Search

Masonry existing buildings are subjected to significant structural damages when seismic events occur. Over the last decades, innovative techniques like composite materials based on inorganic mortar (FRCM – Fiber Reinforced Cementitious Matrices) have emerged as attractive solutions for the strengthening of civil structures. FRCM shows better compatibility with masonry substrates with respect to Fiber Reinforced Polymers. The effectiveness of FRCM reinforcement systems relies on the composite-substrate bond behavior which is affected by many parameters, leading to different failure mechanisms. Although numerous studies investigate the FRCM-substrate bond, few attentions have been paid to the study of fiber grid-matrix interface behavior. In this study, the preliminary results of a wider experimental campaign aimed at investigating the interface behavior between fiber and mortar accounting for the contribution of transversal grid wires are presented. Different typologies of fiber and mortar were tested and the results are compared and discussed.

With the advancement of performance-based earthquake engineering (PBEE), the seismic performance of non-structural elements (NSEs) has gained special relevance. The harmonization of the performance of NSEs and of the seismic force-resisting system (SFRS) in a building is fundamental to the PBEE concept. To provide a consistent level of performance for force-based designed SFRSs, the FEMA P695 Methodology provides an objective framework. No equivalent procedure currently exists for NSEs. This paper develops a framework to quantify seismic performance factors for NSEs. An illustrative case study example is presented for the calibration of the behaviour factor for suspended piping seismic restraint installations.

Direct displacement-based seismic design has been recently proposed for the seismic design of non-structural building elements. This paper deals with the development of damping models, relating equivalent viscous damping ratio to drift amplitude, for suspended piping trapeze restraint installations for direct displacement-based seismic design. The damping models are developed using reversed cyclic test data available in the literature. First, damping models are proposed using Jacobsen’s equal area approach. The damping models developed using Jacobsen’s approach are then assessed and calibrated using nonlinear time history analyses of single degree-of-freedom archetypes representing suspended piping trapeze restraint installations in buildings.

Non-structural elements (NSEs) are not designed to be part of the structural load-bearing system of a building but are subjected to the same dynamic environment as the supporting structure during an earthquake. Non-structural damage and ensuing losses have exceeded structural damage and losses in many buildings during recent earthquakes that have occurred in urban regions around the world. Damage to NSEs is strongly influenced by the amplitude, the frequency content and the duration of floor motions. Although the effects of amplitude and frequency content of floor motions are well captured by floor response spectra, little attention has been given on the characterisation of floor motion duration and how it can impact damage to NSEs, particularly for those responding in the inelastic range. To contribute to a better understanding of these issues, this paper develops a probabilistic strong floor motion duration model through multiple stripes non-linear time-history analyses of a population of 100 code-compliant reinforced concrete frame building models designed for a medium-to-high seismicity site in Italy. The resulting probabilistic model can be used when selecting historical or generating synthetic floor motions for the seismic response assessment of NSEs or when generating shake-table test records for the seismic qualification of NSEs.

Storage tanks represent one of the most critical components in industrial facilities and building plants, when considering the occurrence of seismic events. The release of dangerous materials, due to their collapse, can be a safety issue in terms of both human life and environmental impact. This paper carries out a seismic performance assessment of a liquid-storage tank installed in an industrial steel moment-resisting frame building. The seismic performance is gauged in terms of fragility curves, which are provided for different limit states affecting the liquid-storage tank. Nonlinear dynamic analyses are performed using two different modelling approaches: the first explicitly accounts for the tank-structure interaction; the other considers the tank as only modelled as a seismic mass. The results discuss the importance of the modelling assumptions to estimate the seismic demand on liquid-storage tanks and corresponding fragility models for different intensity measures. Absolute acceleration floor response spectra are also analysed in detail, concerning the demand characerization. Finally, the study indicates that the intensity measure adopted for secondary components (i.e. peak floor acceleration) is not necessarily optimal threfeore future developments should produce updated fragility curves for non-structural elements, using better performing intensity measures.

Direct displacement-based seismic design has been proposed for pallet-type steel storage racks. Damping models are developed in this study for pallet-type steel storage racks in the down-aisle and cross-aisle directions for use in direct displacement-based seismic design. The damping models are developed using results from reversed cyclic tests at a component level or at a system level. Jacobsen’s approach is used to develop a first set of damping models. The damping models are then assessed using results from nonlinear time-history analyses. Finally, the damping models are calibrated using an iterative procedure based on results from nonlinear time-history analyses.

