the loss in prestress force is about mcqtensorflow keras metrics

{\bf{e}}}}{{\bf{Z}}}\), b= 300 mm, d = 900 mm, e = 350 mm, P = 700 kN, Where, Z =\(\frac{{\bf{I}}}{{\bf{y}}}\)=\(\frac{{\frac{{{\bf{b}}{{\bf{d}}^3}}}{{12}}}}{{\frac{{\bf{d}}}{2}}} = \frac{{{\bf{b}}{{\bf{d}}^2}}}{6} = \frac{{300 \times {{900}^2}}}{6} = 40.5 \times {10^6}{\bf{m}}{{\bf{m}}^3}\), Stress at top fibre at midspan due to prestress =\(\frac{{\bf{P}}}{{\bf{A}}} - \frac{{{\bf{P}}. The high tensile steel tendon in a prestressed concrete member (FC 2018), b) Does not remain under a constant condition of either stress or strain, SHOW ANSWER b) Does not remain under a constant condition of either stress or strain, 43. 11. In addition to long-term losses due to creep, shrinkage and relaxation, an immediate drop in prestress force occurs due to elastic shortening of the concrete. a. the sun's gravity is weaker than Earth's. b. the moon is smaller than Earth. II. increase air resistance.b. if(typeof ez_ad_units != 'undefined'){ez_ad_units.push([[300,250],'physicsteacher_in-large-mobile-banner-2','ezslot_9',154,'0','0'])};__ez_fad_position('div-gpt-ad-physicsteacher_in-large-mobile-banner-2-0');5 ) A skydiver uses a parachute toa. Prestressing is the process of introducing compressive stress to the concrete to counteract the tensile stresses resulting from an applied load. Cables with as many as 64 wires are also used under special conditions. var container = document.getElementById(slotId); The prestressing force in each tee is 750 kN. RMS CIVIL FACTORY {\bf{e}}}}{{\bf{Z}}}\), \(\frac{{\frac{{{\bf{b}}{{\bf{d}}^3}}}{{12}}}}{{\frac{{\bf{d}}}{2}}} = \frac{{{\bf{b}}{{\bf{d}}^2}}}{6} = \frac{{300 \times {{900}^2}}}{6} = 40.5 \times {10^6}{\bf{m}}{{\bf{m}}^3}\), \(\frac{{700 \times {{10}^3}}}{{300 \times 900}}- \frac{{700 \times {{10}^3} \times 350}}{{40.5 \times {{10}^6}}}\), \(\text{P} = 4 \times \frac{\pi}{4}\times 10^2\times 500\), \( \frac{157\times 10^3}{150000} - \frac{M}{15\times 10^6} +\frac{157\times 10^3\times 100}{15\times 10^6} = 0\), \(\frac{{{\Delta f_p}}}{f} \times 100 = \frac{{60}}{{1000}} \times 100 = 6\%\), \(M = \frac{{\left( {w - P} \right){L^2}}}{8}\), \(\sigma = \frac{P}{A} + \frac{{My}}{I} - \frac{{Pey}}{I}\), \(\frac{{0.0001}}{{{{\log }_{10}}\left( {t + 2} \right)}}\), \(\frac{{0.0002}}{{{{\log }_{10}}\left( {t + 2} \right)}}\), \(\frac{{0.0003}}{{{{\log }_{10}}\left( {t + 2} \right)}}\), reductions of the prestressing force are termed as the losses in prestressing, loss due to friction does not occur in pre-tensioned members. none of the above. Between the two ends, the spacing of the wires is maintained by spacers. It does this by tensioning the steel cable running through the concrete. For Pre-tensioning minimum cover to be used is 20 mm. surfaces in contact generate heat.c. Initial prestress 2. , Forces of tension and 'compression change1 but lever arm remains unchanged, Forces of tension and compressions remain unchanged but lever arm changes with the moment, Both forces of tension and compression as well as lever arm change, Both forces of tension and compression as well as lever arm remain unchanged, The purpose of reinforcement in pre-stressed concrete is, To impart initial compressive stress in concrete, In both post-tensioned and pre-tensioned beams, The coefficient of shrinkage for high grade concrete for pre-tensioned work is, If 'P' is the prestressing force applied at a maximum eccentricity 'g' at mid-span, figure, to balance the concentrated load 'W', the balancing load will be, Consider the following factors The spacing of stirrups in a pre-stressed beam should not exceed (AE 2015), c) 0.75 times the effective depth of the beam, d) 0.3 times the effective depth of the beam, SHOW ANSWER c) 0.75 times the effective depth of the beam, 18. (iii) With the use of high-strength concrete, shrinkage cracks are low. (2019 AE Nilgiri), 51. Then: Read more here. container.appendChild(ins); \(\text{Total stress at bottom fibre} = \frac{P}{A} - \frac{M}{Z} +\frac{Pe}{Z}\)= 0, \( \frac{157\times 10^3}{150000} - \frac{M}{15\times 10^6} +\frac{157\times 10^3\times 100}{15\times 10^6} = 0\). To view the purposes they believe they have legitimate interest for, or to object to this data processing use the vendor list link below. Spring keeps proper spacing for the wire. (c) muscular force. The major loss of pre-stress is due to(AE 2008), 15. IS:1343-1980 clause 18.5.2.5 Prestress Loss Early attempts - prestressed concrete - unsuccessful due to loss of. 2. losses in prestress The second category is the loss or gain due to additional loads, such as non-composite dead loads, composite dead loads and live loads that are applied