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A Program Development for Prediction of Negative Skin Friction on Piles by Consolidation Settlement
김형주,Jose Leo C. Mission 한국지반공학회 2009 한국지반공학회논문집 Vol.25 No.9
The microcomputer program PileNSF (Pile Negative Skin Friction) is developed by the authors in a graphical user interface (GUI) environment using MATLABⓇ for predicting the bearing capacity of a pile embedded in a consolidating ground by surcharge loading. The proposed method extends the one-dimensional soil-pile model based on the nonlinear load transfer method in OpenSees to perform an advanced one-dimensional consolidation settlement analysis based on finite strain. The developed program has significant features of incorporating Mikasa’s finite strain consolidation theory that accounts for reduction in the thickness of the clay layer as well as the change of the soil-pile interface length during the progress of consolidation. In addition, the consolidating situation of the ground by surcharge filling after the time of pile installation can also be considered in the analysis. The program analysis by the presented method has been verified and validated with several case studies of long-term test on single piles subjected to negative skin friction. Predicted results of negative skin friction (downdrag and dragload) as a result of long term consolidation settlement are shown to be in good agreement with measured and observed case data.
김형주,Jose Leo C. Mission 대한토목학회 2009 KSCE JOURNAL OF CIVIL ENGINEERING Vol.13 No.2
The development of dragload and downdrag on single piles in consolidating ground is investigated in this study with a simplified one-dimensional soil-pile model that combines the nonlinear load transfer method and finite strain consolidation theory to analyze soil-pile interaction under the effects of negative skin friction. In order to directly relate the soil settlements and effective stresses through the strain as a function of time and depth during the consolidation process, the prediction of the soil settlements imposing downdrag are based on Mikasa’s generalized one-dimensional consolidation theory that are formulated in terms of finite strain. An illustrative example and a case study of test pile were analyzed and predicted results of dragload and pile shortening by the presented model were shown to be in fair agreement with measured reference data. The model presented in this study offers a simple and flexible method for the analysis of a variety of soil-pile interaction problems under negative skin-friction that can account for nonlinearity of the soil and pile, a rigid and deformable bearing stratum, and can be applicable for the analysis of floating and endbearing piles as well as for shafts socketed in rocks. The development of dragload and downdrag on single piles in consolidating ground is investigated in this study with a simplified one-dimensional soil-pile model that combines the nonlinear load transfer method and finite strain consolidation theory to analyze soil-pile interaction under the effects of negative skin friction. In order to directly relate the soil settlements and effective stresses through the strain as a function of time and depth during the consolidation process, the prediction of the soil settlements imposing downdrag are based on Mikasa’s generalized one-dimensional consolidation theory that are formulated in terms of finite strain. An illustrative example and a case study of test pile were analyzed and predicted results of dragload and pile shortening by the presented model were shown to be in fair agreement with measured reference data. The model presented in this study offers a simple and flexible method for the analysis of a variety of soil-pile interaction problems under negative skin-friction that can account for nonlinearity of the soil and pile, a rigid and deformable bearing stratum, and can be applicable for the analysis of floating and endbearing piles as well as for shafts socketed in rocks.
Simple Methods for Approximate Estimation of Rehabilitation of Low Volume Roads
박대욱,Jose Leo Mission 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.7
This study presents two methods for the prediction and estimation of Maintenance and Rehabilitation (M&R) works based on the Highway Present Condition Index (HPCI) and statistical trend of rehabilitation period that is applied to paved low-volume roads. Since low volume roads comprised the majority of the country’s highway pavements having damage and distress characteristics that are totally different from high volume roads, specific criteria and guidelines are established. The results of the study have shown that economical costs for M&R must be viewed cumulatively in a specific M&R time frame compared to a yearly evaluation of individual costs. In particular, it has been shown that lower criteria of HPCI for rehabilitation within the serviceable level, although predicting higher individual costs at the later times, are still found to be the most economical option compared to service level criteria with higher HPCI values. Similar trend of results are found with a criteria for M&R based on maximum periods of rehabilitation,which showed a more economical choice compared to that when average and frequent periods of rehabilitations are made.
Congyi, Zhang,Mission, Jose Leo,Kim, Sung-Ho,Youk, Yui-Su,Kim, Hyeong-Joo Korean Institute of Intelligent Systems 2008 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.8 No.1
Typical wireless sensor networks used in structural monitoring are continuous types wherein data transmission is progressive at all time that may include irrelevant and insignificant data and information. Continuous types of wireless monitoring systems often pose problems of handling large-sized data that may deteriorate the performance of the system. The proposed method is to suggest an event-triggered monitoring system that captures and transmits relevant data only. An error signal generated by the Principal Components Analysis (PCA) is utilized as an index for event detection and selective data transmission. With this new monitoring scheme, the remote server is relieved of unwanted data by receiving only relevant information from the wireless sensor networks. The performance of the proposed scheme was verified with simulation studies.
Zhang Congyi,Jose Leo Mission,Sung-Ho Kim,Yui-Su Youk,Hyeong Joo Kim 한국지능시스템학회 2008 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.8 No.1
Typical wireless sensor networks used in structural monitoring are continuous types wherein data transmission is progressive at all time that may include irrelevant and insignificant data and information. Continuous types of wireless monitoring systems often pose problems of handling large-sized data that may deteriorate the performance of the system. The proposed method is to suggest an event-triggered monitoring system that captures and transmits relevant data only. An error signal generated by the Principal Components Analysis (PCA) is utilized as an index for event detection and selective data transmission. With this new monitoring scheme, the remote server is relieved of unwanted data by receiving only relevant information from the wireless sensor networks. The performance of the proposed scheme was verified with simulation studies.
양기현,백상순,Jose Leo Mission,김형주 대한토목학회 2009 대한토목학회 학술대회 Vol.2009 No.10
Traditional practice for the analysis of single piles involves an independent two-step analysis of the axial and lateral load capacities using separate soil-pile models. An uncoupled model and analysis of a single pile subjected to combined axial and lateral load is presented in this study. The method uses an integrated two-dimensional soil-pile model with the load transfer method using nonlinear T-z, P-y, and Q-z soil spring elements. The integrated model can capture the combined responses of the pile by considering P-delta effects in a single model and one-step analysis. Results of a simulation example have shown that the neglect of the P-delta effects in the analysis of single pile underestimates the lateral deflection and bending moment responses.
Hyeong Joo Kim,Jose Leo C. Mission,Il Sang Park KOREAN SOCIETY OF CIVIL ENGINEERS 2007 KSCE JOURNAL OF CIVIL ENGINEERING Vol.11 No.6
<P>A modified analytical model is proposed in this study for the analysis of pile axial load capacity with the load transfer method using nonlinear T-z and Q-z curves to model soil-pile behavior in skin friction or side shear and end bearing respectively. The method uses a three-dimensional (3D) pile model using solid finite elements with nonlinear load transfer curves resolved into components and mobilized around the pile perimeter. The use of multiple T-z component springs is demonstrated to accurately capture the total side resistance of the pile. The 3D pile method produces results of predicted pile axial load capacities from the load-settlement curves comparable to the one-dimensional analysis (1D) method. For a combined vertical and lateral loading on the pile, the proposed 3D pile method can address the limitation of the 1D pile method having vertical and lateral springs only acting at the pile center without rotational springs, which neglects the contribution of the side shear in the computation of pile bending moments. In the case of 3D pile model the moment or couple developed by the side shear around the perimeter can be taken into account, where this moment can be significant especially in strong soil material or in the case of large diameter pile/shafts.</P>