User:Hoskir/Revision Request 4220

REVISION REQUEST 4220

751.8.1.5 Precast Culvert

General

All MoDOT cast-in-place (CIP) concrete box culverts are allowed to be constructed using alternate precast concrete box culvert sections in accordance with Sec 733, unless specified otherwise. Requirements for submitting special or modified designs are described in Sec 1049. Precast split-box designs in accordance with ASTM C1786 with or without modification are not an acceptable precast alternative.The converse is not true and precast concrete box culverts may be specified only. Pay items and quantities shall remain unchanged from those typically used for CIP concrete box culverts. When a box culvert is required to be constructed using precast concrete box culvert sections because of an accelerated timeline for construction, pay item and quantity of the precast box culvert shall be based on the length of the precast culvert to the nearest foot measured along the geometrical center of the culvert floor.

Pedestrian Box

Where a precast concrete box culvert could be used as a pedestrian (or “people”) box for walk-through or bicycle path, having multiple joints typically spaced at not greater than 6 ft. may be unacceptable due to tripping hazards, ponding/freezing (settlement of many smaller length sections) or uncomfortable riding surface. Consideration should also be given to special waterproofing or non-corrosive water stops for watertight construction joints.

Multi-Cells

In multi-cell precast construction the staggered placement of units should be avoided. Staggering units results in an irregular end section that loses continuity over the interior wall(s).

Culvert Ties

Precast box culvert ties in accordance with Sec 733 and Std. Plan 733.00 shall be required for the same reasons as concrete collars are required for CIP concrete box culverts. Typically the regular strength connections details should be used. The extra strength connection details shall be used for special cases requiring higher strengths or greater durability, for example when connecting energy dissipating baffles rings or when under low fills and a roadway. If a precast box culvert is required because of an accelerated timeline and collar beams would otherwise be required then culvert ties shall be specified with the cost of ties being considered completely covered by the contract unit price for the precast box culvert.

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1049.2 Procedure

Inspection and reporting of coarse aggregate, fine aggregate, cement, fly ash shall be as appropriate for those materials.

Prior to concrete being poured, confirm the amount and placement of reinforcement. The amount and placement of welded wire fabric is to be as specified in ASTM C 1577 as applicable.

Compressive tests may be made on either concrete cylinders or cores drilled from the wall of the sections at the option of the manufacturer. If the manufacturer chooses to take cylinders and they fail, the manufacturer then has the option to core sections for possible acceptance.

Cylinders must be made in accordance with AASHTO T 280 and must be capped.

Acceptance cylinders are the responsibility of the manufacturer. An inspector’s job is to review the results for adequacy. It is good procedure to randomly validate the manufacturer results by making cylinders for comparison.

Cores in accordance with AASHTO T 280 must be both capped and lime cured.

The finished sections are to be examined for conformance to dimensions, workmanship and marking. All permissible variations are specified in ASTM C 1577.

Each section shall be marked as follows by the manufacturer by indenting into the concrete or with waterproof paint:

(a) Box section span, rise, table number, design earth cover and specification designation.

(b) Date of manufacture.

(c) Name or trademark of the manufacturer.

(d) Each section shall be clearly marked by indentation on either the inner or outer surface during the process of manufacturer so that the location of the top will be evident immediately after the forms are stripped. In addition, the word "top" shall be lettered with waterproof paint on the inside top surface.

(e) If the manufacturer is allowed to produce under an approved QC program, each section considered by the manufacturer to be specification compliant will be marked by the manufacturer with the indicator required by the QC program. Sections rejected by the manufacturer may be marked or handled in accordance with the QC program but the rejection must be clearly indicated.

(f) If the manufacturer is allowed to produce under an approved QC program, each section to be shipped will be marked by the manufacturer with the Sample ID number provided by the district. If the producer has marked a piece with a Sample ID number, and the section is found to be unacceptable during an audit, the Sample ID number must be neatly obliterated.

Sections accepted by MoDOT inspection are to be marked with "OK-MoDOT" by the inspector. Rejected sections are to be marked with a single vertical mark, near the manufacturers marking and shall be made with weather resistant marking material.

Any modification of a unit, other than constructing a box unit exactly as described in the specifications, is considered a special design, including any pipe cutouts or drainage holes to be made in the unit for any reason, whether prior to, during, or after final placement on site. Any special or modified designs submitted for approval must have been reviewed and sealed by a professional engineer, registered in Missouri, and representing the contractor or producer. Requirements for submitting special or modified designs are described in Sec 1049. Precast split-box designs in accordance with ASTM C1786 with or without modification are not an acceptable precast alternative. Approval of a special design for one job does not constitute approval for any other job.

Submittal of special designs is discussed further in EPG 106.16 Special Designs. Special and modified design units, at the discretion of the district, may not be accepted under a QC program.

If reinforcing bars are proposed in lieu of the welded wire fabric listed in AASHTO, it is considered to be a special design.

If end sections are proposed to be constructed other than by the MoDOT Standard Plans for cast-in-place culverts, it is considered to be a special design. Calculations and other proof of equal or better design must be submitted with the request.