Performance Evaluation of Self-Tapping Screws for Use in Mass Timber-Concrete Composite Floor Connections through Withdrawal from Mass Timber and Concrete Media
Publication: Journal of Materials in Civil Engineering
Volume 36, Issue 2
Abstract
Mass timber construction has seen a growing interest in North America and worldwide. In the US, code provisions allow mass timber buildings to be up to 82 m tall, but with floor slabs requiring a noncombustible, usually cementitious, topping over mass timber panels (MTPs). Designing the MTP and concrete topping to act compositely can increase the strength and stiffness compared to noncomposite MTP floors. Several connections are available to create composite action between an MTP and a concrete topping, with self-tapping screws being the most widely considered practice. A new test fixture and testing method were developed to characterize connection properties and facilitate the selection of fasteners most suitable for developing composite action. Three conventional self-tapping screws were experimentally investigated at the single-fastener scale. The screws were subjected to withdrawal at 90° and 45° orientations to the interface plane between the MTP and concrete. Withdrawal from both the MTP substrate and concrete topping was investigated. Three MTP materials were tested: cross-laminated timber (CLT) consisting of two different wood species and a mass ply panel (MPP). Results demonstrated that the pullout failure of the screwhead from the concrete was the limiting failure mode. Comparisons were made between the experimental results and analytical models for screw withdrawal to assess the applicability of available models to the different MTPs. These models underestimated the capacity of the tested fasteners for all samples except for the fully threaded screws.
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Data Availability Statement
Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
This work was financially supported by the USDA Agricultural Research Service in cooperation with the Tallwood Design Institute under Grant No. 58-0204-6-002. Additionally, the authors would like to thank Brian Demeza for assistance in design and fabrication of the testing fixtures and initial tests, as well as Milo Clauson and Tyler Deboodt for assistance with instrumentation and testing. The authors would like to acknowledge Simpson Strong-Tie for contributing fasteners used in the study. Finally, the authors would like to thank the ARCS Foundation for supporting the first author as an ARCS Scholar.
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Published In
Journal of Materials in Civil Engineering
Volume 36 • Issue 2 • February 2024
Copyright
© 2023 American Society of Civil Engineers.
History
Received: Oct 25, 2022
Accepted: Jul 7, 2023
Published online: Nov 21, 2023
Published in print: Feb 1, 2024
Discussion open until: Apr 21, 2024
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