Wash Bridge on Highway 10 in Southern California, which collapsed on July ... Then, the performance of the new replaced bridge under flood and earthquake.
Analysis of Tex-Wash Bridge under the Effects of Flood and Earthquakes
Maryam Tabbakhha, Abolhassan Astaneh-Asl, and Daniel Setioso University of California at Berkeley 1. INTRODUCTION
4. Nonlinear Analysis of the Replaced Bridge under Flood
Bridges are one of the most important structural elements whose performance plays a critical role after natural disasters. Floods can occur separate from seismic events, or as a result of earthquakes tsunamis. Bridges in high seismic areas are subjected multihazard scenarios. Such scenarios are beginning to receive the attention of bridge engineering and research communities. This project is a multi-hazard case-study of Tex Wash Bridge on Highway 10 in Southern California, which collapsed on July 2015 as a result of flooding unrelated to seismic events. In this study, a realistic 3D nonlinear FE model of the bridge was built using ANSYS to simulate behavior of the bridge until collapse. Then, the performance of the new replaced bridge under flood and earthquake was investigated in detail.
• Based on the “As-Built” drawings the new replacement bridge was added to the model • The pressure at the location of the river turn increases due to Fig.5 (left) Velocity profile (right) Pressure contour of fluid flow of replaced bridge lager span of the replaced bridge • Results show that Caltrans restoration New New method using piles is Replaceme Replaceme adequate to prevent nt Bridge nt Bridge future collapse under the same flood event
In-Fill Soil Added to Narrow the Channel
Fig.6 (left) Von-Mises stresses (right) deformation due to flood of replaced bridge
5. Seismic Analysis of the Replaced Bridge Fig.1 (left) Structure of Tex-Wash bridge (right) Eastbound Tex-Wash Bridge After Collapse
2. Flood Collapse of the Bridge
• Five earthquakes with similar design spectra were applied to the bridges: (1) Imperial Valley (El-Centro) (2) Superstition Hills (3) Tabas (4) Kobe (5) Dinar
In the original design, the California Department of Transportation (Caltrans) had narrowed the width of the flood water delta from about 70 meters to only about 30 meters and abruptly turned the path of flood. This was the main cause of collapse. North
West Bound Tex Wash Bridge
Abutment Support Soil Washed Out
Fig.7 Maximum Von-Mises stresses (left) East-Bound replaced bridge (right) West-Bound bridge Imperial Valley
Fig.2 (left) Flood water rushing the bridge (middle) areal view of bridge before collapse (right) Westbound during flooding
3. Nonlinear Finite Element of the Collapsed Bridge Under Flood • ANSYS-Workbench by coupling ANSYS-Fluent and ANSYS-Structural software was used to simulate the fluid-structure interaction (FSI). Results show that: • The velocity of the flow within the east bound bridge piers is higher than the other parts. • Pressure at the location of river turn was much higher than the other parts and that’s where the relatively soft in-fill soil was located. The soil was washed away easily. • Von-Mises stresses in the slab of first span ( collapsed span) were quite high.
Fig.9 Maximum Von-Mises stresses (left) East-Bound replaced bridge (right) West-Bound bridge Tabas
Fig.3 (left) Velocity profile (right) Pressure contour of fluid flow of Tex-Wash bridge
Numerical study shows that four major design flaws that collectively resulted in the collapse of the Tex Wash Bridge were:1. Turning the flood path 90-degrees right at the abutment, 2. Narrowing the flood path and creating bottle neck, 3. Having wing walls perpendicular to the flood path instead of parallel to the flood path, and 4.Supporting the abutments on in-fill soil instead of piles. The replaced bridge with the piles can sustain the same flood event. Time-history analysis of the bridges shows that the replaced and the Westbound bridge can carry out the loads due to the earthquakes similar to the design spectra except one event. The edge of piles in Westbound bridge fails under the Tabas earthquake.
This study resulted from a project: “Analysis of Failure of the Tex Wash Bridge due to Flood and Lessons Learned” conducted at the UC Berkeley (2015-2016) with Professor Abolhassan Astaneh-Asl, Ph.D., P.E. as Principal Investigator, Dr. Maryam Tabbakhha as Co-PI and Mr. Daniel Christian Setioso as Undergraduate Student Researcher. The support of Ozen Engineering Inc. (ANSYS) is greatly appreciated
