NCARB Sample Questions

Question 1

The most important factor affecting the strength of concrete is the

Answer 1

water-to-cement ratio

Factors affecting the strength of concrete. The higher the w/c ratio the weaker the concrete. In addition, lower w/c is better for durability. A w/c 0.40 is the norm for parking garages. You may see w/c or w/cm on the test. w = water, c = cement, cm = cementitious material. Fly ash and other additives are part of the cm

Question 2

The drilled pier (caisson) shown above is belled in order to

Answer 2

The shaft is belled to increase the bearing area.

The bell also increases uplift resistance. It does not increase frictional resistance. Frictional resistance is achieved through “skin friction”, friction between the sides of the shaft and the soils. Normally you do not use skin friction with under-reamed (belled) piers. Drilled piers and caissons are interchangeable.

Question 3

A slump cone is used primarily to provide an indication of which of the following characteristics of concrete?

Answer 3

Strength and workability

The slump tests measures how much the wet concrete drops under the weight of concrete. The more slump the lower the strength and durability. The more slump the easier it is to work the concrete.
The use of water reducers allow concrete of higher slumps with negatively affecting the strength of the concrete. The slump does affect the finishing of the concrete. A high slump may delay the finishing operations. A low slump may result in harsh finishing due to the concrete setting up faster than it can be finished. Appearance and color are not directly affected by slump but if you have a slab with a 4” slump next to a slab with an 8” slump there will be a difference in color and finish.

Question 4

Since the 1960’s, thin-shell concrete roof structures have seldom been utilized in the United States and Canada primarily because

Answer 4

formwork is prohibitively expensive

Formwork is the easy answer. Formwork is normally 50% of the cost of cast-in-place concrete. For thin shells, the cost of formwork is a higher percentage of the overall cost. Thin shells use less concrete (and I think steel) that other concrete structures. Building codes refer to ACI documents that allow thin shell construction. Design fees are higher but unfortunately (for the SER) nowhere near the cost of formwork.

Question 5

The most frequently used footing type at the exterior wall for load-bearing wall support systems is

Answer 5

continuous wall footings

Shallow spread footings are the common foundation for structures in most areas of the country. Continuous wall footings and isolated pad footings at columns. Areas where you do not use spread footings include areas of highly expansive clays or areas with un-controlled fill material.

Question 6

What is the section modulus for the geometric section illustrated above?

Answer 6

57.3 in3

You cannot determine the S for this member directly (try to if you do not believe me). You must determine “I” and then divide by “c”. This member is symmetrical so the solution is easy. Take the “I” of the gross area (6 * 10^3)/12 [500] and subtract the “I” of the two void areas = 2 * (2.5 * 8^3)/12) [2 * 106.67) = 213.33] = 286.67. “c” equals 1/2 the depth = 5” Therefore S = 286.67/5 = 57.33. This works for member that are symmetrical, (wide flange and channels) where the centroid of the elements used in the calculations coincide with the final member.

Question 7

When considering permitted live load reductions for the column shown above, what is the live load for the floor supported by the column?

Answer 7

67 kips

Trick question. The question is “What is the live load for the floor”. It does not ask for the live load for the design of the column nor the reduced live load. The (I my opinion) correct answer is 80 psf. Since THEY indicate the answer is in kips THEY must want you to multiply the live load (0.080 ksf) times the area of the column 33’-4” x 25’-0” to determine the live load for the floor. Read carefully!!!

Question 8

If the soil bearing capacity is 3000 psf [143 500 N/m2] and the applied load is 48,000 lbs [212 kN], which of the following is the area for the footing?

Answer 8

16 SF

48,000/3000 = 16 sf. They give an easy one after a trick question!

Question 9

Which of the following best defines the P-delta effect?

o Lateral forces on the foundations
o Bending forces in the vertical members
o Horizontal forces in the roof sections
o Moment forces at the joint

Answer 9

Bending forces in the vertical members

Bending forces in the vertical members. P-delta is caused by the drift of the building (delta) under lateral load) times the axial load in the column (P). This may increase the moment in the vertical member (columns) 10 to 15%.

Question 10

Concrete should reach its design compressive strength in how many days?

Answer 10

28

Concrete is specified using the 28-day compressive strength. The 3-day strength is used to determine when shores can be removed. The 7-day strength is used as an indicator of the strength and is normally 75% of the 28-day strength. I have never used the “32”. I have used 56-day strength for slabs-on-grade.

Question 11

When concrete is held under sustained stress, the strain will continue to increase with time. Which of the following defines this time-dependent phenomenon?

o Shrinkage

o Temperature expansion

o Creep

o Contraction

Answer 11

Creep

Shrinkage, temperature expansion and contraction are not related to stress. Creep is time dependent and related to the dead load stress in the concrete.

