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The identification and repair of structural damage in building foundations are critical tasks in ensuring the safety and integrity of civil infrastructure. This research paper proposes a method based on genetic algorithms for the identification and repair of structural damage in building foundations. The proposed approach begins with the identification of structural damage by analysing sensor data, including vibration measurements and strain gauges, obtained from the building's foundation. A genetic algorithm is then employed to optimize the identification process by iteratively searching for the most likely damage scenarios based on the collected sensor data. Once the damage is identified, the algorithm proceeds to develop an optimal repair strategy. It considers various parameters, such as available repair materials, budget constraints, and desired structural performance, to generate a repair plan that minimizes cost and maximizes the restoration of structural integrity. The repair plan is optimized using the genetic algorithm to find the best combination of repair techniques and materials. To evaluate the effectiveness of the proposed method, extensive simulations and case studies are conducted on different types of building foundations. The performance of the algorithm is assessed in terms of its accuracy in identifying structural damage and the efficiency of the repair strategy. [ABSTRACT FROM AUTHOR]

Coastal civil infrastructure is vulnerable to the effects of climate change. Hurricane storm surge and coastal flooding can cause significant hydrostatic and hydrodynamic loads on structures while saltwater intrusion (SWI) may lead to deterioration of foundations. The effects of saltwater intrusion due to Sea Level Rise (SLR) on the foundations of buildings and other civil infrastructure is poorly understood. Such damages may not be detected in a timely fashion nor be insured, leading to significant and unanticipated expenses for building owners. In this study, we evaluate the impact of SWI due to various SLR scenarios on the corrosion of reinforcement in foundations of nearly 137,000 residential buildings in low-lying areas surrounding Mobile Bay, AL. We find that the potential for costly damage is significant. Under an extreme SLR scenario, the annual expected repair costs for the foundations of the studied homes may reach as much as US$90 million by 2100. [ABSTRACT FROM AUTHOR]

Cavities are common subsurface anomalies that have a significant impact on the bearing capacity of footings. While cavities behave three-dimensionally, in previous studies, the analysis of cavities has been limited to two-dimensional plane-strain analysis because of the time-consuming nature and complexity of three-dimensional modeling. However, this study demonstrates that the bearing capacity factor derived from three-dimensional modeling can be up to 10 times higher than that obtained from plane-strain analysis, highlighting the importance of considering three-dimensional effects. The present paper conducted three-dimensional simulations to investigate the impact of spherical cavity on the failure mechanisms and bearing capacity of footings under undrained conditions. An extensive parametric study was performed to investigate the influential parameters, including footing width to cavity dimension ratio (B/D), cover depth ratio (C/D), overburden factor (γD/Su), and void eccentricity ratio (S/D) for both circular or square footings. The results indicate that increasing the overburden factor and void eccentricity ratio leads to a decrease and increase in the bearing capacity of the footing, respectively. Furthermore, changes in other parameters can either increase or decrease the bearing capacity depending on the characteristics of the cavity (size and location) and footing (size and shape). General solutions for the bearing capacity factor are provided for different variations of the dimensionless parameters. This study also examined various failure mechanisms, including both cavity-independent and cavity-dependent failure mechanisms, associated with circular and square footings and influential parameters. These mechanisms are categorized into three zones for cavity-independent failures and four zones for cavity-dependent failures. The changes in the influential parameters including B/D, S/D, γD/Su, and C/D lead to changes in the type of failure mechanism and the size of the failure zones, while the foundation shape does not have a significant effect on the failure mechanism. Sinkholes and underground cavities annually contribute to infrastructure damage and financial losses. The 1981 incident in Winter Park, Florida, exemplifies the real-world consequences. Previous investigations have been limited to two-dimensional models due to the time-consuming nature and complexity of three-dimensional modeling, but the real-world nature of cavities in three dimensions requires a more comprehensive understanding. This study directly addresses this need by investigating the impact of three-dimensional cavities on the bearing capacity of circular and square building foundations, also known as footings. This study thoroughly investigated the factors influencing the results, encompassing cavity size, depth, soil weight, and off-center position. It extensively explored potential footing failures, providing detailed discussions. Our findings are presented as easy-to-understand maps and charts covering a broad range of potential scenarios. These visual tools can help engineers and researchers accurately estimate the stability of a building's foundation when a cavity is present underneath. In simpler terms, this research has created a handy tool for professionals to predict the potential danger posed by hidden cavities to buildings and infrastructure. This knowledge can then be applied to ensure safer building practices, potentially saving a significant amount of money and preventing accidents in the future. [ABSTRACT FROM AUTHOR]

In any high-rise building construction based on piles, it is essential to correctly evaluate their response when subject to high loads to avoid oversizing and consequently high costs. This work falls within the framework of the FONDASILEX project, which studies the behaviour of the pile foundations and the soil within the 'Silex2' tower project built in the Part-Dieu district in Lyon, France. This paper presents the geotechnical instrumentation executed for the foundations and the soil to enable the real-time monitoring of their behaviour. It details its conception, execution and limits. Five different types of electrical and unconventional sensors, including the fibre optic technique, which is based on reflectometry by Rayleigh scattering, were employed. This instrumentation allowed us to measure the soil settlement, the applied load at the head of the pile and the induced deformation in the concrete. The obtained measurements showed good agreement between all the sensors and were compatible with the real applied load. The results of this monitoring completed with an additional specific study to characterize the soil will be used in a future study to calibrate numerical models simulating the behaviour of high-rise building foundations. [ABSTRACT FROM AUTHOR]

