in the heterogeneous model with the power dissipated by a fictitious homogeneous macroscopic plate. Due to the inexpensiveness of the approach proposed, Monte Carlo simulations can be repeated on the REV in order to have a stochastic estimation of in-plane masonry strength at different orientations of the bed joints with respect to external loads accounting for the geometrical statistical variability of blocks dimensions. Two cases are discussed...

## A simplified homogenized limit analysis model for randomly assembled blocks out-of-plane loaded

Milani, G.; Lourenço, Paulo B.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
55.71%
A kinematic rigid-plastic homogenization model for the limit analysis of masonry walls arranged in random texture and out-of-plane loaded is proposed. The model is the continuation of a previous work by the authors in which masonry in-plane behavior was investigated. In the model, blocks constituting a masonry wall are supposed infinitely resistant with a Gaussian distribution of height and length, whereas joints are reduced to interfaces with frictional behavior and limited tensile and compressive strength. Block by block, a representative element of volume (REV) is considered, constituted by a central block interconnected with its neighbors by means of rigid plastic interfaces. Two different classes of problems are investigated, the first consisting of full stochastic REV assemblages without horizontal and vertical alignment of joints, the second assuming the presence of a horizontal alignment along bed joints, i.e. allowing blocks height variability only row by row. A sub-class of elementary deformation modes is a-priori chosen in the REV, mimicking typical failures due to joint cracking and crushing. The model is characterized by a few material parameters and it is therefore particularly suited to perform large scale Monte Carlo simulations. Masonry strength domains are obtained equating the power dissipated in the heterogeneous model with the power dissipated by a fictitious homogeneous macroscopic plate. A stochastic estimation of out-of-plane masonry strength domains (both bending moments and torsion are considered) accounting for the geometrical statistical variability of blocks dimensions is obtained with the proposed model. The case of deterministic block height (quasi-periodic texture) can be obtained as a subclass of this latter case. As an important benchmark...

## Comportamento sísmico de um sistema log-house

Araújo, João P.
Tipo: Trabalho de Conclusão de Curso
Relevância na Pesquisa
55.58%
Dissertação de mestrado (ciclo de estudos integrado em Engenharia Civil); A madeira, enquanto material de construção, já ocupou no passado um lugar de destaque. Contudo, o aparecimento de outros materiais, como o aço e o betão, levou quase ao seu abandono total para fins estruturais. Excepção a esta tendência viveu-se nos países do Norte e Centro da Europa, sendo exemplo o sistema construtivo “Log-house”. Este sistema construtivo consiste na construção de paredes através da sobreposição de troncos de secção circular ou rectangular, geralmente possuindo nas faces superior e inferior um entalhe de forma a aumentar a superfície de contacto e a estabilidade. As paredes que constituem este sistema construtivo conferem-lhe resistência estrutural e estabilidade face às acções verticais e horizontais, quer no seu plano, quer no plano perpendicular. A resistência às acções verticais depende da área de contacto entre os toros e da resistência à compressão perpendicular às fibras da madeira, enquanto as acções horizontais perpendiculares ao plano da parede serão suportadas pelas paredes transversais, dependendo a estabilidade das paredes a acções horizontais no seu plano do atrito desenvolvido nos entalhes que cada toro possui e da resistência oferecida pelas paredes ortogonais. Face à falta de conhecimento do comportamento destas construções em caso de ocorrência de um sismo...

