Generated Ground Motions Research Articles

Seismic margin assessment of a reinforced concrete skewed bridge in a nuclear power plant

This paper presents the seismic margin assessment of a reinforced concrete (RC) bridge using the high-confidence-of-low-probability-of-failure (HCLPF) value. An existing RC skewed bridge built in a nuclear power plant (NPP) in Korea was selected for studying objective. Finite element modeling of the bridge is developed in OpenSees, an open system for earthquake engineering simulation. The reference earthquakes applied for the probability analysis are selected from the set of generated ground motions that using for designing NPP structures in Korea. The HCLPF value is calculated based on the fragility method associated with the approximate second moment approach. The effect of randomness and uncertainty in demand and capacity variables is taken into account in the fragility analysis procedure. Based on the calculated HCLPF values, the seismic fragility assessment of the bridge can be readily implemented.

Probabilistic Seismic Hazard Analysis and Synthetic Ground Motion Generation for Seismic Risk Assessment of Structures in the Northeast India

This article outlines the performance-based seismic risk assessment (PBSRA) of structures requiring probabilistic seismic hazard analysis (PSHA) to obtain hazard curves and an evaluation of the demand model by a nonlinear structural response analysis under properly selected ground motion records. Unfortunately, such site-specific information is not readily available for Northeast region of India. The present study focuses on these two aspects to supplement the PBSRA. The estimations of hazard curves are demonstrated by considering the seismicity within 300 km radius around the considered locations and specified exposure period. Due to limited availability of natural records in this region, synthetic accelerograms are generated using stochastic point source models by identifying the most contributing magnitude distance combinations from disaggregation of the PSHA results. The significant variabilities observed in the estimated hazard, synthetic accelerograms and nonlinear building responses in the various locations indicate the need of explicit site-specific analysis for PBRSA of structures in the region.

Alternative Rupture‐Scaling Relationships for Subduction Interface and Other Offshore Environments

Abstract Alternative fault‐rupture‐scaling relationships are developed for M w 7.1–9.5 subduction interface earthquakes using a new database of consistently derived finite‐fault rupture models from teleseismic inversion. Scaling relationships are derived for rupture area, rupture length, rupture width, maximum slip, and average slip. These relationships apply width saturation for large‐magnitude interface earthquakes (approximately M w >8.6) for which the physical characteristics of subduction zones limit the depth extent of seismogenic rupture, and consequently, the down‐dip limit of strong ground motion generation. On average, the down‐dip rupture width for interface earthquakes saturates near 200 km (196 km on average). Accordingly, the reinterpretation of rupture‐area scaling for subduction interface earthquakes through the use of a bilinear scaling model suggests that rupture asperity area is less well correlated with magnitude for earthquakes M w >8.6. Consequently, the size of great‐magnitude earthquakes appears to be more strongly controlled by the average slip across asperities. The sensitivity of the interface scaling relationships is evaluated against geographic region (or subduction zone) and average dip along the rupture interface to assess the need for correction factors. Although regional perturbations in fault‐rupture scaling could be identified, statistical significance analyses suggest there is little rationale for implementing regional correction factors based on the limited number of interface rupture models available for each region. Fault‐rupture‐scaling relationships are also developed for intraslab (within the subducting slab), extensional outer‐rise and offshore strike‐slip environments. For these environments, the rupture width and area scaling properties yield smaller dimensions than interface ruptures for the corresponding magnitude. However, average and maximum slip metrics yield larger values than interface events. These observations reflect both the narrower fault widths and higher stress drops in these faulting environments. Although expressing significantly different rupture‐scaling properties from earthquakes in subduction environments, the characteristics of offshore strike‐slip earthquake ruptures compare similarly to commonly used rupture‐scaling relationships for onshore strike‐slip earthquakes. Electronic Supplement: Table of rupture parameters.

