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International Concrete Abstracts Portal

Showing 1-10 of 457 Abstracts search results

Document: 

18-424

Date: 

September 1, 2019

Author(s):

Jacob Frappier, Khaled Mohamed, Ahmed Sabry Farghaly, and Brahim Benmokrane

Publication:

Structural Journal

Volume:

116

Issue:

5

Abstract:

The current study investigated the behavior of reinforced concrete deep beams with web openings. Seven deep beams were tested: five had web openings—of which three were reinforced with glass fiber-reinforced polymer (GFRP) bars and two reference specimens were reinforced with steel bars—and two solid deep beams, one with GFRP bars and one with steel bars as reference. The beams were 1200 x 300 mm in cross section and 5000 mm in span. The shear span-depth ratio (a/d) was 1.13. The openings in the beam webs were 304 mm high and 340 mm wide. Different GFRP and steel reinforcement configurations were provided around the web opening. The results were analyzed in terms of cracking pattern, mode of failure, load-deflection behavior, opening effect, and efficiency of the reinforcement configuration. The GFRP- and steel-reinforced solid deep beams exhibited similar resistance, while the GFRP-reinforced deep beams with openings had slightly lower capacity than the steel-reinforced ones. Strut-and-tie models (STMs) available in ACI and CSA design codes and the literature were assessed. The accuracy of each model was confirmed, revealing the applicability of the STMs for complex truss models as in deep beams with web openings.

DOI:

10.14359/51716774


Document: 

18-406

Date: 

September 1, 2019

Author(s):

Aishwarya Y. Puranam and Santiago Pujol

Publication:

Structural Journal

Volume:

116

Issue:

5

Abstract:

Building codes control the minimum and maximum amounts of longitudinal reinforcement in reinforced concrete (RC) elements to avoid brittle failure. A two-phase experimental investigation was conducted to reexamine the existing limits to allow the use of high strength steel reinforcement (HSSR) with fy > 80 ksi (550 MPa). The test results suggested that it is feasible to use HSSR (with fy up to 120 ksi [830 MPa]). Careful projection of existing limits to HSSR produced elements with similar toughness as those with conventional reinforcement (Grade 60, fy = 60 ksi [415 MPa]). The results presented also supported code provisions to allow the use of HSSR introduced in ACI 318-19.

DOI:

10.14359/51716762


Document: 

18-346

Date: 

September 1, 2019

Author(s):

Ahmed E. Salama, Mohamed Hassan, and Brahim Benmokrane

Publication:

Structural Journal

Volume:

116

Issue:

5

Abstract:

Recent years have seen a great interest in testing concrete slab-column connections reinforced with glass fiber-reinforced polymer bars (GFRP-RC). Yet, current fiber-reinforced polymer (FRP) codes and guidelines have not addressed the design of slab-column connections with FRP shear reinforcement. Results from an experimental investigation aimed at evaluating the effectiveness of glass fiber-reinforced polymer (GFRP) stirrups as shear reinforcement in edge slab-column connections reinforced with GFRP bars are presented. Four full-sized slabs with and without stirrups as shear reinforcement were tested to failure under combined vertical load and unbalanced moment. The effect of the GFRP stirrup type and extension on the punching shear response of the tested slab-column connections are analyzed and discussed. In addition, simplified design provisions to predicate the ultimate shear capacity of the tested specimens are proposed. The test results revealed that the presence of GFRP shear reinforcement as either closed or spiral stirrups within the slab around the column perimeter improved the punching-shear response of the tested connections. The results also indicated that the performance of the spiral stirrups was equivalent to or better than that of the closed stirrups in reducing the brittleness of the tested specimens with the same amounts of flexural and shear reinforcement. The proposed design provisions as extensions to those in CSA S806 design code yielded good, yet conservative predictions with an average Vtest/Vpred of 1.28 ± 0.24 for test specimens with FRP shear stirrups, as well as others with different types of FRP shear reinforcement found in the literature. This represents a step forward for engineers in designing two-way concrete slabs reinforced with FRP stirrups.

