Deck 4: Load Resistance the Structural Properties of Materials

Question 1

In relation to its compressive strength, the tensile strength of concrete is

A)nearly the same.
B)slightly higher.
C)much lower.
D)much higher.
E)slightly lower.

Answer 1

C

Question 2

The test specimen used for determining the compressive strength of concrete in the United States is a

A)cube measuring 6 in. × 6 in. × 6 in.
B)cylinder measuring 12 in. in diameter × 6 in. high.
C)cylinder measuring 6 in. in diameter × 12 in. high.
D)prism measuring 6 in. × 6 in. × 12 in.
E)cube measuring 12 in. × 12 in. × 12 in.

Answer 2

C

Question 3

In a typical stress- strain diagram of a material, the stress is generally plotted along the vertical axis.

Answer 3

True

Question 4

The bending stresses along the neutral axis of a beam are

A)zero.
B)maximum.
C)minimum.
D)none of the above.

Question 5

The stress- strain diagram of mild steel is nearly a straight line up to the yield point.

Question 6

The material in an arch is primarily in

A)tension.
B)compression.
C)both tension and compression.
D)shear.
E)none of the above.

Question 7

When a cable or rope is compressed by a force, what is the compressive stress in it?

A)Zero
B)Infinite
C)Equal to the force applied
D)Force divided by the cross- sectional area of rope
E)None of the above

Question 8

Modulus of elasticity refers to how

A)elastic a material is.
B)stiff a material is.
C)strong a material is.
D)serviceable a material is.
E)none of the above.

Question 9

Concrete is

A)an elastic- plastic material.
B)an elastic material.
C)a plastic material.
D)none of the above.

Question 10

Low- carbon (mild)steel is

A)a plastic material.
B)an elastic- plastic material.
C)an elastic material.
D)none of the above.

Question 11

Which of the following beam cross sections is structurally more efficient in bending?

A)I- section
B)Rectangular (solid)section

Question 12

A rectangular column measuring 12 in. × 12 in. in cross section carries a load of 18 kips. What is the stress in the column?

A)125 psi
B)18 kips
C)18 ksi
D)2)25 ksi
E)None of the above

Question 13

Which of the following beam cross sections is structurally more efficient in bending?

A)Tubular section
B)Rectangular (solid)section

Question 14

The unit of modulus of elasticity is

A)GPa.
B)Pa.
C)psi.
D)ksi.
E)all of the above.

Question 15

What is the yield stress of grade 60 reinforcing steel?

A)60 psi
B)60 lb
C)6,000 lb
D)6,000 psi
E)None of the above

Question 16

A 20- ft- high column shortens by 0.6 in. under a load. What is the resulting strain in the column?

A)0)0025 in.
B)0)0025
C)0)0020
D)0)0020 in.
E)None of the above

Question 17

When we determine the strength of concrete using the test specimens, we determine the concrete's

A)ultimate compressive stress.
B)modulus of elasticity.
C)ultimate tensile stress.
D)ultimate shear stress.
E)all of the above.

Question 18

In a suspension bridge, which member(s)is (are)in compression?

A)Hanger cables
B)Support pylons
C)Suspension cable
D)Both suspension cable and hanger cables
E)None of the above

Question 19

In a simple three- member truss consisting of two rafters and a tie, each member is in

A)compression.
B)tension.
C)either tension or compression.
D)shear.
E)both tension and compression.

Question 20

Which gives greater warning before failure?

A)A brittle material
B)A ductile material

Question 21

The primary purpose of longitudinal steel bars in a reinforced concrete beam is to overcome the weakness of concrete in tension.

Question 22

The bearing strength of a material is closely related to its

A)bending strength.
B)compressive strength.
C)tensile strength.
D)modulus of elasticity.
E)none of the above.

Question 23

The allowable stress in a material is generally

A)less than its ultimate stress.
B)equal to its ultimate stress.
C)greater than its ultimate stress.
D)none of the above.

Question 24

The horizontal blocking in wood studs helps prevent

A)tensile failure of studs.
B)compressive failure of studs.
C)buckling of studs.
D)shear failure of studs.

Question 25

In a steel column that rests on a concrete footing, the area of the bearing plate used is generally

A)smaller than the cross- sectional area of the column.
B)equal to the cross- sectional area of the column.
C)greater than the cross- sectional area of the column.

Question 26

What is the relationship between a material's brittleness and its tensile strength?

Question 27

If a concrete test cylinder measuring 6 in. × 12 in. breaks when the load on it reaches 169.5 k, what is the compressive strength of concrete? Express the strength in psi.

Question 28

What is the yield stress of grade 60 reinforcing steel? Of A- 36 structural steel?

Question 29

What is the shape and dimensions of the specimen typically used for determining the compressive strength of concrete?

Question 30

Explain what yielding of a material means.

Question 31

In most materials, the safety margin for compressive stress and bending stress is the same.

Question 32

A material that is weak in tension is

A)weak in bending.
B)strong in bending.
C)no relationship between the tensile and bending strengths of a material.

Question 33

What is the unit of measure for strain?

