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2.0 ANALYSIS AND DESIGN 2.2 STRUCTURAL ELEMENT Reinforced Concrete Column Rearrangement by :- NOR AZAH BINTI AIZIZ KOLEJ MATRIKULASI TEKNIKAL KEDAH

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Column is defined as a structural members subjected to compressive force. Strut – a small compressive member in a framed structure. Column – a larger member, such as the main support for a beam in a building. INTRODUCTION

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Axially loaded compressive member can fail in two principal ways: -short fat member fail by crushing or splitting of the material. -long thin members fail by sideways buckling. INTRODUCTION

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i) Braced column(tiang dirembat) – the lateral loads are resisted by wall or some other form of bracing ii) Unbraced column(tiang tidak dirembat) – the lateral loads are resisted by the bending of the column iii) Short Column (tiang pendek) ● l ex /h and l ey /b < 15 for a braced column ● l ex /h and l ey /b < 10 for an unbraced column iv) Slender(Long) Column ( tiang langsing) ● l ex l ey /b >15 for a braced column ● l ex l ey /b >10 for an unbraced column Types of column

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Short column (p> pcr)usually fail by crushing when the material achieved its ultimate strength. Slender column is liable to fail by buckling The end moment on slender column cause it to deflect sideways exceed a critical values until the column buckles. Failure Mode

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Slender Column - fails by sideways buckling - The load at which a slender column buckles, is known as its critical buckling load, P crit. P crit.= ΩEI / L 2 Where; E = Modulus of Elasticity I = second moment of area L = length between pins Failure Mode

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Column detail

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Longitudinal steel bar - A minimum of 4 bars is required in a rectangular column and 6 bars in a circular column. -The size of the bars should be not less than 10mm Links -Minimum size = ¼ x size of the largest compression bar but not less than 6mm -Maximum spacing = 12 x size of the smallest compression bar Reinforcement detail

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Rectangular column Circular column Types of Reinforced Concrete Column

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Load transfer on column for design

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Factored Axial Load (N) for Column Design ● Interior Column – 1.25 ● Edge/face column – 1.5 ● Corner column – 2 Corner column Interior column Edge /face column

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Short Axially Loaded Column Design Equation N = 0.4 f cu A conc +0.8 f y A sc Where N – Ultimate Axial load f cu – Characteristic of concrete strength A conc – area of concrete cross section f y – Characteristic of reinforcement strength A sc – area of reinforcement cross section N

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Example: A column with 200 mm x 200 mm resists a factored axial load 500kN. Calculate the area of steel required if f y = 460 N/mm 2 and f cu = 30 N/mm 2 Table 1 Diameters and areas of reinforcing bars Bar dia.(mm) C/s area (mm 2 ) Table 1 Diameters and areas of reinforcing bars Bar dia.(mm) C/s area (mm 2 )

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Formula for design column N = 0.4 f cu A conc f y A sc 500x10 3 = 0.4 (30) ( A sc ) (460) A sc = – 12 A sc A sc = A sc A sc = 56.18mm 2 A sc (for each bar) = 56.18mm 2 /4 = 14mm 2 A sc = Πj 2 = ΠD 2 /4=14mm 2 D = 14 x 4 / Π = 4.22mm Standard required 4 number of steel reinforcement bars size 10mm minimum). So size column = 4 T 10 4T10

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