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This study examines how screw diameter, penetration length, and aperture ratio affect self-tapping screw (STS) withdrawal resistance in bamboo/wood-oriented strand board (WOSB/BOSB) to increase bamboo use in construction and furniture. It proposes a widely applicable empirical formula for calculating withdrawal resistance. With its high specific strength, uniformity, and STS withdrawal resistance, BOSB is a promising material for engineering and furniture applications, according to experiments. Screw diameter, penetration length, and aperture ratio significantly influence the STS’s withdrawal behavior. Among these, screw diameter and penetration length are the primary factors affecting screw withdrawal behavior. As the two factors increase, withdrawal resistance increases linearly. However, the relationship between withdrawal resistance and aperture ratio is non-linear, initially increasing and then decreasing as the aperture ratio increases. With an optimal mounting aperture ratio, the STS withdrawal forces in the BOSB face and edge are approximately 3 and 3.5 times greater than in WOSB, respectively. Traditional formulas for withdrawal resistance were refined based on the fitting equation of aperture ratio and withdrawal force, significantly reducing the relative errors of the modified formulas. Notably, the withdrawal resistance results for STSs calculated using the refined equation based on the CCMC 13677-R standard achieve an accuracy of up to 93%.

The nail-holding performance of two major commercial wood species in southern China, P. massoniana (Masson pine) and C. lanceolata (Chinese fir), were investigated in this paper. Nail-holding strength tests on the two kinds of wood were conducted using self-tapping screws and round steel nails, respectively, with the focus on analyzing the impact law of guiding bore diameter on nail-holding performance. Without the guiding hole, the nail-holding force of both kinds of nails was poor. When the guiding hole diameter increased moderately, the nail-holding force showed an upward trend. Nevertheless, if the guiding hole diameter was too large, the nail-holding force would drop sharply. The nail-holding force of self-tapping screws peaked when the guiding hole diameter was 2.0 mm, and that of round steel nails reached the maximum when the guiding hole diameter was 2.5 mm. In addition, there were remarkable differences in the nail-holding force performance of P. massoniana and C. lanceolata wood under different guiding hole diameters, and their load-displacement curve characteristics also varied. Reasonable design of the diameter of the guiding hole can significantly enhance the nail-holding performance of wood, ensuring the stability and reliability of wood structure connections.

Self-tapping screws (STS) are an effective fastener to enhance wooden moment-resisting joints. However, the effects of the arrangement and insertion angle of STS on the mechanical properties of wooden joints are less studied. Therefore, this study investigated the influence of these two factors on the mechanical properties of wooden joints by conducting cyclic loading tests using glulam moment-resisting joints reinforced by STS with different arrangements (round and square) and insertion angles (45° and 90°). The failure modes, bearing performances, and energy dissipation capacities were considered. The results showed that the insertion angle affected the bearing and energy dissipation capacity of the joints significantly, while the effect of arrangement was slight. The anti-rotation bending moments of the joints reinforced by inclined STS were higher by 31.7% and 13.5% when the arrangement of STS was circular and rectangular respectively compared with the joints reinforced by vertical STS under compression state, and were lower by 17.5 % and 22.9 % under tensile state. The restoring force characteristics of the joints were similar when the insertion angle of STS was the same. Furthermore, the joints had optimal ductility and stiffness when the arrangement was rectangular, and the insertion angle was 45°.

‘Mass timber’ engineered wood products in general, and cross-laminated timber in particular, are gaining popularity in residential, non-residential, as well as mid- and high-rise structural applications. These applications include lateral force-resisting systems, such as shear walls. The prospect of building larger and taller timber buildings creates structural design challenges; one of them being that lateral forces from wind and earthquakes are larger and create higher demands on the ‘hold-downs’ in shear wall buildings. These demands are multiple: strength to resist loads, lateral stiffness to minimize deflections and damage, as well as deformation compatibility to accommodate the desired system rocking behaviour during an earthquake. In this paper, contemporary and novel hold-down solutions for mass timber shear walls are presented and discussed, including recent research on internal-perforated steel plates fastened with self-drilling dowels, hyperelastic rubber pads with steel rods, and high-strength hold-downs with self-tapping screws.

The withdrawal resistance of self-tapping screws (STS) in Korean structural softwood in the vertical fiber direction was examined. Four representative softwood species were selected based on their specific gravity. Three STS fastener diameters were used for an STS penetration depth of 50 mm. The withdrawal capacity tended to increase with the specific gravity of the specimens and as the diameter of the STS increased. Primarily, the difference in strength was maximized as the STS diameter increased from 8 to 10 mm. Predictive experimental equations were proposed based on the experimental values of the relationship between the specific gravity of the structural material and the withdrawal resistance according to the diameter of the STS. The values were compared with the predicted values calculated using fastener and screw prediction equations proposed by the National Design Specification for Wood Construction (NDS) and European Standards (EN). The results calculated using the NDS prediction equations yielded a peak difference of 43% compared with the experimental withdrawal capacity, whereas the EN prediction equations yielded a difference of 0.7 to 1.14 times the experimental values. The ratios between the withdrawal capacity predicted by the proposed prediction equations and the experimental withdrawal capacity were the most similar, ranging from 0.80 to 1.15.

