10
vertical tie to the beam. Determine the number of bolts required and check the
adequacy of the connection.
6.*
The connection shown in Fig. is used to attach a vertical load to a California
Redwood 6 x 12 in surfaced- four-sides beam. Wood is seasoned to 15%
moisture content, service conditions are those of covered structures, i.e., the
wood remains continuously dry and at about 15% M.C. Determine the
maximum load that can be safely attached to the beam. (Ans: F = 2330 lb.)
11
7.*
The free-body diagram of a tension member at a joint is shown in Fig.
Connectors are 2½ in. split rings with ½ in. bolts. Wood is Southern pine
select structural KD, surfaced-four-sides and used at 15% moisture content.
The loads N, acting in the near face of the member, are due to the
simultaneous action of permanent loads and wind; the angle of load to grain is
15° and the angle of axis to grain is 30°. Determine the allowable load N that
can be transmitted through the near- face split rings. (Ans: N = 3500 lb.)
8.*
The free-body diagram of a tension member at a joint is shown in Fig.
Connectors are 2½ in. split-rings with ½ in. bolts. Wood is Southern pine
select Structural KD, surfaced- four-sides and used at 15% moisture content.
The loads N, acting in the near face of the member, are due to the
simultaneous action of permanent loads and wind; the angle of load to grain is
45° and the angle of axis to grain is 30°. Determine the allowable load N that
can be transmitted through the near- face split rings.
12
9.*
The joint shown in Fig. corresponding to the bottom chord of a roof truss.
Members are made up of dense wood, Group A, surfaced and used at 15%
moisture content. The loads acting on the members are due to the
simultaneous action of dead load and snow. The connection is made up of four
4-in split-rings and ¾ in. bolts. Determine whether or not the joint is adequate.
(Ans: The joint is adequate)
10.*
The connection shown in Fig. is given as follows: (1) the angle between the
left diagonal and the chord are 60 degrees; (2) the force in the diagonal is 8.18
13
K and; (3) the left force in the chord is 15.48 K. Determine the adequacy of
the connection, assuming that dense wood, Group A, surfaced and used at
15% moisture content. The loads acting on the member are due to the
simultaneous action of dead load and snow. The connection is made up of four
4 in. split-rings and ¾ in. bolts.
11.*
The connection shown in Fig. between two glued-laminated portions of a rigid
frame is subjected to N = 15 K, M = 1800 K-in, and Q = 10 K. Wood for the
laminations is dense Southern pine and connectors are pairs of 4 in shearplates with ¾ in bolts. The values of gage and pitch are g = 6 in. and p = 9 in.,
respectively; also e = 7 in., c = 2 in. The loads are due to the simultaneous
action of permanent loads and snow. Since the frames are covered, dry
conditions of use can be expected at all times. The object of the analysis is the
determination of the adequacy of the connection. (Ans: Connectors A1 , A2 , A3 ,
F1 , and F3 exceed the capacity.)
14
12.*
The problem is this case is a multiple-plate rigid connection similar to that
shown in Fig., except that six sets, instead of four sets of 4 in. shear plates and
¾ in. bolts are used for the flange plates and only two sets, instead of four sets,
are used for the web plates. General dimensions of one half of the connection
are, using the notation shown in Fig., g = 6 in., p = 9 in., e1 = 7 in., e2 = 2 in.,
c = 2 in. The section of the rigid frame at the connection is 8.75 in. wide by 48
in. deep and is subjected to M = 1800 K-in., N = 15 K, and Q = 10 K which
are due to the simultaneous action of permanent loads and snow. The object of
the problem is the determination of the adequacy of the connection.
(Ans: The connection is adequate)
15
13.*
The bottom chord of a simply-supported light truss is made up of a 2 x 8 S4S
wood, surfaced at 15% moisture content. The length of the truss is such that a
splice is necessary at midspan. The force in the bottom chord at midspan, due
to normal loading conditions, is 3000 lb in tension; bending is negligible. If a
¾ in. plywood splice plate is used at each side of the connection, as shown in
Fig. Determine the required number of nails. (Ans: Use 23 nails at each side of
the connection.)
