Load Transfer Function Research Articles

In vitro experimental and numerical study on biomechanics and stability of a novel adjustable hemipelvic prosthesis

Hemipelvic prostheses are used to reconstruct the damaged pelvis due to bone tumors and traumas. However, biomechanical properties of the reconstructed pelvis remain unclear, causing difficulties to implant development and prediction of surgical outcome. In this study, a novel adjustable hemipelvic prosthesis for the Type 1–3 pelvis resection was used to reconstruct the intact pelvic ring. Two types of Pedicle Screw Rod Systems were proposed to improve the stability of fixation between the prosthesis and the bone. Finite Element models of the reconstructed pelvis were built to analyze the performance of the prosthesis and PSRS. Moreover, an in vitro experimental study was performed to measure the deformation of the human reconstructed pelvis. Numerical results agree well with the experimental data. It was found that displacements and stresses bilaterally transferred more evenly in the reconstructed pelvis enhanced by bilateral Pedicle Screw Rod System. The load-transfer function of the pelvis under double-leg standing stance could be recovered. The bilateral pedicle system has better biomechanical performance than the unilateral pedicle system.

Analytical Method for Prediction of Progressive Deformation Mechanism of Existing Piles Due to Excavation Beneath a Pile-Supported Building

After excavation beneath existing basement of a pile-supported building, prediction of the pile response is an interesting topic in geotechnical engineering. This paper presents a new load transfer function to capture the relationship between unit skin friction and shaft displacement. As to the load transfer function of an individual pile in pile groups before and after excavation, load transfer functions of skin friction and end resistance are proposed considering interactive effects among piles. To get a quick estimation on the pile response before and after excavation, a new highly effective iterative computer program is proposed using the proposed load transfer functions. Comparisons of the measured results, the present computed results and the calculated values derived from other approaches are made to check the reliability of the proposed method. Furthermore, a parameter study is carried out to evaluate the ultimate value of skin friction and end resistance of the pile subjected to stress relief due to excavation, and the influence of the parameters related to the proposed load transfer models on the pile response is also evaluated.

A probabilistic design approach for load of metro tunnel induced by surrounding development: Part A: Determination of development intensity

Adjacent development causes metro tunnel problems in soft-soil areas. A mathematical framework based on conventional integration and probabilistic method is purposed to include development-induced external loads into a metro tunnel design. In this framework, the development-induced load on the tunnel is a convolution of development intensity on the load-transfer functions over the adjacent area of the metro line. The development intensity is related to the urban development pattern, which is gathered by using categorized statistics. The load transfer functions adopt analytical solutions and empirical equations describing construction impacts on surrounding soil or structures. Monte Carlo simulations are used to generate the development impact, i.e., the load and displacement, on the basis of which the design value under a certain reliability index can be obtained. Therefore, determination of the development-induced load is divided into two stages. Part A of the paper introduces a statistical description of the development intensity of a location. Street blocks and metro stations are qualitatively cataloged with respect to development trends, periods, and frequencies. Maps, satellite photos, and street views are used to collect data in three Chinese cities: Shanghai, Guangzhou, and Nanjing. For each city, samples include the central station in the new district, and the central station, grouping station, and intermediate station in the built-up areas. In addition, residential districts inside and outside the inner ring in Shanghai are analyzed. The distribution of the building heights and stories with distance, the proportion of urban renewal with time, and the areas/depths/shapes of the excavations are obtained. The development patterns of blocks surrounding the metro line and the residential areas are analyzed. These data become input descriptions of development intensities in Monte Carlo simulations. Part B of the paper introduces the load transfer functions and the generation of loads on the tunnel.

Analysis of the Response of an Axially Loaded Pile Considering Softening Behavior of Pile-Soil System

The skin friction degradation was analyzed by using a softening model, and the relationship between unit end resistance and pile end displacement was simulated using a hyperbolic model. Determinations of the parameters related to the softening model of skin friction were presented. As to the bearing behavior of an axially loaded pile, an iterative computer program was developed by using the proposed softening model of skin friction and hyperbolic model of end resistance. Comparisons of the response of an axially loaded pile demonstrate that the proposed method is generally in good agreement with the field-observed behavior, and can assess the failure characteristic of skin friction. For practical purposes, different load transfer functions can be selected in the proposed method to capture the response of an axially loaded pile.

