Abstract
Abstract This paper presents the development of a formulation, based on Positional Finite Element Method, to describe the viscoelastic mechanical behavior of space trusses. The numerical method used was chosen due to its efficiency in the applications concerning nonlinear numerical analyses. The formulation describes the positional variation over time under constant stress state (creep). The objective is to provide a way to quantify the creep behavior for space truss structures and thus contribute to the encouragement of GFRP usage in such structural components. Time-dependent behavior of such materials is one the most important factors for their use in design of structures, demanding studies about the deformations expected within the operational life of the structural systems. To perform this study, the proposed methodology considers a standard solid rheological model to describe stress-strain time-dependent law. This model is implemented in the formulation for quantify the total strain energy. The effects of the model parameters in the mechanical response of the structure with accentuated geometric nonlinearity were presented. In this analysis, it was possible to identify the influence of the elastic and the viscous moduli on the creep response. Model calibration was performed using test data obtained from literature and a GFRP transmission line tower cross-arm was simulated to predict the evolution of displacements under real operational loads. From the results, it was possible to observe a fast evolution of displacements due to the creep effect in the first 7,500 h. This increase was close to 0.6% in relation to the displacement obtained in the elastic behavior. The presented methodology provided a simple and efficient way to quantify the creep phenomenon in viscoelastic GFRP composites truss structures, as can be seen in the developed analyses.
Highlights
Composites have great potential to be employed in the field of Civil, Mechanical, Maritime and Aeronautical Engineering
Glass Fiber Reinforced Plastics (GFRP) can be subjected to recycling: the waste could be incorporated, for example, into based mortars, as sand aggregates and filler replacements, which is a benefit to the environment and improves the mechanical properties of the host material (Meira Castro et al 2013)
A formulation of geometrical nonlinear analysis was successfully implemented to analyze the creep phenomenon in viscoelastic GFRP composites truss structures
Summary
Composites have great potential to be employed in the field of Civil, Mechanical, Maritime and Aeronautical Engineering. Ascione et al (2012) presented a program of creep tests to validate a mechanical model (based on Maxwell and Kelvin-Voigt rheological models) formulated for the analysis of viscous properties of FRP laminates. The present paper proposes a model for the analyses of creep phenomenon in viscoelastic composites truss structures For this purpose, a positional formulation of geometrical nonlinear analysis is used to introduce the rheological model and describe the behavior of viscoelastic materials in structures with time. It is presented the calibration of the model based on experimental tests performed by Youssef (2010) at different stress levels and the simulation of the time-dependent deformation evolution resulting from the viscoelastic effect for a typical structure of a power TLT cross-arm
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