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The rigid inclusion technique has been used worldwide to reinforce soft soil for road and railway embankments and deep building foundations. This technique is studied through field tests and physical and numerical models. Most studies focus on embankments or slabs on soils reinforced with rigid inclusions. Previous research based on numerical modeling demonstrated that the load-transfer mechanisms for a rigid slab differ from those for an embankment. Here, a simplified physical model was developed to assess the load-transfer mechanism between the inclusion head and the load-transfer platform (LTP) under a rigid slab. This research focused on the use of an alternative material for the LTP, which is a compacted soil with or without cement. When the reinforced soil contribution is neglected, the LTP weight and applied load are transmitted completely to the inclusion cap (load-transfer efficiency of 100%). As the LTP material stiffness increases, the settlement magnitude decreases considerably. The experiments demonstrated that the applied load was transferred to the inclusion head through an inverted truncated load-transfer cone (LTC) over the inclusion; the external angle depended on the LTP material strength in accordance with Coulomb's theory. The principal stress state at the base of the LTC also was determined. Equations are proposed to determine LTP thickness and inclusion spacing. [ABSTRACT FROM AUTHOR]

Issue 1 The authors employed three-dimensional (3D) finite-element software Plaxis 3D ([1]) to model a ring foundation in a cohesive soil, where a quarter of the problem domain (i.e., a 90° sector of the domain) was discretized. The authors employed the commercial finite-element software, namely, Plaxis 3D, to determine the ultimate bearing capacity of ring foundations in cohesive soils. In particular, for both cases of rough and smooth foundations, Eq. (10) of the original paper cannot make a realistic prediction in terms of the change of undrained bearing capacity when the I k i value varies from 1 to 10. Rather, Eq. (10) of the original paper generates almost constant undrained bearing capacity with all I k i values for each interface condition (i.e., rough I q SB ult sb i 363 kPa and smooth case I q SB ult sb i 93 kPa). [Extracted from the article]

Combined piled raft foundation (CPRF) is an effective solution for supporting high-rise constructions. The traditional design philosophy of CPRF does not consider the capacity of foundation based on combined vertical (V), horizontal (H), and moment (M) load. However, V-M-H load acts on the CPRF system concurrently due to the action of wind, wave, earth pressure, and earthquake loading in addition to gravity loading. In this context, the present investigation deals with the effect of combined V-M-H load interaction on the behavior of CPRF in sand and clay, respectively. The response of CPRF under combined loading is obtained using a 3D finite element analysis. First, validation of the numerical model is performed considering the model test results conducted in Agartala sand and another based on the available field test result of Messeturm Tower in Frankfurt clay obtained from the literature. Further, failure and design envelopes for the validated CPRF system are developed considering V-M-H load in both sand and clay deposits attributing a variety of influential system parameters. Simplified expressions for design lateral and moment capacities are proposed based on multiple linear regression analysis. Finally, the implication in design based on the findings of the present study is illustrated using a prototype case study structure. [ABSTRACT FROM AUTHOR]

Drainage techniques can be employed to reduce damage of pile rafts in liquefiable ground by decreasing the build-up of excess pore water pressure and maintaining soil stiffness during earthquakes. This paper aims to evaluate the impact of drainage wells on the seismic response of floating piled rafts in fully saturated ground. In practice, floating piles are commonly employed as underpinning elements beneath the raft foundations to reduce undesirable settlement of the raft. Centrifuge experiments were performed on 2 × 2 piled raft foundations with and without drainage wells in mildly sloping ground. Two types of ground involving a uniform sand layer and a uniform sand layer with a superficial gravel layer were reconstructed, whereas the piles were floating within the liquefiable sand. The models were fully instrumented and sine waves were introduced to the models' base at the 80 g centrifugal acceleration. Records of the transducers demonstrate that the drainage wells system significantly decrease the settlement of foundation, dissipation time under dynamic loading by forming closer drainage routes, and excess pore water pressure ratio. In contrary, presence of drainage systems significantly increases the rafts acceleration response, and the bending moment and the axial force of the piles. Results of the piled raft systems in the presence and absence of the drainage wells and the superficial gravel layer are compared with together and also compared with the far-field in terms of the acceleration response, permanent settlement, and excess pore water pressure. [ABSTRACT FROM AUTHOR]

Based on the recommended range of HT ht by Basile ([2]), HT ht and HT ht are assumed for the present calculations. The interaction factor HT ht is defined in such a way that it decreases with an increase in the raft thickness HT ht but increases with an increase in the raft Young's modulus HT ht [Figs. The induced vertical stresses in the soil reduce to 10% of the applied vertical load HT ht at a depth HT ht three to four times the width of the raft HT ht . [Extracted from the article]

Recently, few nuclear facilities have been proposed on soil sites worldwide. Controlling the overall and differential settlement is a difficult task for a nuclear structure that rests on a soil site. Under these circumstances, a combined piled–raft foundation (CPRF) provides the required level of performance with a significant cost saving compared with a pile foundation. The combined system involves complexities in the interactions between the soil–pile–raft and superstructure system. The literature focuses on simulating the interactions between pile, soil, and raft. Until recently, the behavior of a CPRF that supported a heavy and massive structure had not been well studied and understood. A combined three-dimensional (3D) model of soil–pile–raft–superstructure systems will be developed in this study that considers the soil and interface nonlinearity along with the complex superstructure geometry. The modeling approach for the piled raft system will be validated using the standard benchmark problem and field case histories. Various aspects of a CPRF for a typical nuclear building (NB) will be investigated, such as the effect of the depth of soil medium, comparison of the behavior of the raft foundation, pile foundation, and CPRF, contact pressure distribution, pile behavior, soil behavior; and various performance indicators. The presented systematic procedure to configure the CPRF system could be useful in similar practical applications. This study indicated that the stiffening of the superstructure and sequential construction has a beneficial effect on the combined system. The findings of this study could be useful to frame the general guidelines for the economical design of CPRF systems. [ABSTRACT FROM AUTHOR]

