Nonlinear control of a 20-story steel building with activepiezoelectric friction dampers

Chaoqiang Chen,GendaChen 국제구조공학회 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.6

Nonlinear control of a 20-story steel building with active piezoelectric friction dampers

Chen, Chaoqiang,Chen, Genda Techno-Press 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.1

A control algorithm combining viscous and non-linear Reid damping mechanisms has been recently proposed by the authors to command active friction dampers. In this paper, friction dampers and the proposed algorithm are applied to control the seismic responses of a nonlinear 20-story building. Piezoelectric stack actuators are used to implement the control algorithm. The capacity of each damper is determined by the practical size of piezoelectric actuators and the availability of power supply. The saturation effect of the actuators on the building responses is investigated. To minimize the peak story drift ratio or floor acceleration of the building structure, a practical sequential procedure is developed to sub-optimally place the dampers on various floors. The effectiveness of active friction dampers and the efficiency of the proposed sequential procedure are verified by subjecting the building structure to four earthquakes of various intensities. The performance of 80 dampers and 137 dampers installed on the structure is evaluated according to 5 criteria. Numerical simulations indicated that the proposed control algorithm effectively reduces the seismic responses of the uncontrolled 20-story building, such as inelastic deformation. The sub-optimal placement of dampers based on peak acceleration outperforms that based on peak drift ratio for structures subjected to near-fault ground motions. Saturation of piezoelectric actuators has adverse effect on floor acceleration.

Soil-structure interaction effect on active control of multi-story buildings under earthquake loads

Chen, Genda,Chen, Chaoqiang,Cheng, Franklin Y. Techno-Press 2000 Structural Engineering and Mechanics, An Int'l Jou Vol.10 No.6

A direct output feedback control scheme was recently proposed by the authors for single-story building structures resting on flexible soil body. In this paper, the control scheme is extended to mitigate the seismic responses of multi-story buildings. Soil-structure interaction is taken into account in two parts: input at the soil-structure interface/foundation and control algorithm. The former reflects the effect on ground motions and is monitored in real time with accelerometers at foundation. The latter includes the effect on the dynamic characteristics of structures, which is formulated by modifying the classical linear quadratic regulator based on the fundamental mode shape of the soil-structure system. Numerical result on the study of a $\frac{1}{4}$-scale three-story structure, supported by a viscoelastic half-space of soil mass, have demonstrated that the proposed algorithm is robust and very effective in suppressing the earthquake-induced vibration in building structures even supported on a flexible soil mass. Parametric studies are performed to understand how soil damping and flexibility affect the effectiveness of active tendon control. The selection of weighting matrix and effect of soil property uncertainty are investigated in detail for practical applications.

Impact of tillage practices on soil bacterial diversity and composition under the tobacco-rice rotation in China

Yanping Lei,Yongliang Xiao,Lifeng Li,Chaoqiang Jiang,Chaolong Zu,Tian Li,Hui Cao 한국미생물학회 2017 The journal of microbiology Vol.55 No.5

Tobacco-rice rotation is a common farming system in southChina, and many tillage practices such as straw mulching, dolomitedust, and quicklime application have been adopted toimprove crop production. These agricultural managementpractices alter soil physical and chemical properties and affectmicrobial life environment and community composition. Inthis research, six tillage practices including no tobacco andrice straw mulching (CK), tobacco and rice straw mulching(TrSr), rice straw returning fire (TrSc), tobacco and rice strawmulching with dolomite dust (TSD), rice straw returning fireand quicklime (TSQ), and rice straw returning fire, quicklimeand reduced fertilizer (TSQf) were conducted to detect changesin soil bacterial diversity and composition using Illumina sequencing. The results showed that the total number of operationaltaxonomic units (OTUs) from the six treatments was2030, and the number of mutual OTUs among all sampleswas 550. The TrSc treatment had the highest diversity andrichness, while TSQf had the lowest. Soil physio-chemicalproperties and microbial diversity can influence each other. Proteobacteria and Actinobacteria had the greatest proportionin all treatments. The abundance of Nitrospirae was thehighest in the TrSc treatment. The TSQf treatment had thehighest abundance of Firmicutes. The abundance of Nitrospirain the TrSc treatment was 2.29-fold over CK. Streptomycesaffiliated with Firmicutes improved by 37.33% in TSQf comparedto TSQ. TSQf treatment was considered to be the mostimportant factor in determining the relative abundance atthe genus level.

