Abstract:

Abstract:The Haiyuan M8.5 earthquake occurred on December 16, 1920. Hebei, Shandong, Henan, Shanxi, and Shaanxi provinces suffered severe drought in the early 1920, and the subtropical high, which was related to the great drought, affected the western part of the drought area and had a short-and medium-term promoting effect on the Haiyuan earthquake. The microtremor generated by the Siberian cold wave prior to the earthquake was also related to Haiyuan earthquake, and the cold wave arrived in the earthquake area one day after the earthquake occurred, thus causing additional problems for the victims.

Abstract:In this paper, using seismic data recorded by the active source network of the Qilian Mountain and the digital seismic network of the Gansu Province, we relocated the Zhangye M5.0 earthquake in 2019 and its aftershock using the double-difference location and genetic algorithms. Relocation results of 30 seismic events were also obtained. These results indicated that the main position of the earthquake was 38.502°N, 100.254°E, and the focal depth was 14.7 km. The aftershocks were relatively concentrated and distributed along the Changma-Ebo fault. The source depth was mainly distributed in a range of 5-15 km, while the aftershock sequence was distributed along the SW-NE.

Abstract:Using air gun excitation signal data recorded by the active source observation system in the Qilian Mountain, travel-time change data of the P-wave phases before the Zhangye M5.0 earthquake on September 16, 2019 were obtained at each station of the observation system. Filtering, stacking, deconvolution, cross-correlation, and other data processing were performed. Clear velocity variations were found at the stations near the focal area before the earthquake. These results showed that the stress state of the underground structures in the focal area had changed in the months leading up to the earthquake.

Abstract:Fault zone head waves (FZHW) are seismic refraction waves propagating along an interface of varying physical properties. They carry abundant information about fault zones, and have provided a new method for analyzing the fine structure of the fault zone and its adjacent area. This paper mainly describes the generating principle, waveform characteristics, identification, and analysis methods of FZHW, and describes recent advances in the identification and utilization of the FZHW to analyze the characteristics of the fault zone. Aiming at fault zones with varying physical properties in a seismic risk area, fine structure detection and dynamics monitoring of a fault zone using FZHW and dense array observation technology is described. This review should improve understanding of potential seismogenic environments and mechanisms.

Abstract:In seismological research, picking speed and accuracy of seismic detection and phase identification directly affect their application efficiency and accuracy in precise seismic positioning and tomography. In recent years, machine learning has attracted wide attention in the field of seismology. Machine learning can improve upon traditional seismic detection and phase identification methods, thus achieving more accurate and higher recognition rates. In this paper, we introduced a machine learning method according to the classification of supervised learning and unsupervised learning, then summarized the flow of the machine learning method. Finally, we reviewed those machine learning methods widely used in seismic detection and phase identification, i.e., convolution neural network, fingerprint and similarity threshold, generalized phase detection, PhaseNet, and fuzzy clustering. Results showed that machine learning will be the primary means of seismic event detection and seismic phase identification. Application of data-driven machine learning in seismology combined with the physical model will be the development trend of the future.

Abstract:Overhead pipeline is a typical, long-flexible structure. Ground motions of different support are distinct due to the seismic wave propagation, seismic wave attenuation, and soil nonuniformity. To analyze the effect of differential inputs on the seismic response of overhead pipelines, seismic responses under coherence function input, traveling wave input, and uniform input were simulated and compared. An overhead pipeline model was established using the finite element software Automatic Dynamic Incremental Nonlinear Analysis (ADINA), and artificial seismic waves with coherence effects were compiled by MATLAB. Results showed that:(1) As the apparent wave velocity increased, the axial strain of the pipe decreased, which was close to the case of a consistent excitation; (2) maximum axial strain of pipelines having the same coherence function model was different with and without the consideration of site effect; and (3) for different coherence function models, the maximum axial strain of the pipeline was also distinct. It is concluded that if the site is uniform and the pipeline is short, the traveling wave method can be used for seismic input, the coherence method should be used for seismic response analysis of long flexible pipelines, and the site effect should be considered simultaneously for long flexible pipelines over an uneven site.

Abstract:The Vector Form Intrinsic Finite Element (VFIFE) method was recently proposed for structural behavior analysis based on vector mechanics. It presents great advantages over other analytical methods, especially in the complicated behavior analysis of structures. In this work, viscous damping elements were developed based on VFIFE theory and dynamic analysis of the resisting vertical progressive collapse of a plane steel-frame structure with viscous dampers was performed. A transient unloading method program was developed to realize the unity of static and dynamic analysis before and after component removal. The performance requirements of damper arrangement and parameters during vertical progressive collapse were studied, and the progressive collapse resistance for framed structures with and without viscous dampers were compared considering the vertical displacement curves of failure point, beam-end angles, dynamic magnification factor, and the plastic hinge distribution of the structure as references. The analysis results show that VFIFE is an effective method for studying the dynamic response of vertical progressive collapse of structures and that reasonable arrangement of dampers can effectively control the deformation and vibration of structures, reduce the internal force of the components, reduce the number of plastic hinges, and greatly improve the progressive collapse resistance of structures.

