The Romanian Road Administration Experience in The Field Of NDT for Bridges

Transcription

1 Nantes, France, June 30th July 3rd, 009 The Romanan Road Admnstraton Experence n The Feld Of NDT for Brdges Crstna ROMANESCU 1, Constantn IONESCU, Rodan SCINTEIE 3 1 Romanan Natonal Company for Motorways and Natonal Roads, Bucharest, Romana, crstnaromanescu@gmal.com "Gh. Asach" Techncal Unversty, Ias, Romana 3 Center for Techncal Road Studes and Informatcs (CESTRIN) Abstract In 1993 Romanan Natonal Company for Motorways and Natonal Roads (C.N.A.D.N.R.) decded to perform qualty controls by ts own research branch, Center for Techncal Road Studes and IT (CESTRIN), for works executed on brdges. Thus, three equpments were purchased: Schmdt hammer, ultrasonc concrete tester and pachometer, allowng CESTRIN to perform tests on road brdges, n a mult-year montorng process. After 1989 n Romana almost all brdge techncal data have been lost, thus leadng to errors n rehabltaton desgns. In 009 CESTRIN wll be benefcary of a PHARE Project Improvement of safety, qualty of servces and nsttutonal capacty n transport sector. Thus, new equpments that offer nformaton about road structures and rverbed wll fulfll the needs of C.N.A.D.N.R. Our task s to create a relaton between degradatons and brdge s actual bearng capacty. These quantfable dsorders must lead to an equaton to provde an assessment of structure s behavor under actual traffc loads. Ths paper descrbes actual stuaton n Romana n the feld of NDT of brdges. Résumé En 1993, la Compagne Natonale Roumane pour Autoroutes et Routes Natonales (C.N.A.D.N.R.) a décdé d'effectuer des études de qualté par son département de recherches, Centre pour les Etudes Technques de Route et IT (CESTRIN), pour des travaux exécutés sur ouvrages. Ans, tros équpements ont été achetés: un Marteau Schmdt, un apparel de contrôle ultrasonque de béton et un pachomètre, permettant au CESTRIN de réalser des tests sur des ponts, dans un processus de survellance plur-annuel. Après 1989 en Roumane, presque toutes les données technques des ponts ont été perdues, de ce fat menant à des erreurs dans la concepton de réhabltaton. En 009, le CESTRIN est le bénéfcare du projet PHARE «Améloraton de la sûreté, de la qualté du servce et de capacté nsttutonnelle dans secteur des transports». Ans, nouveaux équpements qu offrent des nformatons sur des structures de route, et lts de rvères, vont répondre aux les besons du C.N.A.D.N.R. Notre tâche est de créer une relaton entre dégradatons et portance réelle des ouvrages. Ces désordres quantfables dovent mener à une équaton pour fournr une évaluaton de structure sous charges de la crculaton réelle. Cet artcle décrt la stuaton actuelle en Roumane dans le domane des technques non destructves applquées aux ouvrages. Keywords degradatons, bearng capacty, structure assessment, brdge statstcal data, case studes 1 Introducton Expermental researches supposed NDT methods appled on dfferent types of concrete havng compresson strength between 150 and 400 dan/cm both on laboratory specmens and

2 Nantes, France, June 30th July 3rd, 009 n stu, on brdges elements. Correlaton curves derve from methods as rebound method, pulse velocty method and combned method. These results show the qualty of concrete n dfferent structures analyzed along 7 years of work. Compresson strength measured s correspondng to 0 cm cubes. Expermental results Between 001 and 007 C.N.A.D.N.R. asked CESTRIN to perform NDT tests on structures located on natonal roads, both for new brdges and brdges that have been rehabltated. All tests compled wth the Romanan regulaton C Nondestructve Testng Norm for Concrete and also STAS 665/1-198 Nondestructve Concrete Testng. Classfcatons and general gudelnes untl August 007; presently, SR EN 1504-:00 Testng concrete n structures-part : Non-destructve testng-determnaton of rebound number and SR EN :004 Testng concrete-part 4: Determnaton of ultrasonc pulse velocty are used. For rebar locator we used BS 1881 part 04 and DIN 1045, as Romana has no regulaton. Durng tests a Schmdt hammer, an ultrasonc concrete tester and a pachometer has been used. Also, auxlary measurng tools have been used, such as: thermometer, crack scale magnfer, water levelng rule, geometrc tools, and rule for measurement of dstances. Chosen ponts for the transducers were optmally arranged wthn a grd where no rebar can be found so results wll not be nfluenced. Drect wave technque has been used n all studes..1. The year 001 Objectve was to assess qualty of concrete and montorng of followng brdges: Natonal Road (NR) 7A at km at Gemenea and NR 1 at km at Predeal. At km dstance between transmtter and recever was of 18 cm, and at km was of 0 cm. If crack depth s bgger than concrete cover, carbon doxde nfltraton to rebar through cracks s thus possble, ncreasng carbonaton rsk. Usng pachometer rebar path, ts dameters and concrete cover were detected. Wdth of cracks was n all sectons of exactly 0.3 mm. Concrete cover vares between 36 and 53 mm. At km as a result of n stu tests the followng were establshed: concrete presents an advanced corroson condton to entre bottom part of slab on all brdge length (ph = 5.5) and concrete segregaton may be observed to beams due to nsuffcent vbraton that occurred n crcumstances of lmted space and a large number of rebar. The use of bg aggregates may be observed, dscordant to rebar dameter. Hgh porosty concrete used allowed water and aggressve envronment to attack. Both, n cross beams and n beams concrete has ts ph = 6, thus favorng rebar corroson. Fgure 1. Tests that have been performed at Gemenea and Predeal Rebar secton s reduced about 50% to transversal rebar, and longtudnal rebar lowered ts dameter by 0% (loosng ts alkal propertes concrete doesn t consttute a protecton for rebar, thus was heavly corroded; a protectve concrete has ts ph over 9). Tests usng

