Bridge Engineering

To construct economical, durable and functional structures, the precise prediction and evaluation of their response due to natural actions and the application of the results to structural design are significant.

In this group, focusing on wind effects on civil life and urban environment, to estimate the structural behavior due to wind action, various investigations related to wind engineering have been conducted, for example, mitigation and prevention of disasters due to strong winds and gusts, investigation on mechanisms and control of aerodynamic instabilities of bluff bodies, creating a new concept of wind resistant design, development of simulation technique of aerodynamic behaviors of structures, and so on.

Academic Staff

Lin AN

Lin ANAssociate Professor (Graduate School of Engineering)

Research Topics

Evaluation and prediction on the environmental actions, material deteriorations and mechanical behaviors of concrete structures are being developed. Specifically, on clarifying the mechanism of chloride ingress into concrete under marine atmosphere, environmental action models and various time-dependent models of required behaviors are being constructed to simulate the long-term deterioration of concrete structures due to air-born salt.


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Research Topics

Mechanisms of flutter instabilities of structures

The flutter phenomenon occurs on the structures due to self excited force induced by their body motion. This vibration diverges beyond a certain critical wind velocity, which may destroy the structures, and then the safety of structure against the flutter must be very important.

Investigation on the flutter mechanism is connected to establishment of advanced wind resistant design and development of more sophisticated structural geometry against the flutter. In this group, the relation between the aerodynamic forces and the responses has been clarified through the wind tunnel tests of unsteady aerodynamic forces and pressures. The bridge decks, which are stable against the flutter, have been found and the continuous studies for their future realization and more precise evaluation of their responses are on going.

photo : Wind tunnel facility
Figure 1. Wind tunnel facility

Wind-induced vibration of inclined stay cables

It is well known that the stay cables of cable-stayed bridges vibrate under wind and rain, which is so called rain-wind induced vibration.

In this group, the wind tunnel tests and field observations using cable models have been tried and then, it becomes clear that this phenomenon induced by the axial flow along the cable axis due to the cable inclination, the upper water rivulet on the cable surface due to rain, unsteady and three dimensional properties of vortices around inclined cables and also mixed phenomena of these. However, there are still many unknown facts for the inclined cable aerodynamics. Then, the further investigations for their mechanisms and the development of rational countermeasures will be tried.

photo : Field observations using large-scale inclined cable model at Shionomisaki
Figure 2. Field observations using large-scale inclined cable model at Shionomisaki

Spatially correlated structure of surface pressure on bluff body in fluctuating wind

Buffeting phenomenon as random vibration due to wind turbulence can be observed in all structures in the atmosphere at any wind velocity. It may induce fatigue problem of structures, and takes an important role on wind load evaluation as well. In the buffeting response analysis, spatial correlation (coherence) of the aerodynamic forces induced by wind fluctuation, or the correlation of surface pressure are assumed to be identical to the correlation of the approaching wind velocity. Whereas, the aerodynamic forces indicates higher correlation in wind tunnel experiments.

This study aims to clarify the mechanism of increase of the correlation. According to the previous investigation, it was found that the flow separation and the separation bubble should be the most important factors. Quantitative evaluation of the spatial correlation and development of the evaluation method for each structural geometry will be investigated.

Development of rational and environmental bridge design assembled by standardized parts

Structural systems assembled by the standardized parts and their design method are investigated. Also, the development of maintenance system, which is possible to extend the lifetime of structures by replacement of the elements and expand the system with social demand, is tried.

First of all, the various types of bridges are considered as assembly of elements, and the bridges will be re-constructed by using the standardized elements again. The standardization of bridge elements can introduce mass production and the drastic reduction of costs is expected. Furthermore, using steel as the material of bridge, the recycling of the bridge parts is considered and then, the reduction of environmental impacts may be possible.

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