Bridge Structures and Design

Bridge Engineering

• Applications of engineering principles and methods are employed to create structures spanning physical obstacles
• These structures must ensure stability, safety, and durability under various loads and conditions
• Expertise in structural analysis, material science, geotechnical, and environmental engineering are required

Historical Bridges

• The Zhaozhou Bridge in Hebei Province, China, constructed circa A.D. 600, may be the oldest still-existing bridge
• Bridge construction materials have evolved from natural to man-made materials like steel and Portland cement concrete
• Reinforced concrete beams were tested in Germany by Wayss and Koenen in 1866, which marked the beginning of the concrete era in bridge building
• In 1867, Monier was given credit for the creation of the first bridge that used reinforced concrete
• The first reinforced concrete bridge, located in Chazelet, Touraine, France, is 13.80 m in length and 4.25 m in width
• It is likely that the first steel bridges were built in the United Kingdom and the United States in the 1880s
• The Eads Bridge was completed in 1874 after being built across the Mississippi at St. Louis, USA, and was the first steel bridge
• James Buchanan Eads designed The Eads Bridge, and it is the oldest bridge still standing on the Mississippi River

Philippine Bridges

• Many old bridges exist in the Phillines including stone arch, concrete, and steel bridges
• The Malagonlong Bridge is a 445 ft (136 m) Spanish-era stone arch bridge in Tayabas, Quezon
• It is considered one of the oldest bridges in the Philippines
• Puente Del Capricho is a historic bridge in Majayjay, Laguna, constructed on the backs of Indios, but it was never finished in 1851 because of faulty engineering
• The Forbes Bridge is the oldest concrete bridge in the Philippines, an arched girder bridge built in Iloilo City in 1909 that replaced the Jaro Bridge
• The Ayala Bridge was built in 1872, which was originally two timber bridges, then became the first steel bridge over the Pasig River in Manila in 1908

Bridge Planning and Design

• They blend art and compromise
• Aesthetic appeal is vital because bridges are often iconic landmarks blending with their surroundings
• Visual designs create aesthetically pleasing structures symbolizing the surrounding environment
• Technical constraints involve balancing engineering feasibility, material limitations, sustainability, regulatory compliance, cost and construction timelines, public acceptance, and cultural significance
• Bridge design is often a compromise becuase of these factors

Types of Bridges

• Classified by strutural form, materials used, purpose, span length and relative position
• According to the American Association of State and Highway Transportation Officials (AASHTO), highway bridges are defined as structures with an opening not less than 20 ft that forms part of a highway, or that is located over or under a highway

Bridge Types Based on Structure

• Beam bridges consist of horizontal beams supported at each end by piers or abutments, where the load is transferred to the supports directly
• Examples of beam bridges include plate girder bridges and box girder bridges
• Arch bridges have curved structures that transfer loads to supports at either end via compression forces
• The Sydney Harbour Bridge is a steell through arch bridge, that is 1,149m-long and 48.8m-wide, with height measuring 134m from the top to the water below
• The Pingnan Third Bridge is a concrete-filled steel tubular (CFST) arch bridge in Pingnan County, Guangxi, China, with a length of 1,035 meters and the longest span of any arch bridge in the world at 575 meters
• Truss bridges are composed of interconnected triangular elements, offering high strength and load distribution
• Suspension bridges use cables suspended from towers to support the deck, allowing long spans
• The Golden Gate Bridge connects the San Francisco Peninsula and the Presidio to Marin County across the Golden Gate Strait, is 8,981 ft (2.7 kilometers) in total length, and 746 feet (228 meters) at its tallest point
• The roadway's height above the water for the Golden Gate Bridge clocks in at 220 feet (67 meters).
• The Akashi Kaikyō Bridge, located in Japan, has the longest suspension bridge in the world (1,991 meters)
• Tsing Ma Bridge is in Hong Kong, is the world's longest suspension bridge carrying both road and rail traffic
  • Main Span: 1,377 meters
  • Total Length: 2,160 meters
  • Deck Width: 41 meters
• Cable-stayed bridges support the deck using cables connected directly to towers and offer balance between stiffness and flexibility
• The Millau Viaduct in France is the world's tallest bridge with a tower height of 343 meters, 342 meters for the main span and 2460 meters for the total length
• The longest cable-stayed span bridge in the world is the Russky Bridge in Vladivostok, Russia, with a main span of 1,104 meters.
• The Cebu-Cordova Link Expressway (CCLEX), is the longest cable-stayed bridge in the Phillipines, linking Cebu City and Cordova on Mactan Island
  • Main Span: 390 meters
  • Total Length: 650 meters
• Cantilever bridges are built using cantilevers extending from piers and supporting loads with balance
• The Quebec Bridge located over the Saint Lawrence River in Quebec, Canada, holds the record for the longest cantilever span ever built:
  • Main Span: 549 meters
  • Total Length: 987 meters

