Actual behaviour of composite externally CFRP-reinforced timber beams stress analysis

Transcription

1 Actual behavour of composte externally CFRP-renforced tmber beams stress analyss Marcela Karmazínová Abstract The paper s focused on the problems of composte CFRP-renforced tmber beams. CFRP renforcement s represented by the lamella externally bonded on the tensle part of the beam for the strengthenng the member to ncrease n the resstance from the vewpont of both the ultmate and servceablty lmt states. Usually for the resstance determnaton the concept of composte structural members based on the substtute (deal, respectvely) cross-secton s appled, but the usage of ths prncple s dependng on the effcency of the shear connecton (here bonded) between CFRP renforcement and basc materal tmber. It s manly nfluenced by the glue type and also by the bonded connecton qualty. The practcal experences obtaned from the s orented to the expermental verfcaton of the actual behavour show that the effcency s very dfferent n dependence on the partcular structural member. The paper presents selected results of the measurement of the stresses n CFRP renforcement and n tmber base, whch can gve the nformaton on the level of the mutual nteracton between both materals and on the rghtness of the substtute cross-secton approach mentoned above n the case of tmber beams. The paper deals wth the verfcaton of the actual normal stresses, manly n the cross-secton part of the contact between tmber and CFRP renforcement (here bottom tensle edge). Actual normal stresses obtaned from the s have been used for the evaluaton of actual characterstcs of the substtute cross-secton, especally the second moment of the area. Applyng those derved cross-secton characterstcs the effects of the longtudnal shear, that means shear forces and stresses, have been calculated amed to the verfcaton of the bonded shear connecton. Keywords Tmber beam, composte, strengthenng, CFRP renforcement, bonded lamella, actual behavour, elastcty, normal stress, shear connecton, longtudnal shear stress, expermental verfcaton, theoretcal analyss, nteracton. I. INTRODUCTION HE mportant attenton to the research actvtes drected Ttowards the usage of progressve hgh-strength materals combned wth tradtonal materals n one structural member s pad on the author's workplace n the recent perod. Wthn the framework of the expermental and theoretcal research the capacty and servceablty of load-carryng CFRP-tmber and Manuscrpt receved August 17, Ths work was supported n part by the Czech Mnstry of Educaton, Youth and Sports under research centre project CZ.1.05/2.1.00/ AdMaS, the unversty specfc research project No. FAST S-11-32/1252 and the Czech Scence Foundaton under the grant project No. 103/09/H085. Marcela Karmazínová, Faculty of Cvl Engneerng at the Brno Unversty of Technology, Brno, Czech Republc (correspondng author to provde phone: ; fax: ; e-mal: karmaznova.m@ fce.vutbr.fce.vutbr.cz). CFRP-steel members are nvestgated and solved from the vewpont of the ncrease n bendng resstance due to strengthenng by external CFRP lamella renforcement bonded to tmber or steel surface of the tenson beam edge. Except the usually measured standard parameters (loadng, deflectons) durng the loadng s also the stresses n the cross-secton have been montored and verfed by way of the stran measurement. For ths reason the stran gauges bonded on the surface both on CFRP lamella and on base materal have been appled. The results obtaned from the measurement have been taken as the base for the verfcaton, accuracy mprovement and, correcton of the theoretcal tenseness analyss. Ths expermental research has been realzed for the specmens wth the several tmber beam cross-sectons: 100/220, 100/200, 100/180, 100/160, 100/140, 100/120. The cross-secton dmenson of used CFRP lamellas was 50/1.2 mm. The