Safety factor forstructural elements subjected to impulsive blast loads
Pierluigi Olmati1a*, Dimitrios
Vamvatsikos2b, Mark G. Stewart3c
1 Department
of Architecture and Wind Engineering, Tokyo Polytechnic University, Japan.
2 School of Civil Engineering,
National Technical University of Athens, Greece.
3 Centre for Infrastructure
Performance and Reliability, The University of Newcastle, Australia.
a Researcher,
fellow of the Japanese Society for the Promotion of Science JSPS.
b Assistant Professor.
c Professor and Director.
* Corresponding author; e-mail: pierluigi.olmati@gmail.com
Abstract
Design of blast loaded structures is usually
carried out following a deterministic rather than a probabilistic approach. The
design load scenario would cover the plausible load conditions (typically some
conservative estimate) that a structure would experience if an explosion occurs
but the probability that the structure will satisfy the design performances for
the considered scenario remains unknown. Applying a performance-based design framework
typically requires arduous Monte Carlo simulations, but a probabilistic design could
also be achieved by a single structural analysis when consistent safety factors
are applied to the load and the structural resistance. Such a factor is
proposed herein for the case of components subjected to impulsive blast loads. The
dependence of the safety factor on the amount of explosive, stand-off distance
and their variability is estimated numerically and provided by means of
regression formulas. A design example using the proposed safety factor is
carried out and Monte Carlo simulation is used for verification. The results confirm
the validity of the proposed safety factor approach and its applicability for the
performance-based design of blast loaded structures using the current design
practice methods.
Keywords:
performance-based design; probabilistic analysis; safety
factor; blast design; terroristic explosions; blast load; vehicle borne improvised
explosive devices.
Figure 16: Probability of
exceeding the limit state P(ϴ>θ) calculated using a Monte
Carlo simulation compared with the APE used in the design carried out
with the proposed safety factor λ. The structural uncertainties have
been considered as well for comparison purpose.
Furthermore the reinforcement percentage is plotted too as design output
for the RC panel. The proposed approach is accurate enough for APEs<15%
while for higher APEs (not suitable for design purposes) it gives a
conservative design.
