交通运输工程学报

2022, 22(5): .

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CHEN Bao-chun, HUANG Fu-yun, XUE Jun-qing, LUO Xiao-ye, ZHUANG Yi-zhou, LIU Yong-jian, XU Ming, ZHAO Qiu-hong, BRISEGHELLA Bruno

Abstract: The technological development of jointless bridges was reviewed, the advatages, application and research hotspots were introduced, the longitudinal stress characteristics, pile-soil interaction, earth pressure of backfill on the autment and seismic performance were analyzed, and the present situation and development direction of the new technology research and application were pointed out. Analysis results show that the technologies of jointless bridges have been attached to importance in many countries, and a large number of field monitoring projects and other researches have been carried out. The temperature-induced deformation is the main cause of longitudinal stress of jointless bridge, and the average temperature difference predicted by the codes is quite different from the data obtained from field monitoring. Therefore, a preciser calculation method should be developed. Pile-soil interaction is the dominant characteristic of integral bridge and is the emphasis and difficulty of the research. In calculating the soil resistance, the m method should be limited to jointless bridges with small movements, while the p-y curve method should be employed when the movements are larger. The piles of the integral abutments are stressed complexly, H-shaped steel piles may be subjected to yielding, fatigue, and buckling, while RC piles are prone to be damaged by cracking. The high earth pressure behind the abutment induced by temperature rise is a hot spot and difficulty in the research. The mechanism, magnitude, and distribution of the earth pressure increasing with the horizontal movement and reciprocating number have not reached a consensus, and need to be further studied systematically. In analyzing the longitudinal behaviour of jointless bridge, the finite element model should involve the whole structure of the bridge, and considering the soil-structure interaction and the nonlinear performance of the joint. The stability of steel girders under compression and the crack-resistance of concrete girders under tension are the key points in research and design. The approach slab is an important and damage-prone component of jointless bridges. For the grade flat approach slabs, the frictional resistance at the bottom should be reduced, and the cracking and end settlement should be avoided. While for the buried inclined approach slabs, the swell and settlement of approach pavement above their ends should be controlled. Many new technologies for jointless bridges have been proposed, applied, and should be further studied, including the application of new materials and new details in various components, abutments, pile foundations, and approach slabs of jointless bridges. Jointless bridges have higher structural robustness and capability to prevent collapse and unseating of the superstructures. The research on the seismic resistance of jointless bridges has made gratified progress, but the relevant design regulations have not been formed in many countries. It is necessary to conduct comprehensive research to provide a scientific basis for engineering application and the formulation of the specifications in the future.More>

2022, 22(5): 1-40. doi: 10.19818/j.cnki.1671-1637.2022.05.001

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Review on long-term performance of reinforced concrete structures under simulated acid rain erosion environments

REN Qing-yang, JIN Hong-hua, XIAO Song-qiang, WANG Fei-fei, CHEN Bin

Abstract: To deepen the understanding of the long-term performance evolution mechanism of reinforced concrete structures under acid rain erosion environments, the corrosion mechanism, erosion model, and time-varying process of physical and mechanical properties of concrete materials under the acid rain erosion action were discussed. The solution corrosion mechanism and atmospheric dynamic scouring mechanism of steel bars corroded by acid rains were analyzed. The research results of morphology characterization and corrosion rate index quantification of the corroded steel bars were summarized, and the existing mechanical property degradation model and constitutive model of corroded steel bars were concluded. The evolution law of bonding performance of steel-concrete interface and the bonding-slip constitutive relation model were reviewed. The latest research progress and shortcomings of the evolution law of static and dynamic mechanical properties of beams, column components, and structures were reviewed in terms of indoor test results, theoretical calculation methods, and numerical simulation results, and future research directions and priorities were predicted. Research results show that the corrosion of concrete by acid rains can be attributed to the interaction of acid rain ion components, and a theoretical model with strong applicability is urgently needed to reveal the corrosion and diffusion mechanisms. The indoor accelerated test reveals the time-varying law of physical and mechanical properties of concrete under the action of acid rain corrosion, and the indoor accelerated test system should be improved. The damage evaluation system and prediction model of concrete should be built by coupling the key indicators at the macro and micro levels. The accelerated corrosion test of steel bars by acid rains is mostly based on the uniform corrosion, and the corrosion method and morphology characterization of steel bars are gradually developing towards uneven corrosion. High-precision scanning technology should be further developed, and the statistical analysis theory should be used to establish the characteristic parameters of uneven corrosion of steel bars, to optimize the mechanical properties degradation model of steel bars. The electric corrosion and pull-out tests deduce the evolution law of bonding performance of the steel-concrete interface, and build the bonding-slip constitutive relationship. However, the mechanical characteristics of the actual reinforced concrete structures are ignored, and the corrosion process is significantly different from the natural corrosion. The complex and changeable characteristics of acid rain environments and material properties should be considered to study the damage behavior of the steel-concrete interface at the micro level and reveal the internal relationship among acid rain environments, material properties, and bonding performance. The research on the aging performance of reinforced concrete structures eroded by acid rains is mostly concentrated on the specimen level, and the corrosion test and bearing capacity test are carried out in stages. The coupling effect of the load-environment is neglected. The test environment is relatively simple, and the test system and method are not unified. The bearing and environmental conditions of the actual structures should be considered according to actual projects, and a long-term load-acid rain erosion coupling test system should be built. The multi-field correlation mechanism of load-environment-material should be explored, and the theoretical calculation and numerical simulation method should be improved, so as to reveal the long-term performance evolution process of the structure, promote the development of field exposure test, quantify the indoor and on-site mapping relationship, and guide the actual projects.More>

