Uplift Resistance Research Articles

Influence of cavity-forming processes on the uplift resistance of bulb piles

Influence of cavity-forming processes on the uplift resistance of bulb piles

An efficient method for evaluating the wind resistance performance of high-vertical standing seam metal cladding systems

Uplift wind-induced responses and failure criteria of high-vertical standing seam metal cladding systems (SSMCSs) are of paramount importance for evaluating their wind resistance performance. This paper proposes an efficient evaluation method that combines a highly efficient finite element (FE) model for structural response analysis with reasonable failure criteria, based on experimental and numerical investigation. The FE model incorporating the developed equivalent spring model is established with the calibrated stiffness from tensile tests and validated through the wind uplift resistance experiments conducted on large-scale prototype structures. The recorded structural responses from the experiments validate the feasibility of the FE model in simulating the geometric and material nonlinearities of the systems. To evaluate the wind resistance performance, the failure criteria are developed based on the observed pullout mechanisms and failure modes from the experiments. These criteria take the relative deformation of standing webs and the pullout resistance strength of seam connections as critical parameters, and the relationship between them is calibrated through a series of tensile tests using a self-designed fixture. Tensile test results show notable variability in the pullout resistance strength of seam connections, with a mean value decreasing as the relative rotational angle of the standing webs increases. According to the developed failure criteria, the ultimate uplift pressures evaluated from the FE analysis exhibit minimal positive deviations of 5.3 % and 7.3 % from the experimental results for different failure modes, respectively. This highlights the effectiveness of the proposed method in evaluating the wind resistance performance of high-vertical SSMCSs.

Application of Advanced Machine Learning Models for Uplift and Penetration Resistance in Clay-Embedded Dual Interfering Pipelines

Application of Advanced Machine Learning Models for Uplift and Penetration Resistance in Clay-Embedded Dual Interfering Pipelines

A Study on the Influence of Anchor Rods’ Layout on the Uplift Resistance Characteristics of Inclined Anchor Short-Pile Foundations Based on FEA

A Study on the Influence of Anchor Rods’ Layout on the Uplift Resistance Characteristics of Inclined Anchor Short-Pile Foundations Based on FEA

A Labor-Saving Method of Pipe Uplifting Countermeasure with Geocell-Geotextile Combination

In this study, we proposed a new method which mitigates pipe uplifting by utilizing geocells and geotextiles. The method resulted in labor saving in construction. To verify the effectiveness of the proposed method, we reproduced pipe uplift by conducting push-up tests using a 150-mm-diameter pipe. The test results showed that the proposed method increased the peak resistance and the resistance at large displacement by 1.47 and 3.35 times, respectively, compared to the unreinforced method. The proposed method also increased the peak resistance by 1.13 times compared to the conventional method widely used in Japan. It demonstrated consistently high resistance even after the peak. This indicated that the proposed method is very effective as a countermeasure against pipe uplift. Furthermore, increasing the overall width of the geocell improved the resistance. In this study, two different approaches were used to evaluate the uplift resistance of the pipe. The approaches showed that, with geocell reinforcement, most of the dead weight at the pipe sides and above them contributed to the peak resistance. It was also found that the peak resistance of the proposed method can be predicted to some extent by modifying the previously proposed equation.

Shake table testing and finite element modeling of a modular prefabricated concrete bridge‐like specimen accounting for geometry imperfections and additional damping

AbstractThis paper presents the shake table testing and finite element (FE) modeling of a modular prefabricated concrete bridge‐like specimen. The specimen comprised four equal‐height cylindrical reinforced concrete (RC) columns capped with an RC slab. The structural connections were non‐monolithic. Hence, controlled relative motion of the members, including rocking (uplift) of the piers, was allowed. The columns were connected to the slab with stiff tendons that provided positive post‐uplift stiffness. The specimen was subjected to 184 triaxial shake table tests, so that a statistical validation of numerical models can be performed. Subsequently, a detailed three‐dimensional FE model of the bridge was developed. The objectives of the present study were to: i) investigate the shake table response of a modular bridge with positive post‐uplift stiffness under multiple ground motions, ii) develop an FE model of the proposed structural system, iii) investigate the influence of geometrical imperfections on rocking bridges, and iv) evaluate the efficiency of using additional dissipative rebars. After being subjected to 184 shake table tests, the specimen showed zero damage, moderate displacements and tendon forces (TFs), low slab torsion, and zero residual displacements. The shake table tests were practically repeatable. The proposed FE model accurately captured the experimental results. Geometrical imperfections heavily affect the response of negative stiffness systems. However, they have a marginal influence on positive stiffness systems. When comparing systems with equivalent uplift resistance and post‐uplift stiffness, the use of additional dissipative rebars results in lower slab torsion and TFs, provided that the rebars do not fracture.

