Comparison of non-prestressed beam (top) and prestressed concrete beam (bottom) under load:
1. Non-prestressed beam without load
2. Non-prestressed beam with load
3. Before concrete solidifies, tendons embedded in concrete are tensioned
4. After concrete solidifies, tendons apply compressive stress to concrete
5. Prestressed beam without load
6. Prestressed beam with load
1. Non-prestressed beam without load
2. Non-prestressed beam with load
3. Before concrete solidifies, tendons embedded in concrete are tensioned
4. After concrete solidifies, tendons apply compressive stress to concrete
5. Prestressed beam without load
6. Prestressed beam with load
Is similar to that taken when designing with reinforced concrete. One difference between these two approaches is that a stress equal to 80% of f’m is assumed to act over the effective area of masonry when evaluating pure axial compression for reinforced masonry (this is 85% for reinforced concrete). “structural concrete reinforced with no less than the minimum amount of prestressing tendons or nonprestressed reinforcement as specified by ACI 318.” Concrete is basically a good insulator. It doesn’t allow heat to pass through it easily.
Prestressed concrete is a form of concrete used in construction. It is substantially 'prestressed' (compressed) during its fabrication, in a manner that strengthens it against tensile forces which will exist when in service.[1][2]:3–5[3]
This compression is produced by the tensioning of high-strength 'tendons' located within or adjacent to the concrete and is done to improve the performance of the concrete in service.[4] Tendons may consist of single wires, multi-wire strands or threaded bars that are most commonly made from high-tensile steels, carbon fiber or aramid fiber.[1]:52–59 The essence of prestressed concrete is that once the initial compression has been applied, the resulting material has the characteristics of high-strength concrete when subject to any subsequent compression forces and of ductile high-strength steel when subject to tension forces. This can result in improved structural capacity and/or serviceability compared with conventionally reinforced concrete in many situations.[5][2]:6 In a prestressed concrete member, the internal stresses are introduced in a planned manner so that the stresses resulting from the superimposed loads are counteracted to the desired degree.
Prestressed concrete is used in a wide range of building and civil structures where its improved performance can allow for longer spans, reduced structural thicknesses, and material savings compared with simple reinforced concrete. Typical applications include high-rise buildings, residential slabs, foundation systems, bridge and dam structures, silos and tanks, industrial pavements and nuclear containment structures.[6]
First used in the late-nineteenth century,[1] prestressed concrete has developed beyond pre-tensioning to include post-tensioning, which occurs after the concrete is cast. Tensioning systems may be classed as either monostrand, where each tendon's strand or wire is stressed individually, or multi-strand, where all strands or wires in a tendon are stressed simultaneously.[5] Tendons may be located either within the concrete volume (internal prestressing) or wholly outside of it (external prestressing). While pre-tensioned concrete uses tendons directly bonded to the concrete, post-tensioned concrete can use either bonded or unbonded tendons.
- 2Post-tensioned concrete
- 4Applications
- 4.2Civil structures
Pre-tensioned concrete[edit]
Pre-tensioning process
Pre-tensioned bridge girder in precasting bed, with single-strand tendons exiting through the formwork
Pre-tensioned concrete is a variant of prestressed concrete where the tendons are tensioned prior to the concrete being cast.[1]:25 The concrete bonds to the tendons as it cures, following which the end-anchoring of the tendons is released, and the tendon tension forces are transferred to the concrete as compression by static friction.[5]:7
Pre-tensioning is a common prefabrication technique, where the resulting concrete element is manufactured remotely from the final structure location and transported to site once cured. It requires strong, stable end-anchorage points between which the tendons are stretched. These anchorages form the ends of a 'casting bed' which may be many times the length of the concrete element being fabricated. This allows multiple elements to be constructed end-to-end in the one pre-tensioning operation, allowing significant productivity benefits and economies of scale to be realized.[5][7]
The amount of bond (or adhesion) achievable between the freshly set concrete and the surface of the tendons is critical to the pre-tensioning process, as it determines when the tendon anchorages can be safely released. Higher bond strength in early-age concrete will speed production and allow more economical fabrication. To promote this, pre-tensioned tendons are usually composed of isolated single wires or strands, which provides a greater surface area for bonding than bundled-strand tendons.[5]
Pre-tensioned hollow-core plank being placed
Unlike those of post-tensioned concrete (see below), the tendons of pre-tensioned concrete elements generally form straight lines between end-anchorages. Where 'profiled' or 'harped' tendons[8] are required, one or more intermediate deviators are located between the ends of the tendon to hold the tendon to the desired non-linear alignment during tensioning.[1]:68–73[5]:11 Such deviators usually act against substantial forces, and hence require a robust casting-bed foundation system. Straight tendons are typically used in 'linear' precast elements, such as shallow beams, hollow-core planks and slabs; whereas profiled tendons are more commonly found in deeper precast bridge beams and girders.
Pre-tensioned concrete is most commonly used for the fabrication of structural beams, floor slabs, hollow-core planks, balconies, lintels, driven piles, water tanks and concrete pipes.
