STR-924: EFFECT OF LOW TEMPERATURE ON THE SHEAR-FATIGUE PERFORMANCE OF REINFORCED CONCRETE BEAMS

This paper investigates the fatigue behaviour of a reinforced concrete beam (without shear reinforcement) at low temperature (-20°C) compared to a similar beam tested near room temperature (+16°C). Two large-scale steel reinforced beams (200 mm x 400 mm x 4200 mm) were fabricated and tested. The beams had temperature differentials over their depth to simulate solar radiation and in-service temperature of the bridges. The beams were cyclically loaded to failure with a stress range representing the ratio of live to dead loads found in most bridges. This study showed that low temperature increased the fatigue life of the reinforced concrete beam by 51%, and changed the mode of failure of the beam from shear fatigue failure at room temperature to flexural fatigue failure at low temperature. It was observed that the low and room temperature beams maintained 65% and 31% of their original flexural rigidity indicating that low temperature mitigated the stiffness degradation of the reinforced concrete caused by fatigue loading. The strains in the tensile reinforcement of the low temperature beam were much lower than the room temperature beam which could be due to the higher strength of concrete and reduction in concrete softening at low temperature which resulted in lower stresses in the tensile reinforcement. The findings of this study show that the contribution of concrete under either static or cyclic load becomes much higher at low temperature

Experimental data of the static behavior of reinforced concrete beams at room and low temperature

This article provides data on the static behavior of reinforced concrete at room and low temperature including, strength, ductility, and crack widths of the reinforced concrete. The experimental data on the application of digital image correlation (DIC) or particle image velocimetry (PIV) in measuring crack widths and the accuracy and precision of DIC/PIV method with temperature variations when is used for measuring strains is provided as well. Keywords: Concrete bridge, Reinforced concrete, Static behavior, Low temperature, Crack width, DIC/PIV technique, DIC error calibratio

Comparing Characteristics of Early-Onset Injection Drug Users to Those With Late-Onset Injection in Kermanshah, Iran

© 2017 Taylor & Francis Group, LLC. Background: Characteristics and behaviors of early-onset injection drug users are under studied topics in Iran. This study aimed to identify and compare the demographic characteristics as well as the drug using behaviors of early-onset and late-onset injection drug users in Kermanshah, West Iran. Methods: In this cross-sectional study using snowball and convenience sampling, we recruited 450 people during the Fall of 2014 from two drop in centers in Kermanshah, Iran. We collected data through face-to-face interviews. Early-onset injection is defined as whether the person reported their first injection at 22 years of age or younger. Subsequently, late-onset injection is defined as 23 years of age or older. We compared the characteristics of the two groups through both univariate and multiple logistic analyses. Results: Overall, 54% (CI 95%: 44.3%, 62.2%) were early injectors. After controlling for low socioeconomic status, initiation of drug use at a young age, multiple drug use and methamphetamine use were all significantly associated with a higher likelihood of early-onset injection. Additionally, early-onset injection was associated with recent syringe borrowing (OR = 2.6, p = 0.001), recent syringe lending (OR = 1.4, p = 0.01), recent cooker sharing (OR = 3.2, p = 0.01) and injecting two or more times a day (OR = 2.2, p = 0.04). Conclusion: Early-onset injectors were more likely to report a lower socioeconomic status, initiation of first drug use at a younger age, using methamphetamine alongside polydrug use, and engaging in higher risk taking behaviors like borrowing needles. With these associations, the study emphasizes the need for drug-prevention programs to focus on the transition to injection drug use at younger ages