This report outlines the structural design of a five-story reinforced concrete office building following ACI 318-11. The framing arrangement and column locations of the building were provided based on architectural and structural requirements. The structure system of the office building is a reinforced concrete frame with a one-way slab and beam floor system. This report covers the design process in the following order: the calculation of the expected loads on the structure, the design of the slab depth, the estimation of the column sizes, the design of the slab reinforcement, the design of the T-beam reinforcement for both flexural and shear, the calculation to check crack control, the calculation to check T-beam deflections and finally the design of the column reinforcement. Additionally, figures displaying the placement of the steel rebar in the structure are contained in the report.
The details of the design can be found within the report. The basic design of the office building includes seven (7) inch slabs throughout, fifteen (15) inch by fifteen (15) inch square columns and T-beam depths of eighteen (18) inches for the exterior column spans and twenty (20) inches for the interior column spans. Due to deflection control issues that arose in this preliminary design, some of the interior beam lines have to be re-designed in further iterations of this design.
The maximum depth of the interior T-beams would be twenty-two (22 inches). The reinforcement is varied throughout the project depending on necessary loads and ACI 318-11. The slab reinforcement spacing would also have to be edited in future designs because it did not comply with ACI 318 crack control limits. All beams were designed to be under-reinforced beams in order to provide extensive warning before failure (should it ever occur) and all beams were design for shear in order to avoid a sudden and catastrophic failure. Finally, the column reinforcement was designed under two different loading conditions, the first of which maximized both the axial and moment in the column and the second which maximized the moment but minimized the axial loads for a maximum eccentricity.
Three recommendations that I would make if I were re-designing this structure from the beginning would be to use deeper T-beams initially so the building would not fail the deflection limits, use #3 bars for the slab reinforcement while limiting the spacing to twelve (12) inches and use smaller columns dimensions. I would still use at least two T-beam depths, however, as the exterior beam lines can be eighteen (18) inches deep while some interior beam lines may need to be twenty-two (22) inches deep.