This paper aims to determine the efficiency of using steel Shear Bolts to strengthen RC slabs in punching shear at interior columns. The Shear Bolts used in this study consists of a vertical rod and anchored from both ends using a washer and nut system. Shear Bolts are installed in holes, drilled in concentric perimeters around column, after casting and just before testing. In this Work, an experimental research program was described in which seven halfscale models representing interior slab column connections were tested. Seven square specimens (2000 x 2000 x 150 mm) were divided into two groups. The first group deals with three specimens with square column 150 x 150 mm; one specimen without strengthening as a control specimen and the other two specimens strengthened with shear bolts with different strengthened length around the column. The second group deals with four specimens with rectangular column 150 x 300 mm; one Specimen without strengthening and the other three specimens strengthened with Shear Bolts with different strengthened length and arrangements around the column. All Specimens were loaded until failure. The ultimate load, deformation, punching perimeter, strain in flexural reinforcing bars, strains in Shear Bolts, and the failure mechanisms of each specimen were generated and analyzed. The load-deflection curves are presented which show how Shear Bolts increases punching shear capacity and post failure ductility of slab-column connections
Trials were made for reprocessing Egyptian blast furnace slag with and without additives or commercial batches to produce glasses. Characterization of the crystallization behaviour using differential thermal analysis was carried to find out the best route of preparing glass-ceramic materials and x-ray diffraction studies were done to identify the crystallization phases separated by two steps regime for controlled crystallization. The corrosion behaviours of the prepared glasses and corresponding glass-ceramics by different leaching solutions were done at both room temperature for 1&2 months and at 95 o C for 1 hour through the grain method. A further corrosion test inside a gamma-irradiation chamber was carried out for both the reference vitrified slag and the highly promising glass and glass-ceramic samples under direct gamma irradiation facility. Infrared absorption spectra of the prepared samples were measured to identify their structural building units. Scanning electron microscope was used to study the morphology of the prepared samples after corrosion and irradiation. X-ray diffraction studies indicate the separation of gehlenite and akermanite as major phases in the base slag. On adding some batches of silica and silicate glasses, wollastonite and diopside were separated as main phases. Infrared spectral data confirm these findings. Corrosion studies indicate that the prepared sample containing equal portion of slag and sodium borosilicate batch is the highest durable glass together with its glass-ceramic derivative and the same stability retains under direct exposure to gamma irradiation.
This paper discuses analytically and by experimentation the influence of near surface mounted (NSM) carbon fiber reinforcement polymer (CFRP) bars, which acted as an external strength, on the punching shear attitude of edge slab-column bonds. It was stated that many researchers used NSM as a new strengthening technique in different constructional elements. Nevertheless, the strengthening of edge slab-column connections that used NSM was the same and was also used for cardinal slab column connection by first author. Seven Reinforced concrete (RC) square slabs with a bordered column were tested. The specimens were buttressed at the column -as an axis point -and at supportive line on the opposite side of the column. One control specimen was tested without strengthening, four specimens were strengthened using NSM-CFRP bar fitted into pre-dug pothole positioned around the column at the tension side of the slab, and two specimens were strengthened using external Bonded (EB) CFRP strips. The (EB) CFRP strips have the same tensile force of the CFRP bars. The place and area of strength to the strengthened materials were also tested differently. The results of the investigation demonstrated that the use of NSM strengthening technique increased the punching shear capacity and ultimate stiffness appreciably compared to that of applying EB strengthening technique. There were ascending outcomes in the punching shear capacity and ultimate stiffness as 9%-15% and 4%-11% respectively. Furthermore, the cracks in the punching shear zone around the columns were remarkably lowered by the NSM-CFRP bars. The measured ultimate punching shear capacity for the tested specimens proved very rational accordance with the calculated punching loads. This capacity based mainly on a diagnostic specimen for edge slab-column connections strengthened by using FRP concerning its area of bars and place from face of column.
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