最新刊期
卷 46 ， 期 3 ， 2024
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Creep characteristics of silty mudstone and nonlinear viscoelastic-plasticity constitutive model AI导读
“在边坡、隧道工程领域，专家采用DZSZ-150型多场耦合岩石三轴压力试验机，开展粉砂质泥岩蠕变试验，建立了非线性黏弹塑性本构模型，成功描述了粉砂质泥岩蠕变-破坏全过程的变形规律，为工程稳定性分析提供了解决方案。”摘要：In order to guarantee the long-term stability of silty mudstone in slope and tunneling projects, the DZSZ-150 multi-field coupling rock triaxial pressure testing machine was used to conduct creep tests on silty mudstone specimens of similar materials under different surrounding pressures. Based on the testing results, a nonlinear viscoelastic-plastic constitutive model describing the whole creep process of silty mudstone was established, and the proposed creep model was verified for its rationality and feasibility by taking the results at a confining pressure of 7 MPa as an example. It show that the steady-state creep rate of the specimen is related to the magnitude of the deviatoric stress, and with increase of the deviatoric stress, the steady-state creep rate and the deviatoric stress conform to an exponential function relationship; the creep rate in the accelerated creep stage is significantly greater than that in the decelerated creep and steady-state creep at low stress levels, and the creep damage occurs in a very short time; a nonlinear viscoelastic-plastic constitutive model is proposed to describe the whole creep process of the silty mudstone, which can describe the creep-deformation law of the whole process of creep-damage of silty mudstone, reflecting the creep characteristics of silty mudstone under different levels of deviatoric stress, and avoiding the problem that the classical model cannot accurately describe the accelerated creep process.关键词：silty mudstone;creep test;accelerated creep;creep characteristics;constitutive model190|30|0更新时间：2024-05-22 - “在地基处理领域，研究者以浙江省31省道北延线绍兴市区路段为例，探索了两种原位固化地基处理方式的适用性及其效果。通过现场试验和监测，结果表明就地固化处理后的地基承载力提高至少30%，人工硬壳层具有较好的扩散应力作用。”摘要：Based on the ground treatment of the north extension of No. 31 provincial road in the urban section of Shaoxing in Zhejiang Province, the feasibility and treatment effect of two methods, i.e., ALLu strong stirring head stirring method with homemade equipment and ALLu strong stirring head combined application, by in-situ curing foundation treatment were studied. Plate loading test, unconfined compressive strength (UCS) test, standard penetration test and static cone penetration test were carried out, respectively. Meanwhile, in order to obtain the stress and deformation of the in-situ curing foundation, field monitoring was carried out by arranging the earth pressure box and settlement plate. The test results showed that the bearing capacity of foundation by in-situ curing were increased by at least 30% compared with the traditional replacement method. At 28 days of curing time, the ratio of UCS of curing soil in-situ to that of indoor value was 0.35-0.65. The bearing capacity of foundation was improved by standard penetration test and static cone penetration test，and the calculating bearing capacity were consistent with the measured results of plate loading test. The stress and additional stress coefficient of the two groups of road sections were analyzed, and the artificial crust layer had better effect on the diffusion stress, which can be used for detection of in-situ shallow stabilization in engineering practice.关键词：road engineering;foundation treatment;in-situ curing foundation;static test;bearing capacity of the foundation97|20|2更新时间：2024-05-22
- “在地基工程领域，重庆某施工现场的土体样本被用于研究桩-土接触面力学特性受温度影响的变化规律。通过改造传统直剪仪，开展室内土工直剪试验，分析了单次和循环温度变化对桩-土接触面力学性能的影响。结果表明，能量桩-土接触面的抗剪强度受温度影响较大，且在低法向应力下温度循环影响显著。该研究为桩基工程中温度因素的考虑提供了重要参考。”摘要：In the working process of energy pile, the pile body will produce thermal deformation influenced by temperature change and induce cyclic shear action on the soil around the pile, which would weaken the bearing capacity of the foundation and bring risks to the normal use of the pile foundation. Because the traditional direct shear apparatus could not simulate the temperature variation of the pile and soil in the working process of energy piles, there was limited research on the mechanical properties of the pile-soil interface affected by the temperature. In this paper, the traditional direct shear apparatus was modified to adjust the temperature of soil samples. The soil used in this test was sampled from a construction site in Chongqing, and the geotechnical direct shear tests of pile-soil interface under different temperatures were carried out. The effects of single and cyclic temperature variation on the mechanical properties of the pile-soil interface were analyzed. Meanwhile, the difference between the mechanical properties of pile-soil interface and soil was compared. The results showed that the shear strength of pile-soil interface was influenced significantly by the temperature. With the increase of temperature, the friction angle and cohesion of the pile-soil interface would firstly decrease and then increase. Temperature cycles had a great influence on the mechanical properties of pile-soil interface under low normal stress, while it had no significant influence under high normal stress. The variations of shear strength, friction angle and cohesion of the soil influenced by temperature was similar to those of pile-soil interface.关键词：energy pile;shear behavior;pile-soil interface;temperature variation91|13|1更新时间：2024-05-22
