3 TH C A N A D I A N M A S O N R Y S Y M P O S I U M H A L I F A X , C A N A D A JUNE 4 TH – JUNE 7 TH 2017 BEHAVIOR OF MASONRY INFILL WALLS IN CASE OF FAILURE OF A SUPPORTING COLUMN (original) (raw)
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Behavior of reinforced concrete frame with masonry infill wall subjected to vertical load
Engineering Structures, 2018
The effectiveness of masonry infill wall on behavior of a Reinforced Concrete (RC) frame subjected to a column failure is studied experimentally. For this reason, one full scale RC frame designed according to Eurocode is statically tested to investigate the behavior of the frame with and without masonry infill wall. The obtained results show that infill wall can significantly increase the load carrying capacity of RC frame and thus serve as an important robustness reserve in the case of unpredictable extreme events (i.e. local impact, blast or earthquake). A photogrammetry analysis is carried out to study the behavior of the structure. Results give valuable information about the alternative load path, transfer of the applied load to the column and beams, and interaction forces between RC frame and infill wall. At the end, the experimental program is simulated by the OpenSees software to study the behavior of the frame. After having demonstrated that this model can predict the load deflection with good accuracy, a parametric study is conducted to evaluate the effect of the percentage of longitudinal reinforcement ratio of beams and columns on the load carrying capacity of the infilled RC frame.
The interaction of unreinforced masonry infill walls with the surrounding frame is the key mechanism for the composite action of the structural element. This interaction is of importance under all types of loads but it is especially important under extreme loads such as earthquakes, vehicle impact, blast action etc. Due to the complex interaction and the resulting lack of knowledge regarding the composite action of the infill wall and the frame, the masonry infill wall is commonly considered in the structural design through oversimplified methods. Nevertheless, the interaction loads affect the infill wall behaviour and at the same time, they affect the failure mode of the frame. Therefore, it is crucial to characterize, understand, and evaluate this interaction and to establish models that can quantify the composite behaviour and assess the failure mechanism and the capacity of the composite system. Achieving these goals can improve the design tools for new buildings, enhance the assessment methods of existing buildings, and enable development of advanced computational models. Aiming at these goals, this paper looks into the complex interaction phenomena. The paper adopts an experimental methodology and an experimental setup that includes a masonry infill wall surrounded by a steel frame is used as the main experimental platform. The new experimental apparatus provides unique parameters of the interaction including the detection of the contact zone between the masonry wall and the frame and the assessment of the magnitude and its distribution of the contact tractions. This paper aims at describing the above and a few of the new findings.
Proceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2019
Past and more recent seismic events worldwide clearly showed that a crucial issue for lifesafety and loss reduction due to earthquakes for existing reinforced concrete (RC) buildings is related to the out-of-plane (OOP) collapse of infill masonry walls. In literature, few studies addressed this paramount topic, above all about the proposal of strengthening strategies to prevent the infills' collapse. This paper presents an experimental work about the assessment of possible strengthening solutions designed to mitigate or prevent the out-of-plane collapse of masonry infills in existing RC buildings. Three nominally identical full-scale one-bay-one-story RC frames were built and infilled with a thin masonry wall made up of horizontal hollow clay bricks. The first specimen was representative of the enclosure of a typical existing RC building in the Mediterranean region in its "as-built" condition. The remaining two specimens were strengthened against the out-of-plane collapse by means of two different strengthening techniques based on the application of innovative systems made up of high-ductility mortar plaster and fibre-reinforced polymer nets. All the tests consisted in the application of a semi-cyclic (loading-unloading-reloading) history of imposed displacements in the OOP direction by means of small pneumatic jacks through a uniform distributed load. Experimental results are shown in terms of OOP force-displacement responses, deformed shapes and damage evolution. In the end, the results of the tests are compared to assess the effectiveness of the selected strengthening techniques and to provide a support towards the choice of the best strategies for future further investigations and applications.
Applied Sciences, 2021
On 16 April 2016, an earthquake of Mw 7.8 shook the coast of Ecuador, causing the destruction of buildings and a significant number of casualties. Following a visit by the authors to the city of Portoviejo during the debris removal and recovery stage, it was noted that several reinforced concrete buildings located on corners had collapsed in the central part of the city. These buildings were characterized by the presence of masonry at the edges of the buildings but not between the two mostly open-plan facades on the corner for practical reasons. This article reviews the effect of masonry infill panels on the seismic response of reinforced concrete structures. For this, a model that contains the geometric and mechanical characteristics typical of collapsed buildings was generated and subjected to nonlinear analysis, with both static and dynamic increments. The results show the clear influence of the masonry infill panels on the structural response through the torsional behavior that ...
Out-Of-Plane Behaviour of Loadbearing and Non-Structural Masonry Walls During Recent Earthquakes
1st Croatian Conference on Earthquake Engineering, 2021
Croatia earthquakes had devastating consequences for the affected population of these countries. Besides substantial structural damage of RC buildings as well as loadbearing masonry buildings, these earthquakes caused significant damage of non-structural masonry elements. This paper presents examples of the damage for loadbearing and non-structural masonry walls (infills and partitions) due to out-of-plane seismic effects, as observed by the authors during the reconnaissance visits to the affected areas. This type of damage can prevent the evacuation of people from the buildings during the earthquake, as the falling masonry elements block the evacuation routes, and hinder the reoccupancy and functional recovery of affected buildings after an earthquake. The authors recognize that both loadbearing and non-structural walls (infills and partitions) experienced out-of-plane collapse due to lack of connection to the floor/frame. Using the examples of the damage or failure of masonry walls during the recent earthquakes, their failure mechanisms were explained and the lessons learned were summarized in the paper.
