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Structural robustness assessment is a hot topic in the field of civil engineering. Although many robustness researches have been conducted on hot-rolled steel, reinforced concrete and timber structures, very few investigations have been reported for cold-formed steel (CFS) structures. This paper proposes a novel risk-based seismic robustness assessment methodology for CFS structures based on vulnerability and fragility, where the consequence and the probability are evaluated by structural vulnerability analyses and seismic fragility analyses, respectively. This insight was used for assessing the conditional seismic robustness (CSR) of CFS structures to predefined local damage events. This paper aims to propose the concept of overall seismic robustness (OSR), where the assumption that the occurrence probability of the local damage event is 1 in CSR is abandoned, and some typical damage states are used as the local damage events instead of the predefined ones. A 5-story CFS shaking table test model is selected as a benchmark model, and this paper quantifies the OSR of the models with different sheathing materials. The results show that: the model with better ductility exhibits a higher OSR, which is the same finding as the finding by Baker et al., indicating the validity of the proposed methodology. The methodology could not only considers the changes in failure consequence and probabilities, various uncertainties and occurrence probability of earthquakes in the service life of structures, but also considers the effects of structural repair, retrofitting and other factors. More importantly, the methodology could be conveniently used in engineering practice. Thus it would be a good choice for structural robustness assessment. [ABSTRACT FROM AUTHOR]

The paper proposes the use of supervised machine learning (ML) methods for quickly predicting the seismic response of rocking systems when subjected to seismic excitations. Different supervised ML algorithms are discussed, while a relatively simple and a more sophisticated algorithm are examined in detail. Specifically, the two algorithms compared are the k-Nearest Neighbor (k-NN) and the Support Vector Machine (SVM). The performance of the ML models is demonstrated considering both sine pulses and different sets of natural ground motion records. The results are practically perfect for sine pulses, while accurate results were also obtained for the case of natural ground motions. The proposed ML-based tool allows to quickly assess the risk of damage for rocking systems, while it is also very important when a large number of rocking blocks have to be studied, e.g. in the case of a building's inventory. [ABSTRACT FROM AUTHOR]

Structural response reconstruction (SRR) and prediction modeling is an area of growing interest in earthquake engineering research. Within the post-earthquake environment, SRR models are useful for estimating seismic demands in uninstrumented buildings using the response measurements from those that are equipped with strong motion sensors. This paper introduces a dual model that uses kriging combined with the extreme gradient boosting (XGBoost) algorithm to reconstruct seismic response demands in buildings during real earthquakes. The model is constructed with data that consists of responses from 207 buildings and 35 earthquakes. Kriging is first used to predict peak ground accelerations (PGAs) at the location of the uninstrumented buildings, using the measured PGAs from instrumented building sites with similar features (e.g., event magnitude, source-to-site distance, and location). The XGBoost algorithm is then used, with PGA as one of several features, to reconstruct the maximum (over the building height) peak (over the response history) story drift ratio and peak floor acceleration in the uninstrumented buildings. The residuals are then examined to assess overall model performance. [ABSTRACT FROM AUTHOR]

Large parts of Asia, Europe, and the eastern USA have high population concentrations in moderate seismic regions (MSR), where very large earthquakes are rare. With rampant construction in the cities located in MSRs, a relatively moderate earthquake can turn into a catastrophe. Limiting the collapse has been the conventional performance objective for regions with high seismicity. However, this does not necessarily translate into a more desirable target of life-safety under design basis earthquake in MSRs. The present paper investigates the seismic performance of non-ductile reinforced concrete (RC) buildings that were common before the advent of modern design standards, and are found in very large numbers. An analytical model capturing the shear failure is employed using a drift-based limit state material. The results show that a hybrid index captures moderate damage more accurately than the prevalent drift-based index. The paper further shows that while a generic ground motion suite accurately estimates the median fragility, it fails to capture the uncertainty. A 7-story non-ductile RC archetype building was found to be at a collapse prevention risk of 2 × 10–4. The seismic risk deaggregation reveals that seismic risk consistency can be enhanced by explicit specification of the seismic forces for retrofitting. The study shows that the stringent seismic risk targets can be met by non-ductile buildings in MSR, provided they are designed or retrofitted with constraints on strong column weak beam factors. The study will facilitate in developing a scheme for prioritizing and devising the retrofit of pre-modern code and non-ductile deficient buildings. [ABSTRACT FROM AUTHOR]

Seismic isolation techniques are hardly implementable on existing historic structures, if their integrity is a matter of concern (Viggiani in 19th International conference on soil mechanics and geotechnical engineering, Seoul Korea, 2017; Flora in Third international symposium on geotechnical engineering for the preservation of monuments and historic sites, Naples, Italy, 2022). Recent results have shown that if a continuous barrier having a low dynamic impedance is created in the soil beneath the structure, both the absolute acceleration and relative displacement demands are significantly reduced without any direct intervention on the structure itself. Super Absorbent Polymers (SAP), mixed with the in-situ soil, are excellent candidates to the creation of these soft barriers. The first part of the paper reports a complete dynamic laboratory characterization of SAP-sand mixtures with different percentages of polymer in the soil. The results clearly show that small percentages of SAP have a minor effect on the reduction of the shear stiffness value, while when the percentage is higher than 40% a sharp drop is observed. It is also shown that SAP largely increases the damping ratio of the treated layer, being this an extremely beneficial effect for its seismically isolating application. In the second part of the paper, one and two-dimensional seismic response analyses were carried out to explore the beneficial effects of SAP-soil filtering barriers as parts of a Geotechnical Seismic Isolation (GSI) system. The paper also proposes a simplified analytical approach to design geotechnical seismic isolation using Super Absorbent Polymers. [ABSTRACT FROM AUTHOR]

The seismic vulnerability of bridges may be reduced by the application of Geotechnical Seismic Isolation (GSI) below the foundations of the columns and the abutments. However, the role of GSI on the seismic response of bridges has been limitedly examined in literature. Therefore, this research has been conducted to study the effect of applying GSI on the seismic response of bridges to address the aforementioned gap in knowledge. Advanced nonlinear dynamic three-dimensional finite element analyses have been conducted using OpenSees to study the influence of the GSI. The cases of traditional and isolated bridges subjected to earthquakes have been considered to assess the GSI effects. The results showed that the GSI reduces the seismic effect on the column while its effect seems to be less significant for the abutments. In addition, fragility curves for the traditional and isolated cases have been developed and compared to provide insights with a probabilistic-based approach. The results of this paper provide a useful benchmark for design considerations regarding the use of GSI for bridges. [ABSTRACT FROM AUTHOR]

Slender storage tanks on tube feet or skirt support are essential components of industrial facilities and often contain large amounts of hazardous liquid. As the geometry of such storage tanks with torispherical heads is somewhat standardised, seismically induced stresses and anchoring forces are often calculated by the equipment manufacturer in a simplified and conservative way. Thereby, the hydrodynamic effects of the stored liquid are usually not taken into account. This often leads to high resulting anchoring forces that may exceed the typical bearing resistance of the discrete anchoring at the tube feet or skirt support. In this paper, a procedure is suggested that lowers the overall stress resultants by determining the tank's response in a more differentiated way. It is based on calculating the hydrodynamic pressure and load components as a function of the geometrical characteristics of the tank. The general concept was developed for flat bottom tanks but can be transferred—with certain adjustments—to the considered slender storage tanks on tube feet or skirts. Emphasis is set on the potential for energy dissipation and on the choice of appropriate response acceleration and response spectra, respectively, which is different for the individual load components. The suggested procedure is prepared for easy-to-use application by providing simple formulas and tabulated coefficients. Its capability for design load reduction in comparison to the simplified calculation method is shown on an exemplary case study. [ABSTRACT FROM AUTHOR]

