Volume 43, Issue 4 (2023)
Specially Invited Article
Summarization of reliability theory for condition assessment of brige structurs
PENG Jianxin, CHAI Ying, and ZHANG Jianren
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.001
This paper briefly reviewed the principles and development of structural design theories, and summarized the current research of structural reliability theories. Meanwhile, various applicable methods of reliability theories were finely described and analyzed, with the latest progress in structural reliability analysis and reliability-based design optimization outlined. Additionally, the uncertainty propagation methods and reliability assessment methods were analyzed, and the development trend of structural reliability was summarized, which can provide a summary and reference for future researchers to study structural reliability.
Subgrade Engineering
Study on laws of surface movement a nd deformation of goaf under subgrade in sand-loess area
LEI Mingxuan, LIU Guotian, SU Weiwei, ZHANG Liujun, and YIN Lihua
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.002
A large number of goaf under sand-loess areas in China greatly restrict the highway construction development in sand-loess areas. Meanwhile, the goaf evaluation beneath under subgrade in sand-loess areas is especially important. According to the characteristics of goaf beneath the highway of sand-loess areas, based on FLAC3D software, this paper selected reasonable parameters to build the model of goaf under subgrade. Additionally, based on the mechanical property analysis of sand loess, the laws of surface movement and deformation parameters of the goaf under the subgrade were summarized, and the surface movement and deformation areas were identified, with the range of the most dangerous areas on the surface in sand-loess areas marked. Finally, important references were provided for the route selection and highway management in the goaf.
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.003
By taking the high vertical sand barriers deployed on the top of the complex longitudinal sand ridges in the hinterland of Taklamakan Desert as the object, this paper investigated the sand protection effect from the long-term perspective on the basis of several years’ comparative observation. The result analysis shows that in addition to the recognized sand blocking effect, high vertical sand barriers also have a more important role of sand fixation, which means that the barriers can change the original overall movement of sand dunes into only the falling sand slope forward, with the windward slopes basically fixed. Even if the barriers are buried by wind and sand, their sand fixation effect will still exist for a long time, which leads to remarkable changes in the wind and sand movement pattern. Consequently, the forward movement of the falling sand slopes is increasingly slower, with the average transportation speed dropping from about 0.99 m/y at the beginning of about half a year to about 0.49 m/y after 16 years. The “sand fixation” effect not only can significantly delay the time of “forward movement of sand dunes and burying the highway”, but also has great efficiency in sand hazard control. Therefore, high vertical sand barriers are indispensable in the sand hazard control system of roads in the mobile dune distribution areas, especially on the upwind side.
Experimental study on dynamic resilient modulus of cement-improved fine-grained soils in wet subgrade
HUANG Chongwei, ZHU Baobing, ZHANG Yi, SUN Yu, and GUO Dandan
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.004
To investigate the design and construction of wet subgrade in southern China, this paper selected three typical soil samples of the new highway subgrade of Ecological Avenue in Chongming District, Shanghai, and improved the samples by cement disposal technology. Meanwhile, the effects of the water content, degree of compaction, cement content, age of maintenance and stress state on the dynamic resilient modulus were analyzed by experimental methods. The results show that the effects of cement content, water content and age of maintenance on the dynamic resilient modulus of three kinds of cement-improved fine-grained soil in wet subgrade are larger, and more cement content and age of maintenance don’t necessarily lead to better effect. Additionally, the influence of the degree of compaction on the dynamic resilient modulus is not significant. Considering the significant effect of the stress state, it is recommended that the dynamic resilience modulus should be set at a conservative value in the design of wet fine-grained soil subgrade.
Study on stability analysis and treatment of a expressway landslide
HUANG Hongchao
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.005
In highway construction of mountainous areas, landslides are easily triggered due to the complex geological conditions, thereby causing serious economic loss and even casualties. Therefore, the study of landslide treatment schemes has caught increasingly more attention from scholars. By taking the giant landslide treatment on a highway of southeastern Yunnan as an example, this paper analyzed the process and cause of giant landslide formation, and then conducted inverse calculations to determine the stability analysis parameters of landslides via combining the topography and geology and slope state before and after slope excavation. Finally, according to the calculation results of the residual sliding force of the designed slope, comprehensive management measures were proposed. Post-construction monitoring data shows that the adopted comprehensive engineering management measures are feasible, reliable and effective.
Discussion on treatment scheme of soft foundation based on cooperative deformation of roadbed and frame structure
LIU Jizhong, CHEN Kai, and YANG Fengyu
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.006
In view of insufficient consideration of cooperative roadbed and structure deformation, by taking the soft foundation with frame structures in the fill roadbed as the research object, this paper adopted Midas GTS NX finite element analysis software to simulate the pavement settlement and plastic zone distribution of the soft foundation treated by cast-in-place piles. Considering that the stiffness difference between the roadbed and the frame structure can easily result in pavement cracking, a variable stiffness composite foundation treatment optimization scheme was proposed. This scheme coordinated the cooperative settlement and deformation of the roadbed and frame structure, and prevented the development of plastic zones of the soil on both sides of the frame structure, thus reducing the cracking risk of the structural layer of asphalt pavement and decreasing the operation and maintenance costs in the later stage.
Study on key technology of landslide investigation and treatment plan of coal stratum in section K 132 of a highway
WEI Dongxu, WANG Guanguo, LI Jian, and ZHENG Guosheng
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.007
Coal strata feature soft lithology, low strength and easy softening under contact with water. During the subgrade excavation, the slopes of the coal strata often form a potential slip surface, which can control the stability of the overall slope. By taking the K132 landslide of Longchuan-Huaiji Expressway as an example, this paper comprehensively determined the characteristics of the landslide in coal strata, especially the characteristics of slip surfaces, by adopting the high-density resistivity and deep-hole displacement monitoring methods and combining geological drilling. The stability analysis results show that the carry-over factor method and Geoslope analysis can calculate the residual sliding force of the landslide and predict the slope stability. After a combination of emergency treatment and permanent treatment measures, the landslide mass in coal strata remains its stability after undergoing the largest rainfall in the last 20 years.
Pavement Engineering
Feasibility study of pavement rutting evaluation method based on driving vibration
ZHANG Jinxi, WANG Peirong, CAO Dandan, and CENG Jingxiang
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.008
To explore the intelligent detection and monitoring methods of pavement performance, this paper utilized the self-developed driving data collection app to collect vibration acceleration and other data of the pavement during driving, and carried out the feasibility study of evaluating the pavement rutting by driving vibration. Firstly, the collected vibration acceleration data was processed for noise reduction, and the driving vibration characteristics in different working conditions were analyzed. Secondly, seven time domain indicators with high correlation between vibration acceleration and the rutting were extracted as the initial set of indicators, and the seven indicators were downscaled into two independent principal components by principal component analysis. Finally, the two principal components and the speed were adopted as the evaluation indexes to build a rutting evaluation model based on convolutional neural networks (CNNs). The results show that the average absolute error of rutting evaluation conducted by the proposed method is 1.03 mm, with the average relative error of 16.4%. The built model can provide more accurate evaluation of the pavement rutting, which can provide certain references for real-time monitoring of the pavement rutting by employing big data.
