Offshore Structure Platform Design - Offshore Structures: Design, Construction and Maintenance - page 123

6. The equations of step 5 are:

P m
M m ω

1 X 1 =

€ x 1 +ω P m /M m X 1 ð t Þ =

2 ð 1

− cos ω 1 t Þ (3.20)

P m
M m ω

2

€ x 2 +ω

2 X 2 =

P m /M m X 2 ð t Þ =

2 ð 1

− cos ω 2 t Þ

(3.21)

P m
M m ω

2

€ x 3 +ω

3 X 3 =

P m /M m X 3 ð t Þ =

2 ð 1

− cos ω 3 t Þ

(3.22)

P m
M m ω

4 X 4 = P m /M m X 4 ð t Þ =

x 4 +ω

2 ð 1

− cos ω 4 t Þ

(3.23)

8
<

9
=

X 1
X 2
X 3
X 4

= fϕ 1 g X 1 ð t Þ + fϕ 2 g X 2 ð t Þ + fϕ 3 g X 3 ð t Þ + fϕ 4 g X 4 ð t Þ

(3.24)

: ;

Using the above equation, we can define the values of drift with time for each
floor.

3.5.5 In-place Analysis According to ISO 19902
To perform in-place analysis of the load resistance factor design according to
ISO 19902, the general equation for determining the design load (action) (F d )
for in-place situations is:

F d = γ f ,G1 G 1 + γ f ,G2 G 2 + γ f ,Q1 Q 1 + γ f ,Q2 Q 2 + γ f ,E o ð E o + γ f ,D D o Þ
+ γ f ,E e ð E e + γ f ,D D e Þ

(3.25)

where G 1 and G 2 are the permanent loads; Q 1 and Q 2 are the variable loads; E o
is the environmental load, which is defined by the owner as the operating wind,
wave and current parameters; D o is the equivalent quasi-static action represent-
ing dynamic response, but caused by the wave condition that corresponds with
that for E o ; E e is the extreme quasi-static action due to wind, waves and current;
D e is the equivalent quasi-static action representing dynamic response; and γ f,G1 ,

γ f,G2 , γ f,Q2 are the partial load (action) factors for the various permanent

and variable actions and for which values for different design situations are given
in Table 3.1 .
On the other hand,

γ f,Q1 and

γ f,D are the partial action factors for the environ-
mental actions and for which appropriate values should be defined by the owner
through the statement of requirement document (SOR),

γ f,E and

γ f,Ee are partial
action factors applied to the total quasi-static environmental action plus equiva-
lent quasi-static action representing dynamic response for operating and
extreme environmental conditions, respectively, and for which values for differ-
ent design situations are given in Table 3.1 .

γ f,Eo and