Question 34

What does the term "strength" of a material imply and how does it differ from a material's ultimate stress?

Question 35

The primary purpose of ties in a reinforced concrete column is to

A)prevent the buckling of vertical reinforcement in the column.
B)increase the shear resistance of the column.
C)prevent the crushing of concrete.
D)none of the above.

Question 36

A material that is weak in tension is

A)strong in shear.
B)weak in shear.
C)no relationship between the shear and tensile strengths of a material.

Question 37

What is the difference between a ductile material and a brittle material?

Question 38

A concrete column 20 ft high shortens to 19 ft 11- 1/2 in. under a load. Determine the strain in the column.

Question 39

List the following materials (aluminum, concrete, steel, and wood)in terms of their ductility beginning with the most ductile and ending with the least ductile.

Question 40

The stirrups in a reinforced concrete beam are used to

A)reduce the deflection of the beam.
B)increase the strength of the beam in shear.
C)increase the durability of the beam.
D)increase the strength of the beam in bending.
E)none of the above.

Question 41

What is the neutral axis of a structural member and in which situation do we refer to it-when the member is in axial compression, axial tension or bending?

Question 42

Explain why shear strength of brittle materials is low.

Question 43

Why is an I- section beam structurally more efficient than a beam of rectangular cross section whose cross- sectional area is the same as that of an I- section beam?

Question 44

What is the unit of measure for modulus of elasticity in U.S. System of units? In SI System of units?

Question 45

Is low- carbon steel an elastic or a plastic material?

Question 46

Explain two methods by which the buckling of a member may be prevented.

Question 47

Does the slope of the stress- strain diagram relate to any property of the material? Explain.

Question 48

What is meant by a "structurally efficient" cross- sectional shape in bending? Note: "in bending" means that the member is used as beam or slab.

Question 49

The saw blades used for cutting masonry, concrete and stone are made of diamond- tipped steel. Why is that so?

Question 50

What is the modulus of elasticity of a material whose stress- strain relationship is a vertical straight line? Name the material with such a stress- strain relationship.

Question 51

For most materials, their strength is directly related to their modulus of elasticity, i.e., the greater the strength of the material, the greater its modulus of elasticity. Is there a material whose modulus of elasticity is not related to its strength but is constant, i.e., it has a fixed value regardless of the material's strength? If so, name the material and provide its modulus of elasticity value.

Question 52

Why do we use the term "bearing strength of soil" and not "compressive strength of soil" when, in reality, the soil is under compression from the load of the structure being supported?

Question 53

Explain the concept of safety margin in the design of structures.

Question 54

Among the commonly used structural materials (steel, concrete, masonry and wood), which has the highest modulus of elasticity and which has the lowest modulus elasticity?

Question 55

When a member buckles, it bends. Explain the difference between buckling and bending.

Question 56

What is the difference between bearing strength and compressive strength?

Question 57

What is the difference between an I- section beam and an open- web I- section beam, called a castellated beam?

Question 58

In the stress- strain diagrams of materials, which axis (X- axis or Y- axis)is typically used for stress and which for strain?

Question 59

Explain the difference between an elastic material and a plastic material.

Question 60

A concrete cylinder specimen is tested by loading it in compression from its top. The cylinder is restrained from expanding laterally (not allowed to bulge horizontally under the load). A second identical cylinder is tested in compression similarly but without any lateral restraint, i.e., this cylinder is allowed to bulge laterally. Will both cylinders fail at the same or a different value of load? Explain your answer.

Question 61

If the ultimate strength of a material is 6,000 psi and the factor of safety is 2.5, determine the allowable stress of the material.

Question 62

Explain what load factor is in structural design.

Question 63

What are the units of stress in the U.S. system of units and the SI system of units?

Question 64

If the bar in Problem 2 is 10 ft long, determine the elongation in the bar. The modulus of elasticity of steel is 29 ×
106 psi.

Question 65

A l- in.- diameter steel bar is subjected to a tensile force of 30 kips. Determine the stress in the bar.

Question 66

Explain what is bearing strength of a material and how it differs from the material's compressive strength.

Question 67

Explain what resistance factor is in structural design.

Question 68

Explain the difference between:
(a)elasticity and modulus of elasticity of a material.
(b)brittleness and ductility of materials.

Question 69

Explain with the help of a three- dimensional sketch the reason for bending inefficiency, that is, why the strength of a material in a component is not fully utilized when the component is subjected to bending.

Question 70

Sketch the stress- strain diagram of low- carbon (mild)steel, showing all of its important parts, and explain why steel should not be stressed beyond its yield stress.

Question 71

Explain with the help of a sketch why a brittle material is weak in shear.

Question 72

Using sketches and notes, explain how we increase the bending efficiency of building components.

Question 73

Explain the modulus of elasticity. Which property of the material does it represent? Give the approximate values of the modulus of elasticity of steel, concrete, and wood.

Question 74

Explain the concept of buckling. Explain whether buckling would occur if a member is subjected to bending. What measures do we adopt to prevent the buckling failure of building components?