This paper presents application of ASCE/SEI 41–17 nonlinear seismic analysis and evaluation procedures to the 10-story reinforced concrete building tested on the E-Defense shake table in December 2015. Primary lateral load resisting system of the building was reinforced concrete frame in the longitudinal direction and RC wall in the transverse direction. Analytical models were developed in OpenSees with nonlinear wall, beam, and column elements, as well as with linear elastic and two types of nonlinear beam-column joint elements: (1) modeling parameters that follow ASCE/SEI 41–17 recommendations, and (2) modeling parameters derived using data from relevant experimental results. Computed responses for the analytical models of the building and predicted damage are compared with measured responses and observed damage for strong motion records from 50 and 100% Kobe earthquake excitations. Results comparisons indicate that the ASCE/SEI 41–17 nonlinear dynamic evaluation procedures are overall able to reasonably identify the general damage extent and distribution for both frame and wall directions. Analysis results further suggest that the beam-column joint modeling parameters in ASCE/SEI 41–17 for nonlinear dynamic procedures likely overestimate the rate of strength loss with increasing deformation demands revealing a potential need for review and update of the joint shear strength and nonlinear modeling parameters and acceptance criteria. [ABSTRACT FROM AUTHOR]

This paper provides a comphrensive review of the critical aspects of nonlinear modeling for evaluating the seismic response of masonry structures, emphasizing the issues relevant to engineering practice. Currently, the specialized technical community shares the opinion that, for a performance-based approach, numerical models are the only tools sufficiently effective to support the seismic assessment of existing buildings. However, their potential often falls short when attempting to accurately describe the behavior of masonry structures. In fact, these structures feature highly complex architectural configurations, different masonry types, and various structural solutions, meaning that extra care is required in numerical modeling. This is especially true when the modelers do not have a solid background in the software chosen and may not be practiced using the vast variety of options offered by the software houses. They are often unaware of the consequences that questionable modeling choices may have on the results obtained by the models. These extremely complex topics are treated in the paper from an engineering practice perspective, providing an in-depth overview of the challenging issues related to the use of different modeling strategies. The paper covers strategies ranging from the Equivalent Frame approach (widely used in common engineering practice) to more refined techniques like 2D and 3D Finite Element procedures based on continuous, discrete, and micro-mechanical approaches. Critical aspects in the modeling of both in- and out-of-plane responses of masonry, as well as the critical issues in wall-to-wall connections and diaphragm roles are investigated. All the examined issues are clarified through numerical examples highlighting also how a consistent and integrated use of different procedures may be beneficial. Finally, some of most relevant challenging issues concerning the use of numerical models in seismic assessment with the nonlinear static approach are presented and discussed. [ABSTRACT FROM AUTHOR]

The paper presents the comparison of the results of nonlinear static analyses carried out using six software packages (SWs) available at professional level and operating in the field of the equivalent frame (EF) approach on a model representative of a complex masonry building. The structure is inspired by the school "P. Capuzi" in Visso (MC, Italy), proposed as one of the benchmark structures in the "URM nonlinear modelling—Benchmark project" funded by the Italian Department of Civil Protection within the context of the ReLUIS projects. The 2-stories building is characterized by an irregular T-shaped plan and load-bearing walls consisting of two-leaf stone masonry with a rather regular bond scheme. The school was severely damaged by the seismic sequence that hit Central Italy in 2016/2017 and essentially exhibited a global in-plane box-type response, with a clear evidence of cracks concentrated in piers and spandrels. The availability of an accurate survey of the crack extension represents a precious and rare reference to firstly address in the paper the rules to be adopted in the EF models for the definition of the structural elements geometry. Then, the comparison of results is made with a twofold aim: firstly, by setting the models adopting shared and consistent modelling assumptions across the SWs; secondly, by investigating the sensitivity of the seismic response to some common epistemic and modelling uncertainties (namely: the adoption of various EF idealization rules for walls, the out-of-plane contribution of piers, the flange effect). In both cases, results are post-processed to define reference values of the achievable dispersion. The comparison is carried out in relation to a wide set of parameters, namely: global parameters (e.g. dynamic properties, pushover curves and equivalent bilinear curves); synthetic parameters of the structural safety (i.e. the maximum acceleration compatible with the ultimate limit state); the damage pattern simulated by SWs. [ABSTRACT FROM AUTHOR]

Seismic modelling of unreinforced masonry (URM) buildings is addressed worldwide according to different approaches, not only at research level, but also in the current engineering practice. The analysts have so many different possible choices in interpreting the response of the examined structure and in transferring them into the model for the assessment that the achievable results may turn out in a huge scattering, as also testified by various comparative studies already available in the literature. Within this context, this paper is an overview of a wide research activity addressed to the benchmarking of software packages for the modelling and seismic assessment through nonlinear static analyses of URM buildings. The activity conveyed the effort of many experts from various Italian universities and was funded by the Italian Department of Civil Protection within the context of the ReLUIS projects. The main objective of the research is the critical analysis and the systematic comparison of the results obtained by using several modelling approaches and software package tools on selected benchmark examples in order to provide a useful and qualified reference to the engineering and scientific community. To this aim, different benchmark examples—of increasing complexity, ranging from the single panel to 3D existing buildings—have been specifically designed. While other papers from the teams involved in the research project delve on the specific results achieved on each of these case studies, this paper illustrates an overview on such benchmark structures, their purpose and the standardized criteria adopted to compare the results. Moreover, the whole set of benchmark case-studies is made available in this paper through their detailed input data allowing to be replicated also by other researchers and analysts. [ABSTRACT FROM AUTHOR]

Timber structures are important components of the architectural and cultural heritage. To enrich literature on reconnaissance and heritage preservation, this paper provides a comprehensive damage survey and assessment of the Shuanghe Confucian temple after the 2019 Changning earthquake Series. Confucian temple is a temple for the veneration of Confucius and the sages and philosophers of Confucianism in Chinese folk religion and other East Asian religions. The Shuanghe Confucian temple, which sits in southwestern China, was first built at about 1241, but have been gradually deteriorating and refurbished for 600 years. It has the supreme structural grade in ancient Chinese architecture and delicate local characteristics. On June 17th, 2019, an Ms 6.0 earthquake stroke Changning County, and another four earthquakes (aftershocks) with magnitude larger than Ms 5.0 took place in the next 20 days. The Shuanghe Confucian temple experienced very distinctive damage during the earthquake series. The paper first present sufficient ground motion information. Characteristics of the all the major structural components are also introduced along with their mechanical functions. Next, the damage of all the typical timber structural components, like roof overhangs drop, column rupture, column bottom lateral residual displacement, and non-structural components failure are carefully documented and assessed. The paper reveals two important aspects that some major damages of the Shuanghe Confucian temple occurred in aftershocks, and that the columns bottom lateral residual displacement was caused by eternal impact induced by adjacent wall collapse, instead of structural inner forces. Thus, this paper helps better understand the seismic performance of traditional timber structures and identify potential weaknesses which might have adverse influences on timber structures. Lessons learnt from the Shuanghe Confucian temple can be used in future to better protect other historical timber structures from earthquakes. [ABSTRACT FROM AUTHOR]

