Section 5 Additional assessments

5.1.1 At the request of the Owner or where required by the local authority, a Seismic Margins Assessment (SMA) is to be carried out in accordance with a recognised national or international standard.

5.1.2 In the assessment for the seismic margins event, some global plastic behaviour can be accepted provided the structural form remains adequate and some structural components can be discarded completely provided viable alternative load paths exist. Full advantage can be taken of sub-system plastic behaviour provided this does not detract from the strength of any main member. Global stability in all three orthogonal directions is to be provided at all times. Some instability in the vertical direction can be accepted subject to agreement with LR.

5.1.3 A full dynamic analysis is to be carried out and is to model:

• boundary conditions including seal stiffness (and variation in seal stiffness);
• hydrodynamic effects;
• distribution of mass within the structure (recognising the possibility of accidental eccentricity);
• the stiffness of individual members and connections;
• damping consistent with anticipated stress levels;
• input motion defined based on the operating context; and
• whole body displacement.

5.1.4 Where a SMA is required, the margin need not be demonstrated by formal structural analysis. Resistance to structural collapse can be assessed through the demonstration of a ductile response, progressive collapse and use of design details which minimise rupture. Margins in the limit state analysis can be used in the engineering justification.

5.1.5 The dynamic assessment is to utilise modal analysis followed by the evaluation of the forces using the Response Spectrum technique. The treatment of missing mass is to be in accordance with a recognised national or international standard.

5.1.6 The dynamic response of the dock gate will be sensitive to the values used for the stiffness of the seals. The prediction of hydrodynamic effects by use of fluid elements will be sensitive to assumptions made about the distance of the dock gate face to any boundary. Both these effects are to be examined in any analyses by carrying out sensitivity studies within an agreed range, related to the physical constraints on the dock gate.

5.2.1 At the request of the Owner, a fatigue assessment in accordance with a recognized National or International Standard is to be carried out for all critical components subject to significant cyclical loading. This will apply especially to dock gates provided with roadways.

5.2.2 Consideration should also be given to details subject to small amplitude motions of the pontoon or other buoyant support causing a high number of cycles at low stress levels.

5.3.1 At the request of the Owner, an impact assessment is to be carried out in accordance with a recognised national or international standard, to verify that the dock gate is capable of meeting the performance requirements agreed with the Owner. The impact loads are described in Pt 2, Ch 2, 2.10 Impact.

5.4.1 At the request of the Owner, a temperature assessment is to be carried out. Note that a stress analysis related to temperature change is not necessary, provided it can be shown that dock gate global expansion/contraction is within the clearance allowed in the restraining slots and provided that global contraction will neither cause the dock gate to come out of its slots nor overload the slots. Calculations undertaken to determine expansion are to account for both global and local differential temperature, and for friction developed against the slots.