Excavation induces stress changes and soil movement on existing floating piled rafts and elevated pile groups. Limited investigation of the effects of deep excavations has resulted in an incomplete understanding of pile foundation performance at the serviceability state. A series of three-dimensional (3D) centrifuge model tests and numerical simulations are conducted in this study to investigate the influence of raft contact on the response of an existing 2×2 piled raft in comparison to that of an elevated pile group when subjected to an adjacent multipropped deep excavation in dry sand. After rising g , an applied axial load was supported by 18% by the raft and 82% by the piles in the piled raft foundation prior to excavation. Owing to stress release and soil movement caused by the 8-m-deep excavation, the pile head load increased by 21% and 3% for the pile closer to the excavation for the piled raft and pile group foundations, respectively. Analysis of pile–soil relative settlement and raft contact pressure shows that a gap formed between the raft and ground surface in the piled raft, resulting in a load transfer from the raft to the embedded piles. A 20% larger settlement was seen in the piled raft foundation than in the pile group, to further mobilize shaft and end bearing resistances for the maintenance of vertical equilibrium. Moreover, 30% additional pile bending moment was induced due to excavation. [ABSTRACT FROM AUTHOR]

This paper investigates the response of framed buildings on raft foundations to tunnel construction using geotechnical centrifuge testing. Five framed building models were considered, and the influence of building configuration, weight, eccentricity, and soil density were evaluated. Soil and foundation displacements, frame deformed shape, maximum structure deformation parameters (deflection ratios and angular distortions), and associated modification factors are illustrated. Results indicate that unlike equivalent isotropic plates, framed buildings primarily exhibit shear behavior and a semi-flexible response. Building deformed shapes indicate that angular/shear distortions (considering bay slope and local tilt) are more appropriate for quantifying framed building distortions than deflection ratios. A relative stiffness parameter is suggested to relate maximum angular distortions to the greenfield settlement slope. Moreover, the efficiency of the available relative stiffness parameters for the deflection ratio modification factors is confirmed. Limitations of the equivalent plate approach and practical implications of the results for framed buildings are discussed. [ABSTRACT FROM AUTHOR]

A new simplified approach based on the pseudostatic method of analysis is proposed to investigate the response of a combined pile–raft foundation (CPRF) and a group pile considering the complex interaction. In this method, the raft is considered as a plate supported by group of piles and soil, where piles are modeled as Euler beam elements resting on elastic Winkler foundation and the raft is divided into square grids attached with horizontal springs. The reliability of the proposed method is verified by laboratory testing results and those of Plaxis3D simulations for a 4-piled raft system. Good agreement between the laboratory results, numerical simulations, and the proposed method is demonstrated, showing the potential applicability of the new simplified method. [ABSTRACT FROM AUTHOR]

In Example 2, HT ht should be 0.849 instead of 1.52 as reported in the paper, HT ht should be 0.021 instead of 0.032 as reported in the paper, and HT ht should be recalculated after revising the HT ht in the equation from 18,816 to HT ht (after performing the previous revisions). The authors have established a simplified method to predict settlement of piled raft foundations using a finite-element-derived database and statistical methods. In Example 1, HT ht should be 1.308 instead of 1.89 as reported in the paper and HT ht should be 0.525 instead of 0.475. [Extracted from the article]

Planning of construction technical specifications (CTS) for deep foundations is critical for ensuring works performed safely. k-nearest neighbors (kNN) is regarded as a practical algorithm for case retrieval in a case-based reasoning (CBR) cycle to search for past similar plans for new plan making. The parameter k and neighbors' weights affect the performance of the CBR cycle deeply but kNN neglects the weights' effect on case retrieval. The massive and multisource data of CTS of deep foundations presents a challenge for retaining case data in a database and for decision making due to an inefficient data process of the traditional tool. This paper presents a new framework to integrate weighted k-nearest neighbors (kkNN) to improve the performance of a CBR system for technical planning of deep foundations. It contains two parts: (1) a process to deal with a large amount of data derived from CTS; and (2) kkNN to obtain similar cases considering k and the weights of neighbors'. The feasibility of the proposed approach is validated through a case study and the evaluation result shows that the approach enhances the performance of the CBR cycle in creating construction technical specifications in deep foundation projects. [ABSTRACT FROM AUTHOR]

This study investigates the influence of soil–structure interaction (SSI) on period and damping of steel moment-resisting frame buildings supported by shallow footings on dry sand deposits. A series of impact hammer tests were conducted on a 3-story and a 6-story model steel frame for this purpose. Different base conditions (e.g., loose and dense sand beds, surface and embedded footings, heavily loaded and lightly loaded footings) were considered to gain a complete understanding of inertial SSI effects. Experimental results were compared with FEMA provisions as well as with analytical results obtained from a finite-element model. The period and damping amplifications are more prominent in the case of the 3-story building than in that of the 6-story building, indicating more sensitivity of short and stiff buildings to SSI over the taller ones. For a heavily loaded 3-story building on loose sand, the period and damping amplifications are 21 and 330%, respectively. Although the analytical results match well with those of the experiment, FEMA provisions tend to overestimate the responses, especially for the 6-story building. [ABSTRACT FROM AUTHOR]

