ITEM 424 PRECAST CONCRETE STRUCTURES (Fabrication) 424.1. Description. This Item shall govern for the fabrication of precast prestressed and precast nonstressed concrete members, in accordance with the plans, approved shop drawings, and this Item. Prestressed members shall be defined as precast concrete members fabricated by the process of pretensioning, post-tensioning, or a combination of the two (2) methods. Nonstressed members shall be defined as precast concrete members which are not subject to pretensioning or post-tensioning. item. 424.2. Materials. Materials shall conform to the material requirements specified in the pertinent 424.3. General. (1) Plant Facilities. (a) Prestressed Members. An inspection laboratory shall be furnished in accordance with Item 498, "Plant Inspection Laboratory (Equipped)". Prior to the casting of members, detailed drawings of the complete facilities to be used in fabrication are required. The design of casting beds and facilities for pretensioned construction, including plans and specifications, shall bear the seal of a registered Professional Engineer. The Contractor shall furnish certification stating that the bed, facilities, and hardware have been constructed in accordance with the above plans and specifications. For central plant fabrication, three (3) copies of facility drawings shall be submitted to the Division of Materials and Tests, Texas Department of Transportation, 125 East 11th Street, Austin, Texas 78701-2483. For job site fabrication, three (3) copies shall be submitted to the Engineer. The facility drawings shall specify the maximum loading for which the bed is to be used. Prior to approval for that loading, the facilities shall be proof loaded to a minimum 10 percent overload for eight (8) hours. Additional proof loads shall be performed at a minimum 10 percent overload for four (4) hours when deemed necessary by the Engineer. Minor changes in facilities will not require proofloading but will require submission of revised facility drawings accompanied with design calculations. Facility drawings and calculations shall bear the seal of a registered Professional Engineer. (b) Nonstressed Members. An inspection laboratory shall be furnished in accordance with Item 498, "Plant Inspection Laboratory (Equipped)". (2) Shop Drawings. (a) Prestressed Members. The Contractor shall submit to the Engineer a proposed sequence of erection by structure and span or unit number. Shop drawings shall be submitted following this proposed sequence. When alternate designs are permitted by the plans, the designs proposed shall be submitted in the format and on forms furnished by the Department. Approval of these designs must be given prior to preparation of shop drawings. Once alternate designs are submitted and approved, subsequent changes will not be permitted.
Clear and legible shop drawings shall be prepared on sheets 22 x 34 inches or on 11 x 17 inch sheets, or full size drawings may be reduced to half-scale size, if they are clear and legible. The margin at the left end shall be 1-1/2 inches wide and the others 1/2 inch wide. Each sheet shall have a title block in the lower righthand corner. The title shall include the sheet index data shown on the lower right-hand corner of the project plans, sheet numbering for the shop drawings, name of structure or stream, name of Fabricator, and name of Contractor. All shop drawings shall be checked by the Fabricator before submitting them for approval. Submission of shop drawings shall be made to the Division of Bridges and Structures, Texas Department of Transportation, 125 East 11th Street, Austin, Texas 78701-2483. Six (6) copies of the Index Sheets, Bearing Sheets, and Fabrication Sheets along with seven (7) copies of Erection Sheets will be required. One (1) additional copy of each sheet will be required for railroad underpass structures. Additional sets may be required by the Engineer. Shop and/or working drawings for precast post-tensioned members will be in accordance with Item 426, "Prestressing". When fabrication is to be at more than one (1) casting plant, two (2) additional sets of shop drawings will be required for each additional casting location. Index sheets shall reflect the plant locations where each member is to be fabricated. After completion of fabrication for railroad underpass structures, the Contractor shall furnish reproducible tracings of approved "as built" shop drawings. (b) Nonstressed Members. Shop drawings for nonstressed members shall be furnished when required by the plans and/or pertinent item. (3) Notice Of Beginning Work. The Contractor shall give the Engineer adequate notice prior to the beginning of work in the Fabricator's plant as follows: Plants in the State of Texas Plants in the Contiguous United States Plants outside the Contiguous United States 7 days 21 days 60 days No work shall be performed in the plant before the Engineer has authorized fabrication. 424.4. Fabrication. Prestressing shall be in accordance with Item 426, "Prestressing". A casting schedule shall be prepared on standard forms furnished by the Department and submitted to the Director of Materials and Tests, or his duly authorized representative, prior to fabrication. Post-tensioning ducts, when required, shall be placed in accordance with the approved prestressing details, and in accordance with Item 426, "Prestressing". It shall be the Contractor's responsibility to maintain all ducts free of obstructions until all post-tensioning operations are complete. Construction of forms, reinforcing steel placement, and concrete placement shall be as follows: (1) Forms. (a) External Forms. All side and bottom forms for precast concrete construction shall be constructed of steel, unless otherwise noted on the plans. Wood forms, when permitted, shall conform to the requirements of Item 420, "Concrete Structures". End headers may be of other material as approved on the shop drawings. Forms shall be of sufficient thickness, with adequate external bracing and stiffeners, and shall be sufficiently anchored to withstand the forces caused by placement and vibration of concrete. Internal bracing and holding devices in forms will not be permitted if such would remain in the finished member.