Study on influence factors of temperature field of CRC+AC composite road surface
CHENG Xiaoliang, ZHANG Hao, and LI Sheng
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.009
In view of the factors influencing the temperature field of CRC+AC composite road surfaces, this paper analyzed the temperature field distribution and influencing factors of CRC+AC composite road surface structures based on the meteorology and heat transfer theories, and conducted 3D solid modeling and numerical simulation by adopting Abaqus finite element software. The results show that in certain conditions, the deeper distance from the road surface leads to smaller temperature change of the road surface structure. When the depth exceeds 0.6 m, the temperature is almost unchanged and has little difference with the outside ambient temperature. By increasing the thermal conductivity, heat capacity, and road surface emissivity of asphalt road surfaces, and reducing the absorption rate of solar radiation, the road surface temperature at high temperatures and the harm of rutting and cracking of the road surfaces can be decreased. In both low temperature at night and high temperature during the day, changing the thickness of the asphalt layer does not have much effect on the road surface temperature, but in the high temperature during the day, the temperature in the surface layer decreases with the increasing thickness of the asphalt layer, with a large decrease range. The results can provide both technical support for the prevention of asphalt cracking and rutting in CRC+AC composite road surfaces, and theoretical basis for material selection and structural design.
Design of polymer optical fiber icing sensor and detection method of road ice thickness
XIE Qingzhong, WANG Ling, GE Jingyong, SHI Ning, and ZHANG Jiupeng
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.010
To detect the icing condition and icing thickness of asphalt pavement in extreme weather conditions, this paper firstly compared the performance indexes of polymer optical fiber and quartz optical fiber, chose polymer optical fiber as the optical transmission medium, and selected the distribution mode of coaxial sensor probes. Meanwhile, it designed the weak signal detection circuit and finally completed the design of a polymer optical fiber road icing sensor. Secondly, it was verified that the effect of temperature on the icing detection results was negligible, and icing tests under different light intensities were conducted under simulated light, with the icing characteristic curve obtained. Finally, the verification test of the icing characteristic curve was carried out under natural light to gain the functional relationship between the sensor output voltage and icing thickness curve. Consequently, this can provide real-time road safety information for road maintenance and management departments as well as pedestrians, reducing the frequency of traffic accidents.
Study on theoretical relationship between acceleration of vehicle suspension and international roughness index
LV Wenjiang and ZHANG Zhen
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.011
The international roughness index (IIRI) has become one of the most widely employed indexes to characterize the surface roughness. However, there are still some problems in the current research on the calculation of this index by adopting vertical acceleration data of vehicles. For example, the influence of vehicle suspension parameters on the test results is not sufficiently taken into account, and the applicability of regression analysis equations between vehicle acceleration and this index is low. This paper studied a method of determining this road surface roughness index with the suspension parameters of the test vehicle considered. The actual road tests show that the relative error between the calculated results and the test results of the road multifunctional inspection vehicle is about 10%, thus verifying the reliability of the researched method.
Study on influence of different subgrade types on low temperature shrinkage performance of asphalt pavement
XU Yongli, GUO Yang, and SUN Zhiqi
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.012
To study the influence of different subgrade types on the low-temperature shrinkage performance of asphalt pavement, this paper designed two kinds of asphalt pavement combination structures for the semi-rigid subgrade and flexible subgrade: AC-16+cement-stabilized gravel and AC-16+asphalt-stabilized gravel. Strain gauges were attached at the center of the sides of the two materials and at the characteristic positions of the interfaces between the layers, and the resistance strain gauge measurement method was employed to carry out the temperature shrinkage test of the combined structure and thus obtain the strain changes at each position during the cooling process, with the influence of the subgrade type on the low-temperature shrinkage performance of the surface layer analyzed. Specifically, the test temperatures were -30–20℃, with every 10℃ as a temperature range. The results show that at the same temperature, the strain value of the flexible subgrade at each characteristic position is very close to the asphalt surface layer, with the absolute difference between the two being 3.1%. The temperature shrinkage of the asphalt surface layer corresponding to the flexible subgrade is closer to the free state of the monolithic deformation. In each temperature range, the constraint strain of the flexible subgrade on the asphalt surface layer is reduced by an average of 76.7% compared with the semi-rigid subgrade structure. With the decreasing temperature, the average interlayer strain difference increases, with the interlayer strain difference of the flexible subgrade structure much smaller than that of the semi-rigid subgrade structure. The results well explain the difference in the low-temperature shrinkage capacity of asphalt pavement layers under different subgrade types, which can provide better theoretical support for asphalt pavement structures in cold regions.
Bridge Engineering & Tunnel Engineering
Research on effect of structural system on static and dyn amic stiffness of large-span and narrow suspension bridges
SONG Songke, HE Jiayong, CHEN Qian, DU Taoming, LI Yongle, and YU Chuanjin
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.013
Large-span and narrow suspension bridges featuring flexible structures and low overall stiffness have prominent wind resistance problems. Structural static and dynamic stiffness is the basic parameter for wind resistance of long-span bridges. By taking a large-span and narrow suspension bridge as the research project, this paper comparatively analyzed the effects of parameters such as stiffened girder stiffness, main cable span ratio, main cable spacing, and lifting point width on the static and dynamic stiffness based on the theory of spatial cable segmental suspension lines and three-dimensional finite element models of bridges under multi-working condition systems. The results show that the stiffened girder stiffness contributes more to the overall stiffness of the bridge, positively correlates with the static and dynamic stiffness of the structure, and especially has obvious influence on the vertical and torsional static and dynamic stiffness of the structure. The main cable span ratio exerts a greater effect on the torsional static and dynamic stiffness of the bridge, while the main cable spacing and lifting point width have limited effect on the static and dynamic characteristics of the bridge.
Research on design method of anti-overturning stability of large cantilever steel truss beam traverse construction based on reliability inversion theory
YANG Shusheng, CUI Fengkun, WANG Jiansheng, SU Baozhong, and XU Shaoxia
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.014
To evaluate the safety of large cantilever steel truss beams in traverse construction, this paper proposed a method of evaluating the safety factor of anti-overturning stability of large cantilever steel truss beams based on the reliability inversion theory. Under the premise of giving the target reliability index and considering the randomness of the structural parameters, this method adopted the reliability inversion theory to solve the anti-overturning safety factor of large cantilever steel truss beams in traverse construction. Finally, the method was utilized to study the anti-overturning stability of the 82 m large cantilever steel truss beam of Weilai High-speed Railway and analyze the sensitivity of the parameters. The calculation results show that in traverse construction of large cantilever steel truss beams, ignoring the effect of parameter uncertainty will result in overestimation of the safety factor of anti-overturning stability of the structure. The safety factor of anti-overturning stability is most sensitive to the two parameters of traverse counterweight mass and counterweight distance. Specifically, the safety factor of large cantilever steel truss beams’ anti-overturning stability decreases rapidly with the increasing variability of the two parameters.
