Load Transfer Analysis Research Articles

LOAD TRANSFER AND DEFORMATION ANALYSES OF PILED-RAFT FOUNDATION IN TAIPEI METROPOLITAN

LOAD TRANSFER AND DEFORMATION ANALYSES OF PILED-RAFT FOUNDATION IN TAIPEI METROPOLITAN

CPT-based p-y analysis for piles embedded in clays under cyclic loading conditions

The design of offshore mono-piles is subjected to various uncertainties more than inland cases, due to experimental difficulties in characterizing required soil parameters under offshore environment. In this study, a CPT-based p-y method is proposed for monopiles embedded in clay under cyclic loading conditions. As offshore mono-piles are particularly targeted in this study, the cyclic loading condition was introduced as an important design consideration. Based on the effective cone factor, the ultimate lateral soil resistance and p-y function were formulated as a function of CPT cone resistance and cyclic loading effect factor with consideration of the number of loading cycle. As the CPT-based p-y function utilizes the continuous CPT profile directly, detailed depth profile of soil characteristics can also be directly taken into account for the analysis without additional sampling and testing procedure. The load transfer analysis using the proposed CPT-based p-y analysis for cyclic loading condition was programmed using the discretized implementation algorithm for the beam-on-elastic foundation model. To validate the CPT-based p-y analysis method, the calculated lateral load responses were compared with the results obtained from the finite element analysis and case examples for static and cyclic loading conditions.

An analytical joint stiffness model for load transfer analysis in highly torqued multi-bolt composite joints with clearances

An analytical tri-linear joint stiffness model accounting for the effect of bolt-hole clearances on the bearing chord stiffness is presented. A single-parameter iteration method is also proposed to solve the nonlinear system of equations of the load transfer analysis, in which the recursive formulae are verified to be monotonic. To verify the present joint stiffness model, a series of single-lap, single-bolt joints with various bolt-hole clearances and bolt tightening torques were tested to empirically confirm the influence coefficients of the joint stiffness model. The load distributions in three single-lap, three-bolt joints with various clearances were also tested under finger-tight and highly torqued conditions. The load distributions in multi-bolt joints predicted by the presented joint stiffness model together with the single-parameter iteration method are in good agreement with the experimental outcomes, verifying the accuracy of the presented joint stiffness model and the feasibility of the single-parameter iteration method. In addition, the effects of the friction forces originated from the bolt-tightening torque and bolt-hole clearances on the load distribution in multi-bolt joints are presented.

A comparative study of the load transfer mechanisms of the carbon nanotube reinforced polymer composites with interfacial crystallization

With the help of shear-lag theory, load transfer analysis is performed on the carbon nanotube reinforced polymer composites with interfacial crystallization of different morphologies, including transcrystallinity layer (TCL) and nanohybrid shish-kebab (NHSK) structures. By comparison, we find that the TCL structures can ease the burden of the CNT while the NHSK structures can lead to a fluctuating distribution of the axial stress in the CNT. Both structures can improve the effective elastic modulus of the composites, though the effect of the TCL structures is more pronounced. Besides, the enhancement of the load transfer efficiency of the composites is also observed, the study of the interfacial stress on different kinds of interfaces shows that the reinforcing effect of the TCL structures is sensitive to both the CNT/crystalline polymer interface and crystalline polymer/amorphous polymer interface, while the major decisive factor for the NHSK structures is confined to be the CNT/crystalline polymer interface because of the interlocking effect. Based on these features, some suggestions are given for tailoring the high-performance carbon nanotube reinforced polymer composites.

An average failure index method for the tensile strength prediction of composite adhesive-bonded π joints

An average failure index method based on accurate FEA was proposed for the tensile strength prediction of composite out-of-plane adhesive-bonded π joints. Based on the simple and independent maximum stress failure criterion, the failure index was introduced to characterize the degree of stress components close to their corresponding material strength. With a brief load transfer analysis, the weak fillers were prominent and further detailed discussion was performed. The maximum value among the average failure indices which were related with different stress components was filtrated to represent the failure strength of the critical surface, which is either the two curved upside surfaces or the bottom plane of the fillers for composite π joints. The tensile strength of three kinds of π joints with different material systems, configurations and lay-ups was predicted by the proposed method and corresponding experiments were conducted. Good agreements between the numerical and experimental results give evidence of the effectiveness of the proposed method. In contrast to the existed time-consuming strength prediction methods, the proposed method provides a capability of quickly assessing the failure of complex out-of-plane joints and is easy and convenient to be widely utilized in engineering.

