دانلود رایگان مقاله انگلیسی طراحی لرزه ای و عملکرد سازه های پیش ساخته مونتاژ شده با اتصالات قابل انعطاف - الزویر 2018

ABSTRACT

Previous research projects and post-earthquake field observation showed that dry-assembled precast frame structures with hinged beams and cantilever columns restrained at their base, if correctly designed and detailed, can attain good seismic performance, mainly due to their flexibility and robustness. Their seismic design is often conditioned by the need of reducing their flexibility by increasing the cross-section of the columns, which, due to minimum reinforcement requirements, results in their over-strengthening. High flexibility may also induce displacement compatibility issues with non-structural elements. The paper concerns the proposal of an innovative enhanced structural frame system, based on the adaptation of hinged beam-column joints into rigid through the activation of special mechanical connection devices performed after the installation of the slab. While keeping all the benefits of the dry prefabrication, the resulting moment-resisting frame is provided with enhanced redundancy and stiffness. A design comparison among three precast frames with similar geometries and different static schemes shows how the joint adaptation can be exploited to optimise the structure by modifying the distribution of bending moment. The results of dynamic non-linear analyses on a three-storey precast structure with adaptable joints tested as a part of the SAFECAST research programme show the seismic performance of this system through different static schemes, and the comparison with the experimental results provides information about the validity of the models and the effectiveness of the technological solutions employed.

5. Conclusions

An innovative solution for dry-assembled precast structures is proposed, where the traditional beam-column hinged joints can be adapted into rigid in desired locations. The potential benefits of precast structures with adaptable joints with respect to both traditional dry-assembled precast frames and cast-in-situ or wet-assembled precast frames are discussed. In particular, the activation of the mechanical connections adapting the joint from hinged into rigid is performed after the dead loads are applied, allowing the end joints not to be stressed in flexure by dead loads. The bending moment envelope of the horizontal members allows a remarkable reduction of the maximum values and an optimal exploitation of the pre-stressing reinforcement. The freedom of selection of the joints to be adapted provides the structural designer with a viable range of options for a more versatile design, offering solutions to complex structural design issues.