DESIGN OF STEEL COLUMN.pptx

Steel column design plays a crucial role in the construction industry, ensuring the structural integrity and safety of buildings and infrastructure projects. Columns are vertical load-bearing members that support the weight of the structure and transmit it to the foundation. This brief presentation provides an overview of steel column design, highlighting key considerations, design principles, and the importance of adherence to codes and standards.

1. DESIGN OF STEEL COLUMN PREPARED BY NAME: SHYAM SUNDAR ROY REG. NO.: D202108759 ROLL.: DHITCES6; NO.: 10008886

2. TABLE OF CONTENTS 01 Introduction 03 Overview of Steel Columns 02 Classification 04 Design and Numerical Problems

3. INTRODUCTION 01

4. DEFINATION A STEEL COLUMN is a structural component commonly used in construction and engineering to provide vertical support and stability to a building or structure. It is a vertical member typically made of steel, which is a strong and durable material with excellent load-bearing capacity. Steel columns are used in: Warehouse structures , Temporary event structures (tents, stages, etc.), Buildings Scaffolding, Renovation projects, Factories, Steel towers

5. KEY CHARACTERISTIC AND FEATURES Steel columns are typically constructed using structural steel. Material Depending on the structural requirements and architectural considerations. S hape and design Depends on factors like its dimensions, steel grade, and the design codes and standards etc. L oad-bearing Capacity The connections ensure stability, transfer of loads, and overall structural integrity. C onnection Fire-resistant coatings, encasement in concrete, or the use of other materials. F ire resistance Supported by foundations that distribute the column loads to the ground. F oundation

6. CLASSIFICATION 02

7. CLASSIFICATION OF COLUMN BASED ON CROSS SECTIONAL SHAPE TYPES OF LOADING TYPES OF REINFORCEMENT SLENDERNESS RATIO SQUARE COLUMN RECTANGULAR BEAM CIRCULAR COLUMN HEXAGONAL COLUMN T, L OR + SHAPED COLUMN AXIALLY LOADED COLUMN COLUMN WITH UNIAXIAL ECCENTRICITY COLUMN WITH BIAXIAL ECCENTRICITY TIED COLUMN SPIRAL COLUMN COMPOSITE COLUMN SHORT COLUMN LONG COLUMN

8. When the ratio of effective length of column to the least lateral dimension is greater than 12 is known as long column. LONG COLUMNS When the ratio of effective length of column to the least lateral dimension is less than equal to 12 is known as short column. SHORT COLUMNS 01 02 DEFINE

9. SQUARE COLUMN RECTANGULAR COLUMN HEXAGONAL COLUMN CIRCULAR COLUMN TRIED COLUMN SPIRAL COLUMN COMPOSITE COLUMN SOME PICTURES

10. AXIAL LOADED COLUMN COLUMN WITH UNIAXIAL ECCENTRICITY COLUMN WITH BIAXIAL ECCENTICITY SHORT COLUMN T & L SHAPE COLUMN

11. Overview of Steel Columns 03

12. EFFECTIVE LENGTH (EQUIVALENT LENGTH) The column’s length where deflection occurs due to the bending moment by the supporting load is known as the EFFECTIVE LENGTH OF THE COLUMN . The bending moment occurs on the column due to the compression load. The load which makes the column to bend is known as BUCKLING LOAD . Effective length of column for different end conditions

13. S. No End Conditions Effective length Recommended 01 Effectively held in position and restrained against rotation at both ends 0.65 L 02 Effectively held in position at both ends and restrained against rotation at one end 0.80 L 03 Effectively held in position at both ends, but not restrained against rotation. 1.00 L 04 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 05 Effectively held in position and restrained against rotation at one end, and at the other end partially restrained against rotation but not held in position. 1.50 L 06 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 07 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 EFFECTIVE LENGTH OF COMPRESSION MEMBERS

14. SLENDERNESS RATIO It is defined as the ratio between the effective length of compression member and its least radius of gyration . Slenderness ratio = l / r l = effective length of compression member. r = least radius of gyration of section of a member. Radius of gyration is the property of a section. It is always worked out with reference to a certain axis by the expression: r = √ I/A where I = Moment of inertia of the section. A = Area of the section

15. The columns are supported on the column bases. Column bases are structural elements used in the design of steel structures to transfer the column load to the footings. If column base is not provided, the column is likely to punch through the concrete block. Types of Column bases 1. Slab base 2. Gusseted base COLUMN BASES

