1. 1. RETROFIT OF EXISTING TWO STOREY RC STRUCTURE WITH THE FUTURE PERSPECTIVE OF ADDING AN ADDITIONAL STOREY 1
2. 2. CONTENTS OF PRESENTATION 1. Introduction 2. Description of the existing RC building; 3. Decision of retrofit method 4. The Methodology 5. Final results - Discussion: 6. General Conclusions 2
3. 3. Having considered a number of different possible projects to be examined and after having discussed the various alternatives with Professor Dr. Christou Petros, we have jointly decided that my final year project should focus on the following matters: the year project should be associated with the immediate present and future of the science of Civil Engineering in the Republic of Cyprus. It is well known that Cyprus is an island and therefore there is a limited ability to construct new buildings because there is no sufficient land for the development of unlimited number of properties. in addition the economic crisis has played an important role in making the owners to consider the most cost efficient way to develop their property. 1. Introduction 3
4. 4. The main objective of this Project will be the evaluation of the capacity of an existing RC building, the subsequent addition of an extra storey and retrofitting of structural elements where is necessary. The purpose of this dissertation will be to evaluate the adequacy of the existing building, to provide a viable solution in connection with its reinforcement (in the instance in which the existing building is deemed inadequate) so that the addition of the extra storey is deemed feasible and subsequently the entire building is in line and in accordance with the European Codes and especially with its provisions in connection with the antiseismic design. Introduction (continue): 4
5. 5. 2. Description of the exist RC Building Clip 2-1: The location of the two storey RC building 5
6. 6. Description of the RC building (continue): Figure 2-1: The two storey RC building during renovation of Ground floor in 2010 6
7. 7. Description of the RC building (continue): Figure 2-2: Plan of Foundation 7
8. 8. Description of the RC building (continue): Figure 2-3: Plan of Ground Floor (after the renovation) 8
9. 9. Description of the RC building (continue): Figure 2-4: Plan of First Floor 9
10. 10. The actual building which will be analyzed for the purposes of my final year project is an existing two floor residential RC building located in Strovolos, Nicosia. The ground floor was built in 1967 and the first floor was subsequently constructed and added in 1980. In 2010 the ground-floor was renovated with the aim to extend its coverage area (figure 2.1). Due to this extension, the majority of the existing columns had to be reinforced and also the section of the columns was increased to 350x400. Description of the RC building (continue): 10
11. 11. At the infrastructure of the building we encounter the method of foundation beams . The dimensions of the ground and first floor respectively as they appear on the plan are the following: 16900x13400 (figure 2.3) and the 16900 x11200 (figure 2.4). on the ground floor the majority of the sections of the columns are 350x400 and the beams are 200x450 and in connection with the first floor the majority of the sections of the columns are 200x300 and the beams are 200x450 and finally the depth of Slabs are 15cm. The basic structural materials that were used were the following: Concrete C20 and Steel S400. Description of the RC building (continue): 11
12. 12. Having reviewed the two types of reinforcement available: on the one hand the FRP reinforcement and on the other hand the reinforced method via jacketing, 3. Decision of retrofit method 12
13. 13. I have reached to the prima facie conclusion that the method of FRP should not be opted for subject to the following considerations: the designing process would have been extremely difficult; and the cost would have been detrimental. Therefore I have decided to apply the method of reinforced concrete jacketing for the purposes of this dissertation subject to the following three principal considerations: it is been widely and customarily used; there is sufficient background knowledge and expertise in its use in similar occasions; and it is less expensive than the FRP method. Decision of retrofit method (continue): 13
14. 14. 4. Methodology The steps that I undertook can be enumerated and listed as follows: Initially I found the drawings relating to the existing RC building; I went on location and I compared the building in connection to the drawings I had in my possession; The next step was to design the model of the exististing RC building with the assistance of the commercial software STEREOSTATIKA; Following, I added an additional floor and I did run the software with different load combinations of Earthquake in accordance to Eurocode 8. Different results were produced and I made use of the results (Nd , Mxd, yd) relating the worst load combination for each problematic column; 14
