Jeffrey S. Olafsen Jeffrey_Olafsen@baylor.edu
Associate Professor of Baylor University
This research is funded by the National Science Foundation: CMS 0532084
The support is gratefully acknowledged. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
CONTROL OF PLASTIC HINGING BEHAVIOR OF RC BRIDGE SYSTEMS
Research Project Statement: This NEESR payload project is to accurately model and control plastic hinging locations in concrete bridge structures through an investigation of actual hinging behavior in large-scale testing of 4-span bridge systems subjected to multiple excitations that includes the effects of joint and foundation flexibility at the NEES site at the University of Nevada Reno (NSF Award #0420347).
Modeling of the 4-span bridge continues. Deformable joint elements and foundation flexibility are being introduced into the OpenSEES model for estimating response before the tests and evaluating modeling techniques.
Proof-of-concept testing of photogrammetry methods took place in the University Nevada Reno (UNR) lab in December 2005. Photogrammetry was used to track relative movement of a reinforced concrete bridge column that was tested on UNR shake tables. For this test, images were recorded using two cameras to capture the curvature of the column. A grid was applied at a location just above the hinging region to capture relative movement of the column and compare with traditional instrumentation. Analysis of the data proceeds as follows: 1) read image files from each camera at a given point in time, 2) determine the rotation angle to align images orthogonally, 3) search the image for vertical and horizontal lines, 4) determine the lines that form centerlines of the grid, 5) create a combined image by overlapping images at the known common point, and 6) save the rotation angles and locations of grid lines. These steps are repeated to form a dynamic image for calculating relative displacements and rotations of the specimen.
For the four-span bridge test conducted at UNR in February 2007, two grid systems were used to capture deformations in the hinging region of one column. The two-column bent piers were subjected to bi-directional earthquake loading, and deformations of one column in Bent 3 were recorded. The grid applied to the top hinging region consisted of a series of dashed lines with target points at the intersection of the lines. The grid used in the bottom hinging region was similar to the grid applied in the proof-of concept test.
Documents from the proof-of-concept test, photographs, video from the full-scale four-span bridge test, and photographs from KU Engineering Expo 2008 are provided below.
Pre-study of plastic hinging mechanisms - Kuntz, G., and Browning, J.P., "Reduction of Column Yielding during Earthquakes for RC Frames," ACI Structural Journal, Vol. 100, No. 5, Sept.-Oct. 2003, pp. 573-580.
More photos from proof-of-concept tests
Large Scale 4-span Bridge Test February 2007
Sharing Experimental Data and Bridge Performance at KU Engineering Expo 2008