Question 12

Steel roof joists are manufactured with camber to

Answer 12

compensate for deflection

My answer is none of the above. Their answer is compensate for deflection. The amount of camber on joists might be enough to compensate for the deflection due to the self-weight of the joist and nothing more. Not even close to providing enough for positive roof drainage.

Question 13

In a renovation of an existing residential building, in which piping of conduit needs to be run through a 2 x 12 [50 x 300 mm] (actual) wood floor joist, which of the following is the minimum dimension required by the IBC [NBC] from the top or bottom of the joist to the bored hole?

Answer 13

2.0 in [50 mm]

Question 14

An 18th century farmhouse on the National Historic Reg- ister with exposed timber framing is to be restored and opened for tours. Which of the following is the most historically correct method of addressing the lack of live- load capacity of the floor framing?

o Replace the undersized framing with new adequately sized members.
o Sister the existing joists and beams.
o Limit the number of visitors in spaces to the available
live load.
o Reduce the span of the floor framing.

Answer 14

o Limit the number of visitors in spaces to the available
live load.

All are acceptable structural methods of correcting the problem but only limiting the number of visitors (which is allowed by code) maintains the historic nature of the facility.

Question 15

Cast-in-place concrete beams and columns with No. 11 [35M] rebar or smaller reinforcing bars that are not ex- posed to weather or in contact with the ground should have a minimum coverage of concrete over the bars of

Answer 15

1.5 inches

The question is for beams and columns, which has a minimum of 1.5 inches of cover for these bars. Concrete exposed to or cast against earth have a different set of criteria.

Question 16

A balcony is hung from steel roof framing over a hotel atrium. Which of the following is the minimum code required increase in live load due to impact?

Answer 16

33%

Section 1607.8 explicitly states, “The live loads of section 1607.3 includes allowance for impact conditions.” However, 1607.8.2 states, “For the purpose of design, the weight of machinery and moving loads shall be increased as follows to allow for impact: (1) elevator machinery, 100 percent; (2) light machinery, shaft- or motor-driven, 20 percent; (3) reciprocating machinery or power-driven units, 50 percent; (4) hangers for floors or balconies, 33 percent. Percentages shall be increased where specified by the manufacturer.”

Question 17

Which of the following is generally the most economical material for the hoistway wall of an elevator in a wood- frame, two-story apartment building?

o Reinforced concrete
o Gypsum shaft wall
o Pre-fabricated concrete

o Concrete blocks

Answer 17

Although concrete block works, it is more expensive than gypsum board. Gypsum board is used often for rated walls. Most elevator shafts require two-hour rated walls.

Question 18

A one-way slab is used typically in which of the following types of buildings?

o Museum

o Parking
o Library
o Warehouse

Answer 18

o Parking

A bit of a trick question because they do not give a complete description of the system. One slabs span between walls or beams. Not preferred for museums or libraries. Garages like clear drive aisles. One-way slabs spanning 22 to 25 feet and beams spanning 60 feet are the preferred system.

Question 19

Which of the following would be most appropriate for a high-rise building in a high-risk seismic zone?

o A building on stilts
o A building with an L-shaped plan
o A building with a symmetrical T-shaped plan

o A building with a symmetrical square plan

Answer 19

A building with a symmetrical square plan

A building on stilts probably has vertical irregularities. An “L” or “T” shape plan both have horizontal irregularities. Therefore all three are not preferred. Square is better than rectangular because the seismic for is the same in both directions.

Question 20

Which of the following is NOT a primary structural system that is employed to resist lateral loads?

o Shear walls
o Braced frames
o Hinged frames
o Moment-resisting frames

Answer 20

o Hinged frames

Easy one, hinged frame. Lateral loads are resisted by some type of frame action or shearwalls. The terms used in the question all come from ASCE 7. There is no such thing as a rigid frame. There are frames with rigid joints. Remember that distinction

Question 21

All of the following are criteria for base isolation systems EXCEPT:

o The system must allow lateral movement.
o The system must control the movement between
ground and structure.
o Energy must be dissipated in the isolators.
o The system must amplify ground accelerations.

