Optimal and reliable design of timber beams for a maximum breaking load considering thermal and hydrological effects

Y Aoues (1) , Rostand Moutou Pitti (2) , H. Riahi (3) , S E Hamdi (2) , E Bastida (4)

1 LOFIMS - Laboratoire d'Optimisation et Fiabilité en Mécanique des Structures
2 IP - Institut Pascal
3 UCAR - Université de Carthage (Tunisie)
4 GeM - Institut de Recherche en Génie Civil et Mécanique

The use of of bio materials in sustainable construction aims to reduce the environmental impact of buildings. However, the wood material suffers from several drawbacks, such as the uncertainties of the timber mechanical properties, the knots of the material and the appearance of cracks. However, the timber elements exhibit micro-cracks, which can propagate due to fatigue, overload or creep loading. Thus, crack initiation is one of the most important factors involved in the collapse of timber component in building structures. To predict the crack initiation, many numerical methods have already been developed to characterize the mechanical fields in the crack tip vicinity [1]. In this work, energy method based on invariant integrals is used to estimate the fracture parameters such as energy release rate and stress intensity factors [2]. The analytical formulation of the T-integral to viscoelastic materials [3] is extended to A-integral in order to take into account the effect of thermal loading and the effect of moisture variation [4]. In fact, the study of the crack growth initiation and crack propagation in wood timber may consider the effect of temperature and the moisture content on the mechanical field distribution in the crack tip vicinity. Structural optimization is widely used for effective cost reduction of civil engineering structure. Several works have used the Deterministic Design Optimisation (DDO) approach to design timber trusses [5]. The Deterministic Design Optimization procedure is based on minimizing an objective function as the structural volume or cost subjected to geometric, stress and deflection constraints. These design conditions are considered in accordance with Eurocode 5 in order to satisfy the requirements of both the ultimate and the serviceability limit states. However, in the context of fracture mechanic limit state, the DDO-based on the partial safety factors is not conservative since these safety factors are not calibrated on the basis of the fracture mechanic limit state.

Mots clés: Reliability based optimization; Finite Element Analysis; Orthotropic materials; Probability of failure; crack growth

Domaines: Matériaux; Construction durable; Matériaux composites et construction; Structures

Y Aoues, Rostand Moutou Pitti, H. Riahi, S E Hamdi, E Bastida. Optimal and reliable design of timber beams for a maximum breaking load considering thermal and hydrological effects. COST Action FP1407 2 nd Conference – Innovati ve production technologies and increased wood products recycling and reuse , Sep 2016, Brno, Czech Republic. ⟨hal-01616946⟩