Abstract:This paper studied the torsional effect of inter-story isolated bi-directional eccentric structures subjected to bi-directional earthquakes. A torsion-lateral coupling analysis model of an inter-story isolated bi-directional eccentric structure under bi-directional earthquakes is presented. Nonlinear properties of both superstructure and substructure were considered. Biaxial force-deformation behavior of the lead rubber bearings (LRB) was simulated by the Bouc-wen model. The influence of eccentric parameters on the inter-story isolated structure was investigated by Matlab software. Numerical simulation was conducted to verify the accuracy of the torsion coefficient formula provided by the Chinese Code of Seismic Design of Buildings (GB 50011-2010). Results showed that the mid-isolation layer significantly reduced the coupling torsion effect of superstructure and substructure under a bi-directional earthquake. The bi-directional eccentric of substructure had an adverse effect on torsion responses. Results obtained from the Chinese seismic code were unsafe when the eccentric ratio of the substructure was too high.

Abstract:Traffic vibration has a negative impact on adjacent ancient buildings, so it is very important to determine the vibration rule when evaluating the stability of ancient architecture. In this paper, we used a vibration detector to obtain vibration data induced by vehicles driving around the ancient Great Wall. By interpreting the vibration waveforms, we determined the influence of vibration intensity on the Great Wall and the relation between various factors and vibration intensity. To evaluate the waveform results, we used the national standard for the allowable vibration in ancient buildings, which provides technical guidelines for the protection of historically valuable sites. The results indicate that the vibration attenuation law is different under different road conditions, and that vibration strength decays rapidly under good road conditions. The speed and load of driving vehicles and road quality can affect the horizontal vibration strength of the Great Wall, that is, the higher the speed, the greater the load, the worse the road quality, and the greater the horizontal vibration strength of the Great Wall. Different positions along the Great Wall respond differently to vehicle driving vibration and the horizontal vibration strength at the foot of the Great Wall is greater than that at the top.

Abstract:Nowadays, reinforced concrete components are widely used in coastal and offshore structural engineering. In harsh environments with seawater corrosion, dry-wet alternation, and extended cyclic loads, steel bar corrosion eventually leads to serious structural damage. In this paper, fatigue tests of six reinforced concrete test beams under corrosion and cyclic loading were carried out. Two kinds of cyclic loading amplitudes (2%-40% P_u and 2%-60% P_u) were designed, and fatigue failures in the atmospheric environment, freshwater environment, and corrosional seawater environment were studied. Mechanical properties and damage to reinforced concrete beams under three kinds of environments and cyclic loads, based on the evolution law of stiffness, were further explored. Failure mode, crack width, deflection development, and fatigue life were analyzed. Study results showed that under the combined action of corrosion and cyclic load, the corrosional solution did not significantly affect the internal reinforcement of the beam in the short term. Durability of the test beam as reduced by 42% within certain cyclic times, and durability of the two test beams were reduced by 54% and 37% when the upper limit of cyclic load was 0.6 P_u.

Abstract:Taking a high-rise steel frame structure building in a 7-degree seismic fortification area as the research object, the seismic technology of high-rise steel frame structure buildings based on isolated-in-place connection technology was studied. Seismic in situ connection technology was used to increase the natural vibration period of the research building by setting elastic skateboard bearings, thick rubber isolation bearings, and viscous dampers in the isolation layer, so as to reduce the influence of earthquakes on the superstructure and enhance seismic performance. Modal and time-history analyses were carried out on the research building. Results showed that the proposed isolation technology only significantly improved the natural vibration period of the structure, but also delayed the formation of torsional vibration mode, significantly reducing the influence of seismic action on the superstructure of the research object. It was shown that the studied technology has a good seismic effect.

Abstract:An earthquake may affect the integrity of building structures or cause their collapse. Recently, the damage assessment of point-supported glass building structures has been rarely investigated even though seismic damage assessment is highly valued in the field of seismic engineering. Therefore, an earthquake damage assessment model with respect to point-supported glass building structures has been constructed in this study. Further, the structural damage identification method based on the HHT transform was adopted to judge the damage location with respect to the point-supported glass buildings in case of an earthquake, and a multiple connection number model was established for conducting the seismic damage assessment of point-supported glass buildings to evaluate the damage to point-supported glass buildings. The experimental results denoted that the evaluation of the seismic damage of the point-supported glass building structure in a certain area is consistent with the actual results; furthermore, the proposed model exhibits considerable controllability and a comprehensive evaluation scope, and the evaluation efficiency is obviously better than those of the remaining evaluation models.

