PPT ON DESIGN OF COLUMN BRACES

PPT ON DESIGN OF COLUMN BRACES

1. PPT ON DESIGN OF COLUMN BRACES SRINIVAS REDDY.S

2. BRACED COLUMN A column may be considered braced in a given plan if lateral stability of the structure as a whole is provided by walls or bracing. These columns have zero value of sway. UNBRACED COLUMN A column may be considered unbraced in a given plan if lateral stability of the structure as a whole is provided by columns only. These columns are subjected to sway.

3. Water tower without brace, would have inherent stability against force applied in every direction (all three axis; left right, up-down, forward and backward) but there is nothing about this arrangement that would effectively prevent bent, rotation, or twisting about the structure’s vertical axis. So the structure needs braces for supporting them in all condition. According to IS: 11682 – 1985 If the height of staging is greater than 6m above foundation, the column shall need of horizontal bracing INTRODUCTION

4. Types of bracing pattern The general basic types of Internal Bracing are as follows; Simple bracing Cross bracing Radial bracing Rectangular bracing

5. Types of bracing pattern The External Bracing are as follows; Without external bracing, “X” type Bracing,  Diagonal Bracing, Chevron Bracing Global Bracing “K” Type Bracing “V” Type Bracing.

6. FACTORS TO BE CONSIDERED FOR THE ANALYSIS OF BRACES DISPLACEMENT ON STRUCTURE Displacement or deflection is the back down form initial position to final moving position of a structural element. It just because of enforces on structure by earthquake/seismic reaction. Fig 4.8 shows the displacement of structure during earthquake. The maximum displacement is possible in element i.e. beam, column, joints, brace and toe of elevated water tank. BASE SHEAR ON STRUCTURE : During seismic activity, seismic wave forms forces on the base of any structures that maximum expected lateral forces estimated as base shear. The structure always fixed at the base foundation level. During seismic forces, foundation cannot hold the structure strongly so structure deflects, and base shear is diffused all along with the height of the structure. Base shear also depend upon the soil condition of the site.

7. FACTORS TO BE CONSIDERED FOR THE ANALYSIS OF BRACES WIND LOADS: Wind loads can be applied the stresses the combination shall be 1.Wind load with tank empty 2.Wind load with tank full Worst combination of stress on account of above shall be considered which working out permissible stress Maximum shear force on structure A shear forces is a forces that acts on a plane passing through the body. It can separates structure in two different parts in inverse directions. It always acts on the large part of structure and fails the design. For detecting the cause of failure we need to analysis of maximum share force for safe design. Maximum bending moment on structure Bending moment is the bend of structure element form its axis when external force or moment is applied on structure. Tensile stress and compressive stress are proportionally increased with bending moment. It gives ideas dealing with forces on structure same in real situation. It shows where and how the moment will act on the structure i.e. how a structure will rove during application of a load

8. DESIGN OF BRACING Brace is designed for a bending moment equal to sum of the moments in a column just above and below the brace level. The maximum moment in a given bracing will be induced for particular direction of wind . The maximum moment in yz bracing is induced when wind blows perpendicular to xy bracing

9. DESIGN OF BRACING If Mc is the moment in the column ,it can be seen from the moment triangle that the moment mb in equally spaced bracings (from upper and lower column) will be If effective length of bracing is L, shear Vb in bracing is assuming the point of contraflexure The bracing shell can be designed for Mb and shear Vb. The nature of moment and shear can be reversed when wind blows form the opposite side

10.   Experimental Analysis of Intze Type Water Tank with Different Staging System & its Optimal Design STAAD Pro Vi8 (series 6) by using response spectrum method

11. The parametric study shows that ‘X’ type of bracing system is most effective to reduce top storey displacement, where Chevron type is least effective for same parameters, in case of 6-storey tank.  Similarly, in case of 5-storey tank ,‘X’ type is most effective and ‘V’ type is least effective to reduce top storey displacement. Study of time period parameters shows that ‘X’ type is most effective to reduce time period and ‘V’ type is least effective to reduce time period in case of 6-storey tank and 5-storey tank. ‘K’ & ‘V’ type of patterns, shows almost same behaviors for all parameters in case of 6-storey tank and 5-storey tank. For study of all parameters, Diagonal and Global type of patterns have a good effect.  As per the formula of base shear from IS:456-2000; V b= Ahx W. Thus, more the weight of structure, the more will be the base shear. Hence as per Table 6 and 7, ‘X’ type have higher base shear and Global type of bracing have least base shear as compared to all other type of bracings. In parametric study for three different plane based internal patterns, cross type of patterns has most effective behaviors for seismic resistance in compares to Radial and Normal. In parametric study for 6-storey & 5-storey structure, both type of structure shows the same behaviors for increasing base shear and decreasing top storey displacement and time periods, from that study it is advisable to make 5-storey structure with suitable bracing patterns.

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