The paper presents the results of experimental tests of some composite steel-concrete, wood-concrete and concrete-concrete elements. Deflections at midspan under monotonically increasing static load were measured. The influence of different composite making means on the results was researched. The emphasis was given to efficiency of different composites with Omnia-slabs that are commonly used in practice

Harapin, Alen

Radnić, Jure

Ćubela, Dragan

English

Hrčak - Portal of scientific journals of Croatia

J. Radniæ, D. Æubela, A. Harapin: Experimental tests of some composite steel-concrete, wood-concrete and concrete-concrete elementsENGINEERING MODELLING 16 (2003) 3-4, 121-127 121SUMMARYThe paper presents the results of experimental tests of some composite steel-concrete, wood-concrete andconcrete-concrete elements. Deflections at midspan under monotonically increasing static load were measured.The influence of different composite making means on the results was researched. The emphasis was given toefficiency of different composites with Omnia-slabs that are commonly used in practice.Key words: experiment, composite element, steel-concrete, wood-concrete, concrete-concrete, static load,deflection.1. INTRODUCTIONFor testing purposes of a numerical model forsimulation of composite structures exposed to short-term static loads, which will be presented in some ofthe next issues of this magazine, experimental tests ofseveral composite elements made of different materialsand with different composite making methods [1] werecarried out. Description of carried out experiments andan overview of the results are presented in this paper.Behaviour of composite girders exposed tomonotonously increasing static load to fracture wasobserved. Load was applied by hydraulic press atmidspan. Load-bearing system of all tested elementswas a simple beam. Deflections at midspan weremeasured. Relationship between the load (force) P andmeasured deflection δ is shown on P-δ diagram for allelements. Obtained diagrams show effects of differentcomposite making methods. It is followed by andoverview of carried out experimental tests per separatecomposite types (steel-concrete, wood-concrete andconcrete-concrete). Three equal elements were madeUDC 539.384:531.7:624.016Preliminary communicationReceived: 05.06.2003.Experimental tests of some compositesteel-concrete, wood-concrete andconcrete-concrete elementsJure Radniæ(1), Dragan Æubela(2) and Alen Harapin(1)(1)University of Split, Faculty of Civil Engineering, Matice hrvatske 15, HR-21000 Split, CROATIAe-mail: Jure.Radnic@gradst.hr, Alen.Harapin@gradst.hr(2)University of Mostar, Faculty of Civil Engineering, Kralja Zvonimira 14, BiH-88000 Mostar,BOSNIA AND HERZEGOVINAand tested for each composite type and compositemaking mean. As decisive, average value of measureddata for all three elements was presented.2. STEEL AND CONCRETE COMPOSITESGeometry of tested composite girder is shown inFigure 1. Composite girder is made of rolled steelsection IPE 100 and reinforced concrete slab. Girderlength is 300 cm, while total height of a compositecross-section is 16 cm.Steel girder IPE 100 is 10 cm high with 5.5 cm wideflange, made of steel St 240/360.Reinforced concrete slab is 45 cm wide and 6 cmhigh. It is made of MB 30 concrete [2] with theaggregate grains ≤ 16 mm because of small slabthickness. Concreting was carried out on vibratingtable, with usual curing. The following concreteproperties were determined experimentally on the dayof testing [2]: compressive strength 31.5 MPa, tensilestrength 2.40 MPa and modulus of elasticity 3.00 GPa.J. Radniæ, D. Æubela, A. Harapin: Experimental tests of some composite steel-concrete, wood-concrete and concrete-concrete elements122 ENGINEERING MODELLING 16 (2003) 3-4, 121-127Slab was reinforced at mid-height by welded wire-fabric reinforcement Q-196 (φ6.0/10 cm in bothdirections). Wire-fabric reinforcement quality was MA500/560 [2]. Experimentally determined tensilestrength was 650 MPa.Steel girder and concrete slab were made compositeby dowels shown in Figure 1c. Dowels are made ofsmooth reinforcement φ8 mm in diameter and steelquality St 500/560. They are 4 cm wide and 5 cm high,welded to the top flange of steel girder in the length of5 cm. They are placed at 10 cm axial distance alongthe composite girder length. Selected dowel typepertains to the so-called slender dowels.Supports and loads of a composite girder are shownin Figure 2. Girder span is 2.8 m. It is supported byFig. 1  Geometry of composite steel-concrete girder (dimensions in cm)steel roller bearings of 30 mm diameter. Force isapplied via stiff steel I section for purposes of uniformforce distribution along concrete slab width.Relationship between applied force P and measureddeflection δ is shown in Figure 3. Linear behaviour ofcomposite girder to about 75% of ultimate bearingcapacity can be observed, after which there is non-linear behaviour due to dowel yielding. The loss ofbearing capacity of composite girder is a consequenceof concrete slab fracture around midspan.For an illustration of the effect of beam and slabcomposite, the same figure shows P-δ relationship for(non-composite) steel section IPE 100. Girder behaviourhas not been monitored to the moment of fracture, butto the occurrence of large deflections (40 mm≈L/70).Fig. 2  Scheme of supports and loads of composite girderFig. 3  Girder deflection at midspan29x10=290453005IPE 100Q-1965.5MB 301016610655 554516a) longitudinal sectionb) cross-section c) dowelsDowel140280140δPRIGID STEEL GIRDERROLLER BEARING1010OF 30 mm DIAEMETER01020304050600 5 10 15 20 25 30 35 40displacement δ (mm)force P (kN)Composite steel girderSteel grider onlyJ. Radniæ, D. Æubela, A. Harapin: Experimental tests of some composite steel-concrete, wood-concrete and concrete-concrete elementsENGINEERING MODELLING 16 (2003) 3-4, 121-127 1233. WOOD AND CONCRETE COMPOSITEGeometry of tested wood-concrete compositegirders is shown in Figure 4. Composite girders weremade of wooden beam and reinforced concrete slab.Girder length is 300 cm, while total height of acomposite cross-section is 16 cm.Wooden beam of square cross-section 10/10 cm ismade of coniferous lumber of Class II. The followingwood properties were determined experimentally on theday of testing [3]: modulus of elasticity in direction ofwood fibers 7.0 GPa, axial tension strength 31.5 MPaand axial compression strength 31.5 MPa. It shall bementioned that there were many natural anomalies inthe wooden beam structure (knots, fiber deviation etc.)along the length as well as per cross-section height.Reinforced concrete slab is 50 cm wide and 6 cm high.It is made of MB 30 concrete [2] with the aggregate grains≤ 16 mm. Concreting was carried out on vibrating table.The following concrete properties were determinedexperimentally on the day of testing: compressivestrength, tensile strength and modulus of elasticity (Table1). Slab was reinforced at mid-height by welded wire-fabric reinforcement Q-196 (φ 6.0/10 cm in bothdirections) of MA 500/560 quality [2]. Experimentallydetermined fracture strength was 650 MPa.Table 1 Tested concrete properties [2]GirdertypeCompressive strength[MPa]Tensile strength[MPa]Modulus of elasticity[GPa]N1 31.5 2.40 30.0N2 32.4 2.41 30.5N3 31.5 2.40 30.0wide and 12 cm high. At the bottom, dowels arepointed for better penetration into lumber. Beforedowel placement, holes of 7 mm diameter were drilledthrough wooden beam and filled with epoxy glue forbetter connection between the dowel and lumber.Dowels are placed at 10 cm axial distance along thecomposite girder length.Girder N2 - composite by epoxy glue and “dry gluing”Wooden beam and concrete slab were madecomposite by two-component epoxy glue NOVOPOXUV, manufactured by Nova-chem, Karlovac. Ratio ofcomponent mixing was A:B=9:5 (volume). For thistype of girder, reinforced concrete slab has alreadybeen concreted. At concrete age of 21 days, beam andslab were glued by “dry gluing”. Beam and slab contactsurfaces were well cleaned. Glued contact withstoodcompression for 48 hours.Girder N3 - composite by epoxy glue and “wet gluing”Wooden beam and concrete slab were madecomposite by the same epoxy glue as for girder N2,but by the “wet gluing”. Namely, glue film was appliedon the top chord of wooden beam immediately beforeslab concreting. Then, fabric reinforcement was placedand concreting was carried out on vibrating table.Load-bearing system and load transfer from thepress to the girder are the same as for steel-concretecomposite girder (see Figure 6). Steel washer of 100/100/8 mm size was added between roller bearing andwooden beam to prevent local pressing of rollerbearing into the wood.Relationship between force and displacement atmidspan for all three composite girder types is shownin Figure 7. As can be observed, behaviour of girdersN2 and N3 is very similar, although deflections aresomewhat smaller and fracture force is somewhatgreater for girder N2. Sliding of joint plane has notbeen observed while fracture occurred through tensilezone of wooden beam. Deflections were greater andfracture force smaller for girder N1, which points tosmaller efficiency of dowels in comparison withcomposite by gluing.Three different wood-concrete composite typeswere analyzed (see Figure 5). Dowels were used forgirder N1 while girders N2 and N3 were madecomposite by gluing. Detail description of compositemaking method is given hereinafter.Girder N1 - composite by dowelsFor this type of girder, composite was made by steeldowels. Dowels are made of smooth reinforcement of8 mm diameter and St 500/560 quality. They are 6 cmFig. 4  Basic geometry of wood-concrete composite girder (dimensions in cm)300TIMBER BEAM (CONIFEROUS LUMBER OF CLASS II)610a) longitudinal sectionMB 30Q-19650106101616b) cross-sectionJ. Radniæ, D. Æubela, A. Harapin: Experimental tests of some composite steel-concrete, wood-concrete and concrete-concrete elements124 ENGINEERING MODELLING 16 (2003) 3-4, 121-127Fig. 5  Wooden beam and reinforcement slab composites (dimensions in cm)Fig. 6  Scheme of supports and loads of composite girderFig. 7  Deflection at girder midspanRelationship P-δ was also shown for (non-composite) wooden beam. There is a drastically greaterdeformability and far smaller bearing capacity ofwooden beam than for composite girder.epoxy glue - "dry gluing"epoxy glue - "wet gluing"longitudinal section1010105 10 10105 10105 10cross-section505050(a) Girder N1 - composite by dowels10 10 10 10 10 10101010101010 101010 10os simetrije1010os simetrijedowel75os simetrijedowel1012epoxy610106epoxyglue1010glue1261616106dowel16longitudinal sectionlongitudinal sectioncross-sectioncross-section(b) Girder N2 - composite by epoxy glue, "dry gluing"(c) Girder N3 - composite by epoxy glue,"wet gluing"28010Pδ10RIGID STEEL GIRDERROLLER BEARINGOF 30 mm DIAMETERSTEEL WASHER 100/100/10 mm051015202530350 5 10 15 20 25 30 35 40displacement δ (mm)force P (kN)Girder N1 - composite by dowelsGirder N2 - composite by  "dry gluing"Girder N3 - composite by "wet gluing"Timber beam onlyJ. Radniæ, D. Æubela, A. Harapin: Experimental tests of some composite steel-concrete, wood-concrete and concrete-concrete elementsENGINEERING MODELLING 16 (2003) 3-4, 121-127 1254. CONCRETE-CONCRETE COMPOSITESConcrete-concrete composites were tested onreinforced concrete Omnia-slabs of 150 cm length,100 cm width and 10 cm total height. Slabs wereconcreted on vibrating table. Because of smallthickness of composite elements, concrete aggregatewith grains ≤ 16 mm was used. Slabs were reinforcedin top and bottom zone by welded wire-fabricreinforcement MA 500/560 of Q-196 type (φ 6.0/10 cmin both directions). Reinforcement protective concretecover in both zones was 1 cm.Several different composite slab types were tested(see Figure 8) in order to observe their efficiency. SlabP1 is monolithic of 10 cm height. Other slabs arecomposite ones i.e. concreted in two phases. Bottomslab of 4 cm height was concreted in phase I while 6cm high top slab was concreted after 21 days (phaseII). Detail description of different composite slab typesis given hereinafter.Fig. 8  Types of tested composite slabs (dimensions in cm)150150150150150150100100100100100100MB 30MB 30MB 30Q-196Q-196Q-196Q-196Q-196Q-196Q-196Q-1964644646MB 30MB 30MB 30Q-196Q-196Q-196Q-1966410MB 30MB 30MB 30Q-196Q-196Q-196Q-196Q-196Q-196Q-196Q-196MB 3010101010Q-196Q-196Q-196Q-196MB 30MB 30106longitudinal section cross-sectionlongitudinal section cross-sectionlongitudinal section cross-sectionlongitudinal section cross-sectionlongitudinal section cross-sectionlongitudinal section cross-section(a) Plate P1 - monolithic slab(b) Plate P2 - oiled contract surfaceOILED CONTRACT SURFACE(c) Plate P3 - roughened contract surfaceROUGHENED CONTRACT SURFACE(d) Plate P4 - composite by dowels and oiled contact surfaceDOWELS DOWELSOILED CONTRACT SURFACEROUGHENED CONTACT SURFACEDOWELS DOWELSDOWELS DOWELSSN-BINDER ONCONTACT SURFACE(e) Plate P5 - composite by dowels and roughened contact surface(d) Plate P6 - composite by dowels and SN-binder on contact surfaceJ. Radniæ, D. Æubela, A. Harapin: Experimental tests of some composite steel-concrete, wood-concrete and concrete-concrete elements126 ENGINEERING MODELLING 16 (2003) 3-4, 121-127130656510δPROLLER BEARINGOF 30 mm DIAMETER10RIGID STEEL GIRDER7 7388Slab P1 - monolithic slabSlab P1 is a conventional monolithic reinforcedconcrete slab, concreted in full height of 10 cm.Slab P2 - oiled contact surfaceBefore concreting of the top slab, top surface of abottom slab was oiled with OPLATAN, formwork oil.The purpose was to diminish slab composite effect.Slab P3 - roughened contact surfaceTop surface of bottom slab of phase I was wellroughened to provide for better connection with thetop slab of phase II.Dowels were used for slabs P4, P5 and P6 (Figure9). Dowels are made of smooth reinforcement of 5 mmdiameter and St 500/560 quality. They are placed inbottom slabs in phase I, at 10 cm axial distance alongthe slab length. There are two rows of dowels within thecross-section, at 50 cm axial distance.Fig. 10  Scheme of supports and loads of Omnia-slabConcreting phase Compressive  strength (MPa) Tensile  strength (MPa) Modulus of  elasticity (GPa) Phase I  32.4 2.41 30.5 Phase II  31.5 2.40 30.0 Fig. 9  Dowels for composite Omnia-slabsSlab P4 - composite by dowels, oiled contact surfaceComposite was made with dowels. Top surface ofbottom slab (phase I) was oiled with OPLATAN.Slab P5 - composite by dowels, roughened contactsurfaceComposite was made with dowels. Top surface ofbottom slab was roughened as for slab P3.Slab supports and loads are shown in Figure 10.Slabs are in the form of simple girder with the span1.30 m. They are supported by steel roller bearings of30 mm diameter. Force is transferred from the press tothe slab via rigid steel I section (for a uniform loaddistribution per slab width). Relationship betweenforce and displacement for all slab types is shown inFigure 11.Slab P6 - composite by dowels, contact surface coatedwith SN binderComposite was made with dowels in combinationwith SN binder film on top surface of bottom slab.One-component acrylic binder NOVACRYL UV,manufactured by NOVA-chem Karlovac, was used.The following concrete properties were determinedexperimentally on the day of testing [2]: compressivestrength, tensile strength and modulus of elasticity(Table 2).Quality of used fabric reinforcement was alsoexperimentally determined. Obtained reinforcementfailure limit was above the rated one, being 650 MPa.Table 2 Tested concrete propertiesFig. 11  Deflection at slab midspan051015202530350 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5displacement δ (mm) force P (kN)P1 - Monolithic slab P2 - Oiled contact surfaceP3 - Roughened contact surfaceP4 - Oiled contact surface with dowelsP5 - Roughened contact surface with dowels P6 - SN binder with dowels P1P6P5P4 P3P2J. Radniæ, D. Æubela, A. Harapin: Experimental tests of some composite steel-concrete, wood-concrete and concrete-concrete elementsENGINEERING MODELLING 16 (2003) 3-4, 121-127 127As can be observed, the best results were obtainedfor monolithic slab P1, while the worst ones were forslab P2. With an exception of oiled slab P2, all slabshave similar deformability at small loads. Linearitylimit is the lowest for slab P4, and the highest formonolithic slab P1. Linearity limit for slabs P3, P5 andP6 is between those two values. After occurrence ofthe first cracks, monolithic slabs showed the bestbehaviour. Composite slabs P5 and P6, showed closeresults. For smaller loads, slab P3 shows better resultsthan slab P4. However, that relation changes with theload increase. Obviously, behaviour of composite slabsstrongly depends on composite making method, whichis particularly pronounced in post-elastic zone (afteroccurrence of the first cracks and begging of compositejoint sliding). Slab P2 showed unexpectedly goodresults, which proves that roughness of contact surfacegreatly affects the composite degree.5. CONCLUSIONSBased on carried out experimental tests of compositeelements of steel-concrete, wood-concrete and concrete-concrete systems, the following can be concluded:− Soft (elastic) dowels for composites made ofsteel beam and compressive concrete slab areefficient and provide high degree of compositecross-section of steel-concrete system.− Wooden beam and compressive concrete slabcomposite made by gluing are more efficientthan composites with conventional dowels.− Wooden beam and compressive concrete slabcomposites made by “dry” gluing and “wet”gluing show similar results. “Dry” gluing wassomewhat more efficient (see Ref. [4]).− Composite level between prefabricated concreteOmnia-slabs and monolithic concrete abovethem, i.e. deflections of composite slabs,strongly depend on composite type.− For composites made of prefabricated concreteOmnia-slabs and monolithic concrete abovethem by adequately shaped dowels, andnormally rough top surface of Omnia-slabcoated with SN binder, very high compositelevel is obtained. Namely, behaviour of suchcomposite element is very close to that of amonolithic slab of the same thickness.Extremely favorable results are also obtainedfor similar composite making without SN-binder, which is commonly used in practice.− Even when dowels have not been used atcontact surface, there is relatively highcomposite level between Omnia-slab andmonolithic concrete by adhesion and frictiononly.6. REFERENCES[1] D. Æubela, Numerical simulation of compositestructures, Master’s Thesis, Faculty of CivilEngineering, University of Split, Split, 2003. (inCroatian)[2] Regulations on Technical Standards for Concreteand Reinforced Concrete, Official Gazette, No.11, 1987. (in Croatian)[3] ENV 1995: Design of Timber Structures,European Committee for Standardization,Bruxelless, 1994.[4] J. Radniæ, D. Graniæ and A. Domazet, Somepossibilities of wood and concrete composites,Graðevinar, Vol. 47, No. 3, pp. 321-327, 1995.(in Croatian)EKSPERIMENTALNA ISPITIVANJA NEKIH SPREGNUTIH ELEMENATA SUSTAVAÈELIK-BETON, DRVO-BETON I BETON-BETONSAETAKU radu su prikazani rezultati eksperimentalnih ispitivanja nekih spregnutih elemenata sustava èelik-beton, drvo-beton i beton-beton. Mjereni su progibi u sredini raspona nosaèa pod monotono rastuæim statièkim optereæenjem.Istraen je utjecaj pojedinih tipova sredstava za sprezanje na dobivene rezultate. Naglasak je stavljen na utvrðivanjeuèinaka razlièitih naèina sprezanja omnia ploèa koje se èesto koriste u praksi.Kljuène rijeèi: eksperiment, spregnuti element, èelik-beton, drvo-beton, beton-beton, statièko optereæenje, progib.

Experimental tests of some composite steel-concrete, wood-concrete and concrete-concrete elements

Abstract

Similar works

Full text

Available Versions

Hrčak - Portal of scientific journals of Croatia