Centrifuge study on the uplift behavior of spread foundation for transmission tower in sand

Realistic simulation of in-situ stresses is an essential consideration in evaluating the bearing capacities of spread foundations. Therefore, this study aimed to investigate the uplift behavior of large spread foundations by performing a series of centrifuge tests. A total of 12 centrifuge test models were constructed considering the variation in the foundation width (3.5–6.5 m), embedment depth ratio (0.67–1.39), and relative density of dry silica sandy soil (40%, 80%). The measured load–displacement curves indicated that the uplift bearing capacity and the corresponding uplift displacement increased with the foundation width at a certain embedment depth ratio. Two sets of empirical equations were proposed by adopting genetic programming to estimate the uplift resistance factor and uplift displacement with consideration of field stress conditions. The proposed equations reasonably matched these parameters under various conditions reported in the literature. Furthermore, a simplified empirical influence zone was proposed on the basis of the measurement of the ground surface displacement. The empirical influence zone, which was a straight line with an inclination angle of ~0.9 times the soil friction angle measured from vertical, could be considered a significant reference for predicting the failure surface of the shallow foundation under uplift loading.

Behaviour of a laterally loaded rigid helical pile located on a sloping ground surface

Offshore wind turbines, crucial for electricity generation worldwide, face challenges from strong winds, waves, and uneven ocean floors. To address these issues while remaining cost-effective, an innovative foundation is essential. The study introduces a helical monopile with a circular helix made of the same material as the shaft, representing a significant advancement. The study employs both 1 g model experimental tests and numerical simulations (PLAXIS 3D) to explore how changing slope conditions, pile positions, and the inclusion of the helix affects the response under monotonic lateral loading. Factors studied include ground slope angles (flat, 1 V:5H, 1 V:3H, 1 V:2H, and 1 V:1H), pile positions along the slope (c = 0Dp, 2.5Dp, 5Dp, and 7.5Dp), and variations in the number and positions of the helix (Hp) (0.25Lp, 0.5Lp, and 0.75Lp). The investigation involved analyzing the spacing between helices about both the length of the pile (Lp) and the diameter of the helix (dh ). The eccentricity to the diameter of pile ratio (e/Dp) is maintained as 12. The main objective is to compare the effectiveness of large-diameter helical piles to conventional monopiles in resisting upward and lateral forces. Results show helical piles offer a 100% improvement in uplift resistance and a 53% increase in lateral resistance compared to monopiles. This significant enhancement in capacity, particularly on sloping surfaces where monopiles typically exhibit reduced performance, underscores the effectiveness of helical piles in enhancing lateral capacity compared to monopiles.

Influence of shaft diameter and soil rigidity on uplift capacity factor of circular plate anchor in uniform clay

ABSTRACT The helix plate of the helical anchor can provide large uplift resistance for offshore floating structures. Although numerous studies have been conducted to estimate the uplift capacity factor of circular plate anchors in uniform clay, few studies have considered the effects of soil rigidity and shaft diameter on the uplift capacity factor. This paper studied the effects of soil rigidity and shaft diameter on the uplift capacity factor of shafted circular plate anchors in uniform clay through large deformation finite element analysis. The numerical analysis results showed that the increase in soil rigidity increased the uplift capacity factors. The increase in the shaft diameter ratio decreased the projected bearing area on the top of the circular plate anchor and uplift capacity factors. For the convenience of design engineers, a design process based on a conservative solution was proposed to estimate the uplift capacity factor of circular plate anchors.