Piezoelectric friction dampers for earthquake mitigation of buildings: design, fabrication, and characterization

Chen, Genda,Garrett, Gabriel T.,Chen, Chaoqiang,Cheng, Franklin Y. Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.3

In this paper, the design, fabrication and characterization of a piezoelectric friction damper are presented. It was sized with the proposed practical procedure to minimize the story drift and floor acceleration of an existing 1/4-scale, three-story frame structure under both near-fault and far-field earthquakes. The design operation friction force in kip was numerically determined to range from 2.2 to 3.3 times the value of the peak ground acceleration in g (gravitational acceleration). Experimental results indicated that the load-displacement loop of the damper is nearly rectangular in shape and independent of the excitation frequency. The coefficient of friction of the damper is approximately 0.85 when the clamping force on the damper is above 400 lbs. It was found that the friction force variation of the damper generated by piezoelectric actuators with 1000 Volts is approximately 90% of the expected value. The properties of the damper are insensitive to its ambient temperature and remain almost the same after being tested for more than 12,000 cycles.

Microstructure Change of Nanosilica-Cement Composites Partially Exposed to Sulfate Attack

Qian Huang,Liang Zhao,Chenggong Zhao,Dongsheng Liu,Chaoqiang Wang 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.3

The deterioration of cement composites containing nanosilica partially exposed to sulfate attack was studied, and the microstructure change of the composites was analysed by a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that nanosilica-cement composites had better sulfate resistance compared to plain cement composite under partial exposure to sulfate attack, and their sulfate resistance increased as the nanosilica content increased (in the range of 0 to 5 wt% replacing cement by weight). The main sulfate products were gypsum and ettringite within the surface and inner parts, respectively in both the immersed and evaporation portions of the nanosilica-cement composites, which was consistent with the plain cement composite. Thus, the incorporation of nanosilica did not change the distribution characteristics of the sulfate products within the composites partially exposed to sulfate attack. However, the addition of nanosilica reduced the amount of sulfate products in both the immersed and evaporation portions, and their amount decreased with the increase of nanosilica content. The evaporation portions of the composites suffered chemical sulfate attack rather than sulfate salt crystallization. Nanosilica-cement composites could be applied in real partial exposure environments containing sulfate ions.

Aligned nanofibrous collagen membranes from fish swim bladder as a tough and acid-resistant suture for pH-regulated stomach perforation and tendon rupture

Zhaohui Luan,Shuang Liu,Wei Wang,Kaige Xu,Shaosong Ye,Ruijue Dan,Hong Zhang,Zhenzhen Shu,Tongchuan Wang,Chaoqiang Fan,Malcolm Xing,Shiming Yang 한국생체재료학회 2022 생체재료학회지 Vol.26 No.4

Background: Wound closure in the complex body environment places higher requirements on suture’s mechanical and biological performance. In the scenario of frequent mechanical gastric motility and extremely low pH, single functional sutures have limitations in dealing with stomach bleeding trauma where the normal healing will get deteriorated in acid. It necessitates to advance suture, which can regulate wounds, resist acid and intelligently sense stomach pH. Methods: Based on fish swim bladder, a double-stranded drug-loaded suture was fabricated. Its cytotoxicity, histocompatibility, mechanical properties, acid resistance and multiple functions were verified. Also, suture’s performance suturing gastric wounds and Achilles tendon was verified in an in vivo model. Results: By investigating the swim bladder’s multi-scale structure, the aligned tough collagen fibrous membrane can resist high hydrostatic pressure. We report that the multi-functional sutures on the twisted and aligned collagen fibers have acid resistance and low tissue reaction. Working with an implantable “capsule robot”, the smart suture can inhibit gastric acid secretion, curb the prolonged stomach bleeding and monitor real-time pH changes in rabbits and pigs. The suture can promote stomach healing and is strong enough to stitch the fractured Achilles tendon. Conclusions: As a drug-loaded absorbable suture, the suture shows excellent performance and good application prospect in clinical work.

A novel ceramic GEM used for neutron detection

Zhou, Jianrong,Zhou, Xiaojuan,Zhou, Jianjin,Jiang, Xingfen,Yang, Jianqing,Zhu, Lin,Yang, Wenqin,Yang, Tao,Xu, Hong,Xia, Yuanguang,Yang, Gui-an,Xie, Yuguang,Huang, Chaoqiang,Hu, Bitao,Sun, Zhijia,Chen, Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.6

A novel ceramic Gas Electron Multiplier (GEM) has been developed to meet the demand of high counting rate for the neutron detection which is an alternative to ³He-based detector at China Spallation Neutron Source (CSNS). An experiment was performed to measure the neutron transmittance of ceramic-GEM and FR4-GEM at the small angle neutron scattering (SANS) instrument. The result showed the ceramic-GEM has higher transmittance and less self-scattering especially for cold neutrons. One single ceramic GEM could give a gain of 10²-10⁴ in the mixture gas of Ar and CO₂ (90%:10%) and its energy resolution was about 27.7% by using ⁵⁵Fe X ray of 5.9 keV. A prototype has been developed in order to investigate the performances of the ceramic GEM-based neutron detector. Several neutron beam tests, including detection efficiency, spatial resolution, two-dimensional imaging, and wavelength spectrum, were carried out at CSNS and China Mianyang Research Reactor (CMRR). The results show that the ceramic GEM-based neutron detector is a good candidate to measure the high intensity neutrons.