DiscussionThe design of the five-story reinforced concrete structure entailed a number of steps and calculations. Each section listed below describes one step in the process of the design. Attached to the end of this report are sample hand calculations for each step in the design process by each of our group member.Slab thicknessThe slab thickness was determined to be one hundred and fifty (150) millimeters. For ease of construction and economical purposes, a slab thickness of 150 millimeters was used throughout the entire building.Loads The load were calculated by using Table 6.2 of BS EN 1991-1-1:2002 in Eurocode 1.For the floors, the permanent loads included the load from the ceiling, finishes, services and also other mechanical equipment is 6.0 kN/m2 and the load from the slab. The imposed load is 8.0 kN/m2 while the partition loading (which was also considered a variable load) was 0.5 kN/m2. The load for the slab was calculated by multiplying the slab thickness with the unit weight of concrete 25 kN/m2.The load combination from Table 6.2 of BS EN 1991-1-1:2002 consisted of a load factor of 1.0 for the permanent load and 4.0 for the variables load. Using this load combination, the floor load was found to be 112.64 kN.

Estimation of the Column SizeThe first step in the process of determining the column size was the calculation of the tributary area of the most heavily loaded column, which in this building plan was a column in the interior section of the building, which resulted in a tributary area of (). The loading of the roof and four floors was multiplied by this tributary area to determine the factored load experience by the ground story column. The area of the concrete needed to support the calculated force was then calculated, taking into account both the strength of the concrete and the steel. Appropriate overall strength reduction factors were included to not only provide a further factor of safety but also account for eccentric loading of the column. It was also assumed that 10% of the area of the column was steel. Using this assumption, the overall area of the column was .Using a rectangular cross-section, the column width and depth were chosen to be 300 x 400 millimeters. It should be noted that this calculation was for preliminary design only and would be checked later in the design process.

Slab designThe slabs were primarily designed with reinforcing steel to the numerical grid lines. This is because the floor system is a two-way slab, which means that bending will occur in two directions and it is supported on four sides, with the largest moment being at the top of the slab near the supports and at the bottom of the slabs at the mid-spans. Steel was also provided in the transverse direction to provide resistance to the temperature and shrinkage cracks in the tension regions.The first step in the slab design was to find the effective span length. For negative moments, the effective length span length is taken as the average of the two adjacent clear spans while for positive moments the effective span length is the given slabs clear span. Next, the moment coefficients were found for a spandrel slab with two or more spans. The spandrel slab was used because the majority of the slab acts as a spandrel (the slab was just supported by beams). Since the portion of the slab that was supported just by the beams is so much greater than the portion that is supported by the columns, the spandrel condition was used for the moment coefficient.Using the moments at the critical sections, the steel required was tabulated along with the minimum steel requirement according to Table 1 and Table 2 in Eurocode 2. The larger quantity of steel governed and a steel size and spacing combination was chosen. Two additional requirements were then checked. The first was that the maximum steel spacing could not exceed three times of the slab thickness. Additionally, a practical limit of the spacing being greater than one and a half times the slab thickness was checked.Crack controlCracks pose not only aesthetic problems to a building, but cracks also can lead to faster corrosion rates that can accelerate the failure of the beam. Therefore, in Eurocode 2 there are limitation for the spacing of the rebar to control the cracking of the concrete.The slab reinforcement was checked. Using equation 7.1 in BS EN 1992 and the assumption that the stress in the rebar was two-thirds the yield stress, the maximum spacing allowed by code was found. The maximum spacing that we got should be compared to the slab reinforcing in the original design. If the maximum spacing smaller than any of the slab reinforcing in the original design. Therefore, the slab reinforcing fails code and must be re-designed with a maximum spacing. The best way to accomplish this would be reduce the size of the bar and use the corresponding spacing needed per the strength requirements, whichever is smaller. This would be the most economical way to change the design, as it would most likely not rely on the minimum anymore.

Deflection controlDeflections must be controlled in any structure in order to make the bulding feels safe and is serviceable. Additionally, deflections must be controlled so that the non-structural components of the building do not fail.The first step in the deflection calculation was to find the effective moment of inertia of the cross-section assuming the full load was applied to the building early on in the construction process (this is in order to be conservative). This effective moment of inertia is the moment of inertia for the beam based on the amount of cracking in the beam (it is always somewhere in-between the moment of inertia of a fully cracked beam and a completely un-cracked beam). Find the moment of inertia was found for the beam cross-sections. Then each critical point on each span (the negative bending moments near the columns and the positive bending moment at the mid-span) was checked to see if the section was cracked. If the section was cracked (which was the case for the majority of the sections), the cracked moment of inertia for the beam was calculated. Next the effective moment of inertia for each section critical section was found according to Eurocode 2. Using the deflection equation for a continuous span, the deflection under the total load was found.

Column design

The determination of the reinforcement for the columns was the next part of designing. The columns are the most critical part of the building because the failure of a column. Especially a column lower in the building, could have devastating ramifications. The failure of a column could result in the failure of a large portion, or all, of the building. Columns are deemed more important in the design of building than the design of the beams or the floor systems because if a beam or floor collapses, the damage may be contained to a much smaller area than if a column fails.

Find the maximum axial and moment loads that each column could experience were found. These loads were divided into the permanent loads (mechanical equipment, roofing material, slab self-weight, column self-weight, beam self-weight) and the variable loads (the partitions, general variable loads). The top and bottom of each column were analyzed by looking at two different loading conditions. Both conditions vary based on which bays the variable load is applied. For both scenarios the simplest loading scenario that causes the maximum bending is assumed to be the starting point (this is typically achieved by applying the live load on the bay that frames into the section of the column being analyzed is not affected. In the second loading scenario, only the initial variable load to cause the maximum moment is applied. In this way, the column is designed for both axial loading and eccentric loading.

Using these loading scenarios, the moment was calculated in the beams and using structural analysis the distribution of the moment in the beam to the moments in the column was computed. Then using this moment in the column along with the axial load in the column, the reinforcement was found using Eurocode 2 for both loading cases at the top and bottom of each column. Next, the governing steel requirement was found for a given column. After the longitudinal steel was chosen, the ties were chosen. Using the constraints that the spacing could be more than 16 times the diameter of the longitudinal steel, forty-eight times the diameter of the ties and the least dimension of the compression member, the tie spacing was determined for every floor of every column as well. The pattern in the column reinforcement is that on the exterior of the building, the roof experiences considerable bending and therefore more steel is needed in these regions.

Using Eurocode 2, a preliminary design of a five-story building reinforced concrete was completed. Overall, the structure is a very efficient building with only a couple of edits needed in future iterations of the design. It was determined that the design did not fully comply with Eurocode 2, but that these flaws would be revised in future edits to the overall design. The loads for the structure were determine from Eurocode 1 with the load combinations from Eurocode 2. This design is only preliminary design for this reinforced concrete building and several further revisions are still needed for this design to be complete.