- “在地基加固领域，研究人员提出了一种新的水平联合竖直排水板真空预压(PHD-PVD-VP)方法，通过模型试验和微观结构分析，发现40 kPa的初始PHD真空压力可显著提升工程废浆的排水固结效果，有效缓解排水板淤堵，改善土体固结均匀性。”摘要：When the vacuum preloading (VP) is used to consolidate the engineering waste slurry, there are several problems, such as the clogging of prefabricated vertical drain (PVD), formation of the soil columns and the attenuation of vacuum degree with depth, resulting in non-uniform consolidation. Considering the characteristics of prefabricated horizontal drain (PHD) in the treatment of soft soil foundation by VP method, a vacuum preloading method combined PHD with PVD (PHD-PVD-VP) is proposed to treat the slurry. Through four groups of large-scale indoor model tests, the drainage, settlement and pore water pressure during consolidation of engineering waste slurry were monitored, combined with the micro pictures of drainage board filter membrane obtained by scanning electron microscope, the consolidation effect of PHD-PVD-VP on engineering waste slurry under different initial PHD vacuum pressures was analyzed. The test results show that the PHD-PVD-VP reduces the radial movement rate of soil particles, delays the formation of "soil column", alleviates the silting effect of soil particles embedded in the filter membrane of drainage plate, and improves the overall consolidation effect of soil; initial PHD vacuum pressure of 40 kPa makes the drainage and consolidation effect of PHD-PVD-VP on engineering waste slurry the best, the average water content and vane shear strength of the treated soil were 40.9% and 25.5 kPa respectively. It not only effectively avoids the clogging of PHD and PVD, but also improves the uniformity of soil. Combined with the microstructure analysis, it is found that the initial PHD vacuum pressure affects the clogging of PHD and PVD filter membranes simultaneously, so as to affect their drainage performance. The initial PHD vacuum pressure of 40 kPa gives full play to the drainage performance of the two drainage boards.关键词：vacuum preloading;horizontal drain;engineering waste slurry;anti-clogging;degree of consolidation80|8|3更新时间：2024-05-22
- “在土木工程领域，一项新研究探索了长江漫滩粉土作为路基填料的潜力。通过改良试验，发现掺加水泥和石灰能显著提升土体力学性能和耐久性。最佳配比为6%水泥+6%石灰，改良土体的28天无侧限抗压强度达2.05 MPa，浸水5天后水稳系数为0.76，展现出良好的路用力学性能。”摘要：To realize the utilization of silt waste from foundation pit excavation, the characteristics of engineering mechanics and stability of the Yangtze river floodplain silt subgrade solidified by cement and lime were investigated. A series of laboratory tests including compaction test, unconfined compressive strength test, water stability test and microscopic test were conducted to analyze the variation of strength and durability of lime-cement solidified silt. Feasibility of using soft soil of Yangtze River floodplain as subgrade filling is demonstrated. The results show that the mechanical properties of silt are greatly improved after addition of cement and lime; after soaking in water for 5 days with different content, the water stability coefficient of the solidified soil is greater than 0.6. The water stability coefficient increases with the increase of cement content, and increases first and then decreases with the lime content. Microscopic tests show that the cementitious substances generated by cement and lime in the soil can encapsulate and bond the soil particle. Considering the strength and water stability of the solidified soil, the Yangtze River floodplain silt can be used as subgrade filling after solidification and the optimum percentage of cement and lime was both 6%. Under this content, the unconfined compressive strength of the improved soil for 28d is 2.05 MPa, and the water stability coefficient after soaking in water for 5 days is 0.76, which shows that the improved soil has good mechanical performance.关键词：Yangtze River floodplain;silt improvement;subgrade filling;mechanics characteristics;water stability;microscopic mechanism97|8|1更新时间：2024-05-22
- “在软土地层盾构掘进稳定性研究领域，TJ-TBM2015多功能微型隧道掘进试验平台成功研制，通过模拟地层损失和动力控制系统，实现了盾构隧道的连续动态机械开挖。通过3种工况的掘进试验，监测地表沉降变形和土体应力变化，研究土体稳定性特征，为解决软土地层盾构掘进稳定性问题提供解决方案。”摘要：In order to investigate general stability during shield tunneling in soft soil stratum, a TJ-TBM2015 multi-functional micro-tunneling test platform is developed independently. The shield shell diameter is changed to simulate the ground loss. By using the dynamic control system, the micro-tunneling boring machine can realize the continuous dynamic mechanical excavation. Based on the test platform, three tests of shield tunneling under different tunnelling conditions are carried out, including no overloading, local overloading and tunneling near the pile group foundation. The surface subsidence and stress variety around tunnel are monitored by transducer to investigate the general stability of different tests, which further give the comparison and discussion on the different test results. The results show that the soil within the one diameter of the tunnel center is greatly affected by tunneling; the influence of local overloading on soil stability is limited, but local overloading may increase the surface settlement; pile group foundation plays a certain role in strengthening and isolating the stratum.关键词：soft soil;shield tunneling;model test;soil stability69|12|0更新时间：2024-05-22
