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YANG Xi, TIAN Chong, FANG Ruyi, LIU Zeyu, ZHANG Yinhang, LEI Kejun
Available online:May 19, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022353
Abstract:The classical maximum eigenvalue detection (MED) algorithm has excellent performance in detecting correlated signals. However, with the increasing signal dimensionality, the MED algorithm faces serious problems in the calculation efficiency and implementation of test statistic and decision threshold, thus greatly limiting the further application of the algorithm in modern cognitive communication systems. To this end, a low-implementation complexity MED algorithm based on a numerical analysis theoretical framework is proposed. The new algorithm uses the Rayleigh quotient accelerated power method to iteratively compute the test statistic, which has a fast convergence rate in detecting high-dimensional signals compared with the classical power method; meanwhile, different from the classical look-up table method, a threshold calculation method based on the cubic spline interpolation method is proposed, which can quickly determine the decision threshold corresponding to any given target false-alarm probability. The proposed MED algorithm effectively improves the computational efficiency and reduces the complexity of algorithm implementation while maintaining the detection performance of the original algorithm, which is particularly attractive for spectrum sensing problems in high-dimensional conditions. Finally, the simulation results demonstrate the effectiveness of the proposed algorithm.
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Available online:May 19, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022355
Abstract:A terahertz fundamental up-conversion mixer with a high local oscillator (LO)/ radio frequency (RF) and local oscillator / intermediate frequency (IF) port isolation was presented, which was in the IHP 0.13μm SiGe BiCMOS process. The mixer adopted Gilbert’s double-balanced structure, local oscillator signal was transmitted through the Coplanar Waveguide (CPW) to suppress the transmission asymmetry caused by the strong parasitic coupling effect in the transmission process, which reduced the characteristic of LO/RF port isolation deterioration caused by the asymmetry. By adopting an asymmetric switch interconnection structure, the imbalance of the parasitic coupling of the local oscillator signal at the collectors of the switching transistors was reduced, and the cancellation efficiency of the local oscillator signal at the collectors of the switching transistors was improved. And the local oscillator signal was suppressed at the port of intermediate frequency by arranging the position of the transconductance transistors in a reasonable layout. The post-simulation results show that under the power supply voltage of 2.2V, the local oscillator signal is 230GHz and the intermediate frequency signal is 2-12GHz, when the up-conversion mixer works at 218-228GHz, the LO/RF port isolation is greater than 24dB, LO/IF port isolation is greater than 20dB, the conversion gain is -4dB to-3.4dB. The output 1dB compression point is -14.8dBm with an intermediate frequency signal is 10GHz. The DC power consumption is 42.4mW, the core area of the chip is 0.079mm2.
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YUAN Yongjie, YANG Liang, CHEN Shenghai, MA Rongchang
Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022296
Abstract:Free space optical (FSO) communications offer high speed, low cost, and strong anti-interference ability. However, the atmospheric turbulence-induced fading causes deterioration in the performance of FSO communication systems. The conventional solution is to use RF links as parallel communication links to improve the system performance. On the other hand, reconfigurable intelligent surfaces (RIS) can be employed to further improve the received signal-to-noise ratio of the RF link due to its advantages of low loss, easy deployment, and no complex coding and decoding. In this paper, an RIS-assisted hybrid RF-FSO transmission system is proposed to improve the communication quality of service. Based on this hybrid model, exact expressions for the outage probability, average BER, and channel capacity are derived, and Monte-Carlo simulations are presented to verify the accuracy of the analytical results. Results show that the performance of the proposed system is significantly improved compared to the conventional hybrid RF-FSO system.
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Available online:May 17, 2022 DOI:
Abstract:The mechanism for asymmetric transmission is an important issue for enhanced sensing, amplification and asymmetric control of elastic waves. Parity-Time symmetric systems may provide a simple solution. The concept of Parity-Time symmetric systems comes from quantum mechanics, and one of its characteristics is unidirectional reflectionlessness. A PT symmetric beam for flexural waves is designed, which is based on piezoelectric shunting technology. Firstly, the PT symmetric condition is derived. Then, based on the effective medium method and finite element simulation, it is verified that the effective parameters of gain and loss unit meet the PT symmetric condition. The tunability of exception points is studied by changing the resonant frequency and the shunting resistance. Finally, the scattering property of the PT sym-metric beam is derived by transfer matrix method and finite element simulation, and the relationship between exceptional points and unidirectional non-reflection is illustrated. The calculated and simulated results show that the PT symmetric beam has several exceptional points including 511Hz and 520.5Hz. When the incident flexural waves of 511Hz is applied at the right side of the PT symmetric beam, the reflection coefficient is close to zero. However, when the frequency of the incident flexural waves changes to 520.5Hz, it should be applied on the left side of the PT symmetric beam in order to gain a total transmission without reflecting. The structure of the proposed PT symmetric beam is simple and the exceptional points of it are tunable, which can be used to achieve better asymmetric transmission of flexural wave.
