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88-648: The fortifications around Metz consisted of casemates , concrete barracks , infantry strong points, and concrete batteries , equipped with rotating steel turrets (100–150 mm). Each position was surrounded by several ditches, or concrete trenches, with shelters and observation cupolas . A large barbed wire belt, defended by machine gun and rifle positions, completed the defensive system. Forts had usually several large blockhouse style barracks. These had 3-meter thick reinforced concrete roofs with 2-meter thick walls. They were partially buried under as much as 6 m (20 ft) of compacted earth. Tunnels connected all of

176-410: A 6-inch gun, and had a 4-to-6-inch (100 to 150 mm) front plate (forming part of the side of the ship), with thinner armor plates on the sides and rear, with a protected top and floor, and weighed about 20 tons (not including the gun and mounting). Casemates were similar in size to turrets; ships carrying them had them in pairs, one on each side of the ship. The first battleships to carry them were

264-419: A casemate gun, which could be worked by hand. The use of casemates enabled the 6-inch guns to be dispersed, so that a single hit would not knock out all of them. Casemates were also used in protected and armored cruisers, starting with the 1889 Edgar class . and retrofitted to the 1888 Blake class during construction. In the pre-dreadnought generation of warships, casemates were placed initially on

352-453: A major role in the evolution of concrete construction as a proven and studied science. Without Hyatt's work, more dangerous trial and error methods might have been depended on for the advancement in the technology. Joseph Monier , a 19th-century French gardener, was a pioneer in the development of structural, prefabricated and reinforced concrete, having been dissatisfied with the existing materials available for making durable flowerpots. He

440-471: A new scheme of fortifications to protect their eastern border, which became known as the Maginot Line . The main element of this line were large underground forts based on the feste principle, whose main armament was in turrets, however the countryside between them was defended by smaller self-sufficient works based on the earlier casemates de bourges , housing either light field guns or anti-tank guns . As

528-419: A reduction in its durability. Corrosion and freeze/thaw cycles may damage poorly designed or constructed reinforced concrete. When rebar corrodes, the oxidation products ( rust ) expand and tends to flake, cracking the concrete and unbonding the rebar from the concrete. Typical mechanisms leading to durability problems are discussed below. Cracking of the concrete section is nearly impossible to prevent; however,

616-470: A rotating turret as much as offensively used tanks, while assault guns were mainly used against fortified infantry positions and could afford a longer reaction time if a target presented itself outside the vehicle's gun traverse arc. Thus, the weight and complexity of a turret was thought to be unnecessary, and could be saved in favor of more capable guns and armor. In many cases, casemate vehicles would be used as both tank destroyers or assault guns, depending on

704-587: A translation of his book and took it to the United States, where it inspired the Second and Third Systems of coastal fortification; the first fully developed example being Castle Williams in New York Harbor which was started in 1807. In the early 19th century, French military engineer Baron Haxo designed a free-standing casemate that could be built on the top of the rampart, to protect guns and gunners from

792-602: A turret for the main gun, the structure that accommodates the gun is also called a casemate. First recorded in French in the mid-16th century, from the Italian casamatta or Spanish casamata , perhaps meaning a slaughterhouse , although it could derive from casa (in the sense of " hut "), and matta ( Latin matta ), "done with reeds and wickers", thus a low-roof hut without windows or other openings set in marshy place. It could also come from casa matta with matta in

880-482: A very low freeboard and their guns on the main deck ('Casemate deck') protected by a sloped armoured casemate, which sat atop the hull. Although both sides of the Civil War used casemate ironclads, the ship is mostly associated with the southern Confederacy , as the north also employed turreted monitors , which the south was unable to produce. The most famous naval battle of the war was the duel at Hampton Roads between

968-426: A well-chosen concrete mix will provide additional protection for many applications. Uncoated, low carbon/chromium rebar looks similar to standard carbon steel rebar due to its lack of a coating; its highly corrosion-resistant features are inherent in the steel microstructure. It can be identified by the unique ASTM specified mill marking on its smooth, dark charcoal finish. Epoxy-coated rebar can easily be identified by