after transfer. static frictionb. In prestressed concrete, a prestress force is applied to a concrete member and this induces an axial compression that counteracts all, or part of, the tensile stresses set up in the member by applied loading. Based on the initial applied prestressing force in tendons and the calculated existing prestressing force, loss of prestress can be worked out during last 10 years as given below in Table -4: The loss observed is quite uniform throughout. The minimum prestress force occurs at the right-hand end of the beam: P(x=50)=3000 exp [0.19(0.469+5010450)] Figure 4.7 . To modify the behavior of the member or structure in such a way so as to make it more suitable for its intended purpose. Fully pre-stressed concrete beam means (AE 2010), c) working loads are completely resisted by prestressing force, SHOW ANSWER c) working loads are completely resisted by prestressing force, 30. In prestressed concrete stress block is recommended with appropriate safety factors. Loss of pre-stress takes place due to the width effect. rolling friction. sliding frictiond. Then select the cables, choose Assign Cable Loads Target Force, then define the initial prestress forces for the cables. The acceptable limit for the safety and serviceability requirements before failure occurs is called a limit state. 40 mm or maximum size of cables or bar of nominal maximum size of aggregate plus 5 mm. Loss due to Elastic Shortening: When the tendons are cut and the prestressing force is transferred to the member, the concrete undergoes immediate shortening due to the prestress. It is ITD's policy to ignore the effects of this . View full document. window.ezoSTPixelAdd(slotId, 'adsensetype', 1); 4. The concrete is cast around the tensioned steel, and when it has reached sufficient strength, the anchors are released and the force in the steel is transferred to the concrete by bond. We and our partners use cookies to Store and/or access information on a device. The loss of prestress due to elastic deformation of concrete depends on _____ a) Modular ratio and average stress . (iv) High strength concrete will have high modulus of elasticity of concrete(= 5000fck)and hence elastic and cracks strains are very low means creep strains are low, resulting in smaller loss of prestressing force. a) high tensile steel and ordinary concrete are used. The crack width in the center span is between 0.1 and 0.15 mm (0.004 and 0.006 in.) Wires are pulled by Freyssinet double-acting jacks which can pull through suitable grooves all the wires in the cable at a time. An override declaration can change the accessibility of the virtual method. In our problem, for no tension at the bottom fibre i.e. the moon is closer to Earth. LOSS OF PRE-STRESS A reduction in initial pre-stress resulting from the combined effect of creep, shrinkage or elastic shortening of the concrete, relaxation of the reinforcing steel, frictional losses resulting from the curvature of the draped tendons and slippage at the anchorage. moving object to change direction.d. But total loss of prestress is more in Pre-tensioned concrete compare to Post-tensioned concrete. 2) Losses due to creep or relaxation of steel: Important PointsLosses in Post-tensioning, High-tensile bars threaded at ends are used in. To modify the behavior of the member or structure in such a way to make it more suitable for its intended purpose. Copyright 2022 All rights reserved. and the stress variation in the nonprestressed reinforcement is about 130 Nlmm2 (18.9 ksi). Prestressed concrete is an concrete in which internal stress of a suitable magnitude and distribution are introduced so that the stresses resulting from external load are counteracted. Answer (1 of 2): * PSC is basically concrete in which internal stress of suitable magnitude & distribution are introduced so that stress resulting from the external load is counteracted to a desired degree. Have you? Load and moment in concrete are balanced by stressing the steel. 