Ultimate bearing capacity of existing heavy haul railway concrete simple double-t girder strengthened by anchoring assisted steel beams

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1 International Conferene on Remote Sensing, Environment and Transportation Engineering (RSETE 03) Ultimate bearing apait of existing heav haul railwa onrete simple double-t girder strengthened b anhoring assisted steel beams Wei Guo Long Shool of Civil Engineering, Central South Universit, Changsha, Hunan, P R. China Shool of Mathematis and Phsis, Universit of South China, Hengang,Hunan, P R. China longwg6767@63.om Li Li The Third Railwa Surve and Design Institute Group Corporation, Tianjing, P R. China lili07@tsdig.om Li Zhong Jiang * Shool of Civil Engineering, Central South Universit, National Engineering Laborator for High Speed Railwa Constrution Changsha,Hunan, P R. China lzhjiang@mail.su.edu.n *Corresponding author Ling Kun Chen Shool of Civil Engineering, Central South Universit, Changsha,Hunan, P R. China lingkunhen08@hotmail.om Abstrat Based on the failure mehanisms analsis of the strengthening method of anhoring assisted steel beams of the existing heav haul railwa onrete simple double-t girders, the plasti ultimate bearing apait analsis method are presented in this paper, the alulation formula of the strengthening of anhoring assisted steel beams of the onrete simple double-t girders is derived, the ultimate bearing apait of the heav-haul railwa onrete simple double-t girders is alulated, the field test is arried out to verif the alulation results of theor analsis. The alulation and test results show that the strengthening method of anhoring assisted steel beams an improve the ultimate bearing apait of the onrete simple double-t girders. Kewords Heav-haul railwa, onrete simple double-t girder, strengthening of bonding assisted steel beams, ultimate bearing apait Ⅰ. INTRODUCTION With China's rapid eonomi development, China's heav-haul railwa annual volume inreases rapidl, the heav haul train axle load and unit train tration qualit are rising, whether the existing heav-haul railwa an meet the requirements of above had beome an important topi of departments of the heav haul railwa. The existing heav haul railwa onrete bridge strutures due to the low design standard and the use of a ertain period and appears of different level of defets and diseases, the bridges ma not meet the heav haul railwa transportation needs, therefore, the bridge must been to re-assess, ensure the train through the bridge safel and smoothl. Proessing methods of the bridge an not meet the requirement usuall has two kinds: one is the demolition of old bridge reonstrution of bridge, onstrution of new bridge will inevitabl affet the normal operation of trains, and the onstrution period is long, investment is large; another is strengthening on old bridge, its main advantages are less investment, short onstrution period, and even sometimes also does not affet the normal operation of the railwa train. How to reasonable use, orret repair and reinforement of the existing heav haul railwa bridges is an important task of 03. The authors - Published b Atlantis Press 68

2 the transport setor, and has great eonomi benefit and soial signifiane. Sine 970 s, lots of researhers at home and abroad pa muh attention to the reinforement tehnolog of onrete bridges struture strengthened b steel plate or setion steel, some researh results have ahieved, and the reinforement tehnolog of onrete bridges struture have been widel applied in the atual engineering. Jones and Swam began to researh the onrete girders strengthened b epox-bonded steel plates and studied its strutural behavior, Basunbul and Sharif studied strengthening of shear damaged RC beams b external bonding of steel plates; In our ountr, in reent ears there are man researhers on onrete girders strengthening onduted a series of studies, is mainl aiming at onrete retangular or box setion beam bottom or ompressive region b pasting steel plate or setion steel to improve the ultimate bearing apait of bridge. Beause of onrete double T girders in China's heav haul railwa bridge is widel applied, the researh literatures of the onrete simpl supported double-t girders reinforement are less, espeiall the researh literatures of on two lateral side of the onrete simpl supported double-t girders anhoring assisted steel beams are less. Beause of the lower edge of flange of the onrete simpl supported double-t girders has greater spae of using, the strengthening method of anhoring two assisted