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1056-450: Is a fortified gun emplacement or armoured structure from which guns are fired, in a fortification , warship , or armoured fighting vehicle . When referring to antiquity , the term " casemate wall " means a double city wall with the space between the walls separated into chambers, which could be filled up to better withstand battering rams in case of siege (see § Antiquity: casemate wall .) In its original early modern meaning,

1144-658: Is a mixture of coarse (stone or brick chips) and fine (generally sand and/or crushed stone) aggregates with a paste of binder material (usually Portland cement ) and water. When cement is mixed with a small amount of water, it hydrates to form microscopic opaque crystal lattices encapsulating and locking the aggregate into a rigid shape. The aggregates used for making concrete should be free from harmful substances like organic impurities, silt, clay, lignite, etc. Typical concrete mixes have high resistance to compressive stresses (about 4,000 psi (28 MPa)); however, any appreciable tension ( e.g., due to bending ) will break

1232-528: Is coating them with zinc phosphate . Zinc phosphate slowly reacts with calcium cations and the hydroxyl anions present in the cement pore water and forms a stable hydroxyapatite layer. Penetrating sealants typically must be applied some time after curing. Sealants include paint, plastic foams, films and aluminum foil , felts or fabric mats sealed with tar, and layers of bentonite clay, sometimes used to seal roadbeds. Corrosion inhibitors , such as calcium nitrite [Ca(NO 2 ) 2 ], can also be added to

1320-495: Is located across the bay from San Francisco . Two years later, El Campanil survived the 1906 San Francisco earthquake without any damage, which helped build her reputation and launch her prolific career. The 1906 earthquake also changed the public's initial resistance to reinforced concrete as a building material, which had been criticized for its perceived dullness. In 1908, the San Francisco Board of Supervisors changed

1408-541: Is one in which both the compressive and tensile zones reach yielding at the same imposed load on the beam, and the concrete will crush and the tensile steel will yield at the same time. This design criterion is however as risky as over-reinforced concrete, because failure is sudden as the concrete crushes at the same time of the tensile steel yields, which gives a very little warning of distress in tension failure. Steel-reinforced concrete moment-carrying elements should normally be designed to be under-reinforced so that users of

1496-428: Is one in which the concrete element is only reinforced near the tensile face and the reinforcement, called tension steel, is designed to resist the tension. A doubly reinforced beam is the section in which besides the tensile reinforcement the concrete element is also reinforced near the compressive face to help the concrete resist compression and take stresses. The latter reinforcement is called compression steel. When

1584-430: Is one in which the tension capacity of the tension steel is greater than the combined compression capacity of the concrete and the compression steel (over-reinforced at tensile face). So the "over-reinforced concrete" beam fails by crushing of the compressive-zone concrete and before the tension zone steel yields, which does not provide any warning before failure as the failure is instantaneous. A balanced-reinforced beam

1672-509: Is the construction period. The first, inner belt of fortifications were completed by the French just prior to the Franco-Prussian War and were in service during the Siege of Metz from 3 September to 23 October 1870. The forts were in a ring approximately 4 km out from the city center, and were (anti-clockwise from the south): The second, outer belt of fortifications were completed by

1760-579: Is the theoretical failure point with a certain probability. It is stated under factored loads and factored resistances. Reinforced concrete structures are normally designed according to rules and regulations or recommendation of a code such as ACI-318, CEB, Eurocode 2 or the like. WSD, USD or LRFD methods are used in design of RC structural members. Analysis and design of RC members can be carried out by using linear or non-linear approaches. When applying safety factors, building codes normally propose linear approaches, but for some cases non-linear approaches. To see

1848-446: Is transferred from the concrete to the bar interface so as to change the tensile stress in the reinforcing bar along its length. This load transfer is achieved by means of bond (anchorage) and is idealized as a continuous stress field that develops in the vicinity of the steel-concrete interface. The reasons that the two different material components concrete and steel can work together are as follows: (1) Reinforcement can be well bonded to

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1936-404: Is usually, though not necessarily, steel reinforcing bars (known as rebar ) and is usually embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In terms of volume used annually, it is one of the most common engineering materials. In corrosion engineering terms, when designed correctly, the alkalinity of