The Technical Features and the Architecture Design of Software for the Troubleshooting Simulation of Distribution Automation and Training Systems

The simulation of distribution automation troubleshooting and the functional design of training system software is discussed by this article, Including: basic platform capabilities, the decision analysis of auxiliary power failure, Power operation mode for load transfer analysis, the ring analysis of grid operation mode , the training simulator of distribution network and the data synchronization of the simulation system diagram and mode. The simulation of distribution automation troubleshooting and the effect of training system operation show the validity and effectiveness of the method.

Functional Design for Troubleshooting Simulation of Distribution Automation and Software of Training System

The simulation of distribution automation troubleshooting and the functional design of training system software is discussed by this article, Including: basic platform capabilities, the Decision Analysis of Auxiliary power failure, Power operation mode for load transfer analysis, the ring analysis of Grid operation mode , the Training Simulator of Distribution Network and the data synchronization of The simulation system diagram and mode .the simulation of Distribution Automation Troubleshooting and the effect of training system operation Show the validity and effectiveness of the method.

Simulation of Fault Treatment Performance for Distribution Automation Systems and Key Technologies of Training Systems

The simulation of fault treatment performance for distribution automation systems and the key technologies of training systems are discussed in this paper, which include key technologies for basic platform, auxiliary decision-making analysis for grid faults, load-transfer analysis for power system operating mode, loop closing analysis for power system operating mode and distribution network training simulation and so on. The results of simulation of fault treatment performance for distribution automation systems and training systems operation show a good accuracy and effectiveness of the method.

ABOUT MECHANICAL JOINTS DESIGN IN METAL-COMPOSITE STRUCTURE

Riveting is still one of the main joining methods of thin-walled aircraft structures. Such features as: simplicity of implementation, possibility of two different material connection (e.g. metallic with non-metallic ones) and the fact that is it a well-known (reliable) method causes popularity of riveting. The never-ending attempt to obtain as low mass as possible (mainly to reduce fuel consumption) is the reason for using material of high specific strength in the aerospace industry. High strength titanium or aluminium alloys (e.g. 2024T3) and composite laminates (e.g. CFRP or Glare) are examples of such materials. The article deals with methods of connecting various materials. The paper presents advantages and disadvantages of different/selected connection types. Strength prediction and failure modes of mechanical joints are described for metallic as well as for composite components. Composites are complex materials having an anisotropic structure (and anisotropic mechanical properties) leading to various failure mechanisms. Main principles for appropriate joint design of composite laminate panels (laminate configuration and typical/specific geometrical dimensions) are indicated/specified. The bearing failure mechanism is accepted to be a safe progressive one. Mechanism of bearing (generally compressive) load transfer into composite laminates by shear of the matrix is analysed. Some examples of improvement bearing strength of laminates are presented/shown according to literature. On the base of presented examples and bearing load transfer analysis, some conclusions for an appropriate solution of this problem are drawn.

Numerical and experimental analysis of time-dependent load transfer in reinforced concrete columns

A study was conducted to assess the influence of the steel reinforcement ratio in concrete columns on their properties of creep and shrinkage. Experimental tests and three-dimensional finite element-based simulations of the experimental curves from plain concrete cylinders and plain concrete columns derived by curve fitting were performed using the ACI 209 model available in DIANA 9.3. Columns with longitudinal reinforcement ratios of 0%, 1.4% and 2.8%, loaded to 30% and 40% of their 7-day compressive strength, were investigated. The results indicated that numerical simulation does not predict experimental data for a long period. However, simulations fitted with experimental curves derived from plain concrete columns presented values close to those of experimental data for 91 days.

Thermal Borehole Shear Device

This paper presents the details of a new modified borehole shear device that has the capability of measuring the impact of temperature on the in situ shear stress–displacement curves for soil–concrete interfaces. The thermal borehole shear device incorporates concrete shoes with embedded heaters, a pneumatic loading device for application of horizontal normal stresses, and an automated loading system with local vertical displacement and load measurement systems that permits either displacement–control or load–control testing. A methodology for measurement of the soil–concrete shear stress–displacement curves and for evaluation of the drained interface shear strength failure envelopes at different temperatures is presented in this study. Typical results from proof-of-concept tests performed in a clay layer compacted in a laboratory tank in a borehole in a silty sand deposit in the field are presented in this paper. The results are synthesized to show how the impacts of temperature and normal stress on the normalized shear stress–displacement curves can be evaluated. These normalized curves can be measured on a site-specific basis for the calibration of thermo-mechanical load transfer analyses or finite element analyses, which are often used to design and evaluate soil–structure interaction in drilled shaft foundations with geothermal heat exchangers (energy foundations).

