Underrun of required crane capacity - Losses of Productivity during reinforcing works

In terms of production logistics, cranes are one of the crucial equipment categories on the construction site; they are key pieces of equipment. They also play a major role as a link to both delivery and disposal logistics. Cranes are used for loading and unloading, moving and lifting of equipment and materials. The crane capacity is considered optimal if no delays occur for the individual members of the various teams working on the job site. However, delays and thus losses of productivity occur because many construction sites lack the minimum number of cranes required from a construction management point of view. Cranes are also crucial for reinforcing works. In an ideal setting, they move the reinforcing material to a position as close as possible to the location of assembly and laying. The reinforcement is usually delivered separately for each structural component and has a lead time of about one week in order to compensate for any variations in work performance or delivery times. Ideally, the reinforcement required soonest is put to interim storage (at a reinforcement storage space within reach of a crane) near the specific position of assembly and insertion in order to keep crane cycles as short as possible. Losses of productivity materialize if insufficient crane capacity is provided on the construction site. This paper uses a situation analysis to highlight the methods described in the literature to show changes in productivity in the event of an underrun of the required crane capacity. An expert survey served to gather data on how productivity decreases during reinforcing works if insufficient crane capacity is provided on the job site. Fifteen experts with extensive experience in costing, process planning, construction and claims management participated in this survey. A standardized questionnaire was used, and the experts were able to clarify issues with the interviewer. This approach enabled them to develop a better understanding of the survey, which resulted in more reliable data. The information collected in the expert survey is subjected to an exploratory analysis. Huber's M estimator method is applied to statistically represent the changes in labour consumption rates and productivity. These changes can be calculated very precisely using the derived equations, or determined graphically using diagrams.