SANS 10120-2 GF-1984 Code of practice for use with standardized specifications for civil engineering construction and contract documents Part 2 Project specification Section GF Pre.pdf

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1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA

2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any

3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. SAAS 0120 : Part 2 Section GF-1964 Prestressed concrete PART 2 : PROJECT SPECIFICATION SECTION GF CONTENTS Clause ESSENTIAL PROJECT SPECIFICATION CLAUSES

4、 . ESSENTIAL DATA ADDITIONAL CLAUSES . General Normal Projects . Calibration of apparatus Prestressing force diagram . . Corrosion protection of cut ends . Protection of external tendons Erection Prestige Projects and Special Construction . General Particular specification for tensioning of a concre

5、te dam Subeconomic and Labour-based Projects Page Number June 1984 Approved by the COUNCIL OF THE SOUTH AFRICAN BUREAU OF STANDARDS SABS 0120 : Part 2 Section GF-1984 Prestressed concrete SABS 1200 GF : PRESTRESSED CONCRETE NOTE a) Number the PSGF clauses in Portion 2 of the project specification in

6、 the sequence in which the clauses to which they relate appear in SABS 1200 GF. b) The clause number(s) giver) at the beginning or after the heading of a clause is/are, unless otherwise stated, the number(s) of the relevant clause(s) of SABS 1200 GF. ESSENTIAL PROJECT SPECIFICATION CLAUSES Set out s

7、uitable clauses in Portion 2 of the project specification to provide essential information, as follows: a) (Subclause 3.3) Specify the characteristic strength of the steel wire to be used in tendons. b) (Subclause 5.4.5.1(i) Specify the order of loading and the magnitude of the load for each compone

8、nt of the tendon. C) (Subclause 5.7.2.2 and 5.7.3) Specify the strength required of the concrete in the in-situ portion of construction joints before temporary supports may be removed. d) (Subclause 5.7.3(d) specify the applicable bond or frictional resistance to be developed at each bearing. ESSENT

9、IAL DATA The availability of certain essential data may affect the prices tendered. Except where such data have been given in the schedule or in the tender drawings, set out in Portion 2 of the project specification suitable clauses covering items such as the following: a) (Subclause 5.4.5.1(kI and

10、(l) State the grade of concrete or minimum specified strength of concrete required before tendons are tensioned and also at designated stages in the tensioning procedure. b) (Subclauses 5.7.3 and 8.2.4) Give full details of each connection. C) (Subclause 6.2) Where a degree of accuracy lower than I

11、is acceptable, specify the permissible deviations. d) (Subclause 7.2.1) State which tests will be required. e) (Subclause 7.2.2) When applicable, specify the characteristic dead and imposed loads to be applied in the deflection test and state the maximum deflection that is acceptable. ADDITIONAL CLA

12、USES GENERAL. Where it is necessary to amplify or otherwise to vary the terms of SABS 1200 GF to render them suitable for use in projects to be carried out in particular locations or under particular circumstances, include in Portion 2 of the project specification clauses dealing with matters other

13、than those covered by Clauses 1 and 2 above. (See a$so Subclause 1.3 of Section GF of Part 3 of the code.) 3.2 NORMAL PROJECTS NOTE: To meet requirements imposed by various norms of economic development, projects are classified as normal, prestige, subeconomic and labour-based projects. (See Clause

14、4 of Section 0 of Part 3 of the code. ) 3.2.1 Calibration of Apparatus (Subclause 4.2). Where the nature of the structure or the program of construction is such as to require calibration of the tensioning apparatus to be done more frequently than is specified in SABS 1200 GF, specify the frequency r

15、equired. 3.2.2 Prestressing Force Diagram (Subclause 5.4.5.1). Where applicable, and if not shown on the drawings, set out the prestressing force requirements in a suitable clause preferably supported by a force-extension diagram. (See also Subclause 1.3.2.2 of Section GF of Part 3 of the code.) Inc

16、lude a clause such as the following: PSGF 1.1 Contractors responsibility for tendon layout drawings, and calculations NOTE: The tender drawings give sufficient information to determine the location of the prestressing tendons and anchorages for the system shown, but they are not intended as working

17、drawings for the purpose of tendon placing and fixing. a) After acceptance of the tender, and before he commences work, the Contractor shall 1) prepare working drawings showing all details of the prestressing work, equipment and operations and also showing details of the recesses which may be requir

