expert meeting macedonia - ethz.ch · igor djolev, meri cvetkovska, ana trombeva gavriloska -...

Ss. Cyril and Methodius University Faculty of Civil Engineering

COST ACTION FP1404

FIRE SAFE USE OF TIMBER CONCRETE COMPOSITE STRUCTURES – WG2/TG2

EXPERT MEETING – MACEDONIA

University “Ss. Cyril and Methodius” Faculty of Civil Engineering - Skopje,

Macedonia

November 28-29, 2017

Editor: Meri Cvetkovska, Tomaž Hozjan

ACTION CONTACTS Chair of the Action Joachim Schmid [email protected] Vice Chair of the Action

Massimo Fragiacomo [email protected]

Local organizers Meri Cvetkovska

[email protected]

Action websites http://www.costfp1404.com http://www.cost.eu

mailto:[email protected]



http://www.costfp1404.com/

http://www.cost.eu/

COST ACTION FP1404 FIRE SAFE USE OF TIMBER CONCRETE COMPOSITE STRUCTURES – WG2/TG2 November 28-29, 2017, Skopje, MACEDONIA

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Contents

Part I – Minutes

1. Participants 1

2. Opening of the meeting 2

3. Approval of the agenda 2

4. Pesentations 2

5. Road map, final discussion and closing 11

Part II – Presentations

Tomaž Hozjan - SOA of timber-concrete composite beams in fire conditions -

review, WG2 – TG2 .....…………………………………………………………………… 15

Alfredo Dias – Design of TCC around the world ..…………………………………… 24

Petr Kuklík, Lukáš Velebil, Anna Kuklíková, Anna Gregorová - Timber concrete

composite floors in fire............................................................................................ 40

Tomaž Hozjan, Robert Pečenko - Numerical modelling of timber-concrete

beams exposed to standard fire – Validation with Frangi test…………………... 49

Cvetanka Chifliganec, Meri Cvetkovska, Milivoje Milanovic, Milica Jovanoska Marta

Stojmanovska – Numerical modelling of timber-concrete composite slab with

screwed connections using the SAFIR program……………………………… 57

Igor Djolev, Meri Cvetkovska, Ana Trombeva Gavriloska - Numerical analysis

of the TCC slab with screwed connections ……………………………................... 68

Tomaž Hozjan, Meri cvetkovska – Design recommendations, future work.......... 82


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Part I - Minutes


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1


Minutes of the expert meeting on the "Fire safe use of timber concrete composite structures – WG2/TG2"

Venue: Faculty of Civil Engineering - Skopje, Ss. Cyril and Methodius University, 1000 Skopje, Macedonia

Day 1: Date: 28.11.2017

Time: 10:00 - 18:00

Day 2: Date: 29.11.2017

Time: 09:30 – 11:30

1. Participants

Name Affiliation

Meri Cvetkovska Ss. Cyril and Methodius University, Faculty of Civil Engineering, Macedonia

Ana Trombeva Gavriloska Ss. Cyril and Methodius University, Faculty of Architecture, Macedonia

Cvetanka Chifliganec Ss. Cyril and Methodius University, Faculty of Civil Engineering, Macedonia

Milica Jovanoska Ss. Cyril and Methodius University, Faculty of Civil Engineering, Macedonia

Marta Stojmanovska Ss. Cyril and Methodius University, Faculty of Civil Engineering, Macedonia

Igor Dzolev University of Novi Sad, Faculty of Technical Sciences, Serbia

Alfredo Dias University of Coimbra, Portugal

Lukáš Velebil Czech Technical University in Prague, Czech Republic

Robert Pečenko Universiy of Ljubljana, Faculty of Civil and Geodetic Engineering, Slovenia

Tomaž Hozjan Universiy of Ljubljana, Faculty of Civil and Geodetic Engineering, Slovenia


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2. Opening of the meeting

The chairman, prof. Meri Cvetkovska welcomed the participants and opened the meeting

at 10:00 am. All participants were according to the above participation list. She asked all

the participants to briefly introduce themselves.

3. Approval of the agenda

In agreement with the participants, slight changes in the agenda of the meeting was

made, since some of the participants had to leave the meeting next afternoon. It was

agreed that all presenters should do their presentations the first day. It was also agreed

that main discussions should be done the first day and the second day the discussions

to be only on: planning for the future work, distribution of the work, determining the

working group leaders with specific goals (validation and modification of design rules and

development of design rules of TCC structures).

4. Pesentations

4.1 Tomaž Hozjan - SOA of timber-concrete composite beams in fire

conditions - review, WG2 – TG2

Abstract:

The presentation was focused on the current state of the art of timber-concrete

composite structures in fire conditions. In majority timber beams with different type of

connections were experimentally investigated through the world by different research

groups. Recently experimental research is also focused into the research of timber

concrete composite slabs. This work is mainly investigated by the group of researchers

at technical university of Prague (CVUT). Calculations design methods are rare but were

developed by some research groups. They need to be harmonized with design methods

of TCC beams at ambient conditions. Since methods were developed based on standard

fire exposure, there is a certain doubt in validity of these methods in case of natural fire

exposure.

DISCUSSION:

No special discussion was opened. Participants only requested access to the report,

which is available at the group Dropbox folder. The report should be finalized before

summer 2018, to be presented as report document for the COSP FP 1404 action.


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4.2 Alfredo Dias – TCC Design – Future TS

Abstract:

Timber-concrete-systems have been increasingly used in recent decades. This

increased interest is due to various reasons, but particularly to the use of timber in new

types of buildings, such as for example, multi-storey buildings or motorway bridges,

where the timber-concrete composites play an important role. In spite of this higher

interest, such development, was not supported by an adequate regulatory framework.

The composite timber-concrete systems are, usually, analysed and designed in

accordance with Eurocode 5, which does not address many important issues that are

specific for the design of this type of structure. To close this gap, CEN/TC 250/SC 5, the

standardization committee responsible for drafting Eurocode 5, decided to establish a

Working Group (WG2) on this issue. This Working Group will be supported by a Project

Team, mandated to draft a Technical Specification which eventually will become a new

Eurocode 5 part on timber-concrete composites.

The organization of the document follow the general structure of the Eurocodes and it

comprises:

1 Scope

2 Normative references

3 Terms definitions and symbols

4 Basis of design

5 Materials

6 Durability

7 Basis of structural analysis

8 Ultimate Limit State

9 Serviceability Limit State

10 Connections

11 Detailing and Execution

Annex

Despite of being based on the approved version of Eurocode 5 it includes some relevant

changes in all sections but particularly in sections 4, 5 7 and 10. The document does not


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give rules or indications for fire design which is expected to be covered on Eurocode 5

part 1-2.

DISCUSSION: In the discussion Alredo Dias pointed out that TCC structures with

notched connections are not treated enaugh and it would be interesting for the Eurocode

if design rules were presented in form of limitations and application recommendations.

The design guidelines should be in scope of Eurocopde principles i.e. referred to the

concrete and timber parts of EC.

4.3 Petr Kuklík, Lukáš Velebil, Anna Kuklíková, Anna Gregorová - Timber

concrete composite floors in fire

Abstract:

Timber-concrete composite structures are coming to be very important in housing sector.

They have many advantages compared to traditional timber floors and are widely used

as an effective method for refurbishment of existing timber floors. Due to the many

benefits they are now being used more in new multi-storey timber framed houses.

The fire resistance of timber-concrete composite floors is mainly influenced by the timber

and the connectors [1]. The temperature inside the timber members depends particularly

on the cross-sectional dimensions, on the density and moisture content of wood and on

the fire load and temperature development during the fire. The temperature development

in the place of the shear connection can be governed by the cross-sectional dimensions,

particularly by the width.

