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AbstractThis paper tests four pre-cracked hybrid GFRP-steel reinforced concrete (HGSRC) beams with CFRP sheets and four intact reference beams under four-point bending to examine the effects of CFRP sheets and steel reinforcement ratios on flexural behavior. The pre-crack width caused by the load is approximately 0.2 mm. The experiments showed that the addition of CFRP sheets transformed the failure mode of the pre-cracked HGSRC beams from shear compression to delamination-plate-end-debonding and resulted in a reduction of up to 54% in their energy ductility index. The incorporation of CFRP sheets significantly enhanced the flexural behavior of pre-damaged HGSRC beams in terms of yielding load and secondary stiffness, while the improvement in their load-carrying capacity was minimal was slight. The addition of CFRP sheets could also delay the development of strains in materials even though the beams were pre-cracked. The analytical models to determine the load-carrying capacity of pre-cracked HGSRC beams strengthened with CFRP sheets are still limited and therefore, a strut-and-tie model (STM) is proposed to fill the gap in this research. The integration of corrected formulas into the strut and tie model for estimating the load-bearing capacity of the pre-cracked strengthened HGSRC beams indicated a strong agreement with the experimental data. [ABSTRACT FROM AUTHOR]

The present article is an effort to quantify the flexural strength of corroded reinforced concrete (RC) beams. Eight RC beams with dimensions of 150 × 200 × 2200 mm were tested in four-point bending, including six beams corroded in a chloride environment with average corrosion of longitudinal reinforcement in the range of 5% to 15%. The remaining two beams were used as control beams. The ultimate strength, failure mode and particularly the relationship between crack width and corrosion level are analyzed and discussed. A two-dimensional non-linear finite element model has been presented to simulate the steel bar corrosion considering the deterioration of concrete strength and steel-concrete bond stress. The generalised regression neural network (GRNN)-based model for the ultimate flexural strength of corroded RC beams has been established based on 123 experimental data collected from previous studies. The experimental results were used to separately validate the non-linear finite element model and novel GRNN model. Experimental results indicate that if the overall corrosion rate is used, the corrosion crack width can be a function of the percentage of section loss. The GRNN model provides superior predictive results compared to previous empirical methods with the highest correlation coefficient (r), and the smallest normalised root mean square error. [ABSTRACT FROM AUTHOR]

Due to low compressive strength and low compressive elastic modulus in comparison with these in tension, GFRP reinforcement is often used for bending elements and is rarely used for compressive structures. In this paper, the authors used finite element (FE) method based on Abaqus software to evaluate the axial load-carrying capacity of GFRP reinforced concrete (RC) columns under varying concrete grades, GFRP reinforcement ratios and tie configurations. The model of the specimens is developed using concrete damage plastic (CDP) model and linear elastic material model for GFRP bar. The consistence of the FE method is verified by the experimental results of a series of columns that tested by current authors. The analytical results show that the selected numerical method can accurately predict the behavior as well as the ultimate capacity of the columns. From simulation results, it is clear that the contribution of GFRP to the load-carrying capacity is considerable in columns with low concrete grades. While using higher concrete grades, the contribution of GFRP decrease, at concrete grade B60, contribution of GFRP is almost unimportant (2.74 %). Influence of tie spacing on load-bearing capacity of columns is also investigated. Accordingly, reducing tie spacing leads to increase load-carrying capacity. Based on study results, the authors recommend to limit tie spacing less than eight times of the GFRP bar diameter.

The article presents the pronouncement of the International Conference for Agent Orange/Dioxin Victims in Hanoi, Vietnam held in March 2006, by Dang Vu Hiep, President of the Vietnam Association for Victims of Agent Orange, which asserts that during the Vietnam War, the U.S. military used toxic dioxin-based herbicides provided by American chemical companies which caused large-scale destruction of the environment and posed long-term public health problems to people exposed to the chemicals and their children.