1,721,428 research outputs found
Numerical simulation of an adobe wall under in-plane loading
No full textAdobe is one of the oldest construction materials that is still used in many seismic countries, and different construction techniques are found around the world. The adobe material is characterized as a brittle material; it has acceptable compression strength but it has poor performance under tensile and shear loading conditions. Numerical modelling is an alternative approach for studying the nonlinear behaviour of masonry structures such as adobe. The lack of a comprehensive experimental database on the adobe material properties motivated the study developed here. A set of a reference material parameters for the adobe were obtained from a calibration of numerical models based on a quasi-static cyclic in-plane test on full-scale adobe wall representative of the typical Peruvian adobe constructions. The numerical modelling, within the micro and macro modelling approach, lead to a good prediction of the in-plane seismic capacity and of the damage evolution in the adobe wall considered
Assessment of seismic strengthening solutions for existing low-rise RC buildings in Nepal
Full text linkThe main objective of this study is to analytically investigate the effectiveness of different strengthening solutions in upgrading the seismic performance of existing reinforced concrete (RC) buildings in Nepal. For this, four building models with different structural configurations and detailing were considered. Three possible rehabilitation solutions were studied, namely: (a) RC shear wall, (b) steel bracing, and (c) RC jacketing for all of the studied buildings. A numerical analysis was conducted with adaptive pushover and dynamic time history analysis. Seismic performance enhancement of the studied buildings was evaluated in terms of demand capacity ratio of the RC elements, capacity curve, inter-storey drift, energy dissipation capacity and moment curvature demand of the structures. Finally, the seismic safety assessment was performed based on standard drift limits, showing that retrofitting solutions significantly improved the seismic performance of existing buildings in Nepal
Experimental assessment and retrofit of full-scale models of existing RC frames
Full text linkPSD tests on two full-scale models of existing non-seismic resisting RC frame structures are
described. The testing program covered several aspects, namely assessment of seismic
performance of existing frames without and with infill panels, retrofitting of the bare frame
using Selective Retrofitting techniques, strengthening of the infill panels using shotcrete and
retrofitting of the frame using K-bracing with shear-link dissipators. The main results from
the tests are summarized and discussed and the conclusions are drawn. The tests on the bare
frame have shown how vulnerable are existing structures constructed in the 60’s and the
beneficial effects of infill panels were confirmed from the tests on the infilled frame.
Important improvements, in terms of seismic performance, were achieved by the retrofitting
of the frames. However, it was also confirmed that strengthening of the existing infill panels
in poorly detailed frames may lead to dangerous ‘local’ failures, such as the shear out of the
external columns
Vulnerability assessment of the S. João de Loure Bridge: Vouga’s river
Full text linkSteel bridges are particularly sensible to corrosion, which can put at risk the structural safety by affecting the joint elements. Having this in mind, the objective of this work was to evaluate the influence of the joint's stiffness in the structural response of the S. João de Loure steel bridge. An improved model was developed for the bridge on the structural analysis software SAP2000. Maximum deflection, axial forces and corresponding stresses, and natural frequencies, were analyzed. Numerical results allow concluding about the influence of the joint's stiffness in the structural response of the bridge
Cyclic response of RC beam-column joints reinforced with plain bars: an experimental testing campaign
Full text linkExisting reinforced concrete (RC) buildings constructed until the mid-70’s, with plain reinforcing bars, are expected to behave poorly when subjected to earthquake actions. This paper describes an experimental program designed to investigate the influence of poor detailing on the cyclic behaviour of RC beam-column joint elements.
Cyclic tests were performed on five interior and five exterior full-scale beam-column joints with different detailing characteristics and reinforced with plain bars. An additional joint of each type was built with deformed bars for an evaluation of the influence of bond properties on the cyclic response of the structural element. The force-displacement global response, energy dissipation, equivalent damping and damage behaviour of the joints was investigated and the main results are presented and discussed. The experimental results indicate that the bond-slip mechanism has significantly influenced the cyclic response of the beam-column joints. The specimens built with plain bars showed lower energy dissipation, stiffness and equivalent damping
Nonlinear finite element model for traditional adobe masonry
No full textA huge fraction of the worldwide built heritage consists of adobe masonry (AM) structures, including cultural heritage sites protected by UNESCO and single countries. In Portugal, the Aveiro district is a region where approximately 40% of the building stock is composed of AM structures with high cultural, social and architectural value. This paper presents a macro-mechanical finite element (FE) model that was developed for future performance assessments of AM structures. Based on available experimental data on Aveiro’s AM, the FE model was validated in two different boundary and loading conditions associated with normal and diagonal compression tests. A satisfactory numerical-experimental agreement was found in terms of load-displacement curves, crack patterns, local stresses and deformations. A sensitivity analysis evidenced that compressive and tensile strengths mostly influence the peak load capacity and post-peak softening behaviour of wallettes, whereas Young’s modulus affects the pre-peak rising branch of load-displacement curves
Stochastic finite element analysis of Portuguese adobe masonry
Full text linkEarth is a construction material which has been used since ancient times in many parts of the world according to its local
availability, low manufacturing cost, and its need for simple construction techniques. Even though earthen constructions
have good thermo-acoustic properties, they typically show a very poor performance under earthquake ground motion.
Rammed earth and adobe masonry are the main types of earthen construction. Nowadays, it is estimated that approximately
30% of the world population lives in earthen buildings and this percentage increases up to around 50% in developing
countries. Such an information highlights the need for a seismic assessment and strengthening of existing earthen structures.
The present study is focused on the mechanical behavior of the traditional adobe masonry (AM) of the Aveiro district,
Portugal, where approximately 40% of existing buildings are made of adobe and many of them have a socio-cultural value.
Extensive surveys have shown a poor state of conservation of AM buildings, the strengthening of which should be based on
a comprehensive knowledge of mechanical properties and behavior. To that aim, a nonlinear finite element (FE) modelling
approach is used to simulate the experimental behavior of AM in different boundary and loading conditions associated with
axial and diagonal compression tests. The latter are amongst the most common experimental tests used for mechanical
characterization of masonry assemblages, particularly to define their macroscopic response to uniaxial compression and
shear. Based on statistics for mechanical properties of adobe bricks and mud mortar provided by past experimental tests, a
macromechanical model of AM was developed within LS-DYNA software and validated against experimental data. The FE
models of two types of specimens subjected to axial compression and diagonal compression, separately, were generated. A
comparative analysis between numerical and experimental results, both in terms of force–displacement curves and crack
patterns, showed that the FE model was able to reproduce the real behavior of AM in different boundary and loading
conditions. Afterwards, a single-parameter sensitivity analysis was performed on each AM model to assess whether and
how the AM behavior changes under varying material properties. That analysis was the basis for a probabilistic assessment
in which a stochastic FE analysis was carried out. Each material property was assumed to be a spatially-distributed random
variable in order to reproduce the high level of inhomogeneity provided by material tests on AM constituents, that is adobe
bricks and mortar. A small number of model realizations subjected to axial compression was randomly generated through
Monte Carlo simulation technique. Two alternative types of stochastic representation were adopted. The former was a
simplified stochastic FE modeling (SFEM) in which the spatial variability of material properties was lumped into single
brick units, each of them fictitiously extended to the middle of mortar joints. In the second case, an advanced stochastic FE
modeling (ASFEM) strategy was used and consisted in a random generation of material properties for all finite elements. It
was found that even a limited number of ASFEM simulations allowed the experimental force–displacement response to be
captured
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