Bridge Construction

Image summary: This is a photograph. The image depicts a large suspension bridge with massive stone towers supporting thick cables that hold up the roadway. The bridge spans across a lush, forested valley with dense greenery surrounding the structure. The architecture suggests a historical engineering style, combining heavy masonry with tension-based cable support to cross a wide gap.

Bridge Construction

Teferi W.

Bridge Constriction

What is a Bridge?

• Bridge is a structure which covers a gap between a natural or artificial obstacle such as, a river, canal or any other obstruction

•A bridge is a structure providing passage over an obstacle. The obstacle may be a river, valley, road or railway. The passage may be for highway or railway traffic, pedestrian, canal or pipeline.

•Generally bridges can be for Highway, Railway, or Pedestrian

•By filling the gap with shortest distance, Bridges facilitate a free flow of traffic and they are the most Significant Component of A Transportation System

Image summary: This is a technical diagram. The figure illustrates a cross-sectional view of a multi-level transportation infrastructure, featuring an upper roadway supported by a bridge structure and a lower tunnel passage. The upper level shows a large truck traveling on a deck supported by beams and pillars that extend deep into the ground, while the lower level depicts a passenger car moving through a carved-out tunnel. The diagram indicates that the upper roadway is elevated and structurally independent of the lower passage, with the supporting pillars providing stability through the underlying soil and rock layers.

- 1-Deck and overpass

- 3-Bearing

- 5-Footing

- 8-Embankment

- 2-Stringer(longitudinal beams)

- 4-Pedestal

- 6-Piles

- 9-Live load

- 7-Underpass

Image summary: This is a photograph. The image depicts a long bridge spanning a body of water, featuring a combination of a large central arch and several smaller supporting arches. The foreground consists of a rocky shoreline. The bridge connects two landmasses under a bright sky with scattered clouds. The structure indicates a complex engineering design intended to facilitate transportation across a wide aquatic expanse.

Bridge is the {Key Element} in a Transportation System

why????????

Image summary: This figure is a photograph. It depicts a large arch bridge spanning across a lush, forested valley with a road deck supported by vertical pillars atop the arch. The image demonstrates a significant engineering feat where the bridge structure successfully traverses a wide natural gap, providing a stable elevated path over the dense vegetation below.

It Controls the Capacity of the System

- If the width of a bridge is insufficient to carry the number of lanes required to handle the traffic volume, the bridge will be a constriction/tighting to the flow of traffic.

- If the strength of a bridge is deficient and unable to carry heavy trucks, load limits will be posted and truck traffic will be redirected.

- The bridge controls both the volume and weight of the traffic carried by the transportation system.

Image summary: This is a photograph. The image depicts several people walking along a pedestrian walkway on a bridge that spans a body of water, with a roadway running parallel to the path and dense vegetation in the background. The scene suggests a common transit route used by pedestrians to cross a river, indicating that the bridge serves as a vital piece of infrastructure for local mobility.

Highest Cost per Mile of the System

Bridges are expensive. The typical cost per Km of a bridge is many times that of the approach roads to the bridge.

Since, bridge is the key element in a transportation system, balance must be achieved between handling future traffic volume and loads and the cost of heavier and wider bridge structure.

If the Bridge Fails, the System Fails

The importance of a Bridge can be visualized by considering the comparison between the two main components of a highway system that is a road and bridge itself.

Example: Suppose in a road there occurs deterioration and ultimately a crack, thus making a sort of inconvenience but it won't result in stopping of the flow of traffic as traffic can pass or otherwise a bypass can be provided. The traffic no doubt will pass with a slower speed but in case of a bridge its flow is completely stopped in case of the failure of the bridge, that is the reason its often called "If the bridge fails the system fails" as the function of the structure could no longer be served at all.

Image summary: This is a photograph. The image shows a bridge with a metal truss upper structure resting on stone arch supports, where one of the stone supports has partially collapsed and crumbled into the dry riverbed below. The structural failure indicates significant damage to the bridge foundation, suggesting that the bridge is unstable and unsafe for use.

Image summary: This figure is a geographic map. It displays a regional area featuring various towns, city names, river networks, and road infrastructures, with specific routes highlighted across the terrain. The map indicates that the region is densely intersected by waterways and connected by a network of roads linking several settlements, with certain primary routes serving as major transit corridors between the larger towns.

Classification of Bridges

Image summary: This figure is a flow diagram. It maps four primary bridge design categories to their corresponding options: Material, Usage, Span, and Structural Form. The diagram indicates that bridge materials include steel, concrete, timber, and stone or brick; usage categories cover pedestrian, highway, railroad, and combinations; spans are classified as short, medium, or long; and structural forms encompass slab, girder, truss, arch, suspension, and cable-stayed designs. The figure concludes that bridge classification is a multi-dimensional process based on these distinct engineering and functional criteria.

Material Usage Span Steel ; Concrete ; Timber Stone/Brick Pedestrian Highway Railroad Combination Short Medium Long Slab Girder Truss Arch Suspension Cable-Stayed

Discussion on Classification According to Structural Form

Slab Bridge Girder Bridge Arch Bridge Truss Bridge Suspension Bridge Cable-Stayed Bridges Slab bridge: examples are most of ring road bridges Slab bridges are most commonly used to span short spans up to 12m. The load carrying mechanism is by plate action, that is, by bending and twisting due to continuity in all directions

Image summary: This is a black and white photograph. The image depicts a large suspension bridge spanning across a wide river, featuring ornate stone towers and heavy cables supporting the roadway. In the background, various city buildings are visible along the riverbank under a cloudy sky. The presence of the bridge and surrounding architecture indicates an urban setting where the bridge serves as a primary transportation link across the waterway.

Image summary: This is a photograph. The image depicts a long bridge spanning across a wide, brown river under a clear sky, with several people walking along the pedestrian path and greenery along the riverbank. The presence of multiple support pillars and the number of pedestrians suggest that the bridge is a significant piece of infrastructure designed to facilitate the movement of people across the water body.

Image summary: This is a photograph. The image depicts a concrete bridge spanning across a wide, brown river, with lush green trees and vegetation in the foreground and background. A series of lamp posts are lined along the length of the bridge. The scene indicates a developed infrastructure integrated into a natural riverine environment, suggesting that the bridge serves as a primary transportation link across the waterway.

Distinctive Features of Girder Bridges

Widely constructed

•Usually used for Short and Medium spans

•Carry load in Shear and Flexural bending

•The most common girder bridge type are T-Girder and Box-Girder Bridges

• Stability concerns limits the stresses and associated economy

•Economical and long lasting solution for vast majority of bridges

• Decks and girder usually act together to support the entire load in highway bridges

Image summary: This figure consists of a real-world photograph and a corresponding technical diagram. The top image shows the active construction of a bridge over water using a large crane system to place segments, while the bottom image provides a schematic representation of a bridge's structural components, labeling the superstructure and substructure. The figure illustrates the relationship between the theoretical design of bridge components and their practical application in large-scale engineering projects, demonstrating how the supporting substructure holds the load-bearing superstructure.

T-Beam bridge/girder-slab bridge or girder bridge:

- The T-beam Bridge is by far the most commonly adopted type in the span range of 10 to 25 m.

- The structure is so named because the main longitudinal girders are designed as T-beams integral with part of the deck slab, which is cast monolithically with the girders.

