Search

The response of an infinite beam on an elastic foundation depends on the property/modeling of the foundation. There is a qualitative difference between the responses of a beam when it is on the Winkler foundation and on the tensionless foundation. A bilinear elastic foundation model, which describes the different behaviors of the elastic foundation in the tensile and compressive zones with two different foundation moduli, is proposed and a straightforward computational method is also formulated. The Winkler and tensionless foundations are shown to be the two special cases of the bilinear elastic foundation model. With this bilinear elastic foundation model, a more general method of modeling an elastic foundation is provided, which can be of some help to the modeling of the support of the ballastless high-speed railway. [ABSTRACT FROM AUTHOR]

Heat losses from a building foundation are affected by both the surrounding conditions and the surrounding soil properties. These include many factors that complicate the analysis of heat loss, such as thermal storage, snow and soil freezing. The effect of snow and soil freezing was studied with a 3D simulation model in a subarctic climate. The heat losses from the most commonly used foundation types in Sweden were studied. This paper shows that it is possible to achieve a good thermal estimation of the air temperatures in a crawl space, with an average difference of 0.4 °C compared with the validation data over a year. Snow and soil freezing reduce the annual heat losses through the different foundation types by 7–10% and the maximum heat loss rate by 13–25%. In order to describe the heat transfer correctly, snow must be included in the calculations, while soil freezing has only a minor impact. The 3D model implemented in this study shows a significant impact on the soil temperatures when these parameters are included. For a subarctic climate, the commonly used calculation methods based on the European standard ISO 13370 are not thorough enough to calculate the heat transfer through a foundation accurately. [ABSTRACT FROM AUTHOR]

Summary: A direct finite element method for nonlinear earthquake analysis of 2‐dimensional dam–water–foundation rock systems has recently been presented. The analysis procedure uses standard viscous‐damper absorbing boundaries to model the semi‐unbounded foundation‐rock and fluid domains and specifies the seismic input as effective earthquake forces at these boundaries. Presented in this paper is a generalization of the direct finite element method with viscous‐damper boundaries to 3‐dimensional dam–water–foundation rock systems. Step‐by‐step procedures for determining the effective earthquake forces starting from a ground motion specified at a control point on the foundation‐rock surface is developed, and several numerical examples are computed and compared with independent benchmark solutions to demonstrate the effectiveness of the analysis procedure for modeling 3‐dimensional systems. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The two prime models used currently to describe rocking of rigid bodies, the Housner’s model and the Winkler foundation model, can capture some of the salient features of the physics of this important problem. These two models involve either null or linear interaction between the block and the foundation. Hopefully, some additional aspects of the problem can be captured by an enhanced nonlinear model for the base-foundation interaction. In this regard, what it is adopted in this paper is the Hunt and Crossley’s nonlinear impact force model in which the impact/contact force is represented by springs in parallel with nonlinear dampers. In this regard, a proper mathematical formulation is developed accounting for the possibility of uplifting in the case of strong excitation. Further, an averaging procedure has been developed to expeditiously derive the steady state response amplitude in case of harmonic base excitation. The analytical study is supplemented by experimental tests developed in the Laboratory of Experimental Dynamics at the University of Palermo, Italy. In this context, because of the obvious relevance for historical monuments, free-rocking tests are presented for several marble-block geometries on both rigid and flexible foundations. Numerical vis-à-vis experimental data are examined, showing that the proposed nonlinear model is sufficiently versatile to capture additional aspects of the physics of the problem even for quite soft foundation materials. [ABSTRACT FROM AUTHOR]

