International Concrete Abstracts Portal

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International Concrete Abstracts Portal

Showing 1-5 of 290 Abstracts search results

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


Document: 

17-275

Date: 

July 1, 2018

Author(s):

Haider M. Al-Jelawy, Kevin R. Mackie, and Zachary B. Haber

Publication:

Volume:

115

Issue:

4

Abstract:

Accelerated bridge construction (ABC) is being increasingly used in new bridge construction and repair. For bridge substructure elements, ABC typically requires connections, such as mechanical couplers, between prefabricated elements where moment demands are largest. Grouted sleeves (GSs) offer good construction tolerances and load transfer between precast concrete elements. Therefore, they have gained interest for use in ABC in seismic regions. Large-scale precast column models using GS splices were designed and tested using a shifted plastic hinge (SPH) concept to minimize the damage in the footing and retain the column ductility. The testing matrix considered aspect ratio, moment gradient, and splicing details. Results showed that SPH can be used for flexural and flexural-shear columns; plastic hinging formed above the sleeve region and footing dowels remained elastic to minimize footing damage. Each precast column exhibited good ductility and energy dissipation, and formed slightly shorter SPH length compared with conventional columns.

DOI:

10.14359/51702233


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