Semi-active model predictive control for 3rd generation benchmark problem using smart dampers

A semi-active strategy for model predictive control (MPC), in which magneto-rheological dampers are used as an actuator, is presented for use in reducing the nonlinear seismic response of high-rise buildings. A multi-step predictive model is developed to estimate the seismic performance of high-rise buildings, taking into account of the effects of nonlinearity, time-variability, model mismatching, and disturbances and uncertainty of controlled system parameters by the predicted error feedback in the multi-step predictive model. Based on the predictive model, a Kalman-Bucy observer suitable for semi-active strategy is proposed to estimate the state vector from the acceleration and semi-active control force feedback. The main advantage of the proposed strategy is its inherent stability, simplicity, on-line real-time operation, and the ability to handle nonlinearity, uncertainty, and time-variability properties of structures. Numerical simulation of the nonlinear seismic responses of a controlled 20-story benchmark building is carried out, and the simulation results are compared to those of other control systems. The results show that the developed semi-active strategy can efficiently reduce the nonlinear seismic response of high-rise buildings.     

Late quaternary seismic stratigraphy and active faults of the Gulf of İzmit (NE Marmara Sea)

The Upper Quaternary seismic stratigraphy and active faults of the Gulf of İzmit were investigated by means of high-resolution shallow seismic profiling data in the source region of 1999 İzmit earthquake. High-resolution seismic reflection data correlated with borehole data indicate that the stratigraphy of İzmit Bay consists of three distinct depositional sequences formed in response to middle Pleistocene-Holocene sea-level changes. Reflector R, separating the pre-Holocene sequences (1 and 2) from the Holocene sequence (3), represents an erosional unconformity produced by the subaerial fluvial erosion of the continental shelves at the time of the last glacial maximum. Occasional, anomalous reflections (acoustic turbidity) observed within the Holocene sequence are interpreted as gas accumulations. The maximum thickness of the Holocene sediments is found to be about 25 m. The isopach map of Holocene sediment implies that the thickness of the Holocene decreases from the east towards the central and western basins of İzmit Bay. Two distinct fault systems are interpreted in İzmit Bay. The main fault system extending roughly in an E-W direction along the Gulf of İzmit is an active right lateral strike slip fault with a normal component. The secondary faults are normal faults striking in different directions and these are identified as being both active and inactive. In addition, prominent compressive features are identified in the seismic cross-sections of some profiles acquired to the east of Hersek Peninsula where the focal mechanisms of the aftershocks of the 1999 İzmit earthquake also reveal predominantly reverse faulting mechanisms, as identified by a local dense seismic network.     

Evaluation of daily precipitation in China from ECMWF and NCEP reanalyses

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An integrated approach to assess the ecological and chemical status of lakes with HOD/AHOD: a case study of two lakes

The thermal strati?cation of the lakes impedes the transfer of atmospheric oxygen into the lower layers of the lake. In lakes which are af fected by diverse anthropogenic in?uences, the increasing organic matter amounts lead to a sharp decrease in hypolimnetic oxygen amounts, aided by thermal strati?cation,and anaerobic conditions arise. The determination of hypolimnetic oxygen demand(HOD) and areal hypolimnetic oxygen demand(AHOD) and their monitoring represent an integrated approach to investigate the oxygenation of lakes, the nutrient conditions, and the physicochemical dynamics. In this study, two lakes dif fering by size and af fected by dif ferent anthropogenic sources, are investigated in this respect. At?rst, bathymetric studies were conducted to determine the depth, surface area, and volume relationships.Then, based on monitoring studies conducted in 2013 and 2014, the thermal strati?cation dynamics and layer properties were established using the relative thermal resistance to mixing(RTRM) index based on temperature and density pro?les. Following this, the oxygen depletion rates were determined by oxygen and temperature pro?ling in the hypolimnion. For the years of 2013 and 2014, the AHOD values for the Borabey Pond which is far from anthropogenic in?uences, were found to be 0.848 and 0.569 g O 2/(m·d), respectively.The AHOD values for the Porsuk Reservoir which was overburdened for years by industrial and domestic pollution were found to be 4.263 and 5.099 g O 2/(m·d), larger than its counterpart by almost sevenfold. The HOD and AHOD monitoring can be considered to a valuable tool for assessing the ecological and chemical status of lakes within Annex 5 of the Water Framework Directive and as an integrated approach to assess and monitor the status of lakes.     

An integrated approach to assess the ecological and chemical status of lakes with HOD/AHOD: a case study of two lakes

The thermal strati?cation of the lakes impedes the transfer of atmospheric oxygen into the lower layers of the lake. In lakes which are af fected by diverse anthropogenic in?uences, the increasing organic matter amounts lead to a sharp decrease in hypolimnetic oxygen amounts, aided by thermal strati?cation,and anaerobic conditions arise. The determination of hypolimnetic oxygen demand(HOD) and areal hypolimnetic oxygen demand(AHOD) and their monitoring represent an integrated approach to investigate the oxygenation of lakes, the nutrient conditions, and the physicochemical dynamics. In this study, two lakes dif fering by size and af fected by dif ferent anthropogenic sources, are investigated in this respect. At?rst, bathymetric studies were conducted to determine the depth, surface area, and volume relationships.Then, based on monitoring studies conducted in 2013 and 2014, the thermal strati?cation dynamics and layer properties were established using the relative thermal resistance to mixing(RTRM) index based on temperature and density pro?les. Following this, the oxygen depletion rates were determined by oxygen and temperature pro?ling in the hypolimnion. For the years of 2013 and 2014, the AHOD values for the Borabey Pond which is far from anthropogenic in?uences, were found to be 0.848 and 0.569 g O 2/(m·d), respectively.The AHOD values for the Porsuk Reservoir which was overburdened for years by industrial and domestic pollution were found to be 4.263 and 5.099 g O 2/(m·d), larger than its counterpart by almost sevenfold. The HOD and AHOD monitoring can be considered to a valuable tool for assessing the ecological and chemical status of lakes within Annex 5 of the Water Framework Directive and as an integrated approach to assess and monitor the status of lakes.     

