Productivity in Multi-storey Mass Timber Construction
This project utilised photogrammetry methods to measure installation productivity of CLT panels in a medium-rise timber building. The analysis of the data indicated that an average floor cycle of 10 timber installation days per floor, was achieved for a large and complex shaped floor plate area of 1280m2.
The study showed different installation speeds for floor panels and wall panels with for CLT floors, the most common (mode) rate in the tower was 78.5 m2/hour where the worst performing floor level was 60.5 m2/hour and the best 89m2/hour.
The findings show that floor productivity is significantly higher (40%) than wall productivity, when comparing mode values. Floor panels have gravity working advantageously when landing panels and manipulating them into place, whilst walls must be placed vertically including the application of temporary holding braces to stabilise the panels. Closing the joint between adjoining panels is also harder. There is also the need to spend time “plumbing” the wall to ensure it is perfectly vertical and then applying sufficient fixing brackets to allow the work to proceed to the next panel.
Crane cycle times are important because they represent the main factor influencing the speed and installation productivity. The case project used a fixed tower crane and a mobile crane. The cranes operation involved two lifting strategies namely single movements or double movements: the single movement strategy (lifting directly from the staging area to the insitu location) and; the double movement (where panel packs are lifted onto the live floor deck and then a second lift places individual panels insitu
The presented data also serves to demonstrate the importance of creating a reliable and rhythmic crane cycle when installing panels. The coefficient of variance was introduced as a tangible metric for recognizing a well-controlled installation process. Achievement of this should be given priority in day-to-day site operations.