Areas Of High Seismic Risk Research Articles

Effects of wire rope isolators on seismic life-cycle cost of UHV bypass switch

The seismic isolation devices reduce the seismic vulnerability of the electrical equipment. Accurately assessing the seismic life-cycle cost (SLCC) of the electrical equipment is beneficial in guiding the design and enhancing the seismic resilience of electrical substations and converter stations. To evaluate the effects of the isolator devices on the seismic life-cycle cost of electrical equipment, a SLCC evaluation model was proposed in this study, and the evaluation was conducted on an ultra-high voltage (UHV) bypass switch (BPS) with wire rope isolators (WRI). The model takes into account equipment purchase, maintenance, transportation and installation costs and indirect losses caused by power outages. Afterward, the SLCC and break-even time of the UHV BPS with and without WRIs in different regions were analyzed. The results indicate that beyond the break-even time, the BPS with WRIs becomes more economically viable. Moreover, its economic viability increases as the service life extends. Therefore, in high seismic cost risk areas, it is recommended to adopt seismic isolation devices to ensure the secure and economically efficient operation of electrical equipment.

Integrated Structural Health Assessment of Industrial Buildings in Areas of High Seismic Risk

Integrated Structural Health Assessment of Industrial Buildings in Areas of High Seismic Risk

Simulating Strong Ground Motion from the Great 1923 Kanto Earthquake in the Tokyo Metropolitan Area Based on Source Model Derived from Seismic Intensity Data

ABSTRACT This study simulates strong ground motions in the Tokyo metropolitan area during the 1923 Kanto earthquake using the stochastic Green’s function method. Source characteristics were modeled using seismic intensity inversion analysis, and path and site characteristics were modeled using inhomogeneous attenuation structure and empirical amplification factors. The results of these simulations were consistent with seismic intensities estimated based on the collapse rate of wooden houses. The distribution of pseudovelocity response spectra averaged at periods of 1–2 s was large: ∼200 cm/s in southern Kanagawa and southern Chiba prefectures, ∼100–200 cm/s in eastern Tokyo, and ∼50–100 cm/s in eastern Saitama prefecture despite its distance from strong-motion generation areas (SMGAs). The simulation results were regressed on site characteristics and fault distance, and the residuals were interpolated using the Kriging method to estimate detailed maps of seismic intensity and response spectra on an ∼250 m mesh reflecting site-specific characteristics. The following conclusions can be made: (1) all SMGAs, other than those in northern Tokyo Bay, were located near large slip areas based on coseismic geodetic and seismic waveform data. Although the SMGAs in the northern part of Tokyo Bay exerted little influence on the southern part of the Kanto region, their consideration was required to reproduce the seismic intensity at the northwest Tokyo and Saitama; (2) intense strong motion in central Tokyo occurred at the back marsh, delta, coastal lowlands, and filled lands, whereas low levels of strong motion were determined at terraces covered with volcanic ash soil. Combined with building distribution, this indicates areas of high seismic risk; (3) the seismic intensity and response spectra in the Tokyo metropolitan area obtained through this simulation were larger than those obtained from seismic records of the 2011 Tohoku earthquake—the most recent megathrust earthquake.

The attenuation of macroseismic intensity in the volcanic island of Ischia (Gulf of Naples, Italy): comparison between deterministic and probabilistic models and application to seismic scenarios

In this paper, we tackle the problem of the intensity attenuation at Ischia, a critical parameter in a high seismic risk area such as this volcanic island. Starting from the new revised catalogue of local earthquakes, we select a dataset of 118 macroseismic observations related to the four main historical events and analyse the characteristics of the intensity attenuation according to both the deterministic and probabilistic approaches, under the assumption of a point seismic source and isotropic decay (circular spreading). In the deterministic analysis, we derive the attenuation law through an empirical model fitting the average values of ΔI (the difference between epicentral intensity I0 and intensities observed at a site IS) versus the epicentral distances by the least-square method. In the probabilistic approach, the distribution of IS conditioned on the epicentre-site distance is given through a binomial-beta model for each class of I0. In the Bayesian framework, the model parameter p is considered as a random variable to which we assign a Beta probability distribution on the basis of our prior belief derived from investigations on the attenuation in Italy. The mode of the binomial distribution is taken as the intensity expected at that site (Iexp). The entire calculation procedure has been implemented in a python plugin for QGIS® software that, given location and I0 (or magnitude) of the earthquake to be simulated, generates a probabilistic seismic scenario according to the deterministic or probabilistic models of attenuation. This tool may be applied in seismic risk analyses at a local scale or in the seismic surveillance to produce real-time intensity shake-maps for this volcanic area.

