NDT ON CONCRETE STRUCTURES UNDER LOAD TESTS Hazard: Extreme Loads

Transcription

1 NDT ON CONCRETE STRUCTURES UNDER LOAD TESTS Hazard: Extreme Loads STUDENT: TODDRICK BROWN AIDICO S MENTOR: JOSÉ VICENTE FUENTE Hosted Institution: University: National Science Foundation:

2 Outline OBJECTIVES: - The main purpose is to show the NDT applicability to characterize and explore the concrete structures. -The characterization involves NDT parameters, extracted for the tests, related with some properties of the concrete. In this action, we focused in load tests process and how to follow the NDT waves (ultrasonic & electromagnetic) in the load status. - The NDT exploration uses the ability to detect and locate inner defects (look inside). We focused on concrete cube (real scaled) placed in AIDICO s facilities. CONTENTS: - Introduction - Ultrasonic Background & Equipments - Ground Penetration Radar Background & Equipments - Experimental Results on Concrete Cube - Experimental Results for Load Test - Conclusions

3 INTRODUCTION NDT vs CONCRETE BOND TEST CARBONATION LIQUIDS CRACK METER CRACK SCOPE REINFORCED SURVEY SONIC TEST ULTRASONIC TEST CORROSION TEST MAGNETIC & EM SURVEY MOISTURE TEST

4 Applied NDT on Concrete Available evaluation for Non-Destructive Testing on concrete Characterization Internal Defective locations in concrete Imaging GPR

5 Ultrasonic for NDT on Concrete ULTRASONIC TEST BACKGROUND: - The UT techniques is based on the elastic/mechanical waves and the parameters that characterize the propagation. - The propagation velocity is usually the desired parameter. - Use a frequency contain of khz for concrete. -There are some information test but should verified by alternative/destructive methods.

6 Resistencias a compresión (MPa) Rc (MPa) Ultrasonic for NDT on Concrete ULTRASONIC TEST BACKGROUND: FUNCION GAUSSIANA DE AJUSTE PARA Vp IN-SITU 25 Vp_histog_2 vs. X_histog_2 fit AJUSTE 4500 DE RC y VELOCIDADES 4600 EN TESTIGOS Velocidades in-situ (m/s) 90 Rc_testigos vs. Vp_testigos Ajuste Potencial Pred bnds (fit 2) AJUSTE DE RC Y VP INSITU Rc( MPa) ( / ) 2 r Vp m s Rc( MPa) ( / ) r Vp m s Rc_para_Vp_insitu vs. Vp_insitu_paratestigos Ajuste Potencial Pred bnds (fit 3) Velocidades en testigos Velocidad in situ (m/s)

7 Information on MIRA Imaging Tests / Methods The MIRA is an ultrasonic tomography device for diagnostics of concrete structures, detecting and evaluate internal reinforced concrete defects such as honeycombs and voids. The ultrasonic testing is one of the most advanced techniques available in non-destructive testing concrete, especially for large structures.

8 Information on MIRA (cont.) Imaging Tests / Methods An array of 10 channels of 4 transducers resulting in scanning aperture of 400 mm by 50 mm. It utilizes 40 transmitting and receiving probes measuring within less than 3 seconds. Scans results in a 2D depth. Also known as the b-scan

9 Information on MIRA (cont.)

10 GPR for NDT on Concrete Methods Ground Penetration Radar (GPR) is a geophysical prospecting method for non-destructive studies that is uses high frequency electromagnetic waves to image the subsurface structure. The wave velocity depends on the changes in the dielectric constant of the medium Has one of the highest resolutions in subsurface imaging

11 GPR for NDT on Concrete Methods The GPR shows images of the scanned subsurface area on the SIR 3000 of large and small concrete element structures. Its a series of pulses over a single area that make up an scan. Its called a radar gram. The strength, or amplitude, of the reflections are determined by the dielectric constants and the two materials

12 GPR for NDT on Concrete Methods Radar energy emits in an cone shape. The two-way travel time for energy at the leading edge of the cone is longer than for energy directly beneath the antenna. When moved over a target, the distance between them decreases until the antenna is over the target & increases as its moved away.

13 Information on GPR (cont.) Electromagnetic waves are radiated from the transmitter into the structure. Buried objects/boundaries causes part of the waves to bounce back to the receiver.

14 Concrete Cube in AIDICO The GPR and MIRA Cara A Cara B Cara A Cara B z Cara D Cara C Cara D y (0,0,0) x Cara C y x z The GPR and MIRA works good together in NDT and gather information and results more effectively. Collects vertical and horizontal resolutions, penetration depth and more.

15 Results of MIRA Concrete cube

16 Results of GPR Concrete cube

17 GPR antenna Experimental Results for Loading Tests Load Machine Flexural Test EN 83509: 2004 Ultrasonic transducer

18 Velocities of P-wave (m/s) Time of Flight of each A-Scan (s) Experimental Results for Loading Tests (cont.) BSCANs of the FPP1 Probe during the loading flexural test Z1 Z2 Z3 FPP1: Polypropilene Fiber reinforced concrete Time of load test (s) Velocity Evolution on FPP1 durting the load flexural test Z1 Z2 Z Time of load test (s) A-Scan each 5 s

19 velocity of P-Wave (m/s) Time of Flisht A-Scans (s) Experimental Results for Loading Tests (cont.) BSCANs Evolution of the FPP2 Probe during the load flexural test Z1 Z Tiime of load test (s) A-Scans each 5s FPP Velocity Evolution of FFP2 during the load flexural test Z1 Z Time of load Test (s) A-Scan each 5 s

20 Time of Flight (s) A-Scan Velocity of P-wave (m/s) Experimental Results for Loading Tests BSCANs Evolution of the FPP3 Probe during the load flexural test Z1 Z Tiime on th Load Test (s) A-Scans each 5 s Velocity Profile of FPP3 during the load test Z1 Z FPP Time on load test (s)

21 GENERAL CONCLUSIONS The right combination of NDT can provide useful information. NDT are most qualitative for inspection elements and should be added to other complementary destructive test In other topics/sectors, NDT are most confident and reliable than construction. There is a lack of knowledge on that point. The technical advance can provide new equipments and methodologies to reduce this gap. SPECIFIC CONCLUSIONS Conclusions GRACIAS POR SU ATENCIÓN THANK YOU FOR YOUR ATTENTION Ultrasonic Velocity does not give us the current stress/strain status along the load process, at least in a flexural test. Ultrasonic Test gives us information about the cracking process (crack growthing) GPR can be used for rebar concrete reconstruction but cannot detect lower spheres MIRA detects worse the geometry but can be detect lower targets.