• Structural Engineering and Mechanics
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• 제73권4호
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• pp.381-395
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• 2020

Study on the inelastic response of bare and masonry infilled Reinforced Concrete (RC) frames repaired using Carbon Fibre Reinforced Polymers (CFRP) and Glass Fiber Reinforced Polymers (GFRP) subjected to quasi- static loading is presented in the work. The hysteresis behaviour, stiffness retention, energy dissipation and damage index are the parameters employed to analyze the efficacy of FRP strengthening of bare and brick in-filled RC frames. It is observed that there is a significant improvement in load carrying capacity of brick infilled frame over bare RC frame. Also FRP strengthened brick infilled frame performs much better than FRP repaired bare frame under quasi static loading. Repair and retrofitting of brick infilled RC frame shows an improved load carrying and damage tolerance capacity than control frame.

• Smart Structures and Systems
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• 제21권4호
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• pp.521-535
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• 2018

The main purpose of this paper is to predict missing absolute out-of-plane displacements and failure limits of infill walls by artificial neural network (ANN) models. For this purpose, two shake table experiments are performed. These experiments are conducted on a 1:1 scale one-bay one-story reinforced concrete frame (RCF) with an infill wall. One of the experimental models is composed of unreinforced brick model (URB) enclosures with an RCF and other is composed of an infill wall with bed joint reinforcement (BJR) enclosures with an RCF. An artificial earthquake load is applied with four acceleration levels to the URB model and with five acceleration levels to the BJR model. After a certain acceleration level, the accelerometers are detached from the wall to prevent damage to them. The removal of these instruments results in missing data. The missing absolute maximum out-of-plane displacements are predicted with ANN models. Failure of the infill wall in the out-of-plane direction is also predicted at the 0.79 g acceleration level. An accuracy of 99% is obtained for the available data. In addition, a benchmark analysis with multiple regression is performed. This study validates that the ANN-based procedure estimates missing experimental data more accurately than multiple regression models.

• Earthquakes and Structures
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• 제8권1호
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• pp.225-251
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• 2015

This paper presents a state-of-the-art review of the nonlinear modelling techniques available today for describing the structural behaviour of masonry infills and their interaction with frame structures subjected to in-plane loads. Following brief overviews on the behaviour of masonry-infilled frames and on the results of salient experimental tests, three modelling approaches are discussed in more detail: the micro, the meso and the macro approaches. The first model considers each of the infilled frame elements as separate: brick units, mortar, concrete and steel reinforcement; while the second approach treats the masonry infill as a continuum. The paper focuses on the third approach, which combines frame elements for the beams and columns with one or more equivalent struts for the infill panel. Due to its relative simplicity and computational speed, the macro model technique is more widely used today, though not all proposed models capture the main effects of the frame-infill interaction.

• Earthquakes and Structures
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• 제22권2호
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• pp.121-135
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• 2022

Many public buildings such as schools, hospitals, etc., where partial infill walls are present in reinforced concrete (RC) structures, have undergone undesirable damage/failure attributed to captive column effect during a moderate to severe earthquake shaking. Often, the situation gets worsened when these RC frames are non-ductile in nature, thus reducing the deformable capability of the frame. Also, in many parts of the Indian subcontinent, it is mandatory to use fly-ash bricks for construction so as to reduce the burden on the disposal of fly-ash produced at thermal power plants. In some scenario, when the non-ductile RC frame, partially infilled by fly-ash bricks, suffers major structural damage, the challenge remains on how to retrofit and restore it. Thus, in this study, two full-scale one-bay, one-story non-ductile RC frame models, namely, bare frame and RC partially infilled frame with fly-ash bricks in 50% of its opening area are considered. In the previous experiments, these models were subjected to slow-cyclic displacement-controlled loading to replicate damage due to a moderate earthquake. Now, in this study these damaged frames were retrofitted and an experimental investigation was performed on the retrofitted specimens to examine the effectiveness of the proposed retrofitting scheme. A hybrid retrofitting technique combining epoxy injection grouting with an innovative and easy-to-implement steel jacketing technique was proposed. This proposed retrofitting method has ensured proper confinement of damaged concrete. The retrofitted models were subjected to the same slow cyclic displacement-controlled loading which was used to damage the frames. The experimental study concluded that the hybrid retrofitting technique was quite effective in enhancing and regaining various seismic performance parameters such as, lateral strength and lateral stiffness of partially fly-ash brick infilled RC frame. Thus, the steel jacketing retrofitting scheme along with the epoxy injection grouting can be relied on for possible repair of the structural members which are damaged due to the captive column effect during the seismic shaking.

• Earthquakes and Structures
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• 제16권3호
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• pp.329-348
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• 2019

The main objective of this experimental research was to investigate the Seismic performance of reinforced concrete frames infilled with perforated clay brick masonry wall of a type commonly used in Algeria. Four one story-one bay reinforced concrete infilled frames of half scale of an existing building were tested at the National Earthquake Engineering Research Center Laboratory, CGS, Algeria. The experiments were carried out under a combined constant vertical and reversed cyclic lateral loading simulating seismic action. This experimental program was performed in order to evaluate the effect and the contribution of the infill masonry wall on the lateral stiffness, strength, ductility and failure mode of the reinforced concrete frames. Numerical models were developed and calibrated using the experimental results to match the load-drift envelope curve of the considered specimens. These models were used as a bench mark to assess the effect of normalized axial load on the seismic performance of the RC frames with and without masonry panels. The main experimental and analytical results are presented in this paper.

