3-D Wind Load And Wind Induced Response Analysis Of High-rise Buildings With X Shape

High-rise buildings are brought into a period of prosperity recent years with the economy booming. Wind load is one of the control loads of tall buildings. The 3-D wind load in alongwind, acrosswind and torsional direction which induced the building's vibration in three direction, will be produced when airflow go through the building. Wind load on high-rise building is always a focal problem in wind engineering because of its' complex mechanism and numerous influencing factors. Presently majority of research has been focus on the buildings with regular shape such as rectangular shape, but few of attention has been attached to buildings with irregular plan figures.Based on the background of the high-rise building with X-shape, investigation and discuss on the wind load and wind-induced vibration of the tall building is carried out in this thesis. The research mainly includes four sections, such as spatio-temporal distribution character of wind load on the tall building, feature of wind pressure and wind load in frequency domain, wind-induced vibration of the building under the state of eccentricity and non-eccentricity and equivalent static wind load of the building.(1) Research on spatio-temporal distribution character of the tall building. Wind tunnel test of mutli-point synchronous pressure measurement on rigid model of the tall building is conducted. Spacial distribution characters of average and peak values of pulsant wind pressure, local and global body coefficient as well as resultant wind force are investigated and discussed.(2) Study of power spectrum and frequency-domain features of wind pressure and resultant wind force. Based on the quasi-static assumption, relationship of power spectrum between wind pressure and wind velocity on windward surface is formed. The power spectrum density(psd) functions of wind pressure on side-ward surface is fitted according to the test data. Horizontal and vertical correlation features between different test points are studied and horizontal and vertical coherence curves between points on windward surface are fitted by using least square fitting algorithm. Law of average and root mean square(rms) value of drag, lift and torque coefficients are discussed. Then the mathematical model of power spectrum density functions of the resultant wind force in alongwind, acrosswind and torsional directions are studied and the fitted formulas are proposed. Coherence functions of wind load in different height in three directions are discussed and their analytical models are also proposed in this thesis.(3) Investigation on wind-induced vibration of high-rise building under status of eccentricity and non-eccentricity. Bending-shear layer model is decided to be used as simplified calculated model of tall building through modal analysis. Result shows that method of complete quadratic combination (CQC) is equal to method of square root of the sum of squares(SRSS) for buildings with frequency sparse distributed. On the basis of mode decomposition method, traditional pseudo-excitation method(PEM) that makes Choleskey decomposition to wind force matrix [S_pp] is modified by making Choleskey decomposition to modal force matrix [S_FF] which enhances the computation efficiency enormously. Equality of this new method to the traditional ones is confirmed by formula deducing. The parametric study over the following variables is processed for wind-induced vibration, such as high mode, first-order frequency, first-order damping ratio and so on. The wind vibration factor based on the first-order inertia force method is generated under different wind angles and is compared with the wind vibration factor given by the Chinese wind load code.Matrix perturbation theory is adopted in solving of the eigenvalue problem of the eccentric high-rise building and the frequency and mode shapes can be expressed in term of those of corresponding torsionally uncoupled system. Influence of eccentric displacement and level to the structural vibration feature is analyzed. Calculation of torsionally coupled wind-induced vibration of the structure under status of different eccentric displacement and level is conducted. Influence of the lateral-torsional coupling items to structural response is also taken in consideration. Variety law of lateral-torsional response ratio for structure under single and double axis eccentricity cases in different eccentric levels with the changing of the ratio of first-order lateral-torsional period is firstly investigated. Concept of equivalent eccentric ratio directly towards the torsional wind load for high-rise building is drawn.(4) Study on equivalent static wind load(ESWL) of high-rise buildings. The computational method for ESWL in alongwind direction of tall buildings is firstly discussed, including the gust loading factors(GLF), load-response correlation(LRC) and gust loading envelope(GLE) method for background ESWL calculation and GLF method, inertia force method for resonant ESWL calculation. The fault of traditional GLF method in calculation of resonant ESWL is elaborated. The linear combination of average, background and resonant items and calculation of background ESWL under different structural response type are analyzed. GLF method is tended to calculation of ESWL in acrosswind and torsional direction. LRC method towards background ESWL is adopted in computation of background ESWL in acrosswind and torsional direction. The ESWL from two different methods is compared and discussed.