Based on an extensive list of research work, expansive soil is renowned for its swelling-shrinkage property. Despite the wealth of research, the strength characteristics of expansive soil, which are more complicated than common clayey soil and characterized by a considerable loss of postpeak strength, have not been fully investigated. Within this area of study, soil reinforcement with discrete, short natural fibers is attracting increased attention in geotechnical applications, in part thanks to the unique advantages that this material possesses. Because of these possible advantages, the objectives of the study presented in this paper are (1) to investigate strategies for improving the strength characteristics of expansive soil through the introduction of jute fibers into soil mass and (2) to ascertain jute fibers’ reinforcing effects in relation to several important parameters known to control the effectiveness of fiber-reinforced expansive soil. The study presents discussions related to fiber content, fiber length, fiber orientation, water content, and dry density. More specifically, an experimental program of direct shear and triaxial compression tests was performed on unreinforced and reinforced specimens. The results demonstrate the beneficial role of jute fibers in enhancing strength parameters, enhancing deviator stress-strain behavior, and, if the considered parameters are properly selected, in reducing the postpeak strength loss of expansive soil. The study also presents a detailed discussion regarding the variation of the reinforcing effects and regarding the mechanisms accounting for how fiber-reinforcing effects are affected at the fiber and grain scale. Finally, limitations of this study and potential work for the future are contemplated.

The prominent features of incremental sheet metal forming (ISMF) process make it suitable to cover the requirements of today's industries and various preferences of costumers. In this article, the forming time aspect in negative ISMF process was studied. This aspect was investigated by disclosing the effects of four different process parameters: forming tool diameter, vertical tool pitch, feed rate, and support type. By using Taguchi analysis with the help of design of experiment (DOE) and analysis of variance (ANOVA), the effects of four process parameters and different influential combinations have been studied to optimize parameter levels to realize minimum forming time. The analysis results have shown that the most important parameter that has the greatest effect on the forming time is the vertical pitch followed by the feed rate and then tool diameter. The confirmation experiments have shown that the interaction between the significant parameters plays a prominent role in the negative ISMF process. It is demonstrated that Taguchi parameter design, response table, response graph, and ANOVA are a systematic procedure where the optimum level for each design parameter and their interactions can be effectively and efficiently identified to produce the minimum of forming time.

This paper uses strains measured by fiber Bragg grating (FBG) sensors to estimate the static or dynamic deflection curve of bending beam structures. The deflection estimation method is only based upon the geometric equations of a beam structure without knowing the material information. At each cross section of a beam structure, two FBG strain sensors are installed, and the curvature at the cross section can be estimated by using the two measured strains from the geometric equation. Then the curvature function is assumed as a polynomial function and the coefficients can be estimated using least squares method. Finally, the deflection curve is estimated by integrating the curvature function twice. For dynamic deflection estimation, since only the geometric equations are used, and at each time step, the geometric equations can be also used for a dynamic system. Therefore, at each time step, the deflection can be estimated using the proposed method and the dynamic deflection can be finally obtained. The method is verified by the simulations of a continuous beam under static loads and experimental tests of a simply supported beam under various static loads. A simply support beam under moving loads is also simulated to verify the method for dynamic deformation estimation. All the numerical and test results show that the method can estimate the static and dynamic deflection curve of beam structures with a high accuracy.

Nonlinear dynamic behaviors of civil engineering structures have been observed not only under extreme loads but also during normal operations. Characterization of the time-varying property or nonlinearity of the structures must account for temporal evolution of the frequency and amplitude contents of nonstationary vibration responses. Neither time analysis nor frequency analysis method alone can fully describe the nonstationary characteristics. In this article, an attempt is made to review the milestone developments of time–frequency analysis in the past few decades and summarize the fundamental principles and structural engineering applications of wavelet analysis and Hilbert transform analysis in system identification, damage detection, and nonlinear modeling. This article is concluded with a brief discussion on challenges and future research directions with the application of time–frequency analysis in structural engineering.