Earthquake Response Of Structures Research Articles

Regional offshore ground motion prediction model from a referenced empirical approach: A case study in the Japan Trench area

With increasing resource exploitation and engineering construction offshore, the seismic safety of offshore structures has received attention from researchers and designers, and an offshore ground motion prediction model (GMPM) can be used to estimate the possible earthquake response of structures and provide the foundation for seismic fortification of structures. Because there are few strong motion records recorded by offshore stations, there are insufficient empirical data in the magnitude-distance range to directly develop a GMPM using empirical regression techniques. To develop a reliable GMPM for data-poor offshore regions, we used a referenced empirical approach based on an onshore empirical prediction model. We collected 2605 records from 138 crustal earthquake events, 2669 records from 125 slab earthquake events and 5693 records from 267 interface earthquake events recorded by S-net stations. We used the existing Japanese onshore GMPM as a reference model. Then, we analyzed the residuals of the reference model for offshore data and calculated its adjustment factors. Finally, we developed a GMPM for the Japan Trench area and compared it with the existing onshore models. The proposed model fit the data subsets at hypocentral distances of 20–300 km reasonably well. There were different spectral accelerations (SAs) for different source types, with considerably larger SAs for short periods of offshore motions from crustal events than for the motions from the other two types, and the difference becomes more obvious with the increase of magnitude. At short periods, the SAs of the offshore motions from slab events were slightly larger than those of the motions from the interface events. The discrepancy of the offshore and onshore GMPM was significant, and the peak ground accelerations (PGAs) and SAs of the offshore ground motions were apparently greater than those of onshore ground motions of the same magnitude and distance. The offshore GMPM established by the reference empirical approach contribute to studying the characteristics of offshore strong ground motions, and this approach can be applied to data-poor regions.

Post-earthquake assessment of monumental building in Croatia by 3Muri software

Abstract. A series of earthquakes in and close to city of Zagreb, Croatia during the 2020 severely damaged the masonry cultural heritage buildings built in the 19th century. The article presents the assessment of post-earthquake design of retrofitting of damaged historic masonry structure of the former synagogue in city of Sisak, Croatia erected in 1890. The former synagogue was severely damaged during the recent earthquake. For the purposes of the post-earthquake retrofitting and strengthening, an analysis of the damaged and retrofitted structure has been carried out to justify the selected retrofitting measures that included a partial reconstruction of heavily damaged structure. The equivalent frame model based on the discretization in terms of piers and spandrels was created (SEM - Structural Elements Model) to obtain the simulation of earthquake response of structure using the 3Muri 13.9 software. In this paper the procedure and results of the analysis of seismic resistance of the strengthened structure is presented because of the successful cooperation of structural engineers, architects and conservators.

Analysis of Adaptive Pushover in Confined Masonry Dwellings with Height Irregularity in the Lima Metropolitan Area

Non-engineered confined masonry dwellings are characterized by having different masonry units. One of the most common cases in the Lima Metropolitan Area is that this type of dwelling has its first floors with handmade solid units and upper floors are composed of industrial horizontal hollowed (tubular) bricks. Nonlinear static analysis by the incrementally increasing loading pattern is inadequate to estimating earthquake response of structures with height irregularity, such as non-engineered confined masonry dwellings, because the loading pattern changes during the history of reversal loads due to damaging earthquakes. This paper presents the effect of nonlinear static analysis using adaptive loading patterns in confined masonry dwellings when the type of masonry units changes drastically. Nonlinear static analyses are applied using non-adaptive and adaptive displacement-based pushover procedures. A series of nonlinear time history analyses are also conducted to measure the error in the estimation of the seismic response. The adaptive loading pattern is based on displacement approximation by the modal analysis at each step of incremental-increasing loads. The load pattern is updated considering the modal analysis of an equivalent linear model using the equivalent stiffness of the structure at the secant of the maximum previous response. The application of the adaptive loading pattern in nonlinear static analysis significantly approximates the earthquake response of confined masonry dwellings with height irregularity provided by the change of masonry bricks.