basc descrpton and results of ths research can be obtaned from prmary nformaton, whch has been already presented, for example, n [7], [8], [9], [11], [14]. II. PRINCIPLES OF THEORETICAL ANALYSIS OF STRESSES IN CROSS-SECTION OF COMPOSITE EXTERNALLY CFRP-REINFORCED TIMBER BEAM A. Normal Stress Strengthenng bended structural members by renforcement based on fbre-renforced polymers s gven by advanced materal propertes of used fbres. CFRP compostes usually use carbon fbres wth very hgh tensle strength and hgh modulus of elastcty (unlke glass fbres). Generally t s assumed, strengthenng by CFRP can be effcent for tmber because of ts hgher Young's modulus than tmber one. Assumng the rgd shear connecton between tmber and CFRP lamella the relatve deformatons of tmber and CFRP renforcement n the contact are the same,.e. ε tmber = ε CFRP. Then, for the calculaton of normal stresses or, respectvely, for the determnaton of predcted elastc bendng moment resstance, the general concept of composte substtute crosssecton (see, for example, [1], [8], [9], [10], [12], [13], [15], [33]) based on the parameter n gven as the rato of E tmber n =, (1) ECFRP Issue 1, Volume 7,

2 where E tmber, E CFRP are Young's modulus of elastcty of tmber and CFRP renforcement, can be appled. substtute (deal) cross-secton concepton, the longtudnal shear force V long,1 (per unt of the length) at the nterface between CFRP renforcement and tmber can be calculated as V long,1 V S = I [N.mm -1 ], (6) where V s the (transverse) shear force, S s the frst (statc) moment of the cut off part of the area, I s the second moment of area. Then, the longtudnal shear stress n the nterface between tmber and CFRP can be gven as V S τ long =, (7),1 b I Fg. 1 elastc stress dstrbuton n CFRP-tmber beam crosssecton The assumed normal stress dstrbuton n CFRP-tmber cross-secton based on the elastc approach s shown n Fg. 1, where σ tmber s tmber stress on the tensle edge of the beam and σ CFRP s the stress n CFRP renforcement. The values of normal stresses anywhere n the cross-secton can be generally calculated usng the followng formulas: M σ tmber = z, (2) tmber I M σ CFRP = z, (3) CFRP n I where b s the wdth n the correspondng place of the crosssecton, that means n ths case t s the wdth of the glued area,.e. the wdth of CFRP lamella, because t s bonded over ts all the wdth. III. EXPERIMENTAL VERIFICATION OF STRESSES IN CROSS-SECTION OF COMPOSITE EXTERNALLY CFRP-REINFORCED TIMBER BEAM For the verfcaton of the objectve resstance and actual stresses n the member, CFRP-tmber beams have been ed. Durng the loadng s, stresses have been montored and subsequently compared wth the predcted calculated values. Materal of the beams was structural tmber of the class C22 wth the characterstc bendng-tensle strength of 22 MPa and mean value of Young's modulus of 10 GPa. Tensle strength of CFRP renforcement was, accordng to the nformaton of the producer, MPa and Young's modulus was 155 GPa. where M s the bendng moment, I s the second moment of area of the substtute (deal) cross-secton and z tmber and z CFRP are the correspondng dstances from the gravty centre of the substtute cross-secton. Basc characterstcs of the substtute (deal, respectvely) cross-secton of the composte member, that means cross-secton area A and the second moment of area I, are generally gven as follows: ACFRP A = Atmber +, (4) n ICFRP, I = Itmber, +. (5) n Of course, the formulas for the cross-secton characterstcs of CFRP parts and for normal stresses n CFRP parts nclude parameter n, whch arses from the prncple descrbed above and t s also evdent from equatons (3), (4), (5). B. Longtudnal Shear Stress In addton to the normal stresses and ther effects, also shear connecton between cross-secton parts s very mportant for the desgn of composte beams n general. Based on the Fg. 2 ed specmen scheme: four-pont bendng The specmens beams of the span of 3 or 4 meters have been smply supported and loaded by the forces ntroduced n the beam thrds (four-ponts bendng) see scheme n Fg. 2 and llustraton of the arrangement and performance of loadng n Fg. 3. The ng usng four-ponts bendng have been chosen wth respect to the ng equpment, but as, f possble, to the best smulate the real loadng, whch s n usual cases approxmately unform. Durng loadng process, except of forces F and deflectons w also stresses σ tmber, σ CFRP n tmber and n CFRP on the tensle edge have been measured through stran gauges for the llustraton of stran gauges see Fgs. 4, 5. Issue 1, Volume 7,

3 Table I Stresses σ tmber,1, σ CFRP,1 [MPa] n tmber and CFRP on the tensle edge: vs. s (obtaned from stran gauges) 100/220-C M u = knm σ tmber, σ CFRP, σ tmber, σ CFRP, /200-C M u = knm Fg. 3 arrangement and realzaton of loadng s σ tmber, σ CFRP, σ tmber, σ CFRP, /180-C M u = knm σ tmber, σ CFRP, σ tmber, σ CFRP, Fg. 4 stran gauges on the bottom (tensle) edge 100/160-C M u = knm σ tmber, σ CFRP, σ tmber, σ CFRP, /140-C M u = knm Fg. 5 vew to the bottom edge wth stran gauges on CFRP lamella and tmber surface A. Normal Stresses The normal stresses n tmber and CFRP renforcement measured on the tensle beam edge are presented n Table I. For the comparson and verfcaton of the theoretcal approach the stresses calculated applyng the elastc method are presented n Table I, too. Ths table shows stress values for the bendng moments equal to 0.25 M u, 0.5 M u and 0.75 M u, where M u s the maxmum (ultmate) bendng moment reached wthn the s, when the falure occurred, both expermental values and calculated values. 100/120-C M u = knm σ tmber, σ CFRP, σ tmber, σ CFRP, σ tmber, σ CFRP, σ tmber, σ CFRP, Issue 1, Volume 7,

4 100/220-C: 0.25 Mu,exp 100/220-C: 0.5 Mu,exp 100/220-C: 0.75 Mu,exp 100/160-C: 0.25 Mu,exp 100/160-C: 0.5 Mu,exp 100/160-C: 0.75 Mu,exp -9,4-11,6-19,2-23,2-29,8-34,8-9,3-12,2-19,7-24,4-32,6-36,6 165,8 141,5 10,7 8,7 331,6 306,8 21,4 17,8 497,4 471,0 32,1 27,6 169,4 111,1 10,9 8,4 338,8 213,3 21,9 17,7 508,1 296,2 32,8 29,3 167,7 142,9 335,4 310,0 503,1 475,9 172,1 112,8 344,2 216,4 516,2 300,5 Fg. 6 theoretcal (calculated) and actual (derved from the s) stresses n composte CFRP-tmber beam subjected to bendng moment: cross-secton 100/220-C Fg. 9 theoretcal (calculated) and actual (derved from the s) stresses n composte CFRP-tmber beam subjected to bendng moment: cross-secton 100/160-C 100/200-C: 0.25 Mu,exp 100/200-C: 0.5 Mu,exp 100/200-C: 0.75 Mu,exp 100/140-C: 0.25 Mu,exp 100/140-C: 0.5 Mu,exp 100/140-C: 0.75 Mu,exp -7,9-11,8-15,9-23,7-35,6-24,2-10,8-13,0-22,0-26,0-34,3-39,0 168,1 99,2 10,8 7,3 336,3 200,7 21,7 14,6 504,4 303,5 32,5 22,2 177,8 151,3 11,5 9,6 355,7 310,7 22,9 19,5 533,5 485,3 34,4 30,4 170,2 100,3 340,5 203,1 510,7 306,9 181,1 153,8 362,2 315,9 543,3 493,4 Fg. 7 theoretcal (calculated) and actual (derved from the s) stresses n composte CFRP-tmber beam subjected to bendng moment: cross-secton 100/200-C Fg. 10 theoretcal (calculated) and actual (derved from the s) stresses n composte CFRP-tmber beam subjected to bendng moment: cross-secton 100/140-C 100/180-C: 0.25 Mu,exp 100/180-C: 0.5 Mu,exp 100/180-C: 0.75 Mu,exp 100/120-C: 0.25 Mu,exp 100/120-C: 0.5 Mu,exp 100/120-C: 0.75 Mu,exp -9,3-11,8-18,9-23,7-29,3-35,5-10,7-15,3-21,7-30,5-33,9-45,8 165,6 134,8 10,7 8,5 331,3 275,5 21,4 17,2 496,8 430,3 32,1 26,7 204,0 150,8 13,2 9,3 407,9 298,9 26,3 18,9 462,2 39,5 29,5 167,9 136,7 335,9 279,0 503,8 435,6 208,4 153,7 416,7 304,6 471,2 Fg. 8 theoretcal (calculated) and actual (derved from the s) stresses n composte CFRP-tmber beam subjected to bendng moment: cross-secton 100/180-C Fg. 11 theoretcal (calculated) and actual (derved from the s) stresses n composte CFRP-tmber beam subjected to bendng moment: cross-secton 100/120-C Issue 1, Volume 7,

