This paper presents a new algorithm based on square time–frequency distribution to detect damages in concrete piers of railroad bridges. In addition, two new damage indices are proposed in this research. The algorithm and damage indices are described and corroborated using finite element model of Qotour railroad bridge. To create the finite element model according to the current condition of the Qotour railroad bridge, extensive in situ measurement results and laboratory tests were used. Some seismic damages were considered in the concrete piers of the model. The results indicate that the algorithm and damage indices can identify all damages from severe to small accurately. The proposed algorithm and damage indices are shown to be not sensitive to noise and even in case of noise-polluted response signal are working properly. The proposed algorithm only uses the response signals without the need for recording the excitation forces. In addition, according to the algorithm, there is no need to create an analytical model of the bridge for damage detection. This feature in modeling of bridge structures and especially complex bridge, which is associated with problems, is very useful. Copyright © 2014 John Wiley & Sons, Ltd.

Today, the accumulation of discarded cigarette butts in the environment, particularly along coasts and near seas, not only poses environmental challenges but also threatens the ecological balance of rivers and aquatic life. Exploring the feasibility of using cellulose acetate fibers from cigarette butts as reinforcements in the production of silica fume concrete has resolved this environmental issue. The inclusion of these hazardous materials has simultaneously improved the mechanical properties of the concrete. In this study, cellulose acetate fibers obtained from cigarette butt filters were added to silica fume concrete in 10 different volume ratios. The compressive strength, Brazilian tensile strength, and flexural tensile strength of these concretes were investigated in 10 mixing designs. The findings indicate that adding 0.2% by volume of fibers to silica fume concrete yields the highest compressive and tensile strengths among the designs. This results in a significant increase of 16% and 34% in the concrete's compressive strength and a 70% and 38% increase in Brazilian tensile strength at 7 and 28 days, respectively, compared to the state without cellulose acetate fibers. The addition of these fiber ratios also increases the flexural tensile stress capacity by 56%. Furthermore, the beam specimens subjected to testing exhibit a 287% higher vertical deformation tolerance compared to the state without fibers. Additionally, the energy absorption capacity of the concrete beam increases considerably.