Shake Level Research Articles

Performance evaluation of suspended ceiling systems using shake table test

The national standard being used in Turkey for suspended ceiling systems (SCS) regulates material and dimensional properties but does not contain regulations regarding installation instructions which cause substandard applications of SCSs in practice. The lack of installation instructions would potentially affect the dynamic performance of these systems. Also, the vast majority of these systems are manufactured using substandard low-quality materials, and this will inevitably increase SCS related damages during earthquakes. The experimental work presented here focuses on the issue of dynamic performance of SCSs with different types of carrier systems (lay-on and clip-in systems), different weight conditions, and material-workmanship qualities. Moreover, the effects of auxiliary fastening elements, so called seismic perimeter clips, in improving the dynamic performance of SCSs were experimentally investigated. Results show that clip-in ceiling system performs better than lay-on system regardless of material and workmanship qualities. On the other hand, the quality aspect becomes the most important parameter in affecting the dynamic performance of lay-on type systems as opposed to tile weights and usage of perimeter clips. When high quality system is used, tile weight does not change the performance of lay-on system, however in poor quality system, tile weight becomes an important factor where heavier tiles considerably decrease the performance level. Perimeter clips marginally increase the dynamic performance of lay-on ceiling system, but it has no effect on the clip-in ceiling system under the shaking levels considered.

Alternative Hybrid Empirical Ground‐Motion Model for Central and Eastern North America Using Hybrid Simulations and NGA‐West2 Models

Abstract An alternative hybrid empirical ground‐motion model for central and eastern North America (CENA) is proposed. The new ground‐motion model (GMM) is developed for the average horizontal components (RotD50) of peak ground acceleration, peak ground velocity, and 5%‐damped pseudospectral accelerations at 0.01–10 s spectral periods. Hybrid empirical estimates are derived using the regional modification factors between two regions (host and target), along with empirical GMMs from the host region. The regional adjustment factors are ratios of the intensity measures from the generated synthetics in the host (western North America [WNA]) and target (CENA) regions. In this study, the recent updated empirical GMMs developed by the Pacific Earthquake Engineering Research Center for the Next Generation Attenuation West2 (NGA‐West2) project (Bozorgnia et al. , 2014) are incorporated. We used a broadband simulation technique proposed by the authors (Shahjouei and Pezeshk, 2015a) to generate synthetics for both the WNA and CENA regions in which the high‐frequency and low‐frequency parts of synthetics are calculated through a stochastic finite‐fault method and kinematic source models along with the deterministic wave propagation, respectively. The updated seismological and geological parameters are deployed in simulations. The new ground‐motion model is developed, as part of the NGA‐East research project, considering multiple shaking scenarios that characterize the magnitude in the M 5.0–8.0 range. The proposed GMM represents the level of ground shaking in the distance range of 2–1000 km and are developed for the reference rock site condition with V S 30 =3 km/s in CENA. The results are compared with some other existing models in the region. In addition, a comprehensive residual analysis is performed using the recorded earthquakes available in the NGA‐East database.

Seismic evaluation of rocking structures through performance assessment and fragility analysis

Numerical studies have been conducted for low- and medium-rise rocking structures to investigate their efficiency as earthquake-resisting systems in comparison with conventional structures. Several non-linear time-history analyses have been performed to evaluate seismic performance of selected cases at desired ground shaking levels, based on key parameters such as total and flexural story drifts and residual deformations. The Far-field record set is selected as input ground motions and median peak values of key parameters are taken as best estimates of system response. In addition, in order to evaluate the probability of exceeding relevant damage states, analytical fragility curves have been developed based on the results of the incremental dynamic analysis procedure. Small exceedance probabilities and acceptable margins against collapse, together with minor associated damages in main structural members, can be considered as superior seismic performance for medium-rise rocking systems. Low-rise rocking systems could provide significant performance improvement over their conventional counterparts notwithstanding certain weaknesses in their seismic response.

