Lecture2NDT - Structural Condi.on Surveys ASCE...

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Unformatted text preview: Structural Condi.on Surveys ASCE Standard 11 ­99 “Guideline for Structural Assessment of Exis.ng Buildings” American Society of Civil Engineers (ASCE) and the Structural Engineering Ins.tute (SEI) CEIE 525 Structural Evalua.on & Remedia.on 1 Structural Condi.on Surveys •  Guidelines and methodology for assessing the condi.on of exis.ng buildings •  Covers concrete, metals, masonry and wood •  Establishes assessment procedures •  Also provides guidance for evalua.ons CEIE 525 Structural Evalua.on & Remedia.on 2 Structural Condi.on Surveys •  Process consists of assembling and analyzing informa.on and data gathered on the building •  Mul.level, or staged, approach recommended – Preliminary assessment (screening) – Detailed assessment CEIE 525 Structural Evalua.on & Remedia.on 3 Structural Condi.on Surveys •  Preliminary Assessment – to collect ini.al data – available documents review – site inspec.on – preliminary analysis – preliminary findings and conclusions CEIE 525 Structural Evalua.on & Remedia.on 4 Structural Condi.on Surveys •  Detailed Assessment – based on ini.al findings – document review – detailed inspec.on – detailed assessment and analysis – detailed findings and recommenda.ons CEIE 525 Structural Evalua.on & Remedia.on 5 Structural Condi.on Surveys •  Documents available – design drawings and specifica.ons – structural drawings – architectural drawings – construc.on drawings – “as ­builts” – shop drawings – reports, other documents, photographs – where to be found? CEIE 525 Structural Evalua.on & Remedia.on 6 Structural Condi.on Surveys •  Sources of available documenta.on – building owner and on ­site staff – local building department records – original designer, architect, contractor – successors to original par.es – insurance company files – professional publica.ons – detec.ve work oXen needed CEIE 525 Structural Evalua.on & Remedia.on 7 Structural Condi.on Surveys •  Inspec.on – interviews with knowledgeable par.es – visual observa.ons from walk through – confirm, or otherwise, findings of the documenta.on review – damage to structural members – sensible procedure and guidelines – measurements – checklists, photographs, sketches CEIE 525 Structural Evalua.on & Remedia.on 8 Structural Condi.on Surveys •  Probing/selec.ve demoli.on – exploratory demoli.on – selec.ve demoli.on to observe condi.ons – selec.ve demo of por.ons of structure – may have to expose por.ons outside/inside – allows observa.ons/measurements – openings are made in non ­structural – cau.on! CEIE 525 Structural Evalua.on & Remedia.on 9 Structural Condi.on Surveys •  Inspec.ons – visual observa.ons/measurements – probing/selec.ve demoli.on – non destruc.ve tes.ng (NDT) of materials – selec.ve destruc.ve tes.ng of materials – structural materials CEIE 525 Structural Evalua.on & Remedia.on 10 Structural Condi.on Surveys •  Concrete: visual observa.ons – difficult to evaluate with confidence – amount and loca.on of reinforcement – level of corrosion of reinforcement? – interior condi.on of concrete? – external signs of cracking, spalling, etc. – need to be good observer/detec.ve CEIE 525 Structural Evalua.on & Remedia.on 11 Structural Condi.on Surveys •  Concrete: Non Destruc.ve Tes.ng (NDT) – Visual observa.ons – an NDT method? – advanced visual, magnifying glass/lupe, etc. – measurements of deflec.on, out ­of ­plumb – need to be a good observer/detec.ve – “join the dots” from the clues observed CEIE 525 Structural Evalua.on & Remedia.on 12 Structural Condi.on Surveys •  NDT methods for concrete using instruments – many useful techniques available – find physical proper.es of concrete – compressive strength – voids/cavi.es – delamina.on of concrete – corrosion of reinforcing steel – follow instruc.ons/need training CEIE 525 Structural Evalua.on & Remedia.on 13 NDT Tes.ng of Concrete