1,721,416 research outputs found
Two-step advanced numerical approach for the design of low-cost unbonded fiber reinforced elastomeric seismic isolation systems in new masonry buildings
No full textIn developing countries, masonry is generally employed in the construction of residential buildings due to its relatively cheap cost. However, these structures are often provided with inadequate seismic protection. A low-cost base isolation aimed at decreasing the seismic vulnerability of masonry buildings is studied in this work from a numerical standpoint. The studied isolator is an unbonded fiber-reinforced elastomeric isolator (UFREI). With fewer rubber pads than conventional isolators, the UFREI is a cheaper option. A 3D finite element analysis is performed to predict the behavior of the UFREI under large displacements. The isolation system is then implemented into a two-story masonry building prototype, where the 3D model of a single UFREI is substituted by a nonlinear spring and a damper. This simplification decreases the computational costs of the analysis. Seven scaled ground motions are applied to the numerical model to investigate the seismic performance of the isolated masonry building subjected to a maximum considered earthquake. Nonlinear dynamic analyses are performed in Abaqus, taking into account the two horizontal components of the seismic motion. Numerical results show an excellent isolation performance of the system, with a significant reduction of the inter-story drift and a suitable deformation of the UFREIs, as well as demonstrate that the simplified numerical approach adopted is useful for practical design and quick safety assessments
Espacio de asesoramiento contable, fiscal y empresarial en el aula.
No full textTavio Hernandez, Laura Victoria; director de proyecto: Martínez López, Fernando2023-2024Máster Universitario en Profesorado de Educación Secundaria Obligatoria y Bachillerato, Formación Profesional y Enseñanza de IdiomasFacultad de Ciencias de la Educació
Propuesta de innovación docente para adolescentes con TDAH de Formación Profesional
No full textCabrera Tavio, Clotilde María; director de proyecto: Sierra Macarrón, Leonor2023-2024Máster Universitario en Profesorado de Educación Secundaria Obligatoria y Bachillerato, Formación Profesional y Enseñanza de IdiomasFacultad de Ciencias de la Educació
Compressive Strength Prediction of Square Concrete Columns Retrofitted with External Steel Collars
Full text linkTransverse confining stress in concrete members, commonly provided by transverse reinforcement, has been recognized to enhance the strength and ductility. Nowadays, the confining method has been further developed to external type of confinement. This type of confinement can be used for retrofitting existing concrete columns. Many confining techniques have been proven to be successful in retrofitting circular columns. However, for square or rectangular columns, providing effective confining stress by external retrofitting method is not a simple task due to high stress concentration at column’s corners. This paper proposes an analytical model to predict the peak strength of square concrete columns confined by external steel collars. Comparison with experimental results showed that the model can predict the peak strength reasonably well. However, it should be noted that relatively larger amount of steel is needed to achieve comparable column strength enhancement when it is compared with those of conventional internally-confined columns
L-Shaped Steel Collars: An Alternative External Confining Retrofit for Improving Ductility and Strength of Rectangular Concrete Columns
Full text linkConfinement in concrete column has been well known to improve its strength and ductility. Such enhancement is primarily essential when needed to improve the behavior of concrete columns particularly in terms of ductility during the earthquake strike. This advantage is in line with the modern concept of moment-resisting frame which requires ductile structural framing members. Up to present, traditional transverse steel is still used as internal confinement in concrete column. Several researches have been conducted extensively to study the behavior of confined column, both analytically and experimentally. All these studies confirmed that internal confining method significantly improves the strength and ductility of the columns. However, sometimes the existing columns in a building do not satisfy the building code requirements either unintentionally or due to the unawareness of seismic hazards in terms of confinement. Once the column is built and cast, there is no way to revise the lack of transverse steel internally. The only way possible is to retrofit the columns by using external means. High demand of strengthening on existing RC buildings has made external confinement becoming increasingly popular as an alternative external confining retrofit for RC columns.
Various types of external confinement have been introduced to increase the strength and ductility of the columns, such as FRP wrap or even the use of steel jacketing. These external confining techniques have been proven to be successful in retrofitting circular concrete columns. Experimental programs as well as confining models for externally confined circular columns have been well developed. It is, however, still uneasy to provide an effective confining stress by external retrofit on square or rectangular concrete column. The non-uniform confining stress on column is due to high stress concentration at column corners. Only a few experimental and analytical studies addressed these issues.
