Finite element analysis of a 108-year-old unreinforced brick masonry tower following the 2015 Nepal earthquakes

Abstract

After a visual inspection following the 2015 Nepal earthquakes, a finite element analysis (FEA) was conducted on a 108-year-old unreinforced brick masonry tower. The focus of study was on the brick masonry clock tower standing at a height of 30.48 m on the Senate Hall (SH) building of Allahabad University in India. This tower, which spans five storeys and features a rectangular cross-sectional shape, exhibits substantial cracks and material degradation across its connections and binding points. The process involved creating geometric plans and a 3D finite-element model through visual inspection and implementing ANSYS Workbench. The study utilised the mechanical properties of the aged materials, sourced from various studies encompassing surveys of old monumental structures, codes, and historical records. The clock tower’s behaviour was assessed through static, modal, and site-specific simulated time history analyses. The static analysis results revealed a maximum deflection of 3.76 mm at the top and a maximum equivalent (von-Mises) stress of 1.81 MPa at the joint of the first-floor level. Modal frequencies for the first three modes were determined to understand the tower’s free vibration behaviour. The time history analyses presented the acceleration, velocity, and displacement response under a peak ground acceleration (PGA) of 1.29 m/s2 simulated for the site. The dynamic analysis highlighted stress responses in critical locations, exposing severe cracks and damages across various points.