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International Concrete Abstracts Portal

Showing 1-10 of 388 Abstracts search results

Document: 

17-254

Date: 

May 1, 2019

Author(s):

Duo Zhang and Yixin Shao

Publication:

Materials Journal

Volume:

116

Issue:

3

Abstract:

Carbonation curing has demonstrated potential of improving concrete performance while facilitating carbon dioxide utilization. However, reinforcement corrosion behavior in carbonation-cured concrete has not been documented. This paper presents a study on chloride-induced corrosion in reinforced concrete subjected to carbonation curing. A special carbonation curing process was developed for precast non-prestressed applications. Performance of carbonation curing was evaluated by concrete compressive strength, pH value, and carbon dioxide uptake, while corrosion resistance of the carbonation-cured concrete was assessed by reinforcing bar mass loss and concrete chloride content. To understand the mechanism, concrete and cement paste were further characterized using mercury intrusion porosimetry, absorption, and electrical resistivity tests. Micromorphology was assessed by scanning electron microscopy. It was found that apart from rapid early-age strength gain, carbonation curing could significantly reduce chloride permeation in concrete concerning both total and free chloride contents. It was attributed to the reduced pore size and pore volume by calcium carbonate precipitation. With subsequent 28-day hydration, the carbonation-cured concrete displayed a pH over 12.0 at the surface of steel reinforcing bars and a micromorphology similar to the non-carbonated reference. The direct corrosion tests showed that the corrosion-induced mass loss of steel reinforcing bar was lessened by 50% in concrete subjected to carbonation curing.

DOI:

10.14359/51714461


Document: 

18-085

Date: 

March 1, 2019

Author(s):

Kai Qian and Bing Li

Publication:

Structural Journal

Volume:

116

Issue:

2

Abstract:

The casualties and economic loss in historic events have revealed that progressive collapse performance of buildings has to be evaluated in structural design to prevent such disastrous events. Integrity and resilience are important characteristics for buildings to prevent total collapse or disproportionate collapse once an unpredictable terrorism event unfortunately occurs. Compared to the extensive studies on behavior of cast-in-place reinforced concrete (RC) buildings for progressive collapse resistance, there is less research on precast concrete (PC) buildings to mitigate progressive collapse. Thus, in this study, three one-story, two-bay largescale frame-floor subassemblies (one RC and two PC) are tested under pushdown loading regime to investigate the effect of PC floor units and transverse beams on progressive collapse resilience of PC moment-resisting frames. It is found that the PC beams and slab systems could provide substantial compressive arch action and compressive membrane action, similar to the cast-in-place RC buildings. However, as PC slabs are discontinuous, insignificant tensile membrane action is able to develop in PC slab systems and the ultimate load capacity in enormous deformation stage is mainly attributed to the catenary action developed in PC beams.

DOI:

10.14359/51710878


Document: 

17-299

Date: 

March 1, 2019

Author(s):

Michael R. Brandes and Yahya C. Kurama

Publication:

Structural Journal

Volume:

116

Issue:

2

Abstract:

This paper describes an experimental investigation on the ultimate load behavior of flexure-critical precast/prestressed concrete beams that use recycled concrete aggregates (RCAs) as replacement for coarse natural aggregates (for example, crushed stone, gravel). Specifically, the measured results from 18 simply supported, normal strength concrete pretensioned beam test specimens are presented and compared with predictions from nonlinear numerical models and existing code methods for conventional concrete. These 18 specimens were obtained by saw-cutting nine longer beams that were previously subjected to sustained service-level loads. The subsequent ultimate load tests of the saw-cut beams were conducted in two series of nine specimens each, with normalized moment-to-shear ratios of 7.6 and 3.6, respectively, defined as the distance from the simple support to the point of load application divided by the depth to the prestressing strands. The other experimental parameters (tested in selected combinations as described in the paper) were the aggregate replacement level (0%, 50%, and 100% by volume), two sources of high-quality RCA (from rejected precast members and a construction demolition recycling yard), and two different levels of prestressing. In general, the use of RCA had a relatively small (as compared with the level of aggregate replacement) effect on the overall ultimate load-versus-deflection behavior of the beams or on the progression of failure. Importantly, the ability of closed-form code design methods and nonlinear numerical models to predict the measured behaviors of the beams was not significantly affected by the level of aggregate replacement.

