Abstract:It is necessary to effectively input seismic motion on artificial boundaries to accomplish finite element simulation of the soil-structure dynamic interaction model subjected to seismic load. There are two kinds of seismic motion input methods commonly used in engineering and scientific research, including the wave input method and the vibration input method. The wave input method exhibits high simulation accuracy; however, its implementation is relatively complicated and is time-consuming. Further, the vibration input method is simple to process even though it exhibits low accuracy. In this study, a new method is proposed to provide the seismic motion input on stress-type artificial boundaries. By imposing the displacement-time history of the free field to the local substructure, containing nodes on the artificial boundaries and adjacent nodes in the soil-structure interaction finite element model, and by performing dynamic analysis, the equivalent seismic loads used to accomplish the effective input of the seismic load were directly obtained. The equivalent seismic loads were imposed on the nodes of the artificial boundaries for performing dynamic analysis. At this point, the seismic motion input and seismic response analysis of the soil-structure dynamic interaction problem were completed. When compared with the original wave input method, the proposed method avoids the complex calculation processes associated with the free field stress on the artificial boundaries and the additional forces caused by the artificial boundaries; further, it also does not require to define the directions of the loads based on the external normal directions of the artificial boundaries. The new method concisely determined the equivalent seismic loads and provided the seismic motion as input. The validity and reliability of the new method were preliminarily verified using the one-dimensional seismic response examples of homogenous elastic half-space and layered half-space.

Abstract:A coupled model of a double-line subway train-track-foundation soil was established on the basis of 2.5D FEM to study the vibration isolation effect of the isolation trench during double-line subway operation.The model addresses the problems introduced by the simplification of track structures into an Euler beam on an elastic foundation and introduces the dynamic parameters of the actual rail.The model was used to analyze the vibration isolation effect of the isolation trench on the surrounding foundation under double-line subway train load.The vibration damping characteristics of open and in-filled trenches were compared, and the trench factors that influence isolation were systematically analyzed.Results showed that under the double-line subway load, the in-filled trench had better isolation and engineering practicality than the open trench.The in-filled trench can exert a good damping effect even with a reduced ditch depth.In addition, the isolation effect can be improved by increasing the depth and width of the in-filled trench.The results of the present work can provide useful reference for the vibration isolation design and construction of double-line subways in the future.

Abstract:Previous seismic retrofitting methods for high-rise buildings have focused on the strengthening of the buckling-resistant bracing of the concrete structures in the post-earthquake stadium; however, they seldom consider the energy dissipation performance of joints in different parts of the structure, resulting in a poor strengthening effect. It is necessary to study the measures for strengthening the concrete structures to improve the restoration quality of the post-earthquake stadium. In this study, the energy dissipation brace structure of concrete is reasonably arranged using the performance- and demand-based energy dissipation design methods. The buckling-resistant energy dissipation braces are installed at joints on the bottom floor of the concrete structure, and viscous dampers are installed at other joints to improve the seismic absorption and reinforcement effect of the structure. The simulation results denoted that the average top drifts of the new energy dissipation structure designed by this method was 62 and 110 mm smaller than those of the original structure under EL-Centro (NS) and Newhall waves, respectively; under earthquakes of different magnitudes, the displacement angle between the nodes of the new structure was smaller than that in the original structure. The concrete structure designed using the proposed method exhibited strong seismic absorption stability, indicating that the proposed energy-dissipating design method is effective in seismic reduction and structural reinforcement.

Abstract:The effect of through-reinforcing rebar on the bearing capacity of the shear connectors of the hybrid bridge is not considered when the Nishiumi algorithm is used for analyzing the ultimate bearing capacity of the joint sections of hybrid bridges under earthquake action; therefore, the analysis results of ultimate bearing capacity are considerably different from the actual results. A new analysis method has been proposed in this study with respect to the ultimate bearing capacity of the joint sections of a hybrid bridge under earthquake action. Further, the ultimate bearing capacities of the stud-type and the RC column-type shear connectors were obtained through analysis and calculation, and a new ultimate bearing capacity analysis test was designed. Using the design of the shear connector specimens, the seismic loading of the specimens, and the test arrangement, the ultimate bearing capacity of the shear connector in the joint sections of a hybrid bridge was analyzed under earthquake action. The analysis results exhibited that the proposed method can accurately analyze the ultimate bearing capacity of the shear connector in the joint sections of a hybrid bridge under earthquake action; the analysis results were almost the same as the measured results and exhibited a difference of less than 7%.

