1. The document summarizes the author's research visit to Portugal funded by the Pavior's Laing Travel Award to study the punching failure of flat slab buildings under seismic loading through experimental testing. 2. The author observed testing of flat slab specimens on a novel testing frame at the University of Lisbon that can simulate seismic loading. Two slab specimens with different amounts of shear stud reinforcement were tested. 3. The first specimen with three layers of shear studs failed through punching at 4% drift, while the second with five layers did not punch and was loaded to 6% drift, demonstrating that more extensive shear reinforcement and a longer reinforced zone improve seismic performance.

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PAVIOR’S LAING TRAVEL AWARD 2016REPORT
Andri Setiawan
Understanding the Punching Failure Phenomenon of Flat Slab Buildings in
Earthquake-Prone Regions through Experimental Test
A. Background of the Research
As generally known, Indonesia is located within the ring of fire region and it has experienced approximately 35
major earthquakes with average magnitude of 7.2
SR since2000 (Fig. 1). At the same time, Indonesia
is currently the fourth biggestpopulated country in
the world where the provision of sufficienthousing
is of major concern, especially in the big cities
which are mostly concentrated in Java Island. Flat
slab structural systemwhich has proved to produce
many practical advantages (e.g. short construction
time, less required formwork, and simple
reinforcement arrangement) may become one of
the most potential solution. However, the
performance of flat slab buildings under seismic
events is not fully understood to date. Therefore,
this research focuses on developing a better
understanding in terms of punching shear of flat
slab buildings subjected to seismic loading. It is
believed that the results of this research would be beneficial, not only for Indonesia but for another country
having the similar issues as well.
B. Experimental Test Visit Funded by Pavior’s Laing Travel Award
With the financial supportprovided by theWorshipful Company of Paviors,theauthor visited Prof.Pinho Ramos
research group in Faculdade de Ciencias e Tecnologia, Unversidade Nova de Lisboa (FCT-UNL), Portugal from
September to October 2016. Structural research group in FCT-UNL invented a novel testing frame which can be
used to perform realisticreversed-cyclic loadingtestfor 2/3 scaleof flatslab specimens. The novelty of the test
setup is the capability to simulate the shifting of the contra-flexure points which enables the redistribution
between hogging and sagging moments. Besides, this novel system is also considered as a self-equilibrating
system where the mechanism of balancing the external load occurs within the system itself. Thus, the gravity
shear ratio at the connection can be kept constant during the test, even when cracking starts to take place at
the column region. Therefore, more realisticsimulation can beperformed which resultingin more accurateand
reliable test outcome. More detailed explanation about how the test setup works can be seen in the recent
publication (Almeida et al., 2016). This testing frame has been used for the whole flat slabs project in the
university that has been started in the last three years (Fig. 2).
Fig. 1- Indonesia seismicity map
(Source: shipdetective.com)

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PAVIOR’S LAING TRAVEL AWARD 2016REPORT
Andri Setiawan
Fig. 2- Experimental test setup for flat slabs subjected to reversed-cyclic loading in the laboratory of FCT-UNL,
Portugal
In total,there were atleast15-20 slab specimens havebeen successfully tested with this testingframe and some
of the test results have also been published into scientific journals.The main differences for these tested slabs
were: the magnitude of the gravity loading; the presence of shear reinforcement, either as the form of
conventional stirrups or post-installed shear bolts; the use of high strength concrete (HSC); and steel fibre
reinforced concrete (SFRC) (Fig. 3).
Fig. 3- Previously tested flat slabs in FCT-UNL, Portugal with: a) post-installed shear bolts and steel fibre
reinforced concrete (SFRC); b) high-strength concrete (indicated with the dark grey region)
During the visit, there were two other flat slab specimens tested using the same test setup. Although both
contained the same amount of transverse reinforcement as a form of shear studs and the same gravity shear
ratio,the one that was tested earlier had only 3 radial layerswhereas thelater onehad 5 radial layers.Therefore,
the main interests of this test are to observe how the shear studs increase the performance of slabs against
seismic loadingwhich will becompared to the previously tested slab withoutshear reinforcement and slabswith
conventional stirrups and to compare the influenceof the extension length of the shear-reinforced zone to the
failure mode.
(a) (b)

