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RISS 인기검색어
- 검색키워드
- 저자 : Ruijun Liang (검색결과 3 건)
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Distribution of Shear Coefficient of Multi-story Buildings Subjected to Near-fault Ground Motions
Wuchuan Pu,Ruijun Liang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.9
In static seismic design, the strength demands of structural members are decided based on the expected shear force in a seismic event. A reasonable shear force distribution pattern leads to a reasonable configuration of structural parameters and thus makes the structure behave as expected in the design stage. In current seismic codes, the shear force distribution patterns are established based on the elastic response of structures subjected to ordinary far-fault ground motions. Because structural responses induced by pulselike near-fault ground motions are substantially different from the responses induced by far-fault ground motions, shear force patterns specified in current codes are not suitable for the structural design against near-fault ground motions, and a shear force distribution pattern considering the near-fault effect should be established. This study aims to investigate the characteristics of shear coefficients resulting from near-fault ground motions and to provide a new shear force distribution pattern specifically for seismic design against near-fault ground motions. To achieve this goal, dynamic time history analyses are performed on elastic shear models based on 50 near-fault ground motions, and the shear force distributions are analyzed statistically. Findings from the study reveal that the higher modes contribute substantially to the shear coefficient, and the contribution is affected by the pulse period of the ground motion and the structural damping. The shear coefficients for floor levels 2/3 of the way up the height of the structure are significantly larger than code-specified values, if the structure has a limited damping ratio. Based on the numerical results, an empirical formula of the shear coefficient pattern is proposed. In this formula, the effects of damping ratio and period ratio are taken into account, and it can be used to derive shear coefficients more suitable for structures subjected to pulse-like near-fault ground motions.
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Wang, Hucheng,Long, Ruijun,Liang, Juan Boo,Guo, Xusheng,Ding, Luming,Shang, Zhanhuan Asian Australasian Association of Animal Productio 2011 Animal Bioscience Vol.24 No.6
The objective of the present study was to examine whether yaks possess any adaptive mechanisms of nitrogen (N) metabolism to survive in the harsh foraging environment of the Qinghai-Tibetan Plateau. A grazing experiment on native alpine meadows was conducted to determine availability of herbage biomass and body weight (BW) change of yaks over the year, followed by two indoor feeding trials to investigate adaptation mechanisms of N metabolism in yaks fed at similar intake level to grazing conditions. Three castrated males of each of three genotypes; yak (Bos grunniens), indigenous cattle (Bos taurus) and their crossbred - cattleyak (Bos taurus male${\times}$Bos grunniens female), were used in the housed trials. Results showed that: i) Monthly herbage biomass production and daily grazing intakes by yaks over the year ranged from 220 to 4,664 kg DM per ha, and 1.90 to 8.50 kg DM, respectively. For about seven months each year, yaks suffer from malnutrition as a result of inadequate pasture conditions; ii) Urinary N excretion and N retention by yaks were significantly affected by feeding level, and yaks had a lower (p<0.05) average daily urinary N excretion (0.39 g/kg $BW^{0.75}$) and a greater (p<0.05) N retention (-0.09 g/kg $BW^{0.75}$) than indigenous cattle (0.47 and -0.16 g/kg $BW^{0.75}$, respectively). Fasting daily urinary N excretion was greater (p<0.05) for indigenous cattle than yaks (353 vs. 248 mg/kg $BW^{0.75}$). Purine derivative N excretion and purine derivative N index (PNI) increased with increasing feeding level, while the value of PNI was greater (p<0.05) for yaks and cattleyak (0.11 and 0.12, respectively) than for indigenous cattle (0.09) during the feeding trials. These results suggest that yaks could rely, in part, on the recycling of N to adapt to the harsh forage environment on the Qinghai-Tibetan Plateau.), were used in the housed trials. Results showed that: i) Monthly herbage biomass production and daily grazing intakes by yaks over the year ranged from 220 to 4,664 kg DM per ha, and 1.90 to 8.50 kg DM, respectively. For about seven months each year, yaks suffer from malnutrition as a result of inadequate pasture conditions; ii) Urinary N excretion and N retention by yaks were significantly affected by feeding level, and yaks had a lower (p<0.05) average daily urinary N excretion (0.39 g/kg $BW^{0.75}$) and a greater (p<0.05) N retention (-0.09 g/kg $BW^{0.75}$) than indigenous cattle (0.47 and -0.16 g/kg $BW^{0.75}$, respectively). Fasting daily urinary N excretion was greater (p<0.05) for indigenous cattle than yaks (353 vs. 248 mg/kg $BW^{0.75}$). Purine derivative N excretion and purine derivative N index (PNI) increased with increasing feeding level, while the value of PNI was greater (p<0.05) for yaks and cattleyak (0.11 and 0.12, respectively) than for indigenous cattle (0.09) during the feeding trials. These results suggest that yaks could rely, in part, on the recycling of N to adapt to the harsh forage environment on the Qinghai-Tibetan Plateau.
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Damping enhancement of the inerter on the viscous damper in mitigating cable vibrations
Hui Gao,Hao Wang,Jian Li,Zhi Hao Wang,Youhao Ni,Ruijun Liang 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.1
This paper systematically investigates the effect of the inerter on the damping enhancement of a cable with a viscous damper (VD) installed close to the cable end. Three cases are considered, including the inerter installed parallel with the VD (PVID), the inerter placed in series with the VD (SVID), and the inerter installed at a higher location of the VD (HVID). The asymptotic solutions of the three cases are derived, which can predict the cable modal damping ratio when the inerter and the VD cause minimal perturbation in the undamped frequency of the cable. The effect of the inerter on the modal behavior of the cable with the VD is investigated. Based on the constrained static output LQR method, the effects of the inerter on the damping enhancement of the VD in mitigating cable multi-mode vibrations are further evaluated. The results show that the inerter can improve the control performance of the VD when the inertance is less than the optimum value. Further increasing the inertance beyond the optimum value, the optimum modal damping ratio of the cable decreases, and mode crossover is observed for the cable with PVID and HVID. Compared with the case where the VD and the inerter are located at the same location, the case of the HVID is more effective in mitigating cable multi-mode vibrations.
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