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Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022297
Abstract:With the rapid development of Internet, virtual communities are emerging. While providing innovative resources, these communities also have problems such as low willingness of users to share and lack of good incentive mechanism. Blockchain can better solve these problems and promote community knowledge sharing. This paper constructs an online community knowledge sharing scheme based on Multi Chain, puts forward the resource access and storage mode of "metadata cloud storage" and designs the metadata information table in detail, designs the overall framework of the knowledge sharing scheme and the key processes of some businesses, puts forward the consensus mechanism of "Nominated Proof of Stake (NPOS) to design the blockchain network, Some functions of online community knowledge sharing are realized. Through analysis and experiment, the scheme of this paper has good scientific rationality, safety and execution efficiency, and has good reference value for the development of other related projects.
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Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022299
Abstract:Affected by suspended particles such as haze in the atmosphere,images taken outdoors often suffer from low contrast and low visibility. Existing dehazing methods fail to make full use of the local feature information of the image, and cannot fully extract the global details of the image. Therefore, there are problems such as incomplete dehazing and loss of image details. For this reason, this paper proposes a T-shaped image dehazing network based on wavelet transform and attention mechanism. Specifically, the proposed network obtains the edge detail features of the hazy image by performing multiple discrete wavelet decomposition and reconstruction on the image, and proposes a feature attention module that takes into account both the global feature and the local information extraction of the image, which strengthens the network"s learning in image visual perception and detail texture. Secondly, in the process of feature extraction, a T-shaped method is proposed to obtain multi-scale image features, which expands the network"s representation ability. Finally, perform color balance on the reconstructed clear image to obtain the final restored image. A large number of experimental results in synthetic data sets and real data sets show that the network proposed in this paper has superior performance compared with other existing network models.
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Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022300
Abstract:This paper proposes a state-sensitive event-triggered H∞ control strategy to solve the problem of unmanned ground vehicle (UGV) path tracking control under communication restriction. Firstly, the corresponding path tracking control model is established according to the dynamics of the connected vehicle. Secondly, a novel state-sensitive event-triggered communication (SS-ETC) strategy according to the state perception of path tracking in real time is proposed. Then, an event-triggered H∞ controller is designed by combining with time delay system modeling method and Lyapunov stability theory. The proposed dynamic event-triggered communication strategy based on state perception can dynamically adjust the communication threshold according to the state measurements of the control system, and effectively realize the adaptive co-design of UGV communication and control. Finally, the effectiveness of the proposed dynamic event-triggered control strategy is verified by simulation experiments.
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Chen jian, Zhuang yao yu, Yang dan, Zhang jun jie
Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022351
Abstract:Although MIMO technology can improve the utilization rate of spectrum, multi-dimensional signal processing brings great challenges to the detection of MIMO signals. Based on the analysis of various MIMO detection algorithms, QR decomposition is selected as the research object, which is a kind of nonlinear algorithm. In order to obtain higher performance of detection, the sorted QR decomposition is further studied and propose the sorting scheme based on L1-norm. Using Matlab for performance simulation, the L1-norm sorting strategy and the L2-nrom sorting strategy have basically the same impact on MIMO system, but the L1-norm sorting strategy reduces the computational complexity. On this basis, the hardware structure of improved sorted QR decomposition by Givens rotation on FPGA is proposed. Comparing with the solution of L2-norm, the L1-norm strategy reduces at least 29.2% combinational logic resources and 32.4% register resources when calculating a single column norm in the realization of 4×4 channel matrix decomposition. Comparing with similar designs, the frequency of operating clock has been significantly improved.
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wangzhenyu, Guo Yang, Li Shaoqing, Zeng Jianping
Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022352
Abstract:With the development and application of communication networks, the Internet of Things carries the safe transmission and storage of a large amount of sensitive information. Since devices are usually small in size and resource-constrained, complex security primitives are not suitable for authentication of lightweight IoT devices. This paper proposes a lightweight anonymous key shared authentication protocol for IoT devices, which generates a shared key by the physical unclonable function(PUF) and uses security primitives such as the MASK algorithm and the Hash function. The security analysis and verification are accomplished by Ban logic and ProVerif to prove that the protocol ensures security attributes such as anonymity, non-repudiation, and forward/backward confidentiality. Compared with other protocols, this protocol has the characteristics of low computing cost, small communication overhead and storage capacity, and high security performance, which is suitable for the secure communication transmission of resource-constrained devices.