In many densely populated cities, buried networks of urban services, such as facilities and sewage tunnels or sewer pipes are constructed adjacent to or beneath nearby building foundations. It is vital to consider the seismic interaction of shallow tunnels with these foundations in liquefiable deposits. In such circumstances, segmental tunnels are of interest due to being considered non-rigid structures, and their utilization has increased in shallow urban tunneling. Using a two-dimensional finite difference code, a shallow tunnel subjected to uplift pressures due to soil liquefaction is studied. An advanced constitutive model (PM4Sand) is employed in the numerical model along with a fully coupled Fluid-Solid solution to simulate soil liquefaction. First, a centrifuge laboratory model was used to validate the coupled hydrodynamic numerical simulations. Additionally, it allows for the use of real sand properties. The validation results indicated a good agreement between the numerical simulations and the centrifuge tests for tunnel uplift (maximum difference of 7 %) and the excess pore water pressure ratio (r u). Next, based on the results, segmentation of the tunnel lining was found to be effective in reducing ground surface uplift by 23 %. Then, a segmental tunnel lining with and without a five-story building on a combined footing foundation is considered under soil liquefaction. The interaction between the shallow foundation of the five-story building and the segmental lining highlights the significant influence of tunnel uplift on shear force, bending moment, tilting and rotation of the foundation and surface structure. Additionally, the presence of the foundation and surface structure leads to a reduction in tunnel uplift (by 29 %) and ground surface uplift (by 21 %). Lastly, a permeation grouting method has been utilized to mitigate seismic soil-surface structure-underground structure interaction (SSSSUSI) during liquefaction, resulting in a 90.7 % reduction. [Display omitted] • A centrifuge laboratory model was utilized to validate the coupled hydrodynamic numerical simulations. • A two-dimensional code for seismic soil-surface structure-underground structure interaction was developed. • Segmented linings exhibit relatively better performance against soil liquefaction compared to continuous linings. • The combined footings foundation mitigates uplift of the tunnel structure and ground surface during soil liquefaction. • Mitigation grout holes effectively reduce soil liquefaction around the tunnel. [ABSTRACT FROM AUTHOR]

Diaphragm walls are rectangular shaped cast in place deep foundations. There are two critical phenomena occurring, according to which the final quality can be affected: bentonite suspension exfiltration and concrete placement. Some imperfections seem to appear recurrently on the surface of the final wall. The defects are known as shadowing pathologies. The main reasons can be attributed to the dual effect of exfiltration mechanisms and kinematics of concrete flow. The objective of this study is developing a numerical tool to prevent the appearance of shadowing pathologies by visualizing the concrete flow in the presence of a bentonite suspension. This paper presents the results obtained from 2D and 3D models of diaphragm wall construction using COMSOL Multiphysics. The CFD model helped in solving a multifluid and particularly a two‐phase flow. The 2D modeling has considered a fresh slurry and an exfiltrated (or polluted) suspension neighboring soil and followed concrete flow with two rheological behaviors in two reinforcement configurations. Then, 3D simulations were compared to actual experimentation results, which were undertaken to construct diaphragm walls in the laboratory. By comparing the results of the simulations to the experimental outcomes, it has been possible to validate the model. The resulting simulations could clearly explain the occurrence of the pathology where the flow pattern and volume fraction of the fluid flow were determined. From the results obtained, it can be conducted that a compliant concrete mix but at the lower limit for the consistency recommendations, leads to pathologies, just like a polluted slurry. [ABSTRACT FROM AUTHOR]

Thickening the foundation slab and improving the subgrade soil using geo-techniques are effective measures for controlling unwanted vibrations at high-tech facilities. In this study, the vibration-reduction performance of 1-m-thick concrete slabs with natural and cement-improved subgrades was investigated based on in situ frequency sweep tests. One 1-m-thick concrete slab rested on 1-m-thick compacted sandy gravel backfill atop an undisturbed subgrade was constructed on the north side of the experimental site, and another identical concrete slab rested on 1-m-thick compacted sandy gravel backfill atop a cement-improved subgrade was constructed on the south side. The vibration-reduction effect was evaluated by comparing the free-field ground vibrations and surface vibrations of the two slabs at three pairs of evaluation locations. In terms of peak velocity, the 1-m-thick concrete slab with the natural subgrade exhibited a slight vibration amplification effect at low frequencies and a significant reduction effect at middle and high frequencies; the 1-m-thick concrete slab with the cement-improved subgrade exhibited a continuous vibration reduction action at all frequencies. In terms of RMS velocity, the vibration-reduction performance of the 1-m-thick concrete slab with the cement-improved subgrade was better than that with the natural subgrade. The results demonstrated that the vibration-reduction effect of the thick concrete slab was significant and could be increased by improving the subgrade using the cement grouting method. [ABSTRACT FROM AUTHOR]

Reliability-based design optimization (RBDO) is a valuable tool for optimizing while considering the impact of uncertainties. However, its application in engineering, specifically in pile foundation design, is complicated due to high computational costs and the potential for nonlinear iteration misconvergence. To address these challenges, we propose a modified optimization calculation method utilizing the mean first-order reliability method (MFORM). The revised function of the reliability index is introduced to ensure computational accuracy and linear regression is employed for its calculation. The results of the case study demonstrate that the modified optimization calculation method not only improves computational efficiency but also enhances computational accuracy. While the form of the performance function significantly influences initial and local optimizations, it has minimal impact on global optimization. Through local and global optimizations, the objective function values are reduced by 20.2% and 24.9%, respectively, for the first form of the performance function. For the second form of the performance function, reductions of 15.0% and 24.9%, respectively, are achieved through local and global optimizations. [ABSTRACT FROM AUTHOR]

Inclined pile foundations are commonly adopted in the support of wharf, harbor, bridge, and wind turbine structures. In the context of offshore wind turbines, inclined piles are typically arranged symmetrically around a circle with an elevated pile cap above sea level, referred to as an elevated pile-cap foundation. However, limited research exists on the impedances of inclined pile foundations with elevated pile caps. In this study, a theoretical model was developed that incorporates a homogeneous soil half-space and an inclined pile foundation with an elevated pile cap. The pile and soil half-space were modeled as Euler-Bernoulli beams and linear-elastic continuum, respectively. The soil's contribution to the pile's dynamics was represented by the receptance matrix, established at discrete interactions points along the pile's embedded section. The effects of the rake angle and scour depth on the dynamic impedances of the inclined pile foundation with an elevated pile cap were investigated. It was observed that the peak frequency of impedance shifts to a lower value as the scour depth increases; whereas the peak frequency shifting effect is less prominent when the rake angle changes. The impedance of the elevated pile-cap foundation is more sensitive to the pile's rake angle compared to the scour depth. [ABSTRACT FROM AUTHOR]

