Composite Behavior of Steel-Precast and Steel-Mass Timber Shallow Floor Systems

Abstract

Girder-Slab Technologies composite shallow structural floor system is primarily used in mid-rise residential structures. The main component is the open-web dissymmetric steel beams (D-Beams), which are integrated between two sections of precast concrete hollow-core slabs using reinforced cementitious grout that encases the upper portion of the beam. The reduced construction height and precast, prefabricated nature of the system can provide cost and time savings during construction. Prior testing of this system at Drexel University and Villanova University established section properties for various D-Beams and verified the composite action present in the system . A new experimental program was developed to further evaluate the composite behavior of the Girder-Slab system. This included the structural performance of the current D-Beam system with hollow-core panels and a new setup with cross-laminated timber (CLT) panels. In addition, the study was conducted to determine the effects of a D-Beam modified top flange and evaluate the structural contributions of a concrete topping slab. As a result, a testing program was developed that included sixteen pushout tests and four component-level tests. These were conducted at the Advanced Structural Engineering Laboratory at Auburn University. Overall, the study found the composite performance of the Girder-Slab system to be more than adequate. The hollow-core system illustrated full composite behavior. The flexural stiffness and flexural strength met and exceeded the current design approach, respectively. The CLT system performed better than expected, with higher flexural stiffness and strength, compared to the hollow-core system. In both cases, the modified top flange did not significantly improve the flexural performance of the system and is not recommended. However, the concrete topping slab contributes to the flexural performance. Further testing is recommended to fully quantify this contribution.