International Concrete Abstracts Portal

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International Concrete Abstracts Portal

Showing 1-10 of 405 Abstracts search results

Document: 

SP-333_07

Date: 

October 1, 2019

Author(s):

Martin Herbrand, Viviane Adam, Josef Hegger

Publication:

Special Publication

Volume:

333

Abstract:

Due to increased traffic loads and changes in the code provisions many highway bridges in Germany exhibit deficits in shear capacity according to current codes. The majority of these bridges’ structures comprises continuous concrete beams whose calculatory shear capacity is often exceeded by now. However, the actual shear capacity of prestressed concrete continuous beams is usually underestimated since the design procedures have been derived on the basis of single-span beam tests and neglect significant shear transfer mechanisms. In order to extend the service life of existing bridges, the reserves in the design procedures can be partially taken advantage of by the application of refined design approaches. For this reason, five shear tests on prestressed concrete continuous beams have been performed at the Institute of Structural Concrete of RWTH Aachen University in Germany. Within these tests, the influence of cross-section type (rectangular and I-shaped cross-section), load distribution (concentrated and distributed loads) and the shear reinforcement ratio are investigated. In this paper, the test results of three beams under concentrated loads will be presented.


Document: 

SP-332_01

Date: 

July 1, 2019

Author(s):

Keith Kesner and Kevin Coll

Publication:

Special Publication

Volume:

332

Abstract:

Evaluation of an existing structure is a task commonly performed by licensed design professionals. An evaluation can be required by a façade inspection ordinance, as part of a due-diligence process prior to the purchase of a structure, or prior to the development of rehabilitation or repair measures. Each of these project types will have differences in the evaluation protocol and portion of the structure to be examined – but in each example, the licensed design professional is expected to provide a minimum “standard of care” to the client and to protect the public. Therefore, in developing the evaluation protocol, a critical question facing the licensed design professional is how much investigative effort is required to complete the evaluation and ensure the evaluation provides a minimum standard of care. The standard of care for an evaluation of existing structures can broadly be defined as the level of effort that a reasonable and prudent licensed design professional would be expected to provide under similar circumstances. Given the range of structure types that can be encountered and the varying levels of damage and exposure conditions, determination of the scope of evaluation can be a difficult task for a licensed design professional. The following sections examine approaches used in industry codes and ordinances to help define a minimum standard of care for the evaluation of existing structures. Industry codes and ordinances to be examined will include the ACI 562-16 Code for Assessment, Repair and Rehabilitation of Existing Structural Concrete, FHWA bridge inspection requirements and building façade inspection standards and ordinances. Based upon these documents, items to be considered in establishing a “Standard of Care” in the evaluation of existing structures will be summarized.


Document: 

SP331-06

Date: 

February 1, 2019

Author(s):

Abheetha Peiris and Issam Harik

Publication:

Special Publication

Volume:

331

Abstract:

An exterior girder of a prestressed concrete bridge over Interstate 65 in Kentucky was damaged due to an over-height truck impact. The damaged section spanned two of the three northbound lanes of the highway. Two prestressing strands were severed and two additional strands were damaged by the impact. In addition, shear reinforcing bars in the vicinity of the impact were cut-off. CFRP Rod Panels (CRPs) were deployed to restore some of the load carrying capacity lost due to the severed prestressing tendons. CRP 195, with CFRP rods of 3.96 mm (0.156 in) diameter, having a capacity of 867 kN (195,000 lbs.) per 305 mm (1 ft.) width of panel, was selected for the flexural strengthening. A triaxial braided quasi-isotropic CFRP fabric was selected for shear strengthening and served as containment of crushed concrete in the event of future over-height impacts. Since the ACI and AASHTO Codes or Guides do not directly address the design with CRPs, strain limits based on debonding of the rods similar to externally bonded CFRP (EB-CFRP) are imposed when determining the retrofitted beam capacity. The load rating evaluation of the impacted beam, the retrofit analysis and design, and the field repair stages are presented and discussed.


Document: 

SP327-49

Date: 

November 1, 2018

Author(s):

Ahmed Abd El Fattah, Mukhtar Azeez, and Hayder A. Rasheed

Publication:

Special Publication

Volume:

327

Abstract:

FRP is customarily used to wrap concrete columns to increase their strength and strain capacities by providing extra confinement. Typically, steel hoops or spirals are used in constructed columns as mandated by codes. The behavior of retrofitted columns becomes thoroughly different because there are two systems with different mechanical response and interaction engaged in confinement. While most of the literature addressed concrete confined with FRP only, a limited number of studies and experimental cases accounted for both actions. This paper developed an axial stress-strain model which utilized geometric and mechanical properties of concrete, steel and FRP. The proposed work adopted Lam and Teng model for concrete confined with FRP, originally implemented in ACI 440.2R-17 guide, and calibrated its parameters against experimental curves. The proposed model correlates well with experimental cases that were collected from the literature.


Document: 

SP327-45

Date: 

November 1, 2018

Author(s):

Alvaro Ruiz Emparanza, Raphael Kampmann and Francisco De Caso y Basalo

Publication:

Special Publication

Volume:

327

Abstract:

One of the main reasons for the degradation of our infrastructure is steel corrosion in reinforced concrete. To com- bat that issue, alternative non-corrosive materials, such as fiber reinforced polymer (FRP) rebars, were developed and implemented as internal reinforcement for concrete structures. Because of significant physio-mechanical advantages (magnetic transparency, high strength, corrosion resistance, etc.), the adoption of FRP rebars increased rapidly through- out the last decades. Due to an increased material demand, the number of FRP rebar manufacturers grew, but each manufacturer started to develop proprietary products, with wide ranging properties — the industry is in need for guidance and unification. Therefore, this study aims to centralize the relevant information by (i) summarizing the globally available regulations, (ii) providing background data for the present production status, and (iii) listing the currently produced FRP rebars in an effort to compare their physio-mechanical properties. Analysis of the market showed that 27 manufacturers produce FRP rebars in 14 countries with diverse output quantities and different distribution logistics. The various production approaches lead to different rebar types with dissimilar surface properties and significant strength differences.