Abstract:In this work, the theory of the coseismic displacement field is first considered in the aseismic design of tunnels. We estimate earthquake dislocation in the engineering area by collecting historical earthquake rupture data. The coseismic displacement field around the tunnel is calculated through the splitting nodes method and applied in combination with the pseudostatic method in the aseismic design of a highway tunnel in Yunnan Province. Results show that the method based on coseismic displacement for the aseismic design of tunnels can provide a powerful quantitative analytical tool for the estimation of possible future earthquake disasters. If the natural vibration period and bedrock response spectrum are unknown, the coseismic displacement field can be used to estimate the far-field shear strain when conducting the quasistatic aseismic design of the tunnel. The forced displacement of the north and south segments of a tunnel in Yunnan is approximately 6 cm if earthquakes occur along the Longling-Lancang Fault Zone. If earthquakes occur along the Longling-Ruili Fault, forced displacement will cause reverse movement in the north and south parts of the tunnel. These movements will exert a pronounced shear effect on the middle of the tunnel, and lateral and vertical differential movements in the tunnel will intensify.

Abstract:In this study, a new test method is proposed to address the problem of low accuracy associated with the test results of the current seismic performance test methods with respect to concrete structures. A function family was obtained using the wavelet function, and a wavelet transform was carried out on the analog seismic signals. When the function family constituted a standard orthogonal basis, the seismic signal was reconstructed from the continuous wavelet transform. After denoising, the seismic signal was considered to be a signal sample for verifying the seismic performance of a concrete structure. The displacement response, velocity response, acceleration response, and restoring force were obtained using a dynamic equilibrium equation exhibiting a single degree of freedom. Further, the strength reduction coefficient and the maximum elastic response of the concrete structure were calculated. The experimental results exhibited that the proposed method can effectively test the seismic performance of concrete structures with a high accuracy.

Abstract:Subway tunnels built in longitudinal inhomogeneous formations will inevitably cause the differential settlement of the underlying soil because of the cyclic loading of trains. Differential soil settlement, in turn, adversely affects the safety of existing tunnels. An analytical solution for the effect of differential foundation settlement on the vertical deformation of existing tunnels and that considers the tunnel shear effect was proposed. The existing tunnel was assumed as a Timoshenko beam resting on a Winkler foundation. The two-stage approach was used to analyze the tunnel response caused by differential soil settlement. First, the dynamic deviator stress caused by the cyclic loading of trains was determined, and static deviator stress and failure deviator stress were calculated by using soil mechanical indexes. Second, the cumulative settlement of the soil underlying the tunnel was calculated by using the empirical equation of cumulative plastic strain and then transformed into the force imposed on the underlying shield tunnel. Finally, the differential equations for tunnel vertical deformation accounting for the shear effect of tunnel were established on the basis of Timoshenko beam theory. Then, the analytical solution was obtained through calculation, and the tunnel internal forces, including tunnel bending moment, shear force, rotation angle, and dislocation between adjacent rings, were further obtained in accordance with the proposed analytical method.

Abstract:This work applies the finite element analysis software ANSYS to establish a finite element analysis model of hyperbolic cooling towers. The model is used to explore the mechanical properties of hyperbolic cooling towers under the action of self-weight, wind load, and earthquakes and to investigate the effect of local opening on the overall and local strength of the tower. The influences of the size and height of the opening hole on the stress distribution of the whole tower and local opening holes are analyzed. Results show that under the action of wind load, the displacement of the cooling tower is large, and wind load acts as the control load of the cooling tower. The opening has negligible effect on the overall strength of the cooling tower within a certain size range. A pronounced stress concentration effect, however, exists around the hole. The stress concentration effect around a hole with a height of 90 m is lower than that around a hole with a height of 15 m but cannot be ignored.

Abstract:A procedure for determining the ground motion parameters of a dam site located on a deep overburden layer that meet the relevant codes in Europe and America is presented. The KH pumped storage power station in Israel is taken as an example. First, the peak ground acceleration and design response spectrum at the bedrock are determined on the basis of SI 413-2013 and the seismic zoning map in Israel. Then, five seeded recorded ground motions are selected on the basis of the geological conditions of the dam site. The input acceleration time histories, peak accelerations, and response spectra of the bedrock for the upper reservoir and reservoirs can be determined on the basis of the five ground motions. Second, site response analysis is performed by using the 1-D elastic wave propagation program SHAKE. Then, the average peak acceleration, average response spectrum, and time histories of response acceleration at the surface of the overburden layer are obtained. Finally, the average response spectrum and peak acceleration in the horizontal direction at the foundation surface are obtained by smoothing the obtained average response spectrum and peak acceleration in accordance with ASCE 7-05. The presented method can retain the real dynamic characteristics, including duration, phase, and frequency, of input ground motion. Thus, this method can be used as an effective and efficient alternative to seismic analysis in geotechnical practices in China.