The ongoing research deals in a complex way with the problems of timber-concrete

composite floor structures. The aim of this research is to determine design models for

timber-concrete composite beams that are applicable for computer simulations as well

as for hand calculations.


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Figure 1: Preparation and end of the fire test General perception of the public is that timber is combustible and therefore it is

considered to be more dangerous than to use steel or concrete. For this reason, it is

necessary to gain deeper knowledge about the behaviour of timber-concrete composite

structures under fire conditions to remove all the unknowns. The knowledge of fire

behaviour of the timber-concrete composite floor and its mechanical connection leads to

more reliable and economic design of this construction in case of fire.

Timber-concrete floor was designed at the Faculty of Civil Engineering CTU to resist fire

according to ISO 834 at least 45 minutes for REI criteria (Fig. 1). During the test structure

showed resistance REI 60. At the time of 62 minutes the test was discontinued, because

the concrete slab partially burnt and the floor has lost its integrity (E) and insulation

function (I) (Fig. 1). The research shows that timber-concrete composite floor can be

designed according to γ-method with charring of the timber part specified by the charring

rate and the stiffness reduction due to elevated temperature. Also concrete is affected

with an increasing temperature and its stiffness and load-carrying capacity is reduced.

The research confirmed that timber-concrete composite floor can be designed according

to the rules prepared by Andrea Frangi and Mario Fontana [1].

The design strength and stiffness values in fire are determined from equations:

20d,fi mod,fi

M,fi

f= f k

and 20

mod,fid,f i

M,fi

S= S k

where 20 fi kf k f and 20 fi 05S k S .

Modification factor taking into account the effects of temperature and moisture on the

mechanical properties is presented in Tab. 1.

http://slovnik.seznam.cz/?q=load-carrying%20capacity&lang=en_cz


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Figure 2: Arrangement of cross section

Table 1: Modification factors for fire according [1]

This outcome has been achieved with the financial support of Czech Technical University

in Prague, project No: SGS17/125/OHK1/2T/11 „Structural fire design of timber concrete

composite floors“.


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[1] Frangi A., Fontana M.: A design model for the fire resistance of timber-concrete

composite slabs. Proceedings of the IABSE Conference on Innovative Wooden Structure

and Bridges, Lahti, Finland, 2001.

DISCUSSION:

Robert Pečenko and Tomaž Hozjan asked whether the slip was measured, or not. Lukáš

Velebil was not sure but later from some of the figures it was concluded that the

measurements were not done. Also there was a comment from Alfredo Dias that this

and similar kind of specific connections, which are well known and usually used in

individual countries, are making problem in giving common recommendations.

4.4 Tomaž Hozjan, Robert Pečenko - Numerical modelling of timber-

concrete beams exposed to standard fire – Validation with Frangi test

Abstract:

The response of timber concrete composites during fire was determined by the advanced

two phase calculation method. In the first phase, thermal analysis was performed based

on the Fourier equation describing heat transfer through solid. Time dependent

temperature field in the characteristic cross-section of the beam was determined. In the

second phase, mechanical model was introduced, which enables to analyse the

mechanical response of TCC simultaneously exposed to mechanical and fire load. The

analysis for the TCC with notched connection was thoroughly investigated. As it turned

out, good agreement between calculated and measured [1] vertical midspan

displacement was discovered. In addition, considering linear or non-linear description of

the contact did not have an influence on the results, due to the almost rigid nature of the

notched connection.

[1] Frangi, A. 2001. Brandverhalten von Holz-Beton-Verbunddecken. ETH Zürich. 252

pp.

DISCUSSION:

Tomaž Hozjan commented that the model used for the analysis gave results that were

in very good agreement with the experimental results and suggested that this numerical

model, made in MatLab, could be used in future analyses of TCC with screwed

connections.


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4.5 Cvetanka Chifliganec, Meri Cvetkovska, Milivoje Milanovic, Milica

Jovanoska, Marta Stojmanovska - Numerical modelling of timber-

concrete composite slabs with screwed connections using the SAFIR

program

Abstract:

Several analyses of fire exposed timber-concrete composite slab with screwed

connections were conducted using the program SAFIR in order to compare the

numerically achieved results with the experimental data and the results obtained by

simplified calculation method (on the basis of the calculation model for mechanically

jointed beams with flexible elastic connections given in EN 1995-1-1 and the reduced

cross section method given in EN 1995-1-2) developed by A. Frangi in ETH Zurich.

In the 2D analysis the TCC slab was treated as simply supported beam. Two different

2D models of the slab with different cross-sections (T and TTTT) were made. The steel

connectors were incorporated in the 2D models, but only as steel elements, so the

connection between the timber and the concrete could not be treated as flexible because

no slip between the subcomponents occurred. The fire resistance for the both models

was 62 minutes (65 minutes in the experiment) but the deflection of the beam was

significantly lower.

In the 3D analysis the slab was treated as simply supported slab with dimensions 2.8x7

m, and the load was considered to be 3 kN/m2. The TTTT cross-section was modelled

without screws i.e. the composite structure was considered as one element with rigid

connection between the subcomponents (timber and concrete). In this case the fire

resistance was 71 minutes (65 minutes in the experiment) but the deflection of the beam

was significantly higher.

DISCUSSION:

Tomaž Hozjan and Robert Pečenko asked about the possibility for modelling the flexible

connection between the timber beam and the concrete slab by using springs. Cvetanka

answered that in the 2D analyses it is not possible. For the needs of the thermal analysis

the cross section has to be discretized by finite elements and there is no option for using

springs. In the structural analysis the option for using springs is available, but the cross

section has to be assigned to the structure as it was defined in the thermal analysis. She

said she will try to improve the model in 3D analyses but Alfredo Dias suggested that it`s

better to stay on 2D analyses. He mentioned his earlier experiences in modelling

connections and how 3D analyses could be sometimes so demanding and useless, while

2D analyses of connections are more simple and usually give better results.


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4.6 Igor Djolev, Meri Cvetkovska, Ana Trombeva Gavriloska - Numerical

analysis of the TCC slab with screwed connections

Abstract

Thermal and structural numerical model of the timber concrete composite slab with

screwed connections is developed in finite element software Ansys. Numerical results

are compared with the results from a full-scale fire test of TCC slab performed by Frangi

et al. at the Institute of Structural Engineering of ETH Zurich.

Thermal and mechanical properties of constitutive materials are adopted according to

available data provided by the authors and Eurocode standards. Finite element model

consists of 3D solid (concrete slab and timber beams/boards) and 1D line elements (steel

reinforcement mesh and screws). Different finite element meshes are used in thermal

and subsequent structural analysis, according to the physical phenomenon. To reduce

the computational time, only 1/4 of the structure is analysed, taking into account a two-

plane symmetry. A perfect bond between concrete slab and timber boards, as well as

timber boards and GL beams is assumed, providing no slip at the interface.

Thermal response of the structure, compared to the test results provided by the authors,

showed a slightly underestimated temperature rise in timber elements. Structural

response, in terms of deflection due to external load and during first 50 minutes of

standard ISO fire showed good agreement between calculated and test data. After 50

minutes, the calculated deflection rate became lower compared to the test results,

postponing the failure time of the TCC slab from 67 minutes (as reported) to 75 minutes.

A possible reason for this could be the rapid increase in the observed slip after 50

minutes of fire exposure. At the time of failure, the calculated maximum temperature in

screws was below 100°C, providing no degradation of mechanical properties of screws

due to temperature rise. Maximum calculated temperatures in concrete slab at the time

of failure were around 260°C.

Further model development would include modification of timber thermal properties, to

fit the test results. Also, to model a contact between concrete and timber elements, a

constitutive relations need to be established, providing sliding but not a separation

between the elements.

