EMERGING TRENDS IN CIVIL ENGINEERING BY : JATIN ARORA, ANUJ ARORA, AKSHAY RUHIL RAHUL CHHOKAR NDT’S ON STRUCTURES NDT-NON DESTRUCTIVE TEST: Detect Defects , Dimensions etc. without Damaging Material. TESTS ON STRUCTRES NON DESTRUCTIVE TEST DESTRUCTIVE TEST NDT Advantages Access to hidden items – “see through walls” Better investigations with NDT Rapid accumulation of data Generally less expensive than destructive testing Minimize interruption of building services Evaluation and quality assurance NDT Disadvantages More than one test method may be required Environmental conditions may effect or distort results Construction details & building components may effect results Some conditions cannot be determined with a reasonable degree of accuracy without destructive testing Typical Conditions to Verify Verification / identification of member sizes Location and spacing of embedded items • Mild reinforcing steel, post-tensioning, conduit • Masonry ties and hardware Locating hidden flaws and defects (voids, trapped moisture, poor consolidation, etc.) Corrosion damage assessment Concrete properties Reinforcing steel properties METHODS FOR NDT ON STRUCTURES: IMPACT-ECHO METHOD SCHMIDT/REBOUND HAMMER TEST COVER METER Impact-Echo Method It is a technique used for flaw detection in concrete surface. Impact-Echo Based upon evaluation of stress waves generated by an elastic impact on a concrete surface Originally developed at Cornell University and NIST by M. Sansalone and N. Carino P – Compression waves R - Rayleigh waves S - Shear waves Impact-Echo Propagating P-waves generated by impact event. Multiply-reflected waves are detected by surface sensor. Reflected waves set up a resonance condition having a characteristic frequency Analogous to a bell’s tone Impact-Echo Effective in determining thickness of slabs and depth of flaws in plate structures Does not work on beams & columns CP D 2f 0.96 for plate IMPACT ECHO Applications Thickness of members – d,b Location of internal defects Voids / delaminations Repair quality assurance Internal damage ASR / DEF / ACR IMPACT ECHO • Summary – Requires significant experience – Powerful method for flaw detection – Applications to quality control – Verification of results is critical REBOUND HAMMER TEST OBJECTIVE : Determine the Compressive Strength of concrete. WORKING OF SRH Rebound value V/S Compressive Strength Advantages & Disadvantages Easy to Handle Used only on Smooth Quick surfaces Moisture Conditions Age of Specimen Inexpensive COVER METER TESTING OBJECTIVE : Determine Nominal cover. PRINCIPLE Works on Electromagnetic Pulse Induction method HOW IT WORKS??? ADVANTAGES & DISADVANTAGES High Accuracy Limited Detection Range Economical Spacing depends on Cover Not Influenced by Moisture depth.