Unreinforced masonry walls subjected to out-of-plane horizontal bending can fail by two alternate modes: stepped failure along the brick-mortar bond, or line failure cutting directly through the bricks. Because of random variations in material properties throughout a panel and the tendency for failure to occur across the weaker elements, vertical cracks will generally exhibit a combination of the two modes. This paper develops a pair of analytical methodologies that treat this phenomenon using a stochastic approach. The first part deals with calculating the ultimate moment capacity by allowing for the weakening effect associated with the mixed (stepped and line) mode of failure. This effect is quantified in terms of strength-reduction factors for mean and characteristic (0.05 quantile) values of strength, which may be applied toward generic ultimate strength design. The second part deals with estimating the relative probability of each failure mode and the probability distribution for the relative proportions of each failure mode along a crack. This is of particular relevance to seismic performance because the two failure modes lead to significantly different postcracking behavior. [ABSTRACT FROM AUTHOR]

In this study, the uplift load-carrying capacity of micropiles was investigated, focusing on the effect of various installation conditions including installation angle (θ), spacing (S), and group configuration. For this purpose, a series of uplift model load tests was conducted using single micropiles (SMP) and group micropiles (GMP). The uplift load capacity of both SMP and GMP increased with θ up to 30° but decreased for a higher installation angle of θ = 45°. Micropile spacing had less effect on the uplift load capacity for GMP. The uplift loadcarrying mechanism of inclined micropiles is proposed based on decomposed axial and lateral loads and resistance components. Based on the proposed load-carrying mechanism, axial and lateral load capacity ratios were proposed and adopted to formulate the uplift load-capacity equation for inclined micropiles. For GMP, the group-effect factor was proposed based on the reduction effect of group micropiles on the overall uplift load capacity. Full-scale uplift load tests were conducted to check the validity of the proposed method. Both SMP and GMP were constructed and tested. It was observed that the estimated results using the proposed method were in good agreement with the measured results. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to establish a complete analytical solution concerning the linear pressure distribution under rigid rectangular spread footings. An eccentricity diagram is developed to map the unique footing deformations and compression zones in each one of five distinct regions. For each region, the linear soil pressure, neutral axis position, and pressure values at the four corners are expressed in closed forms. The accuracy and consistency of the explicit expressions are verified by presenting several special boundary cases, whereas the physical interpretation is brought out by analyzing the eccentricity diagram. A generic nomogram providing the maximum soil pressure is also formed to promote efficient structural footing design. The developed analytical formulas for responses and resultants enable algorithmic implications without iterations and offer high computational efficiency. Proper examples, generated via developed computer software, exhibit how the theoretical content of this article is applied in practice. The software enables three-dimensional (3D) viewing of the deformed and undeformed physical and mathematical model of the structure, allowing detailed visual inspection of the results. [ABSTRACT FROM AUTHOR]

Loss of support as a result of voids underneath concrete slabs can initiate and propagate slab cracking in jointed plain concrete pavements. This paper investigates the hypothesis that foundation voiding occurs because of localized plastic deformation of the depressurized foundation as a result of slab curling and repeated application of traffic loads. Plane strain and three-dimensional (3D) nonlinear finite-element models of the subgrade foundation are presented. The analysis shows that voids underneath concrete slabs usually occur along the edge of slabs adjacent to the shoulder. The sizes of voids are primarily determined by foundation properties (cohesion stress and internal friction angle), slab properties, axle loads, and temperature gradients. Voids along the edge of slabs adjacent to the shoulder lead to high transverse tensile stresses on the top surface, which may result in top-down longitudinal cracking close to the outer wheel path. These same voids increase the longitudinal tensile stresses on the bottom surface at the edge of the slabs, which can increase the potential for bottom-up transverse cracking at the middle of the slabs. [ABSTRACT FROM AUTHOR]

This paper proposes an efficient hybrid approach for analysis of the responses of piled-raft foundations subjected to coupled loads (combination of vertical loads, horizontal loads, and moments) in layered soils. The proposed method comprehensively accounts for pile-pile, pile-soil surface, soil surface-pile, and soil surface-soil surface interactions. Moreover, to capture the influence of embedment and active/passive effects of piles, a modified Vesic's subgrade modulus for embedded piles and passive piles was adopted. To avoid a large number of time-consuming integration processes, the shear displacement method and elastic foundation beam method were employed to calculate the vertical and horizontal responses of a single pile, respectively, and the results were then extended for the pile group. The results calculated with the proposed method for piled-raft foundations in layered soils were found to have good agreement with those obtained from the more rigorous finite-element methods (FEMs) and elastic theory method in layered soils. It was found that the proposed procedure can accurately predict the responses of piled-raft foundations under complex loads in layered soils. [ABSTRACT FROM AUTHOR]

Stone columns are a popular formof ground improvement that can be applied to a variety of foundation solutions involving soft soil deposits. Many design methods are based on an assumption that columns with a length-to-diameter ratio greater than 4 bulge uniformly along their length. This mode of deformation is not valid for small groups of columns in which interaction between individual columns and the footing gives rise to more complex behavior. The deformational behavior of stone columns at serviceability limit state is of utmost importance, because settlement rather than bearing capacity criteria are generally more onerous in soft soils. The results of some high-quality laboratory studies have been informative in this respect, but the extrapolation of results from small-scale tests comes with the caveats associated with single-gravity laboratory testing. The FEM, in combination with advanced constitutive models, can provide a link between the deformational behavior and settlement performance of discrete column groups at working stress levels. A series of analyses was conducted to examine the influence of key design parameters such as column length, spacing, and the number of columns. The influence of a stiff crust was also examined, because the reference soil profile adopted for these analyses was that of the well-characterized Bothkennar test site. The following three modes of deformation were identified by examining the distribution of stress and strain within columns and the surrounding soil: individual punching, block punching, and bulging. Individual and block punching developed in short or closely spaced columns, whereas block punching was more prevalent in larger groups. Bulging develops in long, widely spaced columns and generally occurs at the point of lowest lateral restraint. In addition, novel parameters referred to as compression and punching ratios were developed to validate the in-depth analysis and identify the principal design parameters that influence the behavior of small groups of stone columns. The results indicate that the mode of deformation is governed by column spacing and length rather than the number of columns. This finding is important, because it indicates that settlement design methods that are developed for large groups of columns are applicable to discrete groups at similar spacings and lengths. It was also observed that the influence of the stiff crust forces bulging to occur deeper and might have led authors in the past to suggest the existence of a critical length. [ABSTRACT FROM AUTHOR]

