Pseudo-static Analysis Research Articles

Seismic coefficients for pseudo-static analysis of wrap-faced GRS walls with nonlinear soil fills

Pseudo-static seismic design procedure for Geosynthetic Reinforced Soil (GRS) walls includes the selection of a suitable horizontal seismic coefficient for external and internal stability analysis. The present guidelines for the seismic design of GRS walls have been mostly adopted from studies performed on conventional retaining walls. Hence, it is required to study the seismic response of GRS walls. In the present study, a finite element (FE) model of a wrap-faced GRS wall was developed in OpenSees. It was analysed for multiple earthquake time histories to study the variability in earthquake characteristics. The shaking level was also varied from 0.12g to 0.48g to consider the nonlinear response of backfill soil. The acceleration response and dynamic earth pressure increment in the wall were observed to increase with the shaking level but at a lower rate for higher shaking levels. The reinforcement force increments under seismic loading also showed a similar response. The internal failure plane in the GRS wall was slightly inclined, although not completely aligned with Rankine's active failure plane. Seismic coefficients are recommended for wrap-faced GRS walls as a function of PHA. The coefficients were calibrated using the maximum earth pressure and reinforcement forces obtained from FE analysis. The effect of reinforcement stiffness is also incorporated in the recommendation for internal stability analysis. A seismic coefficient greater than PHA is suggested at low shaking levels. It is in direct contrast to many previous studies as the coefficients are calibrated considering the maximum force demand in the GRS wall. Force-based designs need to consider the applicability of maximum earth pressure and reinforcement forces in the GRS wall, which can cause either external or internal instability in the wall. While at higher PHAs, the seismic coefficient should be almost constant to provide reliable estimates of earth pressure and reinforcement forces.

PENGARUH RENCANA PENINGKATAN VOLUME TAMPUNGAN TERHADAP STABILITAS TUBUH BENDUNGAN KEDUNG OMBO

The strategy to meet the water demands of Semarang and Demak Regencies involves enhancing the storage capacity of the Kedung Ombo Dam. This augmentation will inevitably alter the typical water level, thereby affecting the stability of the dam structure as it bears a greater load. Furthermore, the Kedung Ombo Dam, which is nearly 32 years old, necessitates re-evaluation since it lacks the full benefit of contemporary design methods. This study is confined to examining the slope stability, both static and pseudostatic, at a steady state flow, with the highest normal water level elevation (elevation +92.00) as the focal point. The slope stability analysis was conducted via the finite element method using the Slope/W in Geo-Studio software. The outcome of the static slope stability analysis indicates that the safety factor of the Kedung Ombo Dam body remains above the minimum allowable safety factor. In the pseudostatic analysis, the safety factor during the Operating Basic Earthquake (OBE) remains above the minimum allowable safety factor. However, during the Maximum Design Earthquake (MDE), the safety factor demonstrates a value that is lower than the minimum allowable safety factor. Nevertheless, the analysis of fixed displacement or permanent deformation reveals that the maximum settlement that occurs during the MDE earthquake does not exceed 50% of the available freeboard.

Seismic Performance of Self-reset Piers Assembled with External Replaceable Energy Dissipation Rings

In order to improve the shear and energy dissipation capacity, this paper proposes a kind of external replaceable energy dissipation ring segment assembly self-reset pier. The ABAQUS platform is used to simulate the refined model of pier and energy dissipation device. Then the influence of different energy dissipation modes on the seismic performance of bridge piers is studied by pseudo-static analysis. Finally, the influence of different parameters of energy dissipation ring on the seismic behavior of bridge piers is analyzed. The results show that the capacity of shear resistance and energy dissipation of the pier with two energy dissipation lines is significantly higher than that of the pier without energy dissipation devices. Reducing the radius of energy dissipation ring can effectively improve the lateral bearing capacity and cumulative energy dissipation of bridge piers. The thickness of energy dissipation ring has little effect on the seismic performance of bridge piers. Increasing a pair of energy dissipation rings can increase the cumulative energy dissipation of bridge piers by 31.1%. Although the residual displacement of pier top increases, the residual displacement angle is still less than 0.5%.