Design response spectra-compliant real and synthetic GMS for seismic analysis of seismically isolated nuclear reactor containment building

Due to the severe impacts of recent earthquakes, the use of seismic isolation is paramount for the safety of nuclear structures. The diversity observed in seismic events demands ongoing research to analyze the devastating attributes involved, and hence to enhance the sustainability of base-isolated nuclear power plants. This study reports the seismic performance of a seismically-isolated nuclear reactor containment building (NRCB) under strong short-period ground motions (SPGMs) and long-period ground motions (LPGMs). The United States Nuclear Regulatory Commission-based design response spectrum for the seismic design of nuclear power plants is stipulated as the reference spectrum for ground motion selection. Within the period range(s) of interest, the spectral matching of selected records with the target spectrum is ensured using the spectral-compatibility approach. NRC-compliant SPGMs and LPGMs from the mega-thrust Tohoku earthquake are used to obtain the structural response of the base-isolated NRCB. To account for the lack of earthquakes in low-to-moderate seismicity zones and the gap in the artificial synthesis of long-period records, wavelet-decomposition based autoregressive moving average modeling for artificial generation of real ground motions is performed. Based on analysis results from real and simulated SPGMs versus LPGMs, the performance of NRCBs is discussed with suggestions for future research and seismic provisions.

SOURCE CHARACTERIZATION AND GROUND MOTION MODELING COMPUTED FROM THE 3 SEPTEMBER 2015 EARTHQUAKE, WESTERN DESERT, EGYPT

To obtain the characterized source model for prediction of strong ground motions, the ground motion generation area and rupture geometry of an inland crustal earthquake from near-source ground motion records has been estimated. An earthquake, with a magnitude of 4.3 ML and a focal depth of 18 km occurred on September 3, 2015 at 30.45N, 28.44E in the Western Desert of Egypt about 60 km south of El-Dabaa city. This earthquake is the first instrumentally recorded earthquake occurring in this area in several decades. The waveform data of this event has been used for source characterization and ground motion modeling. The present work describes the results of a preliminary study conducted to obtain fault plane solutions of this earthquake from waveform inversion and P-wave polarity. For this purpose, the source parameters related to the strong ground motion were estimated by waveform data and first arrivals recorded by the Egyptian National Seismic Network (ENSN) are used to arrive at focal mechanism solutions. Fault plane solutions for the main shock indicate strike-slip motion. One nodal plate strikes about 330°, is nearly vertical, and indicates right lateral slip. The other nodal plane strikes about 240°, dips very steeply NW, and indicates left lateral slip. Also the peak ground acceleration (PGA) at the El-Dabaa site has been simulated by taking into account an accurate estimation of the source characterization, the path attenuation model, and site amplification. The results have been validated using an actual recording of PGA at one ENSN station that recorded strong ground motion.

Rupture process of the main shock of the 2016 Kumamoto earthquake with special reference to damaging ground motions: waveform inversion with empirical Green\u2019s functions

In this study, the rupture process of the main shock of the Kumamoto earthquake, particularly the generation of strong ground motions in the frequency range relevant to structural damage, was investigated based on the inversion of strong ground motions. Strong-motion records in the near-source region were mainly utilized because the authors were interested in the generation mechanism of damaging ground motions in the near-source region. Empirical Green’s functions (EGFs) were applied to avoid uncertainty in the subsurface structure model. Four cases of inversions with different combinations of small events were used to investigate the dependence of the inversion results on the selection of the small events. It was found that the dependence of the final slip distribution and peak slip velocity distribution on the selection of the EGF events is small. The results clearly indicate that a region of significantly large slip and slip velocity existed approximately 15 km northeast of the hypocenter. However, no “asperity” was observed between the hypocenter and Mashiki. Thus, it is not appropriate to conclude that the large-amplitude pulse-like ground motion in Mashiki was generated by the forward-directivity effect associated with the rupture of an asperity. As far as the source effect is concerned, the ground motion in Mashiki cannot be interpreted as the worst case scenario. On the other hand, the rupture of the “asperity” 15 km northeast of the hypocenter should have caused significantly large ground motions in regions close to the asperity. The significant damage of highway bridges in the region can potentially be attributed to the rupture of the asperity. The result of this study was compared with an inversion result obtained from numerical Green’s functions for a layered half-space. The two results share the main features in spite of the difference of the Green’s functions and stations used. Therefore, it can be concluded that these two source models capture the main features of the rupture process of the earthquake.Graphical abstractIn this study, the rupture process of the main shock of the Kumamoto earthquake, particularly the generation of strong ground motions in the frequency range relevant to structural damage, was investigated based on the inversion of strong ground motions. Strong-motion records in the near-source region were mainly utilized because the authors were interested in the generation mechanism of damaging ground motions in the near-source region. Empirical Green’s functions (EGFs) were applied to avoid uncertainty in the subsurface structure model. Four cases of inversions with different combinations of small events were used to investigate the dependence of the inversion results on the selection of the small events. It was found that the dependence of the final slip distribution and peak slip velocity distribution on the selection of the EGF events is small. The results clearly indicate that a region of significantly large slip and slip velocity existed approximately 15 km northeast of the hypocenter. However, no “asperity” was observed between the hypocenter and Mashiki. Thus, it is not appropriate to conclude that the large-amplitude pulse-like ground motion in Mashiki was generated by the forward-directivity effect associated with the rupture of an asperity. As far as the source effect is concerned, the ground motion in Mashiki cannot be interpreted as the worst case scenario. On the other hand, the rupture of the “asperity” 15 km northeast of the hypocenter should have caused significantly large ground motions in regions close to the asperity. The significant damage of highway bridges in the region can potentially be attributed to the rupture of the asperity. The result of this study was compared with an inversion result obtained from numerical Green’s functions for a layered half-space. The two results share the main features in spite of the difference of the Green’s functions and stations used. Therefore, it can be concluded that these two source models capture the main features of the rupture process of the earthquake.

