Precast Hybrid Moment Resistant Frame Click small photo for larger view

Pankow, along with an industry consortium, has developed and produced a Precast Hybrid Moment Resistant Frame (PHMRF). This system promises to fundamentally alter the way in which structures are designed and built in regions of high seismic activity. While establishing a new benchmark for building designs, the system is simple to build and requires only common materials and construction technologies already in use throughout the world.

What Does PHMRF Do?
The PHMRF protects the integrity of a building's structural frame through superior seismic performance. PHMRF isolates and separates the strength and energy absorption components within the moment frame joint. High-strength, post-tensioned steel gives the joint its strength to resist the applied dead, live, and seismic loads, with mild steel utilized across the joint to serve as an energy dissipater under seismic loading. The post-elastic performance is concentrated in the connection rather than a structural member, providing a restoring force, which allows the structure to self-center and not suffer displacement after an earthquake.

Benefits after a major earthquake may include:

• Property is better protected due to the enhanced survivability of the structure
• Lenders are less likely to see defaults
• Insurance claims should be less likely and, when they do occur, damage claims should be reduced
• "Down-time" may be dramatically reduced, protecting earnings capabilities and cash flows

In participation with a consortium of industry experts, the National Institute of Standards and Technology (NIST) and the University of Washington, tests were performed on the PHMRF which showed that it can be economically constructed and exhibits a higher performance than the conventionally reinforced cast-in-place concrete frames.

Advantages:

• Design flexibility
• Cost competitive - initial cost of the PHMRF is comparable to steel and cast-in-place frames
• Additional costs savings - could be accruable when used in a building's exterior as both structural and architectural precast, and then by introducing architectural panel design into structural precast forms. This approach would eliminate the need to purchase and attach additional cladding elements to the building's structure.
• Code approved
• Shorter construction duration
• Improved lateral resistance
• Floor-to-floor height reduction
• Effective in mid- and high-rise buildings and parking structures
• Increased recognition by the real estate community and build-to-suit owners that the resale value of buildings using PHMRF will be more than that of those employing traditional monolithic moment frames

Current cast-in-place concrete technology after a 3% story drift. Click small photo for larger view

PHMRF joint after a 6% story drift. Click small photo for larger view