An abstract method is implicitly a virtual method. , 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 An example of data being processed may be a unique identifier stored in a cookie. This loss is generally of the order of 2 to 8% of the initial stress. In our problem, for no tension at the bottom fibre i.e.
Types of Losses in Prestress of Prestressed Concrete the moon is smaller than Earth.c. Loss due to Relaxation:Relaxation is assumed to mean the loss of stress in steel under nearly constant strain at a constant temperature. 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. The lever arm for a given pre-stressed concrete beam section (AE 2010), c) will change if loading in the beam is changed. Table of Content 1. 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. 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. This results in an equal and simultaneous shortening of the pre-stressing steel. The loss of prestress due to shrinkage is obtained by. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); a) high tensile steel and ordinary concrete are, b) high strength concrete and high tensile steel, c) high strength concrete and mild steel bar are, d) high strength concrete and deformed bars are, Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window), Click to share on LinkedIn (Opens in new window), Click to share on WhatsApp (Opens in new window). The number of wires in magnel cable varies between (AE 2018), 37. a) high tensile steel and ordinary concrete are used. and the stress variation in the nonprestressed reinforcement is about 130 Nlmm2 (18.9 ksi).
Solved 2. Determine the final concrete stress (MPa) at the | Chegg.com Approximate Prestress Loss Values For Post-Tensioning . 2. losses in prestress
Friction Characteristics of Post-Tensioned Tendons of Full-Scale slow the descent.d. Considering the parabolic tendon upward force & moment is given by, \(w = \frac{{8Py}}{{{L^2}}}\)&\(M = \frac{{\left( {w - P} \right){L^2}}}{8}\).
Losses in Prestressed Concrete - Civil Ease 1 and 3 . Which two statements are true for any concrete class implementing the java.lang.Runnable interface? i.e M30 grade. The beam supports a live load of 1.2 kN/m. The acceptable limit for the safety and serviceability requirements before failure occurs is called a limit state. Explanation: The prestressing of concrete members is done to reduce the compressive stresses developed in the concrete members to the required extent while tensile stresses is the stress state where the length of member tends to expand in tension side while the volume remains constant, shear forces and bending stresses none of the above, 2 ) Which factors affect friction?a. B) Only in post-tensioned beams. Total Prestress Losses = (13.65 + 20.3) - 9.96 = 23.99Ksi. Prestressing is the process of introducing compressive stress to the concrete to counteract the tensile stresses resulting from an applied load. Prestressed Concrete Sources. 3. 1) Losses due to elastic shortening of concrete: The prestress loss due to elastic shortening in pre-tensioned members is taken as the concrete stress at the centroid of the prestressing steel at transfer, f cgp, multiplied by the ratio of the modulus of elasticities of the prestressing steel and the concrete at transfer. Sign in to download full-size image Relaxation of stress in steel. This method was introduced by a famous engineer. Precast elements may be prestressed during the construction process (pre-tensioning) or structures may be stressed once completed (post-tensioning). has greater acceleration when it falls.b. Loss of prestress affects - the strength of member and - member's serviceability [ Stresses in Concrete, Cracking, Camber and Deflection ] 7 8. The overridden base method must be virtual, abstract or override. has a weaker force of gravity.c. There are two types of the anchorage device in this system: The Freyssinet system was introduced by the French Engineer Freyssinet and it was the.
Loss of prestress, other than friction losses 1 General This lecture is a part of CS3001 Concrete Engineering subject for the third year Civil Engineering students at James Cook University, Townsville Australia. No loss due to elastic deformation if all the wires are simultaneously tensioned. Upward pressure provided by the parabolic cable = 8Ph/L2 M = external moment, Z = sectional modulus. Depth of cable from extreme compression fibre. In general, the stress distribution in the pre-stressed beam is shown in the following figure. Prestressing is the process of introducing compressive stress to the concrete to counteract the tensile stresses resulting from an applied load. a) Minimize elastic creep and shrinkage strains. The following loss does not occur in Pre-tensioning of concrete. Therefore high tensile steel is made for prestress concrete. two of the above, 3 ) What does weight measure?a. 3. depth of cable from extreme compression fibre II. loss due to anchorage does not occur in pre-tensioned members. none of the above.
An Experimental Study to Estimate Loss of Prestress and Determining If fc= prestress in concrete at the level of steel. It took until the 1920s and '30s for its materials development to progress to a level where prestressed concrete could be used with confidence. 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. two of the above, 3 ) If you pick up and carry a piece of heavy furniture, which type of friction do you have with the floor?a. P = prestressing force, A = cross sectional area. Also Read: MCQ worksheet Motion [PDF]Force & Motion Worksheet & numericalMachines MCQ. 7. This loss occurs only in the post tensioned members. The purpose of reinforcement in prestressed concrete is to impart initial compressive stress in concrete. Who should the lessees sue for damages? at the soffit of the beam, total stress at bottom fibre must be zero. 7 ) An object with greater massa. Mcqspage.com is a leading Website which provide Best online MCQ's solution with easy explanations for all competitive examination such as GK mcq question, english mcq question, arithmetic aptitude mcq question, Data Intpretation, Programing, Engeneering etc. Ltd.: All rights reserved. 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 . Please see the attached Screenshot for more information. How are they constructed? Force and Pressure Class 8 MCQs Questions with Answers.