Experimental and simulation study on bond degradation of fractured prestressed tendons
YONG Pan, LI Cong, CHEN Guan, XIANG Dan, HU Xianwei, and QI Honghe
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.015
To solve the corrosion and fracture of prestressed tendons in the end-anchor area of post-tensioned prestressed concrete (PC) girders under the chlorine salt environment, this paper employed electrochemically accelerated corrosion tests to obtain three PC members after the fracturing of prestressed tendons in the end-anchor area, and then carried out the static drawing test to study the effects of concrete strength and stirrup diameter on the bonding performance of prestressed tendons after fracturing. The results show that the bond damage of the strands starts at the drawing end and gradually develops to the free end. Additionally, increasing the concrete strength and stirrup diameter can improve the bonding performance between the prestressed tendons and the concrete interface. The numerical simulation on the bonding performance of the prestressed tendons after fracturing was carried out by utilizing Abaqus software, and the results show that the bonding-slipping numerical simulation results are consistent with the variation rule of the test values, with a high degree of consistency. Meanwhile, the stress cloud maps of the concrete and prestressed tendons demonstrate that the stress of the concrete and prestressed tendons is reduced along the drawing end of the specimen to the free end, with stress loss during stress transfer.
Parameters study on durability of substation structure of multi-tower suspension bridge
QIN Xiao, PAN Ji, and XIAO Rucheng
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.016
Substation structures are important components of the bridge structure, and their durability will affect the service life of the overall bridge structure. Since the overall structure of a multi-tower suspension bridge is more flexible with larger deformation, and the cumulative displacement at the substation structure is also larger, the durability problem of the substation structure is more prominent under multi-tower suspension bridges. To qualitatively analyze the influence of the structural parameters of the bridge structure (including tower-beam connection and cable-beam connection methods) on the durability of the substation structure, this paper built a finite element model of a four-tower suspension bridge, and carried out calculations by influence line loading to obtain the cumulative displacement at the beam ends and supports under different tower-beam connection and cable-beam connection methods. The results show that the tower-beam consolidation method has the most significant effect in reducing the accumulation of the longitudinal and corner displacement at the beam ends. The stronger constraints of the longitudinal tower-beam connections lead to smaller longitudinal displacement at the beam ends and the supports. Additionally, the installation of a central buckle is conducive to reducing the accumulation of longitudinal displacement and corner displacement.
Influence of shear deformation on manufacturing and erection alignment
WANG Jin and CHEN Changsong
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.017
This paper aims to study the effect of shear deformation on the manufacturing and erection alignment of main girders of free cantilever erection steel box girder bridges and better design the state of bridge formation state. To this end, it calculated the shear stress coefficient of uniformity of the steel box girder’s cross-section by adopting the finite element method and conducted comparison with the solid model of the plate and shell units of the steel box girder. The results show that the shear stress coefficient of uniformity calculated by finite element software is accurate and reliable. Additionally, simple modeling indicates that shear deformation leads to changes in the manufacturing and erection alignment of the main girder, and neglecting shear deformation will affect the erection joints of the upper and lower wing plates of the old and new girder segments, ultimately influencing the smoothness of the completed bridge. By comparing the changes in the manufacturing and erection alignment of the main girder of a large-span cable-stayed bridge which was built by the utilization of free cantilever erection, this paper pointed out the importance of the manufacturing and erection alignment.
Study on temperature gradient of long-span single-box double-chamber box girder bridge
YANG Wenbin
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.018
In view of the complex temperature effect of the single-box double-chamber box girders, this paper aimed to carry out the temperature gradient study of box girder cross-sections by employing a short-tower single-box double-chamber cable-stayed bridge with span arrangement of (120+120) m. 21 temperature sensors were installed at the cross-sections of large-mileage closure sections, with the set collection frequency of one time per hour and a wireless collection module for data collection. Meanwhile, temperature observation was carried out for a period of 171 d to obtain the distribution law of the temperature gradient in cross-sections of the closure sections. The study shows that the temperature difference between the box girder body and the atmospheric temperature is closely related, and the average temperature of the box girder body has the same changing trend with the atmospheric temperature. Additionally, the correlation coefficient R of the highest and lowest average temperatures of the box girder body and the corresponding highest and lowest atmospheric temperatures is 0.958 and 0.931 respectively, with high correlation between the temperature difference of the box girder body and atmospheric temperature. In addition, this paper carried out temperature gradient research based on the measured temperature difference at 16:00 when the overall temperature difference is the largest and the predicted maximum temperature difference, and proposed a prediction formula for the vertical overall temperature gradient of box girder cross-sections considering the daily total solar radiation I, daily atmospheric temperature difference T, and daily average wind speed w. Then the formula was compared with the formulas of the literature, thereby proving the validity of the prediction formula proposed by this paper. Finally, to cope with the maximum transverse temperature difference of 4.54℃ at the top and 1.99℃ at the bottom of the tested cross-section, this paper further put forward prediction formulas for the transverse temperature gradients at the top and bottom of the box girder, and found the correlation coefficients to be 0.819 and 0.851 respectively.
Study and implementation of jacking scheme of vertical curve beam with two -way longitudinal slope without adjusting temporary pier top elevation
ZHANG Hongwu, KE Hongjun, CHEN Zhuoyi, and YANG Wu
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.019
The bridge alignment design is the straight line+circular curve+straight two-way longitudinal slope vertical curve variable curvature steel bridge jacking. To deal with this problem, this paper analyzed the shortcomings of existing schemes such as real-time or multiple adjustments to the temporary pier top elevation, and proposed a jacking scheme of taking full advantage of the steel bridge’s characteristics including small flexural rigidity, strong adaptive deformation ability and high material strength, without adjusting the temporary pier top elevation. Additionally, the whole-process finite element simulation analysis was conducted on this scheme via a background project, with the calculation results revealing safety and feasibility. In the adoption of the scheme for jacking of the real bridge, the temporary pier and steel bridge were safe and stable during the whole jacking, and the alignment was smooth after completing the jacking. The parameter analysis of increasing both longitudinal slopes and decreasing the radius of the middle curve shows that under the premise of keeping the tangent length unchanged, even if the gradients of both longitudinal slopes reach the maximum value specified in the specification and the radius of the middle curve is smaller than the minimum value specified in the specification, the jacking scheme which does not adjust the pad thickness can still satisfy the safety requirements, thus broadening the application scope of the proposed scheme.
