minutes 445 2005b kansas city

7/24/2019 Minutes 445 2005b Kansas City

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Minutes approved by committee on March 27, 2006

ACI-ASCE Committee 445 Shear and Torsion Fall 2005 Meeting Minutes

2:00 p.m.6:00 p.m., Monday, November 7, 2005Kansas City Convention CenterRoom 2202

1. Welcome of visitors and Introductions (Sanders)Agenda attached

Voting members present: Neal Anderson, Mark Aschheim, Robert Barnes, Oguzhan Bayrak, ZdenekBaant, John Bonacci, Michael Collins, Robert Frosch, Neil Hawkins, Gary Klein, Dan Kuchma,Adolfo Matamoros, Y.L. Mo, Marianna Polak, Julio Ramirez, Karl-Heinz Reineck, DavidSanders, Raj Valluvan

Voting members not present: Adebar, Darwin, Dilger, Duthinh, French, Gogate, Krauthammer, Ma,MacGregor, Mitchell, Oesterle, Pantazopoulou, Stojadinovic, Wight

Informed Absence by Voting Members: DJ Belarbi, Marc Eberhard, Tom Hsu, Robert Loov

Associate members present: Evan Bentz, Hakim Bouadi, Tim Bradberry, Sergio Brea, MichaelBrown, Gary Greene, Neil Hammill, Paul Kourajian, Andres Lepage, Ghilherme Melo, CarlosOspina, Jose Pincheira, Halil Sezen, Koray Tureyen, Asif Wahidi, Alan Wiley, Paul Zia

Visitors: Esteban Anzola, Gerardo Aguilar, JoAnn Browning, Ken Elwood, Luis Farzier, Salem Faza,Luis Garcia, Maurizio Guadagnini, Riyadh Hindi, Shyh-Jiann Huang, Dominic Kelly, JohnnyKwok, Kelly Levy, Mark Moore, Gustavo Parra, Stephen Pessiki, Randall Poston, Malte vonRamin, Dan Reider, Sami Rizkalla, Carin Roberts-Wollmann, Alaa Sherif, Ted Sherwood, LesleySneed, Dustin Swart, John Tessem, Mike Tholem, Fernando Torrrealvo, John Wallace, DavidWan, Jeff West

2. General Announcements (Sanders)

The committee sponsored two technical sessions on punching shear, which occurred on Sunday, November 6. The 445-C subcommittee organized the sessions and produced a companion special publication (SP). Approximately 30 copies have sold so far. Chairman Sanders extended

congratulations to subcommittee.Agenda attached

3. Approval of minutes of Spring 2005 ACI-ASCE 445 Meeting held in New York (Sanders)

Minutes approved as submitted.

4. Review of Agenda (Sanders)

See attached.

5. Unification of Slender Beam Shear Equations in 318-08 in ACI 318

Five proposals for unification of slender beam shear equations in ACI 318 were submitted during thesummer of 2005. The author(s) of each proposal presented a 15-minute description of the proposedmethod. Ten minutes were allotted for questions and discussion after each presentation. Prior to thefirst presentation, Sanders announced that the committee would assess life-safety concerns with ACI318-05 by means of a straw poll after this portion of the meeting.

Baant presented the proposal of Baant and Yu . The proposal (and resulting discussion) can befound at http://aci.infopop.net/3/OpenTopic?a=frm&s=281294747&f=123105603 .

ACI-ASCE 445 Fall 2005 Page 1
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Related Discussion

Bentz disagreed with the numerical modeling results presented by noting that compressive strainsmeasured in experiments do not agree with those of Baants model in the ligament. Theexperimental strains never exceed strains at the elastic limit. Baant replied that the strains wereimproperly measured in the experiments.

Kuchma asked if the size effect should be addressed in members without stirrups and members withstirrups. Baant indicated that the size effect should be addressed in both cases, and more tests areneeded; finite-element analyses indicate that stirrups mitigate, but do not eliminate, the size effect.

Valluvan asked about w, and Baant clarified that this represented the longitudinal reinforcement.

Tureyen asked if the size effect term could be applied to any proposal. Baant replied that it could,within the scatter of the results.

Bayrak asked if Baant and Yu were extrapolating the size effect. Baant replied negatively, citingtwo test series (Baant & Kazemi, Toronto) as well as the 1996 Palau bridge collapse. Bayrak asked ifthere are actual test data to verify the size effect (at actual depths); Baant responded affirmatively.

Collins presented the proposal of Bentz and Collins . The proposal (and resulting discussion) can befound at http://aci.infopop.net/3/OpenTopic?a=frm&s=281294747&f=123105603 .

Related Discussion

Baant commented on a shear test described by Collins. Collins maintained that instrumentation andacoustic emissions monitoring indicated no microcracking in the region where it would be predicted

by Baants analysis.

Matamoros asked how to explain the f s term to students when we traditionally teach that the steelneeds to yield. Collins pointed out that there is a check of longitudinal steel yielding. In response to afurther question of how to treat prestressed members, Collins responded that f s corresponds to thestress that would be present in nonprestressed reinforcement at the depth of the prestressedreinforcement; it is actually strain (rather than stress) that is critical.

Bayrak asked if the comparison example came from a real structure. Collins replied negatively, butadded that there are many similar structures.

Bayrak asked if the Air Force warehouse failures were due to axial tension. Collins responded thatwas the PCA opinion, but size effect could account for it. (The warehouse girders plot on the samecurve as the Japanese test results). Bayrak asked if the proposal adequately handles axial tension.

Kuchma commented that the range of possible values is flatter than the 45 degrees inherent inACI 318: how should we interpret relative to crack angles in experiments? Collins responded that is not necessarily the angle of the crack and cited the case of axial tension. One should look at thesecondary, inclined cracks at loads close to failure. is the angle just after yield of the stirrups.

