Dmrb Standard Bogie Axle Arrangements

51 is the half distance between axles closest to the centre of gravity of the four axles (m) (see Figure H.1);

52 is the distance between bogie axles (m) (see Figure H.1).

Distance Between Bogie Centres
For asymmetric groups of axles (see Figure H.2):

cos (D + C0S (z (x + ^l)) + P1 cos (S2 ~ + cos (S3 + S2 - x)J

Maximum value of appropriate influence line coincident with centre of gravity of axles

Maximum value of appropriate influence line coincident with centre of gravity of axles

Four axles (two bogies)

Figure H.2 — S1, S2, S3 and x for assymetric and unequal groups of axle loads

Annex J (normative)

Models for traffic loads in transient situations

The characteristic values specified in annex J shall be used for load model 71 for transient situations, unless otherwise specified by the relevant authority.

Annex S (informative) Additional guidance

The Design Manual for Roads and Bridges (DMRB) applies to the design of highway bridges in the UK in versions published by the Department of the Environment, Transport and the Regions — Highways Agency, the Scottish Executive, the National Assembly for Wales and the Department for Regional Development — Northern Ireland. The DRMB includes loading aspects and may be used for additional guidance on loading.

For railway bridges, additional references and/or guidance should be obtained from the relevant railway authority.

Annex T (normative) Design documents T.1 General

Until completion of the ENVs and NADs for design of steel, concrete and composite bridges, the design of highway bridges of these materials shall conform to the strength requirements of the Design Manual for Roads and Bridges of the Department of the Environment, Transport and the Regions — Highways Agency, the Scottish Executive, the National Assembly for Wales and the Department for Regional Development — Northern Ireland, or as otherwise agreed by the relevant highways authority. For railway bridges, design documents shall be as specified by the relevant railway authority.

NOTE Whether the DMRB or the NAD and associated ENV is used for strength, a compatible basis shall be agreed with the relevant authority until final issue of the EN documents and all partial factors on strength and actions are finally established.

T.2 Additional guidance for highway bridges

In relation to T.1 and specific clauses of this NAD the following should be noted.

Assessment and appraisal (1.1.1(4) of ENV 1991-3:1995)

Assessment and appraisal should follow the guidance in the DMRB, but with loading aspects related to the ENV and NAD. Assessment should only be carried out in accordance with the DMRB until all aspects of assessment and appraisal of existing structures are addressed by the relevant EN documents.

Definitions (1.4 of ENV 1991-3:1995)

Differences in terminology, particularly with respect to "carriageways" and "lanes", and with regard to use of persistent/transient "situations" with permanent/variable actions, are defined in ENV 1991-1. Design situations and requirements (clause 3 of ENV 1991-3:1995) Coexistence of loads should generally follow the DMRB requirements. Execution conditions relating to fabrication, erection and construction do not form part of this ENV or NAD, but general aspects should be considered in development of the design prior to specific execution requirements. Additional guidance on design and loading aspects of bridge foundations, abutments, retaining walls, and piers may be found in the BRE/DTp publication Bridge Foundations and Substructures, The Stationery Office, 1979. Representation of actions (4.2 of ENV 1991-3:1995)

The differences between the variable notional lanes of the DMRB (i.e. 2.50 m min. to 3.65 m max.) and the NAD/ENV fixed 3.00 m lanes and remaining areas should be noted.

The expression 3.6 aq1 = aqn = ar used in this NAD implies that areas loaded by load model 1 are effectively loaded by a uniform intensity irrespective of width and length plus associated tandem system defined by aQ1, aQ2 and aQ3.

The NAD/ENV figures are at maximum disparity with the DMRB figures where the numbers of notional lanes change in the DMRB (e.g. around 7.5 m, 11m, 14.6 m, and 18 m). For single lane carriageways (up to 5.0 m width in the DMRB; 5.4 m width in the NAD/ENV), use of asL (= 0.69), produces the same factor on the tandem system and the UDL (i.e. aQ1SL = «q1SL = 0.58). Vertical loads: characteristic values (4.3 of ENV 1991-3:1995) As with the paragraph relating to 4.2 of ENV 1991-3:1995, certain aspects of DMRB loading cannot be matched at all spans or load lengths. In particular with regard to LM3, the variable separation of the HB vehicle axles in the DMRB is not replicated in any of the annex A special vehicles considered alone, but the pair of vehicles given in 4.3.4a), b) or c) cover most arrangements of loaded lengths and continuous span influence lines with regard to total vehicle loads. It should also be noted that LM3 does not cater for axle loads greater than 150 kN, and heavier axle loads are covered by LM1 and/or LM2 under 4.3.2 and 4.3.3 of ENV 1991-3:1995 respectively. However, pairs of axle loads up to 450 kN each relevant to DMRB 45HB loads cannot be catered for by any of the ENV load systems, and special considerations may be required if vehicles with such pairs of axles are not restricted from entry onto the structure.

Horizontal forces: characteristic values (4.4 of ENV 1991-3:1995)

NAD/ENV loads may differ considerably from DMRB values, but generally their secondary nature should not require further consideration as the NAD/ENV loads are compatible with the vehicle loading considered. If horizontal forces are of prime concern, some further considerations may be required. In particular it should be noted that the effects of NAD/ENV centrifugal forces can be significantly less onerous than the forces currently in the DMRB, and if these can affect the design, the difference in forces should be reviewed and a suitable basis agreed with the relevant authority. Similarly amended bases for other horizontal forces may also be required.

Groups of traffic loads (4.5 of ENV 1991-3:1995)

UK designers only familiar with "nominal" and "design" loads of the DMRB should ensure NAD/ENV loads are properly applied where these are stated as "characteristic" or "multi-component actions", and "frequent", "infrequent", "characteristic" values or actions, particularly with regard to T.1, also noting use of "dominant" component action and associated/reduced group actions. Fatigue load models (4.6 of ENV 1991-3:1995)

The appropriate traffic categories and models to be considered should be reviewed and agreed with the relevant authority at the outset of the design requirements. See annex Y for more guidance. Accidental actions (4.7 of ENV 1991-3:1995)

The required basis for all accidental actions should be agreed with the relevant authority at the outset of the design requirements. This relates to vehicle collision forces on or under the bridge, as well as parapet and barrier requirements. The associated vehicular loading should also be considered or specified at the outset, as well as any specific requirements for service vehicles or maintenance requirements. The differences in NAD/ENV and DMRB terminology should be noted, especially with regard to "piers" and "supports", "decks" and "superstructures", "parapets" and "barriers", etc., as well as the different partial factors, that have been allowed for in the tabulated NAD values, by adjustment of the collision forces given in annex X.

Actions on parapets (4.8 of ENV 1991-3:1995)

The comments and guidance on ENV 1991-3:1995, clause 3 and 4.7, given in this annex shall apply. Actions on embankments (4.9 of ENV 1991-3:1995) The comments and guidance on ENV 1991-3:1995, clause 3 and 4.7, given in this annex shall apply. Pedestrian, cycle and other actions specifically for footbridges (clause 5 of ENV 1991-3:1995) The comments and guidance on ENV 1991-3:1995, clause 3 and 4.7, given in this annex shall apply.

Annex X (normative) Summary of boxed values indicated in ENV 1991-3:1995 and reference clause in this NAD

Table X.1 summarizes the boxed values indicated in ENV 1991-3:1995 together with the reference clause. Table X.1 also specifies the values that shall be used to replace the boxed values in application of this NAD.

Table X.1 — Boxed values indicated in ENV 1991-3:1995 and values specified in this NAD

Reference in ENV 1991-3:1995

Item

Unit

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