DISCUSSION:

Tomaž Hozjan suggested the presenter to try to model the same slab without screws

and to find out whether the results will be different, or not. This suggestion was based

on the fact that the presenter`s model worked like rigid connection between the concrete

and the timber beams existed although screws were included in the model. In such case

Igor should compare his results with the results obtained by Cvetanka Chifliganec who


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should try to make a 3D model of the slab with rigid connections. Discussion about

improvement of the model was made, similar as for the Cvetanka Chifligane`s

presentation, in order to find out how to catch the slip and the flexible timber-concrete

connection.


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5. Road map, final discussion and closing

5.1 Tomaž Hozjan – ROADMAP for WG2 – TG2

Tomaž Hozjan presented the draft roadmap for the future work of TCC expert group and

opened a discussion.

Based on the discussions, the following future goals were established:

For notched connections and glued-in rods type of connections, further research

is needed (kmod,fi).

What to cover in future EC in connection to ambient design?

- Screwed connections

- Notched connections etc.

Validation of numerical procedures, parametric studies, what is possible?

Most studies are based on standard fire test. What about non-standard fires?

REPORT, formation of smaller working groups, defined on this meeting.

Numerical modelling (Tomaž):

- The limit for stiffness, influence of contact on response

- Notched, screwed, glued in rods, dowels?

- Report, deadline to be determined at meeting in L’Aquilla, Italy:

Model description, parametric study design rules?

Design recommendations (Michael, Chiara, Lukas):

- Input from experiments, observations, etc…

- Observations from experiments

- SOA report (help)

- Connections

- Based on Table in SOA structural design recommendations


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5.2 Final discussion

For faster communication and in order to get things done before the Italy meeting, Tomaž

Hozjan gave a suggestion for Skype - meetings of the people in the groups that were

created.

The next meeting of the WG2 –TG2 expert group will take place at COST meeting in

L’Aquila, Italy, at the end of January 2018. Meri Cvetkovska said that on these days she

has other important meeting that she has to attend. Tomaž Hozjan said that she could

send other participant in her place.

At the end, Tomaž Hozjan presented the opportunity for the young researchers of this

COST action to attend the Training school on connections in timber structures, organized

in the frame of the COST Action FP1402. The information about this training school was

sheared by Alfredo Dias who is one of the organisers. The training school is planned to

be held in Coimbra, Portugal, 9-13 April 2018.

5.3 Closing

Tomaž Hozjan and Meri Cvetkovska thanked all the participants for joining the meeting,

presenting their work, and for the participation in the discussions.


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Part II - Presentations


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COST Action FP1404Fire Safe Use of Bio‐based Building Products

SOA of timber‐concrete composite beams in fire conditions ‐ review, WG2 – TG2

Tomaž Hozjan

EXPERT MEETINGFIRE SAFE USE OF TIMBER CONCRETE COMPOSITE STRUCTURES – WG2/TG2

Skopje, 2017‐11‐28 and 2017‐11‐29

2. SOA: TCC structures at elevated temperatures

• Experiments are limited• In general ISO 834 fire curve

• Connectors are rarely investigated• Simplified calculation procedures are based on experimental results

Type popularity fire curve

Calculationprocedure

InfoConnection

Tmiber Beam-Concrete Deck

most common

ISO 834 simplifedsome

advanced

YES

Concrete Deck –Timber beam

rare ISO 834 simplified /

Timber deck –Concrete deck

currentlypopular

ISO 834 / /

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3.1 TCC with SCREWED CONNECTIONS, dowels

Extensive experimetnal work done by group at ETH Zurich• Frangi A., Fontana M., Knobloch M.,…

• Frangi, A., and Fontana, M. (2000). “Experimental tests on timber-concrete compositeslabs at room temperature and under ISO-fire exposure.” Rep. No. 249, Institute ofStructural Engineering, ETH Zurich, Switzerland (in German).• The report summarises the results of tests at normal temperature (111 tests), at

constant elevated temperature (46 tests) and fire tests with standard ISO fireexposure (23 tests)

• The behaviour of screwed connections and dowels in timber-concrete compositemembers was investigated

Figure 1. Shear connection with srews arranged at 45° inclination (Frangi et al. 2010)

Figure 2. Shear connection with notches and glued dowels (Frani and Fontana 2000)

• Material tests• Behaviour of connectins in fire,

screwed• Simplified design models• Results published in many journal

and conference papers, reports.• Simplified model: Frangi A, Knobloch M, Fontana M.

(2010) “Fire Design of Timber-Concrete Composite Slabs with Screwed Connections”, ASCE Journal of Structural Engineering, Vol. 136, No. 2, 2010.

Figure 1. Shear connection with srews arranged at 45° inclination (Frangi et al. 2010)

Figure 2. Shear connection with notches and glued dowels (Frani and Fontana 2000)

3.1 TCC with SCREWED CONNECTIONS, notched

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5

• Simplified model: Frangi A, Knobloch M, Fontana M. (2010) “Fire Design of Timber-Concrete Composite Slabs with Screwed Connections”, ASCE Journal of Structural Engineering, Vol. 136, No. 2, 2010.

• The fire tests showed that the load-carrying behavior of the connection with axially loaded screws depends on the temperature dependent reduction of withdrawal strength and stiffness oftimber.

• Simplified design method was developed on the basis of the simplified method known as –method (EN 1995-1-1) and taking into account reduced cross section method (EN 1995-1-2).

• Simplified method was also presented and described in bachlero thesis by V. Nežerka(2010), slight modification of method was made

Notched connections with screews and plate connections, timber composite floor systems

Extensive experimetnal work done by group at University of Canterbury• O’Neill J. W., Buchanan A.,

• O’Neill J. W. 2009. The fire performance of timber-concrete composite floors. MASc.thesis, • The thesis summarises the results of 2 large-scale fire tests of TCC made of LVL

and • results from small scale test to investigate the failure strength and behaviour of the

LVL at different temperatures. In total, 23 compression and 20 shear tests at varying temperatures were carried out.

• Two type of connections were investigated: notched with screws and plate connection

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Notched and plate connection using double LVL beams(O’Neill 2009)

Specimen at 50 oC from small scale tests (O’Neill 2009)

• Simplified calculation design method was developed based on the performed test results (Spreadsheet)

• Observations:• the LVL beams with the steel plate connection

system exhibited stiffer performance and lower deflections when compared with the notched connection beams,

• failure of the TCC systems was governed by the charring rate of the timber,

• the charring rate on the sides of the LVL beams was found to be 0.58 mm/min on average which is lower than reported values of 0.72 mm/min for plain LVL beams

• separation of the double LVL members during the latter stages of burning was noticed, which increased the charring of the LVL beam,

The timber-concrete composite joist floor system and full scale testing of a timber-concrete composite floor system at BRANZ. (O’Neill 2014)

Modelling and experimental displacement results for 300 beam floor (O’Neill 2014).

• Observations from small scale tests:• heat affects timber lost compression strength

with increasing temperature toward 100 °C as the wood softens and behaves in a more plastic manner. After this the strength increased towards 200 °C as the wood starts to harden,

• the same trend was observed also for the stiffness . Pre-dried wood samples exhibited much higher strength characteristics than the samples which were kept at a moisture content of 12 %, moisture influence

• a steady linear decrease in strength to 200 °C was observed,

• the effects of reduced timber material properties due to elevated temperature had a very small impact on the overall performance of the floor units.

• More results published with co-authorsin journal papers also full 3D modell

Experimental vertical displacement for 300mm floor system (O’Neill 2011).

Experimental vertical displacement for 400mm floor system (O’Neill 2011).

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9

Summary of the state-of-the-art of TCC structures exposed to fire in recent years.

