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In reinforced concrete (RC) multi-storey buildings, the important role of the seismic interaction of structural frames with masonry infills has been revealed by several earthquakes and investigated by many authors. Recently, several innovative infill solutions have been proposed to mitigate such interaction, which could result in widespread damage in both the masonry and the RC structure and sometimes jeopardize the building stability and the occupants’ safety. One solution consists in the partitioning of the masonry infill into several sub-panels, relatively sliding along specific joints. This paper investigates the seismic assessment of this technological solution in the framework of performance based earthquake engineering. A two-dimensional five-storey RC seismic-resistant frame is selected as case study and the performance is assessed by comparing the responses of the same structure infilled with different solutions, made of sliding joints or traditional masonry, or in the bare configuration. Incremental Dynamic Analyses (IDA) is used for the probabilistic determination of fragility curves of the structures. Results show the seismic fragility and reliability of the different investigated structures, especially addressing the probabilities of occurrence of damage at different limit states and quantifying the associated expected annual loss.

In the seismic retrofit of the existing masonry buildings, dissipative and deformable roof diaphragms could offer an efficient solution in cases where both the adoption of steel ties or stiff diaph...

The paper describes the set-up and testing of an innovative construction technique for masonry infill, which can provide a flexible and predictable in-plane response to the infill inside the frame, together with a stable and reliable out-of-plane response. The design strategy is to downgrade the infill reaction inside the structural frame thanks to a dramatic reduction of the masonry in-plane stiffness. The infill is partitioned by vertical planks (or equivalent beams) into sub-panels, free to relatively slide and rock on their toes. The planks connected to the beams provide the necessary out-of-plane stability. The solution was tested for application in both new and existing infills and construction details are discussed. A comparison is also presented with the performance of two infills, one continuous and one with horizontal sub-panels, previously tested under the same conditions. The observed infill downgrade makes practically negligible the infill-frame interaction and the post-earthquake masonry damage.

This paper proposes a simplified approach to analyze the seismic performance of masonry infills with sliding joints in moment-resisting frame structures. The proposed methodology uses the equivalen...

In the present paper a numerical study is reported, aimed at investigating the role of openings in the in-plane response of infilled RC frames when masonry infills with sliding sub-panels are adopted. Such innovative infills are meant to reduce post-earthquake damage and infill-frame interaction, with respect to traditional solid masonry infills. Their study was carried out mainly on the fully infilled configuration, and limited information is available about its response in presence of an opening. In the paper focus is made on the interaction of the infill with both the surrounding frame and with the specific post placed at the opening side, which is essential to confine the infill and protect the opening fixtures. The adopted numerical model is calibrated on the experimental results of a test performed on a real scale infill wall with horizontal sliding joints and a full-height opening on a side. A parametric study is carried out to investigate the influence of different design parameters. In detail, the focus is placed on the stiffness of the post and on the geometry of the infill (in terms of position of the opening, infill length and sliding joint configurations). The obtained results show the beneficial effect of the post deformability in reducing the infill-frame interaction, with a significant reduction of the shear action exerted on the frame columns and on the post itself. Moreover, the obtained results allowed to define some preliminary recommendations for the design of the infill and of the post at the opening side.

This paper presents a performance-based earthquake engineering framework aimed at the assessment of fragility, reliability and expected annual loss (EAL) of reinforced concrete (RC) frames with traditional infills (TI) and innovative infills with sliding joints (SJ). The main concern is first related to the modification of seismic reliability levels achievable for structural and non-structural limit states by code conforming RC structures when explicitly considering the influence of masonry infills and the quantification of the gain associated with the eventual use of sliding-joint infills (SJI). Further, expected annual losses within the service life are evaluated and compared for the considered structural typologies. The framework is based on the determination of fragility via incremental dynamic analysis (IDA) in order to consider statistical response to input variability. The analyses are carried out on a reference multi-storey multi-bay 2D structure modeled in OpenSEES using a fiber-section approach. Specific structural and non-structural limit states are individuated for the TI and SJI frame structures. Seismic reliability is evaluated by integrating site hazard and structural fragilities resulting for each limit state. Expected annual loss assessment is performed by directly using period dependent hazard curves to determine annual rates of failures associated with limit states. Results show that similar probabilities of exceedance and loss rates are obtained by traditional infill and sliding-joint infill structures at life safety and collapse limit states. On the contrary significant convenience in using SJI is observed for operational and damage limit states in terms of reduced probability of occurrence and EAL.

