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Operating CMOS circuits at cryogenic temperatures offers advantages of higher mobility, higher ON-current, and better subthreshold characteristics, which can be leveraged to realize high-performance CMOS circuits. However, an ultra-low-voltage operation is necessary to minimize the power consumption and to offset the cooling cost overheads. The MOSFET threshold voltages (Vt) increase at cryogenic temperatures making it challenging to achieve high performance while operating at very low voltage. Ultra-thin body and buried oxide silicon-on-insulator (UTBB-SOI)-based MOSFETs can modulate the transistor threshold voltage using the back-gate bias, unlike conventional FinFETs. This unique UTBB-SOI technology attribute has been leveraged to realize compact pseudo-static storage circuits, namely, embedded dynamic random access memory (DRAM) bitcell and a flip-flop operating at 0.2 V and 77 K. This article presents UTBB-SOI device fabrication details and calibrate experimental device characteristics with BSIM compact models. SPICE simulations suggest the feasibility of three-transistor gain-cell embedded DRAM (eDRAM) capable of reliably storing three distinct voltage levels (1.5 bits/cell) and exhibiting retention time of the order of 104 s. Furthermore, a unique pseudo-static flip-flop design is presented, which can lower the clock power by 50%, transistor count by 20%, and static power consumption by 20%.

An efficient and accurate reliability-based design of the geosynthetic-reinforced slopes (GRS) using the pseudo-static and modified pseudo-dynamic framework is proposed in the present study. Deterministic formulation used in the present study is made robust with the help of nonlinear constrained optimization. The collocation based stochastic response surface method (CSRSM) is used to probabilistically analyze the GRS. The critical modes of failure pertaining to the internal and external stability of the GRS are considered in the formation of the performance functions. The horizontal seismic acceleration coefficient (kh), internal friction angle of soil (φ), soil unit weight (γ), shear wave velocity (Vs), and friction angle at the interface between soil and reinforcement (φb) are chosen as the random variables, owing to their high influence on the stability of the GRS. The influence of correlation on the stability of the reinforced slope is illustrated considering the internal and external stability. System reliability analysis considering the internal and external modes of failure is also performed. An illustrative example is presented showing the steps to design a GRS using the proposed formulation. The results confirm the necessity of performing the system reliability analysis to estimate an accurate value of probability of failure of GRS.

In this paper, the limit equilibrium method with the pseudo-static approach is developed in the evaluation of the influence of slope on the bearing capacity of a shallow foundation. Particle swarm optimisation (PSO) technique is applied to optimise the solution. Minimum bearing capacity coefficients of shallow foundation near slopes are presented in the form of a design table for practical use in geotechnical engineering. It has been shown that the seismic bearing capacity coefficients reduce considerably with an increase in seismic coefficient. Be sides, the magnitude of bearing capacity coefficients decreases further with an increase in slope inclination.

This study investigates the response of pre-stressed anchored excavation walls under dynamic and pseudo-static loadings. A finite difference numerical model was developed using FLAC2D, and the results were successfully validated against full-scale experimental data. Analyses were performed on 10, and 20-m-height stabilized excavated slopes with 60° to 90° of inclination angle with the horizon to represent an applicable variety of wall geometries. In dynamic analysis, the statically stabilized models were subjected to 0.2 to 0.6g of the dynamic peak acceleration to evaluate the effect of ground acceleration on their performance. Furthermore, pseudo-static analyses were performed on the statically stabilized models with pseudo-static coefficients ranging from 0.06 to 0.22. The results revealed that ground anchored slopes generally showed acceptable performances under dynamic loading, while higher axial forces were induced to ground anchors in higher and steeper models. Furthermore, comparing the results of dynamic and pseudo-static analyses showed a good agreement between the two methods' predictions in the mobilized axial force along the ground anchors. Pseudo-static coefficients were then proposed to replicate dynamic results, considering the slope geometry and dynamic load peak acceleration. The results revealed that higher and steeper stabilized slopes required higher values of pseudo-static coefficients to match the dynamic predictions successfully. The results indicate that pseudo-static coefficient tend to increase with the increase in dynamic load peak acceleration in any given model. Doi: 10.28991/cej-2021-03091703 Full Text: PDF