Reference YearNo. and type of tests

Material type Connection type Type of modelling

Frangi and Fontana [2],Frangi [3]

2000,2001

23 large-scale tests ▲,111 tests ●

Glulam beam, concrete slab

Screwed and dowel connections with notches

Simplified model and numerical modelling

Frangi et al. [4] 201015 small-scale ▲,1 large-scale ▲

Glulam beam, concrete slab

Screwed connections Simplified model

O’Neill [5], O’Neill et al. [6, 7]

2009,2011,2014

43 small-scale ▲,2 large-scale with 2 setups ▲

LVL beam, concrete slab

Notched connection with steel screws and steel plates

Full 3D numerical model and simplified model (spreadsheet)

Caldova et al. [8–10],Bednář et al. [11], Blesák et al.[12, 13]

2013 – 2015,2016,2013 – 2015

2 large-scale ▲,1 large-scale ●, 12 small-scale material tests for each SFRC mixture▲

Glulam timber frame, steel fibre reinforced concrete (SFRC) slab

Screwed connectionsFull 3D numerical model and simplified model

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Summary of the state-of-the-art of TCC structures exposed to fire in recent years.

Reference Year No. and type of tests Material type Connection type Type of modelling

Osborne [17] 20152 different TCC systems in 1 large-scale test▲

CLT concrete and laminated wood-concrete assembly

Screwed connections and connections with steel truss plates

None (test report)

Boccadoro and Frangi [14], Boccadoro [15], Klippel et al. [16]

2014, 2016, 2016

2 large-scale ▲Beech LVL,reinforced concrete slab

Notched connections None (test report)

Meena et al. [18] 2014 1 large-scale ▲Reinforced concrete slab with glulam beam on top

Notched connections Only thermal modelling

Pålsson [19] 1998 1 large-scale ▲Reinforced concrete slab with solid timber beam on top

U-shape steel wire connections

None (test report)

▲ Fire test ● Test at normal temperature

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Design recommendations based on described experiments

Type of TCC system Suggestions for the design guidelines.

TCC beams with screwed and plated connections

• Sufficient side cover of the connectors must be provided.• Withdrawal failure of the connection must be prevented.• A gap (at least up to 3 mm) between the beam and timber board need not be

considered.

TCC beams with notched connections with screws and TCC beams with plated connections

• Reduction of the timber section governs a failure mode of the TCC plate –sufficient side and bottom cover thickness must be ensured.

• Fire resistant connections of double beams must be provided in order to prevent their splitting.

• Beneficent positive deflections at the beginning of the fire could be taken into account or could be disregarded in conservative design.

TCC floor systems using steel fibre reinforced concrete and screwed connections

• SFRC may be considered without spalling – additional tests are required. • Membrane action of SFRC plate after loss of secondary beams should be

considered.• Tests present an extension of Eurocode material data database.

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TCC floor systems with notched connections and a beech plate

• Delamination of LVL must be considered.• After burn-out of LVL spalling must be considered.

TCC floor systems using laminated timber with shear connectors

• »1D« heat transfer and charring due to considered TCC system – only bottom cover of the connectors need to be checked

20

13



Reversed TCC floor with grooved and notched connections

• 20 mm thick concrete layer can provide fire resistance of R60 (if spalling is prevented) – additional tests are required. Namely, concrete works as a protective layer and fire resistance can be achieved with proper design of timber beams. If spalling is prevented, thermal resistance of TCC floor could be determined according to the thickness of the concrete. Fire resistance can be improved by thicker concrete slab.

Reversed TCC floor with steel wire bent to a U-shape connectors

• 80 mm thick concrete layer can provide fire resistance R90 (failure occurred due to spalling),

• Concrete mainly works as a protective layer only. • If spalling is prevented, thermal resistance of TCC floor could be determined

according to the thickness of the concrete – additional tests are required.

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According to EC it shall be verified that Ed,fi ≤ Rd,fi, which means that the design effects

of actions in fire should be smaller or equal to the design resistance in fire.

For TCC following verifications should be considered:

• Normal stresses in concrete and timber

• Combined bending and tension

• Compressive stress in the outermost fibre of the concrete slab

• Shear stress in the connector

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The ultimate limit state in fire for the design of the longitudinal shear stress.

, , , , · · ,

• TR,k is the 5% fractile characteristic strength of the connection at normal temperature,

• kfi is the modification factor for fire taking into account the 20% factiles of strength of the

connection,

• kmod,fi is the modification factor for fire that can depend on the type of connection, the

side cover and the fire duration time (R).

• According to Frangi et al (2010) values for screwed connection kmod,fi can be reduced

as strength of timber at elevated temperature.

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FUTURE WORK, desired goals:.

• for notched connections and glued-in rods type of connections, further research is needed

(kmod,fi).

• What to cover in future EC connection to ambient design?

• Screwed connections

• Notched connections,…

• Numerical validations, parametric studies, what is possible??

• Non-standard fires ???

• REPORT, formation of smaller working groups, defined on this meeting

22

17

23

COST Action FP1404Fire Safe Use of Bio-based Building Products

TCC Design – Future TS

Alfredo Dias, Universidade de Coimbra


Skopje, 2017-11-28 and 2017-11-29

DESIGN OF TCC AROUND THE WORLD

• USE STARTED 1920’ DECADE– Engineers expertise – Research studies (Illinois 1943, Oregon 1933)

US 26 – Built in 1934 (83 years) Length 24.1m (11.9m) – ADT 6 500

OR 99W – Built in 1934 (83 years)Length 161.8m (11.6m) – ADT 16 600

24

• FIRST CODE INDICATIONS FROM AASHTO 1949– Assumes perfect interaction– Determination of the effective width– Stress calculation– Some guideline for the shear devices


• SIMILAR APROACHES GIVEN IN LATER EDITIONS - AASHTO 1983 – Gives indications for the determination of the stresses– Indications for the strength to shear and pull loads– Concentrated loads


25

• SIMILAR APROACHES GIVEN IN LATER EDITIONS - AASHTO 2014– Gives indications for the load distribution factors in cast-in-place concrete on wood beams


• CANADIAN BRIDGE CODE– Gives specific indications for the design of TCC bridges, namely regarding the connections. – The aim of the code guidelines is restricted to TCC with deck floors


26

• AUSTRALIA AND NEW ZEALAND GUIDELINES– Guide to help in the design of timber-concrete composite, restricted to TCC with deck floors– Limitation in the maximum spans – Two connection configurations prescribed in the document


• BRAZIL BRIDGE DESIGN CODE– The design approach is meant for TCC bridges with timber deck systems using Roundwood


27

KEY ASPECTS IN THE DESIGN OF TCC

• SHORT TERM ANALYSIS– Special geometries– Special load conditions– Non Linear analysis

• LONG TERM PERFORMANCE AND ANALYSIS– Materials with different time dependent behaviours– Available models might deviate significantly from the experimental observations


28

• COMPOSITE ACTION – CONNECTIONS– Critical to the performance of the TCC– Relevant for both SLS and ULS– Several (rather different) connection systems

0

1

2

3

4

1 10 100 1000 10000

EIef

* 10

12(N

mm

2 )

K (N/mm/mm)

span 9 mspan 6 mspan 3 m


• EXECUTION– Materials with rather different properties– Significant temporary dead loads in cast-in-place solutions– Presence of the water near the timber members


29

TCC IN THE NEW GENERATION OF EUROCODES

• ORGANIZATION– Evolution Group– Working Group

NEW PART IN EUROCODE 5 • Project Team – SC5.T2• Working Group

PT COMPOSITION

• Alfredo Dias (PT)• Joerg Schaenzlin (DE)• Massimo Fragiacomo (IT)• Petr Kuklik (CZ)• Richard Harris (UK)• Vlatka Rajcic (HR)

30

TCC IN THE NEW GENERATION OF EUROCODES• DELIVERABLES

– CEN Technical Specification– Background documents

1st Trim.2nd Trim.3rd Trim.4th Trim.1st Trim.2nd Trim.3rd Trim.4th Trim.1st Trim.2nd Trim.3rd Trim.4th Trim.1st Trim.2nd Trim.3rd Trim.4th Trim.