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LIU Guangyu, CAO Yu, ZENG Zhiyong, ZHAO Enming, XING Chuanxi
Available online:May 17, 2022 DOI: 10.16339/j.cnki.hdxbzkb.2022354
Abstract:Sonar image is seriously polluted by noise, which leads to the problem of low precision in underwater multi-target segmentation.Therefore, an underwater multi-object segmentation technique based on self-adjusting spectrum clustering combined with entropy weight method is proposed.The technology first by self-tuning spectral clustering of sonar image pixel clustering processing, make the image is divided into multiple independent area, and then according to the characteristics of complementarity and more sections of the redundancy of the statistical information entropy characteristics, brightness, contrast, long and narrow degree, entropy weight method is used to analyse the characteristics more empowerment and the optimal selection of a target area,Then the optimal target region is matched with all regions by multi-feature similarity. Finally, all target regions are segmented automatically by adaptive threshold iterative method according to the matching results of similarity. Experimental results show that there is not over-segmented of noise interference regions, and target regions segmented have higher accuracy, which verifies the effectiveness of the proposed method.
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LU Liang1?，WANG Lei1，XIA Wanqiu1，LI Yuanqing2
Abstract:A new type of vertical seismic isolation device， consisting of hydraulic jack and accumulator （VSI-HJA）， is proposed for vertical vibration isolation of building structures. Firstly， the working principle of VSI-HJA is introduced， and the non-linear stiffness model and the energy dissipation model of the isolation system are established. Secondly， cyclic loading tests were conducted to assess the frequency dependence and displacement amplitude dependence， and the equivalent stiffness and energy dissipating parameters of VSI-HJA were measured. The test results indicate that the vertical stiffness of the device varies nonlinearly with an error within ±3% between the theoretical and experimental values， the seismic isolation device develops a full hysteresis loop， shows strong energy dissipation capacity， has velocity-dependent damping property. The test results are in good agreement with the calculated results. Finally， the effectiveness of the proposed VSI-HJA is further investigated by simulating the seismic isolation effect of structures with different device parameters using the finite element method. The research results reveal that the displacement response of the isolated structure increases correspondingly with the weakening of their vertical stiffness， while the acceleration response decreases. The isolated structure demonstrates excellent seismic isolation performance， and the vertical displacement of the isolated structure under the earthquake can be effectively controlled by the damping adjustment.
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YU Jiayong ?，YANG Yuchi，WANG Yudong，ZHOU Cuizhu
Abstract:Point cloud filtering is a crucial processing technique for separating ground points from non-ground points and obtaining the most accurate ground point cloud. It serves as the foundation for landslide identification in highway slope point clouds. To address issues such as slow processing speed， low result accuracy， and high error rates encountered by traditional point cloud filtering algorithms in slope scenarios， an airborne slope point cloud filtering algorithm based on multi-plane segmentation and matrix transformation is proposed. This method initially employs a region growing algorithm based on curvature for multi-plane segmentation of the slopes， resulting in multiple sub-point clouds of the slopes. Subsequently， it fits plane models for these sub-point clouds and uses rotation matrices to spatially transform them onto a horizontal plane. Non-ground points are separated by simulating fabric settling with a distance threshold. Finally， the inverse of the rotation matrix is applied for spatial position restoration， yielding the filtered slope point cloud. High-precision point cloud models are obtained using a fine approximation flight route design method for algorithm testing in various slope scenarios. Results are compared with those of other traditional filtering algorithms， demonstrating that the algorithm in this paper outperforms the others with total errors of 7.11%， 4.15%， 1.45%， and 4.41% in all experiments， respectively. Furthermore， the Kappa coefficient values are 0.77， 0.90， 0.96， and 0.90， all of which are the highest among all tested algorithms. The proposed algorithm exhibits high accuracy and applicability， particularly in complex slope scenarios characterized by varying terrains and vegetation cover. It offers a new solution for point cloud filtering in highway slope applications.
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CHEN Changfu1，2?，LIAO Jiahui1，2，CAI Huan1，2，ZHANG Jiarui1，2，LI Wei1，2
Abstract:Element-scale specimens of cemented soil piles were designed to investigate the mechanical characteristics of the cemented soil-soil interface with different curing ages （i.e.7， 14， 28， 35 and 60 days）. The complete curve of shear stress-displacement at the interface between cemented soil piles and soil was measured at different ages. Based on the element-scale test results， a hyperbolic evolution model was proposed to describe the development of interfacial peak shear strength and residual shear strength. Besides， to obtain the variation of compressive strength and shear strength indicators （i.e. cohesion， c and internal friction angle， φ） of cemented soil piles with curing age， uniaxial and triaxial compression tests of cemented soil samples under the same curing ages， as well as the triaxial compression tests of soil were carried out， respectively. The results showed that there was a linear relationship between the shear strength of the cemented soil-soil interface and the compressive strength of cemented soil. At last， the constitutive model of the cemented soil-soil interface of the specimen comprising curing age was established according to the experimental results and the disturbed state concept theory. The model fits well with the measured data， which provides a reliable calculation model for the theoretical analysis and numerical simulation in cemented soil pile engineering.