DOI:

10.14359/51713287


Document: 

17-454

Date: 

January 1, 2019

Author(s):

Ahmed K. El-Sayed, Abdulaziz I. Al-Negheimish, and Abdulrahman M. Alhozaimy

Publication:

Structural Journal

Volume:

116

Issue:

1

Abstract:

Prestressed, precast concrete hollow-core slabs (HCS) are plant-fabricated members with prestressing strands serving as the primary reinforcement. Shear resistance of such slabs is provided by concrete only because HCS units have no shear reinforcement. Recent studies indicated unconservative predictions for the web shear strength of deep HCS (thickness > 315 mm [12.4 in.]) using the ACI 318-05 equation. This paper investigates web shear capacity of a total of 24 HCS having depths ranging from 200 to 500 mm (7.87 to 19.68 in.). All slabs were manufactured using the dry-cast (extrusion) method and were provided by three different suppliers. The comparison of ACI 318-05 predictions with the obtained web shear strength of the tested slabs showed conservative predictions for shallower slabs, with the level of conservatism decreasing with the increase of slab depth. Moreover, the predictions were unconservative for deeper slabs with thicknesses of 470 and 500 mm (18.5 and 19.68 in.). On the other hand, ACI 318-14 web shear design provisions for HCS yielded very conservative predictions for the test deep slabs. Analysis of web shear strength of the tested slabs was carried out against possible causes of the unconservative ACI 318-05 predictions associated to deeper HCS. Based on that analysis, a modification to the ACI 318-05 web shear design equation was proposed and verified using the test data.

DOI:

10.14359/51706919


Document: 

16-414

Date: 

January 1, 2019

Author(s):

Douglas J. Provost-Smith, Mohamed Elsayed, and Moncef L. Nehdi

Publication:

Structural Journal

Volume:

116

Issue:

1

Abstract:

The grouted dowel connection has been simple, cost-effective, and widely used in precast concrete structural systems. The grouted bar length in this connection is currently designed similarly to a regular steel bar in reinforced concrete. This underestimates the connection’s bond strength, thus resulting in excessive connection length. The effect of the duct’s presence in this connection is examined in the present study and was found to be crucial in generating a considerable confinement effect and relatively larger bond stress than accounted for in current design codes. Full-scale pullout tests were performed, and their results were compared with relevant data in the open literature to develop a more accurate design equation for predicting the required dowel development length. The equation was found to produce results three times smaller than that determined by the ACI 318-14 code while being desirably 10% more conservative than equations proposed in previous research.

DOI:

10.14359/51710860


Document: 

17-422

Date: 

November 1, 2018

Author(s):

Woo-Young Lim, Thomas H.-K. Kang, and Sung-Gul Hong

Publication:

Structural Journal

Volume:

115

Issue:

6

Abstract:

Given that current code provisions do not include a detailed design method for either precast or monolithic concrete walls with steel coupling beams, experimental and analytical studies of precast concrete (PC) wall-steel coupling beam systems were carried out. For the experimental part, large-scale cyclic tests of PC wallsteel beam connection subassemblies were performed with a test parameter of reinforcement details in the PC wall and all the same other design parameters such as the embedment length of steel section in the PC wall and the size and end connection details of the steel coupling beam. The overall design methodology for the said systems was first discussed; the seismic behavior of each test specimen with different reinforcement details was investigated; and using the test results and analytical methods, adequate seismic details were finally proposed. The test results indicate that the reinforcement details in the PC wall had a substantial effect on the seismic behavior of the tested specimens, and that the suggested reinforcement details performed very well under reversed cyclic inelastic deformations.

