X.) Bolted Connections (Steel) A.) Introduction 1.) Types of bolts used with structural steel a.) A307 - low carbon (lowest strength) standard head size. b.) A325 - high strength - heavy duty nut.

X.) Bolted Connections (Steel)

A.) Introduction

1.) Types of bolts used with structural steel

a.) A307 - low carbon (lowest

strength) standard head size.

b.) A325 - high strength - heavy duty nut.

c.) A490 - high strength - heavy duty nut. Sizes range from 1/2” to 1-1/2” in 1/8” increments.

c.) A490 - high strength - heavy

duty nut. Sizes range from 1/2” to 1-1/2” in 1/8” increments.

2.) Types of Connections a.) Tension/Compression Connection (Axial Members - Trusses) i.) Lap Joint - Bolts in single shear - Eccentric - not as good

2.) Types of Connections

a.) Tension/Compression Connection

(Axial Members - Trusses)

i.) Lap Joint - Bolts in single shear

- Eccentric - not as good

ii.) Butt Joint - bolts in Double Shear - concentric - better

ii.) Butt Joint - bolts in Double Shear

- concentric

- better

b.) Shear Connection (Beams) -Simple Support (No moment transferred at connection) - Connect web only - Bolts in Shear + +

b.) Shear Connection (Beams)

-Simple Support (No moment transferred at connection)

- Connect web only

- Bolts in Shear

c.) Moment & Shear (Beam Connections) - Fixed Support - Connect Flange & Web + + d.) Any combination of a.), b.), & c.) + +

c.) Moment & Shear (Beam Connections)

- Fixed Support

- Connect Flange & Web

B.) Possible Way a Bolted Connection could fail (failure modes) 1.) Bolts fail in Shear

B.) Possible Way a Bolted Connection could fail (failure modes)

1.) Bolts fail in Shear

2.) Member or Connection plates fail in bearing or crushing - making the bolt holes oblong (crushing steel in plate) - excessive deformation

2.) Member or Connection plates fail in

bearing or crushing

- making the bolt holes oblong

(crushing steel in plate)

- excessive deformation

3.) Member or Plates fail in tension a.) failure by yielding on gross area is b.) failure by fracture on net area Gross Area Net Area a. b.

3.) Member or Plates fail in tension

a.) failure by yielding on gross area is

b.) failure by fracture on net area

4.) Member or Connecting plates fail by end or edge tear-out end distance too small or edge distance too small

4.) Member or Connecting plates fail by end or edge tear-out

C.) Design of Bolted Connections - check all 4 possible failure modes: 1.) Bolt Shear 2.) Member/Plate bearing failure 3.) Member/Plate tension failure 4.) Member/Plate end or edge tear-out

C.) Design of Bolted Connections

- check all 4 possible failure modes:

1.) Bolt Shear

2.) Member/Plate bearing failure

3.) Member/Plate tension failure

4.) Member/Plate end or edge tear-out

1.) Bolt Shear P V = A B  v,all Nn N= __ P v ___ (solving for N) nA B  v,all P v = allowable load on connection, based on bolt shear (k) A B = C.S.A. of one bolt (in 2 ) N = No. of bolts in connection n= number of shear planes

1.) Bolt Shear

P V = A B  v,all Nn

N= __ P v ___ (solving for N)

nA B  v,all

P v = allowable load on connection, based on bolt shear (k)

A B = C.S.A. of one bolt (in 2 )

N = No. of bolts in connection

n= number of shear planes

 v,all = Allow. shear stress (ksi) ,Table 19-1 a.) Slip Critical - when no slippage of joint can be permitted. b.) Bearing Type - when slippage of joint joint can be permitted so that bolts can bear on connected parts. c.) Threads in or out of shear plane (for bearing connections only)

 v,all = Allow. shear stress (ksi) ,Table 19-1

a.) Slip Critical - when no slippage of joint can be permitted.

b.) Bearing Type - when slippage of joint

joint can be permitted so that bolts can bear on connected parts.

c.) Threads in or out of shear plane (for bearing connections only)

threads in shear plane threads not in shear plane

2.) Member/Plate Bearing P P = dt  p,all N P P = Allowable load on connection based on bearing (k) d = Bolt diameter (in.) t = thickness of member/plate (in.) N = Number of bolts in connection

 p,all = allowable bearing stress of member/plate (ksi) = 1.5  t,ult = 1.5 (58ksi) = 87 ksi for A36 steel  t,ult in Table 19-2 for other materials.

 p,all = allowable bearing stress of member/plate (ksi)

= 1.5  t,ult

= 1.5 (58ksi) = 87 ksi for A36 steel

 t,ult in Table 19-2 for other materials.