Corners shall have a chamfer or radius where shown on the plans. Joints shall be maintained reasonably mortar tight. Where sections of forms are to be joined, an offset of 1/16 inch for flat surfaces and 1/8 inch for corners and bends will be permitted. Offsets between adjacent end header sections shall not exceed 1/4 inch. The grade and alignment of forms shall be checked each time they are set and shall be maintained during the placement of concrete. Metal forms shall be reasonably free from rust, grease or other foreign materials. All forms shall be cleaned thoroughly prior to each casting operation. The facing of all forms shall be treated with form oil or other bond breaking coatings prior to placing of concrete. The oil or other materials used for this purpose shall be of a consistency and composition which prevents build-up on the forms and facilitates form removal. Clear form oil of the same brand shall be used throughout the casting operation for nonstressed retaining wall panels. Materials which appreciably stain or react with the concrete will not be permitted. The forms shall be constructed to facilitate removal without damage to the concrete. The soffit for casting prestressed members shall be constructed and maintained to provide a maximum 1/4 inch variation from the theoretical plane. Additionally, the soffit shall not vary more than 1/4 inch between any two (2) points in any 50 foot length. At the Contractor's option, side forms for prestressed bridge deck panels may be constructed with a 1/8 inch draft to permit ease of removal. (b) Internal Forms. Materials used for forming internal voids in precast concrete members shall be of adequate strength to maintain sufficient rigidity to withstand the forces of flow, vibration, buoyancy and weight of plastic concrete during placing. Forms for internal voids in members shall be anchored securely to prevent movement or misalignment during placement of concrete. Hold-downs for all types of void forms shall be spaced not more than 30 inches and shall provide sufficient bearing area on the void form to prevent indentation or penetration into the void form. Splicing of void form sections shall be such as to prevent separation or misalignment. Internal voids for prestressed piling may be formed with a mandrel provided it can be demonstrated to the Engineer that the correct position and alignment of the mandrel can be maintained throughout the casting operation. The material used for forming internal voids may be one of the following, except that the material used for forming voids in piling shall be inert and nonabsorptive: Corrugated cardboard void forms for box voids shall be manufactured from virgin Kraft completely impregnated with a blend of polyethylene and paraffin with a melting point of not less than 130 F. Void form covers shall be further protected by curtain coating the outside liner with high melting point paraffin at not less than 300 F. Assembled cardboard void forms shall have all seams, joints and raw edges sealed with waterproof pressure sensitive tape. Joint belts and end caps shall be assembled using clinched box staples spaced not more than six (6) inches completely around top, sides and, whenever possible, the bottom of the forms. Cardboard void forms for round voids shall be manufactured from recycled paperboard, spirally wound, with a moisture barrier in the wall of void forms over three (3) inches in outside diameter. The interior and exterior surfaces shall be wax coated, at 124 F minimum, with scale wax having a minimum oil content of two (2) percent. The adhesive used between the plies shall be of a type not sensitive to water. End closures can be made of plywood, metal or plastic and nailed or