Results of a physical modelling study of clear-water scour at a tripod obstacle in uniform bed sediment under steady flow conditions are presented. 4 flow depths, 2 flow velocities and 3 angles of attack were considered. Maximum scour depth increased with increase in flow depth or velocity. For deep flows and high flow rate, the maximum value of the ratio of the equilibrium scour depth to the diameter of the tripod’s leg was 3.5, which is significantly greater than values of 1.3 or 2.5 suggested by guidelines for offshore wind turbine monopiles design. This ratio may be even larger because of the increased shear stress when waves are superimposed on current. All maximum equilibrium scour depths occurred at the upstream surface of a tripod leg despite the centre pile having a larger diameter. The alignment angle had a small effect on scour depth. But it is notable that there is an increase in scour development depth at 60° alignment angle. Equations are suggested for estimating the clear-water scour depth at wind turbine tripod foundations. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to evaluate the improved suction bucket foundation (ISBF) for the offshore wind turbine. The ISBF included the design of two types of internal compartments inside buckets with different aspect ratios (AP). A series of centrifuge tests were performed to investigate the lateral bearing behavior of ISBF in four types of sandy soils. Both static and cyclic lateral loads were applied by an electrical actuator in a load-controlled system. The first method interpolated the lateral bearing capacity from the load-displacement curve and reinforced the results with the stiffness-displacement relationship. Moreover, displacement rate was calculated and plotted to obtain the lateral critical and ultimate bearing capacity as the second method. During cyclic tests, the first several cycles changed the lateral displacement and stiffness significantly, whereas the last several cycles did not obviously affect them. It was demonstrated that the geometric designs of ISBF had limited influence on its lateral bearing behavior, but the soil conditions of the foundation did bring about an obvious difference. The lateral capacity of ISBF was further compared to original suction bucket foundation (OSBF), thereby illustrating the advantages of the ISBF in offshore wind turbine constructions. [ABSTRACT FROM AUTHOR]

In order to make a reasonable security assessment for super-large pile-group foundation in deep water during the construction and operating period, a combination of safety monitoring technology and mathematical method was adopted as modeling the security assessment as per the existing observation results. Based on the analysis of the content of safety monitoring, we firstly fused various sensors to a single target state estimation. Secondly, according to the national standards, industry standards and the existing research and practice experience, we analyzed and determined the set of safety evaluation factor, simultaneously constructed the membership function of each factor with different characteristics and establish the weight of each one. Thirdly, we evaluated result by optimal decision fusion. It comes out that this model can be a good judge method for safety of Super-large pile-group foundation in deep water. [ABSTRACT FROM PUBLISHER]

The article deals with the problem of extrusion of weak layer out of foundation base of finite width using analytical and numerical methods. It contains formulae to define the initial critical load on the foundation base, as well as the formulae to define the rates of the weak layer extrusion and foundation settlement. Design models for the soft ground are viscoplastic models with the undamped and damped rate according to the law of the hyperbolic sine and tangent, as well as S.P. Timoshenko elastoplastic model. [ABSTRACT FROM AUTHOR]

This paper is concerned with the development of the Hencky bar-chain model (HBM) for the buckling and vibration analyses of non-uniform beams resting on partial variable elastic foundation. The HBM allows analysts to obtain beam buckling and vibration solutions by solving a set of algebraic equations instead of a differential equation. To get the HBM, we resort to the first order central finite difference model (FDM) because both discrete models have phenomenological similarities. Based on bending moment, shear force and deflection equivalence between the two discrete beam models, the expressions for the internal spring stiffness, the end spring stiffness and the elastic foundation stiffness for the HBM are obtained. Some example problems are considered to demonstrate the simplicity of the HBM for buckling and vibration analyses of non-uniform beams on partial variable elastic foundation by taking the number of segments of the HBM to infinity. The effects of the foundation length and stiffness on the buckling load and natural frequencies are also discussed. Naturally, the HBM can be used to obtain solutions for articulated beams or beam-like structures with repetitive cells as well. [ABSTRACT FROM AUTHOR]