3.) Tension in member/plates -must satisfy two requirements: P all < A g (0.60  Y ) P all < A n (0.50  t,ult ) A g = Gross CSA of member or connection plate  Y = yield strength of member or plate

3.) Tension in member/plates -must satisfy

two requirements:

P all < A g (0.60  Y )

P all < A n (0.50  t,ult )

A g = Gross CSA of member or connection plate

 Y = yield strength of member or plate

A n = Net CSA of member or plate = A g - A holes  t,ult = ultimate strength of member or plate

A n = Net CSA of member or plate = A g - A holes

 t,ult = ultimate strength of member or plate

4.) Bolt Spacing Edge/End Distance P L B L end L edge L edge L B

4.) Bolt Spacing Edge/End Distance

a.) L end = distance from center of standard hole to end of connected part along the line of transmitted force. Must satisfy two requirements: L end > 2P B __  t,ult (t) L end > Table J3.5

a.) L end = distance from center of standard hole to end of connected part along the line of transmitted force.

Must satisfy two requirements:

L end > 2P B __

 t,ult (t)

L end > Table J3.5

P B = Applied load per bolt = P/N  t,ult = ultimate strength of member/plate t = thickness of member or plate

P B = Applied load per bolt = P/N

 t,ult = ultimate strength of member/plate

t = thickness of member or plate

b.) L edge = distance from center of standard hole to edge of connected part, perpendicular to line of force L edge > Table J3.5

b.) L edge = distance from center of

standard hole to edge of connected part, perpendicular to line of force

L edge > Table J3.5

c.) L B = Distance between centerlines of standard holes. Again, two criteria L B > 2.67 d (all directions) L B > 2P B __ + d (in direction of load)  t,ult (t) 2 d = bolt diameter P B  t,ult , & t defined previously

c.) L B = Distance between centerlines of

standard holes. Again, two criteria

L B > 2.67 d (all directions)

L B > 2P B __ + d (in direction of load)

 t,ult (t) 2

d = bolt diameter

P B  t,ult , & t defined previously

A.) INTRO. TO WELDED CONNECTIONS 1.) 6500 o F electric arc melts the weld electrode to the material being connected ( the base metal). 2.) Weld electrode must be compatible material for the base metal, i.e. same chemical makeup

A.) INTRO. TO WELDED CONNECTIONS

1.) 6500 o F electric arc melts the weld electrode to the material being connected ( the base metal).

2.) Weld electrode must be compatible material for the base metal, i.e. same chemical makeup

3.) E60xx means 60 ksi ultimate strength would use with low carbon (A36 or 1020) steel. 4.) Weld geometry a.) Groove welds: - Full Penetration - Partial Penetration b.) Fillet Welds

3.) E60xx means 60 ksi ultimate strength

would use with low carbon (A36 or 1020)

steel.

4.) Weld geometry

a.) Groove welds:

- Full Penetration

- Partial Penetration

b.) Fillet Welds

B.) WELDED CONNECTION STRENGTH 1.) Groove Welds: Full strength of the connected part is developed if: a.) full penetration b.) full length Edge prep. increases cost

B.) WELDED CONNECTION STRENGTH

1.) Groove Welds: Full strength of the connected part is developed if:

a.) full penetration

b.) full length

Edge prep. increases cost

2.) Fillet Welds Required size (“a” dimension) of weld is controlled by: a.) Minimum size is controlled by thickness of the thicker of two parts joined. (Table 19-4) b.) Maximum size is controlled by the thickness of the welded edge. (Table 19-4)

2.) Fillet Welds

Required size (“a” dimension) of weld is controlled by:

a.) Minimum size is controlled by thickness of the thicker of two parts joined. (Table 19-4)

b.) Maximum size is controlled by the thickness of the welded edge. (Table 19-4)

2.) Fillet Welds b.) Maximum size: a max t

2.) Fillet Welds

b.) Maximum size:

2.) Fillet Welds Required length of weld (L) is controlled by: a.) weld shear strength: P v =  v,all t e (units of lb/in) = (0.3  t,u ) t e t e = “effective throat thickness” = a(sin45 o ) = 0.707a P v =(0.3  t,u ) (0.707a ) P v = 0.212  t,u a (units of lb/in of weld)

2.) Fillet Welds

Required length of weld (L) is controlled by:

a.) weld shear strength:

P v =  v,all t e (units of lb/in)

= (0.3  t,u ) t e

t e = “effective throat thickness”

= a(sin45 o ) = 0.707a

P v =(0.3  t,u ) (0.707a )

P v = 0.212  t,u a (units of lb/in of weld)

b.) L > 4a c.) L > w > width of part d.) L > 5 t min e.) Returns > 2a return L = weld length Section View w t min a

b.) L > 4a

c.) L > w

> width of part

d.) L > 5 t min

e.) Returns > 2a