Shaking table substructure test of tuned liquid damper for controlling earthquake response of structure

For precisely disclosing the seismic performance of tuned liquid damper (TLD) vibration control structures, the shaking table substructure test (STST) method is presented and experimentally validated, and the parametric effects on the reduction efficiency of TLD are further investigated by using the STST method in this paper. Firstly, one optimal design method of TLD for high-rise structures is presented. Secondly, the STST based on three variable control method (TVCM) for the TLD vibration control structures is presented. Thirdly, the effectiveness and robustness of the STST for TLD vibration control structures are validated by a series of tests on one three-story-frame structure with a rectangular TLD. Finally, the parametric effects on the reduction efficiency of TLD, in terms of mass ratio and liquid depth, are investigated using the STST method. Experimental results show that the displacement and acceleration responses of the STST match well with that of the traditional shaking table tests under El Centro (NS, 1940) and Taft earthquake wave record excitations, which indicates the effectiveness and the robustness of the STST based on TVCM for TLD vibration control structures. It is also shown from the experimental results that the best mass ratio and liquid depth are 4% and 40 mm, respectively, which are consistent with the optimal designs of TLD. Moreover, the control performance of TLD is not only related to its parameters but also related to the spectral characteristics of ground motion excitations.

Effects of pulse like ground motion records with and without acceleration pulses on the earthquake responses of structures with varying dynamic properties

This study is focused on the effects of acceleration pulses on the damaging potentials of velocity pulse-like ground motion (GM) records. In the study, previously identified pulse-like GM records with and without acceleration pulses are used together with far fault (FF) GM records. The selected GM records are used in the nonlinear time history analyses of structural systems with different dynamic properties. The structural systems used in the analyses were designed to represent commonly used short and medium height structures. The damaging potentials of GM records are compared in terms of commonly used engineering demand parameters (EDPs); (i) doof drift ratio, (ii) residual displacement, (iii) interstory drift distribution, and (iv) shear force distribution throughout the height of the building. The results of the analyses revealed that the velocity pulse-like GM records with acceleration pulses significantly increase the earthquake demands on short to medium height structures. On contrary to that the velocity pulse-like GM records without significant acceleration pulses don't have any additional damage potential for short to medium height structures. Furthermore, in terms of considered EDPs, the structural demands due to FF GM records are even higher than those caused by velocity pulse-like GM records without acceleration pulses. These results showed that the studies focusing on the damaging effects of pulse-like GM records on short to medium height structures should eliminate the velocity pulse-like GM records without acceleration pulses from their GM pools. Such an elimination may reduce the scatter observed in the results of such studies.

Towards standardized nuclear reactors: Seismic isolation and the cost impact of the earthquake load case

Nuclear energy has a key role to play in global decarbonization. Impediments to the widespread deployment of reactors are their projected high capital cost and levelized cost of energy, and time required to analyze, design, license, construct, and commission them. The earthquake load case is a key cost driver for a new build nuclear plant, because near-surface soils and seismic hazard are different at each site, requiring site-specific analysis, design, engineering, qualification, licensing, and regulatory review, essentially making every design First-of-a-Kind (FoaK). To enable deployment at the scale needed for deep decarbonization, the cost and time impact of the seismic load case must be significantly mitigated, and plants must be standardized. Seismic base isolation has been proven to considerably reduce the earthquake response of structures and equipment but has yet to be applied to a nuclear power plant in the United States, in part because the financial impacts, positive or negative, are not known. Because there are no recent non-proprietary data to characterize the influence of the seismic load case on capital cost, it is difficult to confidently quantify the financial benefits of seismic isolation.Scheme-level designs of two fundamentally different advanced reactor buildings were developed to assemble cost data on the influence of the seismic load case. Both buildings were equipped with three bespoke pieces of safety-related equipment and analyzed for incremented levels of earthquake shaking to quantify the seismic penalty on equipment, in terms of vessel weights and horizontal accelerations. Using analysis results, a questionnaire was developed and transmitted to nuclear utilities, reactor developers, engineers, and equipment suppliers to collect cost data on engineering and fabrication costs for these unique pieces of safety-class equipment. Synthesis of the cost data showed that the seismic load case significantly affects the capital cost (sum of engineering and fabrication cost) of safety-class equipment, with engineering costs being comparable to fabrication costs. Standardization of safety-class equipment is made possible by seismic isolation, that is, equipment designed for minimal seismic robustness can resist earthquake shaking at a site of much higher seismic hazard. The average reduction in the capital cost of the safety-related equipment, enabled by seismic isolation, is a factor of two for FoaK equipment and a factor of five for standardized equipment.

