2020Case5Sisk

Contents Lean Construction Ireland Annual Book of Cases 2020 22 Case 5 To support continuity and to improve cycle times, our team changed the concrete mix design to secure faster curing times for finishing concrete – this allowed us to power-float slabs within the planning hours (18:00 off-site) whilst also ensuring earlier formwork striking times. Reinforcement de- sign was enhanced – the normal commercial priority is to reduce the reinforcement content to the lowest possible tonnage and our Lean approach resulted in us increasing reinforcing steel content for two reasons, namely we stan- dardised bar lengths for ease of fixing and we added steel to facilitate early shutter removal, thus enhancing cycle times. Productivity of labour, measure and monitor output We mapped out the targeted cycle times for each element of work and fine-tuned the resource requirements for each step. This allowed us to “flex” the resources to suit the workload. Output for each crew was visually marked and measured on colour-coded layout drawings daily, and this provided the team with certainty on cycle performance and also identified particular details where excessive labour was being absorbed. We reviewed these areas and fine-tuned details for the next cycle. Measuring the tonnage output of reinforcement allowed us to identify periods of activity where we could reduce and increase resources whilst also under- standing which elements of the reinforcement were more onerous than others, like, for example, with shear links where we changed from a traditional shear link to a shear rail. Direct observation studies to aid productivity We engaged with specialist Lean consultants to undertake Direct Observation studies. We already understood the actual output rates per crew per day, and had identified particular construction details which were absorbing too much time. Direct Observation would provide us with independent data on where and to what extent waste was occurring within key activities, in particular, waiting, excessive transport, and movement. Experienced construction professionals and supervisors understand the reality of moving materials on-site, the challenges of “crew sizing”, and the inevitable intermittent downtime involved during concrete pours, for example. Sometimes we can “know too much” and thus in this project we engaged with a specialist Lean Consultant whose experience was in manufacturing and they would analyse our processes against a manufacturing type standard. Prior to commencing the studies, we engaged with the craft operatives to explain the process and the purpose of the exercises, and everyone was happy to be involved. The following work activities were then observed and recorded on five days over a five week period, with feedback given to the site team after each visit and in advance of an overall report including: • Erection of formwork decking. • Installation of reinforcement. • Pouring of concrete. Erection of decking This was characterised by significant movement and waiting, primarily associated with sourcing ancillary components, like, for example, fixings and ratchet straps. Crews were starting work with all bulk materials available in the correct location and with boxes or stillages of ancillaries to hand, but they subsequently lost a lot of time gathering the remaining components and bringing them to the location needed. The solution was to analyse the propping drawings in advance and organise the correct quantity of all ancillary items and deliver to the work area mechanically with the bulk materials. Installation of reinforcement Significant time was being lost sorting out the different bar sizes and shapes required for each area. The process involved checking the steel drawings to identify the bars needed, checking the steel schedule to identify the bar numbers involved, checking the bar tag to identify the correct bundle, and tape-checking the bar itself to confirm it was correct – all before taking the correct numbers of bars to the fixing location. The obvious solution was to re-design the steel so that there were fewer types of bars needed for each pour. Figure 3. Example of Decking Installation Mark-ups for Progress Tracking