Deflection (engineering)

About: Deflection (engineering) is a research topic. Over the lifetime, 30862 publications have been published within this topic receiving 298849 citations.

Finite element simulation of pavement discontinuities and dynamic load response

Abstract: Assumption of a linear elastic system under static loading is questionable for structural response analysis of pavement-subgrade systems under dynamic nondestructive testing and moving wheel loads, especially if a deteriorated pavement is under study. Presented are the results of a parametric study using the three-dimensional finite element ABAQUS code; it investigates the effects of pavement discontinuities and dynamic analysis on the surface deflection response of a pavement-subgrade model under a standard falling-weight deflectometer (FWD) load. An optimum three-dimensional pavement subgrade model of an 18.3-m (60-ft) pavement length was established with a fixed boundary at the bottom and roller supports on the sides. ABAQUS static deflections are in good agreement with the static deflections calculated from the traditional elastic layer analysis for an uncracked pavement. The ABAQUS dynamic response using backcalculated nonlinear moduli compares reasonably with the measured FWD deflections on an asphalt pavement site. The ABAQUS special-purpose gap elements are used to simulate longitudinal and transverse cracks in the surface layer. Dynamic deflections are 17% higher for a pavement with longitudinal cracks as compared with an uncracked pavement.

Serviceability Limit State criteria based on steel–concrete bond loss for corroded reinforced concrete in chloride environment

Abstract: This paper will focus on the study of reinforced concrete beams stored in a chloride environment for a period of 14–23 years under service loading. According to the experimental results, a Serviceability Limit State (SLS) criteria is proposed based on an excessive steel–concrete bond reduction. Corrosion of reinforcement in chloride environment leads to a specific local steel cross-section loss as well as a steel–concrete bond loss. Experimental results have shown that, in the first stage of corrosion propagation period, the deflection is more sensitive to chloride-induced corrosion than the ultimate capacity due to the effect of the tension steel–concrete bond loss even if both are correlated. Given this high sensibility of the bending stiffness to corrosion pitting attacks, it appears that a Serviceability Limit State (SLS) criteria based on excessive deflection of structural members is an adequate factor for SLS assessment. Later in corrosion propagation period, when the bond is already significantly reduced, only the ultimate capacity is affected by the steel cross-section loss. This does not affect the serviceability, because pitting attacks are very localised with an insignificant influence on the global deflection. Then, once the steel–concrete bond is lost in critical parts of the beams (high bending moment areas), pitting corrosion propagation does not affect anymore serviceability (stiffness reduction, bending or corrosion cracks patterns) but still leads to an ultimate capacity reduction, which is not acceptable. As a result, excessive steel–concrete debonding can be considered as the SLS criteria.

Nonlinear dynamic response of a functionally graded plate with a through-width surface crack

Abstract: A nonlinear vibration analysis of a simply supported functionally graded rectangular plate with a through-width surface crack is presented in this paper. The plate is subjected to a transverse excitation force. Material properties are graded in the thickness direction according to exponential distributions. The cracked plate is treated as an assembly of two sub-plates connected by a rotational spring at the cracked section whose stiffness is calculated through stress intensity factor. Based on Reddy’s third-order shear deformation plate theory, the nonlinear governing equations of motion for the FGM plate are derived by using the Hamilton’s principle. The deflection of each sub-plate is assumed to be a combination of the first two mode shape functions with unknown constants to be determined from boundary and compatibility conditions. The Galerkin’s method is then utilized to convert the governing equations to a two-degree-of-freedom nonlinear system including quadratic and cubic nonlinear terms under the external excitation, which is numerically solved to obtain the nonlinear responses of cracked FGM rectangular plates. The influences of material property gradient, crack depth, crack location and plate thickness ratio on the vibration frequencies and transient response of the surface-racked FGM plate are discussed in detail through a parametric study.