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Newmark Structural Laboratory Report Series (NSEL Report Series ISSN 1940-9826) >
Please use this identifier to cite this item:
http://hdl.handle.net/2142/3737
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| Title: |
Shear Behavior and Capacity of Large-Scale Prestressed High-Strength Concrete Bulb-Tee Girders |
| Authors: |
Sun, Shaoyun
Kuchma, Daniel A. |
| Keywords: |
shear behavior
Shear behavior
Shear capacity
shear cracking
high-strength concrete
pretressed bulb-tee girders
experimental data visualization
crack displacement field theory |
| Issue Date: |
2007-Nov |
| Publisher: |
Newmark Structural Engineering Laboratory. University of Illinois at Urbana-Champaign. |
| Series Name / Report no.: |
Newmark Structural Engineering Laboratory Report Series 002 |
| Abstract / Summary: |
The current shear design provisions of the AASHTO LRFD Bridge Design Specifications
limit the concrete compressive strength to 10 ksi due to a lack of experimental evidence for their
extension to high strength concrete. To overcome this limitation, the National Academy of
Sciences funded National Cooperative Highway Research Program (NCHRP) Project 12-56
“Application of the LRFD Bridge Design Specifications to High-Strength Structural Concrete:
Shear Provisions”. This report presents an analysis of project 12-56 experimental test data from
which an in-depth understanding of the shear response of prestressed girder was obtained and
new models were developed.
The experimental work comprised a total of 20 tests on ten 52-foot long and 6-foot deep
bulb-tee girders. All girders were designed to satisfy the requirements of the LRFD Bridge
Design Specifications and then subjected to a uniformly distributed load until failure occurred in
shear. The primary test variables were concrete compressive strength (ranging from 10 to 18 ksi),
the maximum shear design stress (0.7 to 2.5 ksi), strand anchorage details (straight, unbonded,
and draped), and end reinforcement detailing (bar size, spacing, and level of confinement). A
large number of both traditional and advanced instrumentation systems were used to measure
response. A new data visualization tool was developed to provide a detailed analysis of the dense
experimental test data.
It was concluded that the AASHTO LRFD Sectional Design Method, as well as the
AASHTO Standard Specifications and the Canadian Standard Association A23.3-04 Design
Method, could be extended to up to 18 ksi concrete. It is also recommended that the maximum
shear design stress be reduced from 0.25 fc’ to 0.18fc’. Both the angle and the strength of
diagonal cracking could be accurately predicted using Mohr’s circle of stress. The web shear
behavior could be characterized as a tri-linear relationship separated by web cracking, stirrup
yielding, and failure and the inelastic tangent stiffness before stirrup yielding could be modeled
as a polynomial function of shear reinforcement ratio. Based on the development of 350 crackbased
free-body diagrams, the components of the concrete contribution to resistance (two flanges
and web) over the loading history was characterized as a function of the geometric and material
properties of the girders. A general expression, which adopted the calculated crack angle for the
computation of shear reinforcement contribution and provided clear physical explanation for
every part of concrete contribution, was suggested for the future shear design practice.
From the measured test results, an analytical model, Crack Displacement Field Theory
(CDFT), was developed for predicting the shear response of prestressed/reinforced concrete
members. Compared to other existing models, it could capture the discrete displacement due to
crack opening and crack slip along crack surface and can take account the variation of stresses in
reinforcement due to bond. Based on this model, expressions were derived for shear stiffness and
shear resistance at stirrup yielding, and the derived equations produced good agreement with test
results. |
| URI: |
http://hdl.handle.net/2142/3737 |
| ISSN: |
1940-9826 |
| Type of Resource: |
text |
| Genre of Resource: |
technical report |
| Publication Status: |
published or submitted for publication |
| Appears in Collections: |
Newmark Structural Laboratory Report Series (NSEL Report Series ISSN 1940-9826)
|
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