- ➢ Simply supported T beams of greater spans are now-a-days pre-stressed to reduce deflection and vibration and also to reduce the material. This type of structures can be continuous over some number of piers also.

- For the longer spans, the longitudinal T beams are laterally supported by cross beams called as diaphragms at designed intervals.

- Diaphragms offer resistance against the lateral torsional buckling of the longitudinal T-beams

Hollow box girder bridges

- ▶Reinforced concrete hollow box girder bridges are economical in the span range of 25 to 30 meters.

- The closed box shape provides torsion rigidity, and the depth can be varied conveniently along the length as in continuous deck or in balanced cantilever layout.

- The closed box shape provides torsion rigidity.

- The extra torsion stiffness of the section makes this form particularly suitable for grade separations, where the alignment is normally curved in plan.

- The cells can be rectangular or trapezoidal, the latter being used increasingly in pre-stressed concrete elevated highway structures.

- Reinforced concrete hollow girder bridges are currently not favored, whereas pre-stressing is gaining appreciation

Image summary: This figure is a composite illustration consisting of a photograph and two schematic diagrams. The content displays a real-world example of a bridge structure alongside simplified structural representations of a T-Girder Bridge. The comparison indicates that the T-Girder Bridge design utilizes a series of vertical supports to distribute the load of the horizontal deck, showing a consistent architectural pattern between the theoretical model and the actual physical implementation.

Distinctive Features of Arch Bridge

• Arch action reduces bending moments (that is Tensile Stresses)

• Arch is predominantly a Compression member..

•Can be constructed from different material including stone, steel, concrete, brick, etc

• Suitable site is a Valley with arch foundations on a dry Rock Slopes

•Conventional curved arch rib has high Fabrication and Erection costs

Image summary: This is a black and white photograph. The image depicts an urban landscape featuring multiple bridges crossing a river, with industrial buildings and warehouses situated along the riverbank in the foreground and a city skyline with a prominent church spire in the background. The presence of several different bridge designs and extensive riverside industrial infrastructure suggests that this is a major transportation and commercial hub with a long history of engineering and trade.

Image summary: This is a photograph. The image shows a steel truss bridge spanning a dry riverbed, supported by stone masonry arches. One of the stone arch supports has suffered a significant structural failure, with a large section of the masonry collapsed and lying in the riverbed below. The bridge deck remains intact across the gap, but the supporting infrastructure is severely damaged. The scene indicates a critical structural collapse of the bridge's foundation, rendering the support system unstable and compromised.

- ➤ Girder bridges of reinforced concrete will be uneconomical for spans beyond 35 meters.

- Arch type can be used advantageously in the span range of 35 to 200 m and has been applied up to 305 meters as in the case of Gladesville Bridge in Sydney, Australia.

- A strong point in favor of arch bridges is their pleasing appearance and aesthetic elegance.

- The arch form is best suited to deep gorges with steep rocky banks which furnish efficient natural abutment to receive the heavy thrust exerted by the ribs.

- In the absence of these natural conditions, the arch usually suffers a disadvantage, because the construction of a suitable abutment is expensive and time consuming.

- ➢ All arches develop thrust at the supports and the thrust is to be taken by unyielding abutments.

- This thrust tends to reduce the bending moment at any section of the arch.

- The aim of the designer will be to maximize this reduction, so that the arch will have only compression in the section. While it is possible to nearly eliminate bending moments due to dead load by choosing the arch axis to coincide with the thrust line for bending moment, live load will cause net bending moments.

- four types of arch bridges. a.steel arch bridges b.Stone masonry arch bridges c.spandrel filled arch d.open spandrel arch

•The primary member forces are axial loads

•The open web system permits the use of a greater overall depth than for an equivalent solid web girder, hence reduced deflections and rigid structure

•Both these factors lead to Economy in material and a reduced dead weight

•Other bridge types have rendered the truss bridge types less likely to be used due to its high maintenance and fabrication costs.

Image summary: This is a photograph. The image depicts a long bridge consisting of multiple arched steel truss spans supported by concrete piers crossing a wide body of water. The structure extends from the foreground toward the distant shoreline under a cloudy sky. The design indicates a heavy industrial engineering approach intended to support significant loads across a river, suggesting the bridge was built for durability and functional transport.

Ease of construction is the top most criteria to use steel truss bridge

•It's a light weight structure it can be assembled member by member using lifting equipment of small capacity.

• Rarely aesthetically pleasing complexity of member intersections if viewed from oblique direction

•In large span structures poor aesthetic appearance of the truss bridge is compensated with the large scale of the structure. For moderate spans its best to provide a simple and regular structure

A bridge truss derives its economy from its two major structural advantages, (a) the primary forces in the members are axial forces (stress resultants are less), and (b) greater overall depths permissible with its open web construction leads to reduced self-weight when compared to solid web systems.

Image summary: This is a photograph. The image depicts a large suspension bridge spanning a body of water, with tall towers supporting thick cables and a roadway carrying vehicle traffic. In the background, a coastline with urban development and distant hills is visible under a clear sky. The presence of the bridge indicates a significant engineering feat designed to connect two landmasses across a wide aquatic expanse, facilitating regional transportation and connectivity.

• Major element is a flexible cable, shaped and supported in such a way that it transfers the loads to the towers & anchorage

•This cable is commonly constructed from High Strength wires, either spun in situ or formed from component, spirally formed wire ropes. In either case allowable stresses are high of the order of 600 M.P.A

•The deck is hung from the cable by Hangers constructed of high strength ropes in tension

• As in the long spans the Self-weight of the structures becomes significant, so the use of high strength steel in tension, primarily in cables and secondarily in hangers leads to an economical structure.

•The economy of the cable must be balanced against the cost of the associated anchorage and towers. The anchorage cost may be high where foundation material is poor

Image summary: This figure is a labeled schematic diagram. It illustrates the structural components of a suspension bridge, identifying the anchorage, towers, cable, hangers, and deck. The diagram demonstrates how the deck is supported by vertical hangers that connect to a main cable, which in turn is supported by tall towers and secured at both ends by anchorages.

•It is the only alternative for spans over 600m, and it is generally regarded as competitive for spans down to 300m. However, shorter spans have also been built, including some very attractive pedestrian bridges

•The height of the main towers can be a disadvantage in some areas; for example, within the approach road for an Airport

Image summary: This is a photograph. The image depicts a large suspension bridge spanning across a wide body of water, with forested hills and vegetation visible in the background and foreground. The bridge features tall support towers and a long deck supported by cables. The presence of the bridge indicates a developed infrastructure designed to facilitate transportation across the waterway, connecting two separate landmasses.

- Suspension bridge is currently the only solution for spans in excess of 900 m.

- Suspension bridges consist of two large, or main, cables that are hung (suspended) from towers.

- The main cables of a suspension bridge drape over two towers, with the cable ends buried in enormous concrete blocks known as anchorages.

- The roadway is suspended from smaller vertical cables that hang down from the main cables.

- In some cases, diagonal cables run from the towers to the roadway & add rigidity to the structure.

- The main cables support the weight of the bridge and transfer the load to the anchorages and the towers.

- The world's longest span bridge at present is the Akashi-Kaikyo bridge across Akashi strait in Japan which is a suspension bridge with a main span of 1991m.