Structural system identification based on combining weighted transmissibility and wavelet transform

In this paper, an integrated method called WTs-OMA (weighted transmissibility and wavelet transform-based operational modal analysis) is proposed to identify the structural dynamic characteristics using the earthquake response of structures. The proposed method, which is a time–frequency domain method with both parametric and non-parametric characteristics, utilizes the effective and efficient capabilities of weighted transmissibility and wavelet transform to achieve a proper performance in modal parameter estimation. This method employs weighted transmissibility functions to identify natural frequencies and mode shapes and calculates the damping values using the skeletons or the single frequency signals obtained from wavelet transform of the correlation functions of seismic responses. In this research, a numerical model under El Centro earthquake excitation is used for performance validation of the proposed method; Furthermore, the Karun 3 arch dam is selected as a case study in which the dynamic characteristics of the structure are identified based on the seismic responses from the different earthquakes.

Shear Walls Induced RC Structures

In recent years, the construction of skyscrapers has been on the rise to overcome the shortage of land. These buildings are subject to an external lateral force, such as an earthquake and wind pressure. Pushover analysis (POA) has been broadly used in predicting the earthquake response of structures, and shear walls have been shown to be lateral drag elements. Therefore, in the present work, the effect of placing a shear wall on the periphery symmetrically, the periphery asymmetrically and in the center of the building is performed using the ETABS software. Using the response spectrum methodand thetime history method, a dynamic analysis is performed. Responses such as floor shear, floor displacement, and lateral floor shifts due to seismic forces are evaluated for various locations of the shear wall. According to the results and analysis, the shear wall on the symmetrical periphery of the structure is reducing the displacement and deviation of the floor compared to other cases.

A novel steel lever viscoelastic wall with amplified damper force-friction for wind and seismic resistance

This paper presents a new steel wind- and seismic-resisting wall, called a lever viscoelastic wall (LVEW) that includes a velocity-dependent VE damper and a displacement-dependent friction damper in a device, characterized by two different motion phases. In Phase one motion (i.e., small drifts), the VE damper which is activated by a lever delivers amplified lateral force and energy dissipation to the frame structure. In Phase two motion (i.e., medium-to-large drifts), the VE damper is constrained by a stopper and the friction damper, instead, is activated to provide frictional energy dissipation to the frame. The damping is provided by incorporating VE material and sliding friction in a wall configuration, reducing both the wind and earthquake responses of structures in a single unit. The objectives of the work were to (1) develop the force transfer mechanism and kinematics of the LVEW, (2) verify the cyclic response of LVEWs at low and large drifts, and (3) evaluate the limitation of LVEWs for the applications. Three full-scale LVEW specimens were designed and tested to validate the hysteretic response in two motion phases. The hysteretic response of LVEWs obtained from the test was compared to that from the analytical formulation.

