STUDY ON EARTHQUAKE DAMAGE MECHANISM OF AQUEDUCT STRUCTURE BASED ON DIFFERENT BOUNDARY

Numerically simulating an infinite domain foundation is an important method for solving structural dynamics problems. This paper introduces several artificial dynamic boundaries commonly used in the study of structural dynamics, and elaborates the theory and methods of the dynamic infinite element method boundary (IEMB) and viscous–spring artificial boundary (VSAB). The capacity of different boundary effects on seismic waves energy absorption is verified by establishing a layered half-space model. An irrigation aqueduct is taken as a research object. The IEMB, VSAB, and fixed boundary (FB) models are established and the Concrete Damaged Plasticity (CDP) constitutive is introduced, which is aimed at studying the dynamic failure mechanism and the rules of damage development to the aqueduct structure during the seismic duration. The results for the IEMB and VSAB show better energy absorption for the incident waves and a better simulation result for the damping effect of the far field foundation than that of the FB. Comparing the maximum displacement response rules of the three boundaries, it is seen that the maximum displacement response values of the VSAB and dynamic IEMB increased by 6%–48% and 9%–35%, respectively, over the FB. The calculation results of the VSAB are similar to that of the IEMB. The difference between the maximum acceleration response values is 2%–17% whereas the difference between the maximum displacement response values is 0.4%–19%. The IEMB studied in this paper provides a theoretical reference for large–scale building boundary treatment in structural dynamics calculations

Study on the Influence of Sudden Change of Water Level on High Fill Canal Segment

Extreme conditions will cause the water level of high fill canal segment to change suddenly, which will affect the velocity and pore pressure of the slope. In this paper, numerical method is used to study the influence of water level sudden change on seepage characteristics of high fill canal segment. HyperMesh software is used to establish the finite element model of typical high fill canal segment under complex foundation conditions. Through the combination of secondary development program and fluid-structure coupling calculation method, the fluid structure cou-pling effect of canal under sudden change of water level is analyzed in ABAQUS. The results show that when the water level changes suddenly, the pore pressure below the free water surface and the velocity near the free surface will be greatly affected

STUDY ON EARTHQUAKE DESTRUCTION MODE OF THE LARGEST CANAL CROSSING HIGHWAY BRIDGE BASED ON IEM BOUNDARY IN SOUTH-TO-NORTH WATER DIVERSION

  To study the dynamic failure mechanism and damage development law of highway bridge structure under the boundary effect in the process of seismic dynamic duration, the Wenchang Highway Bridge with the largest canal crossing in the South-to-North Water Diversion is taken as an example for seismic design analysis. Based on the finite element and infinite element coupling theory, the infinite element method boundary is introduced, the concrete damage plasticity is introduced, and the half-space free field model is established to study the energy dispersion phenomenon of waves in the boundary and the absorption effect of the infinite element method boundary on wave energy is verified. Under different peak acceleration intensities, the seismic response analysis of the bridge structure was carried out. The results show that: Under the action of selected artificial waves, the damage location of the bridge mainly concentrated in the junction of the box girder supported by the pier, the bottom of the pier and the junction of the pier and beam. The damage tends to develop downward near the bottom of the box girder. The damage at both ends of the beam extends from both ends to the middle. And the bottom and top of the pier have penetrating damage. These are weak points in seismic design. At a horizontal peak acceleration of 0.6g, in addition to damage to the pier column, damage also occurred to the bottom of the box girder. Therefore, when the horizontal peak acceleration of the seismic wave is greater than 0.6g, the failure of the bottom of the box girder is paid attention to. Moreover, the IEM boundary has a good control effect on the far-field energy dissipation of the wave, which is simpler and more efficient than the viscous–spring boundary

New evidence for ball games in Eurasia from ca. 3000-year-old Yanghai tombs in the Turfan depression of Northwest China

Three leather balls discovered in tombs IM157, IM209, and IM214 of the prehistoric Yanghai cemetery (42 degrees 48'N, 89 degrees 39'E) located about 43 km southeast of the modern city of Turfan, were AMS radiocarbon dated to the time interval between 1189 and 911 BCE (95% probability), and thus predate other currently known antique balls and images of ball games in Eurasia by several centuries. Our study approves the antiquity of the Yanghai balls, but the available data is not enough to answer the question how these balls were played. Although, their use in team and goal sport is likely, a suggested game similar to hockey, golf or polo cannot be confirmed, because no appropriate sticks were found in direct association with the balls. The affiliation of curved wooden sticks in Yanghai with ball games suggested earlier remains hypothetical, as all found sticks are noticeably younger in age, and other forms of use should be verified by future studies. Two of the three balls were found in the burials of the possible horse riders. Given that ball games from ancient times were considered an excellent form of physical exercise and military training, we suggest that balls (and ball games) appeared in the region at the same time as horseback riding and mounted warfare began to spread in the eastern part of Central Asia

Recent advances in the molecular design and applications of proteolysis targeting chimera-based multi-specific antiviral modality