灰色稳健总体最小二乘估计及高铁路基变形预测

最小二乘估计和部分变量误差模型的总体最小二乘估计不具备抵御粗差的能力。鉴于粗差可能同时出现在灰色白化微分方程的观测值和系数矩阵中,本文提出基于IGGⅢ抗差方案的部分变量总体最小二乘稳健估计。结合仿真数据和高铁路基观测数据,系统地比较稳健最小二乘、部分变量总体最小二乘、本文算法参数估计结果和算法稳定性。结果表明,本文算法预测精度高,可以应用到高铁路基沉降预测中。     

Artificial ground motion compatible with specified ground shaking peaks and target response spectrum

1 Introduction Time history analysis is usually needed not only for the seismic design of important structures, such as nuclear plants, large concrete dams and super high-rise buildings, but also for seismic performance based design. Performance-based design requires tha knowledge of the entire process of nonlinear seismic responses of structures be obtained, which depends on the ground motion time history as input for this analysis. However, because the observed strong-motion recordings are l…     

Assessments on slope instabilities triggered by engineering excavations near a small settlement (Turkey)

In this study, the mechanisms of slope instabilities triggered by engineering excavations at location of a planned tunnel portal in the northwest region of Turkey were assessed, and stability of the current slopes which has impacts on safety of a settlement (village) and agricultural fields was investigated. In the first stage of the study, in order to identify the geological units and structural properties of the sedimentary rocks in the area, to clarify the mechanisms of instabilities and to characterize discontinuity and rock mass properties field works were conducted. In this content, geotechnical boreholes, geophysical explorations between the boreholes, line surveys to explore discontinuity properties, preparation of slope profiles using topographical techniques and sampling of rock blocks and discontinuity planes were performed. In the second stage, laboratory tests were carried out on the samples to determine the geomechnical properties of the slope forming materials and discontinuities. Then, back analyses of the instabilities were made to assess the responsible shear strength parameters of the geological units during failures by considering laboratory shear test results too. Based on the backanalyses of the failures, the strength properties of the slope debris were estimated, and it has been clarified that the residual shear strength properties are the factors controlling slip mechanism along the beddings. Following the stability analyses, it is understood that a further instability along the mass or bedding planes in the failed and redesigned area are not expected, if the current slope geometry is not changed. However, safety factor calculated for the slope in the debris is 1.1 which is well below the recommended value in the literature. The minimum safety factor for currently stable slopes which were cut at the eastern part of the failed area is 1.22 which is also less than that suggested in literature. Some remedial measures such as mini-pile or slope flattening are suggested after analyses to increase the factor of safety for this part below the settlement.     

Experimental impact cratering: A summary of the major results of the MEMIN research unit

This paper reviews major findings of the Multidisciplinary Experimental and Modeling Impact Crater Research Network (MEMIN). MEMIN is a consortium, funded from 2009 till 2017 by the German Research Foundation, and is aimed at investigating impact cratering processes by experimental and modeling approaches. The vision of this network has been to comprehensively quantify impact processes by conducting a strictly controlled experimental campaign at the laboratory scale, together with a multidisciplinary analytical approach. Central to MEMIN has been the use of powerful two-stage light-gas accelerators capable of producing impact craters in the decimeter size range in solid rocks that allowed detailed spatial analyses of petrophysical, structural, and geochemical changes in target rocks and ejecta. In addition, explosive setups, membrane-driven diamond anvil cells, as well as laser irradiation and split Hopkinson pressure bar technologies have been used to study the response of minerals and rocks to shock and dynamic loading as well as high-temperature conditions. We used Seeberger sandstone, Taunus quartzite, Carrara marble, and Weibern tuff as major target rock types. In concert with the experiments we conducted mesoscale numerical simulations of shock wave propagation in heterogeneous rocks resolving the complex response of grains and pores to compressive, shear, and tensile loading and macroscale modeling of crater formation and fracturing. Major results comprise (1) projectile–target interaction, (2) various aspects of shock metamorphism with special focus on low shock pressures and effects of target porosity and water saturation, (3) crater morphologies and cratering efficiencies in various nonporous and porous lithologies, (4) in situ target damage, (5) ejecta dynamics, and (6) geophysical survey of experimental craters.     

一种基于熵权法的小波去噪复合评价指标

传统的评价指标在真值未知的情况下不能满足小波去噪质量评价的要求。为此,借助变化率特征重新构建均方根误差变化量和平滑度变化量两个指标,利用熵权法定权将归一化后的两个指标线性组合,所得到的新指标即为复合评价指标。该方法借助指标的变化率随分解层数的增加表现出明显的收敛特性来确定去噪最优分解层数。实验表明,该方法能够在真值未知的情况下准确地指导小波分解,确定去噪最优分解层数,从而达到最优去噪效果。