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Skokie, IL, United States

Khayat K.H.,Universite de Sherbrooke | Omran A.F.,Universite de Sherbrooke | D'Ambrosia M.,CTLGroup
RILEM Bookseries | Year: 2010

Various prediction models, based on experimental results to evaluate formwork pressure exerted by self-consolidating concrete were established based on extensive laboratory evaluation. The models are based on the measurements of the structural build-up of the concrete with rest time and placement characteristics of the concrete. The latter includes the rate of rise of the concrete in the formwork, concrete temperature, and minimum dimension of the formwork. This paper presents the results of two campaigns of field validation carried out at Sherbrooke, Quebec, and Skokie, Illinois, to validate the prediction models. The results confirm that the established models offer adequate prediction of form pressure exerted by self-consolidating concrete. © RILEM 2010. Source

Grasley Z.,Texas A&M University | El-Helou R.,Virginia Polytechnic Institute and State University | D'Ambrosia M.,CTLGroup | Mokarem D.,Virginia Polytechnic Institute and State University | And 2 more authors.
Journal of Engineering Mechanics | Year: 2015

Unreinforced portland-cement concrete exhibits a nonlinear relationship between applied stress and observed strain, even though the strains are at magnitudes that warrant the infinitesimal strain approximation (i.e., the norm of the displacement gradient is appropriately small). Previous efforts to model this nonlinear response of concrete express a dependence of stress on the deformation gradient (via the infinitesimal strain). However, models derived from the class of Cauchy elastic bodies do not allow a nonlinear relationship between the stress and linearized strain. Nonlinear constitutive relations that are implicit relations between the stress and a proper measure of strain, or nonlinear expressions of an appropriate measure of strain as a function of stress, lead to a logical linearization procedure wherein the linearized strain can be a nonlinear function of the stress. Using such a constitutive model, the authors accurately characterize both axial strain and circumferential strain in concrete that occurs under axial compression, up to the peak compressive stress (i.e., the failure stress). The phenomenological coefficients of the constitutive models are given predictive power via correlation with compressive strength and the air content of the ten concrete mixtures (comprising 23 concrete cylinders) that were experimentally tested under unconfined uniaxial compression. © 2015 American Society of Civil Engineers. Source

Murphy M.,CTLGroup | Belarbi A.,University of Houston | Bae S.-W.,Texas Tech University
PCI Journal | Year: 2012

This paper investigates the behavior of full-scale prestressed concrete girders strengthened in shear with externally bonded carbon-fiber-reinforced polymer (CFRP) sheets. The study is aimed at identifying the failure modes and effects on ultimate bearing capacity associated with the application of CFRP laminates as externally bonded shear reinforcement for prestressed concrete I-girders. A total of 16 full-scale prestressed concrete girder tests are reported. Test parameters include the cross-sectional shape, effects of preexisting damage, CFRP strengthening scheme, different anchorage systems, and transverse steel reinforcement ratio. The test results show that the failure modes are complex and can vary considerably with respect to the test parameters. The test results also show that the application of externally bonded CFRP reinforcement for shear may not yield an increase in the load-carrying capacity of a girder compared with a reference member that is not strengthened with CFRP. Source

Roller J.J.,CTLGroup
Journal - American Water Works Association | Year: 2013

Over the past 70 years, prestressed concrete cylinder pipe (PCCP) has been used to construct approximately 19,000 mi of our nation's water transmission mains. Numerous unanticipated performance shortfalls, caused largely by the actions of one manufacturer during the 1970s, have resulted in concerns among owners related to use of PCCP that continue to this day. An emerging PCCP risk management strategy is to use the combination of electromagnetic inspection, finite-element-based structural analysis, and acoustic monitoring to gauge extent, significance, and rate of deterioration. This article examines the state of the art as it relates to PCCP risk assessment and provides constructive input related to the limitations associated with the various technologies currently being used. Additionally, suggestions for getting the most out of a risk assessment are presented. Source

Lim M.K.,Universal Construction Testing | Cao H.,CTLGroup
Construction and Building Materials | Year: 2013

The uses of different nondestructive testing techniques have been well documented over the past decade or so. The techniques provide the opportunity to obtain the problem without having to chip into the test member. Many times, an NDT practitioner uses only one nondestructive test method to perform the evaluation. If the scope of work is straight forward, using a single test method is acceptable. However, there are times when a single test method does not provide enough information on the problem, and thereby combining different methods is essential. Knowing the advantages and limitation of each test method is key to applying the right combination of test methods to the evaluation. This paper provides insight into the different test methods and also provide case history whereby combining different nondestructive test methods were used in the evaluation. © 2012 Elsevier Ltd. All rights reserved. Source

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