Optimization of bridge life cycle maintenance decision based on LCA and LCC
LIU Shuguang, LIU Jun, LIU Yonghua, and WANG Fan
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.020
To study the optimal maintenance strategy for bridges over the whole life cycle under the influence of life cycle environment and life cycle cost, this paper built a multi-objective optimization model for bridge life cycle maintenance decision by adopting preventive maintenance and substantial maintenance as the basic maintenance methods, and bridge reliability, life cycle environment and life cycle cost as the objective functions. Additionally, it derived the quantification method of indicators including the time-varying reliability, life cycle environment and life cycle cost indicators of the bridge, and determined the computational process of bridge life cycle maintenance decision optimization based on the genetic algorithm. The optimal maintenance strategy set for a prestressed concrete continuous T-shaped beam bridge was analyzed as an example. The results show that the implementation of preventive maintenance can improve the bridge reliability probability and reduce the frequency of substantial maintenance. Meanwhile, this can reduce the life cycle cost and environmental effect, and better extend the time of first implementing substantial maintenance, delaying the reduction of the reliability indicators.
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.021
Bilateral box steel main girders are widely employed in large-span double-plane cable-stayed bridges. These bridges are characterized by low frequency, small damping, and relatively light mass, and their wind resistance stability is a key problem to be solved in bridge construction. By taking the Pingnan super major cable-stayed bridge with a main span of 636 m on Pingrong Expressway under construction as the research project, this paper built a finite element spatial model of the bridge and analyzed the structural modal characteristics. Meanwhile, it carried out the main girder segmental model of elastically suspended vortex vibration and chatter vibration wind tunnel tests to study the effect of the cantilevered sidewalk on the wind resistance performance of the bilateral box main girder. The test results show that the bilateral box main girder of the Pingnan super major bridge has sound vortex vibration performance, with no vortex vibration phenomenon observed in the test. Additionally, cantilevered sidewalks improve the chatter stability of the bridge, conducive to wind resistance of the bridge.
Data analysis and early warning platform for bridge health monitoring based on Matlab-JAVA fusion
WANG Zhiwen, MAO Yongjia, and DING Youliang
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.022
Bridge health monitoring provides important support for daily operation and maintenance management of bridges. Meanwhile, real-time analysis, evaluation and early warning of bridge health monitoring data are the core requirements for enhancing bridge monitoring and safety protection, which can help grasp the operation status of bridge structures in real time and guard against major safety risks of bridge operation. This paper combined traditional signal processing and statistical analysis with modern machine learning and deep learning, and developed a platform for real-time analysis and warning of bridge health monitoring data based on Matlab-JAVA integration. Online cleaning, feature extraction, performance evaluation and safety warning of health monitoring data were included to realize automatic analysis of monitoring data, real-time evaluation of structural conditions, and timely warning of abnormal status. Finally, the main functions of the monitoring data analysis and warning platform were demonstrated by taking the Julong super major bridge project as an example. Practice shows that the platform realizes fast and accurate analysis of health monitoring data, and has excellent data analysis and operation efficiency.
Study on long-lasting anticorrosive primer for steel deck paveme nt in marin e environment
YAN Dongbo, ZHUANG Yongyi, LIU Yan, CHEN Zhenfu, and CENG Deliang
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.023
In steel deck pavement, after the occurrence of local diseases, steel plates are prone to rapid rust to exacerbate the disease development. To this end, based on the waterproof adhesive system of polymethyl methacrylate resin for steel deck pavement under the marine environment, this paper adopted the organosilicone-modified epoxy resin as the main raw material, which was combined with the cashew phenol-modified phenolic amine and polyamide mixed curing agent. Meanwhile, this paper added a new type of environmentally friendly rust prevention pigment to produce the long-lasting anticorrosive primer for steel deck pavement. The technical requirements of the long-lasting anticorrosive primer for steel deck pavement were formulated with reference to relevant specifications. By considering the thermal aging effect of asphalt pavement at high temperature, water and chemical medium corrosion and salt spray effect, the performance test of the anticorrosive primer after single-factor and multi-factor combined effect was completed. Additionally, the compatibility between the long-lasting anticorrosive primer and waterproof and pavement layers was experimentally investigated and compared with the traditional anticorrosive primer for steel deck pavement.
Research on structural design of Steel-UHPC light composite beam of large-span self-anchored suspension bridge
ZHANG Xin, LI Yu, and LIU Yong
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.024
To optimize the structural scheme of steel-ultra-high performance concrete (steel-UHPC) light composite stiffening beams for large-span self-anchored suspension bridges, by taking the Qinglongzhou Bridge in Yiyang as the research object, this paper employed finite element simulation and full-scale tests to compare and verify three steel-UHPC composite stiffening beam schemes, and compare the indicators such as static behavior and economic properties. The results show that the UHPC stiffened girder is the best choice for the structural performance and economic characteristics. The results show that the UHPC waferboard, UHPC longitudinal rib plate without web reinforcement, UHPC longitudinal rib plate with long bolts and steel strips can meet the design requirements. Specifically, the UHPC longitudinal rib plate with long bolts and steel strips has higher flexural rigidity and crack-resistant safety reserves, and can reach 5.4 times the demand value. The new type of T joints of the deck plate can realize zero-welding of the deck plate by reasonably reserving the reinforcement, and reduce the breaking joints caused by fiber discontinuity in the high tensile stress area in the UHPC plate. The steel-UHPC light composite beam features superior performance, high applicability, and sound economy and application prospects.
Key technology of demolition and reconstruction design of wudou bridge
LI Huaqiang
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.025
Bridges constructed between the 1960s and 1970s have been damaged to different degrees during operation due to excessive traffic flow and severe overloading of vehicles, and thus cannot meet the requirements for safe passage of vehicles and navigation. Therefore, they need to be demolished and rebuilt. To safely, economically and efficiently demolish the old bridges and rebuild them in-situ, this paper studied a design concept of integrated construction and demolition. Based on the Wudou Bridge demolition and reconstruction project in Foshan, the combination of theoretical analysis and computational simulation was utilized to conduct a multi-scheme study from the perspectives of economy, safety and construction periods after field investigation and site conditions. The results show that the scheme of employing the old bridge as a support for new bridge construction and then leveraging the new bridge to help the demolition of the old bridge after comprehensively considering demolition and construction can save the amount of construction supports for new bridges, especially the amount of water supports and platforms, with the construction measure cost for the whole bridge saved by 33.5%.