The seismic response of monopile foundations is a growing area of research as the offshore wind industry expands worldwide, including in earthquake prone regions of the world. This paper presents dynamic centrifuge tests aimed at investigating the dynamic response of monopiles in both dry and saturated sandy soils. The latter case includes soil liquefaction under strong input motions, with measured excess pore pressures indicating liquefaction. The natural frequency of the monopile-soil system is experimentally determined by measuring the response to a sine sweep motion. Strong earthquakes are then applied at this frequency and its harmonics. This paper discusses the response of the monopile in terms of the peak accelerations observed in the dry and saturated tests, as well as using response spectra and amplification ratios. The dynamic bending moments along the pile are also measured to infer the bending moment profile with depth. Finally, two identical monopiles are pushed-over in each of the centrifuge tests to establish the pre and post-earthquake monotonic response, including the lateral stiffness and capacity, which are compared for the dry model tests and the saturated case. [ABSTRACT FROM AUTHOR]

Spatial variability of seismic ground motion is related to the difference in amplitude and phase of ground motion recorded over a given area. Spatial variability results from different contributions: the wave passage effect due to time delays in the arrival times of various seismic phases, the site response effect due to spatial soil heterogeneity, the attenuation along the ray path and the incoherence effects due to scattering of waves by local heterogeneities, the seismic rupture mechanism and, in near fields, the source directivity. [ABSTRACT FROM AUTHOR]

An effective approach to simulate the multi-support earthquake underground motions is proposed in this paper and the key factor for this approach (i.e. underground cross-correlation function) is presented in advance and elaborated. Previous studies are mainly focused on the multi-support ground motions due to the absence of the necessary conditions to simulate underground motions, i.e., underground power spectral density (PSD), underground response spectrum and, especially, underground cross-correlation function. In this paper, the underground PSD and response spectrum are firstly derived and the cross-correlation function between the underground motions at positions with different horizontal and vertical coordinates is further deduced. The physical meanings of the parameters in this approach are explicitly clarified. Moreover, a program for generating the multi-support earthquake underground motions is developed and the reliability of the generated underground motions is verified. Finally, a two-span bridge is taken as an example to investigate structural responses under multi-support earthquake underground excitations. Numerical results show that the dynamic responses under multi-support earthquake underground motions are significantly different from those under multi-support earthquake ground motions. Results indicate that the simulation of multi-support earthquake underground motions is significant for both study and engineering application. [ABSTRACT FROM AUTHOR]

This paper documents performance of cast-in-place reinforced concrete (RC) buildings in the Durrës municipality during Albania earthquake of November 26, 2019 (MW 6.4). Both mid- and high-rise RC buildings were affected by the earthquake, experiencing structural and/or non-structural damage and even collapse in some cases. The authors performed a reconnaissance study after the earthquake and were involved in seismic assessment of buildings in the affected area. Besides the observations related to physical damage of RC buildings, the paper also presents results of a statistical analysis of damaged RC buildings in the Durrës municipality. The discussion in the paper is focused on damage patterns and failure mechanisms that are relevant for the seismic response of RC structures. Most common damage pattern observed after the earthquakes was related to masonry infill walls, which experienced damage and failure in some cases, and affected the performance of adjacent RC columns due to the infill/frame interaction. Taller RC framed buildings (10 storeys and higher) were expected to have RC shear walls; however, these walls were reportedly absent in the damaged buildings of this type. In some cases, masonry infill walls (instead of RC shear walls) were used in the elevator shaft areas, which resulted in inadequate seismic performance. A case study has been presented to illustrate seismic behaviour of mid-rise and high-rise cast-in-place RC buildings in the November 2019 earthquake, and is based on post-earthquake field observations and a detailed seismic assessment of two earthquake-damaged buildings. Finally, relevant lessons and recommendations are presented in light of the observed performance of RC buildings. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) rigid-frame bridges with tall hollow piers were widely constructed in Southwestern China, an earthquake-prone area. For such bridges, the seismic damages may be underestimated if multiple bends of tall piers are overlooked using a conventional damage measure such as the drift ratio. Moreover, the seismic damage assessment can be inaccurate if tall piers' shear damages are ignored using the sectional curvature as a damage measure. Along these lines, this paper proposes a novel seismic damage measure, the piecewise drift ratio (PDR), involving both shear effects and multiple-bend deformations; it has been validated by hybrid tests and analyzed employing fragility curves. Damage state limits represented by the PDR are estimated through statistical analysis of the 40 existing tests of hollow piers. To validate the PDR, a finite element model of an RC rigid-frame bridge with two tall piers was established and adequately calibrated based on model-updating hybrid simulations. To comprehensively evaluate the PDR, ground motions were selected and grouped into four categories by identifying their first two-class nature frequency and their amplitude ratio; to determine fragility curves, both the spectral acceleration at the fundamental period with 5% damping, Sa(T1, 5%), and the peak ground acceleration have been adopted as intensity measures. Results show the effectiveness of the proposed PDR, provide a more severe ground motion for assessment, and reveal the high exceedance probability of the complete damage state of tall piers under some potential seismic scenarios. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic response of two 21-story buildings was studied to assess the influence of higher modes in their structural performance. While the first building was structured with ductile moment-resisting steel frames and exhibits a global shear-dominated lateral deformation, the second one uses ductile concentrically braced steel frames and has a global bending-type response. Buildings were virtually located in a soft-soil condition of the lake-bed zone in Mexico City. Nonlinear pushover and dynamic analyses were performed through OpenSees on a detailed 3D-model with plasticity spread along the elements. For this purpose, a set of accelerograms recorded during the Mexico Earthquake of September 19, 2017, were selected, and adjusted to represent the actual seismic hazard at the site. A frequency-domain system identification technique was applied to identify the dynamic characteristics of buildings through a moving-window Fourier analysis, that allows for the estimation of the contribution of higher-modes to their overall nonlinear dynamic response. A ratio of the elastic spectral pseudo-accelerations corresponding to the first two vibration modes is proposed to quantitatively anticipate cases and conditions for which the second mode adversely affects the structural performance of upper stories. The discussion includes a comparative study from the lateral global response of the analyzed models. [ABSTRACT FROM AUTHOR]

Slopes have a significant impact on the ground motion characteristics, which can aggravate the damage degree of building structures during a strong earthquake. However, many studies have focused on the design response spectra under flat site conditions and fewer researchers have investigated the impact of slope topography on the design response spectra. In this study, the numerical simulation is used to obtain the seismic response of slopes and the differential evolution algorithm is used to obtain the standardized response spectra of the acceleration time histories along the ground surface behind the slope crest. The impacts of slope height (H), slope gradient (i), average shear wave velocity in the top 30 m (VS30) and distance from the slope crest (x) on the characteristic parameters of the design response spectra are then investigated. The results show that H, i, VS30 and x have a little influence on the normalized second inflection point period (mean(Tg/Tg,ff)) but a great influence on the normalized plateau value (mean(αmax/αmax,ff)). Specifically, both mean(Tg/Tg,ff) and mean(αmax/αmax,ff) show a trend from increasing first to decreasing and stabilizing finally as x increases; the mean(αmax/αmax,ff) shows an increasing trend as H increases, but a decreasing trend as i or VS30 increases. Finally, to provide some guidance for the seismic design of building structures near slopes, two approximate relationships are proposed: (1) between mean(Tg/Tg,ff) and x, and (2) between mean(αmax/αmax,ff) and H, i, VS30, x. The main innovation of this paper is that the relationship between the characteristic parameters of the design response spectra and the slope site characteristic parameters is clearly summarized and quantified for the first time. [ABSTRACT FROM AUTHOR]