- “在深基坑开挖工程领域，专家提出了一种基于贝叶斯参数更新框架和现场监测数据的土体参数反演方法，通过GA-BP神经网络建立土体参数与地连墙侧移的隐式函数关系，结合监测数据建立贝叶斯反分析模型，验证了方法的可行性，为优化基坑支护方案和降低工程风险提供了解决方案。”摘要：In deep foundation excavation projects, using reasonable soil mechanical parameters to calculate the lateral deformation of diaphragm wall is essential to optimize the support design and reduce engineering risks. However, the soil parameters are generally affected by the uneven distribution and geotechnical testing errors, which often show obvious uncertainties and reduce the credibility of the lateral deformation calculated of diaphragm walls. In view of the considerations above, this paper proposes a back analysis method of soil parameters based on Bayesian parameter updating framework and site monitoring data. This method uses GA-BP neural network to establish the implicit function relationship between the soil parameters and the diaphragm wall lateral displacement in the numerical model, and combines the site monitoring data to establish the Bayesian back analysis model of the soil parameters. This method was used to analyze a deep excavation project, and the feasibility of the method was verified. The maximum lateral displacement and multi-point displacement value of the diaphragm wall were used as indicators to invert the soil mechanical parameters, and the updated soil parameters were used to predict the final lateral displacement. The results show that compared with the non-updating soil parameters, the variation coefficient of soil parameters decreases after updating, and the obtained results fit with the monitoring results better in the subsequent construction steps; the prediction effect of using multi-point observations for soil parameter updating is significantly better than that when only the maximum displacement value is used.关键词：deep foundation excavation;soil paraneter;displacement back analysis;Bayesian method;Markov Chain Monte Carlo Simulation (MCMCS)70|11|1更新时间：2024-05-22
- “在边坡稳定性分析领域，专家基于贝叶斯方法校准的多元水力参数联合随机场，建立了非饱和土边坡稳定性分析方法，为评估赣江库岸边坡稳定性提供了解决方案。”摘要：The geotechnical parameter of soil mass in colluvial landslide is uncertain. Saturated hydraulic conductivity and soil-water characteristic curve (SWCC) are important parameters for the unsaturated seepage analysis. It is of great significance to carry out the reliability analysis of reservoir bank landslide considering the spatial variability. In this study, the Jvzhoudao slope in the Ganjiang Reservoir Area is investigated as a case. Firstly, according to the limited laboratory test data of saturation-matrix suction, the statistical characteristics of the SWCC properties, such as VGM, VGB, VG, and FX model parameters are calibrated by the Bayesian method, and the applied probabilities of SWCC model combination are determined by the laboratory measurements. Secondly, combining the random field characteristics of the saturated hydraulic conductivity with the random characteristics of the SWCC models, spatial distributions of the unsaturated hydraulic conductivity are generated in the slide body. Finally, for the extreme conditions in the Ganjiang Reservoir Area in May 2021, the proposed method was applied to the case stability analysis. Results indicate that the combined effect of rainstorm and water level change has a significant impact on the safety factor, and that the safety factor of the deterministic analysis is low. Reliability index calculated after considering the spatial variability of the unsaturated permeability coefficient cannot meet the specification requirements, while additional slope engineering reinforcement measures should be taken to guarantee the long-term stability of the slope.关键词：reservoir bank slope;soil-water characteristic curve;unsaturated hydraulic conductivity;Bayesian method;reliability analysis97|9|0更新时间：2024-05-22
- “在绿色低碳建筑技术领域，微生物加固技术展现出广阔应用前景。专家构建了微生物加固可视化试验系统，通过图像处理和环境监测，为揭示加固机理提供新手段。”摘要：Biocementation is a green and low-carbon building technique that has emerged in recent decades. It shows promising prospects in foundation treatment, slope treatment, and concrete crack repair. Biocementation involves complex bio-physical-chemical dynamic processes, requiring developing a real-time visualization system to figure out the regimes of reaction and reinforcement. The necessity of developing the visualization system for biocementation is analyzed. A framework of the visualization test system is established for biocementation, composing of a solution transport system, microreactor, observation system, as well as environmental control and monitoring system. The solution transport system is used for solution delivery and fixing of boundary conditions. The microreactor is used as a mold for reaction. The observation system is used to visualize the reaction process. The environmental control and monitoring system is used to control the environmental conditions such as temperature and light and also collect the feedback data including fluid pressure. The methods for test data acquisition are based on image processing associated with the data logged by the environmental monitors. Analytical approaches are also proposed to deal with the test data. Results show that the biocementation visualization system can not only directly obtain the image of the reinforcement process and the data of the osmotic pressure change, but also be combined with microscopic test methods such as scanning electron microscopy for material characterization and micro-mechanical characteristics analysis. It can be used for microscopic real-time research of biocementation, providing a new method for study of the microscopic mechanism of biocementation, which is conducive to revealing the mechanism of biocementation.关键词：biocementation;test system;biomineralization;microbially-induced carbonate precipitation;microfluidics71|14|0更新时间：2024-05-22