Although end-bearing energy pile foundations subjected to symmetrical thermal cycles have been extensively studied in the laboratory and in the field, the mechanisms underlying the thermo-hydro-mechanical (THM) interactions in floating energy pile groups and rafts, especially when subjected to asymmetrical thermal loads, are not well understood. In this study, an advanced thermo-mechanical bounding surface model was implemented in finite-element (FE) code to investigate the THM interactions of a two-by-two floating energy pile group and pile raft, focusing on asymmetrical thermal cycles. Computed results are compared with published centrifuge model test results in soft clay. It is revealed that the irreversible volumetric contraction of the soil adjacent to the energy piles accumulates with each thermal cycle, resulting in a decrease in the horizontal stress and hence shaft resistance of the floating piles. During thermal cycles, the stress states of the soil around the energy pile shaft and the soil beneath the pile toe approach the critical state line along different paths. The induced temperature in the soil adjacent to the non-energy pile (NEP) is 5°C lower than that in the soil at the energy pile EP1, which is flanked by the other two energy piles EP2 and EP3. Consequently, the induced excess pore pressure in the soil at the NEP is approximately 20% smaller than that in the soil at EP1. The irreversible volumetric soil contraction at the NEP is about half that at EP1, resulting in approximately 45% less toe settlement. The thermally induced ratcheting settlements of the head and toe of the NEP are less than those of the energy piles, resulting in unacceptable ratcheting tilting of the floating energy pile group. However, the excessive tilting can be reduced by the use of a pile raft. [ABSTRACT FROM AUTHOR]

A comprehensive experimental program was performed in order to understand the mechanical behavior of model piles associated with water infiltration in collapsible loess. Real-time measurements were recorded for pile head settlement, pile shaft friction, and pile base resistance, as well as for the soil behavior, including soil settlement, volumetric water content, and soil suction. The experimental results suggest that both the pile head settlement and pile base resistance increased with water infiltration. The linear pile axial force distribution gradually changed to a "D" shape, with the maximum pile axial force occurring in the middle instead of the end stage of water infiltration. Such behavior can be attributed to a reduction in the contribution of soil suction, degradation of the pile–soil interface shear strength, and settlement of the collapsible soil. In addition, a softening model was proposed by modifying the traditional shear displacement method for interpretation of the mechanical behavior of piles in collapsible loess. There was good agreement between our experimental results and those from the literature and the results predicted using the proposed model, suggesting that the model can be used as a tool in the rational design of pile foundations in collapsible soils. [ABSTRACT FROM AUTHOR]

Building and ground settlement due to construction dewatering is a well-studied topic. However, most previous investigations have not considered the barrier effect of an adjacent underground structure on the drawdowns and resulting settlements. In this study, the barrier effect and its influence during construction dewatering for a metro station foundation pit is investigated. There are five aquifers at the foundation pit site, and a row of buildings supported on pile foundations, which act as an underground barrier to flow, is present on one side of the pit. On the other sides, there are no deep underground structures to impede groundwater flow. Field monitoring of the groundwater level drawdown, diaphragm wall movement, and ground and building settlements on both sides of the pit was carried out during dewatering. The results indicate that on the side with the pile foundations, the groundwater level drawdown, ground settlement, differential settlement, and angular distortion of building incurred by dewatering were relatively greater, but the diaphragm wall movements were relatively smaller. The effect of preexisting barriers should be considered in the assessment of construction dewatering-induced drawdowns, soil settlements, and building movements. [ABSTRACT FROM AUTHOR]

In the random field model's consideration of the spatial variability of soil, soil properties at different locations play different roles in the reliability analysis of the foundation. Investigating the importance distribution of the random field through reliability sensitivity analysis (RSA) is beneficial for understanding how the random field affects the reliability of the foundation. However, many existing RSA methods for the random field model are deficient in terms of efficiency, accuracy, and applicability under complex engineering conditions. Consequently, this study proposes an efficient RSA method for the random field model based on the Karhunen–Loève (KL) expansion method and the first-order reliability method (FORM) to identify the important random field domain in foundation engineering. In the proposed method, the mean reliability sensitivity index (MRSI) is extended to a random field model of continuous form to characterize the importance distribution of the random field. The MRSI is analytically derived based on the results of the KL expansion method and the FORM without additional limit state function (LSF) calculations. Subsequently, the important random field domain, in which the variation of the mean of the soil property contributes significantly to the reliability index, is identified based on the MRSI. Last, two foundation engineering examples that consider the cross-correlated random fields of cohesion and friction angle, including strip footing on single-layer soil and pile in multiple-layer soil, were used to verify the proposed method. The results showed that an important random field domain with a small area dominates the variation of the reliability index of a foundation, and important random field domain area increases with autocorrelation distance (ACD). This innovative identification method holds great engineering significance, because it allows geotechnical practitioners to gain a comprehensive understanding of the failure modes and foundation treatment areas of foundations in spatially varying soil. In the random field model's consideration of the spatial variability of soil, soil properties at different locations play different roles in the reliability analysis of the foundation. Investigating the importance distribution of the random field through RSA is beneficial for understanding how the random field affects the reliability of the foundation. However, many existing RSA methods for the random field model are deficient in terms of efficiency, accuracy, and applicability under complex engineering conditions. Consequently, this study proposes an efficient RSA method for the random field model to identify the important random field domain, in which the variation of the mean of the soil property contributes significantly to the reliability index. Two foundation engineering examples that consider the cross-correlated random fields of cohesion and friction angle, including strip footing on single-layer soil and pile in multiple-layer soil, were used to verify the proposed method. The results showed that the innovative identification will allow geotechnical practitioners to gain a comprehensive understanding of the failure modes and foundation treatment areas of foundations in spatially varying soil. [ABSTRACT FROM AUTHOR]

