Assessment of the Bill Emerson Memorial Bridge Based on Seismic Instrumentation Data

Status

Sequential Number

Matching Research Agency

Missouri Transportation Institute/Missouri Department of Transportation

Principal Investigator

Student Involvement

One graduate research assistant and maybe one undergraduate student will be involved in this project.

Project Objectives

The objectives of the proposed work are to create a database of ground motions at the Bill Emerson Memorial Cable-stayed Bridge site and to verify the assumptions made in the structural design of the Bridge. The approach taken to verify the design assumptions is to develop a well-calibrated nonlinear Finite Element Model (FEM) of the cable-stayed bridge, and to study the behavior and load path of the bridge structure.

Project Abstract

The proposed project will be conducted in one year, including the modeling and responses of a bridge system. To achieve the objectives above, the following tasks are proposed.

1. Develop a methodology and necessary tools for automatic compiling of the peak ground and structural accelerations.
2. Establish a three-dimensional nonlinear Finite Element Model of the bridge including multi-support excitations and soil-structure interaction so that realistic behaviors of the bridge can be simulated numerically. Both the main and approach spans will be modeled with a commercial program such as ADINA or SAP2000 that is suitable for modeling of superstructure, substructure, and pile foundations.
3. E valuate the model by conducting sensitivity analysis, checking boundary conditions and compatibility of various parts of the bridge, and making necessary engineering judgments. Sensitivity analysis will help ensure that the modeling of various parts of the bridge is consistent in terms of member types, geometrical and material properties. Connectivity among various structural members at a joint could be pretty complicated in a cable-stayed bridge. It needs to be properly modeled.
4. Determine the bridge's dynamic characteristics such as vibration mode shapes and periods with the linear behavior of the model that represents the bridge structure at low stress levels. After the United States Geological Survey (USGS) corrected the recorded data for possible baseline drifting or other instrumentation variability, the dynamic characteristics of the bridge will be identified from the measured accelerations due to ambient vibration and they will be compared with the calculated values from the linear model.
5. Verify the assumptions used in the design of the bridge structure by understanding the structural behavior and load path with the well-calibrated FEM when both ground motions and structural responses at critical locations are known.

Anticipated Benefits

There are a significant number of long-span bridges near the New Madrid Seismic Zone (NMSZ), including the Bill-Emerson Memorial Cable-stayed Bridge over the Mississippi River in Cape Girardeau, southeast Missouri. In addition, new river-crossing bridges are being designed including the new Mississippi River Bridge in St. Louis, Missouri. Many of these bridges are subjected to direct threats from the NMSZ. Out of service of these bridges due to earthquake-induced failure will not only cause traffic congestion in region but also sever the nation's ground transportation link along the corridor from California to New York. The public perception to any of these potential incidences is significant.

This study will help understand the level of design earthquakes in the Central United States, the appropriateness of various assumptions used in structural design, and the seismic behavior of the Bill Emerson Memorial Cable-stayed Bridge. It will also help identify key information for inspection and structural evaluation of the bridge during its service life or after a strong earthquake event in the future. In particular, it provides necessary tools to realize the objectives of the current seismic instrumentation project that has been in operation since October 2004.

This study will not only provide the critical information for routine design of bridges but also the necessary tools for future structural condition evaluation so that a proper warning for abnormal behavior of the bridge can be issued on time and appropriate measures can be taken to avoid any potential catastrophic failure in the event of a severe earthquake (stronger than the design earthquake).

Modal Orientation

Bridge Assessment

Milestones

Relationship to other Research/Projects

UMR Earthquake Hazards Mitigation Project.

Technology Transfer Activities

Seminar/presentation

Transportation Research Board Keywords

Bridge Assessment, Computer Modeling