Abstract:The seismic pushover analysis method of underground structures is improved by applying the local deformation peak of the free field is used as the target displacement and the corresponding horizontal acceleration of the soil layer is used as the equivalent inertial acceleration input. The local peak deformation and method of determining the equivalent inertial acceleration are given, and the implementation steps, application, and functional characteristics of the seismic pushover analysis method for underground structures based on local deformation of the free field are introduced in detail. Compared with the pushover method, the proposed method considers the nonlinear characteristics of different buried underground structures and interactions between the soil and the structure. A complete ability curve can be obtained by analyzing the deformation and stress conditions to better evaluate the seismic performance of the underground structure. For validation, the proposed method and finite element dynamic analysis are performed to analyze three practical subway station structures. Results show that the proposed method is superior to the pushover method based on integral deformation of the free field in terms of stability and simulation accuracy and more consistent with the different input seismic waves. In the case of strong earthquakes, the calculation results are slightly larger than the dynamic nonlinear analysis results for deep buried underground structures.

Abstract:Today, high-rise steel-frame structures are widely used in high-rise building design. To improve the seismic performance of high-rise steel-frame buildings under earthquake action, we installed a tuned mass damper on the top of a high-rise steel-frame building structure. By considering several factors, i.e., the building space requirements, the prevention of concentrated load, and the improvement of control, we obtained the optimal stiffness and damping coefficient by setting the tuned mass damper to obtain the extreme equivalent damping ratio of the controlled structure. Then, we determined the modal mass by modal analysis of the obtained results using finite element software and achieved reduction control of the torsional vibration of the high-rise steel-frame building. The experimental results show that by using the proposed method, the peak values of angular displacement and acceleration at the top floor of building structures can be reduced by 50% and 30%, respectively, and the response of the building structure can be decreased by 19-26%, which indicates that this method can improve the stability of the high-rise building structures.

Abstract:In line with efforts to implement sustainable development, recycled concrete made from recycled concrete aggregates could be an ideal solution to preserve resources and the environment. The fatigue behavior of recycled concrete differs from that of other types of concrete on account of the different properties of recycled concrete aggregates. Therefore, using experimental research, the fatigue behavior and multi-scale analysis of recycled concrete are studied in this paper. The present paper investigates the fatigue behavior of the axial and eccentric compression performance of recycled aggregate-reinforced concrete specimens containing 0%, 50%, and 100% recycled aggregates. Then, multi-scale (micro-structural and macro-structural) observations of the specimens are obtained. Analysis of the experiment results reveals the feasibility of applying recycled concrete to practical engineering.

Abstract:Expert experience indicates that there are certain errors and generally low credibility in the assessments of the seismic safety of building structures in relic parks. To address this issue, we propose a new seismic safety assessment method for building structures in relic parks. We constructed a material constitutive model to determine the structural damage that would occur in a relic park, and obtained a local damage index of the structure using the local damage index evaluation model. Then, we calculated an overall structural damage index for buildings in relic parks based on the local damage index. Taking as an example the architectural structure of the ancient Roman ruins park, we performed a seismic safety analysis. The results showed that when the amplitude of the seismic wave reached 800 gal, the seismic safety of this park was poorest, and the degree of damage was high. The analysis results of the proposed method were highly accurate and reliable.

Abstract:To solve the problem of traditional anti-seismic crack design for building wall decoration, i.e., poor stability and a low strength reduction coefficient, a comprehensive seismic design method for building wall decoration based on the vibration method is proposed. Based on analysis of the structure of the wall used in this study, the seismic conceptual design of the building wall was carried out, and a wall structure model, oriented to data extracted, was constructed. According to the specific requirements of anti-seismic crack fortification for building wall decorations, and on the basis of an anti-seismic frame wall structure at the building bottom, the basic design method for the seismic reinforcement of wall decoration was developed. Combined with specific construction methods, the influences of stiffness, strength, and ductility of the wall structure were comprehensively considered, and the seismic cracking design of the wall decoration developed. Experimental results showed that the stability of the proposed method was 2% greater than that of the traditional method; under different densities, the maximum stress and strength reduction factors were much larger than those in the comparative method. This study fully demonstrated that, after reinforcement, improved resistance to shattering of the building wall decoration could be ensured.