## Parametrical study of masonry walls subjected to in-plane loading through numerical modeling

Haach, V.; Vasconcelos, Graça; Lourenço, Paulo B.
Fonte: Elsevier, Ltd Publicador: Elsevier, Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
75.62%
This paper deals with the numerical assessment of the influence of parameters such as pre-compression level, aspect ratio, vertical and horizontal reinforcement ratios and boundary conditions on the lateral strength of masonry walls under in-plane loading. The numerical study is performed through the software DIANA® based on the Finite Element Method. The validation of the numerical model is carried out from a database of available experimental results on masonry walls tested under cyclic lateral loading. Numerical results revealed that boundary conditions play a central role on the lateral behavior of masonry walls under in-plane loading and determine the influence of level of pre-compression as well as the reinforcement ratio on the wall strength. The lateral capacity of walls decreases with the increase of aspect ratio and with the decrease of pre-compression. Vertical steel bars appear to have almost no influence in the shear strength of masonry walls and horizontal reinforcement only increases the lateral strength of masonry walls if the shear response of the walls is determinant for failure, which is directly related to the boundary conditions.

## Numerical modelling of masonry-infilled reinforced concrete frames : model calibration and parametric study

Akhoundi, Farhad; Lourenço, Paulo B.; Vasconcelos, Graça
Tipo: Conferência ou Objeto de Conferência
Relevância na Pesquisa
55.59%
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)

## Experimental investigation on the yield behavior of Nomex honeycombs under combined shear-compression

Zhou,Zhiwei; Wang,Zhihua; Zhao,Longmao; Shu,Xuefeng
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Relevância na Pesquisa
45.66%
This paper presents an experimental investigation on the yield behavior of Nomex honeycombs under combined shearcompression with regard to out-of-plane direction. Four different types of specimens were designed in order to investigate the influence of in-plane orientation angle on the yield behavior of honeycombs under combined loads. Two different failure modes of honeycomb specimens, i.e. the plastic buckling and the extension fracture of cell walls, are observed under combined shear-compression. The experimental results validate that the in-plane orientation angle has a significant influence on the developments of the experimental yield surface. The experimental yield surfaces are compared with a phenomenological yield criterion capable of accounting for anisotropic behavior. The comparative analytical results indicate the experimental yield surfaces are approximately consistent with the theoretical yield surfaces in the normal-shear stress space. These experimental results are useful to develop constitutive models of Nomex honeycombs under combined shear-compression.

## Thermo-mechanical vibration analysis of annular and circular graphene sheet embedded in an elastic medium

Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Relevância na Pesquisa
55.47%
In this study, the vibration behavior of annular and circular graphene sheet coupled with temperature change and under in-plane pre-stressed is studied. Influence of the surrounding elastic medium 011 the fundamental frequencies of the single-layered graphene sheets (SLGSs) is investigated. Both Winkler-type and Pasternak- type models are employed to simulate the interaction of the graphene sheets with a surrounding elastic medium. By using the nonlocal elasticity theory the governing equation is derived for SLGSs. The closed-form solution for frequency vibration of circular graphene sheets lias been obtained and nonlocal parameter, inplane pre-stressed, the parameters of elastic medium and temperature change appears into arguments of Bessel functions. The results are subsequently compared with valid result reported in the literature and the molecular dynamics (MD) results. The effects of the small scale, pre-stressed, mode number, temperature change, elastic medium and boundary conditions on natural frequencies are investigated. The non-dimensional frequency decreases at high temperature case with increasing the temperature change for all boundary conditions. The effect of temperature change 011 the frequency vibration becomes the opposite at high temperature case in compression with the low temperature case. The present research work thus reveals that the nonlocal parameter...

## Effect of harmonic in-plane edge loading on dynamic stability of stiffened shell panels with cutouts

Patel, S.; Datta, P.; Sheikh, A.
Fonte: Imperial College Press Publicador: Imperial College Press
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
65.52%
The effect of non-uniform in-plane pulsating edge loading on dynamic instability behavior of perforated stiffened shell panels is presented in this paper using finite element method. The eight-noded isoparametric degenerated shell element and a compatible three-noded curved beam element are used to model the shell panels and the stiffeners, respectively. Bolotin method is applied to analyze the dynamic instability regions. Numerical results of convergence studies are presented and comparison is made with the published results from the literature. The effects of various parameters like shell geometry, loading type, cutout size and dynamic load factors are considered in dynamic instability analysis of stiffened shell panels with cutout. The buckling results of the cutout stiffened panels are also presented.; S. N. Patel, P. K. Datta, A. H. Sheikh

