Lattice transmission towers are vital components of transmission line systems, which play an important role in the operation of electrical power systems. This paper proposes a new type of tuned mass damper (TMD), the pounding tuned mass damper (PTMD), to upgrade the seismic resistant performance of a transmission tower. In the PTMD, a limiting collar with viscoelastic material laced on the inner rim is installed to restrict the stroke of the TMD and to dissipate energy through collision. The pounding force is modeled based on the Hertz contact law, whereas the pounding stiffness β is estimated in a small-scale test. A multimass model of a 55-m tower is established to verify the effectiveness of the PTMD numerically. Harmonic excitation and time-history analysis demonstrate the PTMD’s superiority over the traditional TMD. Finally, a parametric study is performed for the optimal design.

In structural vibration tests, one of the main factors which disturb the reliability and accuracy of the results are the noise signals encountered. To overcome this deficiency, this paper presents a discrete wavelet transform (DWT) approach to denoise the measured signals. The denoising performance of DWT is discussed by several processing parameters, including the type of wavelet, decomposition level, thresholding method, and threshold selection rules. To overcome the disadvantages of the traditional hard- and soft-thresholding methods, an improved thresholding technique called the sigmoid function-based thresholding scheme is presented. The procedure is validated by using four benchmarks signals with three degrees of degradation as well as a real measured signal obtained from a three-story reinforced concrete scale model shaking table experiment. The performance of the proposed method is evaluated by computing the signal-to-noise ratio (SNR) and the root-mean-square error (RMSE) after denoising. Results reveal that the proposed method offers superior performance than the traditional methods no matter whether the signals have heavy or light noises embedded.

It is important to understand the operational performance of bridge expansion joints in real time. This paper proposes a novel performance-alarming approach for bridge expansion joints using continuous temperature and displacement-monitoring data. It is first shown that the representative temperature used to establish the temperature-displacement relationship (TDR) model was actually a linear combination of temperature measurements collected from different monitoring locations. Then, a new type of representative temperature is proposed and referred to as the canonically correlated temperature, in which the combination coefficients were optimally determined to maximize the correlation between the new representative temperature and expansion joint displacement. A more accurate and reliable baseline TDR model was subsequently established through the canonically correlated temperature. After that, a performance-alarming approach for bridge expansion joints was formulated based on construction of a mean value control chart for the estimation error of the baseline TDR model. In addition, a new way to determine the control limits is presented to solve the problem related to the nonnormal distribution of estimation errors. Finally, an engineering application to a cable-stayed bridge was carried out. The results demonstrate that the proposed approach is superior to traditional ones in terms of modeling and prediction capabilities and is excellent for performance alarming of bridge expansion joints.

Pipeline structures are often very flexible and susceptible to vibrations induced by many sources, such as vortex, external flow, and internal fluid flow. The pounding tuned mass damper (PTMD) is one device that may be employed to absorb and dissipate these undesired vibrations. The PTMD is a combination of the tuned mass damper and the impact damper. It utilizes the tuned mass to absorb kinetic energy and dissipates the absorbed energy through collisions. To examine the vibration control effectiveness of the PTMD, both numerical analysis and experimental study were performed. In the numerical analysis, a pounding force model was established based on the Hertz contact element. The motion equation of a pipeline structure incorporated with a PTMD was derived. Free vibration analysis and forced vibration analysis were performed. In the experimental study, an M-shaped pipeline was fabricated and installed with the PTMD. Due to safety issues the pipe was kept empty during the experiments. A free vibrat...