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61.
The aim of this paper was to propose a design guideline for using visco‐elastic dampers for the control of building structures subjected to earthquake loading as well as suspension roof structures subjected to wind loading. The active control algorithm was used to calculate the control forces. Based on the single‐mode approach the control forces were transformed to the forces which visco‐elastic dampers can provide. Application of the method to the design of the building structure with passive damping devices in the bracing system and to the suspension roof with dampers was studied. Through the application of optimal control theory a systematic design procedure to implement dampers in structures is proposed. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
62.
A sliding mode fuzzy control (SMFC) algorithm is presented for vibration reduction of large structures. The rule base of the fuzzy inference engine is constructed based on the sliding mode control, which is one of the non‐linear control algorithms. In general, fuzziness of the controller makes the control system robust against the uncertainties in the system parameters and the input excitation, and the non‐linearity of the control rule makes the controller more effective than linear controllers. For verification of the present algorithm, a numerical study is carried out on the benchmark problem initiated by the ASCE Committee on Structural Control. To achieve a high level of realism, various aspects are considered such as actuator–structure interaction, sensor noise, actuator time delay, precision of the A/D and D/A converters, magnitude of control force, and order of control model. Performance of the SMFC is examined in comparison with those of other control algorithms such as Hmixed 2/∞, optimal polynomial control, neural networks control, and SMC, which were reported by other researchers. The results indicate that the present SMFC is efficient and attractive, since the vibration responses of the structure can be reduced very effectively and the design procedure is simple and convenient. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
63.
For energy‐based seismic design, energy demand in the form of absorbed energy spectra was established by an attenuation relationship. The absorbed energy is proposed for evaluating the energy demand in an inelastic system because the absorbed energy is directly related to the pseudo‐velocity in the elastic case. Based on a total of 273 ground motion records from 15 significant earthquakes in California, an attenuation relationship of the absorbed energy was established from a two‐stage non‐linear regression analysis. This relationship was established for a given earthquake magnitude, source‐to‐site distance, site class, and ductility factor. A similar expression for the normalized absorbed energy was also developed. This study showed that the absorbed energy for near‐field ground motions can be significantly larger than that predicted by the attenuation relationship for normal ground motions. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
64.
The objective of this paper is to examine the effectiveness of some control algorithms which will be implemented through experimental verification of a seismic-excited full-scale building. A full-scale 3-storey steel building with active bracing control system was tested at a three-dimensional shaking table of NCREE, Taiwan. The active bracing control system was installed at the first floor. Three different control algorithms were used for the experimental verification: static-output-feedback LQR control, modal control with direct output feedback, and static-output-feedback with variable gain. It is concluded that within the maximum capacity of the actuator in the experiment all the three control algorithms performed well and almost 50 per cent of displacement as well as the acceleration of each floor response was reduced. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
65.
Local rainfall thresholds for forecasting landslide occurrence: Taipingshan landslide triggered by Typhoon Saola 总被引:4,自引:2,他引:2
This paper presents a case study of the Taipingshan landslide, which was triggered by Typhoon Saola in 2012. Taipingshan villa is one of the most famous scenic locations within the Taipingshan National Forest Recreation Area in northern Taiwan. Since the early 1990s, evidence of recent landslide activity appeared throughout the Taipingshan villa and included features such as tension cracks, ground settlement, and cracking in manmade structures. In response, a series of geological investigations and in-site/laboratory tests were conducted in 2010 to estimate slope stability and predict critical rainfall thresholds (event accumulated rainfall) for landslide activity. Results revealed that the critical rainfall threshold for the Taipingshan National Forest Recreation Area is 1765 mm. In 2012, that threshold was tested when Typhoon Saola brought tremendous rainfall to northern and eastern Taiwan and triggered activity along the main scarp of sliding mass B located near the History Exhibition Hall. According to in situ extensometer readings and on-site precipitation data, the extensometer was severed at an accumulated rainfall 1694 mm. Field monitoring data during the typhoon event are in good agreement with the rainfall threshold. These preliminary results suggest that the threshold may be useful for assessing the rainfall threshold of other landslides and a good reference for establishing early warning systems for landslides. 相似文献
66.
