Flexural strength of thin pine lamellas relevant to active bending: Results from four-point bending tests

Abstract

The article deals with material testing for the research of shell timber structures constructed using active bending. These structures belong to a category in which the elastic properties of the material are directly involved in the construction process during the design stage. It is therefore essential to determine the material properties that govern both the elastic capacity of the material (modulus of elasticity) and the structural resistance (flexural strength). The paper presents the standardized procedure for determining flexural strength by means of a four-point bending test, carried out on 41 pine specimens with a cross-section of 10 × 40 mm. The results of this test serve as calibration data for the numerical models of ongoing research on active bending at the Slovak University of Technology. Within this framework, experimental testing represents a fundamental requirement for numerical model verification, encompassing both material testing and investigations performed on a scaled experimental shell model. The tests provide the mean flexural strength, the 5th percentile, and the characteristic flexural strength. The results indicate that the value of characteristic flexural strength, after applying the relevant correction factors, may reach up to more than twice as low as the minimum flexural strength obtained from the four-point bending test. The aim of the article is, in addition to obtaining the necessary material parameters, to highlight the potential to increase design efficiency by utilizing the full capacity of the material through knowledge of its actual properties.