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Blind Competition Program A research program at Politecnico di Milano (D. Coronelli), EPFL Lausanne (A. Muttoni), UNOVA Lisbon (A. Ramos) and UTCB Bucharest (R. Pascu) is being developed within the SERA-TA program - H2020 https://sera-ta.eucentre.it/index.php/sera-ta-project-02/.
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Slab STRESS Blind Competition www.slabstress.org
Politecnico di Milano, DICA - Dipartimento di Ingegneria Civile e Ambientale - www.dica.polimi.it
Piazza Leonardo da Vinci, 32 20133 Milano, ITALY
SLAB STRESS BLIND COMPETITION
Slab Structural RESponse for Seismic European Design
CONTENTS
1. INTRODUCTION the Slab STRESS Research Program
2. BLIND COMPETITION
2.1 Test A
2.2 Test B
3 CONTACT and Slab STRESS Team
References
1. INTRODUCTION - the Slab STRESS Research Program
A research program at Politecnico di Milano (D. Coronelli), EPFL Lausanne (A. Muttoni), UNOVA Lisbon (A.
Ramos) and UTCB Bucharest (R. Pascu) is being developed within the SERA-TA program - H2020
https://sera-ta.eucentre.it/index.php/sera-ta-project-02/.
The aim is studying flat slab response for seismic actions and developing the design with European codes.
There is an urgent need to extend the Seismic European Code for reinforced concrete buildings to cover flat
slabs (Fardis, 2009; Pinto et al., 2007). These have been and are intensively used because of the cutting of
construction costs and time, the simplicity of the geometry and increased available architectural space. Flat
slabs cannot be considered to contribute to the primary seismic resistant system and can be designed as
secondary systems supporting gravity loads at the design deformations, due to their compatibility with the
primary system (Fardis 2009; Coronelli and Martinelli, 2017). Particular care is needed for the punching
shear capacity of slab-column connections (Coronelli and Corti, 2014, Drakatos et al. 2017, Pinho Ramos et
al., 2008, 2011). Results aim at providing basis for code and design practice improvement (Pascu et al.,
2015; Muttoni, 2018).
Figure 1. Specimen dimensions, elevation (units: m).
Using the JRC ELSA Reaction wall facility (https://ec.europa.eu/jrc/en/research-facility/elsa), a flat slab
structural system will be tested. The structure is made of two flat slab floors supported on R/C columns.
Each floor has 3 bays in the longitudinal direction and two bays in the transverse direction, and the spans
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are 5m and 4.5m (Fig.1-2). Each floor is made of a reinforced concretemslab, with thickness 20 cm. The 1st
floor does not contain punching shear reinforcement, while the 2nd floor has stud shear reinforcement.
Previous research considered isolated slab-column connections (Almeida et al., 2016; Drakatos et al,
2016).The size is that of a real scale building, designed using the Eurocodes with primary ductile walls and
flat slabs as a secondary system.
In a first seismic hybrid pseudo-dynamic test (Pinto et al., 2004) the response to the design earthquake will
be studied at service and ultimate states, and ductile walls will be modelled virtually (Test A).
A second quasi-static cyclic test will investigate the response up to failure (Test B).
Fig.2 Specimen dimensions Plan (units: m)
The mass for each slab floor is 63 tons without added gravity loads and 108 tons with added loads. The
design was based on uniform distributed load of 3KN/m2for non-structural gravity loads and 2KN/m2 for the
live loads. The materials are normal strength concrete C30/37and steel S450 Class C.
Loading phases and structural scheme
The loading program comprises two types of loading, and related to this different constraints at the base of
the building.
The first test A is for seismic loading and the base of the columns is a fixed constraint; the flat slab system is
connected to the primary walls, modeled numerically, limiting the drift to a design value.
The second phase B is cyclic loading of the flat slab frame to failure. The floors will be tested for gravity and
lateral cyclic loading of increasing amplitude to failure.