Background Documents

End of the Project Team (June 2018)

Start of the Project Team (September 2015)

Final Document

Second Draft

Final Draft

2015

2016

2017

2018

First Draft

September2015 to

June 2016

May 2016 to June

2017

May2017 to January

January2018 to

April 2018

December2015 to

April 2018


• Coordination with other CEN documents and standards

Eurocode 5Part 1-3

Products Standards

Testing Standards

Eurocode 5 Part 1-1Part 1-2Part 2

Eurocode 2

Eurocode 4

Non material codes

31


• Coordination with other initiatives– FP1402 - Basis of structural timber design – WG4 Hybrid structures

2nd 3rd 4th 1st 2nd 3rd 4th 1st 2nd 3rd 4th 1st 2nd

state of the art (science) 1 1 1 2state of the art (application) 1 1 1 2Parameters/Design method 1Proposal for EC5 1Cross-check 1 2 state of the art (science) 1 1 1 2state of the art (application) 1 1 1 2Parameters/Design method 0.5Proposal for EC5 0.5Cross-check 1 2 state of the art (science) 1 1 1 1 1 2state of the art (application) 1 1 1 2Parameters/Design method 1Proposal for EC5 0.5 2Check vrs. EC4 1 0.5Cross-check 1 2 state of the art (science) 1 1 1 2state of the art (application) 1 1 0.5 0.5 1 1 1 2Parameters/Design method 1Proposal for EC5 0.5 2Check vrs. EC4 1Cross-check 1 2

3 3 6 9 6 5.5 4 4 4 4 4 2 0

EC5 1-3 PT - Final Draft (For information purposes)EC5 1-3 PT - Final Document (For information purposes)WG4 - Training SchoolWG4 - Dedicated Workshop

2018

OTHER INITIATIVES

Connectors

Short term analysis and

design for static and dynamic

loads (SLS and ULS and

Long term analysis and

design (SLS and ULS and

requirements)

Sum (active Taskgroups)

Actions & input values

2015 2016 2017

CHALLENGES

• Large amounts of information, spread in many ways (e.g. different documents, different regions, and different approaches)

• Simultaneous revision of standards and codes, closely related to this part

• Multiple national experiences and “state of the art” in terms of use

32

MAIN PRINCIPLES

• Ease of use must be a driving wheel

• Simple approach for the large majority of the constructions (e.g. indoor buildings)

• More complex approach for other types of building

• Do not repeat information given in other code parts (e.g. EN 1995 part 1-1)

• Most current situations are explicitly considered

MAIN PRINCIPLES (cont.)

• Room shall be open for not so common situation (e.g. systems specific from a particular region)

• Service class 3 is allowed but not promoted• General rules are included• Specific rules for bridges or fire situations will not be given

33

STRUCTURE AND CONTENTS

1 Scope2 Normative references3 Terms definitions and symbols4 Basis of design5 Materials6 Durability7 Basis of structural analysis8 Ultimate Limit State9 Serviceability Limit State10 Connections11 Detailing and Execution

Annex


3 Terms definitions and symbols

Definition of quasi-constant environmental conditions and variable environmental conditions

34


4 Basis of design4.1 Requirements4.2 Principles of limit states design4.3 Basic variables4.4 Verification by the partial factor method

Actions and environmental influences for the two environmental conditions


5 Materials5.1 Quasi-constant environmental conditions5.2 Variable environmental conditions

Reference is made to other standards for the material properties.

Indications are given for the two environmental conditions

35


6 Durability6.1 General6.2 Timber decking for composite slabs in buildings6.3 Resistance to corrosion

Makes reference EN1995 part 1-1


7 Basis of structural analysis7.1 Modelling of the composite structure7.2 Propping

-method is suggested

Indications are given for the short term analysis

Indications are given for the lonfg term analysis

Indications are given to consider the construction phases including propping

36


8 Ultimate Limit State8.1 General8.2 Beams and slabs – Verification of cross-sections8.3 Wall panels

Reference is made to the verification equations from EN 1995 part 1-1

Specific verifications are given for concrete and connection


9 Serviceability Limit State9.1 General9.2 Deflection9.3 Vibration9.4 Cracking of concrete timber-concrete

Reference is made to the verification models from EN 1995 part 1-1

Indications are given for the crack control in concrete

37


10 Connections10.1 General10.2 Mechanical properties obtained from test10.3 Mechanical properties determined according to this standard10.4 Detailing

Design data is given for dowel type fasteners, glued-in rods, notches

Indications are given for the design of the axial load carrying capacity


11 Detailing and Execution11.1 General11.2 Detailing of the cross-section11.3 Detailing of the shear connection and influence of execution

General recommendations for timber and concrete

38


Annex Annex A (informative)

Average timber moisture content variations for timber-concrete composite structures

Annex B (informative)Shrinkage of concrete for composite structures for buildings

Annex C (Informative) Fictitious vertical load equivalent to the inelastic strains

Annex D (Informative)Experimental determination of the connection properties

3233333232323222332333233332333333333333233333333323333333332233

39


Timber concrete composite floors in fire

Petr Kuklík, Lukáš Velebil, Anna Kuklíková, Anna GregorováCzech Technical University in Prague


Skopje, 2017‐11‐28 and 2017‐11‐29

Presentation outline

• Example of TCC floor in the Czech Republic• Structural arrangement of TCC floor• Fire test of TCC floor• Behaviour of TCC floor in fire• Evaluation of TCC floor in normal temperature• Evaluation of TCC floor in fire• Conclusion – arrangement of cross section• Ongoing research – prefabricated TCC floor assembly

40

Example of TCC floor in the Czech Republic

• Šumavský dvůr apartmens• SFS screws• Interiors with walls of CLT after

realization of floors

Structural arrangement of TCC floor

• Beam of GLT 180/240 mmwith interlayer of thickness 25 mm

• Concrete slab thickness 60 mm• Connection of beam and slab with

SFS screws• The screws are mounted more

densely at the ends of the beamand less dense in the middle of the beam

41

Fire test of TCC floor

• Test to verify the behavior of the ceiling structure

• Violation the integrity of the concrete slab because of very coarse aggregate

[min]t

C][. temp

View to the fire furnace

Temperature during a fire

Behaviour of TCC floor in fire[min]t

[mm]

• Thermal expansion ofconcret slab – to 15 min. without deflection

42

Behaviour of TCC floor in fire

[min]t

C][. temp

• Measurements on a wooden beam near the fasteners by thermocouples


• Measurements on a interlayer near the fasteners

[min]t

C][. temp

43


• Measurements on a concrete slab betweenwooden beams

[min]t

C][. temp

Evaluation of TCC floor in normal temperature

44

Evaluation of TCC floor in fire - based on heat transfer

TimberC][. temp

com

pre

ssiv

est

reng

tho

fco

ncre

te(%

)


• Deflection for mechanicaland thermal load

• Deflection for thermal load- deflection measured since the start of the fire test

[min]t

[mm]

45


• Decreasing of moment and shear resistance

Conclusion – arrangement of cross section

Parameter Coefficient kmod, fi Valid for

Modulus of elasticity EStrength of timber

1,0 effective cross section

Modulus of elasticityStrength of concrete

≈ 1,0 hs ≥20 mm and t ≤ 60 min

Slip modulus of fastener 0 x ≤ 0,6 t

0,2 x - 0,12 t0,2 t + 3

0,6 t ≤ x ≤ 0,8 t + 3

0,8 x – 0,6 t + 1,80,2 t + 21

0,8 t + 3 ≤ x ≤ t + 24

1,0 x ≥ t + 24

Load bearing capacity offastener

0 x ≤ 0,6 t

0,44 x – 0,264 t0,2 t + 5

0,6 t ≤ x ≤ 0,8 t +5

0,56 x – 0,36 t +7,320,2 t + 23

0,8 t +5 ≤ x ≤ t + 28

1,0 x ≥ t + 28

46

Ongoing research – prefabricated TCC floor assembly

1-concrete slab, 2-timber beams,3- shear connector, 4-reinforcement mesh

• Multi-storey wooden buildings based on LTS

• Shear connector formed by punched steel plates can be pressed between wooden lamellas

• Test specimen of TCC Floor at normal temperature has been already tested

Ongoing research – prefabricated TCC floor assembly

• Specimen failure in wood

• No removal of concrete from the wood

• Tension and pressure areas monitoring of tested specimen using 2D correlation

47

Thank you for your attention.