The use of geosynthetic reinforcement to enhance the ultimate load-bearing capacity and reduce the anticipated settlement of the shallow foundation has gained sufficient attention in the geotechnical field. The improved performance of the shallow foundation is achieved by providing one or more layers of geosynthetics below the foundation. The full wraparound technique proved to be efficient for the confinement of soil mass and reduction in settlement of foundation however lacks the literature to ascertain the performances of such footing under dynamic loading. In view of the above, the present study examines the effect of geosynthetic layers having a finite length with full wraparound ends as a reinforcement layer, placed horizontally at a suitable depth below the foundation using the finite element modeling (FEM) and evaluates the ultimate load-bearing capacity of a strip footing resting on loose and dense coarse-grained earth beds under seismic loading and further compared to those of footing resting on unreinforced earth bed. Moreover, the effect of horizontal seismic acceleration coefficient (kh) on the ultimate load-bearing capacity has been investigated by varying kh from 0.1 to 0.6 at an interval of 0.1, for both reinforced and unreinforced earth bed having loose and dense soil strata. Furthermore, this study demonstrates that by adopting the new practice of using the geosynthetic reinforcement with the full wraparound ends in foundations, it is possible to support relatively heavier structures under static as well as dynamic loading without allowing large footing settlements. From the outcomes of the present study, it is noted that the ultimate load-bearing capacity of footing resting on loose and dense sand bed found to be improved by 60% and 18% for soils having friction angle of 25° and 40°, respectively compared to respective unreinforced earth beds under static condition.

Based on investigation of rural buildings in china, there are more than 20% of the masonry structures constructed in 1970s. Thus, the old blue bricks (OBB) and old red bricks (ORB), which demolished from the typical brick masonry structures was built in 1970s, was chosen in the test. During demolishing the OBB and ORB, the original mortar was destroyed. Thus, the 1:7.8 cement mortar was chosen instead of original mortars and the 1:5 cement mortar was chosen as the reinforcement mortar. In order to know the performant of the reinforcement methods, there are three-level test plan was put forward in the study. Firstly, the mechanical properties of OBB and ORB and mortars was tested; Secondly, the experiment tested the shear strength of the reinforced and unreinforced masonry specimens along mortar joints; Thirdly, there are four walls (OBB reinforced wall and unreinforced wall, ORB reinforced wall and unreinforced wall) have been made for the pseudo-static tests. This research conducted physical performance tests on masonry bricks, masonry components, and masonry walls of typical masonry structures. Through experiments, the shear capacity of the masonry structure reinforced by high-strength mortar and steel bars can be obtained.

Metal magnetic memory (MMM) testing is a nondestructive approach for evaluating the stress concentration and early damage of ferromagnetic components. However, research on the MMM testing of large steel structures has been limited. Thus, this study investigates the suitability of MMM technology for monitoring the damage in steel structures exposed to complex stresses. The normal components of magnetic signals Hp(y) on the beams and columns of a portal frame are obtained through pseudo-static testing. The signal increment ΔHp(y) and its absolute value |ΔHp(y)| under different loads are analyzed. The relationship between the equivalent stress and magnetic signal is investigated through numerical simulation. The results show that the ΔHp(y) curves are similar during the elastic stage but change abruptly during the plastic phase. Moreover, the differences in the magnetic signal directions caused by the varying detection directions cannot be ignored. In the elastic stage, with the increase in the load, |ΔHp(y)| curves initially increase and then decrease. The formation of the ΔHp(y) curve is similar to the distribution of the equivalent stress. The mutation of ΔHp(y) can determine whether a specimen is entering the plastic phase, and can warn against structural failure. The magnetic signal distribution qualitatively reflects the stress distribution.

