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1.
The earthquake response of cantilever retaining walls is explored by means of theoretical analyses and shaking table testing conducted at University of Bristol (EERC - EQUALS). The theoretical investigations employ both limit analysis and wave-propagation methods, which take into account different aspects of the problem such as inertia, strength, kinematics and compatibility of deformations. The experimental programme encompasses different combinations of retaining wall geometries, soil configurations and input ground motions. The response analysis of the systems at hand aims at shedding light onto salient features of the problem, such as: (1) the magnitude of soil thrust and its point of application; (2) the relative sliding versus rocking of the wall base and the corresponding failure modes; (3) the importance of the interplay between soil stiffness, wall dimensions and excitation characteristics, as affecting the above; (4) the importance of wall dynamics and phase differences between peak stresses and displacements. The results of the experimental investigations are in good agreement with the theoretical models and provide a better understanding on the complex mechanics of the problem. 相似文献
2.
In hilly regions, retaining walls along roads, motorways and railway lines are numerous. In some cases the knowledge of the details of the construction is limited. If rehabilitation work becomes necessary, a detailed knowledge of the construction is desirable for the improved planning of maintenance and repair. This paper describes the application of Ground Penetrating Radar (GPR) for the inspection of retaining walls. The work was carried out in two steps. First, an investigation was carried out on large retaining walls at a Swiss motorway within the framework of a service contract. This included the development of an apparatus enabling high precision positioning of the antennas on the walls. Second, a pilot study was performed on a smaller wall with optimized acquisition and processing parameters. This included the use of antennas with different orientations and the fusion of the two corresponding datasets as well as true 3-D data processing. This paper describes the approaches to data acquisition and processing in the form of the two case studies. Results from different acquisition and processing strategies are compared and the benefits and limits are discussed. 相似文献
3.
P.N. Psarropoulos G. Klonaris G. Gazetas 《Soil Dynamics and Earthquake Engineering》2005,25(7-10):795-809
While limiting-equilibrium Mononobe–Okabe type solutions are still widely used in designing rigid gravity and flexible cantilever retaining walls against earthquakes, elasticity-based solutions have been given a new impetus following the analytical work of Veletsos and Younan [23]. The present paper develops a more general finite-element method of solution, the results of which are shown to be in agreement with the available analytical results for the distribution of dynamic earth pressures on rigid and flexible walls. The method is then employed to further investigate parametrically the effects of flexural wall rigidity and the rocking base compliance. Both homogeneous and inhomogeneous retained soil is considered, while a second soil layer is introduced as the foundation of the retaining system. The results confirm the approximate convergence between Mononobe–Okabe and elasticity-based solutions for structurally or rotationally flexible walls. At the same time they show the beneficial effect of soil inhomogeneity and that wave propagation in the underlying foundation layer may have an effect that cannot be simply accounted for with an appropriate rocking spring at the base. 相似文献
4.
Observations from recent earthquakes show that retaining structures with non-liquefiable backfills perform extremely well; in fact, damage or failures related to seismic earth pressures are rare. The seismic response of a 6-m-high braced basement and a 6-m free-standing cantilever wall retaining a compacted low plasticity clay was studied in a series of centrifuge tests. The models were built at a 1/36 scale and instrumented with accelerometers, strain gages and pressure sensors to monitor their response. The experimental data show that the seismic earth pressure on walls increases linearly with the free-field PGA and that the earth pressures increase approximately linearly with depth, where the resultant acts near 0.33 H above the footing as opposed to 0.5–0.6 H, which is suggested by most current design methods. The current data suggest that traditional limit equilibrium methods yield overly conservative earth pressures in areas with ground accelerations up to 0.4g. 相似文献
5.
The dynamic response of an elastic continuously nonhomogeneous soil layer over bedrock retained by a pair of rigid cantilever walls to a horizontal seismic motion and the associated seismic pressure acting on these walls are determined analytically–numerically. The soil non-homogeneity is described by a shear modulus increasing nonlinearly with depth. The problem is solved in the frequency domain under conditions of plane strain and its exact solution is obtained analytically. This is accomplished with the aid of Fourier series along the horizontal direction and solution of the resulting system of two ordinary differential equations with variable coefficients by the method of Frobenius in power series. Due to the complexity of the various analytical expressions, the final results are determined numerically. These results include seismic pressures, resultant horizontal forces and bending moments acting on the walls. The solution of the problem involving a single retaining wall can be obtained as a special case by assuming the distance between the two walls to be very large. Results are presented in terms of numerical values and graphs using suitable dimensionless quantities. The effect of soil non-homogeneity on the system response is assessed through comparisons for typical sets of the parameters involved. 相似文献
6.