An investigation is made to present analytical solutions provided by a Winkler model approach for analysis of piled rafts with nodular pile subjected to vertical loads in nonhomogeneous soils. The vertical stiffness coefficient along a piled raft with the nodular pile in nonhomogeneous soils is derived from the displacement given by the Mindlin solution for elastic continuum analysis. The vertical stiffness coefficients for the bases of the raft and the nodular part in the nodular pile in a soil are expressed by the Muki solution for the 3-D elastic analysis. The relationship between settlement and vertical load on the pile base is presented considering the Mindlin solution and the equivalent thickness in the equivalent elastic method. The interaction factor between the shaft of the nodular pile and the soil is expressed taking into account the Mindlin solution and the equivalent elastic modulus. The relationship between settlement and vertical load for a piled raft with the nodular pile in nonhomogeneous soils is obtained by using the recurrence equation of influence factors of the pile for each layer. The percentage of each load carried by both nodular pile and raft subjected to vertical load is represented through the vertical influence factors proposed here. Comparison of the results calculated by the present method for piled rafts with nodular piles in nonhomogeneous soils has shown good agreement with those obtained from the finite element method and a field test. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Many studies were conducted on the modelling of stress distribution of soil foundations based on the elastic theory or uniformly spread hypothesis, but few works focused on the modelling of dynamic stress distribution in railway substructures. In this study, field monitoring was performed at Vierzon, France, using two embedded stress sensors. Dynamic stress data were recorded during train passages at different speeds, from 60 km/h to 200 km/h. Note that the Vierzon site involves a conventional line that is characterised by the presence of an interlayer soil, sandwiched between the ballast layer and the subgrade. The recorded data was firstly used to verify the existing models currently used in practice, revealing the advantages and drawbacks of such models. Then, based on the theory of stochastic stress diffusion in particulate media, a modified load spread model was developed. Comparison with the recorded data shows the relevance of the proposed model. In particular, significant effect of modulus ratio bewteen two adjacent layers on stress distribution was evidenced. [ABSTRACT FROM AUTHOR]

This paper advocates the use of a multiphase model, already developed for static or quasi-static geotechnical engineering problems, for simulating the behaviour of piled raft foundations subject to horizontal as well as rocking dynamic solicitations. It is shown that such a model, implemented in a FEM code, yields appropriate predictions for the foundation impedance characteristics, provided that shear and bending effects in the piles are taken into account, thus corroborating the findings of the asymptotic homogenization theory. Besides, it is notably pointed out that such a multiphase-based computational tool makes it possible to assess the dynamic behaviour of pile groups in a much quicker way than when using direct numerical simulations, which may face oversized problems when large pile groups are concerned. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Evaluation of the uplift capacity of plate anchors in saturated clay is an important aspect in the design of offshore foundation systems of various structures. In most of the literature reviewed, simple constitutive models such as Tresca or Mohr-Coulomb (MC) have been used in evaluating the plates' pullout capacity. There exists a need to study the pullout capacity of anchors using other advanced soil models and explore differences in computed behavior. In addition to the MC model, two other constitutive models are used herein to represent the soil behavior. These are Modified Cam-Clay and Soft Soil models. A series of finite-element analyses are performed using the three constitutive models. Undrained effective stress analyses are conducted to study the response of both strip and circular plate anchors in saturated soils. The capacities of plate anchors are assessed through the application of the displacement control approach. The effective stress parameters are correlated with the undrained shear strength, and Nc (dimensionless breakout factor) values from the three constitutive models are presented and compared with the lower bound solution, as well as with the data obtained from similar studies and experimental data available in the literature. Differences resulting from the characteristics of the three constitutive models are examined and discussed. [ABSTRACT FROM AUTHOR]

This study presents the results of the mathematical modelling for the micropiles foundation of an investment objective located in Slanic, Prahova county. Three computing models were created and analyzed with software, based on Finite Element Method. With Plaxis 2D model was analyzed the isolated micropile and the three-dimensional analysis was made with Plaxis 3D model, for group of micropiles. For the micropiles foundation was used Midas GTS-NX model. The mathematical models were calibrated based with the in-situ tests results for axially loaded micropiles, embedded in salt rock. The paper presents the results obtained with the three software, the calibration and validation models. [ABSTRACT FROM AUTHOR]

