TECHNICAL SPECIFICATION SERIES 8000 PRECAST CONCRETE

Transcription

1 TECHNICAL SPECIFICATION SERIES 8000 PRECAST CONCRETE

2 TECHNICAL SPECIFICATION PART PRECAST CONCRETE TABLE OF CONTENTS Item Number Page 8100 PRECAST CONCRETE CONSTRUCTION - GENERAL General Approval of Methods Construction Marking Handling Tolerances PRECAST CONCRETE PIPES General Materials Joints Payment PRECAST CONCRETE BEAMS General Dimensions and Tolerance Payment PRECAST PRESTRESSED CONCRETE BEAMS General Approval of Methods Handling of Beams Dimensions and Tolerance Construction Payment PRECAST CONCRETE PILES General Materials Casting Marking of Poles Handling of Piles Stacking of Piles Measurement Payment MISCELLANEOUS PRECAST CONCRETE General Payment 8-11 UNOPS-Afghanistan PART 8-1

3 8100: precast concrete construction general 8101 General a) The Contractor shall construct and erect precast concrete units, in accordance with this Part where and as shown on the Drawings or directed. b) The units may be supplied by a manufacturer or may be manufactured by the Contractor at an approved location. For units, such as precast concrete pipes, which are not detailed on the Drawings, the Contractor shall also submit for approval all details of the individual units, including proposed reinforcement and location of lifting points as hereinafter specified. c) Repairing of damaged units will not be approved except where such damage and repair will not impair the strength or the appearance of the units after installation Approval of Methods Thirty days before commencing manufacture of all precast concrete units the Contractor shall submit for approval all details of the methods to be used in manufacture, handling, transport, storage and erection of the units Construction a) Except as otherwise provided in this Part, all units shall be constructed and created in accordance with the applicable requirements of Parts 6 and 7. b) The maximum size of aggregate for all precast concrete shall generally be 20 mm, except for concrete pipes where the maximum size of aggregate shall be 10 mm. c) The classes of concrete used to manufacture precast concrete units shall be in accordance with Clause 6.2 of this Specification d) All units shall be cast in individual forms and may be cured by steam curing in accordance with Clause e) Where the use of immersion type vibrators is not practicable the Contractor shall consolidate thin precast concrete slabs and units on a vibrating table or by another approved method Marking a) Immediately on removal of forms, each unit shall be clearly marked with the date of casting, the estimated mass and the identification number directed by the Engineer. Temporary identification and date of casting markings shall be scratched into the top surface of beams near an end immediately after screeding off. b) The marking shall be made by an approved indelible marking material using letters approximately 75 mm high. c) Care shall be taken to ensure the marking on outside facing bridge beams is made on the inner face Handling a) At all times, especially during transportation, all precast concrete units shall be supported as in their final positions. Other methods of support may be approved if the Engineer considers that the units will not be damaged in any way by the proposed method of support. b) All units shall be lifted only at the lifting points shown on the Drawings. Where lifting devices have not been detailed the Contractor shall submit, for approval, complete calculations and details of his proposed lifting devices. UNOPS-Afghanistan PART 8-2

4 c) All units shall be adequately braced and supported during erection to ensure proper alignment and safety. Such bracing or support shall be maintained until adequate permanent connections have been made. Special care shall be taken not to damage the flanges of beams. d) Temporary supports for members shall be timber bearers at least 150 mm wide and 100 mm thick, placed on a firm foundation and supporting the members over their full width. The ground or space between the bearers supporting the members shall be carefully cleared and levelled to prevent the member being accidentally supported other than on the bearers. e) No precast unit manufactured away from the site shall be delivered to the site without the approval of the Engineer, nor shall a unit be transported from the place of manufacture prior to the completion of the specified curing Tolerances For the purposes of this Clause the following definitions or interpretations apply: i. Tolerance means the permitted variation from a stated dimension or shape, excluding any deliberate shortening of dimension to provide clearance. ii. Length and Width refer, as the case requires to : the longer and shorter sides of a rectangular precast unit; any side of a unit which is not rectangular; the overall length and width at any location of any unit. iii. iv. Straightness and Flatness mean the tolerance distance of any part of an edge or surface from the nearest point of a straight line joining the ends of the edge or of the surface in any direction. Twist means the rotation of one end relative to the other end. v. Warp means the maximum permissible tolerance distance of any point on a surface from any of the four planes through three of the four corners of a rectangular surface. These corners, if the surface is not rectangular, being those points on the surface which are the corners of a rectangle having the greatest possible area and generally, but not necessarily wholly, within the actual surface of the unit. vi. Squareness means the maximum permissible tolerance distance by which a shorter side may deviate from a straight line through the corner and perpendicular to the longer side. any error in the straightness of the adjacent sides being ignored for the purposes of this definition; and where the included angle between the surfaces or sides is intended to be other than a right angle, the check line being varied accordingly. The dimensions of all finished precast concrete units shall be within the following limits at the time of placement of the units in the structure, unless otherwise specified herein or shown on the Drawings: UNOPS-Afghanistan PART 8-3

