SEMINAR PPT ON PRESTRESSED CONCRETE-1.pptx

This presentation is all about the prestressed concrete chosen as a seminar topic. It includes study of various research papers.
Generally helpful for the undergraduate students.

1. DEPARTMENT OF CIVIL ENGINEERING MID SEMESTER PRESENTATION ON PRESTRESSED CONCRETE SEMINAR SESSION : JANUARY – MAY, 2024 SUBMITTED BY : SUNIL DUTT BATCH : 2022 - 2025 FACULTY SUPERIVISOR ASST. PROFESSOR DEAPRTMENT OF CE JNGEC SUNDERNAGAR

2. CONTENTS INTRODUCTION TYPES OF PRESTRESSING LITERATURE REVIEW ADVANTAGES APPLICATIONS CONCLUSION REFERENCES

3. INTRODUCTION Definition of Prestressed concrete :- The concrete in which reinforcing steel bars are stretched and anchored to compress it and thus increase its resistance to stress. A prestressed concrete structure is different from a conventional reinforced concrete structure due to the application of an initial load on the structure prior to its use. The initial load or ‘prestress’ is applied to enable the structure to counteract the stresses arising during its service period. Need for prestressed concrete :- Prestressed concrete is needed to address the inherent weakness of traditional concrete in handling tensile stresses. As modern construction demands longer spans and slender designs, prestressed concrete provides a solution by introducing compressive stresses before external loads, enhancing durability, enabling material efficiency, and expanding the possibilities of innovative and cost-effective structures

4. BRIEF HISTORY BEFORE PRESTRESSING OF STRUCTURES The prestressing of a structure is not the only instance of prestressing. The concept of prestressing existed before the applications in concrete. Two examples of prestressing before the development of prestressed concrete are provided Force-fitting of metal bands on wooden barrels :- The metal bands induce a state of initial hoop compression, to counteract the hoop tension caused by filling of liquid in the barrels . 2. Pre-tensioning the spokes in a bicycle wheel :- The pre-tension of a spoke in a bicycle wheel is applied to such an extent that there will always be a residual tension in the spoke.

5. BASIC PRINCIPLE OF PRESTRESSING Concrete is strong in compression, but weak in tension, and for this reason, a plain concrete beam has little strength. The principle of prestressing is to compress the beam before it is loaded in such a way that stresses are induced in the section which is opposite in action to those arising under loading. Thus the bottom of the beam is compressed by the prestressing so that tension arising when it is loaded will be entirely neutralized.

6. TYPES OF PRESTRESSING SYSTEMS 1. PRE-TENSIONING – Tensioning of tendons is done before concreting 2. POST-TENSIONING – Tensioning of tendons is done after concreting

7. PRE-TENSIONING Pre-tensioning is a method of prestressing concrete that involves applying a compressive force to the concrete before it is cast, using high-strength steel tendons. This process enhances the performance and load-carrying capacity of the concrete structure. Concrete is placed around previously stressed strands or wires (tendons). Ducts or sheathing are not required in this method. Principally used for pre-cast concrete, where the forces can be restrained by fixed abutments. Once concrete hardens, it grips the stressed strands/wires. When concrete attains sufficient strength, the tendons are released from the abutments.

8. POST-TENSIONING Post – tensioning is the method of prestressing in which the tendons are tensioned after the concrete has hardened and the prestressing force is primarily transferred to the concrete through the end anchorages. Post-tensioning tendons, which are prestressing steel cables inside plastic ducts or sleeves, are positioned in the forms before the concrete is placed. Afterwards, once the concrete has gained strength but before the service loads are applied, the cables are pulled tight, or tensioned, and anchored against the outer edges of the concrete.

9. LITERATURE REVIEW

10. SR. NO. NAME OF RESEARCH PAPER NAME OF JOURNAL/BOOK AUTHOR NAME METHODOLOGY RESULTS AND FINDNGS 1. Comparative study of RCC and prestressed concrete flat slabs International Journal of Modern Engineering research, Vol. 3, May-June, 2013 Vakas K. Rahman, Prof. A.R. Mundhada An R.C.C. SLAB of M30 grade was manually designed by using the limit state method based on IS: 456-2000. An identical procedure was followed for PRESTRESSED CONCRETE FLAT SLAB based on WSM given in book ‘ Prestressed concrete’ by N Krishna Raju and checked by LSM suggested by IS:1343-1980. In PSC slab the concrete grade varies from M30 to M50. Cost comparison was carried out between them. From the statistics, it is cleared that up to 9m , RCC flat slabs are economical as compared to PSC flat slabs. From spans 9m to 12m, PSC flat slabs becomes more economical and as the span increases its economy efficiency increases. The cost advantage in percentage terms goes on increasing in favour of PSC with increasing span. Besides, pre-stressed concrete flat slabs being thinner provide greater headroom & result in lesser seismic forces.