The present research details the remote sensing, geotechnical and seismic aspects of hill slopes in Lower Tons river valley, Garhwal Himalaya, India. The region is a part of Lesser Himalaya and holds religious and strategic importance. The studied span has been a site of slope failures in the past. The remote sensing investigation was used to characterize the geomorphological and hydrological attributes of the area. This information was used to delineate vulnerable locations. Along the road stretch of about 80 km, 80 tests were conducted to ascertain the soil particle distribution and plasticity indices; and 33 tests for shear strength properties. Using the geotechnical parameters, numerical simulation was conducted for two slopes of angle, 40° and 50°, with a consistent height of 50 m. Most of the slopes were stable at an angle of 40°, however, 30.30% (FEM) and 24.24% (FDM) of the analysed slopes failed for the steeper slope. Eventually, the pseudo-static analysis was done. The inclusion of seismicity increased the incidences of slope failure by 33.33% and 39.39% for the slope with an inclination of 40° and 50°, respectively. Afterwards, the slopes were optimized for their critical angle as a function of the safety factor.

Based on the nonlinear Barton-Bandis (B–B) failure criterion, this study considers the system reliability of rock wedge stability under the pseudo-static seismic load. The failure probability (Pf) of the system is calculated based on the Monte–Carlo method when considering parameter correlation and variability. Parameter analysis and sensitivity analysis are carried out to explore the influence of parameters on reliability. The relationships among the failure probability, safety factor (Fs), and variation coefficient are explored, and then stability probability curves of the rock wedge under the pseudo-static seismic load are drawn. The results show that the parameter correlation of the B–B failure criterion has a significant influence on the failure probability, but correlation increases system reliability or decreases system reliability affected by other parameters. Under the pseudo-static seismic action, sliding on both planes is the main failure mode of wedge system. In addition, the parameters with relatively high sensitivity are two angles related to the joint dip. When the coefficient of variation is consistent, the probability of system failure is a function of the safety factor.

Anchored retaining walls are structures designed to support different loading applied in static and dynamic cases. The purpose of this work is to design and study the stability of an anchored retaining wall loaded with different seismic actions to obtain minimal anchor lengths. Mononobe-Okabe theory has been applied for the evaluation of seismic earth pressures developed behind the anchored wall. Checking the dynamic stability of anchored retaining walls is usually done using the classic Kranz model. To take into consideration the effects of the internal forces developed during failure, we have proposed a new model, based on the Kranz model, which will be used as the Kranz model to find the critical angle failure performed iteratively until the required horizontal anchor length is reached for a minimum safety factor. The results of this study confirm that the effect of the seismic load on the design of an anchored retaining wall, and its stability, has a considerable influence on the estimation of anchor lengths. To validate the modifications made to the new model, a numerical analysis was carried out using the Plaxis 2D software. The interpretation of the obtained results may provide more detailed explanation on the effect of seismic intensities for the design of anchored retaining walls.

Using vertical skirts as soil reinforcement in conjunction with strip footing can increase the bearing capacity of a footing located near a cohesionless slope. This paper adopted lower and upper bo...

The lateral pressure generated by liquefied soil on pile is a critical parameter in the analysis of soil-pile interaction in liquefaction-susceptible sites. Previous studies have shown that liquefied sand behaves like a non-Newton fluid, and its effect on piles has rate-dependent properties. In this study, a simplified pseudo-static method for liquefiable soil-pile interaction analysis is proposed by treating the liquefied soil as a thixotropic fluid, which considers the rate-dependent behavior. The viscous shear force generated by the relative movement between the viscous fluid (whose viscosity coefficient varies with excess pore pressure and shear strain rate) and the pile was assumed to be the lateral load on the pile. The results from the simplified analysis show that the distribution of bending moment is in good agreement with experiments data. Besides, the effects of various parameters, including relative density, thickness ratio of non-liquefiable layer to liquefiable layer, and frequency of input ground motion, on the pile-soil rate-dependent interaction were discussed in detail.