5 Table II Actual values of parameter n obtaned from the s usng actual normal stresses: n = E tmber / E CFRP = σ tmber,1 / σ CFRP,2 100/220-C n mean,220 σ tmber, σ CFRP, n /200-C n mean,200 σ tmber, σ CFRP, n /180-C n mean,180 calculaton Young's modulus have been used as descrbed above (see paragraph III). In Table I the maxmum stresses σ tmber,1 and σ CFRP,1 n tmber and CFRP on the tensle edge (see Fg. 1) are lsted. The complete overvew of normal stresses n the cross-secton s depcted n Fgs. 6 to 11, where normal stress dstrbutons for both theoretcal and actual values (derved from the s) are drawn, for the comparson (theoretcal stress dstrbuton rendered by black lnes, actual stress dstrbuton rendered by colour lnes). The partcular values of normal stress show the followng: the actual normal stresses obtaned from the s are less than the theoretcal ones calculated usng the concept of substtute cross-secton, both for tmber and CFRP renforcement, whle the dfferences n tmber normal stresses usually are n the range from 10 up to 30 % and dfferences n CFRP normal stresses are n the range from 5 to 40 %, too. Table III Values of the second moments of area I : vs. s σ tmber, σ CFRP, n /220-C I [mm 4 ] I, /I, /160-C n mean,160 σ tmber, σ CFRP, n /140-C n mean, /200-C I [mm 4 ] I, /I, /180-C I [mm 4 ] I, /I, σ tmber, σ CFRP, n /160-C I [mm 4 ] I, /I, 100/120-C n mean,120 σ tmber, σ CFRP, n Mean value of parameter n: n mean = The actual values of normal stresses verfed usng results have been determned through the relatve deflectons ε, whch have been obtaned from the stran gauges. Measured values of strans (per unt of the length) n [N.mm -1 ] have been recalculated to the stresses accordng to the relatonshp between stress and stran gven by Hooke's law. For the /140-C I [mm 4 ] I, /I, /120-C I [mm 4 ] I, /I, Mean value of the rato: I, /I, = Issue 1, Volume 7,

6 From the values of actual stresses n the place of the contact of CFRP renforcement and tmber the actual values of the parameter n = E tmber / E CFRP can be determned. These values may be calculated usng the rato n = σ tmber,1 / σ CFRP,2, as Table II shows. The resultng mean value determned from the results of ed specmens s n = 0.068, whch s by about 5 % only dfferent (more) wth the theoretcal value. Usng the actual values of parameter n obtaned from the s the second moments of the area correspondng to the calculated n values can be calculated as ther actual values for partcular specmens. Overvew of the second moments of area I, calculated for theoretcal value of n parameter (taken from modulus of elastcty of both materals gven by producer nformaton) and I, calculated for n parameter derved from the s s n Table III. From the values for partcular specmens and ther cross-sectons the rato of to theoretcal values s 1.022, as shown n Table III. B. Longtudnal Shear Stresses Load-carryng capactes of all specmens were hgher than predcted values calculated accordng to elastc approach (see e.g. [7], [8], [9], [11], [13]) and actual stresses obtaned from the s and parameters derved from them ndcate, that the actual behavour of nvestgated members very good correspond wth the elastc prncples assumed as the sutable approach for the stress and resstance analyss. The results also show that the nteracton between tmber and CFRP renforcement s very satsfactory for usng the assumpton of the rgd shear connecton and the concept of the substtute cross-secton followng from ths fact. However, n the case of some specmens the rupture of CFRP lamella (see Fg. 12) and, manly, the separaton of the lamella from tmber occurred (see Fgs. 13 and 14). Therefore, the attenton has been pad to the shear connecton, too, from the vewpont of the actual values of longtudnal shear force and from that arsng longtudnal shear stress, respectvely, between CFRP renforcement