Jose Leo Mission

Analysis of static axial load capacity of single piles and large diameter shafts using nonlinear load transfer curves

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.

Numerical Analysis of One-Dimensional Consolidation in Layered Clay Using Interface Boundary Relations in Terms of Infinitesimal Strain

The interface boundary relations are derived in this study for the numerical analysis of one-dimensional consolidation in multilayered clay profiles. The finite difference solutions are formulated based on Mikasa’s consolidation equation with infinitesimal strains and constant consolidation parameters under the same fundamental assumptions and limitations of the classic Terzaghi equation. Numerical examples are presented for multilayer clay profiles under single and double drainage conditions that validate the predicted excess pore pressures, strains, settlements, and rates of consolidation using interface boundary relations in terms of infinitesimal strains that are equivalent to those expressed in terms of excess pore pressures.

Improved Evaluation of Equivalent Top-Down Load-Displacement Curve from a Bottom-Up Pile Load Test

A modified procedure is presented in this study to evaluate the equivalent top-down load-displacement curve in a bottom-up pile load test considering elastic shortening. On the basis of the results of a parametric study on a bored pile in normally consolidated cohesive soils under undrained conditions, varying shear strength distribution and pile slenderness ratio, it was concluded that the pile shortening caused by the skin-friction component of the load in a top-down test can be related to the measured elastic shortening in a bottom-up test. A λ-factor is used to define this relationship, that is, the ratio of the top-down to bottom-up pile shortening. The factor λ=1.0 is used for the case of a pile in soil with uniform shear strength profile, λ=2.0 for linear profiles, 1.0 2.0 for nonlinear profiles varying below linear. In addition, the method suggests taking the corresponding readings of the skin-friction load component from the upward displace...

Estimation of pavement rehabilitation cost using pavement management data

Estimation and scheduling of future pavement maintenance and rehabilitation (M&R) works are one of the primary concerns of highway agencies due to the limited allocations in budget and resources. Two approximate methods for estimation of pavement rehabilitation cost are presented and compared in this study based on highway present condition index (HPCI) and rehabilitation history. The former is based on pavement condition, while the latter is based on historical and statistical trends. Database from a pavement management system (PMS) of various highway sections surveyed in Korea were used in this study to establish a relationship between HPCI and pavement service life and to analyse the trends of rehabilitation periods. The two simple methods presented provide useful information and probable range for the various highway agencies to guide them in the preliminary planning, budgeting, estimating and scheduling of their future pavement M&R works.

Application of Principal Components Analysis Method to Wireless Sensor Network Based Structural Monitoring Systems

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.