A study of the localized bearing capacity of reinforced concrete K-segment

To control the thrust force of the shield jacks, the localized bearing capacity should be estimated when instability occurs for reinforced-concrete K-segment under eccentric compression. Then a method based on the moment-force interaction and the effect of bolt pockets is proposed. The method considers that the load corresponding to the appearance of the first crack is the load of bond cracking at σ_c {approaches the limit} 0.3 s(-) 0.4 f_c ^′ (f_c ^′ compressive strength of concrete), and assumes that the K-segment is a column which is subjected to axial loading and biaxial bending. Analytical results were compared with experimental values obtained from four reinforced-concrete K-segments. Using the strain gauges in concrete cover during the loading process, load-strain curves can be plotted and used to describe K-segment behavior. It was found that the failure of reinforced-concrete segments is a process, and bolt pockets reduce the bearing capacity of K-segment. The starting point is the cracking load point where cracks initiated on the concrete cover of the cross-section with bolt pockets. The ultimate load point is the top of failure process, namely the stress of this point attains the compressive strength of the concrete. The experimental results are close to the analytical values. The method is rational and can be used for stability analysis of reinforced-concrete segments.