CTRE is an Iowa State University center, administered by the Institute for Transportation.

Address: 2711 S. Loop Drive, Suite 4700, Ames, IA 50010-8664

Phone: 515-294-8103
FAX: 515-294-0467

Website: www.ctre.iastate.edu/

Iowa State University--Becoming the Best

Design of Jointed Precast Building Systems for High Seismic Zones, Phase I

Researcher(s)

Principal investigators:

Project status

Completed

Start date: 01/01/02
End date: 07/31/03

Sponsor(s)/partner(s)

Sponsor(s): Prestressed/Precast Concrete Institute

About the research

Abstract: This project focused on validating seismic design guidelines currently available for two precast concrete structural systems: jointed wall system and hybrid frame system.

Part 1 ? Jointed Wall System Following the satisfactory response of the unbonded post-tensioned precast concrete jointed wall system tested for seismic performance as part of the PREcast Seismic Structural Systems (PRESSS) test building, a set of design guidelines was published. The primary objective of this part of research is to evaluate the adequacy of the design guidelines and make appropriate recommendations so that the guidelines can be adopted for design of jointed precast walls in seismic regions. The test data to date on such systems are those collected during the wall direction testing of the PRESSS test building. Hence, this data set has been employed in the validation process.

Furthermore, in order to validate the design guidelines over a range of lateral displacements, an analytical procedure was first developed by reversing the suggested guidelines. Additionally, because of the shortcomings associated with the use of the equivalent stress block concept in design, an alternative analysis method was also considered, which was based on the monolithic beam analogy (MBA) originally developed for jointed frame systems. The analytical results from monotonic loading were compared to experimental response of the jointed wall established from the PRESSS test data.

It was found that the analysis method based on the PRESSS guidelines underestimated the lateral load resistance of the jointed wall in the PRESSS test building by up to 22% at large lateral displacements and overestimated by greater percentages at small displacements. When the force transferred through the shear connectors was based on the measured force-displacement response, the PRESSS guidelines and MBA underestimated the moment response of the jointed wall by 12% and 5%, respectively, at the maximum measured lateral displacement. However, utilizing the PRESSS guidelines with the measured force in the shear connectors, it was found that the neutral axis depth was overestimated by over 100% and the post-tensioning elongation was underestimated by 26%. It was also revealed that the framing action contributed to the moment resistance in the wall direction of the PRESSS building by as much as 25%. Several recommendations are provided for improving the PRESSS design guidelines, which will simplify the design calculations while providing efficient design details for the precast jointed wall systems. With improvements, the PRESSS guidelines are shown to predict the observed performance of the jointed wall in the PRESSS test building satisfactorily.

Part II ? Hybrid Frame System

The development of hybrid frame systems has enabled application of precast concrete in seismic regions. In addition to the benefits of the precast concrete technology, the hybrid frame systems offer additional benefits during seismic response. Using experimental data from two component tests and one building test, this part of research examined the validity of the design guidelines proposed for hybrid frame systems by (1) Stanton and Nakaki as part of the PRESSS (PREcast Seismic Structural Systems) program (2002) and (2) ACI (American Concrete Institute) Innovation Task Group (2003). By establishing analysis methods based on the proposed design steps and assumptions, and comparing the analysis results with the experimental results, the adequacy of the proposed guidelines was examined. The accuracy of the Monolithic Beam Analogy (MBA) concept in predicting the response of hybrid frame connections was also investigated. Based on the comparisons between the experimental and various analytical results, recommendations were made to improve the design of precast hybrid frame connections.

PUBLICATIONS

Thomas D. J., and S. Sritharan. 2004. An Evaluation of Seismic Design Guidelines Proposed for Precast Jointed Wall System. ISU-ERI-Ames Report ERI-04643, Department of Civil and Construction and Environmental Engineering, 132 pp. June, Iowa State University, Ames, Iowa.

Celik O., and S. Sritharan. 2004. An Evaluation of Seismic Design Guidelines Proposed for Precast Concrete Hybrid Frame Systems. ISU-ERI-Ames Report ERI-04425, Department of Civil and Construction and Environmental Engineering, 172 pp. January, Iowa State University, Ames, Iowa.