Post-tensioned concrete[edit]
Forces on post-tensioned concrete with profiled (curved) tendon
Post-tensioned tendon anchorage; four-piece 'lock-off' wedges are visible holding each strand
Post-tensioned concrete is a variant of prestressed concrete where the tendons are tensioned after the surrounding concrete structure has been cast.[1]:25
The tendons are not placed in direct contact with the concrete, but are encapsulated within a protective sleeve or duct which is either cast into the concrete structure or placed adjacent to it. At each end of a tendon is an anchorage assembly firmly fixed to the surrounding concrete. Once the concrete has been cast and set, the tendons are tensioned ('stressed') by pulling the tendon ends through the anchorages while pressing against the concrete. The large forces required to tension the tendons result in a significant permanent compression being applied to the concrete once the tendon is 'locked-off' at the anchorage.[1]:25[5]:7 The method of locking the tendon-ends to the anchorage is dependent upon the tendon composition, with the most common systems being 'button-head' anchoring (for wire tendons), split-wedge anchoring (for strand tendons), and threaded anchoring (for bar tendons).[1]:79–84
Balanced-cantilever bridge under construction. Each added segment is supported by post-tensioned tendons
Tendon encapsulation systems are constructed from plastic or galvanised steel materials, and are classified into two main types: those where the tendon element is subsequently bonded to the surrounding concrete by internal grouting of the duct after stressing (bonded post-tensioning); and those where the tendon element is permanently debonded from the surrounding concrete, usually by means of a greased sheath over the tendon strands (unbonded post-tensioning).[1]:26[5]:10
Casting the tendon ducts/sleeves into the concrete before any tensioning occurs allows them to be readily 'profiled' to any desired shape including incorporating vertical and/or horizontal curvature. When the tendons are tensioned, this profiling results in reaction forces being imparted onto the hardened concrete, and these can be beneficially used to counter any loadings subsequently applied to the structure.[2]:5–6[5]:48:9–10
Bonded post-tensioning[edit]
Multi-strand post-tensioning anchor
In bonded post-tensioning, prestressing tendons are permanently bonded to the surrounding concrete by the in situgrouting of their encapsulating ducting (after tendon tensioning). This grouting is undertaken for three main purposes: to protect the tendons against corrosion; to permanently 'lock-in' the tendon pre-tension, thereby removing the long-term reliance upon the end-anchorage systems; and to improve certain structural behaviors of the final concrete structure.[9]
Bonded post-tensioning characteristically uses tendons each comprising bundles of elements (e.g. strands or wires) placed inside a single tendon duct, with the exception of bars which are mostly used unbundled. This bundling makes for more efficient tendon installation and grouting processes, since each complete tendon requires only one set of end-anchorages and one grouting operation. Ducting is fabricated from a durable and corrosion-resistant material such as plastic (e.g. polyethylene) or galvanised steel, and can be either round or rectangular/oval in cross-section.[2]:7 The tendon sizes used are highly dependent upon the application, ranging from building works typically using between 2 and 6 strands per tendon, to specialized dam works using up to 91 strands per tendon.
Fabrication of bonded tendons is generally undertaken on-site, commencing with the fitting of end-anchorages to formwork, placing the tendon ducting to the required curvature profiles, and reeving (or threading) the strands or wires through the ducting. Following concreting and tensioning, the ducts are pressure-grouted and the tendon stressing-ends sealed against corrosion.[5]:2
Unbonded post-tensioning[edit]
Unbonded slab post-tensioning. (Above) Installed strands and edge-anchors are visible, along with prefabricated coiled strands for the next pour. (Below) End-view of slab after stripping forms, showing individual strands and stressing-anchor recesses.
Unbonded post-tensioning differs from bonded post-tensioning by allowing the tendons permanent freedom of longitudinal movement relative to the concrete. This is most commonly achieved by encasing each individual tendon element within a plastic sheathing filled with a corrosion-inhibiting grease, usually lithium based. Anchorages at each end of the tendon transfer the tensioning force to the concrete, and are required to reliably perform this role for the life of the structure.[9]:1
Unbonded post-tensioning can take the form of:
- Individual strand tendons placed directly into the concreted structure (e.g. buildings, ground slabs), or
- Bundled strands, individually greased-and-sheathed, forming a single tendon within an encapsulating duct that is placed either within or adjacent to the concrete (e.g. restressable anchors, external post-tensioning)
For individual strand tendons, no additional tendon ducting is used and no post-stressing grouting operation is required, unlike for bonded post-tensioning. Permanent corrosion protection of the strands is provided by the combined layers of grease, plastic sheathing, and surrounding concrete. Where strands are bundled to form a single unbonded tendon, an enveloping duct of plastic or galvanised steel is used and its interior free-spaces grouted after stressing. In this way, additional corrosion protection is provided via the grease, plastic sheathing, grout, external sheathing, and surrounding concrete layers.[9]:1
Individually greased-and-sheathed tendons are usually fabricated off-site by an extrusion process. The bare steel strand is fed into a greasing chamber and then passed to an extrusion unit where molten plastic forms a continuous outer coating. Finished strands can be cut-to-length and fitted with 'dead-end' anchor assemblies as required for the project.