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TANG Hesheng1?， LI Du1， LIAO Yangyang1， LI Rongshuai2
Abstract:The optimization design of structural shapes is fundamentally a problem of solving functional extremum. Traditional variational methods often encounter challenges， such as limited functional types and oscillation in the solution process when solving high-dimensional functional extreme value problems. In this paper， a functional extremum numerical solution method based on physics-informed deep learning （PIDL） is proposed by using the high-dimensional nonlinear mapping ability of deep learning model. The method first embeds the physical information （control equations， initial conditions and boundary conditions， etc.） of the shape optimization problem as regularization terms into the deep learning model， and a loss function based on the objective functional extremum is constructed. Then， a random gradient descent algorithm is used to train the deep learning model， further realizing the solution of functional extremum and optimization design of structural shape. The proposed method is verified through numerical examples of optimizing the shape of surfaces and arch axes， and a comparative analysis is conducted with the computational results obtained from genetic algorithms. The results demonstrate that the method has high prediction accuracy and efficiency for the target task of small samples. As a non-parametric modeling technology， the method is of great significance for solving engineering problems characterized by high data acquisition costs and data collection challenges.
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HE Jia1，2?，LIAO Jiaoyu1，2，ZHANG Xiaoxiong1，2，HU Meifei1，2，ZHANG Ruiyang1，2，CHEN Zhengqing1，2
Abstract:To clarify the influence of near-ground wind fields on tracking photovoltaic （PV） structures， wind tunnel tests and Computational Fluid Dynamics （CFD） simulations are conducted in this paper for the analyses of shielding effects and shape factors under different tilt angles， wind direction angle， and height of PV arrays. Building upon this analysis， the paper investigates the impact of shielding effects of multi-row PV arrays on the values of shape coefficient under different wind direction angles. Results show that the surface wind pressure of a single-row PV component follows a trapezoidal distribution. For multi-row PV arrays， as the tilt angle increases， the shielding effects increase significantly. The shape coefficients tend to be stable when the number of upstream PV arrays becomes large. The height of their heights has a certain impact on the shape coefficient of both individual PV components and arrays.
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JIANG Fangming1，DONG Fangyuan1，YU Jiangtao1，2?，WANG Hanpeng1
Abstract:To improve the flexural properties and reduce the risk of brittle out-of-plane failure in masonry walls， ultra-high ductile concrete （UHDC） layers were introduced to strengthen the masonry members. Four-point bending tests were carried out on seven strengthened masonry members in this study. The failure mode， bearing capacity and deformability of the specimens were comparably analyzed. The experimental results indicated that ductile failure modes were achieved in masonry specimens strengthened with single- and double-sided UHDC layers， and the strengthened specimen showed ductile bending failure modes. The UHDC layers had satisfied restraint effect on masonry flexural members， which can significantly improve their flexural capacity and deformability. The increase of the thickness of UHDC layer could effectively improve the ultimate bearing capacity. The contribution of UHDC layer in tension zone to the flexural bearing capacity was less than that of UHDC layer in compression zone. Finally， the formulas of calculating the flexural capacity of masonry flexural members strengthened with single- and double-sided UHDC layers were individually proposed， providing a design basis for masonry flexural members strengthened with UHDC.
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ZHOU Yun1，ZHOU Hehong1?， WU Jiurong2
Abstract:As it is difficult to accurately evaluate the base shear force of a tall building with non-uniform mass under the equivalent static wind pressure calculated according to the load code， the vertical spatial correlation conversion coefficient ηz and mass conversion coefficient mcn are proposed to consider the effects of the difference in vertical spatial correlation between multi-degree-of-freedom and infinite-degree-of-freedom systems and non-uniform mass distribution on the base shear forces， respectively， modifying the Chinese load code method in the calculation of the wind-induced base shear forces of non-uniform mass high-rise structures. Moreover， it is validated through two example analysis， respectively. The effects of the vibration mode coefficient， building height， and geomorphology on the vertical spatial correlation conversion coefficient ηz are analyzed in terms of parameters. The results show that the vertical spatial correlation conversion coefficient ηz can reflect the effect of the difference in vertical spatial correlation between multi-degree-of-freedom and infinite-degree-of-freedom systems， and the errors in the case study considering this effect or not are 1.2% or 2.8%， respectively； the errors in the case study considering non-uniform mass or not are less than 5% or 28.5% respectively， which indicates that the mass conversion coefficient mcn can reflect the effects of the mass non-uniform distribution on the base shear forces； and the combination of two coefficients with the load code method can accurately calculate the wind-induced base shear forces of high-rise structures with non-uniform mass. The vertical spatial correlation conversion coefficient increases with the increase of ground roughness and building height， and decreases with the exponential increase of the exponential vibration mode coefficients； the minimum value of ηz in parameter analysis is 0.922， and the error can be more than 5%； without consideration of the effect of the difference in vertical spatial correlation between multi-degree-of-freedom and infinite-degree-of-freedom systems on the base shear forces， the calculation is more conservative based on multi-degree-of-freedom system. For different projects， the value of the mass conversion coefficient mcn should be calculated based on each mass and vibration mode coefficient specifically.