5 Table 8-1 Dimensions Tolerances I. Members others than flat panels: 3 Cross-section, overall dimensionsless than 600 mm, but less than 1600 mm, but less than 1500 mm, not less than 1500 mm. 3 Cross-section, dimension of parts such as webs, ribs and flanges less than 1500 mm, not less than 1500 mm. c) Length, critical dimensions of abutting members. 3 Length, non-critical less than 6 m; not less than 6 m. e) Twist. ±3 mm ±6 mm +10 mm, - 6 mm ±6 mm +10 mm,- 6 mm +0, - 6 mm ±length/1000 ±6 mm 10 mm/m width per 3 m of length Table 8-2 II. All units: a) Straightness of edges and flatness of surfaces. b) Warp less than 5 m diagonal not less than 5 m diagonal c) Squareness of corners - less than 2 m, on shorter side; not less than 2 m, less than 4 m, not less than 4 m. d) Holes or openings and the like, diameter or side dimensions. e) Location of holes or openings f) Grooves, width and depth. g) Position of individual connecting bolts, both holes, projecting metal or other devices in any associated group (e.g. the joint of two precast units). h) Longitudinal locations of any such groups (mentioned in item (g) ) Length/ mm 10 mm 3 mm 5 mm 6 mm ±3 mm ±7 mm 2 mm Within 3 mm of their true positions in the group in which they are cast. Within 6 mm of its true position in the unit in which it is cast, if the tolerance does not adversely affect the proper assembly of the whole structure. UNOPS-Afghanistan PART 8-4

6 8200: Precast Concrete Pipes 8201 General a) The Contractor shall manufacture precast concrete pipes for pipe culverts in accordance with this Clause and the applicable provisions of Parts 6 and 7. b) Concrete pipe shall be constructed in accordance with Clause Materials a) Concrete pipes shall be 300 mm, 600 mm, 815 mm and 1700 mm inside diameter and shall conform to the requirements of AASHTO M242M. b) For each diameter of pipe, classes shall differentiate between pipes of different strength designation. c) The strength designation of the pipe shall be the D-load to produce a 0.30 mm crack when tested by the three-edge bearing method of loading all in accordance with AASHTO T280M. The D-load strength is quoted as Kilo Newtons per linear metre (KN/m), and minimum required strengths and classes are. Table 8-3 Diameter mm Class II I II I II III I D-load kn/m d) Pipes to be tested for strength shall be selected at random by the Engineer. At least one pipe for each diameter and class of pipe shall be tested to failure by the Contractor in the presence of the Engineer, and the material cost of this pipe shall be paid for by the Employer. Otherwise, the cost of all equipment and labour required to carry all testing of pipes shall be included in the rates for construction of pipe culvert in Clause e) Minimum clear cover to reinforcement shall be 30 mm. f) Reinforcement shall comply with clause Joints a) In general, concrete pipes shall be manufactured with male and female ends. Joints in concrete pipes shall be of the bell and spigot type. b) All joints shall be capable of transferring the required shear across the joint. The Contractor shall furnish to the Engineer a certificate of compliance that the pipes conform to this requirement. UNOPS-Afghanistan PART 8-5