16
14.** The joint shown in Fig. corresponding to the bottom chord of a roof truss.
Members are made up of dense wood, Group A, surfaced and used at 15%
moisture content. The loads acting on the members are due to the
simultaneous action of dead load and snow. In the connection, 4 in. shear
plates and ¾ in. bolts are used to connect the wood to the steel plates. All
members have the same actual thickness; 2½ in. in this case. The adequacy of
the joint is to be ascertained.
17
15.** A 4 x 4 in. tie is fastened to a 4 x 8 in. beam by two ¼ in. steel side plates as
shown in Fig. Wood is surfaced- four-sides Southern pine No. 1, surfaced dry
and used at 19% maximum moisture content. The connection transmits a 7.5 K
load, due to normal loading conditions, from the suspended vertical tie to the
beam. Design using ¾ in. bolts and 25 /8 in. shear plates. Assume wood is
Group A.
16.*** The joint shown in Fig. corresponding to the bottom chord of a roof truss.
Members are made up of dense wood, Group A, surfaced and used at 15%
moisture content. The loads acting on the members are due to the
simultaneous action of dead load and snow. In the connection, 4 in shear
plates and ¾ in. bolts are used to connect the wood to the steel plates. All
members have the same actual thickness; 2½ in. in this case. The angle
between the left diagonal and the chord is 60 degrees, the force in the diagonal
is 8.18 K and the left force in the chord is 15.98 K. Determine the adequacy of
the connection.
18
17.*** The connection shown in Fig. is subjected to the action of forces due to snowloading conditions. Wood is Group A. The structure is under cover, thus, dry
conditions of use apply. Determine the adequacy of the connection. Show free
body diagrams of each member indicating forces acting on the respective faces
of the connectors. Also, check the geometry of the connection, i.e., the end
and edge distances, and the spacing of the connectors.
19
18.*** Analyze the connection shown in Fig. to determine the forces acting at the
various connectors. Draw free-body diagrams of each member and check
individual capacities.
19.*** Analyze the connection shown in Fig. Determine the force T in the vertical for
necessary equilibrium. Make free-body diagrams of each member, showing
the forces at the face of the respective connectors. Determine the adequacy of
the connection if wood is Group A, surfaced-four-sides, and used under
covered conditions. Loads correspond to wind- loading conditions.
20
20.*** Consider the connection shown in Fig. Assume that g = 8 in. and p = 10 in.,
respectively. If N = 15 K, M = 1800 K-in., and Q = 10 K, determine, for each
connector: (a) X and Y components of force; (b) the total force; (c) the angle
of loads to grain; and, (d) connector capacity.
21
22
CE 06024 Design of Timber structures II
Chapter 1 Design of Wood Bridges
1.*
Design a two- lane highway trestle suitable for H-20-44 traffic with bents at
17 ft. spacing and a minimum 24 ft. width of roadway. For the laminated
decking use rough sawn wood; any unevenness to be covered by the asphaltic
wearing surface. The stringers are to be designed using surfaced-four-sides,
S4S, timbers. Use wood for which Fb = 2.3 ksi, Fv = 0.125 ksi and unit weight,
? = 50 pcf for decking and for stringer, select a grade and species of wood with
the following design stresses; Fb = 1.7 ksi, Fv = 0.105 ksi, E = 1600 ksi, and
unit weight, ? = 50 pcf. Assume unit weight of asphaltic concrete = 150 pcf.
2.**
Design a two- lane highway overpass suitable for HS-20-44 traffic, with a
minimum 24 ft width of roadway and simply-supported on abutments spaced
50 ft apart. Design the laminated decking using rough-sawn wood with the
following allowable stresses: Fb = 2.3 ksi, Ft = 1.55 ksi, Fv = 0.125 ksi,
Fc⊥ = 0.475 ksi, Fc = 1.7 ksi and E = 1900 ksi. The stringers should be gluedlaminated members, made of wood with the following allowable stresses:
Fb = 2.4 ksi, Ft = 1.6 ksi, Fc = 1.5 ksi, Fc⊥ = 0.45 ksi, and 0.385 ksi, (for
tension face and compression face, respectively), Fv = 0.165 ksi, and E = 1800
ksi. Any unevenness of the rough-sawn decking is covered by an asphalticconcrete wearing surface having an average 3 in thickness.