48


Numerical modelling of timber‐concrete beams exposed to standard fire – Validation with Frangi test

Tomaž Hozjan, Faculty of Civil and Geodetic Engineering, University of LjubljanaRobert Pečenko, Faculty of Civil and Geodetic Engineering, University of Ljubljana


Skopje, 2017‐11‐28 and 2017‐11‐29

1. Summary and Research’s objectivesGoal: Validation of advanced numerical model for TCC, based on the experimentconducted by Frangi (2001)

Advanced numerical model:• 1st phase: design fire scenarios (standard fire curve in this case)• 2nd phase: determination of temperature field (FE method)• 3rd phase: Mechanical response of TCC beam exposed to static load and fire

• Self developed numerical model (FE method)

0 1 2 3 40

200

400

600

800

1000

1200

tem

pera

ture

[C

]T

o

time [min]t

EN 1991-2, CH fire curve

EN 1991-2, external

ISO 834

EN 1991-1-2, parametric fire curve

Frangi, A. 2001. Brandverhalten von Holz-Beton-Verbunddecken. ETH Zürich. 252 p.

49

2. Mechanical modelBasic model features:• Each layer of the composite slab is modelled by Reissner’s geometrically exact beam

theory. • Stress-strain state is determined iteratively, where the whole time of the duration is

divided into time intervals [ti-1, ti]. • Interlayer slip is allowed, while uplift between layers is not allowed.• Principle of additivity:

• increment of total strain Di is the sum of strain increments due to temperature, stress and creep strains:

i i i ith σ cr∆D = ∆D + ∆D + ∆D

2. Mechanical modelModelling the connection:• Linear connection

• Non-linear connection,

, , ,max (1 )Et TB kt T ft T tp A k p e

, ,t T ft T connp k k

0 0.5 1 1.50

0.33

0.66

1.0

experiment T = 20 oCT = 100 oC

|| /

||p

pt

Tt

,,m

ax

slip [cm]

( ) b constitutive law for pt T,

maximal capacity of a connector ,

50

3. Material data for the advanced methodAdvanced calculation procedures:• Thermal properties of wood/concrete• Mechanical properties of wood/concrete• Properties of connector (stiffness, deformation, force-slip relationship)

Available material data in EN 1995-1-2 and EN 1992-1-2• Based on standard fire tests (ISO 834)• Properties of connectors/fasteners at elevated temperature

• Available in some research articles (rare)

4. Thermal properties of timber and concrete

0.5

1.0

1.5

2.0

0 200 400 600 800 1000 1200T [ C]o

[W

/mK

]

upper limit

lower limit

0 200 400 600 800 1000 1200800

1000

1200

1400

1600

1800

2000

2200

T [ C]o

c p [

J/kg

K]

o

u = 3 %

u = 1,5 %

u = 0 %

Timber, EN 1995-1-2

Concrete, EN 1992-1-2

51

5. Mechanical properties of timber at elevated T

Stres-strain relationship by Pischl (1980)

Reduction parameters according to EN 1995-1-2

Pischl, R. 1980. Holzbau mit kritischen betractungen und neuen vorschlägen zur bemessung nach theorie 1. und 2. ordnung. Graz, Technische Universität Graz, Institut für Stahlbau, Holzbau und Flächentragwerke.

fm,k?

6. Mechanical properties of concrete and reinforcement at elevated temperatures

fc,T

0.4 fc, T

Ecm, T

cu1, T

c1, T

(a) stress-strain relationship of concrete

Calcareousaggregate

Siliceousaggregate

0.2

0.4

0.6

0.8

1

kf

fc

,c,

ckT

T =

/

0 200 400 600 800 1000 12000

temperature [ C]T o

(b) reduction factors for compresive strength

0 200 400 600 800 1000 12000

0.2

0.4

0.6

0.8

1

kk

kp,

y,,

TT

ET

,,

kp T,

ky,T

t emperature [ C]T o

fsp,T

fsy,T

sp,T

(a) stress-strain relationship of reinforcement (b) reduction factors for hot rolled reinforcement

kE,T

Es,T

st,Tsy,T su,T

Concrete EN 1991-1-2:

Reinforcement EN 1991-1-2:

52

8. Validation of the modelNumerical simulation – ISO fire:• Simply supported TCC beam• Experimentally investigated by Frangi (2001)• ‘‘Hilti‘‘ connectors – Notched connection

F = 10 kN

8. Validation of the modelThermal analysis• Heat model based on the Fourier equation:• 2192 Finite elements: size 0.5 x 0.5 cm

T

C k Tt

53

8. Validation of the model

T

C k Tt

Temperature fields

20 min 40 min

60min

8. Validation of the modelNum1:fyt = 1.4 kN/cm2

fyc = 2.1 kN/cm2

Ep = 20 kN/cm2

kconn = 300 kN/cm

Num2:fyt = 1.8 kN/cm2

fyc = 2.4 kN/cm2

Ep = 20 kN/cm2

kconn = 300 kN/cm

54

8. Validation of the modelNum1:fyt = 1.4 kN/cm2

fyc = 2.1 kN/cm2

Ep = 20 kN/cm2

A = 2, B = 10, pt,max = 1.0 kN/cm

Num2:fyt = 1.8 kN/cm2

fyc = 2.4 kN/cm2

Ep = 20 kN/cm2

A = 2, B = 10, pt,max = 1.0 kN/cm

8. Validation of the model

55

8. Validation of the modelDiscussion: Linear or non-linear connection?

16

56

Meeting of COST ACTION FP1404, Skopje, Macedonia, November 28‐29 2017

Numerical modelling of timber‐concrete composite slab with screwed connections using the SAFIR program

Numerical modelling of timber‐concrete composite slab with screwed connections

using the SAFIR program

Cvetanka Chifliganec Meri Cvetkovska Milivoje MilanovicMilica Jovanoska Marta Stojmanovska

28‐29.11.2017, Skopje, R. Macedonia

COST Action FP1404 ‐ Fire Safe Use of Bio‐based Building Products

Expert meeting – Fire safe use of timber‐concrete composite structures ‐WG2/TG2



Introduction Object of analysis:

Timber‐concrete composite slab with screwed connections in fire,analyzed by A. Frangi and M. Fontana in ETH Zurich.

Aim of research:

Testing the capabilities of the SAFIR program for modeling andcalculation of composite slabs in fire and inclusion of the connectionsbetween timber and concrete as factor that governs the structuralbehavior of these slabs.

Compare the results from numerical models made with the SAFIRprogram and from: experimental tests and the simplified calculationmethod developed by the above mentioned researchers (on the basisof the calculation model for mechanically jointed beams with flexibleelastic connection given in EN 1995‐1‐1 and the reduced cross sectionmethod given in EN 1995‐1‐2).

