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Minutes

ACI Committee 440-FRP Reinforcement

Main Committee Meeting 1:05 pm – 3:59 pm

Tuesday, March 17, 2009 Marriot Rivercenter Hotel, San Antonio, TX

Chairman: Mr. John P. Busel Secretary: Dr. Carol K. Shield

Attendees: Voting Members: ALKHRDAJI, TAREK BAKIS, CHARLES BENMOKRANE, BRAHIM BISBY, LUKE BLASZAK, GREGG BOUADI, HAKIM BRADBERRY, TIMOTHY BROWN, GORDON BROWN, VICKI BUSEL, JOHN EL-HACHA, RAAFAT FALLIS, GARTH

FAM, AMIR GREEN, MARK GREMEL, DOUG GROSS, SHAWN HAMILTON, H. R. (TREY) HARRIES, KENT HENDERSON, MARK HORECZKO, BOHDAN LOPEZ DE MURPHY, MARIA MIRMIRAN, AMIR MYERS, JOHN NANNI, ANTONIO

OKEIL, AYMAN OSPINA, CARLOS PORTER, MAX PROTA, ANDREA RASHEED, HAYDER RIZKALLA, SAMI SEN, RAJAN SHIELD, CAROL SOUDKI, KHALED TUMIALAN, J. GUSTAVO WITT, SARAH

Consulting Members: Associate Members: ACOSTA, FELIPE BONACCI, JOHN BROADWAY, ANDREW CHENG, DAWN CHOI, OAN CHUL

GALATI, NESTORE KIM, YAIL JIMMY MUTSUYOSHI, HIROSHI NELSON, MARK RENDON, JORGE

RODRIGUEZ-NIKL, TONATIUH ROY, NATALIE SERACINO, RUDOLF SIM, JONGSUNG SMITH, SCOTT

Visitors: BISCHOFF, PETER CONNOLLY, DAVID FIELDS, RICH GARNER, ANDE

JOHNSON, CAROL LAGACE, PAUL MATTHYS, STIJIN RODGERS, JEN

ROUSSEAU, CARL SAWICKI, ADAM ZUREICK, ABDUL

1. Mr. Busel called the meeting to order at 1:05 pm. 2. The attendees made self-introductions. 3. Mr. Busel asked to move agenda item 10 before agenda item 9. Dr. Soudki moved to approve

the agenda as amended. Dr. Fam seconded the motion. The motion passed. 4. Mr. Busel welcomed the members of ASTM D30 to the ACI 440 Committee meeting. He

handed the floor to Dr. Rousseau, Chairman of ASTM D30 to provide an overview of ASTM D30. Dr. Rousseau started by recognizing Dr. Gentry for his work interfacing between the two committees and presented him a Certificate of Appreciation for his work on ASTM D7337. He also introduced the committee to Jen Rodgers (ASTM staff), and Chris Sawicki.

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He explained that ASTM documents need to be reapproved every 5 years. Committee D30 deals with advanced composite materials. They produce test standards, the do not produce specifications. D30 has eight subcommittees. Most of the ACI 440 work will go through D30.04 and D30.05. In the ASTM process, the standard is first balloted at the subcommittee level. After it has passed the subcommittee, it is balloted by they main committee. The ASTM Committee on Standards has final approval. ASTM D4762 is a guide that describes all the standards produced by ASTM D30. Over the last 3-4 years, they have primarily been a group of 20 working on about 17 test methods that had their origins in the 440K document. In the future, precision statements will need to be added to the test methods. Their committee cooperates with the Composites Materials Handbook SAE Committee, and ACI 440.

Mr. Horeczko asked if the precision statements were mandatory. Dr. Rousseau answered that they were. Currently the test standards have a statement indicating that the data is not yet available to determine precision. Mr. Gremel asked about the process for having ASTM put out a Specification for FRP rebar. Dr. Rousseau indicated that it would likely come out of D30, but they would have to revisit their by-laws to see if they want to develop specifications. Mr. Bradberry asked if ASTM certified testing laboratories. Mr. Rousseau answered that others do that. Dr. Nanni asked Mr. Rousseau if his slides could be come part of the 440 minutes (see Attachment A). Mr. Busel thanked ASTM for coming to San Antonio to work collaboratively with ACI 440 and apologized for the meeting planning mishaps.

5. Dr. Bakis presented the 440K report. All balloting is now taking place at D30 and D30.05.

If 440 members are interested in participating on the ballots, they need to join ASTM. Dr. Bakis gave a recap of Monday’s joint ASTM D30/440K meeting. During the meeting, they discussed four ballots. • Direct tension pull-off test. This method has been balloted 3 times and everything is

resolved. • Tension test of flat laminates. There is still significant discussion on cross-sectional areas.

The committee is headed toward reporting measured force, displacement, and width for this test method. Area may be part of the report, but not the test method. At this time, this method has been withdrawn. It will be revised and reballoted.

• Overlap splice tension. This method has been balloted once and received a large number of negatives, with the only substantive unresolved issue being thickness. It will be withdrawn, revised, and reballoted at the subcommittee level.

• Transverse shear. This method was balloted for the first time at the subcommittee level, receiving a large number of negatives. It is currently written as a force control test. D30 would like to change it into a displacement control test. It will also be withdrawn, revised, and reballoted at the subcommittee level.

The next test method to be handed off to ASTM D30 is the bar alkali resistance test. 6. Mr. Blaszak motioned to approve the minutes from the Fall 2008 convention as written. Dr.

Brown seconded the motion. The minutes were approved as written. 7. Chairman’s Report - Mr. Busel started his report congratulating the committee members

who became ACI Fellows: Drs. Brown, Brena and Choi. Mr. Busel also thanked the committee for their hard work that led to his receipt of the ACI Delmar L. Bloem

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Distinguished Service Award. Mr. Busel announced that the winner of best of show at Composites and Polycon 2009 went to the peel and stick aramid/polyurethane film for blast protection. He next updated the committee on information presented at the TAC breakfast: (1) One of ACIs major focuses for the upcoming year will be sustainability. ACI would like all committees to think about ways this topic can be included in committee documents. (2) ACI has indicated that they are in a strong financial position. (3) ACI is asking committees to be more flexible in their meeting schedules. Committees are now allowed to have virtual meetings, but they must be announced ahead of time. See the TCM for procedures for virtual meetings. (4) ACI 318 is restructuring its code document, new format due out in 2014. Mr. Busel notified the committee about the following upcoming conferences: ISIS Canada, May 2009 in Toronto see www.isiscanada.com; FRPRCS-9, July 13-15, 2009 in Sydney see www.iceaustralia.com/frprcs9; APFIS 2009, Dec. 9-11, 2009 in Seoul see www.apfis2009.hanyang.ac.kr; Composites + Polycon 2010 February 2-4, 2010 in Las Vegas see www.acmashow.org. He announced that the details are being worked out for ACI 440 to host FRPRCS-10, likely in spring 2011.