As a key guarantee and cornerstone of building quality, the importance of deformation prediction for deep foundation pits cannot be ignored. However, the deformation data of deep foundation pits have the characteristics of nonlinearity and instability, which will increase the difficulty of deformation prediction. In response to this characteristic and the difficulty of traditional deformation prediction methods to excavate the correlation between data of different time spans, the advantages of variational mode decomposition (VMD) in processing non-stationary series and a gated cycle unit (GRU) in processing complex time series data are considered. A predictive model combining particle swarm optimization (PSO), variational mode decomposition, and a gated cyclic unit is proposed. Firstly, the VMD optimized by the PSO algorithm was used to decompose the original data and obtain the Internet Message Format (IMF). Secondly, the GRU model optimized by PSO was used to predict each IMF. Finally, the predicted value of each component was summed with equal weight to obtain the final predicted value. The case study results show that the average absolute errors of the PSO-GRU prediction model on the original sequence, EMD decomposition, and VMD decomposition data are 0.502 mm, 0.462 mm, and 0.127 mm, respectively. Compared with the prediction mean square errors of the LSTM, GRU, and PSO-LSTM prediction models, the PSO-GRU on the PTB0 data of VMD decomposition decreased by 62.76%, 75.99%, and 53.14%, respectively. The PTB04 data decreased by 70%, 85.17%, and 69.36%, respectively. In addition, compared to the PSO-LSTM model, it decreased by 8.57% in terms of the model time. When the prediction step size increased from three stages to five stages, the mean errors of the four prediction models on the original data, EMD decomposed data, and VMD decomposed data increased by 28.17%, 3.44%, and 14.24%, respectively. The data decomposed by VMD are more conducive to model prediction and can effectively improve the accuracy of model prediction. An increase in the prediction step size will reduce the accuracy of the deformation prediction. The PSO-VMD-GRU model constructed has the advantages of reliable accuracy and a wide application range, and can effectively guide the construction of foundation pit engineering. [ABSTRACT FROM AUTHOR]

It is demonstrated that the application of piezoelectric sensors to metallic bars and strands can enable determining the status of the integrity of these elements through the spectrum of their acoustic excitations. The voltage output of the piezo, secured to metal bars or strands, is fed to the input of a Fast Fourier Transform analyzer, which allows displaying the spectrum of the excitations from which information on the length, overall quality of the metal, and the presence of defects can be obtained. We show that the analysis, performed on several materials and strands of different lengths, could be useful for cases in which visible inspection and/or direct access to the entire body of the metallic elements is not possible. Applications of our study for testing metallic structures embedded in concrete foundations are reported for construction sites. [ABSTRACT FROM AUTHOR]

A deep foundation is used to transfer the load of tall and large structures to the underlying soil layers with a sufficient strength. Over the last few decades, a new type of piles has been executed in developed countries using torque with the development of hydraulic devices that can create high torques. Due to the emergence of these deep foundations, the scope of studies in this regard are limited. Thus, studying the behavior of these foundations can increase the breadth of their application in other countries while creating a better understanding of their behavior. In the present research, some models of this type of pile have been created and studied using laboratory equipment and static loading. Execution of drilled displacement and helical piles in the FCV-AUT device as well as running static compression and tension load tests were done according to ASTM D1143 and ASTM D3689 standards. Experiments on the executions have been studied in two modes of density: relative density of 20% to 25% and of 45% to 50%. Accordingly, drilled displacement piles show good performance in terms of compression and tension bearing capacity compared to other piles, while the required installation torque for this pile shows higher values. [ABSTRACT FROM AUTHOR]

We investigate a deep foundation pit for urban substation construction in Chengdu, China. The pit was excavated in a sandy gravel layer and has a depth of 24.6 m. Detailed field surveys and monitoring were carried out to investigate the deformation characteristics of the foundation pit and its supporting structure related to excavation. Flac3D software was used to analyze the influence of pile anchor design parameters, including pile diameters, pile spacing, anchor cable prestress, anchor angle, and the number of rows of anchor cables, on deformation of the deep foundation pit. The results showed the pile diameter was the most critical influencing factor for pile deformation. The influences of anchor cable prestress and anchor angle on the horizontal displacement of the pile were inferior to the influence of the pile diameter and the number of anchor cable rows. The results reported in this paper provide guidance for the optimal design of foundation pits in settings with similar geological conditions. [ABSTRACT FROM AUTHOR]

The fish anchor is an economically viable offshore foundation engineering technology that has been proposed in recent years. By fish anchor, we mean a fish-shaped dynamically installed anchor that can penetrate into the seabed through water by its own weight. However, the existing research studies seldom consider the hydrodynamic characteristics of its free fall installation, resulting in uncertainties regarding its underwater installation characteristics. Therefore, based on OpenFOAM, this study first investigated the directional stability of fish anchors during its underwater falling process through the static model analysis method and dynamic model analysis method. The findings indicated that the directional stability of fish anchors was insufficient, rendering them suitable only for release and installation at low heights (i.e., less than 4.2 times the anchor length) without marine environmental loads. Furthermore, the anchor inclination angle during installation is significant, thereby impacting its penetration depth and pull-out capacity in the seabed. To solve this problem, the concept of an innovative booster-assisted fish anchor is proposed, which can significantly enhance the directional stability of conventional fish anchors. Results show that the maximum installation height of the new booster-assisted fish anchor is increased by 2.4 times compared to the original design, thereby enhancing both the penetration speed and uplift capacity. Based on the findings, recommended installation and construction conditions are provided. Finally, a predictive formula for the installation height and verticality of the new booster-assisted fish anchor under current action is presented to offer guidance for engineering applications. [ABSTRACT FROM AUTHOR]

This study aims to prepare an anti-washout grout using marine soft clay to stabilize the wind power pile foundations. The cement, hydroxypropyl-methyl cellulose ether (HPMC), and sodium silicate were chosen as the main materials to modify the marine soft clay, and the fluidity, bleeding rate, setting time, rheology, anti-washout characteristics, and compressive strength were investigated. The results showed that high cement content, HPMC, and sodium silicate decreased the workability of grout while enhancing the washout resistance. The addition of HPMC and sodium silicate would increase the yield stress and plastic viscosity of the grout. The sodium silicate content was the key factor influencing the early strength, while the cement content and HPMC affect the later strength. The microstructures including the morphology of C-S-H gels and the content of ettringite and calcium hydroxide significantly changed with the addition of sodium silicate, and Friedel's salt was observed through the microstructure analysis. This study can provide effective guidance for the utilization of marine soft clay, the preparation of anti-washout grout, and the control of pile foundation stability. [ABSTRACT FROM AUTHOR]