常時微動による地盤分類とそれに基づく強震時の地盤特性に関する予備的分析

The 2011 off the Pacific coast of Tohoku Earthquake of Mw9.0 produced many strong motion records, owing to dense strong motion observation networks in Japan. About three thousands records are collected and complied. The records provide a unique opportunity to examine site amplifications in strong shaking level. The available site characteristics data for the records, however, are limited. The soil profile data are available at about 100 sites. For the other data, the available site information is geomorphologic classification from the nation-wide digital map, but it is rather crude for the site characterization. To strengthen the site characteristics data, microtremor measurements are conducted at about 500 strong motion sites in the high seismic intensity zone, as shown in Fig. 1. In the measurement, we use the system whose overall response is almost constant with ground velocity up to 2 seconds, as shown in Fig. 2. The H/V spectral ratios of microtremors for different NEHRP site classes (Table 1) are shown in Fig. 3. The following criteria are determined for site classification from the H/V spectral ratio: 1) the site having the H/V spectral ratio with higher amplitudes at periods 0.6 to 1.2 sec. with respect to those at periods 0.1 to 0.3 sec. is the class E (Fig. 4), 2) the site having the H/V spectral ratio constant with periods is the class B (Fig. 5), and 3) the sites having the H/V spectral ratios with larger and smaller amplitudes at periods of 0.3 to 0.8 sec. with respect to those at periods 0.1 to 0.2 sec. are the classes D and C, respectively, and the site having the intermediate amplitude is the class C or D referring the geomorphologic information (Fig. 6). For the sites where the site class is determined from the velocity profile data, the accuracy of the estimated site class is checked. The overall accuracy is 77 % by the proposed method as shown in Table 2, whereas the accuracy of estimations from the geomorphologic information is 51 % as shown in Table 3. By using the criteria for site classification, the target strong motion sites are classified into 30 class B sites, 153 class C sites, 206 class D sites and 77 class E sites, as shown in Fig. 7. Site effects on the strong motion records are preliminarily discussed from the average spectra for site classes B, C, D and E. The average spectrum with standard deviation for each class is shown in Fig. 8. The velocity response spectra tend to be constant with period at class B. The spectral amplitudes become larger at site classes with slower VS30. At site class E, the amplitudes tend to be larger at around 1 second. As shown in Table 3, the average and standard deviation of the peak horizontal accelerations at class B are 0.45 g and 0.19 g, respectively. The small deviation suggests that the shaking level inputted to the bedrock at the sites may not have large difference. Therefore, the ratio of the average spectrum at class C, D or E with respect to that at class B is considered to be an approximate of site amplification. As shown in Fig. 9, the amplification of site classes C to B is almost one, but those of site classes D and E to B are larger at longer periods and smaller at shorter periods. The amplification is compared with the site amplification derived from weak motion records. The difference in both amplifications indicates effects of nonlinear soil response.

Seismic response of triple friction pendulum bearing under multi hazard level excitations

Triple friction pendulum (TFP) bearing is a new generation sliding isolation system having multiple spherical sliding surfaces. The friction isolation system with single sliding surface is designed for a specific level of ground shaking, which may prove ineffective in case of other hazard levels. The TFP bearing on the other hand, exhibits adaptive behaviour and imparts greater amount of flexibility to the designer for various levels of earthquake shaking. Herein seismic response of TFP bearing is studied under 60 records comprising of service level, design basis and maximum considered earthquakes. Two types of surfaces having low and high friction in combination with three different displacement capacities of the bearing, resulting in six isolator design are considered. It is shown that although being a passive device, the TFP bearing stiffens at low input shaking, softens with increasing input reaching a minimum at the DBE, and then stiffens again at higher levels of input and thereby shows adaptive behaviour. Further, the increase of displacement capacity of bearing influences the response under MCE event, however, for DBE and SLE no significant change in demand is observed.

