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RISS 인기검색어
- 검색키워드
- 저자 : Hamed Sadaghian (검색결과 3 건)
- 무료
- 기관 내 무료
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Numerical investigation on punching shear of RC slabs exposed to fire
Hamed Sadaghian,Masood Farzam 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.23 No.3
This paper describes the numerical modelling of an interior slab-column connection to investigate the punching shear resistance of reinforced concrete (RC) slabs under fire conditions. Parameters of the study were the fire direction, flexural reinforcement ratio, load levels, shear reinforcement and compressive strength of concrete. Moreover, the efficiency of the insulating material, gypsum, in reducing the heat transferred to the slab was assessed. Validation studies were conducted comparing the simulation results to experiments from the literature and common codes of practice. Temperature dependencies of both concrete and reinforcing steel bars were considered in thermo-mechanical analyses. Results showed that there is a slight difference in temperature endurance of various models with respect to concrete with different compressive strengths. It was also concluded that compared to a slab without gypsum, 10-mm and 20-mm thick gypsum reduce the maximum heat transferred to the slab by 45.8% and 70%, respectively. Finally, it was observed that increasing the flexural reinforcement ratio changes the failure mode from flexural punching to brittle punching in most cases.
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Experimental & numerical investigation of mechanical properties in steel fiber-reinforced UHPC
Behrooz Dadmand,Masoud Pourbaba,Hamed Sadaghian,Amir Mirmiran 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.26 No.5
This paper presents experimental and numerical investigations on mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC) with four types of steel fibers; micro steel (MS), crimped (C), round crimped (RC) and hooked-end (H), in two fiber contents of 1% and 2% (by volume) and two lengths of 13 and 30 mm. Compression, direct tension, and four-point bending tests were carried out on four types of specimens (prism, cube, dog-bone and cylinder), to study tensile and flexural strength, fracture energy and modulus of elasticity. Results were compared with UHPC specimens without fibers, as well as with available equations for the modulus of elasticity. Specimens with MS fibers had the best performance for all mechanical properties. Among macro fibers, RC had better overall performance than H and C fibers. Increased fibers improved all mechanical properties of UHPFRC, except for modulus of elasticity, which saw a negligible effect (mostly less than 10%). Moreover, nonlinear finite element simulations successfully captured flexural response of UHPFRC prisms. Finally, nonlinear regression models provided reasonably well predictions of flexural load-deflection behavior of tested specimens (coefficient of correlation, R2 over 0.90).
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Effectiveness of steel fibers in ultra-high-performance fiber-reinforced concrete construction
Dadmand, Behrooz,Pourbaba, Masoud,Sadaghian, Hamed,Mirmiran, Amir Techno-Press 2020 Advances in concrete construction Vol.10 No.3
This study investigates the behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) with hybrid macro-micro steel and macro steel-polypropylene (PP) fibers. Compression, direct and indirect tension tests were carried out on cubic and cylindrical, dogbone and prismatic specimens, respectively. Three types of macro steel fibers, i.e., round crimped (RC), crimped (C), and hooked (H) were combined with micro steel (MS) and PP fibers in overall ratios of 2% by volume. Additionally, numerical analyses were performed to validate the test results. Parameters studied included, fracture energy, tensile strength, compressive strength, flexural strength, and residual strength. Tests showed that replacing PP fibers with MS significantly improves all parameters particularly flexural strength (17.38 MPa compared to 37.71 MPa). Additionally, the adopted numerical approach successfully captured the flexural load-deflection response of experimental beams. Lastly, the proposed regression model for the flexural load-deflection curve compared very well with experimental results, as evidenced by its coefficient of correlation (R<sup>2</sup>) of over 0.90.
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