Large Ground Motions Research Articles

Shaking table tests of steel frame with superelastic Cu–Al–Mn SMA tension braces

SummaryShaking table tests are performed on a one‐bay one‐story steel frame with superelastic Cu–Al–Mn shape memory alloy (SMA) tension braces. The frame is subjected to a series of scaled ground motions recorded during the 1995 Kobe earthquake, Japan. The test results demonstrate that the SMA braces are effective to prevent residual deformations and pinching. It is also shown that the time history responses observed from the shaking table tests agree well with the numerical predictions using a rate‐independent piecewise‐linear constitutive model calibrated to the quasi‐static component tests of the SMA braces. This suggests that the loading rate dependence of Cu–Al–Mn SMAs as well as the modeling error due to the piecewise linear approximation can be neglected in capturing the global response of the steel frame. Numerical simulations under a suite of near‐fault ground motion records are further performed using the calibrated analytical models to demonstrate the effectiveness of the SMA braces when the variability of near‐fault ground motions is taken into account. A stopper, or a deformation restraining device, is also proposed to prevent premature fracture of SMA bars in unexpectedly large ground motions while keeping the self‐centering capability in moderate to large ground motions. The effectiveness of the stopper is also demonstrated in the quasi‐static component and shaking table tests. Copyright © 2015 John Wiley & Sons, Ltd.

Jointed Pipeline Response to Large Ground Deformation

AbstractThe performance of segmental pipelines under large ground deformation is strongly influenced by the axial pullout and compressive load capacity of their joints, as well as by the limits on joint rotation during permanent and transient ground deformation. Although ductile iron (DI) pipelines with push-on joints are commonly used in water distribution systems, experimental data and numerical simulation related to their performance under large ground movements are lacking. This paper reports on a series of specially designed four-point bending experiments and finite-element (FE) simulations to characterize 150-mm (6-in.) diameter DI push-on joints. The results were used to develop a relationship between rotation and metal binding as a function of axial pullout, as well as to determine the magnitudes of rotation and moment that initiate joint leakage. FE simulations were performed to investigate the deformation associated with joint leakage. Uniaxial tension and one-dimensional compression tests were ...

C104 ギャップ付き剛性増大機構を備えた制振架構に関する研究(OS5 建設構造物の耐震・免震・制振1)

A new response control mechanism, which is composed of frames equipped with passive dampers and hardening elements with gaps, is proposed. Using this mechanism, the frames response as usual vibration controlled systems within expected amplitude levels, and they show full capacities against unexpectedly large earthquake ground motions, by changing their vibration modes. The authors demonstrate the effectiveness of the system by conducting response analyses of a multi-degree-of-freedom model. And they also reported a loading test results of scaled frames equipped with the proposed system.

北野天満宮の石灯籠建立時系列に記録された京都市街の歴史地震動

Kyoto City has experienced a number of large seismic ground motions since it was established approximately 1200 years ago. Descriptions of these shakings are recorded in written documents which have been used to investigate historic earthquake hazards. In those documents often appears that stone lanterns at major temples and shrines collapsed and suffered damages, and descriptions of such damages are used to determine that the shaking at that site was at least as severe as 5 in JMA Intensity Scale. When stone lanterns are heavily damaged during earthquakes, some of them would be removed from the site and replaced by new ones afterward, which implies that the age distribution of stone lanterns which we observe today is affected by the history of strong ground motions. We examine ages of stone lanterns at Kitano-Tenmangu Shrine, Kyoto and investigate whether the correlation between the ages of stone lanterns and historic earthquakes is evident at this site. Severe damages of stone lanterns caused by strong ground motions in 1830 and 1854 at this site are documented in the historic documents, and we are able to identify that high numbers of stone lanterns that were newly build within a few years of these earthquakes currently remain at this site. We statistically argue that ages of existing stone lanterns at Kitano-Tenmangu Shrine are affected by historical strong seismic ground motions in Kyoto, and that these stone lanterns as a group record occurrence of historic earthquakes in Kyoto.

