Structural steel and welding inspection is a critical service for building construction. A member displacement of a few inches can adversely affect the structural performance or safety of a building. This inspection is important for all buildings, but especially those critical structures such as hospitals that must be able to withstand seismic events.
To protect buildings and their occupants, Terracon’s approach on structural steel projects is to form a close working partnership between project inspectors and structural engineers.
Communication yields the best results
Communication on these complex projects is key. Prefabrication and pre-erection meetings should be mandated to be sure that all team members (general contractor, inspector, fabricator, erector, and structural engineer) understand requirements. These meetings are a good opportunity for the structural engineer to review the important aspects of the structural steel design, such as critical components like brace frames and moment frames. Opening communication between inspectors and structural engineers saves time, allowing the inspector to help clarify project requirements when questions come up during construction.
Welding procedures, applicable to the project, must be submitted and approved by the structural engineer. Many structural engineers do not have the expertise to review welding procedures and will utilize other consultants to advise and recommend acceptance. Terracon has in-house welding experts to perform this welding procedure review.
Fabrication shops can vary considerably with respect to technical capability, welding expertise, quality control resources, and production capacity. Some fabrication shops can be considered “approved fabricators” by local building jurisdictions, which means the shop can self-inspect welding using shop quality control personnel. Fabricator approval programs can include American Institute of Steel Construction (AISC), International Code Counsel (ICC), and city or state agencies. The inspection agency should be utilized to help the design team determine if a fabricator is qualified for a particular project and to perform audits of the fabricator’s quality control program and procedures.
Recent changes to American Welding Society (AWS) and AISC Seismic Codes require even more inspection agency expertise. Special welding procedures and welder qualifications are required. Welding parameters need to be closely monitored and documented by welding inspectors. Nondestructive testing technicians require additional certification. We find that many structural steel contractors are bidding on work containing the new seismic provisions without clearly understanding what is required to successfully perform the welding. Having welding experts on the owner’s team can help avoid expensive mistakes and construction problems.
Details are critical
It is important that structural components such as brace frames, moment frames, and other elements are installed in the proper location, within specified tolerances. For upgrades in existing structures, there can often be existing conditions that interfere with the placement of the new structural steel members.
Inspectors must carefully detail any fit-up issues in the inspection report. The inspector needs to make sure that the contractor accurately describes nonconforming issues in Requests for Information (RFIs) and that she/he receives from the structural engineer and provides an approved fix. Inspectors are required to be certified by the AWS and/or the ICC and also need to be certified to perform, when required, nondestructive testing, such as ultrasonic or magnetic particle testing on welds. These certifications require a high level of training and expertise.
A welding inspector must measure the size and length of every structural weld. Field welds on brace frames are critical. These welds are often welded out of position or can be undersized if there is a gap between the tube and gusset plate. The fillet weld size must be increased by the size of the gap. The alignment tolerances of the brace frame tubes are also critical and are usually detailed on the structural drawings. There is often an erection bolt though the tube and gusset plate. If the erector can’t get the erection bolt through the hole, there is likely an alignment issue that requires an RFI.
When welding new structural steel to existing structural steel, the existing steel must be cleaned to bare steel prior to welding. Welding through coatings such as paint and galvanizing can lead to weld cracking and lack of weld fusion.
Bringing it all together
When structural steel inspection is a required part of the project, it is important to build a collaborative team. Structural steel and welding inspectors must have a high level of expertise and good communication skills. At Terracon, our materials professionals add value to projects at any stage. By joining the team early in the design process, we can identify, evaluate, and recommend the right materials selection, welding procedures, and quality assurance programs, customizing them for the project, which can speed construction and reduce costs.
Michael Mayes is the founder of Mayes Testing Engineers, A Terracon Company, located in Seattle. He is a welding engineer, AWS Certified Welding Inspector, and an ASNT Level III. He is a voting member on the national AWS D1 Welding Code Committee and is the current Chair for the AWS Seismic Welding Code Committee.