CEIE 525 Structural Evalua.on & Remedia.on 14 Rebound Hammer device is spring loaded hammer (rod) is made to strike surface of concrete rebound is measured using calibra.on curves may be able to es.mate concrete compressive strength correla.on with actual core results comparison – poor/good areas CEIE 525 Structural Evalua.on & Remedia.on 15 Original Schmidt Hammer CEIE 525 Structural Evalua.on & Remedia.on 16 Digital Rebound Hammer CEIE 525 Structural Evalua.on & Remedia.on 17 Digital Rebound Hammer CEIE 525 Structural Evalua.on & Remedia.on 18 Rebar Locator oXen called a pachometer or cover meter hand held probe generates magne.c field interference detected by rebar es.mates cover, rebar diameter, spacing confused by some rebar/mesh placements CEIE 525 Structural Evalua.on & Remedia.on 19 Impact Echo mechanical impact generated by tapping steel ball on concrete surface reflected stress wave picked up by receiver provides info on concrete interior, detects internal voids, delamina.ons portable and reliable CEIE 525 Structural Evalua.on & Remedia.on 20 Windsor Probe special gun drives probes into concrete depth of penetra.on approximated to concrete strength can find areas of unsound concrete widely used CEIE 525 Structural Evalua.on & Remedia.on 21 Bond Tester (JamesBond) bond a circular plate to concrete pull off un.l comes away from concrete use calibra.on charts to es.mate compressive strength causes localized damage CEIE 525 Structural Evalua.on & Remedia.on 22 Corrosion Meter uses electric poten.al gradients to es.mate probability of ac.ve corrosion of reinforcing detects signs of corrosion in reinforcing bars by measuring the electrochemical process need training to use CEIE 525 Structural Evalua.on & Remedia.on 23 Chain Dragging / Hammer Sounding of Concrete – use a hammer to strike concrete – used in overhead situa.ons and beams, columns – very quick and easy, low tech method to find surface problems, delaminated areas, voids – gives an indicator of poten.al problem – oXen performed during visual survey – survey/forensic kit CEIE 525 Structural Evalua.on & Remedia.on 24 Chain Dragging / Hammer Sounding of Concrete drag a heavy chain in a waving mo.on across surface of concrete dis.nct change in sound indicates delaminated concrete very quick and easy, low tech method to find surface problems a bit laborious, heavy chain, get into a rhythm gives an indicator of poten.al problems near surface can be confused by exis.ng concrete overlays CEIE 525 Structural Evalua.on & Remedia.on 25 Destruc.ve Tes.ng of Concrete CEIE 525 Structural Evalua.on & Remedia.on 26 Destruc.ve Tes.ng of Concrete •  destruc.ve tes.ng is some.mes needed •  think of as as selec.vely destruc.ve based on the test •  do not think of it as demoli.on •  but the exis.ng concrete structure will be damaged to some degree – oXen repairable CEIE 525 Structural Evalua.on & Remedia.on 27 Concrete Coring cylindrical concrete cores are carefully extracted then condi.oned and prepared for tes.ng in the lab using a compression tes.ng machine the core is tested (to failure) to determine the compressive strength of the concrete strict tes.ng protocol CEIE 525 Structural Evalua.on & Remedia.on 28 Concrete Coring need to avoid cugng rebar may need to retrieve core from underside can provide other proper.es of concrete – density, chloride content, aggregate condi.on cores can be used for petrographic analysis CEIE 525 Structural Evalua.on & Remedia.on 29 Petrographic Analysis can be performed from cores performed in a lab, trained personnel thin sec.ons cut from core are polished then examined under microscope can determine physical and chemical proper.es such as concrete material propor.ons air content presence of chemically reac.ve aggregate depth of carbona.on, etc CEIE 525 Structural Evalua.on & Remedia.on 30 Anchor TesHng used to test pull out strength of anchors in concrete CEIE 525 Structural Evalua.on & Remedia.on 31 NDT