Technical Paper by J.H. Greenwood - IGS - International ...

Discussion and Closure
DESIGNING TO RESIDUAL STRENGTH OF
GEOSYNTHETICS INSTEAD OF STRESS-RUPTURE
TECHNICAL NOTE UNDER DISCUSSION: Greenwood, J.H., 1997, “Designing
to Residual Strength of Geosynthetics Instead of Stress-Rupture”, Geosynthetics
International, Vol. 4, No. 1, pp. 1-10.
DISCUSSER: S-C.R. Lo, Senior Lecturer, School of Civil Engineering, University
College, University of New South Wales, Canberra, Australia, Telephone:
1/61-6-2688349, Telefax: 1/61-6-2688337, E-mail: srl@octarine.cc.adfa.oz.au.
PUBLICATION: Geosynthetics International is published by the Industrial Fabrics
Association International, 1801 County Road B West, Roseville, Minnesota
55113-4061, USA, Telephone: 1/612-222-2508, Telefax: 1/612-631-9334.
Geosynthetics International is registered under ISSN 1072-6349.
REFERENCES OF DISCUSSION AND CLOSURE: Lo, S-C.R., 1997,
“Discussion of ‘Designing to Residual Strength of Geosynthetics Instead of
Stress-Rupture’ by Greenwood, J.H.”, Geosynthetics International, Vol. 4, No. 6, pp.
673-675.
Greenwood, J.H., 1997, “Closure of Discussion of ‘Designing to Residual Strength of
Geosynthetics Instead of Stress-Rupture’”, Geosynthetics International, Vol. 4, No. 6,
pp. 675-677.
Discussion by S-C.R. Lo
The author of the paper has presented a more rational and less conservative method
for assessing the load carrying capacity of geosynthetics under long term loading. However,
clarifications are needed to ensure the proposed method is applied in a way compatible
with the design conditions and philosophy of the design code used. The latter
cannot be over-emphasised because of the introduction of limit state design codes that
use a series of somewhat confusing partial factors.
In a limit state design code, partial factors are used in lieu of a single factor of safety.
The design strength, T D , is obtained by applying a partial factor f m to T CR , the rupture
strength at the specified design life obtained by extrapolation of test data. In the context
of limit state design, f m is used to cover uncertainties in the determination of T CR and the
loss in effective load carrying area (say, due to construction damage). In BS 8006
(1995), f m is considered as the product of a number of partial factors f m11 , f m12 ,etc.in
GEOSYNTHETICS INTERNATIONAL S 1997, VOL. 4, NO. 6
673