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
