Polyvinyl alcohol (PVA) hydrogels are considered to be ideal materials for tissue engineering due to their high water content, low frictional behavior, and good biocompatibility. However, their limited mechanical properties restrict them from being applied when repairing load-bearing tissue. Inspired by the composition of mussels, we fabricated polyvinyl alcohol/hydroxyapatite/tannic acid (PVA/HA/TA) hydrogels through a facile freeze–thawing method. The resulting composite hydrogels exhibited high moisture content, porous structures, and good mechanical properties. The compressive strength and tensile strength of PVA hydrogels were improved from 0.77 ± 0.11 MPa and 0.08 ± 0.01 MPa to approximately 3.69 ± 0.41 MPa and 0.43 ± 0.01 MPa, respectively, for the PVA/HA/1.5TA hydrogel. The toughness and the compressive elastic modulus of PVA/HA/1.5TA hydrogel also attained 0.86 ± 0.02 MJm−3 and 0.11 ± 0.02 MPa, which was approximately 11 times and 5 times higher than the PVA hydrogel, respectively. The PVA/HA/1.5TA hydrogel also exhibited fatigue resistance abilities. The mechanical properties of the composite hydrogels were improved through the introduction of TA. Furthermore, in vitro PVA/HA/1.5TA hydrogel showed excellent cytocompatibility by promoting cell proliferation in vitro. Scanning electron microscopy analysis indicated that PVA/HA/1.5TA hydrogels provided favorable circumstances for cell adhesion. The aforementioned results also indicate that the composite hydrogels had potential applications in bone tissue engineering, and this study provides a facile method to improve the mechanical properties of PVA hydrogel.

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Hidden frame glass curtain walls are one of the most common curtain wall structure forms. This year, the damage identification of panel elements based on vibration has had the problem of an inconsistent calculation model. In this paper, an experimental study on the dynamic characteristics of two full-scale panel elements is carried out, and the main factors affecting the dynamic characteristics of panel elements are analyzed by using a fine finite element model, and the corresponding simplified calculation model is proposed. The experimental and numerical results show that the structural sealant and frame are the important factors affecting the dynamic characteristics of panel units of hidden frame, and the natural frequency of panel elements can be overestimated by more than 40% if a simply supported boundary is adopted. The effect of structural sealant on glass panels and the supporting frame is mainly a translational constraint. The effect of structural sealant on the rotational constraint of a glass panel can be neglected and simplified as a translational spring model. Using a shell element, a translational spring element and a beam element, respectively, the calculation error of the glass panel, structural sealant and supporting frame is about 5%, which shows good calculation accuracy.

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