Buildability of concrete structures : processes, methods and material

Sammanfattning: The causes for the slow development of the construction industry is often attributed the traditional ”peculiarities of construction“, including such factors as one-of-a-kind products, temporary organisation, and on-site production. However, signs of new thinking are becoming apparent in the construction industry in Sweden that emphasise change. Globalization and increased competition are factors for change. The possible future shortage of available qualified workers, demand for shorter construction times and calculated higher risks for projects are also catalysers for the implementation of new and alternative solutions. Still, new production methods and construction ideas are rarely introduced in construction projects, with low or no productivity increase of the industry as a result. Within the scope of this thesis work, the combination of creating buildability during the design phase and utilizing the philosophies of lean construction during the construction phase has been adapted to improve civil engineering concrete construction work. Several full scale projects have been studied and a questionnaire survey has been performed. In order to be able to introduce changes such as prefabricated reinforcement solutions, left concrete form systems and Self-Compacting Concrete (SCC) as a mean to increase productivity at site, there is a need to create projects that are buildable and able to be constructed, i.e. constructions that we know in advance are practically feasible and productive. All involved participants throughout the whole project are therefore responsible for creating buildability in the project. The case studies show that the potential increase in productivity can be vast. The introduction of prefabricated rebar sections, e.g. rebar carpets and rebar cages, decreases time spent on fixing reinforcement with up to 80%. The use of SCC potentially saves 65% on time spent during casting. Both methods improve the working environment substantially. However, the introduction of new methods also put demands on properly planned, communicated and managed construction operations on-site. Thus, the use of Buildability in the design can promote new solutions together with Lean Construction philosophies in management of these alternatives are suitable tools in changing the construction industry. Buildability deals with creating design for “ease of construction” whilst Lean construction focus on planning of a productive flow of work tasks and resources for the selected production methods. The combination of buildability in the “design for” part and lean construction philosophy in the “ease of construction” part within one of the most accepted definitions of buildability i.e. “the extent to which the design of a building facilitates ease of construction” will be able to encourage an increase in productivity at construction sites. This is possible if important factors are considered and utilised sufficiently. Some of these important factors highlighted in this thesis work are: • early project involvement of contractor, to increase construction knowledge during design, a result from the questionnaire survey; • design projects in 3D and create adequate virtual work instructions for workers to study prior to performing the work task, a result from full scale studies; • plan the construction work tasks and material supply thoroughly using lean tools, a result from full scale studies; • make sure adequate attention is spent on the working environment early in a project, this will result in workers feeling confident in a safe work environment, a result from full scale studies. The thesis corroborates the conclusion that, if these factors are considered and encouraged there is a potential for improvement of productivity at site, enhanced quality of finished structures as well as lowered costs for constructing structures in the future.