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Bolted and welded connections Joint capacity checks Shear and moment transfer methods Maintaining structural integrity
Typology: Slides
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Engr. Gabriel Gamana, M.Sc.
2 1.0 Introduction 2.0 Tension Members 3.0 Compression Members 4.0 Beams 5.0 Beam-Columns 6.0 Connections
3 6.1 Introduction 6.2 Bolted Connection 6.3 Welded Connection 6.4 Eccentric Connection
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7 In addition, the riveting operation was noisy and somewhat dangerous because of the practice of tossing the heated rivet from the point of heating to the point of installation. Riveted connection design is no longer covered by the AISC Specification, but many existing structures contain riveted joints, and the analysis of these connections is required for the strength evaluation and rehabilitation of older structures
8 6.2.1 Shear Failure Before considering the strength of specific grades of bolts, we need to examine the various modes of failure that are possible in connections with fasteners subjected to shear. There are two broad categories of failure: failure of the fastener and failure of the parts being connected.
13 6.2.3.1 NSCP 2001 Requirement 𝑓௩ =
Allowable Tension Stress for Fastener in Bearing-Type Connections Threads Exclude in Shear Plane Threads Include in Fastener Shear Plane A 502 Gr. 1 207 − 1.3𝑓௩ < 159 207 − 1.3𝑓௩ < 159 A 502 Gr. 2 262 − 1.3𝑓௩ < 200 262 − 1.3𝑓௩ < 200 A 307 179.2 − 1.8𝑓௩ < 137.8 179.2 − 1.8𝑓௩ < 137. A 325 303 ଶ^ − 4.39𝑓௩ଶ 303 ଶ^ − 2.15𝑓௩ଶ A 490 372 ଶ^ − 3.75𝑓௩ଶ 372 ଶ^ − 1.82𝑓௩ଶ A449 0.43𝐹௨ − 1.8𝑓௩ < 0.33𝐹௨ 0.43𝐹௨ − 1.4𝑓௩ < 0.33𝐹௨
14 6.2.3.2 NSCP 2015 Requirement 𝑅 = 𝐹௧^ ᇱ^ 𝐴 Reduced tensile strength using LRFD 𝐹௧^ ᇱ^ = 1.3𝐹௧ −
Where; 𝐹௧ = nominal tensile stress in absence of shear 𝐹௩ = nominal shear stress in absence of tensile 𝑓௩ = actual shear stress 𝜙 = 0. Reduced tensile strength using ASD 𝐹௧^ ᇱ^ = 1.3𝐹௧ −
Where; Ω = 2.
15 Problem 6- Check bolt spacing and bearing for the connection shown in figure. Use NSCP 2015 LRFD.
16 Problem 6- Determine the strength of the connection shown in figure, based on bearing and shear, for Group A bolt, threads in the plane of shear. Use 𝐹௩ = 54 𝑘𝑠𝑖 and NSCP 2015 LRFD.
17 Problem 6- A bolted single shear connection as shown in figure, with the plates and bolts are A36 steel with Fy = 250 MPa and Fu = 400 MPa. Bolt diameter is 22 mm and the plate size is 300 x 12. mm. Allowable shearing stress of bolts is 117 MPa. Determine the capacity of the connection based on bolt strength. NSCP 2001
18 Problem 6- A bracket must support the service loads shown in figure, which act through the center of gravity of the connection. The connection to the column flange is with eight 7/8-inch-diameter, Group A bearing-type bolts. A992 steel is used for all components. Is the connection adequate? Use 2015 NSCP LRFD
19 Problem 6- Determine the adequacy of the fasteners in figure when 4 layers of 22 mm diameter A325 bolts are used in a bearing type correction with threaded excluded from shear planes. Assume the strength of column flange and the ST section does not govern the strength. 𝐹௩ = 207 𝑀𝑃𝑎 760 𝑘𝑁 26.57°
20 Structural welding is a process whereby the parts to be connected are heated and fused, with supplementary molten metal added to the joint. For example, the tension member lap joint shown in figure can be constructed by welding across the ends of both connected parts.