stapled into place. Assembled voids shall have all joints and raw edges sealed with waterproof pressure sensitive tape. Expanded polystyrene void forms shall be solid and have a minimum compressive strength of 10 psi, a density of 0.9 pound per cubic foot, and an oxygen index of 24.0. Other materials may be used for void forms provided they meet all applicable requirements and are approved by the Engineer prior to use. Certification of conformance will be required for all cardboard and expanded polystyrene void forms. The Engineer may require samples to be submitted when deemed necessary. Prestressed concrete box beam void forms without solid cores shall be vented, except when otherwise required by the Engineer, to eliminate high air pressure caused by heat of hydration. A 3/4 inch diameter plastic tube shall be inserted into the top of the void prior to placing concrete and left in place until there is no possibility of damage from pressure. The plastic tube shall be subsequently removed and the hole sealed with epoxy grout. Other methods of relieving air pressure may be used if approved by the Engineer. Additionally, for prestressed concrete box beams, each individual void form without a solid core shall be vented through the bottom slab. The vent shall be a 3/4 inch hole either drilled or formed by an acceptable hole forming device. (2) Placing Reinforcing Steel. Reinforcing steel shall be placed in accordance with Item 440, "Reinforcing Steel". Reinforcing steel required to extend outside of the member shall not project by more than 1/2 inch or less than 3/4 inch from plan dimension, unless otherwise approved by the Engineer. (3) Quality of Concrete. The values which govern for minimum concrete strengths during different phases of construction shall be as required by the pertinent item. When optional designs are permitted, the minimum concrete strength shall be as shown on the approved shop drawings. The control of concrete shall be by compressive tests of cylinders. For prestressed and nonstressed members, the making, curing, and testing of all required cylinder test specimens for release or handling strength or design strength shall be in accordance with Test Method Tex-704-I. (4) Placing Concrete. All concrete shall be placed during daylight hours unless the fabrication plant or site is provided with a lighting system approved by the Engineer. The method of concrete placement shall minimize segregation of the aggregate and displacement of the reinforcing steel, prestressing steel, or duct. Concrete shall be deposited as near as possible in its final position in the forms. Depositing large quantities of concrete at one location in the forms and running or working it along the forms will not be permitted. Special attention shall be directed toward working the coarse aggregate back from the face of the concrete and forcing the concrete under and around the reinforcing steel, prestressing steel, or duct. Placement of concrete in large members shall be subject to the approval of the Engineer. Concrete may be placed in one (1) lift or in multiple continuous horizontal layers. In the latter case the thickness of the first layer shall be slightly above the juncture of the bottom flange and web of prestressed concrete beams. Not more than one (1) hour shall elapse between the placing of the successive layers. Vibration of subsequent layers of concrete shall extend into the previously placed layers. Prestressed concrete box beams cast monolithically in two (2) stages shall have the concrete in the bottom slab remain in a plastic state until the side wall concrete is placed and vibrated into the bottom slab. When the side wall concrete is placed and vibrated into the bottom slab, the one (1) hour time limit between placement of layers may be waived.
