1. Introduction to DESIGN OF STEEL STRUCTURES (Limit State Method) 1

2. Introduction Steel has made possible some of the grandest structures both in the past and in the present days  Structural steel is widely used in making: Transmission towers Industrial buildings Bridges Storage structures Water tanks

3. Anatomy Beams Columns Floors Bracing Systems Foundation Connections 3

4. Syllabus Module 1: Introduction: Steel as Structural Material; Advantages and disadvantages of steel; Types of sections, I. S. Rolled Sections; Material Overview, Basis for Structural Design; Loadings and Load Combinations Module 2: Connections: TypesofConnections, BoltedConnections;Advantagesand disadvantages of bolted joints Design of bolted connections; Efficiency and design of joints; Welded Connections; Advantages and disadvantages of welded joints, Design of welded connections; Fillet and butt welds, Plug and slot welds 4

5. Module 4: Tension Members Typesoffailures,Grossandnetsectionalarea,Ruptureof criticalsection,Strengthcalculation;Blockshearfailure, Module 3: Eccentric Connections Typesofeccentricconnections,Boltedandweldconnections, load lying in plane of joint, load lying perpendicular to the plane of joint, Design of eccentric connection using bolts and welds Slenderness ratio, Design of tension members; Gusset plates, Lug angles; tension splices; Design of tension member subjected to axial and bending 5

6. Module 5: Compression Members Types of failures, Strength calculation ; slenderness ratio, Design of compression member; Design of eccentrically loaded compression member; Built-up compression members; Design of built-up compression members; Design of lacing system; Design of batten plate Module 6: Flexural Members Introduction to flexural members: Beams; Design procedure of beam members; Design of laterally supported beams; Design of laterally unsupported beams; Built-up beams; Design of purlins Module 7: Column Base Slab Base, Gusseted Base Module 8: Gantry Girders Codal aspects on design criteria on gantry girder 6

7. Text Books/References Design of Steel Structures Dr. Subramanian Narayanan - Oxford Publication Limit State Design of Steel Structures S. K. Duggal –Tata McGraw Hill 7

8. Text Books/References Design of Steel Structures by Elias G. Abu-Saba – CBS Publishers and Distributors Design of steel structures by E.H. Gaylord, C.N. Gaylord & J.E. Stallmeyer – McGraw Hill. Structural Steel work: Analysis and Design by S. S. Ray – Blackwell Science 8

9. Codes  Code of practice for general construction in steel  IS: 800 - 2007  Handbook for structural engineers  SP: 6(1) – 1964 (Reaffirmed 2003)  IS 808 : 1989 (Reaffirmed 2004)  Steel Tables of any standard publication.  Code of practice for design loads (other than earthquake) for buildings and structures  IS 875 : Part I to V : 1987  IRC for vehicle load etc. in Bridge structures 9

10. Indian Standard Junior Beam (ISJB) – JB Indian Standard Light Beam (ISLB)– LB Indian Standard Medium Weight Beam (ISMB)– MB Indian Standard Wide Flange Beam (ISWB) – WB Indian Standard Heavy Weight Beam (ISHB)– HB Indian Standard column section (ISSC) – SC ROLLED STEEL SECTIONS 10

11. I-Section ROLLED STEEL SECTIONS 11

12. Indian Standard Junior Channel (ISJC) – JC Indian Standard Light Channel (ISLC) – LC Indian Standard Medium Weight (ISMC) – MC Indian Standard parallel flange Channel (ISMCP)-MCP Channel – Sections 12

13. Indian Standard Equal Angel (ISA) Indian Standard Unequal Angel (ISA) Angle – Sections 13

14. Angle section

15. Indian Standard Normal Tee Bars (ISNT) – ISNT– NT Indian Standard Deep Tee Bars (ISDT) – ISDT– DT Indian Standard Light Tee Bars (ISLT) –ISLT– LT Indian Standard Medium Tee Bars (ISNT) –ISMT– MT Indian Standard Heavy Tee Bars (ISHT) –ISHT– HT Tee – Sections 15

