TRAIL BRIDGE INSPECTION 101. 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. Trail Bridges 101.
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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.
Trail Bridges 101 Why do we inspect trail bridges? Who can inspect trail bridges? What is a trail bridge? What does that bridge term mean? What are checks, splits, etc? What tools do I need for inspection? What should I wear for safety?
Why do we inspect trail bridges? • Safety!! • National Bridge Inspection Standards It’s just water over the bridge…☺
During the bridge construction boom of the 1950’s and 1960’s, 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. 15,1967. 46 people were killed. 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. Bridge Inspection History
FSM 7736.33 - Qualifications of Personnel Responsible for Trail Bridges Inspection and Condition Assessment Qualification and certification requirements shall be established by Regional guidance (FSH 7709.56b, sec. 05). Forest Service Trail BridgeInspector Qualifications
What is a Trail Bridge? 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.
Classification of Trail Bridges TRAIL BRIDGE MATRIX: • Complex • Major • Minor * Inspection interval for all trail bridge classifications is every 5 years
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
COMPLEX TRAIL BRIDGE Example: Steel Deck Truss
COMPLEX TRAIL BRIDGE Example: Fiberglass
COMPLEX TRAIL BRIDGE Example: Steel Thru Truss
COMPLEX TRAIL BRIDGE Example: Old Railroad Trestle
COMPLEX TRAIL BRIDGE Example: Suspension
COMPLEX TRAIL BRIDGE Other Examples of Complex Trail Bridges: Concrete Masonry Arches Multi-Span Structures Complex Designs
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.
MAJOR TRAIL BRIDGE Wood and >20 ft long and >5 ft high and single span Example: Treated Log Stringer
MAJOR TRAIL BRIDGE Wood and >20 ft long and >5 ft high and single span Example: Untreated Log Stringer
MAJOR TRAIL BRIDGE Wood and >20 ft long and >5 ft high and single span Example: Glulam Beam
MAJOR TRAIL BRIDGE Wood and >20 ft long and >5 ft high and single span Example: Sawn Lumber
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.
MINOR TRAIL BRIDGE Wood and <20 ft long or <5 ft above stream Example: Sawn Lumber
MINOR TRAIL BRIDGE Wood and <20 ft long or <5 ft above stream Example: Log Stringer
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 Quick Summary so Far This class is only for Minor and Major trail bridges
Bridge Terminology Clear Span – Distance between face of support.
Bridge Orientation Terminology APPROACH DOWNSTREAM RIGHT UPSTREAM LEFT
Span Arrangements • SINGLE or SIMPLE SPAN
Span Arrangements • MULTIPLE SIMPLE SPAN Simple Span – many spans, but each acts independently
Span Arrangements • MULTIPLE CONTINUOUS SPAN Continuous Spans – 1 girder spans across 2 or more supports
Approach Types Gravel and Steps Gravel
Rail System Curbs, rails, posts, and bracing provided for user Safety
Deck The Deck supports loads applied to the bridge
Decking Types & Terms • Wearing Surface • Running plank • Non-skid • Gravel • Planks • Glulam panels • Split logs • Puncheon
Superstructure The Superstructure carries loads from the deck to the substructure.
Superstructure Components Is it a girder or a stringer? • 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
Superstructure * Diaphragms (*), Bridging, Cross Bracing
Superstructure Log Stringer, aka Footlog
Substructure The Substructure carries loads to the ground
Substructure Types Sills or Ledgers
Substructure Types Cribs and Gabions
Substructure Types Columns, piers, piles, bents
Stream Channel But stream channels may have problem with aggradation, degradation and floating debris. This stream channel is fairly stable
Stream Channel Bank and bank protection, debris in the waterway, streambed movement
Stream Channel Aggradation is the accumulation of sediment in rivers
Stream Channel Degradation is erosion of the streambed
Stream Channel Floating Debris can be trees and/or vegetation
Scour SCOUR is loss of ground support