Application of digital image correlation system for reliable deformation measurement of concrete structures at high temperatures

Abstract

Reliable deformation measurement is required for proper quantification of fire performance of concrete structures. Predictive capability of models for many critical properties, including Young's moduli, stress-strain relationships and load-induced thermal strains, is first and foremost dependent on such reliable deformation capturing. This paper first presents a state-of-the-art review of existing methods for capturing deformation of concrete structures at elevated temperatures. Key merits, limitations and challenges associated with each measuring technique are discussed. It is shown that existing testing facilities and measuring instruments generally do not allow reliable direct measurement of displacement and strain of high-temperature concrete. As a result, the deformation has typically been captured either indirectly or outside the heated zones, inevitably introducing additional uncertainties and errors that are difficult to be adequately quantified. On the basis of that review, the paper details a new test setup for reliable, non-contact fullfield deformation capturing of concrete structures at high temperatures using 3D Digital Image Correlation technique. Key features of the new setup that enable to successfully address major challenges of thermal boundary condition, thermal stability of speckle pattern, contrast of image and hot air movement are highlighted. Evidence giving confidence to the reliability of the new setup are then presented, together with likely applications of such setup and their potential positive impact on the ongoing transitioning towards performance-based structural fire engineering.

Feasibility Study of Digital Image Correlation in Determining Strains in Concrete Exposed to Fire

“…The methods of monitoring concrete deformation at an elevated temperature can be divided into those requiring direct contact with the tested element and those that monitor deformation without contact. Le et al [9] presented a brief review of contact and non-contact methods. Thus far, in the case of experimental tests on the fire spalling of concrete, contact methods have been more frequently used.…”

“…In the case of testing concrete behavior under fire exposure, the DIC method was only previously used for the small-scale preliminary studies conducted by Le et al [9]. In the experiment presented in [9], the vertical deformation of the loading cylinder was monitored using the DIC method. Then, the results were compared to the displacement of the loading actuator.…”

Research on refraction error correction of digital image correlation technology in strain measurement of airship skin

“…Reference [4] shows that after the camera is equipped with a protective device, the photos taken through the optical window are clear enough to be used as photographic analysis materials, but the influence of optical glass on the measurement accuracy is not analyzed. In study [5], the refraction of glass is attributed to radial distortion by analogy through observing displacement vector map before and after experimental deformation without rigorous explanation and derivation. Lyons [6] had proved that the optical window of the incubator has an impact on the measurement matching, and had given suggestions that the use of high-quality optical quartz glass can reduce the impact of optical window.…”

Thermal Action on Normal and High Strength Cement Mortars

“…Thermal damage in cementitious composites represents a topic of key interest for controlling strength, durability and serviceability conditions of concrete structural components [1]. The most relevant thermo-physical and mechanical properties of cement-based composites (i.e., cohesion, friction, stiffness, strength, cracked configurations and durability parameters) suffer severe degradation as a result of long-term exposure to high temperatures [2,3].…”