An Energy-based Overset Finite Element Method for Pseudo-static Structural Analysis

This paper addresses a simple energy-based overset finite element method (EbO-FEM) to solve pseudo-static deformation problems consisting of overlapped meshes based on the domain composition method (DCM). This scheme is a non-iterative equation-based method for enforcing the continuity of the displacement field. Hence, the scheme consumes possible minimal computational costs for deformation problems with non-conforming overlapping meshes. The system’s total energy is augmented with continuity constraint energy (CCE) which is a function of the gaps in the displacement field between two overlapping regions. Subsequently, two conventional integration schemes, the Gauss-point projection, and the point-to-point projection, are utilized to discretize the CCE. It is confirmed that both schemes can yield accurate and unique solutions in the overlapped region of the finite element meshes. Further, we proposed a dimensionless relative penalty parameter (DRP). We found that DRP ranging between 1 to 10 is appropriate to robustly obtain accurate solutions for a wide range of scales, stiffness, and geometries, which is supported by three numerical simulations without increasing computational costs after assembling the global matrices and vectors.

The effect of geological characteristics and earthquakes on natural slope stability analysis in landslide modeling using static and pseudostatic methods in Cianjur Area, West Bandung, Indonesia

The earthquake in Cianjur occurred on Monday, November 21, 2022. The epicenter was in Cugenang Subdistrict, Cianjur District, West Java Province. Cianjur is an area that is susceptible to landslides, which can be triggered by high rainfall and earthquake shocks. The Cianjur earthquake caused collateral hazard landslides that occurred in several locations. Based on the static and pseudo-static analysis, the pseudo-static analysis will provide information on how much the slope safety number decreases when earthquake loads are applied. This study aims (1) to calculate the safety factor value (SF) of slopes under static and pseudo-static conditions to assess the stability of the natural slope and (2) to determine the influence of geological characteristics and the Cianjur earthquake on slope stability analysis in landslides in Cianjur and its surroundings. Slope stability analysis was carried out using static and pseudo-static methods. This research result shows that the condition of the slopes of the study area before the earthquake occurred was in safe condition. The condition of the slopes in the study area experienced a decrease in the safety value of the slope from natural conditions to increased loads or earthquake shaking.

Static and pseudo-static stability analysis of right earthen embankment of nagarjuna sagar dam by geostudio

To ensure the safety of the dam, stability assessment of the dam is necessary. The objective is to perform slope stability analysis for upstream, downstream and seepage analysis during steady state, transient seepage conditions and to know about the displacement occurred at history nodes by the application of pseudo-static ground motion. The present work deals with the behavior of the Right earthen embankment of Nagarjuna Sagar which is in earthquake prone area of Zone-II (as per IS 1893-2002). Stability parameters slope, seepage and earthquake analyzed by SLOPE/W, SEEP/W, QUAKE/W tools in GeoStudio 2022 (finite element modeling based software). The model with full reservoir level is first analyzed by SEEP/W to find piezometric line which is basis to perform SLOPE/W for finding slope stability. Later an earthquake motion of 0.1 peak ground acceleration is subjected to it by using QUAKE/W. It is concluded from results, that obtained factor of safety lie within safety limits and seepage loss observed during the design life of 100 years is 562290 m3, 3431117 m3 for steady state and rapid drawdown.

Geological and geomechanical evidence from the Sünnet landslides (NW Anatolia) for an Mw8.0 cascade rupture in the North Anatolian Fault 8 ky ago

Although the North Anatolian Fault is one of the most investigated continental transform faults across the globe, the maximum earthquake magnitude (Mmax) expected and the resulting seismic risk to the nearby big settlements is still a matter of debate. Some part of the problem issues from the relatively short paleoseismological record of this fault while the rest is closely related to the uncertainties of probable multiple segment ruptures. This study addresses this issue through the investigation of the Sünnet-W landslide in terms of age and dynamic triggering conditions in NW Anatolia where similar large bedrock failures abound. This landslide is a rotational failure with a volume of 5.75 million m3 and developed in the Jurassic-Cretaceous carbonate successions 16 km off the NAF. Radiocarbon dating of the earliest sediments of the associated dam lake upstream yields a calibrated age of 8000 ± 35 yr BP for the landslide formation. Pseudo-static back analysis of the failure based on the pre-slide morphology, strength, and discontinuity density of the bedrock revealed horizontal accelerations of 0.484 g and 0.976 g for the initiation of failure. The steep topography and especially the height of the failed slope imply that a topographic amplification of 1.5 times would be reasonable based on the previous numerical models. Moreover, the paleoclimatological conditions of the time are estimated not to be sufficient for the complete saturation of the deep sliding surface. Even after the consideration of these site-specific encouraging conditions, a threshold magnitude of about 8.0 for the triggering earthquake of the Sünnet-W landslide is suggested. This estimate is at least six times larger than the anticipation of the previous paleoseismological studies (M7.4) from the western part of the NAF. We suggest that the triggering earthquake of the Sünnet landslides 8 ky ago may have been a huge cascade rupture that involves many, if not all, of the segments between Erdek and Niksar along the western and central NAF. This type of multi-segment rupture was previously conceptualized throughout the NAF but remained unexemplified up to date. The present study demonstrates that they should be seriously traced in far-reaching paleoseismological records due to their huge impacts on the seismic hazard of the region.