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LI Hongqiang1，2，3?，MIAO Sikai1，2，3，LIU Lifang4，MAO Yingjie5
Abstract:A novel multifunctional integrated solar energy utilization system is proposed in view of the lack of research on solar energy technology applied in light steel prefabricated buildings. To better analyze the performance of the system， theoretical models for generation efficiency， generation power， thermal efficiency and hot water temperature are established based on system characteristics and energy conversion relationships. The influences of design parameters including solar irradiance， capacity of hot water tank， preset temperature of hot water tank and system series quantity on electrical and thermal performance of the system are analyzed by using these established models. The results show that， to obtain higher thermal and electrical efficiency， it is essential to comprehensively consider the local solar irradiance and the required hot water temperature to determine the capacity of the hot water tank， the preset value of water temperature and the number of series and parallel connection of the system. Under given collector parameters， when the solar irradiance reaches 550 W/m2， the design requirements can be met. At this time， the hot water temperature of the high-temperature array of the system is 74.5 ℃， the thermal efficiency is 52.6%， the hot water temperature of the low-temperature array is 52.3 ℃， the thermal efficiency is 60.4%， the power generation is 58 W， the power generation efficiency is 9.46% and the comprehensive utilization efficiency of solar energy of the system is 79.1%. Compared with the experimental results of literature research， the overall solar energy utilization efficiency is increased by 30%. The proposed system provides a new idea for the design of solar energy utilization systems and integrated design with light steel prefabricated buildings in the future， which has important reference significance for the efficient utilization of solar energy.
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LIU Gang1，2，TAN Shuaishuai2，ZOU Chunrong3，CHEN Qi2
Abstract:An automatic determination method for the convergence and required posterior samples is proposed to address the problem that the multi-chain MCMC algorithm mainly relies on setting a large number of iteration steps to generate a sufficient number of posterior samples. The optimal competition strategy was introduced at the beginning of the MCMC algorithm iteration， replacing the random difference by the directional difference， so that the samples could be moved to the target direction quickly to accelerate the computational efficiency. Based on the sampling distribution theorem， a t-distribution determination index was constructed using samples within a period of time to automatically determine whether the multi-chain MCMC converged and automatically terminated the algorithm after the sample size meets the statistical requirements， so as to reduce the computational workload of the smooth period. The numerical examples and the results of the real bridge correction show that the proposed determination method can improve the computational efficiency of the multi-chain MCMC algorithm by 30% with the same calculation accuracy， and the entire iteration process can be accelerated by about 50% considering the preset step size， which provides a method to support the application of Bayesian-based finite element model correction in large civil engineering.
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Abstract:To apply ceramic concrete to engineering structural components， the bond behavior of steel bars and ceramic concrete was studied through a central pull-out test， and the bond-slip constitutive model of ceramic concrete and the prediction formula of ultimate bond strength were given. The flexural behavior of reinforced ceramic concrete beams was studied through four-point bending test， and the flexural performance was studied from the aspects of bearing capacity， deflection， longitudinal bar strain， average crack spacing and maximum crack width. The results show that the bond behavior of ceramic concrete is weaker than that of ordinary concrete， the ultimate bond strength is close to that of ordinary concrete， the rate of descent is greater than that of ordinary concrete， and the residual bond strength is lower than that of ordinary concrete. The bending process and bearing capacity of reinforced ceramic concrete beams are similar to those of ordinary concrete beams， but the average crack spacing is greater than that of ordinary concrete， and the calculation of the maximum crack width still agrees with Chinese concrete design code.
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YING Hongwei1，2，CHEN Yu1，WANG Yangyang1?，LIU Guan1
Abstract:Taking the foundation treatment of gravel pile in a proposed hydropower station as the background， an indoor experimental sample preparation method of soft clay composite samples with gravel core was developed， which can improve the consolidation efficiency of remolded soft clay and reduce the disturbance of the samples. The large triaxial tests of composite samples with different confining pressures and gravel core replacement rates were carried out. The results show that composite specimens exhibit strain hardening characteristics under small confining pressures， while they generally exhibit softening characteristics under high confining pressures， and the softening characteristics are more pronounced with a smaller gravel replacement rate. At the same confining pressure， the initial deformation modulus of the composite specimen increases with the increase of the sample area replacement rate. At high confining pressure and low replacement rate， the shear failure surface of the soft clay gravel core composite sample is obvious. At low confining pressure and high replacement rate， there is a more obvious bulging phenomenon in the middle of the composite sample. The maximum bulge amount of the gravel core generally increases with the increase of confining pressure and replacement rate. The current code method overestimates the internal friction angle of the composite specimen （foundation）， and the larger the area replacement rate， the greater the difference between the calculated values and the experimental results. Under high confining pressures， the traditional stress superposition method overestimates the bearing capacity of the soft clay vibroflotation replacement gravel pile composite foundation and underestimates the settlement of the composite foundation. The higher the replacement rate， the greater the deviation stress error between the stress superposition method and the large triaxial test of the composite sample.
