Introduction to Bridge Engineering PDF

INTRODUCTION TO BRIDGE ENGINEERING CE 4241 S4/D  MODULE 1 Part 2 1  COMPONENTS of a BRIDGE 1. SUPERSTRUCTURE  Span and directly Receives the live load  Supported by bearings  deck, girders, slab above the main deck 2....

INTRODUCTION TO BRIDGE ENGINEERING CE 4241 S4/D  MODULE 1 Part 2 1  COMPONENTS of a BRIDGE 1. SUPERSTRUCTURE  Span and directly Receives the live load  Supported by bearings  deck, girders, slab above the main deck 2. SUBSTRUCTURE  Support structures, located below the bearing  Transmits load to ground  piers, abutments, spandrels, caps, bearings 3. FOUNDATION  holds the shallow or deep base of the bridge  Footing; piles 2 3 COMPONENTS of a BRIDGE 4  COMPONENTS of a BRIDGE 1 Deck (and overpass) 6 Pile 2 Stringer 7 Underpass 3 Bearing 8 Embankment 4 Pedestal 9 Live Loading Typical single span slab-on-stringer bridge 5 Footing site and its representative components 5  SUPERSTRUCTURE Wearing Surface Haunch Deck Secondary Member (Diaphragm) Cove Primary r Member Plate (Stringer) 6  SUPERSTRUCTURE 1. WEARING SURFACE  OR Course  Topmost layer of material applied upon the deck to provide smooth riding surface and to protect deck from effects of traffic and weathering  In some instances, this is a separate layer made of bituminous material, while in some it is an integral part of the concrete deck 7  SUPERSTRUCTURE 2. DECK  The physical extension of the roadway across the obstruction to be bridged  Component of the bridge to which live load is directly applied  Provide smooth and safe riding surface for the traffic utilizing the bridge and distribute loads transversely along the bridge cross section 8  SUPERSTRUCTURE 2. DECK  TIMBER DECKS  Normally referred to as decking or timber flooring (limited to the roadway portion that receives vehicular loads) 9  SUPERSTRUCTURE 2. DECK  CONCRETE DECKS  Concrete permits casting in various shapes and sizes and has provided bridge designers and builders a variety of construction methods  It is used together with reinforcement to resist tensile stress (where concrete is weak) 10  SUPERSTRUCTURE 2. DECK  STEEL DECKS  Composed of either  Solid steel plate  Steel grids 11  SUPERSTRUCTURE 3. PRIMARY MEMBERS  Distributes loads longitudinally and are usually designed principally to resist flexure and shear  BEAM TYPE primary members are also referred to as stringers or girders  A haunch is placed between the deck slab and the top flange of the stringer in order for the slab not to rest directly on the member 12  SUPERSTRUCTURE 3. PRIMARY MEMBERS I – girders: Rolled Beams  Efficient for shorter spans  Limited sizes and shapes I – girders: Plate Girders  Deep girders can span very long distances  Vast range of sizes and shapes Box Girders  Box section efficiently resists torsion effects  Vast range of shape and sizes 13  SUPERSTRUCTURE 4. SECONDARY MEMBERS  Are bracing between primary members  designed to resist cross-sectional deformation of the superstructure frame  and help distribute part of the vertical load between stringers  Other secondary members are used to resist lateral deformation caused by loads acting perpendicularly to the bridge’s longitudinal axis 14  SUPERSTRUCTURE 4. SECONDARY MEMBERS CROSS FRAMES  Used on steel girder bridges to provide torsional stiffness during construction and in final condition  Normally used in curved and skewed bridges 15  SUPERSTRUCTURE 4. SECONDARY MEMBERS DIAPHRAGMS  provide stiffening effect to deck slab in case bridge webs are not situated directly on top of bearings  help improve the load-sharing characteristics of bridges  contribute to the provision of torsional restraint to the bridge deck  Typically used on shallow beams 16  SUPERSTRUCTURE 4. SECONDARY MEMBERS LATERAL BRACING  located at either the top or bottom flange of stringer  provide lateral stiffness and limit lateral deflections 17  SUBSTRUCTURE Basic components: 1. Bearings 2. Pedestals 3. Piers (pier cap) 4. Abutments 5. Stem 6. Backwall 7. Wingwall 8. Footing 9. Piles (pile cap) 10. Sheeting 18  SUBSTRUCTURE 1. BEARINGS  Are mechanical systems that allow bridge parts to move freely  Helps reduce stress build up within the structure  Accommodates movement between superstructure and substructure 19  SUBSTRUCTURE 1. BEARINGS  Use and functionality vary greatly depending on the size and configuration of bridge 2 Classifications:  Expansion bearings  Allow both rotation and longitudinal translation  Fixed bearings  Allow rotation only 20  SUBSTRUCTURE 1. TYPES of BEARINGS SLIDING BEARING Provide support and low coefficient of friction (use of lubricants) While allowing load to move (slide) along supporting surface (translation) AASHTO: cannot be used unless the bridge spans is less than 15 m 21  SUBSTRUCTURE 1. TYPES of BEARINGS ROCKER AND PIN BEARINGS Rocker Bearing: Curved surface accommodates translational movement Pin for rotational movement Pin Bearing Allows rotation 22  SUBSTRUCTURE 1. TYPES of BEARINGS ROLLER BEARINGS Single Roller