Design Earthquake Response Spectrum Affected by Shallow Soil Deposit

Site response analyses were performed to investigate the earthquake response of structures with shallow soil depth conditions in Korea. The analysis parameters included the properties of soft soil deposits at 487 sites, input earthquake accelerations, and peak ground-acceleration levels. The response spectra resulting from numerical analyses were compared with the design response spectra (DRS) specified in the 2015 International Building Code. The results showed that the earthquake motion of shallow soft soil was significantly different from that of deep soft soil, which was the basis of the IBC DRS. The responses of the structures were amplified when their dynamic periods were close to those of the site. In the case of sites with dynamic periods less than 0.4 s, the spectral accelerations of short-period structures were greater than those of the DRS corresponding to the site class specified in IBC 2015. On the basis of these results, a new form of DRS and soil factors are proposed.

PSEUDO-DYNAMIC TEST OF CFST BRIDGE PIER UNDER DIFFERENT GROUND EXCITATIONS

The dynamic testing of large-scale structures continues to play a significant role in earthquake engineering research. The pseudo-dynamic test (PDT) is an experimental technique for simulating the earthquake response of structures and structural components in time domain. A Concrete Filled Steel Tube (CFST) built-up pier is a modified form of CFST laced column in which CFST members are connected with RC web in longitudinal direction and with steel tube in transverse direction. For this study, a CFST built-up pier is tested under seven different earthquake time histories having scaled PGA of 0.05g. From the experiment acceleration, velocity, displacement and load time histories are observed. The pier experienced maximum acceleration due to Imperial Valley earthquake and minimum due to Wenchuan earthquake. For the Imperial Valley earthquake the acceleration is magnified by 17 times while for the Wenchuan earthquake the acceleration is magnified by 10 times. The frequency of the pier is found to be 1.41 Hz. The result shows that this type of pier has excellent static and earthquake resistant properties.

Behavior of CFST-RC Pier under Different Ground Motions

The dynamic testing of large-scale structures continues to play a significant role in earthquake engineering research. The pseudo- dynamic test (PDT) is an experimental technique for simulating the earthquake response of structures and structural components in time domain. A CFST-RC pier is a modified form of CFST laced column in which CFST members are connected with RC web in longitudinal direction and with steel tube in transverse direction. For this study, a CFST -RC pier is tested under three different earthquake time histories having scaled PGA of 0.05g. From the experiment acceleration, velocity, displacement and load time histories are observed. The dynamic magnification factors for acceleration due to Chamoli, Gorkha and Wenchuan ground motions are observed as 12, 10 and 10 respectively. The frequency of the pier is found to be 1.42 Hz. The result shows that this type of pier has excellent static and earthquake resistant properties.

Earthquake response of low-rise RC moment frame structures according to energy dissipation ratio of beam-column joints

Seismic response of RC moment frame structures (particularly, in low-rise buildings) is affected by the inelastic hysteretic response and energy dissipation of beam-column joints. In current earthquake design codes, however, the earthquake response of the structures is evaluated without direct consideration of the energy dissipation of beam-column joints. In the present study, non-linear time history analysis using the energy-based hysteresis model was carried out to investigate the effect of the energy dissipation performances of the beam-column joints on the seismic response of the structures. To demonstrate the applicability of the proposed analysis method, it was applied to existing dynamic test results of RC moment frame structures. On the basis of the proposed method, non-linear time history analysis for six different typed low-rise RC moment frame structures under 14 earthquake records was performed. Design parameters were the energy dissipation ratios of beam-column joints (from pinching behavior to elasto-perfectly plastic behavior), moment frame stories (3, 5, and 9 stories), and moment frame configuration (two and four spans). The analysis results showed that the low energy dissipation of beam-column joints increased the ductility requirement of the low-rise RC moment frame structures.

