Comparative Evaluation on Parameters of Seismic Codes for the Design of Masonry Structures

Abstract

Structures are made to withstand specific seismic lateral forces that are related to both the structure and the local seismicity along with dead, imposed and other loads. For design of masonry structure, seismic lateral force needs to be evaluated. The seismic design provisions in three building codes, Nepal (NBC105:2020), India (IS1893:2016) and New Zealand (NZS1170.5:2004) in context of design of masonry structure along with their similarities and differences are presented. Code provisions for the design of masonry structures have been elaborated. The codes and their histories are introduced. Then, the distinctions between the basic period, spectral shape factor, elastic site spectra, seismic zone factor, and importance factor for estimating the seismic load are explored in detail. Following the calculation of the seismic force, base shear coefficients and distribution methods over the building's height are compared. Compressive stress and shear stress are computed on the basis of design load combinations mentioned in respective code and comparison has been carried out. Although the three codes have some subtle differences, they have several characteristics that allow for comparison. The fundamental periods computed from the three codes resides within a contracted range of 0.19 to 0.27s, signifying marginal sensitivity of short-period masonry buildings to formulations of empirical period. Spectral shape factors also exhibit minor variation for short-period structures, whereas differences in ductility and response reduction parameters deliberately influence base shear coefficients and causing masonry stress demand. This comparison shows that the base shear coefficient from NZS is 161% higher than IS and 51% higher than NBC. Stresses obtained from NBC and IS based models shows value in similar range while from NZS based model significantly, larger stresses were obtained. This research improves masonry design safety and competence by comparing NBC, IS, and New Zealand seismic codes, enabling engineers to carry out optimal design, retrofitting, and construction practices, lowering earthquake risks.