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PAVIOR’S LAING TRAVEL AWARD 2016REPORT
Andri Setiawan
The firstslab specimen with three layers of studs was tested on 6th October 2016.Prior to the application of the
lateral loading, uniform gravity load was applied through eight steel plates (Fig. 2) to represent the constant
gravity shear ratio of 0.5 at the slab-column connection. The first slab specimen reached its peak lateral load
capacity at around 3.0% drift and the hysteresis behaviour was relatively stable without significant strength
deterioration for the successive cycles. However, at the second cycle of 4.0% drift, an abrupt punching failure
occurs where the column is punched through the slab and a di stinctpunchingconecan be observed outside the
shear-reinforced region (Fig. 4a).
The second specimen with five layers of studs was tested on 18th October 2016.It consists the same amount of
shear reinforcement and gravity shear ratio as the firstslab specimen.By contrast,this specimen did not fail in
the same punchingdrift with the firstspecimen and the loadingcan be continually applied unti l reaching6.0%
driftlevel. At this driftlevel, the test was stopped sincethe measuringtools (LVDT) has reached their maximum
measurement capacity and they cannot measure any further deformation. Therefore, this drift limit was
assumed as the failuredrifteven before the slab is fully punched through. For the second specimen, no distinct
punchingcone can be observed (Fig. 4b) and the failuremode is more similar to the flexural failuremoderather
than punching failure.
Fig. 4- Top view of the slab specimens after failure: a) first specimen with 3 layers of shear studs; b) second
specimen with 5 layers of shear studs
In conclusion, two important findings can be highlighted from the current test results:
1. Shear studs proved to significantly increase the ductility of the slab-column connections subjected to seismic
loading compared to the control specimen without shear reinforcement. Furthermore, it is also proved that
shear studs perform better than conventional stirrups. Not only they may achieve higher drift limit, it also
produces more stable hysteresis behavior, without significant loss of strength, whereas slab specimen with
stirrups tend to experience more significant degradation before failure. This proves that better anchorage
condition of the studs, provided by the head, produces superior seismic performance.
(a) (b)

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PAVIOR’S LAING TRAVEL AWARD 2016REPORT
Andri Setiawan
2. Comparingthe firstand second slab specimen with shear studs,itcan be concluded that itis notonly important
to consider the amount of shear reinforcement ratio and successive spacing, but the extension length of the
shear studs also needs to be considered carefully atdesign stage. With sufficientlength of the shear-reinforced
zone, failure outside this zone can avoided which results in higher ductility of the specimen before punching
occurs.
Acknowledgements
The author would like to express his sincere gratitude for his supervisor, Dr. Robert Vollum and Dr. Lorenzo
Macorini for their continuous help and support duringthis research project as well as Prof. Antonio Ramos for
giving an opportunity to visit and observe the experimental test conducted in Faculdade de Ciencias e
Tecnologia, Unversidade Nova de Lisboa (FCT-UNL), Portugal. The hospitality provided by the entire structural
engineering research group (Brisid, Helisa, Florian, Miguel, Ricardo, Andre, Hugo, and Dinarte) in FCT-UNL is
gratefully appreciated.
References
1. Almeida, A. F. O., et al. (2016). "Punching behaviour of RC flat slabs under reversed horizontal cyclic loading."
Engineering Structures 117: 204-219.
2. Faria, D., et al. (2010). Punching of reinforced concrete slabs and experimental analysis and comparison with
codes. Proceedings of IABSE-Fib Codes in Structural Engineering–Developments and Needs for International
Practice, Cavtat, Dubrovnik, Croácia.
3. Gouveia, N., et al. (2013). Punching of steel fibre reinforced concrete flat slabs. Proceedings of fib symposium
Tel-Aviv.
4. Gouveia, N. D., et al. (2014). "SFRC flat slabs punching behaviour–Experimental research." Composites Part B:
Engineering 63: 161-171.
5. Inácio, M. M. G., et al. (2015). "Punching of high strength concrete flat slabs without shear reinforcement."
Engineering Structures 103: 275-284.
6. Ramos, A., Duarte, I. and Lúcio, V.; Strengthening of Flat Slabs with Transverse Reinforcement, Proceedings of
CCC 2008 - Challenges for Civil Construction, FEUP, Porto, April, 2008.