Materials
What is the ultimate strength of Grade 60 rebar?
90 ksi
Where is the equation that defines the cracking moment?
Mcr = fr*I/y
Where should tension reinforcement be placed for a cantilever beam?
closer to the top surface
What is development length?
The length required to develop bond to concrete and yield strength in rebar.
What is the ultimate strain of concrete assumed in design?
0.003
What is the shape of the stress distribution of concrete in tension before cracking?
Linear, or 1st degree, or triangular
What is the condition for a beam to be tension controlled?
If the neutral axis depth is smaller, strain in tension rebar is higher/lower?
higher
What is the most commonly used function that fits the concrete stress-strain curve?
parabola
What is the shape of the stress distribution of concrete in compression before cracking?
Linear, or 1st degree, or triangular
What does balanced reinforcement mean?
the reinforcement amount that leads to yielding at the same time concrete crushes.
When the tension rebar area is large, strains in rebar are small/large?
large?
What is the name of the equivalent rectangular compression block?
Whitney
What happens to the neutral axis depth when the section cracks?
neutral axis depth gets smaller
What is the purpose of the minimum reinforcement requirement?
to ensure section doesnt fail right after cracking.
What happens to the neutral axis depth when rebar yields?
Gets smaller so that the compression force can stay constant.
What is the difference between creep and shrinkage?
Shrinkage occurs due to evaporation, creep is due to sustained compression.
What state does concrete have to be (cracked, uncracked, etc) so that section equlibrium can be used to obtain stresses across the cross section?
Any state
List one reason why compression reinforcement may be needed?
To provide additional capacity or ductility, to help with creep, to facilitate construction.
A higher concrete strength would lead to higher/lower rebar strain?
higher