Image summary: This is a black and white photograph. The image depicts a large suspension bridge spanning a body of water, with a dense city skyline featuring numerous illuminated skyscrapers in the background. The bridge's stone towers and intricate cable network are prominent features, with lights lining the span. The scene suggests a nighttime urban environment where the architectural scale of the bridge and the surrounding city are emphasized by the contrast between the dark sky and the artificial lighting.

Brooklyn bridge, Newyork city

Image summary: This is a photograph. The image depicts a large suspension bridge spanning across a wide body of water, connecting two landmasses with a city skyline visible in the background under a partly cloudy sky. The bridge features a tall supporting tower and a long deck supported by cables, indicating a significant engineering feat designed to facilitate transportation over a substantial aquatic gap.

Image summary: This is a photograph. The image depicts a large stone suspension bridge tower with thick cables extending across the scene, set against a clear sky and framed by foliage. The architectural style suggests a historical masonry structure designed to support a heavy load over a distance.

Image summary: This is a photograph. The image depicts a long cable-stayed bridge spanning across a large body of water, featuring tall pylons with multiple supporting cables extending down to the bridge deck. Based on the structural design, it can be inferred that the bridge is engineered to support significant loads across a wide expanse of water, utilizing a modern architectural style to ensure stability and connectivity.

•The use of high strength cables in tension leads to economy in material, weight, and cost..

• As compared with the stiffened suspension bridge, the cables are straight rather than curved. As a result, the stiffness is greater

•The cables are anchored to the deck and cause compressive forces in the deck. For economical design, the deck must participate in carrying these forces

•All individual cables are shorter than full length of the superstructure. They are normally constructed of individual wire ropes, supplied complete with end fittings, pre-stretched and not spun.

•There is a great freedom of choice in selecting the structural arrangement.

• Less efficient under Dead Load but more efficient in support Live Load.

• It is economical over 100 to 350 meters, some designer would extend the upper bound as high as 800 meters.

Image summary: This is a photograph. The image depicts a long cable-stayed bridge spanning a deep valley, with a highway extending into a rural landscape characterized by rolling hills and fields. A vehicle is visible traveling across the bridge deck. The bridge features multiple tall pylons with radiating cables that support the roadway. The infrastructure indicates a significant engineering project designed to facilitate transportation across challenging terrain, connecting distant areas of the countryside.

Image summary: This is a digital architectural rendering. The image depicts a modern cable-stayed bridge crossing a body of water, featuring a single tall, slanted pylon that supports the bridge deck via multiple cables. The surrounding environment consists of a river, lush green trees, and a clear sky. The design suggests a futuristic approach to infrastructure, blending structural efficiency with aesthetic elegance to integrate a transportation link into a natural landscape.

Hidassie bridge

- General: A cable stayed bridge is a bridge whose deck is suspended by multiple cables that run down to the main girder from one or more towers.

- The cable stayed bridge is specially suited in the span range of 200 to 900 m.

- Cable stayed bridges are economical over wide range of span lengths and they are aesthetically attractive.

- Main components of a cable stayed bridge are (a) inclined cables, (b) towers and (c) orthotropic deck. (Orthotropic means having different elastic properties in two mutually perpendicular directions.

Discussion on Classification According to Span

Small Span Bridges (up to 15m)

Medium Span Bridges (up to 50m)

Large Span Bridges (50-150m)

Extra Large (Long) Span Bridges (over 150 meters)

Small Span Bridges (up to 15m)

- Culvert Bridge

- Slab Bridges

- T-Beam Bridge

- ➢Wood Beam Bridge

- Pre-cast Concrete Box Beam Bridge

- Pre-cast Concrete I-Beam Bridge

- Rolled Steel Beam Bridge

Medium Span Bridges (up to 50m)

- Pre-cast Concrete Box Beam & Pre-cast Concrete I-Beam

- Composite Rolled Steel Beam Bridge

- Composite Steel Plate Girder Bridge

- Cast-in-place R.C.C Box Girder Bridge

- Cast-in-place Post-Tensioned Concrete Box Girder

- Composite Steel Box Girder

Image summary: This is a photograph. The image depicts the interior of a long, concrete underground tunnel or bunker with sloping side walls and a flat ceiling. A series of overhead lights illuminate the center of the corridor, and a cable tray runs along the upper right wall. The space appears empty and industrial, suggesting it is a utility tunnel or a structural foundation for a larger facility.

Large Span Bridges (50 to 150m)

- Composite Steel Plate Girder Bridge

- Cast-in-place Post-Tensioned concrete Box Girder

- Post-Tensioned Concrete Segmental Construction

- Concrete Arch and Steel Arch

Extra Large (Long) Span Bridges (Over 150m)

- Cable Stayed Bridge

- Suspension Bridge

Factors Considered in Deciding Bridge Type

In general all the factors are related to economy, safety and aesthetics.

- Geometric Conditions of the Site

- Subsurface Conditions of the Site

- Functional Requirements

- Aesthetics

- Economics and Ease of Maintenance

- Construction and Erection Consideration

Geometric Conditions of the Site

The type of bridge selected will always depend on the horizontal & vertical alignment of the highway route and on the clearances above & below the roadway

For Example: if the roadway is on a curve, continuous box girders and slabs are a good choice because they have a pleasing appearance, can readily be built on a curve, & have a relatively high torsion resistance

•Relatively high bridges with larger spans over navigable waterways will require a different bridge type than one with medium spans crossing a flood plain

•The site geometry will also dictate how traffic can be handled during construction, which is an important safety issue and must be considered early in the planning stage

- The foundation soils at a site will determine whether abutments and piers can be founded on spread footings, driven piles, or drilled shafts

- If the subsurface investigation indicates that creep settlement is going to be a problem, the bridge type selected must be one that can accommodate differential settlement over time

- Drainage conditions on the surface and below ground must be understood because they influence the magnitude of earth pressures, movement of embankments, and stability of cuts or fills

- For Example: An inclined leg frame bridge requires strong foundation material that can resist both horizontal and vertical thrust. If it is not present, then another bridge type is more appropriate.

- The potential for seismic activity at a site should also be a part of the subsurface investigation. If seismicity is high, the substructure details will change, affecting the superstructure loads as well

- All of these conditions influence the choice of substructure components which in turn influence the choice of superstructure

Functional Requirements

- ➤ Bridge must function to carry present & future volumes of traffic.

- Decisions must be made on the number of lanes of traffic, inclusion of sidewalks and/or bike paths, whether width of the bridge deck should include medians, drainage of the surface waters, snow removal, and future wearing surface.

- For Example: In the case of stream & flood plain crossings, the bridge must continue to function during periods of high water & not impose a severe constriction or obstruction to the flow of water or debris.

- Satisfaction of these functional requirements will recommend some bridge types over others.

- For Example: if future widening and replacement of bridge decks is a concern, multiple girder bridge types are preferred over concrete segmental box girders.

The initial cost and maintenance cost over the life of the bridge govern when comparing the economics of different bridge types.

➢ A general rule is that the bridge with the minimum number of spans, fewest deck joints, and widest spacing of girders will be the most economical.

•For Example: By reducing the number of spans in a bridge layout by one span, the construction cost of one pier is eliminated.

Deck joints are a high maintenance cost item, so minimizing their number will reduce the life cycle cost of the bridge.

When using the empirical design of bridge decks in the ashto (1994) Specifications, the same reinforcement is used for deck spans up to 4.1m. Therefore, there is little cost increase in the deck for wider spacing for girders and fewer girders means less cost although at the “expense” of deeper sections.