Comparison between bonded and unbonded post-tensioning[edit]
Both bonded and unbonded post-tensioning technologies are widely used around the world, and the choice of system is often dictated by regional preferences, contractor experience, or the availability of alternative systems. Either one is capable of delivering code-compliant, durable structures meeting the structural strength and serviceability requirements of the designer.[9]:2
The benefits that bonded post-tensioning can offer over unbonded systems are:
- Reduced reliance on end-anchorage integrity
Following tensioning and grouting, bonded tendons are connected to the surrounding concrete along their full length by high-strength grout. Once cured, this grout can transfer the full tendon tension force to the concrete within a very short distance (approximately 1 metre). As a result, any inadvertent severing of the tendon or failure of an end anchorage has only a very localised impact on tendon performance, and almost never results in tendon ejection from the anchorage.[2]:18[9]:7 - Increased ultimate strength in flexure
With bonded post-tensioning, any flexure of the structure is directly resisted by tendon strains at that same location (i.e. no strain re-distribution occurs). This results in significantly higher tensile strains in the tendons than if they were unbonded, allowing their full yield strength to be realised, and producing a higher ultimate load capacity.[2]:16–17[5]:10 - Improved crack-control
In the presence of concrete cracking, bonded tendons respond similarly to conventional reinforcement (rebar). With the tendons fixed to the concrete at each side of the crack, greater resistance to crack expansion is offered than with unbonded tendons, allowing many design codes to specify reduced reinforcement requirements for bonded post-tensioning.[9]:4[10]:1 - Improved fire performance
The absence of strain redistribution in bonded tendons may limit the impact that any localised overheating has on the overall structure. As a result, bonded structures may display a higher capacity to resist fire conditions than unbonded ones.[11]
The benefits that unbonded post-tensioning can offer over bonded systems are:
- Ability to be prefabricated
Unbonded tendons can be readily prefabricated off-site complete with end-anchorages, facilitating faster installation during construction. Additional lead time may need to be allowed for this fabrication process. - Improved site productivity
The elimination of the post-stressing grouting process required in bonded structures improves the site-labour productivity of unbonded post-tensioning.[9]:5 - Improved installation flexibility
Unbonded single-strand tendons have greater handling flexibility than bonded ducting during installation, allowing them a greater ability to be deviated around service penetrations or obstructions.[9]:5 - Reduced concrete cover
Unbonded tendons may allow some reduction in concrete element thickness, as their smaller size and increased corrosion protection may allow them to be placed closer to the concrete surface.[2]:8 - Simpler replacement and/or adjustment
Being permanently isolated from the concrete, unbonded tendons are able to be readily de-stressed, re-stressed and/or replaced should they become damaged or need their force levels to be modified in-service.[9]:6 - Superior overload performance
Although having a lower ultimate strength than bonded tendons, unbonded tendons' ability to redistribute strains over their full length can give them superior pre-collapse ductility. In extremes, unbonded tendons can resort to a catenary-type action instead of pure flexure, allowing significantly greater deformation before structural failure.[12]
Tendon durability and corrosion protection[edit]
Long-term durability is an essential requirement for prestressed concrete given its widespread use.Research on the durability performance of in-service prestressed structures has been undertaken since the 1960s,[13] and anti-corrosion technologies for tendon protection have been continually improved since the earliest systems were developed.[14]
The durability of prestressed concrete is principally determined by the level of corrosion protection provided to any high-strength steel elements within the prestressing tendons. Also critical is the protection afforded to the end-anchorage assemblies of unbonded tendons or cable-stay systems, as the anchorages of both of these are required to retain the prestressing forces. Failure of any of these components can result in the release of prestressing forces, or the physical rupture of stressing tendons.
Modern prestressing systems deliver long-term durability by addressing the following areas:
- Tendon grouting (bonded tendons)
Bonded tendons consist of bundled strands placed inside ducts located within the surrounding concrete. To ensure full protection to the bundled strands, the ducts must be pressure-filled with a corrosion-inhibiting grout, without leaving any voids, following strand-tensioning. - Tendon coating (unbonded tendons)
Unbonded tendons comprise individual strands coated in an anti-corrosion grease or wax, and fitted with a durable plastic-based full-length sleeve or sheath. The sleeving is required to be undamaged over the tendon length, and it must extend fully into the anchorage fittings at each end of the tendon. - Double-layer encapsulation
Prestressing tendons requiring permanent monitoring and/or force adjustment, such as stay-cables and re-stressable dam anchors, will typically employ double-layer corrosion protection. Such tendons are composed of individual strands, grease-coated and sleeved, collected into a strand-bundle and placed inside encapsulating polyethylene outer ducting. The remaining void space within the duct is pressure-grouted, providing a multi-layer polythene-grout-plastic-grease protection barrier system for each strand. - Anchorage protection
In all post-tensioned installations, protection of the end-anchorages against corrosion is essential, and critically so for unbonded systems.
