R10 SUPPLEMENT 7709.56b-91-1
EFFECTIVE 5/6/91
8.02-8.4
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8.02 - Objectives. Apply the requirements of this chapter to retaining walls, Log
Transfer Facilities (LTF's), and other transportation structures on both the Forest
Development Road and Trail Systems.
8.2 - TECHNICAL INSPECTIONS. Use good judgement in applying and modifying
the National Bridge Inspection Standards (NBIS) to develop an inspection program
for retaining walls, LTF's, and other structures.
8.22 - Schedule. Use the 2-year inspection frequency set forth in the NBIS and the
AAHSTO Manual for Maintenance Inspection of Bridges as the basic inspection
interval for road bridges.
An inspection interval of up to 4 years may be used for road bridges in good or
excellent condition (having a composite condition rating of 7 or greater, in
accordance with the basic text of FSH 7709.56b), and the structure age does not
exceed the following age limits:
1. 40 years - Concrete, painted or protected steel, or combination.
2. 30 years - Unprotected steel, treated timber, or combination.
3. 10 years - Untreated timber.
Use a 4-year maximum inspection interval for trail bridges and culvert
installations.
Use sound judgement in selecting the inspection interval for retaining walls, LTF's,
and other transportation structures. Do not extend the inspection interval for these
structures beyond 4 years.
A lesser inspection frequency may be required and should be used where conditions
warrant.
8.25 - Inspection Documents and Forms. Use Regional Inspection forms,
or locally produced forms, that provide information for the coding requirements of
the Transportation Information System (TIS) database and space for narrative
comments on structural features and condition. (See exhibit 01 - Bridge Data
Worksheet and exhibit 02 - Bridge Inspection Worksheet (optional).)
For Region-wide consistency in meeting NBIS standards for exceptions to the 2-year
inspection frequency and other special inspection requirements, use the following
entries in data element "965 Inspection Remarks:"
Element 966 - 1
(Count)
2
3
Element 967 - Inspection Frequency
(Remarks)
Fracture Critical Members
Underwater Inspection Req'd
years
Yes or No
Yes or No
R10 SUPPLEMENT 7709.56b-91-1
EFFECTIVE 5/6/91
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8.26 - Reporting. For all structures on roads identified as "Subject to the Highway
Safety Act" (FSM 7703.4), submit a copy of all inspections to the Regional
Structural Engineer for transmittal to the Alaska Department of Transportation.
Notify the Regional Structural Engineer, if the following actions are recommended
or approved.
1. Bridge closure or load restrictions are established.
2. Emergency repairs for any reason.
3. Repair or replacement of primary structural members.
8.3 - DETERMINING BRIDGE CAPACITY.
8.31 - General. Rate all bridges for the AASHTO vehicles, Types 3, 3S2, and 3-3.
For bridges carrying off-highway log haul traffic, also rate for the standard R10 U80
and U102 vehicles.
Rate retaining walls, LTF's, and other structures for the equipment or traffic
commonly using or expected to use the facility.
Rate trail structures for appropriate pedestrian live load, snow load, stock, or trail
vehicle traffic expected to use the structure.
8.32 - Load ratings.
1. Normal Use load Capacity (Inventory Rating). Use the allowable stresses
published in the National Design Standard for timber structures. Adjust these
values as appropriate for various conditions of use specified in the standard.
Use the allowable stresses in AASHTO 8.15.2.1 and 8.15.5.2 for rating of concrete
structures using the Service Load (Allowable Stress) Design Method.
2. Maximum Allowable Load Capacity (Operating Rating). For analysis of
timber bridges, use the adjusted Inventory Rating stresses multiplied by 1.33. For
analysis of concrete bridges, follow the procedures in the AASHTO Manual for
Maintenance Inspection of Bridges, section 5.4.5.
Strength Design Methods (Load Factor Design) should not be used for rating of
concrete elements.
8.33 - Posting. Post bridges and roadway retaining walls for the appropriate
reduced weight of AASHTO vehicles, Types 3, 3S2, or 3-3, when the calculated load
capacity of any principal structural member, using the Operating Rating stress
level, is inadequate to support any of the standard AASHTO vehicles. When
R10 SUPPLEMENT 7709.56b-91-1
EFFECTIVE 5/6/91
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structural elements are inadequate to support U80 or U102 vehicles, at Operating
Rating stress levels, include weight limits and other restrictions as conditions of
commercial use permits or timber sale documents. Do not post structures for
reduced loads of U80 or U102 vehicle geometry.
