ES1_Supports and Reactions, Trusses, Method of Joints & Sections Flashcards
It deals primarily with the calculation of external forces which act on rigid bodies in equilibrium.
Statics
It is a combination of a large number of particles occupying fixed positions with respect to each other.
Rigid Body
Rotation is not a concern, so equilibrium could be satisfied by: Summation of F = 0 (no translation)
Concurrent Forces
For a rigid body to be in equilibrium, the net force, as well as the net moment about any arbitrary point O, must be equal to zero.
Summation F = 0
Summation M = 0
Non-concurrent Forces
If a support prevents the translation of a body in a given direction, then a ______ is developed on the body in that direction.
Force
If rotation is prevented, a _______ is exerted on the body.
Couple moment
Number of unknown/s in cables
1
Number of unknown/s in contacting surface
1
Number of unknown/s in roller support
1
Number of unknown/s in pin support
2
Pin connections allow rotation. Reactions at pins are _________and NOT _________.
forces, moments
Number of unknown/s in constrained pin
1
Number of unknown/s in fixed support
3
Equations of Equilibrium
Fx=0; Fy=0; M=0
A structure composed of slender members joined together at their end points.
Truss
It is commonly used in construction consist of wooden struts or metal bars.
Members
They lie in a single plane and are often used to support roofs and bridges.
Planar trusses
Truss members are connected at their ________ only; thus NO member is continuous through a joint.
extremities
A structure made up of a number of straight, slender bars that are joined together at the joints only to form a pattern of triangles (e.g. bridge and roof truss)
Plane Truss
When forces tend to pull the member
apart, it is in _______.
tension
When the forces tend to compress the member, it is in __________.
compression
Members of a truss are slender and not capable of supporting large lateral loads. Loads must be applied at the _______.
Joints
A method of solving wherein to calculate the forces in the members of a truss, the equilibrium equations are applied to individual joints (or pins) of the truss.
Method of Joints
Consist of cutting a truss into two sections at a point where the bar force is required.
Method of Sections
The resulting force system after cutting will generally be ____________ and _________
non-concurrent; coplanar
Determinacy of statically determinate trusses
m = 2n - 3
Determinacy of truss with a redundant member which makes it statically in determinate
m > 2n - 3
in determinacy of trusses, m is the total number of __________
members
in determinacy of trusses, n is the total number of __________
joints
If a joint has only two noncollinear members and there is no external load or support reaction at that joint, then those two members are
zero force members
If three members form a truss joint for which two of the members are collinear and there is no external load or reaction at that joint, then the third non-collinear member is a ____________.
zero force member
The region from O to Elastic Limit
Elastic range
The region from Elastic Limit to Rupture Strength
Plastic range
