دانلود رایگان مقاله انگلیسی رفتار لایه پیش کشیده جاسازی شده در بتن مسلح فیبری با عملکرد بسیار بالا - اشپرینگر 2018

Abstract:

This study aimed to investigate the bond properties of prestressing strands embedded in ultra-high-performance fiberreinforced concrete (UHPFRC). Toward this end, two types of prestressing strands with diameters of 12.7 and 15.2 mm were considered, along with various concrete cover depths and initial prestressing force magnitudes. The average bond strength of the strands in UHPFRC was estimated by using pullout tests, and the transfer length was evaluated based on a 95% average maximum strain method. Test results indicated that the average bond strength of the pretensioned strand reduced as the diameter of the strand increased, and was between the bond strengths of round and deformed steel rebars. Higher bond strength was also obtained with a lower embedment length. Based on a comparison of p value, the bar diameter and embedment length most significantly influenced the bond strength of strands in UHPFRC, compared to a ratio of cover depth to diameter and initial prestressing force. Pretensioned strands in UHPFRC exhibited much higher bond strength and shorter transfer length compared with strands embedded in ordinary high-strength concrete. Lastly, ACI 318 and AASHTO LRFD codes significantly overestimated the transfer length of the strands embedded in UHPFRC.

In this study, the bond properties of prestressing strands embedded in UHPFRC were examined. The bond strength of prestressed strands in UHPFRC was evaluated according to the diameter, cover depth, embedment length, and initial prestressing force. In addition, the transfer length of the strands in UHPFRC was estimated based on the 95% AMS method and compared with the predictive values of the ACI 318 and AASHTO LRFD codes. From the above discussion, the following conclusions are drawn: • The average bond strength of prestressing strands embedded in UHPFRC decreased with increasing strand diameter. The bond strength of strands prestressed by 80 and 90% of the yield strength was higher than that of a round steel rebar, but lower than that of the deformed steel rebar. In addition, the bond strength of the prestressing strand in UHPFRC was approximately 2.8 times higher than that in HSC (fc 0 of 55.4 MPa).

• Based on the calculated p-value, only the parameters of bar diameter and embedment length significantly affected the bond strength of strands in UHPFRC.

• A higher average bond strength of the strand in UHPFRC was obtained with smaller bar diameter and embedment length. For the smaller-sized strand, the bond strength was more significantly influenced by the embedment length.