Engineering Building & Infrastructure

Bridges

Examine the scientific principles underlying cable-stayed, extradosed, suspension, and truss structures. Our objective is to enhance the safety, efficiency, and innovation of contemporary bridges through sophisticated structural analysis, advanced materials, and robust design methodologies.

Overview

This work investigates the structural analysis and design of modern cable-stayed bridge systems and associated truss structures. It surveys long-span cable-stayed bridges—now often exceeding 1000 m spans—highlighting their efficiency and aesthetic appeal. The study reviews fundamental design principles and behaviors, drawing on analytical models and finite-element methods. Special emphasis is placed on cable arrangements (fan, harp, semi-fan) and anchorage systems. The goal is to optimize stay-cable configurations and tensioning to balance deck loads and pylon forces, providing design recommendations for future bridge and truss systems.

The analysis details how stay cables and pylons share the bridge’s loads. Decks are supported by post-tensioned inclined cables, which reduce vertical deflections and make towers carry primarily axial compression. The research compares cable layouts: harp, fan, and semi-fan patterns, noting that semi-fan arrangements often offer a practical compromise for long spans. The study also examines deck systems (e.g. composite steel–concrete decks) and how tensioning strategies influence bending moments in the deck and pylons.

For steel-truss components, the paper analyzes member and joint behavior. It reinforces that trusses resist loads through axial action in their triangular geometry and that gusset-plate connections and lateral bracing are critical for stability. Common truss failure modes—such as member buckling or connection failure—are discussed to inform robust design. The team studies various truss types and connection details, including advanced “sliding” gusset connections under cyclic loading.

Practical aspects are also addressed. Two construction sequences (supported vs. cantilever erection) are compared for their effects on cable and girder forces. Fatigue and wind/seismic loads are considered: as span lengths grow, dynamic effects (traffic, wind, earthquakes) become critical to bridge performance. The nonlinear behavior of the cable–tower–deck system is modeled to ensure reliability under these loads.

This comprehensive research underscores the relevance of modern analysis techniques in long-span bridge engineering. By integrating optimization, material behavior, and safety considerations, it supports more efficient and resilient designs in structural practice. Readers are encouraged to explore the full report for detailed findings and to contact the research team for collaborations or inquiries.

05.25

Investigation

Bridge Analysis & Design

This project explores advanced cable-supported bridges, focusing on both extradosed (low-tower) and suspension bridge systems. Extradosed bridges blend cable-stayed and girder design: they use shorter pylons and stiffer decks so that cables both prestress the deck and support loads.

Suspension bridges, by contrast, span long distances using main cables and vertical hangers. Our research models these systems to improve design safety and efficiency, using theory, simulation, and experiments.

Key Topics

Cable configurations

This research evaluates various cable arrangements in cable-stayed and extradosed bridges, including single-plane vs. multi-plane layouts. Multi-plane (typically in fan or harp configurations) provide better torsional control for wide decks, while single-plane systems offer a streamlined profile but require stiffer decks to resist twisting. The role of cable deviation saddles and clamps is also explored—particularly in extradosed designs—where precise alignment and load path optimization are critical to ensure balanced force distribution across towers and deck girders.

Structural Failure Modes

To enhance reliability, the study reviews historical failures (e.g., Tacoma Narrows, Yichang Bridge) and investigates wind-induced vibrations like vortex shedding, galloping, and flutter. These dynamic effects can induce large oscillations in stay cables and trusses, leading to fatigue cracking or instability. Analytical modeling and damping strategies are proposed to mitigate these risks, especially in long-span applications where wind and traffic loads are dominant.

Anchorage Systems

Anchors are a critical link between superstructure and foundation. The study examines gravity-type anchorages, which rely on the self-weight of concrete blocks, and tunnel-type anchors that engage bedrock via bored shafts. Both systems are tested for their pull-out strength, stress distribution, and deformation under sustained cable loads. Innovations like post-tensioned rock anchors and load-distributing plates are evaluated for complex terrain and deep foundation scenarios.

Cable Tension and Stress Management

Proper pretensioning of stay cables is essential to control deflection and internal forces during construction and service. The research highlights that extradosed bridge cables are typically tensioned to 60–70% of their ultimate strength, exceeding conventional levels. Monitoring techniques (e.g., vibrating wire gauges, hydraulic jacks with pressure sensors) are applied to maintain force equilibrium across spans, adjust for creep/shrinkage, and avoid imbalances that lead to deck warping or pylon rotation.

Saddle and Clamp Mechanics

Cable bends at saddles (used atop pylons) and anchorage clamps are susceptible to fretting fatigue and localized stress concentrations. The study evaluates anti-slip saddle designs, friction-reducing materials, and saddle geometry modifications to ensure even load transfer. For clamps, nonlinear bolt tightening behavior and plate deformations are analyzed to prevent slippage under cyclic loads and to extend fatigue life of anchor zones.

Advanced Materials and Composite Structures

The research explores carbon fiber–reinforced polymer (CFRP) cables, which offer exceptional strength-to-weight ratios, corrosion resistance, and long-term durability. Despite challenges in anchorage design due to CFRP’s low transverse shear capacity, wedge-based and resin-bonded solutions are advancing practical applications. Also studied are composite pylons, such as steel–concrete–steel sandwich structures, which improve axial capacity, resist buckling, and allow modular fabrication for rapid assembly in remote or seismic zones.