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					ARE Study Session
General Structures
            Part 2
                presented to
                Portland AIA
                 Spring 2010



                            by
     Nate Ingraffea, P.E., S.E.
        Mark Tobin, P.E., S.E.
  KPFF Consulting Engineers
    Section Properties Examples:

    Determine Ix, Iy, Sx, Sy, rx and ry for each of the following
    cross sections:
          y
                    6”x16”
                    rectangle

x                        x


          y
              16”
              x

y                               y

              x
     Flanges are 1”x6”
     Web is ½” x 14”
Section Properties Examples:

Determine Ix, Iy, Sx, Sy, rx and ry for each of the following
cross sections:

        y                Ix= bh3/12 = (6x163)/12 = 2048 in4
             6”x16”      Iy= hb3/12 = (16x63)/12 = 288 in4
             rectangle
                         Sx= Ix/c, where c= h/2, = bh2/6 = (6x162)/6 = 256 in3
x   h             x      Sy= Iy/c, where c= b/2, = hb2/6 = (16x62)/6 = 96 in3

                         A= bh =96 in2
         b
        y                rx=   Ix/A = 4.6 in

                         ry=   Iy/A = 1.7 in
    Section Properties Examples:

    Determine Ix, Iy, Sx, Sy, rx and ry for each of the following
    cross sections:
                             Ix :
           16”                         Part         b      d      Ipart = bd3/12   A = bd    y     A(y)2

            x
                                                   (in)   (in)         (in4)        (in2)   (in)    (in4)

                                    Left flange    6.00   1.00        0.50          6.00    7.5    337.5

                                       Web         0.5    14.0       114.33         7.00    0.0     0.00

y                        y          Right flange   6.00   1.00        0.50          6.00    7.5    337.5

                                       SUM                           115.33        19.00           675.00

            x                Ix   Ipart   A(y) 2  115.33  675.00  790.33 in4
     Flanges are 1”x6”                                   4
     Web is ½” x 14”         Sx  I           790.33 in                   98.8in3
                                        c                      8.00 in

                             rx=              = 6.4 in
                                      Ix/A
    Section Properties Examples:

    Determine Ix, Iy, Sx, Sy, rx and ry for each of the following
    cross sections:
                             Iy :
           16”                         Part         b      d     Ipart = bd3/12   A = bd   x      A(x)2

            x
                                                   (in)   (in)        (in4)        (in2)   (in)   (in4)

                                    Left flange    1.00   6.00       18.0          6.00     0      0

                                       Web         14.0    .5        0.15          7.00     0      0
y                        y          Right flange   1.00   6.00       18.0          6.00     0      0

                                       SUM                          36.15         19.00            0

            x
                             Iy   Ipart   A(x) 2  36.15  0  36.15 in4
     Flanges are 1”x6”                                4
     Web is ½” x 14”         Sy  I         36.15 in                15.05in3
                                       c                  3.00 in

                             ry=     Iy/A = 1.4 in
    Stress Examples:

    Determine the maximum bending stress on the following cross
    sections given a moment of 200 K-in.
          y
                       Sx= 256 in3
                       Sy= 96 in3
                       A= bh =96 in2
x                x


         y

             x         Sx= 98.8 in3
                       Sy= 15.1 in3
                     y A= bh =19 in
                                    2
y

             x
    Stress Examples:

    Determine the maximum bending stress on the following cross
    sections given a moment of 200 K-in.
          y
                         Sx= 256 in3
                         Sy= 96 in3
                         A= bh =96 in2
x                x                       Fb = sb = M/Sy= 200/96 = 2.1 KSI



         y
                         Sx= 98.8 in3
             x           Sy= 15.1 in3
                         A= bh =19 in2
y                    y
                                         Fb = sb = M/Sy= 200/15.1 = 13.2 KSI
             x
    Stress Examples:

