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Seismic force demands on acceleration-sensitive nonstructural components:a state-of-the-art review

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Earthquake Engineering and Engineering Vibration 2021年第1期20卷 39-62页

作者： Wang Tao Shang Qingxue li jichao Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering MechanicsChina Earthquake AdministrationHarbin 150080China

Nonstructural components(NSCs)are parts,elements,and subsystems that are not part of the primary loadbearing system of building structures but are subject to seismic *** to NSCs may disrupt the functionality of buildings and result in significant economic losses,injuries,and *** past decades,extensive studies have been conducted on the seismic performance and seismic design methods of *** the input for the seismic design of NSCs,floor response spectra(FRS)have attracted the attention of researchers *** paper presents a state-of-the-art review of *** methods for generating FRS are summarized and compared with those in current seismic design codes.A detailed review of the parameters influencing the FRS is *** parameters include the characteristics of ground motion excitation,supporting building and *** floor acceleration response and the FRS obtained from experimental studies and field observations during earthquakes are also *** RC frames are used in a case study to compare the peak floor acceleration(PFA)and FRS calculated from time history analyses(THA)with that generated using current seismic design codes and different methods in the *** knowledge gaps are identified,including uncertainties associated with developing FRS,FRS generation methods for different types of buildings,the need for comprehensive studies on absolute acceleration,relative velocity,and relative displacement FRS,and the calibration of FRS by field observations during earthquakes.

关键词： nonstructural components peak floor acceleration floor response spectra component amplification factor

Lessons from the seismic behavior of a steel grid roof structure heavily damaged in Lushan earthquake

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Earthquake Engineering and Engineering Vibration 2019年第1期18卷 95-111页

作者： li jichao Qu Zhe Wang Tao Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering MechanicsChina Earthquake Administration

The seismic behavior of a school gymnasium, whose steel grid roof was heavily damaged during the Mw6.6 Lushan earthquake in 2013, is simulated through nonlinear dynamic analysis. The simulated damage is compared with field observations to validate the numerical model, based on which a parametric study was performed to provide insight into the failure process and damage patterns of steel grids. The results suggest that the grid damage is strongly related to roofsubstructure interactions. These include not only the substructure's amplification of the vibration, but the uncoordinated displacement of the substructure's columns which support the grid also play an equally important role. In particular, the latter effect may significantly alter the internal force distribution in the steel grid and lead to unexpected buckling of members that are proportioned as tension-only members. While such interactions are generally not accounted for in the design practice for grid structures in China, similar seismic damage may be expected for other existing grid roofs in future earthquakes. As is also demonstrated in this study, seismic isolation of the roof is a promising solution to protect grid roof structures by mitigating the detrimental effects of roof-substructure interactions.

关键词： Lushan earthquake steel space structure roof-substructure interaction nonlinear dynamic analysis seismic isolation vertical ground motion

Seismic fragility of flexible pipeline connections in a base isolated medical building

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Earthquake Engineering and Engineering Vibration 2019年第4期18卷 903-916页

作者： Shang Qingxue Wang Tao li jichao Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering MechanicsChina Earthquake Administration

Flexible pipelines are often used to connect hard pipes from a foundation to a superstructure to accommodate large deformation in the base isolation layer during an earthquake. Although Chinese seismic design guidelines suggest several confi gurations, they are diff erent from the designs that have been proven in practice, e.g., Japanese styles, and extensive experimental investigation into their seismic performance is required. Three types of seals, rubber-, metal- and asbestinebased, were tested quasi-statically with infi lled pressurized water at 2.5 MPa. The asbestine-based seal leaked at a smaller deformation than the other two types of seals. Based on the test results, three damage states were defi ned and the deformation capacity was estimated. To evaluate their performance, a three-dimensional model of a base-isolated medical building was developed using OpenSees, with the fl exible pipelines simulated by a mechanical model calibrated from the experimental data. A probabilistic seismic demand model and the fragility function of the fl exible pipelines were then developed to evaluate the seismic performance.

关键词： fl exible pipeline connections isolated building quasi-static tests fragility curve probabilistic seismic demand model

Network-based structure optimization method of the anti-aircraft system

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Journal of Systems Engineering and Electronics 2023年第2期34卷 374-395页

作者： ZHAO Qingsong DING Junyi li jichao li Huachao XIA Boyuan College of Systems Engineering National University of Defense TechnologyChangsha 410073China International Office of Cooperation and Exchanges National University of Defense TechnologyChangsha 410073China