and tmber base. In ths context, currently research s also orented to the analyss of glue propertes amed to select the most sutable glue for CFRP lamella to tmber bonded connecton. The longtudnal shear forces V long,1 (per unt of the length) and correspondng longtudnal shear stresses τ long at the nterface between CFRP and tmber calculated usng both the actual cross-secton characterstcs derved from the s (see e.g. the second moments of area n Table III) and theoretcal ones, are presented n Table IV. Shear stresses have been calculated for the lamella wdth, whch s correspondng wdth of resstng cross-secton part n the level of longtudnal shear actons. Table IV shows stress values for the shear forces equal to 0.25 V u, 0.5 V u and 0.75 V u, where V u s the maxmum (ultmate) shear force reached wthn the s, when the specmen collapse occurred. Table IV shows that the actual affects of longtudnal shear between CFRP lamella and tmber (longtudnal shear forces and shear stresses) vary n the range of ±10 %, n average, wth theoretcal values. Fg. 12 CFRP lamella rupture together wth tmber falure Fg. 13 CFRP lamella separaton Fg. 14 delamnated CFRP lamella Issue 1, Volume 7,

7 Table IV Longtudnal shear n glued nterface between tmber and CFRP lamella: shear forces V long,1 [N.mm -1 ], stresses τ long [MPa] 100/220-C V u = kn derved from s 100/200-C V u = kn derved from s 100/180-C V u = kn derved from s 100/160-C V u = kn derved from s 100/140-C V u = kn derved from s 100/120-C V u = kn derved from s V long, τ long V long, τ long V long, τ long V long, τ long V long, τ long V long, τ long V long, τ long V long, τ long V long, τ long V long, τ long V long, τ long V long, τ long IV. CONCLUSIONS From the verfcaton, whch results actual normal and shear stresses and from them calculated cross-secton characterstcs are lsted n Tables I to IV and llustrated n Fgs. 6 to 11, the followng conclusons can be deducted: A. Normal Stresses The actual normal stresses n tmber are by about from 10 to 30 % less than the stresses determned by elastc calculaton; the usual dfferences wth theoretcal values are about 20 % n average; these facts ndcate that the elastc approach can be taken as the rght and sutable for the safe calculaton. The actual normal stresses n CFRP renforcement are by about from 5 (sporadcally) up to 40 % less than the calculated elastc stresses; the usual dfferences vary around the values from 20 to 30 %, that means also n the case the calculaton usng elastc approach can be appled, even as safer than n the case n tmber. The values of the parameter n derved from the s usng the measured stresses are n the range from to wth the mean value of 0.068, n comparson wth the theoretcal value of , that the dfference s 5 % only; ths shows relatvely very good nteracton between CFRP renforcement and tmber and confrms the rghtness of the elastc calculaton based on the concept of the substtute (deal) cross-secton arsng from the parameter n as a rato of Young's modulus of both secton materals. The values of the substtute cross-secton characterstcs, namely the second moment of area, calculated usng verfed n parameter (see above) are dfferent from +12 to -4% wth the theoretcal values, whle the mean value of the dfference 2.2 % s very low, so that the second moment of area and other secton characterstcs can be calculated accordng to the formulas mentoned above see, for example, (4), (5). B. Longtudnal Shear Stresses The actual values of longtudnal shear forces at the nterface between CFRP lamella and tmber and longtudnal shear stresses arsng from them, whch have been derved usng the actual parameters from the s (see above), are dfferent n the range ±10 %, n average, wth theoretcal values; ths shows very good match of the theoretcal calculaton of shear connecton wth the realty and the rghtness of ths prncple for nvestgated structural members composed of tmber and externally renforced by CFRP lamellas; but n ths case of bonded connectons CFRP tmber the attenton must be more pad to the nvestgaton of sutable glue and verfcaton of ts propertes from the vewpont of the coherence of both materals, because there s one of the mportant problems whch can sgnfcantly nfluence load-carryng capacty and namely nteracton between both parts. Issue 1, Volume 7,

