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The structural performance improvement of concrete members is by far a crucial theoretical issue for engineers, and the development of modern smart and composite materials makes it possible to gradually enhance the durability design of the concrete structure. In this study, six beams of the same size and reinforcement ratio, the proposed composite beam (SMA-GFRP-ECC) and five comparative beams (RC, R-ECC, SS-ECC, GFRP-ECC, SMA-ECC), were designed and tested under low-cycle unidirectional cyclic loading and unloading conditions. The energy dissipation capacity, displacement ductility, residual deformation, and self-repairing performance of each concrete beam were evaluated. Afterward, a concise calculation model for the studied composite beam is deduced and developed based on the existing relevant constitutive models and concrete assumptions. The test results indicate that compared with RC beams, the composite reinforced ECC beams show obvious multi-cracking and smaller crack width during the loading process and have good bending ductility. The innovative SMA-GFRP-ECC beam is capable of a high bearing capacity, ductility, and damage self-repairing. The new proposed beam has more than 80% of the maximum crack width recovery capacity during unloading. Hence, the proposed SMA-GFRP-ECC beam is a rather good first attempt of strengthened beams, combining the advantages of SMA, GFRP, and ECC. [ABSTRACT FROM AUTHOR]

In existing load models, the crowd bouncing load is often simplified as a single‐point excitation; moreover, these models lack data support from crowd bouncing experiments. Inspired by the random field models widely adopted in seismic ground motion fields, a random field model for crowd bouncing loads was established in this research. The bouncing frequency, time lag, and amplitude of the coherence function were modeled to quantify the crowd synchronization; an auto‐power spectral density (PSD) model from the author's previous study was adopted for an individual bouncing load. The values of these parameters were obtained based on data from a crowd bouncing experiment involving 48 test subjects on the first day and 42 test subjects on the second day, in which the trajectories of reflective markers fixed at the clavicle of every test subjects were simultaneously recorded using three‐dimensional motion capture system. Based on the PSD matrix of the crowd bouncing loads as simulated by the proposed random field model, the structural acceleration can be analyzed using random vibration analysis in the frequency domain. The established random field model and spectral analysis framework can be adopted to evaluate the vibrating performances of lightweight and high‐strength structures. Moreover, the established load model is also the basis of structural vibration control. [ABSTRACT FROM AUTHOR]

Crowd jumping loads are often simplified to a single-point excitation in the existing Fourier series-based models, most of which lack the data support of crowd jumping experiments. A Fourier series-based multi-point excitation model for crowd jumping loads is herein developed, where two parameters, the jumping frequency, and the time lag shift, are selected to quantify the crowd synchronization. After the verification of 3D motion capture technology, the probability distributions of the jumping frequency and the time lag shift are modeled based on the crowd jumping experiment, in which the trajectories of the reflective markers of 48 test subjects were simultaneously recorded by 3D motion capture technology. Through repeated sampling, the jumping load of each person in a crowd is simulated. This model could offer a useful method for evaluating the vibration performance of assembly structures like grandstands, gymnasiums, and concert venues. [ABSTRACT FROM AUTHOR]