Chapter 4 Load Resistance

Load carrying capacity for a simple rectangular been with a concentrated load

1. Inversely proportional to span length -double the span, decrease the length 2. Directly proportional to section modulus 3. Directly proportional to unit strength of the material

The units of modulus of elasticity are

All of the above (psi, ski, pa. Gpa)

Concrete is what type of material

An elastic material

Low-carbon (mild) steel is

An elastic-plastic material Elastic to a certain point - and then plastic. Will return to original shape up until the yield stress. Then permanent deformation.

Ductile and brittle materials

Ductile - deform greatly before failure Brittle - no warning before failure

Which gives greater warning before failure?

Ductile material

In a steel column that rests on a concrete footing, the area of the bearing plate used is generally

Greater than the cross sectional area of the column

In relation to its compressive strength, the tensile strength of concrete is

Much lower

The primary purpose of ties in a reinforced concrete column is to

Prevent the buckling of vertical reinforcement in the column

Stress

Result of the load applied on the tributary area f=P/A

modulus of elasticity refers to how

Stiff a material is

In a suspension bridge, which members are in compression?

Support pylons

In a typical stress-strain diagram of a material, the stress is generally plotted along the vertical axis

True

The bending stresses along the neutral axis of a beam are

Zero

When a cable or rope is compressed by force, what is the compressive stress in it?

Zero

Torsion

act of twisting; stress due to twisting forces exerted on a beam Compression and tension at the same time

Bending

compression and tension at the same time, but in opposite directions

Shear

force directed parallel to a surface compression and then tension failure

bending moment

results from the applied load acting to rotate or twist an object

ultimate strength

the maximal amount of stress a material can withstand without breaking

Strength

Comes from section modulus and tensile strength In simple beams: Proportional to width and proportional to the square of the depth

The horizontal blocking in wood studs helps prevent

Buckling of studs

The material in an arch is primarily in

Compression

The test specimen used for determining the compressive strength of concrete in the United States is a

Cylinder measuring 6in in diameter x 12in high

In a simple three member truss consisting of two rafters and a tie, each member is in

Either tension or compression

The primary purpose of longitudinal steel bars in a reinforced concrete beam is to overcome the weakness of concrete in tension

True

The stress strain diagram of mild steel is nearly a straight line up to the yield point

True

When we determine the strength of concrete using the test specimens we determine the concretes

Ultimate compressive stress