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1 TRAIL BRIDGE INSPECTION 101. 2 Mission Statement This PowerPoint is intended to familiarize the budding inspector with bridge terminology and concepts.

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Presentation on theme: "1 TRAIL BRIDGE INSPECTION 101. 2 Mission Statement This PowerPoint is intended to familiarize the budding inspector with bridge terminology and concepts."— Presentation transcript:

1 1 TRAIL BRIDGE INSPECTION 101

2 2 Mission Statement This PowerPoint is intended to familiarize the budding inspector with bridge terminology and concepts so they are ready and able to participate in a more in-depth discussions during the classroom sessions.This PowerPoint is intended to familiarize the budding inspector with bridge terminology and concepts so they are ready and able to participate in a more in-depth discussions during the classroom sessions.

3 3 Trail Bridges 101 Why do we inspect trail bridges?Why do we inspect trail bridges? Who can inspect trail bridges?Who can inspect trail bridges? What is a trail bridge?What is a trail bridge? What does that bridge term mean?What does that bridge term mean? What are checks, splits, etc?What are checks, splits, etc? What tools do I need for inspection?What tools do I need for inspection? What should I wear for safety?What should I wear for safety?

4 4 Its just water over the bridge… Safety!! National Bridge Inspection Standards Why do we inspect trail bridges?

5 5 Bridge Inspection History During the bridge construction boom of the 1950s and 1960s, little emphasis was placed on safety inspection and maintenance of bridges. This changed when the 2,235 foot Silver Bridge at Point Pleasant, WV, collapsed into the Ohio River, on Dec. 15, people were killed.

6 6 Bridge Inspection History The Federal Highway Act of 1968 required the Secretary of Transportation to establish a national bridge inspection standard and develop a program to train bridge inspectors. National Bridge Inspection Standards were developed for Road Bridges.

7 7 Forest Service Trail Bridge Inspector Qualifications FSM Qualifications of Personnel Responsible for Trail Bridges Inspection and Condition Assessment Qualification and certification requirements shall be established by Regional guidance (FSH b, sec. 05).

8 8 General Definition of a Trail Bridge from the TRAIL BRIDGE MATRIX: A trail structure, including supports, erected over a depression or obstruction such as water, roadway, trail, or railway that provides a continuous pathway and has a deck for carrying traffic or other loads. What is a Trail Bridge?

9 9 Trail Bridge Matrix

10 10 Trail Bridge Matrix

11 11 TRAIL BRIDGE MATRIX: Complex Major Minor * Inspection interval for all trail bridge classifications is every 5 years Classification of Trail Bridges

12 12 Complex Trail Bridge Whose failure likely would put the public at risk Made of wood, concrete, fiberglass, steel, suspension, or trusses Usually greater than 20 ft long & Greater than 5 ft height Single or multiple span Any bridge that requires higher inspection skills Requires a technical inspection by an engineer or engineering technician certified road bridge inspector

13 13 Example: Steel Deck Truss COMPLEX TRAIL BRIDGE

14 14 Example: Fiberglass COMPLEX TRAIL BRIDGE

15 15 Example: Steel Thru Truss COMPLEX TRAIL BRIDGE

16 16 Example: Old Railroad Trestle COMPLEX TRAIL BRIDGE

17 17 Example: Suspension COMPLEX TRAIL BRIDGE

18 18 Other Examples of Complex Trail Bridges: Concrete Masonry Arches Multi-Span Structures Complex Designs COMPLEX TRAIL BRIDGE

19 19 Major Trail Bridge Whose failure likely would put the public at risk Made of wood (log/timber/glulam) Greater than 20 ft long & Greater than 5 ft height Single span Requires a technical inspection by a person: 1. Trained specifically for log and/or timber trail bridge inspections; and 2. Deemed qualified, based on Regional Guidance.

20 20 MAJOR TRAIL BRIDGE Wood and >20 ft long and >5 ft high and single span Example: Treated Log Stringer

21 21 MAJOR TRAIL BRIDGE Wood and >20 ft long and >5 ft high and single span Example: Untreated Log Stringer

22 22 MAJOR TRAIL BRIDGE Wood and >20 ft long and >5 ft high and single span Example: Glulam Beam

23 23 MAJOR TRAIL BRIDGE Wood and >20 ft long and >5 ft high and single span Example: Sawn Lumber

24 24 Minor Trail Bridge –Whose failure poses no significant risk to the public –Made of wood (log/timber/glulam) –Less than 20 ft long or –Less than 5 ft height –Requires a condition assessment by a person trained and qualified, based on Regional Guidance.