This paper outlines the results of an experimental program carried out on centrifuge models of cantilevered and propped retaining walls embedded in saturated sand. The main aim of the paper is to investigate the dynamic response of these structures when the foundation soil is saturated by measuring the accelerations and pore pressures in the soil, displacements and bending moment of the walls. A comparison among tests with different geometrical configurations and relative density of the soil is presented. The centrifuge models were subjected to dynamic loading in the form of sinusoidal accelerations applied at the base of the models. This paper also presents data from pressure sensors used to measure total earth pressure on the walls. Furthermore, these results are compared with previous dynamic centrifuge tests on flexible retaining walls in dry sand. 相似文献
7.
Seismic stability analysis of gravity retaining walls 总被引：1，自引：0，他引：1
A new approach based on the category of upper bound theorem of limit analysis is presented in this study to consider the seismic stability of gravity retaining walls. The retaining wall and the backfill soil were taken as a whole system. For a translational failure mechanism assumed, formulas are provided to calculate directly the yield acceleration and the inclination of the failure surface. An example is shown to illustrate the method. Comparisons are made with limit equilibrium method, and the results are found consistent. Based on a limited parametric study, it is shown that the wall roughness has remarkable influence on the yield acceleration. 相似文献
8.
Mid‐rise to high‐rise buildings in seismic areas are often braced by slender reinforced concrete (RC) walls, which are interconnected by RC floor diaphragms. In design, it is typically assumed that the lateral forces are distributed in proportion to the wall's elastic stiffness. Pushover analyses of systems comprising walls of different lengths have, however, shown that large compatibility forces can develop between them, which should be considered in design, but the analyses have also shown that the magnitude of the computed forces is very sensitive to the modelling assumptions. Using the results of a complex shell element model as benchmark, different simple hand‐calculation methods and inelastic beam element models are assessed and improved to yield reliable estimates of the base shear distribution among the individual walls comprising the interconnected wall system. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
9.
At present, methods based on allowable displacements are frequently used in the seismic design of earth retaining structures. However, these procedures ignore both the foundation soil deformability and the seismic amplification of the soil placed behind the retaining wall. Thus, they are not able to predict neither a rotational failure mechanism nor seismic induced lateral displacements with an acceptable degree of accuracy for the most general case. In this paper, a series of 2D finite-element analyses were carried out to study the seismic behavior of gravity retaining walls on normally consolidated granular soils. Chilean strong-motion records were applied at the bedrock level. An advanced non-linear constitutive model was used to represent both the backfill and foundation soil behavior. This elastoplastic model takes into account both the stress dependency of soil stiffness and coupling between shear and volumetric strains. In unloading–reloading cycles, the non-linear shear-modulus reduction with shear strain amplitude is considered. Interface elements were used to model soil–structure interaction. Routine-design charts were derived from the numerical analyses to predict the lateral movements at the base and top of gravity retaining walls located at sites with similar seismic characteristics to the Chilean subduction zone. Thus, wall seismic rotation can also be obtained. The developed charts consider wall dimensions, granular soil properties, bedrock depth, and seismic input motion characteristics. As shown, the proposed charts match well with available experimental data. 相似文献
10.
This paper aims to shed some further light on the seismic behaviour and design of reinforced concrete (R/C) walls which form part of dual (frame + wall) structures. The significance of post‐elastic dynamic effects is recognized by most seismic codes in the definition of the design action effects on walls, i.e. bending moments and shear forces. However, the resulting envelopes are not always fully satisfactory, particularly in the case of medium‐to‐high‐rise buildings. The relevant provisions of modern seismic codes are first summarized and their limitations discussed. Then an extensive parametric study is presented which involves typical multi‐storey dual systems that include walls with unequal lengths, designed according to the provisions of Eurocode 8 for two different ductility classes (M and H) and two effective peak ground acceleration levels (0.16 and 0.24g). The walls of these structures are also designed according to other methods, such as those used in New Zealand and Greece. The resulting different designs are then assessed by subjecting the structures to a suite of records from strong ground motions, carrying out inelastic time history analysis, and comparing the results with the design action effects. It is found that for (at least) the design earthquake intensity, the first two modes of vibration suffice for describing the seismic response of the walls. The bending moment envelope, as well as the base shear of each wall, is found to be strongly dependent on the second mode effect. As far as the code‐prescribed design action effects are concerned, only the NZ Code was found to be consistently conservative, whereas this was not always the case with EC8. A new method is then proposed which focuses on quantifying in a simple way the second mode effects in the inelastic response of the walls. This procedure seems to work better than the others evaluated herein. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
11.
