Communication Aids Quality Control on Lateral Load Projects
Communication plays an integral role in quality control and assurance. In this article, our three expert interviewees discuss the importance of communication as they relate to steel joists and lateral loads.
- John Rolfes, PE, SE, adjunct professor at Marquette University and former vice president at CSD Structural Engineers
- Mark Maloney, PE, engineering manager at New Millennium Building Systems
- Darrell Marchell, PE, business development manager at Vulcraft
Communication on the job site
The design of a multistory building project in Kansas City was a typical job for John Rolfes, former vice president of CSD Structural Engineers and current adjunct professor at Marquette University.
Until miscommunication led to a problem on a project.
Rolfes and his team had designated the end moments on four joists incorporated in the moment frame system. They identified the moments using plus-minus and minus-plus symbols because, due to lateral loads, moments act in the same direction on the end of the joists.
The joist designer incorrectly interpreted the direction of these moments, resulting in a lack of necessary shear capacity in these joists. In this case, the shear forces from wind moments were significant. When Rolfes visited the job site and saw the joists had six-by-six double-angle chords with web members that were 1 1/4 inches by 1 1/4 inches by 1/8 inch, he knew that something was amiss and, after investigation with the joist designer, web reinforcing details were developed and implemented.
“This story speaks to the importance of communication,” Rolfes says. “A diagram is worth a thousand words.”
Why is communication important?
Every role — from joist manufacturers to engineers of record — must communicate with one another to ensure design intent and quality control philosophies align.
Communicating aspects like design intent and connection principles reduce error down the line. “We can have the best set of drawings, but if there’s poor quality control or assurance in the shop or field, it means nothing,” Rolfes expresses.
As engineers innovate their designs, it’s important to clearly communicate any special requirements that emerge as a result. Engineers should include the joist manufacturer in this conversation to improve communication about special requirements on the manufacturing side of things. “From the joist manufacturer’s perspective,” starts Maloney, “it can be difficult to understand the ‘how’ and the ‘why’ designs are changing. The more we’re involved in the innovation process, the more likely that the new design will be executed successfully.” If innovations in the field aren’t discussed throughout the industry, that lack of communication can propel a project off course.
“I think a lot of structural engineers assume we know as much about the structure as they do. That’s certainly not the case. For example, in a project subject to seismic loads, we don’t always know what the overstrength load factors are or what’s appropriate for joists that are incorporated into the seismic force-resisting systems for the building,” says Marchell. When team members begin a project, they are coming from varying levels of experience and background. Before jumping into the thick of a project, a team should discuss project specifics to ensure everyone understands.
Maloney elaborates on Marchell’s point, noting that engineers of record are responsible for passing on loading requirement information. “Communication is critical here. If there’s an intended path for a lateral load that the engineer of record is expecting, the joist manufacturer needs to be told where the load is going and how much of that load is going there. Without this information, you’re sure to have more RFIs and clouds on joist drawings,” says Maloney.
Design requirements for key elements should be stipulated on the erection drawings for joists. During the engineer of record’s review of the drawings, they can verify that the joist supplier has correctly interpreted these requirements.
Communication beyond your team
While internal communication remains integral to the success of a project, this isn’t the whole picture — teams need to incorporate communication with the public. One area that the public is typically concerned with is environmental impact of joists and overall structures.
Wind tunnel and shaker table studies provide data that help engineers understand the impacts of natural phenomena, such as earthquakes or hurricanes, on structures. “Wind and seismic loads are based on historical data,” Marchell says. “That data is frequently updated to communicate the most up-to-date information.”
In the same vein, teams should welcome regional-specific perspectives when communicating structural needs. Wind lateral loads are often a significant concern for southern coastal states like the Carolinas, Florida and Louisiana because of hurricanes. “Joists in a wind region are going to be subject to some significant uplift forces,” Rolfes states. “On the West Coast, earthquake forces are going to be high, so seismic loads are a more significant consideration”
Where communication can improve
One often forgotten aspect of lateral loads as they relate to open web steel joists is dead load. “A lot of the time in specifying a Steel Joist Institute catalog joist with lateral loads, dead load isn’t provided to us. That’s a pretty important piece of information when it comes to correctly analyzing a joist for lateral loads, like wind and seismic,” says Maloney. Painting a holistic picture — dead loads and all — is crucial when evaluating a project.
Another common miscommunication is grouping axial wind and seismic loads together. Maloney explains that there is often a significant difference between seismic and wind loads. He warns to avoid grouping these together because it can impact the end product.
How the Steel Joist Institute encourages communication
Providing standardized resources for engineers, joist designers and joist manufacturers allows all people involved in a project to be on the same page. “Our SJI specifications clearly define how the various members of the joist or Joist Girders are intended to be designed,” Marchell explains. Since joist manufacturers follow the same SJI Specifications for design, engineers can expect quality design from each manufacturer.
“The Steel Joist Institute provides spreadsheet-based tools for the design of moment end connections for joist and Joist Girders. Those tools are readily available and free on the Steel Joist Institute’s website,” Rolfes elaborates. Technical Digest 11 addresses joists incorporated into lateral load-resisting systems.
Joist Girder Moment Connection Design Tools
These design tools have been developed by the Steel Joist Institute to assist the SER, the connection designer, and the steel fabricator with the complex task of designing appropriate connections between Joist Girders and columns. The tools can be utilized for wide flange and HSS columns and includes reference manual and design spreadsheet
Technical Digest 11 Design of Lateral Load Resisting Frames Using Steel Joists and Joist Girders
TD 11 illustrates procedures for the structural engineer to properly analyze, design and specify open web steel joists and Joist Girder moment frames to resist wind and seismic lateral loads