Slip modulus of screws in timber and lightweight concrete composite structures

Abstract

The use of lightweight concrete in timber-concrete composite structures for the purposes of reconstruction, upgrading, and strengthening has increasing application potential. The correct combination of mechanical properties of both materials can preserve the beneficial aspects of timber in tension and concrete in compression, while reducing the weight of the structure. This paper experimentally evaluated the slip modulus of screw connectors as one of the key issues in the structural design of these types of composite structures. The results of four groups of push-out tests, which were performed on composite samples, are presented. All of the samples had identical cross sections, but each group was made with a different lightweight concrete density class according to Eurocode 2. The obtained results were compared with the values recommended by Eurocode 5. The analysis showed that the code recommendations yielded slip modulus values that were considerably higher than the ones obtained experimentally, which could lead to unsafe timber and lightweight concrete structures.

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

“…Figure 11c shows that the screw is pressed into the concrete and that the proposed approximation of neglecting the deformations in concrete is inappropriate. This fact implies that attention should be paid to this assumption, especially when LWAC with lower density classes than D1.6 are applied [12]. To show the failure mode of the screw and the damage to timber and concrete, parts of the timber and concrete were removed after the test.…”

“…Different failure modes result in different values of the slip modulus for different embedment depths. When considering the different types of concrete, such as normal weight concrete (NC) and lightweight aggregate concrete (LWAC), in accordance with CEN/TS 19103, the proposed expressions for LWAC concrete may lead to an inaccurate estimation of the slip modulus value [12,13] since local failure effects in concrete are not considered. On the other hand, in expressions for the load-carrying capacity of connections (F v,R ), different types of mode failure are taken into account by using expressions for timber-timber connections, with the approximation of the deformation in concrete based on the local strength of the concrete through a coefficient β [3].…”

A serviceability investigation of dowel-type timber connections featuring single softwood dowels

“…The expression is based on several experiments and derivations carried out by Ehlbeck and Larsen, first published in 1993 [17]. While useful as a quick calculation, it is generally regarded as superficial and oversimplified, and can result in the design of conservative connections [18,19]. The expression is assumed to be independent of the thickness of the adjoining members as well as the angle between the members in the connection, however it has been shown that these do influence joint stiffness [20,21,22].…”

Viabilidade da previsão do comportamento de estruturas compósitas madeira-concreto ligadas por parafusos via análise numérica 3D

“…Sabe-se que dentre todos os tipos de ligações existentes, o tipo parafuso/cavilha é o mais utilizado na prática devido às suas vantagens. Estas são: seu baixo valor de aquisição, grande disponibilidade, fácil execução e grande ductilidade apresentada (Berardinucci et al, 2017;Chen et al, 2022;Di Nino et al, 2020;Dias & Jorge, 2011;Du et al, 2019;He et al, 2016;Jiang et al, 2017;Khorsandnia et al, 2012;Kozarić et al, 2018;Mai et al, 2018;Mascia & Soriano, 2004;Moshiri et al, 2014;Schanack et al, 2015).…”