Fib 81 ACI SP-315 Punching shear of structural concrete slabs
Author(s)/Editor(s): Edited by Carlos E. Ospina, Denis Mitchell and Aurelio Muttoni | Size: 82 MB | Format:PDF | Quality:Original preprint | Publisher: FIB | Year: 2017 | pages: 396 | ISBN: 978-2-88394-121-2
fib Bulletin 81 deals with punching of slabs, which is a relevant issue in the design of reinforced concrete. Punching is one of the most frequent reasons for failure of concrete structures, which underlines the importance of this problem. Flat slabs are used in buildings, bridges and other structures. Punching may result in brittle failure, which requires that special attention be paid to the design of new structures and the assessment of existing ones. Punching and shear capacity of structures is often evaluated using empirical methods, which does not always provide a sufficient level of safety. This bulletin is a result of an international symposium where experts from fib and ACI met and exchanged their experience. The papers included in this bulletin provide new experimental evidence and a comprehensive review of analytical and numerical methods that are used to evaluate the structural performance of slabcolumn connections.
This bulletin provides a review of the performance of slabs under static, dynamic and seismic loading. The individual papers generally show the studied phenomena using experiments and analytical evaluation, which makes it possible to compare results obtained according to the European code (EC2), the ACI code and the international code, the fib Model Code for Concrete Structures (MC2010). Particular attention is paid to the so-called size effect (i.e. the nominal load carrying capacity of thicker slabs is lower than that of thin slabs). The arrangement of reinforcement is important for the residual strength after a local failure and robustness, which are instrumental to avoid the progressive collapse of the entire structure after a local failure. It is confirmed that the bottom reinforcement crossing the column is very beneficial to ensure sufficient residual strength and avoid progressive collapse. A paper dealing with the shear capacity of bridge slabs illustrates an extended strip model, which may be used for efficient assessment of bridge slabs under concentrated loads. This bulletin also presents new types of shear reinforcements and shows efficiency of distribution of classical shear reinforcing elements like headed studs. Some papers deal with retrofitting and strengthening of existing slabs. Post-installed shear reinforcing elements may be used for strengthening of existing structures.
This bulletin summarizes several phenomena that influence the performance of slabs sensitive to punching. It is a valuable summary of the state-of-the art knowledge for practicing engineers, academics and also for students. It is also important to appreciate that the opinions and experiences of American and European experts are summarised in one publication.
Finally, it is necessary to thank all authors, as well as the main organizers of the symposium (A. Muttoni convener of fib WP 2.2.3, and C. E. Ospina and D. Mitchell representing ACI committee 445) for their editing of this extraordinary document. Last but not least, many thanks to Laura Vidale for the preparation of the bulletin for publication.
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Dear engineers,
I want to discuss what is the best program or excel sheet for calculating the slab punching shear as per ACI 318, since PROKO software gives error calculations and calculates the shear reinforcement in a stupid way and does not match with code formulas & CSi SAFE has some bugs in checking the adequacy of the slab's effective depth.
thx
Tests have established that punching shear in slabs can be effectively resisted by reinforcement consisting of vertical rods mechanically anchored at top and bottom of slabs. ACI 318 sets out the principles of design for slab shear reinforcement and makes specific reference to stirrups and headed studs. This guide reviews available types and makes recommendations for their design. The application of these recommendations is illustrated through numerical examples.
Author(s)/Editor(s): N S TRAHAIR | Size: 503 KB | Format:PDF | Quality:Original preprint | Year: Jan 2021 | pages: 17
Publisher: School of Civil Engineering, The University of Sydney
RESEARCH REPORT R967
Steel crane runway girders are subjected to torsion by their eccentric loads. The twist rotation of the principal axes caused by torsion induces additional bending moments, and reduces the resistance to lateral buckling. There is little guidance on how to design for torsion, and design procedures are often intuitive, with varying degrees of rationality and precision.
This paper seeks to establish a logical procedure for designing crane runway girders which is based on an extension of the limit states methods of designing for biaxial bending. An additional term for the ratio of the design torque to the section torsion resistance is included in the interaction equations. Proposals are made for determining this section resistance. Research has shown that this addition can allow for the reduction in the lateral buckling resistance caused by the twist rotations. A linear elastic analysis of the twist rotations is used to determine the moment increases caused by torsion.
An example of the proposed method is developed and illustrated by a design example. The small twist rotations are not enough to have a major effect on the bending moments. The additional torsion term is also small, and the design capacity is primarily governed by the resistance to lateral buckling.
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