In this blog post, we’ll examine how the different structural designs of the Gwangandaegyo Bridge and the Incheon Bridge—despite their similar appearances—create distinct mechanical differences and structural characteristics, and how these differences manifest in terms of safety, constructability, and aesthetics.

Appearance and Misconceptions

The Gwangan Bridge and the Incheon Bridge boast long, beautiful spans and are major bridges that represent Busan and Incheon, respectively. In fact, both bridges consist of long spans centered around tall main towers, and many people recognize them solely by the iconic sections seen in photos or videos.
When viewed from a distance, both bridges appear very similar, with tall main towers and cables supporting the deck around them. However, despite their external similarities, the core section of the Gwang-an Bridge is a suspension bridge, while the main span of the Incheon Bridge is designed as a cable-stayed bridge. These structural differences go beyond mere variations in design methodology, giving rise to a range of distinctions—from mechanical behavior and structural vulnerabilities to maintenance methods.

Basic Bridge Structure and Load Transfer Mechanisms

A bridge consists of a deck for vehicles and pedestrians, as well as piers and foundation structures that support it. For a bridge to function stably, it must safely transfer various forces—including the weight of the deck itself, as well as vehicle loads, wind loads, and forces caused by temperature changes—to the ground.
The difference in bridge types ultimately stems from how these loads are transferred.
The method of simply placing the deck on piers features a relatively simple structure; however, as the distance between piers increases, the bending moment acting on the deck increases significantly, making design more challenging. In particular, for offshore sections where large ships must pass, a long-span bridge design is necessary to reduce the number of piers and secure a wide clearance.
Suspension bridges and cable-stayed bridges are the representative structures used in such situations. While both types can span long distances, there is a distinct difference in how loads are transferred. In a suspension bridge, the main cables share the load of the entire bridge and transfer it to the anchorages on both sides. In contrast, in a cable-stayed bridge, each cable directly transfers the load from the deck to the pylon, and the pylon then transfers that load to the foundation and the ground.

Connection Methods of Suspension and Cable-Stayed Bridges and Everyday Analogies

In a suspension bridge, vertical hanger cables connected to the deck are suspended from the thick main cables above. The main cables pass over the pylons and are anchored to massive anchorages at both ends. Simply put, it resembles a clothesline with several hangers attached to it. It’s easier to understand if you think of the clothesline as the main cable and the items hanging on the hangers as the deck.
In contrast, on a cable-stayed bridge, the cables connected to the deck are connected directly to the pylons without passing through a central main cable. Multiple cables are arranged in a fan-shaped or half-circular pattern to support the deck. The pylons receive this force and transfer it to the ground through the foundation.
The easiest way to distinguish between bridge types is to check the direction in which the cables are connected. If the cables extending from the deck are connected to the thick main cable above, it is a suspension bridge; if each cable is connected directly to the main tower, it is a cable-stayed bridge.
As such, this difference in connection method leads not only to a difference in appearance but also to differences in structural behavior and design characteristics.

Differences in Mechanical Behavior

In a suspension bridge, the load on the deck is transmitted vertically to the main cables via the hangers. Therefore, the deck is primarily subjected to bending and tensile forces, and the entire structure exhibits flexible behavior.
In contrast, in a cable-stayed bridge, because the cables are connected diagonally, the deck experiences not only an upward vertical component but also a horizontal component pulling toward the pylon. This horizontal component induces compressive forces in the deck.
These compressive forces increase as the angle between the deck and the cables decreases—that is, as the deck moves farther away from the main tower. Furthermore, the compressive forces also increase as the span lengthens and the weight of the deck increases. Therefore, while cable-stayed bridges are structurally very efficient, they have limitations when it comes to achieving ultra-long spans like those of suspension bridges.
In fact, most of the world’s longest span records are held by suspension bridges, while cable-stayed bridges generally demonstrate high efficiency in the medium- to long-span range.
There are also differences in vibration characteristics. Since the deck of a cable-stayed bridge is directly connected to the main tower, resulting in relatively high structural rigidity, it is relatively resistant to vibrations caused by wind loads or vehicle loads.
In contrast, suspension bridges are highly flexible due to their structural characteristic of having the deck suspended from the main cables, and they can be sensitive to wind loads. While modern suspension bridges have significantly improved these issues through various aerodynamic designs and vibration-damping devices, they fundamentally require more careful consideration of vibration management than cable-stayed bridges.

Safety and Vulnerable Points

In cable-stayed bridges, the deck where the cables are connected and the areas around the main towers are critical structural components. Since these sections are constantly subjected to large tensile and compressive forces, sufficient safety factors are applied from the design stage, and regular inspections and maintenance are conducted during operation.
In particular, the cable anchorage points and the connections to the main towers are key areas that are continuously monitored to ensure structural integrity.
In the case of suspension bridges, the most critical component is the main cable. Since the main cable is the core structural element that supports the entire load of the bridge, any damage to it can significantly impact the overall structural safety. Therefore, suspension bridges are subject to continuous inspections of the main cable’s corrosion status, changes in tension, and any damage to the outer sheath.
Recently, there have been reports of cable damage on various bridges caused by lightning strikes or external impacts. For this reason, lightning protection systems and structural health monitoring systems are being actively implemented in modern bridges.

Construction Costs, Ground Conditions, and Landscape

Suspension bridges generally entail high construction costs because they require large-scale main cables and massive anchorage facilities. Furthermore, since they require solid ground at both ends capable of withstanding enormous tensile forces, they are significantly affected by ground conditions.
Design and construction also demand a high level of technical expertise, and maintenance costs tend to be relatively high.
In contrast, cable-stayed bridges do not require large anchorage facilities, so they are subject to relatively fewer constraints regarding ground conditions. With their high structural efficiency and relatively simple construction process, they are the preferred design for many large bridges being built recently.
In fact, a significant number of large offshore bridges being constructed both domestically and internationally adopt the cable-stayed bridge design, and suspension bridges are often chosen only when very long spans are required.
However, from an aesthetic perspective, suspension bridges possess a unique charm. The beautiful silhouette created by the curved main cables provides an outstanding visual effect when combined with nighttime lighting. For this reason, suspension bridges are often built not merely as transportation infrastructure but as iconic urban landmarks.

Conclusion

In this blog post, we examined the structural differences between suspension bridges and cable-stayed bridges hidden behind the outward similarities of the Gwangandaegyo Bridge and the Incheon Bridge.
While both types represent major achievements in long-span bridge technology, they exhibit distinct differences in load transfer mechanisms, mechanical behavior, vibration characteristics, vulnerable areas, and construction conditions.
While simply admiring the beauty of a massive bridge is a meaningful experience in itself, understanding the structural principles behind bridges like the Gwangandaegyo and Incheon Bridge allows us to appreciate their technical value and the designers’ thoughtful considerations on a deeper level.