Offshore Structure Platform Design - Offshore Structures: Design, Construction and Maintenance - page 185

3.9.2 Riser Guard Design
The riser guard design will be the same as that for the boat landing, but a shock
cell is not required because boats rarely accidentally collide with the riser guard.
Therefore, the riser guard design is based on plasticity, and for the members of
the riser guard design to reach the plasticity limit in case of accident they should
have a minimum cross-section, in order to reduce the lateral load effect. On the
other hand, the design should ensure that maximum deformation of the riser
guard will not affect the risers in an accident.
Using a tubular member 12.5 inch × 0.5 inch (323.9 × 12.7 mm), F y =

240 N/mm 2 (mild steel).
Figure 3.50 presents the situation of the plasticity as all the pipe cross-
sections will be under yield stress.
The plastic modulus = 70.2 inch 3 = 1,150,371.9 mm 3 and M p =240 ×

10 6 kN/m.
The deformation of the riser guard is presented in Figure 3.51 .

1,150,371.9/1000 × 1000 = 276.09 ×

F y

F y

FIGURE 3.50 Member at plastic moment.

θ 2

θ 1

θ 2
θ 1

6283

6283

FIGURE 3.51 Proposed deformation of riser guard.