2024-734: The SU-100 or the ISU-152 . Both Germany and the Soviet Union mainly built casemate AFVs by using the chassis of already existing turreted tanks, instead of designing them from scratch. While casemate AFVs played a very important role in World War II (the Sturmgeschütz III for example was the most numerous armored fighting vehicle of the German Army during the entire war), they became much less common in

2112-519: The Union turreted ironclad USS  Monitor and the Confederate casemate ironclad CSS  Virginia (built from the scuttled remains of USS  Merrimack ). "Casemate ship" was an alternative term for " central battery ship " (UK) or "center battery ship" (US). The casemate (or central battery) was an armored box that extended the full width of the ship protecting many guns. The armored sides of

2200-851: The World War II approached, similar casemate designs were adopted by other European nations as they offered protection from attacking aircraft. The German Organisation Todt undertook the development of casemates for the large coastal guns of the Atlantic Wall . Built of concrete up to 10 metres (33 ft) thick, they were thought to be able to withstand any form of attack. Work by the Western Allies to develop countermeasures that could defeat casemates and other types of bunker resulted in weapons such as tank-mounted spigot mortars , rocket-assisted projectiles , recoilless rifles , various types of demolition charge and earthquake bombs . In warship design

2288-543: The battle of Metz , the German troops had managed to get about 50% of the guns operational in most of the forts listed below. These batteries were lacking range tables, missing sights and other equipment to make the guns fully operational. Below is a list of the fortifications that exist around the area of Metz. Because they switched hands quite often, the French names are listed as well as any applicable German ones. In parentheses

2376-462: The tensile strength of concrete was improved by the reinforcing. Before the 1870s, the use of concrete construction, though dating back to the Roman Empire , and having been reintroduced in the early 19th century, was not yet a proven scientific technology. Ernest L. Ransome , an English-born engineer, was an early innovator of reinforced concrete techniques at the end of the 19th century. Using

2464-413: The 17th century. In the late 18th century, Marc René, marquis de Montalembert (1714–1800) experimented with improved casemates for artillery, with ventilation systems that overcame the problem of smoke dispersal found in earlier works. For coastal fortifications , he advocated multi-tiered batteries of guns in masonry casemates, that could bring concentrated fire to bear on passing warships. In 1778, he

2552-697: The 1890s, Wayss and his firm greatly contributed to the advancement of Monier's system of reinforcing, established it as a well-developed scientific technology. One of the first skyscrapers made with reinforced concrete was the 16-story Ingalls Building in Cincinnati, constructed in 1904. The first reinforced concrete building in Southern California was the Laughlin Annex in downtown Los Angeles , constructed in 1905. In 1906, 16 building permits were reportedly issued for reinforced concrete buildings in

2640-485: The 1990s, favoring it over contemporary turreted designs. Other casemate design ideas, such as the projected German Versuchsträger 1–2 with two main guns, were developed even later. Reinforced concrete Reinforced concrete , also called ferroconcrete , is a composite material in which concrete 's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement

2728-480: The British Royal Sovereign class laid down in 1889. They were adopted as a result of live-firing trials against HMS  Resistance in 1888. Casemates were adopted because it was thought that the fixed armor plate at the front would provide better protection than a turret, and because a turret mounting would require external power and could therefore be put out of action if power were lost – unlike

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2816-673: The City of Los Angeles, including the Temple Auditorium and 8-story Hayward Hotel. In 1906, a partial collapse of the Bixby Hotel in Long Beach killed 10 workers during construction when shoring was removed prematurely. That event spurred a scrutiny of concrete erection practices and building inspections. The structure was constructed of reinforced concrete frames with hollow clay tile ribbed flooring and hollow clay tile infill walls. That practice

2904-592: The English counties of Norfolk and Suffolk. In 1877, Thaddeus Hyatt , published a report entitled An Account of Some Experiments with Portland-Cement-Concrete Combined with Iron as a Building Material, with Reference to Economy of Metal in Construction and for Security against Fire in the Making of Roofs, Floors, and Walking Surfaces , in which he reported his experiments on the behaviour of reinforced concrete. His work played

