Comparative Study of Lateral Loads and Its Cost Effect on RC Moment Frame and Wall-frame Building According to BNBC 2020 in Different Zones of Bangladesh

Abstract

With the advancement in material science, construction technology and structural analysis, a new building code was essential to keep pace with technological advantages. Recently introduced BNBC 2020 bridges the gap largely. A very basic change in lateral loading provision has occurred in the new code, which accounts for several newly defined parameters. For wind analysis, the new code introduces 3-second gust velocity as basic wind speed, wind pressure application in four cases that accounts for eccentricity. It considers topographic and internal pressure effect. A new seismic zoning is introduced in BNBC 2020 with revised PGA values and spectral acceleration. The code also introduces seismic design category and revised response reduction factor. All these changes will affect the design practice. To understand and compare lateral loading in different zones, a FEA of 20 storied RC building with and without core shear wall was analyzed using ETABS V18. The comparison shows that Rajshahi (Zone I) has lowest wind and seismic loading, Chattogram (Zone III) has highest seismic and wind loading while, Dhaka (Zone II) has moderate seismic and wind loading. Wall frame building has slightly larger seismic base shear while shear wall resists major portion of base shear and reduces top story displacement and story drift greatly. The cost of construction in zone III is significantly larger than in zone I and II. In all zones shear wall building imparts economic structural solution compared to bare frame against lateral loading for 20 storied buildings and the margin of economy increases with increasing lateral loading.