S. Venkatramanan S. Y. Chung S. Selvam J. H. Son Y. J. Kim 《Environmental Earth Sciences》2017,76(13):456
This research was conducted at Samrak Park Delta of Nakdong River Basin in Busan Metropolitan City, Korea. The main objective of this study was to evaluate the interrelationship of geochemical elements in sediments and groundwater through multivariate statistical analyses and a multilayer perceptron artificial neural network model. The mean concentrations of chemical elements were Si (46%), Fe (16.9%), Al (15.7%), K (7.5%) and Ca (4.5%) in sediments, and Na (8650 mg/L), Mg (999 mg/L), Ca (432 mg/L), K (293 mg/L) and Cl (17,640 mg/L) in groundwater, respectively. The principal component analysis produced 3 kinds of factors with the variances of 63.37, 27.02 and 9.62%, respectively. It is suggested that the chemical components of sediments and groundwater were mainly originated from source rocks and seawater intrusion, with the minor impacts of irrigation and industry. Cluster analysis also showed that chemical elements were mainly controlled by the natural geogenic sources and seawater intrusion. Multilayer perceptron of artificial neural network (ANN) presented the good interrelationship between sediment and groundwater. The determination coefficients (R 2) between ANN predicted values and observed values in groundwater showed the high values of 0.61–0.97 except Mg, Mn and Sr. It is revealed that the chemical components of sediment and groundwater were derived from local geological origin and from the minor impact of anthropogenic sources. Multivariate analyses and ANN contributed to the identification of the mutual relationship between the geochemical elements of sediment and those of groundwater. 相似文献
67.
We conducted the first quantitative assessment of coral breakage along a gradient of diving activities in Hong Kong, the most densely populated city in southern China. A survey of six 1 × 25 m transects at seven sites revealed a total of 81 broken corals, among which 44% were branching, 44% plate-like and 12% massive. There were 3–19 broken colonies per site. At most study sites, the percentage of broken corals exceeded the recommended no-action threshold of 4%, suggesting that management intervention is justified. There was a significant positive correlation between the number of broken coral colonies and the number of divers visiting the site. The branching Acropora and the plate-like Montipora suffered from much higher frequency of damage than their relative abundance, raising the concern that the cumulative impact of such differential susceptibility to breakage may affect coral community composition. 相似文献
68.
69.
H. S. Jeon S. Cho Y. S. Kwak J. K. Chung J. U. Park D. K. Lee M. Kuzmicz-Cieslak 《Astrophysics and Space Science》2011,332(2):341-351
The atmospheric mass density of the upper atmosphere from the spherical Starlette satellite’s Precise Orbit Determination
is first derived with Satellite Laser Ranging measurements at 815 to 1115 km during strong solar and geomagnetic activities.
Starlette’s orbit is determined using the improved orbit determination techniques combining optimum parameters with a precise
empirical drag application to a gravity field. MSIS-86 and NRLMSISE-00 atmospheric density models are compared with the Starlette
drag-derived atmospheric density of the upper atmosphere. It is found that the variation in the Starlette’s drag coefficient
above 800 km corresponds well with the level of geomagnetic activity. This represents that the satellite orbit is mainly perturbed
by the Joule heating from geomagnetic activity at the upper atmosphere. This result concludes that MSIS empirical models strongly
underestimate the mass density of the upper atmosphere as compared to the Starlette drag-derived atmospheric density during
the geomagnetic storms. We suggest that the atmospheric density models should be analyzed with higher altitude acceleration
data for a better understanding of long-term solar and geomagnetic effects. 相似文献
70.
Ho Seuk Bae Sukjoon Pyun Wookeen Chung Seung‐Goo Kang Changsoo Shin 《Geophysical Prospecting》2012,60(3):413-432
We developed a frequency‐domain acoustic‐elastic coupled waveform inversion based on the Gauss‐Newton conjugate gradient method. Despite the use of a high‐performance computer system and a state‐of‐the‐art parallel computation algorithm, it remained computationally prohibitive to calculate the approximate Hessian explicitly for a large‐scale inverse problem. Therefore, we adopted the conjugate gradient least‐squares algorithm, which is frequently used for geophysical inverse problems, to implement the Gauss‐Newton method so that the approximate Hessian is calculated implicitly. Thus, there was no need to store the Hessian matrix. By simultaneously back‐propagating multi‐components consisting of the pressure and displacements, we could efficiently extract information on the subsurface structures. To verify our algorithm, we applied it to synthetic data sets generated from the Marmousi‐2 model and the modified SEG/EAGE salt model. We also extended our algorithm to the ocean‐bottom cable environment and verified it using ocean‐bottom cable data generated from the Marmousi‐2 model. With the assumption of a hard seafloor, we recovered both the P‐wave velocity of complicated subsurface structures as well as the S‐wave velocity. Although the inversion of the S‐wave velocity is not feasible for the high Poisson's ratios used to simulate a soft seafloor, several strategies exist to treat this problem. Our example using multi‐component data showed some promise in mitigating the soft seafloor effect. However, this issue still remains open. 相似文献