18、ed to accommodate the anchorages, as well as details regarding the clips, stools, hangers and spacers required for the supporting and fixing of the tendons; 2) submit for approval details of jacking forces and calculations of friction losses and extensions; and 3) obtain approval in writing of the w

19、orking drawings. SABS 0120 : Part 2 Section GF-1984 Prestressed concrete b) On completion of the works the Contractor shall furnish permanent records of each working drawing in the form of one of the following: 1) One transparent linen print or a print on an equally durable and acceptable plastic:;

20、material of thickness at least 0,05 mm; or 2) three sets of original microfilms of an acceptable type. Corrosion Protection of Cut Ends (Subclause 5.4.3). Where the cut ends of the tendons wi1.L not be cast into concrete and corrosion of the ends may occur, specify the corrosion protection that is t

21、o be given to the ends of the tendons. protection of External Tendons (Subclause 5.6). Where it is considered necessary to protect external - tendons against corrosion by methods or materials other than those specified in Subciause 5.6 of SABS 1200 GF, set out the details and ensure that the materia

22、ls specified have sufficient stability and hardness to achieve the objective. Erection (Subclause 5.7.2) . When appropriate, give details of precautions to be taken to ensure the - safety of the public during erection. PRESTIGE PROJECTS AND SPECIAL CONSTRUCTION General. For prestige projects apply t

23、he recommendations of Subclause 5.1 of Section GF of Part 3 of the code. Particular Specification for Tensioning of a Concrete Dam. Where post-tensioning for the raising (or construction) of a concrete dam is required, set out requirements such as those given in P l-P 3 below as the basis of a parti

24、cular specification. Alternatively, include these requirements in the project specification. NOTE: Clauses P I-P 3 have been framed to suit a particular project and must be varied appropriately to suit any other project. (PSGF 2.) DRILLING AND SEALING OF HOLES AND ANCHORING, TENSIONING AND GROUTING

25、OF TENDONS FOR A CONCRETE DAM (Subclause 5.4) P l. (or PSGF 2.1) DRILLING AND GROUTING P 1.1 General. All drilling and grouting work shall be carried out in accordance with the techniques specified in P 2 and P 3. As the work proceeds and as knowledge and experience of the behaviour of the natural r

26、ock and of the concrete in the dam wall is gained, modifications to the techniques may become necessary, and the Contractor may be instructed to alter or vary is operations. P 1.2 Drilling P 1.2.1 Method of drilling. Drilling shall be carried out using rotary or percussion type equipment or a combin

27、ation of both. The holes may be drilled directly to the final diameter or a pilot hole of smaller diameter may be drilled and then reamed to full size. The final. diameter of the finished hole shall be at least equal to that scheduled or it shall be the minimum approved for use with the particular t

28、ype of tendon prescribed for the prestressing system being used. When holes are drilled through foundation rock, care shall be taken to use equipment that will provide holes with sides having, along the specified or ordered anchorage length for each tendon, the most effective roughness and mechanica

29、l key for subsequent bonding with the tendon grout. The Contractor shall use no lubricants in drill holes other than an adequate supply of water or air. Drilling muds shall not be used. P 1.2.2 Accuracy of drilling. To ensure accuracy of drilling all drilling machines shall be firmly set up and anch

30、ored before commencement of drilling. Core barrels shall be as long as possible and centralizers of correct diameter shall be provided every 1,s m for the first 6 m and then every 5 m along the rod string to prevent wandering and vibration of the drill bit. Each tendon hole shall be drilled vertical

31、ly or at the angle specified, within the to1e:rance defined by a cone which has its apex at the mouth of the hole and with sides sloping at 1 in 150 to the designated drilling line. The starting position of each hole shall be within 10 nun of the designated position. The direction of drilling shall

32、be maintained throughout the full depth of the hole unless the Engineer orders a deflection to be made. The alignment of each hole shall be che-ked with an approved borehole survey instrument. Should the position of any hole be found to fall outside the specified tolerance for wsition, the hole shal

33、l be grouted up in a manner satisfactory to the Engineer. A new hole shall then be drilled at an adjacent location designated by the Engineer. All costs of grouting up, redrilhng, etc., in respect of such incorrectly positioned holes shall be borne by the Contractor unless the incorrectly positioned

34、 hole is approved by the Engineer, in which case payment wlll be made at scheduled rate:;. P 1.2.3 Loss of hole. If jamming of a hole or any other cause makes continuation of drill.ing impossible, the Contractor shall immediately ask the Engineer for instructions as to the position.ing of a substitu

