Environmental Engineering Reference
In-Depth Information
- Form, size, surface finishes and stiffness of the structure
- Size, form and thickness of ice, rate of advance
- Type of ice and ice formation (ice floes, drifting ice, ice ridges/ramparts)
- Temperature and salt content of the ice plus the strength of the ice dependent on this
- Angle of incidence of the ice on the structure
- Mechanical properties of the ice (compressive strength r
u
, bending strength r
f
)
- Rate of load application
Modelling
The thickness of the ice is an important parameter for calculating ice loads and should
be specified based on local data (Table 2.15).
Another input in the load calculation can be the frost index K, which is defined as the
sum of the mean daily temperatures for a particular location on which the mean
temperature lies below 0
C. The frost index K varies from year to year and can be
presented as a probability function (Weibull) based on statistically evaluated data [24].
The compressive strength r
u
, the bending strength r
f
and the thickness of the ice can be
expressed as functions of the frost index K.
Ice loads
Lateral ice loads should be determined by in situ measurements, model tests at a
suitable scale or other recognised theoretical methods. Ice loads for locations on
the open sea should be determined depending on the current characteristic ice
thickness [24].
Loads other than lateral ice loads can also occur, for example:
- Loads due to a rigid covering of ice, including loads due to arching effects (e.g.
locations near the coast)
- Dead loads due to ice frozen on the structure
- Ice pressures due to pack ice or an ice dam
- Thermal ice pressure (restraint forces) as a result of thermal actions on a rigid
covering of ice
Table 2.15 Measured maximum ice thicknesses as guidance values for design [26]
North Sea
max. h [cm]
Baltic Sea
max. h [cm]
Heligoland
30 to 50
Flensburg Fjord
32 to 40
Wilhelmshaven
40
Eckernf¨rde Bay
50
B¨sum
45
Kiel Fjord
55
Meldorf (harbour)
60
Bay of L¨beck
50
Wittd¨n harbour
60
Bay of Wismar
60
Rostock-Warnem¨nde
40
Stralsund - Palmer Ort
65