2992-663: The Germans prior to the First World War but saw little service. Prior to the Second World War they were incorporated by the French into the Maginot Line defenses, but again saw little action. In October 1944, while occupied by the Germans, the fortifications were assaulted and captured by the American 3rd Army in the Battle of Metz . The forts were in an offset ring from 8–10 km from

3080-621: The Iron Age and peaking in Iron Age II (10th–6th century BC). However, the construction of casemate walls had begun to be replaced by sturdier solid walls by the 9th century BC , probably due the development of more effective battering rams by the Neo-Assyrian Empire . Casemate walls could surround an entire settlement, but most only protected part of it. The three different types included freestanding casemate walls, then integrated ones where

3168-695: The actual available length is inadequate for full development, special anchorages must be provided, such as cogs or hooks or mechanical end plates. The same concept applies to lap splice length mentioned in the codes where splices (overlapping) provided between two adjacent bars in order to maintain the required continuity of stress in the splice zone. In wet and cold climates, reinforced concrete for roads, bridges, parking structures and other structures that may be exposed to deicing salt may benefit from use of corrosion-resistant reinforcement such as uncoated, low carbon/chromium (micro composite), epoxy-coated, hot dip galvanized or stainless steel rebar. Good design and

3256-461: The actual bond stress varies along the length of a bar anchored in a zone of tension, current international codes of specifications use the concept of development length rather than bond stress. The main requirement for safety against bond failure is to provide a sufficient extension of the length of the bar beyond the point where the steel is required to develop its yield stress and this length must be at least equal to its development length. However, if

3344-463: The arrival of "all-big gun" battleship, pioneered by HMS  Dreadnought in 1906, but were reintroduced as the increasing torpedo threat from destroyers forced an increase in secondary armament calibre. Many battleships had their casemates plated over during modernization in the 1930s (or after the Attack on Pearl Harbor , in the case of US vessels) but some, like HMS  Warspite carried them to

3432-472: The behavior of the final structure under working loads. In the United States , the most common methods of doing this are known as pre-tensioning and post-tensioning . For a strong, ductile and durable construction the reinforcement needs to have the following properties at least: François Coignet used iron-reinforced concrete as a technique for constructing building structures. In 1853, Coignet built

3520-423: The box were the sides or hull of the ship. There was an armored bulkhead at the front and rear of the casemate, and a thick deck protecting the top. The lower edge of the casemate sat on top of ship's belt armour . Some ships, such as HMS  Alexandra (laid down 1873), had a two-story casemate. A "casemate" was an armored room in the side of a warship, from which a gun would fire. A typical casemate held

3608-581: The capability to take up the roles and tasks which in the past had to be diverted between several different classes of vehicles. However, vehicles such as the German Kanonenjagdpanzer of the 1960s still let the casemate concept live on, while the Swedish Army went as far as employing a casemate tank design, the Stridsvagn 103 , or "S-Tank", as their main armored fighting vehicle from the 1960s until

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3696-543: The chief reasons for the failure of reinforcement bars in concrete. The relative cross-sectional area of steel required for typical reinforced concrete is usually quite small and varies from 1% for most beams and slabs to 6% for some columns. Reinforcing bars are normally round in cross-section and vary in diameter. Reinforced concrete structures sometimes have provisions such as ventilated hollow cores to control their moisture & humidity. Distribution of concrete (in spite of reinforcement) strength characteristics along

3784-732: The city's building codes to allow wider use of reinforced concrete. In 1906, the National Association of Cement Users (NACU) published Standard No. 1 and, in 1910, the Standard Building Regulations for the Use of Reinforced Concrete . Many different types of structures and components of structures can be built using reinforced concrete elements including slabs , walls , beams , columns , foundations , frames and more. Reinforced concrete can be classified as precast or cast-in-place concrete . Designing and implementing

3872-733: The city, and were (anticlockwise from the south): (anticlockwise from the north): These are a series of small defensive emplacements built between 1912 and 1916 in a line between Driant and Jeanne d'Arc. The name for them was created by the Americans of the U.S. Third Army during the Battle of Metz in the Second World War. They are sometimes (mistakenly) referred to as forts, and their name alludes to their weak defensive strength. From south to north they are: 49°07′04″N 6°11′08″E  /  49.11778°N 6.18556°E  / 49.11778; 6.18556 Casemates A casemate