Seismic response of a ten story concrete building subjected to different earthquakes

The purpose of this paper is to compare the response of a ten story concrete building in San Jose, California, under three different earthquakes. The strong-motion records of the instrumented building obtained during the 1984 Morgan Hill earthquake were used to calibrate a finite element model. Soil-structure interaction was included in the model by adding some translational springs to the foundation. The same model was subjected to 1986 Mount Lewis and 1989 Loma Prieta earthquakes. While for the first case a good match between the recorded data and analytical results was obtained, for the second one the match was not as good as expected. A modal identification analysis of the building was conducted for the three ground motions using both just output operational modal analysis (OMA) and input-output experimental modal analysis (EMA). It was demonstrated that for Loma Prieta, which presents higher amplitude shaking than the other two ground motions, the fundamental period for the transversal mode of the structure was higher than that obtained using the other two earthquakes. Consequently, the springs of the finite element model needed to be updated for Loma Prieta in order to capture the more flexible response of the building. After this adjustment, there was a good match between the recorded motions and analytical results. This study proves that the effects of soil-structure interaction becomes very important when a building is subjected to high levels of shaking. In some cases, a single model of a building with concrete shear walls may not be suitable to predict properly the behavior of the building under different ground motions.

Developing an Application‐Specific Ground‐Motion Model for Induced Seismicity

Abstract A key element of quantifying both the hazard and risk due to induced earthquakes is a suite of appropriate ground‐motion prediction equations (GMPEs) that encompass the possible shaking levels due to such events. Induced earthquakes are likely to be of smaller magnitude and shallower focal depth than the tectonic earthquakes for which most GMPEs are derived. Furthermore, whereas GMPEs for moderate‐to‐large magnitude earthquakes are usually derived to be transportable to different locations and applications, taking advantage of the limited regional dependence observed for such events, the characteristics of induced earthquakes warrant the development of application‐specific models. A preliminary ground‐motion model for induced seismicity in the Groningen gas field in The Netherlands is presented as an illustration of a possible approach to the development of these equations. The GMPE is calibrated to local recordings of small‐magnitude events and captures the epistemic uncertainty in the extrapolation to larger magnitude considered in the assessment of the resulting hazard and risk.

Experimental investigation into amplitude-dependent modal properties of an eleven-span motorway bridge

This paper examines experimentally the effect of forcing and response amplitude on the variability of modal parameters of a bridge. An eleven-span prestressed concrete motorway off-ramp bridge was subjected to multiple dynamic tests with varying excitation levels by using eccentric mass shakers exerting forces in the vertical and lateral direction. The frequency sweeping technique with small increment steps in the vicinity of resonant frequencies was employed to construct frequency response functions at different shaking levels from which the natural frequencies, damping ratios and mode shapes were identified for several vertical, mixed vertical–torsional and lateral modes. Softening dynamic force–displacement relationships were observed for all the modes, and the natural frequencies showed clear and consistent decreasing trends with increasing response amplitude. Modal damping ratios initially increased with increasing response amplitude, but later, for the modes where experimental data were available, stabilised at elevated levels. A finite element (FE) model of the bridge was also created and the experimental modal properties compared to the numerical ones. A good agreement was generally noticed for the lower modes but the higher modes had more error. The FE model was used to assess the likely levels of structural damage that would have a similar effect on the natural frequencies as the amplitude dependence. One numerical damage scenario indicated that a reduction of 20% of stiffness in the middle of the main span would cause larger frequency shifts of some modes but amplitude dependent effects will dominate in other modes. Another numerical damage scenario was a reduction by 50% of stiffness at the bottom of the highest pier, and it was shown this type of damage would result in only one third of the frequency drop caused by the amplitude effects in a single, most affected mode.

Reactivated faulting near Cushing, Oklahoma: Increased potential for a triggered earthquake in an area of United States strategic infrastructure

In October 2014 two moderate-sized earthquakes (Mw 4.0 and 4.3) struck south of Cushing, Oklahoma, below the largest crude oil storage facility in the world. Combined analysis of the spatial distribution of earthquakes and regional moment tensor focal mechanisms indicate reactivation of a subsurface unnamed and unmapped left-lateral strike-slip fault. Coulomb failure stress change calculations using the relocated seismicity and slip distribution determined from regional moment tensors, allow for the possibility that the Wilzetta-Whitetail fault zone south of Cushing, Oklahoma, could produce a large, damaging earthquake comparable to the 2011 Prague event. Resultant very strong shaking levels (MMI VII) in the epicentral region present the possibility of this potential earthquake causing moderate to heavy damage to national strategic infrastructure and local communities.

