Earthquake Resistant Design of Masonry Buildings

Abstract

Brick Masonry building construction is one of the most commonly adopted construction practices, all across the world, due to inherent characteristics of brick material. Brick masonry construction offers flexibility to accommodate itself to changing environmental conditions. Despite influenced by many local parameters like local soil condition, construction practice, etc., brick masonry construction follows common but standardized practices on the field. However, brittleness of the brick material in addition to comparatively weak mechanical properties limits the brick masonry building construction to low-rise. Apart, brick masonry building otherwise performing well under gravity loading shows low resistance against lateral loading induced due to an earthquake. Hence, brick masonry building suffers maximum damages and makes it seismically vulnerable. Therefore, concept of Confined Masonry (CM) building becomes popular amongst Earthquake Engineering community in recent past. However, detailed study on seismic design of Confined Masonry is still limited and is under the state of the development.

In the present major project work, the lateral load analysis and design procedures of conventional masonry building and Confined Masonry building is presented. A detailed study of recently published draft code CED-39 (Draft Code for Confined Masonry) is conducted clause by clause with reference to relevant clauses of codes IS:1905, IS:4326, IS:1893 (Part-I) whenever necessary. A six storey Residential Masonry Building is considered in seismically most active region, i.e. Zone – V as per IS 1893 (Part-I) : 2016. Analysis, including gravity load and lateral load, of CM building is carried out as per provisions defined in Draft CED-39 - IS:2017. Design of Reinforced Concrete (RC) Elements of CM building is performed following Limit State Method. An excel spreadsheet is developed for the analysis and design of the CM building. Parametric studies are carried out to study the variation of Shear Resistance, In-plane Moment Resistance of CM walls in building with number of floors varying from G+1 storey to G+5 storey and situated under different seismic zones. Studies are also carried out to see the variation of Tensile Reinforcement required in Tie-columns of CM building with number of floors varying from G+1 storey to G+5 storey and situated under different seismic zones. Apart, studies are also conducted to differentiate capabilities of brick masonry wall and confining element combinedly to resist Axial Load and Shear Force as compared to brick masonry wall alone. It has been found that thickness of wall at ground storey is substantially reduced by 5 times for CM Building vis-à-vis conventional masonry building. It has been also observed that total stiffness of CM building is increased upto 1.6 times compared to conventional masonry building. At last it is found that Shear Resistance of CM walls decrease by 11%, 23%, 35% and 46% as the number of storey of CM building reduces from G+4 storey to G+1 storey compared to G+5 storey CM building.