Unreinforced masonry (URM) buildings, largely found in Euroasian regions, are particularly vulnerable to in-plane shear failures during seismic events due to the poor shear capacity of masonry walls. In the case of historical masonry buildings, the use of strengthening solutions with polymeric and polymer-modified matrices composites is not recommended since the breathability of the masonry could be reduced, leading to a fast and undesired degradation. In this paper, an innovative fiber-reinforced cementitious mortar (i.e., FRCM) system was used to improve the shear capacity of old-type solid clay brick masonry walls. An experimental program on 24 masonry panels subjected to diagonal compression tests was carried out. The innovative FRCM system consisted of a basalt grid embedded in an improved inorganic matrix, made of lime-based mortar reinforced with short glass fibers (i.e., Fiber-reinforced mortar, FRM). Two sets of specimens were tested, single-leaf masonry panels and double-leaf masonry panels, to investigate the typical configurations of load-bearing walls and partition walls. The effectiveness of the innovative FRCM system was investigated for both a conventional symmetric strengthening configuration and an asymmetric strengthening configuration with anchors, a solution often adopted in the case of internal/external interventions only. Furthermore, the response of masonry panels strengthened with only symmetric FRM with a slightly greater amount of short glass fibers embedded in the matrix was also investigated. The experimental outcomes outlined that panels reinforced with symmetric FRM achieved similar effectiveness in the shear strength increase to panels reinforced with symmetrical FRCM. Conversely, a reduced deformability was observed in FRM panels with respect to those strengthened with FRCM. The experimental results also allowed the quantification of the effectiveness of FRCMs in the case of asymmetric strengthening configurations. Finally, a comparison between experimental results and American Code provisions for FRCM-strengthened systems was reported.
Very large tsunamis are associated with low probabilities of occurrence. In many parts of the world, these events have usually occurred in a distant time in the past. As a result, there is low risk perception and a lack of collective memories, making tsunami risk communication both challenging and complex. Furthermore, immense challenges lie ahead as population and risk exposure continue to increase in coastal areas. Through the last decades, tsunamis have caught coastal populations off-guard, providing evidence of lack of preparedness. Recent tsunamis, such as the Indian Ocean Tsunami in 2004, 2011 Tohoku and 2018 Palu, have shaped the way tsunami risk is perceived and acted upon. Based on lessons learned from a selection of past tsunami events, this paper aims to review the existing body of knowledge and the current challenges in tsunami risk communication, and to identify the gaps in the tsunami risk management methodologies. The important lessons provided by the past events call for strengthening community resilience and improvement in risk-informed actions and policy measures. This paper shows that research efforts related to tsunami risk communication remain fragmented. The analysis of tsunami risk together with a thorough understanding of risk communication gaps and challenges is indispensable towards developing and deploying comprehensive disaster risk reduction measures. Moving from a broad and interdisciplinary perspective, the paper suggests that probabilistic hazard and risk assessments could potentially contribute towards better science communication and improved planning and implementation of risk mitigation measures.
Glazed curtain walls are façade systems frequently chosen in modern architecture for mid and high-rise buildings. From recent earthquakes surveys it is observed the large occurrence of non-structural components failure, such as storefronts and curtain walls, which causes sensitive economic losses and represents an hazard for occupants and pedestrians safety. In the present study, the behavior of curtain wall stick systems under seismic actions has been investigated through experimental in-plane racking tests conducted at the laboratory of the Construction Technologies Institute (ITC) of the Italian National Research Council (CNR) on two full-scale aluminium/glass curtain wall test units. A finite element model has been calibrated according to experimental results in order to simulate the behavior of such components under seismic excitation. The numerical model investigates the influence of the interaction between glass panels and aluminium frame, the gasket friction and the stiffness degradation of aluminium-to-glass connections due to the high deformation level on the curtain walls behavior. This study aims to give a practical support to researchers and/or professionals who intend to numerically predict the lateral behavior of similar façade systems, so as to avoid or reduce the need of performing expensive experimental tests.
The increasing attention of governments and insurance companies toward the evaluation of tsunamis' impacts on coastal communities led to a renewed interest in assessing the behavior of existing buildings under onshore tsunami flows. Codes and standards regulating assessment procedures for existing structures under tsunami loading are currently missing, and only a few design codes for vertical evacuation shelters can be found. Furthermore, structural analysis methods currently assume watertight buildings for the assessment of their performance under tsunami inundation. In this work, a methodology for assessing the performance of reinforced concrete (RC) buildings that considers explicitly the progressive failure of exterior breakaway infill walls hit by tsunami flows is proposed. The effects of the progressive failure of breakaway infill walls on the overall performance of RC buildings have been highlighted on case-study buildings representative of low-, mid- and high-rise buildings built before the 1980s in the Mediterranean area, characterized by masonry infill walls with low out-of-plane (OOP) capacity. In the absence of specific guidelines for assessment, load models provided by existing tsunami design codes for evacuation buildings were adopted and opportunely modified for the case of buildings with breakaway infill walls. The explicit consideration of the failure of exterior breakaway infill walls completely changed the distributions of loads inside the structure, leading to different structural capacity and damage evolution with respect to watertight buildings. The height of the building affected the global capacity but did not influence the damage evolution. The proposed methodology can represent a suitable solution for a realistic performance assessment of frame structures with breakaway claddings.