Answer 21

The system must control movement between the ground and the structure is a given part of base isolation. It must allow movement is also true. The ground is moving and the part below the base isolation is going to move, it cannot be stopped. The isolation system must allow some movement but also must control the movement. Think about wind load on a building with base isolation. There needs to be a system to allow the resistance to the wind but ………………………Movement of the structure below the isolators results in energy, energy that will either move something, be resisted by something or be dissipated by something. Dissipated is allowing some movement

Question 22

An eccentrically braced frame (EBF) utilized to resist lateral seismic forces in a building is a

o frame in which diagonal members are connected to a
beam a short distance from the column joint
o frame in which members are subjected primarily to
axial forces
o frame in which members and joints are capable of
resisting forces by flexure as well as along the axis of
the member
o braced frame whose plan location results in torsion

Answer 22

EBFs do not cause torsion. The others are true. An EBF is a concentric braced frame where the work points are moved so that there is moment in a beam due to lateral forces. The section of beam with the moment is the “link” and is designed to fail before the other members of the frame. The failure of the link is dissipates some of the energy of the earthquake, reducing the forces in the other members. The link may be between the column and the brace member (in a single strut system) or between the brace members in a chevron style system.

frame in which diagonal members are connected to a
beam a short distance from the column joint

Question 23

Base isolation in an office building is most effective for which of the following building heights, assuming that the areas per floor are the same?

o One-story

o Four-story

o Twenty-story

o Forty-story

Answer 23

four story

Base isolation work best for low-rise buildings. However, please finish reading my explanation before you blast me. Base isolation can work for any height building. The cost for using it on high- rise buildings stops it use. In addition, the wind on high-rise building must be address and may control the design of the building (the need to reduce acceleration due to wind loads). The LA City Hall uses base isolation (this was pointed out to me in response to a comment I made in a thread). The use of base isolation on an historic structure is very different from its use on new construction. For the city hall, it was the only way to retrofit the building to current codes without messing up the historic features of the building.

Question 24

Buckling of a column can be reduced by which of the following? Check the four that apply.

o A. Increasing the size of the member

o B. Rotating the column

o C. Bracing the column

o D. Changing the type of end restraints

o E. Reducing the length of the column

o F. Reducing the radius of gyration

Answer 24

ACDE

 The strength (capacity) of a column is directly related to the formula k\*l/r. The higher the value the lower the capacity
 "k" is a factor based on the end restraint of the column. Reducing "k" by adding more restraint at the top and/or bottom reduces the answer and hence an increase in strength. For a column pinned top and bottom k = 1.0. Same column with moment connections top and bottom k = 0.65.
 "l" is the actual length of the column between brace points. Decreasing l will increase the strength. Adding brace points below the top of the column will reduce l.
 "r" is the radius of gyration and relates to the size of the member. An increase in r will reduce the answer and result in an increase in strength. Increasing the size of the member should result in an increased r and strength. Reducing r will increase the answer and result in less strength.

Question 25

A loss of soil shear strength resulting in the movement of the surficial soil layers of a building site in a direction parallel to the ground surface under earthquake conditions is most likely caused by

o a high water table
o liquefiable soils
o a low bearing capacity

o a gently sloping site

Answer 25

o liquefiable soils

A high water table may contribute to the movement but only if the soil is of a type that would be impacted by the water. The other answers may result in some movement but not the type of movement they discuss in the question. Remember you are answering THEIR question not the question you think they asked.

Question 26

Which of the following professionals has primary legal responsibility for the performance of a building in an earthquake?

o Building code official
o Structural engineer
o Architect
o Geotechnical consultant

Answer 26

architect

Based on the answer this is a WTF question. Legal responsibility is a matter of contract law. IF the SE is under contract with the architect then maybe “the architect” is the answer. IF the architect and SE each have a separate contract with the owner “the architect” is not correct (my opinion). Review the Architect’s Handbook if you want to study is further.

Question 27

Which of the following material lists provides ductility in building construction in the order of highest to lowest?

o Steel, reinforced masonry, reinforced concrete, wood

o Wood, steel, reinforced masonry, reinforced concrete

o Reinforced masonry, reinforced concrete, wood, steel

o Steel, reinforced concrete, reinforced masonry, wood

Answer 27

o Steel, reinforced concrete, reinforced masonry, wood

Ductility is the property of bending without breaking once beyond its elastic limit. Steel has more ductility than any other material and therefore is the “highest”. The word “reinforced” in the concrete and masonry means there is steel reinforcement, steel that increases their ductility. Concrete is better than masonry so it wins the coin toss for second place. Wood bends a lot but once beyond its elastic limit it fails.

Question 28

What is the factor of safety against overturning for the concrete shear wall shown if resisted only by gravity forces? Assume the weight of concrete equals 150 lb/ft 3
[23.5 kN/m3], and the dead load equals 240 kips [1060 kN]. Ignore the weight of the soil over the footing.

Answer 28

Step one is to calculate the overturning moment. Force is 24 kips and distance is 40.0’ + 2.0’. Remember that the factor of safety must always be checked at the bottom of the footing.

