The Contractor shall undertake adequate precautions and manage the effects of external sources of vibration from nearby activities and construction equipment, in accordance with the requirements of Clause610.38, to ensure that the freshly placed SCC remains undisturbed and does not segregate. Where extreme conditions of temperature, humidity, wind and/or rain are expected during and after placing the concrete, the Contractor shall implement special precautions to protect the concrete. (ii) Close adjacent traffic lane to the deck widening, stitch pour or deck overlay and ensure a minimum clearance of 4.5metres from the edge of the deck widening or stitch to the nearest wheel path. The Contractor shall manufacture suitable test panels for each type of finish to be used prior to placing concrete. Light plant and equipment shall be as follows: (a) equipment not exceeding 0.5 tonnes in weight (b) maximum axle loads: 5.0tonnes single, 8.0tonnes tandem, 9.0tonnes triaxle (c) tracked vehicles: maximum 15tonnes/m2 pressure over the track area, providing the concrete is protected from surface damage. In-situ concrete girder (left); Precast girder(right). Two (2) cubes shall be tested at seven days and the third cube at 28days to confirm compliance with the minimum compressive strength requirements as specified on the drawings and in this specification and the material manufacturers technical data sheet. Information on the specific materials for a given project resistance, V. Continuous time functions of all parameters needed to solve the equations are given, and sample results included. It may be possible to have higher stress The stress-strain curve for HSC is more linear than for These mechanisms result from an interaction between the concrete and the ambient conditions such as moisture, drying and thermal effects. For prestressed posttensioned concrete, a minimum of 2cylinders per sample shall be tested prior to the application of the posttensioning force. MPa (10.0 kips/inch2 (ksi)). Consequently, the Reinforcement bar chairs and spacers for structures constructed in marine and other saline environments or subject to sulphate and chemical attack shall comply with the requirements of Clause610.29(f) in addition to the requirements of this clause. Element models of a balanced cantilever bridge. In case of continuous structures, the expansion joint system is reduced, which improves mobility and facilitates maintenance. During and immediately after placing, the concrete shall be effectively compacted by internal vibrators of adequate size, number and frequency and supplemented as required by external form vibrators. ACTION: A revision to remove the 70-MPa (10.0-ksi) Concrete which has begun to stiffen shall not be used in the works. If cracking does occur, it will be aligned at right angles to the restraint. The chance of understrength concrete may (27) In the Canadian Standard for Design of Concrete Structures, the 0.85 factor is replaced by (0.850.0015 ) 0.067, in which is in megapascals. very high strengths through the introduction of special admixtures, such as: In these cases, the properties of such materials should be PPVmeasurements shall be made during the period between commencement of concrete placement and when the minimum compressive strength of 32MPa has been achieved. (l) Exposed Aggregate Finish for Unformed Surfaces The prepared surface shall have an exposed coarse aggregate finish free from loose aggregate and laitance. He has worked at both the Cement andConcreteAssociation (C&CA) and theBritish CementAssociation (BCA) where he developed guidance for assessing the safety and service life of deteriorating concrete structures. An article summarising theeffects of corrosion on cracking, bond strength, flexural strength, shear strength and column behaviour is available in thispost. yield strength shall be taken in accordance with Article 5.11.2. (k) Tooled and Bush Hammered Surface Finish The types of tooled and/or bush hammered surface finishes are as follows: (i) Light Bush Hammering sufficient only to break the concrete surface to remove surface mortar without fracturing the coarse aggregate. Construction Health and Safety & CDM 2015, Structural Safety and Service Life of Concrete Structures. the other hand, HPC is produced with stricter quality control and a 610.26 REINFORCEMENT BAR CHAIRS AND SPACERS (a) Steel reinforcement supports All steel reinforcement shall be securely held during placing and compacting of the concrete. (g) Water Left in the Mixer or Agitator Water left in the mixer or agitator from the previous load shall be discharged prior to reloading new concrete in accordance with the requirements of Clause4.1.3(c)(ii) water in mixing chamber of AS1379 and in order to ensure that the maximum W/C ratio is not exceeded in accordance with requirements of this section. The tension development length, ld, for the specified WebPre-Tensioning. Further research is the objective of NCHRP project 12-64. 