Analysis of internal force and deformation of double-row steel sheet pile cofferdam in different working conditions
YANG Qin, FANG Zhongqiang, LIU Yi, and TU Qiliang
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.026
To understand the internal force and deformation generation mechanism of the double-row steel sheet pile cofferdam in complex stress conditions and determine the most unfavorable working condition, this paper adopted the finite element method to analyze the displacement, axial force of steel tie bars and bending moments of steel sheet piles in various construction stages at different water levels and under different load types. The study shows that the deformation and internal force of the cofferdam are affected by the water level, fill light weight, vertical construction load, horizontal wave load, and wind load. The most unfavorable conditions for displacement and steel tie bars are the high water level-horizontal load and the low water level-vertical load respectively, while the most unfavorable condition for steel sheet piles needs to consider a variety of conditions to take the maximum value.
Design of prefabricated deep-water combined steel sheet pile cofferdam
FU Su, CENG Jian, YANG Suhai, WANG Chao, and DENG Songtao
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.027
By taking the pier bearing platform 9# of the non-navigable bridge in the eastern flood-relief area of Shenzhen-Zhongshan Link as the research project, this paper introduced the cofferdam structure of prefabricated combined steel sheet piles using the support-first construction process from the aspects of the cofferdam structural form, cross-section type of steel sheet piles, construction process, and support system, and adopted the finite element method to numerically analyze the whole cofferdam construction process. The combined cross-section of cap-shaped steel sheet piles and H-shaped steel greatly improves the rigidity of steel sheet piles. Additionally, the construction process of the support-first method leads to more reasonable force of sheet piles and internal support, thus making the steel sheet pile cofferdam suitable for larger water depth. Meanwhile, the prefabricated internal support structure system reduces the hidden safety danger of steel sheet pile replacement, with strong operability and high prefabrication degree of components. This enhances the conversion efficiency of the internal support system and turnover efficiency of the materials in the cofferdam and reduces the construction period and cost.
Performance analysis of steel bridge deck reinforced by UHPC based on fracture mechanics
LONG Yiyu, CHEN Shuangqing, TANG Chunyan, PENG Yajun, and ZHOU Zejian
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.028
At the deck-rib welding joints of orthotropic steel bridge decks, cracking can easily occur under the vehicle load, and the fatigue risk of steel bridge decks can be effectively reduced by UHPC reinforcement. To investigate the effect of UHPC-reinforced steel bridge decks, this paper carried out finite element analysis based on linear-elastic fracture mechanics. By taking the orthotropic steel bridge deck test as the reference, the fatigue performance at the weld toe was calculated, and the reliability of the finite element model was verified. Stress intensity factor calculation analysis was performed by inserting an initial crack at the weld detail, with the effects of different loading positions and UHPC layer thickness on the value of the stress intensity factor at the crack tip considered. The results show that the hot spot stress at the weld of the top deck is higher than that at the weld of the U-rib, with the hot spot stress more obviously affected by the loading location. Additionally, the addition of the UHPC layer can increase the rigidity of orthotropic steel bridge decks, thus reducing the stress concentration at the crack tip. The stress intensity factor of the initial crack tip is reduced by about 89% when the UHPC pavement layer with a thickness of 50 mm is added. Therefore, the study can provide references for the design of UHPC-reinforced steel bridge decks.
Structure design of platform for construction of inclined pile foundation on the water under complex hydrogeology conditions
CHENG Tao, FU Su, and DENG Songtao
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.029
Based on the design of the pile foundation construction platform for the Yushan water intake in Daishan Port, this paper introduced the adoption of the support system combining the steel pile casing and steel pipe piles in complex hydrogeological conditions. Most of the pile foundations feature small embedded length and are inclined piles with weak lateral rigidity, and they cannot resist the horizontal loads such as wind-wave-current during the typhoon period. Therefore, this paper introduced several measures taken to improve the overall lateral stability of the platform. The first measure is to improve the boundary conditions of pile foundations by focusing on the filling of rubble at the shallow soil-covered pile foundations. The second is to optimize the selection of the corners around the platform and pile foundations with small embedded length for the construction of the concrete-filled piles. Finally, the design problem of insufficient lateral stability of the platform due to large terrain undulation, complex hydrological and stratigraphic conditions and different tilting directions of pile foundations was solved, thus providing references for the design of similar projects.
Orthogonal analysis of influential factors in construction of portal pier foundations adjacent to existing railway
LI Minghua, FENG Jiahui, and HAN Wenjing
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.030
To study the influencing factors of portal pier foundation construction adjacent to existing railway, this paper adopted the orthogonal test method based on numerical simulation to study the influence of five factors on the existing railway, including the length of bored piles, construction sequence of bored piles, excavation depth of foundation pits of the bearing platform, length of steel sheet piles, and number of steel sheet piles. The results show that during the bored pile construction stage, the most important factor is the construction sequence of bored piles. Meanwhile, during the stage of foundation pit excavation and substructure construction, the most important factor is the excavation depth of foundation pits, and the construction sequence of bored piles and length of steel sheet piles also have a significant effect, with no significant effect exerted by the number of steel sheet piles and length of bored piles. It can be seen that in the construction adjacent to the existing railway, the elevation of bearing platforms should be improved as much as possible, the excavation depth of foundation pits should be reduced, and the length of steel sheet piles should be increased appropriately to better protect the existing railway.
Stress analysis and monitoring of composite cable hanging basket during construction
ZHOU Su, LI Xinsheng, LIU Chentao, and SHAO Mingjie
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.031
Composite cable hanging baskets are also known as front and rear pivot combined hanging baskets. By taking the construction monitoring of a single-tower and double plane cable-stayed bridge as the research project, this paper demonstrated the rationality, practicability and advancement of the composite cable hanging baskets during construction, and carried out modeling analysis of the whole construction stage. Meanwhile, the batch tension values of the construction sections were determined according to the deformation of the hanging basket during the construction stage, and then the theoretical and measured values of the basket’s deformation and stress during the construction stage were analyzed and compared. The results show that during the construction stage, the design of the hanging basket features safety, reliability, and clear force transmission, which can provide references for guiding the hanging basket design of similar bridges in the later stage.
Analysis method and evaluation of fatigue life of welded cable clamp
LI Hongsheng, ZHANG Zhixin, XUE Songling, and WANG Zhicheng
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.032
In view of the practical application of welded cable clamps in Xintian Yangtze River Bridge, this paper adopted numerical calculation to analyze the fatigue performance of welded cable clamps and evaluate the fatigue life of the clamps. Firstly, a finite element model for Xintian Yangtze River Bridge was built to analyze the static characteristics of the bridge under constant and fatigue loads. Then, the geometric configuration of the welded cable clamps was analyzed and a numerical model of welded cable clamps was built, with the submodel technique adopted to analyze the mechanical properties of the clamps under different loads. Finally, the fatigue test data applicable to the welded cable clamps of Xintian Yangtze River Bridge was compared according to relevant specifications. Meanwhile, the fatigue life of the welded cable clamps was calculated by the empirical equations and FE-SAFE. The study shows that the results obtained by numerical calculations and empirical equations are close to each other, with the logarithmic fatigue life of the welded cable clamps being about 10. The welded cable clamps of Xintian Yangtze River Bridge will not experience fatigue damage within the designed service life.
