A recent series of dynamic tests demonstrates that there are several types and doses of steel-fiber reinforcement that can be used in performance-based seismic design of coupling beams—headers that link openings in concrete shear walls—to reduce rebar congestion. The tests, performed at the University of Wisconsin, are called “a step in the right direction” by the structural engineer who pioneered the use of SFR concrete.
“The results show a way forward for the development of a performance-based specification for steel fiber, as opposed to a product-based spec,” says Cary Kopczynski, CEO of the firm that bears his name. “This will open up the competitive marketplace, which is key to the wider use of SFR concrete in tall buildings.”
在地震 - 易发的地区，螺纹钢挤塞，特别是耦合梁中的横向和对角线杆，具有长期讨论的承包商。在分批植物的SFR中混合增强延展性和剪切强度，降低了钢筋需求。Kopczynski说，可以提高建设性和材料性能。
Earlier material research was limited to one dose of fiber from one supplier. In the tests at the Wisconsin Structures and Materials Testing Laboratory, Madison, investigators subjected eight fiber-reinforced concrete coupling beams, without diagonal reinforcement, to large displacement reversals. They conducted bending tests, direct tension tests and compression tests, using different fiber doses and strengths. Wire suppliers Bekaert Corp. and ArcelorMittal provided the fibers.
“基于该研究的结果以及其他地方报道的结果，提出建议，耦合光束漂移和预期剪切应力需求的推导材料性能，使得简化的增强细节可以用作电流对角增强耦合梁的替代方案2014年美国混凝土研究所建设规范中规定的设计，“报告说：”用各种类型的钢纤维钢筋混凝土评估耦合梁的地震行为，“由天使L. Perez-Irizzary和Gustavo J. Parra-Montesinos编写published this month by the research’s main sponsor, the Charles Pankow Foundation.
Pankow和其他赞助商，包括Bekaert，ACI具体研究委员会和美国混凝土承包商协会，为该研究提供了214,240美元。
Each specimen consisted of a precast, rectilinear coupling beam, in a vertical position, connected to two large rectilinear blocks that simulated end regions of two linked walls. The main variables investigated were span-to-depth ratio and peak shear stress demand. The tests showed that several alternative fibers can be used in beams and still achieve the main goal of eliminating diagonal reinforcing bars and reducing transverse rebar, says Parra-Montesinos, the tests’ principal investigator and a Wisconsin professor of engineering.
Satisfactory performance can be achieved with volume fractions—the ratio of fiber to concrete—of 1% and 1.25%, as opposed to the denser 1.5%, which Kopczynski specified for recent high-rise projects in Seattle and Bellevue, Wash.(ENR 9/26-10/3 p. 30). “This may lead to mixes that are pumpable, eliminating the need for bucketing,” says Kopczynski.
Parra-Montesinos补充道，“我乐观地说，鉴于简化强化和[更多承包商]现场经验，设计师将越来越多地使用耦合光束。”
