‘Flexural capacities’ previously assumed in 1965 when structure was built were overestimated by today’s standards, report also concludes; February snow event called ‘minor’ contributor

Medford School District officials Thursday night released the results of a structural evaluation of the collapsed North Medford High School gymnasium, blaming beam failure as a key cause.

Submitted by Portland-based KPFF Consulting Engineers May 5, the report — in an executive summary provided by the district but also released in the full findings — identifies main contributors that led to the gym roof’s dramatic collapse Feb. 11 as “scarf joint manufacturing and potential early delamination in the beams and joints” that “likely initiated the beam failure.”

Delamination is defined as “a significant failure mode, often occurring due to adhesive layer failure or interlaminar damage.”

The report also said “flexural capacities” previously assumed in 1965 when the structure was built “were overestimated by today’s standards.” Flexural capacity is defined as a “material’s ability to resist bending and deformation under load. It’s often measured by its flexural strength, which is the maximum stress a material can withstand before failure in a bending test.”

The Medford School Board was scheduled to discuss the report at its work session Thursday night. District officials did not make themselves available for comment before the meeting.

The North High gym, built in 1965, collapsed Tuesday, Feb. 11, days after cracks were discovered in the wood beams supporting the flat-roof, 192-foot-by-176-foot structure.

The collapse followed a heavy snow event and occurred just months after a more than $3 million seismic retrofit last summer. The snowstorm in early February left a heavy snow load on the flat-roof structure over the main gym area.

Partial collapse was reported the morning of Feb. 11, with total collapse — posted in a video on social media by district officials — occurring within just a few hours. 

No one was injured.

District officials, who fenced off the area and later retrieved sports memorabilia to salvage pieces of the gym’s vaunted history, oversaw partial demolition and assessment by engineering crews beginning Tuesday, March 11, a month following the collapse. 

Factors assessed by engineers were rated as having no role, a minor role or a major role in beam failures. According to engineers, in the report released by the district, the recent seismic retrofit, other roof loads and wood decay were not found to be contributing factors in the structural collapse.

Snowpack on the roof and a basketball hoop affixed to a beam were only “minor” contributors to the collapse, whereas structural capacity of deep glulam timber beams, a common construction method in the 1960s, led to significant reductions in beam flexural capacity, the engineer’s report said.

In addition to the independent investigation of the North Medford High gym, the Medford School District commissioned comprehensive engineering assessments of all large-span structures across the district, the release said.

“It is also our opinion that the use of glulam beams in a low-slope roof (slope less than 15-deg) was, and still is, an appropriate choice to be used for a gymnasium with similar spans and loads,” the engineer’s report said.

“This third-party analysis was designed to identify structural deficiencies that may require retrofitting while also documenting the material, type, and age of roof system components such as trusses and beams,” a district statement said. 

District officials further said proactive measures would “support the ongoing annual monitoring of district facilities to enhance safety and resilience,” according to the release.

The district has set up a FAQ page on its website for community members to access more information on the gym collapse and rebuild process. The most recent timetable outlined by the district in March is for the gym to be rebuilt within a year at a cost of potentially millions. Gym activities and P.E. classes, meanwhile, have been moved outdoors or to the Oakdale Middle School gym.

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Rogue Valley Times Editor Troy Heie contributed to this report.