Synthesis of Spatially Correlated Earthquake Ground Motions Based on Hilbert Transform

A simplified method for synthesizing spatially correlated earthquake ground motions is developed based on Hilbert transform and a reference earthquake record. In this method, one reference earthquake record is treated as the original ground motion, based on a series of generated ground motions. This procedure uses the instantaneous amplitude and the instantaneous phase of the record obtained using Hilbert transform to achieve the nonstationarity of ground motion. To establish the coherency between generated ground motions, an incoherence model is employed to describe the relation between the instantaneous phase at the present station and the instantaneous phases at previous stations. This type of phase is defined as the instantaneous coherence phase. In addition, time lag is included in the instantaneous coherence phase to prescribe the wave passage effect. The proposed Hilbert-transform-based method is efficient and avoids cumbersome parameter estimations as well as other drawbacks involved in some traditional synthesizing methods. Applications of this method demonstrate that the generated ground motions are statistically analogous with the reference record.

Seismic Strengthening of Unreinforced Masonry Walls using Sprayable Eco-Friendly Ductile Cementitious Composite (EDCC)

Abstract In another paper at this workshop, the development of Eco-Friendly Ductile Cementitious Composite (EDCC) and its response to uniaxial tensile is described. Here, its performance when used as a strengthening coat on unreinforced masonry is described. This paper elaborates on the results of shake table tests on full-scale masonry wall specimens, each about 2m wide by 3m high, retrofitted using sprayed EDCCs. Six full-scale unreinforced non-grouted masonry wall specimens were assembled and then retrofitted using Sprayable EDCC. The walls are tested at the Earthquake Engineering Research Facility (EERF) at UBC on the Linear Shake Table (LST) under different ground motions with varying intensities. The wall specimens were fully instrumented and data were collected using 34 different channels including 10 accelerometers, 8 channels of displacement sensors, 8 strain gauges and time synchronized video recording using eight HD cameras. Test indicated that even a single-sided retrofit with appropriate EDCC can significantly enhance the overall ductility of the system and change the fundamental behaviour of the wall from a typical “Rocking Mechanism” to a “Beam” type behaviour, with significant rotations at the hinge supports of the base. The added flexibility to the system resulted in a substantial increase in energy dissipation, and thereby increasing the overall drift limits before collapsing, causing the wall to withstand extensive levels of shaking under different types and intensities of earthquake generated ground motions.

Influence of Twenty Years of Research on Ground‐Motion Prediction Equations on Probabilistic Seismic Hazard in Italy

Abstract This study compares 12 hazard models based on dated and recent ground‐motion prediction equations (GMPEs) to evaluate the improvement provided by new equations on probabilistic seismic‐hazard assessments in Italy. To this end, a statistical procedure is applied to score the outcomes of each hazard model at 56 different accelerometric sites that have been operating for at least 25 years. This procedure, which calculates the likelihood of the outcomes of the hazard models relative to available observations, evaluates the performance of each model and, indirectly, the influence of the selected GMPEs in providing effective hazard estimates. We have found that older GMPEs tend to yield high‐frequency ground‐motion hazard values that are overconservative at shorter mean return periods and underconservative at longer ones. To identify the sources of the different behavior between older and more recent equations, the biasing of each GMPE is evaluated by comparing median predictions with observations available at two accelerometric sites where a relatively large number of ground motions from different earthquakes have been recorded and local soil conditions are well established. Results indicate that two decades of research on GMPEs have resulted in a significant reduction of bias with an improvement in the accuracy of predictions. Major improvements have been observed from 2008 to 2010. These may be related to the increased completeness of regression data sets and to an increased effectiveness of functional forms, which allow a better modeling of the physical process governing the propagation of ground motions. Since then, the GMPE bias has remained almost stable and no significant improvement in the performances of the relative hazard models has been observed. Our results also indicate that worldwide GMPEs applied to Italy are less effective at providing hazard results corroborated by observations.