Abstract:The load-settlement characteristics of a single-pile composite foundation with steel pipe piles are studied through field tests and numerical simulation with the aim of strengthening the weak foundation of a passenger-dedicated line tunnel and understanding the stress state of the pile foundation after reinforcement. The variation rule of side friction, axial force, and bending moment of the pile body are also discussed. Results show that the P-S, S-lgt, and S-lgp curves obtained through field tests lack distinct feature points that are useful for determining ultimate bearing capacity. The characteristic value of the ultimate bearing capacity is 200 kPa in accordance with the code. Numerical simulation can be used as a necessary supplement to field tests in accordance with the total settlement of steel pipe piles in numerical simulation and the normalized curve of load settlement. Numerical simulation results show that the axial force distribution of the pile body has a D-shaped pattern and a maximum value of 59.8 kN. Negative skin friction resistance falls in the range of 2 m from the top of the pile with a maximum value of 130 kPa, and the rest of the pile exhibits positive friction resistance with a maximum value of 50 kPa. The neutral point of the pile is not unique. A small bending moment exists in the upper part of pile body, and its influence on the stability of the steel pipe pile can be neglected.

Abstract:Geo-encased stone columns are novel types of columns wrapped in layers of geosynthetics. They retain the excellent performance of stone columns and fully exploit the tensile properties of geosynthetics, which can improve the rigidity, shear resistance, and drainage effect of stone columns. However, few studies have focused on the liquefaction of sandy soil reinforced by geo-encased stone columns. In this work, shaking table tests on the liquefaction of sandy soil without reinforcement, reinforced with geosynthetic-encased stone columns, or reinforced with stone columns are carried out to investigate and compare the anti-liquefaction performances of the reinforcements. Results show that during vibration loading, the geo-encased stone columns consistently maintained their integrity and good drainage performance. Compared with those of the non-reinforced foundation and the foundation reinforced with stone columns, the total settlement values of the foundation reinforced with geosynthetic-encased stone columns decreased by 50% and 31.8%, respectively. Moreover, the amount of discharged water of the foundation reinforced with geosynthetic-encased stone columns increased by 33.3% and 16.6%, respectively, relative to those of the non-reinforced foundation and the foundation reinforced with stone columns. Excess pore water pressure in the foundation reinforced with geo-encased stone columns has drastically reduced, and sand liquefaction does not occur in lower portion of the foundation. The drainage performance of the foundation reinforced with geo-encased stone column tends to improve as the vertical depth of the soil increases. The seismic performance of geo-encased stone columns is better than that of stone columns.

Abstract:The shear tests of compacted loess with different dry densities were conducted using two different sample preparation methods (pre-humidification and humidification) to study their influence on the shear strength index of the unsaturated compacted loess. The results of this study exhibit the presence of critical moisture content that affects the cohesion and friction angle of the loess in the pre-wetting sample preparation test. When the moisture content of the sample was lower than the critical moisture content, the shear strength increased with increasing moisture content; however, when the moisture content of the sample was higher than the critical moisture content, the shear strength decreased with increasing moisture content. Further, the shear strength index generally increased with the increasing dry density of the sample. During the wetting sample preparation test, the cohesion continuously decreased with increasing moisture content, and the friction angle initially increased and subsequently decreased with increasing moisture content. When compared with the pre-wetting sample, the reduction degree of the moisture content to the friction angle decreased. It can be observed that the sample preparation method significantly influences the cohesion of the unsaturated compacted loess. When the moisture content of the sample was lower than the critical moisture content, the cohesion of the wetting sample was larger than that of the pre-wetting sample; however, when the moisture content of the sample is higher than the critical moisture content, the cohesion of the pre-wetting sample is larger. It can be considered that the wetting sample exhibits a similar "barrel effect"; the pre-wetting sample is related to the overall level of the sample. The research results exhibit a certain reference value for further applicability of the shear strength index of the unsaturated loess.

Abstract:The relationship between strength parameters and critical sliding surface is established to complete derivation in the analysis of seismic performance parameters of slope reinforcement based on the traditional Swedish method. In this work, a novel method for the analysis of the seismic performance parameters of slope reinforcements is proposed to improve the seismic performance of slope reinforcements. The upper-bound limit analysis method based on polar slice and nonlinear Mohr-Coulomb failure criterion is used to analyze the influence of slope reinforcement measurements on slope seismic performance. Slope seismic behavior is determined through the calculation of different energy powers in the presence and absence of reinforcement measures, and the optimal solution for the seismic performance parameters of slope reinforcement is obtained by using MATLAB software. Experiments prove that the potential failure range of the slope is greatly affected by loading on the top of the slope and the reinforcement of the slope. High seismic load coefficients and nonlinear coefficient are associated with the low nonlinear strength of soil and the intense effect of seismic load on slope seismic performance. The optimal seismic support orientation of slope antislide pile is located at X_F/L_x=0.7. When the seismic load increases from 0 to 0.2 with the nonlinear coefficients of 1.2, 1.4, 1.6, and 2.0, the seismic performance of the slope decreases by 40.1%, 46.8%, 57.5%, and 61.5%, respectively. The new seismic performance parameter analysis method can effectively improve the accuracy of results, and the seismic performance of slope reinforcement can be accurately analyzed.

