Behavior and design of precast prestressed concrete inverted tee girders with multiple web openings for service systems

A precast, prestressed inverted tee (IT) girder with multiple large web openings (ITO) allows building services to cross the girder line within the member's depth, reducing a building's floor-to-floor and overall height. This research's objectives are to understand how web openings alter an IT girder's serviceability and ultimate strength, and develop a design procedure for this structural member.; A prototype ITO girder was designed based on the available literature on concrete beams with web openings. Three full-scale ITO girders and an IT girder were tested to evaluate and compare their behavior. The test variables were the transverse reinforcement details between and above the openings. The ITO's behavior was investigated with linear elastic (FE) and nonlinear (fiber model) finite element analyses and truss models.; The tests show an ITO satisfies the required limit states. Until the ITOs' failure, their behavior was similar to the IT's. The ITOs failed suddenly when a diagonal crack occurred above the opening nearest the support, while the IT had a ductile midspan failure. The literature's design approach did not predict the ITOs' failure load or mode. The transverse reinforcement variations between the openings did not affect the ITO's serviceability, behavior or strength. The transverse reinforcement variations above the openings did not affect the ITO's serviceability or behavior, but did affect its strength.; The ITO's openings exhibit frame behavior, confirming previous researchers' findings. The fiber models show that the chord shear forces and moments depend on cracking in the chords, while the chord axial forces depend primarily on the moment at a section and the distance between the chords. The fiber model's midspan opening failure load is nearly identical with an IT's plane section failure load.; Strut-and-tie models show that the opening's span side abutment reinforcement transfers shear to the top chord, and on its support side, transfers shear force from the bottom chord to the section. The design procedure limits the chord forces by limiting the abutment reinforcement. Knowing the chord forces, the chords are designed for strength.