Modeling Load-Transfer Behavior of H-Piles Using Direct Shear and Penetration Test Results

The load transfer analysis (or t–z analysis) has long been used to predict the load-displacement response of axially loaded driven piles. However, the t–z curves along the pile length and q–z curve at the pile tip, required for the t–z analysis, are routinely obtained based on empirical correlations using field and/or laboratory soil tests. This study focuses on the use of a modified Direct Shear Laboratory Test (mDST) to directly quantify the t–z curves and the use of a penetration test, namely the Pile Tip Resistance test (PTR) to quantify the q–z curve, for partial-displacement piles. As part of this study, two instrumented steel H-piles driven in sandy soils were load tested and soil layers at the two sites were characterized using in situ and laboratory tests. A load transfer analysis was conducted utilizing the directly quantified t–z and q–z curves from the mDST and PTR, respectively, to calculate the response of the load tested piles. When compared to the measured load-displacement response and load distribution along pile length, the t–z analysis based on the mDST and PTR measurements showed very good agreement with the measured pile responses. Therefore, and despite the limited database availability at present, the proposed mDST–PTR based model is promising as it represents a simple and cost-effective means to accurately predict the load–displacement response of partial-displacement piles driven in cohesionless soils.

Load transfer and islanding analysis of active distribution network

When fault occurs in distribution network, the loads of faulty line are transferred to adjacent lines to restore the power supply. The interconnection of distributed generator (DG) and energy storage system (ESS) poses challenge to traditional load transfer, and loads that are not restored by the load transfer can be islanded with DG and ESS to further reduce the outage. To address this issue, model of power supply capacity of autonomous local control region and active distribution network line are established, considering the power restrictions of DG and ESS, and this model is effective to simplify the network of load transfer. Constraints for practical islanded operation, including the restriction of backup capacity against the power fluctuation are proposed, and a practical stepwise optimal algorithm is put forward for load transfer and islanding based on the radial characteristic of distribution network. In contrast to traditional intelligence algorithm, the computation amount of load transfer and islanding has been reduced by the proposed stepwise optimal algorithm, and the islanding is also well considered that further reduces the outage. The case study shows that the computation amount is reduced by about 70% comparing with genetic algorithm, and the restored load is increased by about 40%. Copyright © 2014 John Wiley & Sons, Ltd.

Uplift tests of jet mixing anchor pile

The jet mixing anchor pile is a new kind of supporting technology for foundation pit engineering in soft clay. The engineering features of jet mixing anchor pile as well as the difference between it and normal anchor bolt are introduced. The uplift tests of 4 jet mixing anchor piles are presented in detail to obtain the ultimate bearing capacity and load–deformation relationship of the piles. Load-transfer analysis, which is rarely applied in the analysis of uplift piles, is carried out on the piles with a hyperbolic calculation model. The load transfer method focuses on the interface between pile and soil, with which the non-linear behavior, the bearing capacity and the engineering features of the anchor piles can be fully studied. The calculated load–displacement curves of the piles have close agreement with that of the pullout tests, indicating that the proposed analytical solution is reasonable and feasible in predicting the bearing capacity of the piles. Thus, with this study, the supporting stiffness of the anchor pile can be predicted in the design stage of the foundation pit engineering, which is very important and meaningful in practical engineering. The decay curve of shear stress of soil surrounding the pile is derived with the load-transfer method, through which the minimum transverse space of each two piles can be decided against the pile group effect. Engineers can optimize the length and spacing of group piles through this.