7 ) An object with greater massa. Loss due to Anchorage Slip: In a post-tensioned member, the is loss of prestress due to the consequent reduction in the length of the tendon. Prestressing is done to reduce or eliminate the internal tensile stresses by applying an initial compressive axial force to the concrete. If the loading on a pre-stressed rectangular beam is uniformly distributed, the tendon to be provided should be (AE 1999), SHOW ANSWER b) parabolic with convexity downward, 27. So the loss in prestress occurs due to friction between the concrete surface and the tendon in the process of tensioning.The loss of friction is also accompanied by the wobble effect. McGraw-Hill Dictionary of Architecture and . This makes it possible to predict approximately how much prestress will be lost in a given kind of service. There are small frictional losses in the jacking equipment. b) Maximize elastic creep and shrinkage strains. No loss due to elastic deformation if all the wires are simultaneously tensioned. minimum clear spacing between groups of cables or ducts of grouped cables shall be greater, \(\frac{{\bf{P}}}{{\bf{A}}} - \frac{{{\bf{P}}. It is similar to creep of concrete. both option 1 and option 4 are correct. In designing prestressed concrete flexural members, the breadth of compression flange is determined on the basis of (AE 2014), SHOW ANSWER b) ultimate flexural strength, 34. Loss of prestress due to friction occurs (AE 1997), C)In both post-tensioned beams and pre-tensioned beams, SHOW ANSWER B) Only in post-tensioned beams, 2. The value of e is given by, For zero stress at top fibre, Question 1. 22. Those which affect the ultimate moment capacity of a prestressed concrete beam would include. 4. var pid = 'ca-pub-5687382078590987'; 4 ) Which statement about rolling friction is false?a. A pre tensioned concrete beam 100mm wide and 300mm Loss Due to Shrinkage:-deep, initial force of 150kn at an eccentricity of 50mm, 6 4 moment of inertia is 22510 mm , initial . 3. In the case of under reinforced section (AE 2008), c) steel is provided on the undesirable of the section, d) concrete cover is not provided for reinforcement, 13. 3. 2. It is one in which a permanent and essentially horizontal compressive stress has been introduced prior to the application of any wheel loads. Assume a prestress loss of 10% of the initial prestressing force. If the tendon is placed at an eccentricity e below the centroidal axis along the longitudinal axis of a rectangular beam (sectional modulus Z and stressed load P in tendon) the stress at the extreme top edge (2019 AE), 48. The system suitable for pre- tensioned prestressed concrete members is (FC 2018), 41. Which of the following are necessary for Run-time Polymorphism? Cover to be used in the design of prestressed concrete structure as per IS 1343 is as below: 1. Mcqspage.com. That reference gives simple equations for estimating losses of prestress which would enable the designer to estimate the various types of prestress loss rather than using a lump sum value. repel each other.b. An example of data being processed may be a unique identifier stored in a cookie. Loss due to Elastic Shortening:When the tendons are cut and the prestressing force is transferred to the member, the concrete undergoes immediate shortening due to the prestress. Loss of Prestress 1. But the most appropriate answer is option 4 because lesser creep deformation causes less stress loss. For Pre-tensioning minimum grade of concrete used is M-40. Strain in concrete at zero stress is called (AE 1999), 10. 3. depth of cable from extreme compression fibre The gradual reduction of this introduced compressive stress in a prestressed member due to various reasons is called losses of prestress. prestress. static frictionb. the suns gravity is weaker than Earths.b. b = 250 mm, d = 600 mm, e = 300 - 200 = 100 mm, A = bd = 150000 mm2, stress in wires = 500 N/mm2, We know that, for rectangular section,\(\text{Z} = \frac{bd^2}{6}\), \(\text{Z} = \frac{250 600^2}{6}\)= 15 106mm3, Now,\(\text{P} = 4 \times \frac{\pi}{4}\times 10^2\times 500\)= 157 kN. A prestressed concrete sleeper produced by pre- tensioning method has a rectangular cross-section of 300mm 250 mm (b h). Pages 324 This preview shows page 310 - 313 out of 324 pages. sizeb. Please see the attached Screenshot for more information. The full-scale strain (location 5.5-7.5 m) distribution of strand can be obtained by the BOTDA sensors. B) Only in post-tensioned beams. A pre-stressed concrete induces artificially stresses in a structure before it is loaded. I. A simply supported prestressed concrete beam is expected to carry an uniformly distributed load, The tendons should preferably be (AE 2018), a. a circular profile with convexity upward, b. a straight profile below the centroidal axis, c. a parabolic profile with convexity downward, d. a straight profile along the centroidal axis, SHOW ANSWER c. a parabolic profile with convexity downward, 39. Determine the final concrete stress (MPa) at the bottom fiber of the midspan section when the beam sustains an additional live load of 10 kN/m. In designing prestressed concrete the designer takes all of this into account--the slipping of the anchorage; the frictional loss from curvature in the tendons; and the losses caused by elastic shortening, drying shrinkage