Change search
Link to record
Permanent link

Direct link
BETA
Lukaszewska, Elzbieta
Publications (7 of 7) Show all publications
Lukaszewska, E., Fragiacomo, M. & Johnsson, H. (2010). Laboratory tests and numerical analyses of prefabricated timber-concrete composite floors (ed.). Paper presented at . Journal of Structural Engineering, 136(1), 46-55
Open this publication in new window or tab >>Laboratory tests and numerical analyses of prefabricated timber-concrete composite floors
2010 (English)In: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 136, no 1, p. 46-55Article in journal (Refereed) Published
Abstract [en]

This paper describes tests on a novel composite floor system constructed by connecting prefabricated concrete slabs to timber joists. Seven types of shear connectors have been developed and tested: lag screws, either alone or combined with a notch cut from each timber joist; metal plates embedded in the concrete slab and either nailed or glued to the joists; dowels embedded in the concrete and glued to the timber; and toothed metal plates embedded in the concrete and pressed into the timber. Four-point bending tests to failure were performed on five, full-scale, 4.8 m long specimens connected with lag screws or metal plates nailed to the timber. Values of deflection and relative slip between the concrete slab and the timber obtained in these tests showed high correspondence with values obtained from a uniaxial finite element model developed for nonlinear analyses of composite beams. The model was also used to perform a numerical analysis to failure of composite beams with the other four connection systems that were developed but not tested on full-scale specimens. The outcomes of the experimental tests and numerical analyses show that the newly developed system can provide good structural performance, especially if connections with coach screws and notches in the timber are used. The economic advantages of prefabrication and the possibility to disassemble the structure and reuse the timber beams and concrete panels at the end of the service life make the proposed floor system very promising.

National Category
Building Technologies
Research subject
Timber Structures
Identifiers
urn:nbn:se:ltu:diva-6014 (URN)10.1061/(ASCE)ST.1943-541X.0000080 (DOI)000273526300005 ()2-s2.0-73449091543 (Scopus ID)435ae430-56d0-11de-9f57-000ea68e967b (Local ID)435ae430-56d0-11de-9f57-000ea68e967b (Archive number)435ae430-56d0-11de-9f57-000ea68e967b (OAI)
Note
Validerad; 2010; 20090611 (elzluk)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-08-07Bibliographically approved
Lukaszewska, E. (2009). Development of prefabricated timber-concrete composite floors (ed.). (Doctoral dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Development of prefabricated timber-concrete composite floors
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Timber-concrete composite structures were originally developed for bridges and upgrading of existing timber floors, but finds today new applications in multi-storey buildings. Most of the research performed to date has been focused on systems where "wet" concrete is cast on top of timber beams with mounted connectors. A novel composite system where the concrete slab is prefabricated off-site with the connectors embedded and then connected on-site to the timber joists is presented in this thesis.A notable benefit of prefabricating the concrete slab is that most of the concrete shrinkage will develop when the slab is not yet connected to the timber beam, markedly reducing the correlated increase in deflection and flexural stresses in the composite beam. Another advantage of the prefabrication is the reduction in construction cost by moving work from the building site to the workshop. In this research special attention has been paid to develop and use connection systems easy to produce and mount in order to speed up the construction process.Different types of shear connectors suitable for prefabrication were investigated; coach screws (alone or combined with a timber joist notch), metal plates (glued or nailed), dowels, and toothed metal plates embedded in the concrete slab. The experimental test programme includes: (i) direct shear tests to failure of 7 different connection systems, (ii) full-scale bending tests to failure followed by a numerical analysis, (iii) long-term tests under sustained load of full-scale composite beams and a following numerical analysis. The outcomes of the experimental tests show that it is possible to achieve good structural performance with a prefabricated system, particularly using the connection with coach screws and timber notches. The mechanical properties of the prefabricated connections can be used in the design method in Eurocode 5.The experimental-numerical investigations indicate that the new shear connections are suitable for prefabricated timber-concrete composite structures and perform equally well as "wet" systems. It is possible to achieve high load-carrying capacity and stiffness (up to 98%) using the new shear connectors. It is feasible to manufacture timber-concrete composite structures as prefabricated elements. An additional benefit is that some of the systems are fully demountable, allowing the owner to dissemble the timber beams and concrete panels at the end of their service life.From the numerical analysis it was found that at the end of service life (50 years) the prefabricated timber-concrete composite floors behave adequately. The mid-span deflection is within the acceptable limit of L/250. Numerical studies show that prefabrication off-site of the concrete slab results in a reduction of the long-term deflection if the slab is cured for at least 56 days before it is connected to the timber beam. Furthermore, the construction method (propped or unpropped) affects traditional timber-concrete systems with cast-in-situ concrete more. The props should be left in place for at least seven days using cast-in-situ concrete, while for prefabricated concrete slabs the props need to be left in place only for one day, leading to a significant economic advantage. Lastly, the long-term deflection is hardly affected by the time between the end of construction and the live load application.

Abstract [sv]

Samverkanskonstruktioner i trä och betong utvecklades ursprungligen för broar och uppgradering av träbjälklag, men idag används de även i flervåningshus. Merparten av den forskning som genomförts på dessa konstruktionssystem har fokuserat på fallet när förbindare förmonterats i träbalkarna och en betongplatta sedan gjutits ovanpå. I den här avhandlingen presenteras ett nytt sätt att tillverka samverkanskonstruktioner där förbindarna gjuts in i betongplattan och träbalkarna monteras efter att betongplattan härdat. En fördel med att prefabricera betongplattan är att betongens krympning utvecklas innan plattan sätts ihop med träbalkarna, vilket starkt reducerar krympningens ökning av nedböjning och böjspänning i samverkanskonstruktionen. En annan fördel är att prefabricering reducerar kostnaderna genom att flytta arbete från byggplats till fabrik. Forskningen i denna avhandling har särskilt fokuserat på att utveckla förband som är enkla att producera och montera för att effektivisera byggprocessen.Olika typer av förbindare lämpade för prefabricering har undersökts; franska träskruvar (ensamma eller i kombination med ett urtag i träbalken), stålplåtar (limmade eller spikade), dymlingar och spikplåtar som gjutits in i betongplattan. De experimentella testerna har omfattat; (i) skjuvförsök på 7 olika förbandstyper, (ii) böjprov i full skala till brott kompletterat med en numerisk analys och (iii) långtidsförsök i full skala med konstant last kompletterat med numerisk analys. Resultaten av experimenten visar att det är möjligt att åstadkomma goda mekaniska egenskaper för prefabricerade system, särskilt om förbandstypen med franska träskruvar kombinerat med ett urtag i balken används. De mekaniska egenskaperna för de prefabricerade förbanden kan användas i dimensioneringsmetoden i Eurocode 5.De experimentella och numeriska undersökningarna visar att de nya förbandstyperna är lämpliga för prefabricerade samverkanskonstruktioner och att de har samma prestanda som platsgjutna system. Det är möjligt att nå hög bärförmåga och styvhet (upp till 98% samverkansgrad) med de nya förbanden. Det är också möjligt att tillverka prefabricerade samverkansbjälklag och vissa av dem har också fördelen att de kan demonteras när livslängden nåtts.De numeriska analyserna visar att i slutet av livslängden (50 år) har prefabricerade system fortfarande goda mekaniska egenskaper. Nedböjningen i mittsnitt ligger inom den accepterade nedböjningen L/250 (Eurocode 5). Från de numeriska analyserna kan man också konstatera att prefabricering resulterar i en reduktion av nedböjningen över tid om betongplattan får härda åtminstone 56 dagar innan den sätts samman med träbalkarna. Produktionsmetoden för bjälklagen (stämpat eller inte) påverkar de platsgjutna systemen mera. Stämpen skall lämnas kvar i minst sju dagar i ett platsgjutet system, medan i ett prefabricerat system kan stämpen tas bort efter en dag, vilket leder till en ekonomisk fördel. Slutligen kan konstateras att långtidsnedböjningen påverkas mycket lite av tiden mellan montage och påförsel av nyttig last.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2009. p. 300
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Building Technologies
Research subject
Timber Structures
Identifiers
urn:nbn:se:ltu:diva-18042 (URN)680a7ac0-8b2d-11de-8da0-000ea68e967b (Local ID)978-91-86233-85-3 (ISBN)680a7ac0-8b2d-11de-8da0-000ea68e967b (Archive number)680a7ac0-8b2d-11de-8da0-000ea68e967b (OAI)
Note
Godkänd; 2009; 20090817 (elzluk); DISPUTATION Ämnesområde: Träbyggnad Opponent: Professor Hans-Joachim Blass, Universität Karlsruhe, Tyskland Ordförande: Professor Lars Stehn, Luleå tekniska universitet Tid: Onsdag den 30 september 2009, kl 10.00 Plats: F1031, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Lukaszewska, E., Johnsson, H. & Fragiacomo, M. (2008). Performance of connections for prefabricated timber-concrete composite floors (ed.). Paper presented at . Materials and Structures, 41(9), 1533-1550
Open this publication in new window or tab >>Performance of connections for prefabricated timber-concrete composite floors
2008 (English)In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 41, no 9, p. 1533-1550Article in journal (Refereed) Published
Abstract [en]

Timber-concrete composite beams and slabs require interlayer connectors, which provide composite action in the cross-section. A range of mechanical connectors is available on the market with an extensive variety of stiffness and strength properties, which are fundamental design parameters for the composite structure. Another crucial parameter is the cost of the connector, including the labour cost, that if too high may prevent the use of the composite system. In order to reduce the construction cost and make timber-concrete structures more widespread on the market, it is believed that a high degree of prefabrication should be achieved. For a simple and cost effective construction process, the use of "dry" connections, which do not require the pouring and curing of concrete on site, may represent a possible solution. This paper reports the outcomes of an experimental programme aimed to investigate a number of different mechanical "dry-dry" connectors previously embedded into a prefabricated concrete slab. Direct shear tests on small blocks made of a glulam segment connected with a prefabricated concrete slab were performed. The shear force-relative slip relationships were measured and all the relevant mechanical properties such as slip moduli and shear strengths were calculated. It was found that some of the new developed connection systems for prefabricated concrete slab can perform as satisfactorily as those for cast-in-situ slabs, with the additional benefit of being relatively inexpensive.

National Category
Building Technologies
Research subject
Timber Structures
Identifiers
urn:nbn:se:ltu:diva-4940 (URN)10.1617/s11527-007-9346-6 (DOI)000260012300006 ()2-s2.0-54149083234 (Scopus ID)2f0787c0-65de-11dc-8a3f-000ea68e967b (Local ID)2f0787c0-65de-11dc-8a3f-000ea68e967b (Archive number)2f0787c0-65de-11dc-8a3f-000ea68e967b (OAI)
Note
Validerad; 2008; 20070918 (elzluk)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-08-07Bibliographically approved
Lukaszewska, E. & Fragiacomo, M. (2008). Static performance of prefabricated timber-concrete composite systems (ed.). In: (Ed.), (Ed.), Conference Proceedings, 10th World Conference in Timber Engineering: . Paper presented at World Conference on Timber Engineering : 02/06/2008 - 05/06/2008.
Open this publication in new window or tab >>Static performance of prefabricated timber-concrete composite systems
2008 (English)In: Conference Proceedings, 10th World Conference in Timber Engineering, 2008Conference paper, Published paper (Refereed)
Abstract [en]

Timber-concrete composite beams and slabs require interlayer connection, which provides composite action for the cross-section. A range of mechanical connectors is available on the market with an extensive variety of stiffness and strength properties, which are fundamental design parameters for the composite structure. Stiff and strong connection systems are highly desirable in order to achieve high composite action. At the same time, however, the connectors should be inexpensive, so as to make the composite beam an economically viable alternative to the traditional precast concrete and steel-concrete composite floor systems. This paper reports the outcomes of an experimental programme carried out on timber-concrete composite systems with prefabricated concrete slabs. The programme included shear tests to failure of different connection systems and 4-point bending tests to failure of five 4.8m long timber-concrete composite beam specimens. Based on the outcomes of the shear tests, two different connector types were selected for the full-scale beam tests: (i) steel tubes inserted into the concrete slab and screwed to the glulam beam, and (ii) single folded steel plates nailed to both sides of the glulam beam and welded onto a long punched metal plate embedded into the concrete slab. The new systems based on mechanical "dry-dry" connectors embedded into a pre-cast concrete slab have the advantage of not requiring pouring and curing of concrete on site. This will result in a significant improvement in the entire construction process by achieving higher quality while saving resources and simplifying recycling of waste.The beam specimens were ramp loaded to failure to assess the structural performance at ultimate and serviceability limit state. Mid-span deflection, applied load, and slip distribution along the beam length were monitored during the tests. The efficiencies of the new proposed connection systems, calculated by comparing the experimental results with the analytical limits of full and no composite action, were found to be in the same range as for connections with cast-in-situ concrete slabs. Some improvements such as a larger number of nails or larger diameter nails or screws are possible for the connection with metal plates nailed to the glulam beam in order to increase the composite action achievable by the system.The experimental load-displacement curves and slip distribution along the beam length were compared with the outcomes of a numerical analysis performed using a uniaxial finite element model purposely developed for timber-concrete composite beams. The actual shear force-relative slip measured in the shear tests were implemented in the software. Very good agreement was found, enabling the use of the program for parametric studies aimed to extend the experimental results to composite beams with different geometrical and mechanical properties. The use of the analytical formulae suggested by Ceccotti in accordance with the Eurocode 5 was found to provide acceptable accuracy for the design of the composite structure. In conclusion, the new developed composite systems based on the use of concrete slab prefabricated off-site and connected on site with timber beam can represent a viable alternative to the traditional composite systems with cast-in-situ concrete topping, with similar efficiencies achievable but all the advantages of the prefabrication.

National Category
Building Technologies
Research subject
Timber Structures
Identifiers
urn:nbn:se:ltu:diva-31775 (URN)60d59770-d103-11dc-9ad7-000ea68e967b (Local ID)60d59770-d103-11dc-9ad7-000ea68e967b (Archive number)60d59770-d103-11dc-9ad7-000ea68e967b (OAI)
Conference
World Conference on Timber Engineering : 02/06/2008 - 05/06/2008
Note
Godkänd; 2008; 20080201 (elzluk)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Lukaszewska, E., Fragiacomo, M. & Frangi, A. (2007). Evaluation of the slip modulus for ultimate limit state verifications of timber-concrete composite structures (ed.). In: (Ed.), (Ed.), CIB-W18: Meeting forty, Bled, Slovenia, August 2007. Paper presented at International Council for Research and Innovation in Building and Construction : Working Commission W18 - Timber Structures, CIB-W18 28/08/2007 - 31/08/2007. Karlsruhe: Lehrstuhl für Ingenieurholzbau und Baukonstruktionen, Univ. Karlsruhe
Open this publication in new window or tab >>Evaluation of the slip modulus for ultimate limit state verifications of timber-concrete composite structures
2007 (English)In: CIB-W18: Meeting forty, Bled, Slovenia, August 2007, Karlsruhe: Lehrstuhl für Ingenieurholzbau und Baukonstruktionen, Univ. Karlsruhe , 2007Conference paper, Published paper (Other academic)
Abstract [en]

In recent years the strength and stiffness upgrading of existing buildings with timber floors has drawn attention to an efficient type of floor system, the timber-concrete composite slab, which consists of timber members connected to a concrete slab using a connection system. Compared to timber floors the main advantages of this type of composite structure are increased strength and stiffness, improved sound insulation and fire resistance.The structural behaviour of timber-concrete composite members is mainly governed by the shear connection between timber and concrete. A rigid connection develops full composite action between the components and therefore conventional principles of structural analysis can be applied. Full composite action may be achieved by grooved connections. On the other side connections based on mechanical fasteners like screws, nails, glued-in dowels mostly show elastic behaviour and develop only partial composite action. Therefore the structural analysis requires in this case the consideration of the slip between the components. Eurocode 5, Annex B gives a simplified calculation model for mechanically jointed beams, based on the differential equation for the partial composite action. As the shear connection usually shows a non-linear load-slip relationship, two different slip moduli are considered for design purposes: Kser for the serviceability limit state (SLS) and Ku for the ultimate limit state (ULS). The slip modulus Kser is usually evaluated by push-out tests according to EN 26891 and corresponds to the secant value at 40% of the load-carrying capacity of the connection. For the slip modulus Ku it is suggested to use the secant value at 60% (see for example STEP 2). According to Eurocode 5 the slip modulus Ku may be taken as 2/3 of Kser. Depending on the structural behaviour of the connection used (rigid, semi-rigid, etc) the assumption for Ku according to Eurocode 5 may be not adequate, leading to conservative or not conservative results.As the shear connections markedly influence the efficiency of timber-concrete composite slabs, a large number of push-out tests on different connection systems as well as bending tests on timber-concrete composite members have been performed worldwide (Sweden, Italy, Switzerland, Portugal, Germany, USA, etc.). The test results in combination with additional FE numerical simulations permit to check whether the hypothesis of assuming the slip modulus for ULS as two-thirds of the slip modulus for SLS is adequate. The first part of the paper presents the slip moduli K40% and K60% as well as the ratios K60%/K40% evaluated by push-out tests for different connection types. Further the slip moduli K40% are compared to analytical calculations according to Eurocode 5. In the second part analytical calculations are compared to bending test results and numerical simulations for different timber-concrete composite members. For the analytical calculations based on Annex B of Eurocode 5 the slip modulus K60% as suggested in STEP 2 is used. The aim of the analysis is to demonstrate that the use of K40% and K60% leads to accurate results for SLS and ULS, respectively. Finally based on the ratios K60%/K40% the assumption according to Eurocode that Ku may be taken as 2/3 of Kser is verified and if necessary improved.

Place, publisher, year, edition, pages
Karlsruhe: Lehrstuhl für Ingenieurholzbau und Baukonstruktionen, Univ. Karlsruhe, 2007
National Category
Building Technologies
Research subject
Timber Structures
Identifiers
urn:nbn:se:ltu:diva-27832 (URN)16329fb0-65d8-11dc-8a3f-000ea68e967b (Local ID)16329fb0-65d8-11dc-8a3f-000ea68e967b (Archive number)16329fb0-65d8-11dc-8a3f-000ea68e967b (OAI)
Conference
International Council for Research and Innovation in Building and Construction : Working Commission W18 - Timber Structures, CIB-W18 28/08/2007 - 31/08/2007
Note
Godkänd; 2007; 20070918 (elzluk)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Johnsson, H., Stehn, L. & Lukaszewska, E. (2006). Connections for prefabricated timber-concrete composite systems (ed.). In: (Ed.), (Ed.), 9th World Conference on Timber Engineering: WCTE 2006. Proceedings. Paper presented at World Conference on Timber Enginnering : 06/08/2006 - 10/08/2006.
Open this publication in new window or tab >>Connections for prefabricated timber-concrete composite systems
2006 (English)In: 9th World Conference on Timber Engineering: WCTE 2006. Proceedings, 2006Conference paper, Published paper (Refereed)
National Category
Building Technologies
Research subject
Timber Structures
Identifiers
urn:nbn:se:ltu:diva-40548 (URN)41049115647 (Scopus ID)fb908d20-b6d7-11db-abff-000ea68e967b (Local ID)fb908d20-b6d7-11db-abff-000ea68e967b (Archive number)fb908d20-b6d7-11db-abff-000ea68e967b (OAI)
Conference
World Conference on Timber Enginnering : 06/08/2006 - 10/08/2006
Note
Godkänd; 2006; Bibliografisk uppgift: CD-ROM, no. of presentation 2.7.2, Wood-concrete Connection Session; 20070207 (ysko)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-08-07Bibliographically approved
Johnsson, H., Lukaszewska, E. & Stehn, L. (2004). Nailed timber joints with a thick interlayer (ed.). In: (Ed.), (Ed.), 8th World Conference on Timber Engineering: WCTE 2004. Proceedings. Paper presented at World Conference on Timber Engineering : 14/06/2004 - 17/06/2004 (pp. 281-284).
Open this publication in new window or tab >>Nailed timber joints with a thick interlayer
2004 (English)In: 8th World Conference on Timber Engineering: WCTE 2004. Proceedings, 2004, p. 281-284Conference paper, Published paper (Refereed)
National Category
Building Technologies
Research subject
Timber Structures
Identifiers
urn:nbn:se:ltu:diva-31589 (URN)5d026a00-56de-11dc-a7ae-000ea68e967b (Local ID)5d026a00-56de-11dc-a7ae-000ea68e967b (Archive number)5d026a00-56de-11dc-a7ae-000ea68e967b (OAI)
Conference
World Conference on Timber Engineering : 14/06/2004 - 17/06/2004
Note
Godkänd; 2004; 20070830 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-08-07Bibliographically approved
Organisations

Search in DiVA

Show all publications