57



Description of the SAFIR program SAFIR is a special purpose computer program for the analysis of structures under

ambient and elevated temperature conditions, developed at the University of Liège,Belgium. The program, which is based on the Finite Element Method (FEM), allowsmodelling the behavior of structures in fire, taking into account material andgeometrical nonlinearities, the thermal elongation, as well as the reduction of strengthand stiffness of the materials at elevated temperature. It can be used to study thebehaviour of one, two and three‐dimensional structures made of: concrete, steel, RC,wood, composite etc. It.

SAFIR accommodates various elements for different idealization, calculation proceduresand various material models for incorporating stress‐strain behaviour. The elementsinclude the 2‐D SOLID elements, 3‐D SOLID elements, BEAM elements, SHELL elementsand TRUSS elements.

SAFIR can be used for performing three different types of calculations, namely, thermal,torsional and structural analysis. The analysis of a structure exposed to fire may consistof several steps. The first step involves predicting the temperature distribution insidethe structural members, referred to as ‘thermal analysis’. The torsional analysis may benecessary for 3‐D BEAM elements, a section subject to warping and where the warpingfunction table and torsional stiffness of the cross section are not available. The last partof the analysis, termed the ‘structural analysis’, is carried out for the main purpose ofdetermining the mechanical response of the structure due to static and thermal loading.



Description of the timber‐concrete slab with screwed connections

Cross section and longitudinal section of the timber-concrete composite slab tested under ISO fire exposure

58



Comparison of author`s vs our INPUT DATA for the analyses

Screwed connection

Author: the connection consists of a self‐drilling screw with a collar to limit thescrewing depth and a head for connection to the concrete. The threaded part hasa length of 100 mm and a diameter of the net section of 4 mm, while the upperpart of the connector is 50 mm long and has a diameter of 6 mm. By arrangingthe connectors at 45° inclination a virtual truss is formed with the timber andthe concrete as girders and the connectors as diagonals. Such an arrangementimproves the stiffness by a factor of about 3 compared to a vertical arrangementwhere the connectors act in bending (Timmermann and Meierhofer 1993).

Us: modelled as vertical rebars like those of reinforcement grid meshMAR 500/600



Comparison of author`s vs our INPUT DATA for the analyses

Heating regime:

Author: An expression for calculation of the temperature profile in a woodmember was developed, based on all temperatures measured during theETH fire tests :

Us: Standard temperature‐time curve ISO‐834:

T=20+345log10(8t+1)

Fire behaviour of the screwed connection:

Author: determined with shear and axial tests at normal temperaturesand in fire conditions (steady state and transient state tests), incorporatedin the calculation method through modification factors.

Us: rigid connection, steel for reinforcement from Eurocode 2 or Eurocode3.

59



Numerical models in SAFIR

Several models of the composite timber‐concrete slab were made inSAFIR:

2 x 2D models for the timber‐concrete composite slab were made.In the structural analysis the slab was treated as simply supportedbeam with T cross‐section / TTTT cross‐section

1 x 3D model of the slab

Although steel connectors were incorporated in the 2D models, stillthe connection between the timber and the concrete can not betreated as flexible because no slip between the subcomponentsoccurs.




I. Simply supported beam – T section

T cross‐section with Ø6 mm / Ø8 mm bars as connection, with Ø6mm 100/100grid mesh in the concrete slab

60




II. Simply supported beam – TTTT section

1. TTTT cross‐section with Ø6 mm or Ø8 mm bars as connectionbetween the timber beams and the concrete slab, with Ø6 mm100/100 grid mesh in the concrete slab




II. Simply supported beam – TTTT section

2. TTTT cross‐section with Ø8 mm bars as connection between the timber beams and Ø8 mm 150/150 grid mesh in the concrete slab

61




III. Slab – 3D model

Two different shell elements were created.Both have same geometry and represent theconcrete slab and timber board, but the firstshell element is exposed to fire on thebottom side and placed in the zones betweenthe timber beams and the second one is notexposed to fire and it`s placed above thetimber beams. The concrete slab isreinforced with Ø8 mm 150/150 mm gridmesh.



Comparison of the mechanic characteristics

MaterialMechanical

characteristicsExperiment

Model I (T cross section)

Model II (TTTT cross section)

Model III ( Slab with rigid timber‐concrete connection)II.1 TTTTfi6 II.2 TTTTfi8

Concrete

E [N/mm2] 37000 37600* (Silicon ETC)

same same samefc [N/mm2] 47 47

ft [N/mm2] ? 4.7

Timber( glulam GL24h accordingto EN 1194 )

E [N/mm2] 10620

same same same same

fc [N/mm2] 24ft [N/mm2] 16.5

r [kg/m3] 438

ω [%] 13

Reinforcement steel

E [N/mm2] ? 200000 200000 210000 210000

fy [N/mm2] ? 500 500 500 500

diameter [mm] 6 6 /100 mm 6 /100 mm 8/ 150 mm 8 (150/150 mm grid mesh)

Screwed connection

E [N/mm2] ? 200 200000 210000 /

fy [N/mm2] ? 500 500 500 /

diameter [mm] ? 6 or 8 6 or 8 8 /

62



Comparison of the mechanic characteristics

Concrete ‐ Silicon ETC

The ETC model is a uniaxial material model for concrete.

The ETC model is based on the concrete model of Eurocode EN1992‐1‐2 (EC2), except that in the ETC model the transient creep strain istreated by an explicit term in the strain decomposition whereas inthe EC2 model the effects of transient creep strain are incorporatedimplicitly in the mechanical strain term. The variation ofcompressive strength and tensile strength with temperature, as wellas the thermal properties, are taken from EN1992‐1‐2.



Comparison of results

Fire resistance t [min] Deflection [mm] Slip [mm]

Experiment 67 min around 39 around 1.05

Author`s calculation model 65 min around 39 around 0.8

Model ITØ6 62 min 11.9 /

TØ8 62 min 11.7 /

Model II. 1TTTTØ6

62 min (7.5% smaller from experiment)

11.6 (70.26% smaller from experiment)

/

TTTTØ8 62 min 11.5 /

Model II. 2 TTTTØ866 min (1.5% smaller from experiment)

5.8 (85.13% smaller from experiment) /

Model III Slab71 min (6% higher from experiment)

367 (841% higher from experiment) /

63



Graphical display of results ‐ Temperature profiles

Temperature field in T cross‐section with Ø6 mm

NO significant rise in temperature in the

screw!



Graphical display of results

Temperature field in the cross‐section of Model II. 2 (TTTTØ8)

Shear force diagram at the moment of failure (t=66 min) for Model II.2 – shear failure in the connections

64



Graphical display of results – comparison of deflection in different models

Model I (TØ6)

Model II.1 (TTTTØ6)

Model II.2 11.9

11.65.8

39



Displacement (deflection) at the moment of failure

Model III

39

367

Graphical display of results – comparison of deflection in different models

65



Conclusions regarding the SAFIR program and recommendations for improvement in further work

Conclusion:

The SAFIR program can be used to model a timber‐concrete compositeslabs with rigid connection subjected to fire. Although steel connectorswere incorporated in the 2D models, still the connection between thetimber and the concrete can not be treated as flexible because no slipbetween the subcomponents occurs.

2D and 3D analysis of simply supported beam with vertically arrangedscrews as a model of the timber‐concrete composite slab can be done.Modelling 3D slabs with screwed connections is complicated.

Since SAFIR doesn`t have an open source code, the results of theanalysis are highly affected by the chosen material model that describesthe behavior of the material in fire.