To predict the response of masonry buildings to various types of loads, engineers use finite element models, specifically solid-element and macro-element models. For predicting masonry responses to seismic events in particular, equivalent frame models—a subcategory of macro-element models—are a common choice because of their low computational cost. However, an existing bottleneck in modeling pipelines is generating the geometry of the model, which is currently a slow and laborious process that is done manually using computer-aided design tools. In this paper, we address this by automating the modelling process using recent advancements in computer vision and machine learning. We present an image-based end-to-end pipeline that automatically generates finite element meshes for solid-element and equivalent-frame models of the outer walls of free-standing historical masonry buildings. As the input, our framework requires RGB images of the buildings that are processed using structure-from-motion algorithms, which create 3D geometries, and convolutional neural networks, which segment the openings and their corners. These layers are then combined to generate level of detail models. We tested our pipeline on structures with irregular surface geometries and opening layouts. While generating the solid element mesh from the level of detail model is straightforward, generating equivalent frame models required algorithms for segmenting the façade and the meshing. Experts in the field analyzed the generated equivalent frame models and determined them to be useful for numerical modeling. These finite element geometries will be invaluable for future predictions of the seismic response of damaged and undamaged buildings. The codes and dataset are publicly available for future studies and benchmarking (https://github.com/eesd-epfl/FEM%5fbuildings and https://doi.org/10.5281/zenodo.8094306). [ABSTRACT FROM AUTHOR]

A rapid estimate of the damage state of a building after an earthquake event is of crucial importance, having the potential to minimise casualties and mitigate costs associated with structural damage and economic downtime. Visually determining the damage state accurately is often difficult, and so instrumentation can be installed to estimate the extent and locations of damage. However, the current minimum requirements of industry standard instrumentation layouts have thus far proven to be inadequate in providing sufficient information about the health of a structure after an extreme event. This paper investigates a simple, computationally inexpensive method for determining the interstory drift of all floors of a high-rise building using minimal instrumentation. The methodology proposed is applied to the Atwood building, a 20-story structure located in a highly seismic region of Anchorage, Alaska, that has been fitted with an extensive seismic monitoring system. The simulated results are shown to provide comparable results of displacement profile of a structure over time with respect to the elastic performance of the building. Importantly, the displacement profile allows a direct calculation of interstory drift, which can indicate the location and damage state of the building. [ABSTRACT FROM AUTHOR]

Structural reliability methods are employed in this paper for nationwide probabilistic seismic hazard analysis of Iran and in-depth seismic hazard and hazard sensitivity analysis of Downtown Tehran. The companion paper proposes two analysis approaches based on reliability methods and presents the technical framework for such analyses. The first approach was based on Monte Carlo sampling reliability analysis, which is employed here to conduct hazard analysis at a grid comprising 3695 sites throughout Iran. The results are used to produce nationwide hazard maps for the peak ground acceleration, spectral acceleration, and cumulative absolute velocity. The other analysis approach employs the first- and second-order reliability methods and importance sampling and is applied to the seismic hazard analysis of Downtown Tehran. This analysis identifies the seismic sources that are most influential on the seismicity of Tehran. In addition, reliability sensitivity and importance measures are employed to identify the most influential sources of uncertainty on the seismic hazard at Downtown Tehran. For instance, they identify the geometry of, and the rupture location on, adjacent faults, the shear wave velocity, and the intra-event residuals of ground motion prediction models as the most important sources of uncertainty. [ABSTRACT FROM AUTHOR]

This paper presents a new probabilistic framework for seismic hazard assessment and hazard sensitivity analysis. Hazard in this context means the probability of exceeding a measure of ground shaking intensity, such as peak ground acceleration and spectral acceleration. The main components of the proposed framework include structural reliability methods to estimate exceedance probabilities and their sensitivities, and multiple probabilistic models for earthquake occurrence, magnitude, location, and ground motion. This paper presents two analysis approaches. The first approach utilizes the first- and second-order reliability methods and importance sampling. This approach efficiently yields the hazard exceedance probabilities at a single site. The second approach employs the Monte Carlo sampling reliability method and yields the hazard exceedance probabilities at a multitude of sites in a single analysis, which is suited for large-scale seismic zonation. This paper also presents the probabilistic models that are suited for such analyses with an emphasis on characterization of epistemic uncertainties. Finally, novel sensitivity measures are proposed for hazard sensitivity analysis. These measures provide a framework to identify the most important uncertainties and guide the research to reduce these uncertainties over time. The proposed approach is validated and showcased by an illustrative example. The companion paper presents a comprehensive application to hazard analysis of Iran. [ABSTRACT FROM AUTHOR]

Spatially varying ground motion (SVGM) may have influence on certain civil engineering structures with spatially extended superstructure and/or substructures. Conditional simulation of spatially varying ground motion (CSSVGM) may be viewed from two different perspectives. Most procedures available in the literature neglect the spatial variability in auto-spectral density (ASD) and estimate the SVGM through cross-spectral density (CSD) which was computed using the empirical coherency models. This paper proposes a coherency model that accounts for the spatial variability of ASD. A framework has been developed for the CSSVGM, through the mapping of both proposed coherency model and ASD over the footprint of an array. Current framework (existing in the literature) accounts for only the phase variability of SVGM while proposed framework accounts for both phase and amplitude variability. Ground motion generated from both perspectives is then assessed with the data recorded over SMART1 and LSST arrays. For the purpose of assessment, a definition of target spectrum based on the direction of arrival is explored. The effect of choice of coherency model on the simulated spatially varying ground motion is investigated first. Spectra resulting from both the perspectives are assessed against the target spectrum. An attempt has been made to predict the SVGM for a future event using a coherency model calibrated against a past event and an estimate of ASD of the seed ground motion. Finally, the effect of form of ASD (of a seed ground motion) on SVGM simulated is investigated by considering the ASD in different forms. Simulating SVGM through the mapping of both coherency model and ASD seems to be more appropriate than through CSD. [ABSTRACT FROM AUTHOR]

This paper's objective is to obtain exact analytical parameters for Tuned Mass Dampers (TMDs) that derive their efficiency for controlling the seismic response by inducing two modes with equal damping ratios, when affixed to single-degree-of-freedom mechanical systems. The parameters that are derived are intrinsic to the systems and are independent of the ground motion. It is seen that for TMDs tuned with this criterion, as damping is increased a critical condition of multiplicity of eigenvalues is reached. The damping provided by the TMDs calibrated in this manner is effective only in the sub-critical range. As the critical and supercritical conditions are reached, the TMDs lose their efficiency, and are not adequate to reduce the response to seismic excitation. Nevertheless, in this paper the exact analytical parameters are provided for all conditions. It is shown that at the critical condition the derivation of parameters results in a commonly referenced work by others, who also proposed using TMDs for the purpose of seismic response abatement. Finally, some calculations in the frequency and time domains are presented to illustrate the utilization of the parameters that are derived, and to illustrate the effect of the TMD mass on the seismic response. [ABSTRACT FROM AUTHOR]

