Design of Rectangular Openings in Unbonded

Post-Tensioned Precast Concrete Walls

 
Recent research conduced as a part of the PRESSS (PREcast Seismic Structural Systems) Research Program and other research programs has shown that unbonded post-tensioned precast concrete walls offer significant advantages as primary gravity and lateral load resisting systems in seismic regions.  This previous research has focused on walls without openings.  However, the use of large openings in the wall panels may be desirable to accommodate doors, windows, and/or mechanical penetrations due to architectural, functional, and/or safety requirementsThe openings can cause large tensile stresses, and thus, cracking in the wall panels. Under lateral loads, cracking in the panels can also occur due to gap opening along the horizontal joints between the panels and at the base. Without proper design and detailing, these cracks can be detrimental to the load carrying capacity of the walls. The research described here addresses this issue.

The broad objective of the research is to investigate the use of rectangular openings in unbonded post-tensioned precast concrete walls for different seismic regions of the U.S.  Bonded mild steel reinforcement is needed in the wall panels to limit the size of the cracks. An analytical investigation is conducted on the behavior and design of walls with openings for two loading stages: (1) vertical loads due to gravity and post-tensioning; and (2) combined vertical and lateral loads. A finite element model of the walls (using the ABAQUS Program) is used to determine the stresses around the openings under gravity and lateral loads. The finite element results are compared with theoretical results.  For each loading stage, critical regions in the wall panels where reinforcement is needed are identified and design approaches are proposed to determine the amount of the required panel reinforcement. The effect of opening length, opening height, wall length, and initial stress in the walls due to  post-tensioning and gravity on the behavior and design of the walls is investigated.

Research Team

 
Faculty Supervisor: Yahya Kurama
Graduate Research Assistant: Michael Allen (M.S. 2001) (Designer, Degenkolb Engineers)
Undergraduate Student: Matt Nietfeld (B.S.C.E 1999)
 
Publications and Presentations
Final Project Report
  • "Design of Rectangular Openings in Unbonded Post-Tensioned Precast Concrete Walls," by M. Allen and Y. Kurama, Structural Engineering Research Report #NDSE-01-01, Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN, April 2001, 142 pp.
Acknowledgments
 
This research is funded by the Precast/Prestressed Concrete Institute (PCI) through a 1998 Daniel P. Jenny Fellowship and by the University of Notre Dame. The support of the Precast/Prestressed Concrete Institute and the University of Notre Dame is gratefully acknowledged.

The support of the PCI Research Director P. Johal and Past Chairman of the Research and Development Committee H. Wilden, H. Wilden & Associates, Inc.  is gratefully acknowledged. The support and advice provided by the PCI Ad Hoc Advisory Group on the Fellowship is acknowledged: N. Cleland, Blue Ridge Design, Inc.; T. D'Arcy, The Consulting Engineers Group, Inc.; J. Hoffman, Sturm Engineering Company; and S. Pessiki, Lehigh University. The researchers also wish to thank two other individuals for their contributions to the project: K. Baur, High Concrete Structures, Inc. and R. Sause, Lehigh University.

M. Nietfeld helped in the development of the finite element model during the summer of 1998 through the Research Experiences for Undergraduates (REU) Program funded by the National Science Foundation. The support of the National Science Foundation for the REU Program is acknowledged.

The opinions, findings, and conclusions expressed herein are those of the researchers and do not necessarily reflect the views of the individuals and organizations acknowledged above.