Model testing for soft soil foundations with and without a prefabricated vertical drain (PVD) was performed to assess the consolidation and long-term performance of PVDs. Surface settlements and excess pore-water pressures at different depths were monitored throughout the applied multistage loading. Classical methods with improved solutions that considered variations in the discharge capacity and non-Darcian flow were applied via a back-analysis of the consolidation results. Parameters related to the smear effect and well resistance were discussed in these solutions. It was found that the foundation improved with PVD had an approximately 20% increase in the total degree of consolidation compared with untreated soft soil foundations; the well resistance of the PVD system not only existed but it also changed over time; the average discharge capacity in the model test under multistage loading condition was far less than the reported value; and the advanced solutions, especially the solution that considered the varied discharge capacity (with qw0 = 3 cm³/s and Aw = 4.12 × 10-6 1/s), gained a better fitting result than the classical solution. [ABSTRACT FROM AUTHOR]

In the present paper, the response of cylindrical storage tank foundation resting on stone column-reinforced ground has been studied considering the separation between the bottomraft and ground under liftoff condition. The bottomraft of the tank is idealized by a circular plate. The stone column-reinforced ground ismodeled as a tensionless foundation. Soft foundation soil and granular fill are idealized as a spring-dashpot element and Pasternak shear layer, respectively. Stone columns are modeled as stiff nonlinear springs. The stone columns are converted into equivalent concentric rings with one stone column at the center to simulate the axisymmetric condition for the analysis. The governing differential equations are derived fromthe classical theory of thin plate and solved using the finite-difference technique. A parametric study is performed to investigate the differences between the response of tensionless and conventional elastic foundation systems. It is observed that tensionless foundation idealization is essential to analyze the liftoff and avoid erroneous design of the raft for the cylindrical storage tank. Recommendations are also suggested to avoid possible liftoff. [ABSTRACT FROM AUTHOR]

Monopiles are the most commonly used foundation type for offshore wind turbine (OWT) structures and are characterized by relatively large geometric dimensions, compared with offshore pile foundations typically used in the oil and gas industries. To date, there are no established technical guidelines tailored for the design and analysis of OWT monopiles. This paper first identifies various intrinsic drawbacks involved with the existing design and analysis methodologies as applied to OWT monopiles. Next, a comprehensive experimental program of 1g repeated lateral load tests, performed on a scaled rigid monopile installed in dry sand beds, is presented to investigate its behavior under various loading scenarios. The experimental results provide insights into the various blurry issues in the existing literature related to monopile behavior under long-term repeated lateral loading. Lateral soil resistance profiles were determined from the measured pile bending strain data and found to be markedly dependent on the degree of the polynomial function used for curve-fitting of the bending strain data. Finally, an experimental model is presented for estimation of the pile's accumulated rotation, which takes into account various basic characteristics of the applied lateral load cycles. [ABSTRACT FROM AUTHOR]

This paper presents a case study of applying a new device termed deformation adjustor in piled raft foundations to support a highrise building. The deformation adjustors are mounted on a pile head to optimize load distribution of a piled raft foundation so that a relatively uniform foundation deformation can be achieved in complicated load, construction, and soil conditions. In this case study, the project site is located in a coastal city in China, featuring complicated subsurface soil conditions with abundant large boulders. The project was put on hold for a decade because in the complicated soil conditions the piles could not be installed to the required depths. The project resumed with introduction of deformation adjustors which helped to shift the applied loads from piles to subsoil below the raft and thus considerably reduced the pile lengths. This case study describes the preliminary design of pile-raft foundations with deformation adjustors, followed by a comprehensive monitoring program for settlements, earth pressures, and pile top reaction forces during and after building construction. Based on the long-term monitoring, subsoil below the raft was able to bear 83% of total applied loads, whereas the piles carried 17% of the loads. Based on this case study, deformation adjustors were proved to be an effective and economical solution for piled raft foundations to support high-rise buildings in complicated subsurface conditions. [ABSTRACT FROM AUTHOR]

The combined pile-raft foundation (CPRF) has been widely recognized as economic and rational foundation for high-rise buildings when subjected to vertical loading because of its effectiveness in load sharing by both raft and pile components. This results in smaller total and differential settlements with a reduced number of piles as compared with group piles. Until recently, the behavior of CPRF when subjected to lateral and real earthquake loading conditions in addition to vertical loads has not been well understood as a result of the complexities involved in the interaction of the pile, soil, and raft under such loading considerations. In the present study, an attempt has been made to investigate the behavior of CPRF with the use of centrifuge testing and a numerical model under pseudostatic and dynamic loading conditions carried out with finite-element software. After successful validation of the present CPRF model with both centrifuge and numerical model results, the same model was used for further study under El-Centro 1979, Loma Prieta 1989, Bhuj 2001 and Sikkim 2011 real earthquake pseudostatic loading and real acceleration-time history. The maximum displacement and bending moment were observed at the pile head, which is attributable to the rigid fixity of the piles with the raft. The crossover point in the bending moment profile was observed at shallow depths for all cases of loading. The occurrence of the resonance condition that yielded maximum horizontal displacement of the CPRF as a result of one of the input motions is also highlighted in the present study. The difference in the response of soil just below the raft of the CPRF and at the far field indicated that near-field and far-field ground motions were not in tandem. A case study on an existing CPRF of Messeturm Tower, Frankfurt am Main, Germany, is also presented. The existing CPRF of Messeturm Tower was modeled and analyzed under static and pseudostatic loading conditions. Obtained results show good correlation with the static field-measured results. Results in terms of bending moment in piles, total settlements, and normalized lateral displacement (u/D) are reported. The present findings are useful because they provide broader understanding of the response of the CPRF under pseudostatic and dynamic loading conditions. [ABSTRACT FROM AUTHOR]