25 25 MINOR TRAIL BRIDGE Example: Sawn Lumber Wood and <20 ft long or <5 ft above stream

26 26 MINOR TRAIL BRIDGE Wood and <20 ft long or <5 ft above stream Example: Log Stringer

27 27 WHY WE INSPECT TRAIL BRIDGES SAFETY!!!! WHAT IS A BRIDGE? A structure erected over a depression or obstruction such as water that provides a continuous pathway and has a deck for carrying traffic or other loads. WHAT ARE THE THREE CLASSIFICATIONS OF TRAIL BRIDGES? * Complex *Major *Minor This class is only for Minor and Major trail bridges Quick Summary so Far

28 28 Bridge Terminology Clear Span – Distance between face of support.

29 29 LEFT RIGHT UPSTREAM DOWNSTREAM Bridge Orientation Terminology APPROACH

30 30 Span Arrangements SINGLE or SIMPLE SPAN

31 31 MULTIPLE SIMPLE SPAN Simple Span – many spans, but each acts independently Span Arrangements

32 32 MULTIPLE CONTINUOUS SPAN Continuous Spans – 1 girder spans across 2 or more supports Span Arrangements

33 33 Approach Types Gravel and StepsGravel

34 34 Rail System Curbs, rails, posts, and bracing provided for user Safety

35 35 Deck The Deck supports loads applied to the bridge

36 36 Decking Types & Terms Planks Glulam panels Split logs Puncheon Wearing Surface Running plank Non-skid Gravel

37 37 Superstructure The Superstructure carries loads from the deck to the substructure.

38 38 Superstructure Components Girders or stringers or beams – main load carrying members Diaphragms or bridging or cross bracing – provide lateral support to girders (help stabilize the girders) Backwalls – attached to the ends of the girders or stringers. GLULAM GIRDER LOG STRINGER SAWN BEAM Is it a girder or a stringer?

39 39 Superstructure Diaphragms (*), Bridging, Cross Bracing *

40 40 Superstructure Log Stringer, aka Footlog

41 41 Substructure The Substructure carries loads to the ground

42 42 Sills or Ledgers Substructure Types

43 43 Cribs and Gabions Substructure Types

44 44 Columns, piers, piles, bents Substructure Types

45 45 Stream Channel But stream channels may have problem with aggradation, degradation and floating debris. This stream channel is fairly stable

46 46 Stream Channel Bank and bank protection, debris in the waterway, streambed movement

47 47 Stream Channel Aggradation is the accumulation of sediment in rivers

48 48 Stream Channel Degradation is erosion of the streambed

49 49 Stream Channel Floating Debris can be trees and/or vegetation

50 50 SCOUR is loss of ground support Scour

51 51 Scour Undermining is localized scour under a Substructure

52 52 Scour failure is most common in bridges that are too short Scour

53 53 Scour Scour failure is also common in areas where the banks are weak and unprotected by vegetation or riprap

54 54 Scour Is this substructure fully supported?

55 55 Railing Deck Approach Substructure (Sill) Superstructure (Log Stringer) Reviewing Bridge Terminology Isnt this fun?

56 56 HOW A BRIDGE WORKS Live Loads are applied to the DECK. The DECK transmits live loads and deck dead load to the SUPERSTRUCTURE. The SUPERSTRUCTURE transmits these loads and the superstructure dead load to the SUBSTRUCTURE. Deck Superstructure Substructure Earth

57 57 The SUBSTRUCTURE transmits all these loads and the substructure dead load to the EARTH. The EARTH supports the bridge and all its loads Its all about LOAD PATHS. Deck Superstructure Substructure Earth HOW A BRIDGE WORKS

58 58 Loads and Forces Acting on the Bridge Dead Load – weight of bridge and its components Live Load – temporary loads Soil Reaction – support from the earth

59 59 are determined by bridge materials and design Dead Loads

60 60 Dead Loads include weight of stringers, decking, and railing

61 61 Live Loads are loads placed on the bridge People, pack animals, ATVs, groomers…

62 62 … also include snow, wind, and earthquakes… Live Loads

63 63 is the ground supporting the structure Soil Reaction

64 64 How does a bridge react to loads? Is there going to be math?

