Experimental Study of the Mechanical Behavior of Semi-Hardened ASTM Aj 400 Threaded Steel Bar Weld Joints Using Image Processing

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Experimental Study of the Mechanical Behavior of Semi-Hardened ASTM Aj 400 Threaded Steel Bar Weld Joints Using Image Processing

ارائه دهنده: Provider: Parviz Bahrami

اساتید راهنما: Supervisors: Dr. Mostafa Moghadasi

اساتید مشاور: Advisory Professors: Dr. Morteza Heydari Mozaffar

اساتید ممتحن یا داور: Examining professors or referees: Dr. fereydon Rezai and Dr. Amir Rezai Sameti

زمان و تاریخ ارائه: Time and date of presentation: 2024

مکان ارائه: Place of presentation: Faculty of Engineering

چکیده: Abstract: The purpose of this research is to experimentally investigate the tensile behavior of welded splices of rebar type Aj 400 to present a novel connection method. According to the conducted studies, in concrete structures, the continuous use of rebars is not feasible due to production length limitations, transportation, and execution challenges, necessitating the splicing of rebars. The most common method of rebar splicing is the overlap splice, which has drawbacks such as increased splice length that prevents proper concrete compaction and increases costs with longer overlap lengths. This study examines welded splices as an alternative method to overlap splicing. Additionally, the tensile behavior of rebars with welded splices and without splices is investigated using digital image processing methods. Digital image processing is a non-contact measurement method that replaces conventional contact methods such as strain gauges. This method is more cost-effective and accurate compared to conventional methods. Important information obtained from this method includes the strain field across the entire area from the start to the end of the test. Other significant data obtainable without using contact methods include local strain in the weld body, yield strain, re-hardening strain of steel, and maximum final strain. This research was conducted in three main stages. The first stage involved performing tensile tests on non-spliced samples to determine their mechanical properties for comparison with spliced samples, yielding properties such as yield stress, yield strain, ultimate stress, ultimate strain, and other parameters. The second stage involved performing tensile tests on samples with specific short weld lengths to obtain the experimental weld strength and the necessary weld length for the third stage. In the third stage, the mechanical properties of rebars with welded splices were determined by conducting direct tensile tests on three samples of each rebar diameter. During the tensile tests in the third stage, digital image processing methods were used to validate the results obtained from the tensile testing machine. The results from digital image processing were almost identical to the laboratory tensile test results, and the strain field in the weld area and rebar body was obtained using image processing methods. Yield and ultimate stresses in different rebar diameters did not significantly change after splicing. The modulus of elasticity decreased by 55% to 42% after splicing. The ductility ratio decreased significantly due to increased yield strain and decreased ultimate strain. The absorbed energy of the welded splice samples decreased significantly due to the reduced ultimate strain. Using welded splices reduces costs and makes larger diameter rebars more economical

فایل: ّFile: Download فایل