(A) Seismic loading
Seismic loading will be simulated using the pseudo-dynamic technique with nonlinear substructuring (Pinto
et al., 2004) for two levels of seismic motion (service Test A.1 and ultimate state Test A.2). Gravity loading
will be self-weight and supplementary weight supported on the slabs.
(B) Cyclic loading
The floors will be then tested for gravity and lateral cyclic loading of increasing amplitude to near-failure
conditions. Lateral actions will be imposed by displacement controlled jacks connected to reinforcement
bars anchored within the slab, along the centerline between lateral and interior frames.
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Politecnico di Milano, DICA - Dipartimento di Ingegneria Civile e Ambientale - www.dica.polimi.it
Piazza Leonardo da Vinci, 32 20133 Milano, ITALY
2. BLIND COMPETITION
The competition will take place in two parallel parts:
- Simulation of seismic response for Test A
- Simulation of cyclic response for Test B
Table 1 - Time Program 2019-2020
The competition will last 12 months, from Sept. 2019 to Aug. 2020, followed by a final workshop in October
2020.
The competition includes a blind prediction phase in the first semester and a post test prediction phase in
the second semester. Evaluations will be carried out at the end of each semester.
Final workshop
A final workshop will be organized, hosted at the European Commission Joint Research Centre (JRC)
Venue: Ispra (VA), Italy
https://ec.europa.eu/jrc/en/research-facility/elsa
Dates: October 20th, 2020 (to be confirmed).
Proceedings: details on the publication intended of Workshop Proceedings will follow.
JUNE JUL AUG SEP OCT NOV DEC JAN FEB MARCH APR MAY JUNE JUL AUG SEP OCT
Preparation
A-blind 1 launch 30 collect 31 EVALUATION
A-post_test 31 launch 31 collect 18 EVALUATION
B-blind 1 launch 30 collect 31 EVALUATION
B-post_test 1 launch 31 collect 18 EVALUATION
WORKSHOP 20 Workshop
BLIND PREDICTIONS
POST TEST PREDICTIONS
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Piazza Leonardo da Vinci, 32 20133 Milano, ITALY
General Data provided
Structure geometry, reinforcement drawings, design and measured materials properties (details in the
following).
Competition rules
Participation is open for groups and individuals from research, design and industry.
Participants will be requested not to publish the the data received until after the October 2020 Workshop.
Evaluations
Each competitor can take place in either Test A or Test B or both.
Three evaluations will take place, in two moments along the year (April 1st, 2020 and September 18th,
2020):
- Results for Test A
- Results for Test B
- Results for Tests A and B
The rankings will be based on the direct comparison of the predicted and experimental vaues.
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Politecnico di Milano, DICA - Dipartimento di Ingegneria Civile e Ambientale - www.dica.polimi.it
Piazza Leonardo da Vinci, 32 20133 Milano, ITALY
2.1. TEST A
Blind prediction
Data Provided
Geometry, reinforcement details and material data;
Additional loads;
Walls stiffness and damping matrix;
Ground acceleration history.
Prediction requested:
Base shear of the structure (walls included) and displacement at first floor when second floor first
reaches a displacement of 0.005 m.
Base shear of the structure (walls included) and displacement at first floor when second floor first
reaches a displacement of 95% of the maximum predicted.
Base shear of the structure (walls included) and displacement at first floor when second floor first
reaches the maximum predicted.
Maximum displacement at each floor level for the acceleration history provided.
Evaluation:
The predicted results will be compared to the corresponding experimental values. 40% of the score will be
awarded on the base of the last point, 20% each for the other points.
Post test prediction
Additional Data Provided
The experimental floor displacement time history
Prediction requested:
Time-histories of shear forces in each column at the two levels of the structure
Evaluation:
The predicted results will be evaluated comparing at each level of the structure the predictions and
experimental values of the sum of the shear forces in the columns, when the second floor will reach its
maximum displacement.