One of the major reasons for the popularity of reinforced soil structures is their ability to perform better under seismic loading conditions. This could be attributed to the conservatism associated with the design procedure that considers only the axial direction of the pullout force rather than an appropriate seismic design. The kinematics of failure, however, suggests that the direction of the pullout force is not axial, and it is inclined to the horizontal direction. This paper presents the pseudo-static stability analysis of a reinforced soil wall considering the obliquity of the pullout force, where the backfill soil is idealized as a two-parameter Pasternak model. The effect of various controlling parameters such as horizontal seismic coefficient, material properties of the backfill and the wall geometry on the pullout response is also studied under the seismic loading conditions. The results are compared with the conventional methods of analysis. The comparisons show that the present analysis removes the extra degree of conservatism prevailing in the conventional methods and thus gives a better estimation of the pullout capacity. A typical design of reinforced soil wall is also shown to demonstrate that the present analysis can be easily integrated with the existing methods.

This paper investigated the effect of the anisotropy of the internal friction angle on the seismic bearing capacity factor of shallow foundations placed over a frictional soil deposit with the adop...

Accordance with a new EN 1992 the robustness of the structural systems must be analyzed. When applying proposed new strategy, it has been verified that the structure has sufficient redundancy and possibility to mobilize so-called alternate load path (AP-method). Paper presents a modified complex method for robustness estimation in case of the RC-structural systems. Proposed pseudo-static method based on the energy-saving approach. Paper also presents a full probabilistic pseudo-static nonlinear method which was developed for structural robustness assessment, taking into account the statistical variability of the materials properties and, as a consequence, parameters of the plastic hinges and possible failure modes.

Determination of optimum distance between twin tunnels is very important to reduce the construction’s costs in road or railway projects. When two tunnels are located close together, stress concentration in their space increases and it is possible that plastic zones would be merged. In mining engineering and especially underground mining applications, this zone (the distance between twin tunnels) is called pillar and there are some empirical models to estimate its width. However, these models are not completely suitable for all rock types and different tunnel geometries. In this study, an attempt was made to present a new criterion for the design of twin tunnels. It is based on ground reaction curve and takes width to height ratio (w/h) and shear strain of the pillar (obtained by numerical modeling) into consideration. Strain magnitude observed when normal stress (σ1) in the pillar reaches the value of compressive strength of the rock mass (σcm), denotes the allowable ratio of width to height (w/h) which shows the optimum distance between twin tunnels. Pooneh twin tunnels which located in Iran were selected as a case study. These are road twin tunnels excavated in layers of nine different zones (Arak–Khoramabad Expressway). Results of the suggested method show a good agreement between the pillar dimensions seen in the case study and the present method. Taking all aspects of geomechanical and geometrical characteristics of the tunnels into consideration, it is one of the main advantages of this method.

The selection of the appropriate horizontal seismic coefficient (kh) considering the actual conditions governing earth structures is the foremost part of analysis in the pseudo-static approach. In ...

The concept of the spectral pseudo-static procedure has been developed at the Université de Sherbrooke as an alternative to the conventional pseudo-static approach for the seismic stability analysis of clayey slopes. The destabilizing effect of an earthquake is approximated, in the new approach, by an inertial force that hyperbolically varies with depth while being proportional to the maximum acceleration of the seismic event. Its results have been rigorously verified against available static and dynamic laboratory tests, and have been extensively validated by a series of simulations performed using the computer code FLAC. Good agreements have been achieved between the results of the spectral pseudo-static procedure and complete numerical analyses, in terms of the computed safety factors and the critical slip surfaces. This implies that the spectral pseudo-static approach can be integrated into available limit equilibrium (LE) software providing a useful tool to examine the effect of dynamic soil characteristics on the proposed seismic coefficient profiles. The herein-reported study extends the previous endeavors to examine and quantify the effect of plasticity index (PI) (0%, 15%, 30%, 50%, and 100%) on the proposed formula of seismic coefficient profile using the same numerical modelling and assumptions. Original analyses were carried out considering earthquakes compatible with the seismicity of Quebec City (zone 4), and they have been repeated in the current study for earthquakes compatible with other regions having different seismicity (zones 2, 3, and 5). Based on the results of the current analyses, side-formulas were established between the spectral pseudo-static coefficient on ground surface for any value of soil plasticity index (PI) and the corresponding coefficient originally used in the main formula (PI = 30%).

