Abstract
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.
Introduction
The framing plan of the five-story reinforced concrete building was provided and can be seen in
Figure 1. As shown in the framing plan, the building is six bays by three bays. The outer bays
along the six-bay side are 14 feet center-to-center while the inner bays along the six-bay side are
16 feet center-to-center. The outer bays along the three-bay side are 25 feet center-to-center
while the inner bay along the three-bay side is 30 feet center-to-center. The framing plan also
denotes one-way slabs with T-beams that run along the six-bay columns.
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