- ➤ Generally, concrete structures require less maintenance than steel structure. The cost and hazard of maintenance painting of steel structures should be considered in type selection studies.

- One effective way to reduce the overall project cost is to allow contractors to propose an alternative design or designs.

Construction and Erection Considerations

- The length of the time required to construct a bridge is important and will vary with the bridge type.

- ➢ Generally, the use of larger/longer prefabricated or pre-cast members shorten the construction time. However, the larger the members, the more difficult they are to transport and lift into place.

- The availability of skilled labor and specified materials will also influence the choice of a particular bridge type.

- For Example: if there are no pre-cast plants for pre-stressed girders within easy transport but there is a steel fabrication plant nearby that could make the steel structure more economical.

- The only way to determine which bridge type is more economical is to bid alternative designs.

Girder Bridge

Image summary: This is a photograph. The image captures a low-angle perspective from beneath a large concrete bridge, showing the underside of the road deck supported by a series of heavy beams and massive vertical pillars. The structure curves gently into the distance, revealing the repetitive architectural pattern of the support system against a backdrop of natural terrain. The composition indicates a robust engineering design capable of supporting significant weight across a wide span, utilizing reinforced concrete to ensure structural stability and durability.

Figure 3 summary: This figure is a composite of several photographs. The images display various types of bridge supports and bearing assemblies, showcasing different structural designs including concrete piers and steel girders. The visual evidence indicates a variety of engineering approaches to manage load distribution and thermal expansion, ranging from simple concrete interfaces to complex mechanical bearing systems.

Bridge Cap and Damper

Image summary: This figure is a composite of three photographs. The images display various sections of bridge infrastructure, focusing on the structural supports, beams, and concrete surfaces. The photographs reveal signs of wear and deterioration, including visible cracks in the concrete and weathering on the metal components. It can be inferred that the infrastructure is aging and requires maintenance to ensure structural integrity.

Figure 3 summary: This is a photograph of an architectural detail. The image displays a decorative concrete structure featuring a radiating sunburst pattern and a grilled ventilation opening integrated into a textured wall. The design suggests a blend of functional utility and geometric ornamentation, where the structural elements provide both airflow and aesthetic appeal to the building exterior.

Image summary: This is a photograph. The image depicts the underside of a large metal bridge structure, focusing on the heavy steel beams, rivets, and supporting trusses. Another bridge structure is visible in the background under a bright sky. The construction indicates an industrial design characterized by massive scale and reinforced joints, suggesting that the structure is built to support significant weight and withstand high stress.

Image summary: This is a photograph. The image depicts a construction site featuring a large piece of heavy machinery with wooden and metal components in the foreground, a dump truck in the midground, and a multi-story brick building in the background. A small child is sitting on a concrete structure near the truck. The composition highlights the vast difference in scale between the industrial equipment and the young child, suggesting a contrast between the massive scale of urban development and human vulnerability.

Image summary: This is a photograph. The image depicts a detailed view of a structural steel bridge joint where the metal framework connects to a concrete abutment. The assembly features heavy steel plates, beams, and numerous rivets, including a large circular bearing plate that facilitates the connection between the bridge superstructure and the support. The construction indicates a riveted steel truss design, suggesting an older engineering style used for load-bearing infrastructure. The presence of the bearing plate and the robust riveting indicates that the joint is designed to distribute significant weight and allow for thermal expansion or movement of the bridge span.

Image summary: This figure consists of two side-by-side photographs. The images depict two different architectural structures: a large suspension bridge spanning a forested valley and a fortified stone castle with crenelated towers. The comparison highlights the contrast between industrial engineering designed for transportation and medieval military architecture designed for defense.

Image summary: This is a photograph. The image depicts two individuals standing on a high, industrial metal structure that resembles a bridge or a large crane assembly, featuring a series of beams, ladders, and support cables extending outward. The scene suggests that the workers are conducting an inspection or maintenance task on a massive engineering project situated over a body of water. It can be inferred that the structure is designed for heavy-duty industrial use and requires specialized personnel for its upkeep due to its scale and height.

Image summary: This is a photograph. The image depicts a large suspension bridge featuring massive stone towers and thick cable supports, with vehicles traveling across the roadway. The perspective is from the road looking through the architectural arches of the bridge towers. The presence of multiple cars and traffic cones suggests that the bridge is a functional piece of transportation infrastructure used for daily commuting.

2023

Golden Gate Bridge Main Span 4200 ft.

Length of one Cable oilmetter of Cable Wires in lach cable Total Wire Used weight of cama 7650. (23307.1 36______ (924)

27572 40,000—（74,345.1 24500

Image summary: This is a photograph. The image depicts a steel truss bridge spanning across a body of water, featuring a complex network of intersecting beams and supports. The bridge is supported by concrete piers and includes safety railings and vertical signal poles. The structure indicates a heavy-duty engineering design intended for transporting loads across the water, suggesting a functional infrastructure used for transportation.

Image summary: This is a photograph. The image depicts a large metal truss bridge spanning across a body of water, supported by several thick concrete pillars. In the foreground, a person is operating a tractor on a road running parallel to the bridge. A leafless tree stands to the left, and distant hills are visible across the water. The scene suggests a rural or industrial setting where heavy infrastructure coexists with agricultural activity.

Image summary: This is a photograph. The image depicts a large steel cantilever bridge spanning across a body of water, supported by tall concrete and steel piers, with a distant shoreline and mountains visible in the background. The structure demonstrates complex engineering with an intricate network of interconnected steel beams and trusses that support the roadway above the water.

Image summary: This is a photograph. The image depicts a long, multi-span arch bridge crossing over a body of water under a partly cloudy sky. The bridge features a series of reinforced concrete arches supporting a flat roadway with safety railings running along the top. The structure demonstrates a repetitive architectural design with multiple supports anchored in the water, indicating a substantial engineering project designed to facilitate transport across a wide river.

Image summary: This is a photograph. The image depicts a multi-arch stone bridge spanning a body of water, with a forested hillside in the background under a cloudy sky. The bridge consists of several semi-circular arches supported by heavy stone piers anchored in the river. The structure suggests a durable, classical engineering style designed to withstand water flow while providing a stable crossing over the river.

Arch Bridge

Image summary: This is a photograph. The image depicts a suspension bridge with vehicles traveling across its roadway, featuring tall support towers and thick cables extending across the span. The bridge is set against a backdrop of forested hills under a clear sky. The presence of multiple cars and the substantial engineering of the bridge indicate that it serves as a primary transportation route connecting two landmasses across a geographical divide.

Image summary: This is a photograph. The image depicts a large suspension bridge extending across a body of water, with a city skyline and hills visible in the background. Several sailboats are scattered across the water below the bridge structure. The bridge features massive support towers and long cables that hold up the roadway. The image demonstrates the scale of civil engineering required to span wide bodies of water, connecting two landmasses while allowing maritime traffic to pass underneath.

Image summary: This is a photograph. The image depicts a large suspension bridge spanning a body of water, featuring massive support towers, thick suspension cables, and a roadway deck. A small boat is visible on the water below the bridge, and a rocky shoreline is in the foreground. The structure demonstrates the characteristic design of a suspension bridge, where the roadway is hung from cables anchored to tall towers, allowing for a wide span across the water.