The inertial interaction analysis of a structure founded on piles is usually performed assuming the free-field motion as seismic action at the foundation level, thus neglecting the filtering action often exerted by piles. By contrast, the existence of frequency filtering is confirmed through works referring to theoretical and experimental studies, even if this effect is generally neglected in design practice. In this paper the seismic performance of frame buildings, excited by filtered and free-field input motions is evaluated. The results of these analyses, expressed in terms of top displacement and base shear, allow for assessing the importance of the beneficial effect coming from the piles on the inertial response of the superstructure. [ABSTRACT FROM AUTHOR]

This paper reports results from centrifuge model tests that provide insight into the behavior of rectangular foundations (representing earthmoving equipment) during penetration, with freedom in rotation, adjacent to a sand embankment (cover layer), into a weaker clay layer (representing mine tailings). A parametric study was used to explore the relevant range of the setback ratio, slope height ratio, normalized clay strength and its nonhomogeneity, and foundation base geometry. The effect of these nondimensional parameters on the penetration resistance profile is discussed in the context of the likelihood and severity of failure. The failure of a flat-based rectangular foundation was less severe than that associated with a strip foundation, and the corresponding measures reduced with the increasing setback ratio (l) and slope height ratio (h). No rotational failure occurred for λ (Su,av/γcB)cr >8 (where su,av/γcB is the average normalized strength of the lower clay layer) or η≥0:604, regardless of strength nonhomogeneity and the normalized strength of the bottom clay layer. The addition of small skirts to the base of the rectangular foundation assisted in reducing the likelihood and severity of failure significantly, with the exception of γ=0.19 and η=0.264. Expressions were proposed for calculating the modified bearing capacity factors. [ABSTRACT FROM AUTHOR]

The present research intends to study the effects of the seismic soil-pile-structure interaction (SSPSI) on the dynamic response of buildings with various heights by conducting a series of shaking table tests on 5-, 10-story, and 15-story model structures. Two types of foundations for each case are investigated, including (1) a fixed-base structure, representing the situation excluding the soil-structure interaction; and (2) a structure supported by an end-bearing pile foundation in soft soil. An advanced laminar soil container has been designed that uses three-dimensional numerical modeling to minimize the boundary effects and to simulate free-field motion during the shaking table tests. Four real earthquake events, including Kobe 1995, Northridge 1994, El Centro 1940, and Hachinohe 1968, are imposed to each model. According to the experimental measurements, it is observed that the SSPSI amplifies the maximum lateral deflections and in turn interstory drifts of the structures supported by end-bearing pile foundations in comparison with the fixed-base structures. The rocking component plays an important role in increasing the lateral deflection of the superstructures, which can shift the performance level of the structures to near collapse or even collapse levels and as a result should be assessed precisely in the seismic design of buildings resting on soft soils. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new method for the evaluation of the ultimate load of piles by tests not carried to failure is proposed. It allows, by a proper use of the experimental results, a complete analysis of a pile behavior. In fact, the total, shaft and base load-settlement curves can be evaluated. It can be applied when shaft friction is fully mobilized during the test. [ABSTRACT FROM AUTHOR]

A design of the load-bearing capacity and settlement of a pilot base is usually based on the assumption that all of the load from the top of the building is transferred only by pilots. The influence of the adjacent connecting structures, which are in contact with the ground (pile cap, slab, block, belt, etc.), is usually ignored. The necessary data from the experimental measurement of the impact of these structures, concerning the overall bearing capacity of the foundations, was obtained on the testload device (Stand), in the area of Faculty of Civil Engineering, VŠB-TU of Ostrava. The progress of the experiment and the results of the load tests are listed in this paper [ABSTRACT FROM AUTHOR]