OTM = 24 * 42 = 1,008 kip-ft
The stabilizing moment (SM) is the difficult part of the problem. The question you MUST ask is “does the 240K include the weight of the wall and footing”
Try the problem both ways.
1. Weight of wall and footing ARE included in the DL:
SM = 240 * 10.0’, ten feet is the distance from the dead load to the pivot point (lower right point of the footing). If you have not seen the term “pivot point”, STOP; download and read my “Lateral Load Primer”.
2,400 kip-ft
2. Weight of wall and footing are NOT part of the DL
Calculate the weight of the wall:
16.0 * 40.0 * 1.5 * 0.150 = 144 kips
Calculate the weight of the footing
20.0 * 6.0 * 2.0 * 0.150 = 36 kips Total weight = 144 + 36 = 180 kips
SM = 2,400 (from #1) + (180 * 10.0) = 4,200 kip ft
If the weight of the wall and footing ARE included, the factor of safety is
2400/1008 = 2.38
If the weight of the wall and footing are NOT included, the factor of safety is
4200/1008 = 4.17
Your choices are 2.38 or 4.17. Pick 4.2 for your answer. A tip of the hat to Coach and Lug-nut (One of them suggested this method)

Question 29

A primary cause of failure of concrete masonry walls during hurricanes is

o poorly filled mortar joints
o improper base and sill flashing
o an inadequate number of wall anchors

o a lack of vertical reinforcement

Answer 29

a lack of vertical reinforcement

An easy question. Any of the three COULD allow the failure but the word “primary” says it is a frequent occurrence. The first two cannot be considered common. The third one is talking about connection to the backup material but the question concerns CMU not brick. Normally there are no wall anchors with CMU. Reinforcement of masonry walls is difficult; it is designed the way concrete reinforcement was designed in the 60s. A non-loadbearing wall will require the same or MORE reinforcement than a loadbearing wall for the same moment, never less.

Question 30

The earthquake regulations of model codes are intended to provide resistance to which of the following?

o Ground shaking
o Earth slides
o Ground rupture in fault zones

o Settlement

Answer 30

ground shaking

Ground shaking is an obvious choice. What about ground rupture in fault zones? “Fault zone” is NOT the same as earthquake fault. Some areas of the country (Houston) have fault zones not related to earthquakes. Earthquake regulations do not help deign near the ground faults in Houston.

Question 31

A structure will have a better chance of surviving an earthquake if which of the following is true?

o Principal members change section abruptly.
o The load-bearing members are not equally loaded.

o All columns and walls are discontinuous.
o The structure has redundancy.

Answer 31

The structure has redundancy.

Discontinuity and asymmetry are two of the worst thing for structures in an earthquake. Discontinuity of the columns or lateral load resisting system causes stresses in members that can result in sudden failures. Redundancy is the best thing for structures. Redundancy allows one part of the structure to fail and the structure still stands. The last one is the correct answer.

Question 32

Which of the following considerations in structural design are based on probability as a result of historical analysis?

o Water pressures
o Wind forces
o Dead loads

o Soil pressures

Answer 32

I am hoping the answer to this question is wind forces. The other three do not require “historic” analysis. I got it right!

Question 33

According to model codes; Connection of masonry web shear walls to masonry flange walls must be accomplished using which of the following details? Check the three that apply.

Running bond
Bond beams
Stacked bond
Steel dowels High-strength mortar

Metal plate strap anchors

Answer 33

Running bond

Bond beams

Metal plate strap anchors

“Connection” is the key word. Connection relates to transfer of force, transfer of force from the web to the flanges. High strength mortar has nothing to do with transfer of force. Running bond interconnects the walls while stacked bond does not. Running bond is one of the answers. Bond beams have steel reinforcement that connects well. Strap anchors also transfer force. The term “steel dowels” in masonry construction normally connects walls to foundations. These would only work if part of bond beams not as a separate item. YOU may argue this as much as you like!

Question 34

In the elevation of a multi-storied building subject to earthquake forces shown above, at which location is stress concentration most likely to be a problem?
oA

oB

oC

oD

Answer 34

“Problem” is the operative word in this question. “A” is a high stress point, B and D are not. C is a reentrant corner that will have stress concentrations. THEY are saying the reentrant corner is a problem, I say it is a design opportunity!

Question 35

A building form that is ideal for resistance to earthquake forces would be characterized by which of the following? Check the two that apply.

oA. Symmetrical about a reentrant corner
oB. Symmetrical in plan
oC. Heavier at the base than at the top
oD. Asymmetrical in plan
oE. Long linear plan
oF. Asymmetrical in elevation

Answer 35

BC

Discontinuity and asymmetry are two of the worst thing for structures in an earthquake. Discontinuity of the columns or lateral load resisting system causes stresses in members that can result in sudden failures. Redundancy is the best thing for structures. Redundancy allows one part of the structure to fail and the structure still stands.

Long and linear is not as good a symmetrical (square) plan. Symmetrical in plan is one of the answers. Seismic force is distributed (vertical) based on height and weight of the levels. Having heavier at the base than at the top is a benefit