When weight restrictions are necessary for log transfer facilities, include weight
limits and other restrictions as conditions of commercial use permits or timber sale
documents. Determine appropriate weight limits for the various types of equipment
which are expected to use the structure.
Post trail bridges for an appropriate reduced load (maximum number of people,
stock, number, or size of trail vehicles) for all bridges that are inadequate to support
any of the following load conditions at Operating Rating stress level:
1. A load of 1,000 pounds placed over 6 feet of deck length, anywhere on the
span.
2. A uniform load of 85 psf placed anywhere over 50 percent of the span for
bridges less than 40-feet long.
3. A uniform load of 60 psf placed anywhere over 50 percent of the span, for
bridges over 40-feet long.
4. Any reasonable assumption of stock or vehicle loading.
Carefully consider the problems associated with enforcement of use restrictions.
Where stock or vehicle use is anticipated, prohibit all use when the structure is
inadequate to support any reasonable assumption of loading. (If a pack string is
reasonable and the structure can support only two animals, close to all stock
traffic.)
Close or immediately repair all trail bridges that are inadequate to support any of
the following load conditions at Operating Rating stress level:
1. A load of 500 pounds placed over 6 feet of deck length, anywhere on the span.
2. A uniform load of 85 psf placed anywhere over 30 percent of the span for
bridges less than 40 feet long.
3. A uniform load of 60 psf placed anywhere over 30 percent of the span, for
bridges over 40 feet long.
R10 SUPPLEMENT 7709.56b-91-1
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8.4 - INVENTORIES. The TIS is mandatory for R10 Bridge and Major Culvert
Inventory. In addition, inventory all LTIF's, retaining walls, and other
transportation structures. Inventories for other structures should use the TIS
database to the fullest extent possible.
Unless special conditions warrant, do not retain on the Forest Inventory, any
structure under the jurisdiction of another governmental agency (Borough, State, or
Federal).
Consider the need to inventory and inspect privately-owned structures routinely
used by Forest Service personnel or Forest Service contractors, where private
inspection is judged inadequate to safeguard Forest interests.
R10 SUPPLEMENT 7709.56b-91-1
EFFECTIVE 5/6/91
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8.25 - Exhibit 01
TIS-Bridges -- Bridge Data Worksheet -- Page 1
SEE END OF THIS CHAPTER IN THE PAPER COPY
OF THE MASTER SET
FOR SECTION 8.25 - EXHIBIT 01.
R10 SUPPLEMENT 7709.56b-91-1
EFFECTIVE 5/6/91
8.02-8.4
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8.25 - Exhibit 01--Continued
TIS-Bridges -- Bridge Data Worksheet -- Page 2
SEE END OF THIS CHAPTER IN THE PAPER COPY
OF THE MASTER SET
FOR SECTION 8.25 - EXHIBIT 01.
R10 SUPPLEMENT 7709.56b-91-1
EFFECTIVE 5/6/91
8.02-8.4
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8.25 - Exhibit 02
TIS-Bridges -- Bridge Inspection Worksheet -- Page 1
SEE END OF THIS CHAPTER IN THE PAPER COPY
OF THE MASTER SET
FOR SECTION 8.25 - EXHIBIT 02.
R10 SUPPLEMENT 7709.56b-91-1
EFFECTIVE 5/6/91
8.02-8.4
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8.25 - Exhibit 02--Continued
TIS-Bridges -- Bridge Inspection Worksheet -- Page 2
SEE END OF THIS CHAPTER IN THE PAPER COPY
OF THE MASTER SET
FOR SECTION 8.25 - EXHIBIT 02.
R10 SUPPLEMENT 7709.56b-91-1
EFFECTIVE 5/6/91
8.02-8.4
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8.25 - Exhibit 02--Continued
TIS-Bridges -- Bridge Inspection Worksheet -- Page 3
SEE END OF THIS CHAPTER IN THE PAPER COPY
OF THE MASTER SET
FOR SECTION 8.25 - EXHIBIT 02.
PLAN VIEW
CROSS SECTIONS
R10 SUPPLEMENT 7709.56b-91-1
EFFECTIVE 5/6/91
8.02-8.4
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8.25 - Exhibit 02--Continued
TIS-Bridges -- Bridge Inspection Worksheet -- Page 4
SEE END OF THIS CHAPTER IN THE PAPER COPY
OF THE MASTER SET
FOR SECTION 8.25 - EXHIBIT 02.
PHOTOS