A Refined Vs30 Map for Taiwan Based on Ground Motion Attenuation Relationships

Seismic hazard evaluations require an estimate of the expected ground motion at the site of interest usually by using attenuation relationships. The mean shear-wave velocity over the top 30 m (Vs30) is incorporated in the ground motion attenuation relationships in this study. By comparing the standard deviations of the residuals between the observed and predicted values before and after incorporating the site effect term Vs30, the reduction in standard deviation for the peak ground velocity (PGV) is significantly reduced by about 11%. Clearly, the refined attenuation relationships will be more useful for engineering purposes. Analyzing the site effect term using the amplification factor (relative to a site with Vs30 = 760 m s^(-1)), has revealed that the Changhua Plain, Chianan Plain, Pingtung Valley, Ilan Plain, and Taipei Basin have high values, implying large ground motion amplification. Following a disastrous earthquake, quick assessment and timely peak ground acceleration (PGA) and PGV map reporting will be critical for effective emergency response operations. After an earthquake we can combine the simple attenuation relationships, as determined from Model 1, to provide near real-time estimation and reporting of the PGA and PGV values for the Taiwan area. We can also use the relations between the intra-event site residual and the Vs30 to estimate the Vs30 for stations that have recorded strong motions, but do not yet have Vs30 information. Our approach including sites with estimated Vs30 has resulted in a refined Vs30 contour map that can be used for more realistic seismic hazard assessment for Taiwan. This approach is especially applicable to the foothill and mountain areas.

Sensitivity Analysis of Buried Jointed Pipelines Subjected to Earthquake Waves

In this study, a number of nonlinear time-history dynamic analyses are conducted on a part of Tehran water distribution network to investigate its functionality during transient large ground motions. The network is of 950-meter length, consisting of ductile iron pipes segments of 6-meter length. Pipes are modeled using beam elements and springs characterize the connections. Considering the time lag between support inputs, and the nonlinear soil-pipe interaction, by scaling the amplitude of the Tab as earthquake record, incremental dynamic analysis is carried out on the network in two orthogonal directions and the sensitivity of the network response is examined. Furthermore, the effects of variations in soil damping and soil spring stiffness are also studied in the network analysis. Finally the effect of changes in angle between incoming wave and pipeline is considered on a simplified network. Results show that the points other than critical ones at network intersections remain almost intact and when the angle of incidence is 30 degrees the stress and rotation peak.

Characterizing sudden geo-hazards in mountainous areas by D-InSAR with an enhancement of topographic error correction

Differential interferometric synthetic aperture radar (D-InSAR) has been viewed as a promising technique in monitoring sudden geo-hazards (e.g., earthquake and landslide) in mountainous areas. However, the tough natural settings (e.g., steep slopes and vegetation) pose the D-InSAR technique to face many challenges. Among them, phase residuals induced by inaccurate topographic heights that can result in intolerable error have not been paid adequate attention. We present, in this paper, a new strategy of using D-InSAR measurements to characterize sudden geo-hazards with an emphasis on the correction of topographic errors. In the proposed strategy, a least squares model with an outlier detector is constructed to estimate the topographic errors from multi-baseline wrapped differential interferograms, and the error-prone phase unwrapping procedure is not needed. The new strategy is applied to the ALOS PALSAR images acquired for monitoring a giant mudslide occurred in Zhouqu County, China. After refining the topographic height originally from the inaccurate ASTER GDEM, notable improvements to the D-InSAR measurements can be clearly seen, which is helpful to better interpret the deformation signals associated with the mudslide event. It is observed that the Zhouqu mudslide had caused large ground movements in the Luojiayu and Sanyanyu groove valleys. In addition, we find that the Suoertou landslide has been experiencing moderate ground movements during the geologic event.

