High Seismic Area Research Articles

Experimental study on seismic response of precast bridge piers with double-grouted sleeve connections

In recent years accelerated bridge construction (ABC) has become increasingly popular all over the world because of its good quality, cost effectiveness and decreasing bridge construction time. Much attention has been paid to substructure connections for ABC systems. Grouting sleeve (GS) is one of the most widely used connection methods. In this study, three 1/4 scale column models with two joints connected by different technique were conducted according to an actual precast bridge project. Two precast columns (B2, C2) were made to study the location effect of GS. One conventional cast-in-place (CIP) column (A2) was conducted as reference specimen. The seismic performance of the columns was investigated and compared. Experimental results showed that cracks for B2 with GS connectors in the column foot were less and plastic hinge had shifted to the ends of GS. The energy dissipation capacity of B2 was lower than that of reference specimen. Specimen C2 with GS connectors in the pier foundation appeared similar seismic performance to reference CIP A2, and the peak load of each cycle was higher due to the high-strength grout reinforced the interface bonding behavior between column and base. The displacement ductility coefficients for A2, B2 and C2 were 6.87, 5.14 and 6.42 respectively, and the GS connecting technique like B2 was not suggested for application in the high seismic area. The column-cap beam joint of all specimens remained intact throughout the testing from the strain results of the longitudinal bar.

Liquefaction Susceptibility Assessment Using Geotechnical and Geological Manners of Northern Thailand

Soil site investigations such as boring logs, basic soil properties, spectral analysis of surface wave, and the examinations of geologic and geomorphologic were performed in Mae Lao area to investigate the susceptibility of liquefaction after the 6.2 Mw Chiang Rai Earthquake 2014. The study area was found to lay on a complex geological formation and geotechnical behavior with a condition of the high groundwater table. Being located on a high seismicity area (intensity V-VII Mercalli) governs the study area as a concern for high liquefaction hazards. Liquefaction susceptibility-based compositional criteria, soil resistance, and geologic criteria have been established, and consequently, the character of liquefaction potential is defined.

Life-cycle cost assessment of conventional and hybrid sliding-rocking bridges in seismic areas

This article investigates the impacts of the column system on bridge life-cycle costs in high seismic areas. It focuses on hybrid sliding-rocking (HSR) columns, which are an accelerated bridge construction (ABC) technology. The authors conduct a life-cycle cost assessment, quantifying costs of bridge construction and potential earthquake damage and subsequent repairs, as well as the cost of bridge closure time due to construction or repairs. Two prototypical modern seismically designed bridges are considered, each designed with both conventional reinforced concrete (RC) and HSR columns. Construction costs of HSR columns are higher. However, drift demands on the HSR columns are generally lower, damage is less severe and costs of repairing the columns are greatly reduced. Moreover, construction times are about 80% quicker for HSR columns, and repair times are reduced relative to conventional construction. The results suggest substantial advantages to the HSR column system, reducing construction time and expected costs and time for seismic repairs sufficiently to counteract the increase in upfront construction costs. The benefits of the HSR, and by extension other ABC column systems, are particularly significant for highly trafficked bridges in high seismic areas, but hold for a wide range of input assumptions.

Seismic finite element analysis of tailings dam in high seismic intensity area

As an important facility for mine exploitation, the safety of tailings dam is very important in high seismic intensity area. In this paper, the seismic stability analysis of tailings dam located in high intensity area was carried out by taking the example of one tailings dam. Three-dimensional finite element model was established, and the calculation results were analyzed and compared under fixed boundary condition and viscous spring boundary condition. The results showed that, (1) Under the static condition, the deformation value is distributed in layers from top to bottom. (2) Under the seismic condition, it can be seen that the Z direction deformation is the largest, followed by the X direction, and the Y direction deformation is the smallest. (3) It is too conservative to evaluate the seismic stability of dam slope with the minimum safety coefficient, while it is more practical to use the minimum average safety factor as the evaluation index.