Mr. Busel presented an overview on the status of committee documents. The 440M document was reviewed by TAC. He is hopeful that the committee will address the TAC comments and return the document to ACI by the summer. The committee will try to resolve the negatives associated with the changes to 440.1R (440H) during this meeting. The seismic update to 440F has been balloted at the subcommittee level and will be revised and reballoted at the subcommittee level.

Mr. Busel reported on the committee (Attachment B) membership breakdown. The total committee membership is at 232 up from 227 from November 2008. Mr. Busel summarized all the achievements of the committee during his tenure as chair. He distributed a handout summarizing the accomplishes. He indicated Committee 440 produced a phenomenal amount of work. The committee has published a lot of information for the concrete industry to use and collaborated successfully with other committees. He recommended the five following directions for the future of the committee: education, sustainability, codes, outreach, and design guides. Dr. Shield asked the committee to thank Mr. Busel for his dedication and leadership of the committee during the last 11 years. The committee gave Mr. Busel a standing ovation.

8. 440 Activities

440-G – Dr. Brown summarized the student concrete beam competition that was held during the convention. There were 26 teams from 17 schools involved in the competition. First place for strength-to-weight went to Southern Illinois University – Edwardsville (SIUE). First place for prediction went to University of Sherbrooke, Canada. During the next year, the subcommittee is going to look at rules changes to see how best to include other products in the competition. Dr. Brown thanked Dr. Newhook for taking care of the logistics during the competition, as she couldn’t be there. They managed to test 27 beams in 3 hours.

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440-M – Dr. Prota informed the committee that the TAC review of the document resulted in 281 comments: 67 on definitions, 64 general/primary, 147 editorial, and 3 secondary. Forty-two of the comments on definitions do not require committee action, so there are 239 comments that need to be addressed. Dr. Prota felt that the committee could address all of the primary comments without difficulty. The subcommittee will update the document to address the TAC concerns, then those changes will need to balloted by the Main Committee. Mr. Busel hopes to get the ballot out in the next 30-45 days. The TAC comments will be posted on the 440 webpage. 440-H – Dr. Ospina led the discussion on resolution of the negatives from the recent ballot. He shared with the committee the results of the ballot (see Attachment C.1). All items met the ½ and 2/3 rules. He indicated that the negatives had been discussed at the subcommittee meeting. He moved on behalf of Subcommittee 440H that the “negative by Dr. Newhook shown in Attachment C.2 be found persuasive and resolved as shown in the attachment. The motion passed 26 in favor, 0 opposed and 0 abstentions. Dr. Ospina moved on behalf of Subcommittee 440H that the negatives dealing with how the designer should handle the limit in Eq. 8-10 as shown in Attachment C.3 be found persuasive and resolved as shown in the attachment. Dr. Harries asked if an editorial task group could be formed to clean up the language a bit. Dr. Ospina replied that an editorial task group will wordsmith, but not change the meaning. The motion passed with 26 in favor, 0 opposed, and 0 abstentions. Dr. Ospina moved on behalf of the subcommittee that the negative dealing with crack widths by Dr. Shield be found persuasive and resolved by specifying typical crack widths for aesthetic reasons as well as crack widths given by ACI 224 for other situations. Dr. Harries added a friendly amendment to break the sentence into two sentences. Dr. Brown suggested the committee follow the lead of ACI 224 for water tightness. Dr. Shield suggested that any reference to aggressive environments and water tightness be removed, but the limits for aesthetic reasons should remain. Dr. Green also voiced that he would not like to include the ACI 224 limits for aggressive environments. Dr. Nanni agreed that the document should indicate 0.016” to 0.028” for aesthetic reasons. Dr. Ospina indicated that the editorial task group will improve the wording, but the change will indicate crack widths between 0.016” and 0.028.” The version of the resolution voted on prior to editorial review is shown in Attachment C.4. The motion passed with 26 in favor, 0 against and 1 abstention (Mr. Horeczko). Dr. Ospina moved on behalf of the subcommittee that the negatives shown in Attachment C.5 be found persuasive and resolved as shown. He explained that this group of negatives were primarily editorial in nature, not substantive. Mr. Bradberry, Dr. Bakis, and Dr. Harries all offered wording changes. The final resolution as voted on is given in Attachment C.5. The motion passed with 27 in favor, 0 against and 0 abstentions. Dr. Ospina next moved on behalf of the subcommittee that the two negatives in Attachment C.6 by Dr. Rasheed be found nonpersuasive. Dr. Rasheed indicated he voted negative because the proposed equation doesn’t do as good a job at fitting the data as the current