• Earthquakes and Structures
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• 제13권5호
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• pp.473-484
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• 2017

The objective of this paper is to report on a study of the use of unstiffened thin steel plate shear walls (SPSWs) for the seismic performance improvement of reinforced concrete frames with deficient lateral rigidity. The behaviour of reinforced concrete frames during seismic activities was rehabilitated with an alternative and occupant-friendly retrofitting scheme. The study involved tests of eight 1/3 scale, one bay, two storey test specimens under cyclic quasi-static lateral loadings. The first specimen, tested in previous test program, was a reference specimen, and in seven other specimens, steel infill plates were used to replace the conventional infill brick or the concrete panels. The identification of the load-deformation characteristics, the determination of the level of improvement in the overall strength, and the elastic post-buckling stiffness were the main issues investigated during the quasi-static test program. With the introduction of the SPSWs, it was observed that the strength, stiffness and energy absorption capacities were significantly improved. It was also observed that the experimental hysteresis curves were stable, and the composite systems showed excellent energy dissipation capacities due to the formation of a diagonal tension field action along with a diagonal compression buckling of the infill plates.

• Structural Engineering and Mechanics
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• 제50권2호
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• pp.137-149
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• 2014

In this study, modal parameters such as natural frequencies, mode shapes and damping ratios of RC frames with low strength are determined for different construction stages using ambient vibration test. For this purpose full scaled, one bay and one story RC frames are produced and tested for plane, brick in-filled and brick in-filled with plaster conditions. Measurement time, frequency span and effective mode number are determined by considering similar studies and literature. To obtain experimental dynamic characteristics, Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques are used together. It is shown that the ambient vibration measurements are enough to identify the most significant modes of RC frames. The results indicate that modal parameters change significantly depending on the construction stages. In addition, Infill walls increase stiffness and change the mode shapes of the RC frame. There is a good agreement between mode shapes obtained from brick in-filled and in-filled with plaster conditions. However, some differences are seen in plane frame, like expected. Dynamic characteristics should be verified using finite element analysis. Finally, inconsistency between experimental and analytical dynamic characteristics should be minimize by finite element model updating using some uncertain parameters such as material properties, boundary condition and section properties to reflect the current behavior of the RC frames.

• Computers and Concrete
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• 제2권6호
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• pp.423-437
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• 2005

In this study two single-bay, three-storey space frames, one with brick masonry infill in the second and third floors representing a soft-storey frame and the other without infill were designed and their 1:3 scale models were constructed according to non-seismic detailing and the similitude law. The models were excited with an intensity of earthquake motion as specified in the form of response spectrum in Indian seismic code IS 1893-2002 using a shake table. The seismic responses of the soft-storey frame such as fundamental frequency, mode shape, base shear and stiffness were compared with that of the bare frame. It was observed that the presence of open ground floor in the soft-storey infilled frame reduced the natural frequency by 30%. The shear demand in the soft-storey frame was found to be more than two and a half times greater than that in the bare frame. From the mode shape it was found that, the bare frame vibrated in the flexure mode whereas the soft-storey frame vibrated in the shear mode. The frames were tested to failure and the damaged soft-storey frame was retrofitted with concrete jacketing and, subjected to same earthquake motions as the original frames. Pushover analysis was carried out using the software package SAP 2000 to validate the test results. The performance point was obtained for all the frames under study, therefore the frames were found to be adequate for gravity loads and moderate earthquakes. It was concluded that the global nonlinear seismic response of reinforced concrete frames with masonry infill can be adequately simulated using static nonlinear pushover analysis.

• Earthquakes and Structures
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• 제5권1호
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• pp.111-127
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• 2013

This paper describes effects of infill walls on behavior of RC frame with low strength, including numerical modeling, modal testing and finite-element model updating. For this purpose full scaled, one bay and one story RC frame is produced and tested for plane and brick in-filled conditions. Ambient-vibration testis applied to identify dynamic characteristics under natural excitations. Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are used to obtain experimental dynamic characteristics. A numerical modal analysis is performed on the developed two-dimensional finite element model of the frames using SAP2000 software to provide numerical frequencies and mode shapes. Dynamic characteristics obtained by numerical and experimental are compared with each other and finite element model of the frames are updated by changing some uncertain modeling parameters such as material properties and boundary conditions to reduce the differences between the results. At the end of the study, maximum differences in the natural frequencies are reduced on average from 34% to 9% and a good agreement is found between numerical and experimental dynamic characteristics after finite-element model updating. In addition, it is seen material properties are more effective parameters in the finite element model updating of plane frame. However, for brick in-filled frame changes in boundary conditions determine the model updating process.

• Structural Engineering and Mechanics
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• 제22권4호
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• pp.449-467
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• 2006

Most existing concrete structures in Taiwan are considered nonductile due to insufficient transverse reinforcement and poor detailing of frame elements. Such features are fairly typical for buildings constructed prior to 1997, at which time the local building code was revised based on ACI 318-95. Among these structures, many contain perimeter or partition walls made of concrete or clay brick for architectural purposes. These walls, though treated as non-structural components in common design practice, could affect the structural behavior of the buildings during an earthquake. To study the behavior of such structures under seismic load, experiments were conducted on concrete frames of various configurations to show the force-deformation relationships, damage patterns, and other characteristics of the frames. For further interest, similar units with columns jacketed by carbon-fiber-reinforced-polymer (CFRP) were also tested to illustrate the effectiveness of this technique in the retrofit of concrete frames.