Historically, it has been demonstrated that bridges may be vulnerable to fire, and in many circumstances, resulting damage might not be apparent, and bridges could maintain acceptable levels of serviceability. In the absence of proven assessment tools and given the limited research that addresses bridge fire, research that better understands response and strives to improve highway bridge resiliency to fire is needed. Extending the work carried out during an earlier research stage, the present study focused on investigating performance of bridge pier columns that survive fire under coupled vehicle collision and air blast. Numerical models of single reinforced concrete columns supported by a pile foundation system and surrounded by air and soil volumes were created using LS-DYNA. As explicit solvers such as those available in LS-DYNA are infrequently used for fire analysis, an indirect two-step approach that integrated heat transfer and structural analyses was developed and validated against published fire-induced impact and blast test results. A parametric study that examined the effects of various fire exposure conditions and column diameters was completed. Performance was comprehensively assessed based on various structural response parameters, which included failure modes, lateral displacement, residual axial capacities, and shear demand-to-capacity ratios. Column damage was then categorized into six levels to qualitatively assess column performance under the aforementioned multi-hazards. The developed modeling approach was shown to be viable, and results indicated that larger column diameters could potentially remain in service in their final damage states after being repaired for fire durations of less than 120 min. [ABSTRACT FROM AUTHOR]

Designing tunnels in urban areas necessitates an accurate estimation of their construction effects on adjacent structures. This study explores tunnelling impacts beneath raft foundations, focusing on settlement and bending moment variations due to different tunnel depths and soil densities. A verification model validated tunnel modelling with field data, employing a 2D finite element model to assess raft foundation performance above tunnels. It also examines the influence of tunnel depth, soil consistency, and spacing of two tunnels. Key results show raft settlement increasing by over 250% when tunnels are directly below at a 7.5 m depth, regardless of soil density. Soil cover thickness above the tunnel significantly affects the raft's bending moment, with an increase of up to 400% and 300% for 5 m and 7.5 m cover depths, respectively. Final tunnel construction stage settlements varied with soil density. The study also reveals that increasing the spacing between closely spaced tunnels beyond 1.2 diameters reduces both raft settlements and bending moments. These findings emphasize the importance of careful tunnel placement and soil cover management to minimize negative impacts on raft foundations. [ABSTRACT FROM AUTHOR]

Various geometric and mechanical conditions for soil–foundation interfaces affect the superstructure and foundation responses against earthquake. As one of these conditions, 2D asymmetry of soil around the embedded rigid foundation is emphasized in the present paper. Accordingly, a reduced-scaled embedded foundation bearing SDOF superstructure is considered under slow lateral cyclic and dynamic shake table tests in design and service levels at 1 g state, and the system response is compared to those of systems containing surface and embedded foundations with symmetric condition. Test results show the asymmetry in the moment–rotation response curve for system with asymmetric soil condition in static state. While for dynamic response, the behavior under harmonic excitation with the design amplitude level is close to one of system with surface foundation. In addition, the foundation moment capacity of nonlinear dynamic response can be estimated properly through theoretical expression for foundation with asymmetric condition. Moreover, the rocking behavior in two-way excitation causes significant loss of superstructure response relative to the foundation in all three cases. [ABSTRACT FROM AUTHOR]

Pile foundations frequently endure dynamic loads, necessitating an in‐depth examination of the cyclic shear properties at the pile–soil interface. This study involved a series of cyclic direct shear (CDS) tests conducted on sand and concrete with irregular surface, utilizing varying displacement amplitudes (1, 3, 6, and 10 mm) and joint roughness coefficients (0.4, 5.8, 9.5, 12.8, and 16.7). Discrete Element Method (DEM) models, informed by experimental data, facilitated mesoscopic mechanical response analyses. Findings indicate that the sand–concrete interface undergoes softening, with hysteresis loops' morphology dependent largely on displacement amplitude. A maximum ultimate shear stress corresponds to a specific critical surface roughness, while the initial tangent modulus escalates with increased concrete roughness. Volume variations of the specimen inversely correlate with displacement amplitude and directly with surface roughness. As displacement amplitude expands, there is a reduction in the maximum shear stiffness and an elevation in the maximum damping ratio. Empirical formulas for the surface roughness and normalized shear stiffness were proposed. Larger displacement amplitudes result in more substantial shear bands and heightened energy dissipation, yet the incremental energy ratio remains largely unaffected. Predominant energy dissipation mechanisms include both slip and rolling slip, with the former surpassing the latter in energy dissipation capacity. The anisotropy directions of contact normal, normal contact forces, and tangential contact forces consistently fluctuate with shear direction alterations. [ABSTRACT FROM AUTHOR]

Functionally graded materials (FGMs) are commonly utilized in construction projects. They enhance the performance of functionally graded beams (FGBs) under various loading conditions. Therefore, the incorporation of variable-section FGBs theory into the analysis of structural and soil interactions is crucial for advancing engineering applications. Employing the variational principle and the transfer-matrix method, and considering the shear stiffness of the axially FGB structure itself, along with the continuity and shear strength of the soil, a semi-analytical solution for displacement and internal force of axially FGBs on Pasternak foundation (termed as P–T model) is derived in this paper. The semi-analytical solution is subsequently compared with finite difference solution results from prior studies, affirming the accuracy and precision of the proposed computational theory. The P–T model degenerates to the Winkler–Timoshenko model (W–T model) when the foundation's shear layer stiffness is set to zero. Additional analysis is conducted on displacement and internal force variation when the beam stiffness follows different distribution along the axial direction. The results indicate that an asymmetrical distribution of stiffness on either side of the midpoint could increase the displacement at the middle section. Furthermore, when the beam stiffness adheres to a Gaussian distribution along the axial direction of the beam, a significant increase in displacement at the boundary position of the beam is observed. The proposed method is then integrated with the Mindlin stress solution to evaluate construction impact on an existing tunnel within a foundation pit project in Shenzhen. A comparative analysis of theoretical calculations, monitoring data, and numerical simulation results exhibits substantial concurrence across the three methods. The tunnel's overall deflection adopts an "M" shape, and the computation using the variable-section FGB portrays the existing tunnel's deformation trend with heightened accuracy, diminishing the calculation error from 35 to 8.3% compared to the conventional normal section beam. [ABSTRACT FROM AUTHOR]