Abstract:In the study of the seismic behavior of concrete cracks in drained slopes on reservoir dams, neither the degradation yield effect of shear strength parameters of rock and soil nor the aging of concrete cracks are considered. This compromises the accuracy of the results of seismic evaluation. Therefore, a method of analysis of the seismic performance of drained slopes on reservoir dams, incorporating concrete cracks, was proposed in this paper. The cracking and failure process of slope concrete under a strong earthquake was simulated, and a judgment of the concrete material yield of the gate pier, according to D-P yield criteria, was made. The thin-layer integral element and separated crack element were used to simulate the concrete crack. After loading the seismic wave, the response and failure characteristics of the concrete cracks under a strong earthquake were obtained. Results showed that the method presented in this paper was highly accurate in studying the displacement change in a dam body; the crack propagation range of concrete obtained was also accurate, indicating the utility of the proposed method.

Abstract:To improve the accuracy of analyses of the seismic performances of shear walls, in this study, we took the shear wall in a high-rise building as the engineering background. We then combined the static elastoplastic analysis method with the energy-equivalent criterion to determine the trilinear restoring force parameters of the shear wall structure along the direction of the two principal axes. Based on the parameters, we established a close layer model of the shear wall. Then, we simulated the shear wall of the building using a three-dimensional finite element model, and simulated the its dynamic time histories. The results show that with increases in the earthquake magnitude and the number of building floors, the enveloping value of the story and vertex drift angles of the shear wall obviously increase. The correct setting of the viscous fluid damper can improve the seismic response of the building shear wall. Under rare magnitude-9.0 earthquakes, the damping effect on the shear wall structure in the X direction is better than that in the Y direction. The maximum damping of the story drift ratio of a shear wall structure in the X direction is about 38%, and that in the Y direction is about 18%.

Abstract:Based on stratigraphic data from geothermal deep wells, a geological profile was plotted across the Huangzhuang-Gaoliying fault zone, and deep tectonic characteristics are discussed. Combined with existing data, research results showed that at least four transformations of the normal and reverse faults, with features of repeated concussion, occurred along the Huangzhuang-Gaoliying fault. It is held that the cause of the fault was the fracture of a regional plate, with subsequent, frequent horizontal movement of the plate changing many times, resulting in repeated transformations in tension and compression. Decline and thrusting motion of the hanging wall constantly occurred, also exhibiting features of repeated concussion. Formation age of the fault was about 106-140 million years b.p., which was late Jurassic (J₃). The later rock activity produced local extrusion and uplift, which restricted the activities of the south and north ends of the hanging wall, resulting in the phenomenon of uplift and tilt at one end. While movement of the middle segment of the upper plate was relatively more free, the average decline rate was about 3 mm per year. Based on analysis of the structural features and historical seismic records, it is suggested that the monitoring of this activity should focus on the horizontal movement of plates at both sides of the fault zone.

Abstract:According to known annual variations in the lithospheric magnetic field along the eastern segment of the Bayan Har block during the 2011-2014 period and crust stress data, the relationship between the lithospheric magnetic field and stress accumulation in the southern segment of the Longmenshan fault zone was studied. Annual variations in the lithospheric field in the local area was weaker than for surrounding areas during 2011-2012 and 2012-2013. High-stress accumulation was reflected in in-situ crust stress measurement after the Wenchuan M_S8.0 earthquake. Based on analysis of the piezomagnetic effect, it was concluded that the tectonic background of high-stress accumulation and low strain rate in the local area after Wenchuan M_S8.0 earthquake was the main factor controlling the weak variations in the lithospheric magnetic field. Additionally, the horizontal component of the lithospheric field in the area of the epicenter became weak before the Lushan M_S7.0 and Kangding M_S6.3 earthquakes. Both magnitude and direction of the horizontal vector for the 2012-2013 period differed across the surrounding area, which may be a precursor of two earthquakes.

Abstract:Based on observation data from three kinds of ground tiltmeter at Yichang Seismic Station (water tube tiltmeter, VP vertical pendulum tiltmeter, and VS vertical pendulum tiltmeter), China, tidal response functions, non-tidal parameters, and seismic responses were compared. Results showed that:(1) the M₂ wave tide factor for three kinds of tiltmeter in the N-S direction was generally smaller than that in the E-W direction, because the former was easily affected by the local observation environment. Tide rates of three kinds of tiltmeter in the E-W direction were slightly larger than those in the N-S direction. The daily drift of the VS tiltmeter was the largest, followed by that of the VP tiltmeter and the water tube pendulum. (2) The three kinds of tiltmeter were all easily influenced by the observation environment. The data generated different noise, and the performance difference of the three instruments caused synchronous observations. To distinguish the real information of crustal deformation, interferences in the observation data should be removed in order to mutually verify the physical quantities.

