DESIGN AIDS FOR FLEXURAL MEMBER USING IS:

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1 DESIGN AIDS FOR FLEXURAL MEMBER USING IS: Malav sinh J Gahavi 1, D.H. Solanki 2, Prashant Bhuva 3 1Stuent of master of civil engineering (Structure), Gujarat Technological University,Gujarat,Inia 2 Ass. Professor, Dept. App. Mechanics, Shanti lal Shah College, Bhavnagar, Gujarat, Inia 3 Ass. Professor, Dept. of Civil Engineering, Noble Group of Institutions, Junagah, Gujarat, Inia *** Abstract - In Inia RCC Structures are commonly use Like in orinary reinforce concrete, pre-stresse concrete for Resiential as well as commercial Builings for consists of concrete to resisting compression an short span an pre-stresse concrete for longer span. reinforcement carrying tension. Pre-stressing became In Inia, presently there is a rapi nee an increase in essential in many applications in orer to fully utilize the the number of high-rise builings as a basic compressive strength of reinforce concrete an to eliminate infrastructure for resiential an commercial utility. As ue to this cost effectiveness an so many avantages or control cracking an eflection. of pre-stresse concrete it is wiely use in all over the worl. The IS-1343 was first publishe in 1980 an the first revision was publishe in 2012 in between the Inian As the esign ais for reinforce concrete is available stanar IS-456 was revise in 2000 as the fourth revision of as SP-16 but there is no esign ais for pre-stresse Inian stanar IS-456:2000. So the numbers of changes concrete. Here by this work provies some esign ais for pre-stresse concrete flexural member in the form of esign charts. were mae in the secon revision of Inian stanar IS- 1343: INTRODUCTION In moern office builings nowaays it requires open space in such cases longer span system is necessary. The use of Pre stresse reinforce concrete slab results in thinner concrete sections an/or longer spans between supports. As the floor system plays an important role in the overall cost, performance an strength of a builing, a pre stresse floor system is invente which reuces the time for the construction an the cost of the structure an finally give safe an economical structure. By comparison with reinforce concrete, there is a consierable saving in concrete an steel since, ue to the less cross sectional area or epth an use of high strength tenons an thus more slener esigns are possible. As the esign ais for reinforce concrete is available as SP- 16 but there is no esign ais for pre-stresse concrete. Here in this work some esign ais for pre-stresse concrete in the form of esign charts are provie for flexural member. 1.1 Avantages of Pre-stresse Concrete Some avantages of pre stresse concrete slab as compare to the reinforce cement concrete are Smaller eflections compare to with steel an reinforce concrete structures. It offers great technical avantages in comparison with other forms of construction. The cross section is more efficiently utilize. Saving in the materials. Pre-stresse concrete member poses goo resistance to the shearing forces an reuces the principal tensile stresses. 2016, IRJET Impact Factor value: 4.45 ISO 9001:2008 Certifie Journal Page 2322

2 Stiffer, lighter an slener members are possible. High strength concrete an freeom from crack contributes to the improve urability of the structure uner the aggressive environmental conitions. In long span pre-stresse concrete is more economical than the reinforce concrete. Goo crack behavior an therefore permanent protection of the steel against corrosion. Pre stressing results more economical structures with a very high tensile strength instea of normal reinforcing steels. It offers larger spans an greater slenerness which results in reuce ea loa. Subsequently, the overall height of builings reuces which enables aitional floors to be incorporate in builings of a given height. B c k b f ck k b f ck Xu 0.85 Xu X1 xu X2 s se y (a) (b) (c) T T (a) Where, Compressive strain in extreme fibre of the concrete Compatible strain in steel The total strain in the pre-tensione steel is.(b) Where, effective pre-strain in steel Therefore,.(c) The normally accepte strains at failure of a balance section are, ,, 0.004, E s= MPa. By substituting all this value we get Fig 1 (a) Iealize stress blocks in compression (b)rectangular (c)parabolic cum Rerctangular 2. Design charts for pre-stresse concrete Flexure This work inclues charts for concrete graes M40, M50, M60, M70 an M80 for the grae of steel f p = 1500, 1600 an 1700 N/mm 2 as in IS: The value Xu can be obtaine from the compatibility of strains consieration. (refer fig 1)..(1) Xu max/ can be calculate from these equation which is mentione in table A. TABLE-A VALUES OF Xu max/ FOR DIFFERENT GRADE OF STEEL fp N/mm Xu max/ , IRJET Impact Factor value: 4.45 ISO 9001:2008 Certifie Journal Page 2323