Abstract:The sand cushion exhibits the characteristics of convenient material selection, low cost, and simple construction. To better promote and apply the sand cushion isolation technology to the foundation of rural building construction, large-scale shaking table tests of foundations with sand cushion isolation systems and non-isolation systems were performed to study the performance of the foundation isolation system with a sand cushion by making the structural model of the rural houses. Based on the structural acceleration response, structural displacement response, and structural strain response, the seismic isolation performance of the foundation isolation system with a sand cushion was studied by comparing the non-isolation and isolation test results of the cushion isolation system. The results exhibited that the foundation isolation system with a sand cushion can effectively reduce the seismic acceleration response, story drift response, and strain response of the superstructure and achieve a good isolating effect. The magnitude of the input ground motion is an important factor that influences the isolation effect of the foundation system with a sand cushion.

Abstract:This work investigated the seismic response characteristics of a free field in soft soil through a large-scale shaking table test. The seismic response characteristics and failure mechanism of the soft-soil free field were studied from several aspects, i.e., the natural vibration characteristics and subsidence displacement of the model system and the acceleration and dynamic pore pressure ratio of measurement points at different soil depths. The boundary effect of the laminar shear model box was also analyzed to verify the rationality and effectiveness of the soil box system and to test instrument performance. The effective working area of the model foundation was then further determined. Study results showed the following:(1) The characteristic frequency of the saturated soft-soil free field decreased and the damping ratio increased under seismic load. (2) The saturated soft-soil free field exerted short-term filtering and long-term amplification effects on horizontal input seismic waves. Moreover, under strong seismic loads, the failure foundation absorbed and isolated shock. (3) The peak pore pressure ratio of the saturated soft-soil free field was located in a shallow buried soil layer. The advantage of dynamic pore pressure ratio in this area gradually weakened as the input ground motion intensity increased. This research can provide the necessary technical experience for experimental studies on non-free-field soft soil.

Abstract:A comprehensive technology for accelerating the post-earthquake restoration of subgrade road slopes is proposed. The technology is based on root-pile reinforcement and foamed lightweight soil technology, and restoration is performed in accordance with subgrade earthquake damage and the influence analysis results of the geological environment of the subgrade slope. The three-dimensional finite-difference method is used to simulate the restored subgrade slope and to obtain parameters. Then, the design parameters of the optimized root piles are acquired by combining the stability coefficients of the subgrade slope calculated through the strength reduction method. Finally, the post-earthquake subgrade is comprehensively restored. Simulation experiments reveal that the optimal root-pile spacing is 25 cm.

Abstract:Controlling subgrade settlement is essential in highway engineering. Subgrade settlement has a linear and nonlinear relationship with its influencing factors. Over-fitting easily occurs in traditional neural network modeling in the presence of numerous input independent variables and results in the low prediction accuracy of the network model. This work aims to address these issues. Thus, the ability of the genetic algorithm to optimize the weight and threshold of the neural network is investigated, and the influence of the set of genetic parameters on the output results is discussed. Experiments with the proposed method show that the optimized BP neural network has higher prediction accuracy and better prediction effect than the traditional neural network model in the simulation of measured data for the Chengdu-Nanchong Highway. The prediction method can be used as an effective auxiliary means for predicting the long-term settlement of highway subgrades.

Abstract:In this study, we analyzed the records of 30 earthquakes recorded from 11 stations in the China Digital Seismographic Network (CDSN) during 1993-2012. We could observe a PKPdif phase at the epicentral distance from about 120°. The travel-time of a PKPdif wave was shorter than that of a PKIKP wave in the epicentral distance range of 120° to 150°, but longer for epicentral distances of more than 150°. We regarded PKPdif waves as diffracted PKP waves with a long period at the inner core boundary. We discussed the cause and propagation mechanism of PKPdif waves and proposed an assumption, in agreement with the Jeffreys model that a low-velocity layer of a PKIKP wave exists at a depth range of 5 156.1-5 372.2 km under the Earth's surface. We suggested the kinematic characteristics of the PKPdif waves recorded by the CDSN stations. We defined the relationship between the PKPdif travel-time and the epicentral distance, which filled the gap in the current "IASPEI1991 Seismological Tables". We constructed a travel-time table of PKPdif waves within an epicentral range of 119.4° to 176.1°. We also discussed the kinematic characteristics of PKPdif waves to better understand the physical properties of the ICB, improve phase identification, and accumulate analytical experience regarding the seismic phase.

Abstract:The first step to realize earthquake early warning is to pick P-wave arrival time quickly, accurately, and automatically. In the current automatic methods of picking up P-wave arrival time, the anti-interference ability needs to be encountered; thus, in this study, the short-term average/long-term average (STA/LTA) method for detecting amplitude changes is proposed for picking up P-wave arrival times. The study shows that compared with the Allen algorithm, the amplitude change can be used as the characteristic function to highlight the mutation feature of seismic wave arrival time. Moreover, using the STA/LTA method, the pick-up deviation of seismic wave arrival times caused by the interference can be reduced. Analyses of anti-interference in the STA/LTA method and Allen algorithm show that in the presence of a large amplitude interference, the Allen algorithm cannot pick up P-wave arrival times because the peak value does not appear in the P-wave first arrival position; however, the anomaly in the P-wave arrival time position is still obvious when using the proposed method. Under less amplitude disturbance, the two methods are used to pick up the P-wave arrival time of 160 M_S ≥ 4.0 earthquakes, and the accuracy of the new method is slightly higher. The new method can be seen as an extension of the STA/LTA transform method.