Seismic Vulnerability of Masonry Infilled Reinforced Concrete Frames
This study assesses the seismic vulnerability of ductile reinforced concrete frames with masonry infill walls, utilizing nonlinear dynamic analysis of building models. The evaluation is based on structures designed and detailed according to Eurocodes. The research quantifies the effect of presence and configuration of masonry infill walls on the seismic collapse risk using Incremental Dynamic Analysis within the performance-based framework. Seismic vulnerability assessment indicated that of the configurations considered (bare, partially-infilled and fully-infilled frames), the fully-infilled frame had the lowest collapse risk and the bare frame is found to be the most vulnerable to earthquake-induced collapse.
The effect of masonry infill walls on the reinforced concrete frames behavior under lateral load
2020
The reinforced concrete structures with masonry infill walls are widely used to construct buildings in Algeria, as in many parts of the world. According to earthquake analysis, this type of construction can undergo serious damage under seismic load. The interaction between the infill wall and the surrounding reinforced concrete structure is considered a key parameter, which could trigger damage and even collapse in self-stable frame buildings. To study the behavior of this type of structures and the wall–frame interaction, four half-scale single-storey, single-bay reinforced concrete unfilled and unfilled frames were constructed and tested under in-plane lateral load. Furthermore, the experimental results were analyzed using the Digital Image Correlation (DIC) technique giving a detailed analysis of displacement and strain fields. The wall–frame interaction was evaluated in terms of displacement field evolution and interface slip in the contact contour. The masonry infill wall demon...
The Theoretical Prediction of Collapse Mechanisms for Masonry-Infilled Steel Frames
Arabian Journal for Science and Engineering, 2018
The masonry infills in infilled steel frames are generally considered non-structural elements and are neglected in design by different codes. In fact, the presence of these infills should have a decisive influence on the mechanical properties such as lateral stiffness and ultimate strength. In the present work, a new macro-model has been proposed to model the masonry infill by two equivalent pin-jointed diagonal struts connecting the beams and the columns, respectively. To show the infill effect, the theory of plastic hinges has been adopted as an appropriate approach. In this parametric study, the prediction of the nature of failure mechanisms of structures subjected to a combined loading system has been presented, including their collapse loads with information about the location and order of plastic hinges. The model has been validated by theoretical and experimental predictions. In addition, interaction diagrams, λV −λH , were constructed. From the result, the factors that have a direct influence are the infill thickness and the values of α. By comparing the collapse loads for the infilled frames to their corresponding open frames, it was found that the lateral stiffness and the vertical strength were considerably increased. It can be said that the two-strut model proposed can realistically capture the collapse mechanisms of infilled frames and can more accurately estimate the local effects due to the infill-frame interaction. Finally, important conclusions about the failure modes of the infilled frames and their corresponding collapse loads were drawn from this work.
On the Seismic Behavior of Masonry Infilled Frame Structures
Buildings
Infilled frames are usually modelled in the context of global building analysis using simplified procedures without considering the aspects resulting from the interaction between the panel and the frame. Other aspects, such as adequate design of the floor beams and the beam-columns’ joints, and control of potential sliding shear failure of the columns, that significantly affect the structural response, are also typically not accounted for. In the present work it is intended to look over the literature to evaluate the state of the art regarding the lessons learn from recent earthquakes, the evolution of the structural codes considering the infill masonry panels, and how this influences the evolution of the numerical models and the experimental works to overcome the existent gaps.
Bulletin of Earthquake Engineering, 2014
The paper presents the results of an experimental campaign on the behaviour of engineered masonry infill walls subjected to both in-and out-of-plane loading. The aim of the research was to develop a design approach for masonry infill walls capable of solving their vulnerability and detrimental interaction with the frame structure when exposed to seismic excitation. Tests on two large-scale specimens and sub-assemblies were performed in order to evaluate the infill deformation capacity, the damage associated with different drift levels, and the mechanical properties of the components. A design solution with sliding joints to reduce the infill-frame interaction and ensure out-of-plane stability, which was proposed in a previous study, was developed and refined with focus on construction details. The aim of sliding joints is to ensure a predetermined mechanism in the infill wall, which is governed by hierarchy of strength and is capable of ensuring ductility and energy dissipation that can be taken into account in the design practice, thanks to the predictability of the response. The two infill wall specimens, one of them including an opening, reached up to 3 % in-plane drift with very little damage and supported an out-of-plane force equivalent to a horizontal acceleration four times the acceleration of gravity. The force-displacement hysteretic curve, sliding at the joints and crack pattern show the efficiency of the construction technique, based on affordable and tradition-like construction processes and materials. The technique, presented here for hollow fired-clay masonry units, can be extended to different masonry infill typologies.