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Figure 4.1 :Example of the Lane Numbering in the most general case.

(5) Where the carriageway consists of two separate parts on the same deck, only one numbering is used for the whole carriageway. Hence, even if the carriageway is divided into two separate parts, there is only one Lane Number 1, which can be alternatively on the two parts.

(6) Where the carriageway consists of two separate parts on two independent decks, each part is considered as a carriageway. Separate numbering is then used for the design of each deck. If the two decks are supported by the same piers and/or abutments, there is one numbering for the two parts together for the design of the piers and/or the abutments.

4.2.5 Application of the load models on the individual lanes

(1) For each individual verification, the load models, on each notional lane, should be applied on such a length and so longitudinally located that the most adverse effect is obtained, as far as this is compatible with the conditions of application defined below for each particular model.

NOTE : This rule provides conservative results, especially for frequent values and for fatigue verifications based on Fatigue Load Model 1.

On the remaining area, the associated load model is applied on such lengths and widths such that the most adverse effect is obtained, as far as this is compatible with particular conditions specified below.

NOTE : When relevant, the various loading models should be combined together (see 4.5) and with models for pedestrian or cycle loads.

4.3.1 General and associated design situations

(1) Characteristic loads are intended for the determination of road traffic effects associated with ultimate limit-state verifications and with particular serviceability verifications (see ENV 1991-1, 9.4.2 and 9.5.2, and ENV 1992 to 1995).

(2) The load models for vertical loads represent the following traffic effects :

(a) Load Model 1 : Concentrated and uniformly distributed loads, which cover most of the effects of the traffic of lorries and cars. This model is intended for general and local verifications.

(b) Load Model 2 : A single axle load applied on specific tyre contact areas which covers the dynamic effects of the normal traffic on very short structural elements. This model should be separately considered and is only intended for local verifications.

(c) Load Model 3 : A set of assemblies of axle loads representing special vehicles (eg. for industrial transport) which may travel on routes permitted for abnormal loads. This model is intended to be used only when and as far as required by the client, for general and local verifications.

(d) Load Model 4 : A crowd loading. This model should be considered only when required by the client. It is intended only for general verifications.

NOTE : This crowd loading may be usefully specified by the relevant authority for bridges located in or near towns if its effects are not obviously covered by Load Model 1.

(3) Load Models 1 and 2 are defined numerically for persistent situations and are to be considered for any type of design situation (e.g. for transient situations during repair works).

(4) Load Models 3 and 4 are defined only for some transient design situations.

Note : See annex C. Design situations are specified as far as necessary in design Eurocodes and/or in particular projects, in accordance with definitions and principles given in ENV 1991-1. Combinations for persistent and transient situations may be numerically different.

4.3.2 Main loading system (Load Model 1)

(1) The main loading system consists of two partial systems :

(a) Double-axle Concentrated Loads (tandem system : TS), each axle having a weight:

where :

No more than one tandem system should be considered per lane ; only complete tandem systems shall be considered. Each tandem system should be located in the most adverse position in its lane (see however (4) below and Figure 4.2). Each axle of the tandem model has two identical wheels, the load per wheel being therefore equal to O^aQ Qk. The contact surface of each wheel is to be taken as square and of side 0,40 m (see Figure 4.2).

(b) Uniformly Distributed Loads (UDL system), having a weight density per square metre:

where:

These loads should be applied only in the unfavourable parts of the influence surface, longitudinally and transversally.

(2) Load Model 1 should be applied on each notional lane and on the remaining areas. On notional Lane Number i, the load magnitudes are referred to as aQjQjk and aqjQik (see Table 4.2). On the remaining areas, the load magnitude is referred to as aqrgrk.

(3) Unless otherwise specified, the dynamic amplification is included in the values for Qj|< and q^.

(4) For the assessment of general effects, the tandem systems may be assumed to travel along the axes of the notional lanes.

(5) The values of Qk anc* <7ik are given in Table 4.2.

Table 4.2 : Basic values

Location

Tandem system

UDL system

Axle loads Qk (kN)

<7ik (or <ftk) (kN/mZ)

Lane Number 1

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