Concrete placement will not be permitted when impending weather conditions will impair the quality of the finished work. If rainfall should occur after placing operations are started, the Contractor shall provide ample covering to protect the work. The maximum time interval between the addition of mixing water and/or cement to the batch and the placing of concrete in the forms shall not exceed the following: Concrete Temperature Maximum Time Nonagitated Concrete 80 F or above 15 Minutes 50 F to 79 F 30 Minutes Agitated Concrete 90 F or Above 45 Minutes 75 F to 89 F 60 Minutes 50 F to 74 F 90 Minutes The use of an approved retarder in the concrete will permit the extension of each of the above maximum times by 30 minutes, except that for nonagitated concrete, the maximum time shall not exceed 30 minutes. Under conditions of extreme temperature or humidity, the Engineer may require the use of an approved retarder in the concrete. (a) Placing Concrete in Cold Weather. When members are produced in a fabricating plant which has adequate provisions to protect the concrete and which has approved elevated temperature curing facilities, concrete may be placed under low temperature conditions provided: The temperature of the concrete is not less than 50 F when mixed and placed in the forms. The framework and covering are in place and heat is provided for the concrete and forms within one (1) hour after the concrete is placed. This shall not be construed to be one (1) hour after the last concrete is placed but that no concrete shall remain unprotected and unheated for longer than one (1) hour. The air surrounding the concrete shall be kept between 50 F and 85 F for a minimum of three (3) hours prior to beginning the temperature rise which is required for elevated temperature curing. For central fabricating plants or job site casting operations which do not provide facilities necessary to accomplish the above provisions, concrete may be placed when the atmospheric temperature is 35 F or greater. The temperature of the concrete at the time of placement shall not be less than 50 F. The concrete shall not be placed in contact with any material having a temperature less than 32 F or any material coated with frost. Aggregates shall be free from ice, frost, and frozen lumps. When required, in order to produce the minimum temperature specified above, the aggregate and/or the water shall be heated uniformly in accordance with the following: Water may be heated to a temperature not to exceed 180 F and/or the aggregate may be heated to a temperature not to exceed l50 F. The equipment furnished shall be capable of heating the aggregate uniformly to eliminate overheated areas in the stockpile which might cause flash set of the cement.
The temperature of the mixture of the aggregates and water shall be between 50 F and 85 F before introduction of the cement. Protection shall be provided to maintain the temperature of the concrete at all surfaces of prestressed members at 50 F or above until "Release Strength" is reached. All concrete surfaces of nonstressed members shall be maintained at 40 F or above during the specified curing period. Protection shall consist of providing additional covering and, if necessary, supplementing such covering with artificial heating. When weather conditions indicate the possibility of the need for such temperature protection, all necessary heating equipment and covering material shall be on hand ready for use before permission is granted by the Engineer to begin placement of concrete. (b) Placing Concrete in Hot Weather. When concrete is to be placed during hot weather, it shall be placed without the addition of more water to the concrete than required by the design. When field conditions are such that additional moisture is needed for the final concrete surface finishing operation, the required water shall be applied to the surface by fog spray only, and shall be held to a minimum. Fog spraying that will wash the fresh concrete surface or cause water to stand will not be permitted. Control of the initial set of the concrete and lengthening the time for finishing operations under adverse humidity and hot weather conditions may be accomplished with the use of an approved retarder in accordance with Item 421, "Portland Cement Concrete". (c) Consolidation of Concrete. All concrete shall be thoroughly consolidated with approved high frequency vibrators. These vibrators, both internal and external, shall operate at a minimum of 7000 vibrations per minute. External vibrators will be permitted only when steel forms are used. For prestressed concrete beams and box beams, internal vibrators will be required and may be supplemented with external vibrators if desired. At least one (1) stand-by vibrator of the type(s) being used shall be provided for emergency use. Internal vibrators shall be inserted systematically into the concrete immediately after placing. When the concrete is placed in more than one (1) layer, the vibrators shall be operated so that they will penetrate into the previously placed layer of concrete. The size and spacing of external vibrators shall provide sufficient intensity of vibration to the desired area of the form. The spacing, frequency, and/or amplitude of external vibrators shall be varied to produce uniform consolidation of the concrete. Supplemental vibrators or a modification of the vibration system shall be provided, when deemed necessary by the Engineer, to accomplish thorough consolidation of the concrete and complete embedment of the reinforcing steel, prestressing steel, or duct. (5) Finishing of Concrete. All unformed surfaces, when finished, shall not have distortions greater than 1/4 inch. Form marks in excess of permissible tolerances and all fins and rough edges along chamfer lines shall be removed in an acceptable manner. Concrete on exposed reinforcing steel and loose laitance on concrete surfaces to be in contact with cast-in-place concrete shall be removed from all members. (a) Prestressed Members. Top surfaces of prestressed concrete beams and bridge deck panels shall be screeded or rough floated to bring mortar to the surface and cover all aggregate. The surface shall have a rough wood float or stiff broom finish. Aggregate shall not be loosened when roughening the surface. Surfaces at anchor bolt locations shall have a smooth metal trowel finish. The top surface of prestressed concrete piling shall be struck off and finished with a wood or magnesium float by bringing mortar to the surface to cover the aggregate and present a reasonably smooth appearance.
