1、Deformation Capacity and Shear Strength of Reinforced Concrete Members Under Cyclic LoadingEditors:Adolfo MatamorosKenneth ElwoodSP-236searchhelpCopyright American Concrete Institute Provided by IHS under license with ACI Not for ResaleNo reproduction or networking permitted without license from IHS
2、-,-,-iDeformation Capacity and Shear Strength of Reinforced Concrete Members Under Cyclic LoadingSP-236EditorsAdolfo MatamorosKenneth ElwoodCopyright American Concrete Institute Provided by IHS under license with ACI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-
3、iiDISCUSSION of individual papers in this symposium may be submitted in accordance with general requirements of the ACI Publication Policy to ACI headquarters at the address given below. Closing date for submission of discussion is December 2006. All discussion approved by the Technical Activities C
4、ommittee along with closing remarks by the authors will be published in the March/April 2007 issue of either ACI Structural Journal or ACI Materials Journal depending on the subject emphasis of the individual paper.The Institute is not responsible for the statements or opinions expressed in its publ
5、ications. Institute publications are not able to, nor intended to, supplant individual training, responsibility, or judgment of the user, or the supplier, of the information presented.The papers in this volume have been reviewed under Institute publication procedures by individuals expert in the sub
6、ject areas of the papers.Copyright 2006AMERICAN CONCRETE INSTITUTEP.O. Box 9094Farmington Hills, Michigan 48333-9094All rights reserved, including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by any electronic or mechanical devic
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8、ngress catalog card number: 2006925678ISBN: 0-87031-209-XFirst printing, May 2006Copyright American Concrete Institute Provided by IHS under license with ACI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-iiiDeformation Capacity and Shear Strength of Reinforced Co
9、ncrete Members Under Cyclic LoadingPrefaceEarthquakes worldwide have clearly demonstrated the vulnerability of reinforced concrete members to degradation in shear strength when subjected to cyclic loading. Such degradation can lead to significantdamage to the structure and, possibly, even collapse.
10、With the advancement of performance-based earthquake engineering, where the response of the structure must be traced through all levels of damage, there is a significant need to accurately define the deforma on capacity and shear strength for such members. This symposium publication represents an ef
11、fort from researchers across the globe trying to address this challenging problem.Although at the time of publication there are some methodologies that can be used in performance-based earthquake engineering, there is a significant need for improved methods better suited for these ypes of applicatio
12、ns. Furthermore, one of the concerns often expressed by researchers is that test data used in the past to develop and calibrate existing models consisted of relatively small data sets. This problem is compounded by differences between experimental studies in aspects such as the type of load history
13、used, the manner in which deformations were recorded during tests, and the definition of displacement and srength at failure.The recent development of the PEER column database, hosted by the University of Washington, provided a valuable resource to overcome some of these problems. It presented resea
14、rchers with a larger pool of data, which included the full hysteretic response of every column in the data set. Although this represented a very significant step forward, eforts of this kind should continue to improve the ability of researchers to calibrate and evaluate models for shear strength and
15、 deformation capacity.Copyright American Concrete Institute Provided by IHS under license with ACI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-ivA joint technical session was organized by Joint ACI-ASCE Committees 441, Reinforced Concrete Columns, and 445, Shea
16、r and Torsion, during the American Concrete Institutes Fall 2004 Convention in San Francisco, CA. The goal of the technical session was to showcase recent developments in this area, with the hope that continued discussion will lead to improved models that are suitable for performance-based engineeri
17、ng.This symposium publication is a collection of technical articles presented at that meeting and represents an effort from Joint ACI-ASCE Committees 441 and 445 to continue the technical discussion on this topic. EditorsAdolfo MatamorosAssociate ProfessorUniversity of KansasKenneth ElwoodAssistant