- “在风电领域，装配式基础结构的研究进展为风电产业的高质量发展提供了重要支撑。专家总结了梁板基础、多足基础等6类主要的风电装配式基础结构形式，为风电结构的降本增效和转型升级奠定了基础。”摘要：The foundation of onshore wind turbine (OWT) structure is usually constructed by cast-in-situ concrete, which is inefficient, polluting, and difficult to guarantee quality, either not conducive to the high-quality development of the wind power industry. The prefabricated wind turbine foundation adopts the construction method of standardized design and factory production, which can significantly shorten the construction period of wind farms, effectively guarantee the quality of the foundation, and reduce the pollution to the environment. It is one of the important measures for the transformation and upgrading of wind power and reducing costs and increasing efficiency. This paper collects, sorts out and summarizes the research of prefabricated OWT foundation and its state-of-the-art research. According to the characteristics of the wind power prefabricated infrastructure, it lists six main types of wind power prefabricated infrastructure, such as raft foundation and multi-footing foundation, and makes a detailed analysis of the characteristics and research status of each type, and lists some onshore wind farm projects that apply prefabricated wind turbine foundation worldwide. The results show that the design basis of OWT prefabricated foundation structures needs to be further improved, the existing structure forms should be optimized, and further research on design methods and performance control should be promoted.关键词：wind power;onshore wind turbine;prefabricated foundation;foundation type89|10|0更新时间：2024-05-22
- “在土钉墙结构研究领域，专家通过室内试验和三维数值模拟，对装配式柔性面层GFRP筋土钉墙的钉头锚固性能进行了深入研究。研究结果表明，GFRP筋钉头极限承载力在240~290 kN之间，螺纹副应力主要集中在钉头第1环螺纹牙，极限剪切强度与钉头极限荷载关系明确。通过试验确定GFRP筋钉头安全系数在1.8~2.0之间，为土钉墙结构设计提供了重要参考。”摘要：The soil nail head is the weak point in the overall structure of the soil nail wall. In order to study the anchorage performance of soil nail head, this paper takes an assembled flexible surface GFRP reinforced soil nail wall as an example. Through indoor nail head anchorage performance test and 3D numerical simulation the ultimate tensile strength, nail head deformation and damage pattern of hollow GFRP bar nail head with 32 mm outer diameter were investigated. It was found that the ultimate load bearing capacity of such GFRP bar nail head is between 240 kN and 290 kN. When the nut is tightened, the stress of the thread is mainly distributed in the first three rings of threaded teeth, with significant stress concentration exists at the first ring of threaded teeth in the head of the nail. In addition, a mechanical model of the threaded tooth of the nail head was developed using the thread expansion method, and the relationship between the ultimate shear strength of the first ring thread and the ultimate load on the nail head was derived. The ultimate load-carrying capacity of this GFRP bar nail head was calculated to be 244.54 kN, which is consistent with the test results.The brittle damage characteristics of the indoor nail head anchorage performance test determined that the safety factor of GFRP tendon nail head is between 1.8 and 2.0. It is also determined that the safe load of such GFRP tendons is between 125 kN and 135 kN, providing a reference for the research and application of similar projects.关键词：foundation pit;GFRP bar soil nail;soil nail wall;nail head;anchorage performance57|6|0更新时间：2024-05-22
- “在地下工程安全领域，专家通过常规劈裂试验、分级循环荷载试验和非接触变形测量试验，分析裂隙岩石的破坏特征、动弹性模量，研究轴向不可逆变形与疲劳寿命之间的关系。从能量角度出发，计算破坏过程中的总吸收能量、可释放应变能及耗散能，分析能量演化与裂隙扩展模式响应关系。研究结果表明，岩石疲劳变形可分为三个阶段，滞回环曲线呈现出“疏—密—疏”的特性，总吸收能、耗散能和弹性能都呈上升趋势，耗散能在进入破坏阶段后迅速上升，中等倾角的耗散能较多。在破坏过程中均会产生翼裂纹和倾斜次生裂纹，裂纹相互作用和合并，产生连续塑性应变累积，形成压碎的小颗粒碎屑，这与静荷载作用下脆性破坏机制不同。”摘要：The crack propagation mode, fatigue deformation characteristics and energy evolution pattern of cracked rock under graded cyclic loading are of great significance to the safe construction and operation of underground engineering. Conventional splitting test, graded cyclic load test and non-contact deformation measurement test were carried out considering the crack angle, crack number and distribution. The failure characteristics and dynamic elastic modulus were analyzed, and the relationship between axial irreversible deformation and fatigue life was studied. From the perspective of energy, the total absorbed energy, released strain energy and dissipated energy in the failure process were calculated, and the relationship between energy evolution and the response of crack propagation mode was analyzed. The results show that :(1) The fatigue deformation of rock can be divided into the initial deformation stage, stable stage and the accelerated failure stage, and the hysteretic loop curve presents the characteristics of “thin-dense-thinness”. The dynamic elastic modulus of every 200 cycles is analyzed and that of the second loading stage is strengthened. In addition, the dynamic elastic modulus decreases after the third loading stage. (2) The total absorbed energy, dissipated energy and elastic energy all showed an upward trend. The total absorbed energy increased slowly, and the growth rate gradually slowed down with the increase of cycles. The dissipated energy increases rapidly after entering the failure stage, but the elastic strain energy does not change obviously, and the dissipated energy is more in the middle dip angle. (3) During failure process, wing cracks and inclined secondary cracks are generated, and the interaction and merger of the cracks result in continuous plastic strain accumulation and small particle debris, which is different from the brittle failure mechanism under static load.