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Behavior of concrete anchors under sustained elevated temperature conditions
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School of Engineering |
Master's thesis
Electronic archive copy is available via Aalto Thesis Database.
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en
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118
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This thesis investigates the long-term mechanical behavior of cast-in concrete anchors embedded in normal-weight concrete subjected to sustained elevated temperatures between 50 °C and 140 °C. These thermal conditions are representative of environments such as spent nuclear fuel pools, where reinforced concrete structures are continuously exposed to moisture and prolonged heat generated by decay energy.
A detailed literature review was conducted to characterize the degradation of key concrete properties: compressive strength, tensile strength, elastic modulus, density, and thermal characteristics as a function of both temperature and moisture exposure. Special attention was given to moist and saturated conditions, which significantly increase material degradation and are often overlooked in standard anchor design assessments.
To enable practical capacity evaluation, temperature-dependent strength reduction factors were introduced. These coefficients were considered for long-term moist exposure and embedded analytically into the design framework of EN 1992-4:2018 [1], preserving the standard formulation while extending its applicability beyond ambient or fire scenarios. The revised expressions were used to estimate the residual capacity of anchors under various failure modes, including concrete cone, pull-out, blow-out, pry-out, and edge failure.
The results confirm that both compressive and tensile strengths deteriorate significantly with increasing temperature, with tensile strength reductions being especially pronounced in moist and saturated environments. This highlights the importance of accounting for moisture conditions when designing concrete anchorage systems for elevated-temperature applications.
The proposed methodology provides a technical basis for evaluating anchor capacity in nuclear and industrial structures where prolonged thermal exposure is coupled with high humidity or saturation. Future research should focus on the experimental validation of the reduction factors under realistic service conditions, including long-term thermal aging, moisture migration, and creep phenomena.