Valluvan noted that this method could result in a larger V s from minimum stirrups than is obtained

using the current ACI 318.

Brown presented the proposal of Brown and Bayrak . The proposal (and resulting discussion) can befound at http://aci.infopop.net/3/OpenTopic?a=frm&s=281294747&f=123105603 .

Related Discussion

There was an unresolved disagreement with Collins on details of the Japanese tests (involvinglongitudinal reinforcement, bar cutoffs, and whether the specimens were designable according to

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the 1.4D load combination of ACI 318). There was also an unresolved disagreement on tests thatexhibited shear strengths less than 2 roots when minimum stirrups were included.

Baant asked why it is unacceptable to extrapolate from a series of test results that confirms fracturemechanics theory. Bayrak responded that only Shioya (also referred to as Japanese tests elsewherein these minutes) gives experimental shear strengths below 2 roots for distributed loads. Brown and

Bayrak stated that the details of the Shioya specimens do not reflect current ACI 318 practice. Adiscussion ensued about safety margins and scatter of test results.

Reineck presented his proposal. The proposal (and resulting discussion) can be found athttp://aci.infopop.net/3/OpenTopic?a=frm&s=281294747&f=123105603 .

Related Discussion

Baant stated that strut-and-tie models (STM) are inadequate for large members because theyexperience nonductile compression failures. A disagreement resulted about whether or not there aretest results that indicate size effect in members with stirrups.

Baant stated that the 1/3 exponent is a consequence of the size distribution of the test database.Fracture mechanics theory supports an exponent of 1/2; therefore, he cannot accept an exponent of

1/3. Reineck responded that he based his proposed method on an empirical approach because thereare competing theories.

Kuchma asked how serviceability (crack widths under service loads) is handled under this proposal.Reineck replied that crack widths should be checked. Collins indicated that the new limits correspondapproximately with limits in the old code. Kuchma noted that some entities (DOTs) want to havedesigns that do not experience shear cracks under service loads. Additional guidance on how tosatisfy this condition may be justified.

Tureyen and Frosch presented their proposal. The proposal (and resulting discussion) can be foundat http://aci.infopop.net/3/OpenTopic?a=frm&s=281294747&f=123105603 .

Related Discussion

Valluvan noted that this proposal disagrees with other proposals (e.g. Bentz and Collins) that indicatethat the compression zone does not carry the majority of shear. The proposers responded that the proposal matches the test data well.

Hawkins asked if compression steel decreases the shear strength. Response was not recorded.

Baant asked if they were not worried about the size effect. Tureyen indicated that the lower bound ofthe data does not indicate a size effect.

Frosch noted that the test database does not represent the consensus of ACI 445. More agreement isneeded about some items, particularly the effects of self-weight shear.

After a related question from Bentz, an unresolved disagreement ensued about the practicality of theBentz & Collins transfer slab example.

General Discussion of the Issue

Dominic Kelly (member of ACI 318-E) advised that any design method that is proposed for ACI 318should exhibit back of the envelope simplicity.

Sanders asked Ramirez (Chair, ACI 318-E) what input the subcommittee desired from ACI 445.

Ramirez noted that the agenda was full, but there was one critical, relevant item: is this a life-safetyissue? Any resulting proposal needs to be simple. We should be wary of making a change now that

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will require another change later. Change proposals need to reflect the applicability of the buildingcode to practical design .

Ramirez noted that 318-E is also addressing shear reinforcement in slabs and shear-friction. Input iswelcome on these topics.

Sanders stated that ACI 445 needed to issue an opinion on the question of life safety. Is there a life-safety issue in the current code? If so, under what circumstances?After a 10-minute recess, Sanders conducted an informal poll of ACI 445 voting members.

QuestionIs there currently (ACI 318-05) a life-safety issue for shear in one-way slabs andbeams?

Result11 Yes, 0 No, 10 Abstain

Sanders then requested supporting reasons.

Bayrak reported seeing several girders in the last few years that exhibit very wide cracks underservice loads.

Kuchma noted that the problem is critical for members with depths of 18 in. or more.

Bentz noted that ACI 318 is unsafe for reinforcement with yield strength greater than 80,000 psi

Matamoros noted that, for the sake of simplicity, changes should be limited to the particular types ofstructures for which the committee thinks there is a problem.

Sanders asked a more specific question: without qualifications, is there a life-safety problem?

Frosch noted that there is an issue with FRP-reinforced members (which ACI 318 does not address).For these and steel-reinforced members with little longitudinal reinforcement (low ), failures are

being averted primarily due to load factors and resistance factors.

Collins noted that practical continuous members often have regions with little longitudinalreinforcement (low ).

Klein stated that most failures are attributable to mistakes and oversights in details, as well asnonductile response to unexpected loads (e.g. settlement or volume changes).

Kuchma noted that life-safety shortcomings are most obvious in the laboratory, when the designcapacity is not attained. This removes the extra margin of apparent safety that results from loadfactors.

Klein agreed with Kuchma and clarified that he was simply noting the source of actual failures.

Hawkins explained the reason for his abstention. There is no life-safety issue for 9095 percent ofmembers because of the beneficial combination of excess concrete strength, strength reductionfactors, and excess reinforcement. However, he is concerned for the future, as changes in other partsof the code result in changes in our basic implicit assumptions, e.g. increased use of high-strengthconcrete.

Polak agreed that we need to extend design methods to incorporate new materials and strength levels.

Ospina summarized a case study from practice. There were two issues with the design of anunderground structure: (1) the minimum shear reinforcement trigger, and (2) size effect. Much ofthe design load was permanent (earth). The designers were not comfortable with the current code, andtherefore employed Japanese code provisions instead.

Reineck stated that the best thing we could do for the future would be to provide models (like trussmodels) to the engineer.