16. Rolled Steel Bar Section Indian Standard Round Section-ISRO Indian Standard Square Section-ISSQ 16

17. Rolled SteelSections are designated as follows ISRO100 means a round sectionof diameter 100mm, while ISSQ50 means a square section each side of which is 50mm. 100mm 50mm 17

18. Rolled Steel sheets & strip Indian Standard Steel Sheet Section- ISSH-SH Indian Standard Steel Strip Section- ISST-ST Rolled steel flats are designated by width of the section in mm followed by the letter F & thickness. Thus, 50 F 8 means a flat of width 50 mm & thickness of 8 mm. 18

19. Hollow section pipe 19 Square hollow section

20. STEEL AS A STRUCTURAL MATERIAL 1

21. Better quality control Lighter Faster to erect Reduced site time - Fast track Construction Large column free space and amenable for alteration Less material handling at site Less percentage of floor area occupied by structural elements Has better ductility and hence superior lateral load behavior; better earthquake resistance Advantages of steel design 2

22. Skilled labor is required. Higher cost of construction Maintenance cost is high. Poor fireproofing, as at 1000 o F (538 o C) 65% & at 1600 o F (871 o C) 15% of strength remains Electricity may be required. Disadvantages of steel design 3

23. Chemical composition of steel: Steel is an alloy which mainly contains iron and carbon. Apart from the carbon a small percentage of manganese, silicon, phosphorus, nickel and copper are also added to modify the specific properties of the steel. Chemical composition of structural steel (IS 2062-1992 & IS 8500) GradeCMnSPSiCarbon Equivalent Fe410WA0.231.500.050 0.400.42 Fe410WB0.221.500.045 0.400.41 Fe410WC0.201.500.040 0.400.39 Fe 4400.201.300.05(0.04) 0.450.40 Fe 4900.201.500.05(0.04) 0.450.42 Fe 5900.221.800.045(0.04) 0.450.48 Notes: 1.Carbon Equivalent = (C+Mn)/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 2.The terms in the bracket denotes the maximum limit for the flat products. 4

24. Types of structural steel: Different structural steel can be produced based on the necessity by changing slightly the chemical composition and manufacturing process. 1.Carbon steel: In this type of structural steel carbon and manganese are used as extra elements. 2.High Strength Carbon Steel: By increasing the carbon content this type of steel can be manufactured which basically produces steel with comparatively higher strength but less ductility. 3.Stainless Steel: In this type of steel mainly foreign material like nickel and chromium are used along with small percentage of carbon. 5

25. Properties of structural steel 6 The important mechanical properties of steel are: ultimate strength, yield stress, ductility, weldabilty, toughness, corrosion resistance and machinability. The last four properties are important for durability of material and often associated with fabrication of steel members. The mechanical properties of steel largely depend on its  Chemical composition  Heat treatment  Stress history  Rolling methods  Rolling thickness

26. Structural Steel  The steel used for structural works shall confirm to IS 2062 : 2011 (Hot Rolled Medium and High Tensile Structural Steel).  Most Commonly used grade is Fe 410.  Followings are few physical properties of structural steel (As per clause 2.2.4.1 of IS 800 : 2007):  Unit mass of steel, ρ = 7850 kg/m 3  Modulus of elasticity, E = 2.0 × 10 5 N/mm 2  Poisson’s ratio, µ = 0.3  Modulus of rigidity, G = 0.769 × 10 5 N/mm 2  Co-efficient of thermal expansion, α= 12 × 10 -6 / o c

27. Mechanical properties: Followingarethemostimportantmechanicalpropertiesthatare Grade of Steel Yield Stress (MPa)Ultimate Tensile Stress (MPa) Elongation Percentage t<20t = 20 to 40t>40 Fe 410 250240230 41023 Fe 44030029028044022 Fe 49035033032049022 Fe 54041039038054020 frequently used in design of steel structures.  Yield stress, f y  Ultimate stress, f u  Minimum percentage elongation These properties can be obtained by performing tensile tests of the steel sample. Mechanical properties of structural steel products (Table 1 of IS 800 : 2007) 8

