Strengthening of an existing reinforced concrete structure
Structural system of the existing structure:
The building has an area of 750 m2. It consists of two stories. The strength of the concrete is 30 MPa and yield strength is 460 MPa. There are three types of slabs mainly one way Hurdy slabs and the others are two way solid slabs and two way hurdy slabs. Two types of columns were found, rectangular and circular. There are projected beams and hidden beams. The cover of reinforcement for all beams and slabs was 20 mm. The Floor cover was 2 KN/m2 whereas the Live load was 2 KN/m2 too.
5.1- Hand calculations results:
As said before it was decided to use PROKON analysis and design program to solve the beams. So, the slabs load should be calculated as an input for this Program. So, these are the unfactored loads calculation of the one way Hurdy slabs (see figure 5.1):
Dead Load = (hf x 2 x bf/2 x concrete density) + (average bw x h x concrete density) + (5 block x 0.1 KN/block) + (floor cover x b)
Live Load = (live load x b)
Wall load = weight of the square mater of the wall x height of the wall.
Figure 5.1 : Typical section of the Hurdy slab.
The one way hurdy slabs loads were calculated as following:
For ribs 1, 2 &3:
Dead Load = (0.08 m x 2x 0.21m x 25 KN/m3) + ((0.16 m + 0.2 m)/2 x 0.32 m x 25 KN/m3) + (5 block x 0.1 KN/block) + (2KN/m2 x 0.58 m) = 3.94 KN/m.
Live Load = (2kN/m2 x 0.58 m) = 1.16 KN/m.
Wall load = 1.5 KN/m2 x 3.84 m=5.75 KN/m.
For ribs 4 &5:
Dead Load = (0.08 m x 2x 0.21m x 25 KN/m3) + ((0.16 m + 0.2 m)/2 x 0.4 m x 25 KN/m3) + (5 block x 0.1 KN/block) + (2KN/m2 x 0.58 m) =4.3 KN/m.
Live Load = (2kN/m2 x 0.58 m) = 1.16 KN/m.
The previous results were used to enter the loads to the program
5.2- Prokon results:
The prokon software program was used to calculate the bending moment and shear force diagrams for all simply supported and continues beams in the ground floor as seen in the appendix (D). These results will be compared with the results of the same beams after adding the new loads in the graduation project II. This comparison will determine the beams that will be strengthened by FRP material.
5.3- Comparison between hand results and prokon results:
The following beam was solved used Prokon program. The maximum bending moment was found to be 46.1 KN.m and the maximum shear force was found to be 35.5 KN. By comparing the analysis results of hand calculations and software program, it was found that they are very similar.
These are the hand calculations of the selected simply supported beam (B53):
The analysis results of the Prokon program were determined as follows:
Figure 5.2: Shear force diagram of B53.
Figure 5.3: Bending moment diagram of B53.
According to that it was decided to work with computer software program because the designer can reduce the time required for these calculations tremendously and thus supposedly have time to consider alternative designs.