7 c) pipes shall be interchangeable, except for special end sections Payment Payment for precast concrete pipes will be made in accordance with Clause : Precast Concrete Beams 8301 General The Contractor shall furnish and erect precast reinforced concrete beams for bridges to the lines, grades and dimensions shown on the Drawings or directed by the Engineer Dimensions and Tolerances a) The dimensions and shape of precast concrete beams shown on the Drawings shall apply to the beams as close as practicable to 28 days after casting and the beams shall be supported at the positions specified for stacking. b) The dimensions and profile of the forms shall be so constructed to include the upward deviation in the vertical plane, or camber, required as shown on the Drawings. The Contractor shall submit, for approval, details of how he proposes to introduce the camber, and construction of the forms shall not commence without such approval by the Engineer. c) Except where otherwise required by Clause 8.5, tolerances for precast concrete beams shall be in accordance with Clause Payment a) Payment for furnishing and erecting precast reinforced concrete beams will be made at the rate per cubic metre of concrete in the finished beam bid therefore in the priced Bill of Quantities (Item 8.04). b) The rate shall include the entire cost of all labour, equipment and materials required to manufacture and erect the precast beams in their final positions, except that separate payment will be made for reinforcement and miscellaneous metal work in the beams, in accordance with Clauses 7.7 and 12.3 respectively. 8400: Precast Prestressed Concrete Beams 8401 General a) The Contractor shall furnish and erect precast prestressed concrete beams for bridges to the lines, grades and dimensions shown on the Drawings or directed by the Engineer. The beams shall be cast as shown on the Drawings. b) Prestressing of precast beams shall be in accordance with Part Approval of Methods The Contractor shall, at least 30 days before commencement of manufacture of the precast beams: i. Submit to the Engineer for approval full details of his method of forming, placing and curing of the beams and his handling, transporting, stressing, grouting and erection methods. Once approved, the Contractor shall not vary his methods without the written approval or direction of the Engineer; and UNOPS-Afghanistan PART 8-6

8 ii. Submit to the Engineer for approval shop Drawings and details of all metalwork, prestressing tendon anchorages to be embedded in the beams, schedules of locations of material and marks by which individual items can be identified Handling of Beams a) Prestressed concrete beams shall be fully stressed or stressed to the extent shown on the Drawings and all stressed tendons shall have been grouted for 7 days before lifting or handling of the beam unless the moving of the beams off their casting beds before grouting stressed tendons is approved. If such approval is given each ungrouted tendon shall be adequately marked for possible slip and should any slip or damage occur, the tendon shall be replaced and/or re-stressed as directed. b) Completed beams shall not be stacked on top of each other and no superimposed load shall be placed on a member without prior approval Dimensions and Tolerance a) The dimensions and shape of prestressed concrete beams shown on the Drawings shall apply to the beams at the time of their completion when under self weight alone. b) Except where shown otherwise on the Drawings or approved, the dimensions and profile of the forms shall compensate for deformations caused by prestressing so that the dimensions and profile of the completed members shall conform to the Drawings. The Contractor shall submit, for approval, details of the magnitude of these deformations and how he proposes to allow for them. Construction of the forms shall not commence without such approval. c) Except where otherwise required by this subclause, tolerances for prestressed concrete beams shall be in accordance with Clause 8.1. d) Variation in the overall length and length centre to centre of bearings shall be accurate to within 7 mm or ±0.05 per cent of the length, whichever is the greater. e) Sagging profiles in a vertical plane will generally not be permitted but upward deviation (hog) from the required profile of up to 0.1 per cent of the span length will be approved. f) The deviation of a member from straightness in a horizontal plane (bow) shall not exceed 7 mm or ±0.05 per cent of the length of the member, whichever is greater. g) Location of ducts and sheathing shall be accurate to ±4 mm. h) Cover to ducts and sheathing shall be not less than 50 mm Construction a) Sheathing for all ducts shall be placed accurately in the formwork in the position shown on the Drawings and shall be adequately tied and held against movement during concreting. The sheathing shall be fixed so as to ensure the alignment as well as the position of ducts at joints is accurate. All joints in the sheathing shall be mortar tight. Sheathing shall be stiffened during concreting by means of an internal stiffener of equal or greater diameter than the final tendons. Immediately after the whole of the concrete has been placed in a precast concrete beam, all duct internal stiffeners shall be pulled back and forth for about 300 mm to ensure they are perfectly free inside the sheathing. b) All anchorage plates for prestressing tendons shall be accurately positioned square to the line of action of the tendons and held firmly during concreting. Should any mortar adhere to the exposed faces of the anchorages, it shall be removed. UNOPS-Afghanistan PART 8-7