The anti-aircraft system plays an irreplaceable role in modern combat. An anti-aircraft system consists of various types of functional entities interacting to destroy the hostile aircraft moving in high speed. The connecting structure of combat entities in it is of great importance for supporting the normal process of the system. In this paper, we explore the optimizing strategy of the structure of the anti-aircraft network by establishing extra communication channels between the combat ***, the thought of combat network model(CNM) is borrowed to model the anti-aircraft system as a heterogeneous network. Secondly, the optimization objectives are determined as the survivability and the accuracy of the system. To specify these objectives, the information chain and accuracy chain are constructed based on CNM. The causal strength(CAST) logic and influence network(IN) are introduced to illustrate the establishment of the accuracy chain. Thirdly, the optimization constraints are discussed and set in three aspects: time, connection feasibility and budget. The time constraint network(TCN) is introduced to construct the timing chain and help to detect the timing consistency. Then, the process of the multi-objective optimization of the structure of the anti-aircraft system is ***, a simulation is conducted to prove the effectiveness and feasibility of the proposed method. Non-dominated sorting based genetic algorithm-Ⅱ(NSGA2) is used to solve the multiobjective optimization problem and two other algorithms including non-dominated sorting based genetic algorithm-Ⅲ(NSGA3)and strength Pareto evolutionary algorithm-Ⅱ(SPEA2) are employed as comparisons. The deciders and system builders can make the anti-aircraft system improved in the survivability and accuracy in the combat reality.

关键词： anti-aircraft system optimization combat network model(CNM) causal strength(CAST)logic influence network(IN) time constraint network(TCN)

Functionality analysis of an urban water supply network after strong earthquakes

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Earthquake Engineering and Engineering Vibration 2021年第2期20卷 291-302页

作者： li jichao Shang Qingxue Hou Guanjie li Quanwang Wang Tao Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering MechanicsChina Earthquake AdministrationHarbin 150080China Department of Civil Engineering Tsinghua UniversityBeijing 100084China

An urban water supply network(WSN)is a crucial lifeline system that helps to maintain the normal functioning of modern ***,the hydraulic analysis of a significantly damaged WSN that suffers from pipe breaks or leaks remains *** this paper,a probability-based framework is proposed to assess the functionality of WSNs in the aftermath of powerful *** serviceability of the WSN is quantified by using a comprehensive index that considers nodal water flow and nodal *** index includes a coefficient that reflects the relative importance of these two *** demand reduction(DR)method,which reduces the water flow of nodes while preventing the negative pressure of nodes,is *** difference between the negative pressure elimination(NPE)method and the DR method is discussed by using the example of a WSN in a medium-sized city in *** functionality values of the WSN are 0.76 and 0.99 when nodal pressure and nodal demands are used respectively as the index of system serviceability at an intensity level that would pertain to an earthquake considered to occur at a maximum *** the intensity of ground motion is as high as 0.4 g,the DR method requires fewer samples than the NPE method to obtain accurate *** NPE method eliminates most of the pipes,which may be unrealistic.

关键词： water supply network system serviceability hydraulic analysis negative pressure elimination benchmark city

Design and performance investigation of modified dual reflector parabolic trough collector with double planar mirrors

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Science China(Technological Sciences) 2024年第3期67卷 902-918页

作者： li Peijing liU TaiXiu QIN YuanLong li jichao liU QiBin School of Energy Powerand Mechanical EngineeringNorth China Electric Power University Beijing 226China Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Department of Thermal Science and Energy Engineering University of Science and Technology of ChinaHefei 230027China

In a typical parabolic trough collector(PTC), sunlight is concentrated at the bottom of the absorber tube. This concentrated solar flux leads to uneven heat distribution, resulting in high local temperatures and significant thermal stress on the absorber *** limitations have restricted the application of PTCs in solar thermochemistry and other fields and have impacted their safe operation. In this study, a new PTC with dual planar mirrors(DPMS) is proposed to homogenize the circumferential solar flux distribution of the absorber tube. A design method and single-objective optimization of the new PTC with a DPMS are proposed,and an uncertainty analysis of the operational and structural parameters is performed. A coupled light-heat-structure numerical model was developed to study the heat transfer performance and structural mechanical properties. The thermodynamic properties of the PTC with DPMS under different boundary conditions were analyzed. The results show that the circumferential temperature difference of the new PTC is within 2.6 K, and the circumferential thermal deformation is within 0.9 mm under typical working conditions(the inlet velocity of the heat transfer fluid is 3 m/s, inlet temperature is 573.15 K, and the direct normal irradiance is 1000 W/m^(2)). Compared with conventional PTCs, the circumferential temperature difference is reduced by 74%–90%, and the maximum thermal deformation along the y-axis is reduced by more than 95% under all working conditions(1–5 m/s, 373.5–675.15 K, 200–1000 W/m^(2)). The new PTC maintains the uniformity of the circumferential solar flux distribution for different operating parameters(sun incident angle of 0°–3°) and installation errors(±3 mm), is suitable for solar energy applications in various fields, and has the potential for large-scale applications.