Bridge Types Based on Material

• Concrete bridges are made of reinforced or prestressed concrete, providing durability and resistance to weather, and involve segmental and box girder bridges
• Steel bridges are built with steel components, offering high strength-to-weight ratio and flexibility.
• Composite bridges use a combination of materials, such as steel and concrete, to optimize strength and cost.
• Timber bridges are constructed from wood and typically used for short spans in rural areas.

Bridge Types Based on Purpose/Function

• Highway bridges designed to carry vehicular traffic on roads and highways
• Railway bridges designed to support railway loads, often using trusses for strength
• The Forth Bridge (Scotland) is a UNESCO World Heritage Site railway bridge known for distinctive red steel structure and cantilever design
• Pedestrian bridges are designed for foot traffic and commmonly seen in urban areas of parks
• The Husseini Suspension Bridge in Pakistan is the longest pedestrian bridge in the world with a length of 365 meters
• The Zhangjiajie Glass Bridge in Zhangjiajie National Forest Park (China), which is 430 meters in length, the first-ever glass pedestrian bridge in the world opened in 2016
• Aqueduct bridges carry water over obstacles, such as valleys or roads.
• The Pont du Gard is a Roman aqueduct bridge is one of the best-preserved examples from antiquity was built in the 1st century AD to carry water over the Gardon River

Bridge Types Based on Span Length

• Short-span bridges: Lengths up to 15m, and including simple beam or slab structures
• Medium-span bridges: Lengths up to 15m to 100m, including girder and arch bridges for longer road crossings
• Long-span bridges: Lengths over 100m, including cable-stayed and suspensioin bridges for large water crossings
• The Jiaozhou Bay Bridge in Qingdao, China is the longest span, measuring in at 26.4km

Bridge Types Based on Relative Position

• Overpass Bridge: a type of bridge that allows one road or pathway to pas over another.
• Underpass Bridge: The primary route (main road or railway) passes below another structure

Typical Parts of a Bridge

• Typical structures include two parts: Superstructure and Substructure
• Superstructure is the portion of a bridge that carries the load of traffic and transmits that load to the substructure
  • Includes all components: deck, girders/beams, slab, parapet railing, the expansion joint, and bearings above the bridge supports
• Substructure is the part of the bridge supporting the superstructure and transferring loads to the foundation.
  • Includes all components: piers, abutment, wing walls, pile cap, and foundation below the superstructure that hold up the bridge
• Deck: topmost part that supports traffic and is usually made of concrete, or steel
  • Provides a stable and smooth surface for traffic
  • Distributes loads down below
  • Protective layer and water proofing
  • Provides structure for utilities, drainage, and lighting
• Girders or Beams: large horizontal beams made of steel or reinforced concrete
  • Provides primary support and transfers loads down below
  • Enhances strength in terms of bending and shear forces
• Slab: flat, horizontal element of reinforced concrete
  • Support traffic and distributes it
  • Provides level surface and protects from environment
• Parapet (Guardrail): a protective barrier
  • Provides safety, acts as a visual and reduces the impact of wind
• Expansion Joint: Flexible devices to accomodate any movements
  • Prevents structural damage from the element
  • Reduce changes of cracks and smooth traffic flow
• Abutments: the end supports of a bridge that support super structure
  • transfers superstructure loads and has connections to the roadway
• Piers: Vertical supports located between the abutments that provide support
  • Transfers the bridge weight to ground
  • Stability, and can withstand wind and seismic activity
• Bearings: Mechnical devices installed between the bridge parts to allow movement
  • Allows expansion and contraction as well as resists stress
• Pile Cap: A thick, reinforced concrete supporting foundation piles
  • Distributes loads and prevents seetlement
  • resist bending moments and horizontal loads from wind
• Foundations: the base, transfers load to the soil/ground
  • Stability, prevents tilting and enhaces durability
• Wing Walls: Extensions that are built on retaining walls
  • Retains soil, stability and prevents erosion

Explore bridge designs: cable-stayed vs. suspension, multi-modal bridges, and wind resistance. Learn about bridge selection based on span distance, and examples like the Golden Gate Bridge.