page_title: Structural engineering
section_title: Trusses
hierarchical_section_title: Structural engineering / Structural elements / Trusses
caption_attribution_description: English: The James S. McDonnell Planetarium is located in Forest Park in en:St. Louis, Missouri. The en:James S. McDonnell en:Planetarium was built in en:1963 and operated by the city of St. Louis. In en:1983 it became part of the en:St. Louis Science Center, to which it is joined by an enclosed pedestrian bridge across en:Interstate 64, reopening in en:1985 after extensive remodelling. The planetarium features a en:Zeiss Planetarium Model IX projector capable of showing the locations of 9000 en:stars and the en:planets on an 80-foot (24 m) dome. In addition to the planetarium theater, the building is home to many displays on space sciences on two levels.[1] The shape of the building's unique roof is known mathematically as a en:hyperboloid of one sheet.
context_page_description: Structural engineering is a sub-discipline of civil engineering in which structural engineers are trained to design the 'bones and muscles' that create the form and shape of man-made structures. Structural engineers need to understand and calculate the stability, strength and rigidity and earthquake of built structures for buildings and nonbuilding structures. The structural designs are integrated with those of other designers such as architects and building services engineer and often supervise the construction of projects by contractors on site. They can also be involved in the design of machinery, medical equipment, and vehicles where structural integrity affects functioning and safety. See glossary of structural engineering.
  Structural engineering theory is based upon applied physical laws and empirical knowledge of the structural performance of different materials and geometries. Structural engineering design uses a number of relatively simple structural concepts to build complex structural systems. Structural engineers are responsible for making creative and efficient use of funds, structural elements and materials to achieve these goals.
context_section_description: A truss is a structure comprising members and connection points or nodes. When members are connected at nodes and forces are applied at nodes members can act in tension or compression. Members acting in compression are referred to as compression members or struts while members acting in tension are referred to as tension members or ties. Most trusses use gusset plates to connect intersecting elements.  Gusset plates are relatively flexible and unable to transfer bending moments. The connection is usually arranged so that the lines of force in the members are coincident at the joint thus allowing the truss members to act in pure tension or compression.
  Trusses are usually used in large-span structures, where it would be uneconomical to use solid beams.
caption: The McDonnell Planetarium by Gyo Obata in St Louis, Missouri, USA, a concrete shell structure
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