Productivity Optimization of Launching Gantry Operations in Box Girder Installation for Elevated Toll Infrastructure

Abstract

Purpose: Delays in box girder erection activities remain a significant challenge in elevated toll road construction, particularly when launching gantry systems operate below their expected productivity levels. This study aims to analyze the productivity of a launching gantry used in the North Jakarta Elevated Toll Road project, evaluate project acceleration alternatives through extended overtime and workforce addition, and compare their impacts on project duration and cost to determine the most effective productivity improvement strategy.

Methods/Design: This study employed a quantitative case-study approach using Time–Cost Trade-Off (TCTO) analysis. Primary data were collected through direct field observations to determine launching gantry cycle times, while secondary data were obtained from project documents, including box girder erection methods and project budget plans. Productivity under existing conditions was calculated and compared with two acceleration scenarios—extended overtime hours and additional workforce—to identify the optimal balance between productivity, duration, and cost.

Findings: The existing launching gantry productivity was 0.040 span/day, resulting in a project duration of 322 days for 13 spans and a total cost of IDR 36.57 billion. The overtime scenario increased productivity to 0.053 span/day and reduced project duration to 243.25 days; however, the total cost increased to IDR 36.59 billion. Meanwhile, the workforce addition scenario improved productivity to 0.048 span/day and shortened project duration to 268.26 days with a total cost of IDR 36.57 billion. Although overtime achieved the highest productivity improvement, workforce addition provided a more favourable balance between schedule acceleration and cost efficiency.

Practical Implication: The findings provide practical guidance for project managers in selecting acceleration strategies for launching gantry-based box girder erection works. Workforce augmentation can serve as a more cost-effective alternative to extended overtime, enabling productivity improvement and schedule reduction while maintaining project cost efficiency in elevated toll road construction projects.