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Forest Products Laboratory
One Gifford Pinchot Drive
Madison, WI 53726-2398
Phone: (608) 231-9200
Fax: (608) 231-9592
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Development of a Heavy Timber Buckling-Restrained Brace for Tall Wood Buildings

Example of Heavy Timber Buckling-Restrained Brace with failure of the encased steel. Univeristy of Utah
Example of Heavy Timber Buckling-Restrained Brace with failure of the encased steel. Univeristy of Utah
Snapshot: Recent advancements in timber technologies are pushing mass timber systems into larger commercial-scale markets where steel and concrete systems dominate the landscape. One such market, Buckling-restrained braced frames (BRBFs), is a newer type of seismic-force-resisting system used in modern building designs. Buckling-Restrained Braces (BRB) are incorporated into frame structures to dissipate energy or prevent damage to the surrounding structures. Recent research experiments aim to classify both the fundamental timber casing behavior and limit states of the full sized Heavy Timber - BRB. Along with the experiments, analytical formulas and analysis validate and optimize the concept HT-BRB.
Summary:

Timber building construction has been traditionally utilized to reduce inertial demands in high seismic regions. In high seismic regions, mass timber buildings currently are not included in the ASCE 7 code defined lateral force-resisting systems and are limited to traditional timber-framed systems with low ductility. Building on over 40 years of existing BRBF research for steel and concrete buildings, the development of a heavy timber buckling-restrained braced frame (HT-BRBF) could improve ductility. A HT-BRBF system is conceived for application in mid- and high-rise building timber construction and is inspired by the unbonded steel brace technology that today is widely used throughout Japan and the United States. A key need to move this lateral force-resisting system into codes is the development of a wood-based BRB. Both small-scale material and full-scale BRB testing were conducted. Four types of structural composite lumber-glued laminated timber (glulam), laminated veneer lumber, parallel strand lumber, and mass plywood panels (MPP) - were tested to determine the best casing material for the BRB.

Six full scale HT-BRB were constructed with a MPP casing and tested with both a fatigue-based and drift-based loading protocol. The tested HT-BRB met the minimum ASCE 341-16 performance criteria and the hysteresis curves from these specimens prove that sufficient energy dissipation is readily achievable with a T-BRB. Full-scale testing validated the HT-BRB design methodology and at the same time provided cyclic performance data required for design and codification of the HT-BRBF mass timber lateral-force-resisting system. Finally, this work has demonstrated that the development of a HT-BRBF is possible as a tallwood building option.
Princpal Investigator(s):
 Rammer, Douglas R.


Research Location:
  • USDA Forest Products Laboratory
  • University of Utah


External Partners:
  • Freres Lumber Company
  • Katerra
  • University of Utah

Fiscal Year: 2019
Highlight ID: 1334
 
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