Fabrication holes, except box beam vent holes, in the bottom of all beams shall be filled with nonstain, nonshrink mortar and made flush with the surrounding surface. Unless otherwise shown on the plans, strands shall be removed flush with the end of the member, or recessed approximately 3/8 of an inch. In either case, the ends of the strands and a minimum of one (1) inch around each strand shall be cleaned and coated with approximately 10 mils of an approved epoxy or epoxy grout. (b) Nonstressed Members. All unformed surfaces shall be given a uniform wood float finish, unless otherwise shown on the plans. (6) Curing of Concrete. Careful attention shall be given to the proper curing of concrete. Prior to placing concrete, the Contractor shall submit the proposed curing methods and procedures to the Engineer for approval. Elevated temperature curing facilities shall be tested for a minimum of 48 hours prior to approval. Approved equipment and materials for curing shall be available for use prior to casting. Inadequate curing facilities or lack of attention to the proper curing of concrete shall be cause for the Engineer to stop all concrete placement until approved curing is provided. Inadequate curing may be cause for rejection of the member. Curing shall be commenced prior to the formation of surface shrinkage cracks. The mats, sheets, or blankets shall not be placed in contact with the concrete member until such time that damage will not occur to the surfaces. Forms may be removed at the discretion of the Contractor at any time after the concrete has reached sufficient strength to prevent physical damage to the member. Removal of the forms shall be done in such a manner that curing is not interrupted on any member for more than 30 minutes. The following curing requirements shall apply for prestressed members: All concrete shall be cured by the method of elevated temperature or water curing. Type I-D interim membrane curing will be permitted only on the top surface of prestressed concrete piling. Concrete shall be cured continuously, except as allowed during form removal, until the compressive strength of the concrete has reached the "Release Strength" and until detensioning has been performed. Prestressed piling shall be water cured an additional three (3) days after attaining "Release Strength". The temperature at all surfaces of prestressed piling shall be maintained above 32 F during this period. Removal of piling to a storage area shall be done in such a manner that water curing is not interrupted on any member for more than four (4) hours. The following curing requirements shall apply for nonstressed members: All concrete shall be cured by the method of elevated temperature, water, or membrane curing. Concrete shall be cured continuously, except as allowed during form removal, for a period of four (4) days or until the compressive strength of the concrete has reached the "Design Strength" designated on the plans and/or shop drawings. (a) Water Curing. All exposed surfaces of the concrete shall be kept wet continuously for the required curing time. The water used for curing shall meet the requirements for concrete mixing water as specified in Item 421, "Portland Cement Concrete". Sea water will not be permitted. Water which stains or leaves an unsightly residue shall not be used. Water curing will be permitted as follows:
1. Wet Mat Method. For water curing by the wet mat method, cotton mats, polyethylene sheeting, or polyethylene burlap blankets may be used. The mats, sheets, or blankets shall be adequately anchored and weighted to provide continuous contact with all concrete surfaces. Any concrete surfaces which cannot be cured by contact shall be enclosed by mats, adequately anchored, so that outside air cannot enter the enclosure. Sufficient moisture shall be provided inside the enclosure to keep all of the surfaces of the concrete wet for the required curing time. 2. Water Spray Method. For water curing by the water spray method, overlapping sprays or sprinklers shall be used so that all concrete surfaces are kept wet continuously. 