2.48 Mg/m3 (0.155 kips per cubic foot (kcf)), which can Dry stack: Masonry work laid without mortar. development lengths of prestressing strand. Table 610.121 TestMinimum Frequency of TestingGrading of Fine AggregatesOn each day one per 500 tonne or part thereofGrading of Coarse AggregatesOn each week one per 1500 tonne or part thereofWater Absorption of Fine and Coarse AggregatesAt 3 monthly intervalsUnsound Rock ContentOn each day one per 500 tonne or part thereofFlakiness Index of Coarse Aggregate 10mm and LargerAt monthly intervalsDegradation Factor of Crusher FinesAt monthly intervalsOrganic Impurities other than sugarAt monthly intervalsAlkali Reactivity of Aggregate SourcesAt 3 yearly intervalsWet and Dry Strength and Sodium Sulphate Soundness for Pebble AggregatesAt 3 monthly intervals 610.13 MANUFACTURE AND DELIVERY OF PREMIXED CONCRETE (a) General The Contractor shall be responsible for the manufacture and delivery of all concrete which shall comply with the approved or registered concrete mix design and the requirements of AS1379. 5.11.2.1.3, a unit of bundled bars shall be treated as a single bar for HSC, rewording of this article should be considered. WebDrying shrinkage: The change in linear dimension of a concrete masonry wall or unit due to drying. {tphOn h` h{ h h{ h h{ h{ h{ h{ h4 hl mH sH hw h1x h/tc h+ hu hV h R hV h4 mH sH h_M h4 hji 5CJ aJ hji h4 5CJ aJ #j hji h4 5CJ UaJ hji h4 , O P Any drying cracks which appear prior to initial set and before or during finishing operations shall be immediately closed as required with either a wooden or steel float. Webanchorage slip and loss due to friction. ! (vii) Partial Steam Curing Where steam curing is used only to obtain sufficient compressive strength for removal of forms or for lifting, curing shall be continued by one or a combination of the methods specified in Clauses610.23(c), (d) and (e) for a minimum period of seven days from the time of finishing the concrete. The main loads that must be considered are as follows: In the completion stage, additional reviews are carried for superimposed loads, moving loads, and seismic loads. Vibration shall continue at each point until air bubbles cease to emerge from the concrete, then withdrawn slowly to avoid leaving a defect. Loss of bond between steel and concrete is a result of cracking along the line and a reinforcing bar. Special precautions shall include the following measures to ensure compliance with the requirements of this section: (i) heating and blending mixing water to a maximum of 70C and keeping concrete temperature to below 32C (ii) heating the aggregates (iii) use winter grade admixtures (iv) use higher concrete grade (v) control sequence of batching ingredients when some are heated to avoid flush setting and balling within the agitator (vi) avoid delays in delivery to avoid heat loss during transit (vii) improve thermal effects by utilising insulating materials and thermal blankets as part of formwork and curing and maintain uniform temperature conditions within the curing chamber until required strengths are achieved. The Contractor shall undertake temperature differential monitoring and maximum temperature measurements of concrete and control early age thermal cracking to demonstrate compliance with the requirements of Clause610.22. All falsework shall comply with the requirements of Section613. In the UK, freeze-thaw attack occurs in colder regions. This phenomenon occurs in both concrete and steel structures, and when it occurs in steel structures, it is called relaxation. For prestressed pretensioned concrete, a minimum of 1cylinder per sample shall be tested prior to the application of the pretensioning force. Box girders have 1 cell or multi-cell structures. 610.36 EARLY LOADING AND TRAFFICKING OF BRIDGE DECKS, DECK OVERLAYS AND APPROACH SLABS Further to the requirements of Clause610.16 and Clause610.23, bridge decks, deck overlays and approach slabs shall not be loaded or opened to traffic until the concrete is at least 4days (96hours) old and not before a minimum compressive strength of 32MPa after casting has been achieved. For the purpose of satisfying the requirements of this clause, VPV test results may be rounded down to the nearest whole number for the corresponding concrete grade. Each structure has its own pros and cons, so designers and engineers should make appropriate choices according to their plans. Pinelli, J.-P. / Pita, G.L A Comparison of Prestress Losses in a Prestressed Concrete Bridge Made with High Performance, Self Consolidating Concrete. Cementitious grouts shall be as a minimum TypeC Class dual shrinkage compensating. The Contractor shall ensure that arrangements for the supply of concrete are made with the concrete supplier at the commencement of the Works, to ensure that a fully compliant concrete mix design which is supported with all required test results meets the specified time frames of this section. 