25 6.3.1.2 NSCP 2015 Requirement Weld Strength LRFD 𝑅௨ = 𝜙0.707𝑤𝐿𝐹௪ ASD 𝑅 =
Where; 𝑤 = thickness of weld 𝑡 = thickness of the base metal 𝜙 = 0. Ω = 2. 𝐹௪ = Basic strength of weld
26 Base-Metal Shear Strength LRFD 𝑅௨ = 𝜙 0.60𝑡𝐿𝐹௬ ASD 𝑅 =
Where; 𝜙 = 1. Ω = 1.
27 Shear Rupture Strength LRFD 𝑅௨ = 𝜙 0.60𝑡𝐿𝐹௨ ASD 𝑅 =
Where; 𝜙 = 0. Ω = 2.
28 Problem 6- A plate used as a tension member is connected to a gusset plate, as shown in figure. The welds are 3/16-inch fillet welds made with E70XX electrodes. The connected parts are of A steel. Assume that the tensile strength of the member is adequate, and determine the available strength of the welded connection. Use 2010 NSCP LRFD, 𝐹௪ = 0.60𝐹ா , 𝐹௬ = 36 𝑘𝑠𝑖 and 𝐹௨ = 58 𝑘𝑠𝑖
29 Problem 6- An 18 x 200 mm bar is welded to a 20 mm thick gusset plate as shown in figure. Fu = 484 MPa, Fy = 248 MPa and the size of weld is 11 mm. Determine the allowable tensile capacity using SMAW and SAW Process considering weld metal only.
30 Problem 6- A double-angle truss member shown in figure consist of two angle 125 x 88 x 10 mm with the 125 mm side welded to a gusset plate. The member is to carry a total tensile force of 848 kN. Using 6 mm fillet weld with E60 electrode, determine the length of each side fillet weld required for balanced condition. All steels are A36 with Fy = 250 MPa and Fu = 425 MPa.
31 An eccentric connection is one in which the resultant of the applied loads does not pass through the center of gravity of the fasteners or welds.
32 6.4.1 Eccentric Bolted Connections: Shear Only Elastic Analysis The column bracket connection shown in figure is an example of a bolted connection subjected to eccentric shear.
37 Problem 6- A beam-to-column connection is made with a structural tee as shown in figure. Eight 3/4-inch-diameter, Group A, fully tightened bearing-type bolts are used to attach the flange of the tee to the column flange. Determine the unity ratio of the bolt. Assume that the bolt threads are in the plane of shear. All structural steel is A992. 𝐹௧ = 90 𝑘𝑠𝑖 and 𝐹௩ = 54 𝑘𝑠𝑖
38 Problem 6- The connections shown in figure consist of 10 pcs of A490 22 mm diameter bolts and is attached to the column flange. The bolts are subject to shear and tension in a bearing-type connection with no threads in shear plane. Assume the strength of column flange and the plates does not govern the strength. Determine the unity ratio of the bolts if P = 300 kN.
39 6.4.3 Eccentric Welded Connections: Shear Only Elastic Analysis Eccentric welded connections are analyzed in much the same way as bolted connections, except that unit lengths of weld replace individual fasteners in the computations.
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41 6.4.4 Eccentric Welded Connections: Shear Plus Tension Many eccentric connections, particularly beam-to-column connections, place the welds in tension as well as shear. 𝑓 = 𝑓௩^ ଶ^ + 𝑓௧ଶ
42 Problem 6- Determine the size of fillet welds made with E70XX electrodes required for the bracket connection in figure. The service dead load is 10 kips, and the service live load is 30 kips. A36 steel is used for the bracket, and A992 steel is used for the column. 𝐹௪ = 0.60𝐹ா
43 Problem 6- A plate is lapped over and welded to a gusset plate as shown in figure. Determine the maximum force per millimeter of weld due to 90 kN load. Use NSCP 2001.
44 Problem 6- An L6 × 4 × 1/2 is used in a seated beam connection, as shown in figure. It must support a service load reaction of 5 kips dead load and 10 kips live load. The angles are A36 and the column is A992. E70XX electrodes are to be used. What size fillet welds are required for the connection to the column flange? 𝐹௪ = 0.60𝐹ா
