BTECH CHERYY FILES (STRUCTURAL TERMS) PART 2

COLUMN

a relatively slender structural member designed primarily to support axial, compressive

loads, applied at the member ends.

POST

a stiff vertical support especially a wooden column in timber framing

BUCKLING

the sudden lateral or torsional instability of a slender structural member induced by the

action of a compressive load. _____________can occur well before the yield stress of the

material is reached

BUCKLING

the axial load at which a column begins to deflect laterally and becomes unsuitable.

CRITICAL BUCKLING LOAD

the maximum axial load that can theoretically be applied to a column without causing it

to buckle. ____________ for a column is inversely proportional to the square

of its effective length and directly proportional to the modulus of elasticity of the material

and to the moment of inertia of the cross section.

Also called EULER BUCKLING LOAD

BIFURCATION

the critical point at which a column carrying its critical buckling load, may either buckle

or remain undeflected. The column is therefore in a state of neutral equilibrium

CRITICAL BUCKLING STRESS

the critical buckling load for a column divided by the area of its cross section

SLENDERNESS RATIO

the ratio of the effective length of a column to its least ratio of gyration

The higher the slenderness ratio, the lower is the critical stress that will cause buckling.

A primary objective in the design of a column is to reduce its slenderness ratio by

minimizing its effective length or maximizing its effective length or maximizing the radius

of gyration of its cross section

RADIUS OF GYRATION

the radial distance from any axis to a point at which the mass of a body could be

concentrated without altering the moment of inertia of the body about that axis. For a

structural section, the__________is equal to the square root of the quotient of the

moment of inertia and the area

The higher the radius of gyration of a structural section, the more resistant the section is

to buckling. In determining the cross- sectional shape of a column, the objective is to

providethe necessary radius of gyration about the different axes. For an asymmetrical

cross section, buckling will tend to occur about the weaker axis or in the direction of the

least dimension

LONG COLUMN

a slender column subject to failure by buckling rather than by crushing

SHORT COLUMN

a thick column subject to failure by crushing rather than by buckling. Failure occurs

when the direct stress from an axial load exceeds the compressive strength of the

material available in the cross section. An eccentric load, however, can produce bending

and result in uneven stress distribution in the section

INTERMEDIATE COLUMN

a column having a mode of failure between that a short column and a long column, often

party inelastic by crushing and partly elastic by buckling

ECCENTRICITY

The amount by which an axis deviates from another parallel axis.

P-DELTA EFFECT

An additional moment developed in a structural member as its longitudinal axis deviates

from the line of action of a compressive force equal to the product of the load and the

member deflection at any point.

MIDDLE THIRD RULE

The proposition that a compressive load should be located within the middle third of a

horizontal section of a column or wall to prevent tensile stresses from developing in the

section.

EFFECTIVE LENGTH

The distance between inflection points in a column subject to buckling load. When this

portion of a column buckles the entire column falls.

COMBINED STRESSES

A set of tensile and compressive stresses resulting from the superposition of axial and

bending stresses at a cross section of a structural member, acting in the same direction

and equal at any point to their algebraic sum.

KERN

The central area of any horizontal section of a column or wall within which the resultant

of all compressive loads must pass if only compressive stresses are to be applied

beyond this area will cause tensile stresses to develop in the section. Also called kern

area.

KERN POINT

A point on either side of the centroidal axis of a horizontal column or wall section

defining the limits of the kern area.

LATERAL BRACING

the bracing of a column or other compression member to reduce its effective length.

___________ is most effective when the bracing pattern occurs in more than one

plane.

UNBRACED LENGTH

the distance between the points at which a structural member is braced against buckling

in a direction normal to its length.

EFFECTIVE LENGTH FACTOR

a coefficient for modifying the actual length of a column according to its end conditions

in order to determine its effective length. Fixing both ends of a long column reduces its

effective length by half and increases its load-carrying capacity by a factor of 4.

METHOD OF SECTIONS

a method of determining member forces in a truss by considering the equilibrium of any

portion of the truss assembly.