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equation. He also argued that designers are used to Branson’s equation. Dr. Rasheed saw no advantage to change from one semi-empirical equation to a different semi-empirical equation. Dr. Gross mentioned that some of Dr. Rasheed’s comments are resolved by the proposed changes to resolve the next set of negatives – Eq 8-13a is being removed to address those negatives. Dr. Gross also commented that most equations in the field are semi-empirical, but the point to the change is that the model that the equation is based on is more rational. The equation in 440.1R-06 is completely a curve fit with no real theory behind it. The issue dealing with accuracy will be addressed by the proposed changes for the next set of negatives. For now, we need to focus on the issue of empiricism. Dr. Rasheed mentioned that in the presentation today by Dr. Kim, the predictions from the proposed equation fell right on top of the predictions from the current equation. Dr. Ospina mentioned that Dr. Kim’s results were for prestressed beams, this document does not deal with prestressed beams. Dr. Rasheed suggested that we wait until another group independently verifies the results. We should check the results against a set of data that wasn’t used to calibrate the current equation before we make the change, as it appears that the current equation works well. Dr. Benmokrane agrees with Dr. Rasheed, the practitioners are getting comfortable with the current document, now is not the time to make a change. This change is bringing anything that will help the industry. Dr. Ospina mentioned that when we first started talking about these changes in San Francisco, Dr. Bischoff clearly pointed out the problems with the equation in 440.1R-06. The beauty of the proposed equation is that it works equally well for steel reinforced concrete as FRP reinforced concrete with no additional calibration factors. Dr. Ospina is in favor of moving the document in the direction of equations that work equally well for steel reinforcement and FRP reinforcement. Mr. Henderson commented that as a designer, you recognize that all equations are inaccurate; it is likely that construction variance will have a bigger effect than the difference between the two equations we are discussing. We should be trying to make changes to our documents that reduce costs and provide safety. If the additional cost of engineering does not result in a materials saving then what is the point when there isn’t really more in-place accuracy. We should only be making changes if it really changes the end design. Dr. Rasheed again mentioned that it is premature to make this change. Dr. Gross suggested that the committee look at the other proposed changes before we vote on the motion. Mr. Bradberry moved to table the motion. Mr. Bradberry’s motion was seconded by Dr. Brown. Mr. Bradberry’s motion passed with 26 in favor, 1 against (Dr. Rasheed), and no abstentions. Motion 5 was tabled. Dr. Ospina moved on behalf of the subcommittee to consider the negatives by Drs. Shield, Brown, O’Kiel and Rasheed as shown in Attachment C.6 as persuasive and resolved them by the new text shown in Attachment C.7. Dr. Gross commented on the proposed changes to resolve the negatives – Originally, there were two equations that could be used for calculating deflections – 8-13a and 8-13b, which were different forms of the exact same equation. Also, Eq 8-14 had a factor to account for variation of Ie along the beam. The subcommittee resolved this by providing only a single equation that has a fixed gamma factor (i.e. no choice). Dr. Gross indicated that this equation has similar conservativism as the existing equation. Both the old and the new equation were verified using measured cracking moments in the equation. Dr. Gross noted that when he did the work, he found that the measured cracking moment was about 80% of Mcr based on 7.5rtfc’. Dr. Benmokrane asked if there is experimental evidence for the lower cracking moment. Dr. Gross said yes – his

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data shows it. Dr. Rasheed voiced that the rational in the document for the lower cracking moment is based on restraint of the FRP, but FRP cannot give as much restraint as steel and ACI 318 doesn’t recognize the reduced cracking moment. Dr. Myers asked what concrete strengths were included in the database. Dr. Gross indicated that it was a wide range of concrete strengths. He also commented that Dr. Rasheed is correct, steel would give a larger restraint, but that is a problem with ACI 318 that this committee cannot control. Dr. Gross did indicate that ACI 318 has changed the definition of cracking moment for slender walls. Dr. Brown indicated that the changes move us in a more rational direction. Mr. Bradberry indicated that he supports the change, it is at least as accurate as what is in the document. Dr. Nanni indicated that he was bothered that this discussion was occurring at the main and not at the subcommittee. He suggested that the subcommittee work to resolve these negative outside of the meeting. Mr. Gremel made a motion to table the current motion so that the subcommittee could work to resolve the negatives. Mr. Gremel’s motion was seconded by Dr. Porter. The motion passed with 22 in favor, five opposed (Mr. Horeczko, Dr. Ospina, Dr. Myers, Dr. Gross, and Mr. Bradberry). The subcommittee will continue to find a resolution to Dr. Rasheed’s negatives. 440-F – Dr. Green informed the committee that SP-258 Seismic Strengthening of RC Members using FRP had been published. The subcommittee balloted the seismic design guidelines in February. The consensus of the subcommittee was that the guidelines need to be streamlined to address components and subsystems and examples need to be prepared. The task group hopes to have another subcommittee ballot in June. Other issues that the subcommittee is working on include: serviceability, glass transition temperature, and FRP strengthened PT beams. The subcommittee intends to initiate new work on blast mitigation and confined column modulus. It is unclear if blast mitigation for reinforced concrete structures will get combined with masonry structures as a single document, or if it will be added to 440.2R. Members of 440-F are also working in support of ACI 562 on the repair code. The subcommittee is intending to add sustainability to 440.2R. The current intention of the subcommittee is to keep the document in non-mandatory language. Dr. Ospina mentioned that there was good attendance at the sessions on serviceability. Mr. Busel acknowledged the chairs of the sessions for their efforts. Dr. Nanni added to Dr. Green’s comments about its work with ACI 562 – ACI 562 will be the repair code, and should be published in 2012. Committee ACI 563 is tasked with producing the specifications that will be adopted by reference into ACI 562. Dr. Nanni thought that 440F could extract the basis for the specs for FRP from 440.2R, then ACI 563 could translate the material into mandatory language and ballot the document in ACI 563, removing the burden of formatting and balloting the specification from 440. Mr. Brown asked when ACI 563 needs the material. Dr. Nanni indicated that ACI 563 is supposed to trail ACI 562 by one year, however, trailing by one year, really means trailing by 3 to 5 years because of the need for a new version of ACI 562 to reference the new specifications. Dr. Nanni suggested that the subcommittee prepare the information for ACI 563 by late 2009 or early 2010. 440-E – Dr. Bouadi reported to the committee that the subcommittee is working on three webinars. ACI has recently decided that the webinars can be no longer than one hour each, so the subcommittee is working to cut the webinars on internal reinforcement and external reinforcement into two one hour webinars each. There will also be a one hour webinar on

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prestressing with FRP. Dr. Bouadi is hopeful that all five one hour webinars will be ready to turn over to ACI by the end of May. The subcommittee would like to then start work on a webinar on case studies. Mr. Busel remarked that the information in the webinars that are almost complete comes from 440.1R-06, 440.2R-08, and 440.4R-04. 440-J – Dr. Fam reported that the subcommittee plans to start work on two areas: bridge decks and piles. The subcommittee has started a new report based on stay-in-place structural forms used in bridge deck applications under the leadership of Mark Nelson. The subcommittee is looking for contributions for this document. Please contact Dr. Fam if you can contribute. The subcommittee has started interacting with ACI Committee 335 Hybrid and Composite Members. The two committees will cosponsor a session at the Fall 2010 convention on hybrid/composite members. Contact Dr. Fam or Dr. Ziehl if you want to present. 440-D – Dr. Porter reported that the subcommittee continues to discuss the needs for round robin testing in support of the ASTM test methods. Three presentations were made at the 440D meeting in San Antonio: Dr. Bisby – “Strain Localizations in FRP Confined Concrete: New Insights and Implications,” Dr. Myers – “Durability Performance of Polyurea Based Systems for Concrete Member Rehabilitation,” and Dr. Rizkalla – “Use of FRP for the Precast Industry.” 440-I – Dr. El-Hacha reported that the subcommittee developed a draft webinar based on 440.4R-04. In discussing the webinar, a lot of technical issues were raised that the committee will take up as new business as it works to update 440.4R. Dr. Benmokrane mentioned that there is a lot of CFRP tendons being used in precast elements in Canada. Anchors continue to be a problem and perhaps the subcommittee could provide some input to the industry. ISO – Dr. Rizkalla reported that he attended the ISO meeting in Egypt to represent the U.S. The ISO “code” isn’t really a code, and Dr. Rizkalla managed to convince the committee to change its charge and the document title to a performance specification. The document will not have any equations in it. Dr. Rizkalla suggested that Committee 440 continue to send a representative to the ISO committee meetings. Dr. Rizkalla did not know when the next meeting would be. 440-L – Mr. Busel reported on behalf of Drs. Hamilton and Myers. The subcommittee is working on a guide to conditioning protocols and acceptance criteria. They hope to maintain simplicity so the conditioning and resulting tests are useful to industry. The subcommittee currently has two task groups – one on bars and one on bonded FRP systems. They hope to have a draft of the guide completed by Fall 2009.