关键词：fractured rock;crack propagation;fatigue deformation;graded cyclic load;dynamic modulus of elasticity;energy evolution53|7|1更新时间：2024-05-22
- “在风电领域，一项新研究揭示了风机尾流特性及其演化规律。通过风洞试验和大涡模拟结合致动线模型的数值模拟方法，研究了入流风场和偏航角对尾流特性的影响，为风电场优化设计和提高发电效率提供了重要参考。”摘要：With the rapid construction of large-scale wind farms, the upstream wind turbine will deteriorate the wind velocity in the wind turbine wake region and increase the wake turbulence, thereby reducing the power efficiency of the downstream wind turbine and aggravating the fatigue damage of the wind turbine to shorten its service life. Therefore, it is urgent to carry out the study of wind turbine wake characteristics. The main purpose of this study is to reveal the wake characteristics of a standalone wind turbine under different upstream flow conditions and with various yaw angles. Firstly, the accuracy of Large Eddy Simulation (LES) combined with Actuator Line Model (ALM) was verified by the corresponding wind tunnel test. And then, based on the LES-ALM simulation method, the effects of inlet (including velocity and turbulence intensity) and yaw angle on the turbine wake characteristics were studied, and the symmetry of the horizontal profiles of the wind turbine wake at the hub height was clarified with positive and negative yaw angles. The results show that with the increase of the background turbulence intensity, the recovery of the wind turbine wake will be accelerated. Moreover, under the same upstream flow conditions and symmetrical yaw angle, the certain symmetry of wind turbine wake velocity was also identified. When the yaw angle of the wind turbine increases, both the expansion rate of the turbine wake width and the deficit degree of the wake wind velocity would decrease.关键词：wind turbine wake;yaw angle;LES-ALM;upstream flow conditions107|10|0更新时间：2024-05-22
- “在风压信号分析领域，专家通过实际测定测压管路频响函数，揭示了“B-T理论”的不足，并验证了其修正效果，为提高数据分析精度提供了解决方案。”摘要：In the pressure test, the presence of the piezometric tube will distort the pressure signal and affect the accuracy of the subsequent data analysis. Through the actual measurement of the frequency response function of the measuring system, the influence law of the piezometric tube on the signal is obtained, and the shortcomings of the “B-T theory” are revealed. Based on this, under the actual turbulent flow, the influence of the piezometric tube length on the pressure data of a single measuring point and the total force of the model is studied, and the correction effect of the “B-T theory” is verified. The results show that for single-point pressure data, the piezometric tube will not affect the data mean and variation coefficient, the standard deviation increases first and then decreases as the tube length increases, the signal time domain approaches the mean value as the tube length increases, the phase keeps lagging, and the signal frequency domain value gradually deviates from the true value with the increase of the tube length and frequency. For the overall force of the model, the overall resistance, the correlation and coherence of each force can be regarded as not affected by the piezometric tube, the change rule of the force spectrum is the same as that of the frequency domain value of single measuring point. “B-T theory” has a poor correction effect in the signal time domain, and performs well in the frequency domain correction.关键词：pressure measurement experiment;piezometric tube;frequency response function;signal correction;turbulence74|7|0更新时间：2024-05-22
- “最新研究揭示了冷弯薄壁型钢-结构防火一体板自攻螺钉连接的抗剪性能，通过35个试件的试验，分析了多种因素对性能的影响，为提高建筑结构安全性提供了重要参考。”摘要：The shear test of self-tapping screw connection of cold-formed thin-walled steel-structure fireproof integrated board was carried out, and the monotonic tensile and low-cycle reciprocating loading tests of 35 typical specimens were completed, and the effects of structural fireproof integrated plate thickness, screw diameter, screw end distance and loading angle on their shear resistance were analyzed. The results show that the specimens with different loading angles and screw end distance showed different failure modes, mainly including tear failure at the end of the plate, pressure failure of the hole wall of the plate, and the failure of the plate to be pulled off, etc., and the self-tapping screws of the specimens had different degrees of inclination during the failure. For test pieces with screws with a diameter of 4.8 mm and 5.5 mm respectively at the test end,the peak load and ductility coefficient of the specimen have no obvious correlation with the screw diameter, and