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.033
To study the influence of tunnel crossing construction on the existing tunnel structures, this paper took the overcrossing construction of the existing Chenba tunnel of Fuxia railway of Xingquan railway Lyugu No. 2 tunnel as the research project. By adopting the numerical simulation method of finite element, it studied the change rules of the displacement field and stress field of the existing tunnels affected by the overcrossing construction of the new tunnels. The results show that the influencing range subject to the effect of Lyugu No. 2 tunnel’s excavation on the existing Chenba tunnel is roughly within the range of 60 m before and after the interchange section. Meanwhile, the maximum uplift and maximum horizontal convergence displacement are 1.04 mm and 0.254 mm respectively, meeting the displacement control standard. Compared with the new tunnel before excavation, the axial force of the existing Chenba tunnel is reduced by 0.74%, the bending moment is reduced by 6.7%‒1.6%, and shear force is decreased by 1.5%‒7.7%, which meets the requirement for tunnel lining strength. Additionally, as the overall coefficient of safety of the existing Chenba tunnel lining is higher than 2, the coefficient of safety for lining meets the requirement. The numerical simulation results are in sound agreement with the measured results, providing references for the actual construction schemes.
Risk assessment calculation of layered surrounding rock tunnel based on combination Weight-EAHP-NCM model theory
YANG Yongbin, WANG Qing, WANG Yijun, GAO Weizheng, and LI Yongliang
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.034
To accurately assess and calculate the structural stability of layered surrounding rock tunnels during construction, this paper firstly constructed a risk assessment index system for layered surrounding rock tunnels based on the consideration of factors of hydrogeology, structural surfaces, engineering, external forces, and topography and geomorphology. Based on the Delphi method (DELPHI) and entropy weight method (EWM), the combination of indicators was assigned. Based on the typical event samples and the mining of classical domains-joint domains of the assessment system, the extension analytic hierarchy process calculation model (EAHP) and normal cloud computing model (NCM) were built to assess the stability of layered surrounding rock tunnels respectively. The two risk assessment algorithms for two layered surrounding rock tunnels were validated by employing the Gonghe Tunnel. The results show that the assessment results of EAHP, NCM and BP neural network algorithms are in agreement with each other, the stability of the Gonghe Tunnel is in the range of Ⅲ‒Ⅳ, and the tunnel structure is in the “serious‒abnormal” state. This coincides with the frequent deformation of steel arch frames and occasional collapse accidents at the construction sites, and verifies the reliability of the risk assessment system and theoretical algorithms of this study on layered surrounding rock tunnels.
Optimization design of highway tunnel inner contour based on simu lated annealing algorithm
ZHANG Qingwei
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.035
To optimize the inner contour design of road tunnels, this paper regarded the inner contour design of a road tunnel as an optimization problem in certain conditions. By taking the area optimization as the objective, it introduced the simulated annealing algorithm to solve the problem based on the calculation model building of the inner contour of a single-centered circle with an inverted arch, with a program written for verification and analysis. The results show that the optimization design scheme is feasible and can provide an idea way for the inner contour design of road tunnels.
Pavement Structure and Materials
Review of material composition and p erformance evaluation of cold patch asphalt mixture
YANG Yanhai, ZHU Guangxu, and YANG Ye
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.036
To summarize the latest research achievements of cold patch asphalt mixtures at home and abroad, and to promote their development and application, this paper firstly introduced the development history of cold patch asphalt mixtures domestically and internationally, and focused on summarizing the classification and material selection of materials, as well as common mix ratio design methods. Secondly, it reviewed and analyzed the influencing factors of performance evaluation of the mixtures. Finally, such problems as the strength effect mechanism and the link between the material and performance, and the future research directions were combined to establish a unified and effective evaluation system for cold patch asphalt mixtures based on the principle of cold patch materials. As a result, basic theoretical and technical guidance was provided for the prevention and repair of pot hole damage on the roads.
Study on low temperature performance of asphalt mixture under salt freezing condition
SONG Yunlian, GAO Pan, and JIANG Yu
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.037
To investigate the ice-melting ability of snow-melting agents and the effect of different salt freezing conditions on low temperature performance of asphalt mixtures, this paper carried out the ice-melting ability test, beam bending test and beam bending creep test. The results show that under the temperature of -20℃ and concentration 30% or more of the snow-melting agent, the ice can be melted. However, the melting ice quality is small. In terms of melting ice quality, the melting ability of the P-type snow-melting agent is better than that of the H-type snow-melting agent. Under the temperature of -10‒0℃, the recommended concentration for the P-type and H-type snow-melting agents is 20% and 30% respectively. At this time, the ice-melting effect is better, and the damage to asphalt pavement can be reduced. Meanwhile, under the salt freezing time of 24 h, the beam strength injury is close to the maximum, with the maximum reduction being only 2.25% compared with the salt freezing time of 72 h. In contrast, the creep rate decreases with the rising salt freezing time. The grey correlation analysis finds that the concentration of the snow-melting agents has the most significant effect on melting ice quality. Analysis of variance demonstrates that the significance degree of influence on the beam bending and tensile strength is in the order of temperature > concentration of snow-melting agents > salt freezing time.
Research on performance simulation of previous concrete considering characteristics of void structures
ZHENG Shuai, DAN Jingsong, HAN Weiwei, LV Yigang, HE Jie, and PEI Fucai
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.038
Pervious concrete contains a large number of macroscopic voids. To analyze the influence of the void structures on the mechanical properties of pervious concrete, this paper adopted the random void method to build a simulation model of pervious concrete, and study the effect of the characteristics of the void structures on the force properties. Firstly, two kinds of pervious concrete specimens with two void content levels were made indoor, and then the specimens were cut after curing and molding. Next, image enhancement and threshold segmentation were conducted on the section images of the cut surfaces, and two-dimensional digital images of void distribution were extracted to analyze the characteristics of the void structures. Based on the actual void structures, the random elliptic and random circular void simulation models were generated with the help of finite element software Ansys and Monte Carlo method. The simulation results show that under the same void level, the random elliptic void model has larger overall force deformation and more obvious internal stress concentration than those of the random circular void model. By comparing the simulation and experimental results of different void levels, the recommended value of the comprehensive modulus of aggregate-cement slurry material in the random void simulation model was obtained.