28. Some other important mechanical propertiesof steel (i)Ductility: It is defined as the property of a material by virtue of which it undergoes large inelastic i.e. permanent deformation without loss of strength under the application of tensile load. (ii)Hardness: It is one of the mechanical properties of steel by virtue of which it offers resistance to the indentation and scratching. The hardness of steel is measured by  Brinell hardness test  Vickers hardness test  Rockwell hardness test 9

29. (iii)Toughness:Itisoneofthemechanical properties of steel by virtue of which it offers resistancetofractureundertheactionof impact loading. Toughness = The ability to absorb energy up to fracture.  Toughness is generally measured by the area under the stress-strain curve. (iv)Fatigue: It is defined as the damage caused by the repeated fluctuation of stresses which leads to the progressive cracking of the structural element.  Damageandfailureofthematerialundertheactionofcyclic loading. (v)Resistance against corrosion: In the presence of moist air corrosion of steel is an extremely important aspect.  To avoid corrosion paint or metallic coating may be used 10

30. Few important terms associated with structural steel: (a)Residual Stress: Residual stresses are defined as the stresses which are locked into a component or assembly of parts. At the time of rolling of steel sections, fabrication of steel members, they are subjected to very high temperature and after that they are allowed to cool which is basically an uneven process. Due to this uneven heating and cooling, residual stress in the structural member is generated. (b)Stress Concentration: Stress concentration indicates a highly localized state of stress at a particular location of a member. Generally, if there exists an abrupt change in the shape of the member like in the vicinity of notch or holes, the stress generated at that location is several times greater than the stress that would generate without that sudden change in geometry. 11

31. Stress-strain curve for mild steel Stress-Strain diagram for steel specimen is generally plotted by performing tensile test, in which a specimen having gauge length L 0 and initial cross sectional area A 0 is taken. Stress, f Strain, ɛ O A B C D CʹCʹ E F 12 fyfy fufu

32. Part OA- In this region the stress is proportional to strain, and is called the limit of proportionality. Part AB- After reaching ‘A’, change in strain is rapid compared to that of stress but still the material behaves elastically up to elastic limit ‘B’. C ʹ - represents the upper yield point C - represents the lower yield point. Part CD- Beyond yield point the material starts flowing plastically without any significant increase in the stress and material undergoes large deformation. Part DE- After reaching point ‘D’, the strain hardening in the material begins which necessitates requirement of higher load to continue deformation. This phenomenon is called ‘strain hardening’. E represents the ultimate stress f u. Part EF- When the stress reaches point ‘E’ that is the stress corresponding to the ultimate stress, the necking in material begins. F - represents breaking stress – the stress corresponding to the breaking load. 13

33. LIMIT STATE DESIGN

34. DESIGN PHILOSOPHIES Safety at ultimate load and serviceability at working load

35. Working Stress Method: Safety is ensured by limiting the stress of the material. The material is assumed to behave in linear elastic manner. In this approach the stress-strain behaviour is considered to be linear. Permissible stress < (Yield stress / Factor of safety) Details at: IS 800 – 1984. Permissible stress in steel structural members Types of stressNotationPermissible stress (Mpa) Factor of safety Axial tension σ at 0.6f y 1.67 Axial compression σ ac 0.6f y 1.67 Bending tension σ bt 0.66f y 1.515 Bending compression σ bc 0.66f y 1.515 Average shear stress τ va 0.4f y 2.5 Bearing stressσpσp 0.75f y 1.33

36. USM: It is also referred to Plastic Design Method. In this case thelimitstateisattainedwhenthemembersreachplastic momentstrengthM p andthestructureisattainedintoa mechanism. The safety measure of the structure is taken care of by an appropriate choice of load factor. It is multiplied to the working load and it is checked w.r.t to the ultimate load corresponding to the member. Working Load × Load Factor ≤Ultimate Load LSM: In limit state design method, the structure is designed in such a way that it can safely withstand all kind of loads that may act on the structure under consideration in its entire design life. In this approach, the science of reliability based design was developed with the objective of providing a rational solution to the problem of adequate safety. Uncertainty is reflected in loading and material strength.