Optimal seismic isolation characteristics for bridges in moderate and high seismicity areas

This paper aims to identify the optimal properties of seismic isolation systems (SISs) for bridges in moderate seismicity areas (MSAs) and high seismicity areas (HSAs). Amplitude and spectral parameters of ground motions are proposed to identify these areas. A parametric study, with varying SIS properties, is carried out, and the seismic isolation performance is evaluated for several locations within MSAs and HSAs in North America and Europe. The optimal characteristic strength, Qd, and post-elastic stiffness, Kd, of SISs are determined for each seismic area class to minimize seismic forces and displacement demands. Results indicate that ground motions for MSAs have a rich high frequency content, causing seismic acceleration spectrum to decrease more rapidly with the elongation of the structure period. SISs with low-to-moderate energy dissipation capacities show the best performance for MSAs, while HSAs require SISs with higher damping capacities. Ranges for optimal Qd and Kd of SISs for bridges in MSAs and HSAs are proposed.

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.

Different Approaches to Assess the Seismic Capacity of Masonry Bridges by Non-linear Static Analysis

A large portion of the existing masonry arch bridges in Italy are still in service in the infrastructure system and are located in a high seismic risk geographical area. They were mainly built more than 100 years ago taking into account only gravitational loads during the design phase without any seismic analysis. For this reason, a seismic vulnerability assessment is mandatory from the Italian government in order to define the priority of seismic retrofit interventions. In this study, a multi-span slender masonry bridge considered as the most vulnerable typology of masonry bridges to seismic action will be assessed. Then, the results obtained from three different seismic assessment approaches will be discussed and compared. In particular, two approaches based on different FE modelling and the last one built on rigid block analysis are considered. Finally, a detailed 3D finite element analysis allowed representing all the collapse mechanism (global and local) of the bridges are presented. Simplified approaches, even though cannot describe all the collapse mechanisms of the bridges due to seismic action can lead to reliable results.

Definition of seismic performances and fragility curves of unanchored cylindrical steel legged tanks used in wine making and storage

The introduction of stainless-steel legged tanks is rather recent, and their use increased in the last decades in exponential way, especially in food industry and agricultural applications since they proved to be simple to prefabricate and transport, easy to clean and chemically inert. Despite their worldwide diffusion also in high seismicity areas, most of them were not designed with earthquake-based criteria as emerged by the catastrophic consequences and heavy losses observed, even recently, after several major earthquakes. By means of incremental dynamic analyses on the finite element models of 140 winemaking and storage legged tanks, the present paper, evaluates the main features of the dynamic response and for each vessel provides the lognormal cumulative fragility functions, for three different limit states of each vessel. Then, for each limit state, by means of nonlinear regression analyses, the median and the dispersion parameters of the best fitting lognormal function of every tank were statistically elaborated in order to define the response surfaces of the parameters. The response surfaces, provided for 3-, 4- and 5-leg unanchored tanks, are defined on the basis of few geometrical tank data. The analytical expressions provided in the paper, represent a practical and useful tool to directly calculate the fragilities of legged vessel. These, obviously, will allow the fast assessment of the seismic vulnerability of the tanks in agricultural facilities located in seismic prone areas.

Progressive collapse vulnerability assessment of irregular voided buildings located in Seismic-Prone areas

Nowadays, many special architectural forms of voided buildings such as hotels, commercial complexes, etc. are constructed in famous cities. In this paper, the effects of opening in the volume of low- and mid-rise irregular voided structures with low to high seismic resistance on the progressive collapse vulnerability are investigated. The structures are three and nine stories high, seismically designed with a steel moment frame system based on the AISC seismic code, and are located in sites with high, moderate, and low levels of seismicity. Detailed three-dimensional nonlinear dynamic analysis is performed to investigate spatially distributed damage to frame members and the structural robustness against abnormal loads according to the GSA 2016 guidelines. The response quantities are expressed in the form of the displacement of the node above the removed column, the spatially distributed formation of plastic hinges, the stress growth in nearby columns after progressive collapse occurrence, and the connection robustness analysis. The results show moment connections that govern the robustness of the structure and they are the most critical components in the structure. In addition, larger openings and proximity of the column removal scenario to position of the opening play a significant role in reducing the progressive collapse vulnerability of voided structures. However, in the scenarios of removing the internal column away from the opening, the progressive collapse mechanism of the structures with or without opening does not differ. Therefore, in the structural robustness analysis, internal columns away from opening of the voided buildings should be considered as critical and controllable elements in the progressive collapse capacity of structures. Among the modeled buildings, only the buildings located in high seismic areas can pass progressive collapse analyses and the seismicity level of the site is the most important parameter in robustness of the structure in comparison with the height or irregularity of the structure. Increasing the height of structures also reduces the amount of stress growth in the columns adjacent to the demolished column and the taller structures are safer structures in this regard.

