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Page 1 Short Notes on Design of Steel Structures Tension Member ? A tension member in which reversal of direct stress due to loads other then wind or earthquake forces has maximum slenderness ratio =180 ? A member normally acting as a tie in roof truss or bracing system. But subjected to possible reversal of stress resulting from the action of wind or earthquake forces has maximum slenderness ratio =350 Net Sectional Area ? For plate: Net area = (b x t) – nd't 22 12 12 44 ss t gg ?? ?? ?? ?? ? Single angle connected by one leg only. o 12 net AAkA ?? where, A 1 = Net cross-section of area of the connected leg. A 2 = Gross cross-sectional area of unconnected leg. (out stand) o 1 12 3 3 A k A A ? ? o 11 2 t At t ?? ?? ?? ?? o 22 2 t At t ?? ?? ?? ?? o 12 () net A II tt ?? ? ? For pair of angle placed back to back (or a signal tee) connected by only one leg of each angle (or by the flange of a tee) to the same side of a gusset plate: or it the two angles are tagged along a-a. Page 2 Short Notes on Design of Steel Structures Tension Member ? A tension member in which reversal of direct stress due to loads other then wind or earthquake forces has maximum slenderness ratio =180 ? A member normally acting as a tie in roof truss or bracing system. But subjected to possible reversal of stress resulting from the action of wind or earthquake forces has maximum slenderness ratio =350 Net Sectional Area ? For plate: Net area = (b x t) – nd't 22 12 12 44 ss t gg ?? ?? ?? ?? ? Single angle connected by one leg only. o 12 net AAkA ?? where, A 1 = Net cross-section of area of the connected leg. A 2 = Gross cross-sectional area of unconnected leg. (out stand) o 1 12 3 3 A k A A ? ? o 11 2 t At t ?? ?? ?? ?? o 22 2 t At t ?? ?? ?? ?? o 12 () net A II tt ?? ? ? For pair of angle placed back to back (or a signal tee) connected by only one leg of each angle (or by the flange of a tee) to the same side of a gusset plate: or it the two angles are tagged along a-a. o 12 net A AkA ?? o 1 12 5 5 A k AA ? ? where, A 1 = Area of connected leg A 2 = Area of outstand (unconnected leg) ? If two angles are places back to back and connected to both sides of the gusset plate. Then o 12 (1) net AAAk ?? ? when tack riveted. If not tack riveted then both will be considered separately and case (ii) will be followed 1 12 3 3 A k AA ? ? Permissible Stress in Design ? The direct stress in axial tension on the effective net area should not exceeded s at where ? s at = 0.5f y ? f y = minimum yield stress of steel in MPa Lug Angle ? The lug angle is a short length of an angle section used at a joint to connect the outstanding leg of a member, thereby reducing the length of the joint. When lug angle is used k = 1 Compression Member Strength of an Axially Loaded Compression Member ? The maximum axial compressive load P P = s ac x A where, o P = axial compressive load (n) o s ac = permissible stress in axial compression (MPa) o A = gross-sectional area of the member (mm 2 ) o s ac is given as 1/ 0.6 [] cc y nn ac n cc y ff ff ? ? ?? ? o f cc = elastic critical stress in compression 2 2 E ? ? ? ? Page 3 Short Notes on Design of Steel Structures Tension Member ? A tension member in which reversal of direct stress due to loads other then wind or earthquake forces has maximum slenderness ratio =180 ? A member normally acting as a tie in roof truss or bracing system. But subjected to possible reversal of stress resulting from the action of wind or earthquake forces has maximum slenderness ratio =350 Net Sectional Area ? For plate: Net area = (b x t) – nd't 22 12 12 44 ss t gg ?? ?? ?? ?? ? Single angle connected by one leg only. o 12 net AAkA ?? where, A 1 = Net cross-section of area of the connected leg. A 2 = Gross cross-sectional area of unconnected leg. (out stand) o 1 12 3 3 A k A A ? ? o 11 2 t At t ?? ?? ?? ?? o 22 2 t At t ?? ?? ?? ?? o 12 () net A II tt ?? ? ? For pair of angle placed back to back (or a signal tee) connected by only one leg of each angle (or by the flange of a tee) to the same side of a gusset plate: or it the two angles are tagged along a-a. o 12 net A AkA ?? o 1 12 5 5 A k AA ? ? where, A 1 = Area of connected leg A 2 = Area of outstand (unconnected leg) ? If two angles are places back to back and