Study on frost resistance and pore structure of Nano-SiO 2 modified pavement concrete under fatigue load
ZHOU Xuexiang, ZHENG Wenshi, and WU Cong
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.039
To improve the frost resistance of concrete pavement under fatigue load, this paper simulated the freeze-thaw damage of concrete pavement under vehicle load by indoor fatigue loading and alternating freeze-thaw cycling test. Meanwhile, it designed the bending tensile test to test the residual bending tensile strength of nano SiO2-modified pavement concrete after freezing and thawing, and adopted the mercury injection method to test the microscopic pore structures of concrete. Additionally, by employing the electron microscope, the change rules of pores in the concrete under the action of fatigue load were observed, and the effect of nano SiO2 dosage, the number of fatigue load action on the frost resistance of pavement concrete was studied. The results show that under the action of fatigue load, adding appropriate amount of nano SiO2 can significantly improve the frost resistance of concrete pavement, and the increasing number of fatigue load action leads to more significant improvement effect of nano SiO2. Under the nano SiO2 dosage of 2%, the frost resistance is the best. Fatigue load will destroy the stability of the concrete pore structures, bring about pore connectivity, and accelerate the freeze-thaw damage of concrete specimens. Nano SiO2 can fill the concrete pores, reduce the void content of concrete pores, and improve the pore size distribution of concrete. Additionally, the fatigue load-induced pore structure destabilization and pore connectivity can be alleviated to improve the frost resistance of concrete pavement.
Influence of natural environment on the serviceability of emulsified asphalt cold recycled mixture
YANG Puxin
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.040
To improve the early serviceability of emulsified asphalt cold recycled mixtures, this paper studied the effect of curing conditions on the mechanical strength and stability of emulsified asphalt cold recycled mixtures by conducting indoor tests. The results show that in the same test conditions, the indoor emulsified asphalt cold recycled mixture can better characterize the serviceability of practical projects. Compared to the indoor specimen mixture, the stability and cleavage strength of field mixture core samples are increased by an average of 5.5% and 10.7% respectively. Under the curing time of no less than 7 d, the stability, cleavage strength and freeze-thaw cleavage strength ratio of cold recycled mixtures meet the technical requirements specified in Technical Specifications for Highway Asphalt Pavement Recycling (JTG F41-2008), with the increase rates of the above three indicators being 2.5%, 0.8%, and 0.6% respectively. Under the curing temperature of 40℃, the serviceability of cold recycled mixtures is optimal. As the water content increases, the void content of cold recycled mixtures first rises and then decreases, with gradually decreasing serviceability. Under the water content of 3.7% and 4.2%, the cleavage strength of the cold recycled mixture does not meet the technical requirements in Technical Specifications for Highway Asphalt Pavement Recycling (JTG F41-2008). It is recommended that the curing time of emulsified asphalt cold recycled mixtures should be 7 d and the curing temperature should be 25‒40℃.
Experimental study on recycled brick powder foam concrete based on slurry substitution method
LIAO Shixian and HUANG Lei
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.041
Foam concrete is a kind of porous lightweight building material characterized by sound insulation and noise reduction, heat insulation and fire resistance, heat preservation and frost resistance. However, it has defects such as low strength, high porosity and poor integrity, thus limiting its wide application in the field of building materials. Recycled brick powder can be prepared from construction waste of clay bricks and has certain volcanic ash activity. Meanwhile, the mechanical properties of foam concrete can be improved by employing waste bricks as an admixture in cement-based composite materials. In view of the problems of the cement substitution method, in the experiment, this paper adopted the slurry substitution method to prepare recycled brick powder foam concrete, and investigated the brick powder foam concrete from the aspects of compressive mechanical properties and microstructures. The results show that the addition of recycled brick powder can improve the strength of foam concrete. Analysis on the hydration products and micro-morphology of recycled brick powder foam concrete reveals that as the substitution rate of recycled brick powder becomes larger, the recycled brick powder can better leverage its volcanic ash activity, thereby generating more hydration products. Additionally, due to the mixing of recycled brick powder, the specimen produces a micro-aggregate effect. This means that the recycled brick powder fills the tiny pores of foam concrete, making the microstructure more compact.
Study on mix design and performance of permeable concrete considering sand ratio and aggregate to binder ratio
WEI Yazhou and JI Rongqing
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.042
Considering the effect of the sand ratio and aggregate to binder ratio, this paper improved the traditional mix ratio design method-volumetric method, and investigated the influence of the sand ratio, aggregate to binder ratio, and maintenance method on the mechanical properties and permeability coefficient of pervious concrete based on the improved method. The results show that under the sand ratio of 15%, the compressive strength of concrete is significantly increased and the permeability is not affected. When the aggregate to binder ratio is 3.0‒3.1, the compressive strength and permeability coefficient of the concrete can be both considered. Additionally, compared to the standard maintenance, high temperature water maintenance is not an effective way to improve the comprehensive properties (compressive strength and permeability) of pervious concrete. The adoption of the improved mix ratio design method can make it possible to prepare pervious concrete with compressive strength of more than 30 MPa and a permeability coefficient of about 6 mm/s. The permeability coefficient K of pervious concrete is inversely proportional to the 28 d compressive strength S, which can be expressed as K=1/(0.0478+0.00402S). The effective voidage can explain the reasons for the variations of the compressive strength and permeability coefficient of the concrete with the sand ratio, aggregate binder ratio, and maintenance method.
Application of dry SBS modification technology in yanhai highway
ZHANG Han, MENG Chunlin, ZHAO Mingfang, LU Chuanzhong, and JI Guoqi
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.043
Dry SBS-modified asphalt pavement technology is to produce SBS-modified asphalt mixtures by adding specific SBS modifiers, which aims to solve the performance degradation of SBS-modified asphalt in transportation and storage. By relying on the coastal highway repair projects, this paper compared the effects of different dry SBS mixing contents on the test results by the indoor dry SBS and matrix asphalt compatibility test and asphalt mixture performance evaluation test. Meanwhile, based on the test results, the recommended dry SBS mixing content for the coastal highway upper layer milling and resurfacing maintenance project was proposed and applied on a large scale in combination with the project. The application effect shows that under the recommended optimal dry SBS mixing content, the asphalt pavement features excellent performance, reasonable cost, and prominent popularization significance.
Experimental study on mechanical properties of steel-polypropylene mixed fiber rubber concrete
QIU Jiandong
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.044
Waste rubber materials can be recycled to obtain rubber aggregates, which can be employed in cement concrete products. This paper carried out mechanical performance tests on ordinary concrete and rubber concrete (rubber substitution rate of 20%) with different fiber combinations (doped MS, co-doped PP, and mixed MS-PP), and mainly examined the slump, density, compressive strength, modulus of elasticity, split tensile strength, and rupture strength of the concrete. The results show that the relevant performance indexes decrease significantly after 20% of rubber aggregate is added to the concrete. However, the mechanical performance of ordinary concrete and rubber concrete with the combination of 0.9MS+0.1PP and 0.8MS+0.2PP fiber is improved in all aspects. Therefore, the mixing content of rubber aggregate should be strictly controlled in the actual production of rubber concrete, and the steel fiber and polypropylene fiber can be mixed to improve the quality of concrete products if necessary.