Artificial earthquake test of gas supply networks

In this paper, seismic behavior of gas supply networks is investigated by constructing a 24m×24m buried network and conducting an artificial earthquake test by detonating TNT explosives. The pipe network consists of typical welded steel pipes used in gas supply networks. Ground motion is produced by detonating 30kg of TNT explosives buried 5m below ground surface and 15m away from the network. The test preparations are presented, including site selection, network layout, ground motion generation, and arrangements of different sensors. The measured ground acceleration, strain, and acceleration of welded steel pipes, and pipe–soil relative slippage are discussed. The deformation patterns of welded steel pipes are also analyzed and explained, including axial and bending deformations, systematic network characteristics, deformation relationship between ground and pipes, and dynamic response of buried pipes.

Simulation and generation of spectrum-compatible ground motions based on wavelet packet method

This paper deals with the problem of generating spectrum-compatible artificial accelerograms for seismic dynamic analysis of engineering projects. A wavelet-packet-based, two-step procedure for the issue is proposed. The first step is to generate acceleration time history that could account for temporal and frequency non-stationarities of recorded ground motions. The second step is to decompose it into a desired number of wavelet packet vectors with high frequency resolution and non-overlapping frequency contents. Then each wavelet packet vector is scaled suitably and iteratively for the response spectrum of the simulated accelerogram to fit a specified design spectrum. The advantages of this procedure are that it can simulate user-specified acceleration time history with only 6 input parameters and the adjusted accelerogram has similar characteristics to the recorded one. The proposed procedure has been illustrated by simulating and modifying acceleration time history that are compatible with two different design spectrums for nuclear power plants. In addition, iterative efficiency of the method is investigated by simulating and adjusting acceleration time history for 100 successive times. The maximum relative error of the 76 period control points can reach 6% or below. Results show that the proposed method is effective and practical to generate and find spectrum-compatible ground motions with both stochastic and deterministic aspects.

A web‐based educational software for structural dynamics

ABSTRACTIn this work, we present a web‐based educational package for teaching structural dynamics, as well as for providing an easily accessible on‐line tool for interactive experimentation that is useful for both undergraduate and graduate training. Current version of the package comprises five software modules, namely (1) response history analysis of a single‐degree‐of‐freedom system, (2) modal analysis and time history analysis of a single‐storey space frame, (3) modal analysis and time history analysis of planar frames up to three stories in height, (4) generation of response spectra from ground acceleration signals, and (5) generation of synthetic ground motions for layered soil formations. These second‐generation software moduli are now freely available over the internet and were derived from a previously developed educational package that has been used over the past 5 years as a virtual laboratory for teaching structural dynamics fundamentals to civil engineering undergraduates. © 2016 Wiley Periodicals, Inc. Comput Appl Eng Educ 24:599–614, 2016; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.21735

Tuning of stochastic ground motion models for compatibility with ground motion prediction equations

SummaryStochastic ground motion models can facilitate a versatile description of earthquake acceleration time‐histories by modulating a white‐noise sequence through functions that address spectral and temporal properties of the excitation. This is established by relating the parameters of these functions to earthquake and site characteristics through appropriate predictive relationships. This study focuses on the selection of these predictive relationships to establish direct compatibility to the mean predictions of ground motion prediction equations (GMPEs). A record‐based ground motion model is selected as a stochastic ground motion model, and its match to both elastic and inelastic GMPEs is examined. The novel contribution of the present work is that it develops a computationally efficient approach for providing ground motions that can match any chosen GMPE for any desired set of seismicity characteristics or structural periods. Foundation of the methodology is the development of a metamodel to approximate the median predictions of the ground motion model. This is established by selecting a wide range for the parameters of the model, generating ground motions for each of them, and then calculating the median (over different white‐noise sequences) spectral acceleration for different structural periods. Based on this database, a Kriging metamodel is developed to provide an efficient approximation of the predictions of the ground motion model. This metamodel is subsequently used to efficiently select the predictive relationships that optimize the match to the chosen GMPE. The numerical accuracy of the metamodel predictions is also explicitly incorporated in this optimization. Copyright © 2015 John Wiley & Sons, Ltd.