65 65 MOMENT, or BENDING, forces are greatest in the middle of the bridge. They are critical in the design of LONG bridges. SHEAR and MOMENT SHEAR forces are greatest at the ends of the bridge. They are critical in the design of SHORT bridges. compression tension

66 66 Shear SHEAR FORCES are highest at the ends of a bridge. Shear failure is common in short spans

67 67 MOMENT FORCES are highest at the middle of the bridge. Bending failure is common in long spans Moment

68 68 Wood Terminology We can break the terminology for wood into three groups: –Basic Wood Definitions –Natural Defect of Wood –Evaluation or Inspection Terms

69 69 Basic Wood Definitions Different timber shapes are used for different applications. Beams can either be rectangular for sawn or glulam beam bridges or round for log stringer bridges.

70 70 Basic Wood Definitions Dimension Lumber. Lumber with a nominal thickness of from 2 inches up to, but not including, 5 inches and having a nominal width of 2 inches or greater. Rough Lumber. Lumber that has not been dressed but that has been sawn, edged, and trimmed. Sawn Lumber. The product of a sawmill not further manufactured other than by sawing, re- sawing and cross-cutting to length.

71 71 Basic Wood Definitions Glued Laminated Timber (glulam). An engineered, stress-rated product of a timber laminating plant comprised of assemblies of specially selected and prepared wood laminations securely bonded together with adhesives. Log Stringer. Round logs that are used as beams or stringers that have been debarked. Timbers. Lumber that is nominally 5 inches or more in least dimension.

72 72 Basic Wood Definitions Dressed Size. The dimensions of lumber after being surfaced with a planing machine. The dressed size is usually 1/2 to 3/4 in. less than the nominal or rough size. A 2- by 4-in. stud, for example, actually measures about 1-1/2 by 3-1/2 in. Nominal Size. As applied to timber or lumber, the size by which it is known and sold in the market i.e, 2x4, 2x6,4x4,etc. (often differs from the actual size).

73 73 Wood Related Definitions Fastener. Generic term for individual mechanical devices such as bolts, nails, etc., used in a connection. Oil-Borne Preservative. A preservative that is introduced into wood in the form of an oil-based solution. Waterborne Preservative. A preservative that is introduced into wood in the form of a water-based solution.

74 74 Natural Defects of Wood Check – A separation of the wood normally occurring across or through the rings of annual growth and usually as a result of seasoning. Split – A separation of the wood through the piece to the opposite surface or to an adjoining surface due to the tearing apart of wood cells. Shake – A lengthwise separation of the wood which occurs between or through the rings of annual growth.

75 75 Natural Defect of Wood

76 76 Checks Seasoning checks may occur in the wide side of a member at or near the neutral axis. The cracks form because the wood near the surface dries and shrinks first. In larger pieces of lumber, the inner core of the member loses moisture and shrinks much slower. Checking relieves the stresses caused by non- uniform drying.

77 77 Checks

78 78 Checks

79 79 Split

80 80 Shake

81 81 Inspection Terms Crack – Complete separation of wood fibers across short axis of wood cells Decay*** - Decomposition of wood substance by fungi. Some people refer to it as rot Delamination. The separation of layers in laminated wood or plywood because of failure of the adhesive, either within the adhesive itself or at the interface between the adhesive and the adhered. *** Will be covered in the classroom in more detail.

82 82 Crack

83 83 Other Inspection Terms Moisture Content (MC). The amount of water contained in the wood, usually expressed as a percentage of the weight of the oven dry wood. Twist. A distortion caused by the turning or winding of the edges of a board so that the four corners of any face are no longer in the same plane. Warp. Any variation from a true or plane surface. Warp includes bow, crook, cup, and twist, or any combination thereof. Weathering. The mechanical or chemical disintegration and discoloration of the surface of wood caused by exposure to light, the action of dust and sand carried by winds. Weathering does not include decay.

84 84 Inspection Tools & Equipment Basic inspection tools & equipment consists of: Backpack Light Boots Pick Awl

85 85 Backpack A good backpack is needed to store and carry your tools to the bridge site.

86 86 Boots or Waders A set of waders or boots are required for walking in the water to inspect the underside of bridges. Boots with felt soles work well walking in areas with slippery rocks.

87 87 Prospectors Pick A prospectors pick works well for sounding logs and beams with the hammer side and checking for decay with the pick side.

88 88 Probes Narrow screw drivers and awls work best for checking for decay in wood members. Locking knives may be used, but are strongly discouraged. Knives that do not lock should not be used.