Summary The vulnerability of infilled frames represents a critical issue in many regions with high seismicity around the world where infills are typically made of heavy masonry as they are used for thermal control of the buildings because of their thermal inertia. In this context, the use of earthen masonry infills can give a superior performance because of their ability to regulate thermal-hygrometric performance of the building and sustainability of its life-cycle. This paper presents a numerical study on the seismic behaviour of infill walls made of earthen masonry and partitioned with horizontal wooden planks that allow the relative sliding of the partitions. The combination of the deformability of earthen masonry and the sliding mechanism occurring along the wooden planks gives a high ductility capacity to the in-plane response of the infill and, at the same time, significantly reduces its stiffness and strength, as compared with traditional solid infills made of fired clay units. As a result, the detrimental interaction with the frame and the damage in the infill when subjected to in-plane loading can be minimized. The numerical model is validated with results from an experimental study and is used to perform a parametric analysis to examine the influence of variations in the geometry and mechanical properties of the infill walls, as well as the configuration of the sliding joints. Based on the findings of this study, design guidelines for practical applications are provided, together with simple formulation for evaluating their performance. Copyright © 2016 John Wiley & Sons, Ltd.

The paper describes the results of quasi-static tests performed on a real-scale adobe masonry infill wall partitioned into sub-panels by means of the introduction of vertical wooden planks, acting as sliding joints. The specimen was tested both in-plane and out-of-plane, exhibiting good performance in terms of both stability against out-of-plane actions and in-plane deformation capacity and damage control. The results emphasize the applicability of adobe masonry as material for infill walls in seismic prone regions, coupling the good structural response with the inherent positive performance in terms of indoor ambient comfort and production sustainability demonstrated in literature.

The paper discusses the effect of a full-height opening in the in-plane performance, under lateral loading, of a masonry infill wall partitioned with horizontal sliding joints. The innovative infill construction technique, which was already presented in previous works, is here tested implementing the details required by the presence of an opening. The specimen was designed with a vertical post located at the opening side, which is meant to protect the opening fixtures (window or door) from the infill sub-panels’ relative sliding. The results showed the efficiency of the post in governing the sliding mechanism between the infill sub-portions and the role of the post’s stiffness in modifying the in-plane response of the infill. Thanks to the post’s deformability, the overall infill-frame interaction was mitigated, as testified by the reduction of the specimen lateral strength with respect to previously tested similar infills without openings. The role of such deformability was explored by modifying the post’s stiffness with additional steel profiles coupled to the initial wooden post configuration, in different test phases. The direct measuring of the shear action at the post ends and of its deflection provided useful information for the design of the post and for the future calibration of numerical models.

A number of construction techniques have been proposed to improve the seismic performance of infilled RC frames by increasing the strength and stiffness of the infill and/or the frame. The increase of the seismic capacity of infilled frames with these techniques can improve substantially their seismic performance as long as the demand does not exceed the capacity, but it can eventually lead to brittle failures once the capacity is exceeded. This study assesses numerically a new construction technique that introduces flexibility to the system to ensure its ductile behavior and minimal damage by splitting the infill in subportions and allowing the sliding along the horizontal joints connecting these subportions. A numerical model, validated with data from tests on the components of the proposed structural system and able to capture the interaction between them, has been developed to provide insight into the load-transfer mechanism that develops, and to optimize the proposed detailing. A parametric s...

This paper presents the results of an experimental campaign on a small, real-scale masonry transverse arch, under cyclic quasi-static conditions and a dynamic pull-&-release test. The description of the rocking mechanism activated in the specimen and the related tie rod tension modification during the test are described in detail and the test results are compared with analytical predictions based on simple equilibrium equations. The specimen showed a stable response characterized by large deformation capacity and limited damage. Moreover, the pull-&-release test allowed for an insight into the dynamic response of the structure quantifying tie rod tension and the accelerations associated with the impacts during the rocking response.

The seismic vulnerability of masonry infilled frames represents a critical issue in reinforced concrete and steel buildings, widely highlighted by ruinous collapses during earthquakes and studied by many authors. In these structures, the interaction between the flexible frame and the rigid masonry infill modifies the dynamic response of the frame, inducing possible undesired collapse mechanism, and, on the other hand, can cause widespread damage in the infills. To avoid these detrimental effects, a technological solution for the design of the infills has been studied and tested in the last years at the University of Brescia, consisting in partitioning the masonry with wooden planks, working as sliding joints. Tests have shown the potential of the solution for providing a superior performance than traditional masonry infills, thanks to the reduction of the detrimental effects of the infill frame interaction. The benefit comes from a significant reduction of the infill strength and stiffness, a limitation of its damage under in-plane loading and a ductile behaviour, with energy dissipation capacity that can be easily predicted. In this paper a numerical study that extends test results is presented. A parametric analysis of the response of the infills has been performed as a function of some geometrical and mechanical properties: stiffness and strength of the materials, dimension of the infill and configuration of the sliding joints. The results offer information necessary for the application of the construction technique, which is proposed to improve the infilled frame seismic response.