35、te hole. No Fayment will be made for drilling or grouting or any other work on the original hole unless, in the Engineers opinion, the hole has served a useful purpose, and he approves payment, in which case a fresh hole may not be necessary. P 1.2.4 Drilling records P 1.2.4.1 Daily records. The Con

36、tractor shall each day provide the Engineer with an accurate record, on an approved form, of all drilling carried out on the previous work day. The information provided shall include details of the number of holes and, in respect of each hole, the size, the length and where applicable, the nature an

37、d characteristics of the various strata encountered, the changes of formation, the levels at which ground water was encountered, the levels at wh:,ch washwater was lost., all relevant incidents which occurred in the course of drilling ancl in general, any information that will. assist the Engineer i

38、n obtaining knowledge of the conditions in the concrete of the dam wall and in the foundation. SABS 0120 : Part 2 Section GF-1984 Prestressed concrete p 1.2.4.2 Final records. When the drilling of each hole has been completed, the Contractor shall, in respect of that hole and without undue delay, pr

39、ovide the Engineer with a complete log, in duplicate, on an approved form containing all the information specified in P 1.2.4.1 above for the daily records relating to that hole. P 1.3 Grouting P 1.3.1 Grouting to seal a tendon hole a) f leakage of a hole at the grouting pressure is in excess of 0,l

40、 t/min per metre of depth of the hole for a hole of diameter app;oximately 200 mm, and pro rata in the case of a hole of a different diameter, the hole shall be sealed by grouting. Pressures to be used for sealing a hole shall be as high as possible, but not so high as to cause damage to the structu

41、re or foundation. As a guide, an initial pressure at the bottom of the hole of 30 kPa per metre of depth of the hole is acceptable. During the sealing operation, observations shall be made and any movement of the rock or concrete recorded. Should such movement occur, pressure shall be relieved immed

42、iately. b) On completion of the sealing operation, the hole shall be either flushed out or redrilled to the required diameter, as appropriate, and again tested for leakage. The sealing operation shall be repeated until the leakage is reduced to less than that specified in (a) above. c) Grout sealing

43、 and pressure testing of a hole shall be done in stages and no stage shall exceed 10 m of depth of the hole. Records shall be kept of the rate of leakage in each hole before and after grouting. P 1.3.2 Grout mixes P 1.3.2.1 General. Different grout mixes my be required for the anchor and for the pro

44、tection of tendons. P 1.3.2.2 Grout mix for anchors. The grout mix for anchors will depend on the rock condition disclosed during drilling. The initial mix my have a w/c ratio (by volume) of between 10:l and S:1. Such a mix shall gradually be thickened until the w/c ratio is of the order of 1:l to p

45、rovide a arout of strensth at least 25 MPa . P 1.3.2.3 Grout for the protection of tendons. Grout for the protection of tendons shall comply with Subclauses 5.5.3, 5.5.4 and 5.5.8 of SAW 1200 GF. P 1.3.2.4 Cement for grout. Cement for grout shall comply with the relevant requirements of SABS 4711).

46、If a mixture of milled granulated blastfurnace slag and ordinary portland cement is used the said slag shall not be more than 50% (m/m) of the cementitious materials. P 2 BONDING AhJ GROUTING P 2.1 General. Each prestressing tendon shall be intimately bonded to the adjacent rock or concrete (as appl

47、icable) in the two separate grouting operations as specified in P 2.2.1 and P 2.2.3 below. P 2.2 Insertion of tendon, and grouting P 2.2.1 Foundation anchorage. Before the grouting operation is started, the tendon hole shall be flushed out with a dilute solution of sodium hydroxide, after which the

48、hole shall be blown out with compressed air at a rate sufficient to remove all trapped water from the anchorage length. In the case of a vertical or steeply inclined hole, grout for the foundation anchorage shall then be introduced to the lowest part of the hole by means of a temporary tremie pipe,

49、and allowed to fill the hole slowly to the depth ordered. In the case of a horizontal or near horizontal hole, other approved means shall be used to fill the hole. An accurate record shall be kept of the amount of grout so placed in each hole, and measurements shall be taken to ensure that voids in the foundation anchorage are completely filled with grout after insertion of the tendon. P 2.2.2 Insertion of tendon. Immediately before the insertion of each tendon into the hole, the tendon shall be thoroughly cleaned and all traces of oil removed. The tendon shall be inserted slowly into