15. 15. Figure 4-1: 3D/View North-East side of the RC Building Methodology (continue): 15
16. 16. Methodology (continue): Figure 4-2: Results of Element problem check 1C3 16
17. 17. Methodology (continue): Having in mind the following factors: the existing condition of the building and that the method of column reinforcement would be the jacketing method it was evident that part of the capacity of the existing column would have been used for the calculations for the design of the new reinforcement section. As a result of all of the above, the following decisions were taken: Regarding the existing section: safety factor 10% for the strength Grade of reinforced concrete (20 18) safety factor 10% for the strength Grade of steel 400 360 safety factor 30% for the capacity of steel reinforcement 17
18. 18. Methodology (continue): Regarding the proposed section: safety factor 10% for the strength Grade of reinforced concrete (30 27) safety factor 10% for the strength Grade of steel 500 450 New dimensions of the section from 200 300 to 400 300 The next step concerned the use of Excel. In the said software I applied the results of STEREOSTATIKA (Nd , Mxd, yd - see figure 5.2) in combination with the aforementioned parameters and I made use of the end results regarding the proposed cross sectional area of reinforcement ( ) of the new section. 18
19. 19. Methodology (continue): Figure 4-3: Brief report of column 1C3 in STEREOSTATIKA Data collection with the use of STEREOSTATIKA (Nd , Mxd, yd - see figure 5.2) 19
20. 20. Methodology (continue): Figure 4-4: Design with the use of Excel Calculations with the use of Excel (figure 5.3) 20
21. 21. Methodology (continue): I went back to STEREOSTATIKA, and I applied the new data (As, h and b) resulting by the Excel (Five Step Analysis) and I reran it and I observed that the problematic column no longer encountered a capacity problem. Therefore, subject to the above I proceeded with producing the final design of the proposed section. The final step concerned the repetition of the aforementioned procedure for all the problematic columns (please refer to APPENDIX- A) 21
22. 22. The results that have been reached can be characterized as positive and impressive since in certain occasions (for instance in figure 6.1) column 1C3 following the increase of its dimension no longer encountered a capacity problem. In addition, it was observed that by increasing the dimension of 1C3, columns IC7 and IC25 were relieved from the extra load that was affecting them. For the owners of the building, this result is extremely encouraging since it means that by combing strategically a combination of particular columns which would have relieved the problematic columns from the extra load, they would have incurred an economic advantage since a considerable amount would have not have been spend in reinforcing all the columns. 5. Final results - Discussion: 22
23. 23. Final results Discussion (continue): Figure 5-1: Results of Element problem check via the use of STEREOSTATIKA 23
24. 24. Final results Discussion (continue): However, by being professional and with the aim of ensuring the absolute safety and durability of the structure, I have decided that the safest approach is to suggest to the owners to proceed with the reinforcement of all columns irrespective of the results deduced via the use of any given commercial software (see figure 6.1). 24
25. 25. Final results Discussion (continue): Figure 5-2: Design of jacket-section for 1C3 The proposed section for column 1C3: 25
26. 26. 6. General Conclusions: Advantages of STEREOSTATIKA: The 3D graphs' are very realistic and very simple to be design. I was also enabled in a rather simple and fast track way to alter the parameters of the dimensions of the columns, to reach to solutions and to repeat the same procedure numerous times so as to ensure the best possible result. Disadvantages of STEREOSTATIKA: it cannot analyze and design the dimension of a column via the jacketing method; the grade for concrete and steel are predetermined in the set software and therefore you are not allowed to insert your own evaluation; In certain occasions, such evaluation might be necessary in order to accommodate the risk that the given building is an old construction and hence such an evaluation is necessary for safety reasons. 26
27. 27. General Conclusions (continue): Figure 6-1: 3D/View North-East side of the RC Building (after the reinforcement) Figure 6-2: Plan View of the RC Building (after the reinforcement) 27
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