3960-422: The compression zone of a concrete is inadequate to resist the compressive moment (positive moment), extra reinforcement has to be provided if the architect limits the dimensions of the section. An under-reinforced beam is one in which the tension capacity of the tensile reinforcement is smaller than the combined compression capacity of the concrete and the compression steel (under-reinforced at tensile face). When

4048-521: The concrete protects the steel rebar from corrosion . Reinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and/or structural failure. Modern reinforced concrete can contain varied reinforcing materials made of steel, polymers or alternate composite material in conjunction with rebar or not. Reinforced concrete may also be permanently stressed (concrete in compression, reinforcement in tension), so as to improve

4136-541: The concrete resists compression and reinforcement " rebar " resists tension can be made into almost any shape and size for the construction industry. Three physical characteristics give reinforced concrete its special properties: As a rule of thumb, only to give an idea on orders of magnitude, steel is protected at pH above ~11 but starts to corrode below ~10 depending on steel characteristics and local physico-chemical conditions when concrete becomes carbonated. Carbonation of concrete along with chloride ingress are amongst

4224-412: The concrete roof and floors in the two-story house he was constructing. His positioning of the reinforcement demonstrated that, unlike his predecessors, he had knowledge of tensile stresses. Between 1869 and 1870, Henry Eton would design, and Messrs W & T Phillips of London construct the wrought iron reinforced Homersfield Bridge bridge, with a 50' (15.25 meter) span, over the river Waveney, between

4312-416: The concrete, thus they can jointly resist external loads and deform. (2) The thermal expansion coefficients of concrete and steel are so close ( 1.0 × 10 to 1.5 × 10 for concrete and 1.2 × 10 for steel) that the thermal stress-induced damage to the bond between the two components can be prevented. (3) Concrete can protect the embedded steel from corrosion and high-temperature induced softening. Because

4400-559: The crew has to rotate the entire vehicle if an enemy target presents itself outside of the vehicle's limited gun traverse arc. This can prove very disadvantageous in combat situations. During World War II , casemate-type armored fighting vehicles were heavily used by both the combined German Wehrmacht forces, and the Soviet Red Army . They were mainly employed as tank destroyers and assault guns . Tank destroyers, intended to operate mostly from defensive ambush operations, did not need

4488-403: The cross-section of vertical reinforced concrete elements is inhomogeneous. The reinforcement in a RC structure, such as a steel bar, has to undergo the same strain or deformation as the surrounding concrete in order to prevent discontinuity, slip or separation of the two materials under load. Maintaining composite action requires transfer of load between the concrete and steel. The direct stress

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4576-408: The definition was widened to include a protected space for guns in a ship, either within the hull or in the lower part of the superstructure . Although the main armament of ships quickly began to be mounted in revolving gun turrets , secondary batteries continued to be mounted in casemates; however, several disadvantages eventually also led to their replacement by turrets. In tanks that do not have

4664-533: The early 1860s, the British, apprehensive about a possible French invasion , fortified the naval dockyards of southern England with curved batteries of large guns in casemates, fitted with laminated iron shields tested to withstand the latest projectiles. However, in the American Civil War (1861–1865), the exposed masonry of casemate batteries was found to be vulnerable to modern rifled artillery ; Fort Pulaski

4752-584: The end of World War II. The last ships built with casemates as new construction were the American Omaha -class cruisers of the early 1920s and the 1933 Swedish aircraft cruiser HSwMS  Gotland . In both cases the casemates were built into the forward angles of the forward superstructure (and the aft superstructure as well, in the Omahas). In regards to armored fighting vehicles, casemate design refers to vehicles that have their main gun mounted directly within

4840-461: The end of the century, Imperial Germany had developed a new form of fortification called a feste ( German article: Festung#Feste ), in which the various elements of each fort were more widely dispersed in the landscape. These works, the first of which was Fort de Mutzig near Strasbourg , had separate artillery blocks, infantry positions and underground barracks, all built of reinforced concrete and connected by tunnels or entrenchments. Although