8 ACKNOWLEDGEMENT The paper has been elaborated wthn the framework of the followng research projects solutons: the research project CZ.1.05/2.1.00/ (Center of AdMaS ), project of the unversty specfc research FAST S-11-32/1252 (both by the Czech Mnstry of Educaton, Youth and Sports) and the grant project No. 103/09/H085 (by the Czech Scence Foundaton). Wthn the elaboraton of the paper the realzed loadng s have been evaluated applyng the procedures usng the expermental results ncludng methods of the desgn asssted by ng based on the statstcal approach and usng the experences obtaned by the smlar evaluaton of the large sets of data for varous structural members and parts composed of varety of materals, whch are descrbed n [16] - [19], [23] - [32], [35]. In partal, the methods based on the probablstc approaches have been taken nto account, too see e.g. [20], [21], [22], [27], [28]. Author thanks the staff of the room at the authors' workplace for the works wthn the preparaton and realzaton of large number of s mentoned above. REFERENCES [1] Ascone, L., Barber, A., Benedett A. et al. Gudelnes for the Desgn and Constructon of Externally Bonded FRP Systems for Strengthenng Exstng Structures, Natonal research councl: Rome, [2] J. R. Glfllan, S. R. Glbert, and G. R. H. Patrck, The use of FRP compostes n enhancng the structural behavour of tmber beams, Journal of renforced plastcs and compostes, Vol.22, No.15/2003, pp , Sage publcatons, [3] Ľ. Nasch, and A. Tesár, Lmt behavor of lamnated wood grders renforced by carbon fber compostes Theoretcal assumptons and hypothess wth expermental ng, Research Report of the the Slovak Academy of Scence grant No. APVV , USTARCH-SAV, Bratslava, [4] A. Tesar, Ultmate response of boncs shells. Structural Engneerng and Mechancs, Vol. 14, No.2 (2002), pp [5] A. 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Melcher, Possbltes of applcaton of glassfbre-concrete n composte steel-concrete beams, In Proceedngs of the 9 th Internatonal Symposum on Fber-Renforced Polymer Renforcement for Concrete Structures FRPRCS-9 held n Sydney, Unversty of Adelade, 2009, p. 51 (book) + DVD (full verson 4 pages). ISBN [16] M. Karmazínová, Desgn asssted by ng a powerful tool for the evaluaton of materal propertes and desgn resstances from results, Internatonal Journal of Mathematcal Models and Methods n Appled Scences, Vol. 6, No. 1, 2012, pp ISSN [17] M. Karmazínová and J. Melcher, Desgn asssted by ng appled to the determnaton of the desgn resstance of steel-concrete composte columns, In Proceedngs of the 13 th WSEAS Internatonal Conf. on Mathematcal and Computatonal Methods n Scence and Engneerng MACMESE'11, WSEAS Press: Catana, 2011, pp ISBN [18] M. Karmazínová, J. J. Melcher, Methods of the desgn asssted by ng applcable tools for the desgn resstance evaluaton usng results, In Proceedngs of the 2 nd Internatonal Conference on Mathematcal Models for Engneerng Scence ( MMES 11 ), Insttute of Envronment, Engneerng, Economcs and Appled Mathematcs, WSEAS Press: Puerto de la Cruz, 2011, pp ISBN [19] M. Karmazínová, M. Plgr, J. J. Melcher, Methods based on the approach of the desgn asssted by ng appled to the determnaton of materal propertes, In Proceedngs of the 2 nd Internatonal Conference on Mathematcal Models for Engneerng Scence ( MMES 11 ) Mathematcal Models and Methods n Modern Scence, Insttute of Envronment, Engneerng, Economcs and Appled Mathematcs, WSEAS