The major earthquakes that occurred worldwide in the last decades highlighted the seismic vulnerability of industrial structures and their components. Beyond the need to avoid human losses, the damages experienced by industrial facilities, both in terms of structural, non-structural and plant elements, significantly affected the economy of such areas. On the one hand, often the damages of non-structural components and their contents immediately lead to significant monetary loss. On the other hand, the leakage of toxic contents or the disruption of mechanical equipment can conduct to down-time of industrial plants. Following the 2012 Emilia earthquake in Italy, one of the most damaged components in industrial facilities, among others, was the steel storage legged tank. This research aims to investigate the seismic vulnerability of such elements by defining suitable fragility functions, also useful for future loss estimation studies. Several engineering demand parameters (EDPs) were selected in order to line up the damages observed in the aftermath of earthquakes. To draw general conclusions, several legged tanks were selected and analyzed. A suitable record selection has been performed, for which the average spectral acceleration (AvgSa) was selected as intensity measure (IM). Once adequate performance objectives were defined, the legged tank archetypes were analyzed by means of multiple-stripe analyses (MSA) to calculate the fragility functions and to highlight the most critical elements and tank configurations.

Recent seismic events highlighted the importance of non-structural elements in seismic assessment and performance-based earthquake engineering. When referring to industrial facilities, storage tanks represent one of the most critical components for the continuous functionality of industrial and building plants after seismic events. At the same time, the dispersion of dangerous or inflammable materials, due to their collapse, could become a safety issue in terms of both human life and environmental impact. This study focuses on the seismic performance assessment of a liquid-storage tank installed in an industrial steel moment-resisting frame building. The performance is assessed in terms of fragility curves, that are provided for the meaningful limit states that affect the liquid-storage tank and considering several intensity measures. The results related to the structural performance are also discussed in detail in terms of fragility functions and floor response. The assessment is performed through nonlinear dynamic analyses using two different modelling approaches to evaluate the structural and non-structural performance. The first modelling approach explicitly accounts for the tank-structure interaction, while in the second one the tank is only modelled considering its seismic mass. The results show the importance of the modelling assumptions to accurately estimate the seismic demand on liquid-storage tanks and corresponding fragility, which is calculated in terms of different intensity measures (IM): average ground spectral acceleration, peak floor acceleration, and floor spectral accelerations. Peak floor acceleration, drift profiles, and absolute acceleration and relative displacement floor response spectra are instead scrutinised for what concerns demand. The comparison with the code formulations available in the literature for estimating the seismic demand to non-structural elements pointed out their inaccuracy for the analysed liquid-storage tank and the need for further efforts to develop more accurate procedures. Furthermore, the outcomes indicate that the IM adopted for secondary components, i.e. peak floor acceleration, may not always be the optimal one hence additional attention should also be paid to the definition of updated fragility curves for non-structural elements, identifying and adopting more suitable IMs.

The seismic performance of suspended piping systems can significantly compromise the functionality of critical facilities due to the incorporation of inadequate seismic design based on prescriptive empirical regulations and guidelines. The performance-based seismic design (PBSD) of non-structural elements requires the evaluation of performance parameters, based on experimental data or numerical studies, for comparison with engineering demand parameters. Few research studies available in the literature provide the performance parameters required to enable PBSD of piping systems and more specifically of suspended piping restraint installations. This paper discusses the numerical modelling of suspended piping trapeze restraint installations based on component testing. Reliable numerical models capable of predicting the force–displacement (backbone) curves of suspended piping restraint installations are developed based on monotonic and cyclic test data of the components that make up these installations. The prediction capabilities of the numerical models are assessed against the results of monotonic benchmark sub-assembly tests reported in a previous study. The numerical models developed in this study can be used to extract performance parameters from the predicted force–displacement curves to be used within a probabilistic PBSD framework without the need to conduct additional testing.