Nonlinear Seismic Analysis of Ground Structure to Evaluate the Capacity of a Permanent Tunnel Lining

ABSTRACT In this paper, in addition to the linear analysis used for typical tunnels, nonlinear seismic analysis of a tunnel has been investigated using pseudo-static method and a damaged concrete behavior model introduced in ABAQUS® software. The simulations were carried out under three conditions, free field, ovaling and racking, at two hazardous earthquake levels according to an Operation Design Earthquake (ODE) and a Maximum Design Earthquake (MDE). Then, the structural capacity curve and the behavior factor for the final tunnel lining were obtained. In order to extend the studies as well as to verify the pseudo-static analyses, seven nonlinear dynamic analyses compatible with the site under MDE conditions have been performed. The results showed that the tunnel lining procedure created limited tensile cracks under compression. At the bottom corners of the tunnel structure, the resultant stresses in the tunnel lining under two earthquakes caused failure and created tensile cracks. Therefore, it was necessary to reinforce the lining at corners. Comparison between different nonlinear time history seismic analysis and pseudo-static methods indicated that the pseudo-static methods resulted in 10–30% less acceleration than the average results obtained from time history analysis.

Static and seismic design of Dry Stone Retaining Walls (DSRWs) following Eurocode standards

Dry Stone Retaining Walls are structures made of rubble stones assembled without mortar and have been present worldwide for centuries. Today, they still constitute an attractive alternative to building techniques involving higher embodied energy, such as reinforced concrete walls. This study uses a pseudo-static approach to give design recommendations to maintain this built heritage and allow its modern construction. Both non-seismic (Eurocode 7) and seismic (Eurocode 8) cases are addressed. The present work confirms that a seismic design is not critical and is therefore not required for zones with a design acceleration below 0.05g. In addition, this work highlights the significant positive effect of the stone bed inclination and the internal wall face batter. Finally, depending on the wall site conditions and the seismic zone associated with the project, general design recommendations are given to optimise the volume of stones used, which are illustrated in the case of France. These recommendations based on pseudo-static analyses are already usable in practice for low to moderate seismic areas as the required retaining wall dimensions can be easily implemented on-site. In addition, it is also shown that the actual French recommendations for these walls fully comply with Eurocode 7.

Modified pseudo-dynamic based soil-structure interaction of caisson with a novel 3D failure wedge

Passive resistance computation for caissons embedded in layered soil is a complicated problem. In the present study, modified pseudo-dynamic method of analysis has been used to determine both amplification of earthquake waves through the soil strata and the resulting passive earth pressure on the embedded structure. The failure wedge has been idealized based on the results of experimental and numerical studies by previous researchers as log-spiral in vertical plane and oval in the horizontal plane. Earthquake waves are assumed to propagate harmonically in vertically upward direction through layered strata considering modified pseudo-dynamic approach with the entire failure wedge assumed to be lying in a single soil layer. Both, dry and submerged soil conditions, have been considered in the present study. The effect of increase in volume of failure wedge compared to corresponding plane strain condition on earth pressure coefficient has also been discussed in the current study. The earth pressure coefficient due to unit weight component has been reported. The earth pressure coefficient obtained from the current study for structures of different widths are found to be smaller in magnitude than corresponding pseudo-static analysis results.

Mining Induced Ground Motions in a Tailings Dam

Mining induced seismicity can expose tailings dams to ground motions with potential to trigger a failure, if the structure reaches a certain level of vibrations that could exceed the seismic coefficient design criteria from pseudostatic analysis. Despite the cited risk, mainly for dams that are closer to open pits, few dams in Brazil are monitored by microseismic systems, and there are no references in the literature about continuous seismic monitoring both in open pit (source) and tailings dam, which represents the motivation of this paper. A microseismic system was commissioned in Cajati Mine, São Paulo, to record seismic events continuously in an array of 16 geophones (14 Hz and 4.5 Hz), installed in boreholes near the open pit (12 sensors) and in the dam (4 sensors), has measured values of PGA (Peak Ground Acceleration) and PGV (Peak Ground Velocity) related to 2,972 induced events from rock removal in the open pit. During the period monitored, the total of 109 events have triggered sensors in both structures, producing 920 seismograms, with the highest values of PGA and PGV of 0.0135 m/s2 (0.1358% of g) and 0.0892 mm/s. The highest PGA value is 36 times lower than the vertical coefficient of 3% of g defined by Brazilian technical standard to dam design criteria, normally used in common pseudostatic analysis from geotechnical engineers. A routine microseismic monitoring brings a new set of valuable actionable data and information to support the management of geotechnical tailings dams’ risks, under the conditions of vibrations induced by mining production.