Image summary: This is a photograph. The image depicts a large suspension bridge featuring massive stone towers, heavy metal cables, and a roadway with a pedestrian walkway. People are seen walking along the side of the bridge, with a backdrop of green trees and a cloudy sky. The structure demonstrates a combination of traditional masonry and industrial engineering, indicating a design intended to span a significant distance while supporting heavy loads.

Image summary: This is a photograph. The image depicts a pedestrian walkway on a large suspension bridge, featuring massive structural cables and pipes overhead that lead toward a distant bridge tower. A few people are present, including a man resting on a bench in the foreground and a couple standing further down the path. The composition emphasizes the scale of the engineering against a clear sky. The perspective suggests a vast architectural achievement, highlighting the contrast between the immense industrial structure and the small scale of the human figures.

Image summary: This is a photograph. The image depicts a large bridge under construction spanning a body of water, with massive concrete supports and unfinished road decks. Construction equipment, including cranes and scaffolding, is positioned across the structure, set against a backdrop of rolling hills and a residential area. The scene indicates that the project is in an advanced stage of development, as the primary supports are complete and the main spans are being connected. The scale of the infrastructure suggests a major transportation link designed to cross a significant waterway.

Image summary: This is a photograph. The image depicts a construction site featuring a large concrete structure under development, supported by wooden scaffolding and reinforced with metal rods. Workers are present on the site, overseeing the assembly of the massive concrete slab. The scene indicates that the structure is in an intermediate stage of construction, with temporary supports still in place to hold the weight of the concrete as it sets.

Image summary: This figure consists of two side-by-side photographs. The images depict different stages and methods of highway bridge construction, showing elevated concrete road structures supported by massive pillars. The left image shows a multi-level interchange with completed sections and construction blocks on the deck, while the right image shows a single long-span bridge being extended across a forested valley using specialized launching equipment. The comparison indicates a variety of engineering approaches for infrastructure development, ranging from complex urban interchanges to long-distance spans over natural terrain.

Selecting an Ideal Site for a Proposed Bridge. Connection with the Road

- o Firm embankment

- Foundations

- Material and labour

- Square crossing

Design Objectives

The objectives in a bridge design are safety, serviceability, economy, constructability and aesthetics.

Safety – the primary responsibility of the engineer is to ensure public safety in the design by ensuring adequate structural safety (the philosophy of achieving structural safety is treated in subsection 1.5)

○ Serviceability – consists of satisfying requirements of deformation, durability, inspect ability, maintainability and ride ability.

oDeformation – Bridges should be designed to avoid excessive deformations that cause undesirable structural or psychological effects. Limits on deflection or minimum depth to consider are given in codes (ashto 98, Articles 2.5.2.6.2 and 2.5.2.6.3 respectively).

Durability – contract documents specify quality of materials to be used and standards of fabrication and erection of elements to ensure durability. Self-protecting measures of the structure from the effects of the weather will be taken during design and construction Inspectability – inspection ladders, walkways, catwalks and covered access holes will be provided where other means of inspection are not practical. o Maintainability – structural systems whose maintenance is expected to be difficult should be avoided oRideability – the deck of the bridge will be designed to permit smooth movement of traffic. oThe number of deck joints will be kept to a practicable minimum.

○ Economy – structural types, span lengths and materials should be selected based on cost. The cost of future expenditures during the projected service life of the bridge should be considered o Constructability – bridges should be designed in a manner such that fabrication and erection can be performed without undue difficulty or distress and that construction force effects are within tolerable limits

- {Aesthetics} - Aesthetics aspect and space requirement of buildings are designed by architects. Aesthetic, space requirement, hydraulic and structural aspects of bridges are designed by civil engineers. Bridges should complement their surroundings, be graceful in form and present an appearance of adequate strength. Because the major structural components are the largest parts and are seen first, they determine the appearance of a bridge.

Parts of a Bridge

◦Depending on the type of the bridge the elements/components may vary to some extent. However, for conventional bridge structures the following are the basic elements Super Structure Sub Structure Approach slab, Guard Rails Deck/ Slab Girder Bearing Pier & Pier Cap Wing wall Abutment, Seat beam & Back wall Foundation Superstructure

○ Sub-Structure: include elements of the bridge which are below the bearing & transfer loads from the bearing & deck to the supporting structure. ○ Super-Structure: include elements of the bridge above the bearing which receive & transfer loads to the bearing.

○ Bridge bearing is included in superstructure. ○ Deck/Slab is part of the bridge which provide the riding surface for traffic or receive the direct traffic load ○ Girder/Beam: is the main structural element which carry the load & transfer to the bearing. ○ Bearing: is a metal or elastomeric plate which serves to allow different movement between sub structure & superstructure & transfer load

Abutment: is a masonry or concrete structure found at the end sides of the bridge which •retain the soil of the approach road • support the horizontal force of the soil •transfer the traffic load to the footing

Image summary: This figure is a labeled technical diagram. It illustrates the structural components of a bridge support system, specifically identifying the bearing, the abutment, and the footing. The diagram shows that the bearing sits at the top to support the bridge deck, the abutment serves as the main vertical support structure, and the footing provides the base foundation at the bottom.

Wing Wall: is a structure which support & retain the embankment soil of the approaching road & found on both sides of the abutment It can have one of the following shapes depending on the soil to be supported & the adjacent structures T-Girder Bridge Box-Girder Bridge Piers

Image summary: This figure is a schematic diagram. It depicts a horizontal rectangular base flanked by two vertical rectangular blocks on either end, creating a U-shaped configuration. The layout indicates a structural arrangement where a central platform is supported or enclosed by two side pillars, suggesting a symmetrical design used to represent a container, a support system, or a physical boundary.

Image summary: This figure is a schematic diagram. It depicts a structural component shaped like an inverted T or an I-beam, featuring a wide top flange, a central vertical web, and a narrower bottom base. Several small, rectangular contact points are positioned along the top surface of the upper flange. The arrangement suggests a mechanical or electrical interface where the top surface serves as a contact area supported by a rigid structural body.

Image summary: This figure is a schematic diagram. It depicts a structural framework consisting of a top and bottom horizontal beam supported by several vertical pillars, with a central horizontal cross-member and small rectangular blocks resting on the top surface. The arrangement suggests a stable, load-bearing architecture designed to distribute weight across multiple supports.

Image summary: This figure is a flow chart. It illustrates the path of load distribution starting from the bridge deck, which carries both dead and live loads. The load is transferred from the deck through various structural components including stringers, floor beams, and abutments or piers. From the floor beams, the load is further distributed to either trusses at panel points or girders, both of which eventually channel the load into the abutments or piers, and finally down to the foundations. The chart demonstrates that the structural system is designed to redirect loads from the top surface through multiple intermediate supporting elements to ensure the weight is safely transferred to the ground foundations.

Image summary: This figure is a technical schematic diagram. It illustrates the various structural components of a bridge, dividing the architecture into the superstructure and the substructure. The diagram labels specific elements such as the running surface, deck, beams, girders, abutments, piers, and piles, while distinguishing between the approach sections and the main bridge span. The figure demonstrates that the superstructure consists of the elements that carry the traffic load, while the substructure provides the necessary foundational support, transferring the load from the bridge deck down through the piers and piles into the ground.