Precipitation is one of the most common moisture sources on which building designers focus. Water comes from both top down and bottom up. Although foundations are sometimes constructed out of pressure-treated lumber, generally they are constructed from poured concrete. In a wet climate zone, the foundation of a house is often under continuous contact with moisture, which is mainly caused by rundown rainwater, wet soil, a high water table, or a combination of all these factors. This causes rot growth and decay of the wood-frame structure as it sits constantly on the damp foundation concrete. In this research, moisture transfer between concrete and wood is investigated under three different scenarios: a case with direct wood and concrete contact and two cases with different moisture barriers between the two materials. The moisture barrier materials considered in this study are the damp-proofing layer and sill plate gasket. The moisture transfer processes in these three cases are investigated in a field experimental setting using a customized experimental setup for 1 year. The experimental data suggest that using damp proofing and a sill gasket helps restrict moisture transfer. [ABSTRACT FROM AUTHOR]

This study examines the behavior of high-mast lighting pole (HMLP) foundations through the use of nonlinear finite-element modeling. HMLPs utilize nuts and threaded rods to clamp the light pole structure's base plate to the foundation. Inspections by the Alaska Department of Transportation and Public Facilities (AKDOT&PF) have revealed widespread loosening of the nuts used on HMLPs over time. The threaded rods used are F1554 Grade 55, which are heat treated from mild steel rods, Fy = 248 MPa (36 ksi) to gain additional yield strength. This study briefly highlights the difference in postyield behavior in mild steel and high-strength steel, and proposes a probable mechanism behind the clamp-load loss experienced by Alaska's HMLPs. Because the HMLPs are much taller than traditional lighting poles, they experience larger external wind loading. This wind load is potentially stressing threaded rods into the postyield range. A previous study shows that the current tightening procedure is likely not undertightening nuts, which could be a major culprit behind loosening. As a result of this and previous research, it is believed that the nuts aren't loosening in the traditional sense--losing clamp load by rotating on the threads. Instead, the threaded rods undergo significant postyield strain during external loading. This plastic deformation is large enough in magnitude to cause the bolted joint interface to lose clamp load when the external force is removed. One factor that exacerbates this effect in some pole configurations is prying action, which is not accounted for in the design. The clamp loss mechanism is examined by applying wind loads to three pretensioned HMLP configurations using finite-element analysis software (ABAQUS). The analysis uses 3-D solid elements, contact surfaces that allow for separation, bonding surfaces where contact surfaces are not required, boundary conditions that approximate reality, displacement controlled pretension, and external wind loading represented by coupled moments. [ABSTRACT FROM AUTHOR]

The lifecycle analysis and assessment of concrete structures requires an efficient evaluation and prediction of time-variable mechanical and chemical degradation processes. Inspection systems and novel monitoring methods are of valuable support in these important tasks, but due to their practical feasibility and the costs that they entail, they also present limitations. Therefore, information gathered with inspection methods for structural performance assessment needs to be used in the most effective manner possible, e.g., with respect to serviceability limits, bearing capacity, robustness, and redundancy of a given structure, among others. The aim of this paper is to present a framework for the prediction of time-dependent performance indicators of concrete structures prone to fatigue, with emphasis on a wind turbine foundation, including reliability. A theoretical background and selected structural performance indicators as well as associated lifecycle prediction methods--incorporating inspection and monitoring information--are presented. [ABSTRACT FROM AUTHOR]

On the basis of observed data and numerical calculations of dam structural responses, the back-analysis approach is usually used to determine the material parameters of a dam and its foundation. The reasonableness of the obtained result is related to the chosen structural responses and their observations and calculations. To advance the accuracy and efficiency of a back-analysis, some methods need to be adopted to implement the optimal selection for the preceding resource. The criterion of optimal selection is presented. The parameter sensitivity is taken as a key index of optimal selection. The uniform design method is combined with an artificial neural network and support vector machine to build the mapping relationship between multiple material parameters and dam structural responses at different positions. According to the preceding mapping relationship, models are proposed to calculate the sensitivity of a structural response on the material parameter. The parameter sensitivity-based method choosing the optimal resource is developed. One actual concrete gravity dam is taken as an example. The proposed method is used to implement the optimal selection of a back-analysis resource of an elastic modulus on a dam body and a deformation modulus on a dam foundation. The accuracy and efficiency of the optimal resource-based back-analysis is verified. [ABSTRACT FROM AUTHOR]

