Influence of Non-Structural Elements on Dynamic Response of Multi-Storey Rc Building to Mining Shock
In the paper the results of calculations of the dy namic response of a multi-storey reinforced concrete buil ding to a strong mining shock originated from the main region of min ing activity in Poland (i.e. the Legnica-Glogow Copper District) ar e p esented. The representative time histories of accelerations regi st red in three directions were used as ground motion data in calcu lations of the dynamic response of the structure. Two variants of a numerical model were applied: the model including only structural e lements of the building and the model including both structural an d non-structural elements (i.e. partition walls and ventilation duct s made of brick). It turned out that non-structural elements of multi-st orey RC buildings have a small impact of about 10 % on natural freque ncies of these structures. It was also proved that the dynamic res pon e of building to mining shock obtained in case of inclusion of al l non-structural elements in the numerical model is about 20 % small er than in case of consideration of structural elements only. The p rincipal stresses obtained in calculations of dynamic response of mul ti-storey building to strong mining shock are situated on the level of about 30% of values obtained from static analysis (dead load). Keywords—Dynamic characteristics of buildings, mining shocks , dynamic response of buildings, non-structural eleme nts
Vibration serviceability assessment of office floors for realistic walking and floor layout scenarios: Literature review
Over the last two decades, office floors have been built progressively lightweight with increasing spans and slenderness. Therefore, vibration performance of office floors due to walking dynamic loads is becoming their governing design criterion, determining their size and shape, and therefore overall weight and embodied energy of the building. To date, floor design guidelines around the world recommend walking load scenarios in offices featuring some or all of the following standard characteristics: (a) walking loads are assumed to be periodic dynamic excitation represented by the Fourier series, including harmonics corresponding to up to the first four integer multiples of the pacing frequency of which at least one is exciting the floor at a resonant frequency and (b) single person walking. However, the literature surveyed provides evidence that such assessment methodology is potentially an over-simplification which does not reflect real walking load scenarios, since crucial features of the floor vibration source, path and receiver are missing. First, in terms of vibration source, realistic scenarios need to feature (a) moving rather than stationary walking forces, (b) stochastic nature of human gait, (c) simultaneous multi-person walking and (d) human–structure interaction. Second, for the transmission path (i.e. office floor structure), two features are needed to consider: (a) realistic office floor layouts and (b) presence, or absence, of non-structural elements. Finally, for the vibration receivers (i.e. floor occupants), (a) vibrations calculated at floor locations occupied by users (instead of at the potential highest response location which may not be occupied), (b) actual period over which occupants feel vibration due to such excitation and (c) assessment of vibration levels based on their probability of occurrence. This study therefore addresses these seldom considered but increasingly important features and discusses realistic approaches to floor design for vibration serviceability.
Numerical tools applied to power reactor noise analysis
In order to be able to calculate the space- and frequency-dependent neutron noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor noise analysis are then described, including the unfolding of the parameters of the noise source from the induced neutron noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor noise analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.