Local seismic site amplification: effects of obliquely incident antiplane motions

Seismic site amplification studies are generally used to assess the effects of local geology and soil conditions on ground motion characteristics. Although extensive reviews on site amplification phenomena associated with stratigraphic effects can be found in the specialized literature, it should be pointed out that most of the practical applications have been limited to the study of vertically propagating shear horizontal (SH) waves, i.e., to the 1-D soil amplification problem. Furthermore, little attention, if any, has been devoted to the study of the effects of non-vertically incident SH waves on surface accelerograms and on the earthquake response of structures. In the present work, the study is extended to an investigation of 2-D site amplification of non-vertically propagating seismic shear waves in multilayered viscoelastic soil deposits. Sensitivity analyses of the effects of non-vertical incidence on site amplification functions are performed based on site geotechnical data collected from post-seismic investigations of the 1980 El-Asnam earthquake. Analytical results are discussed in terms of seismic site transfer functions, spectral ratios, surface acceleration time histories, and structural response spectra for different values of wave incidence angle. Both bedrock and rock outcropping cases are examined.

Centrifuge Test for Earthquake Response of Structures with Basements

To investigate earthquake responses of structures with basements affected by soil deposits, centrifuge tests were performed using an in-flight earthquake simulator. The test specimen was composed of a single-degree-of-freedom structure model, a basement and sub-soil deposits in a centrifuge container. The test parameters were the dynamic period of the structure model, boundary conditions of the basement, existence of soil deposits, centrifugal acceleration level, and type and level of input earthquake accelerations. When soil deposits did not exist, the earthquake responses of the structures with fixed basement were significantly greater than those of the structure without basement. Also, the earthquake responses of the structures with the fixed basement surrounded by soil deposits were amplified, but the amplifications were smaller than those of the structures without basement. The earthquake responses of the structures with the half-embedded basement in the soil deposits were greater than those estimated by the fixed base model using the measured free-field ground motion. The test showed that the basement and the soil deposit should be simultaneously considered in the numerical analysis model, and the stiffness of the half-embedded was not effective.

Rocking Effect of a Mat Foundation on the Earthquake Response of Structures

AbstractTo evaluate the effect of soil-foundation interaction on the earthquake response of structures, centrifuge tests were performed using an in-flight earthquake simulator. The test specimen was composed of a single-degree-of-freedom structure model, a shallow foundation, and subsoil deposits in a centrifuge container. The test parameters were the dynamic period of the structure model, the centrifugal acceleration level, and the type and level of input earthquake accelerations. The test results showed that the lateral forces of the structures were limited by the soil-bearing strength (i.e., ultimate moment capacity of the foundation) and the damping effect owing to the rocking motion of the foundation. Thus, even when the periods of the structures were close to the site periods, the lateral forces did not significantly increase. However, it should be noted that, because of the damping effect of the foundation, the maximum seismic lateral load of the structures exceeded the load statically determined b...

Shaking Table Test of Eccentric Reinforced Concrete Frame-Shear Wall Structure Model

Reinforced concrete eccentric frame-shear wall structure has been widely used in engineering. However, this structure is mainly used for high-rise structure, and it is difficult to obtain accurate earthquake response of structure through experimental study. Therefore, simulation software needs to be used for study on seismic performance of high-rise structures. This paper produces useful conclusions for the project through shaking table test and the simulation of seismic performance provided by ANSYS finite element analysis software.

Earthquake-Response Analysis of Long-Span Cable-Stayed Bridge under Uniform and Non-Uniform Excitations

Earthquake is a kind of natural disaster which is difficult to predict and the damage degree is very great, occurrence of the strong motion often leads to the tremendous life and property loss. Bridge is very important lifeline engineering and it is very necessary to conduct the comprehensive and systemic investigation on the bridge aseismic. In this paper, the FEM model of a long-span cable-bridge was established; the dynamic characteristic and nonlinear seismic responses under uniform and non-uniform excitations of it were systematic studied. The results show that: 1) the basic cycle of it is about 8.881s. Its first mode of vibration is longitudinal floating mode, which is favorable to the earthquake-response of structures. 2) Its former 40 rank frequency are located between 0.1~2Hz which is avail to the condition of traffic condition.3) the geometric nonlinearity has much influence on the response of this kind of bridge.4) the seismic responses are sensitive to the frequency spectra of the input earthquake wave. 5) The traveling wave excitations are unfavorable to the design of tower and the main girder when considering the three orthogonal seismic wave input. In order to get correct results, artificial seismic wave of the bridge address is necessary to the time-history analysis.

