Irwan Katili

Unified and integrated approach in a new Timoshenko beam element

Abstract This paper presents a new unified and integrated approach to construct locking-free finite elements for bending of shear deformable beam element. The new UI (Unified and Integrated) element, with two nodes and three degrees of freedom (d.o.f.) per node, is formulated based on a pure displacement formulation and utilises vertical displacement, rotational and curvature as three d.o.f. at the nodes. A continuity of C2 Hermite shape functions for bending deflection vb is used in which rotation function of θ and curvature of χ are dependently expressed as the first and second derivatives of bending deflection. The formulation of element takes account of the effect of shear transversal forces in order to behave appropriately in the analysis of thin and thick beams. A shear influence factor of ϕ is expressed explicitly, which is a function of length thickness ratio (L/h), as a control for shear deformation. The resulting UI element is absolutely free from locking and preserves the high accuracy of the standard locking-free finite elements and classical Bernoulli Euler element. Finally, several numerical tests are presented to confirm the performance of the proposed formulations.

Application of DKMQ24 shell element for twist of thin-walled beams: Comparison with Vlassov theory

ABSTRACT This article presents the application of DKMQ24 shell element for twist of thin-walled beams. This element passed the patch tests for membrane, bending and shear problems and gave fine results for plate and shell problems analysis without shear locking. Thin-walled cantilever beams are analyzed using this element. DKMQ24 gives good results for cantilever beams with open cross-section for a very few number of element. Moreover, the comparison of the results obtained with Vlassov analytical solution enables to evaluate the accuracy of the twist rigidity, Jd, which depends on an empirical coefficient in Vlassov theory.

Analytical and experimental analysis of an asymptotic thin-walled beam model

In this paper, we present the study of an asymptotic linear one-dimensional model for thin-walled beams with open strongly curved cross-section, which is different from the classical Vlassov model. After recalling the main steps of the asymptotic procedure leading to the equilibrium equations of the thin-walled beam model, an analytical resolution of the twist equation is performed. Then comparisons with experimental measurements and with the Vlassov model are carried out. The relevance of the asymptotic thin-walled beam model presented is put in a prominent position.

Effect of Fibers Content on the Tensile Properties of Coconut Fibers Reinforced Cement Mortar Composites

The coconut fiber presents higher ductile properties than other natural fibers. In previous studies, it demonstrated than Indonesian coconut fibers presents an improved tensile strength and failure strain after washed with water and dried. The coconut fibers have the potential to reinforce material for construction, especially in earthquake areas such as tropical countries. The purpose of this research is to assess the benefit brought by coconut fibers content on the tensile behavior of mortar composite. Splitting tensile strengths were measured and microstructure observed using scanning electron microscopy (SEM). The influence of fiber content (expressed by a mass ratio fiber/cement) is investigated. The results show that a fiber content of 5% allows a 10 times higher deflection and presents a 1.5 times higher tensile strength than mortar without fiber. Further studies will focus on the bond strength between the fiber and the cement mortar matrix.