Load-transfer analysis after insertion of cementless anatomical femoral stem using pre- and post-operative CT images based patient-specific finite element analysis

Periprosthetic bone remodeling is commonly seen after total hip arthroplasty, but the remodeling pattern differs among patients even in those implanted with the same stem. Remodeling occurs mainly because of the difference in load transmitted from the stem to the femur. In this study, we evaluated the load-transfer pattern in eight female patients implanted with an anatomical stem on an individual basis by patient-specific finite element analysis that is based on pre- and postoperative computed tomography images. Load transfer was evaluated using interface stress between the stem and bone. One of eight patients demonstrated proximal dominant load transfer, while the other patients demonstrated a distal dominant pattern. The results of our biomechanical simulations reveal the differences in load-transfer pattern after surgery among patients with the same anatomical stem.

Axial Force Analysis of the Single Pile Based on FLAC3D

Complex interaction mechanism of pile and soil, pile load transfer analysis is difficult. On the basis of analyzing the load transfer mechanism of the friction pile, using the FLAC3D analysis on the initial ground stress state of equilibrium , axial load under the action of pile axial force and displacement, got the ultimate load bearing capacity of single pile and the stress of the contact surface. Analysis results show that the load and displacement in a certain stage into a proportional relationship. Also shows that simulation is feasible and provide a reliable method for the analysis of pile groups.

Reduction of U<sup>**</sup> Calculation Time for Complementary Load Transfer Analysis in Structures

Reduction of U<sup>**</sup> Calculation Time for Complementary Load Transfer Analysis in Structures

Enhanced Load-Transfer Analysis for Friction Piles Using a Modified Borehole Shear Test

Abstract This study discusses the development and use of a modified borehole shear test (mBST) to improve the prediction of the load-displacement and load-distribution responses for axially loaded friction piles in cohesive soils using the load-transfer analysis method (i.e., t–z analysis). Unlike available approaches that rely on empirical or semi-empirical correlations to generate the shear stress displacement at the soil–pile interface (i.e., t–z curves), the mBST enables direct field measurement of the t–z curves at the soil–pile interface. As part of this study, three full-scale vertical static load tests (SLTs) were conducted on instrumented steel H piles. The t–z analysis was carried out utilizing the TZPILE software with measured t–z curves via the mBST (i.e., the TZ-mBST model). When comparing results of the analysis with the measured responses for the three test piles, it was found that: (1) the TZ-mBST provides proper prediction for the initial part of the measured load-displacement response from SLT results, with a difference not exceeding 10 %; (2) the TZ-mBST analysis provides acceptable prediction of the pile capacity; (3) the TZ-mBST analysis matches the load distribution along the pile length with a maximum difference of 8.3 %; and (4) the analysis with directly measured t–z curves using the mBST provide improved predictions of the pile response when compared to the empirical CPT-based analysis.

Dynamics of a Cylindrical Pile in a Transversely Isotropic Half-Space under Axial Excitations

For the first time, a theoretical formulation is presented for the load-transfer analysis of an elastic cylindrical thin-walled pile immersed in a transversely isotropic half-space under axisymmetric excitations. By generating a set of weakly singular Green’s functions for the embedding medium and using a shell theory for the pile, it is shown that similar to the related interaction analysis in isotropic medium, the soil-structure interaction problem under consideration is reducible to two coupled Fredholm integral equations. Regarding the singular nature of stress transfer, a newly developed adaptive-gradient elements family is employed in the development of an accurate numerical scheme. The effect of soil material anisotropy on the dynamic interaction process is explored by presenting a set of numerical results for various material and geometrical conditions and various excitation frequencies. To confirm the accuracy of the proposed analytical and numerical scheme, numerical results are compared with benchmark solutions for the corresponding isotropic problem.

Integrating finite element and load-transfer analyses in modelling the effects of dewatering on pile settlement behaviour

A method of analysis is developed by integrating finite element (FE) and load-transfer analyses to predict the negative shaft resistance and settlement of piles due to ground water lowering. A program is written in MATLAB for linking the FE results of ground movements with the input interface system of a new pile load–settlement analysis program (named “PILESET”) developed by the author. PILESET is specially designed to allow automatic input of electronic site investigation data, although manual input of laboratory soil test data is also possible. Using PILESET, custom-defined load-transfer relationships can be either input manually or calculated internally by PILESET based on the input data from in situ or laboratory soil tests. To demonstrate the validity of the suggested analysis procedure, a case record is analyzed where sump pumping was to be carried out underneath a deep basement situated close to an existing building supported on 15 m long piles. Based on assumed steady-state flow conditions, ground settlements are calculated using FE analysis and used with site investigation data to predict the negative shaft resistance and settlement induced in the piles. The results are found to agree well with field measurements.