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Politecnico di Milano, DICA - Dipartimento di Ingegneria Civile e Ambientale - www.dica.polimi.it
Piazza Leonardo da Vinci, 32 20133 Milano, ITALY
2.2. TEST B
B-blind prediction
Data Provided
Geometry, reinforcement details and material data;
Additional loads
Ground acceleration history of Test A
Cyclic floor displacement history (up to maximum actuator stroke)
Prediction requested:
Lateral drift capacity of the structure, evaluated as the drift of the two floors for the maximum lateral load
of the structure.
Evaluation:
The predicted results will be compared to the experimental lateral drift capacity of the structure
B-post test prediction
Prediction requested:
Force in each column at the two levels of the structure, in correspondence of the lateral drift capacity
Evaluation:
The predicted results will be compared to the experimental global floor maximum force response
Slab STRESS Blind Competition www.slabstress.org
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Politecnico di Milano, DICA - Dipartimento di Ingegneria Civile e Ambientale - www.dica.polimi.it
Piazza Leonardo da Vinci, 32 20133 Milano, ITALY
3. CONTACT
Dario Coronelli
Slab STRESS Project Coordinator
Associate Professor
Dept. of Civil and Environmental Engineering - Politecnico di Milano
Piazza Leonardo da Vinci 32
20133 Milano ITALY
Tel +39-02-2399-4395
Email: dario.coronelli@polimi.it
Slab STRESS Team
Team Leader:
Politecnico di Milano - PoliMi
Dario Coronelli
Luca Martinelli
Patrick Bamonte
Grigor Angjeliu
Francesco Foti
Charilaos Boursianis
Teresa Netti
Federal Polytechnic of Lausanne EPFL
Aurelio Muttoni
Miguel Fernández Ruiz
João T. Simões
Nova University of Lisbon UNOVA
Antonio Manuel Pinho Ramos
Válter José da Guia Lúcio
Rui Pedro César Marreiros
Technical University of Bucharest UTCB
Ion Radu Pascu
Viorel Popa
Eugen Lozinca
Dragos-Constantin Coțofană- Jianu
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Politecnico di Milano, DICA - Dipartimento di Ingegneria Civile e Ambientale - www.dica.polimi.it
Piazza Leonardo da Vinci, 32 20133 Milano, ITALY
REFERENCES
Almeida, A., Inàcio, M., Lúcio V. & Pinho Ramos, A. 2016 Punching behaviour of RC flat slabs under reversed
hori-zontal cyclic loading, Engineering Structures, Volume 117, 15 June 2016, 204-219
Coronelli, D., Corti, G. 2014 Nonlinear static analysis of flat slab floors with grid model, ACI Structural
Journal, 111,2,p.343-352.
Coronelli, D. & Martinelli, L., 2017. La progettazione sismica dei sistemi a piastra in calcestruzzo armato.
Pàtron Editore Bologna, 115 p.
Drakatos, I., Muttoni, A. & Beyer, K. 2016. Internal slab-column connections under monotonic and cyclic
imposed rotations. Engineering Structures, Volume 123, 15 September 2016, 501-516.
Drakatos, I., Muttoni, A. & Beyer, K., 2017. Mechanical model for drift-induced punching of slab-column
connections without transverse reinforcement. American Concrete Institute, Structural Journal.
Fardis, M., N. 2009. Seismic Design, Assessment and Retrofitting of Concrete Buildings based on EN-
Eurocode 8. Springer.
