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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 11 Abstracts search results
October 4, 2013
National Research Council Canada has recently upgraded its column furnace facility for assessment of columns in fire under not only the applied axial loads but also a potential lateral load. The main goal for this upgrade was to be able to simulate lateral displacement of columns during the fire due to thermal expansion of slabs/floors and to assess a column’s residual seismic/lateral load capacity after fire damage. Furthermore, the new column facility enhancement included a hybrid testing technology in which the column could be tested considering its structural interactions with the remaining of the structure. This paper includes the summary of the new upgrade and testing technology; however, more focus will be on the structural response of a high strength column, with steel fibre, tested using the new upgrade and approach. This includes the fire test of the high strength column specimen as well as lateral load test of the column to determine its residual lateral resistance with fire damage. The results of these tests revealed that fire substantially reduced the residual lateral load/displacement capacity of the high strength concrete column. The new commissioned testing technique/tool could assist researchers to seek and find solutions for more reliable post-fire structural inspection and to develop design tools for the mitigation.
Lonnie A. Marvel and Riyadh A. Hindi
This paper experimentally investigates the behavior of high-strength reinforced concrete columns confined using a new cross spiral confinement technique. The new cross spiral confinement technique uses two opposing spirals to confine circular concrete columns enhancing their strength and ductility, and increasing spiral spacing to facilitate the flow of fresh concrete. The new confinement arrangement is experimentally evaluated and compared to the conventional single spiral confinement arrangement. Twenty-one circular high-strength reinforced concrete columns with four different spiral spacings and longitudinal reinforcement ratios were tested under monotonic axial loading. Seven specimens utilized the conventional single spiral confinement, used as control specimens, while the remaining specimens utilized the new cross spiral arrangement. The new arrangement enables an increase in spiral spacing while maintaining the same volumetric confinement ratio as the conventional. Alternatively, doubling the volumetric confinement ratio without violating ACI 318-081 requirement for minimum spiral spacing. The study showed that the new cross spiral arrangement with the same volumetric confinement ratio as the conventional spiral obtained similar ultimate stress values while it attained about a twenty percent increase in ultimate displacement. The cross spiral confinement using twice the volumetric confinement ratio greatly outperformed the conventional spiral in all aspects.
Hideki Kimura, Yuji Ishikawa, Hiroto Takatsu and Hassane Ousalem
More than 500 high-rise RC buildings with height exceeding 60m (197feet) have been built since early 70's in Japan. The number of stories sometimes exceeds 50. Use of base isolation systems or vibration control devices in high-rise RC buildings has significantly increased since 1995 Kobe Earthquake. Ultra-high-strength materials have also been used in such buildings. The specified concrete strength of 150 MPa (21800psi) or higher is currently practiced and SD685 deformed bars of 685 MPa nominal yield strength are used as the main reinforcing bars.
Such buildings are subjected to intensive large axial and lateral loads in case of sever earthquakes and strong winds, particularly at their lower stories where exterior columns experience varying high-axial loads shifting from compression to tension. Furthermore, as concrete strength increases, fire resistance decreases and cracking behavior of RC members changes which affects the structural performance. A lot of experimental studies with regards to such columns and subassemblies have been carried out to investigate their structural performance and to establish appropriate design methods.
This paper presents some design issues related to the application of high-strength materials to RC columns or subassemblies. It also emphasizes recent research works and design methods for the application of ultra-high-strength concrete for high rise RC buildings.
Editor: Halil Sezen / Sponsored by ACI Committtee 441
Practicing engineers increasingly favor the use of high-strength concrete and reinforcement in their design. The paper included in this CD present results from recent research studies and examples of practical applications and use of high-strength concrete and steel reinforcement in recent projects.
This CD consists of 10 papers that were presented at a technical session sponsored by ACI Committee 441 at the ACI Convention in Toronto. Ontario, Canada in October 2012.
Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order.
Jeffrey M. Rautenberg and Santiago Pujol
The use of high-strength longitudinal reinforcement—having a specified yield stress between 80 and 120 ksi—in concrete elements has been shown to allow for the use of lower reinforcement ratios leading to reductions in fabrication costs and congestion. This is especially relevant to structures built in seismically active regions in which reinforcement ratios are typically higher than in structures in regions with a lower seismic risk. Recent research initiatives related to the use of high-strength reinforcement have largely been focused on the response of isolated elements instead of the response of building frames.
This paper presents results from a suite of numerical analyses designed to investigate the effects of high-strength longitudinal reinforcement on overall building frame response. Using steel with a higher yield stress allows for reductions in reinforcement ratio. Those reductions, in turn, cause a decrease in post-cracking stiffness. To investigate the effects of this relative softening, a series of multiple-degree-of-freedom models were proportioned to represent idealized frames reinforced with high-strength steel. Nonlinear dynamic analyses were conducted to estimate their response to a set of seven strong-motion accelerograms. It is shown that increases in drift demands related to the use of high-strength steel range from negligible to approximately 20 percent, depending on a number of factors including base shear strength, ground motion intensity, and extent of high-strength steel use. This increase in drift demand 1) is modest compared to the uncertainties associated with predicting ground motion intensities and 2) needs to be confirmed through experiments.
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