the elastic stiffness increases significantly with the increase of the screw diameter. With the increase of screw end distance from 15 mm to 25 mm, the elastic stiffness of the specimen did not change significantly, while the peak load and ductility coefficient increased by about 35%. With the increase of plate thickness from 12 mm to 20 mm, the peak load of the specimen is increased by about 40%, the elastic stiffness is increased by about 90%, and the ductility coefficient is reduced by about 30%. Compared with the specimen with a loading angle of 0°, when the loading angle is 45°, the elastic stiffness of the specimen is increased by about 100%, and the peak load and ductility coefficient do not change significantly. When the loading angle is 90°, the elastic stiffness and peak load of the specimen do not change significantly, and the ductility coefficient is reduced by about 40%.关键词：cold-formed thin-walled steel;structural fireproof integrated panel;screw connection;shear resistance;low cycle reciprocating load89|8|0更新时间：2024-05-22
- “在古建筑木构件自然老化材性变化研究领域，专家建立了落叶松木材物理力学性能参数的多元回归评估模型，为评估老化木材性能提供了解决方案。”摘要：In order to explore the change of wood properties of ancient building members under natural aging, a part of larch (Larix principis-rupprechtii Mayr) timber member of ancient building, which is about 350 years old, and a new timber with the same species and similar annual wheel width were used in this study. Small clear specimens were processed to measure the material properties (color, dry density and material mechanics property parameters) and non-destructive testing (NDT) parameters (micro-drill resistance value and velocity of ultrasonic wave). The nondestructive testing, physical and mechanical properties parameters of specimens were compared to analyze the variation and distribution, and then the multiple regression model for the physical and mechanical properties of ancient building timber were established based on the parameters measured in this study. The study results showed that the measured material property parameters and NDT parameters of the natural ageing wood specimens were significantly attenuated. And there is a highly significant difference in the color of natural aging specimens and new timber specimens. It was also found that the coefficients of variation of the parameters of natural aging specimens were all higher than those of new timber specimens, but both of them conformed to a normal distribution. Moreover, the developed model for the evaluation of physical and mechanical property parameters of larch timber members has a good evaluation performance.关键词：ancient building;timber members;Yangxin Hall of the Palace Museum;natural aging;property of wood;attenuation62|7|0更新时间：2024-05-22
- “在高压输电铁塔结构健康监测领域，专家利用ABAQUS软件建立多尺度模型，引入小波包能量变化率作为损伤识别指标，通过试验验证，为输电塔螺栓松动损伤识别提供了有效解决方案。”摘要：The structure health monitoring of high voltage transmission tower was very important to ensure the safe operation of the transmission line. When the transmission tower structure was damaged, the gusset plate bolts would be loosened first. The multiscale model of the transmission tower structure is established by using ABAQUS finite element analysis software. The energy change rate of the wavelet packet was taken as the damage index. The damage identification was carried out under different working conditions when bolt looseness of a joint plate at the tower leg. The signal transmission equipment was a sensor based on Internet of Things technology. The data acquisition equipment was PVDF piezoelectric film strain gauge. Applying excitation loads at the bottom of the actual transmission tower structure, the dynamic strain of the measured points on the gusset plate was extracted to verify the damage identification method. The test results show that the damage index can accurately identify the damage degree of the gusset plate. It is also sensitive to bolt looseness near the measuring point.关键词：transmission tower;wavelet packet;multiscale analysis;piezoelectric film;damage identification57|17|0更新时间：2024-05-22
- “在桥梁工程领域，专家提出了基于细观损伤力学的大跨度钢桥疲劳损伤跨尺度评估方法，为解决大跨度斜拉桥钢桥面板疲劳损伤问题提供了解决方案。”摘要：Orthotropic steel deck (OSD) in a long-span cable-stayed bridge is vulnerable to fatigue damage at the rib-to-deck (RD) joints due to traffic vehicle load. An algorithm for fatigue damage evaluation simulation of long-span bridge based on mesoscale damage model is presented in this paper. Firstly, the fatigue damage evolution model of steel deck based on microscopic damage mechanics is derived. Combined with the measured traffic data, the random traffic flow simulation is realized based on Monte-Carlo method. Finally, it is applied to estimate the damage accumulation of a multi-span cable-stayed bridge. The results indicate that the fatigue damage accumulation at the rib-to-deck (RD) joints is greater than other areas of the OSD. The cumulative rate of fatigue damage at the rib-to-deck (RD) joints shows a strong nonlinear trend. The results are also compared with those estimated by the linear Miner,s model. The predicted fatigue life is far less than that by the linear Miner,s model.关键词：large multi-span bridge;steel deck;mesoscale fatigue;damage evolution;stochastic traffic flow;fatigue prediction42|9|0更新时间：2024-05-22
