2013+bolt+connection - 43 Design of(Bearing Type Bolted Connections Summary Objective Design Strength Rn i Qi Pu Required Strength Basic Design Criteria

2013+bolt+connection - 43 Design of(Bearing Type Bolted...

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43 40.5 51 63 0.75 1.3 nt nt v nv F F f F Design of (Bearing Type) Bolted Connections Summary Objective: Design Strength n i i R Q ( Required Strength) u P Basic Design Criteria: Strength: (Use b t F and b v F values tabulated in AISC Table J3.2) Design tension strength: 0.75 ( 0.75) 0.75 b b n u b t b R F A F A Design shear strength: 0.75(0.563 ) (threads eXcluded X-type) 0.75 0.75(0.450 ) (threads iNcluded N-type) b b u s b n v s b b u s b F N A R F N A F N A Design bearing strength (of plates): 0.75(1.2 ) 0.75(2.4 ) n c u b u R L tF d tF Bolt spacing: Minimum spacing between bolts: 2 2 3 b s d (preferable 3 b d ) Edge distance: 12 value from Table J3.4 6 in e t L Combined shear and tension: 0.75 Tensile bolt stress ' 1.3 nt t nt nt v nt nv F f F F f F F Bolt shear stress v nv f F Other requirements (such as tension member design) also apply. C L S C L S
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44 Bolted Connections Connection bolts: Typical bolt types: A307 (machine bolts with F t = 45 ksi); A325 and A490 (high strength bolts with F t = 90 and 113 ksi, respectively) Examples: Main mechanism : Transfer load through shear Types of bolt for design (N- or X-)Bearing Type: slip resistance at service load is unnecessary -- Snug tight or pretensioned (with no faying surface preparation) installation Slip-critical (friction-type): slip resistance at service load is desired. Slip-critical connection is desirable when the load on connections can undergo many cycles of reversal (causing fatigue), such as for bridge structures. Pretensioned installation.
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45 Feeler Gages DTI’s Before bolt tightening Installation with Tension Indicators After bolt tightening Basic Bolts Installation Mechanisms: Bolt Pretensioning Mechanism Manual (Spud) Wrench Turn of Nut Method Calibrated (Impact) Wrench Installation with direct tension indicator
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46 Installation of twist-off bolt Examples of simple bolted connections
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47 Bearing Type Bolted Connections Assumption : Slip is allowed and both bolt shear stresses and plate bearing stresses occur Bearing Strength (of Plates) φ =0.75 Nominal bearing strength of plate: ? ? = 2?? ? 𝐹 ? 𝑝 (≈ 2?? ? 0.6𝐹 ? ) L c = clear distance, in the direction of force, between the edge of the hole and the edge of the adjacent hole or edge of material; 𝐹 ? 𝑝 = shear strength of plate 0.6 F u AISC Eq. J3-6a (pg. 16.1-127): R n = 1.2 tL c F u 2.4 F u d b t (upper limit to prevent excessive elongation) The clear distance ? ? = ? ? ? 2 or ? ? = ? − ? where d h = d b + 1/16 -in.
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48 L e L e S S P Minimum Spacing : (AISC J3.3, pg. 16.1-122) (related to plate bearing capacity) Tear-out of plate (1) along edge, and (2) between holes Bolts in the line of force or transverse to the line of force: ? ≥ 2 2 3 ?
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  • Spring '14
  • GregoryG.Deierlein
  • Force, Shear Stress, Strength of materials, Tensile strength, in2, pu

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