Abstract:Active faults are not only the original causes of earthquakes but are also the most serious earthquake damage experienced by areas along fault lines. Casualties in areas along fault lines are greater than those in areas on both sides of faults. Thus, active seismic fault exploration and seismic hazard assessment within urban areas are crucial. These approaches can help us understand the characteristics and hazards of active faults in specific areas and enable us to take targeted measures for earthquake prevention and disaster reduction to reduce the severity of urban earthquake disasters. In this work, shallow crustal structures and buried active faults in the northern region of Wuzhong, Ningxia were studied through the shallow seismic exploration method. Several high-resolution shallow seismic reflection lines were deployed to determine the position and depth of active faults and the extension direction, possible activity, and shallow features of buried faults. The results of this study showed that two buried faults exist in the study area:the southern part of the main Yinchuan Fault and Xinhua Bridge Fault. The southern part of the main Yinchuan Fault may be a W-trending normal fault with a nearly NS direction. The strata of the footwall of this fault show a horizontal distribution pattern. In the hanging wall of this fault, layer T_Q and the following strata are inclined toward the direction of the fracture surface, which exhibits reverse drag phenomenon. The southern part of the main Yinchuan Fault breaks up the Quaternary Interior. The drilling geological section and the result of shallow seismic exploration jointly revealed that the Xinhua Bridge Fault is a SE-trending normal fault. Deep and shallow seismic data illustrated that the Xinhua Bridge Fault extends for approximately 9 km and breaks up the T₀₂ interface in the Quaternary Interior.

Abstract:Xiadian Fault is one of the main faults in the North China Plain. Few studies, however, have focused on the southwestern segment of Xiadian Fault. In this work, the shallow seismic prospecting method was applied to study the spatial location, characteristics, and activity of the southwest segment of Xiadian Fault. Three shallow reflection profiles were detected within the depth of 480 m. The seismic data acquisition system USES STRTAVISOR NZXP96 is produced in the United States and has the advantages of high resolution and anti-interference. Moreover, the data acquisition method of small track spacing and additional channels were adopted in this study to detect structures over an extensive depth range and obtain high-resolution detection results. An extended permutation test was performed for the selection of reasonable data acquisition parameters. The working parameters of the seismic section were finally determined through experiments and comprehensive analysis. The seismic wave was stimulated with a 70 kg impact ramming source, which was excited 18-20 times at each point. Data processing was performed with Vista2D/3D seismic processing software. Results showed that the southwest segment of Xiadian Fault consists of three flower-like faults with depths of 280 m and bandwidths of 50-60 m. The faults disrupt the Upper Pleistocene strata and terminate upward at the depth of 96-116 m. The active age of the faults is from the early to the middle stages of the Late Pleistocene.

Abstract:The basic characteristics of vertical and horizontal displacements of the ground surface cannot be effectively simulated, and the obtained results of dislocation characteristics of ground rupture are inaccurate, when using a Trimble GX 3D ground laser three-dimensional scanner to analyze the dislocation characteristics of normal faults in interbedded cemented soil. To address this issue, this paper proposes a new method to study the dislocation characteristics of seismic surface fractures of normal faults in interbedded cemented soil. First, the elastic dislocation model of the earthquake surface was constructed, and the three-dimensional fault characteristics of the normal fault in interbedded cemented soil were analyzed to obtain the surface dislocations. Surface rupture dislocation characteristics of normal faults in interbedded cemented soil were then studied through the centrifuge test. The experimental results showed that the proposed method can effectively analyze the dislocation characteristics of the seismic surface fractures of normal faults in interbedded cemented soil. The fracture depth of the fracture point in the middle and lower parts of the soil model were 22.4 m and 33.4 m, respectively. The fracture was deeper with the fracture point in the lower part of the soil model.

Abstract:In China, the use of strong motion records to study the earthquake fortification of engineering sites has become inevitable with the accumulation of strong motion records. In this work, the strong motion records for southwest Yunnan Province for the period of 2007 to 2011 and the horizontal-to-vertical spectral ratio (H/V) method were used to study several influencing factors in strong motion recording. Results reveal the existence of considerable differences between strong motion records and microtremor records when the H/V method is applied to develop site effects. Strong motion records can be used to acquire additional information on the earthquake epicenter and station site parameters but are more difficult to use than noise because they are more complex than the noise records. The domestic and international findings for site effects obtained by using strong motion records are compared. Next, the potential problems encountered in the use of strong motion records are analyzed. Some suggestions for the investigation of site effects by using strong motion records are provided.