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Bayrak pointed out that in Ospinas example, good engineers were thoughtful enough to realize thelimitations of the current code and to exceed these minimum requirements. Is ACI 318 applicable totunnels? Ospina responded that it was specified for the project.

Sanders stated that the committee had three options:

1) do nothing

2) consider life-safety issue as severe (suggest a change for ACI 318-08)

3) focus on a longer-term solution (ACI 318-11).

In a second informal poll of voting members, Option 1 received zero votes, Option 2 received 5votes, and Option 3 received 17 votes.

Zia noted that the committee had another option: production of a technical report outlining the specialcases for which current provisions may not be adequate. This report could be cited in ACI 318 as areference. Hawkins stated that such a report would be like a commentary that discusses the limitationof the current code expressions.

Sanders stated that he would contemplate the committees next course of action.

6. Presentation and Discussion of Issues Related to Continued Joint Committee Status(ACI/ASCE) (Ramirez)

Ramirez presented a draft Memorandum of Understanding (MOU) about joint ACI/SEI committees.The committee needs to be polled on three options:

1) operate under the MOU

2) not operate under the MOU

3) entertain suggestions for changes to the MOU.

Sanders summarized the draft MOU (attached to the minutes). The committee unanimously agreed tooperate under the MOU once enacted.

7. Subcommittee Reports

a) 445-A Strut and Tie (Reineck)Subcommittee met on Sunday; minutes are attached.

A follow-up special publication (SP) on further design with STM continues to be a focus of thesubcommittee. Seven examples have been proposed thus far. The subcommittee decided that theywill accept new proposals until the end of the year. They could be finished with the SP andaccompanying session(s) in 1.5 years. The subcommittee plans to proceed toward this ambitiousgoal.

Hawkins stated that there have been many questions at ACI 318 seminars concerning design offoundations with STM (particularly regarding three-dimensional models). Reineck noted that the

subcommittee would be grateful for input from these seminars.The subcommittee discussed ACI 318 Appendix A change proposal ideas:

Change of strength reduction factors There is some uncertainty about whether 445-A is the bestgroup to address this issue. Sanders will check on that.

Minimum distributed steel requirements Do these requirements extend to deep beams designedusing Appendix A?

Hanging-up reinforcement SP example may be sufficient, or a change proposal may be needed.



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Triaxially-stressed CCC node The benefit cannot be employed under the current provisions.Reineck is looking for co-workers for developing a change proposal.

One technical session has been approved for Spring 2006 (Charlotte) on the topic of STM forearthquake design.

b) 445-B Seismic ShearEberhard could not attend the convention. There was no meeting and no report.

c) 445-C Slab Shear (Polak) The subcommittee sponsored two successful sessions on punching shear at this convention. Asummary of the companion SP is attached. Because of the sponsored technical sessions, there wasno formal subcommittee meeting at this convention.

Polak discussed the assembly and maintenance of a punching shear database with Ospina. Such adatabase would be a good source of information, but many issues about such a database remainfor committee discussion. Ospina noted that database assembly has already started; 445-C simplyneeds to give it a home and make it available. The subcommittee can work out the details later.

Hawkins advised that the committee congratulate Polak on coordinating the sessions and SP.They are a credit to this committee. The committee congratulated Polak.

Hawkins noted a recent proliferation of slab shear provisions. ACI 318 needs basic information.Specific information for the various reinforcement systems should be in a separate document. Thework of 318-E would be greatly streamlined if 445 would develop such a document. Polak agreedthat slab shear reinforcement is not well served by the confusion inherent in the current code.

d) 445-D Torsion (Belarbi) The subcommittee met Sunday and worked to resolve review comments for the draft report on thestate of the art. The goal is to ballot the report in Jan. 2006.

e) Ad hoc committee on prestressed concrete shear issues (Matamoros) Subcommittee met earlier on Monday. Minutes are attached. Kuchma gave a good presentation.

f) 445-F Beam Database (Reineck)A report is being written on the shear databases. Reineck briefly described the outline. The reportshould be available in March 2006 (in German).

g) Scheduling of subcommittee meetings for Spring 2006 (Charlotte) No subcommittees requested a change of meeting times.

8. Technical Sessions

445Denver (Fall 2006), Spicy Shear Issues , moderated by M. Criswell & A. Lepage

445-ACharlotte (Spring 2006), Applications of Strut-and-Tie Modeling for Seismic Design ,moderated by L. Lowes and S. Sritharan, has received final approval

ASCE/SEI Structures Congress, St. Louis, May 1821, 2006

445 & 446 (Fracture Mechanics)Denver (Fall 2006), technical session on size effects, D. Kuchma

ASCE/SEI Structures Congress, Long Beach, May 1620, 2007, Paper requests due June 1, 2006

9. Adjournment

Meeting adjourned at 6:00 p.m.

Minutes submitted by Robert Barnes on March 5, 2006.



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AGENDA FALL 2005 MEETINGACI 445 SHEAR AND TORSION

KANSAS CITY, MISSOURINOVEMBER 6-7, 2005

445 Shear & Torsion; Monday 2p-6p; Convention Center-2202

445-A -Strut & Tie; Sunday 10a-1p; Convention Center-2214445-B -Seismic Shear; Sunday 11:30a-2:30p; Convention Center-2207(445-B Meeting is being cancelled since they are continuing to work on the database and

model comparison. Marc Eberhard will not be able to attend.)445-C -Punching Shear; Sunday 1p-3p; Convention Center-2210 (Attend the Session!)

