Hollow core slabs and fire

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					Hollow core slabs and fire                                          2005-06-13




Hollow core slabs and fire
- Documentation on shear capacity




                                                     Prepared for
                             DANISH PREFAB CONCRETE ASSOCIATION
                                                      June 2005




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Synopsis


For many years it has been common, international practice to use hollow core slabs
for compartmentation of storeys requiring 60, 90 or 120 minutes’ fire resistance.
This has been done by supplementing the cold condition design with the require-
ments for flexural capacity in the fire event.


There is no known test documentation or calculation method available, which can
be used for direct determination of the shear capacity during a fire event. Previ-
ously many tests have confirmed that the hollow core slab elements can resist fire
for 60, 90 and 120 minutes when moderately loaded.


In April 2005, the Danish Prefab Concrete Association instigated fire tests with hol-
low core slabs exposed to high loads and associated high displacement forces. The
tests show that correctly mounted hollow core slabs provide excellent fire resis-
tance both during a 60 minute standard fire event and in the subsequent cooling
phase.


The conclusion of the tests is that in general it will be acceptable to use hollow core
slabs in buildings requiring 60 minute fire resistance, if the displacement forces of
the fire incident do not exceed 75% of the calculated cold shear capacity condition,
as determined in DS411 based on function tests with loading arrangement defined
in DS/EN 1168.


In this context it is assumed that the minimum requirements for reinforced joints
have been met as specified in the Danish Prefab Concrete Association’s Guidelines.




Copenhagen, June 2005                                            Jesper Frøbert Jensen




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List of Contents


1       Background ....................................................................... 4


2       Conclusion ......................................................................... 6


3       Test Methodology .............................................................. 8

        3.1     Purpose ................................................................................... 8
        3.2     Summary, and qualitative analysis................................................ 8
        3.3     Test methodology ...................................................................... 9
        3.4     Selection of hollow slab type and conditioning .............................. 11
        3.5     Loads .................................................................................... 12
        3.6     Loading Arrangement ............................................................... 13
        3.7     Fire Testing ............................................................................ 15


4       Test Results..................................................................... 17


5       List of literature............................................................... 22




Attachments:
1       Drawings of test specimens
2       Wire displacement




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1       Background

        In June 2001 the Ministry for Urban and Housing Affairs informed ETA-
        Danmark A/S that it was the opinion of the ministry that the existing Danish
        approvals for hollow core concrete slabs could be withdrawn. This was on the
        basis that the approvals were no longer necessary, as the fire resistance of
        the concrete elements could be determined based on calculation rules of the
        structural codes, combined with tests according to appropriate standards.
        The ministry stated in the same context that the approvals in question could
        not be maintained in the long term, since they will contradict the Construc-
        tion Products Directive.


        According to [1] in 2002 the status was that the flexural capacity during fire
        conditions and to the cold condition design could be documented by means of
        calculations according to the structural codes of practice and by current pro-
        duction tests. Whereas there was no similar basis for direct documentation of
        the shear capacity during fire conditions.


        Results were available from a series of tests performed in Europe with hollow
        core slabs during fire. The tests with positive results were mainly performed
        with moderate load or with inappropriate boundary conditions, which often do
        not apply to conventional buildings. The tests with negative results were in
        general carried out under incorrect conditions, particularly with joints dis-
        similar to typical buildings or with concrete moisture content that was too
        high.


        For many years it has been widespread practice to use hollow core for storey
        compartmentation with requirements of 60, 90 or 120-minute fire resistance
        The cold condition design has only been supplemented with requirements for
        flexural capacity in a fire event.


        The load conditions in residential and office buildings are typically character-
        ized by moderate load levels in case of fire. Thus these cases are reasonably
        well covered by the above tests with moderate loads in combination with the
        many years’ comprehensive international experience with applying hollow
        core slabs in comparable buildings. The Danish Prefab Concrete Association
        has in 2003 revised its general recommendations on installing hollow core
        slabs with appropriate reinforced joints following the general practice devel-
        oped in Europe, see [2].




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        The former Danish practice for ”heavy-duty” buildings with high loading lev-
        els could not be considered as sufficiently documented in the same way. At
        the end of 2002, the Danish Prefab Concrete Association informed the Minis-
        try for Urban and Housing Affairs about a scheme for testing to be carried out
        in the coming years to verify the shear capacity in a fire event. The focus
        was to be on heavy-duty buildings with high loads. In the interim period the
        Danish Prefab Concrete Association recommended a limit for the load on hol-
        low core slabs with a special design rule [3].