## Mechanical behavior of hybrid 3D woven composites

Muñoz Sánchez, Raúl
ENG
Relevância na Pesquisa
45.66%
Unidirectional fiber-reinforced composites are widely used in the aerospace industry due to their excellent in-plane mechanical properties, high corrosion resistance, dimensional stability and fatigue life. Nevertheless, they exhibit poor delamination resistance and damage tolerance, particularly under impact. The lack of reinforcement in the through-thickness direction makes them particularly vulnerable to out-of-plane threats caused by foreign objects, such as ice slabs or open-rotor blade fragments impacting on skin fuselages. A cost-effective alternative is the use of 3D woven orthogonal reinforcements, in which delamination resistance and damage tolerance are improved by weaving a yarn in the through-thickness direction. This technique allows the combination of several fiber types (hybridization) and enables the optimization of the composite properties by varying the fiber content. Preforms may be infused by using out-of-autoclave processing techniques, such as Vacuum Assisted Resin Transfer Molding (VARTM), leading to considerable cost savings, as opposed to autoclave consolidation. Despite of the potential of these materials, the use of hybrid 3D woven composites is limited by the lack of experimental data and reliable models able to predict the mechanical response of the material. This work analyzes the mechanical behavior of a hybrid 3D woven orthogonal composite made up of a thermoset polymeric matrix (epoxy-vinylester) reinforced with carbon and glass fibers...

## Behavior of Sandwich Panels Subjected to Bending Fatigue, Axial Compression Loading and In-Plane Bending

Mathieson, Haley
Fonte: Quens University Publicador: Quens University
EN; EN
Relevância na Pesquisa
45.64%

## In-Plane Magnetodrag between Dilute Two-Dimensional Systems

Pillarisetty, R.; Noh, Hwayong; Tutuc, E.; De Poortere, E. P.; Tsui, D. C.; Shayegan, M.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.62%
We performed in-plane magnetodrag measurements on dilute double layer two-dimensional hole systems, at in-plane magnetic fields that suppress the apparent metallic behavior, and to fields well above those required to fully spin polarize the system. When compared to the single layer magnetoresistance, the magnetodrag exhibits exactly the same qualitative behavior. In addition, we have found that the enhancement to the drag from the in-plane field exhibits a strong maximum when both layer densities are matched.; Comment: 4 pages, 3 figures; minor corrections. Accepted in Phys. Rev. Lett

## Conductivity sum rule, implication for in-plane dynamics and c-axis response

Kim, Wonkee; Carbotte, J. P.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
55.52%
Recently observed $c$-axis optical sum rule violations indicate non-Fermi liquid in-plane behavior. For coherent $c$-axis coupling, the observed flat, nearly frequency independent $c$-axis conductivity $\sigma_{1}(\omega)$ implies a large in-plane scattering rate $\Gamma$ around $(0,\pi)$ and therefore any pseudogap that might form at low frequency in the normal state will be smeared. On the other hand incoherent $c$-axis coupling places no restriction on the value of $\Gamma$ and gives a more consistent picture of the observed sum rule violation which, we find in some cases, can be less than half.; Comment: 3 figures. To appear in PRB

## Self-organized synthesis of patterned magnetic nanostructures with in-plane and perpendicular to the plane magnetization

Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.65%
Patterned arrays of ferromagnetic nanoparticles of Co, Ni, and Fe_{\text{50}} Co_{\text{50}} have been synthesized from their ultrathin metal films on SiO_{\text{2}} substrate by nanosecond laser-induced self-organization. The morphology, nanostructure, and magnetic behavior of the nanoparticle arrays were investigated by a combination of electron, atomic force, and magnetic force microscopy techniques. Transmission electron microscopy investigations revealed a granular polycrystalline nanostructure, with the number of grains inside the nanoparticle increasing with their diameter. Magnetic force measurements showed that the magnetization direction of the Co and Ni nanoparticles was predominantly out-of-plane while those for the Fe_{\text{50}}Co_{\text{50}} alloy was in the plane of the substrate. This difference in behavior is due to the dominating influence of magnetostrictive energy on the magnetization as a result of residual thermal strain following fast laser processing. Since the magnetostriction coefficient is negative for polycrystalline Co and Ni, and positive for Fe_{\text{50}}Co_{\text{50}}, the tensile residual strain forces the magnetization direction of the negative magnetostriction materials out-of-plane and the positive magnetostriction materials in-plane. This demonstrates a cost-effective non-epitaxial technique for the fabrication of patterned arrays of magnetic nanoparticles with tailored magnetization orientations.; Comment: 22 pages...

## Reentrant quantum anomalous Hall effect with in-plane magnetic fields in HgMnTe quantum wells

Hsu, Hsiu-Chuan; Liu, Xin; Liu, Chao-Xing
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.67%
Quantum anomalous Hall effect has been predicted in HgMnTe quantum wells with an out-of-plane magnetization of Mn atoms. However, since HgMnTe quantum wells are paramagnetic, an out-of-plane magnetic field is required to polarize magnetic moments of Mn atoms, which inevitably induces Landau levels and makes it difficult to identify the origin of the quantized Hall conductance experimentally. In this work, we study the quantum anomalous Hall effect in the presence of an in-plane magnetic field in Mn doped HgTe quantum wells. For a small out-of-plane magnetic field, the in-plane magnetic field can drive the system from a normal insulating state to a quantum anomalous Hall state. When the out-of-plane magnetic field is slightly above the transition point, the system shows a reentrant behavior of Hall conductance, varying from $-e^2/h$ to 0 and back to $-e^2/h$, with increasing in-plane magnetic fields. The reentrant quantum anomalous Hall effect originates from the interplay between the exchange coupling of magnetic moments and the direct Zeeman coupling of magnetic fields. The calculation incorporating Landau levels shows that there is no qualitative change of the reentrant behavior.

## In-plane and out-of plane experimental characterization of rc masonry infilled frames

Akhound, Farhad; Vasconcelos, Graça; Lourenço, Paulo B.; Palha, Carlos Alberto Oliveira Fernandes; Silva, Luís C.
Tipo: Conferência ou Objeto de Conferência
Relevância na Pesquisa
75.69%
Seismic investigations of typical south European masonry infilled frames were performed by testing two reduced scale specimens: one in the in-plane direction and another in the out-ofplane direction. Information about geometry and reinforcement scheme of those structures constructed in 1980s were obtained by [1]. The specimen to be tested in the in-plane direction was constructed as double leaf masonry while the specimen for testing in the out-of-plane direction is constructed with only its exterior leaf since the recent earthquakes have highlighted the vulnerability of the external leaf of the infills in out-of-plane direction [2]. The tests were performed by applying the pre-defined values of displacements in the in-plane and out-of-plane directions in the control points. For in-plane testing it was done by hydraulic actuator and for out-of-plane testing through the application of an airbag. Input and output air in the airbag was controlled by using a software to apply a specific displacement in the control point of the infill wall. Mid-point of the infill was assumed as a control point for outof- plane testing. Deformation and crack patterns of the infill confirm the formation of two-way arching mechanism of the masonry infill until collapse of the upper horizontal interface between infill and frame which is known as weakest interface due to difficulties in filling the mortar between bricks of last row and upper beam. This results in the crack opening through a welldefined path and the consequent collapse of the infill.

## Traditional timber frame walls: mechanical behavior analysis and retrofitting

Vasconcelos, Graça; Poletti, Elisa
Fonte: IGI Global Publicador: IGI Global
Tipo: Artigo de Revista Científica