Characteristics Of Tall Buildings Research Articles

Seismic Designs Based on Pain Points of High-rise Buildings

With the continuous improvement of the degree of urbanization, in order to alleviate the pressure brought by the increase in population, more and more high-rise buildings appear, and high-rise buildings become the symbol and main body of urbanization. Due to the increase of height, horizontal load and other factors, high-rise buildings have higher requirements for safety and stability. However, with the frequent occurrence of earthquakes, the design requirements for high-rise buildings are more stringent. This paper introduces the structural types and characteristics of tall buildings, studies the effects of earthquakes on them, and discusses four suitable seismic design methods. The establishment of multi-level fortification of structural earthquakes is mainly to take relevant anti-seismic treatment measures and monitoring and maintenance programs to improve the anti-seismic ability of buildings. Reasonable arrangement of lateral force resisting members and uniform distribution of overall stiffness of building structure can realize reasonable building structure system to ensure the ability of building to resist earthquake load. The installation of isolation and shock absorption devices can also significantly improve the seismic level of high-rise buildings.

Large eddy simulation of blockage effects in the assessment of wind effects on tall buildings

The blockage effect on the aerodynamic characteristics of tall buildings is a fundamental issue in wind tunnel test but has rarely been addressed. To evaluate the blockage effects on the aerodynamic forces on a square tall building and flow field peripherally, large eddy simulations (LES) were performed on a 3D square cylinder with an aspect ratio of 6:1 under the uniform smooth inflow and turbulent atmospheric boundary layer (ABL) inflow generated by the narrowband synthesis random flow generator (NSRFG). First, a basic case at a blockage ratio (BR) of 0.8% was conducted to validate the adopted numerical methodology. Subsequently, simulations were systematically performed at 6 different BRs. The simulation results were compared in detail to illustrate the differences induced by the blockage, and the mechanism of the blockage effects under turbulent inflow was emphatically analysed. The results reveal that the pressure coefficients, the aerodynamic forces, and the Strouhal number increase monotonically with BRs. Additionally, the increase of BR leads to more coherence of the turbulent structures and the higher intensity of the vortices in the vicinity of the building. Moreover, the blockage effects on the aerodynamic forces and flow field are more significant under smooth inflow than those under turbulent inflow.

Monitoring the dynamic characteristics of tall buildings by GPS technique

Dynamic characteristics of large structures, such as tall buildings, longspan suspension, cable-stayed bridges and tall chimneys, are key to assess their drift and stress conditions. The dynamic characteristics of large structures are difficult to measure directly under the condition of earthquakes or strong winds using traditional techniques such as laser collimator, total station and accelerometers. Therefore there is a great need for developing new method or technique for this purpose. Recent advances in Global Positioning System (GPS) technology provide a great opportunity to monitor long-period changes of structures reliably. GPS receivers capable to gauge the motion at the centimeter or sub-centimeter level with sampling frequency 10Hz or even 20 Hz are now available from several manufacturers. To the authors’ knowledge, the capability of identifying dynamic characteristics from GPS observations has not been widely verified. For the feasibility study on using kinematic GPS technology to identify the dynamic characteristics of tall buildings, some experiments were conducted in a simulative environment. This paper discusses in detail the experiment device, and the ways through them GPS data are recorded, processed and analyzed. With post-processing version of NovAtel’s Softsurv software and auto-regressive (AR) spectral analysis method, relative displacements and corresponding vibrating frequencies have been derived from GPS observations. The results indicate that the dynamic characteristics can be identified accurately by kinematic GPS technology.

Calculation of vertical dynamic characteristics of tall buildings with viscous damping

The magnitude of the vertical component of earthquake ground motion is often about one-third of the horizontal component. Thus, it is necessary to calculate vertical dynamic characteristics of tall buildings and high-rise structures in design stage for certain cases. In analysing free vibrations of tall buildings and high-rise structures, it is possible to regard such structures as a cantilever bar with variable cross-section. In this paper, the differential equations of free longitudinal vibrations (in vertical direction) of bars with variably distributed mass and stiffness considering damping effect are established. The damping coefficient of a bar is assumed to be proportional to its mass, and the general solutions of mode shapes of damped distributed parameter systems are reduced to Bessel's equations by selecting suitable expressions, such as power functions and exponential functions, for the distributions of stiffness and mass. An approach to determine the natural frequencies and mode shapes in vertical direction for tall buildings with variably distributed stiffness and variably distributed mass is proposed. The presented method is also applicable to the free longitudinal vibration analysis without considering damping effect (damping coefficient in vibration equations is equal to zero). A numerical example shows that the computed values of the fundamental longitudinal natural frequency and mode shape by the proposed method are close to the full scale measured data. It is shown through the numerical example that the selected expressions are suitable for describing the distributions of stiffness and mass of typical tall buildings. A comparison between undamped structural dynamic characteristics and damped natural frequencies, mode shapes is made in this paper.