This paper introduces a new system that utilizes the advantages of boundary element analysis in structural engineering applications. A standardized building information model (BIM) for automated structural analysis and design of reinforced concrete plates based on the boundary element method (BEM) is proposed. Based on the model view definition approach, BIM standards are presented for the preprocessing and postprocessing of BEM analysis. Furthermore, standards are proposed for automated structural design of structural slab and beam elements based on the BEM analysis results. For each of the BIM components, standards are provided for the object structure, data flow, and graphical user interface (GUI). The extensibility of the software and applicability for a wide range of research and practical applications are considered in all the proposed standards. The system created can act as the basis for structural analysis and design of building floor and foundation problems. Object-oriented programming is used to implement the standards in a prototype. The prototype was verified by application to the solution of practical structural engineering problems. The performance of the proposed system is evaluated in terms of the modeling and the processing time required to analyze typical structural engineering applications using the prototype. [ABSTRACT FROM AUTHOR]

Difficulties in obtaining high-quality soil samples from offshore sites and heavy involvement of lab testing and engineering judgment have necessitated increasing reliance on in situ penetrometer tests, giving continuous penetration resistance profiles. This paper reports a framework for estimating spudcan penetration resistance directly from continuous resistance profile of a full-flow penetrometer (T-bar) test in single-layer clays and calcareous silts. The framework was validated chiefly against centrifuge test data, supplemented by some reported field data. [ABSTRACT FROM AUTHOR]

This work provides a detailed description of the full-scale experimental tests performed on the dynamic behavior of a shallow foundation under intermediate strains. Awind tower supported by the foundation was subjected to a snap-off test, i.e., it was first pulled with a cable and then suddenly released, thus inducing free oscillations of nonnegligible amplitude in the whole system. The motion induced was measured with a digital camera, seismometers, and accelerometers attached to the surrounding ground surface and to the wind tower. An innovative interpretation technique based on optimizing a few meaningful parameters obtained from the recorded time histories was required by the heterogeneity of the data collected and the accuracy needed to deduce the behavior of the foundation plinth. The analyses showed that the rotational stiffness of the foundation plinth was approximately 10 times greater than that of the base joint, which in turn was approximately one order of magnitude greater than that of the wind tower. As a result, the vibration phenomenon was driven by the wind tower, which induced a sort of forced, damped, harmonic excitation in the foundation such that the tower's oscillations and the foundation's rocking were decoupled from one another. Seismometer measurements performed on the ground surrounding the foundation plinth enabled an assessment of the geometrical attenuation of the surface vibrations induced by foundation rocking. To the best of the authors' knowledge, the geometrical attenuation assessments reported in this study are the first to be published on the deformations of the ground surrounding a rocking foundation, and could serve as a useful reference to validate constitutive models for simulating small-strain soil response. [ABSTRACT FROM AUTHOR]

The use of recycled materials and sustainability are two factors taken into consideration during the design of environmentally conscious buildings, but structural performance is still the foundation of sound design. Modern day building designs many times incorporate performance-based methodologies to combat the effects of extreme loadings. The key of such designs is to absorb high amounts of energy and sustain loadings under excessive deflections. Fiber-reinforced concrete and concrete containing rubber particles have increased levels of toughness in comparison with conventional concrete. This paper presents the results of an experimental investigation focused on the material properties of fiber-reinforced rubber concrete. Rubber particles were used at various concentrations to partially replace coarse and fine aggregates coupled with the addition of fiber reinforcement. The investigation includes an evaluation of standard fresh and hardened concrete properties. Results show fiber reinforcement counteracts the negative effects of using rubber particles to replace traditional aggregates, confirming the feasibility of combing the two constituents. [ABSTRACT FROM AUTHOR]

A newly built roller-compacted concrete gravity dam is located on the Yalongjiang River in southwest China. Complex geological conditions greatly puzzled the designers of the project. There are abundant joints within the riverbed that form the double- inclined wedge foundation. This is a typical mode of instability of concrete gravity dams. The equal-K method, which falls into the category of conventional limit-equilibrium methods, is provided in the design codes of gravity dams to evaluate the stability of a dam against sliding along deep failure surfaces. The factor of safety calculated by the equal-K method is determined by the angle of the force acting on the interface of the two inclined wedges, denoted by φ, which is unspecified in the design codes. On the basis of Sarma's assumption, this study proposes an algorithm for the determination of ∅, which needs only slight improvement of the algorithm in the existing codes. The justification of the proposed procedure is demonstrated by showing that the results from the proposed procedure are very close to those from a rigorous limit-equilibrium method in which all equilibrium conditions are satisfied. [ABSTRACT FROM AUTHOR]

An experimental program of large-scale direct shear tests was conducted to evaluate shear strength of a composite liner consisting of a textured geomembrane (GMX) over a hydrated needle-punched geosynthetic clay liner (GCL) for a wide range of normal stress, including high-stress conditions (>4 MPa). Tests were conducted with specimens placed between hard backing plates (single-interface) as well as between sand and gravel layers (multi-interface) to investigate the effects of local stress concentrations from coarse soil particles. Single- and multi-interface specimens experienced similar transitions from GMX=GCL interface failure at low normal stress to GCL internal failure at high normal stress. Failure surfaces for the single-interface specimens were essentially planar. Failure surfaces for the multi-interface specimens exhibited out-of-plane deformation (i.e., dimpling) that occurred because of variation in contact stress from the overlying gravel layer and increased with increasing normal stress. This deformation yielded modest percentage increases in peak shear strength and large percentage increases in large displacement shear strength and produced changes in local thickness and local bentonite dry mass per unit area for the GCL specimens. Direct shear tests conducted on single-interface GMX=GCL composite liners placed between hard backing plates are unlikely to reveal geomembrane out-of-plane deformation and damage effects but are likely to yield conservative (low) shear strengths for GMX=GCL composite liners that are placed in close proximity to coarse soils in the field. [ABSTRACT FROM AUTHOR]