The response of a two-storey RC school building in the town of Argostoli, Cephalonia Island, Greece, during the seismic sequence of January and February 2014, is examined. The structure was built following an older generation of seismic codes dating from the 1950s, which provide limited strength and ductility against lateral loads. Despite the severity of ground shaking and the two successive events, the building suffered relatively minor damage, like most of the RC buildings in the town. Following a short presentation of some basic seismological, structural and geotechnical aspects of the seismic sequence, the paper focuses on the seismic performance of the structure at hand. To this end, a series of detailed non-linear static and time-history dynamic analyses are reported, which highlight the interplay of soil, foundation and superstructure in modifying the seismic demand. It is demonstrated that SSI had an unexpectedly important (detrimental) role in the behaviour of the structure, increasing its natural period by about 25% and aggravating ductility demand in almost all columns, despite the moderately soft soil conditions (average VS = 180 m/s). The results shed light on the seismic performance of the building and help drawing conclusions on the engineering effects of the 2014 Cephalonia earthquake sequence. [ABSTRACT FROM AUTHOR]

Seismic losses due to earthquakes have been shown to have significant economic, social and environmental consequences. Over recent years, research to predict potential economic and social impact due to seismic risk has been increasing. Recognizing that the traditional philosophy of life safety design can lead to extensive damage and demolition which has a large environmental cost, incorporating environmental impacts associated with the expected seismic damage over a building's life is a key step as the building industry moves towards both sustainable and seismically resilient design. This paper introduces a framework that uses environmental indicators quantifying losses from seismic response that can then be used to advocate for a change in seismic performance objectives. First, existing literature and previously developed approaches for quantifying potential environmental impact due to seismic damage are summarized. Next, performance based earthquake engineering concepts are used to demonstrate a probabilistic approach to quantify potential environmental impacts using a range of environmental and resource use indicators over the life span of a case study building. In addition, a case study is presented to compare different environmental indicators between a Code Minimum building and the same building redesigned for a higher seismic performance. The majority of the composition of the environmental indicator values are from the inclusion of the non-repairable scenario, and from the repair activities, the majority of the impacts are from damage to drift sensitive components including curtains walls, partitions and elevators. For the Code Minimum building the non-repairable scenario contributes to between 8 to 11% the total seismic cost. For the Stronger Stiffer building, the non-repairable scenario contributes around 3% of the initial impact. Neglecting non-repairable scenarios does significantly reduce the potential environmental impacts when analyzing buildings designed for current code minimum structural standards. [ABSTRACT FROM AUTHOR]

A distributed remote collaborative hybrid test (RCHT) method for complex substructures based on OpenFresco is presented in this paper. Challenges in the RCHT include the modeling of the numerical substructure, boundary degree-of-freedom (DOF) loading, and equivalent communication of the multi-story space frame as a test substructure in OpenFresco. The effectiveness and accuracy of the proposed RCHT method are verified by a series of remote distributed tests that reproduce the seismic response of a three-story five-span space Y-shaped eccentric brace steel frame model consisting of two test substructures and a numerical substructure. The main contributions of this study are the realization of the multi DOF loading RCHT of the space global frame and reasonable simplification of the substructure boundaries, which further promotes the use of the RCHT method to realize the seismic performance simulation of complex substructures. [ABSTRACT FROM AUTHOR]

Summary: The aim of this paper is to demonstrate the efficiency of a low-cost and sustainable timber-based energy dissipation system with recentering ability, which can be used as a seismic isolation system or a tuned mass damper for the seismic protection of structures in developing or developed countries. The system, defined as Dovetail with SPrings (Dove-SP), utilizes the attractive properties of timber to store CO2, thus reducing the carbon footprint of the existing energy dissipation systems: It comprises two timber slabs that are designed to slide against each other in a motion that is restrained by a dovetail sliding joint. Two sliding interfaces that allow this sliding motion at an attractively low friction coefficient are experimentally investigated: A PVC sand-wich (PVC-s) sliding interface, comprising a thin layer of sand that is sand-wiched between two PVC layers and a timber sand-wich sliding interface consisting of a thin layer of sand encapsulated between two beech timber surfaces. A set of low-cost steel springs is designed and installed on both sides of the dovetail joint to recenter the structure back to its original position after the end of an earthquake ground motion excitation. A novel, low-cost and deformable wood material fabricated from delignified balsa wood is used to reduce the pounding effects before the activation of the steel springs. The seismic behavior and the recentering ability of the novel timber-based energy dissipation system subjected to an ensemble of recorded earthquake ground motion excitations was experimentally investigated through a large-scale shaking table investigation at ETH Zurich. [ABSTRACT FROM AUTHOR]

The paper focuses on the detailed analysis of the dynamic characterisation of polyurethane to evaluate the effects of polyurethane injections into soil with the aim of geotechnical seismic isolation. To determine the dynamic properties, resonant column (RC) tests were performed at the University Kore of Enna (Italy) on specimens of pure polyurethane with different values of density and subjected to different mean confining pressures. The results obtained by means of RC tests, in terms of shear modulus G and the damping ratio D as a function of shear strain γc, allowed to develop an analytical formulation for G-γc and D-γc curves, taking into account the linear relationship with density, of both the maximum value of shear modulus Gmax and the minimum value of damping ratio Dmin. The analytical formulation derived from the experimental results is applied for ground response seismic analyses of cohesive soils injected with polyurethane, using a finite element code. The numerical results show that the polyurethane injections reduce the value of maximum acceleration on the ground surface and the reduction varies with the thickness of the soil modified by polyurethane injections. [ABSTRACT FROM AUTHOR]

This paper examines the seismic stability of steel wide-flange columns located in the first storey of Ductile Moment-Resisting Frames (MRFs) with emphasis on their out-of-plane response and proposes improved stability design recommendations for such columns. A five-storey steel MRF is first designed in accordance with the seismic provisions of the Canadian steel design standard. A subassembly consisting of the exterior bay plus half of the adjacent interior bay is then isolated from the prototype MRF, and its finite element model is constructed. The results obtained from the nonlinear response history analysis of the MRF subassembly is used to assess the stability response of the first-storey columns and verify the adequacy of a component-based column model, which is isolated from the MRF, in predicting column nonlinear cyclic response. A total of 26 seismically-compact wide-flange columns covering a wide range of geometrical parameters, including global slenderness, cross-section aspect and section width-to-thickness ratios, are subjected to cyclic strong-axis displacement and weak-axis bending in the presence of a constant axial compression load. The results of the column parametric study are used to identify column out-of-plane instability modes using strength and deformation response parameters, including base moment, axial shortening, out-of-plane displacement, and cross-section twist. Two instability modes, including out-of-plane buckling at the base and member buckling, are observed. A design equation as a function of parameters affecting the out-of-plane stability of columns with base plastic hinging, namely global slenderness, cross-section aspect and axial load ratios, is finally proposed to verify the out-of-plane stability of first-storey columns under seismic loading. [ABSTRACT FROM AUTHOR]

This paper examines the seismic behavior of CLT-steel hybrid walls at 6- and 10-story heights to increase seismic force resistance compared to conventional wooden walls. The ultra-strong shear walls proposed in this paper are called Framing Panel Shear Walls (FPSW), which are based on a robust articulated steel frame braced with CLT board panels and steel tendons. Timber structures are well-known for their ecological benefits, as well as their excellent seismic performance, mainly due to the high strength-to-weight ratio compared to steel and concrete ones, flexibility, and redundancy. However, in order to meet the requirements regarding the maximum inter-story drifts prescribed in seismic design codes, a challenging engineering problem emerges, because sufficiently resistant, rigid and ductile connections and lateral assemblies are not available for timber to meet both the technical and economical restrictions. Therefore, it is necessary to develop strong and cost-effective timber-based lateral systems, in order to become a real alternative to mid- and high-rises, especially in seismic countries. In this investigation, the dynamic response of cross-laminated timber (CLT) combined with hollow steel profiles has been investigated in shear wall configuration. After experimental work, research was also carried out into numerical modelling for simulating the cyclic behavior of a hybrid FPSW wall and the spectral modal analysis of buildings of 6- and a 10-stories with FPSW. A FPSW shear wall can double the capacity and stiffness. [ABSTRACT FROM AUTHOR]

