Papers by Author: C.S. Cai

Abstract: This paper presents a new method to study the impact factor of an old bridge strengthened with high strength materials based on the model updating technique. Using the genetic algorithm (GA) by minimizing an objective function of the residuals between the measured and predicted responses, the bridge and vehicle coupled vibration models were updated. Based on the displacement relationship and the interaction force relationship at the contact patches, the vehicle-bridge coupled system can be established by combining the equations of motion of both the bridge and vehicles. The simulated results show that the present method can simulate precisely the response of the tested bridge.

Abstract: The non-stationary random responses of the moving tires induced by the road roughness in time domain were obtained, and then those non-stationary responses were treated as the non-stationary inputs to study the non-stationary vibration of a high-pier bridge under vehicles with variable speed. The effect of the two inputs on the mid-span deflections was compared with the measured responses under different parameters including vehicle acceleration and vehicle deceleration. The verified results showed that the proposed method can simulate accurately the vibration of bridge under vehicle moving with variable speeds.

Abstract: The current state of bridges in the United States calls for the implementation of a continuous bridge monitoring system that can aid in timely damage detection and help extend the service life of these structures. A typical monitoring system would be one which enables non-invasive, continuous monitoring of the structure. The passive nature of the acoustic emission (AE) evaluation technique makes it an ideal choice to serve this purpose. Although the technique has been successfully used for decades for damage detection in other fields, its potential in bridge monitoring has not yet been fully exploited. This paper presents experimental tests performed on four concrete beams in laboratory. The laboratory concrete beams were tested under different loading patterns. While acoustic emission monitoring of bridge structures is not a new vista, most evaluations conducted before are only qualitative. Though some quantitative methods have been proposed, they have not yet developed to be useful for actual field test of bridges. Therefore, an attempt was made in this study to use the intensity analysis technique for damage quantification. The use of intensity charts may help in better estimating the damage severity, although clearly marked zones of damage are not yet prescribed for certain materials like concrete and steel. All in all, the applications of AE in bridge monitoring reveal the potential of this technique’s versatility. The technological advances made in recent years have made the method more suitable for onsite monitoring situations. Although more research may be needed to implement the current ideas, the future looks promising for the application of this technology in efficient continuous bridge monitoring scenarios.