Abstract:To obtain accurate assessment results on the earthquake monitoring capability of Liaoning seismic network, analyze the spatial and temporal distribution characteristics of earthquake monitoring in Liaoning province and its neighboring regions, and provide scientific basis for seismic network optimization, the probability-based magnitude of completeness (PMC) method was first applied to the Liaoning seismic network. To investigate the seismic detection capability of 37 stations in Liaoning seismic network, this research selected the seismic observation report and station information from January 2010 to December 2017. The results show that the PMC method can objectively reflect the capability of stations to detect earthquake events. Stations around the old Yingkou-Haicheng seismic region exhibit higher detecting capability for earthquakes with smaller magnitudes. Given the network distribution, stations at the edge of Liaoning province present lower detecting capability. The spatiotemporal distribution characteristics of minimum PMC (M_P) demonstrate the following values:1.2 ≤ M_P ≤ 1.5 in Shenyang-Liaoyang-Benxi-Anshan-Panjin area of central Liaoning; M_P ≥ 3.0 in Dalian area of south Liaoning; and 2.5 ≥ M_P ≥ 1.8 in other areas of Liaoning. The study results indicate that to further strengthen the monitoring capability of Liaoning seismic network, more stations should be constructed in east and southeast Liaoning to increase station density. Furthermore, the introduction of Hebei-shared stations in west Liaoning can increase the detecting capability of the study area.

Abstract:With the development of complex velocity structure inversion and improvements in high-performance computational power, it has become possible to calculate accurate 3D strain Green tensors (SGT) by means of high-resolution 3D earth models. Due to more uniform distribution and better point source effects, small-to-moderate earthquakes are widely used in local-scale waveform-based tomography. As it is known, waveform-based tomography methods like wave-equation tomography and full waveform inversion (FWI) require focal mechanism solutions during the whole inversion procedure. However, traditional focal mechanism inversion methods are not very suitable to small-to-moderate earthquakes. In this study, we first used the finite differential method to construct a strain Green tensor (SGT) database and filtered the synthetic and actual waveforms in different frequency band ranges. We then relocated the earthquakes by minimizing the cross-correlation travel time differences, and, next, inverted the focal mechanism by minimizing the waveform residuals. Finally, we used this SGT database method to inverse the focal mechanisms of a series of M_W3.4-5.7 earthquakes in the Longmenshan fault zone, between the eastern margin of the Tibetan plateau and the western part of Sichuan basin. The results indicated that the proposed method can be applied in (near) real-time inversions of focal mechanism solutions since the database can be pre-constructed.

Abstract:Regular calibration of radon-measuring instruments is key to ensuring the accuracy and reliability of measurement results. Based on the internationally recognized measuring instrument AlphaGUARD P2000F and its own water raft measurement components, calibration experiments were carried out on three sets of DDL-1 ionization detectors using dissolved radon in water. The experimental and calibration results with the solid radon source were compared with those of the out-of-factory results. It was found that the relative errors of the K values of the two calibration methods were less than 5%, which meets the requirement of current seismic monitoring techniques. These results showed that the solution of dissolved radon in water, compared with the solid radon source, solved the problems of transportation difficulties, high technical maintenance requirements, strict supervision of national environmental protection departments, etc., and defined a new approach to the calibration of seismic radon observation instruments.

Abstract:A certain correlation exists between geomagnetic curves observed by different geomagnetic stations when the space environment, instrument failure, and other factors are excluded. Electromagnetic properties change, however, during the seismogenic process of strong earthquakes. Thus, the correlation between the geomagnetism of different geomagnetic stations will also change. Therefore, the identification of geomagnetic anomalies before the occurrences of earthquakes can provide useful information for earthquake prediction. In this work, we analyzed the geomagnetic precursor anomalies that occurred prior to the Minxian-Zhangxian M6.6 earthquake in 2013. Analytical results revealed the abnormal phenomenon of low-point displacement at 36 days before the M6.6 earthquake. In addition, an anomaly was identified through the spatial correlation analysis of daily geomagnetic Z values. A good correspondence between the correlation coefficient and earthquake epicenter was observed. The intensity of geomagnetic stations has a considerable influence on the correlation coefficient of the calculated area.

Abstract:The effects of structure-soil-structure dynamic interaction on structural system frequency were studied using the indirect boundary element method. Numerical analysis showed that, compared to those of stand-alone structures, the structure-soil-structure dynamic interaction may increase or decrease system frequency. The influence degree was about 5% under vertical SH incidence and 3% under vertical SV wave incidence. With increasing distance between structures, the effects on the structural system frequency did not show a monotone decrease, which was related to the dynamic characteristics of the site and structure. These results suggest that more attention should be focused on the fact that the influence of structure-soil-structure dynamic interaction on system frequency may affect monitoring results of structural health.