Image summary: This figure is a labeled diagram. It consists of a vertical rectangular block accompanied by a smaller square element and the text Construction Phase. The layout indicates that the block represents the duration or scope of the construction phase within a larger process.

ashto L.R.F.D Bridge Design Specifications

S.I Units Third Edition • 2004 Ethiopeeuh Ethiopeeun Roads Authority Bridge Design Manual Part 3 Appendices to Parts 1 & 2 of the Bridge Design Manual

Image summary: This is a black and white photograph. The image depicts a bridge crossing over a body of water, surrounded by dense foliage and tall trees. The bridge structure is reflected in the still water below. The presence of the bridge and the surrounding natural environment suggests a park or a rural landscape designed for pedestrian or vehicular passage through a wooded area.

Image summary: This figure is a photograph of a document cover. The content shows the cover page of the Bridge Design Manual, specifically Part One regarding standards and specifications for bridge design, published by the Ethiopian Roads Authority for the Federal Democratic Republic of Ethiopia. The document serves as an official technical guideline for engineering infrastructure within the country.

Bridge Design Considerations

Design Philosophy

As per ashto L.R.F.D manual and era Bridge design manual, the design philosophy is stated as

Bridges shall be designed for specified limit states to achieve the objectives of constructibility, safety, and serviceability, with due regard to issues of inspectability, economy, and aesthetics,

Regardless of the type of analysis used, equation 1.3.2.1 to 1 shall be satisfied for all specified force effects and combinations thereof.

Limit States

1.3.2.2 Service Limit State

The service limit state shall be taken as restrictions on stress, deformation, and crack width under regular service conditions.

1.3.2.3 Fatigue and Fracture Limit State

The fatigue limit state shall be taken as restrictions on stress range as a result of a single design truck occurring at the number of expected stress range cycles.

The fracture limit state shall be taken as a set of material toughness requirements of the Technical Specifications.

1.3.2.4 Strength Limit State

The strength limit state shall be taken to ensure that strength and stability, both local and global, are provided to resist the specified statistically significant load combinations that a bridge is expected to experience in its design life.

1.3.2.5 Extreme Event Limit States

The extreme event limit state shall be taken to ensure the structural survival of a bridge during a major earthquake or flood, possibly under scoured conditions.

The limit states specified herein are intended to provide for a buildable, serviceable bridge, capable of safely carrying design loads for a specified lifetime. o Culverts are designed to pass small permanent or periodic streams. How a culvert performs, and in many respects its design is determined according to culvert flow regimes. a)

- High-head flow type culverts are the most cost-effective and have the highest flow capacity; however, the risk that water will seep through the joints between the sections into the fill and that fill material will be washed out (that piping might occur) increase dramatically in such culverts.

- o Culverts shall be designed for low-head flow. It is allowed to design semi high-head and high-head flow type culverts to pass only small discharge. All of the considered standards have these recommendations.

o In order to ensure low-head flow conditions in culverts standards state the super elevation of the highest point of inner surface of the barrel in any cross-section above the water surface in the barrel at maximum flow of designed flood, The selection of bridge location should include due consideration of

Engineering (Geometric Design, Geotechnical Investigation, Hydraulic/Hydrology study....

○Economic (minimum construction cost, maximum cost benefit ...)

Constructability and maintainability

oEnvironmental concerns (Erosion, river bank ...

degree Etc

- o In General, good bridge location should

- oFit the condition created by the obstacle being crossed

- oFacilitate practical cost effective design, construction, operation, inspection and maintenance;

- oProvide the desired level of traffic service and safety

- oMinimize adverse highway impact

Figure 13.1 summary: This figure consists of a series of schematic diagrams. The diagrams illustrate different hydraulic flow regimes occurring within a culvert, showing the relationship between the water levels upstream, inside the structure, and downstream. The illustrations demonstrate varying water surface profiles, ranging from scenarios where the water level is high throughout the culvert to cases where the flow becomes more rapid and drops significantly at the outlet. From these diagrams, it can be inferred that culvert flow is categorized based on whether the flow is controlled by the inlet or the outlet, and whether the flow remains subcritical or becomes supercritical as it passes through the conduit.

Table 13.1 summary: The table specifies the minimum required superelevation for the inner surface of various culvert types based on their height during maximum design flood flow. For shorter culverts, circular and pipe-arch designs require a higher minimum superelevation compared to box culverts. For taller culverts, circular and pipe-arch designs maintain a consistent minimum requirement that is greater than that of box culverts.

Guideline to Select Bridge Location if it is Over Waterway or Flood-Plane

- Locate the bridge away from bends

- Locate the bridge perpendicular to the flow of the river. Avoid skew angle greater than 20 superscript circle

- Locate the bridge where the waterway is Shallow and Narrow

- Locate the bridge at location where the foundation is Rock Bed.

Image summary: This is a photograph. The image depicts a wide river flowing through a valley surrounded by forested hills, with steam or mist rising from the water's surface and rocky terrain lining the banks. The presence of rising vapor suggests that the water temperature is significantly higher than the surrounding air, indicating geothermal activity or a thermal spring within the river system.

Figure 7-9 summary: This figure consists of a composite of aerial imagery and ground-level photographs. The aerial images display a river system with a highlighted right of way crossing a meandering section of the river, while the photographs show a bridge spanning a riverbed and a wide view of the river channel. The imagery illustrates the process of meander migration and the eventual formation of a cut-off, where the river creates a shorter path and abandons a previous loop. It can be inferred that the river's natural tendency to shift its course over time can impact infrastructure, such as the bridge shown, by altering the flow of water and the stability of the surrounding banks.

Planning & Design of Bridge

Hydrological Studies

- o A thorough understanding of the river and river regime is crucial to planning of Bridge over a river

- o Hydrological Studies should include:

- Topographic Survey 2 kilometers upstream and 2 kilometers downstream for small rivers including Longitudinal section and X-sections

- For big rivers 5kms U/S and 2kms D/S should be surveyed

Image summary: This figure is a schematic diagram of a drainage basin. It illustrates a network of streams flowing from various points within a watershed boundary toward a single outlet, with specific junctions labeled as points A, B, and C. The diagram shows that as water moves downstream, smaller tributaries merge into larger channels, indicating that the drainage area increases at each subsequent junction. Consequently, point C represents the largest contributing drainage area among the labeled points, while point A represents the smallest.

Hydrological Studies

Image summary: This figure is a topographic map. It illustrates a river catchment area, highlighting the network of waterways and the surrounding terrain boundaries. The map indicates that the drainage system consists of numerous smaller tributaries that converge into a primary river channel, flowing through a varied landscape of ridges and valleys.

Design Flood Levels

- o ashto Gives Following Guidelines for Estimating Design Flood Levels

2.6.3 Hydrologic Analysis

The following flood flows should be investigated, as appropriate, in the hydrologic studies:

- For assessing flood hazards and meeting floodplain management requirements—the 100-year flood;

- For assessing risks to highway users and damage to the bridge and its roadway approaches—the overtopping flood and/or the design flood for bridge scour;

Estimating Design Flood

o Flood Peak Discharge at Stream or River Location Depends upon:

Catchment Area Characteristics

Size and shape of catchment area

• Nature of catchment soil and vegetation

Elevation differences in catchment and between catchment and bridge site location

o Rainfall Climatic Characteristics

• Rainfall intensity duration and its spatial distribution

Stream/River Characteristics

Slope of the river

Baseline flow in the river

• River Regulation Facilities/ Dams, Barrages on the river

Image summary: This figure is a cross-sectional profile plot. It displays the ground elevation across a specific station range for the Omo Bridge Design, overlaying several flood level indicators including the energy grade line, the water surface level, and the critical depth for a century-scale flood event. The data indicates that the predicted water surface level for a major flood is significantly lower than the surrounding ground elevation at the banks, while the energy grade line remains the highest of the hydraulic levels. It can be inferred that the channel is capable of containing the projected flood volume without overflowing the banks at the specified stations.