Analysis of light reflection and automobile exhaust degradation effect of asphalt pavement coating
SHANG Wenyong, ZHOU Zheng, and CHEN Jun
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.045
To compare the light reflection and exhaust degradation effect of common road coating fillers, this paper prepared three kinds of road surface coatings with Nano-TiO2, Nano-ZnO, and Micro-TiO2 as fillers respectively. Meanwhile, the reflectivity tests of the coatings with different mixing contents of fillers were conducted by adopting a self-developed light reflectivity tester to determine the optimal mixing content of fillers. Under the optimal mixing content of fillers, the reflectivity of three kinds of coating asphalt mixtures was tested to compare the light reflectivity effect of Nano-TiO2, Nano-ZnO and Micro-TiO2. Additionally, a self-developed exhaust concentration analyzer was utilized to test the degradation rate of three kinds of coatings on CO, HC, and NOx gases in photocatalytic conditions, with the degradation effects of the three kinds of fillers compared. The results show that the reflectivity of asphalt mixtures is 5.46%‒6.11% and the optimal mixing content of fillers in reflective coatings is 30%. After coating, the reflectivity of the mixtures decreases greatly, and the order of reflectivity of the three kinds of fillers under the same dosage of coatings is Micro-TiO2>Nano-ZnO>Nano-TiO2. Meanwhile, the reflectivity of the Micro-TiO2 coating reaches 59% under the dosage of 0.9 kg/m2. The exhaust degradation effect exerted by fillers is in the order of Nano-TiO2>Nano-ZnO>Micro-TiO2. Specifically, the coatings have the most prominent effect on the NOx degradation in the three kinds of exhaust.
Study on effect of nanomodified additives on properties of concrete mixtures during winter season
LI Yulin, LIANG Hongjie, LIANG Junlin, RONG Hongliu, and YANG Xiaolong
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.046
To solve the difficult placement of small structures on highways caused by the decreasing workability of cement concrete construction in winter seasons, this paper developed a nanomodified additive to investigate its effect on the performance of cement concrete. Sulfonate naphthaleneformaldehyde (SNF), nanoSiO2, rosin soap (WSR) and sodium nitrate (NaNO3) were formulated into a variety of additives in different ratios and mixing contents to prepare cement concrete, with the fluidity, segregation and compressive strength studied. The results show that the optimal ratio (mass) of nanomodified additives is SNF:0.4%, nanoSiO2:0.1%, WSR:0.05%, and NaNO3:4.0%. The fluidity, segregation and compressive strength of the concrete prepared with the optimal nanomodified additive ratio meet the requirements, thus finding applications in the placement and maintenance of cement concrete for small structures on highways.
Traffic Engineering and Management
Comparison of specifications for highway safety audi ts of China ， the United States ， and Australia
LI Jie, HAN Huanhuan, LI Jia, REN Yabo, and GONG Ruiming
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.047
Traffic safety is one of the three major problems of transportation. To build a transportation power, China has proposed the call of “facilitating the transportation development from pursuing the speed and scale to paying more attention to quality and safety”, and improving the audit specifications of road safety is an important basis for increasing the transportation safety level. This paper firstly introduced the background where China, the United States and Australia issued the audit specifications of road safety, and then compared the differences between the three countries in the aspects of the audit process for road safety, audit indexes and content. Finally, it revealed the deficiencies of the existing specifications in China by analyzing the advanced concepts and experiences of the developed countries in road safety audit, which can provide references for improving the specifications for road safety audit.
Application of BIM forward design in complex three-dimensional traffic design stage
WANG Bo, ZHU Xinghu, PEI Wangjian, and GE Puta
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.048
To improve the accuracy and efficiency of complex three-dimensional traffic design, and provide basic digital data for the whole life cycle, this paper researched and investigated the application of BIM technology in the complex three-dimensional traffic design stage by taking the convergence project of the Qianhai section of Shenzhen Coastal Expressway and Nanping Expressway in Guangdong as a case study. Meanwhile, it put forward the BIM forward design schemes for the fields of roads, bridges, and tunnels, carried out secondary development, and built the three-dimensional parametric model, with the design results optimized. Additionally, design analysis and application were conducted to reduce the problems of errors, omissions, collisions, and deficiencies which will easily occur in traditional design. As a result, the design quality was improved to provide certain references for BIM forward design of relevant projects.
Research on a hub interchange scheme under special terrain conditions
WANG Jie and HE Yajun
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.049
By combining the study process and conclusion of the interchange scheme of the Lugao hub as an important node of G4216 Jinyang-Ningnan Expressway Project, this paper discussed the ideas and methods of selecting the hub interchange shape under complex terrains and high functional requirements. It aimed to provide certain references for the design of hub interchange schemes in special Y-shaped terrain conditions. The Lugao hub interchange location is deeply cut by the Jinsha River and its branches, with narrow valley bottoms, extremely steep cross slopes, and harsh engineering construction conditions. Meanwhile, in the limited space, the specific requirements of the highways for hub conversion and landing function should be satisfied. In addition, there are more controlled factors. In the main line where the bridge tunnel ratio is as high as 92.4%, the hub interchange is extremely limited in the open sections. The ramp connection location is controlled by the super major bridge of the main line (continuous rigid frame). The elevation of the connected highway is 40 m higher than the intersection of the two projects, while that of the ground level intersection is 62 m lower than the intersection. This paper systematically reviewed and summarized the experience of systematically grasping control factors, selecting reasonable schemes appropriately, and continuously optimizing the schemes in complex terrain conditions from multiple perspectives and throughout the entire process. Finally, new ideas are provided for the design of hub interchange schemes in similar terrain conditions.
Research on interchange reconstruction design of minxiao hub
HU Tian, TAN Ximing, YI Xuebin, and WEI Hui
Date posted: 9-14-2023
DOI: https://doi.org/10.14048/j.issn.1671-2579.2023.04.050
Based on the design of the Minxiao hub interchange, this paper analyzed the technical problems of frequent traffic accidents after the initial reconstruction of Minxiao hub interchange, and put forward corresponding reconstruction suggestions. In the interchange design details, the design points about the dual lanes adopting single lanes and speed change lanes only put forward the distance requirement of 60 m for the transition sections, but whether the gradual changes of the travel lanes and hard shoulders are completed in the same road section or not is not clarified. The initial reconstruction of Minxiao hub interchange is designed to complete the gradual changes of travel lanes and hard shoulders separately in different road sections. Although this design meets the requirements of the standard widening gradual change rate and the shortest transition distance, it does not conform to the driver’s driving psychology, resulting in frequent traffic accidents. This interchange reconstruction shows that in the ramp design, the design of the dual lanes employing single lanes and speed change lanes should put the gradual changes of lane width and hard shoulders in the same road section for completion, and should not be set up separately.