4928-403: The examples of a non-linear numerical simulation and calculation visit the references: Prestressing concrete is a technique that greatly increases the load-bearing strength of concrete beams. The reinforcing steel in the bottom part of the beam, which will be subjected to tensile forces when in service, is placed in tension before the concrete is poured around it. Once the concrete has hardened,

5016-452: The first concrete buildings constructed in the United States was a private home designed by William Ward , completed in 1876. The home was particularly designed to be fireproof. G. A. Wayss was a German civil engineer and a pioneer of the iron and steel concrete construction. In 1879, Wayss bought the German rights to Monier's patents and, in 1884, his firm, Wayss & Freytag , made the first commercial use of reinforced concrete. Up until

5104-506: The first iron reinforced concrete structure, a four-story house at 72 rue Charles Michels in the suburbs of Paris. Coignet's descriptions of reinforcing concrete suggests that he did not do it for means of adding strength to the concrete but for keeping walls in monolithic construction from overturning. The, 1872–1873, Pippen building in Brooklyn stands as a testament to his technique. In 1854, English builder William B. Wilkinson reinforced

5192-445: The gun except at the moment of firing. Casemates for secure barrack accommodation and storage continued to be built; the 1880s French forts of the Séré de Rivières system for example, had a central structure consisting of two stories of casemates, buried under layers of earth, concrete and sand to a depth of 18 metres (59 ft), intended to defeat the new high explosive shells. Towards

5280-573: The high-angle fire of mortars and howitzers . The advantages of casemated artillery were proved in the Crimean War of 1853–1856, when attempts by the Royal Navy to subdue the casemated Russian forts at Kronstadt were unsuccessful, while a casemated gun tower at Sevastopol , the Malakoff Tower , could only be captured by a surprise French infantry attack while the garrison was being changed. In

5368-400: The hull and lack the rotating turret commonly associated with tanks. Such a design generally makes the vehicle mechanically simpler in design, less costly in construction, lighter in weight and lower in profile. The saved weight can be used to mount a heavier, more powerful gun or alternatively increase the vehicle's armor protection in comparison to regular, turreted tanks. However, in combat

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5456-399: The inner wall was part of the outer buildings of the settlement, and finally filled casemate walls, where the rooms between the walls were filled with soil right away, allowing for a quick, but nevertheless stable construction of particularly high walls. In fortifications designed to resist artillery, a casemate was originally a vaulted chamber usually constructed underneath the rampart . It

5544-645: The knowledge of reinforced concrete developed during the previous 50 years, Ransome improved nearly all the styles and techniques of the earlier inventors of reinforced concrete. Ransome's key innovation was to twist the reinforcing steel bar, thereby improving its bond with the concrete. Gaining increasing fame from his concrete constructed buildings, Ransome was able to build two of the first reinforced concrete bridges in North America. One of his bridges still stands on Shelter Island in New Yorks East End, One of

5632-811: The light green color of its epoxy coating. Hot dip galvanized rebar may be bright or dull gray depending on length of exposure, and stainless rebar exhibits a typical white metallic sheen that is readily distinguishable from carbon steel reinforcing bar. Reference ASTM standard specifications A1035/A1035M Standard Specification for Deformed and Plain Low-carbon, Chromium, Steel Bars for Concrete Reinforcement, A767 Standard Specification for Hot Dip Galvanized Reinforcing Bars, A775 Standard Specification for Epoxy Coated Steel Reinforcing Bars and A955 Standard Specification for Deformed and Plain Stainless Bars for Concrete Reinforcement. Another, cheaper way of protecting rebars

5720-470: The main armament of these forts was still mounted in armored turrets, local defense was provided by separate protected positions for field guns ; these concrete structures were copied by the French who called them casemates de Bourges ( French article: Casemate de Bourges ) after the proving ground where they had been tested. Following experience gained in the World War I , French engineers began to design

5808-514: The main deck, and later on the upper deck as well. Casemates on the main deck were very close to the waterline. In the Edgar -class cruisers, the guns in the casemates were only 10 feet (3.0 m) above the waterline. Casemates that were too close to the waterline or too close to the bow (such as in the 1912 Iron Duke -class dreadnoughts ) were prone to flooding, making the guns ineffective. Shipboard casemate guns were partially rendered obsolete by