Increasing demands for oil and gas exploration in deep water with soft seabed conditions are resulting in the size and weight of subsea shallow foundations stretching the capabilities of installation technologies. One innovation to reduce foundation footprints involves designing foundations to move in a tolerable manner to absorb applied loads rather than being engineered to resist these loads and remain stationary. Critical design considerations are the evolution of foundation capacity and the mode of foundation displacement. The foundation should be designed to slide with acceptable settlement and rotation to prevent overstressing the joints with connected pipelines. This paper presents observations from centrifuge model tests of a mat foundation designed to slide under applied loading. The foundation is subjected to a simulated lifetime of operation, with many cycles of sliding and intervening periods of consolidation. The results provide insights to assist design, including a remarkable rise in the lateral foundation resistance over the sliding events, through repeated episodes of shearing and reconsolidation, and quantification of the accumulated settlements and rotations. The foundation is shown to translate with minimal rotation. The settlement between sliding events is more significant. This is due to the tendency for soft clay to contract on shearing, as excess pore pressures generated during sliding subsequently dissipate. The sliding-induced consolidation settlements control the tolerability of the performance of the mobile foundation. [ABSTRACT FROM AUTHOR]

Bending stresses produced in pavement concrete slabs are influenced by the contact condition along the slab–foundation interface. A finite element model for the analysis of frictional contact between unbonded pavement layers is presented. A 2D plate element is proposed for the idealization of composite slabs. Interface elements are used to connect the unbonded layers within the composite slab and to model the interface between the bottom slab layer and the foundation layer. Interface elements have the ability to capture the separation and sliding between pavement layers, due to thermal loads, and to calculate the frictional traction at their interface. [ABSTRACT FROM AUTHOR]

Raked piles are believed to behave better than vertical piles in a laterally flowing liquefied ground. This paper aims at numerically simulating the response of raked pile foundations in liquefying ground through nonlinear finite element analysis. For this purpose, the OpenSees computer package was used. A range of sources have been adopted in the definition of model components whose validity is assessed against case studies presented in literature. Experimental and analytical data confirmed that the backbone force density-displacement (p-y) curve simulating lateral pile response is of acceptable credibility for both vertical and raked piles. A parametric investigation on fixed-head piles subject to lateral spreading concluded that piles exhibiting positive inclination impart lower moment demands at the head while those inclined negatively perform better at liquefaction boundaries (relative to vertical piles). Further studies reveal substantial axial demand imposed upon negatively inclined members due to the transfer of gravity and ground-induced lateral forces axially down the pile. Extra care must be taken in the design of such members in soils susceptible to lateral spreading such that compressive failure (i.e. pile buckling) is avoided. [ABSTRACT FROM AUTHOR]

This paper focuses on the establishment of a model factor for the calculation of the ultimate limit state (ULS) bearing capacity of piles in compression from Ménard pressuremeter tests results. First, the requirements of Eurocode 7 are presented: calculation methods used for pile foundations must be validated against the results of static load tests and a model factor can be introduced to reach a target safety. This model factor is meant to take into account the scatter of the calculation model, whereas the spatial variability of the ground properties is dealt with by means of statistical methods. Then an analysis of a database of 174 full-scale static pile load tests carried out by the Laboratoire Central des Ponts et Chausées (LCPC, now called IFSTTAR), over the last 40 years, mainly in France, is performed and a new calculation model is established based on pressuremeter test results. Finally, the calibration procedure for deriving the model factor used in the recent French standard for pile design following Eurocode 7 is explained using two approaches: one compares the dispersions of the former and new calculation models and the other performs statistical analysis combining the scatter of the calculation model and the spatial variability of ground properties. This model factor is introduced into the recent French standard for pile design following Eurocode 7. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights: [•] An analytical modeling method was developed for column-to-footing connection for CFT. [•] The failure mechanisms of the CFT connection were evaluated. [•] A parametric study was conducted and the impact of design parameters were evaluated. [•] Design equations for required embedment depth of the CFT connections were developed. [Copyright &y& Elsevier]

Highlights: [•] We develop a 1/3rd scale model of a light-frame wood structure to determine structural load paths. [•] We followed proper similitude scaling requirements to model all of the building components. [•] The scale structure is instrumented at roof-to-wall and wall-to-foundation connections. [•] Influence coefficients (i.e., load paths) were determined for these connections due to wind uplift loading. [•] The structure was validated with full-scale data and results presented in the literature. [Copyright &y& Elsevier]