3 Nantes, France, June 30th July 3rd, 009 combned method showed followng compresson strength: crossbeam 6 n 6 th span, between 1 st and nd beam - 00 dan/cm and beam 1 - span 6-50 dan/cm. For the brdge at km as a result of tests the followng were establshed: concrete presents an advanced corroson condton to all nferor part of slab on all brdge length (ph = 6). Measurements showed that: rebar s dameters of renforced slab reduced from φ16 to φ13, from φ 10 to φ 8 and from φ 8 to φ 4.5, so to all types of rebar the secton s reduced consderably (by 18.75%, 0%, 43.75%) favorng destructon of slab n several spans; mnmum of concrete cover s 1 mm, and maxmum of 46 mm, so, n case of beam 1 n 1 st span carbonaton rsk s zero for the moment, of course f water does not nfltrate; mnmum of measured crack depth from surface of concrete was of 7.67 cm, and maxmum of cm... The year 00 Based on nspecton forms completed for Suceava Natonal Road Secton and South Bucharest Natonal Road Secton an analyss has been done regardng the behavor of brdges dependng on geographc area and statc scheme. We observed that ntervals of qualty ndexes are comparable n these two areas but for dentfcaton of a real techncal condton a statstcal calculaton was necessary. So, we calculated: average qualty ndex per Secton I average, absolute devaton of each ndex ε, squared average devaton of ndexes S and varaton coeffcent of ndexes C. Statstcal calculaton supposng a Gaussan dstrbuton has been done usng followng formulas: I I = ε S (1) ε = I I () S (3) C = 100% (4) average average n = n 1 where I represent value of each qualty ndex for each brdge; n-number of smple supported beams brdges for each Secton. Thus t became clear that condton of smple supported beams brdges n mountan areas s much worse than n plan areas. Absolute devaton of ndexes Squared average devaton I average Varaton coeffcent SUCEAVA BUCURESTI SUD SUCEAVA BUCURESTI SUD SUCEAVA BUCURESTI SUD Fgure. Charts for qualty ndexes for Suceava and South Bucharest Sectons.3. The year 003 Laboratory tests were performed on a concrete used n dfferent elements of brdges havng a known compresson strength 400 dan/cm. Objectve was to establsh precson of compresson strength evaluaton usng those three methods. A 0 cm concrete cube was tested, and obtaned compresson strength was: 384daN/cm, 45daN/cm and 407daN/cm, so accuracy was hgh enough (+6.6%, -4% and +1.75%, an average of 1.34%)..4. The year 004 In many cases crackng of concrete may pont out overload condton or weakness due to varous reasons. Wdth on concrete surface may be determned usng smple optcal methods. Instead, nvestgaton of ts poston and depth requres use of specal technques, one of them s ultrasonc testng, cracks flled by ar creatng a screen that reflects ultrasonc waves. Accordng to Romanan Norm for concrete testng usng NDT methods C 6-85 depth of crack may calculated as follows:

4 Nantes, France, June 30th July 3rd, 009 h f = l [( t t ) 1] (5) where: h f -depth of the crack, n cm, l-dstance between two transducers, n cm, t 1 -tme that devce shows for secton n front of crack, n µs and t 0 -average tme of readngs on devce between ponts stuated on same dstance for sectons wthout cracks, n µs. Crack wdth and dstance between cracks for elements of exstng renforced concrete structures can be calculate usng both equatons n Romanan regulaton STAS and EUROCOD. 1 0 Table 1. Determnaton of depth of crack F1 on 1 st beam span 1 NR km [ 1] 1 0 Secton Tme Corrected tme Corrected Average tme Dstance between t t 1 0 ( ) t t 1 0 ( t t ) ( t t ) d/ hf readng for etalonaton tme for for crackless transducers (cm) (µs) (µs) temperature concrete (cm) 1' - ' '- 4' '- 6' I II III Crack wdth must be lmted not to negatvely affect behavor of concrete, renforced concrete and pre-stressed concrete brdges n servce and not to affect aesthetcs. In order to nsure a hgh durablty one must take nto consderaton that renforcement protecton to corrosve actons s nfluenced only by thckness of concrete cover and ts qualty, and, mostly by the way crack lmtaton condton s respected. Investgated brdges were: NR at km beam 1 span 1 and NR at km nd abutment. Crack depth varaton dagram on beam 1 span 1 - brdge km at Crack depth varaton dagram on beam 1 span 1 - brdge km Depth of crack hf (cm) Crack depth hf (cm) Crack depth varaton on abutment - brdge km Crack depth hf (cm) Fgure 3. Cracks F1 and F on NR km and crack F3 at km The year 005 Objectve was a comparson between results obtaned usng destructve and nondestructve methods n order to determne the maxmum error percent. Three 0 cm cubes and 3 prsms (55x10x10 cm) of B 50 concrete were tested. Pa 35 cement was used wth a dosage of 300 kg/m 3, rver aggregates wth a maxmum dmenson of 41 mm and smaller than 1 mm fractons n a percent of 17,7%. Concrete maturty age s of 48 days. Tested specmens had the followng hardenng process: 14 days n a dry envronment at 0 C, then 7 days n water at C, and, n last stage, dry envronment at 0 C.