5896-438: The microscopic rigid lattice, resulting in cracking and separation of the concrete. For this reason, typical non-reinforced concrete must be well supported to prevent the development of tension. If a material with high strength in tension, such as steel , is placed in concrete, then the composite material, reinforced concrete, resists not only compression but also bending and other direct tensile actions. A composite section where

5984-656: The most efficient floor system is key to creating optimal building structures. Small changes in the design of a floor system can have significant impact on material costs, construction schedule, ultimate strength, operating costs, occupancy levels and end use of a building. Without reinforcement, constructing modern structures with concrete material would not be possible. When reinforced concrete elements are used in construction, these reinforced concrete elements exhibit basic behavior when subjected to external loads . Reinforced concrete elements may be subject to tension , compression , bending , shear , and/or torsion . Concrete

6072-448: The passivation of steel at the anodic oxidation sites. Nitrite is a much more active corrosion inhibitor than nitrate , which is a less powerful oxidizer of the divalent iron. A beam bends under bending moment , resulting in a small curvature. At the outer face (tensile face) of the curvature the concrete experiences tensile stress, while at the inner face (compressive face) it experiences compressive stress. A singly reinforced beam

6160-588: The post-war period. Heavy casemate tank destroyer designs such as the US T28 and the British Tortoise never went beyond prototype status, while casemate vehicles of a more regular weight, such as the Soviet SU-122-54 , saw only very limited service. The general decline of casemate vehicles can be seen in the technological progress which resulted in the rise of universal main battle tanks , which unified in them

6248-433: The reinforced concrete element is subject to increasing bending moment, the tension steel yields while the concrete does not reach its ultimate failure condition. As the tension steel yields and stretches, an "under-reinforced" concrete also yields in a ductile manner, exhibiting a large deformation and warning before its ultimate failure. In this case the yield stress of the steel governs the design. An over-reinforced beam

6336-636: The resistance of the outer wall against battering rams. Originally thought to have been introduced to the region by the Hittites , this has been disproved by the discovery of examples predating their arrival, the earliest being at Ti'inik (Taanach) where such a wall has been dated to the 16th century BC . Casemate walls became a common type of fortification in the Southern Levant between the Middle Bronze Age (MB) and Iron Age II, being more numerous during

6424-554: The sense of "false". However, it may have been ultimately derived from the Greek chásmata ( χάσματα ), a gap or aperture. The term casemate wall is used in the archaeology of Israel and the wider Near East , having the meaning of a double wall protecting a city or fortress, with transverse walls separating the space between the walls into chambers. These could be used as such, for storage or residential purposes, or could be filled with soil and rocks during siege in order to raise

6512-581: The size and location of cracks can be limited and controlled by appropriate reinforcement, control joints, curing methodology and concrete mix design. Cracking can allow moisture to penetrate and corrode the reinforcement. This is a serviceability failure in limit state design . Cracking is normally the result of an inadequate quantity of rebar, or rebar spaced at too great a distance. The concrete cracks either under excess loading, or due to internal effects such as early thermal shrinkage while it cures. Ultimate failure leading to collapse can be caused by crushing

6600-468: The structure will receive warning of impending collapse. The characteristic strength is the strength of a material where less than 5% of the specimen shows lower strength. The design strength or nominal strength is the strength of a material, including a material-safety factor. The value of the safety factor generally ranges from 0.75 to 0.85 in Permissible stress design . The ultimate limit state

6688-524: The structures. The fort also had deep wide trenches, some as much as 9 m (30 ft) in both dimensions. They were also surrounded by a thick layer of barbed wire entanglements. Each fort had 2–4 batteries , equipped with hydraulic rotating steel turrets (100–150 mm). In the summer of 1944, only 10% of the batteries were fully operational. Most of those were in Fort Driant (Feste Kronprinz) and Fort Jeanne d'Arc (Feste Kaiserin). By November, during

6776-456: The tactical situation. The Wehrmacht employed several casemate tank destroyers, initially with the still- Panzerjäger designation Elefant with an added, fully enclosed five-sided (including its armored roof) casemate atop the hull, with later casemate-style tank destroyers bearing the Jagdpanzer (literally 'hunting tank') designation, with much more integration of the casemate's armour with