Conclusions regarding the SAFIR program and recommendations for improvement in further work

How to improve:

We can create a “user defined function” for the fire temperature,defined as a function of time in accordance with the measuredtemperatures from the fire tests of wood and assign it to fireexposed surfaces

A 3D model of a detail of the screwed connection can be made inorder to observe the loss in stiffness and strength as a function ofthe temperature rise around the connection and to comparethese with the small‐scale fire tests results.

Questions to be answered:

How to model the interlayer slip between the subcomponents ofthe composite?

66


Numerical analysis of the TCC slabwith screwed connections

Igor DŽOLEV 1, Meri CVETKOVSKA 2, Ana TROMBEVA GAVRILOSKA 2

1 Faculty of Technical Sciences, University of Novi Sad, Serbia2 Faculty of Civil Engineering, University “Ss. Cyril and Methodius”, Skopje, Macedonia


Skopje, 2017‐11‐28 and 2017‐11‐29

Personal info

Igor Džolev, MSc Civ Eng, TADepartment of Civil Engineering and GeodesyFaculty of Technical SciencesUniversity of Novi SadSerbia

Membership in Professional Associations• Serbian Chamber of Engineers

• Structural Engineering• licence in design• licence in execution

• Energy efficiency of Buildings• licence in design

68

Personal info

PhD candidate

Nonlinear thermo-mechanical behavior analysis ofreinforced concrete frame structures subjected to fire

Džolev I., Cvetkovska M., Lađinović Đ., Radonjanin V. (2015): Load influence and fire exposure of a simply supported beam, 16th International Symposium of MASE, Ohrid, Macedonia, 1-3 October 2015, pp. 475-482Džolev I., Cvetkovska M., Lađinović Đ., Radonjanin V., Rašeta A. (2015): Thermal analysis of concrete members subjected to fire according to EN 1991-1-2 & EN 1992-1-2, 13th International Scientific Conference iNDiS 2015, Novi Sad, 25-27 November 2015, Proceedings pp. 708-715Džolev I., Jovanović Đ., Cvetkovska M., Lađinović Đ., Radonjanin V. (2016): Lateral torsional buckling of steel beams subjected to fire, 6th International Conference Civil Engineering – Science and Practice, Žabljak, Montenegro, 7-11 March 2016, pp. 85-92Džolev I., Radujković A., Cvetkovska M., Lađinović Đ., Radonjanin V. (2016): Fire analysis of a simply supported steel beam using Opensees and Ansys Workbench, 4th International Conference Contemporary Achievements in Civil Engineering, Subotica, 22 April 2016, pp. 315-322Džolev I., Cvetkovska M., Lađinović Đ., Radonjanin V., Rašeta A. (2016): Fire analysis of a simply supported reinforced concrete beam using Ansys Workbench, 8th Symposium 2016 Association of Structural Engineers of Serbia, Zlatibor, 15-17 September 2016, pp. 322-327Džolev I., Lađinović Đ., Rašeta A., Laban M. (2017): Thermo-mechanical properties of reinforced concrete at elevated temperatures, 12th International Conference Risk and Safety Engineering, Kopaonik, 9-11 January 2017, pp. 88-98Džolev I., Lađinović Đ., Cvetkovska M., Radujković A., Rašeta A. (2017): Seismic response of RC frame structure modelled according to EN 1992-1-1 and EN 1992-1-2, 17th International Symposium of MASE, Ohrid, Macedonia, 4-7 October 2017, pp. 407-413

Content

• Introduction• Material models• Geometry discretization• Thermal and structural model• Loading and boundary conditions• Analysis• Results• Conclusion

69

Introduction

• Fire Design of Timber-Concrete Composite Slabs with Screwed ConnectionsAndrea Frangi, Markus Knobloch, Mario Fontana

• Introduction• Charring of Timber• Experimental Tests on the Fire Behavior of the Screwed Connection

• Tensile Tests• Shear Tests

• Strength and Stiffness Properties of the Screwed Connection in Fire• Design Model for the Fire Resistance of Timber-Concrete Composite Slabs with

Screwed Connections• Fire Test on a Loaded Timber-Concrete Composite Slab• Conclusions

Introduction

• Fire Test on a Loaded Timber-Concrete Composite Slab

• Timber – GL beams and board• Concrete – slab• Steel – screws and reinforcement mesh

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Material models

• Timber• Thermal properties – ρ, λ, c

density – (431 – 445) 440 kg/m3moisture content – 13%EN 1995-1-2

Material models

• Concrete• Thermal properties – ρ, λ, c

density – 2300 kg/m3thermal cond. – lower limitmoisture content – 1.5%EN 1992-1-2

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Material models

• Steel• Thermal properties – ρ, λ, c

EN 1993-1-2

Material models

• Timber• Mechanical properties – εth, E, f

elastic modulus – 10 620 MPaPoisson’s ratio – 0.3GL24h – tensionEN 1995-1-2

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Material models

• Concrete• Mechanical properties – εth, E, f

class – C30/37thermal strain – calcareous agg.EN 1992-1-2

Material models

• Steel• Mechanical properties – εth, E, c

EN 1993-1-2

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Material models

• Stress-strain• Timber• Concrete• Steel

Geometry discretization

• Symmetry

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Thermal and structural model

• Finite element mesh


• Finite elements by material and type

Reinforcement mesh Screws Concrete slab

Timber elements GL beams Timber boards

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Thermal model mesh Structural model mesh

Loading and boundary conditions

• Thermal model

• Symmetry• Conduction – ρ, λ, c• Convection

• αc = 25 W/m2K (hot)• αc = 9 W/m2K (cold)

• Radiation• εm = 0.8 (hot) hot ISO 834• εm = 0.7 (cold) cold ambient temp.

cold

hot

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Loading and boundary conditions

• Structural model

• Symmetry and support

• Self weight• External load• Body emperature

Analysis

• Sequential thermal-structural analysis• Perfect bond – no bond-slip/contact

Project schematic

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Results

• Thermal response

R 30

R 60

R 90

Results

• Thermal response

• Steel – no degradation due to temp.

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Results

• Structural response

Results


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Results


Conclusion

• Numerical analysis of the TCC slab – full-scale fire test• FEM software ANSYS• 1/4 of the slab modelled – computational time• Material models based on available test data and Eurocode standards• Lower temperatures in timber calculated – slower degradation of mechanical

properties – longer time until failure• Steel elements (reinforcement mesh and screws) protected by GL beams, timber

boards and concrete cover – no mechanical degradation due to heating• At 55 minutes of fire exposure – deflection rate rises• Calculated failure time – 75 min > 67 min – Test failure time• Further development

• Thermal properties of timber• Contact between timber and concrete elements

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Thank you!

[email protected]

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Design recommendations, future workWG2


Skopje, 2017‐11‐28 and 2017‐11‐29

2



• for notched connections and glued-in rods type of connections, further research is

needed (kmod,fi).

• What to cover in future EC connection to ambient design?

• Screwed connections

• Notched connections,…

• Numerical validations, parametric studies, what is possible??

• Non-standard fires ???

• REPORT, formation of smaller working groups, defined on this meeting

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3


• Numerical modelling (Tomaž,…):

• The limit for stiffness, influence of contact on response

• Notched, screwed, glued in rods, dowels?

• Report, deadline February 2018 (meeting in Italy):

• Model description, parametric study design rules?

• Design recommendations (Michael, Chiara, Lukas,…)

• Input from Experiments, observations, etc…

• Observations from experiments, SOA report (help), Connections

• Based on Table in SOA structure design recommendations

• Input from institutes with experiments

4


• Connections in fire, overview

• Paper

• Lukas will ask Peter

• Creating the Working Packages (WP‘s)

• Strong goals, with precise deadlines

• Possibilities to include students

• To be determined at L‘Aquila meeting in end of January

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