Used for RC and Allows both rotation and steel bridges translation (longitudinal) Vertical capacity is limited Multiple Roller Translation only Rotation can be accommodated if combined with pin bearing Support large vertical loads 23  SUBSTRUCTURE 1. BEARINGS ELASTOMERIC BEARINGS Can take both translation and rotation through elastomer deformation Inexpensive and does not require considerable maintenance 24  SUBSTRUCTURE 1. BEARINGS POT BEARINGS Consists of neoprene disk confined in a pot (or cylinder) provided with even bridge seat since bending moment is not resisted Suitable for low-profile, high load bearing requirement Suited for curved or skewed bridges and other complex structures where direction of rotation varies or cannot be precisely determined 25  SUBSTRUCTURE 1. BEARINGS KINDS of POT BEARINGS Fixed Pot Bearing Unmoved in all directions; elastomeric bearing pad enables rotation on any axis Guided Pot Bearings Steel guide edge can moved in one direction only Free Sliding Pot Bearing Movable in all directions 26  SUBSTRUCTURE 1. BEARINGS DISC BEARINGS Rotation is accommodated through the deformation of elastomer whereas translation is considered through the application of PTFE slider 27  SUBSTRUCTURE 2. PEDESTALS  Short column on an abutment or pier under a bearing  Main function is to transfer load from deck to the pier or abutment  Provide vertical support to ensure proper load distribution 28  SUBSTRUCTURE 3. PIERS  support the superstructure at intermediate points between end supports  main functions:  transferring vertical superstructure loads to the foundations  resisting horizontal forces acting on the bridge. 29  SUBSTRUCTURE 3. PIERS  Bridges consisting of one span, does not require piers  From aesthetic standpoint:  piers can make a bridge visually pleasing (or unattractive) since it is one of the most visible components of a highway bridge 30  SUBSTRUCTURE 3. PIERS 2.Open Piers Types: Allows water passage 1.Solid Piers Uses bricks, stone, RC 3. Hammer Head 31  SUBSTRUCTURE 3. PIERS  HAMMER HEAD PIER  Also called as solid shaft pier or T pier  constructed in urban areas where space limitation is a concern.  occupy small spaces; provide more room for traffic underneath  provides additional lateral support aesthetically pleasing  Built in major stream crossings where heavy for bridges requiring loads, or sizable debris loads may occur large clearance  Provides minimum restriction to waterway 32  SUBSTRUCTURE 3. PIERS  SOLID /GRAVITY WALL PIER  Provide continuous vertical support from foundation to superstructure  used for most stream crossings to avoid collecting of debris and floating ices between columns  Commonly used in shorter spans and locations where soil conditions allow for direct load transfer 33  SUBSTRUCTURE 3. PIERS  COLUMN BENT PIER  suitable for bridge with significant height  used to support a steel girder superstructure  or as an integral pier for cast-in-place construction technique  either circular or rectangular cross section  by far the most popular forms of piers in modern highway system 34  SUBSTRUCTURE 3. PIERS  PILE BENT PIER  well suited for shallow water crossings and short span structure  Specified when ground is unstable and the low piers are required 35  SUBSTRUCTURE 3. PIERS  Framed Typed  aesthetically superior and rigid due to the monolithic joints between members  Ideally suited to reduce the span length of main girders on either side of the center line of pier resulting in savings in the cost of superstructure  requires two expansion joints at close intervals with increase of maintenance costs 36  SUBSTRUCTURE 3. PIERS  Special types:  Special Shaped Bent 37  SUBSTRUCTURE 3. PIERS  Special types: V leg pier 38  SUBSTRUCTURE 3. PIERS  Special types:  Architectural Pier 39  SUBSTRUCTURE 3a. PIER CAP  horizontal structural element placed on top of a bridge pier  serves as a load-distributing platform for the superstructure elements that rest on the pier  contribute to the lateral stability of the bridge. Note: Typical Arrangement Bridge seat – Bearings –Pedestal – Pier caps – Piers 40  SUBSTRUCTURE 4. ABUTMENTS  Earth-retaining structures which support the superstructure and overpass roadway at both ends of the bridge  resist longitudinal forces of the earth underneath the overpass roadway  Connects the bridge with the approach roadway 41  SUBSTRUCTURE 4. ABUTMENTS  Function 1. Transmit load from bridge superstructure to underlying sub – soil 2. Provide final formation level to bridge superstructure 3. Retain earth’s pressure of embankment of approaches 42  SUBSTRUCTURE 4. ABUTMENTS      43  SUBSTRUCTURE 4. ABUTMENTS 44  SUBSTRUCTURE 4.ABUTMENTS 5 Components a. Bridge Seat Horizontal shelf supporting the bridge deck Is near, or on, the top of the abutment or pier ON abutment Secure end of bridge on embankment Near or along the span Provide support to alleviate long term stress 45  SUBSTRUCTURE 4.ABUTMENTS 5 Components b. Stem  or abutment pile Can be a vertical wall connecting