Emergency Repair of Damaged Bridge Columns Using Mechanical Splices

1 Graduate student assistant and 1 undergraduate student assistant

2 additional graduate students

The objective of the proposed 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.  The deliverable from the project will be dependable, proven practical methods to efficiently repair earthquake-damaged RC columns with fractured reinforcement.

Past effort in seismic design of concrete bridges has been on detailing of bridges to prevent collapse.  Reinforced concrete 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.

The proposed project includes the repair of fractured bars in a series of interlocking spiral bridge column models that are to be tested to failure as part of a study funded by the National Science Foundation at Missouri S&T.  This proposal to the University of Nevada, Reno (UNR) is for work that would be performed as a subcontract of UNR’s proposal to Caltrans.  The proposed work by Missouri S&T and UNR is an extension of a current 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 (FRPs).  The objective of the current project is to develop rapid repair methods for reinforced concrete bridge columns damaged by earthquakes.  Because the repair was intended to be done expeditiously, there was a consensus among the Caltrans bridge maintenance staff, the Caltrans research management, and the UNR researchers that columns with fractured bars would not be included in the current project.  The current project has achieved its objective of successfully developing emergency repair techniques.  However, these techniques do no cover columns with fractured bars.  Thus the proposed project extends this work to the repair of fractured bars.

Anticipated Benefits

The deliverable from the project will be dependable, proven practical methods to efficiently repair earthquake-damaged RC columns with fractured reinforcement.

Milestones

Relationship to other Research/Projects

N/A

Technology Transfer Activities

Results of this study will be disseminated through at least one technical peer-reviewed journal article as well as presentations at national conferences. 

Transportation Research Board Keywords

Bridge superstructures, repair, fiber reinforced polymer