11. SR. NO. NAME OF RESEARCH PAPER NAME OF JOURNAL/ BOOK AUTHOR NAME METHODOLOGY RESULTS AND CONCLUSION 2. Research on the material properties of prestressed concrete girder bridge after exposed to fire IOP Conference series : Earth &environmental science 371 (2019) Hao Chaowei , Liu Kang , Li Hongyin , Wang Laiyong For the quick real performance parameters of the materials of prestressed concrete beam bridge in the post disaster bridge evaluation, the appearance classification and material test of 32 hollow slabs demolished after fire of existing beam bridge in a highway were carried out. The relationship b/w the commonly used detection indexes and the material properties is obtained by statistical analysis ( finite element simulation). The ultimate B.C. of selected beams was tested. The various test results for concrete, prestressing strand and common steel bars ( hot-rolled ribbed & round bars ) are taken. The relationship b/w commonly used detection indexes and material properties is checked. Then finite element simulation is done. The results show that elastic modulus of PSC bars after high temp. hardly changes. Spalling of concrete at high temperature leads to loss of section as well as reduction in strength and bearing capacity. Only bottom of small – span prestressed concrete hollow slab beam is directly fired for this study.

12. SR. NO. NAME OF RESEARCH PAPER NAME OF JOURNAL/ BOOK AUTHOR NAME METHODOLOGY RESULTS AND CONCLUSION 3. System development of mechanism, anchoring devices in pre and post Tensioned concrete structural  elements International Journal of Scientific and Research Publications, Volume 5, Issue 2, February 2015 Pradeep Nath Mathur, Prof. A. K. Sinha Some of the systems shall be studied, analyzed and verified in efficiency and strength so that minimum prestress losses occur. Electric pre-stressing shall be experimented in which bars shall be stretched by means of heating using electrical energy. Chemically pre-stressing shall be experimented in which self stressing cement shall be used that expands chemically after setting and during hardening. Consider Fe-410 steel bars of 8mm dia. Its properties are determined. 4 samples of M15 concrete grade are prepared of required workability . Tests are performed in UTM machine Peak load of PSC beam = 32.50 KN. The Peak load of RCC beam = 31.45 KN. Heat generated about 170 degree C which causes sulphur to be melt. Width, Thickness & Crosshead Travel is first found then Peak Load, Cross Head Travel at Peak & Transverse strength is found. Plotter attached with UTM machine draw complete graph till start to specimen break. We found from study that pre stress concrete anchoring devices influencing greatly to the civil engineering. Hence using anchoring devices better concrete structures are made.

13. SR. NO. NAME OF RESEARCH PAPER NAME OF JOURNAL/ BOOK AUTHOR NAME METHODOLOGY RESULTS AND CONCLUSION 4. Review for study of prestressing systems for all structural element International Journal of Scientific Research in science, Engineering and Technology, 2015 Vaibhav G Tejani , Hitesh K Dhameliya , Jasmin Gadhiya An RCC T- beam and PSC-T beams were compared. The span of 24m was selected for study. The study consists of two important factors economy and complexity. The economy comparison of RCC beam and PSC beam is done. MS excel sheet is prepared for RCC beam design of M30 grade & for post tensioned PSC beam of M35 grade. The economics of continuous RCC beams v/s continuous PSC beams is determined. Programming in MS excel is done to design the beams. 1.From the study, it was found that the resistances to shear force and bending moment is more in PSC T-beam. Economy is also achied in PSC T-beam. 2. Results show that for span 26m, post tensioned PSC beam is 34% cheaper than RCC beam. The cost of difference b/w HYSD bars and high strength steel is reduced to 25-30% from more than 100%. 3. Results reveal that for larger spans PSC beam is cheaper and vice versa is true for smaller spans. From all the above studies it is concluded that PSC system is more reliable, strong and economical than RCC for large spans. It can remove the shrinkage cracks and make water proof.