8. Liaison Report

Dr. Soudki reported that ACI 503 Adhesives and ACI 548 Polymers and Polymer Adhesives for Concrete are combining. Dr. Benmokrane indicated that the updated Section 16 of the Canadian Highway Bridge Design Code will be available soon. This update includes changes to φ factors, crack widths, and shear. Canada hopes to have an update to 8-06 for

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building design completed by September. Dr. Rizkalla mentioned that PCI has a committee on FRP and is working on a state of the art document. Next meeting will be April 25 in Chicago. Dr. Seracino mentioned that some 440 members are working on a SOA report on FE modeling of bonded and internal FRP with ACI 447. Dr. Kim mentioned that Committee 345 is sponsoring a session on bridge repair and maintenance. Contact Dr. Kim if interested in presenting at this session. Dr. Johnson mentioned that it would be possible to use the Army Corps of Engineering blast load simulators. For more information, contact Dr. Johnson.

9. Adjourn Mr. Busel adjourned the meeting at 3:59 pm.

Respectfully submitted, Carol K. Shield Secretary, ACI Committee 440 /attachments

Attachment A Slides from ASTM D30

Slide 1

Committee D30 on Composite MaterialsCurrent Work in Standard Test Methods

DevelopmentCarl Rousseau, D30 Chairman (LM Aero)

Adam Sawicki, D30 Vice-Chairman (Boeing)Jen Rodgers, D30 Staff Mgr (ASTM)

Slide 2

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Outline

ASTM D30 Overview and Overall ObjectiveD30 OrganizationASTM Process DescriptionD30 Standards SummaryNew Standards – 2005 to 2008Current Work ItemsFuture ObjectivesRelationships

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Slide 3

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ASTM International Fast Facts

Formed in 1898World-Wide Development of Voluntary, Full-Consensus Standards for Materials, Products, Systems & Services12,000 Standards Developed by 138 Technical Committees are Administered, Published, and Distributed by ASTM InternationalOver 32,500 Members from 125 CountriesParticipate on ASTM CommitteesASTM Standards are Living Documents, Continually Revised to Meet Stakeholder Needs, Reflecting Current Technology

Each member – not a company or

country – gets a vote

Slide 4

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Committee D30 on Composite Materials

“The Committee will develop standard test methods, practices, terminology, and guides; sponsor symposia; stimulate research; and exchange technical information pertaining to composite materials (primarily those with fibrous reinforcement), as well as to reinforcing fibers with a Young's modulus greater than 20 GPa (3 Msi).

This Committee will not develop standard specifications.”

Committee D30 formed in 1964 (with heritage tothe early ‘50s) out of Committee D20 on Plastics

Current (2008) D30 Scope

D30 ObjectiveA complete, effective, and coordinated suite of testing standards for composites

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Slide 5

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D30 Committee Membership

OEMsTesting LaboratoriesMaterial SuppliersComponent FabricatorsAcademic & Research InstitutionsGovernment and Certification Agencies

US Army, Air Force, Navy, NASAFAA, CAANIST, non-US standards groups

Slide 6

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ASTM Technical Committee Organization

MAIN COMMITTEE

Subcommittee.01

Subcommittee.02

Subcommittee.03

Task Group1

Task Group2

Technical Committees form to address specific industry issues. They develop scopes to define their jurisdiction.

Subcommittees are established to address subsets of specialized subject matter under the scope of the Main Committee.

Subcommittees further organize their expertise into small Task Groups. This is the level at which documents are first developed and are subsequently revised.

The 138 Technical Committees, 2,000+ Subcommittees, & thousands more Task Groups produce 1,200 drafts, or revisions to drafts, annually.

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Slide 7

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D30 Committee Organization

D30.01 Editorial and Resource StandardsD30.02 Research and MechanicsD30.03 Constituent/Precursor PropertiesD30.04 Lamina and Laminate Test MethodsD30.05 Structural Test Methods

D30.05.01 Civil and MarineD30.06 Interlaminar PropertiesD30.09 Sandwich ConstructionD30.90 Executive

D30.91 PlanningD30.92 AwardsD30.93 Standards Coordination and Globalization InitiativeD30.94 Technical Specialists

Slide 8

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ASTM International Balloting Process

TASKGROUP

SUBCOMMITTEE

MAIN COMMITTEE

COMMITTEE ON STANDARDS (COS)

1) Starting Point. Documents are drafted, and continually revised, in the Task Group by a few members who specialize in the subject matter. This is where the bulk of the activity occurs.

2) A completed draft is voted on by the Subcommittee. If approved, it moves to a Main Committee vote. If not, it returns to the Task Group for re-drafting.

3) After S/C approval the Main Committee votes. If approved it is presented to the Committee on Standards for final review. Otherwise it returns to the Task Group for re-work & balloting is repeated.

4) As a final check, a standing committee (COS) of the ASTM Board of Directors reviews the process by which each standard is developed or revised, to ensure compliance with ASTM regulations.

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Slide 9

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D30 Standards Breakdown, 2008

420Sandwich ConstructionD30.091372Total

15Interlaminar PropertiesD30.06

513Structural Test MethodsD30.05

320Lamina/Laminate Test MethodsD30.04

08Constituent/Precursor PropertiesD30.03

NANAResearch and MechanicsD30.02

06Resource StandardsD30.01

DraftPublishedNameNo.

