Basement-addition for existing building plays a crucial role in alleviating urban land shortage. However, the disturbance induced by basement-addition construction to the stability of the building foundation and superstructure has not been well understood. The objective of this paper is to investigate the performance of typical structural components involved in a basement-addition project. They include the columns in the superstructure, the strip foundation beneath the columns, and the piles used for reinforcing the strip foundation during excavation. A three-dimensional finite element model is established, using a basement-addition project of an existing building as a case example. The calculated results by the finite element model align well with the measured data, confirming the model's validity. Based on this, the stress and deformation characteristics associated with the selected structural components during basement-addition construction are investigated. The findings indicate that the stress and deformation characteristics of the structural components are highly sensitive to the depth of the foundation pit excavation, with these characteristics intensifying as excavation depth increases. The excavation of the initial soil layer has the most significant impact. Upon completion of the excavation, the maximum settlement values for the strip foundation (SF), column foot, and pile are -18.6 mm, -13.79 mm, and -16.1 mm, respectively. The underground diaphragm wall (UDW) exhibits maximum vertical and horizontal displacements of 7.6 mm and 18.1 mm, respectively. The pile primarily experiences compressive internal forces, with its axial force showing little sensitivity to excavation depth. The pile's maximum bending moment, shear force, and axial force are 21.2 kNm, 34 kN, and -2,481 kN, respectively. The internal forces and deformations of structural components demonstrate distinct spatial distribution patterns, with values increasing closer to the foundation pit's center. Therefore, it is crucial to enhance monitoring of the displacement and internal forces of the central components of the foundation pit to prevent engineering accidents. These research findings will contribute positively to the design optimization and construction guidance of similar engineering structures.

Mumbai is an elongated island city and spreading towards northern side as the southern side is sea face. Mumbai Metro Line 3 (MML-3) project corridor from Colaba to Seepz, is fully underground metro of a total length 33.5 km twin tunnel. In this project, 17 nos. of TBMs deployed to construct the tunnel. The tunnel is excavated through Basalt underlying filled up material and soil strata (sandy and clayey). A systematic instrument arrays are installed along the tunnel alignment to monitoring at the ground, on the ground and in the tunnel, existing buildings along the tunnel alignment in the influence zone (both side of tunnel alignment) as per monitoring scheme. Monitoring of instruments was done as per the frequency required for tunnelling activities based on the excavation stages and to acquire the recorded data. Based on the monitoring data and their interpretation, design modification has been done to achieve safe tunnelling which is the first and foremost requirement in urban tunnelling. This paper highlights the surface settlement at the ground surface and in the tunnel excavated zone due to tunnelling.

This study analyzes the progression, utilization, and inherent challenges of traditional non-linear static procedures (NSPs) such as the capacity spectrum method, the displacement coefficient method, and the N2 method for evaluating seismic performance in structures. These methods, along with advanced versions such as multi-mode, modal, adaptive, and energy-based pushover analysis, help determine seismic demands, enriching our grasp on structural behaviors and guiding design choices. While these methods have improved accuracy by considering major vibration modes, they often fall short in addressing intricate aspects such as bidirectional responses, torsional effects, soil-structure interplay, and variations in displacement coefficients. Nevertheless, NSPs offer a more comprehensive and detailed analysis compared to rapid visual screening methods, providing a deeper understanding of potential vulnerabilities and more accurate predictions of structural performance. Their efficiency and reduced computational demands, compared to the comprehensive nonlinear response history analysis (NLRHA), make NSPs a favored tool for engineers aiming for swift seismic performance checks. Their accuracy and application become crucial when gauging seismic risks and potential damage across multiple structures. This paper underscores the ongoing refinements to these methods, reflecting the sustained attention they receive from both industry professionals and researchers.