Constantine A. Stamatopoulos Eleni G. Velgaki Arezou Modaressi Fernando Lopez-Caballero 《Bulletin of Earthquake Engineering》2006,4(3):295-318
Gravity walls retaining dry soil are modeled as a system of two bodies: (a) the gravity wall that slides along the wall-foundation soil boundary and (b) the critical soil wedge in the soil behind the wall. The strength of the system is defined by both the frictional and the cohesional components of resistance. The angle of the prism of the critical soil wedge behind the wall is obtained using the limit equilibrium method. The model accounts for changes in the geometry of the backfill soil behind the wall by considering the displacements at the end of each time step under limit equilibrium. The model shows that the standard (single) block model is over-conservative for the extreme case of critical-to-applied-seismic acceleration ratios less than about 0.30, but works well for cases where this ratio ranges between 0.5 and 0.8. The model is applied to predict the seismic displacement of gravity walls (a) tested in the shaking-table and (b) studied numerically by elaborate elasto–plastic analyses. 相似文献
12.
This paper examines in terms of seismic performance, the effectiveness of anchor reinforcement against gravity retaining walls used to stabilize a dry homogenous fill slope in earthquake-prone environment. Both analyzed stabilizing measures have the same design yield acceleration estimated from a limit equilibrium approach. The earthquake-induced displacements are calculated using a sliding block formulation of the equation of motion. Sliding failure along the base of the gravity retaining wall and rotational failure of the soil active wedge behind the wall, as well as rotational failure of the slide mass of the anchor-reinforced slope were considered in the present formulation. For the specific characteristics of the analyzed fill slope and input horizontal ground motion, the slope reinforced with anchors appears to experience vertical and horizontal seismic displacements at slope crest smaller by 12% and respectively, 32% than the vertical and horizontal earthquake-induced deformations estimated at the top of the active wedge behind the gravity retaining wall. 相似文献
13.
In this study, a validated Finite Element procedure was used to investigate the similarities and differences of seismic performances between single- and multi-tiered reinforced soil walls. Three-tiered walls at a total height of 9 m were analyzed together with vertical walls at the same height. It was found from the Finite Element analyses that the resonant frequency of reinforced soil walls might increase with an increase in the tier-offset. The multi-tiered configuration could considerably reduce the residual lateral facing displacement and the average reinforcement load, and the reinforcement load distribution with height was different from that in vertical walls. With the same reinforcement length and spacing, the multi-tiered walls resulted in smaller reinforcement connection loads with the facing blocks. The study filled the gap of seismic behavior of multi-tiered reinforced soil retaining walls and revealed a few unique dynamic properties of this type of earth structures. 相似文献
14.
15.
This note presents an analytical solution of the thrust on retaining walls with short heel, where the seismic action is simulated through the pseudo-static approach. The critical shape of the thrust wedge is assumed to be that minimizing the safety factor against wall sliding. This procedure is also congruent with the original method of Coulomb. The problem is mathematically expressed by a system of two equations, the first cubic and the second quadratic, whose solution converges quickly. 相似文献
16.
This work deals with the evaluation of the dynamic pressures and the associated forces on a pair of rigid vertical cantilever walls retaining a uniform, fully saturated poroelastic layer of soil. Hysteretic damping in the soil skeleton may also be present. Wall pressures and forces are induced by horizontal ground shaking harmonically varying with time and spatially invariant. The problem is solved analytically under conditions of plane strain. The governing partial differential equations of motion, after separation of variables and the simplifying assumptions of zero vertical normal stresses and zero horizontal variation of vertical displacements, reduce to a system of two ordinary differential equations for the amplitudes of the solid skeleton horizontal displacement and the pore water pressure, which are easily solved. The parameters examined include the ratio of the distance between walls to the height of the retained soil material and the soil material properties such as porosity, permeability and damping. The comprehensive numerical data presented indicate that the displacements, wall pressures and resultant forces are highly dependent on the distance between the walls for any values of porosity and permeability. 相似文献
17.
