Damage Evolution of Underground Structural Reinforced Concrete Small-Scale Static-Loading Experiments
Small-scale RC models of both piles and tunnel duct s were produced as mockups of reality and loaded under soil confinement conditionsto investigate the damage evolution of structural RC interacting with soil. Experimental v erifications usinga 3D nonlinear FE analysis program called COM3D, which was developed at the University of Tokyo, are introduce d. This analysis has been used in practice for seismic performance a ssessment of underground ducts and in-ground LNG storage tanks in consideration of soil-structure interactionunder static and dynam ic loading. Varying modes of failure of RCpilessubjected to different m agnitudes of soil confinement were successfully reproduced in the proposed small-scale experiments and numerically simulated as well. Analytical simulation was applied to RC tunnel mockups under a wide variety of depth and soil confinement conditions, and reasonable matchin g was confirmed.
Seismic analysis of underground reinforced concrete structures considering elasto-plastic interface element with thickness
Abstract Since underground reinforced concrete (RC) structures interact with the surrounding soil medium, the behavior of the interfacial zone between the RC structure and the surrounding medium of the underground RC structure should be considered for accurate seismic analysis. In this paper, an averaged constitutive model of concrete and reinforcing bars for the RC structure and the path-dependent Ohsaki’s model for the soil are applied, and an elasto-plastic interface model which considers the thickness of the interface is proposed for seismic analysis of underground RC structures. A finite element analysis program is developed and verified by predicting both static and dynamic behaviors of underground RC structures. Then, the effects of the interface on the behavior of underground RC structures are analyzed. The effect of stiffness of the RC structure due to different reinforcement ratios of underground RC box structures to the behavior of the structures is also analyzed. Finally, failure mechanisms of underground RC structure under seismic action are simulated through seismic analysis of an underground RC station structure.
FLEXURAL STRENGTH AND DUCTILITY OF EXTENDED PILE-SHAFTS. II: EXPERIMENTAL STUDY
Results of an experimental program investigating the lateral strength and ductility capacity of reinforced concrete piles are presented. Four full-scale reinforced concrete piles with details representative of the current California design were tested under combined axial compression and reversed cyclic lateral displacement. Test parameters include confining steel ratio, aboveground height, and soil density. Of particular interests are the lateral strength and stiffness of the soil-pile system, depth-to-maximum-moment, and magnitude of local deformation upon formation of a plastic hinge in the pile. Equivalent plastic hinge lengths were determined using curvatures measured along the length of the pile. Test results indicated that the equivalent plastic hinge length of piles is generally longer than that of an equivalent base-restrained column. The equivalent plastic hinge length of the pile depends primarily on the aboveground height of the pile, but is not overly sensitive to the soil density. Test results also provided the basis for an analytical model presented in a companion paper for assessing the local ductility demand of a yielding pile-shaft.