Reduced thickness of concrete, less traditional reinforcing steel, and adequate crack control. As a general rule, traditional reinforced concrete is the most economic method for a span of up to 6 m. Prestressed concrete is more economical when spans are over 9 m. Between 6 and 9 m, the two options must be considered according to the particular requirements as to which is the most suitable . This set of Prestressed Concrete Structures Multiple Choice Questions & Answers (MCQs) focuses on Advantages and Limitations. View Answer, 9. Absorption is a mechanism that can occur in the absence of hydrostatic pressure. Response Publications, Krishhna Raju N (2007) Prestressed concrete, 4th edn. View Answer, 5. Pre-stressing involves the application of an initial compressive load on a structure to reduce or eliminate the internal tensile forces and thereby control or eliminate cracking. This is achieved by drying the sample to a known moisture content, weighing it, exposing the bottom to water for a period of time and weighing it again. Prestressed Concrete Piles: Prestressed concrete piles have been used extensively in the construction of buildings and marine structures. Threats to concrete durability can originate from many different sources, but there is one primary strategy that will protect against the majority of those risks: reducing the permeability of the concrete and densifying it to prevent intrusion of harmful materials. Once that system is in place and working well, PRAs can offer additional reduction in permeability as well as the associated boost to one of precast concretes most important attributes: durability. Eng Struct 1(70):144157, Bachmann H, Steinle A (2011) Precast concrete structures. University Avenue Berkeley, California, United states of America, Mehetre AJ, BR N (2013) Analysis of pre-stressed floor grid system. PRA technology has come a long way in recent years and continues to evolve. Prestressed Concrete Poles - Design and Manufacturing Methods. It increases the ability of the concrete for energy absorption against sudden impact load. c) Shrinkage concrete Prestressed Concrete Box girder transported from Yard to Site Serviceability and Strength Reduces occurrence of cracks . Using prestressing and continuity, a designer can obtain a depth/span ratio as low or lower than 1:32. PSC uses high-strength steel and concrete in comparison to RC (Reinforced Concrete). c) Transfer Sam Lines, engineering manager with Concrete Sealants, said, As science is allowing us to know more about the cement hydration process, researchers are learning new and innovative approaches to creating nano-scale products which reduce the transport properties of liquids and gases through concrete. Part of Springer Nature. d) 10 to 20 percent Ernst & Sohn, Berlin, Irish precast concrete association IPCA, Precast concrete frames guide, Newlands Business park, Clondalkin, Dublin 22, Maya LF, Albajar L (2012) Beam-column connections for precast concrete frames using high performance fiber reinforced cement composites. The prestressing of concrete by using high tensile steel improve the efficiency of the materials. Disadvantages of Prestressed concrete. The P&PCSL has been implemented in 3 times construction projects after undergoing various performance tests and workability verification tests. The overall project was undertaken on a design-build basis and bid as a lump sum contract. Positive bending about a horizontal axis causes tension in the bottom . Once the concrete cures to its required strength, the tensioning is released. Overall cost optimization of Prestressed Concrete (PC) bridges is investigated in this study. Dense concrete is provided by prestressing systems thus improving the durability. b) Financial and land Home Prestressed Concrete Structures Objective Questions 250+ TOP MCQs on Advantages and Limitations and Answers. d) Loading structures In: Advanced materials research 2012, vol 568. This steel reinforcement is pulled to meet engineering specs. Use of longitudinally tensioned steel embedded in concrete or housed in ducts. a) Life of material View Answer. For low tension applications, such as slabs in buildings, using prestressed concrete is largely impractical. This test is popular because of its speed but is not always the most accurate test to determine permeability depending on mix design constituents. Details of Prestressed Concrete Processes London, CSI educational services (1995) From start to finish: model, design and optimize a multi-story concrete structures using ETABS. Due to its high strength for handling and a high degree of durability in seawater and other adverse environments, the use of prestressed concrete piles became very popular in the construction of marine structures. Concrete surfaces buried below the water table are subjected to hydrostatic pressure. 3. 2011-2022 Sanfoundry. The structures of prestressed concrete are less liable to ___________a) Bendingb) Loadingc) Placingd) CracksAnswer: dClarification: In case of fully prestressed members which are free from tensile stresses under working loads cross-section is more efficiently utilized when compared with a reinforced concrete section that is cracked under working loads. The structures of prestressed concrete are less liable to ___________ Building code requirements for structural concrete (ACI 31808) and commentary. Another reason to use it is to reduce the overall weight of the structure. ACI Committee. 2. Durability. Subject topics: Economics of prestressed concrete Subject layout: A prestressed member, when compared with an equivalent reinforced concrete member, requires less concrete, and about 1/5 . The application of prestressed concrete is done for depth ratios having ___________a) Small spanb) Larger spanc) Same spand) Equal spanAnswer: bClarification: Prestressed concrete is used for the construction of buildings and other structures which are having the value of span to depth ratio in large or for larger span members and other criteria such as equal, small, same span criteria are considered in various other structural members. b) Durability of material b) Prestressed concrete Study with Quizlet and memorize flashcards containing terms like _ is a mixture of portland cement, fine and coarse aggregate, and water that solidifies through a chemical reaction called hydration, A(n) _ is the section of a foundation that supports and distributes structural loads directly to the soil or piles., A(n) _ is a temporary structure or mold used to retain and support concrete . Whether the bag is added to the mixer, or the packaging is opened and the admixture is added manually, considerations must be given to the ease of doing so with every batch, and mitigation of any associated safety risks. Introducing prestress enables the elimination of joint metals and reduces the volume of reinforcement, thus reducing the manufacturing cost of precast concrete segments. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); 2022 National Precast Concrete Association. Good concreting practices aim to minimize these pores, capillaries and cracks and keep ingress and passage of liquids and gases through concrete to a minimum. 6. Some PRAs can bring about additional benefits to plastic and hardened concrete. View Answer, 6. It is economical for large-span structures only. In the next decade, the industry will see even more options available to the precast industry to reduce permeability, enhance durability and provide environmentally green solutions.. Army Corps of Engineers test CRD C48-92, Standard Test Method For Water Permeability Of Concrete.4 This test method consists of subjecting a concrete sample to water under 200 psi (1.38 MPa) of pressure. Lecture Notes in Civil Engineering, vol 221. In short, we can say that prestressed concrete is the method we use to precompress concrete beams using highly tensioned steel tendons (strand), wires, cables, and rods. Low permeability concrete can be achieved through the use of quality materials and proper manufacturing practices. Most PRAs have minimal negative interactions with other admixtures and cementitious materials, but suppliers may suggest slight modifications such as air entrainment dosage and HRWR type and/or dosage. 5. * Pre-tensioning * Post-tensioning Pre-tensioning method In this method, prestressing are induced (i.e . Published by Center for advanced engineering, New Zealand, Group of the New Zealand concrete society and the New Zealand society for Earthquake Engineering, Guidelines for the use of structural precast concrete in buildings, 2nd edn, Parastesh H, Hajirasouliha I, Ramezani R (2014) A new ductile moment-resisting connection for precast concrete frames in seismic regions: an experimental investigation. RCA consist of the original aggregate, surrounded by attached mortar. b) Loading Those considering using PRAs will want to know how they affect plastic concrete properties such as set times and slump or spread. The PRA dosing and sequencing must be determined by the product supplier. Published by the European concrete platform ASBL, Harry H. Design-construction of the paramounta 39-story precast prestressed concrete apartment building, Council FF (1974) National research council. Freezing & thawing durability is higher than non prestressed concrete Using pre-cast pre-cast concrete girder beam in housing projects can save 21% of the cost of reinforced concrete beams without taking into account the cost of connexion costs and actual transport, although a compressive study on the use of pre-tensioned cast-in-situ concrete to minimize the use of costly connexion information is required. The prestressed concrete piles have many . a) Bending All symbols are defined in the text where they first appear. Excess water left behind after the cement hydration may remain in the concrete after it hardens and create water-filled pores or dry out and leave air-filled pores. ASTM C1585, Standard Test Method for Measurement of Rate of Absorption of Water by Hydraulic-Cement Concretes.6 This test method measures absorption of water into a concrete sample. Agas - Agas Bridge The Agas-Agas Bridge is a prestressed concrete beam bridge on the Pan-Philippine Highway.The 1.024-billion bridge was funded partially by the Japan International Cooperation Agency.With a length of about 350 meters (1,150 ft) and a height of 89 meters (292 ft) above ground, the center span of the structure measures . Prestressing enhance shear strength and fatigue resistance of concrete. Pre-stressed concrete is substantially pre-stressed during manufacturing in such a way that it is reinforced against the tensile forces that may occur when in operation with an even stronger structural member Produced in the factory using pre-assembled forms, Casting and curing components transported directly to the site and ready for installation. 4. The overall economy in using prestressed concrete reduces? German standard DIN 1048 (Part 5) Testing of Hardened Concrete, Water Permeability.5 Measures water penetration into concrete samples subjected to 72.5 psi (0.5 MPa) of hydrostatic pressure over a period of three days. Shoring pretensioned beams and slabs before adding the composite topping can reduce member size even further. 11 The prestressing applied should prevent or permit only to a limited extent (partial prestressing) tensile stresses occurring within . It is practically impossible to make concrete completely impermeable, but permeability can be reduced to a point where it no longer poses a threat to a structures durability. The prestressing system works for a span greater than 35m. The concrete is then cast over the tendons. Int J Eng Res Appl (IJERA) 3(4), Ritz P, Matt P, Tellenbach C, Schlub P, Aeberhard HU (1985) Post-tensioned Slabs, 4.2 report series. These products are sometimes called densifiers, waterproofing admixtures or permeability reducing admixtures (PRA). Standard AA (2011) Building code requirements for structural concrete (ACI 318-11). The dead load of the structure will be reduced by using prestressed concrete, and it indirectly reduces the usage of steel and project cost. The prestressed concrete flexural member under working load conditions offers superior amount of ___________a) Flexibilityb) Rigidityc) Transferd) StabilityAnswer: bClarification: A superior amount of rigidity is offered by the prestressed concrete flexural members under the working load conditions when compared with that offered by reinforced concrete members of equal dimensions. c) 35 to 60 percent Click here to navigate to respective pages. Transcribed image text: Question 4 (1 point) Saved Listen The keys to Fabrication Economy in concrete pre casting are, Choice of Surface Texture Repetition and Piece Size Thickness of Panel Weight of Panel Question 5 (1 point) Saved Listen Prestressed concrete uses tension cables for which purpose? ASTM C1202, Standard Test Method for Electrical Indication of Concretes Ability to Resist Chloride Ion Penetration.7 This test method often is called the rapid chloride permeability (RCP) test. View Answer, 8. Required fields are marked *. 1. Required fields are marked *. Longevity of prestressed structure is greater than rcc structure because the reinforcement stays unaffected from outer agencies. While deeper sections will require less prestressing steel, the overall economy of a project may dictate the use of the lowest possible depth/span ratio. Permeability reducing admixtures also can be a valuable asset in the quest for enhancing durability.
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