37. Factors Governing Ultimate Strength Stability Stability Against Overturning Sway Stability FatiguePlastic Collapse Limit State of Strength

38. Limit State of Strength: These are associated with the failure of the structure under the action of worst possible combination of loads along with proper partial safety factor that may lead to loss of life and property. As provided in IS 800: 2007, Limit state of strength includes – Loss of equilibrium of the structure as a whole or in part. Loss of stability of the structure. Failure due to excess deformation or rupture. Fracture due to fatigue. Brittle fracture.

39. Check for Serviceability Limit States Deflection limit Vibration limit Durability consideration Fire Resistance Limit State Serviceability

40. Limit State of Serviceability: Theseareassociatedwiththediscomfortfacedbytheuserwhile using the structure. Excess deflection or deformation of the structure. Excessvibrationofthestructurecausingdiscomforttothe commuters. Repairable damage or crack generated due to fatigue. Corrosion and durability

41. = Partial Safety Factor for Load (Clause 5.3.3, Table 4, IS 800: 2007) Where, = the partial safety factor for k th load or load effect, =Characteristicloadorloadeffect,=Designloadorload effect. Note Characteristic values (loads/stresses) are defined as the values that are not expected to be exceeded within the life of the structure with more than 5% probability. Generally partial factor of safety considered is in all cases higher than unity. Whereas for serviceability limit states unit factor of safety is considered as it is checked under the action of service load for structure.

42. Combinatio ns Limit State of StrengthLimit State of Serviceability DLLLWL/ EL ALDLLLWL/ EL Leadin g Accompa nying LeadingAccomp anying DL+LL+CL1.5 1.05--1.0 - DL+LL+CL +WL/EL 1.2 1.050.6-1.00.8 1.2 0.531.2- DL+WL/EL1.5 (0.9) --1.5-1.0-- DL+ER1.2 (0.9) 1.2------- DL+LL+AL1.00.35 -1.0---- Notes: (i)DL=dead load, LL=imposed (live) load, CL=crane load, WL=wind load, EL=earthquake load, AL=accidental load. (ii)During simultaneous action of different live loads one which has greater effect on the member under consideration is considered as the leading live load. (iii)Value in the bracket should be considered when dead load contributes to the stability against overturning or it causes reduction in stress due to other loads. Partial Safety Factor for Loads, (Table 4, IS 800: 2007)

43. Partial Safety Factor for Material Partial safety factor for material = / Where, = Partial safety factor for material as given in Table 1.5. = Ultimate strength of the material, = Design strength of the material. Generally, a factor of unity (one) or less is applied to the resistances of the material.

44. DefinitionPartial Safety Factor Resistance governed by yielding, 0 1.10 Resistance of member to buckling, 0 1.10 Resistance governed by ultimate stress, 1 1.25 Resistance of connectionShop Fabrication Field Fabrication (a) Bolts, friction type, 1.25 (b) Bolts, bearing type, 1.25 (c) Rivets, 1.25 (d) Welds, 1.251.50 Partial safety factor for material, (Table 5, IS 800: 2007)

45. Type of Building DeflectionDesign Load MemberSupportingMaximum Deflection Industrial Buildings Vertical LL/WLPurlins and girts Elastic CladdingSpan/150 Brittle CladdingSpan/180 LLSimple spanElastic CladdingSpan/240 Brittle CladdingSpan/300 LLCantilever span Elastic CladdingSpan/120 Brittle CladdingSpan/150 LL/WLRafter supporting Profiled Metal sheetingSpan/180 Plastered sheetingSpan/240 CL(manual operation)GantryCraneSpan/500 CL (electric operation up to 50t)GantryCraneSpan/750 CL (electric operation over 50t)GantryCraneSpan/1000 Lateral No cranesColumnElastic CladdingHeight/150 Brittle CladdingHeight/240 Crane + windGantry (lateral) Crane(absolute)Span/400 Relative displacement between rails supporting crane 10mm Crane + windColumn/fra me Gantry(Elastic cladding, pendant operated) Height/200 Gantry(Brittle cladding, cab operated) Height/400 Deflection Limits (Table 6, IS 800: 2007)