Abstract:To investigate the markedly thermal infrared anomalies in epicentral areas before and after the Qingchuan, Sichuan M_S5.4 earthquake on September 30, 2017 and the Lintan, Gansu M_S4.3 earthquake on October 31, 2017, in this study, we collected TBB data from China's geostationary meteorological satellite FY-2G and analyzed the data and spectra using the wavelet- and relative-power-spectrum transform methods. The results show that the thermal infrared anomaly range of the Qingchuan earthquake is mainly distributed in the southeast of the epicenter, and that power spectrum enhancement occurs about four months prior to the earthquake and lasts for about two months. The thermal infrared anomalies of the Lintan earthquake are mainly distributed southwest of the epicenter, with an anomalous enhancement phenomenon occurring about 20 days prior to the earthquake. With the passage of time, this anomaly range expands further southwest. These anomalies begin to shrink and weaken 14 days before the earthquake, and last for about 30 days. A comparison of the two earthquakes shows that there are many common characteristics in their thermal anomalies, which can provide significant reference information for determining the seismic precursor characteristics of moderate-strong earthquakes.

Abstract:This paper used a template matching technique to detect missing earthquakes of the Qilian, Qinghai M_S5.2 earthquake that occurred on November 23, 2015. In existing catalogs, aftershock sequence data, especially from the short time after the main shock, are usually huge so we detected continual waveforms one day after the mainshock. In that day, the seismic network recorded 62 aftershocks, including single-station earthquakes. In this study, we chose 30 M_L>1.0 aftershocks as the templates, and finally found 31 missing earthquakes after detection, which was about 0.5 times the number given by the network catalog. According to the linear fitting relationship between frequency envelope difference amplitude and magnitude, we estimated the magnitude of detected events. We then compared the minimum magnitude of completeness (M_C) before and after detection within one day of mainshock, and found that the minimum magnitude of completeness was reduced from M_L1.2 to M_L0.7, showing that the minimum magnitude of completeness in the Qilian area of the Qinghai Seismic Network was about M_L0.7. In addition, the b value of seismicity decreased slightly after the detection, and the results showed that the b value decreased markedly within a short time after the mainshock. Using the template matching method can effectively reduce the number of loss events caused by the earthquake coda wave interference, and improve the capability of seismic detection. The b value of further accurate calculations of earthquake aftershocks can help us better track earthquake activity.

Abstract:A safety shutdown is required to avoid a nuclear leak when a nuclear power plant encounters an earthquake that exceeds the design earthquake. The peak ground acceleration (PGA) is conventionally used as the early-warning parameter for nuclear power plants shutdown. However, the PGA cannot reflect the characteristics of frequency and duration of ground motion records; therefore, unnecessary shutdown of nuclear power plants may occur. To solve this problem, it is necessary to conduct further research on the selection of early-warning ground motion parameters. In this paper, based on a large amount of actual strong motion records in China, seven typical ground motion parameters are selected and then compared based on the seismic intensity measure. The results show that compared with other parameters, the standard cumulative absolute velocity (CAV_STD) can better reflect the potential of an earthquake to damage a nuclear power plant; thus, it can be appropriately used as the early-warning parameter for nuclear power plant shutdown. Moreover, two methods are proposed to determine the threshold values of CAV_STD. The threshold value of CAV_STD is suggested by considering the characteristics of strong motion records in China. The results can provide reference for the determination of seismic safety parameter of nuclear power plant shutdown in China.

Abstract:The current algorithm for road selection in an earthquake zone is calculated in the form of a single individual that is prone to the problem of roadblock overlapping. Thus, a road selection algorithm based on the vehicle Internet of things is designed to address roadblock overlapping. The topographic pheromone is calculated on the basis of the distributed algorithm steps, and the optimal transit road algorithm model of the automobile Internet of things is constructed. The optimal traffic road pheromone trend is calculated, and the repeated road segment information is calibrated. The obstacle grid is constructed, and the optimal road for the whole path is selected. The expansion of the road selection in the earthquake zone and the road selection algorithm for the earthquake zone are completed. Experimental data show that the proposed algorithm can be used to select the optimal road in earthquake-prone zones.

Abstract:Strong earthquakes may result in secondary disasters, such as building fires, which involve several factors. The traditional mathematical models that are used for assessing the fire risk ignore the randomness and fuzziness of different factors observed in the existing buildings after the occurrence of strong earthquakes, leading to low evaluation accuracy. To solve this problem, a mathematical model was established using a fuzzy mathematics method for assessing the fire risk in existing buildings after the occurrence of strong earthquakes. Further, the factors influencing the occurrence of fire in existing buildings after a strong earthquake were analyzed, and a fire risk assessment system was established for the existing buildings after a strong earthquake. The factors belonging to each layer in the evaluation index system were graded according to their influence on the factors of upper layer. The judgment matrix was further established, and the weight was obtained. The factor and comment sets required for assessing the fire risk in the existing buildings after the occurrence of strong earthquakes were obtained by determining the membership matrix. Single factor evaluation was further performed to realize first-grade fuzzy evaluation. The first-grade evaluation result was considered to be the single factor for performing second-grade evaluation. The fire risk assessment of the buildings after the occurrence of strong earthquakes was completed using the fuzzy mathematical analysis. The experimental results denoted that the proposed model is more suitable for real-life situations and more accurate when compared to other models.