Highlights: [•] The obtained equation is very useful to build a structure above tunnels. [•] The equation is S =(−0.06A −1 CD 3)+(0.0116A −1 B 3 C)+(16AD −2)−12.12. [•] The influence radius at a point close to the tunnel is about 2.3D. [•] Increasing the number of stories from 4 to 6 causes the settlement to be doubled. [Copyright &y& Elsevier]

The main objective of this paper is to review the current state-of-the-art for predicting settlements of shallow foundations in granular soils. The traditional settlement prediction methods are critically reviewed. Present settlement prediction methods generally overestimate the settlements and underestimate the allowable pressures, making the foundation designs very conservative. Some recent developments, including two deterministic methods and a probabilistic approach, are showed as they have significant potential to improve the current state-of-the-art. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: In vapor intrusion screening models, a most widely employed assumption in simulating the entry of contaminant into a building is that of a crack in the building foundation slab. Some modelers employed a perimeter crack hypothesis while others chose not to identify the crack type. However, few studies have systematically investigated the influence on vapor intrusion predictions of slab crack features, such as the shape and distribution of slab cracks and related to this overall building foundation footprint size. In this paper, predictions from a three-dimensional model of vapor intrusion are used to compare the contaminant mass flow rates into buildings with different foundation slab crack features. The simulations show that the contaminant mass flow rate into the building does not change much for different assumed slab crack shapes and locations, and the foundation footprint size does not play a significant role in determining contaminant mass flow rate through a unit area of crack. Moreover, the simulation helped reveal the distribution of subslab contaminant soil vapor concentration beneath the foundation, and the results suggest that in most cases involving no biodegradation, the variation in subslab concentration should not exceed an order of magnitude, and is often significantly less than this. [Copyright &y& Elsevier]

Seismic analyses of concrete gravity dams are usually idealized as two-dimensional structures with a massless foundation in present design procedure. But for gravity dams built in narrow valleys or on sites of very high seismicity, however, interaction between adjacent blocks may influence the seismic responses significantly. Dynamic interaction between dam and foundation affects the dam response as well, including reflection, diffraction and radiation of seismic waves. In the paper, a three-dimensional FEM full dam model was adopted to analyze the seismic responses of a concrete gravity dam, in which, dynamic interaction between dam-foundation, dam-water, energy radiation, dynamic contact between monoliths, etc. were taken into consideration. Comparison was made among the numerical results of a full dam model with a massless foundation, full dam model with or without contraction joints, differences between them and realistic understanding were discussed and proposals were given to improve the aseismic capacity of concrete gravity dams. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this paper is to analyse a colums raft foundation system. The soil, on which it is located the structure, belongs to difficult foundation earth and is characterized by a contractile clay with the presence of underground water. Using geotechnical calculation programs has been evaluated the behaviour of piles with large diameter (columns) based on three modelling types of slab design and considering loaded only with axial force, because, especially in this case, the foundation have to ensure safety for entire building. We analyse a single column with the bigger load provided from the slab, proposing also a reinforcement solution. The interest for analysing the columns is to know that the interaction between foundation system and foundation environment is very important. To accomplish these conditions mentioned before it is necessary to ensure the column strength. This research also wants to determine the quantity of materials (concrete and steel) in columns. The final task of the analyse is to design a resistance and safety foundation system. [ABSTRACT FROM AUTHOR]