18、ProfessorUniversity of British ColumbiaCopyright American Concrete Institute Provided by IHS under license with ACI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-vTABLE OF CONTENTSPreface iiiSP-2361: Deformation Capacity of RC Members with Brittle Details Under C
19、yclic Loads 1by D.V. Syntzirma and S.J. PantazopoulouSP-2362: Effects of Displacement History on Failure of Lightly Confined Bridge Columns 23 by R.T. Ranf, M.O. Eberhard, and J.F. StantonSP-2363: Effect of Shear Reversals on Dynamic Demand and Resistance of Reinforced Concrete Elements . 43by S. Pu
20、jol and M.A. SzenSP-2364: Seismic Performance of Reinforced Concrete Columns: P- Effect 61by S. Bae and O. BayrakSP-2365: Application of a Probablistic Drift Capacity Model for Shear-Critical Columns 81by L. Zhu, K.J. Elwood, T. Haukaas, and P. GardoniSP-2366: Effect of Cyclic Loading on the Shear S
21、trength of RC Members 103by M. von Ramin and A.B. MatamorosSP-2367: Shear-Flexure Interaction for Structural Walls 127by L.M. Massone, K. Orakcal, and J.W. WallaceSP-2368: Drift Capacity of Walls Accounting for Shear: The 2004 Canadian Code Provisions . 151by P. AdebarSP-2369: Effect of Steel Grid O
22、rientation on Seismic Performance of Shear Walls . 171by Y.L. Mo, W.-I. Liao, J. Zhong, C.C. Lin, and C.-H. LohCopyright American Concrete Institute Provided by IHS under license with ACI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-viCopyright American Concrete
23、 Institute Provided by IHS under license with ACI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-1SP-2361Deformation Capacity of RC Members with Brittle Details Under Cyclic Loadsby D.V. Syntzirma and S.J. Pantazopoulou Synopsis: The sequence of failure in reinfor
24、ced concrete (RC) prismatic members is used as a tool in estimating dependable deformation capacity. Response mechanisms that may limit the response leading to damage localization are identified (web diagonal cracking, bar buckling, disintegration of compressive struts due to load reversal, and anch
25、orage failure of primary reinforcement). Deformation components are additive only if stable hysteretic response controlled by flexure prevails. In all other cases, the deformation component associated with the controlling mode of failure dominates the overall deformability of the member. Because the
26、 sequence of failure depends to a large extent on load history, deformation attained at any particular level of load is also load history dependent. This is why experimental values for deformation capacity reported in international literature are characterized by excessive scatter. The proposed meth
27、odology is applied to a number of published column tests. Analytical estimates are evaluated through comparisons with experimental results and by parameter studies conducted in order to examine the sensitivity of the estimated displacement limit at compression bar buckling to important design variab
28、les.Keywords: deformation capacity; displacement-based assessment; nonconforming RC members; seismic design of RC Copyright American Concrete Institute Provided by IHS under license with ACI Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 Syntzirma and Pantazopou
29、louAuthors Profile: D. V. Syntzirma is a Public-Works Engineer in the Province of Thrace, Greece, and a PhD candidate at Demokritus University, Greece. She holds a Civil Engineering Diploma and MSc Degree from the same University. Her research interests are in Seismic Assessment and Earthquake Desig
30、n of Reinforced Concrete (RC) Structures. S. J. Pantazopoulou, FACI is Professor in the Department of Civil Engineering, Demokritus University, Greece. She holds PhD and MSc degrees in Structural Engineering from the U.C.Berkeley, and an Engineering Diploma from the NTUA, Greece. She is member of se
31、veral ACI Committees and fibs task groups. Her interests include the mechanics of reinforced concrete, earthquake design and rehabilitation of RC structures with FRPs. INTRODUCTIONA primary objective of displacementbased assessment of existing RC structures is to ensure that dependable deformation c
32、apacity Rof each individual component exceeds the anticipated deformation demand d. The requirement that Rdrefers to an ultimate limit state; reversal of the inequality signifies excessive damage and even collapse of the structural component. Existing structures, designed up to an array of earlier v
33、ersions of seismic codes as these evolved through the last half century, are generally classed as “low deformation capacity” systems, i.e. they have limited ability to sustain large inelastic deformation reversals without strength loss. In terms of reinforcement amounts, older structural members typ