Response the Cylindrical Elevated Wheat Storage Silos to Seismic Loading

The elevated cylindrical storage silos are lifeline structures and strategically very important, since they have vital use in industries. Silos are special structures subjected to many different unconventional loading conditions, which result in unusual failure modes. In addition silos are cantilever structures with the material stacked up very high vertically. The earthquake response of silo structures for the storage of bulk solids differs for elevated silos and silos supported directly on the ground. The walls of different type of silos are subject to earthquake loads from the stored mass, and these may substantially exceed the pressures from filling and discharge. The assessment of horizontal action of ensiled material due to seismic vent seems to be particular interest. This paper is concerned with the earthquake response of these structures, which has received little attention to date. A cylindrical silo wall and bulk solid is modeled by three dimensional finite solid l elements. The interaction effect between the silo wall and bulk solid is taking account by using the nonlinear approach proposed by Duncan and Chang. A then interface layer proposed by Desia is applied to describe the phenomena taking place on the surface between the granular material and silo wall. Coulomb's friction low was used for modeling of wall friction. An incremental iterative finite element technique is applied for dynamic analysis of wheat silos using SAP2000 structural software package. In this research seven reinforced concrete silo models with different height to diameter ratios were studied and analyzed in time history by using earthquake acceleration 0.5g applied to silos models. The resulting finite element silo pressures as the silo is full with and without earthquake excitation are compared with theoretical filling and discharging pressure. The result obtained revealed that the elevated silos response is highly influenced by the earthquake characteristics and is depending on the height to diameter ratio. Also the findings indicate that the squat silo (large diameter and height) are more resistance to the earthquake and more economical. The seismic responses of the elevated wheat silo such as top displacement, normal forces, shearing forces and bending moments in silo support have been assessed for earthquake records.

RESPONSE OF CYLINDRICAL ELEVATED WHEAT STORAGE SILOS TO SEISMIC LOADING

The elevated cylindrical storage silos are lifeline structures and strategically very important, since they have vital use in industries. Silos are special structures subjected to many different unconventional loading conditions, which result in unusual failure modes. In addition silos are cantilever structures with the material stacked up very high vertically. The earthquake response of silo structures for the storage of bulk solids differs for elevated silos and silos supported directly on the ground. The walls of different type of silos are subject to earthquake loads from the stored mass, and these may substantially exceed the pressures from filling and discharge. The assessment of horizontal action of ensiled material due to seismic vent seems to be particular interest. This paper is concerned with the earthquake response of these structures, which has received little attention to date. A cylindrical silo wall and bulk solid is modeled by three dimensional finite solid elements. The interaction effect between the silo wall and bulk solid is taking account by using the nonlinear approach proposed by Duncan and Chang [5]. A then interface layer proposed by Desia [4] is applied to describe the phenomena taking place on the surface between the granular material and silo wall. Coulomb's friction low was used for modeling of wall friction. An incremental iterative finite element technique is applied for dynamic analysis of wheat silos using SAP2000 structural software package [3]. In this research seven reinforced concrete silo models with different height to diameter ratios were studied and analyzed in time history by using earthquake acceleration 0.5g applied to silos models. The resulting finite element silo pressures as the silo is full with and without earthquake excitation are compared with theoretical filling and discharging pressure. The result obtained revealed that the elevated silos response is highly influenced by the earthquake characteristics and is depending on the height to diameter ratio. Also the findings indicate that the squat silos (large diameter to height ratio ) are more resistance to the earthquake and more economical. The seismic responses of the elevated wheat silo such as top displacement, normal forces, shearing forces and bending moments in silo support have been assessed for earthquake records.