Study of the Compressive Strength of Aluminum Curved Elements

Currently, the Specification for Aluminum Structures (Aluminum Association, 2010) shows thin-walled aluminum plate sections with radii greater than eight inches have a lower compressive strength capacity than a flat plate with the same width and thickness. This inconsistency with intuition, which suggests any degree of folding a plate should increase its elastic buckling strength, inspired this study. A wide range of curvatures are studied—from a nearly flat plate to semi-circular. To quantify the curvature, a single non-dimensional parameter is used to represent all combinations of width, thickness and radius. Using the finite strip method (CU-FSM), elastic local buckling stresses are investigated. Using the ratio of stress values of curved plates compared to flat plates of the same size, equivalent plate-buckling coefficients are calculated. Using this data, nonlinear regression analyses are performed to develop closed form equations for five different edge support conditions. These equations can be used to calculate the elastic critical buckling stress for any curved aluminum section when the geometric properties (width, thickness, and radius) and the material properties (elastic modulus and Poisson’s ratio) are known. This procedure is illustrated in examples, each showing the applicability of the derived equations to geometries other than those investigated in this study and also providing comparisons with theoretically exact numerical analysis results.

Adaptive and Maladaptive Correlates of Repetitive Behavior and Restricted Interests in Persons with Down Syndrome and Developmentally-Matched Typical Children: A Two-Year Longitudinal Sequential Design

We examined the course of repetitive behavior and restricted interests (RBRI) in children with and without Down syndrome (DS) over a two-year time period. Forty-two typically-developing children and 43 persons with DS represented two mental age (MA) levels: `` younger'' 2-4 years; `` older'' 5-11 years. For typically developing younger children some aspects of RBRI increased from Time 1 to Time 2. In older children, these aspects remained stable or decreased over the two-year period. For participants with DS, RBRI remained stable or increased over time. Time 1 RBRI predicted Time 2 adaptive behavior (measured by the Vineland Scales) in typically developing children, whereas for participants with DS, Time 1 RBRI predicted poor adaptive outcome (Child Behavior Checklist) at Time 2. The results add to the body of literature examining the adaptive and maladaptive nature of repetitive behavior.

A Cross-Sectional Survey of Repetitive Behaviors and Restricted Interests in a Typically Developing Turkish Child Population

This study examined compulsive-like behaviors (CLBs) which are higher-order types of Repetitive Behaviors And Restricted Interests (RBRIs) in typically developing children in Turkey. Caregivers of 1,204 children between 8 and 72 months were interviewed with Childhood Routines Inventory (CRI) by trained interviewers in a cross-sectional survey. Factor analysis of the CRI revealed two factor structures comprising "just right behaviors" and "repetitive/sensory sensitivity behaviors". CLB frequency peaked at 2-4 years with declines after age four. In contrast to the previous CRI studies reporting no gender difference, CLBs were more common in males in 12-23 and 48-59 month age groups on both total CLB frequency and repetitive/sensory sensitivity behaviors. Also ages of onsets for CRI items were somewhat later than reported in other samples. Our findings supported the findings of the previous CRI studies while also revealing new perspectives in need of further investigation.