5.7.2.2 is used and for which fpe is not less than 0.5 The basic development length, ldb, modified by the Concrete bar chairs and spacers shall comply with the requirements of Clauses610.26 and 610.29(f). Table C5.4.2.1-1 Concrete Mix Characteristics by Class. They should be barely visible. that more than12.0inches of fresh concrete is cast article for prestressed members with: For lightweight concrete, loss of prestress shall be based on the conventional concrete. comments to specific sections, articles, or tables refer to the Creep refers to a phenomenon in which the internal strain increases when a constant load is applied to the structure for a long period of time. The bond strength between the reinforcement and concrete is reduced with the loss of cover concrete. Use modified Type 2, 3, 4 and 6 girders (most costly and inconvenient due to required forming bed modifications) Class A-1 In a continuous balanced cantilever bridge, after the construction of the cantilever, the closure segment is connected to the cast-in-place or precast segment, and then tension is introduced to integrate all girder segments together. Action shall be taken where levels exceed normal consistency limits derived from routine quality control testing. Related Papers. Tension is taken to be positive and compression is negative, throughout. Mike has worked on the design, inspection, appraisal and site supervision of building, bridge and car park structures. 610.06 MAXIMUM VPV VALUES AT 28 DAYS The maximum VPVvalues at 28days for each concrete grade for both test cylinders and concrete test cores cut from cast insitu and sprayed concrete shall be as shown in Table610.061. (a)Vertical faces of members when height of each day's cast is:5 days(i)Columns greater than 7 metres(ii)Walls greater than 4 metres(b)Load supporting sides of sloping walls of box girders. Further information is contained in Reference 3. required by equation 5.7.4.6-1 may be too high to be practical with Where approved by the Superintendent proprietary power vibrating screeds of suitable widths may be used in narrow or constricted areas or where required by the deck and slab layout, with each new vibrating run overlapping the previous one by a minimum of 300mm, such that uniform consolidation is achieved throughout the deck and slab area. be taken as specified in Article 5.10.11.4.1e. The purpose of this article is to ensure that the section does not WebThe causes of time dependent/long-term loss include creep and shrinkage in concrete, and tendon relaxation. DEF can occur in sections which have undergone abnormal temperature rises in excess of 70C and where a source of moisture is present. Low concrete strength implies a high water-cement ratio (w/c). The concrete represented by a sample shall be deemed to comply with the specified slump if the measured slump is within the limits stated in Table 610162 for the corresponding specified slump. grids shall not exceed 12.0inches. The definition should be expanded for unit weights greater than Copyright 2022 Elsevier B.V. or its licensors or contributors. HP Early loading and trafficking of bridge decks, concrete deck overlays and approach slabs shall not proceed until: (i) the Contractors early loading and trafficking quality procedure and inspection and test plan(s) have been reviewed by the Superintendent (ii) the evidence that the minimum periods stated in this clause have been satisfied and maturity testing, temperature monitoring and compressive strength test results have been reviewed by the Superintendent. One characteristic is that the superstructure is mainly a prestressed box girder. The balanced cantilever bridge is a prestressed girder bridge and refers to a bridge constructed using the balanced cantilever method. (viii) Curing shall remain intact and completed in accordance with the requirements of Clause610.23 unless early trafficking is required in accordance with the requirements of Clause610.36. below the The evaporative retarding compound shall contain a fugitive dye to ensure uniform application and enable clear differentiation between covered and non-covered areas. It is also advantageous for the torsion due to its cross-sectional characteristics. Steel reinforcement supports shall comply with AS/NZS2425. limits in table 5.9.4.2.2-1. Structural use of concrete - Part 1: Code of practice for design and construction. HSC is tests are made to establish the relationships between concrete Webis the absolute value of the variation of stress in the tendons due to creep, shrinkage and relaxation at location x, at time t cs is the estimated shrinkage strain, in absolute value Ep is the modulus of elasticity for the prestressing steel, see 3.3.6 (2) and 3.3.6 (3) Ecm is the modulus of elasticity for the concrete pr Drying shrinkage requirements for special applications shall be as specified in the drawings and specification. ! All concrete shall be special class performance concrete in accordance with AppendixB of AS1379 Specification and Supply of Concrete and the requirements of this section. Reinforcement supports and spacers shall be in accordance with Clause610.29(f). (v) Extent of Radiant Heat Curing Radiant heat curing shall be continuously applied until at least the 7day compressive strength for the specified concrete grade is obtained. Bolts, wires and other embedments shall be set back to the minimum clear cover specified and the ends filled with shrinkage compensating mortar. In addition, blended cement TypeGB shall consist of a specified minimum quantity of portland cement in combination with any one or two of Ground Granulated Blast Furnace Slag (Slag), Fly Ash (FA) or Amorphous Silica (AS) and as specified in this section. [Equation 88], (5.10.11.4.2-3) HSC. Concrete which has been damaged by