Borehole Instability in Malmberget Underground Mine

Borehole instability causes borehole failure, presenting a challenge to the drilling industry (Muller et al. 2009; Zhang 2013). The borehole stability of Marcellus shale wells in long wall mining areas in southeast Pennsylvania, West Virginia, and eastern Ohio has been evaluated by Wang et al. (2014). Here, the ground deformation caused by coal mining generates large ground movement and creates complex stress changes in subsurface rock. This, in turn, triggers interruptions in the operation of the borehole well causing safety and environmental concerns. Borehole walls may fail when the surrounding stress exceeds the tensile, the compressive, or the shear strengths of the rock formation, whichever is reached first (Zhang et al. 2003). Horizontal well borehole stability is analyzed by the new in situ stress prediction model in shale gas reservoirs (Yuan et al. 2013). Besides this, in hard rock underground mining, such as sublevel caving (SLC), uncharged and undetonated blast holes reduce specific charge, result in poor fragmentation and may even lower ore recovery (Zhang 2005). It is often found that boreholes are blocked by stones and the charge work has to stop in the field. In many SLC rings two or three boreholes in each ring are often broken or blocked by either stones or pieces of concrete according to the mine’s production archives that contain daily notes on various production problems met by the miners. In order to get detailed information on the borehole problems occurring in LKAB’s two mines, a preliminary investigation was carried out by Kangas (2007) with a mini-video camera, showing that typical borehole problems were borehole deformation and boreholes jammed by stones. Due to various reasons, the above investigation rested for a while. This study is a follow-up of the previous investigationmade by Kangas (2007) in more ore bodies and more boreholes. The main objective of this study is to identify various instability problems of boreholes by field filming in different ore bodies in the mine.

Long-Period Ground Motion in the Arabian Gulf from Earthquakes in the Zagros Mountains Thrust Belt

The Arabian Gulf is adjacent to the Zagros Mountains, one of the most seismically active regions in the world. We observe that broadband seismic records of Zagros earthquakes recorded on the Arabian side of the Gulf display long-duration surface waves. While shorter periods (<1 s) are attenuated from crossing the deep sediments (>10 km) of the Gulf basin, the long-period energy is enhanced and transmitted efficiently. Consequently, large earthquakes in the Zagros could result in amplified ground motions at long periods (2–10 s) relative to average behavior. Such ground motions are of concern for large engineered structures, such as tall buildings and long bridges with resonant periods in the same period range. Here we present results of investigations of the characteristics of ground motions recorded on the western shore of the Gulf from selected earthquakes in the Zagros Mountains region. Exceptionally, long-duration seismic waves, as compared with standard models, are shown to occur with periods of 2–10 s. This may be due to waveguide effects in the deep sedimentary basin structure of the Arabian Platform. In addition to analyzing recorded ground motion we performed 3D wave propagation simulations using a finite difference method and experimental velocity models of the Gulf, with different shallow sedimentary layers structures. The simulation results confirm our hypothesis that long-period waves with extremely long duration and relatively large amplitudes are caused by the geometry of the basin sedimentary layers and, to some extent, by shallow earthquake depths. Combined effects of basin edge geometry with sharp velocity contrasts and shallow sources (<10 km) on the eastern side of the Arabian Gulf can cause large long-period ground motion on the western side of the Gulf. In contrast, the short-period content of ground motion (<2 s) at long distances is relatively weak. This is mainly due to wave propagation scattering and attenuation in the shallow sedimentary layers of the Gulf basin.

Impact of column-to-beam strength ratio on the seismic response of steel MRFs

The strong-column/weak-beam seismic design concept in moment resisting frames is perhaps one of the least well-understood design provisions. This study is aimed at improving the understanding of the effect of column-to-beam strength ratio (CBSR) on several seismic performance measures. Through nonlinear analyses of 3-, 9-, and 20-story moment resisting frame, the impacts of CBSR on member ductility demands, maximum inter-story drifts, and floor acceleration amplifications are investigated. For each frame, the value of CBSR is varied by changing the yield strength of the material and/or by altering sizes of the columns. The probabilities of exceeding certain performance limits are investigated through fragility analyses. The single curvature bending of the columns within a story is found to be inevitable due to the participation of higher modes of vibration. Consequently, under large ground motions, the yielding of the columns is expected even for CBSRs larger than 2.0. The fragility relationships were used to calculate the design force modification factors needed for achieving a comparable probability of column yielding for different values of CBSR. The values of the yield base shear and the inter-story drifts were found to depend more on the strength of the beams than the value of CBSR. The floor acceleration amplification was found to be the least sensitive demand parameter to the CBSR.