steel beams in both outside of the existing girders of heav haul railwa bridges is put forward, this method an improve the bearing apait and the seismi apait in lateral and vertial of the heav haul railwa bridges. The ultimate bearing apait of the onrete simpl supported double-t girders reinforement with assisted steel beams were analzed, the alulation formula of the ultimate bearing apait of the onrete simpl supported double-t girders anhored b the assisted steel beams reinforement in both outside is dedued, and arried on the test, the test results and the alulation results were ompared and analzed. Ⅱ. REINFORCEMENT METHOD OF HEAVY HAUL RAILWAY BRIDGES The assisted steel beams anhoring is one kind of the setion-enlarging reinforement method, the method an effetivel improve the bearing apait and lateral and vertial stiffness of the heav haul railwa bridges, and it an make full use of the spae under the girders flange, the height of assisted steel beams an be maximall inreased. The assisted steel beams and simpl supported double-t girders fastened b a T shaped onneting plate with the high strength bolts. The elevation of onrete simple supported double-t girder of heav haul railwa ridge is shown in Fig.. The shemati setion view of the enfored simpl double-t girder is shown in Fig.. The assisted steel beams and simpl supported double-t girders an be onneted b two kinds of was, the enfored simpl double-t girder an ooperativel bear the loading. One is asting onrete blok between the upper flange of the assisted steel beams and the flange of the onrete double-t girders at a ertain distane; another is that the assisted steel beams are onneted b a transverse partition plate (T shaped onneting plate) whih an transfer loading effetivel. Fig. Elevation of onrete T girder The main harateristis of the reinforement method: () onveniene in onstrution; () various was an be used to transfer loading, and the integral stress distribution is better; (3) The bearing apait, the horizontal and vertial seismi apait of the girders an be greatl improved. Assisted steel beam Bottom of onrete T girder Roof of onrete T girder C50 onrete High strength bolt T shaped onneting plate Web of onrete T girder Assisted steel beam Transverse partition plate - Fig. Shemati setion view of the enfored simpl double-t girder 69

3 Ⅲ. FORMULA OF FLEXURAL BEARING CAPACITY AFTER STRENGTHENING After reinforement, the setion alulation diagram of the simpl supported double-t girders is shown in Fig.3. The ultimate bearing apait and the strength and rigidit of the heav haul railwa bridges are improved, thereb the deformation of heav haul railwa bridges an be redued. The basi assumptions of the reinfored plasti design in the paper are listed as follows: () The assisted steel beams and the onrete double-t girders have no relative sliding; the anhoring onnetion of the reinforing girders is full shear onnetion; () The axial strain of strengthened girders obes the plane assumption; (3) When the struture reahes the limit state, ompression zone of onrete reahes the ompressive design strength value; (4) The interation of onrete girders in tension zone is ignored. h h s b sa Fig.3 Shemati of reinfored girder normal setion and stress Therefore, aording to the fore balane, fore - balane equation is formulated as fa + f As + f pa f t Ast + f pat () f and f p are separatel the ompressive strength design value of onrete and strength design value of steel; f and f t are respetivel the strength design value of the ompression and tensile reinfored of the onrete girder; A s and A st are respetivel the area of the ompression and tensile reinfored of the onrete girder; A and A t are respetivel the area of the ompression and tensile setion of the assisted steel beam; A is the ompression area of the onrete girder. b b t A s Neutral axis b st f pat t s ft Ast A st f p f f As fa f A p where F f [ b ( h - h ) + b ( h - )] () F F s a s f A (3) s s f A (4) st t st F f [ b t + b ( - t )] (5) t p sa s st s F f [ b t + b ( h - - t )] (6) sa p sa s st s s E[ b h - ( b - ba ) hs ] + Eshs[ bsat s + bst ( hs - ts)] E [ b h - ( b - b ) h ] + E [ b t + b ( h - t )] a s s sa s st s s (7) E and E s are separatel the oung's modulus of steel and onrete; is the distane of the neutral axis to the lower edge of the onrete girder; F is the bearing maximum pressure of the onrete girder; F s is the bearing maximum pressure of the ompression steel of the onrete girder; F st is the bearing maximum tension of tensile steel of the onrete girder; F t is the bearing maximum tensile fore of the assisted steel beam; F sa is the bearing maximum pressure of the assisted steel beam. The bending bearing apait alulation formula of the assisted steel beam reinforement simpl supported double-t girder is where with M F F ( a ) F (8) u, p s s sa b h h b h h h [ b ( h - h ) + b ( h - )] ( - s ) + a( s - )[ - ( s + )] s a s s (9) h - x - x (0) h - - x () When the onrete reahes the limit state, 70