StandardsSubcommittee

Slide 10

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2008 D30 Standards Summary(with most pre-existing standards updated)

Constituent Lamina(te) Structure Other

TensionCompressionShearUnnotched FatigueShort-Beam StrengthFlexure ResponseFiber VolumeMode I FractureMixed-Mode FractureMode I Fracture FatiguePly ThicknessMoisture AbsorptionGlass Transition(and more)

Open-Hole TensionOpen-Hole CompressionFilled-Hole TensionFilled-Hole CompressionBearingBearing-Bypass InteractionBearing FatigueDamage Impact ResistanceResidual Strength After DamageSandwich Beam FlexureSandwich Panel FlexureSandwich Flexure/CreepFastener Pull-Through(and more)

Fiber TensionFiber DensityTow Density Fiber ContentResin ContentVolatiles ContentFiber Areal WeightCore DensityCore ThicknessCore ShearCore CompressionCore Shear FatigueCore Water Absorption(and more)

TerminologyFabrication PracticeOrientation CodeGeneral Test GuideTextile Test GuideDatabase Records

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Slide 11

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D4762 –Gateway to D30 Standards

Standard Guide to Testing Polymer Matrix Composite Materials

– The major 2004 revision now briefly summarizes the scope, advantages, and disadvantages of related D30 standards, as well as other commonly referenced related standards of other ASTM committees.

– An aid in education and selection of appropriate standards for use with advanced composite materials

– 2008 update has been published, includes information on standards published 2004-07

Slide 12

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2005-08: New D30 Standards

D 7078/D 7078M: Test Method for Shear Properties of Composite Materials by the V-Notched Rail Shear Method

D 7136/D 7136M: Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer Matrix Composite to a Drop-Weight Impact Event

D 7137/D 7137M: Test Method for Compression Residual Strength Properties of Damaged Polymer Matrix Composite Plates

D 7205/D7205M: Tensile Properties of Continuously-Reinforced Polymer Matrix Composite BarsD 7248/D7248M: Test Method for Bearing/Bypass Interaction Response of Polymer Matrix Composite

Laminates Using 2-Fastener SpecimensD 7249/D7249M: Test Method for Facing Properties of Sandwich Constructions by Long Beam FlexureD 7250/D7250M: Practice for Determining Sandwich Beam Flexural and Shear StiffnessD 7264/D7264M: Test Method for Flexural Properties of Polymer Matrix Composite MaterialsD 7290: Practice for Evaluating Material Property Characteristic Values for Polymeric Composites for Civil

Engineering Structural ApplicationsD 7291/D7291M: Test Method for Through-Thickness "Flatwise" Tensile Strength and Elastic Modulus of a

Fiber-Reinforced Polymer Matrix Composite MaterialD 7332/D7332M: Test Method for Measuring the Fastener Pull-Through Resistance of a Fiber-Reinforced

Polymer Matrix CompositeD 7336/D7336M: Test Method for Static Energy Absorption Properties of Honeycomb Sandwich Core

MaterialsD 7337/D7337M: Tensile Creep Rupture of Fiber Reinforced Polymer Matrix Composite BarsD 7028: Test Method for Glass Transition Temperature (DMA Tg) of Polymer Matrix Composites by

Dynamic Mechanical Analysis (DMA)

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Slide 13

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Recent Efforts: Civil Infrastructure Standards

D30.05 subcommittee working with ACI Committee 440 to publish civil infrastructure composite test methods.– TG consists of about 20 D30 and ACI subject matter experts.– Key contacts are Drs. Abdul Zureick and Russell Gentry (Georgia Tech).

17 ACI 440 documents being transitioned into ASTM documents.Three ACI standards are currently published as ASTM standards:– D 7205/D7205M: Tensile Properties of Continuously-Reinforced Polymer

Matrix Composite Bars– D 7290: Practice for Evaluating Material Property Characteristic Values for

Polymeric Composites for Civil Engineering Structural Applications– D 7337/D7337M: Tensile Creep Rupture of Fiber Reinforced Polymer

Matrix Composite BarsTwo other ACI standards are in D30.05 subcommittee ballot:– WK17265: Pull-Off Strength for FRP Bonded to Concrete Substrate– WK17184: Tensile Properties of Fiber-Reinforced Polymer Matrix

Composites used for Strengthening of Civil Structures

Slide 14

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Current Standards Initiatives

• Draft standard test methods are currently in-work for a number of other items, including:– Open-hole fatigue testing– Additional testing modes for interlaminar fracture– Sandwich cleavage fracture toughness– Non-ambient environmental testing

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Slide 15

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Future D30 Objectives

• Add more quantitative precision statements based on accurate and effective round-robin test programs

• Improve balance between a concise lab procedure and detailed explanatory guidance or requirements

• Increase exposure and acceptance in non-aerospace and international markets

• Consider standardizing the experimental benchmarking of advanced numerical methods

• Expand into non-aerospace statistical assurance of measured properties

Slide 16

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Current and Future Relationships

Cooperation with CMH-17 (MIL-HDBK-17) on consensus test methods and testing guidance

Cooperation with SAE Committee P-17 on test methods for consensus standard composite material specifications

Cooperation with ACI Committee 440 on civil infrastructure standards

Standards supporting marine product development

Collaboration and joint meetings/conferences with CMH-17, ASC,SAMPE, MACM

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Slide 17

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D30 Committee Contacts

D30 Officers (2008-2009)Chairman, Carl Rousseau (LM Aero)Vice-Chair, Adam Sawicki (Boeing)Recording Secretary, Mark Chris (Bell Helicopter-Textron)Membership Secretary, James Ratcliffe (NASA)Past Chairman, Rich Fields (LM MFC)Past Chairman, Gene Camponeschi (US Navy)

D30 Members-At-LargeBill Bertelsen (Gougeon Brothers)Paul Lagace (MIT)Jian Li (Boeing)Steve Ward (Consultant)

D30 Subcommittee Chairs.01, Editorial/Resource, Paul Lagace (MIT).02, Research & Mechanics, Ron Krueger (NASA).03, Constituent/Precursor (inactive).04, Lamina/Laminate, Mark Kistner (USAF).05, Structural, Mark Chris (Bell Helicopter-Textron).06, Interlaminar, James Reeder (NASA).09, Sandwich, Steve Ward (consultant)

ASTM StaffJen Rodgers, D30 Staff MgrJill DiCicco, D30 Admin AsstKaren Wilson, D30 SecretaryJessica Rosiak, D30 Editor