3. Ponding Method. For water curing by the ponding method, the concrete surfaces shall be covered with a minimum one (1) inch depth of water. Satisfactory provisions shall be made to provide a dam to retain the water. (b) Elevated Temperature Curing. Curing by elevated temperatures will be permitted as follows: 1. Steam Curing. (Steam curing is defined as use of steam above 85 F). When steam curing of concrete is provided, the temperature inside the curing jacket shall not exceed 165 F for more than one (1) hour during the entire steam curing period. Concrete exposed to temperatures exceeding 180 F will not be accepted. wet. Sufficient moisture shall be provided inside the curing jacket so that all surfaces of the concrete are An unobstructed air space of not less than six (6) inches shall be provided between all surfaces of the concrete and the curing jacket. Steam outlets shall be positioned so that live steam is not applied directly on the concrete, forms, or test cylinders. The location of steam lines, location of control points for discharge of steam into the curing jacket, and the number and type of openings for steam distribution within the curing jacket shall be arranged so that temperature variation between any points in the enclosure shall not exceed 20 F. Steam curing shall not commence until the concrete has been in place a minimum of three (3) hours, or until initial set of the concrete, as determined in accordance with ASTM C 403, is attained. During the application of steam, the temperature inside the curing jacket shall be raised uniformly at a rate not to exceed 40 F per hour. 2. Alternate Methods. Other methods of elevated temperature curing may be permitted by the Engineer provided temperature maximums, rate of temperature variation, humidity control, etc., are in accordance with the requirements for steam curing. The use of any alternate method will require the permission of the Engineer, in writing. (c) Membrane Curing. Type 1-D or Type 2 membrane curing compound may be used where permitted herein or in the pertinent item. Material requirements and construction methods shall be in accordance with Item 526, "Membrane Curing". 424.5. Workmanship. (1) Defects and Breakage. All members that sustain damage during fabrication, handling, or storage shall be subject to the following:
(a) Prestressed and Nonstressed Members. Fine cracks on the surface of the member which do not extend to the plane of the nearest reinforcement will not be cause for rejection unless they are numerous and extensive. Diagonal cracks, which indicate damage from torsion, will be subject to a structural review prior to acceptance. Cracks which extend into the plane of the reinforcing steel and/or prestressed tendons, but are acceptable otherwise, shall be repaired by sealing with an approved epoxy or other approved material. Small damaged or honeycombed areas which are purely surface in nature (not over one (1) inch deep) may be repaired with an approved epoxy grout or other approved material. Damage or honeycomb in excess of the above will be subject to a structural review. (b) Prestressed Members. Failure of individual wires in a seven-wire strand, or of wires in a parallel wire tendon is acceptable provided the total area of wire failure is not more than two (2) percent of the total cross-sectional area of tendons in any member. Failure of an entire strand will be subject to structural review. Vertical or horizontal cracks, which are 1/16 inch or less in width and which tend to close upon transfer of stress to the concrete, are acceptable. Cracks in excess of this are subject to review prior to acceptance. Any of the following conditions will be cause for rejection of prestressed bridge deck panels. 1. Any crack that comes within one (1) inch of two (2) adjacent strands. 2. Corner cracks or breaks that involve two (2) strands. 3. Isolated damage or honeycombed areas larger than approximately six (6) inches in diameter or length that involves more than one (1) strand. 4. Narrow honeycomb lines caused by grout leakage over 1/2 inch in depth involving more than one (1) strand. Any condition not covered by the above shall be subject to structural review. (2) Tolerances. (a) Prestressed Members. Allowable tolerances for the dimensions and configurations shown on the approved shop drawings are as shown in Table 1. TABLE 1 ALLOWABLE TOLERANCES Box Panels Beams Beams Tees Piling Length (Normal to strands for ±3/4" ±1" ±3/4" ±1/2" -1"* panels) Width (Parallel to strands for +3/4" ±1/4" ±3/4" ±1/2" ±1/4" panels) -1/4" Nominal Depth (Thickness in case of panels) +1/2" -1/4" ±1/4" ±1/4" ±1/4" -1/8" ±1/4" Top Slab or +1/2" ±1/2" ±1/4" NA NA Flange -1/4" Thickness Bottom Slab or +1/2" Flange -1/4" Web or Wall +3/4" -1/4" ±1/2" NA NA NA ±1/2" ±1/4" NA NA