Uplift behavior of nodular diaphragm wall: Experiment and theory

AbstractThe nodular diaphragm wall (NDW) is a novel foundation that can provide significant uplift load resistance compared to a typical diaphragm wall foundation. With the advantages of low noise, cost‐effectiveness, high work efficiency, and construction abilities close to existing buildings, NDW has excellent engineering application prospects in urbanization construction. However, the scarce knowledge on the uplift resistance, failure mode, and calculation method of the NDW has hindered its application in practice. In this paper, indoor model tests based on particle image velocimetry (PIV) technology are carried out to investigate the uplift behavior of three NDW models with different amounts and locations of nodular parts. The load transfer mechanisms of the three NDW models are discussed in detail, and special attention is given to the failure mode analysis. In addition, a theoretical analysis is implemented based on the load transfer approach. The transfer function and associated critical parameters are discussed in detail. Accordingly, an iterative procedure is proposed to interpret the load transfer information of an uplift NDW in multilayered soils under different loading levels. The findings derived in this paper are helpful to the uplift deformation, capacity calculation, and design of NDW in practical engineering.

Estimation of belled pile uplift resistance in dense sand based on centrifugal experiments

Estimation of belled pile uplift resistance in dense sand based on centrifugal experiments

New geocell utilisation as a pipe uplifting countermeasure and its validation using model experiments

In this study, we proposed a new method for preventing the uplift of a pipe using geocells, to improve the workability of the pipelines and increase the uplift resistance. As a fundamental study, push-up tests were conducted on the model pipe to verify the effectiveness of the geocell reinforcement. The experimental results showed that geocell reinforcement increased the peak resistance by more than 1.5 times and the resistance at large displacement (at a displacement of 40 mm) by more than 3 times at maximum, compared to the unreinforced method, indicating that geocell reinforcement is an effective countermeasure against pipe uplift. The combination of geocells and geotextiles increased the resistance at large displacement (at a displacement of 40 mm) by 1.41 times more than only geocell, contributing significantly to the increase in uplift resistance. In particular, increasing the number of geocells downward from the top of the pipe (on the side of the pipe), and integrating the left and right geocells with the geotextile, increased considerably the peak resistance and resistance at large displacement (at a displacement of 40 mm).

Multi-objective design and optimization of squeezed branch pile based on orthogonal test

In recent years, the emergence of the squeezed branch pile has presented a new avenue for civil engineering, offering a distinctive structure and favorable mechanical characteristics. Squeezed branch piles have strong compressive, uplift, and horizontal load resistance capabilities. Due to the existence of discs, the geometric parameters of squeezed branch piles are abundant but important. This article selects number of discs, disc diameter, disc squeeze angle, and disc spacing as the main influencing factors on the bearing capacity of squeezed branch piles and conducts a qualitative analysis of their mechanical properties. The aim of this article is to analyze the different bearing performances of squeezed branch piles through orthogonal experimental design, simulate test conditions using finite element software ABAQUS, obtain relevant data, and finally determine the weight ranking and optimal combination of influencing factors through range analysis to provide better guidance for engineering practices. Through multi-objective optimization design, six optimization objectives including compressive performance, compressive economic efficiency, uplift performance, uplift economic efficiency, maximum horizontal displacement and maximum bending moment of pile body were analyzed. The analysis methods used included comprehensive balance method, queue scoring method, principal component analysis method, entropy weight method, and analytic hierarchy process. The conclusions obtained are similar, and based on the judgment, the squeezed branch pile with 4 discs, disc diameter of 2.5D, disc squeeze angle of 35°, and disc spacing of 3D is considered as the optimal combination under consideration of all optimization objectives.