The most recent proposed external confinement method is by using the steel collars with hollow square section. This kind of confinement method has been proven to work well as confining system for concrete columns. The strength and particularly the ductility of the columns have been improved significantly. However, it is still too heavy and uneconomical for use as column retrofit. The need of light and economic types of external confining retrofit is urgently required in the country like Indonesia. Thus, an external confining method that is utilizing light L-shape steel section is studied for its capability as an alternative retrofit for rectangular or square concrete columns.
This paper is a part of the first phase of a multiyear research project carried out by the authors. In this paper, a proposed alternative external retrofit for improving the ductility and strength of square concrete columns is presented. Eight columns specimens were cast and tested under monotonic compressive loading. A set of L-shaped steel collars have been introduced externally on square concrete columns prior to testing. The results have confirmed that the proposed external confining techniques considerably enhanced the compressive strength and ductility of the column specimens
Practical designs and seismic performances of residential masonry building isolated with fiber reinforced elastomeric isolators
No full textSince the seismic performance of masonry is considerably low, the masonry structure is not recommended for regions with high seismic risks. However, it is so far the preferred structure for low-class housing, particularly in developing countries. Comprehensive numerical and experimental studies are carried out to evaluate the possibility to build low-rise masonry housing with a suitable isolation system. Low-cost seismic rubber isolators reinforced with fiber are examined to product an innovative isolation device. To reduce the cost, rubber materials considered are recycled compounds derived from manufacturing waste. The utilization of fiber instead of steel can reduce the weight and allows the engineer to implement unbonded application of base isolators. Some technological details for masonry building are proposed to assure that the isolation system works well. In order to evaluate the seismic performance of such isolation system, non-linear static and dynamic analyses are performed through numerical models in a commercial finite element code. The results indicate excellent performances of low-cost isolation system so that this innovative residential masonry building is feasible for real application particularly in developing countries
A low cost rubber seismic isolation system for new masonry residential buildings in developing countries
No full textRubber isolators are used widely in constructions which require a vibration or seismic isolation. It consists of rubber layers and reinforcements that can be steel or fiber lamina. The fiber reinforced isolator results in a lower cost of production and
application than that of steel. Using fiber reinforced isolator allows us to make an unbonded model of rubber bearing. This model leads to a smaller horizontal stiffness and larger displacement of isolators. Researchers consider the Unbonded Fiber Reinforced Elastomeric Isolator (U-FREI) as a low-cost form of rubber bearings. U-FREIs are suitable to isolate seismically a masonry building, which is a common type of housing in developing countries. In this work, we present a finite element model (FEM) to predict the behavior of the U-FREIs undergoing moderate deformations. We adopt a Yeoh hyperelasticity model which is available in the standard package of Abaqus FE software and estimate its coefficients through the available experimental data. Then, we apply tha isolation system onto masonry housing with some simplified methods. We also observe the horizontal behaviors of U-FREIs under different vertical loads and consider a critical condition when the isolators start to be unstable. In parallel, we perform an analytical model to predict the shear behavior and the deformation limit of isolators. Finally, the results show that the analytical model is sufficiently accurate compared to the FE analyses
Low cost rubber seismic isolation of residential new masonry buildings in developing countries
Full text linkA Finite element model was established to examine performance of a low-cost friction base-isolation system in reducing seismic vulnerability of rural buildings. This study adopts an experimental investigation of the isolation system which was conducted in India. Four friction isolation interfaces, namely, marble-marble, marble-high-density polyethylene, marble-rubber sheet, and marble-geosynthetic were involved. Those interfaces differ in static and dynamic friction coefficient obtained through previous research. The FE model was performed based on a macroscopic approach and the masonry wall is assumed as an isotropic element. In order to observe structural response of the masonry house, elastic and plastic parameters of the brick wall were studied. Concrete damage plasticity (CDP) model was adopted to determine non-linear behavior of the brick wall. The results of FE model shows that involving these friction isolation systems could much decrease response acceleration at roof level. It was found that systems with marble-marble and marble-geosynthetic interfaces reduce the roof acceleration up to 50% comparing to the system without isolation. Another interesting result is there was no damage appearing in systems with friction isolation during the test. Meanwhile a severe failure was clearly visible for a system without isolation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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