Recurrent liquefaction-induced failures triggered by 2014 Cephalonia, Greece earthquakes: Spatial distribution and quantitative analysis of liquefaction potential

Two earthquakes occurred on January, 26 and February, 3 2014 of Mw 6.1 and Mw 6.0, respectively, onshore the island of Cephalonia, Greece. The environmental effects e.g. rockfalls, liquefaction and ground cracks triggered by the events were widespread at the western part of the island and mainly in the peninsula of Paliki. The most remarkable characteristics of these two events were the generation of strong ground motion, the highest ever recorded in Greece and the recurrent liquefaction phenomena at the waterfront areas of Lixouri and Argostoli. In addition, the grain size distribution curves of soil samples collected along the seafront area at Lixouri indicated a sandy ejecta and are plotted in the range of possibility of liquefaction defined by Tsuchida (1971).By taking into account the data provided by three post-earthquake field trips that took place immediately after the first and the second earthquake, and the information provided by geotechnical boreholes drilled along the shoreline in Lixouri, a quantitative description of the liquefaction-induced deformations and a preliminary failure mode of the waterfront structures in Lixouri are presented in this study. As an outcome, a post-liquefaction induced settlement of ≈16cm at two sites was computed.

Trade offs between statistical agreement and data reproduction in the generation of synthetic ground motions

This paper discusses a method used to generate synthetic time-series, using a set of 3-dimensional recorded ground motions. The Karhunen–Loève expansion is used to represent the stochastic process, taking into account correlation between the three components of the accelerograms. In this way each accelerogram can be decomposed in a linear combination of a finite number of functions, parameterized by a set of d random variables, d being the number of eigenvalues used to estimate the random process, which will be smaller than the number of recorded accelerograms used to perform the KL expansion. A new synthetic accelerogram can be generated by sampling a new set of d random variables. We study more precisely in this paper several sampling methods and in particular the influence of taking into account dependency between those d random variables. We can see that if no dependency is considered, the new set of ground motions will not have the same statistical properties of the recorded set, which could lead to errors if a statistical analysis is performed with this new synthetic set. On the contrary, due to the so-called curse of dimensionality, if the overall joint density function is used to sample new KL parameters, the method will tend to reproduce each single accelerogram from the recorded set. A new method is discussed, where dependence is considered only in a smaller subspace, which enables us to reach a trade-off between those two objectives. The size of the subspace can then be chosen depending on the application and the user's objectives.

A Computer-Based Environment for Processing and Selection of Seismic Ground Motion Records: OPENSIGNAL

A new computer-based platform has been proposed whose novelty consists in modeling the local site effects of the ground motion propagation using a hybrid approach based on an equivalent linear model. The soil behavior is modeled assuming that both the shear modulus and the damping ratio vary with the shear strain amplitude. So the hysteretic behavior of the soil is described using the shear modulus degradation and damping ratio curves. In addition, another originality of the proposed system architecture consists in the evaluation of the Conditional Mean Spectrum (CMS) on the entire Italian territory automatically, knowing the geographical coordinates. The computer-based platform based on signal processing has been developed using a modular programming approach, to enable the selection and the processing of earthquake ground motion records. The proposed computer-based platform combines in unified environment different features such as: (i) selection of ground motion records using both spectral and waveform matching, (ii) signal processing, (iii) response spectra analysis, (iv) soil response analysis etc. The computer-based platform OPENSIGNAL is freely available for the general public at http://areeweb.polito.it/ricerca/ICRED/Software/OpenSignal.php.