历史震害表明,填充墙与框架的连接刚度对框架结构的抗震性能有重要影响。我国《建筑抗震设计规范》(2010)建议"框架结构中的砌体填充墙,宜与柱脱开或采用柔性连接",但对二者的具体连接刚度,规范并没有做出明确规定。运用ABAQUS软件,对前人开展的考虑填充墙与框架连接影响的框架结构拟静力试验进行数值模拟,对比分析填充墙框架结构破坏特征及滞回曲线等抗震性能指标,验证了有限元模型的可靠性。基于某典型框架结构,建立不考虑填充墙、考虑填充墙与框架不同连接刚度的框架结构有限元模型。模态分析表明,连接刚度对框架结构的频率影响较小,结构的动力特性趋于一致;多遇地震和罕遇地震作用下的弹塑性时程分析表明,合适的连接刚度可以提高结构的抗震性能。研究可为框架结构的抗震设计提供参考。 相似文献
18.
This paper presents a limit equilibrium method, based on the approach of Mononobe and Okabe, for calculating the active thrust on fascia retaining walls, where common methods cannot be used owing to the narrowness of the backfill which does not permit the development of the thrust wedge in the shape and sizes predicted by these methods. The proposed method examines three distinct failure mechanisms, called Mechanism 1, Mechanism 2 and Mechanism 3, where the thrust wedge is formed by one, two or three blocks, respectively; separated by plane slip surfaces. The seismic forces have been simulated with the pseudo-static method. For all three mechanisms, the active thrust is obtained in closed form: in particular, with a cubic equation for Mechanism 2, and with a system of two equations, one cubic and the other quartic, for Mechanism 3. Mechanisms with more than three blocks cannot have analytical solutions. The study is completed by an examination of some significant cases from which the higher attenuation of the seismic thrust, with respect to the static, emerges as the backfill width reduces. 相似文献
19.
The paper focuses on the seismic response of walls in dual (frame + wall) structures, with particular emphasis on shear behaviour.
Although dual structures are widely used in earthquake-resistant medium-rise and high-rise buildings, the provisions of modern
seismic codes regarding design of walls for shear are not fully satisfactory, particularly in the (common) case that walls
of substantially different length form part of the same structure. Relevant provisions of the leading seismic codes are first
summarised and their limitations discussed. Then an extensive parametric study is presented, involving two multistorey dual
systems, one with identical walls, and one with walls with unequal length, designed to the provisions of Eurocode 8 for two
different ductility classes (H and M). The walls of the same structures are also designed to other methods such as those used
in New Zealand and Greece. The resulting different designs are then assessed by subjecting the structures to a suite of strong
ground motions, carrying out inelastic time history analysis, and comparing the results against design action effects. It
is found that although modern code procedures generally lead to satisfactory performance (differences among them do exist),
the design of walls seems to be less appropriate in the case of unequal length walls. For this case a modified procedure is
proposed, consisting of an additional factor to account for the relative contribution of walls of the same length to the total
base and an improved envelope of wall shears along the height; this improved method seems to work better than the other procedures
evaluated herein, but further calibration is clearly required. 相似文献
20.
The objective of this study is to investigate the effect of boundary element details of structural walls on their deformation capacities. Structural walls considered in this study have different sectional shapes and/or transverse reinforcement content at the boundaries of the walls (called boundary element details hereafter). Four full‐scale wall specimens (3000mm (hw)×1500mm (lw)×200mm (T)) were fabricated and tested. Three specimens are rectangular in section and the other specimen has a barbell‐shaped cross‐section (a wall with boundary columns). The rectangular wall specimens are reinforced according to the common practice used for reinforced concrete residence buildings in Korea and Chile. In this study, the primary variable for these rectangular specimens is the content of transverse reinforcement to confine the boundary elements of a wall. The barbell‐shaped specimen was designed in compliance with ACI 318‐95. The response of the barbell‐shaped specimen is compared with those of other rectangular specimens. The effective aspect ratio of the specimens is set to two in this study. Based on the experimental results, it is found that the deformation capacities of walls, which are represented by displacement ductility, drift ratio and energy dissipation capacities, are affected by the boundary element details. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献