Resistance Factor for the Design of Composite Slabs

6.1. General Probability-based design criteria in the form of load and resistance factor design (LRFD) are now applied for most construction materials. The design requirements have to insure satisfactory performance of structures. The main advantage of the approach is the ability to achieve a uniform level of reliability for structural members, or to impose a certain level of reliability (higher or lower) of some certain parts of the structures. This gives a strong rationale to the load and resistance factors as compared to the design safety factors of the allowable stress design. Additionally, a unified design strategy as to setting up common load combinations and load factors can be obtained. In this part of the study, resistance factors, φ, for the flexural design of composite slabs were evaluated based on test data of 39 full scale composite slab specimens. The tests were performed at the Structures and Materials Laboratory of Virginia Polytechnic Institute and State University, Blacksburg, Virginia. The φ factors evaluated correspond to the SDI-M method and direct method described in Section 3.