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O: Precast Concrete Elements [Table of Contents] Sec.8: In-service Inspection, Maintenance and Conditional Monitoring

DNV-OS-C502 Offshore Concrete Structures

[-] Sec.7: Construction
[-] P: Geometrical Tolerances

Sec.7
P. Geometrical Tolerances

Sec.7
P 100   General

Sec.7 P
101   Design tolerances are specified in Sec.6, C400 with design consequences in Sec.6, B607. The design assumption is based on an alternative approach, either:
—design and construct in accordance with the tolerances in Sec.6, C400 with high material factors provided in Sec.6, B607; or
—design and construct the for any tolerances, the maximum positive and negative tolerances have to be included in design in the most design critical way, and the construction work has to confirm compliance with the set of tolerances.


Sec.7 P
102   This clause defines the types of geometrical deviations relevant to offshore structures. See P300, P400 and P500. The list is provided as guidelines, and the designer shall fill in the required tolerances to be used in construction. The tolerances shall be marked on the drawings issued for construction.

Sec.7 P
103   In general, tolerances on dimensions are specified in order to ensure that:
—geometry is such as to allow parts fit together as intended
—geometrical parameters used in design are satisfactorily accurate
—the structural safety of the structural member is ensured
—construction work is performed with a satisfactorily accurate workmanship
—weights are sufficiently accurate for floating stability considerations.


Sec.7 P
104   All these factors shall be considered when tolerances are specified. Tolerances assumed in design (See Sec.6 C400) may be greater than the tolerances actually found to be acceptable for other reasons.

Sec.7 P
105   Changes in dimensions following temperature effects, concrete shrinkage, post-tensioning and application of loading, including those resulting from different construction sequences, are not part of the construction tolerances. When deemed important, these changes shall be considered separately.

Sec.7
P 200   Reference system

Sec.7 P
201   A system for setting out tolerances and the position points, which mark the intended position for the location of individual components, shall be in accordance with ISO 4463-1.

Sec.7 P
202   Deviations of supports and components shall be measured relative to their position points. If a position point is not established, deviation shall be measured relative to the secondary system. A tolerance of position in plane refers to the secondary lines in plane. A tolerance of position in height refers to the secondary lines in height.

Sec.7
P 300   Member tolerances (Guidelines)

Sec.7 P
301   Requirements may be given for the following type of tolerances as relevant:
  1. skirts:
    —deviation from intended centre for circular skirts
    —deviation from intended position for individual points along a skirt
    —deviation from best fit circle for circular skirts
    —deviation from intended elevation for tip and top of skirt
    —deviation from intended plumb over given heights.
  2. slabs and beams:
    —deviation from intended elevation for centre plane
    —deviation from intended planeness measured over given lengths (2 m and 5 m)
    —deviation from intended slope.
  3. walls, columns and shafts:
    —deviation from intended position of centre plane or horizontal centre line
    —deviation from intended planeness- horizontal direction
    —deviation from intended planeness - vertical direction
    —deviation from intended plumb over given heights.
  4. domes:
    —deviation of best fit dome centre from intended centre, horizontal and vertical directions
    —deviation of best fit inner radius from intended radius
    —deviation of individual points from best fit inner dome
    —deviation of individual points from best fit exterior dome.
  5. circular members:
    —deviation of best fit cylinder centre from intended centre line
    —deviation of best fit inner radius from intended inner radius
    —deviation of individual points from best fit inner circle over given lengths
    —deviation of individual points from best fit exterior circle over given lengths
    —deviation from intended plumb over given height.
  6. shaft/deck connections:
    —deviation of best fit centre from intended centre of shaft
    —deviation in distances between best fit centres of shafts
    —position of temporary supports horizontal and vertical
    —position of anchor bolts horizontal plane and verticality.

Sec.7
P 400   Cross-sectional tolerances (Guidelines)

Sec.7 P
401   Requirements may be given for the following type of tolerances:
  1. thickness:
    —individual measured points
    —overall average for area.
  2. reinforcement position:
    —tolerance on concrete cover
    —tolerance on distance between rebar layers same face
    —tolerance on distance between rebar layers opposite faces
    —tolerances on spacing of rebars in same layer
    —tolerances on laplengths.
  3. prestressing:
    —tolerance on position of prestressing anchors
    —position of ducts/straightness at anchors
    —position of ducts in intermediate positions
    —tolerances on radius for curved parts of tendons.

Sec.7
P 500   Embedments and penetrations (Guidelines)

Sec.7 P
501   Requirements may be given for the following type specified of tolerances as relevant. Tolerances shall be for items individually or for groups, as appropriate:
  1. embedment plates:
    —deviation in plane parallel to concrete surface
    —deviation in plane normal to concrete surface
    —rotation in plane of plate (degrees).
  2. attachments to embedments:
    —deviation from intended position (global or local system)
  3. penetrations:
    —sleeves deviation from intended position of centre
    —sleeves deviation from intended direction
    —manholes deviation from intended position and dimension
    —blackouts deviations from intended position and dimensions.
O: Precast Concrete Elements [Table of Contents] Sec.8: In-service Inspection, Maintenance and Conditional Monitoring