ACI 364.14T-2017 Section Loss Determination of Damaged or Corroded Reinforcing Steel Bars.pdf

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1、 1 ACI 364.14T-17TechNoteSection LoSS Determination of DamageD or corroDeD reinforcing SteeL BarSKeywords: concrete repair; corrosion; reinforcing steel bar; section loss; uncoated.IntroductionThis document describes a method for determining the section loss (Fig. 1) of deformed and square, uncoated

2、, round, reinforcing steel bars due to damage, corrosion, or both. A similar procedure can be used to determine the section loss of deformed square and twisted square reinforcing steel bars due to damage, corrosion, or both. Reinforcing bar section loss is the loss of cross-sectional area that can r

3、educe the load-carrying capacity of a member. Section loss is typically caused by corrosion of the reinforcing bar or construction damage, such as saw cutting or drilling into a reinforcing bar.Figure 2 shows examples of reinforcing bars with section loss. This document does not address evaluation o

4、f the load-carrying capacity of a member, or determining if a repair is required. These tasks should be performed by a licensed design professional based on a review of existing conditions (ACI 546R ACI Committee 564 2014).QuestionHow is the section loss of a corroded or damaged rein-forcing bar det

5、ermined?AnswerThe following steps are used to determine reinforcing bar section loss.1. Determine original reinforcing bar diameter (Do): There are several options for determining a reinforcing bars original diameter. If the original reinforcing steel size can be confirmed from existing design drawi

6、ngs, the nominal diameter can be determined based on the specified bar size. If the in-place reinforcing bar includes a legible bar size marking, the nominal diameter based on bar size can be used. For guidance, refer to ASTM A615/A615M and CRSI (2010, 2016). If the original reinforcing bar size is

7、unknown and cannot be determined based on the options mentioned previously, the method described as follows in Step 2 is used at a location on the bar where there is no perceived section loss (Fig. 3).2. Determine reinforcing bar diameter (Dc) in damaged/corroded area: To determine the reinforcing b

8、ars current diameter in damaged/corroded areas, first remove any scale or corrosion products from the reinforcing bar, then:(a) Select the location along the reinforcing bars with the most section loss. Several areas may have to be measured along the bar to determine the location with the most secti

9、on loss. Using calibrated caliper, take two measurements of the reinforcing bars diameter at the same location (Dc1and Dc1), with each measurement taken 90 degrees from the other (Fig. 4). Record each measurement to the nearest 1/16 in. (1.6 mm) and round to nearest 0.01 in. (0.25 mm).(b) Calculate

10、the average diameter (Dca) by taking the average of two measurements (Dc1and Dc2) (Eq. (1). Round average diameter to nearest 0.01 in. (0.25 mm).Fig. 1Section loss in reinforcing bar.American Concrete Institute Copyrighted Material www.concrete.org2 SECTION LOSS DETERMINATION OF DAMAGED OR CORRODED

11、REINFORCING STEEL BARS (ACI 364.14T-17)Fig. 2Examples of reinforcing bars showing section loss: (a) reinforcing steel showing heavy corrosion; (b) exposed reinforcing steel due to corrosion in need of assessment; (c) reinforcing steel damaged by saw cut along edge of repair area; and (d) severely co

12、rroded reinforcing bars.Fig. 3Correct procedure for measuring reinforcing bar diameter. All measurements should be of the core bar without including the deformations. Note the diameter measurements should be taken of the bar without deformations or ribs and rounded to the nearest 1/16 in. (1.6 mm).F

13、ig. 4Procedure for cross-sectional diameter measurement. Note that the measurements should made at a section with the maximum section loss.American Concrete Institute Copyrighted Material www.concrete.orgSECTION LOSS DETERMINATION OF DAMAGED OR CORRODED REINFORCING STEEL BARS (ACI 364.14T-17) 3122cc

14、caDDD+=(1)3. Calculate the cross-sectional areas of the reinforcing bar in original and current (damaged/corroded) areas:original area (Ao) = Do2/4 = 0.785Do2(2)current area (Ac) = Dca2/4 = 0.785Dca2(3)where Dois original diameter of the bar.4. Calculate the amount of area lost:The area lost is calc

15、ulated by subtracting the current area from the original area.area lost (A) = original area (Ao) current area (Ac) (4)5. Determine the percentage of area lost (%A)round to nearest 1.0%:percentage area lost (%A) = area lost (A)/original area (Ao) 100 (5)SummaryThe procedure described in this TechNote

16、 provides guidance to determine the percentage of section loss of a round reinforcing steel bar due to damage/corrosion. A similar procedure can be used for square reinforcing steel bars. A licensed design professional can use this information to evaluate the reduction in load-carrying capacity of a

17、 member and develop appropriate repair strategies.ReferencesACI Committee 546, 2014, “Guide to Concrete Repair (ACI 564R-14),” American Concrete Institute, Farmington Hills, MI, 70 pp.ASTM A615/A615M-15, 2015, “Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcemen

18、t,” ASTM International, West Conshohocken, PA, 8 pp.Concrete Reinforcing Steel Institute (CRSI), 2010, Vintage Steel Reinforcement in Concrete Structures, CRSI, Schaum-burg, IL, 352 pp.Concrete Reinforcing Steel Institute (CRSI), 2016, “Bar Identification,” CRSI, Schaumburg, IL, http:/www.crsi.org/i

19、ndex.cfm/steel/identification (accessed May 17, 2016).American Concrete Institute Copyrighted Material www.concrete.org4 SECTION LOSS DETERMINATION OF DAMAGED OR CORRODED REINFORCING STEEL BARS (ACI 364.14T-17)Reported by ACI Committee 364David A. VanOcker, Chair Marjorie M. Lynch, SecretaryRandal M

20、. Beard Keith E. Kesner Consulting MembersBenoit Bissonnette Erick N. Larson Robert V. GeveckerRyan Alexander Carris John S. Lund Stephen A. JohansonLarry D. Church Pritpal S. Mangat Emory L. KempBruce A. Collins Surendra K. Manjrekar Howard H. Newlon Jr.Paul E. Gaudette James E. McDonald Weilan SongTimothy R. W. Gillespie Jay H. Paul Dela TharmabalaFred R. Goodwin Murat B. Seyidoglu Robert TracyPawan R. Gupta K. Nam Shiu Alexander M. VaysburdJohn L. Hausfeld Thomas E. Spencer William F. WescottRobert L. Henry Valery TokarCharles J. Hookham James WarnerAshok M. Kakade David W. Whitmore