46. Type of BuildingDeflectionDesign Load MemberSupportingMaximum Deflection Other Buildings Vertical LLFloor & RoofElements not susceptible to cracking Span/300 Elements susceptible to cracking Span/360 LLCantileverElements not susceptible to cracking Span/150 Elements susceptible to cracking Span/180 Lateral WLBuildingElastic claddingHeight/300 Brittle claddingHeight/500 WLInter story drift-Story height/300 Deflection Limits (Table 6, IS 800: 2007)

47. Classification of Cross Section Class 1 Plastic Class 2 Compact Class 3 Semi-Compact Cross Sectional Classification (Clause 3.7, Table 2)

48. Load and Load Combinations  Dead loads – [IS:875 (Part-1)]  Imposed loads (i.e. Live loads, Crane loads etc) –[IS:875 (Part 2)]  Wind loads – [IS:875 (Part-3)]  Snow loads - [IS:875 (Part-4)]  Temperature,Hydrostatic,Soilpressure,Fatigue,Accidental, Impact, Explosions etc and load combinations[IS:875 (Part-5)]  Earthquake load – [IS:1893-2002 (Part-1)]  Erection loads – [IS:800-2007 Cl. 3.3]  Othersecondaryeffectssuchastemperaturechange,differential settlement, eccentric connections etc.

49.  In IS:800-2007 (Cl. 5.3.1) the loads/actions acting on a structural system has been classified in three groups, these are as follows:  Permanent actions (Q p ) – Action due to self-weight of the structural components, basically the dead loads.  Variable actions (Q v ) – Action due to loads at construction and service stage such as all type of imposed loads, wind and earthquake loads etc.  Accidental actions (Q a ) – Action due to accidental loads acting on the structure such as due to explosion, due to sudden impact etc.  Whiledesigningthesteelstructurefollowingloadcombination must be considered along with partial safety factors Dead loads + Imposed loads  Dead loads + Imposed loads + Wind / Earthquake loads  Dead loads + Wind / Earthquake loads  Dead loads + Erection loads

50. Wind Load Calculation Cl. 5.3, IS 875 (Part 3) 1987 The design wind speed (m/s) at any height z is = 123 Where, = Basic wind speed (Figure 1) 1 = Probability factor (risk coefficient) (Table 1) 2 = Terrain, height and structure size factor (Table 2) 3 = Topography factor (Clause 5.3.3 ) Basic wind speed, m/s Zone 55 I 50 II 47 III 44 IV 39 V 33 VI

51. The wind pressure at any height of a structure depends on following.  Velocity and density of the air  Height above ground level  Shape and aspect ratio of the building  Topography of the surrounding ground surface  Angle of wind attack  Solidity ratio or openings in the structure Design Wind Pressure (cl. 5.4; IS 875 part 3) Design wind pressure at any height above mean ground level is obtained by = 0.6 2

52. Design Wind Force: 1. The total wind load for a building as a whole is given by = [cl. 6.3 of IS 875 part-3 ] Where, = Force coefficient of the building = Effective frontal area = design wind pressure 2. Wind force on roof and walls is given by = − [cl. 6.2.1 of IS 875 part-3] (cl. 6.2.2 of IS 875 part-3) Where, = External pressure coefficient = Internal pressure coefficient (cl. 6.2.3 of IS 875 part-3) A = Surface area of structural element

53. INTRODUCTION TO CONNECTIONS 1

54. Fabrication of structures between following members: Beam & column Beam & beam Beam & cross beam Column & column Column & brackets Column & caps Base plate of trusses Truss member connections through gussets Purlins & rafter Wind braces and columns Rails & columns 2

