International Concrete Abstracts Portal

Showing 1-5 of 53 Abstracts search results

Document: 

23-198

Date: 

January 1, 2025

Author(s):

Sergio M. Alcocer, Ghassan Almasabha, Julian Carrillo, Shih-Ho Chao, and Adam S. Lubell

Publication:

Structural Journal

Volume:

122

Issue:

1

Abstract:

Recent research data was evaluated with the aim of extending the applicability of using deformed steel fiber-reinforced concrete (SFRC) to enhance the shear strength of beams and one-way slabs. Experimental results were assessed for influences on the shear strength of SFRC members that do not contain stirrups of factors, including size effect, concrete density (normalweight and lightweight) and compressive strength, fiber-volume fraction (Vf), and the longitudinal steel reinforcement ratio. Estimates of steel stresses in longitudinal bars at the time of shear failure were carried out to identify differences in members with distinct longitudinal steel ratios and bar grades, consistent with the range of flexural design parameters in ACI 318-19. Results of these analyses and a reliability investigation of design equations applicable to members without fibers were used for proposing new provisions for the shear design of SFRC beams and one-way slabs based on the ACI 318-19 shear-strength model.

DOI:

10.14359/51742138


Document: 

23-216

Date: 

July 1, 2024

Author(s):

Jacob Yager, Joshua Woods, Evan C. Bentz, and Neil A. Hoult

Publication:

Structural Journal

Volume:

121

Issue:

4

Abstract:

Supplementary cementitious materials (SCMs) have been used to replace portland cement and are used in conjunction with advanced mixture design approaches in reinforced concrete for the purpose of creating low-carbon concrete (LCC). In this research, functionally graded concrete (FGC) was used with LCC to provide strength and serviceability for reinforced concrete one-way slab strips by placing a higher-strength/stiffness concrete in the flexural compression region and LCC in all other locations. The behavior of FGC slab strips with varied connection types, placement methods, reinforcement ratios, and ages were compared to uniform specimens with different types of LCC and conventional concrete. Behavior was evaluated through load deflection, cracking, and strains during four-point bending, which were measured using distributed sensing, including distributed fiber-optic sensing and digital image correlation. Limited differences in behavior existed among specimens with the same reinforcement ratios. However, some FGC specimens had higher stiffness and ultimate capacity. Implications of FGC, including cracking behavior at the interface, are also discussed.

DOI:

10.14359/51740715


Document: 

22-046

Date: 

January 1, 2023

Author(s):

H.-J. Lee, R. D. Lequesne, A. Lepage, J.-X. Lin, J.-C. Wang, and S. Y.-L. Yin

Publication:

Structural Journal

Volume:

120

Issue:

1

Abstract:

This paper reports results from four large-scale interior beam column connections without transverse beams or slabs tested under reversed cyclic displacements. The specimens, which included the first of interior beam-column connections constructed with Grade 100 (690) reinforcement with bar deformations similar to those available in U.S. practice, had Grade 60 or 100 (420 or 690) bars, 4 or 10 ksi (28 or 69 MPa) concrete, and varied column depthto-beam bar diameter ratios. The specimens all exhibited strengths greater than the nominal strength, retained at least 80% of their strength to drift ratios exceeding 5%, and exceeded ACI 374 acceptance criteria at a 3% drift ratio for components of special moment frames, demonstrating that well-detailed joints constructed with high-strength materials behave satisfactorily. The data add evidence that joints constructed with high-strength concrete exhibit less bond decay, and recommendations are made for accounting for this effect in design. Results from the specimen constructed with normal-strength materials, considered in the context of prior tests, suggest a need to increase the minimum joint depth for special moment frames. Considerable improvement in behavior associated with reduced bond damage within the joint is obtained from a 20% increase in the minimum column depth-to-beam bar diameter ratio required in ACI 318-19.

DOI:

10.14359/51737141


Document: 

21-071

Date: 

November 1, 2022

Author(s):

Yail J. Kim and Jun Wang

Publication:

Structural Journal

Volume:

119

Issue:

6

Abstract:

This paper presents the thermal performance of one-way slabs reinforced with glass fiber-reinforced polymer (GFRP) bars, including ordinary concrete, high-strength concrete (HSC), and ultra-high-performance concrete (UHPC). A state-of-the-art simulation technique, called agent-based modeling, is adopted to implement the differential equations of heat transfer in conjunction with ASTM E119 standard fire. Alongside the thermal absorptivity of the concrete materials, the slabs’ time-dependent responses are predicted during a fire rating of 3 hours with and without vermiculite-gypsum insulation. A parametric study is conducted to propose design recommendations. When the external temperature ascends, the conductivity and density of all concrete types increase, whereas their specific heat declines. The temperature profiles of the slab sections change over time and the mitigation of thermal gradients reduces the heat flux differentials near the slab surface. The addition of the insulation layers retards the propagation of thermal distress, which is particularly beneficial for the UHPC. Following the interface deterioration between the concrete and the reinforcement, the degraded modulus of GFRP influences the flexural capacity of the slabs. At a 3-hour fire rating, the remaining capacity of the slab without insulation varies from 34 to 46% of the intact capacity, while the capacity increases up to 75% for the insulated slab. Care should be exercised if either UHPC (180 MPa [26,100 psi]) or high-modulus GFRP (60 to 100 GPa [8700 psi to 14,500 ksi]) is used because premature GFRP rupture can take place before reaching the intended fire rating. Practice guidelines are suggested to accomplish the performance-based design.

DOI:

10.14359/51733141


Document: 

21-180

Date: 

July 1, 2022

Author(s):

Raphael Palmier Manfredi, Flávio de Andrade Silva, and Daniel Carlos Taissum Cardoso

Publication:

Structural Journal

Volume:

119

Issue:

4

Abstract:

The work in hand presents the results of an experimental investigation on the punching shear performance of steel fiber-reinforced concrete (SFRC) slabs-on-ground, a problem that has received little attention worldwide. In the first part of the experimental program, residual strengths are obtained according to different methodologies, namely EN 14651 and ASTM C1609, considering normal concrete matrixes reinforced with hooked-end steel fibers in contents of 20, 30, and 40 kg/m3 (33.71, 50.56, and 67.42 lb/yd3). Then, three slabs-on-ground were fabricated (one for each content) and tested for a central single-point load and it was confirmed that the use of fibers increased ultimate load and ductility. The results are compared with those obtained using the predictions of the fourth edition of Technical Report 34 (TR 34) issued by The Concrete Society, and differences of less than 10% are observed. The influence of rotation and relative displacement between the central shear cone and surrounding slab are studied, confirming the relevance of the latter to the crack kinematics. A simple mechanical model is proposed, revealing that the contributions of each load-transfer mechanism according to TR 34 are unrealistic and that the fiber action responds roughly for 40% of the capacity. Finally, design recommendations are proposed to account in a meaningful way for the actual contributions of concrete, fibers, and subgrade to the punching shear strength.

DOI:

10.14359/51734520


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