Withdrawal behavior of innovatively coated ring-shank nails and scrails in CLT: experimental evaluation and implications for design values
EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS, vol.84, no.5, 2026 (SCI-Expanded, Scopus)
- Publication Type: Article / Article
- Volume: 84 Issue: 5
- Publication Date: 2026
- Doi Number: 10.1007/s00107-026-02480-8
- Journal Name: EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS
- Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chimica, Compendex, ICONDA Bibliographic, INSPEC, The International Construction Database (ICONDA), Natural Science Collection (ProQuest), Earth, Atmospheric, & Aquatic Science Collection (ProQuest)
- Istanbul University Affiliated: Yes
Abstract
Understanding withdrawal behavior is essential to characterize wood-fastener interactions that influence the connection performance of timber structures. In this study, the withdrawal performance of innovatively coated fasteners, namely ring-shank nails (RNs) with resin, phosphate, hybrid resin-phosphate coatings and galvanized-diamond coated scrails (SRs), was investigated in three-layer cross-laminated timber (CLT) specimens prepared separately from black pine and fir. This study is the first comparative experimental assessment on the withdrawal performance of resin-phosphate RNs and galvanized-diamond-coated SRs, encompassing the combined effects of coating type, fastener geometry, and wood density on withdrawal capacity and initial stiffness. A comprehensive test program involving 420 conditioned CLT specimens was conducted. The fasteners were driven perpendicular to the grain, and monotonic withdrawal tests were performed in accordance with EN 1382. Among the RNs, the hybrid resin-phosphate coated RN (RN-PR-1) attained the highest withdrawal load (F max), reaching 2.63 kN in black pine and 2.53 kN in fir specimens, as well as the highest withdrawal strength (f ax) in both wood species. The SRs generally had greater initial stiffness (K ax) than RNs owing to their distinctive shank geometry. Additionally, most current design models underestimated the experimental withdrawal capacities up to 68.6%. Accordingly, fastener-specific log-log regression equations (Model 7 for RNs and Model 8 for SRs) were developed, with very good agreement between predicted and experimental values (R 2 >= 0.90). These models may contribute to future revisions of Eurocode 5 and related timber design standards.