Numerical analysis, design and behavior of rockfill dams with reinforced concrete faces during seismic actions

Introduction. Over the last 10–20 years many rockfill dams with reinforced concrete faces that are 140–200 m high (Mohale in Lesotho, Tian Sheng Yao, Zipingpu in China, etc.) have experienced serious problems, including face slab cracking and perimeter joint opening. Most of these dams were built in high seismic hazard areas, and their seismic resistance to the maximal earthquake exposure, having the magnitude equal to 8–9, raises doubts. The goal of this research is to employ numerical methods to verify the seismic resistance of dams, to project their behavior in case of the seismic exposure that may damage the dam face, cause the face joints to open and the dam face to detach from its toe, etc. Materials and methods. The author offers his analysis of reliability and applicability of numerical methods to the seismic resistance of dams. Incidents have demonstrated the need for a thorough assessment and analysis of each aspect of a new project whenever it is extrapolated from the precedent. Results. The analysis of the dam behavior in the course of the first reservoir filling has demonstrated face top cracking that causes its damage. Deeper in the water, face joints may be exposed to localized damages due to compression and shear; one should expect vertical face joints to open; excessive compressibility of the downstream rockfill zone may cause the water to leak through the dam face. The author offers recommendations for the performance of the dynamic analysis of dams in respect of the boundaries of the computational domain, given that seismic waves are transmitted or absorbed at the interface between the dam face and the transition zone, on the one hand, and between dam slabs, on the other hand. In furtherance of his recommendations, real and synthetic accelerograms are applied to the bottom boundary of the computational domain; the choice of an explicit or implicit computational method should be made; the author’s method pre-sets the intermediate solution which is to comply with the accelerogram digitization pattern. Conclusions. In addition to internationally established measures for improving the static and seismic safety of dams, the author proposes a new effective dam safety improvement method to be used in the course of designing high dams to be con-structed in high seismic hazard areas. This method improves dam safety by drastically reducing face deflections with the help of a support zone made of roller compacted concrete instead of the gravel transition zone, as exemplified by the 275 m high Kambaratinskaya-1 dam in Kyrgyzstan and the 192 m high Sogamoso dam in Colombia (both dams are located in highly seismic regions). The information on China's successful track record in designing and building similar dams, which are 220–250 m high, is also provided.

Structural analysis of Azerbaijan territory horizontal velocity movement based on GPS-measurements

The contemporary kinematics of Azerbaijan is generated by the northward movement of Arabian plate relative to Eurasian one. This continuous «intervention» of Arabian plate into Eurasian one is the reason of the deformation of the Earth’s crust of the Caucasian block causing earthquakes which are registered throughout the territory. For the research of geodynamic processes and intraplate deformations it is applied the methods of global positioning (GPS). GPS-network in Azerbaijan was founded in 1998. For the period between 1998 and 2016, in many GPS-points, the measurements were done 3―6 times. The present paper deals with the research of structure distribution of GPS horizontal velocity field of intraplate zones (domains) for Azerbaijan. The comparative analysis of interrelation of seismic events with distribution of horizontal velocity vectors and deformation obtained from Azerbaijan GPS-network monitoring was done aiming to reveal those zones. Deformation distribution throughout the research area was calculated with the formula and approach of Shen with the use of horizontal components of GPS-velocities. Aiming to conduct the comparative analysis of GPS-velocities with seismicity, a map of distribution of earthquake numbers for Azerbaijan during the period of 2003―2017 with magnitude M ≥ 3 was utilized. As a result, the following domain zones were defined, such as the fold system of the Greater Caucasus, the fold system of the Lesser Caucasus, the Middle Kur, Talysh, Gusar-Shabran depression and Gobustan-Absheron zone. It was determined that the areas of high seismicity were located in the zones of high gradients of GPS-velocities, while the areas of high seismicity coincide predominantly with the areas of high velocity compression. However, Gobustan-Absheron zone with high velocity deformation is not characterized by high seismicity. Probably, the reason of this is due to the elasticity of geological environment.