Several durability-related events are listed below:
- Ynys-y-Gwas bridge, West Glamorgan, Wales, 1985
A single-span, precast-segmental structure constructed in 1953 with longitudinal and transverse post-tensioning. Corrosion attacked the under-protected tendons where they crossed the in-situ joints between the segments, leading to sudden collapse.[14]:40 - Scheldt River bridge, Melle, Belgium, 1991
A three-span prestressed cantilever structure constructed in the 1950s. Inadequate concrete cover in the side abutments resulted in tie-down cable corrosion, leading to a progressive failure of the main bridge span and the death of one person.[15] - UK Highways Agency, 1992
Following discovery of tendon corrosion in several bridges in England, the Highways Agency issued a moratorium on the construction of new internally grouted post-tensioned bridges and embarked on a 5-year programme of inspections on its existing post-tensioned bridge stock. The moratorium was lifted in 1996.[16][17] - Pedestrian bridge, Charlotte Motor Speedway, North Carolina, US, 2000
A multi-span steel and concrete structure constructed in 1995. An unauthorised chemical was added to the tendon grout to speed construction, leading to corrosion of the prestressing strands and the sudden collapse of one span, injuring many spectators.[18] - Hammersmith Flyover London, England, 2011
Sixteen-span prestressed structure constructed in 1961. Corrosion from road de-icing salts was detected in some of the prestressing tendons, necessitating initial closure of the road while additional investigations were done. Subsequent repairs and strengthening using external post-tensioning was carried out and completed in 2015.[19][20] - Petrulla Viaduct, Sicily, Italy, 2014
One span of the viaduct collapsed on 7 July due to corrosion of the post-tensioning tendons. - Genoa bridge collapse, 2018. The Ponte Morandi was a cable-stayed bridge characterised by a prestressed concrete structure for the piers, pylons and deck, very few stays, as few as two per span, and a hybrid system for the stays constructed from steel cables with prestressed concrete shells poured on. The concrete was only prestressed to 10 MPa, resulting in it being prone to cracks and water intrusion, which caused corrosion of the embedded steel.
Applications[edit]
Prestressed concrete is a highly versatile construction material as a result of it being an almost ideal combination of its two main constituents: high-strength steel, pre-stretched to allow its full strength to be easily realised; and modern concrete, pre-compressed to minimise cracking under tensile forces.[1]:12 Its wide range of application is reflected in its incorporation into the major design codes covering most areas of structural and civil engineering, including buildings, bridges, dams, foundations, pavements, piles, stadiums, silos, and tanks.[6]
Building structures[edit]
Building structures are typically required to satisfy a broad range of structural, aesthetic and economic requirements. Significant among these include: a minimum number of (intrusive) supporting walls or columns; low structural thickness (depth), allowing space for services, or for additional floors in high-rise construction; fast construction cycles, especially for multi-storey buildings; and a low cost-per-unit-area, to maximise the building owner's return on investment.
The prestressing of concrete allows 'load-balancing' forces to be introduced into the structure to counter in-service loadings. This provides many benefits to building structures:
- Longer spans for the same structural depth
Load balancing results in lower in-service deflections, which allows spans to be increased (and the number of supports reduced) without adding to structural depth. - Reduced structural thickness
For a given span, lower in-service deflections allows thinner structural sections to be used, in turn resulting in lower floor-to-floor heights, or more room for building services. - Faster stripping time
Typically, prestressed concrete building elements are fully stressed and self-supporting within five days. At this point they can have their formwork stripped and re-deployed to the next section of the building, accelerating construction 'cycle-times'. - Reduced material costs
The combination of reduced structural thickness, reduced conventional reinforcement quantities, and fast construction often results in prestressed concrete showing significant cost benefits in building structures compared to alternative structural materials.
Some notable building structures constructed from prestressed concrete include: Sydney Opera House[21] and World Tower, Sydney;[22]St George Wharf Tower, London;[23]CN Tower, Toronto;[24]Kai Tak Cruise Terminal[25] and International Commerce Centre, Hong Kong;[26]Ocean Heights 2, Dubai;[27]Eureka Tower, Melbourne;[28]Torre Espacio, Madrid;[29] Guoco Tower (Tanjong Pagar Centre), Singapore;[30]Zagreb International Airport, Croatia;[31] and Capital Gate, Abu Dhabi UAE.[32]
- ICC tower, Hong Kong
484m 2010 - Guoco Tower, Singapore
290m 2016 - Sydney Opera House
1973 - Kai Tak Terminal
Hong Kong 2013 - World Tower, Sydney
230m 2004 - Ocean Heights 2, Dubai
335m 2016 - Eureka Tower, Melbourne
297m 2006 - Torre Espacio, Madrid
230m 2008 - Capital Gate, Abu Dhabi
18° lean 2010
Civil structures[edit]
Bridges[edit]
Concrete is the most popular structural material for bridges, and prestressed concrete is frequently adopted.[33][34] When investigated in the 1940s for use on heavy-duty bridges, the advantages of this type of bridge over more traditional designs was that it is quicker to install, more economical and longer-lasting with the bridge being less lively.[35][36] One of the first bridges built in this way is the Adam Viaduct, a railway bridge constructed 1946 in the UK.[37] By the 1960s, prestressed concrete largely superseded reinforced concrete bridges in the UK, with box girders being the dominant form.[38]
