Other materials

The composition, properties, and performance of materials not covered in this Section shall be specified by taking into account the design loads and expected environmental degradation during the design life of the structure.

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3.2 Definitions 41

3.3 Abbreviations and symbols 43 3.3.1 Abbreviations 43

3.3.2 Symbols 43

3.4 Limit states criteria 47 3.4.1 General 47

3.4.2 Ultimate limit states 47 3.4.3 Fatigue limit state 47 3.4.4 Serviceability limit states 47

3.5 Load factors and load combinations 48 3.5.1 General 48

3.5.2 Permanent loads 50 3.5.3 Transitory loads 51 3.5.4 Exceptional loads 51 3.6 Dead loads 51

3.7 Earth loads and secondary prestress loads 52 3.7.1 Earth loads 52

3.7.2 Secondary prestress effects 52 3.8 Live loads 52 3.8.1 General 52 3.8.2 Design lanes 52 3.8.3 CL-W loading 52 3.8.4 Application 54 3.8.5 Centrifugal force 56 3.8.6 Braking force 56 3.8.7 Curb load 56 3.8.8 Barrier loads 56 3.8.9 Pedestrian load 57

3.8.10 Maintenance access loads 57 3.8.11 Maintenance vehicle load 57 3.8.12 Multiple-use structures 57 3.9 Superimposed deformations 58 3.9.1 General 58

3.9.2 Movements and load effects 58 3.9.3 Superstructure types 58

3.9.4 Temperature effects 59 3.10 Wind loads 61

3.10.1 General 61

3.10.2 Design of the superstructure 62 3.10.3 Design of the substructure 63 3.10.4 Aeroelastic instability 64 3.10.5 Wind tunnel tests 65 3.11 Water loads 65 3.11.1 General 65 3.11.2 Static pressure 65 3.11.3 Buoyancy 65 3.11.4 Stream pressure 65 3.11.5 Wave action 66 3.11.6 Scour action 66 3.11.7 Debris torrents 66

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3.12.4 Ice jams 69

3.12.5 Ice adhesion forces 69 3.12.6 Ice accretion 69 3.13 Earthquake effects 69 3.14 Vessel collisions 70 3.14.1 General 70 3.14.2 Bridge classification 70 3.14.3 Assessment 70

3.14.4 Annual frequency of collapse 70 3.14.5 Design vessel 70

3.14.6 Application of collision forces 70 3.14.7 Protection of piers 71

3.15 Vehicle collision load 71

3.16 Construction loads and loads on temporary structures 71 3.16.1 General 71 3.16.2 Dead loads 71 3.16.3 Live loads 71 3.16.4 Segmental construction 71 3.16.5 Falsework 72 Annexes

A3.1 (normative) — Climatic and environmental data 73

A3.2 (normative) — Wind loads on highway accessory supports and slender structural elements 94 A3.3 (normative) — Vessel collision 104

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3.1 Scope

This Section specifies loads, load factors, and load combinations to be used in calculating load effects for design. Resistance factors required to check ultimate limit states criteria in accordance with Clause 3.4.2

are specified elsewhere in this Code. Loadings provisions for evaluation of existing structures are covered in Section 14 and for rehabilitation in Section 15.

This Section includes requirements related to the vibration of highway and pedestrian bridges. It also includes requirements related to construction loads and temporary structures; these apply to partially completed structures and structures necessary for construction purposes. Snow loads are not specified because in normal circumstances the occurrence of a considerable snow load will cause a compensating reduction in traffic load.

3.2 Definitions

The following definitions apply in this Section:

Acceptance criterion — the acceptable frequency of collapse due to the design vessel collision. Buffeting — the loads induced in a structure by the turbulence in the natural wind.

Damping — the dissipation of energy in a structure oscillating in one of its natural modes of vibration. It is normally expressed as a ratio of the actual value of damping to the critical value of damping. The critical value of damping is the lowest value at which an initial motion decays without oscillation.

Dead load — the load from material that is supported by the structure and is not subject to movement. Debris torrent — a mass movement that involves water-charged inorganic and organic material flowing rapidly down a steep confined channel.

Design lane — a longitudinal strip that is a fraction of the deck width and within which a Truck or Lane Load is placed for the purpose of design or evaluation.

Divergence — an aerodynamic instability in torsion that usually occurs at wind speeds higher than those normally considered in design.

Drag — the load in the direction of the wind, induced by an airstream acting on a body.

Dynamic load allowance — an equivalent static load that is expressed as a fraction of the traffic load and is considered to be equivalent to the dynamic and vibratory effects of the interaction of the moving vehicle and the bridge, including the vehicle response to irregularity in the riding surface.

Effective temperature — the temperature that governs the thermally induced expansion and contraction of a superstructure.

Exceptional loads — the loads due to forces of nature or accident that would not be expected to occur more than once in the life of a bridge.

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Exposed plan area — the net area of an object as seen in plan from above. For a superstructure, the plan area of the deck and of any laterally protruding railings, members, or attachments.

Factored load — the product of a load specified in this Code and the corresponding load factor. Factored load effect — the load effect caused by a factored load.

Falsework — a temporary structure used to support another structure or a part of the other structure. Flexural frequency — a natural frequency of vibration of an unloaded bridge based on the longitudinal flexural stiffness and mass distribution of the superstructure.

Flutter — an instability caused by the interaction of the wind and the bridge structure involving either pure torsional motion or coupled vertical and torsional motion of a bridge deck.

Galloping — the cross-wind vibrations that arise from the aerodynamic instability of many slender structures.

Gust effect coefficient — the ratio of the peak wind-induced load on a structure or response of a structure, including both static and dynamic action, to the static wind-induced load or response. It is also referred to as the gust coefficient.

Ice accretion — the buildup of an ice layer on the exposed surfaces of a body due to freezing rain or in-cloud icing.

Live load — a load imposed by vehicles, pedestrians, equipment, or components that are subject to movement.

Load — a load, force, deformation, or volumetric change that is imposed externally on or internally within a structure.

Natural frequency — the frequency of vibration of one of the natural modes of a bridge, expressed in cycles per second, and being the inverse of the natural period.

Natural period — the duration of one complete cycle of free vibration of a normal mode of vibration of a structure.

Normal mode shape — the geometric configuration of a structure associated with vibration at one of its natural frequencies.

Pedestrian load — the load due to pedestrians on a bridge.

Permanent loads — the loads that do not vary unless physical changes are made to the bridge. Reynolds number — the ratio of inertial forces to viscous forces of a fluid.

Service life — the number of years a structure is intended to be in use.

Slender structural element — a structural member with an aspect ratio of 20 or more.

Strouhal number — a non-dimensional parameter that characterizes the frequency of vortex shedding and represents the ratio of the width of a body placed in an airstream to the wavelength of vortices shed from the body.

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nature.

Travelled lane — a strip of roadway marked for use by a single line of vehicles.

Vessel collision — the impact of a ship with the substructure or superstructure of a bridge over a navigable waterway.

Vortex shedding — an instability of the wake behind a bluff (i.e., not streamlined) body in an airstream, comprising a more or less periodic shedding of vortices. The vortices are shed alternately from opposite sides of the body, producing an alternating lateral load normal to the wind direction.

Wake buffeting — the loads induced in a structure by the turbulence caused by the wake of an upwind structure.

Water loads — the loads from static or moving water, including pressure, buoyancy, waves, and debris torrents.