Site Effects on Large Ground Motions at KiK-net Iwase Station IBRH11 during the 2011 Tohoku Earthquake

Abstract Large horizontal ground motions with peak ground accelerations (PGAs) of more than 800 cm/s 2 and peak ground velocities of nearly 60 cm/s were observed at a KiK‐net station, Iwase (IBRH11), during the 2011 M w 9.0 Tohoku, Japan, earthquake. We investigated site effects on the large ground motions by inverting the subsurface structure and simulating ground motions considering soil nonlinearity. The structure from the seismic bedrock to the surface in the linear regime was inverted from (1) array records of microtremors using Rayleigh‐wave inversion, (2) surface‐to‐borehole spectral ratios of weak motions using S ‐wave inversion based on the 1D wave propagation theory, and (3) horizontal‐to‐vertical spectral ratios of weak motions using the inversion based on the diffuse‐field theory for plane waves. The main cause of the large ground motions was found to be a strong impedance contrast between soft layers with an S ‐wave velocity ( V S ) of less than 381 m/s and a layer with V S =2371 m/s at a depth of 30 m. The strong motions at the surface during the 2011 Tohoku earthquake simulated by equivalent‐linear analysis using borehole records at a depth of 103 m are in reasonable agreement with the observed records, whereas those simulated using linear analysis were approximately twice as large as the observed values. The results showed that the nonlinearity of the surface soils reduced the amplification factors and the PGAs by half compared with the values for the linear regime. The PGAs of the bedrock motions with V S =2371 m/s were estimated, using equivalent‐linear analysis, to have reached approximately 500 cm/s 2 .

Disorder and damage of base‐isolated medical facilities when subjected to near‐fault and long‐period ground motions

SUMMARYA series of full‐scale shaking table tests were conducted at E‐Defense for a four‐story base‐isolated hospital. The operation room in the specimen was chosen for detailed examination of its disorder and damage during large ground motions. It was arranged with various medical appliances in as a realistic manner as possible, and the appliances were characterized by casters installed at the bottom to ensure mobility. Two types of ground motion, the near‐fault ground motion and long‐period ground motion, were adopted, and the responses of the appliances were recorded using the motion capture technique. Thanks to the base isolation, the floor response was greatly reduced, and no disorder or damage was observed in the operation room except for the case when subjected to a long‐period ground motion. In this case, the unlocked appliances moved seriously (by more than 3 m), and collisions occurred between the appliances and between appliances and the surrounding wall. The force of collision reached 36 kN, which is sufficient to injure a person. The acceleration due to collision was as high as 10 g, which is far beyond what can be tolerated by acceleration‐sensitive appliances. It is notable that such large motion was not observed once the appliances were locked. The test was also carried out for the corresponding fixed‐base structure. Among all cases in the experiment, by far the most serious damage occurred in the fixed‐base structure when subjected to the near‐fault ground motion, clearly because the floor response was significantly amplified from the ground motion. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Strong Motion Simulation of the Weihe Basin in Wenchuan Earthquake

Seismic response of the Weihe basin generated by 5.12 Wenchuan earthquake is simulated by using the spectral-element method and parallel computing technique, considering 3D basin model incorporated with real topography. The wave propagation and the comparison of the synthetic and observed records are studied in detail in this paper. The result shows that appropriate source and detailed basin model and accurate numerical technique can simulate the wavefield and large basin ground motion well.

Influence of Hysteretic Behavior on Seismic Strength Demands: An Analysis for Romanian Vrancea Earthquakes

The paper presents the results of a study performed on a large ground motion database, containing records obtained during the three strongest earthquakes that occurred during the past four decades in the Vrancea seismogenic zone. In order to express strength demands imposed by these earthquakes, constant-ductility nonlinear acceleration spectra were computed for two sets of seismic records, selected as representative for narrow frequency band and broad frequency band ground motions, respectively. The spectra, determined for various types of bilinear hysteretic models, were normalized with respect to peak ground acceleration and mean values, as well as coefficients of variation, were computed for each analysis case. The sensitivity of spectral values to the variation of strength hardening and stiffness degradation parameters was determined, with reference to the elastic-perfectly plastic model. Conclusions were drawn, separately for the two distinct types of ground motion frequency content, on the significance of the considered hysteretic model parameters for the assessment of seismic strength demands.