- “在海工高性能混凝土梁领域，研究人员设计了10根试验梁，通过重复荷载试验、氯盐干湿试验及两者共同作用试验，研究了梁的变形发展规律。研究结果表明，荷载水平按梁纯弯段弯矩等于0.4Mu确定时，施加30次重复荷载后混凝土的损伤度接近15%。结合试验结果，采用损伤效应折减系数对梁短期刚度计算公式进行修正，验证了修正公式的合理性和有效性。”摘要：Under long-term loading, the deformation of reinforced concrete flexural members is an important evaluation index and it is one of the checking contents of the serviceability limit state. To study the degradation law of bending stiffness of marine high-performance concrete beams after action of repeated loads, a total of 10 test beams were designed and fabricated. After exposure to the repeated load test, the chloride solution dry-wet cycle test and their coupled test, the mid-span deflection development and stiffness degradation of the test beams were evaluated using the four-point bending test. A modified method for the code formula of beam short-term stiffness is proposed. The test results indicate that when the load level is determined according to the moment of the beam’s pure bending section equal to 0.4Mu, the damage degree in concrete approaches 15% after 30 cycles of repeated load. For the test beams exposed only to the chloride solution dry-wet cycles, their mid-span deflection develops slower than that of the reference beam. After the action of repeated loads, the mid-span deflection of these test beams develops faster than that of the reference beam. When the damaged beams were exposed to chloride solution dry-wet cycles, their degradation of bending stiffness became more obvious. Based on the experimental results, the damage effect reduction factors were proposed to revise the calculation formula of beam,s short-term stiffness. The rationality and effectiveness of the revised formula are verified by the test data.关键词：repeated load;marine concrete beam;damage degree;chloride environment;bending stiffness40|7|0更新时间：2024-05-22
- “在建筑领域，一项新研究揭示了持续负温（-5℃）条件下含气混凝土抗压强度的发展规律。实验结果表明，负温养护对含气混凝土强度增长有明显抑制作用，引气剂掺量与混凝土强度呈负相关。研究明确了负温条件下含气混凝土引气剂的最优掺量，为保证混凝土抗压强度和孔径结构优化提供了解决方案。”摘要：In this experiment, by comparing the compressive strength values and internal pore structure of five different aerated concrete test blocks at different ages under the conditions of negative temperature curing and standard curing, the development law of the compressive strength of aerated concrete is analyzed based on the (-5 ℃) curing condition, and the range of less harmful pores under this condition is further clarified based on the relationship between the pore size and the pore water; and the inherent lack of strength of aerated concrete is analyzed from a microscopic point of view. The experimental results show that the continuous (-5 ℃) curing has an obvious restraining effect on the growth of the compressive strength of aerated concrete, and the strength is less than the standard curing test block at the same content; under the same curing conditions, the strength and content are affected by the air-entraining agent. There is a negative correlation between them; based on the negative temperature curing environment, the high content of aerated concrete will reduce the compactness of the concrete due to the increase in the number of pores in the slurry, which will affect the compressive strength of the concrete to a certain extent, but it will cause the resistance of the aerosol to the negative temperature environment cannot be ignored. In order to analyze the balance between the negative temperature environment and the amount of air-entraining agent, the pore structure development law and strength growth system of cement-based materials under negative temperature are used to ensure that the compression the strength of aerated concrete is low and the pore structure is relatively optimized. Under the premise of finding the content of aerated concrete under the condition of negative temperature (-5 ℃).关键词：aerated concrete;air entraining agent;negative temperature curing;compressive strength;pore structure38|10|0更新时间：2024-05-22
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Experimental study on the physical and mechanical properties of straw fiber reinforced foam concrete AI导读
“在建筑材料领域，研究人员采用物理发泡法制备稻草纤维增强泡沫混凝土，通过全因子试验研究了纤维掺量对混凝土性能的影响，为提高泡沫混凝土性能提供了解决方案。”摘要：In order to study the properties of straw fiber reinforced foam concrete, fiber-reinforced foam concrete was prepared by the physical foaming method with ordinary Portland cement as the main cementitious material, silica fume, metakaolin and fly ash as the supplementary cementitious materials, and rice straw fiber as reinforcement material. The effects of straw fiber content on the density, water absorption, compressive strength, flexural strength, splitting tensile strength and frost resistance of foam concrete were investigated by full factorial tests at different water-to-binder ratios and foaming agent dosages. The results showed that the density, compressive strength and splitting tensile strength of straw fiber reinforced foam concrete increased first and then decreased with the increase of fiber content for different water-to-binder ratios and foaming agent dosages. The compressive strength increased with density as a power function. The splitting tensile strength increased exponentially with the increase of compressive strength. When the water-to-binder ratio was 0.45, the flexural strength increased first and then decreased with the increase of fiber content. When the water-to-binder ratio was 0.50, the flexural strength increased with the increase of fiber content. The incorporation of fiber increased the pore size and water absorption rate of foam concrete, and reduced its frost resistance.