Hazard-consistent ground motions generated with a stochastic fault-rupture model

Conventional seismic probabilistic risk assessments (PRAs) of nuclear power plants consist of probabilistic seismic hazard and fragility curves. Even when earthquake ground-motion time histories are required, they are generated to fit specified response spectra, such as uniform hazard spectra at a specified exceedance probability. These ground motions, however, are not directly linked with seismic-source characteristics.In this context, the authors propose a method based on Monte Carlo simulations to generate a set of input ground-motion time histories to develop an advanced PRA scheme that can explain exceedance probability and the sequence of safety-functional loss in a nuclear power plant. These generated ground motions are consistent with seismic hazard at a reference site, and their seismic-source characteristics can be identified in detail.Ground-motion generation is conducted for a reference site, Oarai in Japan, the location of a hypothetical nuclear power plant. A total of 200 ground motions are generated, ranging from 700 to 1100cm/s2 peak acceleration, which corresponds to a 10−4 to 10−5 annual exceedance frequency. In the ground-motion generation, seismic sources are selected according to their hazard contribution at the site, and Monte Carlo simulations with stochastic parameters for the seismic-source characteristics are then conducted until ground motions with the target peak acceleration are obtained. These ground motions are selected so that they are consistent with the hazard. Approximately 110,000 simulations were required to generate 200 ground motions with these peak accelerations.Deviations of peak ground motion acceleration generated for 1000–1100cm/s2 range from 1.5 to 3.0, where the deviation is evaluated with peak ground motion accelerations generated from the same seismic source. Deviations of 1.0 to 3.0 for stress drops, one of the stochastic parameters of seismic-source characteristics, are required to obtain these acceleration deviations. A similar tendency can be found for some other seismic-source characteristics, meaning that ground motions obtained in this study cannot be generated by simulations of deterministic fault-rupture models with averaged seismic-source characteristics. Generated ground motions incorporate differences between each seismic-source characteristic, and they are effectively available for PRAs of structures.

Damage State Identification and Seismic Fragility Evaluation of the Underground Tunnels

An efficient seismic fragility assessment method is proposed for underground tunnel structures in this paper. The ground response acceleration method for buried structure (GRAMBS), an efficient quasi-static method considering soil-structure interaction (SSI) effect, is used in the proposed approach to estimate the dynamic response behavior of the underground tunnels. In addition, the pushover analyses are conducted to identify the damage states of tunnels and Latin Hypercube sampling technique is used to consider uncertainties in the design variables. A large set of artificially generated ground motions satisfying a design spectrum for specific earthquake intensity are generated and fragility curves are developed. The seismic fragility curves are represented by two-parameter lognormal distribution function and its two parameters, namely the median and log-standard deviation, are estimated using the maximum likelihood estimates method.

Maximum Possible Ground Motion for Linear Structures

This article develops a method to generate ground motion time histories that maximize the response of a given linearly elastic structure. The root mean square (RMS) level of the input power spectral density (PSD) is used as a strong motion parameter. It is related to seismological data that is readily available. An empirical relation to estimate RMS value of the PSD from peak ground acceleration, magnitude, rupture distance, and shear wave velocity is derived from world-wide strong motion data. The ground motion is obtained by solving the inverse problem such that the structural response is maximized under the constraint of fixed value of RMS level of the input PSD enforced using a Lagrange multiplier. The proposed methodology is illustrated for a single-degree of freedom system, a six storey building and an earthen dam. It is shown that the critical PSD obtained in all the cases is a narrow band process resulting in stochastic resonance and not a Dirac-delta function with the entire energy of the system concentrated at its natural frequency. Moreover, the critical excitation samples generated using this critical PSD resembles actual earthquake acceleration time histories.

The effect of seismic uplift on the shell stresses of liquid‐storage tanks

SummaryPrevious theoretical studies have shown that tank uplift, that is, separation of the tank base from the foundation, generally reduces the base shear and the base moment. However, there is a paucity of experimental investigations concerning the effect of uplift on the tank wall stresses, which is the principal parameter that controls the seismic design of liquid‐storage tanks. This paper reports a series of shake table experiments on a polyvinyl chloride model tank containing water. A comparison of the seismic behaviour of the tank with and without anchorage is described. Stochastically generated ground motions, based on a Japanese design spectrum, and three tank aspect ratios (liquid‐height/radius) are considered. Measurements were made of the stresses at the outer shell of the tank, the tank wall acceleration and the horizontal displacement at the top of the tank. While the top displacement and the tank shell acceleration increased when uplift was allowed, axial compressive stresses decreased by between 35% and 64% with tank uplift. The effect of uplift on the hoop stresses was variable depending on the aspect ratio. A comparison of experimental values with a numerical model is provided. Copyright © 2015 John Wiley & Sons, Ltd.