Seismic Vulnerability Assessment & Retrofit — University Women’s Federation College (Dhaka, Bangladesh)

Detailed engineering assessment

This project is an example of seismic vulnerability assessment and school-retrofit projects in the city of Dhaka, Bangladesh. Field assessment findings show that:

1) University Women’s Federation College is a five-story academic building with approximately 902 sq.m at ground level, constructed using local practices in 2002 and 2008. 2) Based on the current status of the structure, it can be concluded that it was not built using engineering codes and/or practices. 3) The structure height is about 14.9 m from plinth to rooftop; the typical floor height is about 3.0 m. 4) The building is used as a school at Amin R/A, Bondor Upazila, Narayanganj. 5) The lateral force resistance system is the Moment-Resisting Frame system. 6) The floor system consists of concrete beams and a cast-in-place reinforced concrete slab. 7) The mean expected concrete strength obtained from the Schmidt Hammer test and ultrasonic pulse velocity is about 14 MPa.

Vulnerable columns

The positions of the vulnerable columns at the ground-story level are depicted in red in the figure below.

Retrofit solution: concrete shear walls

To overcome the vulnerabilities associated with this structure, performance-based engineering calculations were provided, alternatives for strengthening were designed, the most cost-effective method was selected among all alternatives, and a 3-D finite element analysis was provided. Considering the number of vulnerable columns, the high inter-story drifts and the poor ductility detailing of the existing frames, the addition of concrete shear walls was selected as the final retrofitting solution — 4 shear walls in the longitudinal direction and 4 in the transverse direction, with thicknesses of 35 and 40 cm. The arrangement of the introduced shear walls is shown here.

Retrofitted structure — analysis results

The results of the retrofitted structure analysis reveal that the retrofitting operation is effective and adequate to improve seismic performance and upgrade the building to the target performance. In addition, by providing significant stiffness, the inter-story drifts are considerably decreased and the risk of pounding between adjacent buildings is mitigated.