Load-Transfer Method for Piles under Axial Loading and Unloading

AbstractThis paper presents two modifications to the traditional formulation of the load-transfer method; a distinct unloading path is defined for the load-transfer functions, and the displacement ...

URANS predictions of wave induced loads and motions on ships in regular head and oblique waves at zero forward speed

The paper presents predictions on the hydrodynamics of a conceptual floating liquefied natural gas (FLNG) and a liquefied natural gas (LNG) carrier in regular head and oblique sea waves using an unsteady Reynolds-Averaged Navier–Stokes (URANS) solver. Initially, a verification and validation study is performed on estimating the numerical uncertainties in the presented URANS simulations. Using the verified numerical setup, ship hydrodynamic properties including wave induced loads as well as ship motion responses are investigated for different wave conditions. The computed time history results are decomposed by Fourier Series to estimate the wave load and ship motion transfer functions. These results show good correlation with predictions from model tests and potential flow calculations. From the computations, it is observed when increasing the wave length, wave diffraction around the ship becomes less profound and the water depth starts to influence the transfer functions. Full scale computations in head and oblique sea waves are also presented and compared with model scale predictions for investigating possible scale effects. The differences are found to be close to the numerical uncertainties, indicating minor influences of scale effects on the prediction of wave loads and ship motion responses for the tested cases.

Analysis on response prediction of a single pile and pile groups based on the Runge-Kutta method

The conventional load-transfer approach can not consider the interaction of piles, and can not be directly used in the analysis of the response of pile groups. The interactive effects among piles can be taken into account in the shear displacement method based on the principle of superposition. In the present analysis, the shaft displacement of a single pile at a given depth is assumed to be composed of the pile-soil relative displacement developed at the disturbed soil around pile and the elastic vertical soil displacement developed in the soil mass. A new load-transfer function which is very similar to a hyperbolic model is then established to describe the relationship between unit skin friction and shaft displacement at a given depth. Furthermore, a hyperbolic model is used to simulate the relationship between unit end resistance and pile end displacement. As to the analysis of the response of pile groups, the interactive effects among piles are considered by using the shear displacement method. For an individual pile in pile groups, new load-transfer functions are established to capture the relationship between unit skin friction and shaft displacement and the relationship between end resistance and pile end displacement. Based on the fourth order Runge-Kutta method, a modified load-transfer method is proposed to analyze the response of pile groups considering the interactive effects among piles. The reliability of the present method is checked by using comparisons of the present calculated results, the measured results and the computed values derived from other methods.

Discussion on “An analytical approach for the prediction of single pile and pile group behaviour in clay”

In the paper of Sheil and McCabe (2016), the ‘t–z method’ was used to capture the nonlinear response of single pile and pile group. However, some key questions on the skin friction and end resistance were not clearly addressed in their paper. In the present paper, analyses of the load transfer functions of the skin friction and end resistance are discussed in detail.

Analysis on Modification of the Measured Results of Test Pile Due to the Influence of Reaction Piles in Static Loading Test

Abstract In static load testing, the measured displacement of the test pile is different from that of an individual pile loaded by the same load. This is because the transferred load of the reaction piles through the soils causes an opposite movement of the test pile. To modify the measured results of test pile due to influence of reaction piles in static loading test conducted by using reaction piles as the reaction system, this paper presented a simple analytical approach for the analysis of the influence of reaction piles on the test pile response in static load testing. This was done by using the load-transfer approach. In this paper, the shaft displacement at a given depth was assumed to be composed of the pile-soil relative displacement developed at the disturbed soil around pile and the elastic vertical soil displacement developed in the soil mass. A load-transfer function which is similar to a hyperbolic model was then established to simulate the relationship between unit skin friction and shaft displacement at a given depth. Furthermore, a hyperbolic model was used to describe the relationship between unit end resistance and pile end displacement. Considering interactive effects between reaction piles and test pile, the load transfer function of the test pile in static load testing conducted using reaction piles as the reaction system is proposed. As to the analysis of the response of an influenced test pile considering progressive deformation of pile-soil system, a highly effective iterative computer program was developed to modify the response of an influenced test pile in static load testing. Comparisons of the load-settlement responses of a single pile and an influenced test pile in static load testing demonstrated that the proposed method is generally in good agreement with the observed behavior and the calculated results derived from other approaches.

