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70-467: The basic tools, methods and skills of the banker mason have existed as a trade for thousands of years. It is one of the oldest activities and professions in human history. Many of the long-lasting, ancient shelters , temples , monuments , artifacts , fortifications , roads , bridges , and entire cities were built of stone. Famous works of stonemasonry include Göbekli Tepe , the Egyptian pyramids ,

140-467: 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. Unbonded post-tensioning can take the form of: 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

210-508: 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

280-425: A crane reduces labor, accelerates construction, and allows the masons to precisely and quickly position the blocks. MP stone is defined by four design attributes. MP stone construction has advantages over conventional masonry and concrete construction. Fernand Pouillon pioneered the use of massive precut stone in modern architecture. During the post-war period, his innovative approach to stone construction led to

350-572: A fine finish on the stone. A drove chisel is used for smoothing off roughly finished stones. Mixing mortar is normally done today with mortar mixers which usually use a rotating drum or rotating paddles to mix the mortar. The masonry trowel is used for the application of the mortar between and around the stones as they are set into place. Filling in the gaps (joints) with mortar is referred to as pointing. Pointing in smaller joints can be accomplished using tuck pointers , pointing trowels , and margin trowels , among other tools. A mason's hammer has

420-417: A good way to learn about stonemasonry also. Those wishing to become stonemasons should have little problem working at heights, possess reasonable hand-eye coordination, be moderately physically fit, and have basic mathematical ability. Most of these things can be developed while learning. The modern stonemason undergoes comprehensive training, both in the classroom and in the working environment. Hands-on skill

490-541: A long thin head and is called a Punch Hammer. It would be used with a chisel or splitter for a variety of purposes A walling hammer (catchy hammer) can be used in place of a hammer and chisel or pincher to produce rubble or pinnings or snecks. Stonemasons use a lewis together with a crane or block and tackle to hoist building stones into place. Today power tools such as compressed-air chisels, abrasive spinners, and angle grinders are much used: these save time and money, but are hazardous and require just as much skill as

560-575: A masonry engineer at a quarry in Fontvieille, to adapt high-precision saws from the timber industry to quarrying and stone sawing. The key technique of massive precut (MP) stone is to cut stone ashlars to precise dimensions that match the architect's plan such that the stones can be dropped into place by crane for rapid construction. The blocks may be numbered so that the masons can follow the plan procedurally. The use of massive blocks reduces costs by minimizing sawing and fixer-masonry costs. The use of

630-653: A prestressed concrete member, the internal stresses are introduced in a planned manner so that the stresses resulting from the imposed 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 concrete slabs , foundation systems , bridge and dam structures, silos and tanks , industrial pavements and nuclear containment structures . First used in

700-609: A proof-loaded, redundant and monitorable pressure-containment system. 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 utilize layers of horizontally-curved hoop tendons for containment in combination with vertically looped tendons for axial wall pre-stressing. Heavily loaded concrete ground-slabs and pavements can be sensitive to cracking and subsequent traffic-driven deterioration. As

770-419: 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

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840-626: A railway bridge constructed 1946 in the UK . By the 1960s, prestressed concrete largely superseded reinforced concrete bridges in the UK, with box girders being the dominant form. 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. Medium-length structures of around 40 to 200 metres (150 to 650 ft), typically use precast-segmental, in-situ balanced-cantilever and incrementally-launched designs . For

910-508: 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. Initial works have also been successfully conducted on

980-532: A significant permanent compression being applied to the concrete once the tendon is "locked-off" at the anchorage. 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). Tendon encapsulation systems are constructed from plastic or galvanised steel materials, and are classified into two main types: those where

1050-591: A simple ‘quality assurance’ system. The Renaissance saw stonemasonry return to the prominence and sophistication of the Classical age . The rise of the humanist philosophy gave people the ambition to create marvelous works of art. The centre stage for the Renaissance would prove to be Italy, where Italian city-states such as Florence erected great structures, including the Florence Cathedral ,

1120-530: A single piece, but drill limitations and other considerations mean it is typically an assembly of multiple components with mortar between pieces. PT stone has been used in both vertical columns (posts), and in horizontal beams (lintels). It has also been used in more unusual engineering applications: arch stabilization, flexible foot bridges, and cantilevered sculptures. Tensioned stone has a close affiliation with massive precut stone as two central techniques of modern stonemasonry . "Post-tensioned stone increases

1190-503: 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. The tendon sizes used are highly dependent upon

1260-572: A wide variety of tools to handle and shape stone blocks ( ashlar ) and slabs into finished articles. The basic tools for shaping the stone are a mallet , chisels , and a metal straight edge . With these one can make a flat surface – the basis of all stonemasonry. Chisels come in a variety of sizes and shapes, dependent upon the function for which they are being used and have many different names depending on locality. There are different chisels for different materials and sizes of material being worked, for removing large amounts of material and for putting