Loss of Prestress due to Slip Calculator 7 losses in prestress - SlideShare 1. It has a higher modulus of elasticity and smaller creep strain. Prestress does not remain constant (reduces) with time. High strength steel used in prestressed concrete can take how much maximum strain? repel each other.b. Between the two ends, the spacing of the wires is maintained by spacers. Initial losses occur during stressing operation and include anchor seating, elastic shortening, and friction between prestressing steel and post-tensioning ducts or tendon deviators and harped. A concrete beam is pre-stressed by a cable carrying an initial pre-stressing force of 300 kN, the area is 300 mm2. 8Ph/L 2 = w = 40 h = 0.2 m h = 200 mm Test: Prestress Concrete - 2 - Question 4 Save For Post tensioning minimum grade of concrete used is M-30. The total acid-soluble chloride content should be calculated from the mix proportions and the measured chloride contents of each of the constituents. Let us discuss the types of losses in prestress given in the article below. 1 and 2 . Answer: Loss of prestressing in " pre-tensioned " members 1. ins.dataset.adClient = pid; It is stronger than sliding friction.d. 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. The major loss of pre-stress is due to(AE 2008), 15. forced. container.appendChild(ins); Manage Settings Reduction of prestress is nothing but the loss in prestress. Hence the concrete generally remains in compression. Shrinkage of concrete. The bursting stresses in pre-stressed concrete members are developed at, (GROUP 1-1998). (v) Use of high strength concrete reduces the size of concrete members thereby resulting in the reduction of self-weight of the member. This loss is generally of the order of 2 to 8% of the initial stress. 1. c) high strength concrete and mild steel bar are used. No loss due to elastic deformation if all the wires are simultaneously tensioned. But the most appropriate answer is option 4 because lesser creep deformation causes less stress loss. is a force.b. In a pre-stressed concrete member (AE 2007). It occurs when ball bearings are used.c. Choose the correct option. Load and moment in concrete are balanced by stressing the steel. \(\text{Total stress at bottom fibre} = \frac{P}{A} - \frac{M}{Z} +\frac{Pe}{Z}\)= 0, \( \frac{157\times 10^3}{150000} - \frac{M}{15\times 10^6} +\frac{157\times 10^3\times 100}{15\times 10^6} = 0\). In order this upward pressure may fully balance the external loading. This makes it possible to predict approximately how much prestress will be lost in a given kind of service.
Prestressed Concrete (Prestress loss) PC6 - YouTube (ii) Bursting stresses at the ends can not be effectively resisted by low-strength concrete. In a pre-stressed member, it is advisable to use (AE-1998), C) Low strength concrete but high tensile steel, D) High strength concrete & high tensile steel, SHOW ANSWER D) High strength concrete & high tensile steel, 7. After five years, the building developed cracks and its stairway eventually gave way and collapsed due to poor quality of materials used in the construction, resulting to injuries to some lessees. An abstract inherited property cannot be overridden in a derived class. 23. ab. SHOW ANSWER d) because high strength is desirable. III. If the bars are successively tensioned, there will be loss of prestress due to elastic deformation of concrete.
Losses in prestress - SlideShare In pre-stressed concrete, for post-tensioned members, the minimum 28 days compressive strength of concrete prescribed in IS 1343 (AE 2015), 19. It is weaker than static friction. c. Earth already orbits the sun. The box has less mass when it is moving.c. is less affected by gravity.d. Cover to be used in the design of prestressed concrete structure as per IS 1343 is as below: 1. 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. A listing of sources with accepted quality control plans. 3 ) Why is it easier to slide a heavy box over a floor than it is to start it sliding in the first place?a. Copyright 2022 All rights reserved. = 40h = 0.2 m Which of the following are necessary for Run-time Polymorphism?
