Set Based Design for Lean Delivery of Reinforced Concrete Structures

Introduction

Professors Iris D Tommelein and Glenn Ballard have been conducting research on rebar delivery, which has included interviews and workshops with industry practitioners. We have spoken with people working at rebar mills, detailers and fabricators, structural designers, general contractors, owners, as well as CRSI. Major opportunities exist for improvement if participants in the rebar supply chain can be brought together so that they will better understand each other's value added tasks and business processes, then show willingness to makes changes to their own practices in order to achieve better overall performance in the supply chain.

Many players are involved in the rebar supply chain today, including owners, designers, detailers, fabricators, steel mills, general contractors, and others. Clearly, the rebar industry is fragmented, which leads to a sub-optimal delivery time for reinforced concrete projects, as is described in the attached Construction Research Congress paper by Professors Tommelein and Ballard. In order to reduce this delivery time, the organizers propose a restructuring of the rebar supply chain driven by the adoption of lean principles in the design and construction of reinforced concrete structures.

Research Objectives

The goal of this research is to develop a new design representation to specify rebar by area as opposed to having the structural engineer explicitly detail specific rebar sizes and placement. The reason for postponing these specifics is to allow design of product and process for better fabrication and construction. If this new design representation is successful in the case of rebar, the organizers anticipate that the methodology will be expanded to other building systems.

The working hypotheses are that (1) A language can be developed to represent data about design and component attributes, so that this data can be carried forward through all phases of rebar delivery. (2) Design rules can be formulated by a team of specialists to reflect their knowledge, skills, and ability to work together while taking into account the specific circumstances of the project they are jointly working on. (3) Tools including set-based design and visualization enable members of the team to jointly explore many design alternatives in a systematic and efficient way and choose solutions that meet many if not all of their constraints and preferences. (4) Multi-disciplinary teams of specialists engaged in concurrent engineering can generate a design that is of greater value than today's point-based designs.

Acknowledgement

This research was funded by grant CMS-0511044 from the National Science Foundation (NSF) and by a grant from the Concrete Reinforcing Steel Institute (CRSI) whose support is gratefully acknowledged. Any opinions, findings, conclusions, or recommendations expressed are those of the writers and do not necessarily reflect the views of the NSF or CRSI.