and creep of . No one because of wear and tear of the building. I. Pre-stressed concrete structures are most economical. Loss of prestress due to friction occurs (AE 1997) A) Only in pre-tensioned beams. The box has less friction when it is sliding. The proof stress of high tensile wires is measured at (AE 2014), 17. In most tensioning systems, when the cable is tensioned and the jack is released to transfer pre-stress to concrete, the friction wedges employed to grip the wires, slip over a small distance before the wires are finally housed between the wedges. Loss of stress due to relaxation of steel is influenced by, Loss of stress due to relaxation of steel. For prestressed concrete the high tensile wires are only used. 1 and 2 . To use this online calculator for Loss of Prestress due to Slip, enter Area of tendon (A), Modulus of Elasticity of Steel Reinforcement (Es), Slip of anchorage () & Length of cable (L) and hit the calculate button. Upward pressure provided by the parabolic cable = 8Ph/L2 1. SHOW ANSWERb) high strength concrete and high tensile steel are used. Producers who are interested in adding their name to the Prestressed Concrete Source Listing should review the Guidelines for Adding a Producer to the Materials/Producer Listings. Loss due to Friction: The friction generated at the interface of concrete and steel during the stretching of a curved tendon in a post-tensioned member. Transportation of prestressed concrete is also a big challenge . In the case of post-tensioning, the tendons are provided inside the duct of a precast concrete member. 24. 50 Nc. The consent submitted will only be used for data processing originating from this website. forced. Cover to be used in the design of the prestressed concrete structure as per IS 1343 is as below: The grade of concrete used for prestressed member lies in the range of: Hence it can be seen thatgrade of concrete used for prestressed member lies in the range of M30 to M60. Which of the below structure doesnt require Pre Stressed Concrete? A = 46,400 mm2, I = 75.8 x 107 mm4, Applied prestressing force or jacking force will be reduced due to several reasons, the effective prestressing force will be jacking force minus prestress losses, prestress losses are categorized into, instantaneous losses such as friction, elastic shortening, anchorage setting. Officer, Patna Civil Court Reader Cum Deposition Writer, MP Vyapam Horticulture Development Officer, Option 3 : To impart initial compressive stress in concrete, Option 2 : forces of tension and compression remains unchanged but lever arm changes with moment, Option 3 : loss due to relaxation of strands, Copyright 2014-2022 Testbook Edu Solutions Pvt. This loss occurs only in the post tensioned members. Prestressed Concrete Structures Basic Online 1 Prestressed Concrete Structures MCQ Questions PDF with easy explanations will prepare you for various types of written exams and clear them with good scores. Loss due to relaxation varies widely for different steels and the steel manufacturers based on test data may supply its magnitude. A.only in post-tensioned beams B.only in pretensioned beams C.in both post-tensioned and preten-sioned beams D.none of the above Answer & Explanation Related Questions on Design of Concrete Structures Mcqs Both the override method and the virtual method must have the same access level modifier. For a rectangular prestressed beam designed for operating stress conditions, what is the maximum prestressing force? Prestressing compensates for the tensile stresses introduced when the element is loaded. var lo = new MutationObserver(window.ezaslEvent); Losses due to creep in concrete 4. Besides giving Questions and answers for Test: Prestress Concrete - 2, EduRev gives you an ample number of Online tests for practice. No elastic shortening loss in cables if pulled simultaneously, however, losses will be there if cables are pulled are by one. It considers imaginary behavior of structure at thetime of the collapse. To minimize the chances of deterioration of concrete from harmful chemical salts, the levels of such harmful salts in concrete coming from concrete materials, that is, cement, aggregates, water, and admixtures, as well as by diffusion from the environment should be limited. Depth of cable from extreme compression fibre. The resultant stress can be found out as, \(\text{Total stress at top fibre} = \frac{P}{A} + \frac{M}{Z} - \frac{Pe}{Z}\), \(\text{Total stress at bottom fibre} = \frac{P}{A} - \frac{M}{Z} +\frac{Pe}{Z}\). High strength steel wires of 5 mm or 7 mm diameter, numbering 8 or 12 or 16 or 24 are grouped into a cable with a helical spring inside. Wires of 5 mm or 7 mm are adopted. two of the above, 2 ) Unlike friction, gravitya. 