445-E - SOA Torsion; Sunday 2p-5p; Convention Center-2209423-445 Adhoc Group Shear in Prestressed Concrete; Monday 11:30a-1p; Conv. Center-

2205

318-E Code-Shear & Torsion; Tuesday 2p-6:30p; Convention Center-2204TG1 Code-TG-Min. Torsional Reinforcement; Tuesday 10a-11:30a Convention Center-2202

Punching Shear in Reinforced Concrete Slabs, Part ISunday from 9:00 AM NOON, Session Moderator: Polak, Maria-Anna

Conference Center C4202A

Punching Shear in Reinforced Concrete Slabs, Part IISunday 2:00 PM - 5:00 PM, Session Moderator: Polak, Maria-Anna

Conference Center C4202A

Congratulations to the subcommittee for preparing an SP!!!SP232: Punching Shear in Reinforced Concrete Slabs

Editor: Maria-Anna Polak

1. Introductions (Sanders)2. Welcome to visitors (Sanders)

3. Approval of the Minutes - Spring 2005 ACI Meeting held in New York (Sanders)

4. Unification of Slender Beam Shear Equations in 318-08 in ACI 318(15 minute limit for presentation) Presentations will start shortly after 2 pm.

We have had 5 proposal submitted as part of our effort to bring forth proposal to 318Efor the Unification of Slender Beam Shear Equations in 318. The forum has alsoprovided an opportunity for dialog. Each presenter will be allowed 15 minutes. This willbe closely enforced. We will then allow for 10 minutes for discussion. At the end ifthere is time, we will open the flow for additional questions.

Zdenek Bazant and Qiang YuEvan Bentz and Michael CollinsMichael Brown and Oguzhan BayrakKarl-Heinz ReineckA. Koray Tureyen and Robert Frosch



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5. ACI 318-E Actions (Ramirez)445 assistance to 318E

6. Memo of Understanding between ACI and ASCE (Sanders)

7. Subcommittee reports

445-A Strut and Tie (Reineck) Proposed Changes to Appendix A for 318E445-B Seismic Shear (Eberhard)

445-C Slab Shear (Polak)

445-E Torsion (Belarbi)445-F Beam Database (Reineck) Presentation on Database by Reineck.Ad hoc committee on prestressed concrete shear issues (Matamoros)

8. Technical SessionsApplication of Strut-and-Tie Modeling for Seismic Design (Final Form Submitted)Convention: Spring 2006 Session Moderators: Laura Lowes and Sri Sritharan

General Session (Denver) Marvin Criswell and Andres Lepage

ASCE/SEI Structures Congress, St. Louis, May 1821, 2006 Halil Sezen: "ShearBehavior of Reinforced Concrete Members"

445 & 446 (Fracture Mechanics)Denver (Fall 2006), technical session on sizeeffects, D. Kuchma

445-F RC beam database with no transverse reinforcement TBD445-F RC beam database with transverse reinforcement. TBD

Future Conventions

ASCE/SEI Structures Congress, Long Beach, May 1620, 2007??

Session/Paper Requests Due: June 1, 2006

Spring 2006 - Charlotte, NC, Fast Track Innovations, March 26-March 30Fall 2006 - Denver, CO, November 5-November 8Spring 2007 - Atlanta, GA, Hardscape April 22-April 26Fall 2007 - Puerto Rico, Bridges the Americas October 14-October 18Spring 2008 - Los Angeles, Design & Construction Compatibility, March 30-April 3

9. Technical Presentations (10 Minutes)

Paul Zia and Salem Faza, Shear Capacity of Beams and Decks using MMFX Steel

Please note two subcommittee meetings (A, E and Adhoc) are scheduled prior to the 445main committee meeting. All members are welcome and encouraged to attend.Subcommittees B and C will not be meeting at this convention.



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Title: SP232: Punching Shear in Reinforced Concrete SlabsYear of Publication: 2005; Number of Pages: 302;Nonmember Price: $65.50; ACI Member Price: $40.00Order Code: SP232; Abstract: Editor: Maria Anna Polak

PREFACE

The development of high-performance materials and advanced computational tools hasallowed the building of relatively thin concrete slabs supported on columns. The simpleappearance of such structural systems and ease of their construction make themeconomically attractive and popular. However, these structures develop complex three-dimensional stresses in the slab, at the columns, which can eventually lead to a potentiallycatastrophic brittle punching shear failure. Although structural failures are rare, in part dueto high safety factors, understanding punching shear phenomenon is crucial for safe andrational design of flat reinforced concrete slabs supported on columns.

As part of the activities of the ACI/ASCE Committee 445, Shear and Torsion, members ofSubcommittee 445-C, Punching Shear, organized a symposium in conjunction with this

special publication devoted to the state of the art on punching shear. The symposium will beheld during the ACI Fall 2005 Convention under the sponsorship of ACI/ASCE Committee445.

The last significant and comprehensive overviews on this topic were completed severalyears ago by the fdration internationale du bton (fib) in their state-of-the-art report onpunching shear (2001)1 and in the Proceedings of the International Workshop on PunchingShear Capacity of RC Slabs (2000)2 published by the Royal Institute of Technology inSweden. Subcommittee 445-C has compiled a series of papers that present updateddevelopments in the state of the art and research regarding behavior, rational design, andevaluation of code provisions related to punching shear. The papers are grouped into twoparts. The first part contains a report, coauthored by members of Subcommittee 445-C, onissues related to design philosophy, code provisions, contributions of flexural and shearreinforcements, and seismic and blast loads. The second part includes papers on newdevelopments obtained from different research centers from around the world. The aim is topresent comprehensive and objective information on the topic of punching shear.

It is hoped that this publication will be important for the engineering design community inits efforts to improve long-term strength and ductility of slab-column structural systems.

