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Steel DesignII Page : Connection - 1 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
Chap. 7 Structural FastenersChap. 7 Structural Fasteners.
types of Mechanical Fasteners1. Rivets. Obsolete2. Unfinished Bolts,A307Lightly Loaded Member,
Cheap3. H. S. Bolts, A325, A490
Steel DesignII Page : Connection - 2 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
4. Ribbed Bolts ( Interference Body Bolts )
- with Longitudinal Ribs,
- with Longitudinal Ribs and Serrations around
shank.
Steel DesignII Page : Connection - 3 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
H. S. Bolts In Korea. – KS B1010
F10T
F8T
Steel DesignII Page : Connection - 4 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
Basic Assumptions
1. No Misalignment, Pe is neglected on Ultimate
Strength.
2. No Bolt – Plate Clearence
3. Equal. Distribution of forces to each fastener.
4. Bending of Bolts Ignored.
Details of H. S. Bolts
Steel DesignII Page : Connection - 5 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
INSTALLATION PROCEDURES
1. BEARING TYPE CONNECTION – NO PRETENSIONING
--- TIGHT “ SNUG-TIGHT”
SNUG TIGHT – Results of 1) a few impact of an impact
wrench or 2) the full effort of a man using an ordinary spud
wrench.
2. SLIP-CRITICAL CONNECTION – FULL
PRETENSIONING
PROOF LOAD
= {0.785 + ( – ) }
= A) 0.5% EXTENSION METHOD.
B) 0.2 % OFFSET METHOD.
PROOF LOAD STRESS { 70% OF TENS. STRENGTH
(A325) OR 80% OF TENS. STRENGTH (A490) }
MINIMUM BOLT TENSION
= 70% OF TENS . STRENGTH
= PROOF LOAD FOR A325
= 85~90% PROOF LOAD FOR A490
a) TURN-OF THE-NUT METHOD
b) CALIBRATED WRENCH TIGHTENING
c) ALTERNATIVE DESIGN BOLTS.-
Steel DesignII Page : Connection - 6 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
TWIST-OFF TYPE, YIELDING TYPE
d) DIRECT TENSION INDICATOR TIGHTENING
HARDENED WASHER WITH PROTRUSIONS.
Steel DesignII Page : Connection - 7 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
TYPICAL BOLTED CONNECTIONS.
SHEAR CONNECTION , TENSION CONNECTION
Depending on types of load transfer
1) BEARING TYPE CONNECTION.-- failure limit state.
Should meet
A) TENSION STENGTH,
B) SHEAR STRENGTH,
C) BEARING STRENGTH
Steel DesignII Page : Connection - 8 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
2) SLIP-CRITICAL CONNECTION - serviceability limit
state
In addition to A), B) and C), should meet 2) SLIP-
CRITICAL REQUIREMENT.
LOAD TRANSFER IN BEARING TYPE CONNEC.
LOAD TRANSFER IN SLIP-CRITICAL TYPE CONNEC.
Steel DesignII Page : Connection - 9 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
FAILURE MODES OF BOLTED CONNECTIONS.
Steel DesignII Page : Connection - 10 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
NOMINAL STRENGTH OF FASTENERS.
A) TENSION STENGTH
cf) In 도로교시방서 허용응력설계법 - N=0.85 For F8T - N=0.75 For F10T
where
=120ksi for A325 cf) A36: =36ksi, =58ksi =150ksi for A490 A572, G50: =50ksi, =65ksi
B) SHEAR STRENGTH1) Thread Excluded
Using
2) Thread included Take 25% Reduction in Area (i.e A =0.75 )
Steel DesignII Page : Connection - 11 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
C) BEARING STENGTH
Steel DesignII Page : Connection - 12 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
A. Strength Limit State
L ; edge(end) distance
1-1, 2-2 actual failure line but for conservative design, assume
0
BEARING STENGTH(cont’d)
* 3rd Ed
2t L (0.6 )=1.2 L t
* Cf) 2nd Ed
; Shear strength of plate =0.62 ; tensile strength d ; bolt diameter
=
Steel DesignII Page : Connection - 13 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
=1.24 t
Assuming that 1.24
Excessive hole deformation limit state
(upper limit)
Steel DesignII Page : Connection - 14 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
Steel DesignII Page : Connection - 15 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
OTHER DESIGN DETAILS.
1) MIN. SPACING OF BOLTS.For intermediate bolts, =( s-d/2 )
(S-d/2) → correspondent to where, P= factored load acting on one bolt d= diam. of bolt
LRFD-J3.3 states that s=3.0d preferably, and s
2) MIN. EDGE DISTANCE IN THE DIRECTION OF FORCE
LRFD-J3.4 states that
larger of ( , value in table J3.4)
Steel DesignII Page : Connection - 16 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
3) MAX. EDGE. DISTANCE (J.3.5)
Le 12t 6 in.
To prevent corrosion resulting from moisture entering joints.
To ensure enough clamping action.
Steel DesignII Page : Connection - 17 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
4) MAX. SPACING OF CONNECTORS
A) For painted members or unpainted members not subject to
corrosion.
s 24t 12 in.
B) For unpainted members of weathering steel subject to
atmospheric corrosion.
s 14t 7 in.
Steel DesignII Page : Connection - 18 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
Steel DesignII Page : Connection - 19 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
Shear Strength
Steel DesignII Page : Connection - 20 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
Common Bolts vs High Strength Bolts
1) Common Bolts (A307)
- But currently not very common.
-
Steel DesignII Page : Connection - 21 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
Steel DesignII Page : Connection - 22 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
Steel DesignII Page : Connection - 23 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
Steel DesignII Page : Connection - 24 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
2) High Strength Bolts (A325, A490)- thread included in a plane of shear → ex) A325N thread excluded in a plane of shear → ex) A325X-
Steel DesignII Page : Connection - 25 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
Steel DesignII Page : Connection - 26 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
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Steel DesignII Page : Connection - 28 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
SLIP-CRITICAL Req’t @ Service Load.
(LRFD A-J3.8b)Slip Limit State : Serviceability Requirement.
: Thus, same as ASD.
- Pretension Load ( Tb ) = 70 % of Tensile Strength of Bolts
- Tb = friction force for each shear plane = FvAb where Fv = Nominal slip shear resistance ( Table 4.9.1)
= Slip coeff ( 0.2 – 0.6 depending on surface cond.)
- Design Slip Resistance of a Bolt in a single shear plane= FvAb
where = 1.0 for standard, oversized, shorted-slotted and long
slotted holes when the long slot is perpendicular to the line of force. = 0.85 for long slotted holes when the long slot is parallel to the line of force.
Steel DesignII Page : Connection - 29 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
SLIP-CRITICAL Req’t @ Factored Load.
(LRFD J3.8a)
Steel DesignII Page : Connection - 30 Tel.(02) 3290-3317 Fax. (02) 921-5166 Prof. Kang,YoungJong Date :2005/ /
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