This paper investigates the interference effect of closely spaced foundations on the modulus of subgrade reaction (k) and provides an insight into some of the factors affecting the k-value of a raft foundation when other foundations (isolated footings or other identical rafts) are closely placed on both sides. The investigation adopted a three-dimensional, non-linear, finite-element numerical analysis based on a case study of a residential project with several multi-storey buildings constructed on sand underlain by weathered limestone. A site-specific ground investigation was conducted to determine soil properties, which were used to construct three-dimensional numerical models to simulate different arrangements of foundations and estimate the corresponding k-values. The results show that the k-value starts to decrease when the spacing between the foundations becomes less than three times the raft width, and the percentage of reduction in k-value increases in a non-linear way as the spacing decreases further. In addition to spacing, the study revealed that the effect of adjacent foundations depends on their size and the magnitude of their applied pressure. The case study provides a framework for developing a correction factor that can be applied to k-value for improving the structural and geotechnical design of closely spaced shallow foundations. [ABSTRACT FROM AUTHOR]

This paper aims to analyze and describe the geotechnical behavior of a piled raft foundation of a tall building (53 floors, 172.4 m high) through the monitoring of strains in the building's columns and piles, the stresses at the raft–soil interface, and the foundation settlements. Field and laboratory tests were performed, and associated with axisymmetric and three-dimensional finite element analysis to the assessment of the measured data. The monitoring of the pile strains suggests the occurrence of soil expansion, caused by the raft excavation process, up to approximately 6 months after the excavation was completed. The presence of different soil profiles under the raft, with different mechanical properties, affected the distribution of the foundation settlements and the pile loads. Initially, the average pile loads were concentrated in the perimeter elements, but, as the construction of the building evolved, they tended to become more uniform. The effect of the superstructure stiffness caused successive load redistributions in the columns, which contributed to the maintenance of the maximum angular distortion of the building within the allowable values and reduced the load difference between the piles positioned in opposite soil profiles. [ABSTRACT FROM AUTHOR]

Pile foundations are still the preferred foundation system for high-rise structures in earthquake-prone regions. Pile foundations have experienced failures in past earthquakes due to liquefaction. Research on pile foundations in liquefiable soils has primarily focused on the pile foundation behavior in two or three-layered soil profiles. However, in natural occurrence, it may occur in alternative layers of liquefiable and non-liquefiable soil. However, the experimental and/or numerical studies on the layered effect on pile foundations have not been widely addressed in the literature. Most of the design codes across the world do not explicitly mention the effect of sandwiched non-liquefiable soil layers on the pile response. In the present study, the behavior of an end-bearing pile in layered liquefiable and non-liquefiable soil deposit is studied numerically. This study found that the kinematic bending moment is higher and governs the design when the effect of the sandwiched non-liquefied layer is considered in the analysis as opposed to when its effect is ignored. Therefore, ignoring the effect of the sandwiched non-liquefied layer in a liquefiable soil deposit might be a nonconservative design approach. [ABSTRACT FROM AUTHOR]

In excavation engineering, most of the retaining structures are subjected to asymmetrical loads, including in asymmetrical excavation and asymmetrical overloading. However, a theoretical solution to, and deformation-controlling method for, this problem has remained elusive to date. In this work, a semianalytical solution for determining the deformation of retaining structures subjected to asymmetrical loads was derived based on the principle of minimum potential energy. The retaining structures were viewed as flexible, and the overall deformation of the retaining system was evaluated by our proposed theoretical model. This model was verified by comparing it with practical monitoring data. Subsequently, the theoretical solution was applied to analyze the stress and deformation characteristics under the conditions of asymmetrical excavation and asymmetrical overloading, which can be controlled to ensure the safety of a project. Finally, because of the requirement for a small amount of deformation in the foundation pit retaining piles, the earth pressure on the retaining piles is close to the static earth pressure. Reducing the length of the retaining pile on one side had a greater influence on the deformation on that side, but less of an influence on the other side. Thus, the proposed model can be used for optimizing the asymmetrical design of a retaining structure in order to balance the economy and safety of a project. Our design theory can be applied to a variety of engineering projects. A typical case is the Guangzhou Baiyun District Comprehensive Transportation Hub Project in China. The method was used to analyze the status of the subway foundation pit, offering a new design scheme to reduce the design length of the retaining piles, which resulted in great economic benefits in its practical application. The findings provided in this paper can be applied to the engineering of any long, narrow foundation pit that can be simplified into a two-dimensional plane–strain calculation model, being used to realize more accurate deformation control over the foundation pit envelope. The core of this calculation method is that it can accurately describe the magnitude of the earth pressure. The distribution of the earth pressure is worthy of further study. [ABSTRACT FROM AUTHOR]