Numerical Investigation of the Performance of Segmental CFST Piers with External Energy Dissipators under Lateral Cyclic Loadings.

In order to improve the construction efficiency of piers and reduce the local damage of piers, concrete-filled steel tubes (CFST) are used to precast pier segments. Aiming at the problems of the poor integrity and insufficient energy dissipation capacity of dry joint segmental assembled piers, segmental assembled concrete-filled steel tubular piers with external replaceable energy dissipators are being developed. Based on the low cyclic test of a segmental assembled CFST pier, the finite element numerical simulation model of a CFST pier is established based on ABAQUS software, and the validity of the numerical model is verified by the experimental results. The effects of the section ratio, axial compression ratio, and initial prestress on the seismic performance of piers are studied through a pseudostatic analysis. The results show that an increase in the section ratio can improve the lateral bearing capacity and energy dissipation capacity of the pier. When the section ratio is increased to 4%, the energy dissipation capacity of a CFST pier is increased by 77.8% and the lateral bearing capacity is increased by 33.9% compared with a section ratio of 2%, but the residual displacement of the pier top also increases. With an increase in the axial compression ratio, the energy dissipation capacity of the pier is significantly improved; when the axial compression ratio is increased to 0.30, the energy dissipation capacity of CFST piers is increased by 27.5% compared with a section ratio of 0.05, the residual displacement of the pier top is reduced, and the self-resetting effect of the pier is improved. A change in the initial prestress has no effect on the energy dissipation capacity of piers. Finally, based on an analysis of mechanical theory, a formula of bending capacity suitable for this type of pier is proposed, and the error is within 10%.

Importance of 3D analyses on static and seismic stability of jointed open-pit mine slopes

Most studies on open-pit mine stability have been performed in two-dimensional (2D) mode, which neglects the effect of the circular shape and thus the effect of third-direction boundary conditions. The aim of this work was to study the effect of the third dimension on static and dynamic stability analyses of pit slopes by comparing results from two- and three-dimensional (3D) numerical and limit equilibrium analyses. Geomechanical data from Choghart open-pit mine, located in the seismically active area of central Iran, were considered under a historical earthquake (M = 6.4). Kinematic analyses showed that two tectonic blocks of the mine – BL1 and BL2 – are susceptible to wedge and planar failures, respectively. The 2D and 3D static analyses showed that both blocks are stable, with higher safety factors (SFs) obtained using numerical 3D analyses. In the dynamic analyses, both 2D and 3D analyses showed wedge instability for BL1. However, for BL2, the 2D numerical analyses showed instability whereas the 3D numerical and pseudo-static analyses indicated block stability. The results revealed that the 3D SFs are generally 20–40% greater than those from 2D analyses. This can be explained by the consideration of the third-direction effect, verifying the importance of 3D analyses.

Dynamic p-y analysis method based on cone penetration test results for monopiles in sand

In this study, a CPT-based dynamic p-y analysis method was proposed for the seismic design of piles in sand. The proposed method is aimed at establishing an effective seismic design method for monopiles by directly incorporating in-situ test results into the design process. For this purpose, the continuous and in-situ soil profiling capability of CPT is utilized, which can further enhance the seismic design of monopiles by minimizing uncertainties involved in soil characterization process based on sampling and lab testing procedure. The proposed method was established based on the pseudo-static analysis with the dynamic p-y curve and equivalent static load. The CPT-based p-y curve was formulated as a function of the cone resistance considering damping effect. The load responses of dynamic load test were compared with results obtained from the proposed method and the finite element analysis. It was shown that the proposed CPT-based dynamic p-y method was effective for the seismic design of monopiles.

