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Showing 1-5 of 16 Abstracts search results

Document: 

SP232-02

Date: 

October 1, 2005

Author(s):

N.M. Hawkins

Publication:

Symposium Papers

Volume:

232

Abstract:

The 2005 Edition of ACI 318 contains a new provision in Sec. 21.11.5 that is aimed at reducing the potential for punching shear failures at columns in two–way-slabs located in regions of high seismic risk or in structures assigned to high seismic performance or design categories. The provision requires that slab-column connections in two-way slabs without beams, where the slabs are assumed not to contribute to the lateral resistance of the structure, shall be provided with slab shear reinforcement unless: (1) it is shown that punching will not occur under the design shear and the moment induced between slab and column at the design displacement; or (2) the design story drift does not exceed a limiting value that is a function of the ratio of the design shear to the nominal shear strength of the connection under gravity loading. This paper presents an overview of the ACI 318-05 provisions for moment transfer to columns, summarizes background information on the existing provisions and the irrelation to the new provision and summarizes existing information on how to calculate the lateral load stiffness of two-way slab structures in accordance with ACI Code 318-05 requirements. The paper describes how to utilize the provisions of Sec. 11.12.6 (shear resulting from moment transfer to columns) and Sec. 13.5.3 (reinforcement requirements for moment transfer to columns and moment redistribution between columns) to determine if the first alternative for application of the new provision can be satisfied. The paper summarizes the background information for the new provision and also discusses the relation between these provisions and those of Sec. 21.12.6 for intermediate moment frames consisting of two-way slabs without beams.

DOI:

10.14359/14934


Document: 

SP232

Date: 

October 1, 2005

Author(s):

Editor: Maria Anna Polak

Publication:

Symposium Papers

Volume:

232

Abstract:

SP-232 The development of high-performance materials and advanced computational tools has allowed the building of relatively thin concrete slabs supported on columns. The simple appearance of such structural systems and ease of their construction make them economically attractive and popular. However, these structures develop complex three-dimensional stresses in the slab, at the columns, which can eventually lead to a potentially catastrophic brittle punching shear failure. Although structural failures are rare, in part due to high safety factors, understanding punching shear phenomenon is crucial for safe and rational design of flat reinforced concrete slabs supported on columns. As part of the activities of the ACI/ASCE Committee 445, Shear and Torsion, members of Subcommittee 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 be held during the ACI Fall 2005 Convention under the sponsorship of ACI/ASCE Committee 445. The last significant and comprehensive overviews on this topic were completed several years ago by the fédération internationale du béton (fib) in their state-of-the-art report on punching shear (2001)1 and in the Proceedings of the International Workshop on Punching Shear Capacity of RC Slabs (2000)2 published by the Royal Institute of Technology in Sweden. Subcommittee 445-C has compiled a series of papers that present updated developments in the state of the art and research regarding behavior, rational design, and evaluation of code provisions related to punching shear. The papers are grouped into two parts. The first part contains a report, coauthored by members of Subcommittee 445-C, on issues related to design philosophy, code provisions, contributions of flexural and shear reinforcements, and seismic and blast loads. The second part includes papers on new developments obtained from different research centers from around the world. The aim is to present comprehensive and objective information on the topic of punching shear. It is hoped that this publication will be important for the engineering design community in its efforts to improve long-term strength and ductility of slab-column structural systems.

DOI:

10.14359/14960


Document: 

SP232-04

Date: 

October 1, 2005

Author(s):

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

Publication:

Symposium Papers

Volume:

232

Abstract:

This paper starts with a review of the major international codes with regardto the effect of the flexural reinforcement on the design equations for punching shearof two-way slabs. A review of experimental programs in which the main parameter isthe flexural reinforcement ratio follows. In addition to the flexural reinforcement ratio,the type and grade of reinforcement, the arrangement of the reinforcement and theconcrete cover are also investigated.Evaluation of the parameters investigated shows a distinct decrease of the punchingshear resistance with decreasing reinforcement ratio. If shear failure occurs beforeflexural yielding has developed, the value of the yield strength does not affect theshear resistance of slabs. A concentration of the flexural reinforcement in the vicinity ofthe column resulted in a strength increase only if the reinforcement was well anchored,otherwise the reduced bond of closely spaced reinforcing bars will not lead to anincrease in the punching shear strength. The test results on concrete cover are not fullyconclusive, but it is argued that it is the effective depth rather than the slab thicknessthat governs the shear and flexural behavior of a slab.

DOI:

10.14359/14936


Document: 

SP232-14

Date: 

October 1, 2005

Author(s):

A. Pisanty

Publication:

Symposium Papers

Volume:

232

Abstract:

The bearing capacity under punching shear has been addressed in a seriesof experiments. Three types of shear reinforcement of the stirrups type have beenopted as well as the most suitable position of the shear reinforcement. Reinforcementquantities have been modified versus code requirements. Tests results indicate that thesuggested shear reinforcement performed very well. Some requirements in the twoNorth American Codes appear to be conservative compared to the European codes.Bearing capacity assessment in some codes appears to be conservative (bearing inmind, however, that a variety of additional considerations are taken while codedrafting) . Behavior in serviceability was very satisfactory.

DOI:

10.14359/14946


Document: 

SP232-12

Date: 

October 1, 2005

Author(s):

J. Hegger, A. Sherif, and R. Beutel

Publication:

Symposium Papers

Volume:

232

Abstract:

The new DIN 1045-1 and the German Construction Approval Z-15.1-213 fordouble-headed studs are discussed and essential background information ispresented. In addition, comparison is made with the ACI 318-02 Code and the ACI 421report. Differences between the codes are reviewed and highlighted. Emphasis is seton the parameters affecting the punching resistance of slab-column connections, themoment transfer between slab and column, shear reinforcement (stirrups and headedbars), and punching of reinforced concrete footings. The code provisions are evaluatedby comparing with test results.

DOI:

10.14359/14944


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