Cyclic behavior of typical screwed connections for cross-laminated (CLT) structures

Abstract

This paper presents the results of an extensive experimental programme on typical cross-laminated timber (CLT) screwed connections conducted at CNR-IVALSA research institute. In-plane monotonic and cyclic shear and withdrawal tests were performed on screwed wall-to-wall, floor-to-floor and wall-to-floor CLT connections. Mechanical properties such as strength, stiffness, energy dissipation, ductility ratio and impairment of strength were evaluated. The experimental results showed good performance of CLT screwed joints under cyclic loads when ductile behaviour was achieved. Brittle response occurred only in cases where requirements for end and edge distances were not satisfied. The experimental characteristic shear strength and mean slip modulus of the connections were compared with values obtained using analytical design equations. The Eurocode 5 (EC5) formulas overestimated the characteristic strength values in some cases, while the Uibel and Blaß formulas specifically developed for CLT connections provided more accurate and conservative predictions. In cases where brittle failures were attained, the analytical values overestimated the experimental ones. This issue can be avoided when the requirements for minimum edge and end distances stated by EC5 are fulfilled. EC5 empirical formulas for the prediction of the screw connection slip modulus at serviceability limit state corresponded well with the experimental elastic values. The overstrength factor, which is of great importance in capacity-based design, was also evaluated, and a conservative value of 1.6 can be recommended for screwed CLT connections.

Seismic drift demands in multi‐storey cross‐laminated timber buildings

“…() The range of degradation parameters were calibrated to experiments, and values between 0.2 and 0.8 were found to represent the closest estimation to the hysteretic behaviour of connectors . Similarly, the structural joinery used to assemble vertical joints between adjacent wall panels was simulated by means of experimentally calibrated nonlinear springs …”

“…Figures 3 to 6 summarize typical comparisons between predictions obtained with the numerical modelling approach implemented in this study and the experimental results described in previous studies. () To this end, Figure 3 presents the calibration of nonlinear springs to a BMF 90×48x3×116 mm angle bracket and a HTT22 hold‐down connector. Similarly, the numerical and experimental hysteretic force‐displacement relationships and cumulative dissipated energy corresponding to a single‐panel CLT wall tested by Gavric et al under cyclic conditions are presented in Figure 4.…”

“…37 Similarly, the structural joinery used to assemble vertical joints between adjacent wall panels was simulated by means of experimentally calibrated nonlinear springs. 41…”

Dissipative Stahlblechverbindungen für aussteifende Wandscheiben aus Brettsperrholz

“…Relativverschiebung liegt der Mittelwert v eq,3 zwischen 21,8 % und 28,7 %. Geschraubte Laschenverbindungen erreichen in den Schmalseitenfugen von BSP bei ähnlichen Amplituden dagegen nur etwa 7–8 % . In Bild links sind die Mittelwerte des Dämpfungsverhältnisses im dritten Zyklus aufgetragen.…”

“…Im Gegensatz zu den Stahlblechen weisen Verbindungen mit Stahlstiften mit Kreisquerschnitt ausgeprägte Tragfähigkeitsminderungen auf. Im Vergleich weisen geschraubte BSP‐Verbindungen im Mittel Tragfähigkeitsminderungen von etwa 20 % auf und erfüllen damit gerade noch den Grenzwert von 20 % nach DIN EN 1998. Durch den Kreisquerschnitt sind Lochleibungsspannungen nicht nur faserparallel orientiert, sondern es treten zusätzlich lokale Querzug‐ und Schubspannungen auf, welche die Holzmatrix schädigen und dazu führen, dass die Lochleibungsfestigkeit für kreisrunde Stifte deutlich geringer ist als die Druckfestigkeit in Faserrichtung.…”