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Inspection of Brid ges. No. OF BRIDGES AS ON 31.03.2013. More than 100 years old= 36,731 (28%). DEFFINITELY , THIS IS NOT WHAT WE ALL WANTS TO SEE. AND UNFORTUNATELY THIS IS NOT COMPUTER GRAPHICS. Photo Just before collapse on 11.4.2008 at 09:00 hours. After collapse of spandrel wall.
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No. OF BRIDGES AS ON 31.03.2013 More than 100 years old= 36,731 (28%)
DEFFINITELY, THIS IS NOT WHAT WE ALL WANTS TO SEE. AND UNFORTUNATELY THIS IS NOT COMPUTER GRAPHICS.
KADALUNDI TRAIN MISHAP Calicut – Shoranur Section of Palghat Division on 22-6-2001 at 17.04 hrs. Reminds us of importance of proper Bridge Inspection
BridgeInspection Systematic observation of condition and behavior of various components/ parts of a bridge is called bridge inspection
Why Bridge Inspection • To know whether the bridge is structurally safe, and to decide the course of action to make it safe. • To identify actual and potential sources of trouble at the earliest possible stage. • To record systematically and periodically the state of the structure.
Why Bridge Inspection • To impose speed restriction on the bridge if the condition/situation warrants the same till the repair/ rehabilitation of the bridge is carried out. • To determine and report whether major rehabilitation of the bridge is necessary to cope with the natural environment and the traffic passing over the bridge. • To provide a feedback of information to designers and construction engineers on those features which give maintenance problems.
Provisions in IRBM for Inspection of Bridges Open Line Officials • Para 102 (a) (ii) AEN open line will inspect after monsoon every year. • Para 117 (1) & (2) SE (Works / P. Way) will inspect steel girders smaller than 12.2 m length including bearings in detail once in 5 years • Track on bridge & its approaches • Guard rails, foot path, notice boards, name boards, trolley refuges, sand bins etc. • Clearing of waterway of Bridges • Superstructure of all other bridges before monsoon every year.
Schedule of inspection SSE/JE Bridge • Steel girders including bearings > 12.2m span – once in 5 years • Welded, RCC, PSC and Composite Girders – initial inspection within 1 year of installation (CS No.33 dt.21.03.2016), than once in 5 years (Except welded girders – to be inspected once in 3 years) • Overstressed girders – at least once in a year • Early steel girder – Floor System– once in a year : rest-once in 5 years. • Other nominated steel structures- Once in 5 years. • Steel work, rivet testing, weld test etc.
Schedule Of Inspection AEN/DEN (Bridge) • Scrutinize – register sent by BRI • Inspect Bridges referred to him • Bridges call for inspection • All overstressed bridges – camber loss • 10% test check of BRIs work every year Dy. CE/Bridges • Scrutinize bridge inspection register • Inspect Bridges referred to him or call for inspection
Provisions in IRBM for Inspection of Bridges • Para 107 (1) (a) SSE (Br) will inspect all RCC, PSC and Composite girders within one year of installation (CS No.33 dt.21.03.2016) • Para 107 (1) (d) SSE (Br) will inspect all PSC/RCC/ Composite girders and all steel girders ˃ 12.2 m span once in five years on planned basis • Para 1107 (15) (b) SSE (Br) will measure camber of PSC girders once a year with any reliable method • Camber of steel open web girders to be measured once in 5 years • Para 107 (1) (f) Proper installation of Bearings before allowing traffic on any bridge) (CS No.33 dt.21.03.2016) • Para 105 (2) (c) AEN (Br) shall test check 10% of the bridges inspected by the bridge inspector
Type of Inspections Routine OR General inspection • This consists of broad general visual inspection by AEN once a year. Detailed inspection • This is known as technical inspection where thorough examination of each component of superstructure is carried out once in 5 years. Special Inspection • After an accident on the bridge • After an earthquake in the area OR after unusual floods • If signs of weaknesses are revealed by the general inspection
ADDITIONAL INSPECTON OF DISTRESSED BRIDGES • Cat. I • Inspector Once a month • AEN/ABE Once in two months • +Sr. DEN Once in three months • Cat. II • Inspector Once a three months • AEN/ABE Once in six months • Sr. DEN Once a year • Para 102 (b), 504 to 509 & Annexure 5/1 is deleted vide CS No.30 dt.25.11.2014 • Now, in accordance with the unique rating number repairs / Maintenance/Rehabilitation /Rebuilding of bridges is planned.