The use of High Performance Fibre Reinforced Cementitious Composite (FRCC) systems as a repair/strengthening of RC columns is an innovative technique for increasing their capacity and preventing brittle failures when a seismic event occurs. This study presents and discusses the results of an experimental program carried out on nine scaled RC columns under compressive axial load. In particular, six columns were strengthened with FRCC, two columns were confined with uniaxial carbon fibres (CFRP) and one unstrengthened coloumn was used as control specimen. The strengthening with FRCC consisted of the total replacing of the existing concrete cover with a thin layer of FRCC for the entire length of the specimen. The behaviour of columns strengthened with FRCC is compared with the two columns confined by using CFRP. The effectiveness of the FRCC repair/strengthening technique was investigated by means of comparisons with the response of the control specimen and columns confined with CFRP. The specimens' response has been analysed in terms of failure modes and strength/deformation capacity.
In long-term structural health monitoring (SHM), one of the main challenges is to correlate an observed variation in dynamic properties of a structure (i.e., natural frequencies, mode shapes, etc.) to a certain damage level.This correlation is fundamental for a fast damage quantification trough SHM data that can trigger warnings for maintenance works, in the case of minor damage, or for immediate evacuation to protect the life of occupants in the case of a heavy damage.This paper focuses on seismic damage assessment, and adopts a methodology proposed by the authors to quantify the damage experienced in a building from SHM data.In detail, the study focuses on the damage evaluation of Reinforced Concrete (RC) buildings with masonry infill walls and adopts the variation of fundamental frequency as a damage intensity measure.Results from refined numerical simulations on a 2D infilled RC frame are reported for the structural and non-structural damage evaluation.
Reinforced concrete (RC) columns typical of existing structures often exhibit premature failures during seismic events (i.e., longitudinal bars buckling and shear interaction mechanisms) due to the poor quality concrete and the absence of proper seismic details in the potential plastic hinge region. The Fiber Reinforced Polymers (FRP) externally bonded reinforcement is known to be a valid technique to improve the shear capacity or the ductility of existing RC columns. However, few experimental tests have proven its effectiveness in the case of columns affected by shear interaction mechanisms. In this work, the behavior of existing RC columns with border line behavior between flexure and shear have been investigated in the case of poor quality concrete and light FRP strengthening with local jacketing and medium quality concrete and strong FRP strengthening with local jacketing, in order to highlight the effect of concrete strength on the effectiveness of the retrofit intervention. As an alternative to FRP jacketing; the effectiveness of the Fiber Reinforced Cementitious Composite (FRCC) jacketing for the seismic strengthening of columns with highly deteriorated concrete cover or columns already damaged by an earthquake is also evaluated. Six full-scale RC columns have been tested under cyclic loading: one was used as a control specimen; four were strengthened in the potential plastic hinge region with carbon FRP (CFRP); and one was fully jacketed with FRCC. The comparison between poor and medium quality concrete columns showed that the CFRP local jacketing is more effective in the case of poor quality concrete. The FRCC jacketing appears to be a sound repair strategy and a suitable alternative to the FRP jacketing in case of poor quality; however, more experimental research is needed for improving this retrofit technique.
In long-term structural health monitoring (SHM), one of the main challenges is to correlate an observed variation of vibration period with a damage level for a structure. The aim of this paper is to propose a methodology to quantify the seismic damage in a building through SHM data. For this purpose, an existing reinforced concrete building has been selected as a case-study and non-linear dynamics analyses have been carried out to estimate local and global damage levels. Ranges of variation of the vibration period of the building are derived for each damage level, and are compared with those previously assessed by the authors for single columns.
Abstract Currently available performance-based methodologies for assessing the fragility of structures subjected to tsunami neglect the effects of tsunami-induced vertical loads due to internal buoyancy. This paper adopts a generalized methodology for the performance assessment of structures that integrates the effects of buoyancy loads on interior slabs during a tsunami inundation. The methodology is applied in the fragility assessment of three case-study frames (low, mid and high-rise), representative of existing masonry-infilled reinforced concrete (RC) buildings typical of Mediterranean region. The paper shows the effect of modelling buoyancy loads on damage evolution and fragility curves associated with different structural damage mechanisms for existing RC frames with breakaway infill walls including consideration of blow-out slabs. The outcomes attest that buoyancy loads affect the damage assessment of buildings during a tsunami, especially in the case of mid and high-rise structures with blow-out slabs. The rate of occurrence of slabs uplift failure increases with the number of stories of the building, indicating the need to account for such damage mechanism when assessing the performance of structures. It is also found that buoyancy loads slightly affect the fragility curves associated to other structural damage mechanisms for existing RC buildings commonly monitored for fragility assessment.
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