5 Nantes, France, June 30th July 3rd, 009 Fgure 4. Laboratory tests on a concrete cube wth 50 dan/cm No. Element Rebound number Table. Rebound number, pulse velocty and compresson strength Pulse Compresson strength wth velocty (dan/cm ) (km/s) Schmdt hammer Ultrasonc Combned Compresson strength at hydraulc press (dan/cm ) 1 Cube Cube Cube Prsm Prsm Prsm Usng obtaned data values were determned for each non-destructve method as follows: Table 3. Measured error for each non-destructve method Compresson strength usng the hydraulc press (dan/cm ) Schmdt hammer method Ultrasonc method Combned method Average(daN/cm ) Error ±% N/A The year 006 Objectve was to assess compresson strength for followng brdges on NR 15: km , km , km , km and km Table 4. Rebound number, pulse velocty and compresson strength wth SONREB Beam Beam Beam Abutment Abutment km km km km km Rebound number Pulse velocty (km/s) Compresson strength (dan/cm ) Compresson strength (dan/cm) Compresson strength (dan/cm) Wave's pulse velocty (km/s) Rebound number km km km km km km km km km km Fgure 5. Rebound number/pulse velocty versus compresson strength on NR 15

6 Nantes, France, June 30th July 3rd, The year 007 Objectve was to assess concrete qualty for followng brdges: NR 1B at km at Cresoaa and at km at Cerdac. compresson strength values for two nvestgated beams (3 and 5) of the brdge at km 5+033, and two beams ( and 5) of the brdge at km are around 300 dan/cm, good values for a 59 years old renforced concrete used to superstructure Compresson strength (dan/cm) y = e 0.056x R = Compresson strength (dan/cm) y = 1.83e x R = Rebound number km km Average devaton Wave's pulse velocty (km/s) km km Average devaton Fgure 6. Rebound number/pulse velocty, compresson strength and test ponts on NR 1B 3 Conclusons One may observe the effcency and effcacy of usng NDT methods versus destructve methods, fast assessment of brdge elements beng a prortary drecton for European road admnstrators. It s recommended to use NDT for hgh resstance because errors are consderably smaller. Combned SONREB method gves the best results of compresson strength. Because concrete s a complex materal nterpretaton of results may be a challenge for all structural engneers f they do not dspose of a long experence n ths feld. Nondestructve tests may represent, f properly used, a very mportant tool n brdge assessments actvtes and are, for sure, a very useful for determnaton of relatve resstances of concrete n dfferent areas of the same element of a brdge. References 1. Romanescu, C., Scntee, R., Padure, V., Padure, M., (001) NDT tests of brdges and tme montorng of rehabltated brdges. Romanescu, C., Romanescu, C., Padure, M., (00) NDT tests and tme montorng of rehabltated brdges 3. Romanescu, C., Scntee, R., Padure, V., Padure, M., (003) NDT tests and tme montorng of rehabltated brdges 4. Romanescu, C., Romanescu, Cl., Padure, M., (004) NDT tests and tme montorng of rehabltated brdges 5. Dragomrescu, I., Romanescu, C., Padure M., (005) Tme montorng of rehabltated brdges usng specfc methods. Brdges requested by CNADNR 6. Sandu, L, Romanescu, C., Dragomrescu, I., Padure, M., Istrate G., (006) Tme montorng of rehabltated brdges usng specfc methods 7. Sandu, L, Romanescu, C., Istrate G., (007) Tme montorng of rehabltated brdges usng specfc methods. Brdges requested by CNADNR 8. Mgoun, N.P., Novkov, S.A., (008) Non-Destructve Testng n Belarus 17 th World Conference on Nondestructve Testng, Shangha, Chna 9. Shen, G. (008) Progress of Nondestructve Testng and Evaluaton n Chna 17 th World Conference on Nondestructve Testng, Shangha, Chna 10. Klyuev, V.V., Fedosenko, Yu. K. (008) 50 th Annversary of non-destructve testng n Russa 17 th World Conference on Nondestructve Testng, Shangha, Chna