Effect of Curing Temperatures on High Strength Concrete Bridge Girders

Park

2017

Sensors

Concrete is one of the most common materials used to construct a variety of civil infrastructures. However, since concrete might be susceptible to brittle fracture, it is essential to confirm the strength of concrete at the early-age stage of the curing process to prevent unexpected collapse. To address this issue, this study proposes a novel method to estimate the early-age strength of concrete, by integrating an artificial neural network algorithm with a dynamic response measurement of the concrete material. The dynamic response signals of the concrete, including both electromechanical impedances and guided ultrasonic waves, are obtained from an embedded piezoelectric sensor module. The cross-correlation coefficient of the electromechanical impedance signals and the amplitude of the guided ultrasonic wave signals are selected to quantify the variation in dynamic responses according to the strength of the concrete. Furthermore, an artificial neural network algorithm is used to verify a relationship between the variation in dynamic response signals and concrete strength. The results of an experimental study confirm that the proposed approach can be effectively applied to estimate the strength of concrete material from the early-age stage of the curing process.

Section: Introductionmentioning

confidence: 99%

Artificial Neural Network-Based Early-Age Concrete Strength Monitoring Using Dynamic Response Signals

Kim

Park

2017

Sensors

Int J Concr Struct Mater

“…Breccolotti and Materazzi (2015) performed experimental testing on the deformative behaviour in storage of a widely diffused wing-shaped roof element. The influence of the curing process and thermal history during early stage hardening was described in Roller et al (2003), Storm et al (2013) and Lee et al (2016a, b). Rosa et al (2007) calibrated a visco-elastic model on the basis of a series of field measurements of the camber evolution in bridge girders.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Assessment of the Service Behaviour of an Innovative Long-Span Precast Roof Element

Lago

2017

The control of the deformative behaviour of pre-stressed concrete roof elements for a satisfactory service performance is a main issue of their structural design. Slender light-weight wing-shaped roof elements, typical of the European heritage, are particularly sensitive to this problem. The paper presents the results of deformation measurements during storage and of both torsional-flexural and purely flexural load tests carried out on a full-scale 40.5 m long innovative wing-shaped roof element. An element-based simplified integral procedure that de-couples the evolution of the deflection profile with the progressive shortening of the beam is adopted to catch the experimental visco-elastic behaviour of the element and the predictions are compared with normative close-form solutions. A linear 3D fem model is developed to investigate the torsional-flexural behaviour of the member. A mechanical non-linear beam model is used to predict the purely flexural behaviour of the roof member in the pre-and postcracking phases and to validate the loss prediction of the adopted procedure. Both experimental and numerical results highlight that the adopted analysis method is viable and sound for an accurate simulation of the service behaviour of precast roof elements.

“…In mass fabrication of precast pretensioned concrete, steam curing is used to accelerate the hydration process and to achieve the specified release strength. Relatively recent research has reported that thermal prestress loss occurs during steam curing (Ahlborn et al 2000;Bruce et al 2001;Roller et al 2003;Tadros 2003; Barr et al 2005;Erkmen et al 2008;Newhouse and Wood 2008;Rizkalla et al 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Barr et al (2005) estimated the thermal prestress loss of 3-7% of the initial prestress if bonding occurred within the range of 6-10 h after casting. Roller et al (2003) suggested that thermal prestress loss prior to release was 6% if bonding occurred within 6 h after casting. Erkmen et al (2008) assumed that thermal prestress loss occurred until the concrete reached its maximum temperature.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Bond Stress–Slip Relationships of a Strand in Concrete during Steam Curing

Shin

Int J Concr Struct Mater

et al. 2017

The restrained thermal expansion of a pretensioned strand causes thermal prestress loss during steam curing until sufficient bond strength develops. The amount of thermal prestress loss is directly related to the characteristics of the interfacial bond stress-slip relationship at different maturity phases of concrete. For a rational assessment, the bond stress-slip relationship needs to be investigated experimentally at different maturity phases. In this study, a total of 12 pull-out tests were performed using seven-wire strand of 12.7 mm diameter, at different concrete equivalent ages of 7.8, 23.5, 53.8 and 85.2 h. Based on the test results, an empirical model of the bond stress-slip relationship was developed. The model comprised four segments: a curvilinear ascending region, a constant maximum region, a linearly descending region, and a region of constant frictional bond stress. The characteristic values in the model were expressed as functions of equivalent age. The model was able to predict the test results with reasonable accuracy.