关键词：straw fiber;foam concrete;bubble pore size;mechanical properties;frost resistance39|8|0更新时间：2024-05-22 - “在建筑材料领域，研究人员通过电通量试验、电镜扫描观测及基本力学性能试验，分析了不同纤维尺度、掺量及复合比例对水泥基材料抗氯离子渗透性能和基本力学性能的影响。结果表明，多纤维复合增强水泥基材料的抗氯离子渗透性能明显优于单一纤维增强水泥基材料，且抗压强度与氯离子侵蚀深度及电通量大致呈反比例关系。此外，研究人员还建立了氯离子侵蚀深度计算模型，为多纤维复合增强水泥基材料的抗氯离子渗透和侵蚀性能评估提供了解决方案。”摘要：The electric flux tests, scanning electron microscope and mechanical tests were carried out respectively on cementitious composites with single mixing and compound mixing CaCO3 whisker and PVA fiber to investigate chloride ion resistance of multi-scale fiber reinforced cementitious composites. The effects and mechanisms of different fiber sizes, amount of admixture and mixing ratios on the chloride ion resistance and basic mechanical properties of cementitious composites were analyzed. In addition, the calculation method of the depth of chloride ion erosion was proposed. The results showed that different types of fibers can enhance cementitious composites at different structural levels, and the chloride ion resistance of multi-scale fiber reinforced cementitious composites is much better than that of single fiber reinforced cementitious composites. The compressive strength of composites is inversely proportional to the depth of chloride ion erosion and the electric flux. When the compressive strength of the composite was increased by 13.6%, the depth of chloride ion erosion and the electric flux were decreased by 39.1% and 44.7%, respectively. Based on the experimental data, a calculation model of chloride ion erosion depth considering the influence of compressive strength is established, which can be used to evaluate the chloride ion penetration and erosion resistance of cement-based materials reinforced by multi-fiber composite.关键词：fiber reinforced concrete;cementitious composite;chloride ion resistance;electric flux;compressive strength56|7|0更新时间：2024-05-22
- “最新研究揭示，在常温养护下掺入少量水泥颗粒的粉煤灰地聚物混凝土，其力学性能与不含水泥颗粒且接受热固化的混凝土相近，为实际工程应用提供了新思路。”摘要：Previous studies show that the fly ash geopolymer concrete cured at room temperature can be significantly improved if mixed into a small dosage of ordinary Portland cement. However, this modified material has rarely been compared with the traditional fly ash geopolymer concrete, cured at high temperature and not mixed with any ordinary Portland cement. In order to meet the needs of practical engineering applications, the basic mechanical properties, including Poisson,s ratios, were tested and compared between two different materials, i.e., the thermally cured fly ash polymer concrete without cement and the room temperature cured fly ash geopolymer concrete with a small dosage of cement particles. Also, to clarify the mechanism in results of the mechanical tests, the microscope and chemical elements tests, including SEM, EDS, XRD, FTIR and CT, are performed. The results show that the mechanical properties of room-temperature cured fly ash polymer concrete containing a little cement are close to those of thermal cured FGC without cement particles. Before compressive failure of prism specimens, the lateral to the vertical strain ratio is close to 1.0, exhibiting a significant lateral deformation capability. After adding 8% cement particles, the degree of polymerization reaction at room temperature is close to that of high temperature curing measures without cement. In forming a more reasonable microscopic pore structure, the samples cured at room temperature are better than those cured at high temperatures.关键词：compressive strength;microstructure;polymerization reaction;hydration products;asymmetric stretching vibration58|11|0更新时间：2024-05-22
- “在2022年四川泸定6.8级地震中，公路沿线地质灾害频发，严重影响救援工作。调查发现507处受损点，崩塌滑坡占90%以上。公路震害与地震烈度正相关，与断层、河流距离负相关。抢通保通阶段，利用水运资源建立生命通道，提高公路抗灾能力及韧性。”摘要：On September 5th, 2022, an earthquake with magnitude 6.8 happened in Luding, Sichuan Province, which caused severe geological disasters and brought heavy workload for rescue. It was urgent to find out the damaged roads in the disaster-hit area and assess the difficulty of rescue work. Multiple damaged roads were investigated and 507 damaged points were found. Characterized by large number, small scale, and continuous distribution, landslides and collapse accounted for more than 90% of the total damage. The severity of highway damage was positively correlated with the seismic intensity, while it was negatively correlated with the distance from fault zones and rivers. Under the combination of adverse impact, the degree of disasters on high way significantly increased. In some regions, even 92.5% roads were damaged. During the road reopening and recovery, a strategy of using the water transport resources in the reservoir area of Longtoushi and Dagangshan Hydropower Station to quickly establish five wharves and a green pathway to the epicenter was proposed. The reconstruction of the transportation network made full use of the water way instead of focusing on the road grade and indicator, aiming to improve the road resistance to natural disasters.关键词：highway engineering;Luding Earthquake;coseismic hazard;emergent transport recovery;highway damage rate69|8|0更新时间：2024-05-22
Civil Engineering
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