By application of the limit equilibrium method associated with Coulomb failure mechanism, the effect of variation of undrained shear strength with depth on seismic bearing capacity was eval...

In this study, the well-established pseudo-static approach along with the horizontal slices method (HSM) is employed to investigate the seismic internal stability of geosynthetic-reinforced earth slopes. Previous simple HSM analyses were based on a primary assumption stating that the normal inter-slice forces are exerted on the mid-length of horizontal sections. However, this simplifying assumption could give rise to substantial errors in the calculation of design parameters, specifically in the case of high seismic excitations or low soil strength parameters. To address this deficiency, a balancing moment is considered as a new variable to account for the corresponding eccentricity. In the current HSM, two sets of unknown variables, including horizontal inter-slice forces and shear forces along failure surface, are determined using the well-known λ coefficient and the Mohr-Coulomb failure criterion. In this new technique, the traditional ‘5N-1ʹ type of HSM analysis is reduced to a robust and rigorous ‘3N’ one with the same predictive capability. The influence of various parameters, including soil characteristics, slope geometry and different earthquake coefficients are rigorously examined. Moreover, a number of useful graphs is provided to help engineers in the preliminary seismic design of geosynthetic-reinforced earth slopes.

Ecuador is exposed to seismic events, which cause a reduction in soil resistance due to vibration loads and their effect is the landslide. This work analyzes the stability of the soil slopes that are located on the abscissa 25 + 280 and 63 + 040 of the Garrapata - Santa Maria road located between the Chone and El Carmen cantons of the Manabi province, through the determination of the safety factor using the GeoSlope software, performing a dynamic and pseudo-static analysis, to observe the variations that exist when applying horizontal forces (Kh). In addition, the comparison of the Fellenius, Bishop, Janbu and Morgenstern-Price limit equilibrium methods was carried out based on the SPT results, which allowed classifying the soil strata. The results of the triaxial test determined the geotechnical parameters such as cohesion and friction angle.

In the previous chapter we discussed ways how to characterize DML cells into several libraries and use these with standard EDA tools. In this chapter we outline an optimized synthesis procedure for DML design. In a nutshell, this methodology involves changing certain steps within the tools. We present an algorithm for DML-optimized synthesis and show the implementation of this algorithm in Perl language. The synthesis results indicate that while this approach still has a significant room for improvement, it can boost performance gains and reduce the energy consumption of a design.

Pseudo-static approaches often become handy due to their simplicity compared to the complex coupled continuum dynamic analysis and yield satisfactory results. A pseudo-static approach is employed herein to evaluate the response of a pile-supported structure located in a highly active seismic zone in northeast India. Pseudo-static approach essentially involves two main steps: estimation of maximum ground deformations and surface accelerations from a free field ground response study, combined with static analysis considering the surface acceleration and superstructure mass. In the present study, dynamic behavior of underlying soil strata was investigated using two high-quality element testing techniques—resonant column and dynamic simple shear tests. The dynamic soil properties were established and site-specific ground response study was conducted for the chosen site, using the artificially generated ground motions for the region. Equivalent static load was estimated from the surface acceleration obtained from free field ground response study. A three-dimensional finite element model has been developed and validated against the field lateral load test results. An increased magnitude of displacement and bending moment was observed with increased ground motion intensity. The peak bending moments induced for the scenario ground motions is higher than the plastic moment capacity of the pile section, displaying the probable failure of considered pile-supported structure.

New Delhi is a city affected by near/far-field earthquakes, where underground metro construction activities have been undertaken since the early 2000s. Due to the seismic effects, these structures are designed by conventional force/displacement methods. The present study validates the efficacy of these methods, numerically. For this, varying geotechnical conditions in static and seismic cases were quantified with the expected ground motion. Bored tunnels at different cover depths were modeled in 2D and 3D, to ascertain the static response of these structures, followed by a true dynamic analysis. It was found that conventional design procedures using force methods gave conservative estimates for increments on the tunnel liner. Also, the importance of a full dynamic analysis could not be ignored because (i) higher surface spectral responses were found at the tunnel pillar location and (ii) the cumulative strains on the tunnel liner were found to exceed permissible limits.