The paper reports on four cyclic tests of brick masonry spandrels in reference state and strengthened state. The tests were carried out on full-scale, H-shaped masonry panels to investigate the coupling role of the spandrel in connecting two piers in a historical masonry wall subjected to in-plane lateral actions. Two 250-mm-thick solid-brick masonry samples were tested—one single-leaf, the other two-leaves masonry. Both samples were tested before and after strengthening by applying a Composite Reinforced Mortar (CRM) coating on one surface. The CRM coating consisted of a lime mortar coating (nominal thickness = 30 mm), reinforced with mesh made of Glass Fibre-Reinforced Polymer (GFRP) that was anchored to the wall by GFRP transverse connectors. For the double-leaf masonry, there were additional transverse connectors made of steel bars in concrete cores (artificial diatones) to prevent masonry leaves separation and to improve the bonding of the CRM coating to the masonry. The test responses are compared in terms of crack pattern, failure mode, resistance, displacement and energy dissipation capacity. The tests showed the effectiveness of the proposed CRM system, which increased the spandrel resistance by 33% and 125% in the single—and double-leaf masonry, respectively, with the ultimate drift being 3.2% (one order of magnitude greater than for the unstrengthened reference samples). Data on energy dissipation and the equivalent viscous damping are also collected and compared. Importantly, the presence of the reinforcing mesh and the composite action of the coating and the wall changed the damage evolution and response mechanism, which resulted in a much better seismic response. [ABSTRACT FROM AUTHOR]

This paper introduces a framework to estimate the seismic response of buildings at a regional scale by using representative indicator buildings. A robust database of buildings is required in the proposed framework to provide high-level structural and site information of the buildings. In this study, a database of 234 reinforced concrete buildings with five or more stories located in the central business district of Wellington, New Zealand was selected as a case study. In a prior phase of the research, the buildings were clustered into typologically similar clusters and eight representative indicator buildings were selected, where an indicator building was the closest building to the mean cluster structural and site characteristics. In this work, the concept of using indicator buildings to estimate building response across each cluster is investigated. First, three-dimensional structural models of each of the eight selected indicator buildings from the Wellington database were developed using the opensource structural analysis program OpenSeesPy. Five models were developed for each indicator building: one nonlinear model, one linear model, and three linear supplementary models where the effective stiffness of the structural members were modified to represent the period range of all buildings across a given cluster. The supplementary models were used to develop a period correction relationship to modify the estimated drifts based on the spectral shape of the imposed ground motion. Ground motions from the 2016 Kaikōura and 2013 Seddon earthquakes in New Zealand, as well as the 1995 Kobe earthquake in Japan, were selected to evaluate the proposed framework. The relationships between predicted elastic and inelastic drifts were explored, and polynomial regression models were investigated to provide drift correction accounting for the spectral shape of the three earthquakes. Finally, the efficacy of the proposed framework in estimating the response of all buildings across all clusters and the applicability of this framework as a near real-time impact tool were demonstrated using post-earthquake damage reports from the Kaikōura and Seddon earthquakes. [ABSTRACT FROM AUTHOR]

The track structure has an effect on the dynamic characteristics of the bridge structure, which makes the seismic response of the bridge structure complicated. In this paper, an assessment method is proposed to evaluate the seismic risk of bridge structure, including over-limit risk and over-limit scale. Based on a newly proposed simplified model with high accuracy and high computational efficiency, a total of 3000 calculation conditions are analyzed and the sample stability of response is validated to ensure the reliability of the seismic risk analysis. The seismic risks in the longitudinal direction of the track-bridge model are compared with that of the trackless model, and the influence of the constraint effect of China Railway Track System II ballastless track structure on the seismic risk of the structure is obtained. The influence of the number of spans and PGA on track constraints is also revealed. The analysis results, based on a large number of samples, show that although track constraints can reduce the seismic risk of some phenomenon, such as girders' collision, the expected enhancement of longitudinal seismic safety of the system cannot be guaranteed in general, especially when the number of spans is large. However, it is noted that the track constraint can effectively control the over-limit scale of the system, which can reduce the expected repair cost after an earthquake. Therefore, it can be considered that the positive effect of the track constraints is more significant in economy than in structural safety when the bridge is subjected to a longitudinal earthquake excitation. [ABSTRACT FROM AUTHOR]

Aim of this paper is to investigate the effectiveness of the seesaw system in mitigating the seismic response of elevated steel tanks for water storage. This is accomplished by conducting a number of non-linear time-history (NLTH) analyses to a specific in terms of shape and water storage capacity elevated steel tank. To conduct the NLTH analyses: (i) the two (horizontal) or the three (two horizontal and one vertical) translational components of the seismic motions are utilized; (ii) two different water heights are considered, representing the cases of a partially-filled and an almost filled tank; (iii) the tank is assumed founded either on a rigid or on a flexible ground, permitting, thus, an assessment of the influence of soil-structure interaction (SSI). The NLTH analyses are performed first for the tank without the seesaw system and then with it. The response metrics to be compared are the drift and residual drift ratio of the tank, the axial and shear stresses exerted to the shell of tank, the maximum forces developed to the members of the seesaw system as well as the formation of plastic hinges to the steel framing system that supports the tank. Interpretation of the results provided by the aforementioned response metrics leads to the conclusion that the effectiveness of the seesaw system to elevated steel tanks of the type studied herein is limited. [ABSTRACT FROM AUTHOR]

The present work offers a comprehensive overview of methods related to condition assessment of bridges through Structural Health Monitoring (SHM) procedures, with a particular interest on aspects of seismic assessment. Established techniques pertaining to different levels of the SHM hierarchy, reflecting increasing detail and complexity, are first outlined. A significant portion of this review work is then devoted to the overview of computational intelligence schemes across various aspects of bridge condition assessment, including sensor placement and health tracking. The paper concludes with illustrative examples of two long-span suspension bridges, in which several instrumentation aspects and assessments of seismic response issues are discussed. [ABSTRACT FROM AUTHOR]

In this paper a novel approach named Multi Pier Macro MPM method is proposed for seismic analysis of steel moment frames. Based on the model an arbitrary multi-bay and multi-story moment frame is substituted by a single bay braced frame consists of two piers and two braces at each story. Piers are continuous and braces are pinned to piers. Both piers and braces are 1D truss elements. The axial, flexural and shear stiffness of the moment frame are provided by axial behavior of piers and braces. MPM method was benchmarked against four steel moment frames including two mid-rise and two high-rise buildings. The seismic responses of equivalent braced frames including maximum floor displacements and story drifts was compared with original moment frames responses as exact results, by means of Non-linear Static Procedure NSP and Non-linear Response History Analysis NL-RHA. NL-RHA was performed using twelve ground motion records scaled to Maximum Design Earthquake MDE and Maximum Considered Earthquake MCE hazard intensities. The results proved the simplified braced frame is able to estimate the seismic responses of mid and high-rise moment frame buildings with high accuracy meanwhile the analysis time and computational cost were limited remarkably. [ABSTRACT FROM AUTHOR]

