This work investigates the finite-element implementation of a piezoelectric energy harvester subjected to traffic-induced vibration of a railway bridge. To derive the electromechanical coupled framework, Hamilton’s variational principle is employed and the mechanical and electrical energy balance equations are considered in conjunction with suitable boundary conditions of the mechanical and electric fields. For the finite-element implementation, the output voltage is considered as an additional degree of freedom together with the displacement field. The developed finite-element model is then validated by comparison with the numerical results of the current finite-element model with closed-form solutions. The characteristics of the moving train load and corresponding train-induced vibration data measured on single- and double-span bridges are analyzed and the maximum vertical deflection is also evaluated for the safety assessment of the bridge. Lastly, the capability of the piezoelectric energy harvester as an energy-scavenging device on a railway bridge, the optimum location of the harvester, the optimum speed of the moving train, and the effect of resonance are discussed in terms of the generated output voltage and total energy.

This study investigates the electrical heating (also known as Joule heating) characteristics of cementitious composites containing multi-walled carbon nanotubes (CNT) and carbon fibers (CF) as electrically conductive media in an attempt to develop an eco-friendly and sustainable solution to snow and ice removal on roadway pavements during the winter season. Various dosages of CNT and CF between 0 and 1.0% (by weight of cement) were tested to find the optimum mixture proportions that yield high-energy and efficient electrical-heating performance with superior mechanical properties. The electrical properties were characterized by measuring the electrical resistivity and temperature rise when attached to a power source. Furthermore, this study examined how the crack width affects the electrical resistivity of cementitious composites containing CNT and/or CF. Compressive and flexural strengths were also measured at different ages of 1, 3, 7, and 28 days to identify how the additions of CNT and CF affect the mechanical properties. Results have shown that adding CF in combination with CNT substantially reduces the electrical resistivity and, in turn, improves the heating performance, as CFs further densify the electrically conductive network in the hydrated matrix; adding either CNT or CF alone was not an effective option to enhance the electrical characteristics. The findings of this study are expected to provide essential information for the design and construction of an electrically heated concrete pavement system with promoted energy efficiency, which will offer a promising solution to enhance winter road maintenance, improve public safety, and provide substantial social cost savings.

A new constitutive model for Q235B structural steel is proposed, incorporating the effect of dynamic strain aging. Dynamic strain aging hugely affects the microstructural behavior of metallic compounds, in turn leading to significant alterations in their macroscopic mechanical response. Therefore, a constitutive model must incorporate the effect of dynamic strain aging to accurately predict thermo-mechanical deformation processes. The proposed model assumes the overall response of the material as a combination of three contributions: athermal, thermally activated, and dynamic strain aging stress components. The dynamic strain aging is approached by two alternative mathematical expressions: (i) model I: rate-independent model; (ii) model II: rate-dependent model. The proposed model is finally used to study the mechanical response of Q235B steel for a wide range of loading conditions, from quasi-static loading ( $\dot{\epsilon }=0.001 s^{-1}$ and $\dot{\epsilon }=0.02 s^{-1}$ ) to dynamic loading ( $\dot{\epsilon }=800 s^{-1}$ and $\dot{\epsilon }=7000 s^{-1}$ ), and across a broad range of temperatures ( $93K-1173K$ ). The results from this work highlight the importance of considering strain-rate dependences (model II) to provide reliable predictions under dynamic loading scenarios. In this regard, rate-independent approaches (model I) are rather limited to quasi-static loading.