Slide 18

ASTM InternationalCommittee D30 on Composite Materials

www.astm.orgwww.astm.org/COMMIT/D30.htm

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Slide 19

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Recent Efforts: UpdatesC271/C271M: Core DensityC272: Sandwich Water AbsorptionC273/C273M: Sandwich ShearC274: Sandwich TerminologyC297/C297M: Sandwich Flatwise Tension StrengthC363: Honeycomb Core Delamination Strength (Node-Bond)C364/C364M: Sandwich Edgewise Compression StrengthC365/C365M: Core Compressive PropertiesC366/C366M: Core Thickness MeasurementC393/C393M: Sandwich Core Properties by Long Beam FlexureC394: Sandwich Shear FatigueC480: Sandwich Flexural CreepC481: Sandwich Laboratory AgingD6416/D6416M: Sandwich 2D Plate Flexure PropertiesD6772: Core Dimensional StabilityD6790: Core Poisson’s RatioD7249/D7249M: Sandwich Facing Properties by Long Beam FlexureD7250/D7250M: Determining Sandwich Beam Flexural & Shear StiffnessD7336/D7336M: Honeycomb Core Static Energy AbsorptionF1645/F1645M: Honeycomb Core Water Migration

8 D30.09 standards updated to standard

D30 format to improve

consistency.

Slide 20

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Recent Efforts: Sandwich Long Beam Flexure Standards

In 2006, C393-00 was replaced with 3 standards:C393: core shear stiffness and strength by long beam flexure (test method)

– 3-point loading configuration is standard; alternative configurations retained for historical continuity.

– Includes guidelines for specimen design to promote core shear failure.D7249: facing stiffness and strength by long beam flexure (test method)

– 4-point loading configuration is standard.– Includes guidelines for specimen design to promote facing failure.

D7250: determining sandwich beam flexural and shear stiffness (practice)– Data reduction and calculations for flexural and shear stiffness determination

using C393 and D7249.

C393 D7249

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Slide 21

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Recent Efforts: New DMA Tg Standard

D 7028 for glass transition temperature by Dynamic Mechanical Analysis (DMA) was published in 2007.– Based upon process improvements derived from a round-robin study.– Significant efforts by Mike Stuart (Cytec) and Joy Wu (Hexcel).

Key process improvements:– Guidance on equipment calibration.– Methods for characterizing and interpreting DMA thermograms.

A research report from the round-robin testing is in preparation.

Slide 22

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Possible New Standards

Other technical areas for possible D30 standards development include:– HPLC and FTIR– Large-scale CAI– Creep– Stress-rupture– Notched laminate testing guide

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Attachment B

Membership Report

ACI 440 Committee Breakdown – March 11, 2009 Total Members 232

ACI Category Voting Member Non-Voting Consultant Member

Non-Voting Associate Member

User 14 27% 8 35% 37 23% Producer 7 14% 1 4% 17 11%

General Interest 30 59% 14 61% 104 66% Total 51 22% 23 10% 158 68%

ACI 440 Committee Breakdown – October 28, 2008 Total Members 227

ACI Category Voting Member Non-Voting Consultant Member

Non-Voting Associate Member

User 14 26% 8 35% 33 22% Producer 8 15% 1 4% 17 11%

General Interest 31 58% 14 61% 101 67% Total 53 23% 23 10% 151 67%

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Attachment C.1 440H Ballot Summary

ACI COMMITTEE 440 BALLOT – SPRING 2009

VOTE SUMMARY

Proposed Revisions to "Guide for the Design and Construction of Concrete Reinforced with FRP Bars (ACI 440.1R-06)" reported by ACI Committee 440

Item Approve (Total)

Approve with

Editorial Comment

Negative Abstain Not returned

1 Revision to 8.3, 8.3.2.1 and 8.3.2.2 (deflections)

34 9 7 1

2 Changes to 8.3.1 (crack control) 37 9 4 1

3 Revisions to Example Problem 38 6 5 1 1

N = This comment must be addressed to satisfy a negative vote AC = This is a comment that needs only be considered by the committee, it does not need to be resolved to satisfy a negative

vote

All Items meet 1/2 and 2/3 rules Item 3 will be revised and reballoted as a result of the ballots on item 1 and 2.

Attachment C.2 440H Ballot Motion 1

MOTION 1: Move to find the following negatives PERSUASIVE and resolve them as shown:

Item Reviewer Line N/AC Comment Response by Serviceability Task Group 2 Newhook 6 N “Flexural cracks can be controlled directly or

indirectly.” The directly or indirectly refers to design calculations/reinforcement proportioning methods. The calculations used in the respective design methodologies do not inherently control cracking – the reinforcement does. The mechanics of how this reinforcement controls cracking does not change based on the method chosen, merely the amount and layout of reinforcement. Hence the crack control is not direct in one case and indirect in the other – the methods are merely labeled this way. A revised wording could be “Two design methodologies exist for proportioning reinforcement to control flexural cracking: crack width prediction and bar spacing limits.” Reasonable editorial changes to this wording are acceptable.

Persuasive. We propose the following text: ”Two design methodologies exist for proportioning reinforcement to control flexural cracking: a direct procedure in which crack widths are calculated, and an indirect procedure in which maximum bar spacing limits are specified”.

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Attachment C.3 440H Ballot Motion 2 MOTION 2: Move to find the following negatives PERSUASIVE and resolve them as shown:

Item Reviewr Line N/AC Comment Response by Serviceability Task Group 2 Parretti 39-41 AC Sentence from line 39 to 41 is unclear.

1) Why the stress level in the FRP reinforcement needs to be reevaluated? Such stress level will be the one that comes out from the calculation irrespectively of the value assumed by dc in Eq. (8-10). 2) In which manner should I reevaluated the maximum crack width limit? Are we suggesting that the limitation given between lines 6-16 are no longer acceptable if dc is larger than the recommended value expressed by Eq. (8-10)? If this is the case, guidance should be given on the correct value that the designer should take for w.

The dc limit established by Eq. 8-10 defines a maximum limit for dc in Eq. 8-9 so this equation can be used to adequately model Frosch’s ellipsoid. If the designer intends to use a dc value greater than this limit, and assuming that the max crack width limit can not be relaxed, then the max bar spacing given by Eq. 8-9 will have to be reevaluated based on a reduction of the FRP stress that results in a larger ellipsoid. The following sentence is proposed, after the line 38-39 sentence: If a larger dc value is required for specific durability requirements or any other reason, and the maximum crack width limit cannot be relaxed, it is then necessary to reduce the stress level in the FRP reinforcement for example by adding additional reinforcing bars.