Planning Inspections • Go through previous Inspection records • Go through history of the bridge • Go through drawings of the girders to identify critical locations • Plan for temporary inspection arrangements • Plan inspection tools to be taken • Plan staff to attend inspections • Plan safety arrangements
Preliminary Arrangements • Install inspection arrangements in position • Divide the inspection area into convenient sub parts for inspections • Keep arrangements for recording of inspection results handy • Test the safety arrangements
Inspections SAFETY IS FOREMOST • Wear suitable dress • Proper temporary arrangements • Properly trained manpower • No short cuts at any cost • Lookout men and protection wherever required
Carrying out Inspections • Work systematically from one side to other or from top to bottom or from bottom to top etc. • Inspect carefully each sub division of the girder • Keep time factor into mind • Inspect each sub-part in one go and do not break in-between • Record inspection results in rough simultaneously with inspections
INSPECTION OF STEEL SUPERSTRUCTURE Check the camber • Loss of camber / Sagging due to • Heavy overstressing - Loss of cross section due to corrosion or increased load then the design load / fatigue or due to age of structure • Overstressing of joint rivets at splice joint in plate girder and at panel point in open web girder • Play between holes and rivetsdue to elongation of holes or crushing of rivet shank
Inspection of Steelwork • In Plate girder upto span 35.0 m no camber is provided as per Steel Bridge Code Clause 4.16.1. • Camber to be recorded for Open web girders • Camber to be recorded at nominated points on the cross girders or bottom chord as feasible • Separate camber reading for G1 and G2 • Camber reading to be taken in one go. If train comes in between, the complete set of readings shall be taken again • Camber readings to be taken carefully to nearest millimeter and at the ambient temperature as mentioned in stress sheet and compared with initial camber
Inspection of PSC Girders • CS No.22 dt.28.03.2011 - Para 1107 (15) (b) (i) & (ii) • Assessment of loss of Camber to be done. • Camber measurement should be at centre upto 20 m span • Camber at centre & quarter points for spans more than 20 m • Camber reading to be recorder in column 8 of Annexure 11 / 9 • Camber of PSC girders to be checked once in a year by any reliable method and to be recorded. • Points to be marked where camber is measured and Temperature also to be recorded for reference
DISTORTION Plate girder • Top flange – being a member carrying compressive stresses • Web plate near bearings – due to heavy concentration of stress likely to buckle • Cross frame angles & Top lateral bracing – excessive lateral vibration
DISTORTION Open web girder • Top chord – carrying compressive stresses and likely to distort if not sufficiently restrained • Diagonal web member – made of flat in mid span due to stress reversal and vibration during passage of train • Bottom chord member – carry tension and longitudinal forces if not braced properly • Top lateral/ portal bracing are likely to distort due to excessive lateral forces • Frozen bearings (due to variation in temperature)
Loose rivets Critical locations PLATE/COMPOSITE GIRDER • Web plate to flange angle at end of girders • Bearing stiffener • Splice rivets of flanges/ web • Bracing and cross frame connection • Stringer/ Cross – girder connection (If present)
Loose rivets OPEN WEB GIRDERS - Critical Locations: • Rail bearer – cross girder and cross girder to panel point connections - are subjected to direct shear and some time induce tension due to excessive deflection of rail bearer / cross girder • More critical where rail joints are there • At all Panel points (with main gussets to truss components) of top chord and bottom chord (field connections) • Top/bottom lateral bracing connections • Splices in Main chords
Corrosion Inspect for corrosion/loss of section Critical locations • Under wooden sleepers • Formation of water pocket due to construction (bottom chord panel points and in plate girder behind bend stiffener. • Places where dust accumulate • In vicinity of drainage system • Area directly affected by diesel loco fumes
Corrosion • Top lateral/portal bracing of open web girder • Parts exposed to sea breeze and salt water spray • Interface between steel and Rcc in composite girder • Seating of wooden floor in FOB as well as column base. • Steel work in vicinity of bearing
Corrosion… CANTI LEVER BRACKET CORROSION LOSS
Corrosion … GIRDER BOTTOM FLANGE CORROSION LOSS
Corrosion … TOP CHORD CORROSION AT JOINT
Corrosion … BRACING MEMBER CORROSION LOSS
Corrosion … BOTTOM TRUSS CHORD CORROSION
Corrosion … BOTTOM CHORD CORROSION AT JOINT
Inspection of Steelwork • Locations subject to excess wear and tear • Locations exposed to the elements and accumulating dust/ moisture. • Secondary members such as bracing, gussets etc • Holding down bolts • Appurtenances such as inspection arrangements, railings, ladders, expansion arrangements etc.
Inspection of Steelwork-Cracks • Locations critical from the loading point of view • Maximum shear location • Maximum bending location • Bearing and nearby area • Bearing Stiffener • Splice Locations • Locations liable to be hit by vehicles/ boats etc
Fatigue Cracks • Is tendency of metal to fail at lower stress level subjected to cyclical loading then static loading • Are common where stress concentration due to sharp corners and abrupt change of cross section • Due to growing volume of traffic at greater speed and higher axle load • It is in the form of cracking of steel section due to repeated stresses.
Fatigue Cracks locations • Ends of diagonal members at middle of span due to reversal of stress • Sharp edge at cut notch in stringer flanges at connection with cross girder • Top flange plate of flange angles of plate girder or rail bearer below sleepers • Roots of beam at ends
Cracks in Steel Works • Establish cause and further propagation. • A small hole of 7mm dia. Drilled at the end. • Strengthen cracked member by cover plate. • Defective member may have to be replaced.
Critical Locations • Location already having problem – whether or not repaired