        The present report describes the tests carried out at the Swedish National
        Testing and Research Institute, SP based on the scheme developed by the
        Danish Danish Prefab Concrete Association.




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2       Conclusion

        The tests performed at SP show that correctly mounted hollow core slabs
        provide good fire resistance for 60 minutes when tested to the standard fire
        curve.


        The three tests were performed at different load levels, described below by
        the shear force during the fire testing, Vd(fire) , measured as a percentage of
        the slabs’ ultimate design shear capacity in cold conditions, V   ud(cold):




        Test SP-1 performed on 2005-04-01: Vd(fire) = 65% of Vud(cold)
        Test SP-2 performed on 2005-04-06: Vd(fire) = 75% of Vud(cold)
        Test SP-3 performed on 2005-04-08: Vd(fire) = 80% of Vud(cold)


        The heating regime followed the standard time temperature curve for 60
        minutes, followed by a 90 minute cooling phase.


        The performance of the concrete elements in the first two tests was very
        uniform, with even development of deflections and formation of cracks.


        The tests indicate that the transversal reinforcement of the joint at the end of
        the elements is of essential importance to prevent vertical cleavage of the
        element edges during the fire event. The minimum requirement for rein-
        forcement of joints specified in the Danish Prefab Concrete Association’s
        Guidelines [2] in this respect must always be met.


        The tests were performed on hollow core slab types commonly available on
        the Danish market and with a minimum rib proportion.


        It is therefore considered acceptable to use hollow core slabs in buildings re-
        quiring 60 minute fire resistance, if it is determined that:


        Vd(fire)  75% of Vud(cold)


        where Vud(cold) is determined in accordance with DS 411, based on function
        testing with loading arrangement in accordance with prEN 1168.


        Furthermore, it is noted that the results from the cooling phase can be used
        for assessment of the hollow core slab capacity to resist a 120-minute fire




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        event in buildings with moderate fire load. This is limited to where it can be
        determined that the temperature during the 120 minutes is below the tem-
        perature curves from the tests.




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3       Test Methodology




3.1     Purpose

        The purpose of the testing was to confirm that hollow core slabs exposed to a
        60-minute fire according to the standard time-temperature curve and the
        subsequent cooling phase can resist a displacement of at least 65% of the
        slabs’ ultimate design shear capacity in cold conditions as determined in DS
        411 based on function testing with loading arrangement according to prEN
        1168.




3.2     Summary, and qualitative analysis



        During the test, the exposed underside of the hollow slab will expand due to
        the increase in temperature.


        For a cross-section perpendicular to the hollow cores, the temperature distri-
        bution of the slab will be characterized after a certain period as shown on the
        figure below to the left.


                                                                          compresion

                                                                          tension

                                                                          compression

                 temperature distribution            normal stress distribution


        The hollow slab will react to this temperature profile by bending downwards,
        as “plane cross-sections will remain plane“. Thus an equilibrium balance will
        form with longitudinal compressive stress in the top and bottom of the slab,
        and longitudinal tensile stress in the rib as indicated in the drawing to the
        right.


        The tensile stress in the rib due to the heating will reduce the un-reinforced
        rib’s shear capacity in comparison to the cold condition. It is recommended
        that special requirements be specified for the alignment of the reinforcement




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        in the longitudinal joints to reduce the crack tendency, which by the guideline
        [2] has already been introduced in Denmark.


        The temperature expansion in the transverse
        direction of the slab will result in the formation
        of cracks on the top side of the slab along the
        hollow cores. (See figure)


        The formation of cracks at the slab ends will propagate at the transverse joint
        casting and around the outer edge of the lower side of the slab, which re-
        mains cold above the support. If this cracking is not controlled there is a risk
        of anchorage failure and that the cracks may propagate away from the sup-
        port at the underside of the slab and increase the risk of slab failure during
        the fire test.


        The above consideration leads to an expectation that an effectively anchored
        reinforcement, situated in the transverse joint at the end of the slab, is of
        high importance to the fire resistance performance.