This paper presents a case history of the successful application of observational method to instruction microtunneling with successive pipe-jacking. The microtunneling project is the construction of four parallel pipes under Guan River in Jiangsu, China. Four parallel tunnels with external diameter of 4,160 mm and horizontally spaced at 4.8 m apart were jacked over 450 m in cemented silty clay and sand by two slurry-balance microtunnel boring machines (MTBM) at a depth of 4.6 m under the river bed. Since the overburden soil is very thin, proper control of tunneling operations was of utmost importance for maintaining the stability of the river bed. In order to optimize the operation parameters prior to construction under the river bed, a field trial was conducted, which included measurement of ground surface settlement, subsurface settlement, and lateral displacement of the subsurface soils, as well as excess pore water pressure and earth pressure. The relationship between ground response and construction operation parameters is summarized. Appropriate operation parameters were applied during tunneling under Guan River. Although tunneling and pipe jacking under the river was successfully carried out, a difficulty was encountered when the MTBM reached the opposite bank and large settlements were observed. This paper discusses the technical issues faced and lessons learnt from interpretation of the monitoring data collected. [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 examined the vibrations of a hinged-free nonlinear beam placed on a nonlinear elastic foundation. The authors found that specific combinations of an elastic modulus in the elastic foundation resulted in 1:3 internal resonances in the first and second modes of the beam. This prompted adding a dynamic vibration absorber (DVA) on the elastic beam in order to prevent internal resonance and suppress vibrations. When the DVAwas placed at the free end of the beam, the boundaries were time dependent. Thus, a shifting polynomial function was used to convert the nonhomogeneous boundary conditions into homogeneous boundary conditions. The authors analyzed this nonlinear system using the method of multiple scales (MOMS). Fixed-point plots were also used to facilitate the observation of internal resonance. This made it possible to study the influence of nonlinear geometry and nonlinear inertia associated with the vibration of the elastic beam. The authors also examined the combination of optimal mass ratio and elastic modulus for the DVA in order to prevent internal resonance and achieve optimal damping effects. In the nonlinear beam investigated in this study, the placement of a DVA between 0.25l and 0.5l from the hinged end of the beam proved the most effective for damping; locations between 0.7l and 0.8l on the beam were ineffective. Finally, numerical methods and simple experiments were studied to compare the results from MOMS and demonstrate the effects of the DVA of this model. [ABSTRACT FROM AUTHOR]

Soft subgrades are not strong enough to provide the required degree of compaction for a pavement embankment's foundation. Therefore, it is required to treat the subgrade soil or construct a working platform on top of the soft subgrade to ensure proper compaction of the subsequent layers. The constriction sizes of the granular materials used for a working platform are comparatively higher to restrict the erosion of overlying embankment materials. This condition would lead to severe material loss in the embankment layer in cases where the embankment is constructed with dispersive soil, which becomes structurally unstable in wet conditions and appears to disperse in water. This paper investigates the contact erosion failure at the foundation of a pavement embankment constructed with dispersive soil as a result of groundwater fluctuation. Experimental studies were conducted on a laboratory model test apparatus designed to simulate the conditions in the pavement embankment's foundation. The experimental studies revealed that the magnesium dominant clayey soils also susceptible to contact erosion failure due to soil dispersion. Also, the experimental results show that even a small percentage of dispersive clay particles present in the embankment soil would influence the contact erosion failure. [ABSTRACT FROM AUTHOR]

Failure of foundations induced by earthquakes occurred many times in the past. There is a general lack of data recorded during earthquakes in the field about seismic response of such foundations. According to the results of some previous laboratory tests and numerical analyses, anisotropy of fabric of soil grains has significant influence on dynamic soil response. However, there is hardly any realistic physical data available to analyze the influence of fabric anisotropy on the response of foundations during earthquakes. Centrifuge tests are small scaled model tests which have been widely used to study the mechanism of response and to verify and validate design methods and numerical simulations. In this study, 12 centrifuge tests were carried out to study the effect of fabric anisotropy on seismic response of foundations. Important parameters in the response are evaluated and implications for design are discussed. [ABSTRACT FROM AUTHOR]

Growing urbanization is leading to more structures being constructed close to each other, resulting in substantial interaction between their foundations. Although the interaction between two shallow foundations and between piles in a pile group has been studied by several researchers, the effects of interaction between shallow and deep foundations are not very well understood or studied. Not much published literature is available for practicing engineers to analyze and design shallow and deep foundations that are constructed adjacent to each other. The second author of this paper was recently involved in a project in which a structure designed to be supported on drilled shafts was supposed to be constructed adjacent to another structure designed to be supported on a large mat foundation with high floor load. Although the authors have performed a detailed parametric study using finite-element techniques to better understand stress distributions and develop a simplified method to analyze this type of problem, this paper is only focused on estimating lateral stresses on the shafts and their lateral load analysis. A stress bulb for lateral stresses under a uniformly loaded square foundation is proposed, which is a significant tool for practicing engineers to understand lateral stress distribution below a uniformly loaded square area and estimate lateral stresses on nearby deep foundations. [ABSTRACT FROM AUTHOR]

Finding an optimum reinforcement layout for underground excavation can result in a safer and more economical design, and is therefore highly desirable. Some works in the literature have applied topology optimization in tunnel reinforcement design in which reinforced rock is modeled as homogenized isotropic material. Optimization results, therefore, do not clearly show reinforcement distributions, leading to difficulties in explaining the final outcomes. To overcome this deficiency, a more sophisticated modeling technique in which reinforcements are explicitly modeled as truss elements embedded in rock mass media is used. An optimization algorithm extending the solid isotropic material with penalization method is introduced to seek for an optimal bolt layout. To obtain the stiffest structure with a given amount of reinforced material, external work along the opening is selected as the objective function with a constraint on the volume of reinforcement. The presented technique does not depend on material models used for rock and reinforcements and can be applied to any material model. Nonlinear material behavior of rock and reinforcement is considered in this work. Through solving some typical examples, the proposed approach is proved to enhance the conventional reinforcement design and provide clear and practical reinforcement layouts. [ABSTRACT FROM AUTHOR]