METHOD OF JOINTS

a method for determining member forces in a truss by considering the equilibrium of the

various joints idealized as points in free body diagrams

ACTIVE EARTH PRESSURE

a soil pressure acting on any structure that will tend to push the structure wherein the

structure or a wall tends to move away from the soil

ACCELEROGRAPH

is an instrument which measures the velocity and acceleration of an earthquake in the

ground

ANCHOR BOLTS

a round, steel bolt embedded in concrete or masonry used to hold down machinery,

steel columns or beam casting, shock beam plates and engine heads

BALANCED DESIGN

is one which both the concrete and the steel are so proportioned as to work to their full

working stresses when the member carries its full allowable load

BATTER PILES

are piles at an inclination to resist forces that are not critical. This is also known as brace

pile or spur pile

BEARING WALL SYSTEM

a structural system without a complete vertical load carrying space frame

BORED PILE (bearing pile)

a concrete pile which concreted either with a casing or without a casing at its permanent

location. This is a cast in place pile

CAISSON

a watertight, cylindrical or rectangular chamber used to in under water construction to

protect workers from water pressure and soil collapse

CEMENT GUN

is an ejector operated by compressed air to force gunite into cavities or cracks in rocks

or cement works

CHUTE

is an open-top through which bulk materials are conveyed and by gravity

COFFER DAM

a temporary dam- like structure constructed which excludes water from the site of the

foundation during its excavation and construction

CONSTRUCTION JOINT

the vertical or horizontal face in a concrete structure where concreting has been stopped

and continued later

COLD JOINT

formed when a concrete surface hardens before the next batch o f concrete is placed

CREEP

he tendency of most material to move or deform over time under a constant load The

amount of movement varies enormously depending upon the material. The area that is

highly stressed will move the most. The movement causes stresses to be redistributed.

COUNTER

a cantilever wall that is reinforced with a masonry structure extending upward from the

foundation or from the inner face of the retaining wall to provide additional resistance to

thrust and are placed at regular intervals.

COFFER DAM

a temporary watertight enclosure around an area of water or water bearing soil, in which

construction is to take place, bearing on a stable statum at or above the foundation level

of new construction. The water is pumped from within to permit free access to the area

DIAPHRAGM

a horizontal or nearly horizontal system including horizontal bracing system, that act to

transmit lateral forces to the vertical resisting elements

DIAPHRAGM STRUT

a structural member of a horizontal bracing system that takes axial tension or

compression. It is parallel to the applied load that collects and transfers shear to the

vertical resisting elements or distributive loads within the horizontal bracing system

DIVING BELL

a watertight bell- shaped steel chamber which can be lowered to or raised from a fresh

or seawater bed crane. It is opened at the bottom and filled with compressed air so that

men can prepare foundations and undertake similar construction work under water.

DOWEL

a short steel bar extending from one concrete element to another as for instance a

concrete foundation to a concrete column. It may or may not transfer direct stress

DRIFT BOLT

is a long pin of steel or wood, made with or without the head, driven through the timber

and into an adjacent timber to hold them together and to transmit stresses

EXPANSION OR CONTRACTION

a joint designed to take ___________

the designed break in a structure to allow for the drying and temperature shrinkage of

concrete, brickwork of similar material, thereby preventing the formation of harmful

cracks

FATIGUE

is a phenomenon of failure under repeated stresses. A fact, based experience and

experiments, is well known that stresses which are applied to a body a few times without

causing apparent structure injury may, if applied repeatedly or causing a great number

of times, causes failure

GUNITE

is a rich cement mortar which is applied by spraying under high air pressure

GRADE BEAM

a concrete beam placed directly on the ground to provide foundation for the

superstructure

GRANOLITHIC FINISH

a surface layer or granolithic concrete which maybe laid on a base of either fresh or

hardened concrete

GRILLAGE

is a footing which consist of steel beams arranged to distribute a concentrated load to

the supporting masonry or soil

DISTRIBUTION OF HORIZONTAL SHEAR

design analysis requirement, considered as the basis for the structural design of

structures where the total lateral forces are distributed to the various vertical

elements of the lateral force resisting system in proportion to their rigidities

considering the rigidity of the horizontal bracing system or diaphragm

HYBRID STEEL GIRDER

is a fabricated metal beam composed of flanges with a material of a specified minimum

yield strength different from that of the web plate

INTENSITY

the measure of the damage level of an earthquake (subjective to visual assessment)

INFLECTION POINT

a point in the moment diagram where it changes from positive to negative moment of

vise versa and the value of the moment at this point is zero

JETTING

a method of driving piles or well points into the sand in the situations where a pile

hammer might not be suitable owing to the risk of damage by vibration to the piles of

adjacent buildings.

LINTEL BEAM

a beam especially provided over an opening for a door, window, to carry the wall over

the opening