Broadband Ground-Motion Simulation of an Intraslab Earthquake and Nonlinear Site Response: 2010 Ferndale, California, Earthquake Case Study

Intraslab earthquakes are generated by fault ruptures, which occur at shallow (20–60 km) or deep (>60 km) parts of a subducting tectonic plate slab. In both cases the rupture occurs in the vicinity of a zone with large velocity contrast and increased regional stress caused by the subducting plates. These conditions have significant effects on fault geometry, rupture dynamics, and seismic energy, which in turn affect the amplitude and duration of ground motion. Consequently, intraslab earthquakes can generate larger ground motion than shallow crustal earthquakes of same magnitude. Therefore their study is very important for strong ground motion prediction and seismic‐hazard assessment. In an effort to develop a methodology for simulating strong ground motion from intraslab earthquakes we tested the broadband ground‐motion simulation technique of Graves and Pitarka (2010) in modeling ground motion recorded from the M 6.5 2010 Ferndale, California, intraslab earthquake. The Graves and Pitarka (2010) method was originally developed for simulating crustal earthquakes. To our knowledge this is the first attempt to apply a broadband ground‐motion‐simulation method in modeling ground motion from intraslab earthquakes in the United States. A similar approach (Matsuzaki et al. , 2010) was applied to studying the rupture process of the 2001 Geiyo, Japan, intraslab earthquake using the recipe developed by Irikura and Miyake (2006). In this study we simulate and analyze ground‐motion‐acceleration time history recorded during the earthquake in a zone between Ferndale and Eureka, and Humboldt Bay. The earthquake was very well recorded in a geotechnical array located in the Humboldt Bay soft sediments. The ground‐motion acceleration recorded by the array’s instruments at several depths provided a good opportunity for testing numerical techniques and empirical models of the nonlinear seismic response of soils for input motion with moderate amplitude. A large part of our investigation is focused on modeling the observed nonlinear response …

Telescopes for space-based gravitational wave missions

Space-based observation of gravitational waves promises to enable the study of a rich variety of high energy astrophysical sources in the 0.0001 to 1 Hz band using signals complementary to traditional electromagnetic waves. Gravitational waves represent the first new tool for studying the sky since gamma ray telescopes debuted in the 1970s, and we expect compelling science to be the result. The fundamen- tal measurement is to monitor the path length difference between pairs of freely falling test masses with laser interferometry to a precision of picom- eters over gigameter baselines. The test masses are arranged in an equi- lateral triangle to allow simultaneous measurement of both gravitational wave polarizations. The heliocentric orbital space environment enables the test masses to be shielded from large ground motions at low frequen- cies, and allows the construction of long measurement baselines that are well matched to the signal wavelengths. Optical telescopes play an impor- tant role in the measurement because they deliver laser light efficiently from one spacecraft to another. The telescopes are directly in the meas- urement path, so there are additional performance requirements to sup- port precision metrology beyond the usual requirements for good image formation. © 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) (DOI: 10 .1117/1.OE.52.9.091811)

Occurrence mechanism of recent large earthquake ground motions at nuclear power plant sites in Japan under soil-structure interaction

The recent huge earthquake ground motion records in Japan result in the reconsideration of seismic design forces for nuclear power stations from the view point of seismological research. In addition, the seismic design force should be defined also from the view point of structural engineering. In this paper it is shown that one of the occurrence mechanisms of such large acceleration in recent seismic records (recorded in or near massive structures and not free-field ground motions) is due to the interaction between a massive building and its surrounding soil which induces amplification of local mode in the surface soil. Furthermore on-site investigation after earthquakes in the nuclear power stations reveals some damages of soil around the building (cracks, settlement and sand boiling). The influence of plastic behavior of soil is investigated in the context of interaction between the structure and the surrounding soil. Moreover the amplification property of the surface soil is investigated from the seismic records of the Suruga-gulf earthquake in 2009 and the 2011 off the Pacific coast of Tohoku earthquake in 2011. Two methods are introduced for the analysis of the non-stationary process of ground motions. It is shown that the non-stationary Fourier spectra can detect the temporal change of frequency contents of ground motions and the displacement profile integrated from its acceleration profile is useful to evaluate the seismic behavior of the building and the surrounding soil.