    Determine the maximum tension stress on the following cross
    sections given a load of 500 Kips.
          y
                       Sx= 256 in3
                       Sy= 96 in3
                       A= bh =96 in2
x                x


         y

             x         Sx= 98.8 in3
                       Sy= 15.1 in3
                     y A= bh =19 in
                                    2
y

             x
    Stress Examples:

    Determine the maximum tension stress on the following cross
    sections given a load of 500 Kips.
          y
                       Sx= 256 in3
                       Sy= 96 in3
                       A= bh =96 in2
x                x
                                       FT = sT = T/A = 500/96 = 5.2 KSI


         y

             x         Sx= 98.8 in3
                       Sy= 15.1 in3
y                    y A= bh =19 in2

             x                         FT = sT = T/A = 500/19 = 26.3 KSI
Question 25

An 18th century farmhouse on the National Historic
Register 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 :

   Replace the undersized framing with new adequately
    sized members
   Sister the existing joists and beams
   Limit the number of visitors in spaces to the available
    live load
   Reduce the span of the floor framing
Question 25

An 18th century farmhouse on the National Historic
Register 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 :

   Replace the undersized framing with new adequately
    sized members
   Sister the existing joists and beams
    Limit the number of visitors in spaces to the
    available live load
   Reduce the span of the floor framing
Question 26

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

   ½ in [12 mm]
   ¾ in [19 mm]
   1 in [25 mm]
   1½ in [37 mm]
Question 26

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

   ½ in [12 mm]
   ¾ in [19 mm]
   1 in [25 mm]
    1½ in [37 mm] => Per ACI 318 Chapter 7.7
Question 27

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

   0 percent
   25 percent
   33 percent
   50 percent
Question 27

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

   0 percent
   25 percent
    33 percent => Per IBC Section 1607.8.2
   50 percent
Question 28

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 :

   Reinforced concrete
   Gypsum shaft wall
   Pre-fabricated concrete
   Concrete blocks
Question 28

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 :

   Reinforced concrete
    Gypsum shaft wall
   Pre-fabricated concrete
   Concrete blocks
Question 29

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

   Museum
   Parking
   Library
   Warehouse
Question 29

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

   Museum
    Parking
   Library
   Warehouse
Question 30

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

   A.   Increasing the size of the member
   B.   Rotating the column
   C.   Bracing the column
   D.   Changing the type of end restraints
   E.   Reducing the length of the column
   F.   Reducing the radius of gyration
Question 30

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


    A. Increasing the size of the member
   B. Rotating the column
    C.   Bracing the column
    D.   Changing the type of end restraints
    E.   Reducing the length of the column
   F.   Reducing the radius of gyration
Question 31

Which of the following soils has the smallest angle of
repose and produces the largest lateral forces against a
retaining wall:

   Gravel
   Hardpan
   Saturated silt
   Dense, moist sand
Question 31

Which of the following soils has the smallest angle of
repose and produces the largest lateral forces against a
retaining wall:

   Gravel
   Hardpan
    Saturated silt
   Dense, moist sand
Question 32

A two-story library is planned with overall dimensions of 96
feet by 84 feet [30 m x 24m]. The structural system is a
beam-column-girder having a standard bay size of 24 feet
by 28 feet [7.5 m x 8m]. There are no special soil
problems. The cost of the structure (footings, foundations,
columns, beams, girders, and decks) should be
approximately what percentage of the total construction
costs:

   5%
   25%
   50%
   70%
Question 32

A two-story library is planned with overall dimensions of 96
feet by 84 feet [30 m x 24m]. The structural system is a
beam-column-girder having a standard bay size of 24 feet
by 28 feet [7.5 m x 8m]. There are no special soil
problems. The cost of the structure (footings, foundations,
columns, beams, girders, and decks) should be
approximately what percentage of the total construction
costs:

   5%
    25%
   50%
   70%
Question 33

For the steel lintel shown below, what is the maximum
bending moment induced by the masonry wall alone if the
unit dead load of the wall = 90 psf [5.4 kN/m2, factored]:

   94 ft-lb [0.152 kN-m]
   235 ft-lb [0.380 kN-m]
   469 ft-lb [0.759 kN-m]
   938 ft-lb [1.520 kN-m]
Question 33

For the steel lintel shown below, what is the maximum
bending moment induced by the masonry wall alone if the
unit dead load of the wall = 90 psf [5.4 kN/m2, factored]:

   94 ft-lb [0.152 kN-m]
   235 ft-lb [0.380 kN-m]
    469 ft-lb [0.759 kN-m]
   938 ft-lb [1.520 kN-m]
Question 34

If the two wood joists shown below are of the same species
and grade, then the 2-inch by 12-inch [50 mm x 300 mm]
joist is about how many times as strong as the 2-inch by 6-
inch [50 mm x 150 mm] joist in bending:

   2
   4
   8
   16
Question 34

If the two wood joists shown below are of the same species
and grade, then the 2-inch by 12-inch [50 mm x 300 mm]
joist is about how many times as strong as the 2-inch by 6-
inch [50 mm x 150 mm] joist in bending:

   2
    4
   8
   16
Question 35

In addition to aesthetics, brick masonry veneers provide
which of the following benefits for structural masonry or
light wood-frame construction:
        I. Increased thermal performance
        II. Sound penetration resistance
        III. Increased fire resistance
        IV. Increased overall structural performance
 I and IV only
 II and IV only
 I, II, and III only
 I, II, III, and IV
Question 35

In addition to aesthetics, brick masonry veneers provide
which of the following benefits for structural masonry or
light wood-frame construction:
        I. Increased thermal performance
        II. Sound penetration resistance
        III. Increased fire resistance
        IV. Increased overall structural performance
 I and IV only
 II and IV only
    I, II, and III only
   I, II, III, and IV
Question 36

Loads associated with all of the following are calculated as
impact loads EXCEPT:

   Elevator machinery
   Cab-operated traveling cranes
   Hangers for floors supporting machinery
   Automobiles parked in garages
Question 36

Loads associated with all of the following are calculated as
impact loads EXCEPT:

   Elevator machinery
   Cab-operated traveling cranes
   Hangers for floors supporting machinery
    Automobiles parked in garages
        => Per IBC Section 1607.8 the standard live loads
        listed in table 1607.1 (such as garage loads) already
        include allowances for impact loads.
Question 37

For the block shown below, what is the factor against
sliding if the coefficient of friction is 0.5:

   2.5
   5
   25
   50
Question 37

For the block shown below, what is the factor against
sliding if the coefficient of friction is 0.5:


    2.5
   5
   25
   50
Question 38

All of the following are advantages of welded trusses over
bolted trusses EXCEPT:

   The truss is stronger
   Tension members may be designed on the basis of
    cross section
   There is a saving in material
   There is generally less detailing required
Question 38

All of the following are advantages of welded trusses over
bolted trusses EXCEPT:


    The truss is stronger
   Tension members may be designed on the basis of
    cross section
   There is a saving in material
   There is generally less detailing required
Question 39

Which of the following materials requires the greatest
allowance for thermal expansion and contraction when
used in the construction of a building:

   Cast iron
   Wrought iron
   Mild steel
   Aluminum
Question 39

Which of the following materials requires the greatest
allowance for thermal expansion and contraction when
used in the construction of a building:

   Cast iron        a = 6.7x10-6/°F
   Wrought iron     a = 6.4x10-6/°F
   Mild steel       a = 6.5x10-6/°F
    Aluminum                 a = 13.1x10-6/°F
Question 40

Bending stress is a function of the bending moment and:

   Modulus of elasticity
   Cross-sectional area
   Section modulus
   Radius of gyration
Question 40

Bending stress is a function of the bending moment and:

   Modulus of elasticity
   Cross-sectional area
    Section modulus
   Radius of gyration

				
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