The ability of an intensity measure (IM) to accurately reflect the characteristics of ground motions is of utmost importance for seismic fragility assessment. Traditional investigations focused on selecting the optimal IM have primarily been conducted based on ordinary reinforced concrete (RC) structures. The direct application of IM specifically tailored for ordinary RC structures in the fragility analysis of self-centering prestressed RC (SCP-RC) structures will potentially introduce increased uncertainties of ground motions. This paper aims to conduct a comprehensive analysis to identify the optimal vector-valued IMs (vIMs) for the fragility assessment of SCP-RC structures. A total of eight vIMs were constructed by combining various scalar-valued IMs (sIMs) associated with the peak values and spectra of ground motions. A 5-story SCP-RC structure was designed to evaluate the efficiency and correlation of the established vIMs using a multi-parameter damage measure (mDM). Probabilistic seismic demand models for the eight examined vIMs were developed. A comparative analysis between the fragility surface slices obtained using the identified optimal vIM and the fragility curve derived from the corresponding sIM was performed. The results indicate that (PGV, I N p /PGV) is the most suitable vIM for accurately quantifying the fragility of SCP-RC structures. The seismic fragility surface is more efficient than fragility curve in estimating the seismic performance of SCP-RC structures. [ABSTRACT FROM AUTHOR]

The method for the direct determination of floor acceleration spectra, previously developed by the authors, is extended in order to take into account the nonlinear component behaviour. In the case of a linear elastic response of both the primary structure and the component, the component may be exposed to very high accelerations during seismic actions. The component accelerations can be greatly reduced if the response of the structure and/or the component is nonlinear. Considerable research work on the effect of the nonlinearity of structures has already been performed, whereas relatively sparse information is available on the quantitative influence of the component nonlinearity on its response. In the paper, first, the results of a parametric study of floor acceleration spectra for nonlinear components are shown and discussed. Then, the proposed extension of the existing authors' method is described and validated by test examples. In addition, an approximate approach for the estimation of floor acceleration spectra for nonlinear components by using an increased component damping value is presented. In the proposed method, floor acceleration spectra are, to a great extent, based on the theory of the dynamics of structures, and partly combined with empirical values and well established approaches for considering nonlinear effects. Floor acceleration (response) spectra explicitly take into account ground motion spectra and dynamic characteristics of buildings and components. The advantage of such an approach is its general applicability, which allows diverse design options. [ABSTRACT FROM AUTHOR]

The structural behavior prediction of the multistory reinforced concrete (RC) buildings with masonry infill walls (MIWs) during earthquakes is challenging. This paper presents a nonlinear macromodeling strategy seeking a simple, reliable, and low-cost computational analysis of the multistory RC buildings that comprise MIWs, and that use frames or shear walls (SWs) for resisting the lateral load. The strategy employed four plastic hinge (PH) models for tracking the deformations (flexural, shear, and torsion) of the frame elements and joints, a multilinear plastic link for modeling the MIW, and a nonlinear multilayer shell element for modeling the SW. A flexural PH model characterized by discretization into fibers, a recommended position, and an iterative estimating for the PH length using a distinct formula for each loading level was proposed. This strategy was validated through eleven macromodels investigating four bare frames, four MIWs frames, and a SW where the average ultimate lateral load error was 9.2%, 3.6%, and 0.4%, respectively. Finally, the structural behavior of real ten-story buildings with/without MIWs was investigated. The results showed that the MIWs increased the shear capacity and the lateral stiffness with an average of 44.3% and 118.6%, respectively. Also, both the frames buildings with MIWs and the bare SWs buildings showed approximately equal lateral load capacities. Local damages in the RC vertical elements and yielding of the MIWs were recorded simultaneously. However, the MIWs yielding (and also failure) occurred earlier for the frames buildings compared with the SWs buildings in which the stress was relaxed in their MIWs. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of soil–structure interaction and site amplification on the seismic response of one of the towers of the Theodosian walls of Constantinople during the Kocaeli earthquake in 1999, that largely damaged it. The interacting system is first analysed in the frequency domain by the well-known replacement oscillator model, turning out that the effect of soil–structure interaction could be relevant. The complete system is then examined by the direct approach considering non linearity of the behaviour of both the structure and the soil. The failure mechanism detected from where stress and plasticization concentrate into the masonry panels is consistent with the out-of-plane mechanism of one of the tower façades triggered by the reference earthquake. The focus was then set on the effectiveness of some retrofitting interventions, including the lateral disconnection of the embedded sides of the tower from the surrounding soil, the soil treatment by grouted columns and the classical technique for masonry rehabilitation. Even though the latter choice is the most common one, retrofitting interventions concentrated into the soil could be effective as well. Their use should be properly considered when the scope of the intervention is the preservation of cultural heritage. [ABSTRACT FROM AUTHOR]

Pin-supported (PS) walls represent a possible solution for the seismic retrofit of existing reinforced concrete (RC) buildings, enabling linearization of the frame deformation along its height and consequently inhibiting soft storey collapse mechanisms. The effectiveness of this rehabilitation technology is strongly related to the characteristics of the existing frames, especially to the vertical distribution of the frame storey lateral stiffness. Since a larger 1st storey lateral stiffness may lead to a detrimental structural response of the retrofitted system, an alternative solution obtained from removing the connecting link between the 1st floor of the existing building and the pin-supported wall is investigated in this paper. An analytical method is proposed to derive the distribution of the internal actions in a dual 2D RC frame-PS wall system without the link at the 1st floor level, considering both a linear and nonlinear behaviour of the frame. It emerges that some parameters describing the structure type can provide straightforward information on the suitability of this solution in the seismic retrofit of existing RC buildings. As a result, a simplified procedure has been derived to preliminarily define the retrofit system configuration and evaluate the maximum demand in the PS wall. Such a procedure is finally applied with reference to a frame representing a RC building and finite element model analyses are carried out for validation purposes. [ABSTRACT FROM AUTHOR]

A new hybrid system consisting of wood shear walls, concrete columns, bracing system, and viscous damper devices is introduced in this paper. A benchmark wood building is adopted here as a case study, and different configurations of the new hybrid system are applied on it in order to investigate its seismic performance under some near-fault ground motion records. The performance base design method is used to design the considered models. In order to make the models comparable, their performance levels are considered to be identical. Detailed finite element models are built in OpenSees software to conduct nonlinear static and dynamic analyses. The parametric study is done to optimize the viscous damper system parameters. At the end, the damage potential of the models is investigated through their fragilities. The results demonstrate the high potential of the proposed system in improving the seismic performance of the mid-rise wood buildings. It is also observed that the good behavior of the system is achieved when the viscous damper coefficient and its supporting tendon cross-sectional area is dependently increased. [ABSTRACT FROM AUTHOR]

Telecommunication tower with height of 155 m is located on the top of Vodno Mountain near Skopje, R. N. Macedonia. The complexity of the structure, the extreme building conditions as well as the high seismic zone and exploitation period led to a design and construction phase accompanied by experimental testing to validate the performance of the structure. A physical model of telecommunication tower with a height of seven meters and geometrical scale of 1:16 was designed, built and tested on the shake table at the laboratory for dynamic testing in the Institute of earthquake engineering and engineering seismology in Skopje. Synthetic accelerograms were developed for the specific location and structure, used as an input during the testing. The assessment consisted of two phases, determination of the dynamic characteristics and determination of seismic response of the physical model. The instrumentation comprised of two different types of transducers, accelerometers and linear potentiometers. In this paper the response of the structure will be presented in terms of a time history records of accelerations, displacements and relative displacements. The comparisons between the prototype and the test model will be also discussed. [ABSTRACT FROM AUTHOR]

