Dynamic Behavior of a Pile-Foundation Building With the Effect of Irregular Pile-Supporting Stratum

Abstract eng:
After the 2011 Tohoku Earthquake, many pile-foundation buildings were found to have been damaged by the strong shaking caused by the main shock. A pile-foundation building supported on an irregular pile-supporting stratum is the focus of this study. One of the important characteristics of this building is that its pile lengths are different on each foundation. The maximum difference of the pile length is 10m between the north and south side with the same structural frame. It is estimated that the pile-supporting stratum is inclined from south to north according to the design documents and the cut and fill distribution map of this area. The thickness of the soft surface layer on the north side of the building is greater than that on the south side. The authors conducted a damage survey, microtremor measurements, and aftershock observations on this pilefoundation building. Although the damage to the building was not severe, the staircase towers adjacent to the building were severely damaged. Based on the investigations, the shear wave velocity of the surface soil at this site is estimated to be approximately 160 to 180 m/s, and the natural frequencies of the superstructure are 3.5 Hz in the transverse direction and 3.2 Hz in the longitudinal direction. The irregularity of the pile-supporting stratum is also estimated based on the pile lengths of each foundation described in the design documents. Based on the findings of the field investigations including the damage survey, microtremor measurements, and aftershock observations, a numerical analysis of the building and one of the staircase towers is carried out with the 2D FEM model to simulate the damage caused by the 2011 Tohoku Earthquake. The dynamic characteristics of the surface ground and superstructures, and the piles of the building and the staircase tower are induced by the results of the field investigations. From a practical standpoint, the numerical model is organized to simulate the predominant frequency of the surface ground and the natural frequency of the superstructure. Based on the results of the numerical analysis, the dynamic behavior of the pile-foundation building is estimated for the main shock and compared with the results of the field investigations. The bending moment at the pile head of the short pile (close to the inclination of the pile-supporting stratum) appears to be larger than the longer pile because of the difference in the pile stiffness and the nonlinear soil response caused by the irregular pile-supporting stratum. The bending moment of the right piles of the building and the staircase tower is close to the capacity of the ductility factor. The responses of the pile of the building tend to be large compared to the damage. However, the bending moments of the piles of the staircase tower are in good agreement with the extent of the damage. It turns out that the effect of the irregular pilesupporting stratum plays an important role in the extent of the damage and the dynamic behavior of the building and the staircase tower.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket