- 2.1 – Scope
- 2.2 – Determination of Bridge Load Capacities
- 2.3 – Protection of Bridges from Over-weight and Dimensional Loads
- 2.4 – Protection of Safe Railway Operations during Repairs or Modifications
2.1 – Scope
The railway company BSMP should prevent the operation of railway equipment that could damage a bridge by exceeding safe stress levels in its components or by extending beyond the horizontal and vertical clearance limits of the bridge.
2.2 – Determination of Bridge Load Capacities
- The railway company should determine the load capacity of each of its bridges.
- The load capacity of each bridge should be documented. The railway company BSMP should outline the method(s) by which the capacity is determined.
- The load capacity shallFootnote 3 be determined by a Railway Bridge Engineer using engineering methods and standards applicable to the particular class, configuration, and type of bridge being evaluated.
- Bridge load capacity may be determined from existing design and modification records of a bridge, provided that the bridge substantially conforms to its recorded configuration. Otherwise, the load capacity of a bridge should be determined by measurement and calculation of the properties of its individual components, or other methods as determined by a Railway Bridge Engineer.
- Where a bridge inspection reveals that the condition of a bridge or any of its components might adversely affect the load capacity of the bridge to carry the traffic operated, a Railway Bridge Engineer should determine a new capacity.
- Railway bridge load capacity may be expressed in terms of numerical values related to a standard system of railway bridge loads, but should in any case be stated in terms of weight and length of individual or combined cars and locomotives, for the use of transportation personnel.
- Bridge load capacity may be expressed in terms of both normal and maximum load conditions. Operation of equipment that produces forces greater than the normal capacity should be subject to any restriction or conditions that may be prescribed by a Railway Bridge Engineer.
Section Analysis 2.2 - Determination of Bridge Load Capacities
The current standards for railway bridge design and analysis are found in the ``Manual for Railway Engineering'' of the American Railway Engineering and Maintenance of Way Association (AREMA), and the chapters in this Manual dealing with Timber, Concrete and Steel structures, and Seismic Design, are under continuous review by committees consisting of leading engineers in the railway bridge profession.
However, it is recognized that alternative methods and standards exist and are employed by some railway companies to determine load capacity.
A rigorous, exact method of rating is not practicable with some types of bridges. The Railway Bridge Engineer will necessarily use judgment in determining the loads that should be permitted to operate over these bridges, and ensure that adequate inspections are performed so that any developing deterioration or signs of overload are detected before they progress to become a safety problem.
2.3 – Protection of Railway Bridges from Over-weight and Dimensional Loads
The railway company should have, and ensure the implementation of documented procedures for the operation of equipment exceeding the usual weight or dimension restriction on a bridge. Equipment exceeding the usual weight or dimension restriction should only be operated under conditions determined by a Railway Bridge Engineer.
The railway company is expected to advise other railway companies operating over a railway bridge of the usual loads permitted over it. Railway companies should develop, maintain, and enforce written procedures to restrict a load that exceeds those limits, unless specific authority has been granted and in accordance with restrictions placed by the railway company.
Each company should issue instructions to the personnel responsible for the configuration and operation of trains over railway bridges to prevent the operation of cars, locomotives and other equipment that could exceed the capacity or dimensions of railway bridges.
A Railway Bridge Engineer should be informed of any substantial change in train operation or traffic patterns, which may affect railway bridge safety.
Section Analysis 2.3 - Protection of Bridges from Over-Weight and Dimension Loads
Bridges can be seriously damaged by the operation of loads that exceed their capacity. Movement of equipment that exceeds the clear space on a bridge is an obvious safety hazard. This section proposes that the railway company should issue instructions to personnel who are responsible for the consist and operation of trains over railway bridges to prevent the operation of cars, locomotives and other equipment that would exceed the capacity or dimensions of bridges. Transportation personnel of a company are ultimately responsible for the movement of trains, cars and locomotives. It is essential that they should know and follow any restrictions that are placed on those movements.
The instructions regarding weight should be expressed in terms of maximum equipment weights, and either minimum equipment lengths or axle spacing. Transportation personnel have information on the weights and configuration of cars and locomotives, and they must be able to relate that information to any restrictions placed on the movement of that equipment.
The instructions regarding dimensions should be expressed in terms of feet and inches of cross section and equipment length, in conformance with common railway industry practice for reporting dimensions of exceptional equipment in interchange in which height above top-of-rail is shown for each cross-section measurement, followed by the width of the car or the shipment at that height. In the industry, a standard format exists for the exchange of information on dimensions of railway equipment. Use of the industry practice is necessary to avoid error and confusion.
The movement instructions may apply to individual structures or to a defined line segment or groups of line segments where the published capacities and dimensions are within the limits of all structures on the subject line segments. Railway companies commonly issue instructions related to equipment weights and dimensions to be effective on line segments of various lengths. It is not necessary that transportation personnel be advised of the capacity of every bridge as long as the railway bridge in the line segment has the capacity to safely carry the loads permitted on that line.
When there is a change proposed in train operation or traffic patterns, which may affect railway bridge safety, the transportation department should have a procedure in place for ensuring that the designated Railway Bridge Engineer is advised of the change so that the safety of the railway bridges can be verified.
2.4 – Protection of Safe Railway Operations during Repairs or Modifications
The railway company BSMP should specify procedures for any repair or modification that materially modifies the capacity of a bridge or the stresses in any primary load-carrying component of a bridge. At a minimum, the procedures for repairs or modifications shallFootnote 4 be performed under the direction of a Railway Bridge Engineer and should specify the manner in which traffic or other live loads may be permitted on the bridge while it is being modified or repaired.
Designs and procedures for repair or modification of bridges of a common configuration, such as timber trestles, or instructions for in-kind replacement of bridge components, may be issued as a common standard. Where the common standard addresses procedures and methods that could materially modify the capacity of a bridge or the stresses in any primary load-carrying component of a bridge, the standard shallFootnote 5 be designed under the direction of a Railway Bridge Engineer.
Bridge repair(s) or modification(s) should be performed under the direction of a Railway Bridge Engineer to ensure that the repair(s) or modification(s) are completed in conformity with the design.
Section Analysis 2.4 - Protection of Safe Railway Operations during Repairs or Modifications
For the purposes of Section 2.4 , a "primary load-carrying component" is a bridge component, the failure of which would immediately compromise the structural integrity of the bridge, "bridge modification" means a change to the configuration of a bridge that affects the load capacity of the bridge, and "bridge repair" means remediation of damage or deterioration which may have affected the structural integrity of a bridge.
Transport Canada does not intend that minor repairs that do not affect the capacity of the bridge must be designed by a Railway Bridge Engineer, but the supervision of that work should be performed by a person who is competent to assure that the work does not inadvertently compromise the integrity of the bridge.
Railway companies have typically issued standard instructions for the performance of common maintenance repairs, such as replacement or upgrading of components of timber trestles.