CONTENTS .. 51.NoPage No. 1.Syllabus 2.Unit - 11 Analysis andDesign of Concrete Bridges: 3.Unit - 229 SteelBridges:Steel superstructure: ...!i 4.Unit - 355 Substructure andFoundations: 5.Unit - 480 Construction and Maintenance: 6.Unit - 5104 Case Studies: 6 SYLLABUS BRIDGE ENGINEERING(BCQ 3.12) AnalysisAndDesignofConcreteBridges:Loadingstandards:IRCandRailway loadingsReinforcedconcretebriqge decks: slab,T-beamandslab,arch,bow string girder typesPrestressed concrete bridges:simplespans,continuous decks;cantilever construction; anchorage of tendons ;grounding oftendons. Steel Bridges: Steel superstructure: Plate girder, box girder truss and arch typesCable stayedbridges andsuspensionbridges;principles of design,aerodynamic stability and vibrations; simplified designs. Substructure AndFoundations:Substructure design:piers andabutments of different typesFoundations:Shallow foundations,deep foundations,piles,wells andpneumatic caisonsRiver training works. ConstructionAndMaintenance:Bearing;metallicandelastomerictypes;fixedand movablebearingsJoints:expansionjoints;ContractionjOints;jointsealsInnovative constructionmethods;incrementalpushlaunching;cantilever construction;erectionof precastelementsBridgemaintenancemanagement:inventory,inspectionand rehabilitation. CaseStudies:Casestudiesof recentlyconstructedmajorbridgesCriticalstudiesof failure of major bridges. UNIT - 1 : ANALYSIS ANDDESIGNOF CONCRETE BRIDGES SECTION A MULTIPLE CHOICE QUESTIONS 1.Whiledesigningroadbridgesandculvert,whichofthefollowingloadisnot considered? a)Dead Load b)Live Load c)Machine Load d)Snow Load 2.From consideration of safety and effective utilization of carriageway, it is desirable to provide footpath of atleast a)1.5m b)2.0m c)2.5m d)3.0m 3.What is the weight oftracked vehicle considered in IRC Class MLoading: a)500kN b)600kN c)700kN d)None of the above 4.What is the weight of wheeled vehicle considered in IRC Class MLoading: a)300kN b)400kN c)500kN d)600kN 5.What is the weight of tracked vehicle considered in IRC Class 70R Loading: a)500kN b)600kN c)700kN d)None ofthe above BCO-3.12 6.What is the weight of wheeled vehicle considered in IRC Class AA L,oading: a)500kI\J b)BOOkN c)1000 kN d)1200kN 7.What is the value of Impact Factor for concrete bridge of 3m span? a)0.5 b)0.6 c)0.7 d)O.B B.What is the value of Impact Factor for steel bridge of 3m Span? a)0.525 b)0.545 c)0.565 d)None ofthe above 9.On whatfactorthe actual Impact Factor will depend: a)load on the bridge b)span ofthe bridge c)spring constant ofthe bridge d)none ofthese 10.No live load is considered to be acting on the bridge, ifthe wind velocity at the deck exceeds: a)100km/h b)130km/h c)150km/h d)200km/h Answer Key: 1.cI 2.8 3.c4.bS.c6.c 7.88. b9. c1 10. bI 2BCO-3.12 SECTION B TRUE FALSE TYPE QUESTIONS 1 .A member is referred as post tensioned member,if the tendons are stressed and anchoredateachendof themember after the concretehasbeencast andhas attained sufficient strength. 2.A special type of concrete arch bridges has been developed by Robert Maillart. 3.A fixed arch is statically determinate structure. 4.Therigidconnectionsresultsinmorestablesupports,thanpossiblewith independent piers of comparable dimensions. 5.The continuous girder bridge suffers less vibration and deflection AnswerKey: 1. T2.T3.F5. T 3BCO-3.12 SECTION C SHORT ANSWER TYPE QUESTIONS 01 :What are the various loads considered in designing the road bridge? Ans:Whiledesigningroadbridgesandculverts,thefollowingloads,shouldbe considered, where applicable: (a)Dead load (b)Live load (c)Snow load (d)Impact or dynamic effect due to vehicles (e)Impact due to floating bodies or vessels (f)Wind load 02:What are the various forces considered in designing the road bridge? Ans:While designing road bridges, the following forces should be considered: (a)Longitudinal forces caused by the tractive effort of vehicles or by braking of vehicles. (b)Longitudinal forces due to frictional resistance of expansion bearings. (c)Centrifugal forces due to curvature. (d)Horizontal forces due to water currents. (e)Buoyancy (f)Earth pressure, including live load surcharge. (g)Forces and effects due to earthquake 03:What is the role of IRC in designing the road bridges? Ans:TheIndianRoadCongress(IRC)hasformulatedStandardSpecificationsand Codes of Practice for