Evaluation of Seismic Performance of Bridge Columns with Couplers and Development of Design Guideline

Link to  FINAL REPORT

BACKGROUND
Accelerated bridge construction (ABC) relies heavily on prefabricated reinforced concrete members. One method to connect prefabricated columns to footings or cap beams is through the use of mechanical couplers. It is convenient to locate these couplers in the plastic hinge zone of the columns, even though current seismic codes do not allow couplers in plastic hinge zones in moderate and high seismic areas. Recent research has revealed the feasibility and sufficient seismic performance of columns utilizing couplers in the plastic hinge.

OBJECTIVE
The overall objective of the proposed study is to compile and interpret data on seismic performance of different types of couplers and establish characteristic column plastic hinge behavior for different coupler types. The study will further categorize the couplers with respect to their seismic performance. The results of the study will be transformed into draft design guidelines for possible adoption by AASHTO.

SCOPE
Five tasks will be completed: (1) conducting literature search, (2) determining characteristic seismic performance of different couplers, (3) evaluating constructability of different coupler types, (4) developing methods to estimate plastic hinge length and rotational capacity, and (5) developing draft design guidelines for prefabricated columns with coupler connections.

A range of steel bar couplers are available with different characteristics and installation methods. The mechanism of force transfer through the coupler also varies depending on the coupler type. Fig. 1 shows some of the more common coupler types.

These couplers and some variations of these couplers have been used in reinforced concrete construction, but application of couplers is prohibited in plastic hinges in most codes.

Even though satisfactory seismic performance have been obtained in many experimental studies when couplers were incorporated in plastic hinges, it has become clear that plastic hinging can be affected by the coupler types. The purpose of the study is to utilize test data from past and current research projects to develop seismic design guidelines for prefabricated column-footing and column-cap beam connections that use different types of couplers.

RESEARCH TEAM
Principal Investigators: M.Saiid Saiidi, PhD, PE. and Ahmad Itani, PhD, PE.
Research Associate: Kshitij C. Shrestha, PhD and Mostafa Tazarv, PhD.

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