Papers by Author: Yong Ding

Abstract: To explore the noise generated by bridges during operational period, the equivalent continuous sound pressure levels of 12 bridges in the city of Ningbo were measured and analyzed. The measured data show that (1) Although the measured sound levels of these bridges meet the requirement of Chinese codes, they are near the maximum limit and the vibration and noise reduction is necessary; (2) A-weighted sound level of bridge is close to that of the road nearby; (3) Z-weighted sound level of bridge is much greater than that of the road nearby, it indicates that the bridge noise contains much low frequency noise, so that A-weighted sound level can’t reflect the noise of bridge accurately, and Z-weighted sound level shall be used to evaluate the acoustic environment near bridges.

Abstract: The bottom surface of the bridge beam, which is made of C50 high-strength concrete, is heated to 800°C in fire-resistant experiment. Then the elastic modulus and strength of the concrete are measured by the rebound method and core sampling method, and the test results are used to validate the theoretical methods. The study shows that the strength and elastic modulus of concrete decrease with the increasing of temperature. The strength from the current theoretical analysis agrees well with that from the experiment. But for the elastic modulus, there is a great difference between the theoretical and experimental analysis. The strength of the concrete after fire gotten from the rebound method has a bigger error than that from the core sampling method, so that the core sampling method should be used in preference.

Abstract: In this paper, one certain space under bridge which was used as a storehouse has been simulated numerically. The flow was considered turbulent and buoyant. A simple geometry was adopted, consisting of a room with a door that plays the role of inlet and another of outlet for the air. Four bundles of wood burners which considered as a volumetric heat source were placed evenly in the space. The problem was simulated by using the RNG K-ε turbulence model, modified to account for buoyancy effects. Several useful results were obtained.

Abstract: The damping makeup of large span cable-stayed bridges is complicated. The damping matrices of such structures cannot be easily accurately determined. On assumption of the damping coefficients of substructures in cable-stayed bridge (such as girder, tower, cable and support et al) are constants, a method to estimate the damping coefficients and damping matrices of such structures is presented. The method is based on several known modal damping ratios and the calculation of complex eigenvalue and eigenvector utilizing the state-space methodology. Numerical simulation was carried out by the example of Tatara Bridge. Through comparison between the calculated damping ratios utilizing the approximated damping matrices and the field test data, the method is proved valid.

Abstract: The microscopic mechanism of ultrasonic wire bonding is investigated by molecular dynamics simulation on the interfacial contact and adhesion. Considering that the real bonding area is in the state of plane strain, a two-dimensional atomic model is presented. Sutton-Chen potential is adopted for the interaction between gold atoms. Computational results indicate that a strong adhesion generates at the interface after intimate contact between the wire and the bond pad, and the adhesive force should be the mechanism of ultrasonic wire bonding. Combining the real contact area from finite element analysis with the adhesive force from molecular dynamics simulation, the bonding strength of ultrasonic wire bonding is estimated.