Abstract:The current model for the post-earthquake economic loss assessment of buildings has low evaluation accuracy and efficiency. In this work, the neural network method is improved, and the application of the LM-BP neural network in the post-earthquake loss assessment model of buildings is proposed to resolve the problem of the easy production of the local extremum by the single neural network. The input sample elements are five factors that affect the post-earthquake economic loss of buildings, and the output samples are the evaluation results of the post-earthquake economic loss of buildings. The LM-BP neural network is used to transform the training set into the least-squares problem, and the number of hidden layer nodes is redefined through combination with the LM algorithm. The model based on the LM-BP neural network for post-earthquake economic loss evaluation is constructed and used to obtain the optimal evaluation results for the post-earthquake economic loss of buildings. Simulation results show that the minimum evaluation error of the proposed model is 0.1%. Given its high accuracy, the proposed model is a more reliable model for the assessment of the post-earthquake economic loss of buildings than other models.

Abstract:The current method for the multi-factor cost control of post-earthquake reconstruction projects has low control accuracy because it ignores the deviation caused by the factors that affect project cost. Therefore, the multi-factor model based on the gray model for the cost control of post-earthquake reconstruction projects is necessary. In reference to the factors that affect the cost of reconstruction projects, we analyze the schedule deviation caused by the absence of management procedures for post-earthquake reconstruction projects, the quality deviation caused by the influence of design capability, and the price deviation caused by the instability of supply and demand in the construction materials market. In addition, we calculate the deviation coefficients caused by various factors and obtain results for the overall deviation of reconstruction projects with increased accuracy. The cost control constraint function is constructed and used in combination with the gray model, and the multi-factor cost control model of the post-earthquake reconstruction project is then established. Experimental results show that the model has high accuracy, low deviation from the actual value, and high credibility. The model can reduce project costs when used in the omnidirectional dynamic management of reconstruction projects.

Abstract:To evaluate the seismic performance of masonry structures based on Building Information Modeling (BIM), we (1) analyzed the requirements for seismic performance improvement of masonry structures from four aspects, (2) calculated the seismic capacity with the strength and ductility of such a building structure, and (3) constructed an evaluation index system of seismic performance for masonry structures. On this basis, a fuzzy judgment matrix of the seismic performance indexes of masonry structures was quantitatively calculated using triangular fuzzy numbers, and the single-level sequence of seismic performance indexes was analyzed by calculating the fuzzy comprehensive value of seismic performance. Combined with calculation of the index weight coefficient and the single-item score of the seismic performance evaluation system, a BIM-based seismic performance evaluation of masonry structures was ultimately realized. Combined with analysis of a simulated project, the seismic performance of a masonry structure was tested with the collapse probability of the structure, while the accuracy of the proposed method was tested by the fitting degree of evaluated results and actual results. The results showed that the proposed method not only has good seismic performance, it can also accurately obtain the seismic performance evaluation results of masonry structures.

Abstract:While using the assessment model of the degree of earthquake damage to buildings based on deformation and accumulated energy consumption, the buildings were divided into five state levels, and the environmental performance of the buildings was not studied, resulting in large errors in the evaluation results. A building information modeling (BIM)-based assessment model was designed in this study for evaluating the degree of building damage after an earthquake. The BIM-based evaluation method of the building environment was used to study the environmental performances of buildings. On this basis, the damage evolution equation was obtained based on the Mazars damage model of concrete under the triaxial condition, and the increment equation of damage evolution was obtained when the strain was greater than the damage threshold. Further, the concrete damage assessment model was constructed. It has been experimentally proved that the building structure is generally intact when the peak acceleration of the earthquake is less than 0.31g; however, when the peak acceleration is 0.61g, the building earthquake damage index exceeds 0.8, and the building collapses. The average error of the designed model was less than 0.03; the average evaluation time was 2.86 s, indicating that the designed model can effectively assess the degree of earthquake damage for a building and that the accuracy and efficiency are relatively high.

Abstract:The traditional cost control method exhibits several problems, i.e., nonsimultaneous quality and cost optimization, low cost prediction accuracy, and poor cost control effect. Therefore, a method based on BIM for the cost control of reconstruction projects is proposed in this work. The gray system theory is used to forecast the concrete problems associated with construction cost, and the construction cost-related information data of each period is used as the model data base. The dynamic model of cost control is constructed in combination with BIM technology. Then, the relative importance of each cost index is set by introducing a discernibility matrix. The relationship between the different indexes of construction cost is further investigated, and the rules underlying the connection between subcost and total cost are obtained. The control strategy is developed in accordance with the identified rules, and the cost control dynamic model is adjusted to dynamically control construction cost. Experimental results show that the cost prediction accuracy of the proposed method consistently exceeds 75% and that the fitting degree between the cost control result and the actual value reaches 95%. The proposed method has better control performance than the currently applied method.

