ES - amace

Engineering mechanics

The science that considers the effects of forces on rigid bodies

Force

Is what exchanges or tends to change the state of motion of a body

External effects

1.shear

2.moment

3.torque

Internal effects

Stress

Resultant force

Is a single force that represents the net effect of a force system

Moment of a force

Measure of the tendency to rotate at a point force, moment arm rotation and moment center

Free body diagram

A drawing of the structure/part of the structure under consideration

Types of supports

1.cable

2.roller support

3.pin or hinge support

Equilibrium

The state or condition in a body wherein the resultant is zero

Conditions of equilibrium

1.resultant is zero

2.the sum of the moments about any point in the system is zero

Moment arm

The distance between the axis of rotation and the perpendicular of the line of action of a force

Components of a force

Fx-F x cos and Fy- Fx sin

Statics

The part of mechanics that considers the effects of and the distribution of forces on rigid bodies which are and remain at rest

Rigid body

A definite amount of matter whose parts are fixed in position relative to one another

Concurrent force system

A type of force system wherein the lines of action of forces meet at a common point

Method of joints

Finding the reactions at each support

Method of sections

Utilizes the principle of moments and the resolution of a force into its components

Axial force

This component measures the pulling or pushing action over the section

Shear force

These are components of the total resistance to sliding the portion to one side of the exploration section

Torque

This component measures the resistance to twisting the members

Bending moments

These components measure the resistance to bending the member about the Y or Z axes

Stress

Unit strength of a material

Concentrated load

Load acting on a particular point

Uniformly distributed load

(Rectangular loading) uniform magnitude

Uniformly varying load

(Triangular loading) distributed load which uniformly varies with the distance

Simple beam or simply supported beam

Supported by a roller and a hinge at both ends

Overhanging beam

Supported by a roller and a hinge with one or both extending beyond supports

Cantilever beam

Supported by a fixed support at one end only

Fixed or restrained beam

Fixed support at both ends

Propped beam

...

Continuous beam

With three or more supports

Mechanics

Science of mechanics treats on forces, motion and the effects of forces on the bodies which they act

Applied mechanics

Concerns mainly on the applications of the principles of mechanics to the solution of problems commonly encountered

Structural system

A system of structural components that makes up a structure. It is interconnected as to provide rigidity and resist the effect of forces whether directly or indirectly

Structural system components

These are structural elements such as beams, girders, columns, trusses, etc

Statics

Deals with forces and effect on rigid bodies at rest

Dynamics

Deals with motion and with the effects forces acting on rigid bodies in motion

Kinematics

Study of motion without consideration of forces causing the motion

Kinetics

Study of forces acting on rigid bodies in motion and their effect in changing such motion

Force

Influence on a body producing a change in shape or movement

Compressive force

An applied force which produces compression in an elastic material

Tensile force

An applied force which produce tension in an elastic material

Vector

A quantity possessing both magnitude and direction represented by an arrow whose length is proportional to the magnitude. Force, velocity, acceleration, moment

Scalar

Quantity having magnitude only. Ft, kg, newton

Characteristics of a force

Magnitude

Line of action

Point of application

Direction

Applied or contacting forces

Push or pull produced by mechanical effort

Acting force

Acting directly on a body

Reacting force

Generated by the action of one body to another

Non-applied or non contacting force

Gravitational pull, magnetic force or inertia force

Coplanar

Condition where all forces lie on one plane

Parallel

Non-concurrent forces having parallel lines of action

Concurrent

Where the lines of action of all the forces intersect at a common point

Non-coplanar

Forces do not lie on one plane

Non-concurrent

Lines do not intersect at a common point

Collinear

All forces in a parallel system act along a single line of action

Triangle method

Graphic technique for finding the vector sum of 2 concurrent forces by displacing one force vector parallel to itself completing the triangle with a vector that represents the resultant force

Parallelogram law

System of determining the resultant force of 2 concurrent forces obtained from the diagonal at a parallelogram having adjacent sides which represent the 2 force vectors being added

Polygon method

Graphic technique for finding the vector sum of a coplanar force system of several concurrent forces by drawing to scale each force vector in succession with the tall of each of the head of one preceding it and completing the polygon with a vector that represents the resultant force

Strength of materials

Extends the study of forces that was begun in mechanics. Deals with relations between externally applied loads and their internal effects on bodies

Theory of structures

Deals with the principles and methods by which the direct stress, shear and bonding moment and the deflection art any section of each constituent member in the structure may be calculated

Moment

Tendency of a force to produce rotation of a body about a point or line, equal in magnitude to the product of the force and the moment arm acting in a clockwise/counter direction

Moment center

Point at which the axis of a moment intersects the plane of the forces causing the moment

Moment arm

Perpendicular distance from the line of action of a force to the point or line about which a moment occurs

Couple

Force system of 2 equal, parallel forces acting in opposite directions and tending to produce rotation

Moment of a force

Tendency to produce a rotation of the body on which it acts about an axis

Static equilibrium

Condition in which forces in a state of rest are acting in opposite direction of the same magnitude

Force law of equilibrium

Implies a balance of opposing forces within a system

Stress

Resistance to external forces

Strain

Subjected to an external force

Tensile stress

Pull

Compressive stress

Push

Normal stress

Perpendicular to stressed surface

Shearing stress

Parallel

Axial stress

External stress acting on a member parallel to its major axis and member is of constant cross section

Bearing stress

Compressive stress exerted on an external surface of a body

Ultimate stress

Greatest unit stress a material can withstand

Allowable stress

Portion of the ultimate strength which may safely be used in design

Live load

Moving load on a structure, acts downward

Dead load

Static load, downward

Dynamic load

Often with rapid change in magnitude and location

Moving load

Kinetic load of a short duration due to moving vehicles

Occupancy load

Live on structure resulting from the weight of people, etc

Wind load

Exerted by the kinetic energy of a moving mass of air

Transverse load

Load applied perpendicular to the longitudinal axis

Axial load

Tensile acting along the longitudinal axis

Roller type support

Offers resistance in a direction normal to the surface beneath the roller, does not resist movement parallel to the supporting surface

Hinge type support

Prevents movement along the horizontal and vertical directions but does not resist rotation about the hinge

Link type support

Offers resistance in the direction along the link and through 2 pins

Fixed-end type support

Resists rotation about the support and to movements along the horizontal and vertical directions

Section properties centroid

Center of one or two dimensional figure about which the sum of the displacements of all points is zero

Center of gravity

Point at which the entire weight is considered concentrated

Center of mass

Point at which the entire mass of is concentrated

Moment of inertia

Sum of the products obtained by multiplying an element of mass by the square of its distance from the axis

Radius of gyration

Distance from its moment of inertia axis at which the entire area is considered concentrated without changing the numerical value of its moment of inertia

Modulus of elasticity

The ratio of the shearing stress to the shearing strain

Modulus of rigidity

Coefficient of elasticity expressing the ratio between shearing stress and strain produced by stress

Truss

Structural frame based on the geometric rigidity of the triangle and composed of linear members subject to axial tension and compression

Creep

Property which causes some materials under constant stress to deform slowly over a period of time

Machinability

Readiness with which a material yields to shaping with cutting tools

Strength

Resist stress without failure