Investigating the effect of using Multi-Level Yielding Pipe Damper dampers in steel structures under earthquake force in the horizontal direction

Multi-level Pipe Damper (MPD) recently proposed by the authors is a passive control device to reduce the seismic vibration. In this research, seismic response of steel structures equipped with MPD is studied. To evaluate the effects of the proposed damper, typical 8 story steel buildings are modeled and their seismic responses under three earthquake excitations are investigated using dynamic nonlinear time-history analyses by ETABS program. Results show the effectiveness of MPD to altering the seismic response of the structures. Moreover, using MPD decreases the structural and nonstructural damages noticeably by limiting the inter story drifts because of the secondary hardening branch of force-displacement respectively proving the effectiveness of the proposed damper as a retrofitting technique for structures at high seismic risk areas.

Research on Seismic Reduction and Isolation Design of Prefabricated Viaduct in Areas of High Seismic Risk

Seismic isolation design is an effective and economical method to protect precast viaducts from severe earthquake damage. Correct selection of bearings is one of the common methods to achieve this goal. In order to optimize the vibration isolation performance of prefabricated viaducts, this paper compares the vibration isolation performance of lead rubber bearings (LRB) and laminated bearings (LB). The lead rubber bearing (LRB) and laminated bearing are respectively applied to the same analysis model of prefabricated viaduct. The seismic responses of bearings and structural members are analyzed by dynamic analysis method, and the typical seismic responses, including internal force, displacement, hysteresis curve and residual deformation, are compared. The results show that LRB has higher isolation efficiency and better self centering ability.

Structural Health Monitoring and Dynamic Identification of the Historical Town-Hall of Borgo Val di Taro

A good structural knowledge of heritage buildings is a key factor for their conservation and for the planning of retrofit interventions, especially in high seismic risk areas, like Italy. Within this context, structural health monitoring techniques, like those based on ambient vibrations under operating conditions, represent powerful tools for evaluating the dynamic behavior of existing structures. The presented methodology is particularly interesting for historic and monumental buildings due to its non-invasiveness. This work illustrates the installation of a monitoring system in the historical masonry Town-Hall of Borgo Val di Taro, dating back to the fifteen century, for its ambient vibration modal identification. The so collected data are then used for the construction of a refined numerical model for the simulation of the dynamic response of the building, and for the updating of its parameters. A comparison between numerical and experimental results is finally provided.

Tribological investigation on metal mating surfaces to explore real use conditions of a novel friction damper for seismic applications

The seismic rehabilitation of existing buildings is a strategic goal for many countries located in high seismic risk areas of the globe. Retrofit techniques based on energy dissipation by implementing additional mechanical dampers into the structure have proved to be very efficient. Among the others, friction-based dampers have revealed to be particularly simple and cheap; nonetheless, for this kind of device, the selection of mating surfaces set a crucial point. This paper shows the experimental investigation performed for the development of a novel Friction Damper (FD) using Pin-on-Disk (PoD) tests and highlights the main tribological aspects useful for the full-scale tests. PoD tests have been set to simulate the real use condition of the device in development under the action of subsequent earthquakes. Sliding surface’s material and machining processes have been selected taking into account the S355JR steel main body of the device in development, and the need of reducing the friction’s abrasive component and the particle formation during sliding. The experimental campaign has been addressed to highlight the influence of surface roughness, machining processes, additional treatment, and different coupling materials on Coefficient of Friction (COF) mean value and its statistical dispersion.

In-plane behavior of clay blocks externally reinforced

The objective of this research work was to determine the resistance to cutting of clay block walls of size 1.20 m × 1.20 m without and with external reinforcement. Blocks of width equal to 0.10 m were used for four manufacturers, one located in Ocaña, Colombia, and three more established in San José de Cúcuta, Colombia. Reinforcement with electrowelded mesh is an alternative to reduce the seismic vulnerability of homes in areas of intermediate and high seismic risk. Ocaña, Colombia, is located in an intermediate seismic hazard zone and therefore the use of simple masonry in homes is not allowed. This made it necessary to determine the mechanical properties of the clay block pieces, such as compressive strength, compressive strength of the bonding mortar, compressive strength of clay block prisms, diagonal tensile strength, modulus of elasticity and shear modulus of reinforced and unreinforced walls. The tests were carried out on a universal machine with a compression capacity of 100 t, a tensile capacity of 60 t class B with a precision of 0.1% ± 0.05 mm. This research established the physical parameters of the clay block prisms and the physical behavior of shear deformation vs. Shear stress without and with exterior reinforcement, necessary to establish physical models of structural reinforcement of houses vulnerable to seismic movements, and with this avoid human losses.

