Experimental Assessment of Strengthening Strategies Against the Out-Of-Plane Collapse of Masonry Infills in Existing RC Structures (original) (raw)
Related papers
Engineering Structures, 2020
Seismic events worldwide clearly showed that a crucial issue for life-safety and reduction of losses due to earthquakes for reinforced concrete (RC) buildings is related to the out-of-plane (OOP) collapse of infill masonry walls. In the literature, few studies addressed this paramount topic. This paper presents an experimental work about the assessment of possible strengthening solutions to prevent the out-of-plane collapse of masonry infills in RC buildings. Four 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 as-built condition. The other specimens were strengthened against the out-of-plane collapse by means of Textile Reinforced Mortar (TRM) strengthening techniques based on the application of high-ductility or common mortar plaster and fiberglass reinforcing bidirectional nets, varying the TRM-to-RC frame connection's effectiveness. Tests consisted of a semi-cyclic history of imposed displacements in the OOP direction through small uniformly distributed pneumatic jacks. Experimental results are shown and 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.
A Simple Strengthening Method for Preventing Collapsed of Vulnerable Masonry Infills
Buildings
A series of structural tests were conducted to examine the seismic performance of masonry infills strengthened with particular materials on infilled reinforced concrete (RC) frame structures. Six 1:4 scaled-down RC frame specimens had been prepared, including one brick-infilled frame without strengthening and five brick infills strengthened with innovative strengthening materials. The materials were steel wire mesh, chicken hexagonal wire mesh, plastic wire mesh, fiber-reinforced polymer (FRP), and plastic stretch film. The strengthening was diagonally applied on both surfaces of the masonry infill. The steel wire mesh, chicken hexagonal wire mesh, and plastic wire mesh were sewn using steel wire, while the FRP sheet was glued using epoxy resin and the plastic stretch film was glued using synthetic rubber adhesive. The specimens were tested following the FEMA 461 standard testing protocol, which involved applying lateral static cyclic loading to the specimens. The displacement trans...
The in plane behavior of masonry infill walls that are subjected to lateral loading simulating the effects of earthquakes on buildings has been the subject of many studies. The present work is focused on a problem that has been hardly studied and refers to the vertical action on such walls. In particular, it concerns a vertical action that evolves when a supporting column of a multi-story reinforced concrete frame with infill masonry walls fails. Such failure may happen as a result of extreme loadings for instance a strong earthquake, car impact, or military or terror action in proximity to the column. Without infill walls, the loss of a supporting column may lead to a partial or even full progressive collapse of the bare reinforced concrete frames. The presence of masonry infill walls may restrain the process and even prevent the development of a progressive collapse mechanism. The aim of this study is to look into the role of the composite action of a frame and an infill wall in the event of loss of a supporting column. The study adopts an experimental methodology and numerical methods aiming to evaluate the contributions of the unreinforced masonry infill, to examine its interaction with the frame, and to quantify its contribution to the resistance of the bare frame under such circumstances.
2016
Recent earthquakes demonstrated a significant contribution of the masonry infill walls in the structural response of the existent reinforced concrete buildings. When subjected to seismic actions, they tend to interact with the surrounding RC frames, which can result in different failure modes depending on the combination of the in-plane and the out-of-plane behaviour. From the surveys on damaged and collapsed RC buildings in the L'Aquila (Italy) and Lorca (Spain) earthquakes a large number of buildings that suffered severe damage or collapse had their poor performance associated with the influence of the infill panels. The masonry infill walls are considered non-structural elements but, their contribution should be considered in the structural response analysis of existing buildings, for which the understanding out-ofplane non-linear behaviour of infill walls is of full importance in order to develop efficient strengthening solutions to prevent and improve their performance in future earthquakes, and consequently reduce their seismic vulnerability. The main objective of the present paper was to obtain further knowledge concerning to the out-of-plane response of masonry infill walls panels. For this an experimental testing campaign on full scale infill walls was carried out in three experimental (cyclic and monotonic) out-of-plane tests with and without previous in-plane damage. The experimental campaign, material characterization and the test setup will be described along the manuscript as well as the main experimental tests results will be presented and discussed.