To achieve the assembled connection between dovetail profiled steel sheets and the boundary members in dovetail profiled steel concrete composite shear walls (DPSCWs), self-tapping screws were employed. Three DPSCW specimens connected with self-tapping screws were tested under combined axial and cyclic lateral loads to evaluate their hysteretic response, focusing on the influence of the number of self-tapping screws and the axial compression ratio. The self-tapping screw-connected DPSCWs exhibited a mixed failure mode, characterized by shear failure of the profiled steel sheets and compression-bending failure of multiple wall limbs divided by ribs on the web concrete. Except for slight deformation at the screw holes located on the profiled sheets at the corners of the wall, the connections exhibited minimal visible damage. The yield drift ratio of the DPSCW specimens in the test ranged from 1/286 to 1/225, and the ultimate drift ratio ranged from 1/63 to 1/94, both meeting the relevant deformation standards specified in the “Code for Seismic Design of Buildings. Increasing the number of self-tapping screws enhanced the development of local tensile fields on the profiled steel sheets, thereby improving the wall’s load-carrying, deformation, and energy dissipation capacities. However, increasing the axial compression ratio improved the initial stiffness of DPSCWs but reduced their load bearing and deformation capacity. Moreover, a design method for the self-tapping screw connections in DPSCWs was proposed.

Screw connection is a type most commonly applied to timber structures. As important commercial tree species in China, Masson pine and Chinese fir have the potential to prepare wood structures. In this study, the effects of the diameter of the self-tapping screw and the guiding bores on the nail holding performance on different sections of Masson pine and Chinese fir dimension lumbers were mainly explored. The results showed that: (1) The nail holding strength of the tangential section was the maximum, followed by that of the radial section, and that of the cross section was the minimum. (2) The nail holding strength of Masson pine was higher than that of Chinese fir. (3) The nail holding strength grew with the increase in the diameter of self-tapping screws, but a large diameter would lead to plastic cracking of the timber, thus further affecting the nail holding strength. Masson pine and Chinese fir reached the maximum nail holding strength when the diameter of self-tapping screws was 3.5 mm. (4) Under a large diameter of screws, prefabricated guiding bores could mitigate timber cracking and improve its nail holding strength. (5) Prefabricated guiding bores were more necessary for the screw connection of Masson pine. The results obtained could provide a scientific basis for the screw connection design of Masson pine and Chinese fir timber structures.

The experimental study presented in this paper aimed to investigate the effects of bolt number and their pattern on the failure time of minimally fire-protected glulam beam bolted connections. Four full-size glulam beam-end connection configurations reinforced perpendicular to wood grain with self-tapping screws (STS) were experimentally tested under exposure to elevated temperatures that followed the CAN/ULC S101 (Standard methods of fire endurance tests of building construction and materials. Underwriters Laboratories of Canada, Fifth edition, Ottawa, Canada, 2019) standard fire time–temperature curve. All metal connecting components (i.e., bolt heads and nuts and steel plate edges) were fire protected using wood plugs and strips, respectively. Throughout the duration of fire tests, all specimens were subjected to monotonic load causing bending moment equivalent to the maximum moment design capacity of the weakest unreinforced connection configuration. Fire test results show that the failure time of all four proposed wood–steel–wood connection configurations surpassed the 45-min mark, which is the minimum prescribed fire resistance rating for timber connections in applicable codes, with the two configurations that employed six bolts sustained the applied load for more than 60 min in standard fire conditions. Increasing the number of bolts from four to six enhanced the failure time of the proposed connection configurations with time increments more than those due to changing the bolt pattern. Most importantly, test results confirm that reinforcing the connections with STS fully curtailed wood splitting and averted row shear failure that is frequently encountered in similar but unreinforced connection configurations.

The embedment strength performance of the self-tapping screw (STS) connector, used as a cross-laminated timber fastener, was evaluated considering tree species’ density and load direction as parameters. The STS had a diameter of 8, 10, and 12 mm. Considering the characteristics of the STS, the embedment strength of the threaded area and the shank area were compared. A larger diameter of the STS resulted in a higher yield load in all directions of the respective wood. The effective embedment area can estimate a more accurate value for the embedment strength. The embedment strength of the longitudinal cross section as the embedment area was higher than that of the radial and tangential sections. For the loading direction, the ratio of the embedment strength parallel and perpendicular to the grain of the specimens was 0.40 to 0.58 by wood species. The embedment strength predicted based on the specific gravity and diameter of the fastener differed considerably by 38% to 56% from the actual embedment strength of STS using the effective embedment area. This paper provides data for setting the adjustment factors predicting the embedment strength of STS connection.

PurposeIn fire condition, the time to failure of a timber connection is mainly reliant on the wood charring rate, the strength of the residual wood section, and the limiting temperature of the steel connectors involved in the connection. The purpose of this study is to experimentally investigate the effects of loaded bolt end distance, number of bolt rows, and the existence of perpendicular-to-wood grain reinforcement on the structural fire behavior of semi-rigid glued-laminated timber (glulam) beam-to-column connections that used steel bolts and concealed steel plate connectors.Design/methodology/approachIn total, 16 beam-to-column connections, which were fabricated in wood-steel-wood bolted connection configurations, in eight large-scale sub-frame test assemblies were exposed to elevated temperatures that followed CAN/ULC-S101 standard time-temperature curve, while being subjected to monotonic loading. The beam-to-column connections of four of the eight test assemblies were reinforced perpendicular to the wood grain using self-tapping screws (STS). Fire tests were terminated upon achieving the failure criterion, which predominantly was dependent on the connection’s maximum allowed rotation.FindingsExperimental results revealed that increasing the number of bolt rows from two to three, each of two bolts, increased the connection’s time to failure by a greater time increment than that achieved by increasing the bolt end distance from four- to five-times the bolt diameter. Also, the use of STS reinforcement increased the connection’s time to failure by greater time increments than those achieved by increasing the number of bolt rows or the bolt end distance.Originality/valueThe invaluable experimental data obtained from this study can be effectively used to provide insight and better understanding on how mass-timber glulam bolted connections can behave in fire condition. This can also help in further improving the existing design guidelines for mass-timber structures. Currently, beam-to-column wood connections are designed mainly as axially loaded connections with no guidelines available for determining the fire resistance of timber connections exerting any degree of moment-resisting capability.