Chapter 5 Flashcards
(6 cards)
List 3 things that bonding depends on
1) Chemical adhesion btw steel and concrete
2) Friction due to roughness of bar
3) Mechanical Anchorage of the ribs on the bar
What are the 2 modes of bond failure and explain them.
1) Splitting Bond Failure: Splitting of the concrete cover. Occurs when there is a small concrete cover and the spacing of the bars is small, less than min, and there is no concrete btw bars to resist the shear forces.
2) Pull out Failure: The crushing of the concrete in between the ribs on the bar. Occurs when there is a large concrete cover, large spacing and small bar diameters.
What is development length?
Development length is the length required to prevent the bar from pulling out of the concrete. The length needed for the steel to resist a given stress.
What are k1,k2,k3,k4?
k1 = Bar location factor k2 = Coating factor k3 = concrete density factor k4 = Bar size factor
List 5 reasons why ACOP is used?
1) To minimize possible diagonal cracks. - @ TCOP the effects of the discontinuity tends to open up cracks
2) Variations in bending moment
3) stress concentrations - where the previous bar is cut, there is a large stress transfer from the cut bar to the continuing bars
4) needs to be sufficient development on either side of the critical section
5) when cut in areas of high shear, stress concentrations form.
Why use bent bars?
contribute to shear reinforcement
effective in resisting the spread of diagonal cracks