Tes.ng of Steel CEIE 525 Structural Evalua.on & Remedia.on 32 Structural Condi.on Surveys •  Structural Steel: Non Destruc.ve Tes.ng (NDT) – Visual observa.ons – an NDT method? – missing bolts, nuts, damaged members – corrosion, weld condi.on – measurements of deflec.on, out ­of ­plumb – need to be a good observer/detec.ve – “join the dots” from the clues observe – most common method of evalua.ng steel CEIE 525 Structural Evalua.on & Remedia.on 33 Radiography x ­rays or gamma rays u.lized radia.on detects internal defects/voids expensive and poten.ally harmful, needs shielding CEIE 525 Structural Evalua.on & Remedia.on 34 Ultrasonic TesHng ultrasonic waves are reflected by interior defects/voids can detect hidden cracks, lamina.ons, and very small inclusions very effec.ve but needs trained operator CEIE 525 Structural Evalua.on & Remedia.on 35 Liquid Penetrant 1. Sec.on of material with a surface ­breaking crack that is not visible to the naked eye. 2. Penetrant is applied to the surface. 3. Excess penetrant is removed. 4. Developer is applied, rendering the crack visible. CEIE 525 Structural Evalua.on & Remedia.on 36 MagneHc ParHcle The por.on of steel being tested is magne.zed and covered with magne.c powder. Orienta.on of the par.cles indicates flaws and surface cracks. A simple effec.ve test, but needs trained personnel to interpret the results. Limited to shallow depth of flaws and cracks. CEIE 525 Structural Evalua.on & Remedia.on 37 Destruc.ve Tes.ng of Steel CEIE 525 Structural Evalua.on & Remedia.on 38 Destruc.ve Tes.ng of Steel •  To determine material proper.es of steel, specimens need to be obtained from the structural member to perform laboratory tes.ng. •  Care has to be exercised in obtaining the specimen (sample) so as not to weaken the structure. •  Specimens are rela.vely small and depending on the test are formed into “coupons”. CEIE 525 Structural Evalua.on & Remedia.on 39 Destruc.ve Tes.ng of Steel •  Coupons are oXen called “dog bone” or “bow .e” samples, because of their general shape. •  The coupons have to be cut carefully, following strict procedures, so as not to alter the proper.es of the original steel and to be able to quan.fy sizes / cross sec.onal areas CEIE 525 Structural Evalua.on & Remedia.on 40 Destruc.ve Tes.ng of Steel •  Tensile strength: Coupon is held in a tensile tes.ng machine, and subjected to axial tension. Strict procedures for tes.ng/loading. Physical proper.es such as yield strength, ul.mate strength, elonga.on, stress/stain characteris.cs. CEIE 525 Structural Evalua.on & Remedia.on 41 Destruc.ve Tes.ng of Steel •  Chemical Tests: The specimens are tested to determine chemical proper.es such as carbon content, weldability, corrosion resistance, etc. Requires specialty laboratory and personnel CEIE 525 Structural Evalua.on & Remedia.on 42 Full ­Scale Load Tes.ng •  •  •  •  •  •  •  •  some.mes used for concrete structures not oXen done for wood and steel structures common for concrete slabs and beams used for unusual systems construct test apparatus load with water, some.mes other material measure deflec.ons, etc. – Codes, ACI, etc. cau.on needed, monitoring, safety concerns CEIE 525 Structural Evalua.on & Remedia.on 43 Post Tensioned Concrete •  •  •  •  •  •  •  special challenges due to built ­in stresses stressed tendons surrounded by concrete bonded or unbonded tendons strands or wire common can use NDT techniques to determine spacing visual inspec.on of tendons, anchors, etc. destruc.ve tes.ng not easy/not advised CEIE 525 Structural Evalua.on & Remedia.on 44 Structural Condi.on Surveys •  Wood: Non Destruc.ve Tes.ng (NDT) – Visual observa.ons – an NDT method? – advanced visual – measurements of deflec.on, out ­of ­plumb – need to be a good observer/detec.ve – “join the dots” from the clues observed CEIE 525 Structural Evalua.on & Remedia.on 45 Structural Condi.on Surveys •  •  •  •  •  •  •  •  Wood: Visual observa.ons natural material sawn