Nonlinear random motion analysis of coupled heave-pitch motions of a spar platform considering 1st-order and 2nd-order wave loads

In this study, we consider first- and second-order random wave loads and the effects of time-varying displacement volume and transient wave elevation to establish motion equations of the Spar platform’s coupled heave-pitch. We generated random wave loads based on frequency-domain wave load transfer functions and the Joint North Sea Wave Project (JONSWAP) wave spectrum, designed program codes to solve the motion equations, and then simulated the coupled heave-pitch motion responses of the platform in the time domain. We then calculated and compared the motion responses in different sea conditions and separately investigated the effects of second-order random wave loads and transient wave elevation. The results show that the coupled heave-pitch motion responses of the platform are primarily dominated by wave height and the characteristic wave period, the latter of which has a greater impact. Second-order mean wave loads mainly affect the average heave value. The platform’s pitch increases after the second-order low frequency wave loads are taken into account. The platform’s heave is underestimated if the transient wave elevation term in the motion equations is neglected.

Nonlinear analysis of pile load—settlement behavior in layered soil

A simplified approach is presented to analyze the single pile settlement in multilayered soil. First, a fictitious soil—pile model is employed to consider the effect of layered soil beneath pile toe on pile settlement behavior. Two approximation methods are proposed to simplify the nonlinear load transfer function and simulate the nonlinear compression of fictitious soil—pile, respectively. On this basis, an efficient program is developed. The procedures for determining the main parameters of mathematical model are discussed. Comparisons with two well-documented field experimental pile loading tests are conducted to verify the rationality of the present method. Further studies are also made to evaluate the practicability of the proposed approach when a soft substratum exists, and the results suggest that the proposed method can provide a constructive means for assessing the settlement of a single pile for use in engineering design.

The Torsional Upper Crossed Syndrome: A multi-planar update to Janda's model, with a case series introduction of the mid-pectoral fascial lesion as an associated etiological factor

The Upper Crossed Syndrome (UCS) was presented by Janda to introduce neuromotor aspects of upper body muscle imbalances, describing sagittal plane postural asymmetries as barriers to recovery from chronic locomotor system pain syndromes. The UCS describes muscle imbalances of key antagonists causing forward postures of the head and shoulders and associated changes in the spinal curves -particularly an increased thoracic kyphosis - as well as changed function in the shoulder girdle. The role of fascial tissue has gained remarkable interest over the past decade, previously emphasizing its anatomic compartmental and binding role, while more recently emphasizing load transfer, sensory and kinetic chain function. The authors introduce the Mid-Pectoral Fascial Lesion (MPFL) as a myofascial disorder, describing 11 ipsilateral chest wall cases. While managing these cases, the authors encountered and subsequently designated the Torsional Upper Crossed Syndrome (TUCS) as a multi-planar addition to Janda's classic sagittal plane model. This article integrates published updates regarding the role of posture and fascia with the effects of chest wall trauma and a newly described associated postural syndrome as illustrated with this case series. An effective therapeutic approach to release the MPFL is then briefly described.