connected to both sides of the gusset plate. Then o 12 (1) net AAAk ?? ? when tack riveted. If not tack riveted then both will be considered separately and case (ii) will be followed 1 12 3 3 A k AA ? ? Permissible Stress in Design ? The direct stress in axial tension on the effective net area should not exceeded s at where ? s at = 0.5f y ? f y = minimum yield stress of steel in MPa Lug Angle ? The lug angle is a short length of an angle section used at a joint to connect the outstanding leg of a member, thereby reducing the length of the joint. When lug angle is used k = 1 Compression Member Strength of an Axially Loaded Compression Member ? The maximum axial compressive load P P = s ac x A where, o P = axial compressive load (n) o s ac = permissible stress in axial compression (MPa) o A = gross-sectional area of the member (mm 2 ) o s ac is given as 1/ 0.6 [] cc y nn ac n cc y ff ff ? ? ?? ? o f cc = elastic critical stress in compression 2 2 E ? ? ? ? o ? = slenderness ratio = I r Maximum Slenderness Ratio ? A member carrying compressive loads resulting from dead load and superimposed loads has maximum slenderness ratio = 180 ? A member subjected to compressive loads resulting from wind/earthquake forces provided the deformation of such members does not adversely affect the stress in any part of the structure= 250 ? A member normally carrying tension but subjected to reversal of stress due to wind or earthquake forces=350 Sl. No. Degree of end restraint of compression member Recommended value of effective Length Symbol 1. Effectively held in position and restrained against rotation at both ends 0.65 L 2. Effectively held in position at both ends restrained against rotation at one end 0.80 L 3. Effectively held in position at both ends, but not restrained against rotation 1.00 L 4. Effectively held in position and restrained against rotation at one end, and at the other end restrained against rotation but not held in position. 1.20 L 5. Effectively held in position and restrained against rotation at one end, and at the other end partially restrained against rotation 1.50 L Page 4 Short Notes on Design of Steel Structures Tension Member ? A tension member in which reversal of direct stress due to loads other then wind or earthquake forces has maximum slenderness ratio =180 ? A member normally acting as a tie in roof truss or bracing system. But subjected to possible reversal of stress resulting from the action of wind or earthquake forces has maximum slenderness ratio =350 Net Sectional Area ? For plate: Net area = (b x t) – nd't 22 12 12 44 ss t gg ?? ?? ?? ?? ? Single angle connected by one leg only. o 12 net AAkA ?? where, A 1 = Net cross-section of area of the connected leg. A 2 = Gross cross-sectional area of unconnected leg. (out stand) o 1 12 3 3 A k A A ? ? o 11 2 t At t ?? ?? ?? ?? o 22 2 t At t ?? ?? ?? ?? o 12 () net A II tt ?? ? ? For pair of angle placed back to back (or a signal tee) connected by only one leg of each angle (or by the flange of a tee) to the same side of a gusset plate: or it the two angles are tagged along a-a. o 12 net A AkA ?? o 1 12 5 5 A k AA ? ? where, A 1 = Area of connected leg A 2 = Area of outstand (unconnected leg) ? If two angles are places back to back and connected to both sides of the gusset plate. Then o 12 (1) net AAAk ?? ? when tack riveted. If not tack riveted then both will be considered separately and case (ii) will be followed 1 12 3 3 A k AA ? ? Permissible Stress in Design ? The direct stress in axial tension on the effective net area should not exceeded s at where ? s at = 0.5f y ? f y = minimum yield stress of steel in MPa Lug Angle ? The lug angle is a short length of an angle section used at a joint to connect the outstanding leg of a member, thereby reducing the length of the joint. When lug angle is used k = 1 Compression Member Strength of an Axially Loaded Compression Member ? The maximum axial compressive load P P = s ac x A where, o P = axial compressive load (n) o s ac = permissible stress in axial compression (MPa) o A = gross-sectional area of the member (mm 2 ) o s ac is given as 1/ 0.6 [] cc y nn ac n cc y ff ff ? ? ?? ? o f cc = elastic critical stress in compression 2 2 E ? ? ? ? o ? = slenderness ratio = I r Maximum Slenderness Ratio ? A member carrying