The achievement of adequate performance objectives for buildings under increasing seismic intensities is not only related to the performance of structural members but also to the behavior of nonstructural elements. The need to properly design nonstructural elements for earthquakes has been largely demonstrated in the last few years and has become an important objective within the earthquake engineering community. A crucial aspect in the proper design of nonstructural elements is the definition of the seismic demand in terms of both absolute acceleration and relative displacement floor response spectra. In the first part of this study, relative displacement and absolute acceleration floor response spectra were computed for four reinforced concrete moment-resisting archetype frames via dynamic time-history analyses and were compared with floor response spectra predicted by means of two recent simplified methodologies available in the literature. It was observed that one of the existing methodologies is generally unable to predict consistent absolute acceleration and relative displacement floor response spectra. An improved procedure is developed for estimating consistent floor response spectra for building structures subjected to low and medium-high seismic intensities. This new procedure improves the predictions of a relative displacement floor response spectrum by constraining its ordinates at long nonstructural periods to the expected peak absolute displacement of the floor. The resulting acceleration and relative displacement response spectra are then consistently related by the well-known pseudo-spectral relationship over the entire nonstructural period range. The effectiveness of the proposed methodology was appraised against floor response spectra computed from nonlinear time-history analyses.

Past earthquake evidence has shown the high vulnerability of Italian school buildings, given by the extensive damage observed to structural and non-structural elements. Such vulnerability demonstrates the need to undertake a seismic risk assessment and reduction strategies for critical facilities and allocation of national funds for retrofit interventions to those regions where seismic risk is higher. To do so, Expected Annual Losses (EAL) are evermore considered one of the main seismic risk metrics, which can, however, be largely affected by the epistemic uncertainty that typically characterizes the material and geometrical properties of existing buildings, particularly masonry-infilled reinforced concrete (RC) ones. This paper investigates the implications of accounting for a thorough identification of sources and characterization of uncertainty in seismic loss estimates on the risk assessment of a typical Italian masonry-infilled RC school building. The variability in masonry infill properties and modeling assumptions, as well as the subsequent epistemic uncertainty, are explicitly considered in the loss estimation of the RC school building. Specifically, the impact on the expected annual loss ratio is quantified in terms of both structural and non-structural components, depending on the engineering demand parameter to which they are sensitive. The results show that, when considering the uncertainty related to the variability in masonry infills, higher loss ratios of up to 30% are obtained with respect to the available literature estimates.

Recent studies evidenced that non-structural damage in buildings caused by earthquakes leads to high economic losses and can represent a threat for life safety. Particularly, piping network damage has been widely documented in post-earthquake inspections. In this study, a cascade analysis is conducted to evaluate the seismic demand on two types of piping networks installed in a reinforced concrete framed building. The cascade analysis is performed employing floor acceleration time-histories obtained through non-linear dynamic analyses of infilled and bare frames. The dynamic response of the piping networks is defined accounting for the non-linear behaviour of pipe joints and suspended piping restraint installations. The results show that the acceleration demand and the damage on the network significantly increase in infilled frames compared to bare frames. Additionally, a different seismic damage rate was observed comparing the two piping networks. The outcome of this study is used to provide design recommendations for suspended piping restraint installations, aimed at reducing the seismic vulnerability of the piping networks.

The seismic assessment of existing masonry infilled reinforced concrete (RC) building portfolios is a highly relevant issue in Italy and other Mediterranean countries, particularly in regions where a large part of the built environment was not designed according to modern seismic codes. In the past, masonry infills were generally considered as non-structural elements and were not accounted for in the design process. However, the results of experimental tests and past earthquake evidence demonstrated the influence of masonry infills on the global and local behaviour of RC buildings. Furthermore, the acknowledgment of different construction practices points out the significant variability affecting the masonry infills in terms of material properties, thickness, presence of openings and manufacturing techniques. This paper deals with the large-scale performance analysis of existing masonry infilled RC building portfolios accounting for the uncertainty related to the variability in the mechanical properties and the modelling of masonry infills. To accomplish this goal, a fully integrated building stock, representative of masonry infilled RC buildings designed according to the Italian codes in force between 1960 and 1980, was developed, using a simulated design approach. Statistical data and results of experimental tests were used to identify the main masonry infill typologies adopted in the Italian context. Detailed numerical models, whose prediction capability was appraised through the results of cyclic quasi-static tests, were developed to estimate the lateral response of the analysed RC buildings. Different response parameters, which can be easily implemented in seismic risk assessment frameworks, were considered and quantified, at the portfolio level, to understand the uncertainty propagation and impact of the masonry infills’ variability on the expected performance of existing RC buildings. The results demonstrated that the variability related to the definition and modelling of the masonry infills induces significant dispersion, with respect to the mean, on the lateral response of different classes of buildings within a given portfolio. Moreover, the provided parameters for multi-linear idealised capacity curves can be used in simplified seismic fragility and risk models for existing buildings, including a proper estimate of the associated uncertainty, leading to a more accurate quantification of economic losses.