Adding a masonry floor on top of a reinforced concrete high building in a seismic area

The paper studies the influence of adding an aerated autoclaved concrete (AAC) masonry walls story above a reinforced concrete structure of a high building. This structure is situated in a high seismic area (0.30g, where g is the gravity acceleration) in Bucharest, Romania. The new story will be lightweight because of the AAC. It is necessary to establish if the existing structure can bare the new story gravity loads and to determine the new building’s seismic behaviour. It is also determined if the new AAC masonry walls can bare the seismic loads they are to be subjected to. Both elastic and plastic analysis are present in the study.

Effect of residual displacement and sequence of events on Design Force Ratio spectrum

In the areas of high seismicity, where several medium-to-strong events may occur before the design event, the cumulative damage due to earthquake events expected during the design life of the structure should be kept within safe limits. This may be achieved by raising the design force level corresponding to the largest seismic event anticipated during the design life of the structure by a factor known as Design Force Ratio (DFR). This study is an attempt to generalize the existing DFR spectrum by modifying how the damage during an event is computed and how the power spectral density function (PSDF) of the ground motion process for that event is estimated. As the existing models do not estimate incremental damage during an event of a sequence, the modified Park-Ang damage model is proposed to be modified further such that its estimates for the individual events add up to the cumulative damage index for the entire sequence as well as the effects of residual displacements are accounted for. The proposed model can estimate additional damage due to an event (in a multiple-event situation) without requiring the excitation time-history. The generalized procedure for DFR spectrum is based on using this model and the concept of spectrum-compatible PSDF. A numerical study on a hypothetical seismic environment shows that the DFR spectrum is very sensitive to the directions of the residual displacements and that all residual displacements should be assumed in the same direction for a conservative estimate of the DFR spectrum. It is also shown that in that case, the event with maximum damage potential should be assumed to occur as the last event in the sequence in order to maximize the cumulative damage.

Seismic response of partially saturated soils beneath shallow foundations under sequential ground motions

Induced partial saturation is an innovative soil improvement technique intended to mitigate earthquake-induced liquefaction. Historical records indicate that successive earthquakes may occur in high seismic areas. Therefore, a comprehensive understanding of the response of partially saturated soils to sequential ground motions is of great significance for the rational design and execution of this method in engineering practice. In this study, a series of dynamic centrifuge experiments were conducted to investigate the impacts of sequential ground motions on the behavior of partially saturated soils beneath shallow foundations. Two different shallow foundation models with a bearing pressure of 135 kPa and 50 kPa were examined. Three seismic simulations, in order of increasing amplitudes, were sequentially applied to loosely-packed partially saturated sand models prepared with air injection technique. The assessment of the test results indicated that shallow foundations resting on saturated models of loose sand did suffer excessive settlements with each event, producing a large embedment of the foundation. However, much smaller settlements were recorded for partially saturated ground, and the level of the foundation embedment remained limited in this case. The deformation vector fields also indicated that different displacement mechanisms were observed for each successive event.

Probabilistic seismic landslide hazard assessment: a case study in Tianshui, Northwest China

