A component-level methodology to evaluate the seismic repair costs of infills and services for Italian RC buildings

AbstractThe reliable estimation of seismic losses due to damage to buildings is paramount for the post-emergency management and the planning of recovery activities. For residential reinforced concrete (RC) infilled buildings, a significant role in the computation of seismic loss is played by non-structural components, above all infills, partitions and services, as shown in past earthquakes. In this work, a component-based methodology is proposed to assess seismic losses for residential RC buildings in Mediterranean region. The attention is focused on the repairing activities for masonry infills (typical enclosure or partitions elements in Italian and Mediterranean RC buildings), and for services (plumbing systems, electric equipment, floor/wall tiles…), commonly enclosed within the infill panels for the considered building typology. The described methodology can be used starting from the expected damage level to infills and partitions. It adopts given repair unit costs at different damage states of infills. The loss estimation methodology has been, first, validated by comparing predicted and actual repair costs for specific case-study buildings damaged by L'Aquila (Italy) 2009 earthquake. Then, the methodology has been applied to a wide dataset of RC buildings (about 2500 residential buildings) damaged by L'Aquila earthquake available from the literature, to show its possible application at a large-scale level. A good agreement between observed and predicted costs is obtained both for specific case-study buildings and for the wider building stock, especially when damage to structural components is very limited

Experimental investigation on the influence of the aspect ratio on the in-plane/out-of-plane interaction for masonry infills in RC frames

Abstract The analysis of the behaviour of masonry infills under out-of-plane (OOP) and in-plane (IP) loading is paramount to correctly assess the seismic performance of reinforced concrete (RC) frames. A very important issue about this topic is certainly the IP/OOP interaction, namely the analysis of how the IP damage, which affects infills during earthquakes, can influence their OOP behaviour (and vice-versa). Some studies about this topic were developed in the last years; nevertheless, only a dozen of tests currently exists in the literature to experimentally explore this key issue. This work first presents an experimental campaign carried out on square infill walls in RC frames to investigate about the OOP behaviour of the masonry infills, and about the IP/OOP interaction. On the whole, four specimens have been tested under OOP monotonic loading. Three of them have been first damaged under cyclic IP actions, with different extent; the remaining one, used as a reference, was tested under OOP loading only. The experimental campaign is described in detail in terms of specimens' characteristics, material properties, adopted setup and instrumentation layout. The experimental results are analysed in terms of IP and OOP force-displacement responses, vertical arch strength contribution evolutions, and damage state evolutions, and compared with prediction proposals from the literature. Then, the influence of the infill aspect ratio (width (w)-to-height (h) ratio) on the IP/OOP interaction is investigated by means of the comparison between data presented herein (collected on infills with w/h = 1) and a companion experimental campaign previously performed on nominally identical infills except that for the aspect ratio of the specimens (in that case, higher than the unit). It has been observed that under given IP drift levels, square infills presented lower IP damage levels with respect to rectangular infills (with w/h > 1), thus generally producing a less pronounced detrimental effect of the IP imposed drift on the OOP strength. Nevertheless, none of the predictions from literature takes into account the role of the aspect ratio on the IP/OOP interaction, generally resulting in conservative predictions, to be improved in future works

Assessment of strengthening solutions for the out-of-plane collapse of masonry infills through textile reinforced mortars

Out-of-plane (OOP) collapse of infill masonry walls in existing reinforced concrete (RC) buildings due to earthquakes represents a paramount issue for life safety and seismic economic loss estimation. Few studies from literature deal with this topic, particularly regarding possible strengthening strategies to prevent the infills’ OOP collapse. This work presents the first results of a proper experimental campaign about the assessment of different strengthening solutions designed to mitigate or avoid the out-of-plane collapse of masonry infills in existing RC buildings. The investigated strengthening techniques were based on the application of a very thin high-ductility mortar plaster and glass fibre-reinforced polymer nets with different types of anchorage to the surrounding RC frame. Each specimen was built with horizontal hollow clay bricks and was tested through the application of a semi-cyclic OOP displacement pattern by means of uniformly distributed small pneumatic jacks. Mechanical properties of the adopted materials, test setup and procedure are described herein. Tests results are presented and commented in terms of OOP force-displacement responses and damage evolution during the test. Details about the effectiveness of each retrofitting solution are provided and compared to support the selection of the best strategy for further investigations and future applications

Experimental assessment of strengthening strategies against the out-of-plane collapse of masonry infills in existing RC structures

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

Experimental analysis of Textile Reinforced Mortars strengthening strategies against the out-of-plane collapse of masonry infill walls

