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Numerical Approaches in Modeling Soil-Foundation Interaction of Tall Bridges
NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering
01 Jan 2014
Abstract
Inherent assumptions in the modeling of soil-foundation interaction can significantly affect the nonlinear seismic response of bridges. Pushover analyses on one of the two piers of the Mogollon Rim Viaduct are conducted herein to examine the sensitivity of the pier response to modeling approaches. The Mogollon Rim Viaduct, located on SR 260 in Central Arizona, is a three-span bridge with a total length of 910 ft, and spans of 280 ft, 340 ft and 280 ft. The bridge superstructure is a continuous, precast, prestressed concrete girder on a curve, with an uphill grade. The clear height of the piers is 52 ft and 71 ft. Their cross-section changes with increasing height with base dimensions of 9 ft × 18 ft and top dimensions of 9 ft × 28 ft. The pile cap is supported on nine drilled shafts with a diameter of 4 ft and consists of two different parts, fully embedded in the soil: the super cap with horizontal dimensions of 18 ft × 18 ft and depth of 7.5 ft, and the sub cap with horizontal dimensions of 30 ft × 30 ft and depth of 7.5 ft. The investigation models the 52 ft-high pier with three-dimensional fiber section elements using the open-source software platform OpenSees, and analyzes its response in both the weak and strong directions. The influence of bond-slip and P-[Delta] effects on the nonlinear response of the pier are examined. In addition, p-y, t-z and Q-z nonlinear springs are applied for modeling the soil-pile interaction, and equivalent nonlinear springs are used for modeling the soil-pile cap interaction. The effects of the pier embedment and the slope of the ground surface on the lateral resistance and the total capacity of the pier are also considered. Preliminary results indicate that bond-slip effects are not important since the pier is overdesigned; however, the P-[Delta] effects for both directions are amplified due to the pier height, the soil structure interaction along the strong direction, and the pier drift due to the plastic rotation along the weak direction. Neglecting the pier embedment, pile cap resistance and frictional forces can considerably modify the force distribution along the pier. The pier embedment is more important for the weak direction, and the pile cap resistance is more important for the strong direction. Since a small rotation in the foundation level can cause a large displacement at the top of the pier along the strong direction, it appears that more caution should be applied in modeling the pile foundation system of tall bridges. Furthermore, the increase of the natural slope of the ground surface causes the maximum moment along the system (pier and foundation) to occur in the pier instead of the pile foundation. Hence, the point of fixity becomes closer to the ground surface level, causing a significant reduction in the contribution of the piles to the lateral resistance of the system; however, the piles are still effective in resisting the vertical loads.
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Details
- Title
- Numerical Approaches in Modeling Soil-Foundation Interaction of Tall Bridges
- Creators
- Mohammad Reza Falamarz SheikhabadiAspasia Zerva
- Publication Details
- NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering
- Conference
- NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering, 10th
- Publisher
- Network for Earthquake Engineering Simulation (NEES)
- Resource Type
- Other
- Language
- English
- Academic Unit
- Civil, Architectural, and Environmental Engineering
- Scopus ID
- 2-s2.0-84929007975
- Other Identifier
- 991019174668804721