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International Concrete Abstracts Portal

Showing 1-5 of 31 Abstracts search results

Document: 

SP356_11

Date: 

October 1, 2022

Author(s):

Ahmed G. Bediwy and Ehab F. El-Salakawy

Publication:

Symposium Papers

Volume:

356

Abstract:

Deep beams are common elements in concrete structures such as bridges, water tanks, and parking garages, which are usually exposed to harsh environments. To mitigate corrosion-induced damage in these structures, steel reinforcement is replaced by fiber-reinforced polymers (FRPs). Several attempts have been made during the last decade to introduce empirical models to estimate the shear strength of FRP-reinforced concrete (RC) deep beams. In this study, the applicability of these models to predict the capacity of simply supported deep beams with and without web reinforcement was assessed. Test results of 54 FRP-RC, 24 steel-fiber-reinforced concrete (FRC), and 7 FRP-FRC deep beams were used to evaluate the available models. In addition, a proposed model to predict the shear strength of FRPFRC deep beams was introduced. The model was calibrated against experiments conducted previously by the authors on FRP-FRC deep beams under gravity load. The model could predict the ultimate capacity with a mean experimental-to-predicted value of 1.04 and a standard deviation of 0.14.

DOI:

10.14359/51737270


Document: 

SP-332_03

Date: 

July 1, 2019

Author(s):

William Wilson and Daniel Moser

Publication:

Symposium Papers

Volume:

332

Abstract:

This is a case study involving an aging parking structure that deteriorated to the point where the structural floor slab failed. The lines of responsibility between parties involved with owning, managing and repairing the existing, exposed structures are not always clear, based on contractual language. This case ended in litigation to determine who was responsible for repair costs when the structural slab reached the end of its service life, taking into account the root cause of the slab failure. In this case study, we review the field and background information obtained for this case as well as the court interpretation of lines of responsibility and contract language regarding parking structure maintenance and normal wear and tear.

DOI:

10.14359/51719122


Document: 

SP-315_11

Date: 

April 1, 2017

Author(s):

Denis Mitchell, William D. Cook

Publication:

Symposium Papers

Volume:

315

Abstract:

Factors influencing the punching shear resistance of two-way slabs are presented. Factors discussed include: construction errors; effects during construction; earthquake effects; deterioration of parking garage slabs; and design with older, deficient codes of practice. Experiments on the size effect are discussed and the provisions of the CSA Standard for the Design of Concrete Structures for the treatment of the size effect are presented. The provisions of the CSA Standard requiring structural integrity reinforcement in order to provide a secondary defense mechanism capable of preventing progressive collapse are explained. The results from experimental and analytical studies on the post-punching response of two-way slabs are described. The effects of deterioration of parking garage slabs subjected to chloride contamination and the provisions of the CSA Standard on Parking Structures to improve durability are discussed. The effects of delamination due to corrosion of the reinforcement in older parking structures are discussed and experimental studies on the effects of simulated delamination are presented. The progressive collapse in 2008 of an older parking structure in St-Laurent, Quebec, is described to illustrate some key factors influencing such a collapse.


Document: 

SP290-02

Date: 

September 14, 2012

Author(s):

John Roberts, Randy Butcher, Bruce Jones, Max Kalafat, and Ron Vaughn

Publication:

Symposium Papers

Volume:

290

Abstract:

First noticed by T. C. Powers, et al in 1948, [22] as beneficial for hydration by supplying water internally, specifiers and contractors in 2012 have grasped how the process of internal curing is implemented, how hydration behaves, and how improvements in mechanical properties, durability, and cost may be beneficial. To meet the time-dependent hydration needs of the concrete, having sufficient water internally available, when, as, and where needed, is vital for achieving optimum characteristic qualities. There is lower life cycle cost with internal curing (IC) and frequently lower first cost. In 2012, the number of projects using internal curing is increasing at an escalating rate, because the process is simple and economically implemented. Pavements, bridges, buildings, and pervious parking lots are being started now in this recession, because specifiers and contractors are saving dollars, as they build longer lasting structures while costs and interest rates are low. Developed initially to reduce autogenous shrinkage in low water-cement ratio and high performance concretes, internal curing has been found to reduce drying shrinkage. Other benefits found include reduced permeability, increased compressive and flexural strengths, less warping, stronger interfacial transition zones, greater durability, and lower carbonation.

DOI:

10.14359/51684171


Document: 

SP290-13

Date: 

September 14, 2012

Author(s):

Daniel Cusson and Jim Margeson

Publication:

Symposium Papers

Volume:

290

Abstract:

Highway bridges and parking structures, subject to coupled effects of mechanical loads and corrosion, often show early signs of distress such as concrete cracking and rebar corrosion leading to reduced structural performance and shortened service life. One solution to this problem is to use low-shrinkage low-permeability high-performance concrete (HPC) for bridge decks exposed to de-icing salts and severe loading conditions. A new HPC was formulated to achieve low shrinkage and low permeability, high early-strength, and 28-day compressive strength over 60 MPa (8,700 psi). Its mechanical performance and durability were tested both in the lab and field under severe test conditions, including restrained shrinkage, cycling loading, freezing and thawing cycles, and application of de-icing salts. Models were developed and calibrated to predict structural performance and service life of concrete bridge decks under severe exposure conditions. Prediction models indicate that bridge decks designed with low-shrinkage HPC can achieve a service life up to 100 years. Compared to normal concrete decks, short-t t-to-medium span bridge decks using low-shrinkage HPC could be built at a comparable initial construction cost, but at less than 35% of the life-cycle cost.

DOI:

10.14359/51684182


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