IRJET, 2022
Buildings are subjected to a variety of natural hazards over their mean lives and around the globe structural multi-hazard analysis and design has become a hotbed of research. Earthquake and progressive collapse seem to be two of the major threats for these constructions. Consequently, limited research on the effects of seismic and progressive collapse designs on multi-story buildings has been done. A building's construction also contains a variety of structural and non-structural parts for various functions. When examining structural members, we as structural engineers, tend to focus on the structural members for resistance of buildings against any hazard and Non-structural components are often overlooked. However, several studies have shown that non-structural parts, such as infill walls, play a key role in increasing building resistance to natural disasters. As a result, the role of the infill wall against various risks must be investigated. The effect of infill walls in the case of progressive and seismic collapse of RC structures has received far less attention. In this study, it is decided to evaluate effect of different infill wall configuration in case of combine study of seismic and progressive collapse of reinforced concrete structures by using ETABS software. For this purpose four models 1) Bare Frame 2) Fully In-filled Frame 3) Open Ground Frame and 4) Open Ground & Intermediate Frame have been considered.
Reinforced Concrete Frames with Masonry Infills. Damages and Consolidation Measures
This paper presents a synthesis of the typical damages recorded in reinforced concrete frames and masonry infills after recent earthquakes. The behavior and failure modes of the infill walls are of great importance, especially since no clear recommendations are provided in the current design codes for the performance of these types of walls. In the present time, masonry infill walls are considered to be non-structural building elements, while the seismic behavior of reinforced concrete frame structures having these type of walls, indicated a structural behavior of the infills. Several proposals for the improvement of the out-of-plane behavior of infill walls are presented in this paper. The investigation of these solutions can lead to the development of innovative systems of masonry infills, and can also provide viable consolidation measures for existing buildings.
Bulletin of Earthquake Engineering, 2019
It is generally known that reinforced concrete frame structures with unreinforced masonry infills frequently suffer severe damage when subjected to earthquake loading. Recent earthquakes show that the damage occurs to both older buildings and new seismically designed buildings. This is somehow surprising as this construction type has been the subject of intensive research projects for decades and simplified verification concepts are available in standards. However, these concepts are based on the separate verification of in-plane and out-of-plane loading although the importance of the design for combined loading conditions is already known. This situation was the reason to perform comprehensive investigations of the seismic behaviour of this traditional construction type for separate and combined in-plane and out-of-plane loading within the framework of the collaborative European research project INSYSME (Innovative systems for earthquake resistant masonry buildings in reinforced concrete buildings). These investigations are helpful to develop innovative approaches to improve the seismic behaviour of infilled frames. This article presents the fundamental project results of experimental investigations on reinforced concrete frames filled with high thermal insulating clay bricks under separate, sequential and combined in-and out-of-plane loading. The test results clearly illustrate that the load-bearing capacity severely depends on the boundary conditions in the connection area between the infill and the frame.
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.
Seismic Strengthening of Masonry Infilled Reinforced Concrete Frames
Structural frames are often filled with masonry panels for architectural purposes as divisional walls or cladding. There has been much work conducted into the seismic behaviour of infilled frame buildings (e.g., Abrams, 1994–1996; Chrysostomou et al, 1992; Žarnić and Tomažević, 1984). However, the most significant outcome is perhaps the general consensus that brickwork infill can have a beneficial effect on the overall seismic performance of the building if it is properly tied into the rest of the building. The purpose of the present study was to investigate possible seismic strengthening options for use in the seismic upgrade of a infilled frame structures with an emphasis on strengthening brick masonry infill walls. In order to test the numerical models and to define a simple method for analysing the behaviour of reinforced concrete frames with infill in earthquake regions, we have done a series of tests with the aim to investigate the behaviour of strengthened infills of RC frame...
Engineering Structures, 2019
Reinforced concrete frame structures with masonry infills often exhibit serious damage after earthquake events, as the infills are generally installed without additional constructive measures in contact to the reinforced concrete frame. The masonry infills constructed in this way experience an unplanned interaction with the surrounding RC frame and thus become part of the horizontal load-bearing system with in-plane loading. This interaction combined with seismically induced loads perpendicular to the infill panel often leads to total collapses of the masonry infills and heavy damages to the RC frames. This fact was the motivation to develop an innovative system for decoupling the RC frame and the masonry infill with a special profile made of elastomeric cellular material within the collaborative European research project INSYSME (Innovative Systems for Earthquake Resistant Masonry Enclosures in Reinforced Concrete Buildings). The profile allows relative displacements between the RC frame and the masonry infill and serves at the same time as a support for out-ofplane loads. The article first explains the design and installation of the system and provides an overview of the load bearing capacities determined through small specimen tests on the system components. Subsequently, fundamental experimental investigations on traditional and decoupled RC frames infilled with high thermal insulating clay bricks for separate and combined in-plane and out-of-plane loading are presented. Based on a detailed evaluation and comparison of the test results, the performance and effectiveness of the developed system are illustrated.