1330-400: Is a form of concrete used in construction. It is substantially "prestressed" ( compressed ) during production, in a manner that strengthens it against tensile forces which will exist when in service. It was patented by Eugène Freyssinet in 1928. This compression is produced by the tensioning of high-strength "tendons" located within or adjacent to the concrete and is done to improve

1400-592: 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. 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. Building structures are typically required to satisfy

1470-520: Is a modern method of building with load-bearing stone. Precut stone is a DFMA construction method that uses large machine-cut stone blocks with precisely defined dimensions to rapidly assemble buildings in which stone is used as a major or the primary load-bearing material. Massive precut stone construction was originally developed by Fernand Pouillon in postwar period who referred to the method as "pierre de taille" or "pré-taille" stone. It became possible through innovations by Pouillon and Paul Marcerou,

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1540-401: Is complemented by an intimate knowledge of each stone type, its application, and best uses, and how to work and fix each stone in place. The mason may be skilled and competent to carry out one or all of the various branches of stonemasonry. In some areas, the trend is towards specialization, in other areas towards adaptability. Today's stonemasons undergo training that is quite comprehensive and

1610-498: Is despite the advantages of stone over concrete. Those advantages include: Modern stonemasonry is in the process of reinventing itself for automation, modern load-bearing stone construction, innovative reinforcement techniques , and integration with other sustainable materials, like engineered wood . Stone has been used in construction for thousands of years, in many contexts. Listed below are six types of classical stonemasonry techniques, some of which still see widespread use. In

1680-754: Is done both in the work environment and in the classroom. It isn't enough to have hands-on skills only. One must also have knowledge of the types of stones as well as its best uses and how to work it as well as how to fix it in place. Stonemasons use all types of natural stone: igneous , metamorphic and sedimentary ; while some also use artificial stone as well. Many of the world's most famous buildings have been built of sedimentary stone, from Durham Cathedral to St Peter's in Rome . There are two main types of sedimentary stone used in masonry work, limestones and sandstones . Examples of limestones include Bath and Portland stone . Yorkstone and Sydney sandstone are

1750-418: 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. 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

1820-423: Is most commonly used for the fabrication of structural beams , floor slabs , hollow-core slabs, balconies , lintels , driven piles , water tanks and concrete pipes . Post-tensioned concrete is a variant of prestressed concrete where the tendons are tensioned after the surrounding concrete structure has been cast. The tendons are not placed in direct contact with the concrete, but are encapsulated within

1890-560: Is one of the earliest trades in civilization 's history. During the time of the Neolithic Revolution and domestication of non-human animals, people learned how to use fire to create quicklime , plasters , and mortars. They used these to fashion homes for themselves with mud, straw or stone, and masonry was born. The Ancients heavily relied on the stonemason to build the most impressive and long-lasting monuments to their civilizations. The Egyptians built their pyramids ,

1960-465: Is the most popular structural material for bridges, and prestressed concrete is frequently adopted. 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. One of the first bridges built in this way is the Adam Viaduct ,

2030-486: 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: Several durability-related events are listed below: Prestressed concrete

2100-417: 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. Bonded post-tensioning characteristically uses tendons each comprising bundles of elements (e.g., strands or wires) placed inside

2170-668: The Fountain of Neptune , and the Laurentian Library , which was planned and built by Michelangelo Buonarroti , a famous sculptor of the Renaissance. When Europeans settled the Americas, they brought the stonemasonry techniques of their respective homelands with them. Settlers used what materials were available, and in some areas, stone was the material of choice. In the first waves, building mimicked that of Europe, to eventually be replaced by unique architecture later on. In

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2240-548: The Renaissance , the stonemason's guild admitted members who were not stonemasons, and eventually evolved into the Society of Freemasonry ; fraternal groups which observe the traditional culture of stonemasons but are not typically involved in modern construction projects. A medieval stonemason would often carve a personal symbol onto their block to differentiate their work from that of other stonemasons. This also provided

2310-703: The Taj Mahal , Cusco 's Incan Wall, Taqwesan , Easter Island 's statues , Angkor Wat , Borobudur , Tihuanaco , Tenochtitlan , Persepolis , the Parthenon , Stonehenge , the Great Wall of China , the Mesoamerican pyramids , Chartres Cathedral , and the Stari Most . While stone was important traditionally, it fell out of use in the modern era, in favor of brick and steel-reinforced concrete. This