Image summary: This is a schematic diagram. It illustrates the fluid dynamics and flow patterns around a vertical cylindrical structure embedded in a medium. The figure depicts the interaction between a horizontal flow, the structural barrier, and the resulting turbulence, showing flow lines that curve around the cylinder and form vortices both at the surface and within the medium. It can be inferred that the presence of the cylinder disrupts the uniform flow, leading to the creation of swirling eddies and a localized scour zone at the base, indicating significant turbulence and material displacement caused by the obstacle.

Image summary: This is a photograph. The image shows a long concrete bridge spanning across a wide, shallow riverbed with several support piers. Some of the piers are reinforced with additional vertical piles driven into the riverbed. The surrounding terrain consists of sandy banks and sediment deposits. The presence of supplementary support structures suggests that the bridge has undergone reinforcement to address stability issues or erosion around the original foundations.

Scour is a site-specific process that is a function of the following:

• Flow velocity and duration;

- The geometry of the structural elements exposed to the flow of water;

- The geomorphology of the channel; and

- The properties of the foundation and channel bed materials.

Image summary: This figure is a cross-sectional line plot. It illustrates the bridge scour profile, showing the relationship between the station distance and elevation, including the ground level, the water surface during a major flood event, and the predicted total scour depth. The data indicates that the riverbed is significantly lower than the surrounding ground and the flood water level. The predicted total scour extends from the flood water surface down to the deepest points of the riverbed, suggesting that the most substantial erosion occurs near the center of the channel.

The satisfactory performance of a river crossing such as a bridge or culvert normally depends on the proper selection, investigation and design of the foundations. While it is more appropriate to think about the location of river crossings at the time of route selection, the investigation during design assists in delivering appropriate foundation data for design and reduces the risk of facing unanticipated ground conditions during construction.

Image summary: This is a photograph. The image shows a large industrial drilling rig positioned on a rocky, uneven terrain with hills in the background and a few people standing at a distance. A large metal container is placed next to the machinery, and various cables and pipes connect the equipment. The scene indicates an active geotechnical or mineral exploration site where deep soil or rock sampling is being conducted in a remote, mountainous environment.

Core drilling for Omo river Bridge Geotechnical Investigation

To investigate Bridge foundation sites, deep drilling is recommended. Accordingly,

- Drill bore holes at the specified support locations centers to he minimum depth

- Log the core collected in oil profile

• Conduct laboratory test to determine different soil properties

Image summary: This is a photograph showing a geological sample collection. The image displays several rows of cylindrical rock core samples organized within a wooden storage crate, resting on a rocky ground surface. The samples vary in size and texture, with some appearing as solid segments and others as fragmented pieces. Based on the arrangement and the accompanying documentation, it can be inferred that these samples were extracted from a drilling operation to analyze the subsurface geological composition at a specific site.

Image summary: This figure is a technical engineering diagram and cross-sectional profile. It illustrates a bridge structure consisting of multiple piers supported by a foundation, set against a geological profile of the underlying soil layers. The diagram details the spacing between piers and the stratification of the ground, which includes layers of fine sand, high plasticity clay, and a base of boulders and gravels, while also indicating the maximum water level and areas of potential undermining. The figure indicates that the structure is susceptible to both general and local undermining, with the risk being most prominent where the soil layers are thinner or more eroded beneath the pier foundations.

Image summary: This figure consists of two photographs. The first photograph shows a cross section of an excavated earth wall composed of coarse soil and rocks, while the second photograph displays a drilling rig positioned on a rocky surface, actively boring into the ground. The images indicate that geological site investigations are being conducted, involving both surface observation of soil stratification and subsurface sampling through drilling to analyze the composition of the terrain.

There are different types of foundations for Bridges. However, the following are commonly used

1. Shallow Foundation – Footings

2. Deep Foundation – Piles & well foundation

Deep foundation is used, when

- The soil is weak and shallow foundation is not appropriate

- o When the span length is very long structure load is heavy

- o When anchoring is needed to avoid lateral and overturning loads

Piles are the most common deep foundation type

Image summary: This is a schematic diagram. It illustrates a load structure supported by a pile cap, which distributes the weight through several vertical piles driven into different layers of soil. The piles penetrate through layers of lower density and medium density soil, terminating within a layer of high density soil. The diagram indicates that the structural load is transferred from the surface structure through the piles to the most dense soil layer to ensure stability and support.

Based on load Transfer End bearing piles Friction pile Friction cum end bearing pile

Image summary: This figure consists of two comparative diagrams. The diagrams illustrate the mechanical differences between a friction pile and an end bearing pile, showing how downward loads are transferred from the pile into the surrounding soil layers. In the friction pile, the load is distributed along the sides of the pile through skin friction within a weak stratum. In contrast, the end bearing pile transfers the load directly to a deeper, more stable bearing stratum at the base of the pile. The conclusion is that friction piles rely on surface area contact with weak soil for support, whereas end bearing piles rely on the structural integrity of a hard underlying layer to support the load.

Based on construction Bored or replacement pile Driven or displacement piles Major challenge in foundation construction

- o Sub-surface soil condition

- o Presence of near Ground water table

- o Water course of the river or the obstacle

Methods to exclude water from work area

1. River Diversion

2. Making temporary island

3. Continuous pumping

4. Making cofferdam

5. Combination of any of the above

Figure 1 summary: This figure is a composite image consisting of technical diagrams and a photograph. The content illustrates the machinery and mechanical setups used for bored pile drilling and pile driving, highlighting components such as the telescopic boom, rotary head, drill head, hammer, cushions, leads, and crane. Based on the figure, it can be inferred that bored piling involves a rotational drilling process to remove soil, whereas pile driving utilizes a percussion-based method to force a pile into the ground, demonstrating two distinct engineering approaches for establishing deep foundations.

River diversion River diversion can be

1. Full river course diversion

2. Partial river course diversion

3. Through channel section Flow This method will be economical if only the river discharge is relatively small

Image summary: This figure is a schematic diagram. It illustrates a water diversion system used for construction or maintenance, featuring a main river path that is blocked by upstream and downstream barriers to create an isolated work area. A temporary diversion channel is shown routing the water flow around the blocked section. The diagram indicates that the diversion allows the designated work area to remain dry and separated from the water flow, while noting that the downstream barrier may be optional depending on the project requirements.

Image summary: This figure is a schematic diagram. It illustrates a river diversion system used to create a dry work area. The setup consists of an upstream barrier and an optional downstream barrier that isolate a section of the riverbed, while a pipe or flume redirects the river flow around the isolated zone. The diagram indicates that this configuration effectively separates the work area from the water flow, allowing maintenance or construction to occur in a dry environment while maintaining the continuity of the river's current.

Image summary: This figure is a photograph. It depicts a wide, murky river flowing between banks lined with dense green vegetation and a foreground consisting of a steep, rocky earthen slope. The image suggests significant soil erosion or excavation along the riverbank, as evidenced by the exposed, unstable terrain in the foreground compared to the forested areas in the distance.

