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Large grandstands provide areas for human activities and leisure pursuits. The degree of vibration comfort for people has an important effect on the functionality of grandstands. In this paper, the changes of the dynamic properties of the stand owing to different human postures are demonstrated. The comfort degree for human vibration in the large stand is also examined by full-scale measurements and questionnaire surveys. In addition, the analysis of the influence of different parameters on acceleration responses of the stand is presented via numerical simulation. Thereafter, it has been observed that ISO10137-2007 and BS6472 are more suitable than GB10070 and AISC-11 for evaluating vibration serviceability owing to crowd jumping loads during football matches in the large grandstand environment. Moreover, it has been observed that females and the staff are more likely to feel uncomfortable during matches, whilst students younger than 30 years old are the least sensitive group to vibrations of large stands. When the frequency of the jumping loads is close to the fundamental frequency of the stand or the synergy rate is high, the resonance is more likely to occur, which should be avoided by designers and users. [ABSTRACT FROM AUTHOR]

Reciprocal grid structure is a structural system consisting of mutually supporting bars. Its geometry should satisfy not only the demands of architectural intents but also the requirements of the lapping relationship of the bars. Thus, form generation is the key problem in its design. Inspired by the physical building process of a reciprocal grid structure, self‐adaptive form generation method is proposed. In this method, an initial plane grid with the topology of required structural configuration is created first. Next, elements are iteratively lapped to realize a self‐adaptive generation of structural form. Two new parameters, bar lapping factor and rotation angle, are proposed to describe reciprocal grid structures quantitatively and make the form generation process easy. The efficiency and accuracy of the method are illustrated by comparisons with other form generation methods. Numerical examples demonstrate the applicability of the proposed method in the complex and realistic reciprocal grid structures. [ABSTRACT FROM AUTHOR]

Cross-linkable poly(arylene ether nitrile)s containing side propenyl groups (DPEN) were synthesized through nucleophilic aromatic substitution polymerization from biphenol, 2,2′-diallylbisphenol A (DBA), and 2,6-dichlorobenzonitrile. The structures of resultant copolymers were characterized by Fourier transform infrared and proton nuclear magnetic resonance spectroscopies. The properties of copolymers were investigated by thermal (differential scanning calorimetry and thermogravimetric analysis) analysis, inherent viscosity measurements, and mechanical tests. The results showed that allyl groups rearranged into propenyl groups during the polymerization. The copolymers with increasing content of DBA had high glass transition temperatures ranging from 207°C to 169°C and good thermal and thermo-oxidative stability with the 5 wt% loss temperatures in the range of 511–423°C under nitrogen and 471–402°C in air atmospheres, respectively. They also exhibited good mechanical property with tensile strength of 105–79 MPa. Meanwhile, the cross-linking reaction was studied through heat treatment. The result showed that the properties of DPEN containing side propenyl groups changed obviously after heat treatment, due to the fact that the double bond of PEN can be readily cross-linked to form net-shape polymers at high temperature. [ABSTRACT FROM AUTHOR]