Masonry existing structures are prone to significant structural damages when subjected to seismic actions. Over the last decades, innovative techniques emerged as attractive solutions for repair and retrofit of structures. In particular, composite materials with inorganic matrix (FRCMs-CRMs) have emerged as an alternative to fiber reinforced polymers for their better compatibility with masonry substrates. The effectiveness of the strengthening relies on the FRCM-substrate bond behavior, which needs to be characterized for the design of the reinforcement elements. Shear bond tests are able to determine the stress-slip law and the failure mode that rules the FRCM-substrate stress transfer capacity. In the last years, several experimental investigations on shear bond tests of strengthened masonry prisms were performed even if the knowledge about the influence of each variable parameter is not fully known. In this context, the numerical simulation may be a rapid and economic tool to study the incidence of the most relevant parameters in the bond mechanism. In this paper, a numerical study aimed at simulating the fiber-mortar bond behavior and at calibrating a shear stress (τ)-slip (s) constitutive bond law, is presented. Advanced 2D numerical models, able to simulate the most probable failure mode occurring in shear bond tests, have been developed. The results of the numerical simulations have been compared with the experimental results of a large database of tests on FRCM/CRM strengthened masonry prisms. An inverse analysis procedure has been used to fit the experimental bond stress versus slip curves and to predict the failure modes.

Post-earthquake damage reports have continuously highlighted the significant vulnerability of nonstructural elements to seismic events. Nonstructural damage has severe impact in the building recovery, increasing the socioeconomic losses even for low intensity events. In the last few years, research efforts have focused on the development of innovative nonstructural solutions, to be combined with damage-resistant structural skeletons in order to obtain an overall highperformance building. As part of a European Union (EU)-funded project, the effectiveness of such integrated skeleton&envelope low-damage system in reducing the earthquake related losses was investigated. Tridimensional shake table tests on a 1:2 scaled timber-concrete low-damage structural skeleton, “dressed” by different innovative nonstructural elements (glass/concrete facades, gypsum/ masonry partitions), were performed at the National Laboratory for Civil Engineering (LNEC) in Lisbon, Portugal. The shake table testswere carried out at increasing seismic intensities to investigate the structural and nonstructural performance up to a higher-than Collapse Prevention Limit State according to the Italian Code (975 years return period). This paper focuses on the dynamic behavior of nonstructural elements with detailed discussion on construction detailing, seismic demand and performance of the innovative solutions. The high performance of nonstructural elements proved the potential of the details introduced in the partitions/facades. Minimal or no damage was observed up to the end of the overall testing sequence, which reached moderate-to-high interstory drift ratios (more than 1.00%) - typically expected to cause severe damage to traditional nonstructural partitions/infills/facades.

Research on infilled reinforced concrete frames is fundamental for the vulnerability assessment of existing buildings. The analysis of the interaction between infill and frame is an open issue in performance-based earthquake engineering due to its importance in predicting the dynamic behavior and failure modes of buildings. This study provides an open access database of laboratory tests on masonry infilled reinforced concrete frames, collected from the literature and harmonized in a consistent framework. The database is named Masonry Infill Database 1.1 (MID 1.1). The data were grouped in categories to calibrate a piecewise linear curve representing the lateral response of the infill depending on the masonry wall and the frame details. The gathered data were used to assess analytical models and numerical studies from the literature with the aim of revising the formulations currently used in the equivalent strut approach. An empirical model for the equivalent strut was developed through a power-law multiple regression of the database. The open access database in its spreadsheet form is intended to provide a useful tool for the analysis of infilled reinforced concrete frames.