Out-of-plane (OOP) collapse of masonry infill panels in existing reinforced concrete (RC) buildings due to seismic events is a key issue for life safety and seismic economic loss estimation. Few studies in the literature deal with this topic and, above all, with possible strengthening strategies against the OOP collapse. This work presents the main results of an experimental campaign about different strengthening solutions to mitigate the OOP collapse of masonry infills in RC buildings. The investigated strengthening techniques were based on the application of a thin mortar plaster and fiber-reinforced polymer nets with different connection typologies with the surrounding RC frame. The specimens were realized with traditional horizontal hollow clay bricks and were tested through the application of a semi-cyclic OOP displacement pattern by means of uniformly distributed small pneumatic jacks. Tests data and results are presented and commented in terms of OOP force-displacement responses and damage evolution. Details about the effectiveness of each retrofitting solution are provided and compared to support the selection of the best strategy for future applications

Seismic Loss Estimation in Pre-1970 Residential RC Buildings: The Role of Infills and Services in Low–Mid-Rise Case Studies

The lessons learned after recent earthquakes have highlighted the key role played by infills and services in damage and loss of Reinforced Concrete (RC) buildings. Their influence in seismic performance and loss estimation of selected RC building case studies is thoroughly analyzed here. The case study selection aims to be representative of existing buildings built in Italy before 1970, and covers a different number of stories and design typologies. The seismic responses of the case-study buildings are numerically analyzed by means of non-linear static pushover analysis (PO) considering a lumped plasticity approach with a quadri-linear flexural response for beam/column elements (properly calibrated for RC elements reinforced with plain bars) and a tri-linear compressive-only axial response with diagonal concentric struts for infill panels (empirically derived from experimental data on hollow clay masonry walls). Economic loss estimation is carried out via a component-based methodology that relies on the main repairing activities and resultant costs required for the refurbishment of infills and services for different damage levels. Accordingly, a damage analysis is performed herein, given the intensity measure, based on a comparison between Interstory drift demand from PO analysis and drift-based fragility functions specific for masonry infills. Loss curves, relating the total building repair cost to peak ground acceleration (PGA), are presented and compared for the analyzed case study buildings to show their trends and quantify the incidence of infills and services with respect to the reconstruction cost. A comparison between these outcomes and those recently found in the literature emphasizes the robustness of the considered approach and the reliability of the hypotheses about damage and loss assessment

Lysosomal dysfunction disrupts presynaptic maintenance and restoration of presynaptic function prevents neurodegeneration in lysosomal storage diseases

Lysosomal storage disorders (LSDs) are inherited diseases characterized by lysosomal dysfunction and often showing a neurodegenerative course. There is no cure to treat the central nervous system in LSDs. Moreover, the mechanisms driving neuronal degeneration in these pathological conditions remain largely unknown. By studying mouse models of LSDs, we found that neurodegeneration develops progressively with profound alterations in presynaptic structure and function. In these models, impaired lysosomal activity causes massive perikaryal accumulation of insoluble α-synuclein and increased proteasomal degradation of cysteine string protein α (CSPα). As a result, the availability of both α-synuclein and CSPα at nerve terminals strongly decreases, thus inhibiting soluble NSF attachment receptor (SNARE) complex assembly and synaptic vesicle recycling. Aberrant presynaptic SNARE phenotype is recapitulated in mice with genetic ablation of one allele of both CSPα and α-synuclein. The overexpression of CSPα in the brain of a mouse model of mucopolysaccharidosis type IIIA, a severe form of LSD, efficiently re-established SNARE complex assembly, thereby ameliorating presynaptic function, attenuating neurodegenerative signs, and prolonging survival. Our data show that neurodegenerative processes associated with lysosomal dysfunction may be presynaptically initiated by a concomitant reduction in α-synuclein and CSPα levels at nerve terminals. They also demonstrate that neurodegeneration in LSDs can be slowed down by re-establishing presynaptic functions, thus identifying synapse maintenance as a novel potentially druggable target for brain treatment in LSDs

ADVANCED NONLINEAR MODELLING AND PERFORMANCE ASSESSMENT OF MASONRY INFILLS IN RC BUILDINGS UNDER SEISMIC LOADS: THE WAY FORWARD TO DESIGN OR RETROFITTING STRATEGIES AND REDUCTION OF LOSSES

The project aims at performing a step forward towards future guidelines for design of new buildings or assessment and retrofit of existing or new infilled RC buildings, to reduce seismic vulnerability and, consequently, direct and indirect losses due to earthquakes