Abstract: Recycling rubber from waste tires has become one of the major challenges worldwide. The use of waste tires in geotechnical applications may be feasible as an alternative way to consume the huge stockpile of scrap tire, with a better understanding of the behavior of rubber–soil mixture. The objective of this study was to investigate the feasibility of using rubber shreds, randomly distributed into the soil, as soil reinforcement beneath the footing. A series of laboratory tests were conducted to obtain the bearing capacity of a square footing rested on shredded rubber-reinforced soil. The results show that the efficiency of rubber reinforcement was increased by addition of rubber content, the thickness of rubber-reinforced soil layer and the soil cap thickness up to the optimum values of these parameters, after that, with a further increase in each of these parameters, the bearing capacity decreases. For the optimum value of rubber content of 5% at footing settlement level of 5%, the maximum improvement in bearing capacity of rubber-reinforced bed was obtained as 2.68 times of the unreinforced bed. This value of improvement was achieved using the optimum thickness of reinforced layer of 0.5 times of footing width and the optimum thickness of soil cap of 0.25 times of footing width. The findings strongly suggest the use of rubber shreds obtained from non-reusable tires as a viable alternative way for improving the soil behavior, particularly when environmental interest is considered. [Copyright &y& Elsevier]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Performing a dynamic analysis of an offshore wind turbine with an aero-elastic solver relies on the inclusion of a model to represent the behavior of the piled foundations. The most commonly used solution is the p-y method, which was developed for offshore oil and gas applications and has been extended to the offshore wind energy industry. There are several shortcomings with this method, however, which can affect the accuracy of wind turbine simulations. These shortcomings are identified and explained in this work. More advanced pile foundations models which account for many nonlinear behaviors ignored by the traditional p-y method have been developed in the past for applications unrelated to offshore wind turbines. These models can nevertheless be applied to offshore wind turbine simulations and are discussed herein. A proposed method for incorporating these so called ‘dynamic p-y’ models into wind turbine simulations is laid out and discussed. [Copyright &y& Elsevier]

In the design of foundations in case specifically of reinforced concrete square footings subjected to axial load and bidirectional flexure are presented different pressures in each corner, these are exerted for the floor. In this paper is developed a mathematical model to obtain the most economical dimension of the contact surface in square footings, when is applying the load that must support said structural member. The classical model is developed by trial and error, i.e., it is proposed a dimension, and using the formulates of the bidirectional flexure for to obtain the stresses acting on the four corners of the square footing, which must meet the following conditions: 1) The minimum stress should be equal to or greater than zero, because the soil is not capable of withstand tensile stresses. 2) The maximum stress must be equal or less than the allowable capacity that can withstand the ground. Therefore normal practice to use the classic model will not be a recommended solution. Then, it is best to use the proposed model since it is more economic. [ABSTRACT FROM AUTHOR]

Abstract: Geocell mattresses are widely used in soil reinforcement due to their three-dimensional configuration, which can effectively confine and reinforce soil filled in their pockets. However, design of geocell mattresses has not been well described in the literature. In this paper, a decoupled iterative method is presented to assess the behavior of a geocell mattress subjected to symmetric loads by modeling the mattress as a geometrically nonlinear beam resting on a nonlinear foundation. The nonlinearity of the foundation soil is represented by an elastic-perfectly plastic model. The tensionless nature of the soil is also taken into account in the model. Classical Winkler foundation beam theory is extended to solve the geocell reinforcement problem, with consideration of the lateral interfacial shearing resistance at the top and bottom of the beam. This resistance is assumed to be linearly proportional to the relative lateral displacement of the beam. The solution presented in this paper is verified by comparison with the two other existing published solutions for this problem. The effects of the two nonlinear parameters, i.e., the soil yield displacement and the beam geometric nonlinearity coefficient, on the deflection and tensile force within the beam are discussed. The results indicate that both the nonlinearity of the subgrade soil and the geometric nonlinearity of the beam significantly affect the beam’s response, especially when the beam undergoes a large deflection. [Copyright &y& Elsevier]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Anchor foundations of various embedment ratios, shapes, and sizes are frequently used in civil engineering structures to provide uplift resistance. Therefore, to achieve economic and safe design of such foundations, engineers should understand the failure mechanism associated with them. In the present study, a three-dimensional (3D) finite element model incorporating an elastoplastic material model coupled with the isotropic strain-softening law, the nonassociated flow rule, and the shear-band effect, is used to investigate the failure mechanisms of vertically uploaded shallow rectangular anchor foundations buried in dense Toyoura sand. Satisfactory agreement was found between the experimental and numerical uplift resistance-displacement factor relationships. In particular, the peak uplift resistance, response stiffness, and passive plastic zone development are found to be functions of the embedment ratio, shape, and size. However, previous design approaches cannot capture the size effect on the peak uplift resistance factor of the rectangular anchor foundation. [ABSTRACT FROM AUTHOR]

