Evaluation of lateral resistance of damaged pile based on full scale lateral load test

What is it about?

It is useful to reuse existing piles when the building is rebuilt, but the piles can be damaged by earthquakes. This paper describes the evaluation method of the lateral resistance of damaged piles. The major findings are summarized as follows: 1) It is important for evaluating the lateral resistance to consider the decrease in elastic modulus of pile and the formation of hinge region caused by the pile damage. 2) When the location of damage is below 2.1/beta, the lateral resistance of the damaged pile is roughly equivalent to that of the fine pile despite the extent of damage.

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Why is it important?

1) Experiments and simulation analysis showed that the evaluation of the horizontal resistance of a damaged pile depends on the reduction of the modulus of elasticity of the pile due to damage and the evaluation of the hinge region due to flexural yielding of the damaged section. 2) If the modulus of elasticity of the damaged part is about 1/2 of that of the sound part, the effect on the horizontal resistance of the pile is small, regardless of the location of the damage. This is because the distribution of the ground reaction force is almost the same over the entire length of the pile as in the case of a sound pile if the damage is slight. As a result, a slightly damaged pile will deflect to the same degree as a sound pile, and its horizontal resistance will be almost the same as that of a sound pile. 3) When the modulus of elasticity of the damaged part is about 1/6 of that of the sound part, the pile head displacement tends to increase as the damaged part becomes shallower than the sound pile up to about 0.6/beta. This is because the damaged area acts as a hinge at shallower failure locations, and the pile will bear more ground reaction forces at the shallowest point of the damage, resulting in a deformation mode that causes a rapid increase in pile displacement. In the range of analyses conducted, this deformation mode occurs when the damaged area is shallower than about 2.1/beta relative to 1/beta obtained from the horizontal ground reaction force coefficient, kh, at 1 cm displacement. 4) On the other hand, if the damaged pile is deeper than about 2.1/beta, the pile head bears most of the ground reaction force, so that the horizontal resistance force can be expected to be the same as that of a sound pile even if the damage becomes large.