2380-435: The guild , gave rise to three classes of stonemasons: apprentices , journeymen , and master masons . Apprentices were indentured to their masters as the price for their training, journeymen were qualified craftsmen who were paid by the day, and master masons were considered freemen who could travel as they wished to work on the projects of the patrons and could operate as self-employed craftsmen and train apprentices. During

2450-659: The 1960s , the concept of "Shelter" intervenes as one of the key concepts of the Whole Earth Catalog , and expresses an alternative to the modes of teaching architecture practiced in American academies. In the context of Maslow's hierarchy of needs , shelter holds a crucial position as one of the fundamental human necessities, complementing other physiological imperatives such as the need for air, water, food, rest, clothing, and reproduction." Prestressed concrete#Post-tensioned concrete Prestressed concrete

2520-420: The 20th century, stonemasonry saw its most radical changes in the way the work is accomplished. Prior to the first half of the century, most heavy work was executed by draft animals or human muscle power. With the arrival of the internal combustion engine , many of these hard aspects of the trade have been made simpler and easier. Cranes and forklifts have made moving and laying heavy stones relatively easy for

2590-405: 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

2660-468: 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. The benefits that bonded post-tensioning can offer over unbonded systems are: The benefits that unbonded post-tensioning can offer over bonded systems are: Long-term durability is an essential requirement for prestressed concrete given its widespread use. Research on

2730-641: The civilizations of Central America had their step pyramids , the Persians their palaces, the Greeks their temples, and the Romans their public works and wonders (See Roman Architecture ). People of the Indus Valley Civilization , such as at Dholavira made entire cities characterized by stone architecture. Among the famous ancient stonemasons is Sophroniscus , the father of Socrates , who

2800-433: 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. Pre-tensioned concrete is a variant of prestressed concrete where the tendons are tensioned prior to the concrete being cast. The concrete bonds to the tendons as it cures , following which

2870-404: 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

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2940-1042: 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). Similar bodies include the Canadian Precast/Prestressed Concrete Institute (CPCI), the UK's Post-Tensioning Association, the Post Tensioning Institute of Australia and the South African Post Tensioning Association. Europe has similar country-based associations and institutions. These organizations are not

3010-411: The development of numerous noteworthy projects, with a particular focus on housing. Throughout his long career, Pouillon played a crucial role in the development and popularization of massive precut stone construction techniques. His pioneering work laid the foundation for subsequent architects to build upon and innovate, leading to the resurgence and expansion of this construction method in the 2020s, with

3080-413: The ducting. Following concreting and tensioning, the ducts are pressure-grouted and the tendon stressing-ends sealed against corrosion . 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

3150-426: The durability performance of in-service prestressed structures has been undertaken since the 1960s, and anti-corrosion technologies for tendon protection have been continually improved since the earliest systems were developed. 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

3220-399: The end-anchoring of the tendons is released, and the tendon tension forces are transferred to the concrete as compression by static friction . Pre-tensioning is a common prefabrication technique, where the resulting concrete element is manufactured off-site from the final structure location and transported to site once cured. It requires strong, stable end-anchorage points between which

3290-437: The experience of the tradesmen, and college work where apprentices are given an overall experience of the building, hewing and theory work involved in masonry. In some areas, colleges offer courses which teach not only the manual skills but also related fields such as drafting and blueprint reading or construction conservation. Electronic Stonemasonry training resources enhance traditional delivery techniques. Hands-on workshops are

3360-843: The failure load of stone in bending, but also the stiffness of a structure by reducing joint cracking. This method of construction is widely used for concrete structures, but the advantages of using similar techniques with stone are only just being realised". Stone has great compressive strength, so is ideal in compressive structures like stone arches . However, it has relatively weak flexural strength (compared to steel or wood), so in isolation cannot be safely used in wide spans under tension. For concrete, this problem has been long solved: in addition to conventional tensile reinforcement, engineers developed prestressed concrete methods starting around 1888. Such tension-reinforced concrete applications combine compressive strength with pre-stressed tensile compression for combined strength much greater than either of

3430-451: 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

3500-544: The hand tools that they augment. But many of the basic tools of stonemasonry have remained virtually the same throughout vast amounts of time, even thousands of years, for instance when comparing chisels that can be bought today with chisels found at the pyramids of Giza the common sizes and shapes are virtually unchanged. Traditionally medieval stonemasons served a seven-year apprenticeship . A similar system still operates today. A modern apprenticeship lasts three years. This combines on-site learning through personal experience,

3570-408: The individual components, and have been in wide use for decades. As for concrete, post-tensioning maintains stone in compression, thereby increasing its strength. Post-tensioning is achieved steel tendons either threaded through ducts within the stone elements or along their surface. Once the stone components are in place, the tendons are tensioned using hydraulic jacks, and the force is transferred to

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3640-404: The late nineteenth century, 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. Tendons may be located either within

