Repair of Earthquake-damaged Bridge Columns with Fractured Bars

1 Graduate Research Assistant

The objective of this study is to repair three, half-scale RC bridge columns that will be tested to failure under slow cyclic loading.  These columns will have fractured longitudinal and transverse steel.  The ultimate goal is to develop repair methods for these columns using different techniques.  In the first two columns, different Caltrans approved ultimate splices will be used, and in the third column, an enlarged section will be built in the plastic hinge area.  The target performance for the repaired columns is to restore the lateral load and ductility capacity to the level that is comparable to that of the original columns. 

Past effort in seismic design of concrete bridges has been on detailing of bridges to prevent collapse.  Reinforced concreLeslesneedhte bridge columns are designed to undergo cracking, spalling, and yielding of steel and provide significant rotational capacity at plastic hinges so that the integrity of the overall structure is maintained.  With proper design and construction this objective can be met.  However, the serviceability of the bridge after the earthquake is in question.  The level of damage to different columns of a bridge varies depending on the intensity of the ground shaking, type of earthquake, and the force/deformation demand on individual members.  Based on the inspection of the damaged columns engineers have to determine whether the bridge is sufficiently safe to be kept open to traffic.  They should also recommend repair methods for the columns.  Any delay in opening of the bridge to traffic can have severe consequences on the passage of emergency vehicles, detour lengths, and traffic congestion in the area.  Rapid and effective repair methods are needed to enable quick opening of the bridge to minimize impact on the community.

This project includes the repair of fractured bars in a series of interlocking spiral bridge column models that were tested to failure as part of a separate study funded by the National Science Foundation at Missouri S&T.  This project is a new collaboration between the University of Nevada, Reno (UNR), Missouri S&T, and the University of Houston. Work performed by Missouri S&T and the University of Houston is being performed as a subcontract to UNR’s contract with Caltrans. The work performed in this project is an extension of a project by UNR (Caltrans Contract No. 59A0543), which is aimed at developing guidelines for reliable and efficient reinforced concrete repair methods using fiber reinforced polymers (FRP).  This project extends the work to the repair columns of with fractured bars.

Relationship to other Research/Projects

This project is currently funded by UNR via Caltrans.  Results from a previous pilot project conducted by the PI entitled “Rapid Repair of Severely Damaged Reinforced Concrete Columns” that was funded by the University of Missouri Research Board (UMRB) led to this project.

Transportation-Related Keywords

Technology Transfer Activities

Results will be documented in journal publications and reports to CIES;

Results can be used in both undergraduate and graduate classes in M S&T, such as CE 416 Soil Stabilization and CE 374 Infrastructure Strengthening with Composites

Project Deliverables

Anticipated Benefits

Research in this field is currently limited to the repair of columns with slight to moderate damage levels; thus this research will fill in a critical gap in the literature with respect to the severe damage level. Additionally since the current literature contains little information with respect to repair of columns subjected to torsion, the inclusion of torsion in the combined loading is a significant contribution to the state of knowledge, and represents a more comprehensive and realistic loading condition than without. Results will serve as the basis for and add credibility to future proposals on repair of bridge columns, with high potential for collaboration with leading researchers in this field.

Milestones