2022, 22(5): 41-72. doi: 10.19818/j.cnki.1671-1637.2022.05.002

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Theoretical model of drying shrinkage behavior of recycled coarse aggregate concrete

CHOI Donguk, ENKHBOLD Odontuya, YANG Sungchul

Abstract: To investigate the drying shrinkage behavior of recycled coarse aggregate concrete, 12 studies and 32 sets of shrinkage data were collected and compared. The test period was between 41 and 480 d, and the analysis parameters were as follows: the water-cement ratio (0.36-0.68), compressive strength of normal concrete (27-60 MPa), replacement ratio of recycled coarse aggregate (20%-100%), relative humidity (43%-65%), time for wet cure (1-28 d), and time of shrinkage measurement (41-480 d). Three existing theoretical models, such as the ACI 209R-92 model, Bazant-Baweja B3 model, and fib MC2010 model, were evaluated by comparing the test data with the theoretical predictions using multiple statistical indicators based on the experimental drying shrinkage data of natural aggregate concrete. The approach proposed by Fathifazl et al. was used to evaluate the increase in the drying shrinkage of concrete. The increments of the drying shrinkage rate of recycled coarse aggregate concrete were also evaluated by the three selected models, and the experimental data were evaluated by the statistical indicators including the residual evaluation, as well as the variation coefficient, mean square error, and mean deviation of Comité Euro-International du Béton (CEB). Research results show that the most accurate predictions of the total shrinkage evolution are possible when part or all coarse aggregates of natural aggregate concrete with known shrinkage behavior is replaced with the recycled coarse aggregate with known residual mortar content. When the residual mortar coefficient is applied to the measured shrinkage of natural aggregate concrete, a relatively accurate prediction of the shrinkage of recycled coarse aggregate concrete is possible. The residual mortar coefficient ranges from 1.03 to 1.08 when the replacement ratio of recycled coarse aggregate is 20%-33%, and it is between 1.07 and 1.16 when the replacement ratio is 50%. In other words, the increase in the drying shrinkage rate of recycled aggregate concrete over that of the natural aggregate concrete is about 16% or smaller. When the replacement ratio of recycled aggregate concrete is 100%, the residual mortar coefficient ranges from 1.18 to 1.76. When the replacement ratio of natural aggregate concrete is greater than 50%, the increase in the drying shrinkage rate of recycled coarse aggregate concrete is more significant than that of the natural aggregate concrete. It can be seen that the current research methodology can be used to further improve the theoretical prediction of the drying shrinkage behavior of recycled coarse aggregate concrete using an expanded database.More>

2022, 22(5): 73-84. doi: 10.19818/j.cnki.1671-1637.2022.05.003

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Temperature action and zoning of concrete jointless bridge in Shaanxi