关键词： solar thermal energy parabolic trough collector secondary reflector solar flux distribution optical optimization

Automatic Efficiency Optimization of an Axial Compressor with Adjustable Inlet Guide Vanes

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Journal of Thermal Science 2012年第2期21卷 120-126页

作者： jichao li Feng lin Chaoqun Nie Jingyi Chen Key Laboratory of Advanced Energy and Power Chinese Academy of Sciences Beijing 100190 China Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China Graduate University of Chinese Academy of Sciences Beijing 100190 China

The inlet attack angle of rotor blade reasonably can be adjusted with the change of the stagger angle of inlet guide vane (IGV); so the efficiency of each condition will be affected. For the purpose to improve the efficiency, the DSP (Digital Signal Processor) controller is designed to adjust the stagger angle of IGV automatically in order to optimize the efficiency at any operating condition. The A/D signal collection includes inlet static pressure, outlet static pressure, outlet total pressure, rotor speed and torque signal, the efficiency can be calculated in the DSP, and the angle signal for the stepping motor which control the IGV will be sent out from the D/A. Experimental investigations are performed in a three-stage, low-speed axial compressor with variable inlet guide vanes. It is demonstrated that the DSP designed can well adjust the stagger angle of IGV online, the efficiency under different conditions can be optimized. This establishment of DSP online adjustment scheme may provide a practical solution for improving performance of multi-stage axial flow compressor when its operating condition is varied.

关键词： DSP Inlet guide vane Efficiency Axial compressor Variable condition Control algorithm

Entropy Generation Analysis in a Mixed-Flow Compressor with Casing Treatment

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Journal of Thermal Science 2019年第5期28卷 915-928页

作者： ZHANG Qianfeng DU Juan li Zhihui li jichao ZHANG Hongwu Advanced Gas Turbine Laboratory Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China

Casing treatments(CT) can effectively extend compressors flow ranges with the expense of efficiency penalty. Compressor efficiency is closely linked to loss. Only revealing the mechanisms of loss generation can design a CT with high aerodynamic performance. In the paper, a highly-loaded mixed-flow compressor with tip clearance of 0.4 mm was numerically studied at a rotational speed of 30,000 r/min to reveal the effects of axial slot casing treatment(ASCT) on the loss mechanisms in the compressor. The results showed that both isentropic efficiency and stall margin were improved significantly by the ASCT. The local entropy generation method was used to analyze the loss mechanisms and to quantify the loss distributions in the blade passage. Based on the axial distributions of entropy generation rate, for both the cases with and without ASCT, the peak entropy generation rate increased in the rotor domain and decreased in the stator domain during throttling the compressor. The peak entropy generation in rotor was mainly caused by the tip leakage flow and flow separations near the rotor leading edge for the mixed-flow compressor no matter which casing was applied. The radial distributions of entropy generation rate showed that the reduction of loss in the rotor domain from 0.4 span to the rotor casing was the major reason for the efficiency improved by ASCT. The addition of ASCT exerted two opposite effects on the losses generated in the compressor. On the one hand, the intensity of tip leakage flow was weakened by the suction effect of slots, which alleviated the mixing effect between the tip leakage flow and main flow, and thus reduced the flow losses;On the other hand, the extra losses upstream the rotor leading edge were produced due to the shear effect and to the heat transfer. The aforementioned shear effect was caused by the different velocity magnitudes and directions, and the heat transfer was caused by temperature gradient between the injected flow and the incom

关键词： numerical simulation mixed-flow compressor loss mechanism casing treatment

Thermodynamic analysis of auto-thermal chemical looping hydrogen production systems

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Science China Technological Sciences 2024年第12期67卷 3707-3723页

作者： li PeiJing liU TaiXiu li jichao QIN YuanLong liU QiBin School of Energy Power and Mechanical Engineering North China Electric Power University Institute of Engineering Thermophysics Chinese Academy of Sciences University of Chinese Academy of Sciences Department of Thermal Science and Energy Engineering University of Science and Technology of China

Chemical looping hydrogen production is of interest because of its ability to simultaneously produce hydrogen and capture CO2at the same time. Achieving an energy balance is crucial in chemical-looping hydrogen production systems. Decreasing the external heat duty can effectively reduce carbon capture and energy conversion efficiency. In this study, two auto-thermal chemical looping H2generation systems are proposed. An adiabatic counter current moving bed chemical looping H2generation system using CH4as fuel and Fe2O3and Al2O3（inert carriers） as oxygen carriers（OC） is proposed to analyse the energy balance and exergy balance of the systems. A parametric analysis was conducted to investigate the influence of the reaction ratio and temperature on the product outcomes, leading to the determination of optimal operating conditions. Subsequently, the impact of hydrogen production efficiency and reduction reactor outlet stream ratio and inert component proportion in the oxygen carrier on the system's thermal balance was analysed under these optimal conditions, culminating in the identification of key parameters for the two auto-thermal systems. Energy balance and exergy balance analyses were employed to compare the energy efficiency and irreversible losses of the autothermal and reference systems. The results demonstrated that the autothermal system enhanced the energy efficiency by 2.5% and the CO2capture rate by 11%（percentage points） compared with the reference system.

关键词： chemical looping hydrogen generation hydrogen production auto-thermal energy balance analysis exergy balance analysis