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HUANG Wei1，LIU Gang1?，MIAO Xinwei2，WANG Wei1，ZHANG Chenlong1，ZHANG Hao1
Abstract:To study the failure mechanism and seismic performance of prefabricated steel reinforced concrete composite walls with steel castings， quasi-static tests were carried out on steel reinforced concrete composite walls with a scale of 1∶2. The steel reinforced concrete composite walls under low cycle reciprocating loads were contrastively analyzed on failure processes， failure modes， hysteretic characteristics， shear capacity， deformation capacity， wall damage and energy dissipation capacity by changing their built-in steel types. The experimental results showed that the steel castings used for welded structures have high strength， stiffness and safety， and can be applied to the on-site prefabricated connections of steel reinforced concrete composite walls. The overall shear failure occurred in steel reinforced concrete composite walls， and their shear capacity， energy dissipation and deformation capacities were greatly improved compared with those of reinforced concrete composite walls. In combination with engineering practice， an on-site assembly scheme for steel reinforced concrete composite walls was given.
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SHAO Xudong1，2，XIONG Manhua1，2?，HUAI Chenzi3，MO Ran4，YANG Ji3
Abstract:In order to solve the engineering problem of continuous box girder bridges with severe cracking due to excessive self-weight， a combined PC and steel-UHPC composite beam continuous hybrid girder bridge is proposed. To investigate the mechanical properties of the UHPC layer in the new type of bridge as well as its effect on the force transfer mechanism of the joint section of steel-UHPC composite girder， a Midas integral FE model was established to obtain the internal force of the structure under the design load effect， taking Binzhou Yellow River Bridge in Shandong Province as the engineering background. Meanwhile， two FE sub-models of the joint section of the steel-UHPC composite girder with and without UHPC layer were established by using ANSYS， respectively. The differences between the two models in the force performance and load transfer mechanism of the steel-concrete joint section were compared， and the mechanical properties of the UHPC layer were analyzed. The FE results show that： 1） Except for some stress concentration areas， the stresses in all parts of the new structure are lower than the strength design value， meeting the design requirements； 2） Under the most unfavorable bending moment， the maximum tensile stress of the top plate of the new structure’s steel box girder is significantly reduced， which can significantly improve the fatigue life of the steel structure； 3） The stress at the interface of the top plate of the new structural concrete beam is decreased by about 5%~29%， which can improve the cracking resistance； 4） The maximum tensile and compressive stresses of the UHPC layer are lower than their design strength， meeting the design requirements， and the UHPC layer can share 4%~10.9% of the bending moment of the joint section.
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HE Sheng1，3，QIN Yu1，QIN Danglin4，YU Peng1，2?
Abstract:To explore the effect of concrete binary mixed metakaolin and silica fume on the resistance of hydrochloric acid， the specimens were prepared according to 5% metakaolin and 5%， 10% or 15% silica fume by weight of total cementitious materials， and the immersion test of hydrochloric acid was carried out. The effects of corrosion on the thickness of the damage layer， pore structure and hydration products of concrete were investigated by ultrasonic， mercury intrusion porosity （MIP）， X-ray diffraction （XRD）， thermogravimetric analysis （TGA） and scanning electron microscopy （SEM）. Moreover， the relationship between the thickness of the damage layer and the pore structure is compared and analyzed. The results show that M5S5 has the best acid resistance based on compressive strength， splitting tensile strength and flexural strength. The thickness of the damage layer is negatively correlated with ultrasonic velocity， and positively correlated with porosity， average pore size and total pore area. The combination of metakaolin and silica fume can improve the acid resistance of concrete. However， the increasing content of silica fume slightly reduces the improvement effect.
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QUE Yun1?，DAI Yi2，XUE Bin1，ZHANG Chanlin1，MU Honglin3，YUAN Yan1
Abstract:To improve the predictive ability of existing models for predicting the compaction density of asphalt pavement， a test site was set up on the upper layer of the Xiang’an Airport Highway Project in Xiamen. The CCV， DMV and VCV， which represent the change of harmonic ratio， energy， and mechanics in the vibration and compression process， respectively， as well as the temperature， were chosen as indicators. The isolation forest algorithm was used to detect outliers in indicators. The density prediction model was established based on the partial least squares regression. The results show that the isolation forest can effectively recognize outliers of high-dimensional data， covering the shortage that traditional methods can only process one-dimensional data. There are different degrees of positive correlation between temperature， other indicators， and asphalt pavement density. The multiple regression model based on CCV， DMV， and VCV obtains better fitting ability than the unitary regression methods， proving the feasibility of multiple indicators. The partial least squares regression can restrain the adverse impact caused by the approximate collinearity between independent variables， correct the incorrect weight of temperature， and improve the fitting degree compared with the common multiple linear regression methods. The final determination coefficient of the model on the training set is 0.83， and on the test set is 0.81， indicating good predictive ability for asphalt pavement density.
