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Subject: Subaru Ring-Shaped Reinforcement Frame
Topic: Design and construction of Subaru Ring-Shaped Reinforcement Frame
Objective: Develop an action plan for extrication tasks requiring removal of select model Subaru B-pillars
Task: Describe the tools and techniques that could be used by your department to cut through or remove the B-pillar of a Subaru Impreza, WRX, WRX STi, Forester, Legacy, Outback or Baja model vehicle.
As an emergency responder, I've noticed that occupants of late-model Subaru vehicles are surviving some pretty severe side-impact collisions with relatively minor injuries, if any at all. Although the doors may be jammed when we get there, the side of the vehicle most likely held up well.
During an extrication seminar I was conducting in the Fishkill, NY, area in 2004, several members of an area fire department approached me with a question and a challenge. They had encountered a Subaru Forester involved in a crash and were unable to cut through the B-pillar with any of their extrication tools. Their cutter and their reciprocating saw were both unable to sever the pillar. They went back to the junkyard the next day and used a gasoline-powered rotary saw with an abrasive blade to remove the B-pillar. They brought it to the seminar to show me.
When I saw the pillar that day, it was clear that something was very different with the Forester's B-pillar construction. The pillar was eight layers thick! One of the layers of steel was a round steel rod that resembled a concrete rebar. That B-pillar had more layers of steel than I had ever seen before in a vehicle.
In September 2005, the Orangeburg, NY, Fire Department responded to an incident involving a four-door Subaru WRX STi. The Subaru collided with a Dodge minivan at an estimated speed of 75 miles per hour. The broadside impact required the rescue team to remove the roof. The Subaru's A-pillars cut through quickly but the B-pillars again resisted every effort by the department to cut them.
With the cooperation of the corporate communications department at Subaru of America Inc. headquarters, I was able to study this vehicle construction feature in more depth. I learned that the reinforced B-pillars are just one component of what Subaru calls its "Ring-Shaped Reinforcement Frame body structure."
Rings of Safety
This innovative Ring-Shaped Reinforcement Frame body structure provides certain Subaru vehicles manufactured since model year 2002 with some unique crash protection. It also presents us with some unique extrication challenges.
The Ring-Shaped Reinforcement Frame is part of a structural body construction in which body side panels and the pillars around them are connected and reinforced to form three rings. The A-pillars and the front firewall structure make up one ring. Both B-pillars along with two structural frame members in the floorboard and two specially shaped structural members running across the roof area make up the center ring. The third ring is formed by the C-pillars and a strengthened lower rocker sill area. This construction design resists collision failure quite well and maintains passenger compartment integrity by dispersing the impact of the crash away from the occupants.
The Subaru Impreza, WRX, WRX STi, Forester, Legacy, Outback and Baja models all feature heavily reinforced B-pillars. The pillars are perfectly normal looking. The design of this structural member and the choice of steel used, however, make it a very substantial component of the vehicle "crashworthiness" system and a true rescue challenge at a crash scene.
The metal of the entire B-pillar is high-strength, high-tension steel. Boron is an example of this type of exotic metal. In addition, the individual roof pillars are called tailored-blank welded B-pillars and are cut with a laser then welded along their edges to form the eight-layer pillar.