A study was conducted to evaluate the potential for using three-dimensional (3-D) computer modeling to assist Missouri Department of Transportation Soils and Geology personnel and Bridge Division personnel in developing accurate and realistic understanding of subsurface conditions for bridge structures. Secondary objectives of the study included developing a preliminary procedure for development of 3-D geologic models of bridge sites and identifying key issues to be addressed for more widespread use of 3-D modeling activities. The site of a proposed new bridge across the Missouri River near Lexington, Missouri was selected as a demonstration case study for 3-D geologic modeling. Several separate models of this site were developed during the project to demonstrate the different levels of abstraction for a 3-D model of a particular site. The computer models developed are presented and described in this report.

Continued advancements in high-speed computing and increased availability of earthquake strong motion data have been allowing for further progress in the area of soil-structure-interaction (SSI). Efforts in this dissertation are mainly concerned with three-dimensional (3D) computational analyses of pile foundations and bridge-foundation-ground systems. This includes Finite Element (FE) modeling of ground-pile foundation systems, documentation and assessment of recorded bridge strong motion data, and identification of dynamic bridge-foundation system characteristics. Currently, simplified approaches, such as p-y curves or the foundation stiffness matrix representation, are employed mainly when considering Soil-Structure-Interaction. However, there is much interest in more representative modeling techniques in order to improve our assessments of seismic pile foundation response. In an effort to address this challenge, 3D FE numerical investigations are conducted related to the response of piles and pile groups under lateral load. Distribution of loads and moments among the piles within the group is investigated. Effects of permeability and loading rate on lateral pile response are addressed for saturated relatively impervious cohesionless soil condition. Insights concerning the soil-pile interaction mechanisms are obtained based on the conducted analyses of the soil-pile foundation subsystems. Furthermore, numerical studies are conducted of long-span highway bridge-foundation systems under seismic loading conditions. Three-dimensional FE models of two existing bridges at Eureka California (the Samoa Channel Bridge and the Eureka Channel Bridge) are developed. Methodologies combining numerical modeling with insights gained from strong motion sensor records are investigated to capture the essential structure-foundation-ground system-response mechanisms. Focus is placed on the evaluation of dynamic properties and validation of the bridge FE models based on the recorded earthquake response. An optimization tool (SNOPT) is employed to evaluate the bridge foundation lateral stiffness. The studies show that computational modeling, along with analysis of the recorded ground-pile foundation data, provide an effective mechanism for understanding the entire structure-foundation-ground system response. The OpenSees platform and the user-interfaces OpenSeesPL, MSBridge, as well as SNOPT are employed in various sections of the study. In the domain of highly expensive and time consuming foundation design and/or retrofit, major beneficial outcomes can result from adoption of analysis tools which have been calibrated/verified by actual recorded seismic performance data sets.

This report documents practical modeling procedures adopted in the bridge engineering community involving seismic dsigns and retrofits of long span bridges relative to treatment of wave propagation problems. It also discusses wave scattering issues arising from irregular foundation boundaries affecting seismic loading of the bridges, which is not explicitly considered in th current design practice. Wave scattering is generally implemented in the nuclear power plant industry for seismic designs of various containment systems often using frequency domain computer programs. To examine the subject of wave scattering for application to long span bridge foundations, systematic modeling is exercised using a time domain based computer program and verification is made against a frequency domain computer program. For present day seismic designs of major bridges, nonlinear time history analysis is a common procedure to examine seismic loading of the structure permitting plastic hinging and ductility to be implemented. Thus, the current trend is to adopt time domain based computer programs for performing wave scattering analyses which can also serve as a common platform to be used by both geotechnical and structural engineers for the global bridge model. A major benefit is to minimize the amount of work for data transfer and potential error arising from two different groups (geotechnical and structural engineers) working on different computer codes requiring different input/output. By using the same computer code by both geotechnical and structural engineers, many problems are eliminated. Typically, wave scattering analyses are conducted in the frequency domain. This report presents studies of wave scattering using a time domain computer program. The same computer program can be used by structural engineers to proceed with coding the superstructure model, directly using the results from the wave scatterings analysis. The report presents various sensitivity analyses in order to minimize wave reflection and refraction at the model's side boundaries. Numerical integration schemes and implementation of Rayleigh parameters are discussed. Careful examination of waves traveling the bottom boundary allows proper modeling of the half-space below the region of interest. The studies explore the effects from wave scattering on large pile groups and soft ground conditions, and findings on the frequency ranges where significant scattering is observed are reported. Large caissons are know to affect seismic wave scattering due to the large wave length implied by the dimensions of the foundation embedded in soil. Parametric studies are performed to examine the shaking level that is altered by the wave scattering mechanism. From the current findings, it appears that the wave scattering tends to reduce the shaking level, especially in the high frequency range, and hence is beneficial to the bridge design

For undergraduate/graduate-level foundation engineering courses. Covers the subject matter thoroughly and systematically, while being easy to read. Emphasizes a thorough understanding of concepts and terms before proceeding with analysis and design, and carefully integrates the principles of foundation engineering with their application to practical design problems.