2 Newhook 40 N “… the stress level in the FRP reinforcement and the maximum crack width limit need to be reevaluated.” The meaning of this is not clear to the designer. More specific guidance should be provided.

See previous.

2 Shield 42 AC What does the designer do if his beam does not meet equation 8-10? I’m confused here. dc is what it is, you don’t want to pick a bigger w, adding more bars only makes the RHS smaller… In the rationale, it says “the limit on dc per 8-10 acts as a capping for the maximum bar spacing… If that is the case, why not put it in the document that way, instead of as an equation on dc.

See previous.

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Attachment C.4 440H Ballot Motion 3 MOTION 3: Move to find the following negatives PERSUASIVE and resolve them as shown:

Item Reviewr Line N/AC Comment Response by Serviceability Task Group

2 Shield 55-58 N I think the committee has to provide a recommendation or at least some guidance of acceptable crack widths. Guys, we are the experts.

Persuasive. In general crack widths in FRP reinforced members will be larger than those in steel reinforced members. The procedure allows controlling different levels of flexural cracking. In situations where crack widths are limited by aesthetic reasons. Typically crack widths in the range of 0.016 in to 0.028 in.

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Attachment C.5 440H Ballot Motion 4 MOTION 4 : Move to find the following negatives PERSUASIVE and resolve them as shown:

Item Reviewr Line N/AC Comment Response by Serviceability Task Group 1 Lee 9 N Replace with following: “Cracking - Control of

cracking is desirable for aesthetic, functional, and durability reasons (for example, to prevent water leakage and moisture-induced concrete deterioration); and”

Persuasive. The proposed changes triggered this revision. Text corrected to read “Cracking - Control of cracking is desirable for aesthetic, functional, and durability reasons (for example, to prevent water leakage and moisture-induced concrete deterioration); and”

1 Bradberry 14-17 N Revise committee’s proposed modified sentence to read, “The serviceability provisions given in ACI 318 for deflection (9.5) and crack control (10.6) need to be modified to accommodate for FRP reinforced members by to accounting for the increased flexibility when using the lower stiffness FRP reinforcement and having relaxed crack width requirements. when using reinforcement not susceptible to corrosion.,. Rationale for revision: The revisions noted above are intended to make the sentence simpler, more concise, and clearer. Also, it is not true that FRP reinforcement is not susceptible to corrosion, only that it is not susceptible to galvanic corrosion which produces an expansive corrosion product. The committee’s provision of CE factors are an admission that deterioration of FRP reinforcement properties (i.e. chemical corrosion) occurs and must be taken into account in the design of FRP reinforcement. There is no need in this section to explain why there are relaxed crack width requirements. This is already covered in section 8.3.1 which had not been balloted. Increased flexibility results from the lower stiffness and the relaxed crack width requirements regardless of why these things are so.

Persuasive. Text will be edited to read “The serviceability provisions given in ACI 318 for deflection (9.5) and crack control (10.6) need to be modified to address FRP reinforced members by accounting for increased flexibility resulting from the use of the lower stiffness FRP reinforcement and relaxed crack width requirements.

1 Bank 170 N λ appears to be missing from term in (8-15) Persuasive. This is a typo. λ will be added. 1 Bouadi 170 N Equation 8-15 is missing λ is the most right

expression. It should be modified to:t

gc

yIf '6 λ

Persuasive. This is a typo. λ will be added. SI equation will also be added.

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1 Bouadi 173 N λ is missing in the expression of fr. Change to fr = 7.5 λ √f’c 

Same as above.

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Attachment C.6 440H Ballot Motion 5 MOTION 5 : Move to find the following negatives NonPERSUASIVE

Item Reviewr Line N/AC Comment

1 Rasheed 100-160 N There is NO point, NO advantage and NO tangible benefit in proposing this major change. The current ACI 440.1R-06 equation does the job! If you look at the 4 graphs on page 8, it is clear that ACI 440.1R-06 equation does a better job fitting the data with better mean value and less scatter. It is confusing to the engineer to use Branson equation with ACI 318 and use something completely different in ACI 440.1. Such a change is only warranted if new data show that the current equation cannot do the job. Bischoff in one of his papers has given a different βd correction factor to use with equation 8-13a of ACI440.1R-06. If he can demonstrate that this will give better results for the database, it will be a more appropriate change to propose.

1 Rasheed 159-160 N In continuous beams, the curvature distribution along the beam is unknown at any load level because the moment variation in the beam is nonlinearly varying in a statically indeterminate structure. So it is NOT possible to integrate the curvature. Weighted average of Ie can not be reliably computed based on linear elastic analysis because the moments are nonlinearly varying due to the continuous spread of cracking.

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Attachment C.7 440H Ballot Motion 6 MOTION 6 : Move to find the following negatives by Shield, Brown, O’kiel and Rasheed

PERSUASIVE and resolve them as shown and to find the negative on definition of Mcr by Rasheed non-persuasive:

Item Review

r Line N/AC Comment Response

1 Shield 136-140 N Pick one form or the other. We don’t need to show algebra to our readers. I suggest keeping 8-13b and then keeping the text about it coming from weighted average on flexibility. The reader can get the paper if they want to see the form in 8-13a

See proposed wording

1 Brown 150-159, 162, and 178-180

N I think it would be cleaner and more in keeping with the philosophy of section 9.5.2.3 of the 318 Code (which begins with “Unless stiffness values are obtained by a more comprehensive analysis, immediate deflection shall be computed with…” and then presents the equation to be used for calculation of Ie), if we omitted the specifics on the more accurate closed form solutions with I’e and instead referred the reader to the appropriate reference for those details, if it is available in the published literature. Why are we presenting details on curvature integration methods when 318 does not do so, particularly given that Eq. 8-14 and Table 8.3 apply only to a limited number of simplified beam geometries and loading cases and when it appears that the relevant reference for Eq. 8-14 and Table 8.3 (Bischoff and Gross) has yet to be published? My suggested language would be to omit lines 150-159 from “Closed-form” in line 150 through “cracking moment” in line 159, along with Table 8.3. That would also necessitate deleting the reference to Eq 8-14 in line 162. I believe the guide should, wherever possible, be based on work that has been published (or accepted for publication) in peer-reviewed venues. Furthermore, in this instance should the reader require a more exact analysis he or she is free to integrate the moment-curvature diagram, as lines 149-150 clearly state. I think inclusion of Eq. 8-14 and Table 8.3 is

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unnecessary and may cause confusion. 1 Shield 179 N Is it clear in the text that superposition DOES NOT HOLD with respect

to the table (i..e if you have both a distributed load and a point load, you can’t add the delta for the point load to the delta for the distributed load). I think having the table makes it seem like superposition is ok.