Losses in prestressed concrete - SlideShare ins.style.minWidth = container.attributes.ezaw.value + 'px'; 3 alone . 8Ph/L2= w It is obvious from Hooke's law, that if we have a change in strain, there will be a change in the stress. b. has a weaker force of gravity. Ravindra and Markandeya Raju (2012) [34] formulated a procedure for finding loss of prestress in prestressing steel beams and studied the performance of prestressed steel I-beams and compound . motion.b. But total loss of prestress is more in Pre-tensioned concrete compare to Post-tensioned concrete. Even during prestressing of tendons, and transfer of prestress, there is a drop of prestress from the initially applied stress. The consent submitted will only be used for data processing originating from this website. The primary purpose of prestressing steel is to apply a force to a concrete, either by bond or by means of special anchoring devices. World's best MCQs website Civil Engineering, Consider the following factors :1. 2. a. the sun's gravity is weaker than Earth's. b. the moon is smaller than Earth. All constituents may contain chlorides and concrete may be contaminated by chlorides from the external environment. the suns gravity is weaker than Earths.b. As per IS 1343 1980, the minimum 28 days compressive strength for pre-tensioned member is: the minimum 28 days compressive strength for pre-tensioned member is: M 40 or40 N/mm2, The purpose of reinforcement in prestressed concrete is. P/A = Pe/Z pre-stressed concrete structure for long spans. The diameter of the bar is between 12 and 28 mm. 11. Cables with as many as 64 wires are also used under special conditions. a. has greater acceleration when it falls. The gradual reduction of this introduced compressive stress in a prestressed member due to various reasons is called losses of prestress. MCQ Geeks 0 : 0 : 1; . Initial prestress 2. The change of prestress loss is highly related to the distribution of cracks.
Losses in Pre Stress due to Elastic Shortening Losses due to shrinkage of concrete The frictional losses and losses due to anchorage slip are observed . 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. var ffid = 2; (If pre-tensioning is asked then M40 will be the answer), The minimum grade of concrete that can be used for pre-tensioned beam system is. It considers imaginary behavior of structure at thetime of the collapse. 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 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. 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. friction.c. The pressure which is exerted by air around us is known as. d, 1) Friction occurs becausea. 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. Figure 14 shows the 3-D time-dependent prestress loss of the loaded beam measured by the BOTDA sensors in the smart steel strand at the normal service limit state. 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. I. Pre-stressed concrete structures are most economical. Then select the cables, choose Assign Cable Loads Target Force, then define the initial prestress forces for the cables. To impart initial compressive stress in concrete, Limit state of collapse: Maximum compression, In absence of test data, the approximate value of shrinkage strain for design shall be considered as -, The value of the total shrinkage strain is given by -. Answer: a Clarification: The loss due to elastic deformation of concrete depends on the modular ratio and the average stress in concrete at the level of steel, consider a post tensioned member which is prestressed by a single tendon and the shortening of concrete occurs till the tendon is jacked and no shortening of concrete is observed after it. A had a 4-storey building which was constructed by Engineer B and at the same time the contractor. Which of the below structure doesnt require Pre Stressed Concrete? (ii) If the beam is tensioned from both ends, the minimum prestress force is at the centre of the beam.
Prestress Loss| Concrete Construction Magazine In the calculation of the design forces in tendons at various stages considered in design, allowance should be made for the appropriate losses of prestress resulting from: b) the elastic deformation and subsequent shrinkage and creep of the concrete; c) slip or movement of tendons at . 31.
Prestressed Concrete Design - SlideShare Loss in prestress = Initial prestress - effective prestress. {\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. In this question, many options are correct i.e. The main effect of creep of concrete on a reinforced concrete member is to (AE 1999), b) Increase the modulus of elasticity of concrete, c) Decrease the modulus of elasticity of concrete, SHOW ANSWER c) Decrease the modulus of elasticity of concrete, 26. Anupam M (NIT graduate) is the founder-blogger of this site. Friction loss has two components, including the length or wobble effect and the curvature effect. Theloss due to anchorage does not occur in pre-tensioned members. Loss of pre-stress takes place due to shrinkage of concrete.
Design of Prestressed Concrete Part 2 - CivilDigital acts between objects that are not touching.d. all of the above, 2) Examples of forces includea. It is similar to creep of concrete. The loss of strength in compression due to overloading is known as (AE 2008), 14. 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. 2. 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. mcqsclouds.com Prestress loss due to friction occurs________________?
bc.
[MCQ] If the loss of prestress is excessive resulting in tensile cracks II. 1 Crore+ students have signed up on EduRev. two of the above, 3) If gravity pulls you down toward the center of Earth with a force of 500 N, how much upward force does the ground exert on you?a. (adsbygoogle = window.adsbygoogle || []).push({}); Precast prestressed concrete used in the construction of dynamically loaded structures such as railway bridges and machine foundations and in the construction of long-span floors and roofs. 3. 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. For Post-tensioning minimum grade of concrete used is M-30.
Loss in Prestress when Shrinkage Strain is Given Calculator Assume a prestress loss of 10% of the initial prestressing force. 500 Nd. 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. The class definition must include the words implements. The cable is inserted into the duct. A minimum grade of concrete to be used in the design of the prestressed concrete structure as per IS 1343 is as below: 1.
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