compressive loads resulting from dead load and superimposed loads has maximum slenderness ratio = 180 ? A member subjected to compressive loads resulting from wind/earthquake forces provided the deformation of such members does not adversely affect the stress in any part of the structure= 250 ? A member normally carrying tension but subjected to reversal of stress due to wind or earthquake forces=350 Sl. No. Degree of end restraint of compression member Recommended value of effective Length Symbol 1. Effectively held in position and restrained against rotation at both ends 0.65 L 2. Effectively held in position at both ends restrained against rotation at one end 0.80 L 3. Effectively held in position at both ends, but not restrained against rotation 1.00 L 4. Effectively held in position and restrained against rotation at one end, and at the other end restrained against rotation but not held in position. 1.20 L 5. Effectively held in position and restrained against rotation at one end, and at the other end partially restrained against rotation 1.50 L 6. Effectively held in position at one end but not restrained against rotation, and at the other end restrained against rotation but not held in position 2.00 L 7. Effectively held in position and restrained against rotation at one end but not held in position nor restrained against rotation at the other end 2.00 L Built-up Compression Member Tacking Rivets ? The slenderness ratio of each member between the connections should not be greater than 40 nor greater than 0.6 times the most unfavorable slenderness ratio of the whole strut ? The diameter of the connecting rivets should not be less than the minimum diameter given below. Thickness of member Minimum diameter of rivets UP to 10 mm Over 10 mm to 16 mm Over 10 mm 16 mm 20 mm 22 mm Lacings Type of lacing Effective length I e Single lacing, riveted at ends Length between inner and rivets on lacing bar (= I, as shown in Fig. 17) Double lacing, riveted at ends and at intersection 0.7 times length between inner end rivets on lacing bars (= 0.7 x I) Welded lacing 0.7 times distance between inner ends of effective lengths of welds at ends (0.7 xI) For local Buckling criteria min sec 50 0.7 c whole tion L r ? ? ? Page 5 Short Notes on Design of Steel Structures Tension Member ? A tension member in which reversal of direct stress due to loads other then wind or earthquake forces has maximum slenderness ratio =180 ? A member normally acting as a tie in roof truss or bracing system. But subjected to possible reversal of stress resulting from the action of wind or earthquake forces has maximum slenderness ratio =350 Net Sectional Area ? For plate: Net area = (b x t) – nd't 22 12 12 44 ss t gg ?? ?? ?? ?? ? Single angle connected by one leg only. o 12 net AAkA ?? where, A 1 = Net cross-section of area of the connected leg. A 2 = Gross cross-sectional area of unconnected leg. (out stand) o 1 12 3 3 A k A A ? ? o 11 2 t At t ?? ?? ?? ?? o 22 2 t At t ?? ?? ?? ?? o 12 () net A II tt ?? ? ? For pair of angle placed back to back (or a signal tee) connected by only one leg of each angle (or by the flange of a tee) to the same side of a gusset plate: or it the two angles are tagged along a-a. o 12 net A AkA ?? o 1 12 5 5 A k AA ? ? where, A 1 = Area of connected leg A 2 = Area of outstand (unconnected leg) ? If two angles are places back to back and connected to both sides of the gusset plate. Then o 12 (1) net AAAk ?? ? when tack riveted. If not tack riveted then both will be considered separately and case (ii) will be followed 1 12 3 3 A k AA ? ? Permissible Stress in Design ? The direct stress in axial tension on the effective net area should not exceeded s at where ? s at = 0.5f y ? f y = minimum yield stress of steel in MPa Lug Angle ? The lug angle is a short length of an angle section used at a joint to connect the outstanding leg of a member, thereby reducing the length of the joint. When lug angle is used k = 1 Compression Member Strength of an Axially Loaded Compression Member ? The maximum axial compressive load P P = s ac x A where, o P = axial compressive load (n) o s ac = permissible stress in axial compression (MPa) o A = gross-sectional area of the member (mm 2 ) o s ac is given as 1/ 0.6 [] cc y nn ac n cc y ff ff ? ? ?? ? o