4 x bsat s + bst ( hs - - ts)( hs - + ts) [ b t + b ( h - - t )] sa s st s s bsat s + bst ( - ts )( + ts ) x [ b t + b ( - t )] sa s st s is the distane of the tensile enter of the assisted steel beam to ompression enter of the onrete girder; is the distane of the tensile enter to the ompression enter of the assisted steel beam; is the distane of the ompression enter to upper edge of the onrete girder; x is the distane of the ompression enter to the upper edge of the assisted steel beam; x is the distane of the tensile enter to the lower edge of the assisted steel beam; a s respetivel are reinforement protetion laer thikness of the onrete girder. Ⅳ. TEST OF THE FLEXURAL BEARING CAPACITY Test plan Fig.4 Shemati of testing girders The loading on both ends of the bearing l/4, as shown in figure 5. The original girders A, A(Unit: mm) T shaped onneting plate 600 The strengthening girders A3,A4(Unit: mm) 400 P P reinforement stell - Assisted steel beam AFTER STRENGTHENING 4. Making of the testing girders Aording to the atual size of the original girders of the heav haul railwa bridges, all of testing girders are ast b C50 onrete with the sale of :0, the length of the girders is 700mm; the alulation length is 600mm. There are four testing girders speimens (A, A, A3, A4) need to be made. A, A as the original girders, A3, A4 are the strengthening girders b the assisted steel beams, the I-shaped assisted steel beams are welded b the steel plates, the thikness of the steel plates are mm, there is the T shaped steel plate between the assisted steel beams and the onrete double-t girders at intervals of 00mm, the assisted steel beams is welded to the T-shaped steel plate, and the onrete double-t girders is onneted b 4 6 expansion high strength bolts with the T-shaped steel plate. The shemati of testing girders is shown in Fig Experiments and results 600 Fig.5 Shemati of load A, A are reinfored onrete girders, the failure mode is a tpial normal setion flexural failure. A3, A4 are the strengthening omposite girders b the assisted steel beams, to maintain its stabilit, the onrete plate are ast between two T girders at intervals of 400mm, an ooperativel bear the loading. Their failure forms are the same. The appear as elasti deformation before loaded to nearl 60% of failure loads, when the loading reah 5 kn m, the surfae raks of the onrete girders are appear, with the load inreases, the rak enlarges graduall, but the assisted steel beams and onrete girders there are not appear obvious relative slip, when the loading reah 35 kn m, the relative slip the assisted steel beams and onrete girders are appear, when the loading reah 38.7 kn m, the relative slip of the assisted steel beams and onrete girders are about mm, the limit bending moment of this girder is 38.7 kn m. The test urve of the moment-urvature of the eah girder is shown Fig.6. Fig.7 for the loading proess of reinforement beam, Fig.8 for the damage of original beam, Fig.9 for the 7

5 damage of reinforement beam. Moment/ (kn.m) A A A3&A Curvature/ (mm - ) Fig.6 Test urve of moment-urvature of girder it illustrate that the ultimate bending moment of strengthening girders is muh larger than of the original girders; () there is the smaller relative slip between the assisted steel beams and girders A3, A4, it illustrate that the strengthening girders are shear onnetion well; (3) all of the girders appear rebound phenomenon after unloading, the strengthened girders are obvious, it show that the elastiit of strengthened girders are better than of the original girders; (4) the strengthened girders have good dutilit and strength reserve apait. Ⅴ. ANALYSIS OF FLEXURAL BEARING CAPACITY AFTER STRENGTHENING Fig.7 Loading proess of reinforement beam The alulation results ompared with test results of the flexural bearing apait of the onrete simpl supported double-t girders strengthened b the assisted steel beams b formula 7 in Table.. Table COMPARISONS OF TEST RESULTS AND CALCULATED RESULTS Flexural bearing Test result/ Calulation Relative apait (kn m) result/(kn m) error/(%) The original girder (A) The original girder (A) Fig.8 Damage of original beam The