In short-span bridges of around 10 to 40 metres (30 to 130 ft), prestressing is commonly employed in the form of precast pre-tensioned girders or planks.[39] Medium-length structures of around 40 to 200 metres (150 to 650 ft), typically use precast-segmental, in-situbalanced-cantilever and incrementally-launched designs.[40] For the longest bridges, prestressed concrete deck structures often form an integral part of cable-stayed designs.[41]
Dams[edit]
Concrete dams have used prestressing to counter uplift and increase their overall stability since the mid-1930s.[42][43] Prestressing is also frequently retro-fitted as part of dam remediation works, such as for structural strengthening, or when raising crest or spillway heights.[44][45]
Most commonly, dam prestressing takes the form of post-tensioned anchors drilled into the dam's concrete structure and/or the underlying rock strata. Such anchors typically comprise tendons of high-tensile bundled steel strands or individual threaded bars. Tendons are grouted to the concrete or rock at their far (internal) end, and have a significant 'de-bonded' free-length at their external end which allows the tendon to stretch during tensioning. Tendons may be full-length bonded to the surrounding concrete or rock once tensioned, or (more commonly) have strands permanently encapsulated in corrosion-inhibiting grease over the free-length to permit long-term load monitoring and re-stressability.[46]
Silos and tanks[edit]
Circular storage structures such as silos and tanks can use prestressing forces to directly resist the outward pressures generated by stored liquids or bulk-solids.Horizontally curved tendons are installed within the concrete wall to form a series of hoops, spaced vertically up the structure. When tensioned, these tendons exert both axial (compressive) and radial (inward) forces onto the structure, which can directly oppose the subsequent storage loadings. If the magnitude of the prestress is designed to always exceed the tensile stresses produced by the loadings, a permanent residual compression will exist in the wall concrete, assisting in maintaining a watertight crack-free structure.[47][48][49][50]:61
Nuclear and blast-containment structures[edit]
Prestressed concrete has been established as a reliable construction material for high-pressure containment structures such as nuclear reactor vessels and containment buildings, and petrochemical tank blast-containment walls. Using prestressing to place such structures into an initial state of bi-axial or tri-axial compression increases their resistance to concrete cracking and leakage, while providing a proof-loaded, redundant and monitorable pressure-containment system.[51][52][53]:585–594
Nuclear reactor and containment vessels will commonly employ separate sets of post-tensioned tendons curved horizontally or vertically to completely envelop the reactor core. Blast containment walls, such as for liquid natural gas (LNG) tanks, will normally utilise layers of horizontally-curved hoop tendons for containment in combination with vertically looped tendons for axial wall prestressing.
Hardstands and pavements[edit]
Heavily loaded concrete ground-slabs and pavements can be sensitive to cracking and subsequent traffic-driven deterioration. As a result, prestressed concrete is regularly used in such structures as its pre-compression provides the concrete with the ability to resist the crack-inducing tensile stresses generated by in-service loading. This crack-resistance also allows individual slab sections to be constructed in larger pours than for conventionally reinforced concrete, resulting in wider joint spacings, reduced jointing costs and less long-term joint maintenance issues.[53]:594–598[54] Initial works have also been successfully conducted on the use of precast prestressed concrete for road pavements, where the speed and quality of the construction has been noted as being beneficial for this technique.[55]
Some notable civil structures constructed using prestressed concrete include: Gateway Bridge, Brisbane Australia;[56]Incheon Bridge, South Korea;[57]Roseires Dam, Sudan;[58]Wanapum Dam, Washington, US;[59]LNG tanks, South Hook, Wales; Cement silos, Brevik Norway; Autobahn A73 bridge, Itz Valley, Germany; Ostankino Tower, Moscow, Russia; CN Tower, Toronto, Canada; and Ringhals nuclear reactor, Videbergshamn Sweden.[51]:37
- Gateway Bridge
Brisbane, Aust. - Incheon Bridge
South Korea - Autobahn A73
Itz Valley, Germany - Ostankino Tower
Moscow, Russia - CN Tower
Toronto, Canada - Norcem silos
Brevik, Norway - Roseires Dam
Ad Damazin, Sudan - Wanapum Dam
Washington, US - LNG tanks
South Hook, Wales - Ringhals nuclear plant
Videbergshamn, Sweden
Design agencies and regulations[edit]
Worldwide, many professional organizations exist to promote best practices in the design and construction of prestressed concrete structures. In the United States, such organizations include the Post-Tensioning Institute (PTI) and the Precast/Prestressed Concrete Institute (PCI).[60] Similar bodies include the Canadian Precast/Prestressed Concrete Institute (CPCI),[61] the UK's Post-Tensioning Association,[62] the Post Tensioning Institute of Australia[63] and the South African Post Tensioning Association.[64] Europe has similar country-based associations and institutions.
It is important to note that these organizations are not the authorities of building codes or standards, but rather exist to promote the understanding and development of prestressed concrete design, codes and best practices.
Rules and requirements for the detailing of reinforcement and prestressing tendons are specified by individual national codes and standards such as:
- European Standard EN 1992-2:2005 – Eurocode 2: Design of Concrete Structures;
- US Standard ACI318: Building Code Requirements for Reinforced Concrete; and
- Australian Standard AS 3600-2009: Concrete Structures.
