Finite Element Modeling of A Pier-On-Bank Bridge Scour

1 online resource (159 pages) : PDF

2021

University of North Carolina at Charlotte

Scour is a critical condition change for a bridge hydraulic system, especially during storms and subsequent flooding. Caused by swiftly moving water, scours remove sand and soil, creating holes surrounding a bridge pier compromising the integrity of the bridge structure. Flooding and scour are the number one causes of bridge failures in the United States and are responsible for almost 60% of bridge failures. The danger of bridge scour failures lies in the fact that they can occur without warning. Moreover, depending upon the formation of the soil stratum surrounding the bridge foundation, scour can attain maximum depth within days, months, and even years. Thus, frequent and accurate monitoring of existing scour conditions is vital for long-term bridge management. Early detection of the capacity loss of bridge foundations resulting from extreme scour conditions would benefit DOTs in minimizing expenditures and preventing severe losses from bridge failures. Thus, DOTS are always looking for fast and effective bridge monitoring techniques and accurate, comprehensive analysis methods to aid in investigating bridge scour susceptibility. This dissertation addressed a unique scour problem addressing bridges with piers-on-bank. Many research studies have been carried out to examine the effect of extreme scour conditions on bridge piers located in the water. However, only limited studies were focused on the investigation of scour effects on piers-on-bank bridges. The objective of this study was to understand the potential scour effects on the pier-on-bank bridge foundations. The investigative approach involved use of terrestrial LiDAR scanning to quantify local scour area around bridge piers. Finite element (FE) modeling technique is then applied to simulate the scouring effect on the bridge pier. In this study, a case study bridge with piers-on-bank was first selected, the Phillips Road bridge at the University of North Carolina at Charlotte campus spans over the Toby Creek. The bridge has multiple piers on both banks of the creek and the piers have experienced scour problems. LiDAR scans of the bridge help quantify the dimensions of the scours resulting in simulated square scour holes. To understand the impacts of current scour conditions on the case study bridge, comprehensive three-dimensional finite element models of the bridge piers were developed using ABAQUS. Non-linear finite element analysis was carried out on the bridge pier models. The Element Removal (ER) technique was used to simulate the mass losses resulting from the scour. To study the performance of bridge piles under critical scour conditions, different scour of the case study bridge were analyzed. Both single and two-pier models were developed to determine the effect of localized scour holes around multiple piers and the potential impact of widened scour area (combined scour) between the adjacent piers. The two-pier model was analyzed for the different load case scenarios subjected to combined actions of axial load, lateral load, and moments. The analytical results show that local scours around a single pier can significantly affect the lateral behavior of the bridge piers and resulted in considerable increase in pile displacement and the bending moments along the pile. Comparison of the local and combined scour between the two-piles shows that the combined scour exponentially increases the pile head displacement. However, the effect of combined scour on the bending moment response is not significantly different from the results of the local scour effect alone. This research work demonstrated clearly that scour problems can be significant even for piers-on-bank structures and should be addressed in the design. The nonlinear FEM analysis with ER technique can be used for analyzing scour problems. However, the current study only focuses on the soil-pile interaction problem and a more in-depth analysis considering soil-pile-flow interactions should be conducted.

doctoral dissertations

Civil engineering

Ph.D.

Finite Element
Lidar
Scour
Structural

Infrastructure & Environmental Systems

Chen, Shen-En

Tang, Wenwu
Diemer, John
Braxtan, Nicole
Allan, Craig

Thesis (Ph.D.)--University of North Carolina at Charlotte, 2021.

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Chavan_uncc_0694D_12981

http://hdl.handle.net/20.500.13093/etd:2906