6864-671: The tank hull itself. Examples are the Jagdpanzer IV , the Jagdtiger and the Jagdpanther . Assault guns were designated as 'Sturmgeschütz', like the Sturmgeschütz III and Sturmgeschütz IV . In the Red Army, casemate tank destroyers and self-propelled guns bore an "SU-" or "ISU-" prefix, with the "SU-" prefix an abbreviation for Samokhodnaya Ustanovka , or "self-propelled gun". Examples are

6952-454: The tension on the reinforcing steel is released, placing a built-in compressive force on the concrete. When loads are applied, the reinforcing steel takes on more stress and the compressive force in the concrete is reduced, but does not become a tensile force. Since the concrete is always under compression, it is less subject to cracking and failure. Reinforced concrete can fail due to inadequate strength, leading to mechanical failure, or due to

7040-490: The term "casemate" has been used in a number of ways, but it generally refers to a protected space for guns within a ship's hull or superstructure. The first ironclad warship, the French ironclad  Gloire (1858), was a wooden steamship whose hull was covered with armored plating, tested to withstand the largest smoothbore guns available at the time. The response by the British Royal Navy to this perceived threat

7128-432: The term referred to a vaulted chamber in a fort , which may have been used for storage, accommodation, or artillery which could fire through an opening or embrasure . Although the outward faces of brick or masonry casemates proved vulnerable to advances in artillery performance, the invention of reinforced concrete allowed newer designs to be produced well into the 20th century. With the introduction of ironclad warships,

7216-403: The water mix before pouring concrete. Generally, 1–2 wt. % of [Ca(NO 2 ) 2 ] with respect to cement weight is needed to prevent corrosion of the rebars. The nitrite anion is a mild oxidizer that oxidizes the soluble and mobile ferrous ions (Fe ) present at the surface of the corroding steel and causes them to precipitate as an insoluble ferric hydroxide (Fe(OH) 3 ). This causes

7304-410: Was breached in a few hours by only ten such guns. In contrast, hastily constructed earthworks proved much more resilient. This led to casemates for artillery again falling out of favor. In continental Europe, they were often replaced by rotating gun turrets, but elsewhere large coastal guns were mounted in less expensive concrete gun pits or barbettes , sometimes using disappearing carriages to conceal

7392-577: Was commissioned to build a fort on the Île-d'Aix , defending the port of Rochefort, Charente-Maritime . The outbreak of the Anglo-French War forced him to hastily to build his casemated fort from wood but he was able to prove that his well-designed casemates were capable of operating without choking the gunners with smoke. The defenses of the new naval base at Cherbourg were later constructed according to his system. After seeing Montalembert's coastal forts, American engineer Jonathan Williams acquired

7480-404: Was granted a patent for reinforcing concrete flowerpots by means of mixing a wire mesh and a mortar shell. In 1877, Monier was granted another patent for a more advanced technique of reinforcing concrete columns and girders, using iron rods placed in a grid pattern. Though Monier undoubtedly knew that reinforcing concrete would improve its inner cohesion, it is not clear whether he even knew how much

7568-418: Was intended to be impenetrable and could be used for sheltering troops or stores. With the addition of an embrasure through the scarp face of the rampart, it could be used as a protected gun position. In bastion forts , artillery casemates were sometimes built into the flanks of bastions , but in action they quickly filled with smoke making them inoperable and for that reason, had fallen out of favor during

7656-422: Was strongly questioned by experts and recommendations for "pure" concrete construction were made, using reinforced concrete for the floors and walls as well as the frames. In April 1904, Julia Morgan , an American architect and engineer, who pioneered the aesthetic use of reinforced concrete, completed her first reinforced concrete structure, El Campanil, a 72-foot (22 m) bell tower at Mills College , which

7744-411: Was to build an iron-hulled frigate, HMS  Warrior  (1860) . However, it was realised that to armor all of the hull to fully withstand the latest rifled artillery would make it unfeasibly heavy, so it was decided to create an armored box or casemate around the main gun deck, leaving the bow and stern unarmored. The American Civil War saw the use of casemate ironclads : armored steamboats with

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