SS - Notes

Question 1

The resultant is directed away form the starting point

Answer 1

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Question 2

The resultant is concurrent with the original forces (their lines of action pass through a common point)

Answer 2

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Question 3

Equilibrium:

1. The summation of all the horizontal forces acting on the body must equal zero.
2. The summation of all the vertical forces acting on the body must equal zero.
3. The summation of all the moments acting on the body must equal zero.

Answer 3

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Question 4

The order in which the forces are drawn in the force polygon makes no difference; the resultant will be the same in both magnitude and direction regardless of the order followed.

Answer 4

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Question 5

The value of the moment (M) at the supports of a simple beam is zero.

Answer 5

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Question 6

Positive values of shear are shown above the base line and negative values below the base line.

Answer 6

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Question 7

The value of shear changes abruptly at concentrated loads and reactions and is indicated by a vertical line

Answer 7

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Question 8

Where the value of shear is constant, the shear diagram is horizontal.

Answer 8

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Question 9

The two points on the shear diagram that are of greatest interest in structural design are: (1) where the shear has the maximum value, and (2) where the shear passes through zero; that is, where it changes from positive to negative or vice versa.

Answer 9

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Question 10

The value of shear changes at a uniform rate at uniformly distributed loads, and therefore the corresponding shear diagram is a line of constant slope.

Answer 10

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Question 11

Positive values of moment are shown above the base line and negative values, if any, below the base line.

Answer 11

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Question 12

The slope of the moment diagram is equal to the value of the shear diagram at the same point on the beam. Thus, where the shear is constant, the shear diagram is horizontal and the moment diagram is a line of constant slope. At concentrated loads, the shear changes abruptly, and therefore the slope of the moment diagram changes abruptly.

Answer 12

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Question 13

The bending moment is maximum where the shear passes through zero.

Answer 13

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Question 14

The change of moment between any two points is equal to the area of the shear diagram between those two points.

Answer 14

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Question 15

Simple beams are bent concave upward; the upper beam fibers are stressed in compression, while the lower fibers are in tension. This is called positive moment. simple beams supporting downward vertical loads have positive moment across the entire span.

Answer 15

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Question 16

Cantilever beams are bent concave downward; the upper beam fibers are stressed in tension, while the lower fibers are in compression. This is called negative moment. Cantilever beams resisting downward vertical loads have negative moment throughout their length.

Answer 16

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Question 17

Overhanging beams may have both positive and negative moment.

Answer 17

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Question 18

Continuous beams supporting downward vertical loads have negative moment over the interior supports, positive moment between supports, and no moment at the exterior supports.

Answer 18

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Question 19

Fixed end beams supporting downward vertical loads have negative moment at their ends and positive moment between the ends.

Answer 19

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Question 20

In general, a simple beam will have greater maximum moment and more deflection than either a continuous beam or a fixed end beam supporting the dame load on the same span.

Answer 20

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Question 21

Shear stress in a beam varies parabolically, from zero a the outermost fibers to a maximum value at the neutral axis

Answer 21

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Question 22

The magnitude of the moment is the magnitude of the force (in pounds or kips) multiplied by its distance from the given point (in feet or inches).

Answer 22

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Question 23

The moment produced by a couple is equal to the value of one force multiplied by the distance between the two forces

Answer 23

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Question 24

The unit stress (f) is equal to the load (P) divided by the cross-sectional area (A)

Answer 24

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Question 25

The shape of the moment diagram at a uniformly distributed load is a parabolic curve

Answer 25

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Question 26

In wood, the greatest shrinkage occurs perpendicular to the grain

Answer 26

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Question 27

In wood construction it is permissible to neglect loads within a distance from either support equal to the depth of the beam

Answer 27

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Question 28

In steel, a small amount of carbon generally results in an increase in strength and a decrease in ductility

Answer 28

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Question 29

Most steel beams designed for flexure are adequate to resist shear. Two exceptions are (1) short, heavily-loaded beams and (2) beams with large loads near the support.

Answer 29

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Question 30

The deflection limit for steel members is L/360 for live load only.

Answer 30

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Question 31

Generally, floor beams having a depth at least 1/22 of the span length will no deflect excessively

Answer 31

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Question 32

Composite construction is most efficient with heavy loading, relatively long spans, widely-spaced beams, and slab thicknesses of 4 to 5-1/2 inches.

Answer 32

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Question 33

Concrete is strong in compression but weak in tension

Answer 33

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Question 34

A reinforced concrete beam is unsymmetrical and non-homogeneous

Answer 34

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Question 35

Type I Concrete is suitable for all normal uses

Answer 35

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Question 36

Type II Concrete is used where precaution against moderate sulfate attack is important. It usually generates less heat at a slower rate than Type I, especially important where the concrete is placed in warm weather.

Answer 36

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Question 37

Type III provides high early strength, usually in a week or less

Answer 37

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Question 38

Type IV is intended for use in massive concrete structures, where the rate and amount of heat generated must be minimized. It develops strength at a slower rate than Type I.

Answer 38

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Question 39

Type V is used only in concrete exposed to severe sulfate action.

Answer 39

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Question 40

The most important factor that determines the strength of concrete is the water-cement ratio. The higher the water-cement ratio, the lower the concrete strength

Answer 40

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