DOI:

10.14359/51702414


Document: 

15-186

Date: 

November 1, 2018

Author(s):

Douglas Tomlinson and Amir Fam

Publication:

Structural Journal

Volume:

115

Issue:

6

Abstract:

The axial load-moment interaction diagram for a 2.7 m (106 in.) long partially composite precast concrete sandwich panel was developed using five full-scale tests and nine stub specimens. The load-bearing sandwich panel comprised a ribbed structural wythe and a façade wythe connected through angled steel shear connectors passing through a layer of insulation. The panels were first subjected to axial compression loads applied to the structural wythe only, then were loaded transversely in flexure while subjected to the various levels of axial loads. One panel was only loaded axially to failure. At axial loads between the classical tension- and compression-controlled failure regions in the interaction curve, a third failure mode unique to sandwich panels was observed—namely, shear connection failure by excessive slip and yielding of connectors. This failure mode dissipated energy similar to conventional flexural tension failure. The interaction curve of the panel was compared to analytical interaction diagrams developed for the cases of fully composite and noncomposite panels. The study considered second-order effects from slenderness of the panel. Also, the location of the effective centroid of the partially composite panel was established to calculate the end eccentricity of the axial load, which contributes to the total moment. The level of composite action was assessed using a variety of methods. Based on the strength method, composite action decreased from 87% in pure flexure to 11% at an axial load equal to 31% of the pure axial capacity of the structural wythe.

DOI:

10.14359/51710834


Document: 

17-275

Date: 

July 1, 2018

Author(s):

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

Publication:

Structural Journal

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


Document: 

17-001

Date: 

July 1, 2018

Author(s):

Regina N. Waweru, Guillermo Palacios, and Shih-Ho Chao

Publication:

Structural Journal

Volume:

115

Issue:

4

Abstract:

The ability of a composite beam to act as a monolithic member relies heavily on the bond between the precast beam and the cast-in-place (CIP) slab. Insufficient anchorage of the interface reinforcement could lead to direct pullout due to localized fracture of the surrounding concrete, thereby failing to develop the reinforcement’s yield stress. The short embedded length of approximately 2 in. (50.8 mm) used for interface shear reinforcement is a common practice for the box and slab bridge beams in 70% of the states in the United States. In this study, 18 push-off specimens were tested to evaluate the effect of clamping action of reinforcement on the friction component of the interface (or “horizontal”) shear capacity. In addition, 24 pullout specimens were tested to evaluate the effect of width and bend angle on the pullout strength of interface shear reinforcement. The tests conducted in this research indicated that the American Association of State Highway and Transportation Officials (AASHTO) equation used to account for interface shear in composite concrete beams can overestimate the contribution of the interface shear reinforcement to the friction force for composite beams with a short embedded length less than 4 in. (101.6 mm). Experimental results indicate that, while the clamping force is considerably lower for short embedded length, the presence of the reinforcement effectively engages the concrete in the CIP slab, which enhances the interlocking action and, hence, the overall shear resistance. A modification to the current AASHTO equation is proposed to provide more accurate estimation of the friction force from interface shear reinforcement with a short embedded length.

DOI:

10.14359/51702061


Document: 

16-399

Date: 

July 1, 2018

Author(s):

Marianna Ercolino, Crescenzo Petrone, Gennaro Magliulo, and Gaetano Manfredi

Publication:

Structural Journal

Volume:

115

Issue:

4

Abstract:

A systematic parametric study is performed to both (a) investigate the influence of P-Δ effects on the seismic response of reinforced concrete (RC) precast one-story structures; and (b) assess the efficiency of the corresponding code provisions. At this aim, different design approaches are considered to critically review current design provisions included in current building codes with particular focus on Eurocode 8. Numerical analyses demonstrate the significance of the P-Δ effects on the seismic demand in precast structures in terms of displacement ductility. A modification of the approach of current building codes is proposed, which is demonstrated to ensure both a safer behavior and more economic structures.

DOI:

10.14359/51701915


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