Contents: Part ISP-2321: ACI 318-05, CSA A23.3-04, Eurocode 2 (2003), DIN 1045-1 (2001), BS 8110-97 and CEB-FIP MC 90 Provisions for Punching Shear of Reinforced Concrete Flat Slabsby N.J. Gardner

SP-2322: ACI 318 Moment Transfer Strength and Stiffness Considerationsby N.M. Hawkins

SP-2323: Effects of Size, Geometry and Material Properties onPunching Shear Resistanceby D. Mitchell, W.D. Cook, and W. Dilger

SP-2324: Effect of Flexural Reinforcement on Punching Shear Resistance



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by W. Dilger, G. Birkle, and D. Mitchell

SP-2325: Shear Reinforcement for Concrete Flat Slabsby M.A. Polak, E. El-Salakawy, and N.L. HammillSP-2326: A Design Perspective on Punching Shearby S.D.B. Alexander and N.M. Hawkins

SP-2327: Reinforced Concrete Slabs Subjected to Blast or Localized Impactby T. Krauthammer

SP-2328: Slab-Column Connections Under Seismic Actionsby W.H. Dilger, D.C. Dechka, and S.J. Brown

Part IISP-2329: Interior Slab-Rectangular Column Connections Under BiaxialLateral Loadingsby Y. Tan and S. Teng

SP-23210: Effect of the Column Dimensions on the Punching Shear Strengthof Edge Column-Slab Connectionsby A.G. Sherif, M.B. Emara, A. Hassanein, and S.A. Magd

SP-23211: Punching Shear Strength of Post-Tensioned Concrete Flat Platesby N.J. Gardner

SP-23212: Punching of Reinforced Concrete Flat SlabsACI and German Guidelinesby J. Hegger, A. Sherif, and R. Beutel

SP-23213: Punching Research at the Royal Institute of Technology (KTH)in Stockholmby H. Sundquist

SP-23214: Eurocodes and North American Codes Predictions of Punching Shear Capacityin View of Experimental Evidenceby A. Pisanty

SP-23215: Effect of HPC and FRHPC Precast Heads on Punching Shear Resistanceof Flat Platesby A.B. Ajdukiewicz and J.S. Hulimka



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DRAFT

MEMORANDUM OF UNDERSTANDING (MOU)Technical Committees that are Jointly Sponsored by the American Concrete

Institute (ACI) and the Structural Engineering Institute of the American Society ofCivil Engineers (SEI), for which ACI acts as the Lead Sponsor

ACI and SEI agree to jointly sponsor technical committees with the followingunderstanding:

Committee Name and Logo Use:The name of the committees will reflect the joint nature of the committees and willinclude the abbreviation ACI-SEI in all appropriate printed materials. The logos of

both ACI and SEI will appear on all published works of the committees.

Committee Operations:The committees shall follow the operating procedures of the ACI TechnicalCommittee Manual (TCM.) In addition:

1. Proposals to organize sessions at SEI Structures Congresses shall besubmitted according to SEI requirements (Technical Activities DivisionsPolicy and Procedures Manual) .

2. Documents produced by the committees will be concurrently reviewed byACI and SEI oversight technical committees. ACI will send suchcommittee documents to SEI at least five weeks before the ACI reviewsession, and SEI will provide any review comments in the requestedformat at least one week before the ACI review session. SEI may sendrepresentatives to the review session to support their comments.

3. ACI will provide meeting space at ACI conventions, will maintain anofficial web page, and perform committee mailings upon request. SEI will

provide meeting space at SEI functions

Standardization:When a committee develops a new standard or a revision to an existing standard, a

public review shall be conducted in accordance with ACIs TCM and with SEI/ASCE Rules of Standards Committees . For revised standards, all proposed changes shall beclearly identified. ACI shall attest to SEI/ASCE that all relevant requirements of theTCM , including ACIs balloting and balance rules, have been met.

Chair Appointments:Approximately six months before the end of a chairs term ACI will request that SEI

submit nominations for chair. SEI will submit any nominations at least six weeks before the relevant ACI meeting. ACI will appoint the chair from the submittednominees and others that ACI might identify. After all action is final, ACI will notifySEI of the result.

October 14, 2005


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Intellectual Property:The work and intellectual property developed by the committees is owned jointly by

both ACI and SEI.

Publications:1. ACI shall publish the documents created by committees covered under this MOU,

and will maintain the source computer files. SEI identified errata shall betransmitted to ACI for verification and incorporation in future printings.

2. ACI will sell printed committee documents to SEI or ASCE (not less than 10 perorder) at 25% of the ACI non-member price, plus postage. SEI or ASCE shall not

print individual copies, but resell those purchased from ACI.3. Both ACI and SEI have the right to sell the committee documents, and may

advertise as they see fit, each bearing their respective marketing and selling costs.4. Committee documents may be packaged and sold with other publications by both

societies.5. If either ACI or SEI has an agreement to license a third party to market the

societys publications, documents created by committees covered under this MOUcan be included. Each organization will notify the other if they wish to pursueselling the published works of a committee through a third party.

6. Without written permission from both SEI and ACI, no other entity mayincorporate significant portions of a committee document into another publication(printed or electronic).

7. Committee requests to publish their document in an SEI Journal shall accompanythe document when submitted for technical review. If SEI agrees to publish acommittees document in an SEI Journal, then ACI shall deliver the source file toSEI for this purpose.

AppendicesThe benefits and opportunities provided to the committees and the required oversight andexpectations of ACI and SEI are listed in Appendix A. This MOU applies to thecommittees listed in Appendix B

Termination of MOUThis Memorandum of Understanding will remain in force until subsequently amended,renewed or terminated. This MOU will be terminated ninety days after official writtennotification of termination from either ACI or SEI.

William Tolley, Executive Vice-President of ACI Date

James Rossberg, Director of SEI Date

October 14, 2005


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Appendix A

Society Benefits toCommittees

Opportunitiesprovided toCommittees

Each SocietyExpectations of

Committees

SponsorSociety

RequiredOversight

ACI

1. Meeting space atACI Conventions;2. Home web pageon ACI web site;3. TAC Contact andACI staff providesupport to chair;4. ACI logo appearson committeedocuments.

1. Technical sessions atACI Conventions andrelated symposium

publications;2. Committee reportsmay be published in the

ACI Manual of ConcretePractice and separately.