strengthening girder (A3&A4) Note:Relative error [( Test results - Calulation result)/test results] 00% Fig.9 Damage of reinforement beam The following onlusions an be drawn: () the original girders A, A are damaged earl, the girders A3, A4 strengthened b the assisted steel beams are damaged later, Obviousl, the flexural bearing apait of alulation with the formula 7 is agree exellent with the pratial situation; ompared with the test result, relative error alulated b the alulation result is smaller. The auses of errors mainl inluded two aspets: ) beause of the supposed the whole ross setion of the assisted steel beams full step into the plasti stage, and atual ondition is not suh, when the assisted steel beams is in elasti stage, the reinforement steel of the tension region of the onrete girders have been rupture, the whole ross setion of the assisted steel beams ould not be full into plasti state; ) the interation of 7

6 tension zone of the onrete girders is ignored. But beause the error is small; therefore, the ultimate bearing apait of the onrete simpl supported double-t girders strengthened b the assisted steel beams alulated b formula 7 is feasible. Ⅵ. CONCLUSION Through the theoretial analsis and the test verifiation, the test results and the alulation results arries on the ontrast analsis, the reinforement method of the simpl-supported onrete double-t girders strengthened b the assisted steel beams an be used in the strengthening of heav haul railwa bridges. The following onlusions are drawn: ) The flexural apait alulation of the onrete simpl supported double-t girders strengthened b the assisted steel beams is still in the explorator stage, the hpothesis put forward in this paper also waits for further disussion, the flexural apait alulated b the simplified formula are lose to the test results, the error is small, the formula an be applied to pratial engineering. ) B testing, the strengthened girders have good shear performane, dutilit, elastiit and strength reserve apait. 3) The bearing apait and seismi apait of horizontal and vertial of the strengthened girders inrease. REFERENCES [] Nie, J. G., and Yu, Z. W. (999) Researh and pratie of omposite steel-onrete beams in China, China Civil Engineering Journal, Vol.3, No., pp.3-7. [] Mkenna, J. K. M., and Erki, M. A. (994) Strengthening of reinfored onrete flexural members using externall applied steel plates and fiber omposite sheets-a surve, Canadian Journal of Civil Engineering, Vol., pp.6-4. [3] Sharif, A., Al-Sulaimani, G. J., Basunbul, I.A., Baluh, M.H., and Husain, M. (995) Strengthening of shear damaged RC beams b external bonding of steel plates, Magazine of Conrete Researh, Vol.47No.73, pp [4] Hussain, M., Sharif, A., Basunbul I. A., Baluh, M. H., and AL-Sulaimani, G. J. (995) Flexural Behavior of Preraked Reinfored Conrete Beams Strengthened Externall b Steel Plates, Strutural Journal, Vol.9, No., pp.-3. [5] Jones, R., Swam, R. N., and Charif, A. (988) Plate separation and anhorage of reinfored onrete beams strengthened b epox-bonded steel plates, The Strutural Engineer, Vol.66,No.5, pp [6] Swam, R. N., Jones, R., and Bloxham, J. W. (987) Strutural behavior of reinfored onrete beams strengthened b epox-bonded steel plates, The Strutural Engineer, Vol.65,No.A(), pp [7] Yu, Q., Sun, and H. L. (00) Researh on the Mehanial properties of onrete beam reinfored b hannel steel, Low Temperature Arhiteture Tehnolog, Vol.39, No., pp [8] Tong, G. B., and Lu Y. Y. (004) Analsis of the bearing apait of RC beams b steel-boned reinforement, Speial Strutures, Vol., No., pp [9] Wang, X. L., and Zhang Y. T. (006) Analsis of the flexural apait of steel-bonded reinforement in ompressive zone for onrete beams, Journal of Huazhong Universit of Siene and Tehnolog (Urban Siene Edition), Vol.3, No., pp [0] Sinan Altin, Özgür Anil, and M. Emin Kara. (005) Improving shear apait of existing RC beams using external bonding of steel plates, Engineering Strutures,Vol.7, No.5, pp [] Roberts, T.M., and Hajkazemi, H. (989) Theoretial stud of the behavior of reinfored onrete beams strengthened b externall bonded steel plates, ICE Proeedings, Vol.87, No., pp [] Zhang, S., Raoof, M., and Wood L. A.(995) Predition of peeling failure of reinfored onrete beams with externall bonded steel plates, Proeedings of the Institution of Civil Engineers. Strutures and Buildings, Vol.0, No.3, pp [3] Vilna, O. (988) The analsis of reinfored onrete beams strengthened b epox bonded steel plates, International Journal of Cement Composites and Lightweight Conrete, Vol. 0, No., pp