RAILWAY LIVE LOADS General

4.4.6.1 In the design of railway structures, the nominal primary and associated secondary railway live loads shall be in accordance with BS5400, Part 2, Section 8, except that the nominal type RU and RL loading shall be replaced by the primary railway live loads given in Cl. 4.4.6.3.

4.4.6.2 All other secondary railway live loads shall be calculated in accordance with the provisions for type RL loading given in BS5400, Part 2, Section 8. These loads shall be applied to all structures unless indicated otherwise in Cl.4.4.6.4 to 4.4.6.17.

Primary Railway Live Loads

4.4.6.3 The standard design loading for railway vehicles of various line shall be the most onerous in Fig. 4.4.6.F1. This loading shall be applied to each and every track. The most onerous effect on the railway structures shall be determined by applying the loading at any point along the track.

Design loading due to XRL vehicles is set out in the XRL Design Standards manual.

Associated Secondary Railway Live Loads

Fatigue Loads

4.4.6.4 Allowance for fatigue loading in accordance with the provisions of HKSDM Chapter 10 shall be made in all structures which support railway, highway or other significant cyclical loading.

Dynamic Loads

4.4.6.5 The dynamic load factors for railway vehicles given in Cl. 8.2.3.2 of BS5400, Part 2, for type RL loading shall be used in the design of all structures except in the following circumstances:

i) for design of trackform (see Section 3 of the NWDSM);

ii) for structures with eccentric track support structures, including bridges carrying tracks on cantilever slabs;

iii) for steel and composite steel and concrete superstructures; and iv) for structures with spans of 100 m or greater.

4.4.6.6 In the case of items (ii), (iii), or (iv) of Cl. 4.4.6.7, detailed analyses, design and reporting of the dynamic effects of the structure shall be undertaken in accordance with Subsection 4.8 Dynamic Analysis requirements. In all cases structural forms particularly sensitive to cyclic dynamic railway loads shall be avoided. Where this is not possible, the elements fitness for purpose shall be demonstrated by carrying out analyses in accordance with Subsection 4.8.

4.4/9 4.4 Design Loads

NWDSM-Section 4(4.4)-A5 April 2013

4.4.6.7 For underground structure design only the dynamic load factors given in Cl. 8.2.3.2 of BS5400, Part 2, shall be replaced by the following:

i) For spans along the lengths of the track, whether simply supported or continuous:

Spans of 3 m or less, dynamic factor 1.55 Spans of 10 m or more, dynamic factor 1.20

For spans between 3 m and 10 m, the dynamic factor shall be calculated as follows:

I = 1.55 - 0.05 (x-3) I is the dynamic factor x is the span length.

ii) For spans at right angles to the direction of the track, whether simply supported or continuous, the dynamic factor shall be 1.40.

4.4.6.8 For all structures it shall be ensured and checked that structure dynamic response when considered in conjunction with the trackform response is compatible with the achievement of the design standard requirements for 'Ride Quality' given in Section 3 of the NWDSM. The trackform response shall be based on an assessment of the specific trackform type for the location being considered.

Lurching Loads

4.4.6.9 Lurching loads from railway vehicles shall be applied in accordance with BS5400, Part 2, Section 8. The track or tracks selected shall be those in which the transfer of load has the greatest effect on the element under consideration.

Centrifugal Loads

4.4.6.10 The equation for the nominal centrifugal load for railway vehicles given in Cl. 8.2.9 of BS5400, Part 2, may be simplified to:

Fc = 3811 kN/m

R

Where R = radius of the curve, provided the loaded length of the element being considered is less than 2.88 m and the greatest speed envisaged on the curve in question is less than 120 km/h.

4.4.6.11 In all other cases the nominal centrifugal load shall be calculated using the full equation in Cl. 8.2.9 of BS5400, Part 2 with a value of P = 40 kN/m.

Traction and Braking Loads

4.4.6.12 Traction - all axles of a train shall be considered as driven axles and the total traction force shall be equivalent to 30% of the maximum standard axle loads, subject to a maximum of 600 kN.

4.4/10 4.4 Design Loads

NWDSM-Section 4(4.4)-A5 April 2013

4.4.6.13 Braking - all wheels of a train shall be considered as braked and the total braking force shall be equivalent to 25% of the maximum normal axle loads, subject to a maximum of 800 kN.

4.4.6.14 Where the length of the structure under consideration is greater than a train length, the total traction and braking forces to be applied shall be that equivalent to one train. In the case where the length of structure considered is less than the length of a train, then as many axles as possible shall be considered as acting on that length.

Derailment Loads

4.4.6.15 Derailment loads shall be derived in accordance with BS5400, Part 2, Cl. 8.5, with the exception that condition (c) shall not apply to underground structures. For bridges the clause shall be reworded as follows:

i) For overturning or instability checks, four EMU Train or Works Train bogies, whichever is more onerous, (with axle centres as defined in Cl.4.4.6.3) shall be considered to have come to rest with the four Train bogies centre of gravity located on the line of the inside face of the parapet, whilst the remaining Train bogies centre of gravity lie not more than 0.25 m from the track centre line. Under this loading the structure as a whole shall not overturn and the superstructure shall not lift off the bearings. However, it may be assumed that local damage may occur. (See Fig. 4.4.6.F2 for details.)

ii) The parapets to railway bridges shall not be designed to withstand the effect of impact from a derailed train.

4.4.6.16 Local damage means, at worst, the loss of a parapet and/or an enclosure unit. The structure on which the train runs shall be capable of being rapidly brought back into full use after minimal repairs. For a structure carrying double tracks, the derailment of a train on one track shall not restrict the operation of trains on the other track, except in the case of physical obstruction.

4.4.6.17 Design loads shall be applied in accordance with BS5400, Part 2, Cl. 8.5.2 except; in (a)(2) the vertical load shall be amended to 100 kN; in (b) each of the concentrated loads shall be 130 kN and in (c) the length of the line load shall be limited to 25 m.

4.4.7 HIGHWAY LIVE LOADS

4.4.7.1 Highway structures and pedestrian bridges shall be designed to resist the live loading and fatigue loading given in the HKSDM. The level of abnormal or HB loading for each particular highway structure shall be agreed with the Highways Department.

4.4.7.2 For underground structures beneath an existing or proposed highway, the structure shall be designed to resist the load defined in Cl.4.4.7.1. Where there is 2 m or more cover to the elements under consideration, these loads may be represented by the following:

4.4/11 4.4 Design Loads

NWDSM-Section 4(4.4)-A5 April 2013

Type HA Loading = 12 kN/m² 45 units HB Loading = 24 kN/m²

4.4.7.3 Structures adjacent to highways which support vehicle and/or pedestrian parapets shall be designed in accordance with the requirements of HKSDM. Particular attention shall be paid to the effects of parapet horizontal vehicle collision loading and concurrent vehicle vertical accidental wheel loading adjacent to the parapet, in accordance with Subsection 2.8 of the HKSDM.