9 c) Concrete shall not be placed until all formwork, block outs, installations of sheathing, grout points or vents, anchorage plates for prestressing tendons, reinforcement, embedded metalwork and any other fittings shown on the Drawings or required by the Specification have been approved by the Engineer. Placing of concrete shall be performed only in the presence of the Engineer. d) The parts of the top surface upon which the concrete deck is to be placed shall be suitably roughened to the extent shown on the Drawings by compressed air nail hammering or other approved means. Care shall be taken to protect corners from damage or disfiguration Payment a) Payment for furnishing and erecting precast prestressed concrete beams will be made at the rate per cum. bid therefore in the priced Bill of Quantities. b) The rates shall include the entire cost of all labour, equipment and material required to manufacture the precast beams and to erect the prestressed concrete beams in their final positions, except that separate payment will be made for supply and installation of prestressing materials and prestressing, reinforcement and miscellaneous metalwork in the beams, in accordance with Clause 10.3, 7.7 and 12.3 respectively. Pay Item Unit 84/1 Payment for furnishing and erecting precast prestressed concrete beams Cum 8500: Precast Concrete Piles 8501 General The Contractor shall construct precast reinforced concrete piles in accordance with this clause as shown on the Drawings or directed by the Engineer. b) Piles shall be manufactured to the lengths and cross sectional dimensions to conform to the toe levels shown on the Drawings or directed by the Engineer and in accordance with Part Materials a) Concrete in precast concrete piles shall comply with Parts 6 and 7 of this Specification. b) Pile shoes and splice plates shall be manufactured from mild steel plates welded to reinforcement and cast into the head or toe of the pile as shown on the Drawings or directed by the Engineer. c) Piling shall be in accordance with Part 11 of this Specification Casting a) Piles shall be cast on a horizontal platform in box moulds as approved by the Engineer. Fillets shall be fixed to the formwork to provide all chamfers as shown on the Drawings. b) The placement of concrete in each pile shall be completed in one continuous operation and no interruption to the placement will be permitted. c) Lifting holes shall be cast into the piles in the positions shown on the Drawings. UNOPS-Afghanistan PART 8-8

10 8504 Marking of Piles a) Each pile shall be clearly marked within 600 mm from the pile head. The date, identification number required by the Engineer and the overall length of the pile shall be marked. The marking shall be in indelible paint which is not injurious to the concrete and the letters shall be at least 75 mm high. b) Commencing at 5 m from the toe, and thereafter at 1 m intervals up to the head, each pile shall be marked by a lightly scribed line across the full width of one face of the pile, and square to its length. The distance of each such line from the toe shall be lightly scribed Handling of Piles a) Piles shall have reached a concrete compressive strength of at least 25 MPa prior to removal from the casting bed. b) All piles shall only be lifted at the lifting holes provided as shown on the Drawings, unless otherwise approved by the Engineer. c) The Contractor shall ensure that piles are not subjected to high impact loads during the handling operations Stacking of Piles a) For the stacking of piles heavy, sill logs shall be well embedded into the ground and flattened on the top surface to give a bearing width of not less than 200 m with a minimum clearance above the ground of 150 mm. b) Sill logs shall be positioned as shown on the Drawings or directed by the Engineer. c) Piles shall be stacked on top of each other for up to 5 layers, providing that the ground foundations are deemed suitable by the Engineer. d) When layering piles for stacking, each layer shall be separated by timber bearers 150 mm wide by 100 mm high. The bearers shall be centrally placed above the sill logs Measurement Measurement for payment for constructing precast concrete piles will be made of the volume of concrete in the driven piles below the underside of the pile caps as shown on the Drawings or directed by the Engineer Payment a) Payment for constructing precast concrete piles will be made at the rate per cubic metre bid therefore in the priced Bill of Quantities (Item 8.07/1). This rate shall include the entire cost of all labour, equipment and materials required except that separate payment will be made for reinforcement. b) Payment for Furnishing precast concrete piles will be made at the rate per linear metre of piles driven and accepted (Items 8.07/2) which rate shall include the cost of pile shoes and splice plates. c) Payment for reinforcement in concrete piles shall be in accordance with Clause 7.7. Pay Item Unit 85/1 constructing precast concrete piles Cum 85/2 Furnishings, placing and driving of pre-cast concrete piles Linear-m UNOPS-Afghanistan PART 8-9

11 8600: Miscellaneous Precast Concrete 8601 General The Contractor shall furnish and install miscellaneous precast concrete not specifically shown on the Drawings, but as directed by the Engineer Payment Payment for furnishing and installing miscellaneous precast concrete will be made at the rate per cubic metre bid therefore in the priced Bill of Quantities. Payment for metalwork embedded in the concrete will be made in accordance with Clause Installation, materials, shuttering included except reinforcement. Pay Item Unit 86/1 Furnishing and Installing Pre-cast reinforce concrete Cum 86/2 Furnishing and Installing Pre-cast plain concrete Cum UNOPS-Afghanistan PART 8-10