Seismic Stochastic Model And Structural Response Control

the paper consists of two parts: The first part is about stochastic model of ground motion and the structural random response, the second part is on the energy dissipation and vibration control. The study contents of first part include: the power spectra density model of earthquake ground motion, using uniform amplitude modulate model to simulate ground motion and the algorithm synthesizing artificial seismic waves based on uniform modulation process, the structural random response under excitation of uniform modulation process, and mode superposition standard deviation spectra algorithm for analysing the random dynamic response of multi-degree-of-freedom structures. The second part include the case studies on two new type of dampers and a novel vibration control system with distributed damping, and the seismic design, conducted as well as seismic response anlyses of structures equiped with two dampers under excitation of extrem earthquake..1. A Markov model is put forward, which is very simple , the corresponding random response of the structure also very simple. Baseed on Markov model the modified Kanai-Tajimi spectra and high order Markov model were proposed, these two model have some advantiges respectively, in particular, the modified Kanai-Tajimi spectra, made up of deficiencies of Kanai-Tajimi model at low-frequency range, and maintain high-frequency contents almost unchanged. this model can be used as a substitute for Kanai-Tajimi model.2. This paper presents a method for examining whether the power spectra mode is reasonable or not, this method on the based of simulation of variance response spectra of structures, and useing structural response to check input model. As we know the seismic model is used to solve the structural response. So, it is important to appropriately descrip the earthquake response of structure by using a suitable earthquake model, the other additional restrain conditions are trivial. Based on this line of thought, following conclusions are attained: if the seismic design was based on the force method, as long as the power spectra of the model can be close enough to fit the actual average power spectra of the earthquake acceleration records, the model can be used to simulate seismic process; if the seismic degsin was based on the displacement methods, the more stringent constrains should be applied to the power spectra to model. 3. A synthesizing algorithm of artificial seismic waves for fitting multi-damping response spectra is presented, which has the following four characteristics: first, a number of initial artificial waves were generated, the closest one to the target spectra was selected for iteration calculation; second, in aspect of selection of periond control point in iteration calculation, the longer period component was adjusted preceded to shorter ones; the third, in the same interation cycle, optimization algorithms was adopted to fitting the values of multiple damping ratio response spectras; the fourth, the modulation is performenced by using a amplitued modulated cosine function in the time domain, and thus the parameters in each iteration can be easily obtained. The proposed algorithm is of fast convergence and high efficiency. To sythesizing a artificial earthquake series for meeting three damping ratio response spectras, only about one minute was need in case of using personal computer.4. To obtain the analytical solution of random response of the structure excited by uniform modulation model is very difficult in general. This paper proposes a large mass-extended-order method which could transfer a general modulated filter white noise process to modulated white noise,then gives a simply calculating formula of random reponse of structures. Several power spectra models are transformed into filter white noise models, and the efeectiveness is verified.5. The current seismic design method is based on deterministic analysis, the probability of structural seismic design is relatively vague. This paper presents a mode superposition standard deviation spectral method, which can be used to calculate the standard deviation of the structure response. On the hypothesis of earthquake being a Gaussian process with zero mean, the probability distribution of structural design demand will be solved according to the standard deviation. This method could serve as a useful complement to the normally used deterministic analysis.6. The additional damping provided by the general displacement type dampers are mostly associated with the deformation amplitude. This paper presents a variable friction device, which almost has linear damping characteristics, and the equivalent stiffness of its hysteretic model equals to 0. this character is same as the viscous dampers, can thus provides constant additional damping ratio independent of the movement amplitude and unchanging the vibration frequency of structures as well. However, the viscous damper is not suitable for long-period structure, in contrast the linear variable friction device right can be used to control the seismic response of long-period structure. The nonlinear time-history analysis procedures, as well as adding variable friction hysteretic model has been added to the IDARC software, and the damping effect of several hysteretic model of variable friction damper was studied. The results showed that the vibration reduction performance is excellent.7. A simplied shear lead damper with stable hysteretic performance and cost-effective is proposed. By finite element analysis and laboratory test, the mechanism and the parameter optimization were investigated. The performench tests showed that this damper had excellent performance, suitable for application in civil engineering, and has been successfully applied to two practical projects8. Because of aesthetic or functional requirements in some engineering projects it is very difficult to get necessary installation space of dampers. For this reason this paper presents a approach to use distributed structural damping, the method do not need extra installation space, and do not need for the maintenance and repairing work as well .