ARCH 324 Structures II Primer Questions Peter von Buelow
Deflection
1. What roof top phenomena, which can lead to dangerousdeflections, is show in the photo?
A) Ponding
2. What is the equation for the maximum deflection ofthe uniformly loaded beam below?
A)
5wL4
384EI
3. Which of the following statements about cantilever beams is true?
A) The fix end has maximum moment but zero slope and deflection
4. In all simple beams, the point of zero slope is the point of maximum deflection.True or False?
A) True
5. For the loading shown below, where will the deflection be equal to zero?
A) A
6. What three factors affect a structural member’s stiffness?
A) Material Stiffness, EB) Sectional Stiffness, IC) Beam Length, L
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7. Which beam has the greater center line deflection?The two beams at the right have the same span,section and uniform loading.
A) A
8. Determine the maximum deflection for a simply supportedbeam shown:
P = 5 kips
L = 10 ft
E = 29,000 KSI
I = 400 in4
A)
9. Is the amount of deflection a beam should be designed for an absolute restriction?
A) No, although absolute guidelines are given in codes, the amount of tolerable deflectionis ultimately a matter of judgment.
10. What is the most commonly used limit for floor live load deflections?
A) Deflection should not exceed 1/360 of the span
11. The deflection limit of 1/360 of the span was originally determined based on the serviceabilityrequirements of what material?
A) cracking of plaster ceilings. It was determined that plaster ceilings crack with adeflection larger than 1/360 of the span.
12. The calculation of deflection in beams is primarily performed to anticipate which type of structuralproblems?
A) Serviceability
13. In the mathematical sequence of diagrams by integration what follows a load diagram, a sheardiagram, and a moment diagram?
A) A slope diagram and then a deflection diagram
14. For a simply supported symmetrically loaded beam, where is the maximum slope of the elasticcurve?
A) At the ends (equal and opposite each other)
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15. What values need to be multiplied with the areas of the moment diagram in order to calculate theangle of the elastic curve and the deflection value?
A) 1/(EI), that is the inverse of the modulus of elasticity times the moment of inertia of themember.
16. For a symmetrically loaded simply supported beam, where is the maximum deflection?
A) At midspan
17. Can the diagram method of analysis be used to determine the value of the deflection for a simplysupported beam that is not symmetrically loaded?
A) Yes, although a solution requires some additional work because the point of zero slopecannot be assumed to be at the midspan of the beam.
18. In a simply supported and symmetrically loaded beam, the maximum deflection occurs at the:
A) The center line
19. A 30 ft. beam is calculated to have a deflection of 1.25”. Would the beam pass or fail a deflectionlimit criteria of L/240?
A) L/240=360/240=1.5>1.25 , therefore it passes
20. In diagrams, how is the slope of a beam measured?
A) The angle in radians of a tangent to the elastic curve
21. Is deflection always located at the point of maximum moment?
A) No, it is located at the point of zero slope.
22. Where is the slope maximum for a cantilever beam?
A) At the free end
23. When determining deflection of asymmetric beams using the diagram method what is a difficulty inbuilding the diagrams?
A) Locating the point of zero slope or maximum deflection
24. When solving deflection equations, if lengths are taken in feet, what is the conversion to finddeflection in inches?
A) 1728 in3 / 1 ft3
25. For simple span beams using the diagram method, what observations about the slope diagramhelps to find the point of maximum deflection?
A) The positive and negative areas of the diagram will be equal. The point between the leftand right parts of diagram will be zero and be the point of maximum deflection.
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26. For a simple span beam with 1/3 point loading, where would the approximate location of themaximum deflection be?
A) Between the load and the center line, and closer to the center
27. Of the parameters which determine deflection, which has the greatest effect when changed? Forexample if each were changed by 10% which would have the greatest effect on deflection?
A) The length of the beam
28. For simple span beams, where is the vertex of the slope curve located?
A) At the ends.
29. What additional information beyond the moment diagram is needed to calculate slope or deflection?
A) E and I
30. When using superposition of equations to find the maximum deflection of an asymmetrically loadedbeam, what must be observed regarding location?
A) The location of the maximum deflection of each case is not the same as thecombined case.
31. In the beam shown, where is the slope greatest?
A) B
32. The maximum deflection for a simply supported, asymmetrically loaded beam is always located at:
A) The point of zero slope