55. Stiffeners in plate girders Diaphragms in plate girders Flange and web connections in plate girders Stiffener plates in column joints Methods of Fabrications:  Rivet Joints  Bolt Joints  Weld Joints  The combinations of two or three of the above 3

56. Requirements of good connection 1.It should be rigid enough to avoid fluctuating stresses which may cause fatigue failure. 2.It should be such that there is the least possible weakening of the parts to be joined. 3.It should be such that it can be easily installed, inspected, & maintained. 4

57. Head Shank Nominal Diameter Rivet Head Diameter RIVET CONNECTION 5

58. Advantages of Riveted connections Ease of riveting process. Rivet connection is permanent in nature Cheaper fabrication cost. Low maintenance cost. Dissimilar metals can also be joined, even non-metallic joints are possible with riveted joints. Rivet connection is possible without electricity in remote area

59. Disadvantages of Rivet Connection: (i)Necessity of pre-heating the rivets prior to driving (ii)High level of noise (iii)Skilled work necessary for inspection of connection (iv)Cost involved in careful inspection and removal of poorly installed rivets (v)Labor cost is high 7

60. Rivet Power driven riveting or Hot rivet Hand driven riveting or Cold rivet Power driven shop rivet(PDS) Power driven field rivet(PDF) Hand driven shop rivet(HDS) Hand driven field rivet(HDF) 8

61. 1.6d Length 0.7d d Snap Head Commonly used rivet head 9 2d2d d 0.25d Length Flat head

62. 1.Friction between the plates is neglected. 2.The shear stress is uniform on the cross section of the rivet. 3.The distribution of direct stress on the portion of the plates between the rivet holes is uniform. 4.Rivetsingroupsubjectedtodirectloadssharethe load equally. 5.Bending stress in the rivet is neglected. 6.Rivets fill completely the holes in which they are driven 7.Bearing stress distribution is uniform and contact area isd × t Assumption: 10

63. BOLT CONNECTION Clause 2.4: Bolts, nuts and washers shall conform as appropriate to: IS 1363-1967, IS 1364- 1967, IS 1367-1967, IS 3640-1967, IS 3757- 1972, IS 6623-1972 and IS 6639-1972

64. Advantages: Less Manpower High strength bolts are much stronger than rivet. Hence, bolted connections need less fasteners than rivet joints Bolting operation is much faster Bolting operation is very silent in contrast to hammering noise in riveting Bolting is a cold process; No risk of fire Bolt can be removed, replaced or retightened easily in the event of faulty bolting or damaged bolts due to accidents/hazards

65. Disadvantages: Bolted connections have lesser strength in axial tension as the net area at the root of the threads is less Under vibratory loads, the strength is reduced if the connections get loosened Unfinished bolts have lesser strength because of non uniform diameter Architectural look

66. TYPES OF BOLT According to material and strength (i)Ordinary structural bolt (ii)High strength steel bolt According to Type of Shank (i)Unfinished or black bolt (ii)Turned bolt (iii)High strength friction grip (HSFG) bolt According to pitch and fit of thread (i)Standard pitch bolt (ii)Fine pitch bolt (iii)Coarse pitch bolt According to shape of head and nut (i)Square bolt (ii)Hexagonal bolt

68. Terminology 16 Pitch, p  Pitch is the centre to centre distance of adjacent rivets or bolt holes measured in the direction of stress. Minimum pitch: 2.5 d ( clause 10.2.2) To prevent bearing failure between two bolts Sufficient space to tighten bolts

69. Terminology Maximum pitch: Desirable to place bolts sufficiently closed (clause 10.2.3) (1)To reduce length of connection and gusset plate (2)To have uniform stress (Distance between two consecutive bolts) < 16 t or 200 mm in tension < 12 t or 200 mm in compression (Distance between two adjacent bolts)< 32 t or 300 mm Gauge, g  A row of rivets which is parallel to the direction of stress is called gauge line. The normal distance between two adjacent gauge lines is called gauge. Edge distance, e  The distance between the edge of a member or cover plate from the centre of the nearest rivet/bolt hole. Minimum edge distance for rivet: 1.5 d 17

