Titel_SS06

vulnerability of the structure and the robustness of the structure, see Figure 12.1.

Direct consequences to the structure:Component failure

Corrosion damageErosion

FatigueSpalling

WearYielding

Cracks.

Exposures:Wind loads

Traffic loadsSnow loads

Current loadsEarthquake loads

Ship/vehicle impactFire/explosions

Temperature loadsWater

Deicing salt.

&RQGLWLRQLQGLFDWRUV

LoadsEnvironment

UseAccidents

Age.

Design basisDurability

.

DamagesDegradation

Response

Condition Redundancy

DuctilityInsp./maint. strategy

Emergency prep. plans

Indirect consequences to the structure:Collapse

Exposure

Vulnerability

Robustness

Exposure

Vulnerability

Robustness

Condition

Figure 12.1: Main characteristics of a given structure.

In Figure 12.1 exposure relates to all effects of the environment, loads and hazards which the
structure is exposed to during its lifetime. The vulnerability of the structure is related to the
direct effects (e.g. damages) on the structure due to the different exposures. Damages can be
due to e.g. aggressive environments, overloading and accidents. Usually structural design
codes ensure the appropriate design of structural members such that their vulnerability, i.e.
their probability of failure is acceptably low, but do not directly consider systems effects.

The robustness of the structure reflects the ability of the structure to sustain the effect of
different types and extents of direct damages. Design codes generally only provide indirect
provisions for robustness by requiring that structures should be designed such that the effect
of damages are not over-proportional to the causes of the damages. However, robustness can
and should also be viewed upon in a broader perspective as an indicator of the structure as a
system to sustain general deviations from the assumptions subject to which the structure
originally was designed. The structural performance may in general be controlled by control
of the exposure conditions and by design measures. However, whereas structural vulnerability
may be reduced only by design provisions structural robustness may be improved also by
suitable strategies for inspection and maintenance as well as emergency and rescue
procedures.

Value of information

A structure can be assessed by collecting (measuring/monitoring/inspecting/testing)
information (through indicators) about the exposure, the vulnerability and the robustness.
Sometimes information about indicators are not only collected specifically through an
assessment/inspection but also continuously through monitoring.