Yoshitaka Murono

Single beam analogy for describing soil–pile group interaction

Abstract Most laterally loaded piles are flexible in the sense that they are not deformed over their entire lengths. Instead, pile deflections become negligible below an ‘active pile length’ L a . This L a is an important parameter that governs the overall behavior of a rigidly capped pile group. In the present approach, piles closely grouped together beneath a superstructure are viewed as a single equivalent upright beam whose stiffness matrix determines L a . This idea is verified for different cases of pile spacing, and is further extended for nonlinear behavior of soils surrounding grouped piles.

Verifying adequacy of the seismic deformation method by using real examples of earthquake damage

Abstract In a seismic design, the dynamic loads are generally dependent on the inertial interaction caused by earthquake. But for the foundations embedded in soil, the dynamic loads are influenced by both the inertial and kinematic interactions among superstructure, foundation and soil. Especially, when a foundation is embedded in soft surface ground, the effects due to the kinematic interaction increase and should be considered in seismic design. For this reason, a method called seismic deformation method (SDM), which is suitable for an intensive earthquake motion (level 2 earthquake motion), has been stipulated recently in a new design code called Seismic Design Code for railway structures (the Railway Code, drawn up by Railway Technical Research Institute, Japan, 1999) [Railway Technical Research Institute. Seismic Design Code for railway structures. Tokyo: Maruzen; 1999]. In order to grasp the suitability of the SDM to actual structures, pile foundations, which experienced the Hyogoken-Nanbu earthquake, were taken as the objects for investigations. Comparison studies between the SDM analysis and reconnaissance were conducted. As a result, the adequacy of the SDM to actual foundations was confirmed to prove good agreement between the two results from the viewpoint of engineering practice. In addition, determination of indices for seismic-performance evaluation and speculation of damage mechanism of the foundations are also discussed in this paper.

Outline of the "2011 off the Pacific Coast of Tohoku Earthquake" and Related Activities of RTRI

On March 11, 2011, an 9.0-magnitude earthquake occurred off the coast of Japan. A large-scale fault slide occurred at the plate boundary stretching from the offshore area of Iwate to Ibaraki, and caused heavy tremors of level 7 (Japanese Seismic Intensity) at Kurihara City, and of level 6+ in wider areas in four prefectures. This article describes the earthquake and the resulting tsunamis, focusing on the damage that occurred to the Japanese railroad network. The earthquake forced the suspension of train operations on a section of the Shinkansen high speed rail network. Several narrow-gauge lines were also destroyed, with many stations and tracks lost or washed away in coastal areas hit by the tsunamis. An early warning system on Shinkansen lines cut the power supply and activated emergency brakes on all passenger trains immediately after detecting minor vibrations during the early stages of the earthquake. There were no injuries on either Shinkansen or narrow-gauge lines. However, over 4,400 instances of damage occurred on narrow gauge lines and approximately 1,200 instances of damage occurred on Shinkansen lines. Immediately after the earthquake, the Railway Technical Research Institute (RTRI) set up a disaster recovery support task force. RTRI researchers surveyed damage and proposed a program of recovery work. Although many railway networks have been restored to normal operating condition, recovery for coastal lines may be prolonged.