Experimental Study of Interfacial Shear Strength between Precast Prestressed Concrete Joist and Polypropylene-fiber Reinforced Topping Concrete

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: Experimental Study of Interfacial Shear Strength between Precast Prestressed Concrete Joist and Polypropylene-fiber Reinforced Topping Concrete

ارائه دهنده: Provider: Arsalan Jafari

اساتید راهنما: Supervisors: Dr. Freydoon Rezaie

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr. Mahmoud Nili And Dr. Mohammad Sadegh Ketabi

زمان و تاریخ ارائه: Time and date of presentation: 2026

مکان ارائه: Place of presentation: سالن امفی تئاتر دانشکده مهندسی

چکیده: Abstract: Appropriate transfer of shear stress at the interface between precast joists and the topping concrete plays an important role in the composite action and structural behavior of composite systems. In this study, the shear behavior of the interface between precast prestressed concrete joists and polypropylene fiber-reinforced cast-in-place topping concrete was experimentally investigated. For this purpose, 24 specimens were constructed with two interface surface conditions, namely smooth and longitudinally grooved surfaces, and three volumetric polypropylene fiber contents of 0%, 0.5%, and 1%. The specimens were tested using a modified push-off test. The interface shear strength, initial stiffness, ultimate load, and absorbed energy of the specimens were evaluated. In addition, to quantitatively investigate the surface roughness, a number of specimens were surveyed and analyzed using a three-dimensional optical scanner.The results showed that increasing the polypropylene fiber content from 0% to 1% increased the interface shear strength by approximately 31% for the specimens with smooth surfaces and by approximately 35% for the specimens with longitudinally grooved surfaces. Furthermore, compared with the specimens having smooth surfaces, the specimens with longitudinal surface roughness exhibited increases in shear strength of approximately 83%, 86%, and 89% for fiber contents of 0%, 0.5%, and 1%, respectively. The shear strength of the smooth-surface specimens ranged from 2.23 to 2.91 MPa, while that of the specimens with longitudinal surface roughness ranged from 4.08 to 5.50 MPa. The highest shear strength, equal to 5.50 MPa, was obtained for the specimen with a longitudinally grooved surface and 1% polypropylene fiber, representing an approximately 147% increase compared with the smooth, fiber-free specimen. Moreover, increasing the fiber content was accompanied by improvements in initial stiffness and increases in the absorbed energy of the specimens. The three-dimensional surface investigation also showed that the reconstructed areas of the smooth surface and the longitudinally grooved surface were approximately 9.9% and 63.2% greater, respectively, than the nominal area of 15000 mm². Overall, the results indicated that, within the range of the investigated variables, both increasing the interface surface roughness and incorporating polypropylene fibers improved the shear behavior of the interface. Among the investigated specimens, the combination of longitudinal surface roughness and 1% polypropylene fiber resulted in the highest shear strength, obtained for specimen RT1.