16. 01. Slab Base: Slab base is provided to the column subjected to only axial load. A steel plate is used to transfer the load to the concrete pedestal in the case of a slab base. In the slab base, the column is connected to a cleat angle. The critical moment will be at the edge of the column. Area of base plate= (load of column)/(permissible bearing stress in concrete) PLAN ELEVATION

17. 02. Gusseted base Gusseted bases are provided for columns carrying heavier loads requiring large base plates. A gusseted base consists of a base of reduced thickness and two gusseted plates are attached one to each flange of the column. The gusseted plates, cleat angles and fastenings (bolts, rivets) in combination with bearing area of shaft shall be sufficient to take all loads. PLAN ELEVATION

18. Design and Numerical Problems 04

19. The maximum permissible axial compressive load on a columns is given by P = σ ac X A where P = Axial compressive load or buckling load or crippling load (N) σ ac = permissible stress in axial compression (N/mm 2 ) A = Effective cross-sectional area of the member (mm 2 ) = Gross cross-sectional area minus deduction for any hole not filled complete by rivets or bolts. STRENGTH OF AN AXIAL LOADED COLUMN

20. DESIGN OF AXIAL LOADED COLUMNS The following steps are followed for designing an axially loaded columns: Step 1. Approximate gross sectional area required = Axial compressive load / Assumed permissible compressive stress For single I-section columns assume permissible compressive stress = 80 N/mm2 For built-up columns assume permissible compressive stress = 100 or 110 N/mm2 (because Such members have lesser slenderness ratio) Step 2. Choose a trial section having area = Approximate gross sectional area required Step 3. Calculate slenderness ratio ( λ) of trial section. Step 4. Determine the actual permissible compressive stress corresponding to the calculate slenderness ratio. Step 5. Calculate the safe load to be carried by trial section. It is calculated by multiplying, the actual permissible stress by the area of the trial section. If the safe load is equal to or slightly more than the applied axial load, then the trial section is suitable for selection, otherwise try another section. Step 6. Check for the maximum slenderness ratio. The maximum slenderness ratio of the selected section should not exceed the values.

21. Problem 1: Calculate the load carrying capacity of ISMB 350 @ 514 N/m to be used as a column. The effective length of the column is 4 m. Solution:- From Steel tables, properties of ISMB 350 @ 514 N/m are: a = 66.71 cm 2 = 6671 mm 2 r xx = 14.29 cm = 142.9 mm and r yy = 2.84 cm = 28.4 mm Minimum radius of gyration, r = 28.4 mm (Least of r xx and r yy ) Effective length of column, l = 4 m = 4000 mm Slenderness ratio, λ = l/r λ = 4000 / 28.4 = 140.85 For λ = 140.85 and f y 250 N/mm 2 σ ac = 51 – (51 – 45) × (140.85 – 140) / (150 -140) = 50.49 N/mm 2 Load carried by column = σ ac × A = 50.49 × 6671 = 336818.8 N

22. Problem 2: Calculate the safe axial load carried by built-up column consisting of ISHB 400 @ 759.3 N/m with a plate 400 mm × 20 mm is welded to each flange. The column is 4.5 m long and is effectively held in position at both ends but not restrained against rotation. Take f y = 250 N/mm 2

23. Solution:- From Steel tables, properties of ISHB 400 @ 759.3 N/m are: I xx = 28083.5 cm 4 I yy = 2728.3 cm 4 a = 98.66 cm 2 Effective length , l = 4.5 m = 4500 mm Area of built-up section , A = 98.66 + 2 × 40 × 2 = 258.66 cm2 = 25866 mm 2 I xx of the built-up section = = 28083.5 + 2 ×(40 × 23 / 12 + 40 × 2 × 212) = 28083.5 + 2×(26.67 + 35280) = 98696.84 cm 4

24. I yy of the built-up section = 2728.3 + 2 ×(2 × 403 / 12) = 2728.3 + 21333.33 = 24061.63 cm 4 Since I yy < I xx  Least radius of gyration, r = √ I yy / A = √ 24061.63 / 258.66 = 9.64 cm = 96.4 mm Slenderness ratio, λ  = l / r = 4500 / 96.4 = 46.68 For λ  = 44.68 and f y = 250 N/mm 2 σ ac = 139 – (139 – 132) × (46.68 – 40) / (50 – 40) = 134.32 N/mm2 Safe load = σ ac × A = 134.32 × 25866 = 3474321 N

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