STEEL AND TIMBER 1

Shear

• certain type of stress inside a structural member due to some applied load

• type of stress inside a structural member

• a construction method of resisting wind and earthquake loads.

Shear Stress

a resistive force developed per unit area in a body due to the applied

Shear force

causes shape changes without changing the volume of the body

Strength

• it is the ability of a material to resist external load against failure

• a property and fixed for a particular material

• the primary design factor

Shear strength

• is the ability of the material to resist shear load until failure

• is a property and is constant for material

• is the maximum shear stress developed at the time of failure

When is a body considered to be in equilibrium?

A body is said to be in equilibrium if no net force acts on it.

Two cases in which a body can be inequilibrium:

1. When the body is at rest.

2. When the body is moving at a constant speed without changing direction

Moment

• also sometimes called a torque

• "tendency of a force to rotate a body".

  
  

Pivot

• Forces that create a moment act around a point.

• The point around which the object can rotate or turn

Principle of Moments

• also known as Varignon's theorem

• is a fundamental concept in physics and engineering that describes the equilibrium of a rigid body under the influence of external forces

  
  

Equation for Varignon’s theorem

ΣM = Mr 

• ΣM represents the sum of the moments of the individual forces about a point.

• Mr represents the moment of the resultant force about the same point.

Dead loads

• Self-weight of the structure, and which are always present,

• To calculate the dead load of a building: By calculating the volume of each member and multiplying it by the unit weight of the materials from which it is composed, an accurate dead load can be determinedfor each component.

Live loads or Imposed loads

Embrace all loads except DEAD LOAD, for example, weight of machinery, stores, vehicles, cranes, and people, as well as loading due to wind or water pressure. Unlike dead loads, imposed loads may, or may not, be present.

TYPES OF BEAMS

• SIMPLY SUPPORTED BEAM

• CANTILEVER BEAMS

• FIXED BEAMS

• OVERHANGING BEAMS

• CONTINUOUS BEAMS

  
  

  
  

SIMPLY SUPPORTED BEAM

• rests on two supports and is free to move horizontally or we may say that simply supported beams are defined as having two supports at either end – one pinned and one roller.

• simplest type of beam

  
  

SCHEMATIC DIAGRAM OF SIMPLY SUPPORTED BEAMS

CANTILEVER BEAMS

• are supported from one end, using a fixed support

2 meter to 2.5 meters

Maximum span length of cantilever slab/Beam For normal structure

SCHEMATIC DIAGRAM OF CANTILEVER BEAMS

FIXED BEAMS

have fixed supports at either end – offering moment resistance at either end

SCHEMATIC DIAGRAM OF FIXED BEAMS

OVERHANGING BEAMS

are those with two supports, but unlike simply supported beams, one of the supports is not at the end of the member

SCHEMATIC DIAGRAM OF OVERHANGING BEAMS

CONTINUOUS BEAMS

Are multi-spanned beams that have multiple supports across the length of the beam

SCHEMATIC DIAGRAM OF CONTINUOS BEAM