www.www.buonovino.com

[alpa_sheth]

Dear Dr Subramanian,

I have started a new thread but am responding to your mail in the precast thread re. shear wall behaviour.

Thanks for the references. I think they are perhaps dated, esp with regard to shear wall behaviour. Our understanding of shear wall behaviour has undergone a sea change in past 5-10 years. The spurt of earthquakes has given us a lot of new insight into their performance- especially the 2010 Chile earthquake and the 2011 Japan and NZ earthquakes

Of particular concern has been the compression buckling of walls seen in these earthquakes, much of it due to lack of boundary element confinement (large spacing of hoop steel)

pl see the foll paper:
http://www.jaee.gr.jp/event/seminar2012/eqsympo/pdf/papers/176.pdf

best regards,

Alpa Sheth


[quote="Dr. N. Subramanian"]Dear Prof. Murty,

You may find more info. in the following:
[1] Seismic Design of the International Federation for Structural Concrete (fib), �State-of- the-Art Report on The Seismic Design of Precast Concrete Building Structures,� Draft Report of Task Group 7.3 of Commission 7,.
[2] Fintel, M., �Performance of Buildings With Shear Walls in Earthquakes of the Last Thirty Years,� PCI Journal, Vol. 40, No. 3, 1995, pp. 62-80.
Another report which may be of interest you:
An Evaluation of Seismic Design Guidelines
提出了预制混凝土混合框架系统[http://srg.cce.iastate.edu/Final%20reports/PCMAC%20Hybrid%20Frame%20Validation%20-%20FINAL%20REPORT.pdf]

[SanjeevKrSharma]

Dear All
I agree with the comment of Mr Swaminathan and as a practice only the reinforced structural topping typically varying from 60mm to 100mm is considered to transfer the diaphragm forces in seismic areas.
Though some guide lines for design of diaphragms exist in PCI handbook, Precast Concrete Institute (US) has initiated a research project DSDM (Diaphragm Seismic Design Methodology) where a full scale shake table was done and some reports are published on the observations. A list of these can be found at url below
http://nees.org/resources/4420/download/List_of_DSDM_Publications.doc
在欧洲在低地震地区,但是有一个practice not to do any structural topping over hollowcore slabs, but instead make shear keys at the edges of hollowcore, reinforce them and grout them with a specially designed low shrinkage mix.
As a remark on comparing hollowcore with the formwork in one of the earlier threads, I would like to add that hollowcore slab does not act as formwork alone but is very effective in transferring gravity loads and along with structural topping it acts as a composite slab. It is pretensioned hollowslab typically made with M40 to M60 greater grade of concrete with special mix having low water cement ratio. Middleast and Europe has seen large scale application of these slabs in multistory buildings, villas, shopping malls, large span carparks etc. We also see many references of their use in Australia and Newzeland.
Mr Murthy gave a very valid observation on HCS behavior in vertical accelerations as there might be stress reversal and disintegration in case they are not well connected into to the topping that can bind or hold them together in such cases. It might be possible to use the shear key formed at the edges to integrate HCS with topping in case of vertical accelerations though tests may be required to substantiate.
Finally, I also think that since these are primarily one way behaving slabs with no reinforcement (only strands) in precast part, a very careful detailing is required to mitigate effects of deformation incompatibility that may arise with adjacent beams, shear walls, columns etc. in highrise buildings and in high seismic zones.

Warm Regards
Sanjeev K Sharma
Principal Consultant
Melior Structural Solutions
www.meliorstructural.com

[Dr. N. Subramanian]

Dear Prof. Murty,

PCI Journal-Winter 2012 has the following reconnaissance reports of Chile, NZ and Japan EQs

Preview of PCI's New Zealand earthquake reconnaissance team report by Robert B. Fleischman, Jos� I. Restrepo, Joseph R. Maffei, and Kim Seeber
http://www.pci.org/view_file.cfm?file=JL-12-WINTER-9.pdf

Preview of PCI's Japan Earthquake Reconnaissance Team Report By
Richard Sause, Robert Frosch, S. K. Ghosh, Jason Lien, Clay Naito, Larbi Sennour, and Toshi Yamanishi
http://www.pci.org/view_file.cfm?file=JL-12-WINTER-10.pdf

Observations from the February 27, 2010, earthquake in Chile By
S. K. Ghosh and Ned Cleland
http://www.pci.org/view_file.cfm?file=JL-12-WINTER-11.pdf

I have not gone through them- but hope will provide latest info. on behavior of diff. structures in latest EQs

The Link provided by Er Alpa is good and deals with shear wall behaviour in EQs.

Regards,
NS

[Dr. N. Subramanian]

Dear Er Alpa,

Thanks for the link of the paper authored byProfs. Wallace and Jack Moehle, who are the leading researchers in USA and have published a number of papers in this area. This particular paper synthesizes the concepts in shear walls.

As you have rightly noted, the behaviour of barbell-shaped walls,Low-rise wall, slender walls, perforated walls, and coupled walls are different and have to be designed and detailed properly. Barbell walls have boundary columns which improve wall stability as the boundary columns have additional longitudinal reinforcement for moment resistance. In addition they help to anchor beams framing into the wall.

Flanged walls like T, L, C, and I configurations and Core walls may provide better safety.

Like columns, the axial force level and slenderness have to be considered carefully in the design, as the vertical bars may buckle in slender walls, as shown in the recent EQs.

Coupled wall in which cantilever walls are connected by coupling beams may be a bit difficult to construct, as the coupling beam with diagonal reinforcement may pose constructability. The Recent issue of Concrete International (Nov. 2012) contains the description of a building in SFO which has post tensioned shear walls (which will make the wall back to the vertical after the seismic event) as well as innovative composite coupling beam.

In the following document Prof. Wallace provides a designers guide to Displacement-Based Design of RC Structural Walls

http://www.seas.ucla.edu/~wallace/Files%20-%20Teaching%20Page/CE%20243A/ho%20DBD%20wall.pdf

In USA, the 'shear' walls are referred correctly as structural walls as the name shear wall is a misnomer!

Regards,
萨勃拉曼尼亚

[quote="alpa_sheth"]Dear Dr Subramanian,

I have started a new thread but am responding to your mail in the precast thread re. shear wall behaviour.

Thanks for the references. I think they are perhaps dated, esp with regard to shear wall behaviour. Our understanding of shear wall behaviour has undergone a sea change in past 5-10 years. The spurt of earthquakes has given us a lot of new insight into their performance- especially the 2010 Chile earthquake and the 2011 Japan and NZ earthquakes

Of particular concern has been the compression buckling of walls seen in these earthquakes, much of it due to lack of boundary element confinement (large spacing of hoop steel)

pl see the foll paper:
http://www.jaee.gr.jp/event/seminar2012/eqsympo/pdf/papers/176.pdf

best regards,

Alpa Sheth

[prof.arc]

Dear Co-ordinators [Dr. CVRM & Dr. Alpa Sheth],

I note with interest the flood of emails on this e-conf
The effort of SEFI can be fruitful only if the outcome results in a NEW BIS Code
on TALL BUILDINGS

Based on the e-conference, I hope you could organise a group of
research persons working under you to prepare
a draft code and send it to CED-39 for consideration

best wishes
sincerely
ARC

On 11/27/12, cvrm wrote:

[Dr. N. Subramanian]

Dear Prof. ARC,

I also feel that SEFI should take action to prepareva code on Tall Buildings.
The committee should consist of researchers as well as practioners, and a few contractors also!

Regards,
NS

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