lumber studs, joists plywood, oriented strand board (OSB) manufactured trusses glulam beams engineered products CEIE 525 Structural Evalua.on & Remedia.on 46 Structural Condi.on Surveys •  •  •  •  •  •  •  Wood: Visual observa.ons subject to water damage subject to insect damage some wood has manufacturer’s markings notches and holes in .mber members work of other trades wood rot – mold and fungi damage CEIE 525 Structural Evalua.on & Remedia.on 47 Wood NDT Common NDT Methods – Moisture Meter – Probing – Hammer Sounding – radiography – Impact Echo CEIE 525 Structural Evalua.on & Remedia.on 48 Moisture Meter pin or prong type is common hand ­held instrument usually works on dielectric/ resistance determines moisture content of wood direct reading qualita.ve/quan.ta.ve? CEIE 525 Structural Evalua.on & Remedia.on 49 Probing – use a pointed tool – indica.ons of early decay – sound wood breaks in long pieces – unsound wood breaks in shorter pieces – qualita.ve, simple indicator of decay – can’t detect deep decay CEIE 525 Structural Evalua.on & Remedia.on 50 Hammer Sounding – use a hammer to gently strike the wood – check if rebounds, or if makes a hollow sound – may indicate loose connectors – inexact, only a possible indicator, but useful – may iden.fy areas to further evaluate CEIE 525 Structural Evalua.on & Remedia.on 51 Radiography and Impact Echo – similar techniques to concrete NDT – to detect decay or voids – typically larger members – other proper.es of wood are needed (density, etc.) CEIE 525 Structural Evalua.on & Remedia.on 52 Destruc.ve Tes.ng of Wood •  Iden.fica.on of species – small sample analyzed under microscope in lab – species determined – allows approximate determina.on of allowable stresses – needs trained specialist •  Coring – core is extracted and visually examined – sent to lab for analysis – determine physical and mechanical proper.es – determine depth of decay, density, other proper.es – care and .me needed to collect the cores CEIE 525 Structural Evalua.on & Remedia.on 53 Structural Condi.on Surveys •  Masonry: – brick, block (CMU) or stone units bonded together with mortar – some.mes reinforced ver.cally and/or horizontally with rebar – common, used for long .me – loadbearing walls – veneer – cavity walls CEIE 525 Structural Evalua.on & Remedia.on 54 Structural Condi.on Surveys •  Masonry: Visual Observa.ons – Visual observa.ons – an NDT method? – bowing, bulging – cracking, seoling – deteriora.on of the units or the mortar or both – cracked or spalled brick / block / stone – missing ,cracked, pioed, crumbling mortar – efflorescence or signs of water damage – need to be a good observer/detec.ve – “join the dots” from the clues observed CEIE 525 Structural Evalua.on & Remedia.on 55 Masonry NDT Common NDT Methods – many concrete NDT methods can be used – cover meter – hammer sounding – Windsor pin – radiography – impact Echo CEIE 525 Structural Evalua.on & Remedia.on 56 Masonry DestrucHve tesHng – samples taken for laboratory tes.ng – oXen sample needs to be of a large size – care needs to be exercised obtaining sample – assembly of masonry (prism) removed – prism tested in compression in lab – determine allowable compressive strength – other parameters useful for design – chemical tes.ng, moisture, freeze ­thaw CEIE 525 Structural Evalua.on & Remedia.on 57 Visual Survey Kit (some ideas) hammer screwdrivers inspec.on mirror tape measure markers/chalk s.ckers/arrows plumb bob bubble level flashlight magnifying glass crack measuring gauge duct tape, etc. pre ­drawn outline sketches checklists camera moisture meter arrange on site (ladder) other misc items, simple tools CEIE 525 Structural Evalua.on & Remedia.on 58 Video of Brick Masonry Prism Tes.ng hop://www.youtube.com/watch? v=x4XcqWvF9vA CEIE 525 Structural Evalua.on & Remedia.on 59 Thank you! See you next week! CEIE 525 Structural Evalua.on & Remedia.on 60 ...
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