Probabilistic analysis in the field of seismic landslide hazard assessment is often based on an estimate of uncertainties of geological, geotechnical, geomorphological and seismological parameters. However, real situations are very complex and thus uncertainties of some parameters such as water content conditions and critical displacement are difficult to describe with accurate mathematical models. In this study, we present a probabilistic methodology based on the probabilistic seismic hazard analysis method and the Newmark’s displacement model. The Tianshui seismic zone (105°00′–106°00′ E, 34°20′–34°40′ N) in the northeastern Tibetan Plateau were used as an example. Arias intensity with three standard probabilities of exceedance (63%, 10%, and 2% in 50 years) in accordance with building design provisions were used to compute Newmark displacements by incorporating the effects of topographic amplification. Probable scenarios of water content condition were considered and three water content conditions (dry, wet and saturated) were adopted to simulate the effect of pore-water on slope. The influence of 5 cm and 10 cm critical displacements were investigated in order to analyze the sensitivity of critical displacement to the probabilities of earthquake-induced landslide occurrence. The results show that water content in particular, have a great influence on the distribution of high seismic landslide hazard areas. Generally, the dry coverage analysis represents a lower bound for susceptibility and hazard assessment, and the saturated coverage analysis represents an upper bound to some extent. Moreover, high seismic landslide hazard areas are also influenced by the critical displacements. The slope failure probabilities during future earthquakes with critical displacements of 5 cm can increase by a factor of 1.2 to 2.3 as compared to that of 10 cm. It suggests that more efforts are required in order to obtain reasonable threshold values for slope failure. Considering the probable scenarios of water content condition which is varied with seasons, seismic landslide hazard assessments are carried out for frequent, occasional and rare earthquake occurrences in the Tianshui region, which can provide a valuable reference for landslide hazard management and infrastructure design in mountainous seismic zones.

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.

Risk analysis of seismic bridge damage: case study after Lombok and Palu earthquake

Indonesia is known as an earthquake-prone region, lies in the ring of fire zone. This potential hazard can impact several infrastructures, including bridges. Seismic bridge damages could possibly disrupt traffic flow furthermore cut off the regional connectivity. In this study, risk analysis is carried out on several bridges after Lombok and Palu earthquake. Visual inspection has been undertaken on 38 bridges on-site, and several damages identification are reported. Risk analysis was then carried out according to the severity of element damages and the frequency of occurrence. From the analysis, it is concluded that embankment settlement in the approach road is found to be the most potential element with the highest risk of damage due to earthquakes. Besides, the superstructure displacement and crack in the wing wall are at moderate risk. This finding makes the substructure become the most vulnerable element which needs more attention. Therefore, it is recommended to specify a higher design specification for substructure to mitigate seismic bridge damages, especially for bridges located in the high seismic zone area.

The effect of seismic base isolation on structural response of a 12-story hotel building in Padang, Indonesia

The amount of potential investment in Padang City, Indonesia since 2017 attracted many investors to contribute to the city. One of the investments is a 12-story hotel that will be constructed in By Pass Street of the city. The hotel is located in a high seismic zone area, so the seismic base isolation has been proposed to be used in the hotel building. The main aim of using a seismic base isolation device is to reduce the inertia forces introduced in the structure due to earthquakes by shifting the fundamental period of the structure out of dangerous resonance range and concentration of the deformation demand at the isolation system. An analytical study on the Reinforced Concrete (RC) hotel building with and without rubber bearing (RB) base isolation is carried out using the response spectrum and time history analysis methods. The results show that internal forces and inter-story drift of the building with high damping rubber bearing (HDRB) are lower than that of the fixed base with a remarkable margin. From this study, it is recommended to use the HDRB base isolation for medium and high rise buildings with soft soil in Padang City, Indonesia.

Full-Scale Testing and Design of Special Truss Moment Frames for High-Seismic Areas

AbstractThe US design code provisions for steel special truss moment frames (STMFs) were formulated based on research work carried out in the 1990s with double-angle sections as truss members. To p...

Comparison of the RSNI 1726:2018 and the SNI 1726:2012 design response spectra of 17 major cities in Indonesia

Based on the 2017 Indonesian Seismic Map and the ASCE 7-16, the proposed Indonesian Seismic Design Code - RSNI 1726:2018, was developed to renew the current SNI 1726:2012 code. Taking a sampling of 17 major cities representing all regions in Indonesia, this paper presents the comparison of the RSNI 1726:2018 and the SNI 1726:2012 design response spectra. All cities located in high seismic areas have an anomaly characteristic, where the design response spectra of site class SE (soft soil) is less than that of site class SD (medium soil), or even less than that of site class SC (hard soil), contrary to what Structural and Geotechnical Engineers think so far, that the design response spectra of site class SE is always higher than that of site classes SD and SC.