frost as a result of failing to maintain the temperature of the concrete surface above 5C will be rejected. as 60 strand diameters and the development length shall be taken as The specification will be satisfied if the compressive strength of each sample, as determined from the average value of the test cores, is not less than the specified minimum 28day compressive strength and provided that the compressive strength of any core in each sample is not less than 90% of the specified minimum 28day compressive strength. (c) Repair of Inactive Cracks Repair of inactive cracks shall be as follows: (i) Cracks up to 1mm wide shall be repaired by pressure injection of low viscosity epoxy resin. Rajesh M N. Download Free PDF View PDF. (m) Scabbled Finish Scabbling shall remove all laitance and loose or porous material without leaving excessive depressions. With HSC precast concrete I-girders, thinner webs are often used to carrying on further mathematical manipulation, the equations can be Where the use of air entraining admixture is approved, the Contractor shall determine the air content of the freshly mixed concrete at the point of discharge in accordance with AS1012.4 and Clause5.4 of AS1379, and it shall not exceed the nominal value of 5%. and adjoining tension ties (deg. by: the ratio of spiral reinforcement to total volume of concrete core, measured out-to-out of spirals, shall not be less than: Spirals are less effective for confinement in HSC. BARSReinforcing bars distributed throughout the concrete to minimize cracks due to temperature changes and concrete shrinkage. [Equation 96], (5.13.2.5.4-1) tensile force in the concrete computed on the assumption The environmental benefits of using timber are not straightforward; although it is a natural product, a large amount of energy is used to dry and process it. Cores containing steel reinforcement shall not be tested. Test certificates, material data sheets and health and safety data sheets shall be available for all materials. Water may be added to the freshly mixed concrete prior to commencement of discharge provided no more than 60minutes have elapsed from the time of adding cement to the aggregate and a means of accurately measuring the volume of water is available to ensure that the maximum design amount of water and the agreed maximum W/C ratio are not exceeded. The specification will be satisfied if the compressive strength of each sample, as determined from the average value of the test cylinders, is not less than the specified minimum 3, 7 and 28day compressive strengths and provided that the compressive strength of any cylinder in each sample is not less than 90% of the specified minimum 3, 7 and 28day compressive strengths. tensile and exceeds 0.095. An approach similar to that of ACI 318 could be NZS 3101.1&2:2006 A1. (d) Mix Constituents The concrete shall consist of a mixture of cementitious material, fine aggregate, coarse aggregate and water. based on NCHRP project 18-07 are proposed. 4.8.2 Forces on connections. The stopper method is a type of continuous girder bridge in which one or several piers with fixed supports are installed, and additional stoppers or dampers are installed on piers that have movable supports installed. The development length, ld, for deformed bars in The consequences include a reduction in bond between the top reinforcement and the surrounding concrete. where: N = number of identical prestressing tendons. The cross sectional stiffness is excellent compared to other types of girders, so it can be used for bridges that have long spans. The cement paste is gradually scaled away by this freezing and thawing action. (iv) Curing Covers To prevent drying out, curing covers shall be placed over the units after the top surface of the concrete has taken its initial set and the watering hose has been placed on the concrete. If the value obtained from the repeat test falls within the limits given in Table610.162, the concrete represented by the sample shall be deemed to comply with the appropriate nominated mix design slump, otherwise it shall be rejected. To make a camber diagram, it is necessary to calculate the deflection at the construction stage. specified in Article 5.11.4.2. But under what conditions is this really the case? 0.65. Mg/m3 (155 lb/ft3). supported by analysis or experimentation, the concrete compressive section. Bridge Design Specifications, Second Edition, 1998, and the ACTION: Revisions to include strength design for in table 1 and modified for the W/C ratio, unless otherwise 610.46 DIMENSIONAL TOLERANCES (a) General The dimensional tolerances listed in Tables610.461, 610.462, 610.463 and 610.464 are the allowable deviations of the completed concrete member from the dimensions shown on the drawings. resistance may be taken as: LRFD specifies a T-section behavior if c > (15) The stress-strain behavior of (j) Limitations on Drying Shrinkage One sample per trial mix shall be taken. either 12.0 inches or the following for Class A, B, or C splices: Class A stress in the concrete to 0.0948 . h8$ ^J hq3 h8$ ^J h8 h8$ 5PJ hmH sH h8$ PJ hmH sH hfN hl PJ hmH sH hZ hl hl h( hl 5 hlC 5(j hlC 5UhmH nH sH tH u h4 h h4 h 5h h 5

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