LIU Yong-jian, MA Zhi-yuan, LIU Jiang, ZHU Wei-qing, WANG Xu, LI Ming-hui

Abstract: In order to study the regional difference of temperature action of concrete jointless bridge, a long-term temperature field test was carried out for an integral jointless bridge. The accuracy of temperature field FEM (finite element model) was verified based on the recorded data. The meteorological data from 1993 to 2015 were collected from 46 national meteorological stations in Shaanxi Province and surrounding provinces, the missing solar radiation data were supplemented, and the daily data of meteorological stations were decomposed into hourly data for temperature field analysis. The long-term temperature field was simulated with the meteorological data for 23 years, and the representative values of effective temperature and temperature gradient with a 50-year return period were further calculated by the generalized Pareto model based on the New Zealand canonical temperature gradient model. The isoline map of temperature action was drawn by the spatial interpolation method and further simplified as a zoning map of temperature action. The temperature action mode was modified by considering different beam heights and pavement thicknesses, and an application case of zoning map was given to calculate the total span limit of the whole jointless bridge in each zoning of Shaanxi Province. Research results show that the effective temperature zoning map in Shaanxi Province coincides well with the General Specification for Design of Highway Bridges and Culverts (JTG D60—2015), while the values in Guanzhong and parts of Southern Shaanxi are more unfavorable than the specification. However, the top temperature differences of temperature gradient in most areas of Northern Shaanxi and Southern Shaanxi exceed the specification value of 14 ℃. There is no corresponding isothermal section recommended in the New Zealand standard temperature gradient model when the beam height is less than 1.4 m. The modified temperature gradient model can reasonably reveal the temperature distribution patterns with different beam heights. The thickness of asphalt pavement only has a great influence on the top temperature difference, and the difference can be corrected by the linear interpolation under different thicknesses. The longitudinal deformation of main girder of integral jointless bridge increases linearly with the length of the bridge, and its calculation can be simplified by introducing the longitudinal expansion reduction coefficient based on the free expansion deformation. The bridge length can be controlled by the bending failure of the abutment under heating and the low-cycle fatigue failure of the pile under cooling, and calculated according to the actual closing temperature. In the proposed three temperature zones, the maximum theoretical bridge length at the optimal closure temperature is 290, 240 and 220 m, respectively.More>

2022, 22(5): 85-103. doi: 10.19818/j.cnki.1671-1637.2022.05.004

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Tensile performance and application of LEM-SHCC road-bridge link slab mixed with rubber powder for fully jointless bridge

ZHAN Xue-fang, WANG Xian, YAN Heng-li, ZHAO Yi-bin, SHI Yuan-yuan

Abstract: In order to solve the problems of excessive crack width and excessive internal force of the road-bridge link slab for a fully jointless bridge, the isopyknic rubber powder was added to a strain-hardening cementitious composite (SHCC) material to partly replace the fine sand, then the SHCC material with a low elastic modulus (LEM-SHCC) was made, which was used for the road-bridge link slab for a fully jointless bridge. The basic material properties (density, compressive strength, and elastic modulus) and tensile property of LEM-SHCC with five different rubber powder contents (0, 5%, 10%, 15%, and 20%) were tested. The effect of rubber powder content on the strength and deformation performance of LEM-SHCC was analyzed. Meantime, the difference of ratio of tensile strain to compressive strain was used to evaluate the effect of rubber powder content on the SHCC material, and an optimal mix proportion of LEM-SHCC was obtained. For a LEM-SHCC road-bridge link slab with a rubber powder content of 15%, its absorptive deformation capacity, tensile deformation performance, and crack distribution law after cracking under the most unfavorable load (temperature drop load) were studied and compared with all the performance of the SHCC road-bridge link slab with the same size. A finite element comparative analysis for the sensitive parameters of the LEM-SHCC road-bridge link slab (the main influencing factors such as the rubber powder content, friction coefficient at the slab bottom, slab length, and so on) was carried out. Research results show that when the rubber powder is added, the elastic modulus of SHCC decreases, and the ductility of SHCC increases. When the rubber powder content reaches 15%, the elastic modulus of SHCC decreases by 40%, while the ductility increases by nearly 50%, with the crack width effectively controlled within 60 μm. When the absorptive longitudinal deformation of the LEM-SHCC road-bridge link slab reaches 10 mm, the micro-cracks on the surface of the LEM-SHCC road-bridge link slab are dense (nearly 180 micro-cracks), and the crack spacing is small (15-80 mm). The crack width after cracking is controlled within 60 μm. At the same time, the slab stress of the tension end is 2.1 MPa, and the anchoring force of the anchorage end is 150.5 kN. After unloading, the cracks are closed, and no fibers are pulled out or broken. The internal force of the LEM-SHCC slab which absorbs the same longitudinal deformation of 10 mm is smaller than that of the SHCC slab with the same size. The internal force of the LEM-SHCC slab is greatly affected by the rubber powder content, and the LEM-SHCC slab has optimal performance when the content is 15%. The internal force of the LEM-SHCC slab is slightly affected by the friction coefficient at the slab bottom. In addition, the mechanical performance of the LEM-SHCC slab can be effectively improved by an increase in the slab length. It is recommended that the design length of the LEM-SHCC slab should be 8.5 m.More>