14. SR. NO. NAME OF RESEARCH PAPER NAME OF JOURNAL/ BOOK AUTHOR NAME METHODOLOGY RESULTS AND CONCLUSION 5. A case study on pre-tensioning & post tensioning Systems of a prestressed concrete. International Journal of Engineering Technologies and Management Research, Feb, 2018 Veerat Srilaxmi , K. Majnu, M. Vijaya The Pre-tensioning and Post-tensioning both methods are used under pre-stressing process. In which has few edges over the orthodox non-stressed structures like greater span to depth ratio, higher moment and shear capacity. These methods are generally adopted in the making of PSC girders, sleepers, Bridges, Slabs in buildings, Concrete Pile, Repair and Rehabilitations, Nuclear Power Plant etc. Various materials used are cement concrete, steel, cables & bars etc. Among the types of concrete’s such as generally normal concrete, reinforced cement concrete, prestressed concrete is the best concrete for obtaining much strength in the major constructions of a structure and also for getting more life span of a structure.

15. SR. NO. NAME OF RESEARCH PAPER NAME OF JOURNAL/ BOOK AUTHOR NAME METHODOLOGY RESULTS AND CONCLUSION 6. Comparative Study of prestressed concrete girder and steel plate girder for Roadway over Bridge. International Journal of Scientific Research in Science, Engineering and  Technology. Bhagyashree C. Jagtap, Prof. Mohd. Shahezad A steel plate girder was manually designed by using the limit state method based on IS: 800-2007. Based on the steps a design program was prepared in MS EXCEL. The veracity of program was checked by first designing the manually designed girder by using the program & comparing result. The PSC girder was manually designed, checked by first solving manual problem & comparing results. Programs were also prepared for estimating & costing. Rates are based on the latest CSR in Maharashtra. Based on the design the detailing was made for different span. Table I below gives the cost in rupees for various spans for both prestressed concrete girder & plate girder. Figure 3 below is a short form of Figure 4 where prestressed concrete girder is compared with plate girder with different span. Figure 5 below gives the depth for various spans for both prestressed concrete girder & plate girder. Based on the study , it could be concluded that prestressed concrete girder are economical than plate girder. As the span length increases the cost goes on increasing. Durability of prestressed concrete girder is more than steel plate girder.

16. Prestressed member is free from crack, so the resisting impact, shock and reversal of stresses is much more than reinforced concrete. It is more durable than reinforced concrete. The section of prestressed concrete member is less compared to the reinforced concrete member as it utilizes the maximum tension and compression of concrete, so it reduces the cost. Prestressed concrete can be used in long spans as the section of member can be reduced. As the sections are lighter, they can be transported easily. The concrete diagonal tension can also be reduced. Shear resistance can be increased using curved tendons stressed concrete girder ADVANTAGES OF PRESTRESSED CONCRETE

17. APPLICATIONS Foundations :- Prestressed concrete piles Rock / Soil anchors 2. Bridges :- Simply supported bridges Cantilever bridges Cable – stayed bridges

18. 3. Marine structures Coastal jetties Wharves Navigation structures Bulkheads 4. Water carrying structures Aqueducts Water tanks

19. 5. Industrial structures 6. Pretensioned products

20. 7. Nuclear structure

21. CONCLUSION Prestressed concrete structures offer numerous advantages such as increased strength, durability, and reduced maintenance costs. We explored the principles of prestressing, various types of prestressing methods, and applications in real-world construction. Understanding these concepts is crucial for engineers and architects to leverage the full potential of prestressed concrete in creating innovative and sustainable infrastructure. As we move forward, let's continue to explore and advance the possibilities of prestressed concrete to meet the evolving needs of modern construction."

22. References :- www.ijmer.com Http://www.ijetmr.com International Journal of Modern Engineering Research (IJMER) Vol. 3, Issue. 3, May.-June. 2013 pp-1727-1730 https://iopscience.iop.org/article/10.1088/1755-1315/371/4/042027 IOP Conference series : Earth &environmental science 371 (2019) www.ijsrp.org International Journal of Scientific and Research Publications, Volume 5, Issue 2, February 2015 2015 IJSRSET | Volume 1 | Issue 6 | Print ISSN : 2395-1990 | Online ISSN : 2394-4099 https://doi.org/10.29121/ijetmr.v5.i2.2018.169 http://www.dailycivil.com/difference-pre-tensioning-post-tensioning/ © 2016 IJSRSET | Volume 2 | Issue 1 | Print ISSN : 2395-1990 | Online ISSN : 2394-4099

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