70. Nominal diameter, d  It is the diameter of the shank of the rivet. For bolts the diameter of the unthreaded portion of the shank is called its nominal diameter. Gross diameter, D  The diameter of the rivet hole or bolt hole is called its gross diameter. For rivet: As per clause 3.6.1.1 of IS 800:1984 D = d + 1.5 mm for d < 25mm = d + 2 mm for d25mm 18

71. For Bolt: Minimum and maximum edge distance and end distance are given in clause 10.2.4.2 and 10.2.4.3 The minimum edge/end distances > 1.7 times the hole diameter (In case of sheared or hand-flame cut edges) > 1.5 times the hole diameter (In case of rolled, machine-flame cut, sawn and planed edges.) The maximum edge distance < 12tε where ε = (250/f y ) 1/2 (t is the thickness of the thinner plate)

72. Bolt hole = bolt diameter + clearances of hole (Clause 10.2.1, Table 19) Diameter, dStandard clearanceOver sizeShort slotLong short 12-14134 2.5 d 16-22246 2.5 d 24268 2.5 d >243810 2.5 d Bolt holes: Bolt holes are required to facilitate the insertion of bolts to make connection between steel members. Bolt holes are usually made larger than the nominal diameter of bolt to smooth the progress of erection and accommodate minor discrepancies.

73. INTRODUCTION TO BOLT CONNECTIONS 1

74. TYPES OF JOINTS (i)Depending upon arrangement of bolts& plates (ii)Depending upon mode of load transmission (iii)Depending upon nature and location of load 2

75. TYPES OF BOLT JOINTS (i) Depending upon arrangement of bolts and plates Lap Joint Single line bolting Chain bolting Staggered or zig-zag bolting Butt Joint Single bolting Chain bolting Staggered or zig-zag bolting 3

76. Bolting pattern Chain bolting Zig-Zag bolting Diamond bolting

77. Single bolted Lap Joint: Triple bolted lap joint: Single bolted single cover butt joint: Single bolted double cover butt joint Double bolted double cover butt joint (i) Depending upon arrangement of bolts and plates 5

78. TYPES OF BOLT JOINTS (ii)Depending upon the mode of load transmission (a)Single shear (b)Double shear (c)Multiple shear 6

79. (ii) Depending upon the mode of load transmission (a) Single shear (b)Double shear (c)Multiple shear 7

80. TYPES OF BOLT JOINTS (iii)Depending upon nature and location of load (a)Direct shear connection (b)Eccentric connection (c)Pure moment connection (d)Moment shear connection 8

81. (a) Direct shear connection 9

82. (b)Eccentric connection 10

83. (c)Pure moment connection 11

84. (d) Moment shear connection 12

85. The following are the failure modes of a bolted joint: Shear failure of the bolt Bearing failure of the bolt Tensile failure of bolt Shear failure of the plate Bearing failure of the plate Tensile failure of plate

86. (a) Single shear (b) Double shear 14 Shear Failure of Bolt

87. Things to remember for bolted connections: Stress concentration results in a considerable decrement in the tensile strength. Loose fit of the joint can reduce the stiffness which may result in excessive deflections. Vibrations can cause loosening of nuts which can jeopardize the safety of structure.

88. Criteria for designing bolted joints with axially loaded members The length of joint should be as small as possible to save material on cover plates and gusset plates. The center line of all the members meeting at a joint should coincide at one point only. Otherwise the joint will twist out of position. The number of bolts should be increased gradually towards the joint for uniform stress distribution in bolts.

89. Criteria for designing bolted joints with axially loaded members The arrangement should satisfy the pitch, gauge and edge distance requirements. The strength of joint reduces due to the bolt holes. The reduction in area due to bolt holes can be minimized by arranging in a zig-zag form.

90. A B C DE