Simple Method to Develop Seismic Microzonation Maps for Cities in Northern Haiti and Elsewhere

Many developing nations are situated in zones of high seismicity where earthquakes can lead to widespread property loss and loss of life. Similar-sized earthquakes are not nearly as devastating in developed nations because of access to state-of-practice engineering methods. Earthquake engineering to reduce property loss and loss of life includes geotechnical engineering to predict likely amounts of ground shaking. Herein, a simple geotechnical approach was implemented in four cities in northern Haiti, including Port-de-Paix, Cap-Haitien, Fort Liberte, and Ouanaminthe based. The approach was based on the use of a simple geophysical technique and the application of International Building Code criteria to calculate design levels of ground shaking. The Spectral-Analysis-of-Surface-Waves (SASW) method is a geophysical technique that was employed in the four test cities during a five-day test period utilizing three workers and a backpack full of equipment. As a result of this investigation, microzonation maps depicting design ground surface shaking parameters were rapidly and inexpensively developed, which can be used by structural engineers for guidance in designing earthquake-resistant structures. This method can be easily deployed in other developing nations to provide these populations with nearly the same level of knowledge and protection against earthquakes that is realized in developed nations.

Updating of an instrumented building model considering amplitude dependence of dynamic resonant properties extracted from seismic response records

Summary This paper presents system identification and numerical analyses of a three-story RC building. System identification was performed using 50 earthquake response records to obtain the frequencies and damping ratios, taking into account soil–structure interaction. Trends in the resonant parameters were correlated with the peak response accelerations at the roof level. A general trend of decreasing resonant frequencies with increasing level of response was observed and quantified, whereas for the damping ratios, no clear trends were discernible. A series of finite element models (FEMs) of the building were updated using a sensitivity-based method with a Bayesian parameter estimation technique to follow the changes in the resonant frequencies with response amplitude. The FEMs were calibrated by tuning the stiffness of structural and non-structural components and soil. The updated FEMs were used in time history analyses to predict and assess the building seismic performance at the serviceability limit state. It was concluded that the resonant frequencies depend strongly on the response magnitude, even for low-to-moderate levels of shaking. The structural and non-structural components and soil make contributions to the overall building stiffness that depends on the level of shaking. The FEM calibrated to the largest responses was the least conservative in predicting the serviceability limit state inter-story drifts, but the building performed satisfactorily. Copyright © 2015 John Wiley & Sons, Ltd.

Probabilistic seismic landslide hazard maps including epistemic uncertainty

Seismic landslide hazard maps are used in regional planning to identify zones that require detailed, site-specific studies. Most seismic landslide hazard maps are based on predicted sliding block displacements for a given level of shaking, but this deterministic approach does not fully consider the aleatory variability in the sliding displacement prediction or the epistemic uncertainty in the soil and slope properties. Probabilistic approaches incorporate aleatory variability through a sliding displacement hazard curve and they incorporate epistemic uncertainties (e.g., soil shear strength, empirical displacement model) through a logic-tree approach. This fully probabilistic approach can be implemented efficiently on a regional scale for seismic landslide hazard maps using ground motion hazard data and the Mean λD Threshold approach. This paper applies the probabilistic approach to develop a seismic landslide hazard map for Anchorage, Alaska. The results show that incorporating epistemic uncertainty can increase the area of high seismic landslide hazard by a factor of 2 to 3 as compared to analyses without any epistemic uncertainty. Additionally, incorporating a logic-tree avoids using overly conservative input parameters in a deterministic approach to capture these uncertainties, which can lead to an unrealistic inflation of the seismic landslide hazard.

Microzonation of Banja Luka for performance-based earthquake-resistant design

New microzonation maps for the city of Banja Luka in the Republic of Srpska in Bosnia and Herzegovina are presented based on the uniform-hazard-spectrum (UHS) methodology. The results are compared with the previous generation of microzonation maps published in the early 1970s, which were determined for the largest expected levels of shaking and for the spatial variations based on the soil site properties and the observed damage during the 1969 earthquake. The old and new methods are compared with emphasis on their role in the long-term criteria for regional earthquake-resistant design guidelines and the associated consequences.

