Technical Dictionary for structural mechanics
analysis model the mathematical representation of the behaviour
of a system.
axial force a force that is in the line of a longitudinal axis of
a member; internal force action at a section of a member the resultant
of which acts at the centroid of the section and at right angles to the
axis a line, normally straight, used for reference
bending action load transfer via bending moments
bending moment an internal moment at a section of a member that
acts about an axis that is in the plane of the section.
centroidal axis an axis in the plane of an area that passes
through the centroid of the area.
compression the effect on a body of a force that tends to shorten
cut an imaginary separation of parts of a structure used in
equilibrium calculations; to make such a separation
deflection translation of a body in relation to an external
deformation the relative movement of parts of a structure that
result from a change in shape..
degree of statical indeterminacy the number of force actions in a
frame system that can be released in order to make it statically
direct force a force in a direction that is perpendicular to the
surface on which it is considered to act: see axial force.
direct strain the ratio of the change, due to deformation,
in displacement between two points in a body and the displacement
between the points before deformation
direct stress direct force per unit area
displacement a vector that defines the movement of a point in
relation to a set of axes; a translation or a rotation
equilibrant the single force that balances a set of forces; the
equal and opposite of the resultant.
equilibrium in physics: the condition of static
equilibrium; in engineering mechanics: the condition of static
equilibrium or of dynamic equilibrium
free body diagram a diagram that shows the forces at the
cuts that define a part of a structure.
flange the horizontal parts of an I section
force that which tends to cause or to resist
motion of a body. The SI unit for force is the Newton defined as the
force that will cause a mass of 1 kilogram to accelerate by 1 metre per
second per second. more
force action a direct force, a shear force, a moment or a
fully fixed support
a support for a structure that restrains movement in the coordinate
directions and for rotation
global axis an axis that relates to the geometry of a system.
gravity force a force that causes the reciprocal attraction
of bodies under the effect of their masses: in general,
gravity force is defined by Newton’s universal law of gravitation but in
mechanics ‘gravity force’ is normally defined as the force exerted by
the mass of the Earth on a mass M at the surface of the earth. The
gravity force for a mass M at the surface of the Earth (based on
Newton’s universal law of gravity) is defined by: Fg =
Mg where g is the local gravity constant.
internal force action a force at a cut in a member.
I section a section commonly used for members of steel
joint the position at which members are connected in a structure.
lever arm the perpendicular distance from the line of action of a
force to the line of an axis about which the value of a moment of the
force is to be calculated.
local gravity constant - g the constant, based on
Newton’s Universal Law of Gravitation, used to calculate the gravity
force between the mass of the Earth and a mass M at the surface of the
Earth: the gravity force is: Fg = Mg; g = 9.8
m/sec/sec; g is sometimes denoted as ‘little g’ or as the
‘acceleration due to gravity’
longitudinal axis an axis in the line of a member normally at the
centroid of the area of the member
member part of a structure normally defined between a pair of
moment the tendency of a force to rotate an object; the
value of a moment is the product of the value of the force times the
lever arm about an axis; see bending moment, torque.
moment connection a
connection between members of a frame where there is no relative
rotation between the ends of the members and hence moments can be
transmitted at the member ends
Newton’s universal law of gravitation the
relationship that defines the attractive force - Fgravity between 2
masses m1 and m2 distance r apart: Fgravity = G x m1 x
m2/r2 G is the universal gravity constant (G
= 6.67384 × 10-11 m3 kg-1 s-2)
pin connection a joint in a
frame where the ends of the connected members are free to rotate
pin support a support for a
structure that restrains movement in the coordinate directions but
does not restrain rotations
of a member or component, or a cross-section of a member or
component of a structure. to withstand actions without mechanical
failure e.g. bending resistance, buckling resistance, tension
resistance’ (definition from EN 1990)
resultant a single force that is equivalent to a
set of forces: equal and opposite to the equilibrant.
resultant force action 1. see
resultant 2. an internal force action that
is mainly due to applied forces that are not close to the position
at which it is defined; for example, a bending moment is a resultant
force action because it is not caused by local forces;
roller support a support
that restrians only horizontal movement
rotation a vector that represents the angular movement
about an axis; normally measured in degrees or radians.
scalar a variable defined only by its magnitude
second moment of area property of an area
section the area revealed at a cut
shear force a force in a direction that is parallel to
the surface on which it is considered to act; internal force action
at a section of a member that acts parallel to the section.
shear strain the change, due to deformation, in the angle
between two lines on a body
shear stress shear force per unit area
spring force the force exerted by a body due to strain
statics the mechanics of bodies under the influence of
forces that do not cause them to move.
statical equivalence a force action or set of force
actions that balances a set of forces, equal and opposite to the
static equilibrium the condition that the vector sum of
the static forces on a body is zero
static force a force in a context where there is
a frame structure for which the release of one restraining force
action would convert it to a mechanism. i.e. to being unable to
strain direct strain or shear strain
strength of materials models that predict the
resistance properties of a material as part of a structure.
stress force per unit area
structure ‘organised combination of connected parts
designed to cary loads and provide adequate rigidity’ (EN
structural analysis the use of structural mechanics to
predict the behaviour of structures under load.
structural mechanics the mathematical logic and
procedures used both for structural analysis and for technical
technical assessment the use of design rules, that are mainly
based on structural mechanics and set out in code of practice
provisions, to assess the adequacy of structural members and
tension the effect on a body of a force that tends to shorten
validation consideration of the potential of a process to
satisfy the requirements; consideration of whether a process has
satisfied the requirements.
vector a variable that has properties of magnitude, position
and direction and conforms to the rules of vector algebra.
vector algebra a set of rules for manipulating vectors
vector component a vector that together with other components
can represent a single vector, based on vector algebra.
vector sum the sum of a set of vectors.
web the vertical part of an I section
Young’s modulus the the ratio of direct stress to
direct strain in a material, assumed to be linear.