SEISMIC PERFORMANCE ASSESSMENT OF RC BUILDINGS ACCOUNTING FOR STRUCTURAL AND NON-STRUCTURAL ELEMENTS

Among the natural hazards, earthquakes are paramount due to their impact on civil structures worldwide. The considerable direct economic losses (property losses) due to earthquakes in conjunction with social impact and indirect economic losses have prompted a great interest in performance assessment of the civil structures to future seismic events. Therefore, performance evaluations beyond the traditional goal of life safety, are required to rightly estimate expected losses. A key ingredient of this evaluation process is the fragility, that describes the probability of failure to meet a performance objective depending on demand on the system, providing the link between seismic hazard and building losses estimation. A correct fragility evaluation necessitates the development of reliable nonlinear analysis models that are able to simulate the behavior of structures from the onset of damage through collapse. Therefore, proper prediction of the nonlinear behavior and formulation of analytical models are essential prerequisites for a reliable evaluation of structural fragility and, then, of seismic performance and risk assessment of Reinforced Concrete (RC) structures. Moreover, within the performance-based approach, it is also essential to understand which mechanisms/elements have the higher influence on seismic performance depending on the analyzed performance level. A lot of work should still be done towards this direction, especially for existing under-designed or non-ductile structures. With under-designed or non-ductile terms it will be referred to structures designed for gravity loads only or according to obsolete seismic and technical codes. A contribution towards this direction is carried out in this work. Starting from the analysis of typical deficiencies of non-ductile RC frames and the definition of performance levels of interest, this work aimed to contribute to PBEE framework with (i) a critical overview on analysis methodologies and modeling approaches of the salient components of RC frames, namely flexural or shear-dominated beams and columns, and more in detail, beam-column joints and masonry infills, the core of this work, and (ii) with new proposals in terms of nonlinear modeling and analysis procedures to provide a more reliable evaluation of seismic performance and risk assessment of infilled RC structures, accounting for structural and non-structural (in particular masonry infills) elements at different performance levels. For these purposes, existing analytical modeling techniques for RC frames' critical components were first reviewed and discussed. Then, a deep investigation on the influence of infills on seismic performance at different limit states, also for new constructions, has been carried out, in order to highlight the critical points that can interest also this kind of structures regarding infill presence. The effect of infills on the global seismic behavior of RC frames was investigated, by analyzing their influence on global stiffness and strength, on the kind of collapse mechanism, on the displacement capacity and, consequently, on seismic capacity and seismic fragility at different performance levels, depending on the main characteristics of the RC frame, such as the design typology and the number of stories. Recognized the importance of infills especially at lower seismic intensity and the widespread of linear analysis methodology among practitioner, new procedures are proposed as tools to better taking into account damage to infills also in linear analyses with or without the explicit modeling of infills in the numerical model. The attention has been focused both on the design of new constructions and the assessment of existing structures, providing a contribution towards desirable more comprehensive future code prescriptions at lower seismic intensity - that depend on mechanical properties of infills and proper displacement capacity thresholds - within the context of linear analyses. From the point of view of the bare structure (without infills in the structural model) and in particular referring to higher intensity levels, proceeding from Damage Limitation (DL) LS towards Near Collapse (NC) LS, the analysis of RC frames different for design typology has highlighted the vulnerability points of such frames, already pointed out by experimental tests and past seismic events. In particular the influence of beam-column unreinforced joints is deeper investigated. In literature there is not yet a commonly accepted approach for the determination of the shear strength and for nonlinear modeling of RC beam-column joints in moment resisting RC frames. In many studies, beam-column connections are modeled as rigid. However, many nonlinear joint models are available, but most of them may be unsuitable for modeling all sources of nonlinearity for the assessment of older concrete buildings. Some of them were developed and calibrated for confined beam-column joints or they are too complicated to implement. On the basis of an extensive and critical review of previous experimental tests and existing joint modeling approaches, a new cyclic shear constitutive relationship is proposed for exterior unreinforced joints, different for failure typology, in order to describe nonlinear behavior of joint panels, to be used in conjunction with an explicit bond-slip spring, thus taking into account all sources of nonlinearity and different possible kinds of deficiencies. Then, the influence of joint behavior on seismic performance at different performance levels, both in terms of strength and deformability contribution, also taking into account the record-to-record variability, was investigated in nonlinear dynamic analyses of under-designed frames. Finally, after the investigation about the sensitivity of joint response to the main mechanical and geometrical properties of beam-column sub-assemblages, the results of two experimental tests are presented and discussed. The specimens have deformed bars and show different failure typology. These tests conducted under cyclic loading aim to improve the understanding of exterior joints seismic performance without transverse reinforcement in existing RC buildings. Experimental results are analyzed herein and compared with numerical results carried out through the adoption of the proposed numerical model