Abstract:Methods based on system dynamics for controlling the cost of house reconstruction have poor control effects because they lack processes for the collection and processing of post-earthquake building cost data and cannot control cost links in depth. A method for the cost control of post-disaster housing reconstruction in earthquake disaster areas is studied, and the cost control model for building reconstruction based on BIM technology is introduced. The model can be used to budget the cost of construction projects. Based on the budget results, BIM technology is used to collect cost data, and the BIM data platform is then used to store and control the collected cost data. The cost of post-earthquake building reconstruction can be controlled effectively by using the cost control system, and the financial ERP system can be applied to control each cost link to optimize costs. Experimental results obtained by using the proposed method reveal a small gap of approximately 1 000 RMB between the budget cost and the actual construction cost. After controlling all costs, 11.91% of the original budget cost is saved. The proposed method has a good cost control effect and can effectively reduce the costs of building reconstruction projects in earthquake-stricken areas.

Abstract:Due to the lack of well-designed human-computer interaction in the contemporary earthquake simulation system, problems arise that the user cannot resolve in a timely way, resulting in an inaccurate feedback system. An improved design method of human-computer interaction for earthquake simulation system is proposed, and an entire interactive-flow earthquake simulation system was constructed. Data transmission between keyboard and display, and user instruction transmission were accomplished through the design of 4×4 key and LCD interface circuits. The script and code of human-computer interaction were designed by introducing virtual reality technology, leading to the fully-developed earthquake simulation system. The experimental results showed that the stability and accuracy of the human-computer interaction mode of the designed earthquake simulation system were 98.9% and 99.6%, respectively. This system can effectively actualize successful human-computer interaction in earthquake simulation.

Abstract:To solve the problems associated with traditional air conditioning and ventilation systems in roadways, i.e., low accuracy of information acquisition, poor performance, and poor environment of anti-seismic roadway, a new air conditioning and ventilation system in anti-seismic roadways has been proposed in this study. First, the overall system architecture was divided into the acquisition layer, the control layer, and the supervision layer. With the main controller as the core, the executive components of the system were accurately judged, and the components were uniformly controlled to complete the hardware design of the system. Subsequently, the information treatment process of the central server was created. The operation instructions of the fan were set, and the environmental information, such as wind speed, was actively collected to obtain the actual loop. The set value and the actual value were compared to determine whether the fan was normally operated. Based on these procedures, the system software functions were developed. The experimental results exhibited that the system can effectively improve the seismic roadway environment when earthquakes of different magnitudes occur; the information acquisition accuracy of this system is as high as 85%, which completely verifies the applicability of the system.

Abstract:Rock collapses along highways in earthquake-prone areas are hazardous. Dangerous post-earthquake rockfalls on high-steep slopes on both sides of highways are difficult to investigate through the traditional contact survey method given their concealed nature. In this work, an oblique photogrammetry technology based on unmanned aerial vehicles (UAVs) is proposed. The technology involves the deployment of a UAV at an ultralow altitude to collect the high-definition image data of high-risk rock masses. Then, it constructs a three-dimensional space model to extract the characteristic parameters of dangerous rock masses. These parameters can provide data support for the stability analysis of dangerous rock masses. The UAV is utilized to investigate a geologically hazardous section of a highway that had experienced a highly dangerous rock collapse. The oblique photogrammetry results of the UAV are then analyzed. The characteristics of dangerous rockfalls and the formation mechanism of rock collapses in the survey area are analyzed to evaluate the stability of typical dangerous rockfalls. Rockfall software is used to simulate and analyze the movement track of typical dangerous rockfall collapses, and the danger posed by rock collapses to highways is studied. The results of this work provide important references for the investigation and evaluation of high-level dangerous rock collapses along mountain highways in earthquake-prone areas.

Abstract:The reason why the three strong earthquakes (the 1975 Haicheng, the 1976 Horinger, and the 1976 Tangshan earthquakes) occurred at the same period is discussed in this paper based on the relationship among the seismic activities along the seismic zone in north latitude 40°. The energy transmitted from the 1975 Haicheng and the 1976 Horinger earthquakes which first occurred on the seismic zone made the seismogenic energy accumulate in Tangshan area; while the energy of another NE-trending creep slip fault in lower crust transmitted to Tangshan fault and unlocked the fault, then the Tangshan earthquake occurred. The trigger action of seismic waves was another reason. Besides the direct trigger of fault plane, the accumulation and adjustment of single seismic wave in the combined mode will also act as a trigger. In addition, the synchronization is also discussed from the cycle of 25 yeas of the M=8 earthquakes in China.