Representativeness of the fiber parallel elasticity modulus value referring to the Brazilian standard C40 strength class in the design of timber structures

Abstract

Brazil has the world’s second largest forest area, which makes the exploitation and use of varied species in civil construction conducive. One of the traditional uses of wood is to build roofs for different purposes. Considering that the most recurrent pathologies in the roof structures are related to the excessive deformations observed in the structural elements, particularly in those subjected to bending. This study verified the effective representativeness of the stiffness value established by the Brazilian Class wood standard, C40. Batches of eight different tropical wood species were considered, whose framing occurred in the referred Class. Results obtained from the confidence intervals for each evaluated species led to the conclusion that the value of 19500 MPa for the modulus of elasticity is not representative for Class C40 because the value observed in this study was 14467 MPa, which is 26% lower than the normative reference. This observation is an initial indication that the adoption of the value of 19500 MPa by the standard is unfavorable to the safety of the structure, justifying the pathologies observed in the service performance of the roof structures.

Comparative Analysis of the Mechanical Performance of Timber Flat Truss Typologies for Different Strength Classes via Optimization Algorithm

“…The optimization process of the present work aims to minimize the total weight of the truss structural system, a decision based on the study by Kromoser et al [50], considering nodal displacement constraints, mechanical strength of the bars, minimum dimensions, minimum areas, and geometric criteria due to structural instability. The objective function (OF) is the total weight of the structure, presented in Equation (1), where A i and L 0 i are the cross-sectional area and the length of bar i, ρ i is the material density of bar i, and n is the number of bars present in the truss.…”

“…Wood is a widely used natural resource in civil construction, both in Brazil and around the world. Its versatility and numerous economic and environmental benefits make it a popular choice for roof structures, bridges, and sheds [1][2][3].…”