STRUCTURE IDENTIFICATION

SANA PUMASA KAY SIR JOLLY

The prediction of the performance of a given structure under prescribed loads and/or other external effects, such as support movements and temperature changes

Structural Analysis

Is an integral part of this process

Structural Analysis

Its function being the prediction of the performance of the proposed structure

Role of Structural Analysis in Structural Engineering Projects

The science of planning, designing and constructing safe, economical structures

Structural Engineering

These members are subjected to pure tension under the action of external loads

Tension Structures

Susceptible to buckling or instability, the possibility of such a failure should be considered in their designs, if necessary, adequate bracing must be provided to avoid such failures

Compression Structures

These are composed of straight members connected at their ends by hinged connections to form a stable configuration

Trusses

A structure is in ____ initially at rest, it remains at rest when subjected to a system of forces and couples

Equilibrium

if a structure is in equilibrium, then all its members and parts are also in?

equilibrium

A structure is ____ or rigid, if it maintains its shape and remains a rigid body when detached from the supports.

Internally Stable

A structure is ____ (or nonrigid) if it cannot maintain its shape and may undergo large displacements under small disturbances when not supported externally

internally unstable

An internally stable structure is ___ externally, if all its support reactions can be determined by solving the equations of equilibrium

Statically Determinate

If a structure is supported by more than three reactions, then all the reactions cannot be determined from the three equations of equilibrium, such structures are termed _______ _______ _______

Statically Indeterminate externally

Formula for Determinancy of Structure

i = r - (3 + ec)

where;

r - number of external reactions

ec - equations of condition

for determinacy of structure, what does
i < 0
i = 0

i > 0
stands for?

If i < 0 -it is statistically unstable externally

If i = 0 -it is statistically determinate externally

If i > 0 -it is statistically indeterminate externally, and its degree if indeterminacy is the value of “i”

Alternative Approach for Determinacy of Structure

i = (r + fi) -3n

where;

r - number of external reactions

fi - number of internal reactions

n - number of rigid members in the structure

Is an assemblage of straight members connected at their ends by flexible connections to form a rigid configuration

truss

are commonly used for supporting decks of bridges and roofs of buildings

plane trusses

Determining Internal Stability

m < 2j - 3; the truss is internally unstable

m > or equal to 2j - 3; the truss is internally stable

where

m - number of members

j - number of joints

Static Determinacy, Indeterminacy, and Instability of Plane Trusses

m + r < 2j ; statically unstable truss

m + r = 2j ; statically determinate truss

m + r > 2j ; statically indeterminate truss

i = (m + r) − 2j ; degree of indeterminacy

where m – number of members

j – number of joints

r – number of external reactions