Simple structures
A structure can be defined as an assembly of structural components so arranged that loads can be supported without failure .
Collapse may be due to incorrect geometrical arrangement of components comprising the structure or to a failure of one of the components because of an overloading of that component.
Forces that are always present and do not move are called dead loads.
Loads that are not always present and vary in intensity are live load or imposed loads .
Wind forces are assumed to act at right angle to the surface on which wind is blowing .
Loads are applied over a area but the area is small compared with the dimensions of the structure ,it is therefore sufficient to consider the load as being concentrated at a point.
Structures are maintained in equilibrium by reactive force provided by supports of various kinds.
A structural member in tension is called a tie and has internal reactive forces developed within it.
A structural member forming part of a frame and which is in compression is called a strut or a column.
Frictional forces will develop to resist sliding between any 2 surfaces in contact .
Coefficient of friction is the ratio of maximum frictional force to the normal force between the surfaces.
It is unnecessary to provide pin at both ends as one pin is enough to maintain horizontal equilibrium.The other end must be free to move horizontally to allow for bending and other movement under load.This also allows expansion and contraction.
A frictionless roller will give horizontal movement but provide complete vertical restraint .
Fixed support provides 3 restraints .It prevent any rotation of the structure at the support.
Cantilevered structure is completely fixed at one end with no support at the other end .
To be EQUILIBRIUM
Sum of vertical forces, horizontal forces and moments ALL MUST BE ZERO
It is externally statically determinate if have not more than 3 restraints of unknown restraints .
Collapse may be due to incorrect geometrical arrangement of components comprising the structure or to a failure of one of the components because of an overloading of that component.
Forces that are always present and do not move are called dead loads.
Loads that are not always present and vary in intensity are live load or imposed loads .
Wind forces are assumed to act at right angle to the surface on which wind is blowing .
Loads are applied over a area but the area is small compared with the dimensions of the structure ,it is therefore sufficient to consider the load as being concentrated at a point.
Structures are maintained in equilibrium by reactive force provided by supports of various kinds.
A structural member in tension is called a tie and has internal reactive forces developed within it.
A structural member forming part of a frame and which is in compression is called a strut or a column.
Frictional forces will develop to resist sliding between any 2 surfaces in contact .
Coefficient of friction is the ratio of maximum frictional force to the normal force between the surfaces.
It is unnecessary to provide pin at both ends as one pin is enough to maintain horizontal equilibrium.The other end must be free to move horizontally to allow for bending and other movement under load.This also allows expansion and contraction.
A frictionless roller will give horizontal movement but provide complete vertical restraint .
Fixed support provides 3 restraints .It prevent any rotation of the structure at the support.
Cantilevered structure is completely fixed at one end with no support at the other end .
To be EQUILIBRIUM
Sum of vertical forces, horizontal forces and moments ALL MUST BE ZERO
It is externally statically determinate if have not more than 3 restraints of unknown restraints .
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