A common source for the destructive earthquakes in the volcanic island of Ischia (Southern Italy): insights from historical and recent seismicity

The island of Ischia, located in the Gulf of Naples, represents an unusual case of resurgent caldera where small-to-moderate magnitude volcano-tectonic earthquakes generate large damage and catastrophic effects, as in the case of 4 March 1881 (Imax-VIII-IXMCS) and 28 July 1883 (Imax X-XI MCS) historical earthquakes, and of the recent 21 August 2017 MW = 3.9, event. All these earthquakes struck the northern area of the island. With about 65,000 inhabitants, Ischia is a popular touristic destination for thermals baths, hosting more than 3,000,000 visitors per year, thus representing a high seismic risk area. Assessing its seismic potential appears a fundamental goal and, to this end, the estimate of the magnitude of significant historical events and the characterization of their source are crucial. We report here a reassessment of historical data of damage of 1881 and 1883 earthquakes to evaluate the main source parameters of these events (obtained with the BOXER and EXISM software) and quantitatively compare, for the first time, the results with the source characteristics, obtained from instrumental data, of the recent 2017 earthquake. The results allowed us to assess the location, as well as the possible dimension and the related maximum magnitude, of the seismogenic structure responsible for such damaging earthquakes. Our results also provide an additional framework to define the mechanisms leading to earthquakes associated with the dynamics of calderas.

Backprojection Imaging of the 2020 Mw 5.5 Magna, Utah, Earthquake Using a Local Dense Strong-Motion Network

Abstract We present the application of a backprojection method for imaging the detailed rupture of the 2020 Mw 5.5 Magna, Utah, earthquake. This is the first time that this method is applied to an earthquake smaller than Mw 6 in a local scale using a dense strong-motion network. The 2020 Magna earthquake occurred in a very well instrumented area, the Salt Lake valley, with tens of strong-motion seismic stations. We use envelopes of high-frequency S waves recorded on the transverse component at 45 seismic stations that are located at distances up to 100 km from the epicenter. The nearest station is ∼4.5 km. Backprojection resolves the epicentral location of the mainshock with an absolute error of less than 1 km, whereas the depth resolution is within the centroid depth range of multiple moment tensor solutions. Spatial distribution of the imaged subevents shows an up-dip unilateral west-northwest–east-southeast rupture with a length of ∼10 km, consistent with the distribution of early aftershocks. The average rupture speed is between 2.9 and 3.2 km/s for the first 2 and 3 s, respectively. The shallow dip (∼35°) of the Wasatch fault at depth, which failed during the Magna earthquake, combined with the up-dip unilateral rupture, indicates that ground-motion scenarios for future larger earthquakes in the Salt Lake Valley should be re-evaluated. This study underlines the need for instrumenting metropolitan areas of high seismic risk and adopting backprojection techniques in the near-real-time network products immediately after a strong earthquake.

Satellite radar interferometry for assessing coseismic liquefaction in Portoviejo city, induced by the Mw 7.8 2016 Pedernales, Ecuador earthquake

The Portoviejo city, located in the central part of the Ecuadorian Pacific Coast (province of Manabi), was severely affected during the Pedernales Mw 7.8 earthquake of April 16, 2016, accompanied by coseismic liquefaction phenomena that induced processes of ground subsidence, lateral spreading, sinkhole, and sand boils. The present study proposes the detection and delimitation of the areas affected by the relief deformation, associated liquefaction processes, which occurred in the urban area of Portoviejo city and especially in the Zero Zone of greater destruction after the earthquake, through the application of Differential Interferometry Synthetic Aperture Radar (INSAR) methodology, using Sentinel 1A satellite images, plus the support of geological–geotechnical data obtained from boreholes and standard penetration tests to evaluate the liquefaction potential of the layers of the subsoil based on the Potential Liquefaction Index, considering the seismic scenario of amax 0.5 g for the urban area and the Zero Zone. This procedure allowed the delimitation of areas of high seismic risk for the proper coordination and management of the construction and reconstruction processes in the city of Portoviejo and specifically in the Ground Zero.