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ZHU Qiankun1?，CUI Yage1，WANG Xianyu1，2，DU Yongfeng1
Abstract:The cable is a key load-bearing component of cable-stayed bridges， and its stress state is an important indicator for assessing the safety of bridge structures. Accurate measurement of cable forces is crucial to ensure the safety of the bridge. Based on this， this paper establishes a set of cable force identification system for cable-stayed bridges that can achieve long-distance， non-target， and high-precision measurements. The system utilizes an improved line segment detector （LSD） to track the cables and identify their vibration information. The valid vibration signals of the cables are then discretely extracted using the variational mode decomposition （VMD） method to obtain their frequency information. Finally， the cable forces are estimated using the vibration frequency method based on the cable’s frequency information. The accuracy and robustness of the improved LSD and the cable force identification system are confirmed through experiments conducted in the laboratory on a model with a large slenderness ratio and low pixel ratio， as well as cable force identification on a large-span cable-stayed bridge. In the laboratory experiment using a steel ruler model， the improved LSD identified the vibration information of the ruler with an error of only 0.63% compared with the laser displacement sensor. In the experiment on a large-span cable-stayed bridge， the error in the identified cable forces by the system compared with the contact sensors was less than 3.0%. Both experiments demonstrate that the proposed system can accurately identify cable forces in complex engineering field environments.
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Abstract:The Timoshenko beam model on a two-parameter foundation is presented for the flexural analysis of light type abutment in its self-plane. Its degenerating formulations and adaptability are discussed briefly. Based on the initial parameter solutions to the differential equation， the transfer matrix method is established for the Timoshenko beam on the two-parameter foundation. Based on the interpolation functions of the Timoshenko beam element， the finite element formulation of the Timoshenko beam on the two-parameter foundation is achieved. Numerical example results demonstrate that there are two phenomena found with the maximal moment position located on and deviating from the symmetrical center. Spatial finite element analyses of ANSYS are carried out and verify the phenomena. The variation laws of deformations and internal forces of the abutment in its self-plane are investigated along the tread width and non-uniformity of foundation. Given that the maximal moment position in the self-plane of light abutment deviates from the symmetrical center， the quantity is greater than that of the symmetrical center， and the moment at the symmetrical center is a local minimum， the current simplified method and design process with the center moment as the maximal result are suggested to be abandoned in many bridge engineering literature. The relevant theories need to be improved and refined. The unevenness of the foundation affects the deformations and inner forces in light abutment. The simple operation adopting the relevant parameters of the softest or the hardest foundations fails to achieve the maximum results， which is not safe for design practices.
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WANG Yan，XIAO Yifu?，SHANG Shouping
Abstract:The tensile stress of rubber bearings is critical for the design of isolated structures. To study the force state of isolation bearings after the occurrence of tensile stresses， a hypothesis of bearing lift-off behavior is proposed， and the lift-off state is summarized as a force-balanced bearing reduction system， thus obtaining a straightforward solution for the lift-off state. The concept of load equivalent eccentricity， which is suitable for measuring overturning effect， is proposed by analogy with eccentric compression members， and a conversion coefficient is adopted to express load combinations uniformly， so as to obtain a more concise expression. The analytical formulas of equivalent eccentricity， internal force and stress of bearing and overall rotation angle at each stress stage were derived. The critical average compressive stress of bearing was proposed， and the corresponding height-width ratio limits were calculated. The results show that the tensile stress of the bearing is mainly affected by horizontal earthquake action， height-width ratio， bearing performance and arrangement； in the area of 8 degrees （0.2g）， 8 degrees （0.3g）， 9 degrees （0.4g）， the limit of the equivalent eccentricity when the bearing is allowed to have tensile stress is 0.24， 0.22， 0.2， respectively， and the height-width ratio limits is 4.5， 3.5， 2.5， respectively.
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YU Yunyan1，FENG Yifan1，WANG Li’an2?
Abstract:To study the displacement response of pile foundations， the dynamic response of pile-soil interface， and the law of stress distribution in the soil around the pile when the top of the pile is subjected to horizontal transient loads， such as impact， under the condition of continuity of the pile-soil interface， the simplified model of pile-saturated soil coupling vibration is established using the Euler beam based on the Biot theory and Novak plane strain assumption. The system’s dynamic control equations are solved using Laplace transformation and potential function decomposition. The focus is on the time-domain analysis of the vibration response of the pile-soil system under horizontal triangular impact loading， including pile displacement response， pile-soil interface， and dynamic response of the soil around the pile. The research reveals that the displacement field response of the pile-soil system lags behind the stress field response. Moreover， as the pile-soil modulus ratio decreases， the effective radial stress， shear stress， and pore pressure responses at the pile-soil interface become more pronounced. A decrease in soil permeability coefficient leads to increasing pore pressure at the pile-soil interface， causing a reduction of effective radial stress. The shear stress at the pile-soil interface remains almost unchanged with varying permeability coefficients. For higher permeability coefficients， the pore pressure distribution around the pile is more dispersed， and the maximum effective radial stress occurs near the pile-soil interface. Conversely， for lower permeability coefficients， the pore pressure distribution around the pile is more concentrated， and the maximum effective radial stress occurs at a greater distance from the pile-soil interface.