Viral infections represent a major threat to human health and the global economy; however, most of the currently available antiviral drugs are not fully effective in restricting viral replication and selecting for drug-resistant variants. Targeted protein degradation technologies are promising strategies to avoid or delay the emergence of drug resistance. Among the protein degradation-based multi-specific approaches, proteolysis targeting chimera (PROTAC) is the main strategy applied in the antiviral field. In this review we will introduce the elements and mechanisms of action used by PROTAC technology, as well as the advantages of PROTACs over available antiviral drugs. We also summarize the latest progress in the application of PROTACs in antiviral research, discuss existing challenges and look into future opportunities for antiviral drug discovery

23 MHz widely wavelength-tunable L-band dissipative soliton from an all-fiber Er-doped laser

Via careful choice of Er-doped fiber length in the cavity, a widely wavelength-tunable L-band dissipative soliton all-fiber Er-doped laser incorporating a L-band optimized polarizing fiber grating device is experimentally demonstrated. The laser delivers 15.38 ps dissipative soliton pulses centered at 1597.34 nm with 3 dB bandwidth of 34.6 nm under 622 mW pump power. The pulse repetition rate is 23 MHz. After using single mode fiber at external cavity, the pulse duration is compressed to 772 fs. With nonlinear polarization rotation-based intracavity comb filter, the central wavelength of the generated dissipative soliton can be tuned from 1567 nm to 1606 nm with a spectral tuning range of 39 nm, which, to the best of our knowledge, is the widest tuning range yet reported for a dissipative soliton fiber laser working in communication band

Dynamic Damage Mechanism and Seismic Fragility Analysis of an Aqueduct Structure

The Concrete Damaged Plasticity (CDP) constitutive is introduced to study the dynamic failure mechanism and the law of damage development to the aqueduct structure during the seismic duration using a large-scale aqueduct structure from the South-to-North Water Division Project (SNWDP) as a research object. Incremental dynamic analysis (IDA) and multiple stripe analysis (MSA) seismic fragility methods are introduced. The spectral acceleration is used as the scale of ground motion record intensity measure (IM), and the aqueduct pier top offset ratio quantifies the limit of structural damage measure (DM). The aqueduct structure’s seismic fragility evaluation curves are constructed with indicators of different seismic intensity measures to depict the damage characteristics of aqueduct structures under different seismic intensities through probability. The results show that penetrating damage is most likely to occur on both sides of the pier cap and around the pier shaft in the event of a rare earthquake, followed by the top of the aqueduct body, which requires the greatest care during an earthquake. The results of two fragility analysis methodologies reveal that the fragility curves are very similar. The aqueduct structure’s first limit state level (LS1) is quite steep and near the vertical line, indicating that maintaining the excellent condition without damage in the seismic analysis will be challenging. Except for individual results, the overall fragility results are in good agreement, and the curve change rule is the same. The exceedance probability in the case of any ground motion record IM may be estimated using only two factors when using the MSA approach, and the computation efficiency is higher. The study of seismic fragility analysis methods in this paper can provide a reference for the seismic safety evaluation of aqueducts and similar structures

New evidence for ball games in Eurasia from ca. 3000-year-old Yanghai tombs in the Turfan depression of Northwest China

Three leather balls discovered in tombs IM157, IM209, and IM214 of the prehistoric Yanghai cemetery (42°48′N, 89°39′E) located about 43 km southeast of the modern city of Turfan, were AMS radiocarbon dated to the time interval between 1189 and 911 BCE (95% probability), and thus predate other currently known antique balls and images of ball games in Eurasia by several centuries. Our study approves the antiquity of the Yanghai balls, but the available data is not enough to answer the question how these balls were played. Although, their use in team and goal sport is likely, a suggested game similar to hockey, golf or polo cannot be confirmed, because no appropriate sticks were found in direct association with the balls. The affiliation of curved wooden sticks in Yanghai with ball games suggested earlier remains hypothetical, as all found sticks are noticeably younger in age, and other forms of use should be verified by future studies. Two of the three balls were found in the burials of the possible horse riders. Given that ball games from ancient times were considered an excellent form of physical exercise and military training, we suggest that balls (and ball games) appeared in the region at the same time as horseback riding and mounted warfare began to spread in the eastern part of Central Asia

Optical Fiber Interferometric Humidity Sensor by Using Hollow Core Fiber Interacting with Gelatin Film

An optical fiber Fabry–Perot interferometer (FPI) is constructed for relative humidity measurement by fusion splicing a short hollow core fiber (HCF) to the end of a single-mode fiber and coating the tip of the HCF with a layer of gelatin. The thickness of the gelatin film changes with ambient humidity level and modulates cavity length of the FPI. Humidity measurement is therefore realized by measuring the wavelength shift of the interreference fringe. RH sensitivity of 0.192 nm/%RH is achieved within a measurement range of 20–80%RH. Dynamic measurement shows a response and recovery time of 240 and 350 ms, respectively. Sensor performance testing shows good repeatability and stability at room temperature but also reveals slight dependence of the RH sensitivity on environmental temperature. Therefore, a fiber Bragg grating is cascaded to the FPI sensing probe to monitor temperature simultaneously with temperature sensitivity of 10 pm/°C