Estimating the Seismic Performance of CFRP-Retrofitted RC Beam-Column Connections Using Fiber-Section Analysis

Over the past two decades, many experimental techniques have been developed to improve the efficiency of the externally-bonded fiber-reinforced polymers (FRPs) in order to improve the structural performance of reinforced concrete (RC) beam-column connections. Numerical analysis is also being used as a cost-effective tool to predict the experimental results and to further investigate the parameters that are beyond the scope and capacity of experimental tests. In this study, at first, a fiber-section modeling approach is developed for estimating the seismic behavior of RC beam-column connections before and after application of FRP retrofits. The accuracy of the analysis results were validated against a series of the available experimental data under both monotonic and cyclic loadings. It was pointed out that the proposed model can predict the strength and displacement of un-retrofitted and FRP-retrofitted RC beam-column connections up to the failure points. The verified model was then used to perform a parametric study pertaining to the effect of longitudinal reinforcement ratio on the efficiency of the adopted FRP retrofitting technique to improve the structural behavior of RC beam-column connections.     

Identification of surface dyeing agents of two bookbinding leathers from 19th-century Qajar,Iran, using LC–MS, μXRF and FTIR spectroscopy

Identifying tanning and dyeing agents of historical leathers is one of the less studied subjects. Therefore, this study aims to distinguish the surface dyeing agent of historical leathers along with the tanning agents. It helps to better understand the leather-making process of past centuries. For this purpose, two Iranian historical bookbinding leathers belonging to the Qajar era were investigated. The tannins were examined by ferric spot test and ATR-FTIR spectroscopy after being extracted from the leather corium layer. ATR-FTIR and μXRF spectroscopy were also used to study the characteristics of the leathers' surface, in both grain and corium layers. LC–MS was also used to analyze the extracts taken from the surface of the leather samples. The results showed the corium layer of leathers has a significant number of hydrolysable tannins, especially gallotannins, as tanning agents. The characteristics of their FTIR spectra are significantly similar to those of sumac. LC–MS results showed the presence of ellagic acid, as an indicator analyte, on the surface of the leathers. It indicates that tannin-rich plants, such as oak, have been used for dyeing these leathers. Investigation of the structural properties of the grain and corium layers also revealed the accumulation of copper and iron on the surface of the leathers. Accordingly, copper and iron, which reacted with tannins to give a black color, were the main dyeing factor used in both historical leather samples.