roadbridges with a view to estab.lish a common procedure for the designandconstructionof roadbridgesinIndia.Thespecificationsare collectively known as the Bridge Code.Prior to the formulation of the IRC Bridge Code, There was no uniform code for the whole country. Currently, we would follow the IRC Bridge Code. 04:What arethedifferent typesof IRCStandardsLiveLoadconsideredduring the design of road bridge? Ans:There are four types of Standard Loadings for which road bridges are designed: a)IRCClassAALoading b)IRC Class 70 R Loading c)IRCClassALoading d)IRC Class B Loading 4BCO-3.12 05:What are the different types of gauges used on Indian Railways? Ans:There are three gauges used onIndianRailways with the widthof track between the inner faces of rails as indicated below: (a) (b) (c) Broad Gauge (BG) Metre Gauge (MG) Narrow Gauge (NG) 1676 1000 762 mm mm mm (5'6) (3'3-3/S) (2'6) 06:What are the various standards the r a i ~ w a ybridges are to be built to conform to the Indian Railway Standard laid down by the Ministry of Railways? Ans:Railway bridges in India are to be built to conform to the Indian Railway Standards (IRS) laid down by the Ministry of Railways, Government of India, as below: (a)The loads to be considered in design are given in IRS Bridge Rules. (b)Thedetailsof designofsteelbridgeshouldconformtoIRSSteelBridge Code. (c)The details of design of bridge members in plain, reinforced and prestressed concrete should be in accordance with IRS Concrete Bridge Code. (d)Masonry ad plain concrete arch bridges should be detailed so as to conform to IRS Arch Bridge Code. (e)ThesubstructureforbridgesshouldbeinaccordancewithIRSBridge Substructure Code. 07:What is the role of Admixture in Concrete? Ans:Admixturesareavailable forincreasing the workabilityof concrete(plasticizers) facilitatingthereductionof watercementratioandforretardationof settingof cementduringhot weatherconcreting.Concretepropertiessuchasdurability, strength and service life can be enhanced by use of suitable mineral and chemical admixtures. os:What are the various component of RMC Plant? Ans:A typical RMC plant has the following components: (i)Central batching plant with a capacity of 30 to 200m3 of concrete per hour; (ii) (iii) Transit mixer trucks to transport concrete to construction sites with the help of rotating type transit mixers of capacity about 6 m3 ;and Concrete pumps and conveyors to deliver concrete at the work sites. 09: Ans: What do you mean by Ready Mix Concrete? Atmanybridgesites,speCiallyinurbanareas,preparationofconcreteat the constructionsitebecomes difficult due to non-availability of adequate space for storage and handling of the constituent materials and for mixing operations. When 5BCO-3.12 the construction activities in a city are of such magnitude as to assure a sustained demandforlargevolumeof concrete,itisdesirabletoestablishreadymixed concrete (RMC)plants in the outskirts of the city and to transport the concrete in special transit mixer trucks to the construction site at the right time. Though the use of RMC is not yet widespread in many Indian cities, this development is inevitable in the near future. 010:What are the different types of Concrete Bridges? Ans:The usual types of reinforced concrete bridges are: j1.Slab brtdges; 2.Girder and slab (T-beam) bridges; 3.Hollow girder bridges; 4.Balanced cantilever bridges; 5.Rigid frame bridges; 6.Arch bridges; 7.Bow string girder bridges. 011 :What are the different components of T-beam bridge? Ans:The T-beam superstructure consists ofthefollowing components: (i)Deck slab (ii)Cantileverportion (iii)Footpaths; if provided, kerbs and handrails (iv)Longitudinal girders, considered in design to be ofT-section (v)Cross beams or diaphragms (vi)Wearing course. 012:What are the disadvantages of Continuous Girder Bridge? Ans:(a)Unevensettlement of foundations may lead to disaster.Hence this type of structuresshouldnotbeusedinsituationswhereunyieldingfoundations cannot be obtained at a reasonable cost. (b)The detailing and placing of reinforcements need extra care. (c)The sequence of placing concrete and the sequence of removing formwork have to be carefully planned. (d)Being statically indeterminate, the design is more complicated than simple beams. 