Document: 

SP327-44

Date: 

November 1, 2018

Author(s):

Emmanuel Ferrier, Carmelo Caggegi, and Laurent Michel

Publication:

Special Publication

Volume:

327

Abstract:

In design of structures, both the ultimate limit state (ULS) and the serviceability limit state of the structure must be verified. Carbon fiber reinforced polymer (CFRP) materials have high strength, and large amounts of CFRP are not needed for ULS. On the other hand, CFRP may be needed to introduce enough stiffness for meeting the serviceability design criteria and reduce the crack of concrete. The effects of externally bonded composite plates on the mechanical behavior of a cracked RC beam, loaded in flexure, are obtained by an experimental approach. The problem of crack width prediction is addressed. The model values are compared to experimental data obtained using a digital image correlation method. The crack width and spacing is measured as a function of load to analyze crack propagation. Finally, the study focuses on the validation of the codes model for calculating crack widths and curvatures in strengthened beams.


Document: 

SP327-42

Date: 

November 1, 2018

Author(s):

Morteza Khatibmasjedi, Antonio Nanni

Publication:

Special Publication

Volume:

327

Abstract:

This paper presents partial results of an international collaborative project named ‘SEACON’ that aims at demonstrating the safe and durable utilization of seawater and salt-contaminated aggregates (natural or recycled) for a sustainable concrete production when combined with noncorrosive reinforcement. Seawater and salt-contaminated aggregates use in reinforced concrete (RC) is currently prohibited by building codes due to corrosion of the steel reinforcement. In response to this challenge, concrete made with seawater and salt-contaminated aggregate is combined with noncorrosive reinforcement (i.e. Glass-Fiber-Reinforced-Polymer (GFRP) or stainless steel). The initial results presented herein evaluate the durability of GFRP bars embedded in concrete mixed with seawater and exposed to seawater at 60 °C (140 °F) as accelerated aging. The residual mechanical properties of the embedded GFRP bars after one-year exposure to accelerated conditioning were compared to pristine bars. The experimental results showed comparable performance between GFRP bars embedded in seawater concrete and pristine bars. In addition, the bond strength of GFRP bars in seawater and conventional concrete was measured by pull out testing after being aged for six months in the same accelerated conditioning. The bond strength of the GFRP bars embedded in seawater concrete was comparable to the ones in conventional concrete.


Document: 

SP327-20

Date: 

November 1, 2018

Author(s):

Pedro Silva and Ravi Kanitkar

Publication:

Special Publication

Volume:

327

Abstract:

The ACI440.2R document represents state-of-the-art design and construction guidelines for the strengthening of concrete structures using externally bonded FRP systems. A significant number of FRP field applications are related to seismic strengthening of existing reinforced concrete structures. The 2008 edition of ACI440.2R does not provide design guidance for the use of FRP in seismic applications. As such, ACI Committee 440 has developed seismic guidelines for inclusion in the newly released 2017 edition. The new seismic design guidelines include the most common applications observed in the industry, such as confinement of beam and column sections, as well as flexural and shear strengthening of concrete members. Since seismic retrofit can be based on a variety of codes and standards, these guidelines are intended to be compatible with the selected code or standard. The seismic guidelines are incorporated in a separate chapter within the ACI440.2R document but, where applicable, reference other chapters for design provisions. This paper summarizes common deficiencies found in existing reinforced concrete buildings and the mitigation of some of these deficiencies using FRP and the provisions of the 2017 edition of ACI 440.2R.


Document: 

CI4011Q&A

Date: 

November 1, 2018

Publication:

Concrete International

Volume:

40

Issue:

11

Abstract:

Can ACI codes, specifications, guides, and reports be referenced in building codes, project specifications, or contract documents?


Document: 

SP328-06

Date: 

September 12, 2018

Author(s):

Perry Adebar

Publication:

Special Publication

Volume:

328

Abstract:

Presents the background to Canadian Standard CSA A23.3 requirements for design of concrete wall buildings for seismic shear. Design provisions are simplified versions of general procedures that can be used to do refined calculations when needed. Design of squat walls utilizes a variable angle truss model with shear resistance of cracked concrete Vc=0 and inclination of diagonal compression θ chosen freely. Contribution of distributed vertical reinforcement to overturning resistance depends on wall height-to-length ratio. For flexural walls, θ used to determine steel contribution Vs depends on axial compression applied to wall, while Vc and maximum shear force to prevent diagonal crushing depend on inelastic rotation of wall. Thus, drift capacity of flexural walls may be limited by shear failure modes. CSA A23.3-2014 permits a lower-bound estimate of higher mode shear demand because analysis procedures do not account for shear ductility, maximum shear demand occurs during a single short pulse, and maximum shear force demand usually does not occur at the same time as maximum flexural demands. Shear strains of flexural walls may significantly increase interstory drifts at lower levels of a building where gravity-load columns are less flexible. CSA A23.3-2014 requires that gravity-load frames be design for the increased interstory drift demands.


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