Fragility analyses of mid-rise T-stub PR frames in the Mid-America earthquake region

Mid-America region is defined as the region of the central and southeastern United States compromising those states that have expected large but infrequent seismicity. Although earthquakes in this region are less frequent than in western U.S., they affect much larger areas than those of similar magnitude in western U.S. due to the deep and loose subsurface conditions. However, as little research has been carried out for partially restrained (PR) steel moment frame structures in this region, it is necessary to evaluate their seismic performance. To achieve this, seismic performance of three proto-type 6-story steel moment frames with T-stub PR connections was evaluated in accordance with FEMA 273/356 limit state criteria using fragility analyses. Three PR frames were designed using the appropriate design codes representing mid-1950s, late 1980s, and current practice. Two different types (“Conventional” and “New”) of fragility curves are developed and compared. In addition, the fragility curves at Los Angeles site representing western U.S. were generated and compared with those at the Mid-America region. Two different fragility analysis results show the same trends. Three proto-type 6 story PR frames in the Mid-America earthquake region performed well and may not collapse. It can be concluded that the seismic performance of the mid-rise PR frames in the Mid-America region will be satisfactory even under large but infrequent ground motions.

Low cycle fatigue effects in integral bridge steel H-piles under seismic displacement reversals

Under the effect of medium and large intensity ground motions, the seismically-induced lateral cyclic displacements in steel H-piles of integral bridges (IBs) could be considerable. As a result, the piles may experience cyclic plastic deformations following a major earthquake. This may result in the reduction of their service life due to low-cycle fatigue effects. Accordingly, low cycle fatigue in integral bridge piles is investigated under seismic effects in this study. For this purpose, IBs with two spans are considered. Three dimensional nonlinear structural models of these IBs including dynamic soil-bridge interaction effects are built. Then, time history analyses of the IB models are conducted using a set of ground motions with various intensities representing small, medium and large intensity earthquakes. In the analyses, the effect of various properties such as soil stiffness, pile size and orientation are considered. The magnitude of cyclic displacements of steel H piles are then determined from the analyses results. In addition, using the existing data from experimental tests of steel H-piles, a fatigue damage model is formulated. This fatigue damage model is used together with the cyclic displacement obtained from seismic analyses to determine the remaining service life of IBs under cyclic displacement due to thermal effects. The fatigue analyses results reveals that earthquakes with large intensity may reduce the service life of the piles with non-compact sections.

Rotational Motions Recorded at Hualien during the 2012 Wutai, Taiwan Earthquake

It is widely accepted that the effects of rotational motions on seismic waves can be neglected when ground motion is small and might be underestimated in near-fault and/or with extremely large ground motions. However, quantitative validation of these assumptions is still needed. During the 2012 Wutai earthquake in Taiwan (6.4 ML), a set of small rotation ratestrong motion velocity data was recorded at the HWLB (Hualien) seismographic station. This station is 161 km away from the epicenter and the recorded peak ground acceleration and rotation rate are about 7 cm s -1 s -1 and 0.1 mrad s -1 , respectively. This data set is useful for evaluating the lower bound of ground motion that can be neglected regarding the effects of rotational motions. In this study, we apply the algorithm developed by Chiu et al. (2012) and derive the time histories of the rotation angle, the centrifugal acceleration and the gravity effect due to the rotational motions. The results show that all three-component rotation angles are less than 3 × 10 -4 degrees. The maximum centrifugal acceleration and effect of gravity are about 5 × 10 -5 and 5 × 10 -3 cm s -1 s -1 , respectively. Although the amount of induced ground motions due to the rotational motions is small, the effect on the waveforms is significant; the maximum waveform difference before and after rotation-motion correction is about 10% of the Peak Ground Acceleration. We also found that the effects of rotational motions are always present and are proportional to the ground acceleration except that centrifugal acceleration and the vertical component of gravity effect decrease faster compared to the decrease in ground accelerations.