See also[edit]
Wikimedia Commons has media related to Prestressed concrete. |
- Dyckerhoff & Widmann AG (Dywidag)
References[edit]
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- ^Schofield, Jeff (2012). 'Case Study: Capital Gate, Abu Dhabi'(PDF). CTBUH Journal (11). Retrieved 2 September 2016.
- ^Man-Chung, Tang (2007). 'Evolution of Bridge Technology'(PDF). IABSE Symposium Proceedings: 7. Retrieved 5 September 2016.
- ^Hewson, Nigel R. (2012). Prestressed Concrete bridges: design and Construction. ICE. ISBN9780727741134. Retrieved 2 September 2016.
- ^R. L. M'ilmoyle (20 September 1947). 'Prestressed Concrete Bridge Beams Being Tested in England'. Railway Age. 123. Simmons-Boardman Publishing Company. pp. 54–58.
- ^'History of Prestressed Concrete in UK'. Cambridge University. 2004. Retrieved 25 August 2018.
- ^Historic England. 'Adam Viaduct (1061327)'. National Heritage List for England. Retrieved 25 August 2018.
- ^'History of Concrete Bridges'. Concrete Bridge Development group. Retrieved 25 August 2018.
- ^Main Roads Western Australia. 'Structures Engineering Design Manual'(PDF). www.mainroads.wa.gov.au. MRWA. pp. 17–23. Retrieved 2 September 2016.
- ^LaViolette, Mike (December 2007). Bridge Construction Practices Using Incremental Launching(PDF). AASHTO. p. Appendix A.
- ^Leonhardt, Fritz (September 1987). 'Cable Stayed Bridges with Prestressed Concrete'. PCI Journal: 52–80.
- ^Roemermann, A. C. (February 1965). 'Prestressed Concrete Dams: 1936-1964'(PDF). PCI Journal: 76–88. Retrieved 2 September 2016.
- ^Brown, E. T. (February 2015). 'Rock-engineering design of post-tensioned anchors for dams - A review'. Journal of Rock Mechnanics and Geological Engineering. 7 (1): 1–13. doi:10.1016/j.jrmge.2014.08.001. Retrieved 6 September 2016.
- ^Institution of Engineers Australia. 'Catagunya Dam Tasmania'(PDF). www.engineersaustralia.org.au. IEAust. Retrieved 2 September 2016.
- ^Xu, Haixue; Benmokrane, Brahim (1996). 'Strengthening of existing concrete dams using post-tensioned anchors: A state-of-the-art review'. Canadian Journal of Civil Engineering. 23 (6): 1151–1171. doi:10.1139/l96-925. Retrieved 2 September 2016.
- ^Cavill, Brian (20 March 1997). 'Very High capacity Ground Anchors Used in Strengthening Concrete Gravity Dams'. Conference Proceedings. London UK: Institution of Civil Engineers: 262.
- ^Priestley, M. J. N. (July 1985). 'Analysis and Design of Prestressed Circular Concrete Storage Tanks'(PDF). PCI Journal: 64–85. Retrieved 5 September 2016.
- ^Ghali, Amin (12 May 2014). Circular Storage Tasnks and Silos (Third ed.). CRC Press. pp. 149–165. ISBN9781466571044. Retrieved 5 September 2016.
- ^'Circular Prestressing'. theconstructor.org. The Constructor.org. Retrieved 5 September 2016.
- ^Gilbert, R. I.; Mickleborough, N. C.; Ranzi, G. (17 February 2016). Design of Prestressed Concrete to AS3600-2009 (Second ed.). CRC Press. ISBN9781466572775. Retrieved 5 September 2016.
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- ^Gerwick, Ben C. (13 February 1997). Construction of Prestressed Concrete Structures (Second ed.). New York: John Wiley & Sons. pp. 472–494. ISBN0 471 53915 5. Retrieved 5 September 2016.
- ^ abRaju, Krishna (1 December 2006). Prestressed Concrete(PDF) (Fourth ed.). New Delhi: Tata McGraw Hill. ISBN0 07 063444 0. Retrieved 5 September 2016.
- ^'Building Post-Tensioned Slabs on Grade'. www.concreteconstruction.net. Concrete Construction. Retrieved 5 September 2016.
- ^Merritt, David; Rogers, Richard; Rasmussen, Robert (March 2008). Construction of a Precast Prestressed Concrete Pavement Demonstration Project on Interstate 57 near Sikeston, Missouri(PDF). US DOT Federal Highway Administration. Retrieved 5 September 2016.
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- ^South African Post Tensioning Association
External links[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Prestressed_concrete&oldid=897972841'
Reinforced concrete has reinforcing bars (calledrebar) simply embedded in the pour. With prestressedconcrete, reinforcing rods or cables are stretched (stressed) andthen the concrete is poured around them. After the concretehardens, the tension on the reinforcing members compresses theconcrete, making it more resistant to failure where poor soilconditions or severe loads exist.
Prestressed construction is usually done in-plant because of theequipment involved, and the completed assembly shipped to the sitefor installation.
A similar method, called post-tension, is usually done on site,and involves the tensioning of reinforcing cables after the slab ispoured, using a special hydraulic jack.
What has the author Jun Yamazaki written?