Probabilistic assessment of seismic response of toe-excavated hillslopes retained using anchored sheet-pile-wall

This paper reports the probabilistic seismic stability analyses conducted for toe-excavated hillslopes, both for unsupported slopes and that retained by anchored sheet pile wall system. Both pseudo-static and nonlinear dynamic analyses are carried out to decipher the seismic response of toe-excavated hillslope. It is found that due to incorporation of uncertainty in the soil parameters or seismic coefficients, slope sections otherwise rendered safe from deterministic analyses can exhibit significant probability of failure. Further study highlights that pseudo-static analysis overestimates the slope failure probability as compared to the nonlinear dynamic analysis. In this study, the probability of failure of the cut slope obtained from the nonlinear analysis (ranges between 21.4% and 70.1%, with a mean Pf value hovering at approximately 45%) is highly overestimated in a pseudostatic analysis, approximately in the tune of 68%. A significant effect of the correlation length characterizing the spatial variation of soil shear strength parameters on the seismic response of toe-excavated slopes is also manifested and reported. The present study shows that a cut slope retained with SPAR system exhibits a very low probability of failure for dimensionless correlation length value up to 0.1 under the cases of dynamic excitation.

Retraction statement: A Comparative Study between Pseudo-static and Dynamic Analyses of Keddara Dam

Retraction statement: This article has been retracted. The above authors were identified and corrected for alleged falsification of research, data fabrication and other misconduct.JAESER editorial team takes the issue of integrity seriously and does not allow any tampering with scientific articles. We apologize for any inconvenience this retraction may cause to JAESER readers.Refers to :We, the Editors and Publisher of Journal of Architectural Environment & Structural Engineering Research, have retracted the following article:Article title: A Comparative Study between Pseudo-static and Dynamic Analysesof Keddara DamAuthor: Manish SharmaJournal: Journal of Architectural Environment & Structural Engineering ResearchBibiliometrics: Volume 5, Number 2, pages 16-24.DOI: https://doi.org/10.30564/jaeser.v5i2.4675

A Study on the Seismic Passive Earth Pressure on Rigid Retaining Walls Considering Seismic Acceleration Field

ABSTRACT The seismic passive earth pressure is typically calculated by a pseudo static analysis by the PGA on the ground surface which is often assumed to be constant within the soil mass. This may result in an underestimation of the limit load. On the other hand, variations of the acceleration field over time and space render the interpretation of the seismic limit load either very difficult, if a complete elasto-plastic solution is sought at each time step, or argumentative. A rather new procedure is presented in this study which considers the variable seismic acceleration field behind a rigid retaining wall during an earthquake and applied to a series of acceleration time histories. The method of stress characteristics is implemented to estimate the limit load at each time step. This method seems to be more convenient with a clear interpretation of the actual limit load. Results indicated that the conventional pseudo static analyses provide an over-conservative estimate or an underestimation of the passive earth pressure.

SLOPE STABILITY ANALYSIS UNDER SEISMIC LOADS (COMPARATIVE BETWEEN NUMERICAL AND TRADITIONAL PSEUDO-STATIC METHODS)

Slopes are the most geotechnical systems that experience kinetic changes due to the development of human activity and its expansion towards the mountainous areas and to many other reasons. It is necessary to understand the mechanism of its collapse, static balance, and degree of kinetic stability to determine the possibility of establishing projects and predicting displacement that can occur during and after construction. For this purpose, the analysis is varied from traditional to numerical methods. GEOSLOPE is an analytical software. However, PLAXIS Dynamic is a numerical one, so those two programs have been used in the pseudo-static analysis based on Terzaghi Model-ignoring the cyclical loadings that could be developed by an earthquake at Al-Madik Castle in Syria, with many case studies. It has been concluded that numerical methods such as PLAXIS software are more accurate, and it is an effective tool in calculating the static and the dynamic stability coefficient, especially with existence of water, or when estimating the slope response at selected points according to seismic time record.

SEISMIC DESIGN OF EMBANKMENTS - NUMERICAL AND ANALYTICAL STUDY

In this paper, a dynamic shear strength analysis was performed in a finite elements environment to evaluate the stability of embankments under seismic loadings. In addition, a dynamic factor of safety depending on the results of the numerical analysis was defined. To study these parameters' effects on the embankment's stability, a parametric study concerning the embankment inclination and the soil type was performed. Finally, the numerical analysis results were compared with the results of the pseudo-static analysis according to the EC8. The results of this study show the significance of the numerical seismic analyses in comparison with the analytical calculations.

RETRACTED:A Comparative Study between Pseudo-static and Dynamic Analyses of Keddara dam

Retraction statement: This article has been retracted. The above authors were identified and corrected for alleged falsification of research, data fabrication and other misconduct.JAESER editorial team takes the issue of integrity seriously and does not allow any tampering with scientific articles. We apologize for any inconvenience this retraction may cause to JAESER readers.