International Concrete Abstracts Portal

Showing 1-5 of 31215 Abstracts search results

Document: 

24-372

Date: 

December 19, 2024

Author(s):

Ariel A. Suselo, Wassim M. Ghannoum, Adolfo B. Matamoros

Publication:

Structural Journal

Abstract:

This paper presents important revisions to the shear strength provisions for seismic assessment of reinforced concrete columns in the ACI 369.1-22 Code. A new formulation based on a strut-and-tie model is introduced to expand the range of application of existing provisions to include columns with shear span-to-depth ratios lower than 2. Revisions are proposed to the slender column provisions to improve their precision, reduce estimate bias, and eliminate instances where they produce unconservative estimates of shear strength. The proposed relations were calibrated using shear strength data from 94 shear-critical rectangular columns subjected to load reversals from a database developed at UTSA.

DOI:

10.14359/51745487


Document: 

24-263

Date: 

December 19, 2024

Author(s):

Anmol S. Srivastava, Girish N. Prajapati, and Brahim Benmokrane

Publication:

Structural Journal

Abstract:

The present study demonstrates the feasibility of using longitudinal hybrid reinforcement in concrete columns in seismic zones. In this research, four concrete columns were constructed and subjected to quasi-static cyclic loading, featuring a combination of steel and glass fiber-reinforced polymer (GFRP) longitudinal reinforcement. Two reference columns were fabricated and reinforced in the longitudinal direction with steel bars. These columns had a 400 × 400 mm (15.8 × 15.8 in.) cross-section and 1850 mm (72.8 in.) overall height. All the columns were reinforced with GFRP crossties and spirals in the horizontal direction. The variable parameters were the transverse reinforcement spacing, axial load ratio, and column configuration. The outcomes of this research clearly showed that reinforced concrete (RC) columns that are properly designed and detailed longitudinally with hybrid reinforcement (GFRP/steel) could achieve the drift limitation in building codes with no strength degradation. Further, these hybrid-RC columns displayed enhanced energy dissipation capacity, superior ductility, and improved post-earthquake recoverability compared to columns reinforced longitudinally with steel. The promising results of this study represent a step towards the use of longitudinal hybrid reinforcement in lateral-resisting systems.

DOI:

10.14359/51745488


Document: 

24-169

Date: 

December 19, 2024

Author(s):

Eman Ibrahim, Abdoulaye Sanni B., Ahmed E. Salama, Ammar Yahia, and Brahim Benmokrane

Publication:

Structural Journal

Abstract:

This study investigated the serviceability behavior and strength of polypropylene-fiber (PF) reinforced self-consolidating concrete (PFSCC) beams reinforced with glass fiber-reinforced polymer (GFRP) bars. Five full-scale concrete beams measuring 3100 mm long × 200 mm wide × 300 mm deep (122.1 × 7.9 × 11.8 in.) were fabricated and tested up to failure under four-point bending cyclic loading. Test parameters included the longitudinal reinforcement ratio (0.78, 1.18, and 1.66%) and polypropylene fiber (PF) volume (0, 0.5, and 0.75% by concrete volume). The effect of these parameters on serviceability behavior and strength of the test specimens is analyzed and discussed herein. All the beams were evaluated for cracking behavior, deflection, crack width, strength, failure mode, stiffness degradation, and deformability factor. The test results revealed that increasing the reinforcement ratio and PF fiber volume enhanced the serviceability and flexural performance of the beams by effectively restraining crack widths, reducing deflections at the service and ultimate limit states, and decreasing residual deformation. The stiffness exhibited a fast-to-slow degradation trend until failure for all beams, at which point the beams with a higher reinforcement ratio and fiber volume evidenced higher residual stiffness. The cracking moment, flexural capacities, and crack width of the tested beams were predicted according to the North American codes and design guidelines and compared with the experimental ones. Lastly, the deformability for all beams was quantified with the J-factor approach according to CSA S6-19. Moreover, the tested beams demonstrated adequate deformability as per the calculated deformability factors.

DOI:

10.14359/51745489


Document: 

24-134

Date: 

December 19, 2024

Author(s):

Jung-Yoon Lee and Min Jae Kang

Publication:

Structural Journal

Abstract:

Reinforced concrete (RC) structure design codes stipulate various design limits to prevent the brittle failure of members as well as ensure serviceability. In the structural design of RC walls, the maximum shear strength is limited to prevent sudden shear failure due to concrete crushing before the yielding of shear reinforcement due to over-reinforcement. Despite the increase in wall shear strength provided by a compression strut, the maximum shear strength limit for walls in the ACI 318-19 code is the same as the maximum torsional strength. Consequently, the shear strength of large-sized walls with high-strength concrete is limited to an excessively low level. The ACI 318-19, Eurocode 2, CSA-19, and JSCE-17 standards provide similar equations for estimating wall strength, but their maximum shear strength limits for walls are all different. In this study, experimental tests were conducted on nine RC wall specimens to evaluate the maximum shear strength. The main variables of the specimens were the shear reinforcement ratio, compressive strength of concrete, and the failure mode. The experimental results showed that the maximum load was reached after the yielding of shear reinforcement even when the shear reinforcement ratio was 1.5 times higher than the maximum shear reinforcement ratio specified in the ACI 318-19 code. In addition, the measured shear crack width of all specimens at the service load level was less than 0.42 mm (0.017 in.). The shear strength limits for walls in the current codes were compared using 109 experimental results failing in shear before flexural yielding or shear friction failure, assembled from the literature. The comparison indicated that the ACI 318-19 code limit underestimates the maximum shear strength of walls, and it particularly underestimates the maximum shear strength of walls with high-strength concrete or barbell-shaped cross-sections. Additionally, this study proposes an equation for estimating the maximum shear strength limit of walls based on the truss model. The proposed equation predicted the maximum shear strength of RC walls with reasonable accuracy.

DOI:

10.14359/51745490


Document: 

24-046

Date: 

December 19, 2024

Author(s):

Xinmin Zhang, Chaoyuan Wu, Zengwei Guo, Fanxiang Xia, Xianhu Ruan

Publication:

Structural Journal

Abstract:

It is well known that the estimates of most shear capacity prediction models for reinforced concrete (RC) components are of high dispersion, due to its elaborate failure mechanism and elusive. A probability prediction model is more appropriate for estimating the shear capacity of RC members than a deterministic prediction model. Therefore, this study proposed a probabilistic model to evaluate the shear capacity of RC T-beams and employed a Bayesian-Markov Chain Monte Carlo (MCMC) approach to determine the posterior parameter in the shear strength prediction model by Bayesian updating. The analysis results indicate that the probabilistic model achieves minimal variance, offering the most accurate predictions that closely match test data compared with other prediction models. The shear capacity of the T-beam increases with changes in flange width and flange height ratio but remains constant once beyond a certain level. The shear capacity varies rapidly when the shear-span ratio (λ) is less than 2.5 or larger than 4.0, due to a notable shift in the failure mechanism. Besides, the shear capacity raises linearly by increasing the characteristic value of stirrups (ρvfyv).

DOI:

10.14359/51745491


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