Probabilistic analysis of the seismic activity and hazard in northern Thailand

The seismic activity and hazard level in northern Thailand, including at the Mae Moh Coal Mine (MMCM), were clarified. For the probability of exceedance (POE), Chiang Mai, Lamphun, and Lampang provinces have a 70–90% and 20–40% POE of a MW-5.0 and MW-6.0 earthquake, respectively, in the next 50 y. In the case of a MW-7.0 earthquake, the POE is less than 10% in the whole study area. Regarding the probabilistic seismic hazard analysis, the ground shaking maps indicated that the southeastern part of the MMCM and northwestern part of Phayao provinces were high hazard areas, with an earthquake ground shaking of around 0.28–0.32g and 0.18–0.24g for a POE of 2% and 10%, respectively, in the next 50 y. In addition, the probability maps revealed that these high hazard areas showed a 60–80% and 30–40% POE of a modified Mercalli intensity (MMI) level III and IV, respectively, in the next 50 y. The low hazard areas of Chiang Mai and Uttaradit provinces had a ground shaking level for a 2% and 10% POE in the next 50 y of around 0.16 and 0.08, respectively, with a POE of a MMI level III or IV of less than 20% each.

Seismic response of reduced-scale modular block and rigid faced reinforced walls through shaking table tests

This paper focuses on understanding the seismic response of geosynthetic reinforced retaining walls through shaking table tests on models of modular block and rigid faced reinforced retaining walls. Reduced-scale models of retaining walls reinforced with geogrid layers were constructed in a laminar box mounted on a uniaxial shaking table and subjected to various levels of sinusoidal base shaking. Models were instrumented with ultrasonic displacement sensors, earth pressure sensors and accelerometers. Effects of backfill density, number of reinforcement layers and reinforcement type on the performance of rigid faced and modular block walls were studied through different series of model tests. Performances of the walls were assessed in terms of face deformations, crest settlement and acceleration amplification at different elevations and compared. Modular block walls performed better than the rigid faced walls for the same level of base shaking because of the additional support derived by stacking the blocks with an offset. Type and quantity of reinforcement has significant effect on the seismic performance of both the types of walls. Displacements are more sensitive to relative density of the backfill and decrease with increasing relative density, the effect being more pronounced in case of unreinforced walls compared to the reinforced ones. Acceleration amplifications are not affected by the wall facing and inclusion of reinforcement.

The contribution of EMCA to landslide susceptibility mapping in Central Asia

<p>Central Asia is one of the most exposed regions in the world to landslide hazard. The large variability of local geological materials, together with the difficulties in forecasting heavy precipitation locally and in quantifying the level of ground shaking, call for harmonized procedures to better quantify the hazard and the negative impact of slope failures across the Central Asian countries. As a first step towards a quantitative landslide hazard and risk assessment, a landslide susceptibility analysis at regional scale has been carried out, by benefitting of novel seismic hazard outcomes reached in the frame of Earthquake Model Central Asia (EMCA) project. By combining information coming from diverse potential factors, it is possible to detect areas where a potential for landslides exists. Initial results allow the identification of areas that are more susceptible to landslides with a level of accuracy greater than 70%. The presented method is, therefore, capable of supporting land planning activities at the regional scale in places where only scarce data are available.</p>

Seismic stability of braced excavations next to tall buildings

It can take many years to complete the construction of deep, wide and long excavations in urban environments. In seismically active areas, there is a finite probability that a significant earthquake could take place during the construction period. The designer and builder are confronted with the need not only to maintain control of ground and retaining wall movements during the normal construction conditions but also to protect surrounding buildings during a seismic event. It follows that the seismic loads from adjacent structures and their foundations must be considered together with the available load pathways through the propping system. The paper considers the available methods of design and proposes a performance-based design philosophy in which the temporary shoring system and permanent installation are designed for static loading conditions and for the seismic condition only in as much as the performance objectives of adjacent buildings are achieved for various levels of earthquake shaking. An example of the use of performance-based design is presented for the effects of a 130 m tall building of 30 m square plan upon the temporary shoring system for a long and wide excavation. The results obtained are compared with code-based calculations and general conclusions are drawn.

