Civil Engineering Reference
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Figure 22.27
Arrangement of tendons (Soria & Wittke 1985)
The increase in pre-stressing forces with advancing excavation was measured with
the aid of anchor load cells mounted at the heads of 23 tendons. The location of the
load cells is shown in Fig. 22.27. The increases in anchor force reveal a very large
scatter. Mean values of 0.1 to 0.2 MN were recorded, depending on the time of in-
stallation, with a maximum value of 0.4 MN. The row of tendons installed after ex-
cavation of bench III had to be released during the course of further excavation. The
need to release subsequently installed tendons arose only in individual cases because
these tendons were no longer fully pre-stressed in view of the displacements, which
were to be expected. As an example, in Fig. 22.28 the increase in anchor force
Δ
F
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