89 89 Lights A good light for use under bridges is highly recommended. Both for safety and to perform a good bridge inspection. Shining the light under a bridge before entering is a good safety practice, while it helps the inspector see animals and other obstacles that may cause problems.

90 90 Optional Tools A pair of binoculars is good for looking at the underside of a bridge when you can not get right up on the member you need to look at. A telescoping pole can be used to look for scour holes and help to steady the inspector while walking in the stream.

91 91 Optional Tools A mirror can be used for inspecting hard to reach locations or around corners. A plumb bob will help to check if things are perpendicular to the ground. A wrench can be used for checking bolt tightness.

92 92 Essential Items Dont forget the essentials!!! Duck tape for fixing everything and toilet paper for when nature calls.

93 93 Record Keeping Basic record keeping tools are: Clipboard Inspection Forms Write-in-rain notebook Pencils Camera Maps

94 94 Maps Maps are a necessity for working for the Forest Service. Getting lost is not fun. Taking the time to mark the location of the trail bridges on the map makes them easier to find in the field

95 95 Bridge Inspection Forms & Tools Make sure you have enough pencils, write-in-the- rain paper, forms and a clipboard to write on before going into the field.

96 96 Camera Take a camera along and take lots of pictures and document any deficiencies or problems.

97 97 Optional Recording Tools Other optional tools maybe a straight edge, triangles, compass and scale for drawing up sketches of the bridge. Who knows, a calculator may even be handy to have.

98 98 Surveying Equipment Surveying equipment will be used for taking measurements of the bridge. The basics are a 6-foot rule, 25-foot tape, 100-foot cloth tape, a level and a GPS unit.

99 99 GPS or Compass A GPS unit will help you from getting lost and to get the coordinates of the site. Some people still like to use a compass in the woods.

100 100 Levels Levels or a pocket level & ruler are not required, but maybe useful for checking slope of the bridge and settlement of the structure.

101 101 Measuring Devices Tapes and rulers should be used to take measurements of the bridge and problems. At minimum, the inspector should carry a 6- foot rule and a 100-foot cloth tape.

102 102 Safety Equipment Basic Safety Equipment consists of: Hard Hat Safety Glasses Orange Vest Gloves Cell Phone Hiking Boots

103 103 Hard Hat Hard Hats protect your head from sharp or protruding objects under the bridge.

104 104 Safety Glasses & Gloves Glasses protects eyes from flying debris when sounding timbers and sharp objects when walking under bridge Gloves protect hands from blisters, slivers and cuts. They also protect against biting insects and poisonous plants.

105 105 Boots Boots should provide ankle support to prevent sprains and twisted ankles The treads should provide good traction

106 106 Safety Vests Safety vests are needed to provide visibility from traffic using the trail

107 107 Communications A proper communication device should be carried at all times in case of emergency Examples are Forest Service Radios, cell and satellite phones

108 108 First Aid Kit A first aid kit should be carried into the field for emergency use.

109 109 Optional Safety Equipment Optional safety equipment can include: Snake Chaps Bear Spray Insect Repellent Sun Screen Rain Gear Coveralls

110 110 Snake Chaps (optional) Snake chaps should be worn in areas where poisonous snakes are known to live. Do not provoke or handle snakes.

111 111 Insect Repellent & Sunscreen (optional) Insect repellent should be used when mosquitoes, flies and other biting bugs are present. In addition, long sleeve shirts and pants should be worn. Gloves and head nets may also be a good idea. The same holds true for sun screen. Prevent sunburn by wearing long sleeves and hard hat. Use sun screen if needed.

112 112 Rain Gear (optional) A light weight packable rain coat is a great way to go. You need to wear clothing suited to the weather. A layering approach works best for working in unpredictable weather conditions.

113 113 Acknowledgments Thanks to R6 & R10 bridge engineers for their past training presentations and information to help develop this training. Thanks to Michael Knutson and John Kattell for reviewing the training.

114 114 References FHWA Bridge Inspection Reference Manual FHWA Field Manual for Timber Bridge Inspection, Draft FPL Timber Bridges Design, Construction, Inspection and Maintenance FSM 7736 FSH b, Chapter 8 R1 Major Trail Bridge Inspection Form & Minor Trail Bridge Condition Assessment Form R2 Trail Bridge Inspection Guidelines R4 Trail Bridge Inspection Guidelines R6 Trail Bridge Inspection R10 Training PowerPoints


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