3710-432: The longest bridges, prestressed concrete deck structures often form an integral part of cable-stayed designs . Concrete dams have used prestressing to counter uplift and increase their overall stability since the mid-1930s. Prestressing is also frequently retro-fitted as part of dam remediation works, such as for structural strengthening, or when raising crest or spillway heights. Most commonly, dam prestressing takes

3780-501: The modern era, stone has been largely relegated as a cosmetic element of buildings, often used as decorative cladding on steel-reinforced concrete . This is despite its wide historical use in large compressive structures: 50-m bridges and colosseums in Roman times, ~65-m tall cathedrals since the middle ages , and 12-story apartment buildings built in the 1690s. Massive precut stone is also known as "prefabricated", or "pre-sized" stone

3850-486: The most commonly used sandstone. Categories: Shelter (building) A shelter is an architectural structure or natural formation (or a combination of the two) providing protection from the local environment. A shelter can serve as a home or be provided by a residential institution. It can be understood as both a temporary and a permanent structure. In the American Counterculture of

3920-647: The performance of the concrete in service. 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 . 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. In

3990-410: The rise of interest in low-carbon durable construction. Post-tensioned stone is a high-performance composite construction material: stone held in compression with tension elements. The tension elements can be connected to the outside of the stone, but more typically uses tendons threaded internally through a duct formed from aligned drilled holes. Post-tensioned stone ("PT stone") could consist of

4060-522: The stone through anchorages located at the ends of the tendons. The tensioning process imparts a compressive force to the stone, which improves its capacity to resist tensile stresses that could otherwise cause cracking or failure. Stone is 'natural precast concrete' so only needs to be cut (and strength tested) and post-tensioned prior to use in construction. Compared to concrete and steel, post-tensioned stone production has dramatically lower energy costs, with concomitant lower carbon emissions. Stonemasonry

4130-439: The stonemasons. Motor powered mortar mixers have saved much in time and energy as well. Compressed-air powered tools have made working of stone less time-intensive. Petrol and electric-powered abrasive saws can cut through stone much faster and with more precision than chiseling alone. Cemented carbide -tipped chisels can stand up to much more abuse than the steel and iron chisels made by blacksmiths of old. Stonemasons use

4200-553: 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. Individually greased-and-sheathed tendons are usually fabricated off-site by an extrusion process. The bare steel strand

4270-579: The structure to counter in-service loadings. This provides many benefits to building structures: Some notable building structures constructed from prestressed concrete include: Sydney Opera House and World Tower , Sydney; St George Wharf Tower , London; CN Tower , Toronto; Kai Tak Cruise Terminal and International Commerce Centre , Hong Kong; Ocean Heights 2 , Dubai; Eureka Tower , Melbourne; Torre Espacio , Madrid; Guoco Tower (Tanjong Pagar Centre), Singapore; Zagreb International Airport , Croatia; and Capital Gate , Abu Dhabi UAE. Concrete

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4340-475: 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. Unlike those of post-tensioned concrete (see below),

4410-432: 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. 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

4480-546: 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 de bonded from the surrounding concrete, usually by means of a greased sheath over the tendon strands ( unbonded post-tensioning). 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

4550-418: 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. The amount of bond (or adhesion ) achievable between the freshly set concrete and

4620-406: 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. In bonded post-tensioning, tendons are permanently bonded to the surrounding concrete by the in situ grouting of their encapsulating ducting (after tendon tensioning). This grouting

4690-662: The tendons of pre-tensioned concrete elements generally form straight lines between end-anchorages. Where "profiled" or "harped" tendons 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. Such deviators usually act against substantial forces, and hence require a robust casting-bed foundation system. Straight tendons are typically used in "linear" precast concrete elements, such as shallow beams, hollow-core slabs ; whereas profiled tendons are more commonly found in deeper precast bridge beams and girders. Pre-tensioned concrete

4760-677: 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. Some notable civil structures constructed using prestressed concrete include: Gateway Bridge , Brisbane Australia; Incheon Bridge , South Korea; Roseires Dam , Sudan; Wanapum Dam , Washington, US; 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. Worldwide, many professional organizations exist to promote best practices in

4830-491: The wall concrete, assisting in maintaining a watertight crack-free structure. 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 pre-stressing 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

4900-679: Was a stone-cutter. Castle building was an entire industry for the medieval stonemasons. When the Western Roman Empire fell, building in dressed stone decreased in much of Western Europe , and there was a resulting increase in timber-based construction. Stonework experienced a resurgence in the 9th and 10th centuries in Europe, and by the 12th-century religious fervour resulted in the construction of thousands of impressive churches and cathedrals in stone across Western Europe. Medieval stonemasons' skills were in high demand, and members of

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