1. Meet regularlyand work tofulfillCommittees mission;2. Submit ACIreport ofcommitteeactivity.3. Procedures andactivities shouldconform to theACI TechnicalCommitteeManual

1. TAC assignsthe mission;2. TACappoints thechair;3. TACapprovessessions at ACIConventionsand relatedsymposium

publications.4. TAC hearsappeals;5. TAC reviewsall documents.

SEI

1. Meeting space atSEI StructuresCongress;2. SEI staff providesupport to chair;3. SEI logo appearson committeedocuments.4. Access toTechnical ActivitiesDivision ExecutiveCommittee(TAD/EXCOM)through assignedcontact member

1. Technical sessions atStructures Congress andrelatedcongress/symposium

publications;2. Committee reportsmay be published in the

Journal of Structural Engineering or the Journal of Bridge Engineering .

1. Meet regularlyand work tofulfillCommittees mission;2. Have access toannual report ofcommitteeactivity and plansfrom ACI.3. Organizesessions

periodically atStructuresCongresses.

1. Chairresponds toTAD EXCOMcontactmemberrequests;2. TADEXCOMreviewsdocuments and

provides inputto TAC.

Appendix B

Committees Jointly Sponsored by the American Concrete Institute (ACI) and theStructural Engineering Institute of the American Society of Civil Engineers (SEI) forwhich ACI acts as the Lead Sponsor:

334 - Concrete Shell Design and Construction; 343 - Concrete Bridge Design ; 352 -Joints and Connections in Monolithic Concrete Structures ; 421 - Reinforced Slabs; 423 -Prestressed Concrete ; 441 - Reinforced Concrete Columns ; 445 - Shear and Torsion ; 447- Finite Element Analysis of Reinforced Concrete Structures ; 550 - Precast ConcreteStructures

October 14, 2005
http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000334-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000343-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000352-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000352-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000423-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000423-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000441-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000445-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000447-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000447-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000550-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000550-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000550-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000550-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000447-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000447-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000445-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000441-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000423-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000423-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000352-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000352-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000343-00http://www.concrete.org/COMMITTEES/committeehome.asp?committee_code=0000334-00


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15/22

ACI 445-A "Strut-and-tie models": Minutes of the meeting in Kansas City, 6 November 2005 2

3.2 Database for deep beams

The task force was formed and consists now of Hakim Bouadi, Oguzhan Bayrak and KarlReineck.

3.3 General topics None

4 Changes and amendments to Appendix A of ACI 318-02

4.1 Should the -factor remain constant?

Karl Reineck briefly summarized the topic and proposed to hand it over to Comm. 445 and318-E, because it is not an item only related to strut-and-tie models; the Subcommitteeagreed.

4.2 Minimum steel requirement of App. A Hakom Bouadi presented the report of a task force (Hakim Bouadi, Dan Kuchma, AsifWahidi), see Attachment. The item was forwarded to Comm. 445 for possible transfer toComm. 318-E.

4.3 Maximum limits for shear in App. A may exceed that defined in Ch. 11 This topic should be further followed up by the task force formed (Dan Kuchma; KarlReineck; Lawrence Novak), and it could possibly be taken up by an example.

4.4 STM for point load near support; hanging-up reinforcement

Karl Reineck had sent around a change proposal for Appendix A of ACI 318 before themeeting, see attachment. The proposal was discussed and different proposals were made. JimWight doubted that such an extensive amendment of App. A would have chances to survive inACI 318 and suggested, to concentrate on urgent code changes and to deal with the othertopics in other documents.

4.5 Triaxially stressed CCC-node and bearing stress acc. to ACI 318, 10.17

Karl Reineck summarized the topic which was brought up by Mike Hemstad, Minneapolis based on his experience with the design of a pile cap. It appears that in App. A there is nodefinition of a node which would allow to utilize the strength increase allowed in section

10.17 of ACI 318. The Subcommittee agreed that a corresponding proposal for App. A should be made.

4.6 Curved ties

Some time ago Gary Klein had pointed out that curved ties and radial struts should be treatedin App. A, but the topic was not followed up further. The Subcommittee agreed that acorresponding proposal for App. A should be made.


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ACI 445-A "Strut-and-tie models": Minutes of the meeting in Kansas City, 6 November 2005 3

5 Strut-and-tie models for earthquake design

5.1 Session at the Spring Convention 2006 in Charlotte, NC

Laura Lowes briefly reported on the state of the preparations of the session, where she and SriSritharan are session Co-moderators

5.2 Other items None

6 Membership No discussion

7 Next meeting

It was agreed that the chair of 445 should apply for Sunday from 10.00 to 13.00 h.

8 Research Presentations

The following presentations were given:

- Dan Kuchma: Further development of CAST.

- Malte von Ramin: Capacity of struts

9 Other items None

Karl - Heinz Reineck 30 January 2005

Attachments: Draft proposal: Modifications to the minimum steel requirements of deep beams


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Modifications to the Minimum Steel Requirements in Deep Beams Page 1

Draft Proposal:Modifications to the Minimum Steel Requirements of Deep Beams

By: Hakim Bouadi 1, Asif Wahidi 2,, and Dan Kuchma ,3

1 Walter P. Moore and Associates / Structural Diagnostics Service Group, 3131 Eastside Street, Houston,

TX 77098; ph: 713 630-7300. email: [email protected] 2 Walter P. Moore and Associates / Structural Engineering Service Group, 3131 Eastside Street, Houston,TX 77098; ph: 713 630-7300. email: [email protected] 3 University of Illinois, 2106 NCEL, 205 N Mathews Ave, Urbana, IL 61801-2350, ph.217 333-1571; e-mail: [email protected]

1. Proposal

Remove the following paragraph from Chapter 11:11.8.6 It shall be permitted to provide reinforcement satisfying A.3.3 instead of theminimum horizontal and vertical reinforcements specified in 11.8.4 and 11.8.5

2. Review of Current Requirements

The shear design of deep beams, covered in Section 11.8 of the ACI 318 code allows deep beamsto be designed using either a nonlinear analysis or the Strut-and-Tie provisions of Appendix A.Paragraphs 11.8.4 and 11.8.5 specify the minimum web reinforcement as two perpendicular mats,one in the horizontal direction and one on the vertical direction. This requirement is howeverwaived (paragraph 11.8.6) if a deep beam is designed according to Appendix A and therequirements of A.3.3 are followed.