VERNACULAR LANGUAGE WITHIN THE TRADITIONAL BELL TOWERS: BETWEEN STAIRS, LANDINGS AND FLOORS

Abstract. The monumental heritage of European historic centres is characterised by special building types that have drawn, more than others, on the vernacular language of the local traditional architecture. The traditional bell towers, even if built by a specific (but not always known) designer, often have some building elements transliterated from the construction tradition of poor and rural buildings. This language can be found in many examples from different historical periods and in faraway areas, such as Italy and Spain. The external monumentality may not correspond to a complex spatial articulation inside the towers. Instead, it is usual to find belfries in which the vertical connections and any horizontal structures are solved by wooden stairs and floors to reach the bell cell. The used materials and building techniques reveal the design simplicity but also the evidence of a lost “know-how”. Due to the nature of the materials, possible damages and lack of maintenance, many of these structures have undergone restoration or transformation works, also whit their replacement for the benefit of most modern construction systems. The research aims to underline the central importance of preventive knowledge of these traditional structures and illustrate some significant cases in Eastern Sicily, a high seismic risk area. These case studies are emblematic for the evidence of several original structures or the extreme effects of the 20th-century interventions. These last works have often compromised the historical and documentary trait of the wooden structures, introducing new vulnerabilities due to the excessive stiffening of the masonry.

Low-LOD code-driven identification of the high seismic risk areas for industrial buildings in Italy

The identification of the areas with high seismic risk for industrial buildings is of paramount importance for decision-makers to implement risk reduction policies. In this context, this study aims at performing a low-LOD (Level of Detail) code-driven identification of areas in Italy where industrial buildings face high seismic risk. Firstly, the hazard, vulnerability, and exposure models are introduced. Then, such input data are validated by comparing the predictions of the proposed framework with the observational data obtained after the Emilia-Romagna earthquakes of 2012. The validated framework is used to predict the conditional (to a certain return period) and unconditional risk in terms of elements-at-risk and economic losses. The unconditional risk in terms of economic losses expressed in terms of Expected Annual Losses (EAL) is used to rank areas in Italy in terms of seismic risk for industrial buildings. As expected, the area hit by the Emilia-Romagna earthquakes in 2012 is included among those with the highest seismic risk, indicating the predictability of large damage occurred on industrial buildings during the seismic event. Finally, some conclusions are drawn about the implications for future policies and studies for seismic risk reduction of industrial buildings in Italy.

Grouting performance of the Pandan Duri dam shacked by Lombok earthquake 2018

The Pandan Duri dam has an important role in water supply in the East Lombok District. Unfortunately, Lombok Island is located in a relatively high seismic risk area, as earthquakes occurred in 2018 have ruined almost one third of the island and destroyed thousands of buildings. The Pandan Duri dam is one of many infrastructures shacked by the earthquake. Modelling the dam shows that the grouting installation of the dam has supported the dam after the earthquake. The factor of safety (FoS) of the dam was still 1. 76 after the earthquake for the flood water level conditions; but, the displacements could be significant to the stability of the dam, as the dam might displace up to 1. 64 m. Although, the current grouting support system might provide the stability to the dam during earthquake events, the dam will certainly require further stability enhancement and close monitoring for possible similar events in the future.

Experimental modal identification and fem updating of a seven story isolated educational building

The construction of isolated structures is increasing in recent decades in seismic countries. In Peru, the national regulation indicates that important buildings such as hospitals located in areas of high seismic risk must incorporate isolation systems to reduce structural and nonstructural loss. These systems protect the main structure from the effects of a seismic event by separating its base from the earth movement and by reducing the relative displacements and accelerations between adjacent stories. In the structural design process of buildings and seismic protection systems, having numerical models that properly represent the real behavior of the buildings is of high importance. In this context, experimental modal tests represents an attractive cost-effective non-destructive tool to obtain an accurate characterization of the experimental structural response. This paper presents the experimental tests carried out in a base-isolated educational building built in 2014 that has seven stories and three basements with a total built area of around 7500 m2. Data acquisition was accomplished with autonomous units (acquisition system and transducers incorporated in a single unit) whose versatility allowed measuring a significant number of degrees of freedom in a limited amount of time. The dynamic properties experimentally identified were used to calibrate the finite element model of the building. The results showed that the design model approximates correctly to the experimentally identified ambient vibration response when considering rigid supporting conditions as well as the interaction of partitioning elements such as walls and parapets.

