The working group convened at Dipoli, in Otaniemi, on the 6th of March 2020. Seven presenters provided an overview of current high-rise construction technologies both in Finland and the USA. They also shared interesting examples from designed and completed projects.
Benchmarking with Californian High-Rise Projects
Builders in the USA have a long tradition of high-rise construction and are therefore a perfect benchmark for Finnish developers and contractors. Aalto researchers Ergo Pikas and Joonas Lehtovaara reported on their visit to California, where they’d met with local contractors.
From several interviews and site visits, Pikas and Lehtovaara learned about the strategies and practices of high-rise contractors in the USA. The researchers also received BIM models from a few projects for further analysis.
Although there are no developer-contractors in California as we have in Finland, on larger projects, the developer and GC always take part in a joint development phase. It’s important for the contractors to grasp the client’s business case because this determines the critical parameters of the project, including the feasibility of prefabrication. Volumetric construction could be beneficial in high-rise projects, but only if it is taken into account at the early stages of the process.
Pikas pointed out that the biggest risks pertaining to high-rise construction in California is in a potential sub-grade. For example, the soil could be contaminated with chemicals or even asbestos from previous buildings. Any unexpected delays have to be compensated for during the erection of the building frame.
Pinpointing the Differences
The researchers met with Suffolk and Skanska to learn from their production planning and control practices. It became evident that at least these two contractors did not practice Takt production in their high-rise projects, as we’re increasingly doing in Finland. Instead, they use the traditional critical path scheduling. They focus on five to six critical tasks and use buffers for the less critical activities. This often leads to a hustle at the end of the project as the workers have to catch up with the schedule.
Getting the interior elevators to work is critical in U.S. high-rise construction. Once it’s operational, the contractors can get rid of the man-lifts and start finishing the interiors.
A noticeable difference between Californian and Finnish high-rise construction is the extensive use of drywalls. Whereas Finns use concrete or brick walls, especially in residential construction, the Americans always use lighter drywalls, which speeds up the process considerably.
The main takeaway for Pikas and Lehtovaara was that in high-rise construction, the product and process have to be developed concurrently. You have to plan the whole production system holistically from planning to commissioning. In a project with a lot of repetition, a design or planning decision scales up and can make or break the client’s business case.
Joonas Lehikoinen, an Aalto student, is doing a special study that complements Pikas’s and Lehtovaara’s assignment. He’s collecting models of high-rise projects from the USA and Asia, and analyzing them in terms of costs, schedules, structural solutions and architectural characteristics.