Horizontal Alignment (Upon Release of Stress) - Deviation from straightness of mating edge of panels Deviation of Ends from Shop Plan Dimension (bearing edge in case of panels) Horizontal Skew Vertical Batter ±1/8" per 10 of length ±1/4" ±1/8" per 1 of depth Beams ±1/4" ±1/4" ±1/8" ±1/8" per 10 of length ±1/4" per 1 of width ±1/4" per 1 of depth ±1/8" per 1 of width ±1/8" per 1 of depth Box Beams Tees Panels ±1/2" ±1/8" NA ±1/8" Piling Notched End Areas (for diaframs) Depth ±1/4" ±1/4" ±1/4" NA NA Length +2" -1" +2" -1" +2" -1" NA NA Bearing Surfaces Anchor Hole Location Perpendicular to Vertical Axis Deviation from Plane From End of Member ±1/8" NA ±1/16" NA NA ±1/16" ±1/8" ±1/16" NA NA +3/4" - 1/4" ±1/4" +3/4" - 1/4" Longitudinal ±3/4" ±1/2" ±3/4" NA NA Spacing Transverse ±1/4" ±1/4" ±1/4" NA NA Location Diafram or Lateral Tie Location ±1/2" ±1/2" ±1/2" NA NA Position of Void** (Longitudinal NA ±1" NA NA ±1/2" for Box Beams) Position of Strands ±1/4" ±1/4" ±1/4" ±1/8" Vert. # ±1/2" Horiz. ±1/4" Position of Hold-Down Points ±6" ±6" ±6" NA NA Position of Handling Devices ±6" ±6" ±6" NA ±6" # Measured from bottom of panel. * Maximum length approved by the Engineer. ** Length of Box Beam Void Material +1" -6". NA NA Variations greater than specified in Table 1 shall be corrected to within these tolerances or be subject to structural review. Horizontal alignment (sweep) in beams and girders only, which may increase at a later time over that shown in the table, will be acceptable if the members can be hauled, erected, and aligned to within the allowable tolerance without being damaged. These members shall be stored in a manner that will minimize the sweep. When prestressed concrete box beams are cast monolithically in one stage the Fabricator shall furnish positive verification to the Engineer that the bottom slab, after casting, is within the dimensional tolerances specified herein.
Weld clips, hangers, and other inserts for forming purposes shall be longitudinally spaced not more than one (1) inch greater than the spacing specified on the approved shop drawings. Weld clip inserts shall not be placed greater than 1/16 inch from the beam edge. All inserts shall be firmly held in position to avoid movement during concrete placement. (b) Nonstressed Members. Unless otherwise shown on the plans, the allowable tolerances (+/-) for nonstressed members shall be as follows: Concrete Traffic Barrier: Length 1" Insert Placement 1/2" Horizontal Alignment 1/8" per 10 of length Deviation of Ends: Horizontal Skew 1/4" Vertical Batter 1/8" per ft. of depth Retaining Wall Panels: All Dimensions 3/16" Angular distortion with regard to the height of the panel 0.2" in 5 Formed Surface Defects 0.1" in 5 Connection Hardware 1/2" Inlets and Manholes: All Dimensions 1/4" Thickness in excess of that required shall not be cause for rejection provided proper jointing or operation is maintained as determined by the Engineer. Precast (Formed) Box Culverts: Tolerances for precast (formed) box culverts shall be as specified in Item 462, "Concrete Box Culverts and Sewers". 424.6. Storage and Handling. (1) Prestressed Members. Storage and handling of prestressed members shall be in accordance with Item 425, "Prestressed Concrete Structural Members". Prior to shipping to the job site, all beams, box beams, panels, piling and other prestressed members shall be marked for identification, as shown on approved shop drawings, with other project identification as required by the Engineer. (2) Nonstressed Members. All nonstressed members shall be handled, stored, and shipped in a manner to avoid chipping, cracking, fractures, and excessive bending stresses. These members shall be supported on firm blocking. Nonstressed members, prior to shipment, shall be marked in accordance with the requirements of the pertinent item. 424.7. Measurement and Payment. The work performed, materials furnished and all labor, tools, equipment and incidentals necessary to complete the work under this Item will not be measured or paid for directly, but will be considered subsidiary to the various bid items of the contract.