Concrete building

Research & Publications from OSES Engineering in Ottawa

Shear Stress Prediction: Steel Fiber-Reinforced Concrete Beams without Stirrups
American Concrete Institute - Structural Journal

Document Name: 108-S29
Author(s): Sam (Haisam) Yakoub
Publication: ACI- Structural Journal
Volume: 108
Issue: 3
Pages: 304-314
Keywords: absolute reduction factor; failure; geometry factor; shear stress; steel fiber-reinforced concrete; strain; volume fraction
Date: May 1, 2011

Abstract:
This paper develops an equation to predict steel fiber contribution to the shear strength of steel fiber-reinforced concrete (SFRC). This equation is used to modify the CSA A23.3-04 general shear design method and Bažant and Kim equations so that the modified relations safely predict the shear strength of SFRC without stirrups. This paper analyzes 218 shear failure tests previously conducted on SFRC without stirrups and 72 tests on reinforced concrete—with no stirrups and no steel fibers—to verify the applicability, accuracy, and efficiency of the two equations developed in this paper and five other equations from the literature. Furthermore, it shows that hooked steel fibers are not as efficient as crimped fibers, and that round fibers are among the most efficient fibers used in those tests. Moreover, it recommends a procedure to calculate steel fiber geometry factors, another factor to evaluate engineering equations, and further research on different SFRC aspects.

None Rocking Seismic Isolation System for Continuous Serviceability.
None Rocking Seismic Isolation System for Continuous Serviceability is a seismic protection system that consists of a unique seismic bearing which does not rock horizontally, but vibrates vertically slightly, where all buildings and most other structures, have dynamic capacity to resist slight vertical movements as their material resistance is higher under shortly applied dynamic loads. Our system, extremely reduces transmitted seismic energy to isolated superstructures, so that protected structures (by means of our system) would have limited or no damage due to seismic forces, so that the isolated building/structure would continue to function normally aftermath. Finite element analyses for a 10m x 10m x 6m high, one story building module under time history of a historical earthquake, which scaled to have max accelerations 2.0g, which returns max 0.06g horizontal response accelerations in the dynamic analyses. Our system might work for all structures, earthquakes, and site characteristics combinations, whatsoever. In addition, the system was tested using 2storey small scale 1/10 wood model 1.5mx0.8mx1.3m height loaded with 350lbs. The model was shacked with 0.25m max displacements, with periods 0.5-0.8 sec, and the shacking lasted 60 secs. The model responses estimated using 2 cups of water, one on top and the other on the base, where the cup on the top of the building, did not spell at all, while the cup on the base spelt a few times before it overturned. A part of our system, is the seismic controller, which might be used alone with other seismic isolators such as pendulum seismic isolation bearings, to reduce excessive displacements, and further reduce transmitted forces, allowing using less friction of the contacted surfaces, and preventing the resonance in that device. Our system is patented US 9021751, and CA2672314 C, with pending applications in both US and Canada. Our system will reduce the cost of construction which was spend on seismic protection, and allows to reach much higher building heights in the seismic countries.