Geosynthetics such as geogrids or geotextiles are often used for the reinforcement of weak soils. Much research has been performed to investigate the bearing capacity of reinforced shallow foundations using the limit equilibrium method with Mohr-Coulomb failure criterion. In this paper, the loading behavior of reinforced strip footings was studied numerically using a commercial finite difference program with a double-yield soil model. First, the load-settlement curve of an unreinforced strip footing was simulated using both Mohr-Coulomb failure criterion and the double-yield model. The simulated bearing capacities were then compared with Terzaghi's solution. The effects of various parameters, such as burial depth and length of the reinforcement, as well as arrangement of two reinforcement layers, were also studied. Results of this study indicate that the loading behavior of strip footings simulated with the double-yield model is more realistic, and the optimum burial depth and length of reinforcement obtained from this study also agree with values reported by previous investigators. [ABSTRACT FROM AUTHOR]

This paper describes a systematic approach of inspection, diagnosis, and repair for masonry walls and their claddings, aiming at facilitating the inspection process and deciding on the repair of these elements. It also helps to combat their degradation. Based on a visual analysis, the inspector is able to identify anomalies and use the proposed system tools to establish correlations with its source, delineate an accurate diagnosis, and determine the best repair technique. The tools that allow a faster and simpler inspection and decision are presented here. The nature of the anomalies, their related causes and appropriate repair techniques are classified, listed, and then related through correlation matrices to create a database. This equips the inspectors with the information they need about the pathology in masonry walls, as well as its classification through suitable terminology, so that a statistical analysis can be performed to find the chief causes of the anomalies. The system was developed under a strategy of proactive maintenance, and it represents an innovation that is as useful to rehabilitation in southern Europe as it is in other regions where masonry walls are a widely used technique. [ABSTRACT FROM AUTHOR]

This paper presents the earthquake response of three low-rise frame-wall-foundation centrifuge building models, including a structural hinging-dominated, foundation rocking-dominated, and balanced design model. The models were designed such that the capacities of the dominant inelastic elements varied; however, each was subjected to a similar sequence of earthquake shaking in a 30-g centrifuge environment to facilitate comparison. Experimental results reveal that the traditional frame-wall building with a strong foundation (i.e., a hinging-dominated system) has the least potential to recover from displacements induced during earthquake shaking. As a result, this system suffered the most significant residual deformation. In contrast, systems with rocking foundations sustained a smaller peak roof acceleration, residual drift, and peak base shear despite the relatively larger peak transient drift demand. Consistent with slow cyclic test results, dissipated hysteretic energy was reasonably distributed amongst superstructure and substructure inelastic components in the balanced model during moderate and high intensity shaking. [ABSTRACT FROM AUTHOR]

The mechanism of foundation rocking has received much attention recently due to its appealing seismic resistant features, namely, self-centering tendency and energy dissipation capability. It is well recognized, however, that other inelastic mechanisms will contribute to a system's seismic resistance. Considering the strength difference between a rocking footing and a shear wall structural fuse, and the system symmetry, six different two-story-two-bay frame-wall-foundation building models were constructed and tested in a geotechnical centrifuge. In this paper, the test program and experimental results when the models were subjected to slow cyclic loading are presented. A companion paper presents results from the dynamic phase of testing. Results indicate that, with the aid of foundation rocking, the system behaves in a ductile and stable manner with no strength degradation, even when the model is pushed to a drift of more than 2.5%. Importantly, when structural and foundation component strengths are approximately equal, the hysteretic energy is reasonably distributed among the superstructure inelastic components and the rocking foundations. Finally, numerical analyses predictions demonstrate comparable local and global response to measurements obtained during the experiments. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid numerical method for the evaluation of dynamic impedance of rigid foundation embedded in anisotropic multilayered soil. The proposed approach includes two main parts: (a) the solution of wave propagation in anisotropic multilayered soil in the frequency wave-number domain; (b) the evaluation of Green's functions for a buried source lying in the anisotropic multilayered soil in the frequency spatial domain. The derivation of part (a) is based on the precise integration method (PIM) and the mixed variable formulation (MVF) of wave motion equations, which ensure accuracy of the solution and make it convenient to deal with the assembly of layers for multilayered soil. Part (b) can be preceded by applying the inverse Fourier transformation directly. Finally, the flexible volume method is used to obtain the impedance of foundation embedded in anisotropic multilayered soil. A comparison of the numerical results with those available in the literature validates the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Tables 2 and 3 list the calculated results of HT ht obtained by the discussers, along with the values of HT ht , HT ht , HT ht , and the shape factor HT ht for the piled raft foundation cases listed in Tables 1 and 2, respectively, in the original paper. None of the calculated values of HT ht are greater than 1.15. [Extracted from the article]

The discussers considered two possibilities: (1) 10% of the pile load transferred to the pile toe and 90% to the pile shaft and (2) 50% of the pile load transferred to the pile toe and 50% to the pile shaft. With the loading carried by the raft and the pile group, the settlement of the piled raft could be simply evaluated by the Aoki and Lopes ([1]) equations. The calculation of the raft and pile group stiffness allowed the estimation of the load shared by the raft and that shared by the pile group. [Extracted from the article]

What will be the limiting condition for the maximum number of piles in a raft that can be used for the reliable and accurate calculations of HT ht and HT