|
|
|
Steel Connector Design: |
|
This design guide is intended to provide guidance for the safe and economical design
of steel connectors and bolted steel connections. This design guide and the corresponding
calculations are based on the 14th edition of the AISC Steel Construction Manual.
All calculations can be performed for Load Resistance Factor Design, LRFD or Allowable
Strength Design, ASD.
|
Steel Connector Design Using The 14th Edition AISC Steel Construction Manual:
|
|
|
Design of Bolted Steel Connections:
|
|
The design of bolted steel connections is a simple process left to the descretion
of the engineer. The design process can be broken down into two principle
considerations: (1) type of connection and (2) type of load.
|
Type of Connection:There are two principle types
of bolted connections: bearing connections and slip-critical connections.
Bearing connections are connections where the members bear on each other or come
in direct contact with each other and the shearing resistance of the fasteners is
relied on to resist the loading. Slip-critical connections are constructed
from high-strength steel, and a high preload can be placed on the bolts. This
preload will clamp the plates together, and friction alone will keep the plates
from sliding.
|
Type of Loading:There are two types of loading
that a connection will see: concentric loading and eccentric loading.
Concentric loading is the case where the connection will only have to resist the
effects of direct shear and/or direct tension alone. Eccentric loading is
where the connection will have to resist the effects of moment load as well as the
direct shear and/or tension. Eccentric loading is broken down to analyze the
loads derived by the moment into additional shear or tension loads placed on the
fasteners.
|
|
In summary the design of connections varies by the requirements and unique loading
of each connection and each situation that the designer sees. Calculations
used for the design of bolts and fasteners in bearing connections are also used
to check the loading on slip critical connections. Also eccentric connections
are broken down into the required shear and tension forces in the bolt resulting
from the moment loading on the connection, and then the bolts are designed for that
resultant shear and/or tension just like a concentric loading. The connection
itself can be either a bearing connection or slip-critical connection.
|
|
The following calculations come from Chapter 8 and Section J.3 of the AISC Steel
Construction Manual, and are used for the design of bolted steel connections:
|
|
|
|
|
|
The following are some useful tables to be used in the design of bolted connections:
|
Bolts - Yield Strengths and Tensile Strengths:
|
Fastener Description
|
Nominal Tensile
Stress, Fnt,
ksi (MPa)
|
Nominal Shear
Stress, Fnv,
ksi (MPa)
|
|
A307 bolts
|
45 (310)
|
27 (188)
|
|
Group A, A325/A325M bolts, when threads
are not excluded from the shear
planes.
|
90 (620)
|
54 (372)
|
|
Group A, A325/A325M bolts, when threads
are excluded from the shear
planes.
|
90 (620)
|
68 (457)
|
|
Group B, A490/A490M bolts, when threads
are not excluded from the shear
planes.
|
113 (780)
|
68 (457)
|
|
Group B, A490/A490M bolts, when threads
are excluded from the shear
planes.
|
113 (780)
|
84 (579)
|
|
Threaded parts, when threads
are not excluded from the shear
planes.
|
0.75Fu
|
0.450Fu
|
|
Threaded parts, when threads
are excluded from the shear
planes.
|
0.75Fu
|
0.563Fu
|
|
|
|
Minimum Bolt Pretension For Slip Critical, Kips
|
Bolt Size (in)
|
A325 Bolts
|
A490 Bolts
|
|
1/2
|
12
|
15
|
|
5/8
|
19
|
24
|
|
3/4
|
28
|
35
|
|
7/8
|
39
|
49
|
|
1
|
51
|
64
|
|
1-1/8
|
56
|
80
|
|
1-1/4
|
71
|
102
|
|
1 -3/8
|
85
|
121
|
|
1-1/2
|
103
|
148
|
|
Minimum Bolt Pretension For Slip Critical, kN
|
Bolt Size (mm)
|
A325M Bolts
|
A490M Bolts
|
|
M16
|
91
|
114
|
|
M20
|
142
|
179
|
|
M22
|
176
|
221
|
|
M24
|
205
|
257
|
|
M27
|
267
|
334
|
|
M30
|
326
|
408
|
|
M36
|
475
|
595
|
|
Nominal Hole Dimensions, in.
|
Bolt Diameter (in)
|
Standard
(Dia.)
|
Oversize
(Dia.)
|
Short-Slot
(Width x Length)
|
Long-Slot
(Width x Length)
|
|
1/2
|
9/16
|
5/8
|
9/16 x 11/16
|
9/16 x 1-1/4
|
|
5/8
|
11/16
|
13/16
|
11/16 x 7/8
|
11/16 x 1-9/16
|
|
3/4
|
13/16
|
15/16
|
13/16 x 1
|
13/16 x 1-7/8
|
|
7/8
|
15/16
|
1-1/16
|
15/16 x 1-1/8
|
15/16 x 2-3/16
|
|
1
|
1-1/16
|
1-1/4
|
1-1/16 x 1-5/16
|
1-1/16 x 2-1/2
|
|
>= 1-1/8
|
d + 1/16
|
d + 5/16
|
(d+1/16)x(d+3/8)
|
(d+1/16)x(2.5xd)
|
|
Nominal Hole Dimensions, mm.
|
Bolt Diameter (mm)
|
Standard
(Dia.)
|
Oversize
(Dia.)
|
Short-Slot
(Width x Length)
|
Long-Slot
(Width x Length)
|
|
M16
|
18
|
20
|
18 x 22
|
18 x 40
|
|
M20
|
22
|
24
|
22 x 26
|
22 x 50
|
|
M22
|
24
|
28
|
24 x 30
|
24 x 55
|
|
M24
|
27
|
30
|
27 x 32
|
27 x 60
|
|
M27
|
30
|
35
|
30 x 37
|
30 x 67
|
|
M30
|
33
|
38
|
33 x 40
|
33 x 75
|
|
>= M36
|
d + 3
|
d + 8
|
(d+3)x(d+10)
|
(d+3) x 2.5d
|
|
Minimum Edge Distance, in., from Center of Standard Hole to Edge of Connected Part.
|
Bolt Diameter (in)
|
Minimum Edge Distance
|
|
1/2
|
3/4
|
|
5/8
|
7/8
|
|
3/4
|
1
|
|
7/8
|
1-1/8
|
|
1
|
1-1/4
|
|
1-1/8
|
1-1/2
|
|
1-1/4
|
1-5/8
|
|
> 1-1/4
|
1-1/4 x d
|
|
Minimum Edge Distance, mm, from Center of Standard Hole to Edge of Connected Part.
|
Bolt Diameter (mm)
|
Minimum Edge Distance
|
|
M16
|
22
|
|
M20
|
26
|
|
M22
|
28
|
|
M24
|
30
|
|
M27
|
34
|
|
M30
|
38
|
|
M36
|
46
|
|
> M36
|
1.25d
|
|