The seismic design of pile foundation–supported structures has gained significant attention in the last few decades; there have been several failures during moderate to severe earthquakes. Seismic soil–pile foundation–structure interaction (SSPSI) was reported as the governing phenomenon behind the failure mechanism of such structures. In this context, in this study an attempt is made to investigate the influence of SSPSI (mainly the inertial part of the interaction) in a pile-supported structural system with variation in dynamic characteristics and the ratio of superstructure stiffness to pile foundation stiffness (Ks/Kp) through physical model experiments using a shake table. The primary aim in this study is to assess the extent of the effect of dynamic soil–structure interaction in a scaled-down pile foundation–supported bridge structure in nonliquefied ground with the help of a simplistic normalized parameter, i.e., Ks/Kp, for different ranges of the period of the superstructure system. The study primarily highlights variation of the normalized lateral period of the whole interaction between the superstructure and pile foundation as a function of the practicable range of Ks/Kp, which may be helpful for designers in predicting the dynamic characteristics of the system as a first step in seismic design. Similarly, the trend of normalized spectral acceleration and displacement response at the superstructure and pile head with respect to Ks/Kp is presented for the prediction of design forces. Finally, an idealized case study prototype design problem is used to verify the outcome of the study and illustrates simplified design steps for pile foundation–supported structures in general. [ABSTRACT FROM AUTHOR]

Although three-dimensional finite-element analysis has been introduced to foundation design for years, simplified computer-based calculations based on the spring analogy of soils and structural elements are also frequently used in many engineering projects. Using coefficients of subgrade reactions and pile stiffness is a straightforward way to design and analyze a piled raft foundation. This paper discusses the determination of the coefficients of pile reactions for embedded piled raft foundations in soft clays subjected to vertically uniform loads through a series of finite-element analyses. The geologic property was assumed to be composed of homogeneous soft clays with the shear-wave velocities varying at 100–140 m/s. The foundations with a square raft ranging from 16 to 36 m and embedment depths of 8 and 12 m were studied. Load intensity approximating 1.5 times the excavated soil pressures was considered where the maximum uniform load was applied to the foundation. The foundation settlements and reactions of the piles were obtained first from a three-dimensional finite-element analysis. For design convenience, the dimensionless pile displacements, pile reactions, and coefficients of pile reactions were developed and presented in plots. The embedment depth-to-raft size ratio, pile slenderness ratio, and pile-to-pile spacing distance-to-pile diameter ratio were examined to find their optimized correlation. Finally, a design example was given to verify the proposed suggestions. We conclude that the proposed method can be an alternative to the piled raft foundation design. [ABSTRACT FROM AUTHOR]

This study investigates the ultimate bearing capacity (UBC) of an eccentrically loaded strip footing of width, B, resting above circular dual cavities in the rock mass using the Generalized Hoek–Brown (GHB) yield criteria for the rock mass. The stability number (Ns) is determined using upper and lower-bound finite element limit analysis (FELA), incorporating an adaptive meshing technique. The study considers two configurations: symmetrical and parallel outlines based on the relative positions of the dual cavities and the footing. The effects of the numerous governing parameters, including the load eccentricity (e/B), the vertical distance of dual cavities from the ground surface (δ/B), the spacing between dual cavities (β/B), the uniaxial compressive strength of intact rock, ( σ ci /γB), geological strength index (GSI), and material constant for intact rock (mi) on the Ns are studied. The study finds that the magnitude of e/B significantly affects Ns. For symmetrical outline, Ns improves with increasing δ/B, and the effect of δ/B is insignificant when δ/B ≥ 3, corresponding to β/B = 4 irrespective of e/B. Moreover, Ns increases with β/B for δ/B ≤ 3 and e/B ≤ 0.2. However, the effect of β/B on Ns is insignificant beyond δ/B > 3, irrespective of e/B. For the parallel outline case, the strip footing achieves maximum Ns under centrally placed load (i.e., e/B = 0), regardless of β/B and δ/B values. The study presents potential failure envelopes that might include all representative cases to provide insights into the possible failure mechanism of such foundation systems. [ABSTRACT FROM AUTHOR]

In this manuscript, the long-term behaviour of piled-raft foundations (PRFs) due to the consolidation of clayey soils has been investigated by 3D finite element analysis. The validation of the numerical prototype has been carried out using the field test outcomes performed in the field laboratory and other reported results. The ultimate load capacity of the PRFs has been assessed by varying the number of piles, diameter of piles, width of raft and ground water level. Compressive loads are provided starting from an increment of 10% of the ultimate load till the ultimate load capacity of the PRFs. Settlements of PRFs have been observed till a time period of 1 month for each increment of loading and for a period of 1 year after the ultimate load capacity has been applied. The influence of load sharing behaviour, interaction effects and factor of safety on consolidation settlement of PRFs have been analysed, and predicted expressions are suggested. Average, differential and reference settlements are evaluated. Multiple linear regression analysis is implemented for estimating consolidation settlement. The proposed design equation has been validated using an example. It is inferred that load sharing ratio increased by about 34–48%, 6–19% and 11–20% with increase in the number of piles, pile diameter and width of raft in the PRF, respectively. The reduction rate of factor of safety of PRFs is insignificant and nearly minimizes to a constant value at higher settlement magnitude. The reference settlement increases from 49 to 54% as the value of load sharing ratio decreases. [ABSTRACT FROM AUTHOR]

This paper intends to investigate the effect of tunnelling on the response of a framed building on different types of foundations with the help of shake table test. For the test, effect of utility tunnel on response of scaled prototype steel building has been determined with the help of accelerometer mounted at different floors. For experimental tests, three types of foundation (isolated foundation, mat foundation, and pile foundation) and two different heights of scaled prototype steel building frame have been considered. The analysis was performed in Heavy Structural Engineering Lab at N.I.T Patna, and soil has been excavated from the campus. To consider the ovalling effect of tunnel, shake table was vibrated perpendicular to the axis of tunnel by taking El Centro N-S as input motion. After the analysis it was found that ovalling effect of circular tunnel mostly affects the displacement of building when the tunnel was situated just below the centre axis of building. Same result was found for all types of foundation. Influence of ovalling effect of circular tunnel diminished as the distance between the building frame and tunnel increases. Response of building, constructed over isolated foundation was found to be the mostly effected as compared to the building constructed over other two types of foundation, while building constructed over pile foundation was the least affected. Shake table results show that high-rise prototype scaled steel building is much affected as compared to low-rise prototype scaled steel building frame. The results help in acknowledging the fact that foundation type should be considered for investigating the effect of tunnels during seismic excitation. [ABSTRACT FROM AUTHOR]

