Abstract
The assembly efficiency of prefabricated buildings significantly depends on the productive time taken to complete the hoisting operations of components. Therefore, the on-site measurement of the effective time needed for component assembly is crucial for identifying time wastage and improving construction efficiency. This study utilizes MODAPTS (Modular Arrangement of Predetermined Time Standards) and the stopwatch time method to determine the effective working hours of the assembly process. The component hoisting process is broken down into the following five operations, hooking & slinging, hoisting to the operating surface, adjusting the position, removing the load hook, and backing up. A case study of a Nanjing project showed that the average times for five assembly operations of steel components were 227, 279, 760, 160, and 94 seconds. The time variation in crane arm movements is more stable than that of component adjustments during connection operations. Human factors like phone usage, exiting the operation area, along with hoisting point design and production mistakes, greatly reduce hoisting operation efficiency. The results of this study can not only effectively identify the time waste in the assembly process, but also lay a foundation for standardized hoisting operations and calculation of standard working hours in the prefabricated construction industry. In addition, these results will help optimize the construction organization plan at the early decision-making stage and improve the efficiency of resource use, thus shortening the construction period and reducing the construction cost.