Details:

Creators:
Russell, Henry G. ; Roller, John J. ; Bruce, Robert N.
Russell, Henry G. ; Roller, John J. ; Bruce, Robert N. Less -
Corporate Creators:
Tulane University. Department of Civil and Environmental Engineering
Corporate Contributors:
Louisiana Transportation Research Center
Subject/TRT Terms:
[+]
Bridge Girders Fatigue Fatigue (Mechanics) Flexural Strength Girders High-strength Concrete High Performance Concrete Loads Prestressed Concrete Shear Strength Testing Welded Wire Reinforcement
Publication/ Report Number:
FHWA/LA.05/395
Resource Type:
Tech Report
Geographical Coverage:
Louisiana
Corporate Publisher:
Tulane University. Department of Civil and Environmental Engineering
Abstract:
Five 96-ft. (29.3-m) long, 72-in. (1.83-m) deep, precast, pretensioned bulb-tee girders were tested to evaluate their behavior under flexural fatigue. Three of the girders were also tested to measure their static shear strength. One girder was tested after the fatigue test to measure its flexural strength. The five girders had a design concrete compressive strength of 10,000 psi (69.0 MPa) and incorporated 0.6-in. (15.2-mm) diameter, Grade 270, low relaxation prestressing strands. The shear reinforcement quantities at the ends of three girders were selected to evaluate the applicability of the shear strength design provisions of the AASHTO Standard Specifications for Highway Bridges and the AASHTO LRFD Bridge Design Specifications. Shear reinforcement consisted of conventional bars or deformed welded wire reinforcement.

The five prestressed concrete girders were produced in a commercial plant. Prior to testing, a 10-ft. (3.05-m) wide reinforced concrete deck slab was added to each girder. Three girders were intentionally cracked at midspan before the start of the fatigue test. Two girders were uncracked. After completion of fatigue testing, the three intentionally cracked girders were cut in half and the six girder ends tested to evaluate static shear strength.

The cracked bulb-tee girders performed satisfactorily under 5 million cycles of flexural fatigue loading when the tensile stress in the extreme fiber of the bottom flange was limited to a maximum value of 610 psi (4.21 MPa). When the concrete tensile stress was 750 psi (5.17 MPa) or larger, fatigue fractures of the prestressing strand in the cracked girders occurred, and the fatigue life of the girder was reduced. However, the uncracked girders performed satisfactorily under 5 million cycles of flexural fatigue loading when the tensile stress was 600 and 750 psi (4.14 and 5.17 MPa).

The measured flexural strength of one girder, after being subjected to 5 million cycles of flexural fatigue loading, exceeded the strengths calculated according to the AASHTO Standard Specifications for Highway Bridges and the AASHTO LRFD Bridge Design Specifications using both design and measured material properties.

Measured shear strengths of six bulb-tee girder ends consistently exceeded the strengths calculated according to the AASHTO Standard Specifications for Highway Bridges and the AASHTO LRFD Bridge Design Specifications using both design and measured material properties. Based on the results of the shear tests, the existing limitation of 60,000 psi (414 MPa) for the design yield stress of transverse reinforcement cited in both AASHTO specifications is conservative. Higher reinforcement yield strengths can be utilized in the design of prestressed concrete beams. Welded wire deformed reinforcement can be used as an equally effective alternate to deformed bars as shear reinforcement.


Format:
PDF
Funding:
State Project Number: 736-99-0821 ; LTRC Project Number: 00-6S
State Project Number: 736-99-0821 ; LTRC Project Number: 00-6S Less -
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:dc4a97f73e21631585920a7bcb9cddaba439b4d555d5dc1e8c5aa04484cf5b3a
Download URL:
https://rosap.ntl.bts.gov/view/dot/22148/dot_22148_DS1.pdf
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