3 Limiting percentage of steel can be calculate from the following equation. T = C (Refer fig. 1) Design charts for pre-stresse concrete section for flexure for M40 are rawn below. Therefore, For preparing this charts the equation use for fining out the percentage steel is,.(2) By using this equation we are getting ifferent values of Ps lim for ifferent graes of pre-stressing steel. (refer table B) TABLE-B LIMITING REINFORCEMENT INDEX FOR SINGLY REINFORCED RECTANGULAR SECTIONS (3) From above equation esign charts for M40 are prepare for characteristic strength of steel f p= 1500 N/mm 2 for ifferent epth of 50 to 300 mm, 300 to 550 mm an 550 to 800 mm. fp N/mm Ps lim*fp/fck Mu lim/(fck b 2) An the maximum percentage of steel can be further calculate as in table C. TABLE-C MAXIMUM PERCENTAGE OF TENSILE REINFORCEMENT Ps lim fck N/mm2 fp N/mm , IRJET Impact Factor value: 4.45 ISO 9001:2008 Certifie Journal Page 2324

4 Chart -1: Fp = 1500 N/mm 2 Fck = 40 N/mm 2 Chart -2: Fp = 1500 N/mm 2 Fck = 40 N/mm 2 = mm = mm 2016, IRJET Impact Factor value: 4.45 ISO 9001:2008 Certifie Journal Page 2325

5 3. METHOD OF REFFERING THE DESIGN CHARTS Determine the main tension reinforcement require for a rectangular beam section with the following ata: Size of beam 30x6Ocm Concrete mix M 40 Characteristic strength of pre-stressing steel 1500 N/mm 2 Factore moment 250 kn.m Assuming 25 mm clear cover, Effective epth = = 575 mm From Table C, for f p = 1500 N/mm 2 an f ck = 40 N/mm 2 Mu lim/(fck b 2 ) = Therefore Mu lim = 0.128*40*300*600 2 = 553 KN.m. > 250 KN. m. Therefore the section is therefore to be esigne as singly reinforce (uner-reinforce) rectangular section. METHOD OF REFFERING THE DESIGN CHARTS For referring to Chart no 1, we nee the value of moment per metre with. Mu/b = 834 kn.m per metre with. Referring to chart, corresponing to Mu = 834 kn.m an = 575 mm, Chart -3: Fp = 1500 N/mm 2 Percentage of steel pt = 0.22 Ap = 0.22*300*600/100 = 396 mm 2 Fck = 40 N/mm 2 = mm 2016, IRJET Impact Factor value: 4.45 ISO 9001:2008 Certifie Journal Page 2326

6 4. CONCLUSIONS BIOGRAPHIES As shown the esign charts for flexural member of prestresse pre-tensione concrete can be prepare an which can be use in esigning office to quickly fin the percentage require for the given sectional imensions an for esire moments. One can use this esign charts to fin percentage of prestressing steel require instea of going for so many an trials an errors metho. This will save the time of esigner. REFERENCES Malav sinh J. Gahavi Stuent of Master of Civil Engineering (structure), Gujarat Technological University, Gujarat, Inia. Ass. Prof. Deepak H. Solanki Ass. Professor at S.S. Shah (Government Engineering) college, Bhavnagar, Gujarat, Inia Books 1. Dr. H. J. Shah, Reiforce concrete vol-1, 10 th eition, Charotar publishing house Pvt. Lt., Ass. Professor Prashant Bhuva Ass. Professor at Noble Group of Institutions, Junagah, Gujarat, Inia 2014, Anan, Gujarat, Inia. 2. Dr. H. J. Shah, Reiforce concrete vol-2, 7 th eition, Charotar publishing house Pvt. Lt., 2014, Anan, Gujarat, Inia. 3. N Krishna Raju, Pre-stresse concrete, 5 th eition, Tata McGraw-Hill publishing company limite, New Delhi, Inia. Stanar specifications 4. SP: 16 FOR REINFORCED CONCRETE by bureau of Inian stanars. 5. IS 456: 2000 CODE OF PRACTICE FOR PLAIN AND RCC. 6. IS 1343: 2012 CODE OF PRACTICE FOR PRESTRESSED CONCRETE. 7. IS 1343: 1980 CODE OF PRACTICE FOR PRESTRESSED CONCRETE. 2016, IRJET Impact Factor value: 4.45 ISO 9001:2008 Certifie Journal Page 2327