Mechanical Properties of High and Very-High Strength Steel at Elevated Temperatures and After Cooling Down

High-strength steels (HSS) are produced using special chemical composition or/and manufacturing processes. Both aspects affect their mechanical properties at elevated temperatures and after cooling down, and particularly the residual strength and the ductility of the structural members. As HSS equates the design of lighter structural elements, higher temperatures are developed internally compared to the elements designed with conventional carbon steel. Therefore, the low thickness members, along with the severe effect of high temperature on the mechanical properties of the HSS, constitute to the increased vulnerability of such structures in fire. Moreover, the re-use and reinstatement of these structures are more challenging due to the lower residual mechanical properties of HSS after the cooling down period. This paper presents a review of the available experimental studies of the mechanical properties of HSS at elevated temperatures and after cooling down. The experimental results are collected and compared with the proposed material model (reduction factors) of EN1993–1-2. Based on these comparisons, modified equations describing the effect of elevated temperatures on the mechanical properties of HSS are proposed. Also, the post-fire mechanical properties of HSS are examined. A comprehensive discussion on the effect of influencing parameters, such as manufacturing process, microstructure, loading conditions, maximum temperature, and others is further explored

Dyeability, Kinetics and Physico-Chemical Aspects of Bombyx Mori Muslin Silk Fabric with Bi-Functional Reactive Dyes

Bombyx mori muslin silk fabric was dyed with three different bi-functional reactive dyes in exhaust method. Dyeability of the silk fabric was analyzed by reflectance spectra, microscopic appearance, color strength, and saturation limit. Thermal influence on dye exhaustion, migration index, level dyeing factor, and color fastness properties were also investigated. Different kinetic models were approached to study dynamic behavior of dye adsorption and predictability of the models was assessed by co-efficient of regression (r2), root mean square error (RMSE), and mean absolute error (MAE). Some physico-chemical parameters such as activation energy and chemical potential of dyeing were also evaluated. Brilliant color was observed on silk by all class of reactive dyes. A controlled dyeing condition was also suggested to avoid the risk of unlevel dyeing. Wet fastness properties exhibited excellent results on silk fabric. The adsorption data conformed to the pseudo second-order kinetic model with r2 ≥ 0.94 and the activation energy (ΔE) valued (≥55 kJ/mol) within the range of chemisorption for all dyes. The increase of negativity of chemical potential supported higher dye uptake on silk at elevated temperature

Development of a local bond shear stress-slip model of RC beams externally strengthened with FRP materials

This paper presents an analysis of the numerical investigation of RC beams, strengthened with CFRP and tested in flexure, using the ANSYS © numerical analysis code. In the first part of this paper, finite-element models of RC beams (control and CFRP-strengthened), subjected to four-point bending, are developed based on experimental tests as reported in the literature. Then, a 3D nonlinear finite-element analysis (NLFEAs) with perfect bonding, along with 12 cohesive zone material (CZM) models proposed by researchers in literature, are explored to simulate the behaviour of CFRP-strengthened RC beams. In the second part of this work, the compressive strength of the concrete and the elastic modulus of the epoxy resin are examined to study their effect on the same CFRP-strengthened RC beam. On the basis of those two studies, a bilinear CZM model is modified to predict the behaviour of RC beams strengthened with FRP materials, and interfacial shear debonding phenomena. The modified CZM model is verified against a database of experimental results that includes 23 RC beams, strengthened with FRP tested in flexure, with different concrete compressive strength, FRP modulus of elasticity and resin elastic modulus. The experimental and predicted ultimate loads are compared to verify the accuracy of the modified CZM model. The level of fitness between the modified CZM model and experimental results is elaborated with statistical metrics such as integral of the absolute error (IAE), root mean square error (RMSE) and coefficient of determination (R 2 ). The results show good agreement between the experimental and predicted ultimate loads

Synthesis and properties of some new 5-fluoro-6-(heterocyclyl) benzofuroxans

A series of 5-fluoro-6-(heterocyclyl) benzofuroxans (3b-e) have been prepared by hypochlorite oxidative cyclization of the respective 4-fluoro 5-(N-heterocyclyl)-2-nitroanilines (2b-e). The heterocyclyls include piprazine, N-(2-hydroxyethyl) piprazine, morpholine and thiomorpholine. Some bio-properties and spectral data these new derivatives are presented

Bulletin 108 de la fib. Approche performancielle de la sécurité incendie des structures en béton

editorial reviewedIntroduction. Scope. Description of the thermal / structural response of concrete in fire. Design strategy for fire safety of concrete structures. Quantification of the performance of concrete structures in fire. Guidance for use of advanced calculation methods. Guidance for use of probabilistic methods