CressHelp - Ice forces

Cress Help - Ice forces - A21.1

Ice characteristics

Ice characteristics see [a] and [b]:

maximum stresses:

Tensile strength = ca. 1000 to 1500 kN/m2 (when T = -5 °C)

Compression strength = ca. 2000 g tot 3500 g kN/m2 (g = 1+0.21¦T¦0.78 )

Sheer strength = ca. 700 kN/m2 (when T = -5 °C)

Bending strength = ca. 500 tot 1700 N/m2 (when T = -5 °C)

In which T = ice temperature (°C) If no data is available on the local strength of the ice, the following recommendations are made (see [h]):

Cubic compression strength sc (kN/m2)

Salt content of Ice [%] (1) sc (kN/m2)with average(2) daily airtemperature (°C) of :

0 -3 -15 -30

<1 (fresh water) 450 740 1200 1500

1 - 2 400 650 1050 1350

3 - 6 300 500 850 1050

These values are applicable to ice velocities > 0.5 m/s.

note 1 :
The salt content of the ice is 2 % of the salt content of the water for ice younger than 2 months. The salt content is 1.5 % of the salt content of the water for ice older than 2 months.

note 2 :
For ice thicker than < 0.5 m the average air temperature of the last three days can be taken
For ice thicker than > 0.5 m the average at temperature of the last 6 days can be taken.

The fracture bending stress for fresh water ice is: sb = 0.75 sc
The fracture bending stress for salt water ice is: sb = 0.5 sc
The fracture bending pressure stress is: sd = kdsc

b/h	1	3	10	20	30 and over
kd	2.5	2	1.5	1.2	1

In which :

b = construction width at the height of the ice surface [m]
h = design ice thickness [m]

For the design ice thickness:

river ice = 80 % of the maximum ice thickness during a winter period with a probability of 1%

sea ice = maximum ice thickness with a probability of 1%

density of pure ice density of pure ice at 1 atm: r = 916.8 (1 - 1.5310-4 T) kg/m3

density of sea density of sea ice at 1 atm: r = 850 (old pack ice ) tt 920 kg/m3 (fresh ice )

thermal expansions coefficient: au = 5.510-5 °C-1

elasticity modulus : E = 3.106 to 9.106 kN/m2

Average temperatures for Dutch conditions (see [c] Appendix 4).

The probability that the average temperature of a frost period is lower than a negative temperature T (?C): (according to the Weilbull-distribution)

equation 1

with aP = 2.089 and b = 0.0672

References
[a] ing. C.J.A. Zijlmans, IJsbezetting -bestrijding op de grote rivieren in Nederland, Literatuurstudie, Rijkswaterstaat, Dir. benedenrivieren, afd. AXB, org. IJsopruiming, sektie onderzoek, nov. 1980.
[b] Stormvloedkering Nieuwe Waterweg, document ontwerp, deel 1, RWS Directie sluizen en stuwen, 31 juli 1989, BMK.
[c] ir A.W. de Haas, april 1986, Ice afvoerproblematiek voor de grote rivieren en de Rijndelta, bijzondere onderwerpen, RWS dir. Benedenrivieren, Organisatie IJsopruiming Sectie Onderzoek.
[d] ir T. Stoutjesdijk e.a. Grondmechanica Delft, oktober 1991, Taludbekledingen van gezette steen, bijzondere belastingen, co-320030/3.
[e] H.R. Kivisild, Proceedings 8th IAHR-congres 1959, Montreal-Canada-Volume III, "Ice problems in hydraulic structures.
[f] ir F. Gerritsen, Proceedings POAC-conference "The first international conference on port and ocean engineering under Arctic conditions", Vol. I Norway 1971, Ice problems in Dutch rivers and estuaries, blz. 582 e.v.
[g] Korzhavin, K. N., Action of ice on engineering structures, Novosibirsk, Akad. Nauk. USSR 1962.Vertaling: TL 260 van CRREL Hanover, New Hampshire, 1971
[h] Russische ontwerpregels uit 1986.
[i] Carstens T. editor, Working group on ice forces on structures, A State-of-the-art report, special report 80-26, june 1980.

Salt content of Ice [%] (1)	sc (kN/m2)with average(2) daily airtemperature (°C) of :
	0	-3	-15	-30
<1 (fresh water)	450	740	1200	1500
1 - 2	400	650	1050	1350
3 - 6	300	500	850	1050