보강날개로 보강된 수중잠제 지지말뚝의 보강효과 분석

본 연구에서는 보강날개로 보강된 수중잠제 지지말뚝의 보강효과를 분석하기 위하여 하중전이거동을 분석하였다. 먼저 3차원 유한요소해석을 통해 말뚝의 변위 및 하중전이곡선(지반반력) 결과로부터 보강효과를 확인하고, 하중전이곡선에서 극한저항력 비율로 보강말뚝의 수평 및 인발하중에 대한 보강계수를 산정함으로써 보강효과를 정량화 하였다. 산정된 보강계수를 쌍곡선 하중전이함수의 극한저항력 <TEX>$p_u$</TEX>와 <TEX>$t_{max}$</TEX>에 곱해서 보정상수(fitting parameter)로 적용하여 보강효과를 고려한 하중전이함수를 제안하였다. 제안된 하중전이함수가 수치해석 결과를 잘 반영하고 있는지 확인하기 위해 3차원 유한요소해석을 비교하여 보강말뚝의 하중전이거동을 분석하였다. 제안된 하중전이함수를 하중전이법 해석에 적용하여, 실제 수중잠제를 해석한 결과 보강말뚝의 전단력, 휨 모멘트, 변위가 무보강말뚝보다 작게 발생하고, 지반반력은 더 크게 발생하여 비교적 경제적인 설계가 가능할 것으로 판단된다. The use of pile reinforcement is considered as one of the most promising techniques for improving load carrying capacity of piles in offshore area. In this study, to consider the horizontal and uplift bearing capacity of submerged breakwater bearing pile, exclusive analysis on load-transfer behaviour of pile was conducted. First of all, check the reinforcing effect from the three-dimensional finite element method, and estimate load transfer curve (ground reaction force). Based on these results, the reinforcing effect was quantified by estimating the coefficients of horizontal and uplift reinforcement of reinforced piles. Load transfer function with consideration of the reinforcing effect was proposed from estimated coefficients. A comparison of the analysis using the proposed load transfer function with three-dimensional finite element analysis has resulted that the proposed load transfer function is displaying good accuracy of predicting behavior of the load transfer between the pile and soil reinforcement. Interpretation of the submerged structure by applying a load transfer function considering the reinforcing effect, has shown that the reinforced pile's shear, bending moment and displacement are less than that of non-reinforced piles, while the subgrade reaction modulus arises greater. Thus, it is expected to be relatively cost effective in terms of design.

Mechanical properties of the compass depressors of the sea-urchin Paracentrotus lividus (Echinodermata, Echinoidea) and the effects of enzymes, neurotransmitters and synthetic tensilin-like protein.

The compass depressors (CDs) of the sea-urchin lantern are ligaments consisting mainly of discontinuous collagen fibrils associated with a small population of myocytes. They are mutable collagenous structures, which can change their mechanical properties rapidly and reversibly under nervous control. The aims of this investigation were to characterise the baseline (i.e. unmanipulated) static mechanical properties of the CDs of Paracentrotus lividus by means of creep tests and incremental force-extension tests, and to determine the effects on their mechanical behaviour of a range of agents. Under constant load the CDs exhibited a three-phase creep curve, the mean coefficient of viscosity being 561±365 MPa.s. The stress-strain curve showed toe, linear and yield regions; the mean strain at the toe-linear inflection was 0.86±0.61; the mean Young’s modulus was 18.62±10.30 MPa; and the mean tensile strength was 8.14±5.73 MPa. Hyaluronidase from Streptomyces hyalurolyticus had no effect on creep behaviour, whilst chondroitinase ABC prolonged primary creep but had no effect on secondary creep or on any force-extension parameters; it thus appears that neither hyaluronic acid nor sulphated glycosaminoglycans have an interfibrillar load transfer function in the CD. Acetylcholine, the muscarinic agonists arecoline and methacholine, and the nicotinic agonists nicotine and 1-[1-(3,4-dimethyl-phenyl)-ethyl]-piperazine produced an abrupt increase in CD viscosity; the CDs were not differentially sensitive to muscarinic or nicotinic agonists. CDs showed either no, or no consistent, response to adrenaline, L-glutamic acid, 5-hydroxytryptamine and γ-aminobutyric acid. Synthetic echinoid tensilin-like protein had a weak and inconsistent stiffening effect, indicating that, in contrast to holothurian tensilins, the echinoid molecule may not be involved in the regulation of collagenous tissue tensility. We compare in detail the mechanical behaviour of the CD with that of mammalian tendon and highlight its potential as a model system for investigating poorly understood aspects of the ontogeny and phylogeny of vertebrate collagenous tissues.