Abstract:Reasonably and effectively simulating pile-soil-structure dynamic interaction is important in the seismic response analysis and foundation treatment of the nuclear island building over soft ground conditions. In this paper, based on the actual project of a proposed nuclear island plant, the contact effect between the pile and soil around the pile was simulated with the Goodman element, and the nonlinear characteristics of the near-field soft soil foundation are described by equivalent linear method. At the bottom and side of the model, the viscous boundary was introduced to simulate the radiation damping effect of the semi-infinite ground, so that the analysis model for the pile-soil-nuclear island structure interaction was established under the condition of the soil foundation. Furthermore, by comparing and analyzing the floor response spectrum and relative displacement (absolute value) of structure nodes under conditions of the original foundation and rock-socketed pile foundation, respectively, the influence of the rock-socketed pile foundation, considering the contact effect between the pile and soil on the nuclear island building, was analyzed. The results can provide some reference for the foundation treatment of nuclear island structures under similar soil foundations in practical engineering.

Abstract:To analyze the horizontal dynamic responses of a pile considering the interaction between the pile and surrounding soil, the layered soil resistance coefficient method, which is based on the Winkler model, is widely used in engineering. Shear action of soil around piles is neglected in this method, which does not correspond with engineering practices. Also, application of the transfer matrix method or central difference method in resolving the dynamic response of variable cross-section piles, such as belled piles, wedge piles, etc., has some challenges. This paper proposes an approximate calculation method for the horizontal dynamic response analysis of piles based on the Pasternak model and the Adomian decomposition method, in which shear actions of the soil around the pile were considered. The method has a simple solution procedure and is suitable for the problems of variable cross-section piles. Using this method, the horizontal dynamic response of the belled pile and influencing factors on this response were analyzed. Results indicated that the expansion radius and elastic modulus of the soil around the upper pile had an important impact on the horizontal dynamic response of the pile. In addition, the amplitude of the horizontal vibrational displacement of the pile gradually decreased with increasing radius of the expansion and elastic modulus of the soil around the upper pile. Also, the shear action of soil on the pile should be taken into account under low frequency load excitation.

Abstract:The plastic deformation characteristics of permafrost are the key to understand the stress response state and the degradation of overload. The topic is also an active research area in the field of permafrost engineering and geotechnical engineering in recent years. Based on a triaxial test, the physico-mechanical parameters of soil layers, such as -1℃ and -2℃ permafrost soil elastic modulus; cohesion; and internal friction angle under 9%, 12%, and 15% water content conditions, were used to establish a typical railway embankment. The plastic deformation law of the railway subgrade in the permafrost region subjected to natural earthquake loads under temperature increase and strength degradation was analyzed. The results show that with increasing temperature, the frozen soil degraded. At the foot and subgrade center, plastic deformation at -1℃ was greater than that at -2℃. The plastic deformation of the left and right slopes followed a symmetric distribution law. The soil temperature of the typical railway subgrade was raised from -2℃ to -1℃. In 9% moisture content, the plastic slope of the soil layer was 3.5 times larger in the left slope and 4.9 times in the right slope. Moreover, the 12% water content test showed that the plastic strain in the soil layer was 1.6 times larger in the left slope and 2.5 times in the right slope. The tested soil layer with 12% moisture content under permafrost degradation showed good stability, and under the same stress conditions, the plastic deformation increased minimally.

Abstract:The Wangjiadun landslide in Qin'an County of Tianshui City passes through the Qin'an tunnel and is a giant ancient landslide group along the Baoji-Lanzhou PDL. This study selects the Wangjiadun landslide to assess the static and dynamic anti-sliding stability problems in the project. Internal factors such as geological structure and site engineering condition, which affect the stability of the Wangjiadun ancient landslide, are evaluated through laboratory tests and field investigation. The dynamic response of the Wangjiadun ancient landslide under seismic load is analyzed by dynamic finite element method. The dynamic anti-sliding stability is studied using the combination of dynamic finite element method and strength reduction method. Displacement mutation is employed to determine the dynamic instability and dynamic safety factor of the slope. Results show that the horizontal thrust of the earthquake has a great influence on the stability of the Wangjiadun ancient landslide. The effect is represented by the overall slip of the upper slope and the collapse of the loess deposit in the entrance section of the tunnel. In the natural state, the slope is in the stable state. In the event of strong earthquakes in the region in the future, the slope will be unstable. The overall sliding surface of the loess slope is most likely to occur in the third slope body, along with the sliding surface with the maximum plastic strain. The safety factor F_S is 0.92.