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ZHANG Jingke1，2?，ZHANG Hao1，WANG Nan1，BAI Dongming1，ZHANG Lixiang1，SUO Chenyang1
Abstract:Salt solutions based on Na2SO4， NaCl， MgSO4 and their pairwise mixed salts were set up to conduct drying-wetting cycle tests on blue brick samples， and the effects of soluble salts in the drying-wetting cycles on the quality， surface hardness， elastic wave velocity and color difference of blue bricks were studied. The deterioration mechanism of blue bricks was analyzed from the perspectives of macroscopic， fine and microscopic multi-scale and mineral composition changes. The results show that the mass， wave velocity and hardness of the test all increase first and then decrease， and the hardness continues to decrease. The compressive strength and capillary water absorption rate are reduced to varying degrees. Na2SO4 causes serious damage to the surface layer and a certain depth of blue bricks. MgSO4 destroys the pores in the brick， resulting in small cracks， but it is difficult to damage the surface layer of blue bricks. In contrast， NaCl only weakly erodes the surface layer of the brick. The interaction between the mixed salts changes their location of crystallization， quantity， and solubility， then it results in different deterioration patterns. Compared with single salt， the deterioration characteristics in the mixed salt chamber are more consistent with the disease characteristics in the actual occurrence environment. The results of this research will provide a reference for the protection and restoration of related buildings of brick cultural heritage.
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YUAN Zhishen1，YAO Yao2?，SHEN Hua2
Abstract:The study on the hot spot stress distribution along the intersecting weld of circular hollow section（CHS） T-joints under in-plane bending moment was carried out. A finite element mesh model of CHS T-joints was established by radial tension method. A mesh density analysis and experimental comparison analysis were conducted on the reliability of the hot spot stress analysis results， and a basic density mesh that meets the calculation accuracy requirements was proposed. The distribution law of hot spot stress along the intersection line and the influence of geometric parameters were summarized through dimensionless geometric parameter analysis. The phenomenon of wave-crest-splitting at the crown point and three pattern of curve near wave crest were discovered during the splitting process. On this basis， by using a coefficient with a period π， a curve shape correction method and distribution curve parameter formula were proposed to correct the curve shape near the crown point. A statistical analysis compared with formulas and experimental data from two scholars at University College London（UCL） shows that the formula in this paper has a more concise expression and higher accuracy.
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PAN Qinxue1?，JIANG Shunjun1，ZHENG Jianlong1，Lü Songtao1，ZHANG Junhui1，SONG Xiaojin2
Abstract:To solve the problem of mismatch between design parameters and actual mechanical properties of pavement structure， typical cement stabilized macadam was selected to carry out uniaxial compression and direct tensile tests under different cement dosages and loading speeds. The stress-strain characteristics were studied， and the variation of compressive and tensile strength（Rc & Rt）/ modulus（Ec & Et）/ Poisson’s ratio（μc & μt） and their relationships were analyzed， revealing the different mechanical properties of cement stabilized macadam under tension and compression. The results show that the stress-strain properties of cement stabilized macadam under tension and compression are in accordance with the bilinear characteristics of bi-modulus theory. A cement dosage range of 2% to 3% is identified as the transition zone where the mechanical properties change. The tensile and compressive parameters exhibit a strong nonlinear relationship with the loading speeds and cement dosages. Among the influencing factors， the influence of cement dosage on tensile and compressive parameters is much greater than the loading speed. In terms of mechanical parameters， the modulus is most affected by cement dosage and loading speed， followed by strength， and Poisson’s ratio. Compared with compressive parameters， tensile parameters are more significantly affected by these two factors. The Ec/Et and the μc/μt are less affected by loading speed and cement dosage. The Rc/Rt decreases gradually with the increase of cement dosage. When the cement dosage exceeds 3%， the Rc/Rt tends to be stable. Based on these findings， a quantitative value model for the tensile and compressive mechanical parameters of cement stabilized macadam is established. The research results can provide a basis for the parameter value of pavement structure design based on bi-modulus theory.
Vol, , No.11, 2024
Special Issue
Virtual Special Issue中国科学引文数据库来源期刊(CSCD)
第二届国家期刊奖百种重点期刊
教育部中国高校百佳科技期刊
湖南省十佳科技期刊