연직진동말뚝의 동적 하중전이 특성

Abstract In this study, the dynamic load transfer function, which is necessary for analyzing a pile installed by avibro hammer, was determined by comparing the results of the analyses and instrumented tests. The static load transfer function was modeled by the Ramberg-Osgood model through an analytical method before determining the dynamic load transfer curve. The parameters of the Ramberg-Osgood model were correlated with the N value of thestandard penetration test and average values of the correlation coefficient were 0.97 for the shaft load transfer and0.98 for the base load transfer. The dynamic load transfer function was simulated using the modified Ramberg-Osgoodmodel. The results showed that there were little differences in the characteristics of dynamic load transfer betweenthe results of the measurement and prediction. Key Words : Dynamic load transfer function, Static load transfer curve, Ramberg-Osgood model, Modified Ramberg-Osgood model * Corresponding Author : Ki-Yong Yoon(Sunmoon University)Tel: +82-41-530-2326 email: kyyoon@sunmoon.ac.krReceived March 3, 2014 Revised March 21, 2014 Accepted June 12, 2014

Response Evaluation of Axially Loaded Grouted Drilled Shaft

A rational approach of predicting the response of the grouted shaft has been developed in this paper. The mechanisms of how base grouting affects the end bearing and side friction are analyzed in detail. Based on this analysis, four improvement factors are introduced into the hyperbolic load transfer function to account for the improvement of the shaft performance due to base grouting. The rational ranges of these factors have been determined by statistical analyses of a large group of in-situ testing results. The improvement load-transfer function was used to predict the behavior of the grouted shaft and the results show that the measured response of the shaft lies between the predicted upper and lower bound, which indicates the validity of the approach.

EPAIA: Design, modelling and control of a novel electro-pneumatic adaptable impedance actuator

In this contribution we present the novel electro-pneumatic adaptable impedance actuator (EPAIA) consisting of a brushless DC-motor and a rotational pneumatic actuator, applied in series to the gear train. The pneumatic actuator is employed as a pneumatic torsional spring with a continuously adaptable stiffness, controlled by air inflow and pressure control. Thus, a rotary variable stiffness actuator is obtained, for which the stiffness can be expressed as a smooth nonlinear function of chamber pressures. The mechanical design furthermore utilises a planetary and a bevel gear reduction, to provide a torque amplification ratio necessary for human assistive knee joint actuation. Besides large and precise torque generation, the actuator provides a smoothly adjustable output impedance, backdrivability and a low cost, yet quality sensitive torque sensor. Following a detailed description of the mechanical design of the actuator, a dynamical model is derived using the Lagrange formalism. We propose a robust H2-torque-controller design procedure for the linearised actuator model, for which a constraint for passivity of the load transfer function is employed. The resulting controller is tested in simulations using the nonlinear validated model.

Proposed point bearing load transfer function in jointed rock-socketed drilled shafts

The point bearing behavior of rock-socketed drilled shafts under axial loading is investigated by numerical analysis and a load transfer approach (q–w). A numerical analysis using the distinct element method (DEM) is carried out to investigate the effects of pile diameter and the elastic modulus, discontinuity spacing and the inclination of rock mass on the point bearing behavior. The emphasis is quantifying the point bearing mechanism by taking rock discontinuity into consideration based on field loading tests performed on 39 instrumented piles. A new hyperbolic q–w function is proposed considering the point bearing resistance influence factors, including rock mass discontinuity. Through comparisons with other field data, the proposed q–w function represents a significant improvement in the prediction of the point bearing load transfer characteristics of jointed rock-socketed drilled shafts.

Theory and Experiment Research on P-S Curve of Anchor in Soil

Based on the shear displacement constitutive relationship of the interface between anchorage body and surrounding soil, the load transfer function method is applied to build a elastic-plastic space model. Accordingly the relationship between drawing force and displacement of prestressed anchor is analysed to acquie theoretical formula of P-S curve. The pullout test is carried out on six prestressed anchor in soil to get P-S curves. The experimental results agree quite well on the theoretical results.

Normalized Numerical Analysis for Load-Displacement Curve of Uplift Pile in Soft Soil

On the basis of Hsiung’s normalization analysis method, the soil is assumed to be in accordance with the elastic-plastic model. Some normalized parameters are selected to normalize different load-displacement curves to a single one, which is obtained by using the parabolic load transfer function. At last, we get a regression formula of the single curve with the regression analysis method. By comparing the results of regression formula with the practical test data of projects, the fact that the calculation results of regression formula coincide well with test data show that this analysis method is correct and it can provide reference for the research and application of uplift pile.