the seat with the foot or a row of columns On embankments, it provides retaining wall Its main function is to transfer loads from superstructure to the foundation 46  SUBSTRUCTURE 4.ABUTMENTS 5 Components c. Backwall  Only included in abutments connected to embankments  Acts as a retaining structure on top of the stem  Also supports the approach slab  Provide horizontal brace from bridge deck and reduce erosion at connecting point 47  SUBSTRUCTURE 4.ABUTMENTS 5 Components d. Wingwall  Only included in embankment walls  Sidewall of abutment backwall or stem that connects to the embankment  Short retaining walls designed to assist in confining earth behind the abutment to prevent erosion and add stability 48  SUBSTRUCTURE 4.ABUTMENTS 5 Components e. abutment footing  Connects the vertical, load bearing portion of abutment to the ground  Usually buried on the earth, prevents the abutment from sinking to ground surface  Consist of horizontal surface, sometimes wider than the bridge for weight distribution 49 SUBSTRUCTURE 50  SUBSTRUCTURE Wingwall 51  FOUNDATION the base of a bridge and a significant structural piece that plays a crucial role in maintaining the structural stability of the entire bridge built under the pier/abutment and over the fundamental soil/rock Distributes all loads into supporting strata/ bearing region including the loads from the abutments, piers, and wings ensure the solidness of the bridge against shifting and settlement; avoid soil shear failure must be sufficiently deep to prevent the effect of scour caused by the flow in the river 52 FOUNDATION 53  FOUNDATION 7. FOOTING  As bearing transfer the superstructure loads to the substructure; abutments and pier footings transfer load from the substructure to the subsoil or piles  A footing supported by soil without piles is called a spread footing  A footing supported by piles is known as a pile cap 8. PILES  When soil under a footing cannot provide adequate support for substructure (in terms of bearing capacity, overall stability, or settlement), support is obtained through piles, which extends down from the footing to stronger soil layer or bedrock 54  SUBSTRUCTURE 9. SHEETING  Vertical planks driven to the ground to act as temporary retaining wall permitting excavation Steel sheeting used as economical abutment material 55  APPURTENANCES and SITE-RELATED FEATURES APPURTENANCE  Any part of the bridge or bridge site which is NOT a major structural component yet serves some purpose in the overall functionality of the structure  i.e. guide rails  Bridge site, as an entity, possesses many different components which, in one way or another, integrates with the structure 56  APPURTENANCES and SITE-RELATED FEATURES EMBANKMENT AND SLOPE PROTECTION slope protection - slope that tapers from the abutment to the underpass (embankment) is covered with a material, which should be both aesthetically pleasing and provide for proper drainage and erosion control - form of slope protection varies greatly from region to region and is mostly dependent on specific environmental concerns and the types of material readily available - For water way crossings, large stones are usually used for foundation scour protection. 57  APPURTENANCES and SITE-RELATED FEATURES UNDERDRAIN - provide proper drainage of a major substructure element, such as an abutment, - a drainage system made of perforated pipe or other suitable conduit that transports runoff away from the structure and into appropriate drainage channels (natural or man-made APPROACH - Section of overpass roadway which leads up to and away from the bridge abutments - Helps evenly distribute traffic loads on the soil behind the abutment and minimize impact to the abutment which can result from differential settlement between abutment and approach 58  APPURTENANCES and SITE-RELATED FEATURES TRAFFIC BARRIERS - protective device “used to shield motorists from obstacles or slope located along either side of roadway - can range from a guard rail made of corrugated steel to reinforced concrete parapets - On bridges, they are usually called bridge railings. GUIDE RAILS - Designed to keep people or vehicles from losing their way into dangerous or off-limit areas 59  Other Parts 1. BRIDGE TOWER  Sometimes called mast or pylons  Vertical supporting part used for cable stayed or suspension bridge  Made of high strength in-situ concrete 2. SPANDREL  the almost triangular space between the main pillar of the bridge and decking 3. EXPANSION JOINT  The space between two parts of the structure that allows expansion and contraction 60  Other Parts 4. PARAPET  A low wall that forms a barrier around the outer edges of a bridge 5. ANCHORAGE  A point where the supporting elements of the bridge are connected to the ground 6. APEX  the uppermost portion o a bridge  Called a CROWN for arch bridges 61 Other Parts 62 Other Parts 63  Reference: Lecture Notes, Engr. YLA Suba, Saint Louis University Bridge Engineering, 2nd Edition, Tonias, D and Zhao, J 64