The pseudo-static approach has been conventionally applied for the design of gravity type quay walls. In this method, the seismic coefficient (kh), expressed in terms of acceleration due to gravity, is used to convert the real dynamic behavior to an equivalent pseudo-static inertial force for seismic analysis and design. The existing kh is simply defined as the expected peak ground acceleration (PGA) of the ground divided by the gravitational acceleration (g), which does not sufficiently reflect the real dynamic behavior. In order to improve the kh definition, a number of studies have been performed for reducing the differences between pseudo-static and true dynamic behavior. In this regard, questions regarding the need for considering the effect of frequency characteristics of input earthquake, natural period of the backfill soil and the subsoil underneath the wall, and wall height on the deformation of quay wall crown (Dh) have been explored. In this study, dynamic centrifuge tests were conducted using the gravity type quay wall models designed with a kh value of 0.13 to assess the behavior of the model wall during earthquakes. Three different variables: input earthquake motions, wall heights and the thickness of subsoil underneath the wall were considered, and the test results were compared and analyzed to assess the validity of the conventional kh concept under these conditions. In addition, some improvements that should be considered for the future revision of the kh definition are discussed.

In this paper, the horizontal slice method (HSM) is employed to examine the stability of reinforced soil slopes. In this method, the soil mass is divided into a series of horizontal slices, and then the stability of each slice is examined. Unlike the previous studies, the formulation presented in this paper is able to analyse any type of the sliding surface. In addition to the log-spiral slip surface, the general slip surface is also examined. The genetic algorithm (GA) optimization method is employed to find the critical slip surface. Furthermore, the distribution of reinforcements along the depth is assumed to be uniform or non-uniform. Seismic effect is considered through the pseudo-static method. The HSM is implemented through a computer program written in MATLAB. After solving the problem, the critical slip surface, the amount of force and the length of reinforcements for the purpose of slope stabilization are obtained. Finally, the results are compared with other studies. These comparisons indicate that the method presented in this paper provides accurate results. The results also demonstrate that the general sliding surface is more critical than log-spiral sliding surface, thus leading to a larger amount of required reinforcement.

Well foundation is commonly used in India for road and railway bridges over rivers. It is a massive structure and hence it is generally considered to be safe under laterally loaded condition. Indian Roads Congress Codes (IRC:45-1972 and IRC:78-1983) suggests limit equilibrium approach to determine lateral load capacity of well foundation. It considers well foundation as a rigid body and surrounding soils as elastic in design state and plastic in limit state. Design procedure stated in Indian standard codes determines ultimate lateral load capacity of Well-Soil system. However, it does not yield the magnitude of lateral displacement of a well foundation at the ultimate load. Because of this, it is difficult to decide whether the lateral displacement at estimated ultimate lateral load capacity of a well foundation is allowable or not. Over the years, few methods to analyze the lateral response (both force and displacement responses) of well foundation are developed. These methods consider surrounding soil as linear elastic material which is modeled by linear elastic springs, and well foundation as a rigid body. Recently developed methods consider lateral stiffness as well as rotational stiffness of the surrounding soil and represent soil by parallel combination of lateral linear springs and rotational springs. Some of these methods also consider flexibility of well foundation and model well foundation by Euler-Bernoulli beam element. In this article, we present a comparative study of the available methods of analysis of laterally loaded well foundation. This study indicates significant differences in the response of Well-Soil system obtained from different methods. Validation of existing methods is done with two-dimensional continuum model to identify accuracy in existing models. It highlights the need for proper evaluation of available methods of analysis with realistic incorporation of foundation stiffness and interface effect in modeling the Well-Soil system for pseudo static loading conditions.