f cc = elastic critical stress in compression 2 2 E ? ? ? ? o ? = slenderness ratio = I r Maximum Slenderness Ratio ? A member carrying compressive loads resulting from dead load and superimposed loads has maximum slenderness ratio = 180 ? A member subjected to compressive loads resulting from wind/earthquake forces provided the deformation of such members does not adversely affect the stress in any part of the structure= 250 ? A member normally carrying tension but subjected to reversal of stress due to wind or earthquake forces=350 Sl. No. Degree of end restraint of compression member Recommended value of effective Length Symbol 1. Effectively held in position and restrained against rotation at both ends 0.65 L 2. Effectively held in position at both ends restrained against rotation at one end 0.80 L 3. Effectively held in position at both ends, but not restrained against rotation 1.00 L 4. Effectively held in position and restrained against rotation at one end, and at the other end restrained against rotation but not held in position. 1.20 L 5. Effectively held in position and restrained against rotation at one end, and at the other end partially restrained against rotation 1.50 L 6. Effectively held in position at one end but not restrained against rotation, and at the other end restrained against rotation but not held in position 2.00 L 7. Effectively held in position and restrained against rotation at one end but not held in position nor restrained against rotation at the other end 2.00 L Built-up Compression Member Tacking Rivets ? The slenderness ratio of each member between the connections should not be greater than 40 nor greater than 0.6 times the most unfavorable slenderness ratio of the whole strut ? The diameter of the connecting rivets should not be less than the minimum diameter given below. Thickness of member Minimum diameter of rivets UP to 10 mm Over 10 mm to 16 mm Over 10 mm 16 mm 20 mm 22 mm Lacings Type of lacing Effective length I e Single lacing, riveted at ends Length between inner and rivets on lacing bar (= I, as shown in Fig. 17) Double lacing, riveted at ends and at intersection 0.7 times length between inner end rivets on lacing bars (= 0.7 x I) Welded lacing 0.7 times distance between inner ends of effective lengths of welds at ends (0.7 xI) For local Buckling criteria min sec 50 0.7 c whole tion L r ? ? ? Where, ? L = distance between the centres of connections of the lattice bars to each component ? min c r = minimum radius of gyration of the components of compression member ? For a single lacing system on two parallel faces, the force (compressive or tensile) in each bar, 2sin V F ? ? ? For double lacing system on two parallel planes, the force (compressive or tensile) in each bar, 4sin V F ? ? ? If the flat lacing bars of width b and thickness t have rivets of diameter d then, ? Compressive stress in each bar force gross area ac F bt ? ??? ? ? Tensile stress in each bar force net area ( ) at F bd t ? ?? ? ?? ? Numbers of rivets required 2Fcos Rivet value ? Welded connections ? Lap joint: Overlap (14) ? times thickness of bar or member, whichever is less. ? Butt joints: Full penetration butt weld of fillet weld on each side. Lacing bar should be placed opposite to flange or stiffening member of main member. Slab Base ? Area of slab base= axial load in the column permissible compressive stress in concrete ? The thickness of a rectangular slab base as per 2 2 3 4 bs wb ta ? ?? ?? ?? ?? ? The thickness of a square slab base plate under a solid round column. 0 90 10 16 ( ) bs WB t Bd ? ?? ? Structural Fasteners Riveting ? Gross dia of rivet or dia of hole d' = d + 1.5 mm for d = 25 mm d' = d + 2.0 mm for d = 25 mm where d = Nominal dia of rivet d' = Gross dia of rivet or dia of hole… ? Unwins formulaRead More
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1. What are the common formulas used in steel structures for a civil engineering exam? |
2. How is Euler's formula for buckling used in steel structures? |
3. What is the significance of the yield strength formula in steel structures? |
4. How can the moment of inertia formula be used in steel structure design? |
5. Why is the deflection formula important in steel structure analysis? |
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