][ STEEL STRUCTURES ][

 				Design of a bolted SPLICE Connection
						P&A 351

SAMPLE Problem:
==============
Design a bolted connection,
that achieves a splice between two members
( 2 angles pre selected by designer)
A tension force of 54 kips is to be transmitted
The intention is to use a single row 
( single row pre selected by designer)
of A325F bolts
( A325 F bolts pre selected by designer)
and a splice plate.

	1. bolted connection
	2. splice connection
	3. two (2) pairs of angles
	4. tension connection
	5. tension force 54 kips
	6. single row of bolts
	7. A 325 F bolts
			A 325 = high-strength bolt
			F = denotes bolt for which
				the limiting resistance is
				that of friction
				P&A 342 = definition
				P&A 344 = Capacity

	1. Size of bolts
		a. diameter of the bolts
		b. length of the bolts

	2. Number of bolts
		a. single row pre-selected

	3. Size of the angles
		a. leg 1
		b. leg 2
		c. thickness

	4. Size of splice plate
		a. thickness
		b. width
		c. length	

1. Loading Condition of Bolt:  
======================
	Bolts are in Double Shear
	(see PA 343)

2. Capacity of Bolts:
===============
	Table 11.1 P&A 344
	A 325 	F 	-   	Friction - given
		D 	-	Double Shear
		5/8" 	= 10.4 kips / bolt
		3/4"	= 15.0 kips
		7/8"	= 20.4 kips
		1"	= 26.7 kips	

3. Number of Bolts:
===============
		N = P / F 
		P = 54 kips tension force given
		F = capacity of bolt from T11.1 P&A 344
		5/8" 	= 54/10.4	= 5.19 = 6 
		3/4"	= 54/15		= 3.60 = 4
		7/8"	= 54/20.4	= 2.65 = 3
		1"	= 54/26.7	= 2.02 = 3
 	
	6 bolts per leg make a long joint
 	3 bolts make a shorter joint - design issue

4. Edge Distance for rolled shapes:
=========================
	Table 11.2 P&A 345
	Angle = rolled edge

		Edge Distance			Angle Size	
1" bolt		= 	1.25"			2.5"
7/8"		=	1.125"			2.25"
3/4"		=	1			2."
5/8"		=	0.875"			1.75" 
Leg Angle Size 2.5"

5. Gage g for Angles
===============
	Table 11.4 P&A 347
	g = edge distance for angle	2.5 " angle

	gage 				1 3/8		1.375
	edge distance			1 1/4		1.250
	---------------------------------------------------------------------------
							2.625
	2.5" angle will not work
	try 3" angle

	gage 				1 3/4		1.75
	edge distance			1 1/4		1.25
	-----------------------------------------------------------------------------
							3.00 works
	1" bolts require a 3.0 inch angle
	3/4" bolts require a 2.5 inch angle
	7/8" bolts require a 2.5 inch angle
	5/8" bolts require a 3.0 inch angle

7. Answer:
========
		Due to design and construction
		considerations (all 3/4" bolts)
		we selected
		4 bolts
		3/4" 
		on each side of the joint

8. Stress on unreduced area:
====================
	Table 8.1 P&A 267
Ft = 0.60 Fy
Ft = 0.60 x 36 ksi
Ft = 22 ksi

9. Unreduced Area
=============
A = P/Ft
A = 54 / 22
A = 2.46 sq.in. per pair
A1= 2.46 / 2 
A1= 1.23 sq in per angle

10. Double Angle
=============
Table 4.2 P&A 174
(Book typo Table 4.3 P&A 175)
Area = 1.23 sq. in.
3 x 2 x 5/16 selected
Area = 1.46 sq. in.
 	based on stress through entire section
	and edge distance and pitch

11. Angle Design-Net Area:
====================
	based on the previous section
	and also considering the net area.

12. Bolt Hole:
==========
	Bolt hole = Nominal Diameter + 1/8"
			    = 3/4" + 1/8"
			    = 0.75 + 0.125
			    = 0.875"	

13. Net Area - Angle:
================
        2 Angles      3" leg
A = (2)  (15/16)  ( 3 - 3/4" - 1/8)"
	Thickness     Bolt    Extra
	      Angle

A = (2) (0.9375) (3 - 0.875)
A = 1.328 square inches

14. Stress in Net Section:
==================
	ft = 54/ 1.328 = 40.7 ksi

15. Allowable Stress on Net Area:
=========================
Table 8.1 P&A 267
Allowable Stress on net area
F t = 0.50 x Fu 
F t = 0.50 x 58
     = 29 ksi
Note: you use Fu not Fy!
common mistake students make

16.
	ft> Ft
	40.7 ksi > 29 ksi
	will not work exceeds allowable stress

17. Allowable Stress on Net Area:
=========================
	Try a higher strength angle
	Table 8.1 P&A 267
You can get A36 with a Fu of 80 max!
See Steel Manual 1-7

Allowable Stress on net area
Ft = 0.50 x Fu 
Ft = 0.50 x 80
Ft = 40 ksi

18.
	ft> Ft
	40.7 ksi > 40 ksi
	The stress seems a bit high.
We may want to increase the thickness 
from 5/16" to 3/8"

19.  Double Angle:
==============
Table 4.2 P&A 174
3 x 2 x 3/8 selected
Area = 1.73 sq. in.

20. Critical Area:
============
	single row of bolts
	critical area will be at cross-section

21. Stress on unreduced area:
=====================
	Table 8.1 P&A 267
Ft = 0.60 Fy
Ft = 0.60 x 36 ksi
Ft = 22 ksi

22. Unreduced Area:
===============
A = P/Ft
A = 54 / 22 
A = 2.46 sq.in. 

23. Trial Sections:
=============
3/8" x 7" = 
0.375 x 7 =2.625 sq. in.

24. Trial Sections:
=============
1/2" x 5" = 2.5 sq. inch

Table 11.2 P&A 345 Pitch & Edge Distance
Table 11.4 P&A 347 Min. Pitch
edge distance 	= 1.5 " 	angle
edge distance 	= 1.75" 	plate
s pitch		=  3"   	angle/plate
g gage		= 1.25" 	angle
gap		= 0.5"	between angles