Muttoni, A. (2018) Shear design and assessment: The coming steps forward for fib Model Code 2020,
Structural Concrete Volume 19, Issue 1, Februaryy 2018, Pages 3-4
Pascu, R., Craifaleanu, I.G., Anicai, O., Stefan, L. (2015) Educational software platform in support to the
active assimilation of the European harmonized Romanian seismic code by the professional community
15th International Multidisciplinary Scientific Geoconference and EXPO, SGEM 2015; Albena; Bulgaria; 18
June 2015 through 24 June 2015, SGEM Volume 3, Issue 5, Pages 861-866
Pinho Ramos, A., Lúcio, V.J.G. (2008) Post-punching behaviour of prestressed concrete flat slabs
Magazine of Concrete Research 60(4), pp. 245-251
Pinho Ramos, A., Lúcio, V.J.G., Regan, P.E. (2011) Punching of flat slabs with in-plane forces Engineering
Structures, Volume 33, Issue 3, March, Pages 894-902
Pinto, A., Taucer F. & Dimova, S. (2007). Pre-Normative Research Needs to Achieve Improved Design
Guidelines for Seismic Protection in the EU. JRC EUR 22858 EN 2007, 34 pp.
Pinto, A. V.; Pegon, P. Magonette G. & Tsionis G. 2004 Pseudo-dynamic testing of bridges using non-linear
substructuring Earthquake Engng Struct. Dyn. 2004; 33:11251146.
Postelnicu, T., Lozincǎ, E., Pascu, R (2010) The new Romanian code for seismic evaluation of existing
buildings 6th International Conference on Concrete under Severe Conditions-Environment and Loading,
CONSEC'10; Merida, Yucatan; Mexico; 7 June 2010 through 9 June 2010; Volume 2, Pages 1647-1655
Ramos, A., Marreiros, R., Almeida, A., Isufi, B., Inácio, M. (2016) Punching of flat slabs under reversed
horizontal cyclic loading ACI-fib International Symposium on Punching Shear of Structural Concrete Slabs
2016; Philadelphia; United States; 25 October 2016 through 25 October 2016, American Concrete Institute,
ACI Special Publication Volume 2016-October, Issue SP 315, Pages 253-272
... [3][4][5][6][7] In a few cases only, the experimental investigation has been performed on scaled subassemblies of two or three-bay prototypes. [8][9][10][11][12] To date, the only test performed and reported on a full-scale three-story flat-plate building has been provided by Fick et al. 13 An experimental program dealing with full-scale flat-plate building, entitled SlabSTRESS (Slab STructural RESponse for Seismic design in Europe), has been recently started, 14 but the results are not available yet. Nevertheless, experimental programs with isolated specimens or reduced scale prototypes are usually preferred to full-scale flat-plate buildings, due to size and cost limitations. ...
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This paper analyses the performance of the experimental setups to assess the punching strength of slab-column connections in continuous flat slabs under vertical and horizontal loading. In the last years, several experimental campaigns have been performed to investigate the punching strength of slab-column connections, but most of the experimental tests concerned isolated slab-column connections. Among the few setups aimed at reproducing the eccentric punching failure in continuous flat slabs, the setup developed at the NOVA School of Science and Technology in Lisbon is considered in this paper. The performance of the Lisbon setup is assessed through nonlinear finite element analyses, calibrated on experimental data, by comparison with numerical results of a theoretical continuous setup. Then, the performance of the isolated setups, used in many researches and at the base of some international codes, is also evaluated through the same finite element model. Numerical analyses highlight that the setup developed in Lisbon could provide reliable ultimate rotations of continuous flat slab connections, but it underestimates the punching strength. Despite isolated setups lead to similar results when compared with the Lisbon setup, the latter seems to provide a better representation of a continuous slab-column connection. The numerical analyses presented in this paper have been performed assuming monotonic lateral loading.
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Reinforced concrete flat slabs supported by slender columns are often used as gravity load resisting system for buildings in regions of moderate seismicity. Current codes of practice determine the displacement capacity of slab-column connections using empirical formulas which were calibrated against experimental studies. This article reviews and compares test configurations used in past experimental studies and presents the adopted configuration for an experimental investigation on 13 full-scale internal slab-column connections without transverse reinforcement. The objective of the test campaign was to assess the influence of the loading history (monotonic vs. reversed cyclic) for different gravity loads and reinforcement ratios. The study showed that cyclic loading led in particular for slabs subjected to low gravity loads to significant moment strength and deformation capacity reduction when compared to results obtained from monotonic loading tests. The effect of cyclic loading was more pronounced for slabs with low reinforcement content. The experimental results are compared to the predictions of ACI-318, Eurocode 2 and fib-Model Code 2010. All codes predict the moment strength on the safe side. For the deformation capacity of the cyclic tests, only ACI-318 provides estimates, which are, in average, accurate enough but unconservative for slabs subjected to high gravity loads.