Probabilistic wind uplift resistance framework for the relative evaluation of wood-frame load paths

Past failure risk analyses of wind-impacted wood-frame structural load paths have tended to consider simplified resistance models that account for a few key load path connections, in which connection capacity distributions are generally based on benchmark experimental results. However, recent post-storm reconnaissance studies have demonstrated that connections in the load path of light wood-frame structures are themselves composed of multiple elements with many configurations and possible failure modes. This study presents a flexible approach for modeling wind uplift resistance in wood-frame load paths that includes a more exhaustive set of potential failure points yet is computationally efficient and readily adaptable to various load paths composed of different assemblages of structural members and connections. In this framework, ultimate capacities of connections and wood members are either based on design equations provided in the National Design Specification for Wood Construction or another applicable standard or computed from a comparable mechanics-based model. Analytical capacity estimates for roof sheathing, roof-to-wall connections, and wall-to-slab-foundation connections accord well with the range of published experimental results for these connections. Capacities of connections that act in parallel are summed to transform the load path into an analogous load chain of series components. System-level wind uplift resistance, defined by the weakest component in series, is evaluated by Monte Carlo simulation. By providing a more complete description of resistance than previous simplified models have done while avoiding the expense of a detailed finite-element or other solid mechanics model, the method proposed here holds promise as a rapid, consistent, and accurate way to quantify wind resistance in any arbitrary wood-frame load path, with applications including insurance risk analysis, hybrid data science frameworks utilizing post-storm reconnaissance data, and estimation of hazard intensity from structural damage observations.

Horizontal and Uplift Bearing Characteristics of a Cast-In-Place Micropile Group Foundation in a Plateau Mountainous Area

Micropile groups have been progressively more frequently adopted in the construction of transmission tower bases due to their compact size and flexible construction advantages. However, the load-bearing characteristics and deformation mechanisms of micropile groups are complex, and the study of their coupling effects under combined loads remains unclear. Consequently, this paper presents a field static load test of micropile groups in a highland mountainous area. The analysis encompasses the axial force distribution and load-sharing ratio of micropiles. With a focus on micropile groups subjected to both uplift and horizontal combined loads, the coupled effects under different load combination ratios are examined using numerical simulation methods. The key findings are as follows: During the uplift loading process, the load distribution among individual piles is relatively uniform, with lower side friction resistance gradually coming into play to counterbalance the top load. The load–uplift displacement curve exhibits a steep characteristic, making it susceptible to sudden failure in practical engineering applications. Under the simultaneous action of uplift (V) and horizontal (H) loads, the unbalanced lateral frictional resistance on both sides of the pile segment induces additional bending moments, which is an important part affecting the load-coupling mechanisms. The uplift resistance capacity of micropile groups decreases with an increase in horizontal load, while the horizontal load-carrying capacity initially decreases and then increases with an increase in uplift load. The space enclosed by the yield envelope under combined load, and the vertical line of the ultimate load, is divided into a ‘failure zone’ and a ‘safety zone.’ In the design of the pile foundation, the uplift bearing capacity reduced by the ‘failure zone’ should be taken into account.

A machine learning regression approach for predicting uplift capacity of buried pipelines in anisotropic clays

The uplift capacity of pipeline systems in geotechnical engineering is influenced by internal loading and external factors, making it a significant consideration in pipeline design problems. Previous research has conducted experimental tests and numerical solutions to investigate the relationship between force and displacement or the resistance of pipelines in numerous soil media. This paper proposes a machine-learning regression technique to predict the uplift capacity of buried pipelines in anisotropic clays with parametric analysis. Specifically, the Multivariate Adaptive Regression Spline (MARS) is employed to establish the relationship between input parameters, namely the depth ratio (H/D), anisotropic strength ratio (re), load inclination (β), overburden factor (γH/Suc), adhesion factor (α), and the output uplift resistance (N) obtained from the finite element limit analysis (FELA), utilizing the AUS material model integrated with the OptumG2 commercial program. Furthermore, the sensitivity analysis outcome shows the embedded depth ratio is the most critical parameter, followed by the anisotropic strength ratio, overburden factor, load inclination, and adhesion factor. Additionally, the shear velocity field contours show that when the depth ratio and the load inclination increase, the dissipation of shear changes. Design data visualizations, tables, graph contours, and empirical equations are created and can be utilized to aid in the development of practical designs.

