Strategies for successful delegated design in structural steel.
For decades, delegating the design of steel connections and stairs to engineers under the steel fabricator’s contract has become increasingly popular. Projects with delegated design have had mixed results. Very often, the outcome of delegated design is significantly impacted by the way delegated design is specified in the construction documents. This article provides Engineers of Record (EoR) strategies to improve efficiency and economic benefit to the project owner when they specify the delegated design of steel components.
It is important to understand that delegated design was originally developed to allow steel fabricators and steel erectors the flexibility to complete the design in a manner that saves both time and money in the construction of the projects. Under the ideal delegated design model, fabricators can design connections and stair configurations that maximize their fabrication equipment and procedures’ best and fastest methods. Delegated design allows erectors to influence the design to minimize construction obstacles and leverage their experience to provide more efficient construction sequences. EoRs should ensure that the specifications they are writing maximize the ability of fabricators and erectors to influence the project.
When an EoR specifies delegated design, they invite the fabricator, erector, detailer, and specialty engineer (the engineer responsible for designing the connections and the stairs) to the design process. The design process, by its very nature, is collaborative. The EoR should ensure the project is set up to make the relationship as collaborative as possible.
AISC has made considerable progress in defining the methods that EoRs should specify delegated design. Section 3.2.3 (3) of ANSI/AISC 303-22 “Code of Standard Practice for Steel Building and Bridges” has been updated to facilitate delegated connection design. Projects that follow this section of the Code of Standards typically run smoother and more efficiently. AISC has also created the use of Substantiating Documents, which makes the communication between the EoR and Specialty Engineer much simpler. It is highly recommended that EoRs familiarize themselves with Section 3 of the Code of Standard Practice and specify delegated design accordingly.
The Coalition of American Structural Engineers (CASE) have three documents that can assist EoRs with making their construction documents efficient. These are:
- 962 National Practice Guidelines for Structural Engineers
- 962-B National Practice Guidelines for Specialty Structural Engineers
- 962-D A Guideline Addressing Coordination and Completeness of Structural Construction Documents
EoRs should also concentrate on some straightforward strategies to help make their projects with delegated design run more smoothly.
- Make sure the use of ASD vs. LRFD is clearly defined.
- The construction documents should provide accurate reactions where possible. When universal methods of calculating reactions are provided, such as 55% of the Uniform Load Tables, the project can be designed for overly conservative reaction forces. This can cause inefficient conditions. Short small beams used can often have specified reactions that will exceed the actual reaction by as much as 300%
- When connections are designed to resist wind and seismic forces, the reactions should be broken up into dead, live, wind, and seismic forces. This allows the Specialty Engineer to take advantage of reductions in forces allowed by ASCE 7 load cases.
- Clearly define connection types that are not acceptable.
- Provide sufficient information for the fabricator and erector to bid on the project without the need to design connections during the bidding process.
- Provide specific instructions on what is expected regarding the Substantiating Documents. The instruction can include drawing and details required, calculation format and requirements for correlation to the shop drawings. This will avoid the need for resubmittals and project delays.
EoRs should also consider the methods used to specify a delegated design for stairs. First, the EoR should take an active part in assisting the architect in properly defining the stairs. This is especially true with monumental stairs. The architect often needs help determining the size and configuration of stair members along with the location of supports. The EoR must clearly define where the stairs are expected to attach to the primary structure. “AISC Design Guide 34 – Steel-Framed Stairway Design” provides an excellent resource for assisting with the design of stairs and how to specify the delegated design of stairs correctly.
How documents that are prepared under the contract of the steel fabricator are signed and sealed can also be a point of contention on projects with delegated design. Signing and sealing shop drawings can be problematic for Specialty Engineers. This can present the Specialty Engineer with excessive liability and uninsurable conditions. Therefore, specifying that the Specialty Engineer stamp shop drawing is not recommended. Substantiating Documents allows Specialty Engineers to sign and seal their work while not creating liability conflicts. As mentioned above, the EoR should be explicit regarding the expectations for the substantiating documents in the construction documents.
Mr. Stubbs will present strategies EoRs can employ to make delegated design projects more efficient at the 2024 North American Steel Construction Conference. This presentation will provide a more detailed discussion on improving the delegated design.■