DOI:

10.14359/51716757


Document: 

18-319

Date: 

September 1, 2019

Author(s):

Jose Pacheco

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

The presence of uncontrolled or unexpected nonstructural cracking in reinforced concrete structures generally leads to conflict and disputes. The current industry practice aims to prevent or mitigate the presence of cracking at early ages (that is, plastic shrinkage, thermally induced cracking) or due to volumetric changes (restrained or drying shrinkage). However, cracking of concrete can still occur and lead to questioning the durability of concrete with prolonged service life expectations such as bridge decks, piers, or waterfront structures, to name a few. The effect of cracks on chloride penetration has been thoroughly studied, and evidence of the effect of cracks on accelerated ingress of chlorides is well established. Structural codes and guides, on the other hand, consider that the integrity of the concrete element is not significantly affected as long as the crack width does not exceed a recommended limit based on exposure conditions. Similarly, service life predictions based on chloride ingress modeling disregard the effect of cracks. Because crack-free concrete cannot be guaranteed, service life predictions that neglect the effect of cracks can be significantly inaccurate. A simplified approach is presented in this paper, where a correction to the chloride diffusion coefficient of concrete is performed to account for the effect of cracks. This correction is similar, in principle, to the so-called aging or decay coefficient in concrete. Results of Monte Carlo simulations on chloride ingress and estimations of the time-to-corrosion initiation are presented and discussed. Results indicate that a decrease of the reliability index (β), or an increase in the probability of failure (pf), can be calculated when accounting for the effect of cracks.

DOI:

10.14359/51716835


Document: 

18-295

Date: 

July 1, 2019

Author(s):

Ahmed Faleh Al-Bayati, Teck Leong Lau, and Leslie A. Clark

Publication:

Structural Journal

Volume:

116

Issue:

4

Abstract:

This paper presents test results of six one-tenth-scale micro-concrete waffle slabs subjected to edge punching shear in the presence of moment transfer perpendicular to the slab’s free edge. Although the observed punching failure mechanism of a waffle slab was found to be very similar to that of a flat slab; the shear capacity is reduced relatively because some of the potential failure surface is lost when it extends into the waffle section. Because the current codes of practice do not consider the punching shear mechanism of waffle slabs, comparisons with test results revealed that ACI 318-14, BS 8110, and Eurocode 2 overestimated the punching capacities of waffle slabs. An upper-bound plasticity theory model was proposed to predict the punching shear failure load, which gave good agreement with the tests. The proposed model assumes the concrete to be rigid perfectly plastic with the modified Mohr-Coulomb as failure criterion.

DOI:

10.14359/51715630


Document: 

18-267

Date: 

July 1, 2019

Author(s):

Eva O. L. Lantsoght, Cor van der Veen, Rutger Koekkoek, and Henk Sliedrecht

Publication:

Structural Journal

Volume:

116

Issue:

4

Abstract:

Previous research showed that the capacity of existing slab-between-girder bridges is larger than expected based on the punching shear capacity prescribed by the governing codes, as a result of compressive membrane action. A first series of fatigue tests confirmed that compressive membrane action also acts under cycles of loading. However, a single experiment, in which first a number of cycles with a higher load level and then with a lower load level were applied, seemed to indicate that this loading sequence shortens the fatigue life. This topic was further investigated in a second series of fatigue tests with three static tests and 10 fatigue tests. The parameters that were varied were the sequence of loading and the effect of a single or a double wheel print. The results show that the sequence of load levels does not influence the fatigue life.

DOI:

10.14359/51715563


Document: 

18-266

Date: 

July 1, 2019

Author(s):

A. Hadhood, H. M. Mohamed, B. Benmokrane, A. Nanni, and C. K. Shield

Publication:

Structural Journal

Volume:

116

Issue:

4

Abstract:

Recent years have seen a great interest in testing concrete columns reinforced with glass fiber-reinforced-polymer bars (GFRP-RC). Yet, current codes and guidelines have not addressed the design of GFRP-RC columns. This paper aims at providing a set of recommendations and provisions based on analytical investigations, past knowledge about steel-reinforced concrete columns, and correlations with the experimental results from several studies of GFRP-RC columns. A database of 144 experiments was assembled; the results are reported and analyzed. The assembled database includes a selected number of parameters that can represent numerous practical cases. Based on this study, the calculation of the effective flexural stiffness (EIeff) was assessed with several equations and compared to experiments. As a result, a modified expression is recommended for EIeff at the factored load level. The design axial and flexural strengths were developed based on four approaches that were recently assessed with nominal and experimental results. It was found that the experimental-to-design strength ratio varied from 1.43 to 2.09. The minimum and maximum reinforcement limits were reviewed against the experimental results to ensure the integrity of the GFRP bars. In addition, the limits in the recent editions of ACI 318 and CSA A23.3 on steel transverse reinforcement (ties and spirals) were reviewed and modified to fulfill the performance requirements of GFRP tied and spirally reinforced columns.

DOI:

10.14359/51715663


Document: 

18-250

Date: 

July 1, 2019

Author(s):

Sana Amir, Cor van der Veen, Joost C. Walraven, and Ane de Boer

Publication:

Structural Journal

Volume:

116

Issue:

4

Abstract:

Most Dutch bridges were constructed around the middle of the twentieth century and considering the fact that traffic has increased exponentially since, it is important to find out if these bridges are still safe for use. Experiments on a 1:2 scale were carried out in the laboratory of the Delft University of Technology to investigate the bearing capacity of transversely prestressed concrete bridge decks subjected to concentrated wheel loads. All the tests showed failure in punching shear at loads much higher than expected from the current codes. This paper presents the results of the experimental parametric study including the effect of the transverse prestressing level (TPL), location of the load, number of loads, size of the loading area (wheel print/loading plate), and influence of previous damage to the deck slab panel, on the bearing capacity.

DOI:

10.14359/51715565


Document: 

18-070

Date: 

July 1, 2019

Author(s):

Krešimir Nincevic, Lisa-Marie Czernuschka, Marco Marcon, and Roman Wan-Wendner

Publication:

Structural Journal

Volume:

116

Issue:

4

Abstract:

A large experimental campaign was completed with the objective to determine how concrete composition and age affect the tensile load capacity of mechanical anchors with concrete cone breakout, tested in three different normal-strength concretes. Structural tests for cast-in headed stud anchors were performed at 28 and 70 days and compared to results obtained on post-installed undercut anchors. The concretes were fully characterized in terms of Young’s modulus, compressive and tensile strength, and fracture energy. The evolution of the concrete compressive strength is consistent with the aging function proposed in codes. Because the history of environmental conditions influences the development of material properties with age, three different curing conditions are considered for the material characterization, including indoor moist-curing and outdoor storage with the slabs. The structural data clearly show a pronounced aging effect, even after normalization by compressive strength, regardless of the curing protocol considered.

DOI:

10.14359/51715575


Document: 

17-374

Date: 

July 1, 2019

Author(s):

Pietro G. Gambarova and Francesco Lo Monte

Publication:

Structural Journal

Volume:

116

Issue:

4

Abstract:

Six one-way reinforced concrete slabs, simply supported along the short sides by means of corbels (dapped ends), were recently tested for bending and shear behavior in Milan under two different crosswise load distributions and with three partially different reinforcement layouts in the supporting corbels and in the main body (size 2200 x 1300 mm [7.22 x 4.27 ft]; thickness/length ratio close to 1/14; corbel depth and overhang/length ratio close to 1/23). The tests in bending under the service loads and in shear up to and beyond the peak load show that load crosswise-distribution plays a minor role. In shear, the quite complex crack patterns in the D-regions close to the dapped ends clearly indicate the formation of very effective strut-and-tie systems if the bottom bars of the main body are bent up, and of shallow arch-and-tie systems if the same bars are straight. In the former case, a proper introduction of the bond along the tension bars of the corbels is a must to define the position of bond-related joints and to make strut-and-tie models more reliable in predicting the bearing capacity, while in the latter case, the design equations provided by the codes for constant-section shear-unreinforced beams (ACI 318, EC2, and fib Model Code 2010) prove to be adequate also in the case of corbels.

DOI:

10.14359/51715572


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