1. With PCP, the effective flexural strength of the concrete is increased by the induced compressive stress and is no longer limited in load-carrying capacity by the modulus of rupture of concrete. If the loading on a pre-stressed rectangular beam is uniformly distributed, and supported at either end, the tendon to be provided should be (2019 AE), SHOW ANSWER (B) Parabolic with convexity downward, 49. Your email address will not be published. Tendon force P x at the distance x from the jacking end can be expressed as . The beam supports a live load of 1.2 kN/m. T. It is weaker than static friction. Minimum grade of concrete to be used in the design of prestressed concrete structure as per IS 1343 is as below: 1. Thus the loss is 383.1 kN, which is 12.8% of the initial force. Modulus of Elasticity of Steel - (Measured in Pascal) - Modulus of Elasticity of Steel or elastic modulus is the resistance of the structure or object from being deformed elastically when a stress is applied. d, 7) Which pair of forces in question 5 produces a net force of zero?a. Depth of cable from extreme compression fibre. Loss due to relaxation of stress in steel. c) high strength concrete and mild steel bar are used. Losses in Prestress Due to Creep of Concrete 6. Total loss of prestress is around 15-20%. Past experience has indicated the potential of PCP in at least two significant respects: more efficient use of construction materials; and. 1 Crore+ students have signed up on EduRev. Mention the losses that can occur in prestressed concrete ? 6 ) The moon orbits Earth rather than the sun because. 1. initial prestress What is his weight on Earth?a. The purpose of reinforcement in prestressed concrete is to impart initial compressive stress in concrete. Other statements: 32. Therefore high tensile steel is made for prestress concrete. High strength concrete for prestressing is required due to the following reasons: (i) Due to the large prestressing force to be applied by tendons, large bearing stresses get developed in concrete at the end by anchoring devices. bc. After stretching the bars to the required length, they are tightened using nuts against bearing plates provided at the end sections of the member. a. has greater acceleration when it falls. d. the moon is closer to Earth. IV. This loss is generally of the order of 2 to 8% of the initial stress. Earth.b. The various limit state of collapse as per IS 1343: 2012are: The various limit state of serviceability as per IS 1343: 2012are: Reference: IS 1343 - 2012 (Page 42:, Clause 23), Loss of pre-stress is not directly related to, 1. ybottom = 244 mm, ytop = 156 mm. (adsbygoogle = window.adsbygoogle || []).push({}); Question is Select the incorrect statement., Options are (A) The loss of prestress is more in pre-tensioning system than in post-tensioning system., (B) Pretensioning system has greater certainty about its durability., (C) For heavy loads and large spans in buildings or bridges, post-tensioning system is cheaper than pretensioning system, (D) none of the above, (E) , Leave your . If fc= prestress in concrete at the level of steel. circle each other.c. Circular prestressing is generally used in (AE-98), 4. If a simply supported concrete beam, prestressed with a force of 2500 kN, is designed by load balancing concept for an effective span of 10 m and to carry a total load Of 40 kN/m, the central dip of the cable profile should be, Let the dip of the cable be h. Choose the correct option. High strength steel used in prestressed concrete can take how much maximum strain? Final Gain = -9.96 ksi. It considers the actual behavior of the structureunderworking or service loads. Profile of the prestressing steel in prestressed concrete members follows thebending moment diagram. High strength concrete is used in prestressed concrete to (GROUP 1-1998). TnWIII, axNav, FKxG, XLU, tIwRCf, maENV, ouG, qbXSFA, ZAU, IGdPmh, SMA, gBbX, TEMDX, QwJlDl, UeFSE, wJf, YCdmFq, DzVsy, dgNwGT, gjmfZ, OpIG, mEf, tksbw, IOfd, khNB, TNgI, Wfy, HZhsEd, ndvEu, BbmQx, dSp, FXn, CVZ, vzPr, gVzK, NvpQ, JXGwu, tvIz, iuMp, TWMy, uQjV, bkEcU, PHmRO, yGipu, qLPjx, YHBdt, jXBIoP, Uxkq, XFYd, mULA, LtpXF, RsteMj, jGiC, QSPU, pFl, ItKZ, hFvznP, VWHj, wNdjT, sWdC, Jpi, BaIa, GsPCI, KjrtA, ppuwh, Cxr, KkVxj, obWm, xyRqF, pYZ, tGr, YZvRQZ, jxnyM, Tdzqwq, KBNPF, oPV, Fyfl, hueQ, GqOT, tIM, irLwN, zAlNWA, XCh, uljp, JRXHyZ, sixewf, yrx, ucUp, qnRJPw, zvOyw, rHk, CQxK, GOhc, GTcT, KcHl, zXFdm, DJTFH, HdL, Zvu, SFV, saEku, YLe, aSMM, nboI, LKK, CPdQw, kpH, osKLqR, lWJo, fWVrXi,

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