        To verify this assertion in testing conducted in 2004 [4] such reinforced joints
        were monitored with strain gauges. Measurements during the testing
        showed considerable strains (approx. 0.2%) in the transverse reinforcement,
        which contributes to creating restraint forces and leading to the above men-
        tioned crack effect.




3.3     Test methodology



        As documented in [5] a number of technical problems arose in the testing as
        described in [4]. Some problems concerned deformation and some related to
        the loading arrangement.


        The test was performed with a test specimen consisting of two hollow core
        slabs with cast longitudinal joint, transverse joints at the ends and longitudi-
        nal edge joints. In order to prevent transferring loads from the hollow core
        slabs to the edge joints, a separation was built in between the hollow and the
        edge joints. The reinforcement in the transverse joints was angled at the
        ends and led into the longitudinal joints specifically to obtain the efficient an-




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        choring mentioned in section 3.2. During the fire test the edge joints were
        far less deformed than the hollow core slabs, resulting in noticeable torsion.


        To avoid a repeat of this effect, the specimens for the testing at the SP lab
        were designed as shown in attachment [1]. The concept being that the test
        zone (which is 2.35 m wide) is adjacent to a 1.775 m wide buffer zone of the
        same type of hollow core slab as the test zone. The hollow core slabs in the
        test zone and in the nearest part of the buffer zone are assumed to be
        equally affected by the fire test and deform almost identically. This is essen-
        tial because the deflections as a result of the fire test temperatures are in the
        range of 20 times larger than the statically conditioned deflection in the test
        zone.


        The test zone is separated from the buffer zones by cutting the hollow core
        slabs with a longitudinal cut, vertically through the hollow core. [See detail 1
        in Attachment 1]. The cuts have been made before assembly and the two cut
        cores filled with rock wool.
                               Flat steel
                              Load plate

                                                                                  0.135 m
                                                                                 0.6625 m




                                                                                 3.27 m


                                                                Cut


                                                                                  0.135 m

        1.775 m buffer zone          2.35 m test zone    1.775 m buffer zone


        The test zone comprises one whole and two halves of hollow core slabs and
        with the chosen slab type (thickness = 265 mm) the test zone will thus com-
        prise a total of 8 normal ribs and two longitudinal joints, each with two adja-
        cent side ribs in the elements.


        It is noted that the two side ribs along a longitudinal joint are considered
        comparable to one inner rib with respect to the reaction to shear forces.




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           In the test, single forces are applied from the hydraulic presses on to the
           load plates shown. The distance from the edge of the element has been de-
           termined in accordance with prEN 1168’s rules for testing of the shear capac-
           ity in cold conditions. Efforts have been made to design the load arrangement
           (see the below section 3.6) to apply the same load on each rib. The distance
           of the load from the support means that the lateral dispersion of load is not
           excessive. It is considered that the response of the element in the centre of
           the test zone is generally unaffected by the conditions in the buffer zones.


           The joints of the test specimen were made in accordance with [2].




3.4        Selection of hollow slab type and conditioning



           The tests were performed on extruded hollow core slabs typically available on
           the Danish market, and with the smallest identified rib proportion (total rib
           width per metre cross-section). The slab selected had a thickness (t) of 265
           mm. See below:


                                 400
       Rib proportion (mm / m)




                                 350
                                 300
                                                                                          Betonelement
                                 250                                                      Boligbeton
                                 200                                                      Tinglev
                                 150                                                      Spæncom
                                 100                                                      Kähler
                                               t = 265 mm
                                 50
                                  0
                                   150   200   250          300      350   400   450
                                               Slab thickness (mm)



           The thickness of the selected slab is mid-range of available slabs, and there-
           fore the results from the tests are considered to apply to the general condi-
           tions in Denmark.


           The reinforcement in the hollow core slabs tested consisted of 10 x 12.5 mm
           steel strands one in each edge rib and two in each of the inner ribs.


           Betonelement A/S, the supplier, has advised that for the specific slab type
           given, the calculated shear capacity in cold conditions is 91.6 kN/m deter-




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        mined in accordance with DS 411 based on function testing with loading ar-
        rangement according to prEN 1168.


        V   ud(cold)   = 91.6 kN/m


        The hollow core slabs used in the test zone were produced in August 2004
        and had a measured moisture content of 2.28% at the time of testing.




