2013 Session: 598

• Probabilistic Framework for Strength Limit and Service Limit Checks of Drilled Shafts Considering Soil Spatial Variability
  Abstract: This paper presents a performance-based, probabilistic framework for design of a drilled shaft under axial and lateral loading that can consider spatial variability of soil properties at a project site. The performance criteria of a drilled shaft are stated in terms of limiting and tolerable deformations for strength limit and service limit, respectively. The computational algorithm for calculating the deformation of a drilled shaft is based on the commonly adopted load transfer method and the p-y method. Geotechnical failure is defined as the event that the specified performance criteria are not met. Three failure modes are considered, including axial movement, lateral deflection, and angular distortion. The spatial variability of soil properties is considered by using random field modeling techniques in which correlation length is introduced to account for site variability, in addition to mean and variance. The method of fitting a sample autocorrelation function to a prescribed correlation function using the method of ordinary least squares is introduced for determining site specific correlation length for soil parameters. Geostatistical principles known as kriging are employed to estimate unknown parameters at unsampled locations from neighboring sampled locations. A numerical example is given to illustrate the application of the proposed methodologies. It demonstrates that correlation length is one of important statistical descriptors for characterizing site variability. Performance-based design provides unified consideration for both strength and service limits. Finally, the overall probability of failure for a drilled shaft considering all three failure modes is greater than the failure probability for any individual failure mode.
  Authors: Liang, Robert; Fan, Haijian
  Authors: Liang, Robert; Fan, Haijian
  Year: 2013
  Document Type: Paper
  Subject: Bridges and Other Structures; Geotechnology
  Session: 598
  Paper Number: 13-0520
• Effect of Foundation Rigidity on Contact Pressure Distribution
  Abstract: The effects of foundation rigidity and applied stress level on contact pressure beneath surface circular foundations resting on sandy soil were investigated. The finite element (FE) program (ABAQUS) with the built in material models was used to closely capture the pressure at the contacting surfaces between the soil and the foundation at different applied stresses. The foundation was modeled as elastic material while the soil was modeled as elastoplastic material according to Mohr-Coulomb failure envelop.The FE analyses indicated that the contact pressures are largely dependent on the foundation rigidity index (Kr) and the applied stress on the foundation relative to the ultimate state of stress (q*). Foundation can be described as rigid when Kr ¡Ý 1. The general shape of the contact pressure distribution is of a saddle shape with a peak pressure moving towards the foundation edge as q* (applied stress level) is decreased. The assumption of the flexible foundation behavior with uniform pressure distribution as in the current practice is imprecise and leads to erroneous results. FE model accuracy and validity of boundary conditions were verified using available theoretical and experimental results in the literature.
  Authors: Yamin, Mohammad; Ashteyat, Ahmed M.; Alldin, Izz; Mahmoud, Enad
  Authors: Yamin, Mohammad; Ashteyat, Ahmed M.; Alldin, Izz; Mahmoud, Enad
  Year: 2013
  Document Type: Paper
  Subject: Bridges and Other Structures; Geotechnology
  Session: 598
  Paper Number: 13-1489
• Evaluation of Constructed, Steel Tubular, Cast-in-Place Piling Properties
  Abstract: Bridge foundations have significant contributions to serviceability and efficiency of in-service transportation networks. Their failure may lead to catastrophic failure of the entire structure, which in turn results in system failure, loss of life and detours. When the soil within the ground surface layers fail to satisfy the bearing capacity requirements, deep foundations such as steel tubular concrete filled piles are commonly utilized in actual practices. A challenge that often exists with these systems is the uncertainty sounding in-service capacity as well as condition, which is difficult to determine from the surface. As a consequence, transportation agencies such as the Wisconsin Department of Transportation use conservative approaches to design these systems such as neglecting the steel tubular contribution or bounding the compressive strength of the core concrete. This approach, while effective for safety, can yield overly conservative and costly designs.The main purpose of this investigation is to evaluate the behavior of steel tubular, concrete filled, Cast-In-Place (CIP) pilings, with a concentration on the compressive strength and composite behavior between concrete core and steel shell. In this regard, a series of experimental studies including: composite and non-composite compression loading, core samples, push-through, and flexural testing together with a compatible finite element analysis have been conducted on a series of field-cast piles with different geometrical properties. The results obtained indicated that the steel shell has a significant contribution to the axial loading capacity of the CIP piles. Moreover, no evidence of bond loss was observed during the corresponding experimental studies.