Jun Yamazaki has written: 'Shear and moment transfer between reinforced concrete flat plates and columns' -- subject(s): Concrete Columns, Reinforced concrete, Testing 'A comparison of the behavior of post-tensioned prestressed concrete beams with and without bond' -- subject(s): Prestressed concrete beams, Testing Read More
Difference between reinforced cement concrete and pre-stressed concrete?
What is the difference between reinforced concrete and pre stressed concrete?
Both are methods of making concrete better at dealing with tension. Reinforced concrete is concrete that has a material that is good at dealing with tension added to it, typically steel, in the areas that are going to be subjected to tension. Prestressed concrete is concrete that is subjected to an extra compressive force, usually applied by placing a steel rod inside of the concrete that is stretched and then releasing the rod during curing… Read More
What is the difference between concrete and reinforced concrete?
Concrete is composed of cement and other cementitious materials such as fly ash and slag cement, coarse aggregate made of crushed stone, fine aggregate such as sand, water, and chemical admixtures. In reinforced concrete, steel is introduced in to the concrete. In plain concrete, no steel reinforcement is introduced. Generally tensile and compressive strength is taken by reinforced concrete and only compressive strength is taken by plain concrete Read More
What is the difference between lean concrete and mass concrete?
Mass concrete is concrete cast without Rebars. They are good in compression and are mostly used for the construction of gravity structures such as Dams. While reinforced concrete have reinforcement bars in them, which increases the tensile strenght of the concrete. Read More
What are the differences between the mass concrete and reinforced concrete?
Mass concrete is concrete cast without Rebars. They are good in compression and are mostly used for the construction of gravity structures such as Dams. While reinforced concrete have reinforcement bars in them, which increases the tensile strenght of the concrete. Read More
Difference between mild steel and tor steel?
Mild steel bars are used for stress of reinforced cement concrete beams and concrete. The tor steel are used as lugs and ribs and are to minimize slippage. Read More
What is the difference between glass fiber reinforced concrete and ordinary reinforced concrete?
Glass fibres do not rust like steel reinforment can and they meld togeter like fiber glass dose, they (if mixed properly, for at least 10 mins beforehand) are more consistent throughout the mix too. Allow one bag of XT fibres (cost about £6 each) per cubic meter of concrete. Regards Colin Read More
What is the difference between Gunite Pools and Fiberglass Pools?
gunite is a type of sprayed sand cement used for the bottoms and sides of pools then fiberglass panels are fitted in to form the complete side to the top Fiberglass pools are also produced as complete pools and shipped to site by truck. the obvious difference here is that one pool is made from reinforced cement 'Gunite', reinforced concrete, 'shotcrete' and reinforced fiberglass and all kinds of systems in between. Read More
Difference between frp and gre pipes?
FRP stands for Fiberglass Reinforced Plastic Pipe and GRE stands for Glass Reinforced Epoxy. The difference between FRP and GRE pipes are the materials they are made with. Read More
What is the difference between lean and blind concrete?
What is the difference between a carbon fiber reinforced plastic and a carbon fiber reinforced polymer?
Carbon fibre reinforced polymer is just a long chain of molecules and carbon fibre reinforced plastic is a group of these molecules Read More
Difference between rcc and pcc?
PCC is plain cement concrete. It consists of cement, sand, aggregates and water. It is good at resisting compression. RCC is reinforced cement concrete. It consists of cement, steel, aggregate and water. It is good at resisting tensile stresses also. Read More
Comparision between insitu concrete and precast concrete?
What has the author Duff Andrew Abrams written?
Duff Andrew Abrams has written: 'Quantities of materials for concrete' -- subject(s): Concrete, Tables 'Effect of curing condition on the wear and strength of concrete' -- subject(s): Concrete 'Tests of bond between concrete and steel' -- subject(s): Reinforced concrete 'Effect of vibration jigging and pressure on fresh concrete' -- subject(s): Concrete 'Test of a 40-foot reinforced concrete highway bridge' -- subject(s): Bridges Read More
what is the-Christ the Redeemer-made-of?
It was sculpted by Paul Landowski of reinforced concrete and soapstone between 1926 and 1931. Read More
What is the difference between 3500 psi concrete and 4000 psi concrete?
What is the difference between monocoque and semimonocoque?
monocoque is a muttai... semi-monocogue is a reinforced muttai... Read More
What is the difference between mortar and concrete?
What is the difference Between under reinforced section and over reinforced section?
When the maximum stresses in steel and concrete simultaniously reaches allowable value the section is called balanced section when the %of steel in a section is less than that required for a balanced section it is under reinforced section when the %of steel in a section is more than that required for a balanced section it is over reinforced section over reinforcement is as per section design I.e Ast1+Ast2>Ast Ast1+Ast2<Ast it is under reinforced section… Read More
What is the difference between concrete paint and concrete stain?
The main difference between concrete paint and stain is that stain is colored and thinner. Concrete paint is used mainly to paint over top of existing concrete while stain will change the color. Stain is used more indoors than the paint. Read More
What is the difference between fiber reinforced plastic and glass reinforced plastic?
