DESIGN OF FLEXURE WALLS FOR DUCTILITY

Abstract

In multistoreyed buildings as the height of the building increases the effect of lateral loads due to wind and earthquake gains paramount importance. They cause drift (i.e. the horizontal displacement of the top most storey from its mean position). The frame structure consisting of conventional beam and column type cannot resist the drift due to insufficient stiffness. 0 The flexure walls are used to impart required stiffness to the structure. They are provided at suitable locations in the plan of the building so that they work efficiently from structural and serviceable aspects. The flexure walls are the most economic means to resist lateral loads effectively. They should be designed for strength, stability, stiffness and ductility. Ductility of the shear walls can be achieved by adopting proper design and detailing. In this dissertation, the behaviour of flexure walls under various parameters, (viz, height/length ratio, type of loading,.. flexural reinforcement etc.) is discussed. The provisions of design and detailing of flexure walls as per IS:13920-1993, ACI:318-1993, and CANS: A23.3-1984 are presented elaborately. The formulae for flexure and axial loads are derived for different: locations of neutral axis by analytical method. The discrete (i) elemental method to generate load-moment interaction data for uniformly reinforced rectangular flexure wall is presented. The load moment interaction curves data for Fe250, Fe415 grade of steel for various non-dimensional depth of neutral axis (0.0 to`. 10.0) against different p%/fck (0.005 to 0.20) ratios are given in the form of tables and graphs. These curves can be conveniently adopted to assess the flexural strength under a given axial load and p%/fck, and also suitable value of p%/fck can be chosen if P~ and Mu of section are known. Therefore, these curves can be used as design hand tables for design of flexure walls. The shear strength provisions for flexure wall under axial force and flexure as per IS:13920-1993 (i.e. IS:456-1978), 15:456- 1996 (Draft), ACI:318-1993 and CAN3; A23.3-1984 are discussed. The relative comparison of shear strength of beam and flexure wall as'',' per ACI:318-1993 is also presented. One design example of the 10 storeyed two-bay flexure wall building is given. For analysis purpose of the building, DYANA-2D has been used. The design of building is carried out as per provisions of IS: 13920-1993. The final design of the flexure wall as per ACI:318-1993 and CAN3:A23.3-1984 ore also given. kr r- The relative comparison of the design of flexure wall by the above mentioned codes is also given.