Press, Puerto de la Cruz, 2011, pp ISBN [20] A. Omshore, Optmzed Stochastc Based Desgn of Structures, In Proceedngs of the 4 th WSEAS Internatonal Conference on Engneerng Mechancs, Structures, Engneerng Geology (EMESEG 11), WSEAS Press: Corfu Island, 2011, pp , ISBN [21] A. Omshore, Uncertanty Analyss of the Cross-sectonal Area of a Structural Member, In Proceedngs of the 4 th WSEAS Internatonal Conference on Engneerng Mechancs, Structures, Engneerng Geology (EMESEG 11), WSEAS Press: Corfu Island, 2011, pp ISBN [22] J. Melcher, M. Škaloud, Z. Kala, M. Karmazínová, Senstvty and statstcal analyss wthn the elaboraton of steel plated grder resstance, Advanced Steel Constructon, an Internatonal Journal, Vol. 5, No. 2, Hong Kong Insttute of Steel Constructon, June 2009, pp ISSN X. [23] M. Karmazínová, M. Štrba, V. Kvočák, Steel-concrete composte members usng hgh-strength materals n buldng constructons structural desgn, actual behavour, applcaton, In Proceedngs of the 2 nd European Conference on Cvl Engneerng ( ECCIE 11 ), North Atlantc Unversty Unon, WSEAS: Puerto de la Cruz, 2011, pp ISBN [24] M. Karmazínová, J. J. Melcher, Analyss of the resstance of steelconcrete composte members composed of hgh-strength materals, In Proceedngs of 10th Internatonal Conference on Steel, space and composte structures SS 11, Famagusta, CI-premer: Sngapore [25] M. Štrba, M. Karmazínová and J. Melcher, Relable and effectve desgn of composte members Steel-concrete composte members usng hghstrength materals, In Proceedngs of the 6 th European Conference on Issue 1, Volume 7,

9 Steel and Composte Structures EUROSTEEL 2011, Budapest, ECCS 2011, pp ISBN [26] M. Karmazínová, J. J. Melcher, V. Röder Load-carryng capacty of steel-concrete compresson members composed of hgh-strength materals, In Proceedngs of the 9 th Internatonal Conference on Steel- Concrete Composte and Hybrd Structures ASCCS 2009, Leeds, Research Publshng Servces: Sngapore, 2009, pp ISBN [27] Z. Kala, L. Puklcký, A. Omshore, M. Karmazínová, J. Melcher, Stablty problems of steel-concrete members composed of hgh-strength materals, Journal of Cvl Engneerng and Management, 2010, 16(3), pp do: /jcem [28] Z. Kala, M. Karmazínová, J. Melcher, L. Puklcký, A. Omshore, Senstvty analyss of steel-concrete structural members, In Proc. of the 9 th Internatonal Conference on Steel-Concrete Composte and Hybrd Structures ASCCS 2009 n Leeds, Research Publshng Servces: Sngapore, 2009, pp ISBN [29] M. Karmazínová, J. Melcher, Z. Kala, Desgn of expanson anchors to concrete based on the results of expermental verfcaton, Advanced Steel Constructon, an Internatonal Journal, Vol. 5, No. 4, Hong Kong Insttute of Steel Constructon, December 2009, pp ISSN X. [30] M. Karmazínová, J. Melcher, Z. Kala, Load-carryng capacty of postnstalled steel anchors to concrete subjected to shear, In Proceedngs of the 3 rd Internatonal Conference on Steel and Composte Structures ICSCS 07 held n Manchester, Unversty of Manchester, 2007, pp ISBN [31] M. Karmazínová, J. Melcher, Z. Kala, Actual Behavour and Loadcarryng Capacty of Steel Expanson Anchors to Concrete, In Proceedngs of the 5 th Internatonal Conference on Advances n Steel Structures, Research Publshng Servces: Sngapore, 2007, Vol. III, p ISBN [32] M. Karmazínová, J. Melcher, M. Štrba, Fastenng of steel structural members to concrete usng post-nstalled mechancal fasteners, In Proceedngs of 9 th Internatonal Conference on Steel-Concrete Composte and Hybrd Structures ASCCS 2009, Leeds, Research Publshng Servces: Sngapore 2009, pp ISBN [33] EN Desgn of Composte Steel and Concrete Structures Part 1-1: General Rules and Rules for Buldngs, CEN Brussels, [34] EN Desgn of Tmber Structures Part 1-1: General Rules and Rules for Buldngs, CEN Brussels, [35] EN 1990 Bass of Structural Desgn: Annex D Desgn asssted by ng, CEN Brussels Issue 1, Volume 7,