013:What are the various consideration taken into account in case of arch axis? Ans:The arch axis is generally governed by three considerations: 6BCO-3.12 (a)spanandrisefromtheroadgradient andnavigationor trafficclearances below, (b)the economical shape from point of view of saving of materials, and (c)the beauty ofthe intrados. 0.14.What do you mean by post-tensioning? Ans.A member is referred as post-tensioned member, if the tendons are stressed and anchored at each end of the member after the concrete has been cast and attained sufficient strength to withstand the prestressing force. 015:What is the role oftendons in pretensioning? Ans:The tendonprovides a pre compression force to reduce crackingunder service load and also serves as tension reinforcement under the ultimate load condition. The integrity of the grout duct and the surrounding concrete governs the corrosion protection of the high-strength, low ductility steel tendon.Grouting also helps to avoid fatigue failure in the steel at the anchorages. 016:What are the various conditions which meet the prestressing force? Ans:The prestressing force must meet two conditions: 1.Itmust providesufficientcompressivestresstooffset thetensilestresses which will be caused by the bending moments. 2.It must not induce either tensile or compressive stresses which are in excess ofthose permitted by the specifications. 7BCO-3.12 SECTION 0 LONG ANSWER TYPE QUESTIONS Q. 1.What are the various loads, forces & stresses to be considered indesigning road bridge & culverts? Ans.Whiledesigningroadbridgesandculverts,thefollowingloads,forcesand stresses should be considered, where applicable: (a)Dead load (b)Live load (c)Snow load (d)Impact or dynamic effect due to vehicles (e)Impact dueto floating bodies or vessels (f)Wind load (g)Longitudinal forces caused by the tractive effort of vehicles or by braking of vehicles. (h)Longitudinal forces due tofrictional resistance of expansion bearings. (i)Centrifugal forces due to curvature. (j)Horizontal forces due to water currents. (k)Buoyancy (I)Earth pressure, including live load surcharge. (m)Temperature effects (n)Deformation effects (0)Secondary effects (p)Erection stresses (q)Forces and effects dueto earthquake (r)Grade effect (for design of bearings for bridges built in grade or cross fall) (s)Wave pressure. The basic philosophy governing the design of bridges is that a structure should be designed to sustain with a defined probability allactions likely to occur withinits intendedlifespan.Inaddition,thestructureshouldmaintainstabilityduring unprecedented actions andshould have adequate durability during itslife span. Typical combinations of loads and forces to be considered in design and allowable increases in permissible stresses for certainare given in the Code. It willbenecessarytoensurethatwhensteelmembersareused,themaximum stressunderanycombinationdoesnotexceedtheyieldstrengthofthesteel. Based on observations from recorded earthquakes, it isnot considered probable that wind load and earthquake will occur simultaneously. 8BCO-3.12 Q.2.Describe theIRCClass Mloadings andindicate theconditions under whichit should be used. Ans.(a)IRC Class AA Loading. This loading consists of either a tracked vehicle of 700 kN or a wheeled vehicle of 400 kN with dimensions as shown in Fig. 1.1. The tracked vehicle simulates a combat tank used by the army. The ground contact length of the track is 3.6 m and the nose to tail length of the vehicle is 7.2 m. The nose to tail spacing between two successive vehicles shall not be lessthan90m.Fortwo-lanebridgesandculverts,one trainof Class M trackedor wheeled vehicles whichever creates severer conditions shall be considered for every two-lane width. No other live load shall be considered onany part of the above two-lane carriageway whenthe Class Mtrainof vehicles is on the bridge. The Class Mloading is to be adopted for bridges locatedwithincertainspecifiedmunicipallocalitiesandalongspecified highways. Normally, structures on National Highways are provided for these loadings. Structures designed for Class Mloading should also be checked for Class A loading, since under certain conditions, severe stresses may be obtai ':led under Class A loading. f-------------------------------------------...-------------------------------------------.

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