Effect of historical earthquakes on pre-stressed anchor tie back diaphragm wall and on near-by building

Abstract EN

Pre-stressed tie back anchored diaphragm walls are considered one of the safest lateral supports which help in overall stability when there is a significant difference in land level between back and front of these walls.

Permanent lateral supports to these walls are frequently represented by supporting it laterally with foundation and floor slabs of the building.

In this paper a special study of one raw anchor diaphragm wall subjected to different earthquake dynamic loads will be presented.

The wall retains an excavation of 9.5 m and supports laterally a near-by 5 floor building.

Five historical strong motions with different fundamental frequencies are subjected on the wall.

The wall displacement, straining actions, anchor extreme force and the influence of variation of anchor stiffness are calculated using a dynamic Plaxis finite element program.

The soil is considered as elasto-plastic material and represented using Mohr–Coulomb criteria, the wall and the anchor are considered to behave elastically.

Prescribed displacement at the lower bottom boundary represents the earthquake motion.

Far left and right absorbent boundaries are assumed to prevent dynamic wave reflection.

Four static phases representing construction procedure and one dynamic loading phase are considered.

It is found that the straining actions of different historical earthquakes match in shape with each other, the only change is in the amplitude which is affected by earthquake fundamental frequency and its intensity.

The maximum dynamic lateral displacement of the wall is at its free top.

The near-by building shows a differential settlement towards the wall which causes a change in the sign and amplitude of the straining actions.

Increasing the stiffness of anchor was also studied and it was found that it reduces too much the maximum dynamic top wall lateral displacement