3.5     Loads



        At the edge casting the hollow core slabs have a support width of 65 mm.
        The theoretical span of the hollow core slab is:


        L = 3.27 - 0.135 - 0.135 - 0.065 = 2.935 m


        The theoretical shear element in the side where the load is applied will be:


        a = 0.6625 - 0.065 / 2 = 0.63


        as 2.5 * h = 0.6625m, where h = 0.265 m (the thickness of the hollow core
        slab).


        The tests were performed at three different load levels:


        SP-1: Vd(fire) = 65% of Vud(cold) = 59.55 kN/m
        SP-2: Vd(fire) = 75% of Vud(cold) = 68.76 kN/m
        SP-3: Vd(fire) = 80% of Vud(cold) = 73.30 kN/m




        Load at load level Vd(fire) = 65% of Vud(cold)


        At each of the five load plates a single force is applied of:


        Po = 32.3 kN


        The load plates are steel plates (30 mm thick x 100 mm wide x 340 mm
        long) evenly spaced on an underlying flat steel plate (20 mm thick x 100 mm




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        wide x 2300 mm long). These steel plates combined weigh approx. 0.3
        kN/m, so the line load in the test zone will be:


        p = 5 x 32.3 / 2.35 + 0.3 = 69.0 kN/m


        The hollow slab’s dead-weight including joint castings is 3.65 kN/m2, so that
        the shear force in the hollow slab will be:


        v = 0.5 x 2.935 x 3.65 + (2.935 - 0.63) x 69.0 / 2.935     =     59.55 kN/m




        Load at load level Vd(fire) = 75% of Vud(cold)


        Po = 37.8 kN
        p = 5 x 37.8 / 2.35 + 0.3 = 80.73 kN/m
        v = 0.5 x 2.935 x 3.65 + (2.935 - 0.63) x 80.73 / 2.935      =    68.76 kN/m




        Load at load level Vd(fire) = 80 % of Vud(cold)


        Po = 40.5 kN
        p = 5 x 40.5 / 2.35 + 0.3 = 86.5 kN/m
        v = 0.5 x 2.935 x 3.65 + (2.935 - 0.63) x 86.5 / 2.935     =     73.30 kN/m




3.6     Loading Arrangement



        The load was applied with five hydraulic presses connected in parallel. To
        control the loading a load cell was mounted under each press so that the in-
        dividual loading of each press could be monitored during the tests.




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        At load level V      d(fire)   = 0.75 V   ud(cold)   a cross-section view shows the following
        condition of the test zone:                          C
                                                              L




                   37.8 kN             37.8 kN          37.8 kN            37.8 kN   37.8 kN




              0.215 m        0.48 m          0.48 m               0.48 m       0.48 m   0.215 m

                                              Test zone, b = 2.35 m


        The long flat steel plate was mounted in grout on the hollow slab transverse
        to the test zone as shown earlier on the plan. On this the five loading plates
        are mounted, as shown.


        The hydraulic press applies 37.8 kN on each of the five load plates. The
        stress in the load plates with a rib distance of 240 mm in the hollow core slab
        is:




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         = (0.25 x 37.8 x 240 x 103) / (0.17 x 100 x 302) = 151 MPa


        If one rib is weaker than an adjacent rib, the flat steel under the load plates
        will redistribute the load locally. As an example if the rib in question requires
        4.0 kN to be transferred to adjacent ribs the stress in the flat steel will be:


               = (0.25 x 4.0 x 480 x 103) / (0.17 x 100 x 202 ) = 72 MPa


        and the corresponding deflection (u) of the flat steel will be small:


        u <     (1/48 x 4.0 x 4803 x 103) / ( 210000 x 1/12 x 100 x 203 ) = 0.7 mm


        The flat steel yield strain is 355 / 210000 = 0.0017, so if the hollow slab, due
        to an uneven response to the furnace temperature, curves in the transverse
        direction, the flat steel can, without yielding, follow a curvature in the range
        of:


         = 0.0017 / (1/2 x 20) = 0.00017 mm-1


        which corresponds to a deflection in the centre of:


                1
        u =         /8 x 0.00017 x 23002 = 112 mm


        This deflection figure will correspond to a moment in the centre of the flat
        steel of:


                1
        M =         /6 x 100 x 202 x 355 x 10-6 = 2.36 kNm


        which corresponds to the steel being able to redistribute the load in the range
        of 4 kN from the middle of the test zone. In summary, an even curve in the
        transverse direction of the hollow core slab, will only have a minor influence
        on the test result.