  Authors: Harris, Devin K.; Gheitasi, Amir; Ahlborn, Theresa M.; Mears, Kevin A.
  Authors: Harris, Devin K.; Gheitasi, Amir; Ahlborn, Theresa M.; Mears, Kevin A.
  Year: 2013
  Document Type: Paper
  Subject: Bridges and Other Structures; Geotechnology
  Session: 598
  Paper Number: 13-2373
• Numerical Study on Laterally Loaded Drilled Shaft Group
  Abstract: Drilled shaft groups are sometimes built within a mechanically stabilized earth (MSE) wall to support lateral loads such as wind loads, bridge loads. Due to limited knowledge on the interaction between laterally loaded drilled shaft groups and MSE walls, current design methodology assumes that no interaction between the drilled shaft group and MSE walls, and also no interaction among drilled shafts. Such assumption has led to inappropriately designed shafts as well as MSE walls. This paper presents a numerical study, based on a completed full-scale field test, to investigate the behavior of a laterally loaded shaft group within an MSE wall. The numerical model, calibrated by lab testing data, simulated a group of three shafts loaded towards an MSE wall. The numerical results were compared with the field test data in terms of the load-deflection relationships of the group shaft, the deflection profiles of the MSE wall, and the strain distribution in geogrid reinforcement. Good agreement between the numerical simulation results and the test data was found. The numerical simulation allowed a detailed examination of the geogrid strain and the lateral earth pressure distribution. The maximum strain was developed at the edge of each shaft and decreased rapidly with further distance from the shaft. The lateral earth pressure increase induced by the laterally loaded shaft group is non-linear and non-monotonic.
  Authors: Huang, Jie; Bin-Shafique, Sazzad; Han, Jie
  Authors: Huang, Jie; Bin-Shafique, Sazzad; Han, Jie
  Year: 2013
  Document Type: Paper
  Subject: Bridges and Other Structures; Geotechnology
  Session: 598
  Paper Number: 13-4815
• Recommendations for The Use of Spread Footings on Soils to Support Highway Bridges
  Abstract: Recent FHWA national surveys revealed that: (a) highway bridges supported on spread footings bearing on competent and improved natural soils, and engineered granular and MSE fills have been safely and economically constructed by many state departments of transportation (DOTs); and (b) many DOTs may be missing an opportunity to save time and money by not actively considering spread footings to support highway bridges. The goal of this report is to promote the use of spread footings on soils when appropriate to support highway bridges. Perceived obstacles in using spread footings are identified, and recommendations to address these obstacles are developed and centered around: 1) deployment of AASHTO/FHWA technical resources; 2) highlighting practices of DOTs that actively use spread footings, especially for selection of spread footing; 3) performance review of bridges constructed with spread footings bearing on soils; and 4) LRFD implementation for spread footings design. Excessive settlement of bridges with spread footings bearing on soils is the main concern for the DOTs that do not consider spread footings. To address this concern, detailed recommendations are presented for accurate estimation of both the bridge tolerable settlements and the bridge settlements that impact bridge performance. The paper demonstrates that bridges with spread footings bearing on soil perform very well with respect to settlement, and concerns of bridge settlement should not limit DOTs from using these spread footings.
  Authors: Abu-Hejleh, Naser Mahmood
  Authors: Abu-Hejleh, Naser Mahmood
  Year: 2013
  Document Type: Paper
  Subject: Bridges and Other Structures; Geotechnology
  Session: 598
  Paper Number: 13-4352
  Practice-Ready: Yes
• Recommendations for The Use of Spread Footings on Soils to Support Highway Bridges
  Authors: Abu-Hejleh, Naser
  Authors: Abu-Hejleh, Naser
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Bridges and Other Structures; Geotechnology
  Session: 598
  Paper Number: 13-4352
• Numerical Study on Laterally Loaded Drilled Shaft Group
  Authors: Huang, Jie
  Authors: Huang, Jie
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Bridges and Other Structures; Geotechnology
  Session: 598
  Paper Number: 13-4815
• Probabilistic Framework for Strength Limit and Service Limit Checks of Drilled Shafts Considering Soil Spatial Variability
  Authors: Fan, Haijian
  Authors: Fan, Haijian
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Bridges and Other Structures; Geotechnology
  Session: 598
  Paper Number: 13-0520