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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 80 Abstracts search results
Document:
24-041
Date:
April 25, 2025
Author(s):
Gustavo J. Parra-Montesinos and Jacob Zeuske
Publication:
Structural Journal
Abstract:
Two large-scale beam-column connections with beam longitudinal headed bars were tested to evaluate their susceptibility to breakout failures. The specimens were designed following the strength and transverse reinforcement detailing provisions in Chapter 15 of ACI 318-19. The variable investigated was the headed bar embedment length, which was determined based on either Chapter 25 of ACI 318-19 or recent research at the University of Kansas, the latter leading to a 22% shorter embedment length. Both specimens exhibited beam flexural yielding, but the specimen with shorter bar embedment length experienced significantly more connection damage followed by a concrete breakout failure. Based on the limited test results, it is recommended that nominal joint shear strength be calculated based on a joint effective depth equal to the headed bar embedment length and a shear stress of 1.0λ√(fc' ) (MPa) [12λ√(fc' ) (psi)]. A method for calculating headed bar group anchorage strength in exterior beam-column connections is proposed, which led to reasonable and conservative strength estimates in the test specimens.
DOI:
10.14359/51746793
22-242
May 1, 2023
Brock D. Hedegaard, Timothy J. Clement, and Mija H. Hubler
Materials Journal
Volume:
120
Issue:
3
A new semi-empirical concrete shrinkage and creep model called the CPRH Model is proposed and calibrated. The new model proposes a coupling between autogenous and drying shrinkage using a volume-average pore relative humidity and treats drying creep as an additional stress-dependent shrinkage, linking together all these phenomena. The proposed expressions are designed to facilitate traditional integral-type analysis, but also uniquely support ratetype calculations that can be leveraged by analysis software. Model calibration uses the Northwestern University (NU) database of creep and shrinkage tests to determine new model parameters. The proposed model uses minimal inputs that are often known or may be assumed by the design engineer. Comparison of the proposed model to historical time-dependent models indicates that the new model provides a superior fit over a wider range of inputs.
10.14359/51738709
19-437
May 1, 2022
Vasiliki Palieraki, Elizabeth Vintzileou, and John F. Silva
119
Provisions for the calculation of interface shear strength have remained unchanged in ACI 318 since the 1980s. The shear friction concept, while simple to apply, does not address many of the most important influencing parameters for interface shear strength. It is silent on cyclic loading, intermediate levels of interface roughness, and the strength of interfaces reinforced with short dowels. To assess the approach included in ACI 318 and to enable the formulation of a new approach, a comprehensive database of test results has been assembled. The results of recent cyclic shear tests performed at the National Technical University of Athens (NTUA) have been combined with the results of investigations conducted worldwide between 1960 and 2020—a total of nearly 1240 tests—to provide a definitive basis for the development of a model for the accurate prediction of interface shear strength under both monotonic and cyclic displacements.
10.14359/51734519
20-418
January 1, 2022
Esteban Villalobos-Vega and Guillermo Santana
1
In this paper, the results of the proposed ductile precast concrete end-diaphragm beams for the transverse seismic resistance and protection of the substructure of slab-on-girder concrete bridges, tested at the facilities of LanammeUCR structural laboratory, University of Costa Rica, are detailed and discussed. The proposal can be used as part of an accelerated bridge construction (ABC) solution for moderate- to high-risk seismic areas. The hysteretic results showed adequate energy dissipation performance of the transverse end-diaphragm beams system; however, the envelopes obtained in both load directions evidenced a marked difference: the negative envelope showed a more noticeable ductile behavior and close enough to the predicted theoretical monotonic curve than the positive envelope. The damage observed at the precast concrete diaphragm beams was negligible, and the concrete deterioration was concentrated in the corners of the connections with the bridge girders, where the grout mortar at the joint gap evidenced a poor performance. Even if the bridge girders showed cracking both due to shear and flexure, the residual crack width was low: on average 0.10 mm. The final conclusion is that even if the test showed some issues that have to be revised, the system has the potential to demonstrate an outstanding performance under lateral seismic load.
10.14359/51733140
19-201
July 1, 2020
Michael P. Collins, Phillip T. Quach, and Evan C. Bentz
117
4
Thick reinforced concrete members not containing shear reinforcement can fail at shear stresses significantly lower than those specified by the 2014 ACI Code. This is because the traditional ACI shear provisions were based on tests of small specimens, and do not account for the size effect in shear. This paper focuses on an experimental program in which a 4000 mm (13 ft) thick slab strip specimen and a 300 mm (12 in.) deep companion specimen were constructed and tested to failure. These tests extend the range of a series of 17 such slab strip experiments previously tested at the University of Toronto. The results show that the 2014 ACI Code can give dangerously high estimates of shear capacity for very thick slabs not containing shear reinforcement. The research also shows that minimum shear reinforcement greatly increases both the strength and deformability of thick slabs.
10.14359/51724666
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