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In February 1976, work commenced to automate the methods contained in the USAF Stability and Control DATCOM, specifically those contained in sections 4, 5, 6 and 7.The work was performed by the McDonnell Douglas Corporation under contract with the United States Air Force in conjunction with engineers at the Air Force Flight Dynamics Laboratory in Wright-Patterson Air Force Base.
The vertical stabilizer is the fixed vertical surface of the empennage. A vertical stabilizer or tail fin [1] [2] is the static part of the vertical tail of an aircraft. [1] The term is commonly applied to the assembly of both this fixed surface and one or more movable rudders hinged to it. Their role is to provide control, stability and trim ...
The overall mass of concrete can be reduced by 35–50% depending on the design, [1] as a consequence of reduced slab mass, as well as lower requirements for vertical structure and foundations. Biaxial slabs commonly span up to 20 metres at a thickness of around 500 mm. [ citation needed ] The added strength also reduces the acoustic ...
Concrete has a very low coefficient of thermal expansion, and as it matures concrete shrinks. All concrete structures will crack to some extent, due to shrinkage and tension. Concrete which is subjected to long-duration forces is prone to creep. The density of concrete varies, but is around 2,400 kilograms per cubic metre (150 lb/cu ft). [1]
A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. Steel- reinforced slabs, typically between 100 and 500 mm thick, are most often used to construct floors and ceilings, while thinner mud slabs may be used for exterior paving ( see below ).
The precast concrete slab has tubular voids extending the full length of the slab, typically with a diameter equal to the 2/3–3/4 the thickness of the slab. This makes the slab much lighter than a massive solid concrete floor slab of equal thickness or strength. The reduced weight also lowers material and transportation costs.
(2) The thermal expansion coefficients of concrete and steel are so close (1.0 × 10 −5 to 1.5 × 10 −5 for concrete and 1.2 × 10 −5 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.
Depending on the climate, the curing process may take longer and require more frequent wetting. Once the concrete is cured, it sits for two to three weeks before the process is complete. [citation needed] When hydrophobic concrete is made through the use of an admixture, a powder with the hydrophobic chemicals is added during the batching process.