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The aim of this work is to study the behaviour of reinforced concrete flat slab structures under combined vertical and horizontal cyclic loading. A total of five specimens were cast and tested: a control specimen was punched without eccentricity, one specimen was tested under constant vertical loading and monotonically increased eccentricity until failure and the remaining three were tested under constant vertical load, at different shear ratios, and cyclic horizontal loading with increasing horizontal drift ratios. All slabs were similar, measuring 4.25 × 1.85 × 0.15 m3. The reinforced concrete slab specimens were connected to two steel half columns by 0.25 × 0.25 m2 rigid steel plates, prestressed against the slab using steel bolts, to ensure monolithic behaviour. The cyclic tests were performed using an innovative test setup that allows bending moment redistribution, line of inflection mobility, assures equal vertical displacements at the North-South borders and symmetrical shear forces. Results show that cyclic horizontal actions are very harmful to the slab–column connection, resulting in low horizontal drifts and energy dissipation.
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A grid model has been set up for the nonlinear response of a flat slab subjected to gravity and lateral cyclic loading. The model requires the definition of the grid geometry and properties of point hinges in beam finite elements, and modelling the nonlinear response in bending, torsion, and shear. The simulation is carried out for experimental tests on a floor under gravity and lateral biaxial cyclic loading of increasing amplitude. Pushover analyses have been performed under gravity and horizontal loads in the two principal directions. Predictions are shown of the global response and the connections of different column shapes and slab reinforcement with the strength, drift capacity, and failure modes. The accuracy is different in the two directions of loading due to the damage of the test slab for biaxial cyclic loading. The results show the potential of the model for design and analysis of existing fat slab structures.
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The experimental analysis of reduced scale flat slab models under punching, subject to in-plane forces is described and the results are compared with the Eurocode 2 (2004) [1] provisions, the FIP Recommendations for the Design of Post-tensioned Slabs and Foundation Rafts (1998) [2] and ACI 318-08 (2008) [3], to evaluate their validity. The tests presented here consist of two sets of experimental models: Ramos’s tests Ramos (2003) [10] with six reduced scale flat slab specimens and Regan’s tests Regan (1983) [7] that comprised seven experimental specimens. This work aims to improve the understanding of the behaviour of flat slabs under punching load, in order to properly evaluate the effect of the in-plane forces on the punching resistance.
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Pseudo-dynamic tests on a large-scale model of an existing six-pier bridge were performed at the ELSA laboratory using the substructuring technique. Two physical pier models were constructed and tested in the laboratory, while the deck, the abutments and the remaining four piers were numerically modeled on-line. These tests on a large-scale model of an existing bridge are the first to have been performed considering non-linear behavior for the modeled substructure. Asynchronous input motion, generated for the specific bridge site, was used for the abutments and the pier bases. Three earthquake tests with increasing intensities were carried out, aimed at the assessment of the seismic vulnerability of a typical European motorway bridge designed prior to the modern generation of seismic codes. The experimental results confirm the poor seismic behavior of the bridge, evidenced by irregular distribution of damage, limited deformation capacity, tension shift effects and undesirable failure locations. Copyright © 2004 John Wiley & Sons, Ltd.
La progettazione sismica dei sistemi a piastra in calcestruzzo armato
  • D Coronelli
  • L Martinelli
Coronelli, D. & Martinelli, L., 2017. La progettazione sismica dei sistemi a piastra in calcestruzzo armato. Pàtron Editore Bologna, 115 p.