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<p>Column design as Per BS 8110-1:1997</p><p>PHK/JSN</p><p>Contents : </p><p>General Recommendations of the code Classification of columns Effective Length of columns & Minimum eccentricity Design Moments in Columns Design</p><p>General Recos of the code </p><p>Km for concrete 1.5, for steel 1.05 Concrete strength CUBE STRENGTH Grades of steel Fe250 & Fe460 Primary Load combination 1.4DL+1.6LL E of concrete Ec = 5.5fcu/ Km 10% less than IS Ultimate stress in concrete 0.67fcu/ Km Steel Stress-strain curve Bilinear E of steel 200 kN/mm2</p><p>Classification of columnsSHORT both lex/h and ley/b < 15 for braced columns < 10 for unbraced columns else SLENDER</p><p>BRACED - If lateral stability to structure as a whole is provided by walls or bracing designed to resist all lateral forces in that plane. else UNBRACED Cl.3.8.1.5</p><p>Effective length &minimum eccentricityEffective length le = lo depends on end condition at top and bottom of column.</p><p>emin = 0.05 x dimension of column in the plane of bending 20 mm</p><p>Contd..</p><p>Deflection induced moments in Slender columns Madd = N au where au = aKh a = (1/2000)(le/b)2 K = (Nuz N)/(Nuz Nbal) 1 Nuz = 0.45fcuAc+0.95fyAsc Nbal = 0.25fcubd Value of K found iteratively</p><p>Contd..</p><p>Design Moments in Braced columns :</p><p>Maximum Design Column Moment Greatest of a) M2 b) Mi+Madd Mi = 0.4M1+0.6M2 c)M1+Madd/2 d) eminN Columns where le/h exceeds 20 and only Uniaxially bent Shall be designed as biaxially bent with zero initial moment along other axis.</p><p>Braced and unbraced columns</p><p>Design Moments in UnBraced columns :The additional Moment may be assumed to occur at whichever end of column has stiffer joint. This stiffer joint may be the critical section for that column.Deflection of all UnBraced columns in a storey auav for all stories = au/n</p><p>Design Moments in ColumnsAxial Strength of column N = 0.4fcuAc + 0.8 Ascfy Biaxial Bending Mx/h My/b Mx/h My/b</p><p>Increased uniaxial moment about one axis Mx = Mx + 1 h/bMy My = My + 1 b/hMx</p><p>Where 1 = 1- N/6bhfcu (Check explanatory hand book) Minimum Pt =0.4% Max Pt = 6%</p><p>Shear in Columns</p><p>Shear strength vc = vc+0.6NVh/AcM To avoid shear cracks, vc = vc(1+N/(Acvc) If v > vc, Provide shear reinforcement If v 0.8fcu or 5 N/mm</p><p>Design Construction of Interaction Curve0.67fcu/Km 0.0035 f1 0.5h d h f2 M N 0.9x xI2 I1</p><p>A1</p><p>d1</p><p>A2</p><p>Section</p><p>Stress</p><p>Strain</p><p>Distribution of stress and strain on a Column-Section</p><p>Equilibrium equation from above stress block</p><p>N = 0.402fcubx + f1A1 +f2A2 M =0.402fcubx(0.5h-0.45x)+f1A1(0.5h-d1)+f2A2(0.5h-d) f1 and f2 in terms of E and f1 = 700(x-d+h)/x f2 = 700(x-d)/x The solution of above equation requires trial and error method</p><p>THANK YOU</p>
<p>Column design as Per BS 8110-1:1997</p><p>PHK/JSN</p><p>Contents : </p><p>General Recommendations of the code Classification of columns Effective Length of columns & Minimum eccentricity Design Moments in Columns Design</p><p>General Recos of the code </p><p>gm for concrete 1.5, for steel 1.05 Concrete strength CUBE STRENGTH Grades of steel Fe250 & Fe460 Primary Load combination 1.4DL+1.6LL E of concrete Ec = 5.5fcu/ gm 10% less than IS Ultimate stress in concrete 0.67fcu/ gm Steel Stress-strain curve Bilinear E of steel 200 kN/mm2</p><p>Classification of columnsSHORT both lex/h and ley/b < 15 for braced columns < 10 for unbraced columns</p><p>else SLENDER</p><p>BRACED - If lateral stability to structure as a whole is provided by walls or bracing designed to resist all lateral forces in that plane. else UNBRACED Cl.3.8.1.5</p><p>Effective length &minimum eccentricity Effective length le = lo depends on end condition at top and bottom of column.</p><p>emin = 0.05 x dimension of column in the plane of bending 20 mm</p><p>Contd..</p><p>Deflection induced moments in Slender columns Madd = N au where au = aKh a = (1/2000)(le/b)2 K = (Nuz N)/(Nuz Nbal) 1 Nuz = 0.45fcuAc+0.95fyAsc Nbal = 0.25fcubd Value of K found iteratively</p><p>Contd..</p><p>Design Moments in Braced columns :</p><p>Maximum Design Column Moment Greatest of a) M2 b) Mi+Madd Mi = 0.4M1+0.6M2 c)M1+Madd/2 d) eminN Columns where le/h exceeds 20 and only Uniaxially bent Shall be designed as biaxially bent with zero initial moment along other axis.</p><p>Braced and unbraced columns</p><p>Design Moments in UnBraced columns :The additional Moment may be assumed to occur at whichever end of column has stiffer joint. This stiffer joint may be the critical section for that column.Deflection of all UnBraced columns in a storey auav for all stories = au/n</p><p>Design Moments in ColumnsAxial Strength of column N = 0.4fcuAc + 0.8 Ascfy Biaxial Bending Mx/h My/b Mx/h My/b</p><p>Increased uniaxial moment about one axis Mx = Mx + 1 h/bMy My = My + 1 b/hMx</p><p>Where 1 = 1- N/6bhfcu (Check explanatory hand book) Minimum Pt =0.4% Max Pt = 6%</p><p>Shear in Columns</p><p>Shear strength vc = vc+0.6NVh/AcM To avoid shear cracks, vc = vc(1+N/(Acvc) If v > vc, Provide shear reinforcement If v 0.8fcu or 5 N/mm</p><p>Design Construction of Interaction Curve0.67fcu/gm 0.0035 f1 d 0.5h h M 0.9x N f2 x e2</p><p>A1</p><p>d1</p><p>e1</p><p>A2</p><p>Section</p><p>Stress</p><p>Strain</p><p>Distribution of stress and strain on a Column-Section</p><p>Equilibrium equation from above stress block</p><p>N = 0.402fcubx + f1A1 +f2A2 M =0.402fcubx(0.5h-0.45x)+f1A1(0.5h-d1)+f2A2(0.5h-d) f1 and f2 in terms of E and f1 = 700(x-d+h)/x f2 = 700(x-d)/x The solution of above equation requires trial and error method</p><p>THANK YOU</p>
Length of a rectangular slab are accounted for approximately by designing. Concrete slabs are often carried directly by columns without the use of beams or girders. Should be used for rectangular columns and six for circular columns.