Appendix A presents the use of a Strut and Tie Model for the design of Discontinuity(D) regionsin structural concrete. A D-region is the portion of a structure for which there is a complexvariation in strain such that plane sections theory is not applicable. A deep beam, as defined in11.8.1, is a D-region. The minimum reinforcement requirements of Appendix A can becategorized as follow:

No implicit minimum amount of reinforcement is required for struts of uniform cross section(A3.2.1)

No web reinforcement is required for bottle-shape struts designed with an efficiency factor,s = 0.60.

Minimum web reinforcement in accordance with A3.3 is required for struts designed with ahigher efficiency factor (0.75). The minimum reinforcement in A3.3 relates to the combinedvertical and horizontal reinforcement and not to the reinforcement in each direction. Thiscriterion can be satisfied for a deep beam by providing horizontal web reinforcement and no

vertical web reinforcement provided that the angle from the reinforcement to the axis of thestrut is greater than 40 degrees.


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3. Comparisons to Other Codes

3.1. Canadian codeClause 11.5.5 of the CSA (1994) code requires the use of an orthogonal grid of reinforcing barsnear each face with the ratio in each direction not less than 0.002 and with a maximum spacingof 300 mm (about 12 inches).

3.2. EuroCodeSection 9.7 on deep beams of the Eurocode 2 (CEN, 1992) recommends the use of an orthogonalreinforcement mesh near each face with a minimum ratio of 0.001 in each direction and in eachface and with a maximum spacing of 300 mm (about 12 inches).

3.3. Main Body of ACI 318-05 CodeParagraph 10.6.7 of ACI 318-05 requires a minimum horizontal reinforcement for a distance ofd/2 near the tension reinforcement on each face of a beam having a depth in excess of 36 inches.In practice and in order to ease construction, designers tend to locate this face reinforcementalong the full depth of a member rather than along d/2 only. In deep beams, which most often

have a depth of more than 36, this minimum reinforcement may end up satisfying A3.3.1 and noadditional vertical reinforcement will be required. In other cases, this minimum horizontalreinforcement contributes greatly to the minimum requirement of A3.3.1 and only a low ratio ofvertical web reinforcement will be required.

Sections 11.8.4 and 11.8.5 for deep beams requires the use of a minimum vertical shearreinforcement ratio of 0.0025 and a minimum horizontal shear ratio of 0.0015. The commentarysection of the code indicates that larger amount of vertical reinforcement is required since testshave shown than vertical shear reinforcement is more effective than horizontal shearreinforcement.

4. Evaluation with Relevant Experimental Work

4.1. Need for minimum reinforcementThe strut-and-tie model is derived from the lower-bound theorem of plasticity, therefore amember designed using this model requires sufficient amount of reinforcement to ensure a ductilebehavior and a re-distribution of the internal forces in the cracked state (Marti, 1985). AppendixA by implying that a bottle-shaped strut can be designed without any reinforcement provided alower efficiency factor is utilized (A3.2.2 a), appears to contradict the general assumptions of thestrut-ant-tie model.

In addition to allowing force re-distribution, web reinforcement controls cracking at service andpermits a more ductile behavior (Smith and Vantsiotis, 1982; Rogoswky et. all, 1986, Tan et al.,1977)

4.2. Web Reinforcement Effectiveness

Smith and Vantsiotis (1982) tested 52 deep beams to investigate the effects of shear to span ratioand of the effectiveness of vertical and horizontal reinforcement. Their research showed that aminimum amount of web reinforcement was needed to control cracking. The addition of verticalweb reinforcement improved the ultimate shear strength of deep beams while the addition ofhorizontal web reinforcement had no or little influence on the ultimate strength. Their research


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has also showed that for beams with a/d (shear span to depth) ratio less than 1.0 effect of verticalweb reinforcement diminishes while the effect of horizontal steel is more noticeable.

Tests of 7 simply supported beams and 17 two span deep beams were conducted byRogoswky et. al. (986) to investigate the effect of web reinforcement. Their research showed thatbeams with vertical web reinforcement had a higher shear strength and failed in a ductile mannerwhile beams without or with very limited amount of ties failed in a sudden manner. Horizontalweb reinforcement was found not to have a significant effect on capacity.

Tan et al. (1997) investigated the effect of the web reinforcement on 18 high-strength concretedeep beams. The study concluded that orthogonal web reinforcement was the most effective incontrolling cracks and increasing the ultimate shear strength. In addition vertical webreinforcement was found to be more effective than horizontal web reinforcement.

Kong et al. (1970) tested to failure 35 simply supported deep beams with different span to depthratios and with varying types of web reinforcement. Their research indicated that for span todepth ratio less than 1.0, horizontal reinforcement near the tension face of the beam is the mosteffective type of web reinforcement at controlling cracks and increasing strength. However for

other span to depth ratio, the use of vertical reinforcement is clearly the most effective.

5. Conclusions

The current requirements of the ACI code allows the design of struts without any amount of webreinforcement for uniform struts or for struts designed with a lower efficiency factor. The coderequires minimum web reinforcement expressed a combination of vertical and horizontalreinforcement for struts designed with a higher efficiency factor. This formulation allows for theuse of only horizontal reinforcement or for the use of a higher reinforcement ratio in thehorizontal direction.