Landslide susceptibility analysis in data-scarce regions: the case of Kyrgyzstan

Kyrgyzstan is one of the most exposed countries in the world to landslide hazard. The large variability of local geological materials, together with the difficulties in forecasting heavy precipitation locally and in quantifying the level of ground shaking, call for harmonized procedures to better quantify the hazard and the negative impact of slope failures. By exploiting new advances in Geographic Information System (GIS) technology, together with concepts from Bayesian statistics, and promoting the use of open-source tools, we aim to identify areas in Kyrgyzstan where the potential for landslide activation exists. A range of conditioning factors and their potential impact on landslide occurrence are quantitatively assessed on the basis of the spatial distribution of landslides by applying weights-of-evidence modelling based on (1) a landslide inventory of past events, (2) terrain-derived variables of slope, aspect and curvature, (3) a geological map, (4) a distance from faults map, and (5) a seismic intensity map. A spatial validation of the proposed method has been performed, indicating sufficient measures of significance to predicted results. Initial results are promising and demonstrate the applicability of the method to all of Kyrgyzstan, allowing the identification of areas that are more susceptible to landslides with a level of accuracy greater than 70 %. The presented method is, therefore, capable of supporting land planning activities at the regional scale in places where only scarce data are available.

Seismically induced landslide hazard and exposure modelling in Southern California based on the 1994 Northridge, California earthquake event

Quantitative modelling of landslide hazard, as opposed to landslide susceptibility, as a function of the earthquake trigger is vital in understanding and assessing future potential exposure to landsliding. Logistic regression analysis is a method commonly used to assess susceptibility to landsliding; however, estimating probability of landslide hazard as a result of an earthquake trigger is rarely undertaken. This paper utilises a very detailed landslide inventory map and a comprehensive dataset on peak ground acceleration for the 1994 Mw6.7 Northridge earthquake event to fit a landslide hazard logistic regression model. The model demonstrates a high success rate for estimating probability of landslides as a result of earthquake shaking. Seven earthquake magnitude scenarios were simulated using the Open Source Seismic Hazard Analysis (OpenSHA) application to simulate peak ground acceleration, a covariate of landsliding, for each event. The exposure of assets such as population, housing and roads to high levels of shaking and high probabilities of landsliding was estimated for each scenario. There has been urban development in the Northridge region since 1994, leading to an increase in prospective exposure of assets to the earthquake and landslide hazards in the event of a potential future earthquake. As the earthquake scenario magnitude increases, the impact from earthquake shaking initially increases then quickly levels out, but potential losses from landslides increase at a rapid rate. The modelling approach, as well as the specific model, developed in this paper can be used to estimate landslide probabilities as a result of an earthquake event for any scenario where the peak ground acceleration variable is available.

Updated predictive equations for broadband (0.01–10 s) horizontal response spectra and peak ground motions, based on a global dataset of digital acceleration records

Presented herein is an updated model for empirical prediction of 5 %-damped elastic response spectra in the period range 0–10 s, peak ground acceleration and velocity, based on a global dataset of digital acceleration records. The predictive model features saturation of the shaking parameters with both magnitude $$M_{W}$$ and distance $$R_{ RUP }$$ , magnitude-dependent distance attenuation, alternative parameterisations of the amplification effects due to local site conditions (based either on ground types or $$V_{S,30}$$ ) and corrective terms for style-of-faulting. The calibration dataset comprises more than $$1{,}880\times 2$$ orthogonal horizontal accelerometer records with $$R_{ RUP }< 150$$ km from 98 global earthquakes with $$4.5\le M_{W}\le 7.9$$ . The processing technique applied to the acceleration data optimises the reliability of the predictions at long periods, as required by displacement-based design techniques. Developed independently of the recent NGA-West2 and RESORCE-based models, the new predictive tool effectively contributes to capturing the epistemic uncertainties associated with the prediction of seismic shaking levels for engineering applications.