Shear Strength of a PCBT-53 Girder Fabricated with Lightweight Self-Consolidating Concrete

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Virginia Center for Transportation Innovation and Research

Lightweight self-consolidating concrete (LWSCC) is advantageous in the bridge industry because members fabricated with this material have a significantly lower self weight and in its fresh state, LWSCC has a low viscosity that eliminates the need for vibration during fabrication. Unfortunately, lightweight, self-consolidating concrete typically has lower tensile strength and possibly a lower aggregate interlock strength. This combination may result in a lower overall shear strength. In addition, this type of concrete has a lower modulus of elasticity, which leads to higher elastic shortening losses and higher deflections. In order to evaluate the affect of lightweight, self-consolidating concrete on the shear strength of prestressed concrete bridge girders, the study described herein was performed. A single PCBT-53 bridge girder was fabricated and tested. The girder itself was cast with lightweight, self-consolidating concrete and a composite cast-in-place deck was fabricated using lightweight concrete. In this study, the girder and deck were tested using three different loading conditions. These tests aimed to experimentally quantify the beam's overall web shear strength and flexure-shear strength. Data pertaining to each test are presented in this report. Results include material properties, deflection plots, strain plots, and temperature change plotted with respect to time. The measured shear strength is compared to several design methods. With respect to web shear strength, the current AASHTO LRFD Sectional Model and the Simplified Method for shear were conservative for the self-consolidating lightweight girder if the measured cracking angle was used in calculations. Both the LRFD Sectional Model and the Simplified Method are recommended for shear design of LWSCC prestressed bridge beams. The tests to evaluate flexure-shear strength were inconclusive because the beam failed in flexure prior to a flexure-shear failure.

Self-consolidating concrete, Lightweight concrete, Prestressed concrete bulb tee bridge girders, Shear strength
Benjamin Z. Dymond, Carin L. Roberts-Wollmann, and Thomas E. Cousins. "Shear Strength of a PCBT-53 Girder Fabricated with Lightweight Self-Consolidating Concrete," Virginia Transportation Research Council 530 Edgemont Road Charlottesville, VA 22903, Report No. FHWA/VTRC 09-CR11, Apr. 2009.