Energy piles are gaining popularity worldwide as both pile foundations and ground source heat producers. While considerable research has been conducted on energy pile design and evaluation, implementing these approaches effectively remains challenging for engineers. This study presents a novel approach based on Load and Resistance Factor Design (LRFD) with First-Order Second-Moment (FOSM) reliability analysis and target reliability ( β T ) for energy pile design. Additionally, three soft computing techniques, namely 1D-CNN, LSTM, and Bi-LSTM, were employed to enhance the design process. To conduct this research, datasets from each model were analyzed using various statistical indices, including R2, RMSE, RMSLE, MAPE, BF, AARD, NSE, U 95 , t-stat, TIC, and PI. The results indicated that the Bi-LSTM model demonstrated superior performance for heating operations, with R2, RMSE, and RMSLE values of 0.975, 0.021, and 0.007 for training and 0.984, 0.019, and 0.006 for testing datasets, respectively. For cooling operations, the LSTM model exhibited the most suitable predictive capabilities, achieving R2, RMSE, and RMSLE values of 0.969, 0.022, and 0.008 for training and 0.982, 0.019, and 0.007 for testing datasets, respectively. Comparative analyses, including rank analysis, Williams plot, accuracy matrix, and Taylor's diagram, were performed to assess the accuracy of the proposed models. The results demonstrated that the Bi-LSTM model for heating and the LSTM model for cooling outperformed other soft computing models within the reliability-based LRFD approach for energy pile design. This research contributes to the advancement of energy pile design methodologies, providing engineers with a more efficient and reliable LRFD-based framework. The successful application of soft computing techniques further enhances the accuracy of predictions for both heating and cooling operations. Overall, the findings of this study hold significant implications for the design and evaluation of energy piles, contributing to sustainable and energy-efficient construction practices. [ABSTRACT FROM AUTHOR]

The foundation is the lower part of a structure used as a load distributor for the loads generated by the upper structure, which are then transmitted into the hard soil layers. The selection of foundation types in building construction must consider the type and characteristics of the soil at the construction site to avoid construction failures. This analysis is conducted to determine the bearing capacity of pile foundations using analytical and finite element methods. The type of foundation used in this analysis is a pile foundation with a pile length of 8 meters and a pile diameter of 0.4 meters. For the analytical calculation, Standard Penetration Test (SPT) data obtained from PT. Adhi Karya (Persero) for the Infrastructure Green House Biodiversity LIPI Cibinong-Bogor project are used, employing the analytical method (Alpha Method) and the finite element method with the assistance of Plaxis 2D V.8 software. The results of the analysis show that the bearing capacity of the group pile foundation (Qg) for a pile diameter of 0.4 meters and a pile length of 8 meters on clayey soil, based on SPT data using the analytical method (Alpha Method), is 60.432 tons. Meanwhile, the bearing capacity of the horizontal pile foundation using the Broms method is 6.03 tons. The bearing capacity obtained using the Finite Element Method yields an ultimate load on the group pile (Qq) of 57.89 tons. The bearing capacity of the group pile foundation (Qg) from both sets of data, with a difference of 2.5%, meets the requirement, being greater than the axial load (P) of 42.6 tons that must be supported. [ABSTRACT FROM AUTHOR]

Existing simplified procedures for evaluating soil liquefaction potential or for estimating excess pore pressures during earthquakes are typically based on undrained cyclic tests performed on saturated soil samples under controlled loading and boundary conditions. Under such conditions, the effect of excess pore pressure (ue) dissipation and redistribution to neighboring soil layers cannot be accounted for. Existing simplified procedures treat liquefiable layers as isolated soil layers without any boundary conditions even if dense and loose layers are very thin, permeable, and adjacent to each other. However, redistribution is likely to increase and decrease ue in the neighboring dense and loose layers respectively. Until now, no procedure short of fully coupled numerical analysis is available to estimate the importance of redistribution. This paper presents an approximate analytical procedure for assessing the effects of ue redistribution in (1) soil layers that would have liquefied if they were undrained, and (2) soil layers that would have not liquefied even if undrained. It is found that a layer that is initially assumed liquefied under undrained conditions might not even liquefy accounting for the ue redistribution to neighboring layers. On the other hand, a layer initially assumed to not liquefy can develop significant ue and can even liquefy due to pore pressure migration from the neighboring layers. Thus, accounting for redistributed ue is important for liquefaction consequence assessment quantification, particularly in systems that span the depth of these effects like deep foundations. Migration of u toward the tip of a pile can reduce its capacity, even if the tip is embedded in a dense sand layer. On the other hand, if redistribution can result in the reduction of ue in initially assumed liquefied layers, risks associated with liquefaction might be avoided. A criterion is also developed to evaluate the thicknesses of a layer below which redistribution could prevent liquefaction even if the layer is deemed liquefied according to the existing liquefaction-triggering procedures. Finally, the proposed procedure is illustrated by application to selected shaking events of centrifuge tests involving liquefaction of layered soil profiles. The predictions from the procedure matched the centrifuge test results reasonably. [ABSTRACT FROM AUTHOR]

In projects such as highway bridges and offshore wind farms, understanding the kinematics of soil layers and their displacement is important for accurately predicting the behavior of caissons and monopiles under lateral loads. To better predict the distribution of soil deformation around the foundations, this paper presents an extensive usage of the energy-based variational method in laterally loaded deep foundations (caissons or monopiles) with very large diameters. By adding an assumption of soil deformation in multilayered soils, the displacement distribution around the foundations can be better described. The responses of deep foundations were obtained by minimizing the potential energy and virtual work of the foundation-soil system. After that, static lateral loading tests on two caissons with the same embedment depth of 36 m and the same diameter of 6 m were performed, and the displacement field in soils and the deflection profiles of the caissons were measured. Results show that the lateral displacement and the decay distribution fields calculated from the theory in this paper agree with the measured data from the static loading tests and the corresponding finite differential method (FDM) results. At last, a series of case studies performed by MATLAB and FDM analyses were also conducted to study the influence of uz on the response of foundations, as well as the influence of foundation parameters and soil modulus on the value of ϕz. [ABSTRACT FROM AUTHOR]