Abstract:The residual deformation behavior of dam inverted filler was investigated by means of a medium dynamic triaxial test. On this basis, numerical simulation was carried out using the two-dimension particle flow code. Based on comparison and analysis, some conclusions are summarized as follows:(1) Stress level has no effect on the slope of the relationship curve; (2) initial values of volumetric strain are smaller; (3) overvaluing confining pressure and dynamic stress will produce rather large simulation errors; (4) the correct microscopic parameters should be obtained according to results of specific triaxial tests.

Abstract:Accumulative deformation characteristics of red clay in southern Jiangxi, China, subjected to drained cyclic triaxial loading, were investigated at different cyclic stress ratios, confining pressures, and consolidation ratios. Results indicated that the accumulative strain of red clay showed a tendency, first, toward rapid accumulation, then slow growth, and finally, stability under different cyclic stress ratios, confining pressures, and consolidation ratios. After a certain number of cycles, the cumulative strain and cycle number under different initial consolidation stress levels and initial stress ratios showed a linear relationship, with the smaller the initial consolidation stress and initial stress ratio, the better the linear correlation. There was also an obvious linear relationship between the average cumulative strain rate and the number of cycles under different cyclic stress ratios. Based on the relationship, the cumulative deformation prediction model under long-term cyclic load was established for red clay in southern Jiangxi, and feasibility of the formula was verified by comparison.

Abstract:In this paper, based on the geological and geomorphological characteristics of western Taiwan and the results of the 1999 M_W7.6 Chi-Chi earthquake, we established a 3D velocity structure model and source model to simulate the near-fault pulse-like ground motion generated by the Shuantung fault using the 3D finite-difference method. Results showed that the double-sided velocity pulses caused by the directivity effect were mainly concentrated perpendicular to the fault sliding component, while the single-sided velocity pulses caused by the fling-step effect were concentrated parallel to this component. Due to mutual modulation of the directivity and the hanging wall effects, the near-fault pulse-like ground motions reflected an asymmetrical zonal distribution, and the velocity pulses were mostly distributed within a range of about 10 km from the fault plane. Characteristics of the asperities influenced the temporal and spatial distribution of the ground motions, and the seismic wave field showed that Nantou and Taichung are in the risk region for strong ground motion. The study of near-fault pulse-like ground motion has significance for analyzing the mechanism of velocity pulse, earthquake prevention and disaster reduction, and seismic hazard.

Abstract:Since high-rise buildings are prone to collapse under the action of earthquakes, thus seriously affecting people's personal safety, prediction of seismic safety distances of high-rise buildings is very important. A prediction system for seismic safety distance of high-rise buildings, with a basic database as the core, was designed in this study. Basic data of height, width, and structural type of a set of high-rise buildings was collected through a basic information system, and then stored in the seismic damage database system. The seismic hazard model analysis system, based on the basic information of the buildings stored in the database system, first analyzed the seismic hazard, then calculated the safe, protective distance by studying the height of the upper structure of the weak layer under three landing states. Experiments showed that, under the action of artificial seismic waves, a sketch map of safe, protective distances of high-rise buildings in the experimental area was effectively obtained through the prediction system. The safe distance of "flying stone," as well as the distribution and main influence ranges of seismic safe protective distances under three kinds of seismic waves were accurately analyzed. The predictive power of this method was good.

Abstract:To ensure public safety and protect property, the presence of urban commercial building shelters is very important. Decisions regarding the spatial layout of and division of responsibility for indoor emergency shelters involve several factors, i.e., population density, building environment, evacuation methods, and so on. To date in China, the design of these shelters and research in their regard has been limited, and the safety of personnel in commercial building is at stake. In this paper, we propose a spatial design for indoor earthquake emergency shelters located in commercial buildings. To realize evacuation efficiency, we designed an optimal zoning model for a shelter based on the P-median model. After model calculation and analysis, we obtained the optimal position of the isolation layer in a commercial building, and designed the interior space of an emergency shelter. Lastly, we determined the practicality of the design by analyzing the accessibility of the shelter. The results of the simulation experiment prove that the emergency shelter designed in this study is accessible to a wide urban area, can serve a large number of people, and demonstrates good performance.