23
Chapter 2. Glued-laminated Timber
1.*
Write a short note on the advantages of glued- laminated timbers compared
with sawn timbers as well as other structural materials.
26
Chapter 5. Maintenance of Timber Structures
1.*
Write a short not on the two general classes of wood preservatives, such as
oilborne preservatives and waterborne preservatives.
27
Chapter 6. Formwork Design
1.*
Design the formwork as shown in Fig. for an elevated concrete floor slab 6 in
thick. Sheathing will be 1 in (nominal) thick lumber, while 2 x 8 in lumber
will be used for joists. Stringer will be 4 x 8 in lumber. Assume that all
members are continuous over three or more spans. Commercial 4000 lb shores
will be used. It is estimated that the weight of the formwork will be 5 psf. The
adjusted allowable stresses for the lumber being used are as follows:
Sheathing (psi)
Other members (psi)
Fb
1075
1250
Fv
174
180
Fc⊥
-
345
Fc
-
850
E
1.36 x 106
1.4 x 106
Maximum deflection of form members will be limited to L/360. Use the
minimum value of live load permitted by ACI. Determine appropriate joist
spacing, stringer spacing, and shore spacing.
(Ans: Decking : 1 in lumber.
Joist
: 2 x 8's at 24 in. spacing.
Stringers : 4 x 8's at 84 in. spacing.
Shores
: 4000 lb commercial shores at 48 in. intervals)
28
2.*
Forms are being designed for an 8 ft high concrete wall to be poured at the rate
of 4 ft/h, internally vibrated, at 90°F temperature as shown in Fig. Sheathing
will be 4 x 8 ft sheets of 5/8 in thick class I plyform with face grain
perpendicular to studs. Studs and double wales will be 2 x 4 in lumber. Snap
ties are 3000 lb capacity with 1½ in wide wedges bearing on wales. Deflectio n
must not exceed L/360. Determine stud, wale, and tie spacing. Allowable
stresses for studs and wales are.
Fb = 1810 psi
Fv = 120 psi
Fc⊥ = 485 psi
E
= 1.7 x 106 psi
(Ans: Sheathing: 4 x 8 ft sheets of 5/8 in Class I plyform placed horizontally
Studs
: 2 x 4's at 12 in on center.
Wales
: Double 2 x 4's at 16 in on center.
Ties
: 3000 lb snap ties at 24 in on center.)
29
3.*
Determine the maximum spacing of 2 x 4 in lateral braces for the wall form
placed as shown in Fig. The design lateral force per linear foot of form,
H = 100 plf. Allowable stress values for braces are E = 1.4 x 106 psi, Fc = 850
psi, Ft = 725 psi,
(Ans: Maximum strut spacing = 10.8 ft)
30
4.*
Determine the design lateral force for a slab form 6 in thick, 20 ft wide, and
100 ft long as shown in Fig. The slab is to be placed in one pour. Use design
weight of framework is 15 psf.
(Ans: H20 = 180 plf; H100 = 36 plf (min:))
31
Chapter 7. Wood Foundation Structures
1.*
An embedment of a class 2 pole in compact, well- graded sand in order to
support a lateral load Q = 2000 lb due to wind applied at H = 21 ft from the
ground surface. The pole is rotationally restrained at the top by the supported
structure, as shown in Fig., but is otherwise free to move laterally. In addition,
the pole is subjected to a vertical load p = 3000 lb, applied at the top and to its
own weight W. Determine the structural adequacy of the class 2 pole. Assume
D = 6.6 ft. Consider Fc = 1.2 ksi, Fb = 2.15 ksi, Fv = 0.13 ksi, Fc⊥ = 1.26 ksi,
and E = 1600 ksi.
(Ans: The selected pole is acceptable.)