Diagonal compression tests on masonry wallets coated with mortars reinforced with glass fibers

Low shear strength of historical masonry constructions is a matter of great concern, especially when these buildings are located in areas of high seismic risk. In recent years this issue has led to many investigations on the development of innovative reinforcement techniques. The application of cement mortar, commonly used in this type of reinforcements, involves a number of material incompatibility problems that could be overcome with the use of lime-based binder mortars. The present article presents the results of an experimental study on solid mock brick wallets reinforced with thin layers of mortar mixed with glass fibers; Diagonal compression tests have been carried out to determine the behaviour of the reinforced masonries, evaluated both in terms of shear strength and deformation capacity. Test results verify that the coating of mortar mixed with fibers is practically as effective as cement mortar regarding shear strength, while they improve deformation capacity.

Structural and thermal retrofitting of masonry walls: An integrated cost-analysis approach for the Italian context

Constructions ageing is a relevant problem in developed country like Italy. In particular, in case of existing masonry buildings, retrofitting interventions aimed at improving structural and thermal performances represents an obvious need. At the same time, sustainability awareness of buildings life-cycle has grown in the last years. Consequently, the whole life-cycle of constructions should be analyzed and assessed during the design of retrofitting interventions. In order to take into account these aspects new design and planning methods are necessary. This paper presents an integrated approach to evaluate structural and thermal retrofitting strategies for masonry walls. Economic and ecological costs of each examined retrofitting solution are compared, taking into account thermal and seismic capacity demand of the construction site. Given the economic cost, a set of retrofitting solutions for masonry panels have been mapped with a couple of parameters (structural strength Vs thermal insulation). An analogous mapping, considering the ecological cost due to equivalent CO2 production, have been performed. A methodology to find the best solution among a set of retrofitting solutions is presented, depending on the location of the building and its seismic and thermal characteristics. Examples, based on six retrofitting techniques located in four different sites in Italy, are analyzed to explain the effectiveness and the feasibility of the proposed method. The comparison between ecological and economical cost allowed to highlight the characteristics of the different interventions. Thermal performance proved to be more important in cold weather conditions while structural retrofitting is preferable in high seismic risk areas.

Performance Evaluation of a Low-Cost Sensing Unit for Seismic Applications: Field Testing During Seismic Events of 2016-2017 in Central Italy

We propose a low-cost and low-power consumption device for seismic monitoring consisting of three single-axis accelerometers connected to a data logger with acquisition, synchronization, and transmission functionalities. The device was designed to be densely and prolifically deployed in high seismic risk areas, thus strengthening the Italian seismic network and providing a more accurate estimation of shaking maps. Moreover, the availability of such low-cost and high-performance units can allow the widespread diffusion of smart systems for seismic and structural monitoring, finalized to collapses prevention in critical structures, such as schools and hospitals, as well as constitute the founding nucleus of early warning systems based on Internet of Things architectures. The realized station was submitted to a testing phase, placing it contiguously to a high-performance seismic station located in central Italy and responsible for national seismic monitoring. The test station, installed from September 2016 to March 2017, was able to record the significant and numerous earthquakes that devastated central Italy during this period. The simultaneous acquisition of these seismic events by the sensors of the national seismic network, including that co-sited with the device under test, has furnished sufficient data for the device validation and performance quantification. A comparative analysis was performed through waveforms correlations study, strong motion parameters estimation, and spectral analysis. The proposed device demonstrated performances very close to those of more sophisticated and expensive systems. Therefore, it can effectively replace them or be added in engineering and civil protection applications and, finally, be used in earthquake early warning systems.

The implications of post-tensioning losses on the seismic response of Pres-Lam frames

Since 2010, twelve post-tensioned timber (Pres-Lam) buildings have been constructed throughout the world. In high seismic areas, Pres-Lam technology typically combines unbonded post-tensioning tendons and supplemental damping devices to provide moment capacity to beam-column, wall-foundation or column-foundation connections. Over time creep within the timber elements leads to losses in post-tensioning forces reducing the connection moment capacity. This paper analyses how different post-tensioning loss scenarios, depending on the beam-column joint detailing, impact the building’s seismic response. Two case study buildings were designed and investigated using the Acceleration Displacement Response Spectrum (ADRS) method and Non-Linear Time History Analysis (NLTHA) to predict seismic performance. These buildings were considered to be located in areas of high and low seismic risk, leading to designs with and without the use of damping devices, respectively. The results show that the building with additional damping responded with similar peak displacements, even under extreme loss scenarios. In comparison, when supplemental damping was not used, peak displacements increased significantly with post tensioning losses.