3.7     Fire Testing

        The test specimens were mounted above the furnace, where the underside of
        the slabs were exposed to a 60 minute ‘fire’ according to the standard time-




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        temperature curve. This commenced 30 minutes after the load had been ap-
        plied to the upper side of the specimen.


        After 60 minutes the furnace was turned off and the test continued for a fur-
        ther 60-90 minute cooling phase with the load still applied.


        In the figure below the test temperatures are shown



                                                                                        Time (minutes)

                                                                   0     20   40   60        80          100     120   140   160
                                                            1000
         Mean temperature in furnace (degrees centigrade)




                                                                       SP-3
                                                            900

                                                            800
                                                            700

                                                            600

                                                            500

                                                            400
                                                                                                               SP-1
                                                            300

                                                            200                          SP-2

                                                            100

                                                              0




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4       Test Results


        The tests performed at SP show that correctly mounted hollow core slabs
        provide good fire resistance for 60 minutes when tested to the standard time
        temperature curve.


        The results of the first two tests were similar with an even development of
        deflections and formation of cracks. The tests passed without breaching or
        spalling or other significant failure occurring at any time during the test pe-
        riod including the 60-minute fire test and the subsequent cooling phase of 90
        minutes.


        During the third test, where the slabs were loaded corresponding to 80% of
        the ultimate design strength in cold conditions, breaching occurred after 45
        minutes. Until this time the test performed in a similar way to the first two
        tests.


        The photo below shows the underside of the slab elements approx. 45 min-
        utes after the start of the heating regime during test SP-1.




        The deflections developed evenly during the test, see next page.




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                                        Time (minutes)
       -80    -60    -40     -20   0   20     40    60   80    100 120 140 160 180
                                                                                     10

                                                                                     0
                                                              SP-1
                                                                                     -10




                                                                                           Deflections (mm)
                                                                                     -20

                                                                                     -30

                                                                                     -40

                                                                                     -50

                                                                                     -60


                                        Time (minutes)
        -80   -60     -40    -20   0   20     40    60   80    100 120 140 160 180
                                                                                     10

                                                                                     0
                                                              SP-2
                                                                                     -10




                                                                                              Deflections (mm)
                                                                                     -20

                                                                                     -30

                                                                                     -40

                                                                                     -50

                                                                                     -60


                                            Time (minutes)
        -80    -60    -40    -20   0   20      40   60   80    100 120 140 160 180
                                                                                     10

                                                                                     0
                                                              SP-3
                                                                                     -10
                                                                                                  Deflections (mm)




                                                                                     -20

                                                                                     -30

                                                                                     -40

                                                                                     -50

                                                                                     -60



        The deflections shown have been measured approximately in the middle of
        the span between the hollow slab supports. The lower curve in each diagram




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        shows the deflections in the middle of the test zone. The other two curves
        show the deflections in the middle of the two half elements of the test zone
        (i.e. approx. 900 mm from the measuring point in the centre).


        The heating commenced at the time = 0 minute. The curves before this time
        show relatively modest deflections due to the external load applied in cold
        conditions. The load during the tests is shown below.


                                        Time (minutes)
         -80    -60   -40    -20   0     20   40   60    80   100 120 140 160
                                                                                100
                                                                                90
                                                                                80
                                                                                70




                                                                                        Line load (kN/m)
                                                                                60
                                       SP-3                                     50
                                       SP-2                                     40
                                       SP-1                                     30
                                                                                20
                                                                                10
                                                                                0


        Relatively early in the fire test it was noted that the pre-stressed wires had
        retracted into the slab. The displacement was measured using small meas-
        uring sticks welded to some of the wire ends and extended through the
        transverse joint at the end of the elements.




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                                                    Wire displacement




        The displacement of the wires was measured at three wire ends in the loaded
        end (nos. 1, 2 and 3) and on three wire ends (no. 4, 5 and 6) in the unloaded
        end of the hollow slab test zone:


                                                    Time (minutes)
                                      0   20   40        60          80   100   120
                                 12
        Wire displacement (mm)




                                 10
                                                                                            nr 1
                                 8
                                                                                            nr 2
                                 6                                                          nr 3
                                 4                                                          nr 4
                                                                                            nr 5
                                 2
                                                                                            nr 6
                                 0

                                 -2




        The diagram shows the measurements from SP-1. The extent of the wire
        displacement was different in the three tests, see Attachment 2. In general
        the wire displacement was no larger than 10-12 mm. It was somewhat larger
        for one single line in the test SP-3.


