Over the last few years, the use of building information modeling (BIM) technology in design practice has grown dramatically. Once considered applicable only to the largest and most sophisticated projects, design firms of all sizes now use BIM in their work in a variety of settings. The perceived benefits of the technology in the AEC industry are so great that clients often expect, or even require, that designers use BIM in the performance of their services.

The lack of a clear standard of care for designers using BIM, including acceptable model uses and content, can introduce significant business risk and uncertainty to a project. For example, a firm may produce a model as part of its design services, but other design professionals or contractors may rely on that model for other purposes, such as coordination, quantity takeoffs, or estimation, that were not intended by the engineer. Errors or omissions in the model can have downstream impact. With a poorly defined scope of responsibility for BIM, designers can face a struggle to manage client expectations, and even increase their professional liability exposure.

The American Institute of Architects (AIA) several years ago introduced a series of "digital practice documents" as part of its suite of contractual agreements. The documents include licensing agreements and protocol exhibits intended to better define the responsibilities of designers using BIM on different types of projects. AIA Document E 202 "Building Information Modeling Protocol Exhibit," establishes a framework for managing BIM requirements for different phases of a project using a "model element table" that is filled out by each designer. The CASE National Guidelines Committee, together with the joint CASE/SEI BIM committee, has developed a white paper (available at www.acec.org/case) that explores the implications of the AIA "digital practice documents" for the structural engineer of record (SER). This white paper provides commentary and sample model element tables to assist SERs in developing a scope of services for BIM that is consistent with CASE Document 962 (National Practice Guideline for the Structural Engineer of Record) and 962-D (Guideline on the Coordination and Completeness of Structural Construction Documents). While the paper focuses on the AIA documents, SERs may use the basic concepts to establish more generalized standards suitable for other contracts and types of projects.

Clearly, the modeling responsibility of the SER will vary for different projects and different types of contracts. AIA Document E 202 is intended to complement either a traditional form of agreement or integrated project delivery (IPD) and serves to define the BIM scope of work and deliverables for the project. AIA Document E 202 uses levels of development (LOD) to define the maturity and completeness of a BIM at different stages of a project.

The end use of the model will determine the LOD necessary for the BIM. These end uses can include quantity takeoff, cost estimating, schedule development, bidding/procurement, structural analysis, component engineering, shop drawing development, fabrication, and facilities management. The basic LODs are as follows:

LOD 100 – This basic model may be considered as a schematic design level, which provides primarily massing and volumetric information.

LOD 200 – This model is a little more developed and is akin to a design development, or 35% level of design. There is generally sufficient information to allow basic analysis of the structural and other systems.

LOD 300 – At this level, there is sufficient information to allow for the preparation of traditional construction documents.

LOD 400 – In this level, the BIM model includes additional detail and all primary and secondary framing elements. It includes complete fabrication, assembly and detailing information and as such can be used for shop fabrication.

LOD 500 – All elements and systems are accurately modeled as specific, constructed assemblies. This model can be used for maintaining, altering or adding to the project, or building.

Levels of development should be agreed upon with the project team early in the project schedule and should be based on the overall project goals. The engineer must take care to identify the scope of work clearly in each design phase of involvement. The AIA E 202 levels of development do not clearly map to the traditional project phases defined in the AIA contract documents (conceptual design, schematic design, design development, and construction documents). For example, in a traditional project, the engineer of record may not produce any model at all for LOD 100 (just a narrative) or may simply produce a volumetric model showing the space occupied by the structural framing with no specific member sizes or even framing systems identified.

Andrew Rauch, P.E., S.E. is a principal with BKBM Engineers in Minneapolis and CASE's chair-elect and current chair of CASE's National Guidelines Committee. He can be reached at arauch@bkbm.com.