Load-carrying capacity of self-tapping lag screws for glulam-lightweight concrete composite beams

Abstract

When a lag screw with a large diameter is used as the shear connector in timer-concrete composite beams, the procedure of pre-drilling is required during the construction process. In this paper, a new type of lag screw was proposed to omit the pre-drilling step. To investigate the shear behavior of the self-tapping lag screws for glulam-lightweight concrete composite beams, a total of 18 push-out tests were conducted. Based on the push-out test results, the influences of concrete type, screw diameter, and penetration length of screw into timber on the load-carrying capacity were analyzed in detail. The push-out test results showed that the concrete type had no remarkable effect on the load-carrying capacity. The load-carrying capacity was improved with increased screw diameter and penetration length. In addition, an analytical model for load-carrying capacity of lag screw connectors was proposed based on the push-out test results. By comparisons, it was found that the timber-timber and steel-timber models proposed in Eurocode 5 made very conservative predictions on the load-carrying capacity of lag screws. The results of the analytical method presented in this paper showed a better agreement with the experimental results.

Simulation of Load–Slip Capacity of Timber–Concrete Connections with Dowel-Type Fasteners

“…In the timber-concrete connection, according to experimental tests, the coefficient of friction between concrete and timber is µ = 0.45-0.66 [42,43]. Using the simplified EYM model and based on the experimental tests, Hao Du et al [44] concluded that the angle of rotation of the screw has a significant part in contributing to the load-carrying capacity due to the rope effect. The coefficient of friction is in the range of 0.35-0.50 (µ = sin(90 − θ)) for an angle θ that varies from 20 to 30 degrees (for the slip in connection up to 15 mm).…”

Shear behavior of notched connection for glubam-geopolymer concrete composite structures: Experimental investigation

“…Currently, there are no relevant reports on the composite structures of glubamgeopolymer concrete. However, a significant number of studies on the connection mechanism, flexural performance, long-term performance, and design method of timberconcrete composite (TCC) structures have been conducted by a large number of academics (Clouston et al 2005;Du et al 2019;Jiang et al 2021). These have been widely used in floor structures and bridges (Yeoh et al 2011a), and the shear connectors have been a focus of research, since the service performance of the composite structure depends on the appropriate connection of two materials.…”