1 Shield all N I am opposed to having so much conservativeness in a SERVICEABILITY criteria. The mean test-to-predicted ration is 1.31. There is no need for this for serviceability, we aren’t talking strength here. This is especially important when this criteria has a pretty good chance of controlling the design. I do not believe that the cop out of well, the practitioner can integrate and get less conservative answers works. I don’t think it is practical to think that more than a handful of practitioners would go to the trouble of integrating. I also don’t find the tables helpful, as superposition doesn’t hold

1 Rasheed 178 N Table 8.3 should be removed 1 Okeil >290 N In comparing various methods, the scatter is also important. It seems that

ACI 440.1R-06 is doing a decent job on average, and the scatter is not bad. Bischoff (2005) on the other hand is more conservative, but the scatter is higher. Bischoff and Gross (2007) seem to have a similar scatter as 440.1R-06, but on average it is more conservative. It is not possible to assess which method is resulting in better estimates without quantifying this scatter (Standard Deviation or Coefficient of Variation). A better method on average that results in more scatter may not be my choice.

1 Shield 147 & 160

N The term “critical section” needs to be defined. Do you mean maximum moment – what is meant here. I suggest getting the wording out of 318 (I think they use critical moment section, but I’m not sure)

1 Shield 159 N For continuous members, it says to use a “weighted average” of Ie. How would one pick the weightings?

1 Rasheed 162-170 N We shouldn’t have a cracking moment that is different from ACI 318. The 7.5 factor has worked for cracking with steel reinforcement in which case the restraint shrinkage is higher and no one has complained about that for all these years.

Non-persuasive, or change proposed resolution to put 0.8 in equation

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Bischoff (2005) and Bischoff and Scanlon (2007) proposed an alternative section-based expression for the effective moment of inertia Ie that works equally well for both steel and FRP-reinforced concrete members without the need for empirical correction factors. Branson’s original expression represents a weighted average of the uncracked and cracked member stiffness (EI), while Bischoff’s proposed approach represents a weighted average of flexibility (1/EI). The approach using a weighted average of flexibility represents better the deflection response of members with discrete cracks along their length (Bischoff and Scanlon 2007). The section-based expression proposed by Bischoff (2005) is modified to include an additional factor γ to account for the variation in stiffness along the length of the member. The modified expression for the effective moment of inertia is given byThis approach provides reasonable estimates of deflection for GFRP, CFRP and AFRP reinforced concrete beams and one-way slabs. This expression is given by either :

gcra

cr

ga

cr

e IIMM

IMM

I11111

22

≥⎥⎥

⎦

⎤

⎢⎢

⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛−+⎟⎟

⎠

⎞⎜⎜⎝

⎛= (8-13a)

or

g

g

cr

a

cr

cre I

II

MM

II ≤

⎥⎥⎦

⎤

⎢⎢⎣

⎡−⎟⎟

⎠

⎞⎜⎜⎝

⎛−

=

112

γ

(8-13b)

with η = 1-Icr/Ig. This approach provides reasonable estimates of deflection for GFRP, CFRP and AFRP reinforced concrete beams and one-way slabs. The factor γ is dependent on load an boundary conditions and accounts for the length of the uncracked regions of the member and for the change in stiffness in the cracked regions. The committee recommends that The factor is dependent on load and boundary conditionsthe factor , but may be taken as

( )acr MM72.072.1 −=γ , which is the result from integrating the curvature over the length of a beam with a

uniformly distributed load in lieu of a more comprehensive analysis. Unless stiffness values are obtained by more comprehensive analysis, immediate deflections shall be computed with the effective moment of inertia given by Eq. (8-13) using Branson’s original expression represents a weighted average of the uncracked and cracked member stiffness (EI), while Bischoff’s proposed approach represents a weighted average of flexibility (1/EI). The approach using a weighted average of flexibility represents better the deflection response of members with discrete cracks along their length (Bischoff and Scanlon 2007). When computing deflection, eI is determined with Eq. (8-13) for the maximum service load moment aM in the memberat the critical section (where moment is maximum).and is assumed uniform along the length of member to provide a conservative estimate of deflection as member stiffness is lowest at the critical section. If warranted, a more accurate calculation of deflection can be carried out by integrating curvatures along the length of the member based on the calculated eI value at each section. Closed-form solutions for simple loading cases give an equivalent value of the effective moment of inertia eI ′ that includes an additional factor γ to account for curvature integration.

gacr

cre I

)M/M(II ≤

−=′ 21 γη

(8-14)

The integration factor γ is defined in Table 8.3 for different beam types and loading cases. For all cases, γ > 1 such that setting γ = 1 results in Eq. (8-13) and provides a conservative estimate of deflection. The increase in member stiffness with Eq. (8-14) depends on the type of load, reinforcing ratio and level of service load relative to the cracking moment. Deflection of continuous members can be estimated using either a weighted an average of Ie computed at the critical positive and negative moment sections or, as recommended by ACI 318. , if warranted, by integrating curvature along the member length.

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When the Ma > Mcr , the effects of cracking must be taken into account by using Equations (8-13) or a more comprehensive analysis. and (8-14) areis only valid when the maximum unfactored moment in the member is equal to or greater than the cracking moment (Ma > Mcr). Recommended minimum thickness values in Table 8.2 assume this condition. The assumed Mcr value has a significant effect on computed values of deflection. A lower Mcr can be used to account for the tensile stresses that develop in the concrete from restraint to shrinkage (Scanlon and Bischoff 2008). It is recommended that deflection be computed using the ACI 318 value for the elastic modulus of concrete along with 80 percent of the cracking moment definedsuggested by ACI 318. This is equivalent to a cracking

moment based on a reduced concrete rupture modulus cr ff ′= λ6 , as compared to cr ff ′= λ5.7 as defined in

ACI 318.

t

gc

t

gccr y

Ify

IfM

'6'5.78.0

λλ=

⎥⎥⎦

⎤

⎢⎢⎣

⎡= (8-145)

The use of a reduced Mcr also accounts for cases where the calculated maximum unfactored moment is only slightly less than the unrestrained Mcr (based on cr ff ′= λ5.7 ) as factors such as shrinkage and temperature can still cause

the section to crack over time. If the designer finds the maximum unfactored moment to be lower than Mcr as calculated by Eq. (8-145) then the deflection calculated according to Sections 8.3.2.2 and 8.3.2.3 should be based on Ig.

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