Approaches commonly used to assess the seismic stability of slopes range from the relatively simple pseudo-static method to more complicated nonlinear numerical methods, e.g., finite element (FE) and finite difference (FD). The pseudo-static method, in particular, is widely used in practice as it is inexpensive and substantially less time consuming compared to the much more rigorous numerical methods. However, the pseudo-static method is widely criticized because it does not take into account the effects of the earthquake on the shear strength of the slope material nor the seismic response of the slope. Hence, some researchers recommend its use only in slopes composed of cohesive materials that do not develop significant pore pressures or that lose less than about 15% of their peak shear strength during earthquake shaking. However, the use of the pseudo-static method in these soils is also problematic as clayey slopes generally fail in pseudo-static stability analyses (i.e., factors of safety are less than 1) and the failure surface is completely predominated by the thickness of the clayey layer in the slope or foundation. The reliability of the pseudo-static method in natural clayey slopes is examined here based on rigorous numerical simulations with FLAC. The numerical results are compared and verified using available static and dynamic 1g laboratory tests. This article then addresses some of the crude assumptions of the pseudo-static method and provides practical suggestions to be applied to refine the outcomes of pseudo-static analyses not only in terms of the computed safety factors, but also in the prediction of the failure surface through the consideration of additional aspects of the dynamic responses of the clayey slopes.

International audience; Dry stone retaining walls (DSRWs) are vernacular structures which can be found all over the world. Most of them have been built in the 19 th century but they can be as old as two hundred years. Because of decades of neglect, many of these walls are highly damaged; however, in the absence of national rules for this peculiar heritage, any intervention on these constructions is made difficult. A number of former studies in France have tried to settle the bases for a standard aimed at designing slope DSRWs. This paper complement those works in order to give clues for a seismic design of slope DSRWs following the simplified approach proposed by the Eurocode 8 and denoted pseudo-static approach. Firstly, scaled-down experiments have been carried out using a mock-up composed of a wall made of clay bricks retaining a sandy backfill. This mock-up was then tilted and the characteristics of the system at failure were reported and analysed. A particularity of failure in DSRWs is that the failure surface crosses the wall leaving a part of it intact. Secondly, an analytic method based on the limit equilibrium using the Coulomb wedge theory has been designed to predict the tilting angle and validated on the basis of these experimental results. Finally, some preliminary implications for the seismic design of DSRWs have been proposed for walls built in moderate seismicity areas which is typical of mainland France. In low seismicity zones, the extra width required to bear the seismic motion does not exceed 25% of the width identified through the static design. Results are also given for more critical cases associated to zones of higher seismicity as well as for different wall configurations.

Existing ancient Chinese timber buildings are frequently subjected to seismic or strong wind loads throughout their lifetime, hence their lateral structural performance can undergo significant changes. It is essential to employ tests in the laboratory to study these variations to protect these existing timber buildings. In this paper, a single-layer model of a timber building with a geometrical ratio of 1:2 was fabricated according to the pre-Ming dynasty construction method. Six pseudo-static tests were conducted under three levels of vertical loads. The timber structure displayed visible rocking characteristics during the tests, and the column feet and mortise-tenon joints were the weak links in the structure. The features of hysteresis curves, envelope curves, strength reduction, energy dissipation, and lateral stiffness of the timber structure were obtained, and their variations associated with loading courses were discussed. Moreover, a simplified restoring force model was built for this type of timber structure.

Although deformation along a weak joint under a strong seismic event can seriously damage the tunnel, the effect of joint has not yet been well understood or quantified. We perform a series of pseudo-static discrete element analyses to evaluate the effect of deformation along rock joint on the seismic response of circular tunnels. We also perform parallel continuum analyses to compare and quantify their differences. A comprehensive set of joint parameters are considered in this study. The results illustrate that the joint significantly increases the moment demand in the tunnel lining, whereas it has a secondary influence on the thrust. The joint stiffness and shear strength have critical influence on the tunnel response. Widely spaced joint set produces a larger tunnel response. The tunnel response is highest for vertical and horizontal joints, and the lowest when the joint dips at an angle of 45°. The moment in jointed rock may be 20 times higher than that in intact rock. The pronounced deviation from continuum analyses highlights the need to estimate the influence of discontinuities on the seismic response of underground tunnels from discrete element analyses. This may be of concern for critical structures such as nuclear facilities.

