Document Type

Thesis - University Access Only

Award Date

2012

Degree Name

Master of Science (MS)

Department / School

Civil and Environmental Engineering

First Advisor

Francis C.K. Ting

Abstract

In this study a Two-Dimensional or 2-D hydraulic model was used to better understand the unique hydraulic characteristics of a complex bridge site. This is because One-Dimensional or 1-D hydraulic models may not model these characteristics accurately. Additionally, new scour prediction equations that incorporated the soil properties of the bed material were used in conjunction with the computed results from the 2-D hydraulic model to predict contraction scour. This study attempts to illustrate how better information on bridge hydraulics and soils may lead to improved predictions of bridge scour The bridge site studied was the Highway 37 bridge crossing of the James River North of Mitchell, South Dakota. In total there were three different hydraulic models used to examine the bridge site which included two 2-D models and one 1-D model. The 1-D model used was the Hydraulic Engineering Center- River Analysis System (HEC-RAS) and the 2-D model was the Finite Element Surface Water Modeling System (FESWMS) interfaced with the Surface Water Modeling System (SMS). The HEC-RAS model along with one of the FESWMS models were constructed using survey data and the other FESWMS model was constructed using existing data. The survey data was collected using a Light Detection and Ranging or LiDAR apparatus and the existing data was from the National Elevation Dataset or NED (Gesch 2007 and Gesch et al., 2002). The results were compared to determine whether a 2-D model constructed using NED data is adequate for predicting the flow conditions at a complex site. After the models were constructed, they were compared to measured data over a range of flows which included a 25, 50 and 100 year-flood event. This was done to qualitatively determine how accurate the models were over a range of flows and which produced results that best matched the measured data. A sensitivity analysis was performed for the FESWMS model that was constructed using the LiDAR data to determine how the computed results varied with input parameters such as the Manning's n value and the downstream water surface elevation. Then the unique hydraulic characteristics of the bridge site were examined. These included the general flow patterns, flow concentration on the right side of the main channel upstream of the bridge, a detailed analysis of the exchange of flow between the main channel and the flood plain and the water surface profiles. Finally contraction scour was predicted using the HEC-18 method (Arneson et al., 2012) and a scour prediction method for cohesive soils modified from Gi.iven et al (2003).

Library of Congress Subject Headings

Streamflow -- James River (N.D. and S.D.)
Scour at bridges -- South Dakota -- Mitchell

Publisher

South Dakota State University

Download

Share

COinS
 

Rights Statement

In Copyright