34、ically are lacking in properly detailed transverse reinforcement (confinement and shear reinforcement in beams, columns, joints and lap splices). Reconnaissance studies of damage from past earthquakes show that the above requirement of Rdmay not be always secured by old designs, either because the i
35、ntrinsically available deformation capacity is negligible due to poor detailing, or because the demand is excessive due to inherent conceptual flaws in the structural system (excessive localized flexibility); the latter is seen frequently even in modern construction. To estimate the dependable defor
36、mation capacity of RC members, it is important to determine simple models that are capable of reproducing the most prevailing parametric sensitivities observed in tests of brittle components. This objective has been pursued in the present paper through analytical modeling and evaluation of published
37、 experiments. The analysis is based on a comprehensive concept of sorting through the various alternative failure mechanisms that could control member behavior (often prior to development of full inelastic flexural action), seeking the weakest link of member response for a given cyclic displacement
38、history. This framework is referred to hereon as Capacity-Based Prioritizing, or CBP. Departing from earlier concepts that center or expand on the estimation of drift components using crosssectional and material properties and aspect ratio, the present approach determines the actual pattern of depen
39、dable deformations associated with the prevailing failure mechanism. In identifying the weak link of member behavior the basic premise has been that this Copyright American Concrete Institute Provided by IHS under license with ACI Not for ResaleNo reproduction or networking permitted without license
40、 from IHS-,-,-Deformation and Shear Capacity of RC Members 3mechanism becomes the fuse of the member response, i.e., upon increase of the imposed end displacement, deformation is expected to localize in that fuse, and hence, beyond that stage, all other forms of nonlinear behavior may be irrelevant.
41、 Particular emphasis is placed on alternative failures that would prevail due to poor confinement. Web diagonal tension failure, buckling of compression reinforcement, disintegration of concrete due to reversal of load, and limited anchorage or lapsplice capacity of primary reinforcement are candida
42、te scenarios. The influence that these failure modes may have upon the deformation capacity of a poorlydetailed member depends upon the sequence in which they develop. Thus, the sequence of failure, if seen as a chain of successive events in the response history of the member, uniquely defines defor
43、mability, although it is not necessarily unique in itself, for it depends on the imposed loading history. As a rule, the various strength mechanisms do not degrade proportionately with load reversals. This point is reflected repeatedly in the available experimental evidence and it is why, applicatio
44、n of the proposed analysis framework affirms conclusively that the process of assessment of deformation capacity is rather complex and cannot easily be treated by unidirectional closed form expressions. The proposed methodology is tested on a number of tests published in international literature. Re
45、levant experiments concern brittle columns with lap splicing in the critical regions under cyclic load reversals. In the paper, comparisons are made between analytical estimates and experimental results, whereas the sensitivity of the proposed methodology to important design variables is also explor
46、ed through parameter studies. RESEARCH SIGNIFICANCE Quantifying the dependable deformation capacity of RC members, particularly members nonconforming to modern standards, is a milestone in the process of assessment of seismic resistance of existing structures. Existing methods of calculating deforma
47、tion capacity are marked by excessive scatter even when applied to well-detailed members. In this paper a method of capacity-based prioritizing of the alternative modes of failure is used to identify localization of failure and to estimate the associated deformability of reinforced concrete members
48、with substandard detailing representative of former construction practices. FRAMEWORK FOR ESTIMATING DEFORMATION CAPACITY Deformation capacity of a RC member as defined for the needs of seismic assessment is the maximum relative translation (or relative drift) the member may sustain without excessiv
49、e loss of lateral load strength. To evaluate this response parameter, the usual approach is to calculate contributions to drift of the various modes of deformation that occur along the member, namely flexural, shear, and rotation due to reinforcement pullout, which are then superimposed as they are generally