Image summary: This is a photograph. The image depicts a construction or excavation site located in a valley near a river and a hillside. Heavy machinery, including an excavator and a drilling rig, are being operated by workers on a dirt terrain. There is a large stone structure visible in the background on the right side. The scene shows active land modification and engineering work taking place in a rural, natural environment. It can be inferred that a significant infrastructure project is underway, involving soil removal and deep foundation work, likely related to the nearby river or the existing stone structure.

Diversion may not be a solution for all rivers

Image summary: This is a landscape photograph. The image depicts a wide, muddy river flowing through a valley surrounded by lush, green hills covered in dense vegetation and trees. A rustic wooden fence is visible in the foreground along the riverbank. The scene indicates a humid or rainy environment, as evidenced by the saturated greenery and the turbid, sediment-heavy appearance of the water, suggesting recent rainfall or significant erosion upstream.

Foundation Construction Pumping

- o Pumping is a common practice used in almost all cases of dewatering

- It can be done at the foundation pit or at well point

Image summary: This figure is a schematic diagram. It illustrates a dewatering system for an isolated working area, featuring a pump housed within a perforated container and placed on a layer of gravel, with a temporary cofferdam acting as a barrier against the surrounding water. The setup demonstrates a method for removing water from a specific site by filtering it through gravel and a perforated casing before pumping it away from the area.

Image summary: This is a photograph. The image depicts a person standing beside a portable motorized water pump in a rugged, excavated landscape featuring steep earthen banks and a small stream of water. The presence of the industrial pumping equipment and the heavily disturbed terrain suggests an active mining or construction operation where water management is necessary to clear the site.

Image summary: This is a photograph. The image depicts a construction or excavation site characterized by disturbed earth, rocky terrain, and several pools of muddy water. A concrete structure is partially submerged within one of these pools, and a portion of heavy machinery is visible on the left side. The presence of standing water and displaced soil suggests recent excavation activity or poor drainage conditions at the site.

Making Coffer dams

Cofferdams are temporary enclosures to keep out the water and soil so as to permit dewatering and construction of permanent structure in dry working area.

It involves interaction of the structure, the soil and water.

The loads on the coffer dam includes

Hydrostatic force of the water

• Dynamic forces from water current

Load from construction equipment & operation during installation & constructio

Since workers will work inside the cofferdam and exposed to risk of flooding and collapse, High Level of Safety is required

Image summary: This figure consists of a conceptual diagram and a corresponding photograph. The diagram illustrates a cross-section of a construction technique where vertical barriers are driven into the ground to create a sealed enclosure, isolating a specific working area from the surrounding body of water to keep it dry. The photograph shows a real-world application of this concept, featuring a large cylindrical steel cofferdam installed in a river with construction equipment positioned nearby. The combination of the diagram and photo demonstrates that this engineering method effectively creates a dry, contained environment within a waterway, allowing for construction or repair work to be performed below the natural water level.

Shallow foundation

o Conduct Surveying or lay out

O Excavate to the required design grade with due consideration of the soil type

Dewater the working area

o Conduct excavation with sufficient working space and slope stability of the soil

○ Check the design grade (leveling)

Ensure sufficient length of starter bars are used

Image summary: This is a photograph. The image depicts an active construction or excavation site where workers are operating heavy machinery, including a drilling rig and an excavator, within a large dirt pit. Several personnel are positioned around the site, some working inside the excavation area and others managing materials on the periphery. The scene indicates a large scale engineering project involving deep earthwork and specialized drilling operations, suggesting that significant subsurface preparation or foundation work is being conducted.

Image summary: This is a photograph. The image shows a large concrete cylindrical pillar resting on a square concrete base, which is partially submerged in murky water. A metal drum stands on the base next to the pillar, and several wooden poles are positioned around the structure. The surrounding area consists of excavated earth and muddy water. The image indicates a construction site in an aquatic or flooded environment, suggesting that the foundation is being established in wet ground conditions.

Construction of Substructures Pier Construction

- Pier can be constructed either from Masonry stone, mass concrete, Reinforced concrete or pre-stressed concrete

- Masonry/ mass concrete piers usually

- Massive

- oSignificantly obstruct linear water way

- Has excessive load on foundation and need larger footing

- Used for short height piers

Image summary: This is a photograph. The image depicts a stone arch bridge crossing a dry or shallow riverbed, showing significant structural damage and deterioration. A large section of the bridge deck and supporting masonry has collapsed, leaving a jagged edge and exposed internal materials. The remaining stone piers show signs of wear and erosion at the base. The extent of the collapse suggests a severe structural failure, indicating that the bridge is unstable and unsafe for use.

- Reinforced concrete Piers on the other hand

- o Have reduced cross section

- Have relatively lighter weight and load on footing

- o Lesser obstruction to water way

- The only option for tall piers and piers supporting long span superstructures

Image summary: This figure is a technical engineering schematic. It displays a detailed structural cross-section of a reinforced concrete frame, featuring vertical columns and horizontal beams that form a grid-like support system, complete with annotations and dimension lines. The layout indicates a robust load-bearing architecture where the central and outer vertical members provide primary support for the overhead structure, suggesting a design intended for high stability and weight distribution.

Image summary: This is a photograph. The image shows a reinforced concrete bridge pier consisting of a vertical column supporting a horizontal cap, situated next to a river with a vegetated hillside in the background. The structure exhibits significant surface discoloration and staining across both the column and the cap, suggesting exposure to environmental elements or material degradation.

Abutment Construction

• Abutment can be constructed from masonry stone or reinforced concrete

Masonry abutments can be used only for short height up to 8m

Masonry abutment and wing wall are common and they are cost effective than Reinforced concrete abutments

Image summary: This figure is a technical architectural elevation drawing. It depicts a cross-section of a masonry wall structure, detailing a base foundation, a main body composed of masonry blocks, and a capping layer of concrete. The drawing includes various dimension lines and labels specifying the materials used, such as Class A masonry and Class A concrete. Based on the drawing, it can be inferred that the structure is designed with a slight taper, being wider at the base than at the top, which suggests a design intended for stability and load-bearing capacity.

Reinforced Concrete Abutment

- Are used when the height of the abutment is greater than 8m

- If counterforts are involved in R Abutment, the construction need precaution particularly in prepar the reinforcement bars and formwork

- Provision of appropriate weep hol is essential both in R.C and Masor abutments

• Construction of Approach slab helps to reduce material loss, differential settlement & ultimatel dynamic impact on the bridge

Image summary: This figure is a technical diagram. It illustrates the disassembled components of a bridge abutment structure, including the footing, abutment wall, backwall, capping beams, and wingwalls. The layout indicates that the footing serves as the base, supporting the central abutment, which is flanked by wingwalls and topped with a backwall and capping beams, collectively forming a structural support system for a bridge end.

Image summary: This is a photograph. The image depicts a concrete construction project featuring a retaining wall or foundation structure with vertical steel reinforcement bars protruding from the top. In the background, a concrete bridge or overpass is visible. The structure is situated on uneven, natural terrain. The presence of exposed rebar indicates that the construction is currently in progress and that additional concrete pours are expected to extend the height of the walls. The overall scene suggests a civil engineering project focused on infrastructure support.

Thank you

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