Flexural performance of spliced beam connected and reinforced with self-tapping wood screws

• Published in: Engineering structures 2017-12, Vol.152, p.523-534
• Main Authors: Li, Hongmin, Lam, Frank, Qiu, Hongxing
• Format: Article
• Language: English
• Subjects: Analytical model; Beams (structural); Bending; Capacity; Ductility; Ductility tests; Failure; Fibers; Full thread self-tapping screws; Glulam; Historical structures; Mathematical analysis; Mathematical models; Restoration; Screws; Self tapping; Spliced beam; Splicing; Stiffness; Tapping screws; Wood; Wood fiber reinforcement; Wood fibers
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/j.engstruct.2017.08.032

•The spliced beam reinforced by self-tapping screw was investigated experimentally and analytically.•This technique could keep the original appearance of the damaged historic elements and be easy to install and design.•Force-displacement relationships and probability distribution were used to determine capacity, stiffness and ductility.•The failure mode changed from the brittle failure to a failure with low ductility for the spliced beam.•The analytical model proposed could calculate the spliced beam reinforced with self-tapping screw corresponding to the specific failure mode correctly. Splicing method of bending elements is important for the restoration of ancient timber structures due to the principle of preserving as much as possible the original material. This study investigates the flexural performance of spliced beams connected and reinforced with self-tapping wood screws. An experimental program based on four-point bending test configuration was conducted to examine the strength, stiffness and ductility of spliced beams. The test results showed that the spliced beams’ average ultimate bending capacity reached 59.5% of the size and load duration adjusted specified bending capacity of the intact beam. Their stiffness achieved 64.3% of the specified design value in Canadian Wood Design Manual. The spliced beams experienced head pull-through failure of the self-tapping screws. This failure mode led to ductile behavior different from the typical tension failure mode of the wood fibers in glulam beam. Based on the experimental results, an analytical model that addressed the specific head pull-through failure mode was proposed to predict the flexural capacity of spliced beams. The analytical model was calibrated by the data of the head pull-through resistance test results and verified by full-size tests. Comparisons of the analytical and the test results reveal that the model can adequately predict the moment capacity of the spliced beams with the corresponding specific failure mode.