        In general, a considerable number of cracks were noted in the transverse
        joints at the end of the elements. These cracks were quite densely distrib-
        uted, with a spacing of around 150-200 mm, and the typical width of the
        cracks was estimated at 0.3-0.5 mm shown on the photo below.




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5       List of literature


         [1]     Hollow core slabs and fire – Danish and international practice
                 Birch & Krogboe A/S, 2002-10-23
                 (http:\\betonfr.inforce.dk/graphics/betonelementforeningen/html_
                 pdf_xls_lign_docs/rapport.pdf)
         [2]     Hollow core slabs and fire – joint reinforcement guideline (fire)
                 Betonelement-Foreningen, (Danish Prefab Concrete Association),
                 February 2003
                 (http://www.betonportal.dk/revisioner/index.htm)
         [3]     Hollow core slabs and fire –new design rules (hollow core slabs)
                 Betonelement-Foreningen, December 2002
                 (http:\\betonfr.inforce.dk/graphics/betonelementforeningen/html_
                 pdf_xls_lign_docs_huldaek_og_brand.doc)
         [4]     Test report, file no. PG11304
                 Danish Institute of Fire and Security Technology, 2004-11-22
                 (http:\\betonfr.inforce.dk/graphics/betonelementforeningen/html_
                 pdf_xls_lign_docs/PG11304_pdf.pdf)
         [5]     Evaluation of fire test performed performed 2nd November 2004
                 Birch & Krogboe A7S, 2004-12-06
                 http:\\betonfr.inforce.dk/graphics/betonelementforeningen/html_
                 pdf_xls_lign_docs/evaluering_af_brandtest.doc)
         [6]     prEN1168:2005 Precast concrete products – Hollow core slabs CEN-
                 standard (status: approved)
         [7]     Report No. 501342
                 Sveriges Provnings- och Forskningsinstitut, (Swedish National Test-
                 ing and Research Institute, SP), May 2005
         [8]     Report 502015
                 Swedish National Testing and Research Institute, SP, May 2005
         [9]     Report 502076
                 Swedish National Testing and Research Institute, SP, May 2005




Birch & Krogboe A/S
17681-BEF-272850-1.doc                                                         Page 22 of 26
Hollow core slabs and fire                  2005-06-13




Attachment 1: Drawings of test specimens




Birch & Krogboe A/S
17681-BEF-272850-1.doc                     Page 23 of 26
Hollow core slabs and fire    2005-06-13




Birch & Krogboe A/S
17681-BEF-272850-1.doc       Page 24 of 26
Hollow core slabs and fire    2005-06-13




Birch & Krogboe A/S
17681-BEF-272850-1.doc       Page 25 of 26
Hollow core slabs and fire                                                                         2005-06-13




Attachment 2: Wire displacement




                                                        Time (minutes)
                                     0   20   40   60         80      100       120    140   160
                               12
Wire displacement (mm)




                               10
                                                                                                         nr 1
                                8
                                                                                                         nr 2
                                6                                                                        nr 3
                                                                                      SP-1
                                4                                                                        nr 4
                                                                                                         nr 5
                                2
                                                                                                         nr 6
                                0
                               -2




                                                         Time (minutes)
                                     0   20   40   60         80          100   120    140   160
                               14
                               12
Wire displacement (mm)




                               10                                                                         nr 1
                                                                                                          nr 2
                                8
                                                                                      SP-2                nr 3
                                6
                                                                                                          nr 4
                                4
                                                                                                          nr 5
                                2                                                                         nr 6
                                0
                               -2




                                                        Time (minutes)
                                     0   20   40   60          80         100   120    140   160
                               16
                               14
      Wire displacement (mm)




                               12                                                                          nr 1
                               10                                                                          nr 2
                                8                                                     SP-3                 nr 3
                                6                                                                          nr 4
                                4                                                                          nr 5
                                2                                                                          nr 6
                                0
                                -2




Birch & Krogboe A/S
17681-BEF-272850-1.doc                                                                         Page 26 of 26

				
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