In contract both the Canadian and the Euro code require the use of web reinforcement in both

directions.

Research has shown that the use of web reinforcement controls cracking, allows for forceredistribution and helps to prevent brittle failures. The use of web reinforcement was found to bemore effective if used in both directions. In addition, vertical web reinforcement was found to bemore effective than the horizontal web reinforcement in most beam configurations. Thehorizontal web reinforcement was found effective only when located near the tensionreinforcement in beams with span to depth ratio of less than 1.0. In the case of such very deepbeams, the load is transmitted directly to the support with a compression strut (ASCE-ACICommittee 445, 1998) and the horizontal reinforcement near the tension face increases thetension tie capacity.

The lack of web reinforcement or the use an orthogonal web reinforcement mesh with a higherratio in the horizontal direction is inappropriate for the design of deep beams by Appendix A.Therefore ACI 318 code provisions for deep beams should be modified to require the use ofminimum web reinforcement in both directions with a higher steel ratio in the vertical direction.Minimum distributed reinforcement requirements should be considered for all planar structuresdesigned by Appendix A.


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6. References

ACI Committee 318 (2005), Building Code Requirements for Structural Concrete (ACI 318-05)and Commentary (ACI 318R-05) , American Concrete Institute, Farmington Hills, Michigan.

ASCE-ACI Committee 445 on Shear and Torsion (1998), Recent Approaches to Shear Design of

Structural Concrete ASCE Journal of Structural Engineering , Volume 124, No 12, December1998, pp. 1375-1417.

Canadian Standards Association, CSA (1994), A23.3-94, Design of Concrete Structures ,Canadian Standards Association, Rexdalle.

Commit Europen du Bton, CEN (1992), Eurocode 2 Design of Concrete Structures Part 1.1:General rules and rules for buildings , European Committee for Standardization, Brussels,Belgium.

Kong, F.K., Robin P. J., and Dole D. F. (1970) Web reinforcement effects on deep beams ACIJournal 12, 1010-1017.

Marti, P. (1985), Basic Tools for Reinforced Concrete Beam Design, ACI Journal , Volume 82,No 4, January-February 1985, pp. 46-56.

Rogowsky, D. M., MacGregor, J, G., and Ong S. Y. (1986), Tests of Reinforced Concrete DeepBeams, ACI Journal , Volume 83, No 55, July-August 1986, pp. 614-623.

Smith K.,N. and Vantsiotis, A. S. (1982), Shear Strength of Deep Beams, ACI Journal , Volume79, No22, May-June 1982, pp. 201- 213.

Tan K. H., Kong, F. K. , Teng S., and Wang L.W. (1997). Effect of web reinforcement on highstrength concrete deep beams ACI Structural Journal Volume 94, No 5, 572-582.


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MINUTES Fall 2005 MEETING423-445 Adhoc Group on Shear in Prestress Concrete

Monday November 7, 11:30am to 1:00 pmConvention Center 2202

Kansas City

Attendance:

Committee Members:Dan Kuchma, David Sanders, Adolfo Matamoros, Bruce Russell, Carin Roberts-Wollman, Karl-Heinz Reineck,

Visitors:

Paul Kourasian, Justing Norvell, Larry Kahn, Neil Hawkins, Dan Reider, Halil Sezen.

1. Introductions

The meeting was called to order at 11:45 am.

2. Presentations

Presentation by Dan Kuchma, NCHRP Project Presentation

The presentation focused on the results obtained from a dense sensor array used in testsof precast beams with high-strength concrete. Dan has developed a visualization tool tointerpret the results from the sensors and infer the fraction of the total shear force that iscarried by the concrete at different stages of loading. The students working in the projectare still in the process of reducing and interpreting the data and developing designrecommendations.

One of the observations from the project is that when shear cracks propagate through thedevelopment length of debonded strands, there was significant slip.

Presentation by Adolfo Matamoros, detailing of end regions

The presentation discussed the interaction between horizontal, vertical reinforcement, andthe strength of struts in end regions.

3. Discussion on different alternatives for detailing of end-regions.

It was proposed that the committee address two different action items related to the code provision. The first action item has to do with the amount of transverse reinforcementthat can be added for shear strength. The second will focus on development length

provisions for strand.


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Item 1. Additional transverse reinforcement, horizontal or vertical

The consensus of the committee was to prepare a code change proposal on the basis ofequilibrium of the end region, allowing designers to account for the reduced strand stressat the intersection of the prestressing reinforcement and the inclined crack.

It was discussed that this model has two main drawbacks, as implemented in theAASHTO Code

The first is related to the angle of inclination of the crack. In the AASHTO procedure theangle of inclination of the inclined crack is determined based on theory intended for Bregions. The relationship between reinforcement strain and angle of inclination of thecrack in the AASHTO Code may lead to relatively flat inclined cracks, which leads tohigher demands on the longitudinal reinforcement at the point of intersection with theinclined crack. It was expressed by members of the committee that the angle ofinclination of the critical shear crack observed experimentally in these types of members

is closer to that estimated on the basis of elastic theory.The second limitation is related to the fact that the AASHTO Code allows the design ofthese regions without the use of horizontal (mild) transverse reinforcement. It wasexpressed that this may present safety concerns in particular for members withouttransverse reinforcement in which there may be deficiencies related to construction or thequality of the materials. One of the alternatives suggested to address this problem is to

preserve the limit of Vc/2 as the maximum for members without transversereinforcement.

Adolfo Matamoros will prepare a code change proposal and circulate that betweencommittee members.

An additional proposal will be prepared addressing anchorage requirements for thestrand. One of the alternatives suggested was placing limits on the percentage ofdebonding allowed by the code.

4. Next Meeting

The next meeting will be held at the same time slot (Monday 11:30 am to 1:00 pm)during the next convention in Charlotte.