Abstract:Yinchuan City is located in the core earthquake belt of northwest China, where earthquakes occur frequently. Under rapid development of urbanization, due to the high density of the domestic population, earthquake emergency shelter allocation should be regarded as a key study component of community disaster prevention and mitigation planning. In this study, based on the current community spatial structure and demand for a community earthquake emergency shelter, we established a community earthquake emergency shelter allocation model using the LA model theory and GIS spatial analysis. We selected the Yulin Lane community in Yinchuan City as a case study to test its effect. Results showed that, when the length of the refuge route reached 700 meters, the shelter service area could cover all the demand points. Following optimization of the allocation model, the current shelters could satisfy the shelter demands of 90% of the residents in the community. We suggest that the local government should increase effective shelter space to better meet demand. These results can offer a theoretical basis for the optimal allocation of shelter facilities for disaster mitigation planning in urban earthquake-prone communities.

Abstract:To be effective, the assessment of earthquake disaster loss must be timely and reliable with respect to the real-time situation of the earthquake disaster area, improve the reaction capacity of the victims of destructive earthquakes, and meet the requirements of the emergency command. To improve the accuracy of assessments of earthquake disaster loss, remote-sensing images are processed by filtering and local gray-level adjustment. In this paper, we propose the identification of earthquake damage loss based on the template matching of remote-sensing images. To do so, remote-sensing images of the earthquake zone are acquired, then template matching is conducted with respect to the deviations between the acquired and template images. The eigenvalue of the feature region is extracted, and the imaging values of the spatial grid points are obtained. In this way, the earthquake disaster loss can be automatically evaluated according to the referenced imaging points, whereby the points with maximum energy indicate where the earthquake damage loss is greatest. Using this approach, the damage characteristics of the whole earthquake disaster area can be determined and extracted. The simulation experiment results show that the proposed method can extract the earthquake disaster loss and provide a preliminary reference for its assessment, although further study is needed to improve the general applicability of the proposed method.

Abstract:To optimize the safety and environmental protection performance of green steel structure buildings, the seismic and environmental protection performances of a 40-story, steel-braced frame structure were analyzed. According to the actual building parameters, a profile of the green steel structure is presented, and the variations in horizontal displacement with time under different seismic waves were recorded using a time-history analysis method. Based on the Pushover analysis method, the base shear force and elastic-plastic deformation of special-shaped, square, concrete-filled steel tubular (SCFT) columns were analyzed under rare earthquakes conditions. Results of the comparative experiments lead to the following conclusions:the special-shaped SCFT building columns met national requirements for seismic performance. Compared with reinforced concrete and brick-concrete structures, green steel structures can effectively save water and electricity consumption during construction and reduce construction noise, and show strong earthquake resistance and excellent environmental protection.

Abstract:To prevent re-damage caused by the inadequate reinforcement of post-earthquake construction projects, provide reasonable suggestions for reinforcement and repair projects, and promote the smooth performance of post-earthquake disaster relief work, in this paper, we present our research on the reinforcement and repair methods used to address concrete defects in post-earthquake construction projects. First, we arranged concrete beam and concrete column specimens for testing and conducted cyclic load tests of these specimens using two types of reinforcement methods:carbon-fiber-reinforced polymer (CFRP) and enveloped steel. Then, based on the hysteretic curves, skeleton curves, ductility, and energy dissipation of the concrete beam specimens, we analyzed their seismic performances after they had undergone different reinforcement and repair methods. Lastly, based on the ductility, energy dissipation, stiffness degradation, and load-bearing degradation of the concrete column specimens, we analyzed their seismic performances after they had undergone different repair and reinforcement methods. The test results show that a high reinforcement ratio can improve the hysteretic characteristics of concrete beams, concrete beams strengthened with enveloped steel exhibit high hysteretic saturation and little energy consumption, and beams strengthened with CFRP can restrict loading displacement from 10 mm to 30 mm. Strengthening the CFRP can improve the ductility of concrete columns, and strengthening enveloped steel can restrain the degradation of stiffness and bearing capacity of these columns. The test results verify that CFRP reinforcement can improve the ductility of concrete structures in post-earthquake construction projects, and enveloped steel reinforcement can restrain the degradation of stiffness and bearing capacity of concrete structures.

Abstract:Dynamic control of the projected cost of building groups in post-earthquake restoration and construction stages is more changeable than during other stages. Pre-control systems with high precision and flexibility are needed to ensure that there is no deviation in projected cost. In this paper, a dynamic pre-control system of projected cost in the restoration and construction stages of a post-earthquake building group was designed. Relevant personnel entered the system interface through the user login module. In the project information management module of the system, an improved genetic algorithm was used to develop the projected repair cost model of the building group as part of the overall system design. Experimental results showed that the dynamic cost pre-control system, based on an improved genetic algorithm, effectively realized dynamic cost pre-control in the restoration and construction stage of the post-earthquake buildings. With increasing number of cost samples, the error rate gradually decreased; moreover, the flexibility of pre-control was always >95%, and the use practicability was only 0.04. This system can provide a reference for cost control of post-earthquake construction.