Serviceability Margin and Foundation Reserve Assessment of a Reinforced Concrete Airport Terminal Structure in Bolaang Mongondow, Indonesia

Abstract

This paper presents a serviceability-centered reappraisal of a reinforced concrete airport terminal structure in Bolaang Mongondow, Indonesia. Unlike the earlier design-oriented report that mainly documented member reinforcement and general structural safety, this study focuses on the location and magnitude of performance margins after design. Secondary structural outputs from an ETABS v.21 model, response spectrum parameters, wind pressure results, bored-pile bearing capacity, and settlement estimates were reorganized into demand-capacity ratios. Inter-story drift, bored-pile bearing, and foundation settlement were selected as the primary observation variables because they directly indicate serviceability, reserve capacity, and potential operational risk for a public terminal building. The analysis shows that the upper story drift is the controlling serviceability indicator. The maximum drift demand in both X and Y directions reaches 29.04 mm against an allowable value of 30.00 mm, producing a demand-capacity ratio of 0.968 and leaving only 3.2% residual drift margin. In contrast, the bored-pile foundation still has a bearing-capacity demand ratio of 0.715, equivalent to a capacity reserve of about 39.8% relative to the applied maximum axial demand. The estimated pile settlement of 4.956 mm corresponds to only 19.5% of the 25.4 mm serviceability limit. These findings indicate that the foundation response is not the controlling issue; instead, construction tolerance, diaphragm action, cladding connection, and nonstructural components at the upper level deserve closer post-design verification. The proposed reserve-based reading provides a practical quality-control layer for airport terminal structures located in seismic regions