definitions Flashcards
centroid/ barycentre
geometric centre of mass/ gravity as defined by x and y coordinates from a reference axis
neutral surface and axis
the neutral surface where the fibers are neither contracted nor extended (under stress), the axis is where this intersects the cross section
second moment of area or the moment of inertia (I)
geometrical property conveying how the points of a section are dispersed with respect to an arbitrary axis in the cross-sectional plane
parallel axis theorem
moments of inertia with respect to different parallel axis can be added together (also with the sums of Ah^2) to find the second moment of area for the whole section
Equilibrium
When a structure is initially at rest and remains at rest when subjected to a system of forces and couples
Couple(t)
a system of forces with a resultant moment but no resultant force
(Externally) Statical Determinancy
all the support reactions can
be determined by solving the equations of equilibrium
Degree of redundancy
The no. of external restraint greater than the no. of equilibrium equations (3/ more with internal supports)
factor of safety
an indication of a structure’s capacity to withstand load beyond its intended/necessary value
principle of superposition
if a structure of linear elastic material is subjected to loads which do not cause strain beyond the linear elastic region, the resultant effect is equal to the algebraic sum
bending moment
reaction induced by external force or moment causing element to bend
Shear(ing) force
internal resistance across a cross section to a transverse external load
point of contraflexure
the point of zero moment where the moment changes from sagging (+ve) to hogging (-ve) or vice versa
bending stress
longitudinal stresses acting parallel or longitudinal to the beam (tensile or compressive) induced by bending moment application
truss
a pin jointed structural frame of triangles (created by members jointed at nodes)
