International Concrete Abstracts Portal

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International Concrete Abstracts Portal

Showing 1-5 of 291 Abstracts search results

Document: 

18-021

Date: 

January 1, 2019

Author(s):

Youngjae Choi and Shih-Ho Chao

Publication:

Volume:

116

Issue:

1

Abstract:

This paper presents an experimental study on the seismic performance of reinforced concrete (RC) perimeter interior special moment frames (SMFs) that use high-performance fiber-reinforced concrete (HPFRC) in joint and beam plastic hinge regions. This research evaluates the feasibility of using both HPFRC joint and beams as major sources of energy dissipation in an effort to reduce overall damage and repair cost after earthquakes and to provide ease of construction for beam-column connections. A balanced damage concept was used so the energy dissipation was shared by the joint and beam plastic hinges, thereby preventing severe damage from occurring to the beams. This concept together with the mechanical properties provided by HPFRC, including high shear and bond strength, reduce the need of placing a large number of transverse reinforcement in the joint and beam plastic hinge regions. A full-scale HPFRC slab-beam-column (SBC) subassemblage designed with this concept was tested under large displacement reversals. This specimen used a small amount of transverse reinforcement (approximately 20% of that used in a typical RC joint) in the joint and no transverse reinforcement in the beam plastic hinge regions, thus significantly enhancing the constructability. A counterpart conventional RC specimen compliant with ACI 318-14 was tested under the same loading protocol. Both specimens showed stable hysteretic responses up to 3.5% column drift ratio without significant strength degradation, which meets the collapse prevention structural performance according to the criteria given in ACI 374. Experimental results show that the damage in the HPFRC specimen was distributed in both joint and beam ends, whereas the conventional RC specimen had severe damage concentrated in the beam plastic hinging regions. This research proves the feasibility of using ductile HPFRC joint to dissipate seismic energy, thereby balancing the damage between the joint and beams.

DOI:

10.14359/51710875


Document: 

17-181

Date: 

November 1, 2018

Author(s):

A. C. Altunısık, O. S. Karahasan, A. F. Genç, F. Y. Okur, M. Günaydın, E. Kalkan, and S. Adanur

Publication:

Volume:

115

Issue:

6

Abstract:

The aim of this paper was to determine the effect of fiber-reinforced polymer (FRP) strengthening on the dynamic characteristics of reinforced concrete (RC) frames using ambient vibration-based automated model updating procedure. Four different structural conditions were examined: undamaged, damaged, “repaired with injections”; and “strengthened with FRP composites”. Ambient vibration tests were conducted to extract the experimental dynamic characteristics using enhanced frequency domain decomposition (EFDD) and stochastic subspace identification (SSI) methods. To validate the experimental results, an initial finite element (FE) model was constructed and numerical dynamic characteristics obtained. To eliminate the differences between initial FE and experimental results, global and sensitivity-based automated model updating procedures were applied to account for various uncertain parameters. The maximum differences were reduced from 38.38% to 4.14% and 0.21% with global and automated model updating. The updated FE model was used as the initial model for the damaged condition. This procedure was followed for each structural condition in turn to demonstrate the effect of FRP strengthening.

DOI:

10.14359/51706894


Document: 

16-129

Date: 

November 1, 2018

Author(s):

Katelyn S. Low, Gloriana Arrieta Martinez, David M. Wald, and Oguzhan Bayrak

Publication:

Volume:

115

Issue:

6

Abstract:

As concrete infrastructure ages or is repurposed, there is an increasing need for efficient retrofit solutions. A possible retrofit technique to increase the capacity of members with deficient tension lap splices is to use post-installed, undercut anchors. The anchors can provide active confinement in the splice region. This solution requires access to only one face of the reinforced concrete element being repaired, greatly facilitating its implementation in existing structures. To evaluate this retrofit solution, four large-scale tests on beam specimens were completed at the University of Texas at Austin. One specimen contained the full tension lap splice length required by ACI 318-71 provisions and served as a control specimen. The other three specimens contained half of that tension lap splice length. One of the latter specimens was tested without a retrofit to determine baseline behavior while the other two were retrofitted. Results from these tests indicated that post-installed anchors could enhance the strength of members with deficient lap splices up to half the specified length.

DOI:

10.14359/51702378


Document: 

17-480

Date: 

September 1, 2018

Author(s):

Yao Luan, Osamu Sanada, and Hiroshi Mutsuyoshi

Publication:

Volume:

115

Issue:

5

Abstract:

The durability of concrete structures is increasingly being compromised by corrosion of the steel reinforcement resulting from chloride attack. Although mortar containing a nitrite compound is often used in repair work to inhibit corrosion, a harmless and more economical material is sought. The authors investigated adding an ion-exchange resin (IER) to mortar as a possible way to remove chloride from old concrete. IERs, which are widely used in water purification, are capable of exchanging chloride ions in aqueous condition. The anion exchange capacity of an IER in cement solution is experimentally investigated. Then, two chloride diffusion experiments, one involving immersion and drying cycles and the other inverse diffusion from a mortar substrate, are carried out with IER mortar. Chloride profiles are determined by titration and the chlorine distribution is visualized. The results confirm that the IER accelerates chloride diffusion in the mortar as a result of its ability to exchange chloride ions.

DOI:

10.14359/51706845


Document: 

17-196

Date: 

September 1, 2018

Author(s):

D. G. Mapa, A. Markandeya, A. Sedaghat, N. Shanahan, H. DeFord, K. A. Riding, and A. Zayed

Publication:

Volume:

115

Issue:

5

Abstract:

Jointed plain concrete pavement (JPCP) replacement slabs can experience early-age cracking from early-age volume change. These slabs are often made of high-early-strength (HES) concrete characterized by high cement content and low water-cement ratio (w/c), which can result in large temperature rise and high levels of autogenous shrinkage, and ultimately an elevated cracking potential. This study investigated the effects of reduced paste content and base restraint minimization on reducing concrete early-age cracking potential. The effect of each of these measures was evaluated in place by measuring the stress and temperature development in concrete test slabs instrumented with concrete stressmeters and thermocouples. Calorimetry studies and mechanical properties testing were used with modeling software to assess field trends. The findings indicated that it is possible to achieve higher strengths and lower stresses with low-paste mixtures. Changes in concrete stress during the first 24 hours after placement, due to moisture loss to the base, were seen in slabs with polyethylene sheet or geotextile fabric underneath the slab.

DOI:

10.14359/51702241


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