Modelling and simulation of factors influencing on-site construction of concrete frameworks : Studying the effects of resource allocation, weather conditions, and climate-improved concrete

Abstract: Concrete is the most common material used to build the structural framework in multistory buildings. However, the construction works carried out on the building site are affected by many different factors that may reduce productivity. Delayed material deliveries, poor planning and coordination of work tasks and production resources, as well as unfavorable weather are examples that reduce productivity. Reduced productivity results in extended construction duration and increased costs for the concrete framework, which ultimately can affect the entire construction project. It is therefore important to increase knowledge about how different factors affect productivity to avoid construction delays and increased costs.Studying how different factors affect productivity is complex as a production system may consist of a large number of factors that can affect the outcome. One method that makes it possible to describe and study complex production systems is discrete event simulation (DES).The aim of this research is to increase knowledge about how DES can be used to systematically analyze the impact of factors that affect productivity during construction of a concrete framework structure. Three factors that are considered to be particularly important for concrete production methods are included in this research study, namely: 1) utilization of labor and crane resources, 2) impact of varying weather conditions, 3) use of climate-improved concrete.Considering utilization of labor and crane resources (factor 1), this study shows that DES is a suitable method for studying in detail how the utilization of these resources affects construction time and cost of the framework. The study highlights the importance of describing the production process in detail to enable identification of workflow bottlenecks caused by resource allocation conflicts. To support identification and analysis of bottlenecks and corrective measures, it is suggested that the traditional performance measures time and cost are supplemented with two additional indicators, namely waiting time and utilization rate.Regarding the impact of weather (factor 2), this study contributes with new knowledge about how this can be described and studied by using DES. The basis for this is a definition of a weather function that describes the relationship between weather and labor productivity. In addition, another function is described that considers the effect of actual weather conditions on the development of concrete strength, which is also important for the productivity of the concrete production cycles. In this way, the impact of weather when using climate-improved concrete can also be studied (factor 3). By implementing these functions in a discrete-event simulation model together with weather statistics, the impact of different weather conditions was simulated. A separate calculation tool was also developed to supplement simulated construction duration of the framework with cost and climate impact. The results from the simulations show that the weather has a significant impact on construction duration of the concrete framework. For example, the construction duration increases in the range 8-42% compared with a reference scenario that is unaffected by weather. The extended duration depends on the season for construction and where the project is located, but also on the extent to which climate-improved concrete is used. The results also show that climate-improved concrete has a significant potential to reduce CO2-emissions of a concrete framework during the construction phase. But to realize the potential of climate-improved concrete also in periods with colder weather, selection of appropriate curing methods becomes imperative. At a more detailed level, a questionnaire survey was also conducted in which contractors estimated the impact of weather on productivity for typical concrete work. These results confirm the importance of the impact of the weather also at a work task level.This study describes how DES can be used to systematically study and analyze how the productivity of construction-related production systems is affected by various factors. The study also provides new insights into how resource utilization, weather, and climate-improved concrete affect the construction of concrete frames. In overall, this can lead to a better basis for planning and selection of production methods to enable increased productivity.