Analytical exploration of damage to piles-structure system caused by liquefied ground motion

The object of this study is to explore the reasons resulting in the failure of pile foundations built on the soft reclaimed ground due to the 1995 Hyogo-ken Nambu Earthquake. Based on the case investigation results, at first, numerical analyses have been perfomed to examine the dynamic bahavior of the soil-pile-structure system during earthquake shaking. Then, the seismic capacity of piles was investigated when the permanent ground displacements occurred due to the softening of liquefied soils. The following main conclusions have been drawn. 1) The collapse of middle parts of piles may be caused by the lateral forces due to soil liquefaction; 2) The damage of the pile tips may be attributed to the permanent ground displacements due to post-liquefaction.(AU)

Damage to water pipes during the 1994 Northridge earthquake

This paper presents damage to pipes of a water supply network system under the control of the Department of Water and Power of City of Los Angels(LADWP). Site investigation was conducted at San Fernando Valley where the damage to trunk lines, distribution pipes and service pipes were concentrated. Sixteen breaks of large diameter trunk lines and approximately 1.670 breaks of small diameter distribution pipes and service pipes were damaged during the earthquake. The damage to the trunk lines contains breaks of joints and pipes of an oldriveted trunk line buried along Roscoe Street, which breaks were occurred just over or very close to the epicenter. Other typical damage to the trunk lines were telescopic crashes and failures in tension of welded bell joints due to slight permanent ground movement at Balboa Boulevard. Most of the breaks of small diameter distribution pipes were caused to old and weak gray cast iron pipes connected with sockets and spigot joints, whose flexibility or strength against dynamic and permanent ground movement could not be expected. And the breaks include those of the service pipes were concentrated in Northridge district including Granada hills, San Fernando district and Sherman Oaks district.(AU)

Study on dynamic interaction analytical methods of structure on pile foundation

It is important for seismic design of the structure on pile foundation to examine the dynamic soil-structure interaction. Not a few method are proposed on seismic response analysis of pile foundation, in practical on seismic response analysis of pile foundation, in practical design, the methods of lumped mass-spring system, i.e. so-called Penzien model proposed by J. Penzien (1964), modified Penzien model proposed by S. Kawamura (1975), and two-dimensional FEM are widely used. But, there is few study on the accuracy or characteristics of some analytical methods simultaneously. in this paper, analyses on these methods were perfomed all together on single-degree-of-freedom system of superstructure supported by pile foundation in the uniform soil. The result of these analysis were compared with rigorous solution obtained by the method based on three-dimensional elastic wave propagation theory, and then, accuracy and characteristics of analysis and matters, which we should pay attention at practical use, were examined.(AU)