Fiber reinforced plastic and glass reinforced plastic are the same. The fiber used to make the FRP is made of glass i.e. the glass is processed and woven as a fiber matt, therefore we can call it fiber reinforced plastic or glass reinforced plastic, both of them are one and the same thing i.e. FIBERGLASS. Read More
What is the difference between abstract and concrete?
I think you are asking the difference between abstract nouns and concrete nouns. A concrete noun is something that can be seen or touched like a cat or a tree. An abstract noun is something more intangible like happiness or peace. Read More
What is the difference between slump and creep?
slump:(fresh concrete) The difference in level between the height of the mould and that of the highest point of the subsided concrete ismeasured. This difference in height in mm. is taken as Slump of Concrete. creep:(hardended concrete) long term deformation of concrete structure under sustain loading Read More
What is the difference between the singly reinforced beam and doubly reinforced beam?
A singly reinforced beam only has steel reinforcement on the tension side (along the bottom of the cross section) where as a doubly reinforced beam has steel reinforcement on both the tension and compression sides, ie. the top and bottom of the cross section. Read More
What does the mean of 'slump'?
The difference in level between the height of the mould and that of the highest point of the subsided concrete is measured. This difference in height in mm. is taken as Slump of Concrete. Read More
Conclusion of slump test?
The difference in level between the height of the mould and that of the highest point of the subsided concrete is measured. This difference in height in mm. is taken as Slump of Concrete. Read More
What is a floating slab foundation?
Floating slab is a type of mat foundation. It consists of a hollow mat formed by a grid of thick reinforced concrete walls between two thick reinforced concrete slabs. The weight of the soil excavated from the ground is equal to the weight of the entire building, so that pressure on the soil is unchanged from the original condition, making the building float on the soil Read More
What is the distance between steel bars used in reinforced concrete?
The 'Field' or 'mat' is normally 16' on center. Some engineers will specify 12' centers. It really depends on your application. Read More
What is the design life of reinforced concrete structures?
It can depend on the governing agency standards mostly, but the typical design life used by ACI (American Concrete Institute) is an average of 75 years. The normal range given in between 50-100 years. Read More
What is the difference between concrete and dry cast stone?
Concrete Is made out Of Clay..Dry Cast Stone..Is made Out Of Stone.. ;D Read More
Explain the difference between preoperational and concrete operational processes?
What is the difference between portland cemant and portland concret?
What is difference between normal truck and CBS armored truck?
An armored vehicle is reinforced on the body with bullet proof steel or metal. Read More
What is the difference between noun and concrete noun?
There is not a 'difference' between a noun and concrete noun: a concrete noun is one of the types of noun. concrete noun - a noun that appears physically; you can use your five sense to check if the noun is concrete. ex: ball - you can see it perfume - you can smell it air - you can feel it ice cream - you can taste it thunder - you can hear it Read More
What is the difference between concrete and general evidence?
Concrete evidence is specific and fact-based, although general evidence is vague and and possibly an opinion. Read More
What is the Difference between wet concrete and hard concrete?
Wet Concrete: In Wet concrete the property of the concrete is suggested based on the individual material contribution . Hardened Concrete: In Hardened concrete the property of the concrete is identified as a whole. Read More
What is the difference between a supposition and a suppository?
One is abstract and the other is concrete (not literally, of course). Read More
What is the difference between fc and fcu in concrete?
f ′c: concrete compressive strength at 28 days (compression is negative) fcu: concrete crushing strength (compression is negative) Read More
How many cubic meters of reinforced concrete are there on an average house?
The only place you'll find concrete on the 'average house' is its footing. The average house footing will contain between 5 and 8 cubic yards (3.8 and 6.1 cubic meters) of concrete. Note: house footings contain very little or no reinforcement. Read More
What is the Difference between concrete and abstract thinking?
Concrete thinking is considered to be thinking that is proven to be logical and work. Abstract thinking is thinking that is new and innovative. Read More
What is the difference between the setting and hardening of concrete?
Setting occurs in concrete when it is mixed, before it is even poured. Hardening occurs in concrete when the mixture gains strength as the water dries off the mixture. Read More
What is the difference between a concrete block and a brick block?
A concrete block is made from concrete, a brick block is made from brick. They are two different building materials. Both have their respective advantages and disadvantages. Read More
What is the difference between concrete and transferable skills and give an example of each?
What is the difference between a patio block and a concrete block?
extrusion is different from forging. Idhu eppadi Read More
What is the difference between splice and joint?
joint is connection between same member.In general you may say in between steel.splice is connection between different member.between concrete and steel. Read More
What difference suspended concrete slab between unsuspended concrete slab?
Supended slab are slab not sit on the ground directly Suspended slab is a slab supported by beams. Read More
What is the difference between a normal weight concrete and a lightweight concrete by volume?
cement is binding material while concreat is an homogeneous mixtur of cement sand and soil water etc. Read More
What is the density of conncrete?
Density of concrete (reinforced) can be taken between 2400 to 2500 kg/cubic meter 2500 is recommended where good and heavy/solid aggregate is used. Also recommended for max. dead weight calculations. Read More
What is the difference between laen concrete and ready mix concrete?
Laen concrete contains very little actual cement. Laen cement is used as a base that is found under other cements. Ready mix concrete is used for primary uses of cement structures. Read More