Influence of Steel Reinforcement and Boundary Conditions on Cracking in Massive Concrete Caissons
Author(s)
Wasson, Isaac Hunt
Advisor(s)
Kahn, Lawrence
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Abstract
The purpose of the experimental research was to characterize and understand the
conditions which lead to thermal cracking in massive concrete caisson drilled shafts. Seven
circular column specimens with a diameter of 122 cm (48 in) and a height of 91 to 116 cm
(36 to 46 in) were constructed with varying boundary conditions to represent likely field
conditions of massive drilled concrete caissons. Both commercially available cardboardbased formwork and steel formwork were used. The formwork was surrounded by air, soil,
or water. Thermistors were casted at mid-height of each column along the diameter to
provide a higher resolution of temperature observation than what is typically required in
industry monitoring practice. Cracking was monitored in the columns for up to 33 days
after the casting of each specimen. Thermal boundary conditions of the specimens and the
presence of reinforcement were found to be highly influential in predicting the formation
of cracks. This text also describes a computational procedure to obtain an approximate
stress state for massive concrete caisson specimens during early age. Stress states were
predicted for larger specimens, up to 244 cm (96 in) in diameter, using predicted thermal
data from the software B4CAST. The results show steel reinforcement can, in the presence
of high temperatures, cause stress concentrations at the steel-concrete interface which may
exceed the early age tensile strength of the concrete.
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Date
2023-07-31
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