Earthquake-induced landslide databases indicate that failure modes, observed in the field following earthquakes, include sliding, toppling, and slumping. Methods based on simplified, discrete, single block models are limited to rectangular blocks on a plane or wedge blocks that restrict the potential failure modes to sliding or toppling. This paper expands the geometry assumptions so that additional failure modes will be kinematically admissible. A simple, yet broadly applicable, two-dimensional (2D) single block framework is introduced that does not restrict the geometry to orthogonal fracture sets . This framework allows for the slumping failure mode to naturally occur and can identify a new failure mode, confined toppling. Using simple failure mode charts, this framework can be easily applied to a wide range of analysis and design applications. In addition to the identification of new failure modes, seismic yield acceleration equations are presented for all four modes of failure: sliding, toppling, slumping, and confined toppling. The equations for slumping and confined toppling are derived for the first time. Although the model may be simple in its formulation and implementation, it is quite powerful, allowing for significant implications to be developed. Complex shaped blocks can be easily evaluated knowing just their centers of mass and contact points with supporting fractures. The failure mode of a discrete rock block is shown to be independent of the primary fracture inclination on which the block rests upon and the scale of the block itself. Seismic failure modes are demonstrated to be different from those induced by static forces alone and can even change modes depending on the amount of displacement during the ground motion. In addition, it is shown that the characteristics of an earthquake ground motion acting on these blocks in combination with geometric variability can influence the abundance of failure types observed in the field. Finally, an example mode and yield acceleration evaluation of Alaskan rock slope is presented.

The seismic earth pressure problem is considered for the special case of a vertical wall with horizontal backfill. Using upper and lower bound finite element limit analysis, earth pressure coefficients are derived for a range of seismic coefficients and soil-wall interface friction angles. The coefficients presented have a verifiable error of at most ± 1 % . Finally, the earth pressure coefficients are applied in a limit equilibrium framework to the design of various embedded retaining structures. For the resulting designs, factors of safety are computed using upper and lower bound strength reduction finite element analysis and it is concluded that the limit equilibrium approach, using the new earth pressure coefficients, is fairly accurate, albeit slightly unconservative.

Calculation of permanent seismic displacement of reinforced soil slopes plays a very important role in proper and optimal design of these structures in earthquake-prone regions. In the Newmark’s sl...

The static and dynamic performances of historical masonry churches are closely related to the behaviour of each substructure, as well as to the mechanical properties of the constituent materials. Information on damage location and extent, collected after recent violent Italian earthquakes, highlighted that masonry vaults are among the most vulnerable elements. The investigation of their dynamic behaviour under earthquake excitation (stress and deformation states) is a fundamental issue for effective structural interventions. During an earthquake ground motion, cross vaults are basically subjected to two phenomena: (i) the "shaking"/dynamic response of the vault system itself, vibrating above the lateral walls and piers, and (ii) the response of the vault to imposed displacements at its springings, accommodating the significant movements of the lateral walls and piers. Within this context, this paper aims at improving the knowledge of the structural behaviour of cross vaults under static shear deformation at the springings, by means of an experimental test representative of a Gothic cross vault from the aisle of the Holyrood Abbey in Edinburgh (UK). The experimental test was performed on a 1:4 scaled specimen built with timber and lime mortar. The shear displacement was applied by moving two abutments until failure. The deformation of the vault was recorded in space with a Total Station. The results of the tests are reported in this paper in terms of crack pattern evolution, vertical displacements of the transverse ridge, identifying the shear displacement levels corresponding to significant damages in the vault.

The nonlinear response of K8 pattern single-layer reticulated domes of different rise-span ratios under vertical rare earthquakes are analyzed by using the dynamic time-history analysis method and the pseudo static elasto-plastic analysis method. Comparison of these analysis results indicates that the structural members would be in different plastic deformation states under vertical rare earthquakes because of different rise-span ratios. The analysis results of the dynamic time-history method indicate that the vertical displacement response decreases with the increase of the rise-span ratio in condition of the same member section. Through the comparison the analytical results of pseudo static elasto-plastic analysis with the analytical results of dynamic time-history analysis, it is found that the difference of plastic members and region and error of the vertical displacement response, which may be a reference for future vertical seismic study of single-layer reticulated domes.