Effect of wing plate structure on uplift resistance capacity of marine aquaculture anchor piles

As the main component of the anchorage system in marine aquaculture facilities, the anchor pile is key to ensuring safety and stability. However, conventional monopiles have limited capacity to withstand uplift forces, thus rendering them susceptible to deviations and potentially causing damage to facility structures. Hence, a new winged monopile is proposed to improve and optimize the anchor pile. In this study, laboratory experiments are conducted to investigate the effect of load inclination angle (θ = 0°, 30°, 45°, and 60°), wing length (L = 30, 50, and 70 mm), and wing width (W = 10, and 20 mm) on the uplift resistance capacity of anchor piles in silty clay. The results show that: the winged monopile exhibits at least a 15% improvement in uplift performance compared with the conventional monopile (without wings) when the smallest wing plate parameters are selected (W = 10 mm, L = 30 mm). Additionally, the effect of the wing width on the uplift resistance under an oblique load is more evident than that of the wing plate length. As the area of the wing plate increases, the range of improved wing plate efficiency first increases, and then gradually decreases. This study can be used as a reference for the design optimization of uplift piles and the construction of marine aquaculture.

Comparative Analysis of Helical Piles and Granular Anchor Piles for Foundation Stabilization in Expansive Soil: A 3D Numerical Study

This study investigates the performance of granular anchor piles and helical piles in expansive soils. Expansive soils pose challenges for engineering due to their significant swelling and shrinkage characteristics. Special considerations are required for constructing foundations on expansive soil to mitigate volumetric changes. While helical piles provide uplift resistance in light structures, they may not fully stabilize foundations in expansive soils. In contrast, granular anchor piles offer a simpler alternative for resisting uplift forces. A numerical study was conducted to analyze the pullout loads, compressive loads, and heave behavior of these anchor techniques. The results demonstrate that granular anchor piles outperform helical piles in terms of pullout and compressive performance, with improvements ranging from 17% to 22.5% in pullout capacity and 0.5% to 19% in compressive capacity, depending on specific pile lengths and diameters examined. However, both techniques show similar effectiveness in reducing heave, achieving reductions of over 90% when specific conditions are met. Additionally, the use of high-rise cap piles contributes to significant heave reduction, effectively minimizing heave to nearly negligible levels compared to low-rise cap piles. It is found that the relative density of the granular material has a more pronounced effect on the pullout load compared to the compressive load, and its impact varies depending on the length of the pile. Therefore, it is recommended to avoid high relative density when the pile is entirely within the expansive soil while utilizing higher relative density is beneficial when the pile penetrates and settles in the stable zone.

Coupling FEA with XGBoost Model for Estimating Uplift Resistance of Circular Anchor in NGI-ADP Soils

Coupling FEA with XGBoost Model for Estimating Uplift Resistance of Circular Anchor in NGI-ADP Soils

Determination of minimum overburden depth for underwater shield tunnel in sands: Comparison between circular and rectangular tunnels

With the development of global urbanization, the utilization of underground space is more critical and attractive for civil purposes. Various shapes of shield tunnels have been gradually proposed to cope with different geological conditions and service purposes of underground structures. Generally, reducing the burial depth of shield tunnel is conducive to construction and cost saving. However, extremely small overburden depth cannot provide sufficient uplift resistance to maintain the stability and serviceability of the tunnel. To this end, this paper firstly reviewed the status of deriving the minimum sand overburden depth of circular shield tunnel using mechanical equilibrium (ME) method. It revealed that the estimated depth is rather conservative. Then, the uplift resistance mechanism of both circular and rectangular tunnels was deduced theoretically and verified with the model tests. The theoretical uplift resistance is consistent with the experimental values, indicating the feasibility of the proposed equations. Furthermore, the determination of the minimum soil overburden depth of rectangular shield tunnel under various working conditions was presented through integrated ME method, which can provide more reasonable estimations of suggested tunnel burial depth for practical construction. Additionally, optimizations were made for calculating the uplift resistance, and the soil thickness providing uplift resistance is suggested to be adjusted according to the testing results. The results can provide reference for the design and construction of various shapes of shield tunnels in urban underground space exploitation.