In this study, three-dimensional finite element models, incorporating an elastoplastic material model coupled with isotropic simple softening law, nonassociated flow rule, and shear-band effect, are validated for the evaluation of the shape effect of the square and rectangular vertically uploaded anchor foundations embedded in dense Toyoura sand with embedment ratio of 2 and width of 50 mm. The proposed numerical model has closely predicted experimental uplift load-displacement relationships. The shape effects on the results are also discussed in relation to the progressive failure around the foundations and the shape of the failure boundaries on the ground surface. [ABSTRACT FROM AUTHOR]

For a large pile foundation in China, four 1.0 m diameter 15 m long reinforced concrete bored piles are laterally jacked to their ultimate condition. The lateral deflections and bending moments of the piles under different horizontal loads as well as the failure pattern at ‘Ground’ level are measured. The moment distribution, the maximum moment and its location determined from several Winkler's models are compared with the in-situ measurements. Based on the full-scale measurements, the lateral stress-strain relationship for the soil is back-calculated. It is found that no single set of parameters is applicable to every load level if a simple stress-strain relationship is adopted. 3D finite element analysis was also performed for the test piles, and the predictions of the deflections and moments by 3D finite element analysis are found to be only slightly better than those of the simple Winkler's models. The failure pattern at ‘Ground’ level predicted by 3D finite element analysis is basically similar to the failure mechanism as measured on site. [ABSTRACT FROM PUBLISHER]

Abstract: When general-purpose finite element analysis software is used to model glacial isostatic adjustment (GIA), the first-order effect of prestress advection has to be accounted for by the user. We show here that the common use of elastic foundations at boundaries between materials of different densities will produce incorrect displacements, unless the boundary is perpendicular to the direction of gravity. This is due to the foundations always acting perpendicular to the surface to which they are attached, while the body force they represent always acts in the direction of gravity. If prestress advection is instead accounted for by the use of elastic spring elements in the direction of gravity, the representation will be correct. The use of springs adds a computation of the spring constants to the analysis. The spring constant for a particular node is defined by the product of the density contrast at the boundary, the gravitational acceleration, and the area supported by the node. To be consistent with the finite element formulation, the area is evaluated by integration of the nodal shape functions. We outline an algorithm for the calculation and include a Python script that integrates the shape functions over a bilinear quadrilateral element. For linear rectangular and triangular elements, the area supported by each node is equal to the element area divided the number of defining nodes, thereby simplifying the computation. This is, however, not true in the general nonrectangular case, and we demonstrate this with a simple 1-element model. The spring constant calculation is simple and performed in the preprocessing stage of the analysis. The time spent on the calculation is more than compensated for by a shorter analysis time, compared to that for a model with foundations. We illustrate the effects of using springs versus foundations with a simple two-dimensional GIA model of glacial loading, where the Earth model has an inclined boundary between the overlying elastic layer and the lower viscoelastic layer. Our example shows that the error introduced by the use of foundations is large enough to affect an analysis based on high-accuracy geodetic data. [Copyright &y& Elsevier]

The saturated sand surrounding an offshore pile foundation under quasi-static cyclic lateral load can show the physical phenomena of macromechanical densification and convective granular flow. Based on the results from physical model tests at different geometrical scales, this paper provides a certain quantification of such phenomena and discusses their causes and consequences. The progressive sand densification leads to subsidence of the soil surface and a significant stiffening of the pile behaviour. Conversely, the ratcheting convective motion of two closed cells of soil beneath the pile-head is responsible for an endless grain migration at the soil surface, the inverse grading of the convected material and a direct shear of the sand at the distinct boundary of the revolving soil domain. In this respect, and from a macromechanical perspective considering the soil as a continuum, it appears that the convecting material tends to follow gradient lines of shear stress during its ratcheting motion. Concluding the paper, the practical relevance of these phenomena and their extrapolation to other conditions are briefly discussed. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)