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15.4.1

Base Section Circumferential Reinforcement—

Circumferential reinforcement shall meet all the requirements

of Section

, except that Paragraph 14.5 is not permitted.

15.4.2

Base Slab Reinforcement:

15.4.2.1 A layer of reinforcement shall be placed above the

midpoint, and shall have a minimum area of 250 mm

/linear m

in both directions.

15.4.2.2 The minimum protective cover over the reinforce-

ment shall be 25 mm.

15.4.3

Longitudinal Members—

Longitudinal bars or mem-

bers used to maintain a cage of circumferential reinforcement

in shape and position within the form shall meet all the

requirements of Section

15.4.4

Joint Reinforcement—

The mating surface of the base

section joint is not required to contain circumferential rein-

forcement.

OTE

4—(Advisory) Base sections with multiple openings, large

openings, or both may require special consideration of their handling

reinforcement.

15.5

Physical Requirements—

Physical requirements for test

shall conform to the requirements of Section 8.

15.5.1

Proof-of-Design Test:

15.5.1.1 If

15.2.2.1

has been designated as the basis of

acceptance, one base section or base slab for each design shall

be tested unless the owner has indicated otherwise.

15.5.1.2 The base section or base slab proof-of-design test

procedures shall be in accordance with Test Methods

C497

15.5.1.3 The ultimate test load shall be the sum of at least

130 % of the dead load on the base section or base slab plus at

least 217 % of the live load on the slab. Dead load is the weight

of the column of earth cover plus the weight of the riser

section(s) plus surcharge transmitted through the riser sec-

tion(s) to the base section or base slab. Live load is the

maximum anticipated wheel load that may be transmitted

through the riser to the base section or base slab. The ultimate

test load shall be applied to the base section or base slab as a

uniformly distributed load.

15.5.1.4 The base section or base slab shall be acceptable if

it supports the required ultimate test load without failure.

Ultimate strength failure is defined as the inability of the slab

to resist an increase in the applied load.

15.5.1.5 When agreed upon by the owner and manufacturer,

the base section or base slab shall be acceptable based on

certified copies of the results of tests performed on identical

base sections or base slabs instead of requiring new proof-of-

design acceptance test.

15.6

Joints—

Precast reinforced base sections shall be de-

signed and manufactured with a male or female ends, so that

the assembled manhole base, riser and top will make a

continuous and uniform manhole, compatible with the toler-

ances given in

15.7

15.6.1 Joints are designed to perform in axial compression;

therefore, shear or load testing of the joint is not required.

15.7

Permissible Variations:

15.7.1

Internal Diameter—

The internal diameter of base

sections shall not vary more than 1 %.

15.7.2

Thickness—

The thickness of a base slabs with or

without benching shall be not less than that prescribed in the

design by more than 5 %. A thickness greater than that

prescribed in the design shall not be cause for rejection.

15.7.3

Height of Two Opposite Sides—

Variations in laying

heights of two opposite sides of base sections shall be not more

than 16 mm.

15.7.4

Height of Sections—

The underrun in height of a base

section shall be not more than 20 mm/m of height with a

maximum of 13 mm in any one base section.

15.7.5

Position of Reinforcement—

For base slabs with

monolithic benched inverts with a 100 mm thickness, the

maximum variation in the position of reinforcement from that

prescribed in

15.4

shall be

10 % of the thickness or

6 mm,

whichever is greater. For base slabs with a thickness greater

than 100-mm, the maximum variation shall be

10 % of the

thickness or

16 mm, whichever is the lesser. In no case,

however, shall the cover over the reinforcement be less than 19

mm. The preceding minimum cover limitation does not apply

to the mating surfaces of base section joints.

15.7.6

Area of Reinforcement—

Steel reinforcement areas

that are 10 mm

/linear m less than called for by design shall be

considered as meeting the required steel reinforcement area.

15.8

Rejection:

15.8.1 Base sections shall be subject to rejection for failure

to conform to any of the specification requirements. In

addition, an individual base section shall be subject to rejection

because of any of the following:

15.8.1.1 Fractures or cracks passing through the riser wall,

except or a single end crack that does not exceed the depth of

the joint.

15.8.1.2 Defects that indicate mixing and molding not in

compliance with

7.1

or surface defects indicating honey-

combed or open texture that would adversely affect the

function of the base section.

15.8.1.3 The planes of the ends are not perpendicular to the

longitudinal axis of the base section, within the limits of

permissible variations prescribed in

15.7

15.8.1.4 Damaged or cracked ends, where such damage

would prevent making a satisfactory joint.

15.8.1.5 Any continuous crack having a surface width of 0.3

mm, or more and extending for a length of 300 mm or more,

regardless of position in the base section.

16. Steps and Ladders

16.1

Scope:

16.1.1 This section covers manhole steps and ladders used

for providing access through manholes for use in sewer and

water works.

16.1.2 The user of this specification is advised that access

through manholes may be by steps that are cast, mortared, or

attached by mechanical means into the walls of base, riser, or

conical top sections or by ladder.

16.2

Acceptance—

Unless otherwise designated by the

owner at the time of, or before, placing an order, acceptance of

steps and ladders installed in manholes will be on the basis of

tests and inspection of the completed product.

C478M − 15

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