In this paper, empirical equations are proposed to calculate the moment-chord rotation response envelope of ductile rectangular reinforced concrete columns with deformed bars. The proposed envelope accounts for cyclic strength degradation and is defined by four characteristic points: yielding, maximum, conventional ultimate, and collapse. Also, the proposed envelope is implemented by adopting Pinching4 Material model in OpenSees and, based on the experimental data, the hysteretic parameters governing unloading and reloading stiffness degradation, as well as pinching effect, are calibrated. The proposed model is applied at the element level, thus showing the potential advantages and limitations of its use, also in comparison with other analogous proposals presented in the literature. The proposed model has two main advantages with respect to proposals existing in the literature: (i) the response envelope already includes cyclic degradation of force capacity, thus fulfilling the requests of current standards regarding the need of accounting for members' mechanical softening within nonlinear static procedures; (ii) the hysteretic parameters governing unloading and reloading stiffness degradation, and pinching, allow a more accurate reproduction of members' and structures' seismic response within nonlinear dynamic procedures. [ABSTRACT FROM AUTHOR]

The evaluation of seismic risk in structures requires information on both site hazard and structural vulnerability. Hazard can be quantified via probabilistic seismic hazard analysis, while seismic vulnerability can be quantified using structural analysis; the former is typically specified via predefined national hazard models, whereas the latter is more structure-specific and can be computationally expensive depending on the numerical modelling and analysis procedure complexity. As a compromise, various simplified seismic response evaluation methods have emerged and been implemented in assessment codes and guidelines (e.g., N2 method in Eurocode 8, SPO2IDA in FEMA P695). Furthermore, the seismic assessment and rehabilitation of existing structures have seen the introduction of risk classification guidelines. These are tools to primarily assist practitioners and decision-makers in understanding and managing seismic risk and the possible implications of different retrofitting schemes. Risk classification guidelines typically use loading-based quantities such as the seismic capacity-to-demand ratio. However, several drawbacks are associated with adopting loading-based quantities, namely the lack of uniformity of the actual seismic risk, expressed as a mean annual frequency of limit state exceedance. To address these drawbacks, this paper outlines a relatively simple pushover-based methodology for the direct evaluation of seismic risk (PB-Risk) for non-ductile infilled frame structures. The article describes a step-by-step framework for the simplified characterisation of hazard, vulnerability and subsequently seismic risk. It is quick and easy to implement within a practical and code-based setting and can be adopted within risk classification guidelines. The application of the proposed PB-Risk methodology is demonstrated via several case study applications, and its robustness in characterising seismic risk with respect to other simplified non-linear static formulations for infilled frame buildings is shown. [ABSTRACT FROM AUTHOR]

In recent years, the tuned mass damper inerter (TMDI) has been demonstrated in several theoretical studies to be an effective vibration absorber for the seismic protection of non-isolated buildings. Its effectiveness relies on careful tuning of the TMDI stiffness and damping properties, while its performance improves with the increase of the inertance property which is readily scalable. Nevertheless, in all previous studies, the energy dissipative TMDI element has been modelled by a linear viscous damper. Still, commercial viscous dampers display a nonlinear velocity-dependent power law behavior. In this regard, this paper investigates, for the first time in literature, the potential of the TMDI fitted with nonlinear viscous damper (NVD) for seismic response protection of multi-storey buildings. This is supported by an efficient optimal nonlinear TMDI (NTMDI) tuning approach which accounts for any absorber connectivity to the building structure and employs statistical linearization to treat the nonlinear damping term. For the special case of white-noise excited undamped buildings, optimal NTMDI tuning is derived analytically in closed-form which is shown to be sufficiently accurate for lightly damped structures. Comprehensive numerical data are presented to delineate trends of optimal NVD damping coefficient with the NVD power-law exponent and the inertance. Further, nonlinear response history analysis results pertaining to optimally tuned NTMDI application for a benchmark 9-storey steel structure demonstrate that reduced NTMDI stroke and inerter force can be achieved with negligible change in storey drifts and floor acceleration performance by adopting lower NVD exponent values, leading to practically beneficial NTMDI deployments. [ABSTRACT FROM AUTHOR]

Rocking bodies can be found at all structural scales, from small museum exhibits to uplifting buildings. These structures, whose dynamic stability springs from the difficulty of mobilizing their rotational inertia, are ideal candidates for benefiting from the supplemental inertia provided by inerters. This benefit can be limited, however, if the inerter drives the structural response towards potentially undesirable motions by transferring back the kinetic energy accumulated within it at inconvenient times. To control this phenomenon, a clutching system can be employed to direct the interaction between the interter and the structure improving further its dynamic behaviour. To date, however, most of the studies dealing with clutching inerto-elastic or inerto-rocking systems under seismic excitation have adopted a rather simplistic idealisation of the clutch engagement-disengagement response. In this paper, we re-visit the impact effects on inerto-rocking structures and propose an improved mechanistic model of the clutching system. First, the effects of the inerter on the transition upon impact and the impact effects on the acceleration response of rocking blocks are analysed. Then, a set of original analytical expressions for rigid and flexible rocking structures equipped with a pair of clutched inerters are derived. The newly proposed models are used to examine the evolution of the energy dissipation in the device and the influence of key parameters like the clutch stiffness, gears play, viscous damping and dry friction on its response. We conclude by evaluating the behaviour of the detailed rocking model with clutched inerters to a set of realistic earthquake ground motions. Although important differences are observed in the evolution of energy dissipation and engagement response depending on the type and characteristics of the clutch model, largely comparable peak values of displacement are obtained. On the other hand, a more accurate representation of the clutch behaviour leads to potentially larger acceleration demands. Our analyses also show that, in general, the inclusion of the inerter results in higher coefficients of restitution, indicating lower energy dissipation during impact and that the infinite acceleration spikes predicted by Housner's model can be ignored if impact forces are sufficiently distributed over time as to cause continuous velocity transitions, but sharp enough not to appreciably affect the rotation response. [ABSTRACT FROM AUTHOR]

This paper studies the application of the inerter-based passive structural control in seismic response mitigation for a wind turbine. The inerter-based passive control system used here is called inerter-based dynamic vibration absorber (IDVA), in which a spring and an inerter-based mechanical network are connected in parallel. A multi-degree-of-freedom (MDOF) system is used to describe the wind turbine system with the consideration of the interaction between wind turbine structure and soil. For the purpose of mitigating seismic response, the inerter-based mechanical network is regarded as a controller to be designed using two different methods. Then, a variety of different network configurations are selected in the fixed-structure method, and only the low-order admittances are taken into account in the network synthesis method. By optimizing the controller parameters with H 2 optimization method, response parameters such as tower-top displacement are improved. The comparisons of the tower-top displacement performance corresponding to the traditional tuned mass damper (TMD) and the inerter-based dynamic vibration absorbers (IDVAs) show that the inerter-based control can use a smaller additional mass ratio to achieve the same tower-top displacement performance as the TMD control. Finally, the numerical simulation results obtained with different types of ground motions for a 5-MW NREL wind turbine also demonstrate the superiority of IDVAs compared to TMD, and a similar decreasing trend is observed for tower-top displacement performance and tower bottom bending moment performance. [ABSTRACT FROM AUTHOR]