2022, 22(5): 104-118. doi: 10.19818/j.cnki.1671-1637.2022.05.005

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Seismic responses of abutment steel piles in integral skewed bridges

ZHAO Qiu-hong, GUO Hao-meng, DONG Shuo, WANG Qing-wei, CHEN Bao-chun, ZHOU Yong-jun

Abstract: A three-dimensional structural model of a integral skewed bridge was established by using finite element analysis software SAP2000, and the interactions of abutment-soil behind the abutment and H-shaped steel pile-soil around the pile were simulated through a discrete nonlinear spring element. Through nonlinear time-history analysis under a series of bi-directional seismic actions, the influence rules of pile orientation, stiffness of the soil around the pile, and rotational stiffness of pile head on the seismic responses of the H-shaped steel pile in the skewed integral abutment bridge were studied. Research results show that under bi-directional seismic actions, the transverse displacement of the H-shaped steel pile is significantly greater than the longitudinal displacement, and greatly affected by the pile orientation. The bending moments around the strong and weak axes distribute in both positive and negative directions. The maximum values of yield surface function are generally located at the pile top, while the other peak values are located at the 2-4 m where the pile body is buried. When the steel pile is arranged around strong axis bending, the longitudinal displacement at the pile top reduces by 18.2% compared with that around weak axis bending, but the transverse displacement increases by 47.7%. The bending moment around the strong axis at the pile top increases by about 3.9 times, while the bending moment peak value of reverse strong axis of the pile body decreases by about 67.0%. The bending moment around the weak axis at the pile top basically unchanges, while the bending moment peak value around the reverse weak axis of the pile body increases by about 1.0 times. With the decrease in the stiffness of the soil around the pile, the longitudinal and transverse displacements at the pile top improve, and the yield surface function value at the pile top reduces slightly, while the peak value of the yield surface function of the pile body increases. The pile body is difficult to be elastic. When a flexible connection is adopted at the pile head, the longitudinal and transverse displacements at the pile top both rise. The yield surface function value at the pile top decreases, and the pile head can be protected effectively, but the peak value of the yield surface function of the pile body increases. When the rotational stiffness of the pile head is too low, the peak value of the yield surface function of the pile body may be higher than the value at the pile top, and thus the pile body may enter the plastic stage first under rare earthquakes.More>

2022, 22(5): 119-130. doi: 10.19818/j.cnki.1671-1637.2022.05.006

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Test on interaction of semi-integral abutment and soil based on displacement effect of medium-long-term ambient temperature

HUANG Fu-yun, LIU Zheng-feng, SONG Da-hao, LIN Zhi-ping, CHEN Bao-chun

Abstract: To study the influence of ambient temperature effect on the interaction mechanism between a semi-integral abutment and soil behind the abutment, a simplified model of the semi-integral abutment-soil structure was taken as the research object to carry out a displacement-based quasi-static test on the semi-integral abutment-soil interaction under the action of ambient temperature. Research results show that the hysteresis curve of the semi-integral abutment varies as the seasonal temperature changes. The seasonal warming and cooling transformation sections have a highly significant effect on the abutment-soil interaction, while the continuously increasing or decreasing sections have less effect on it. The first warming period of a year has a greater impact on the abutment-soil interaction. With several quarters of temperature loading, the soil behind the abutment is gradually compacted. The earth pressure variation tends to be stable, and the increasing trend slows down. The effect of day-night temperature change on the abutment-soil interaction varies from season to season, with daytime warming in summer having a small effect on the abutment-soil interaction while nighttime cooling having a large effect, and vice versa in winter. With the gradual increase in the seasonal temperature, the hysteresis curve of the abutment-soil interaction develops from concave to convex, showing a fuller shuttle shape. The medium-long-term ambient temperature has a large effect on the abutment-soil interaction. After a full year of temperature action, the earth pressure behind the abutment increases significantly, which produces the ratcheting effect. There is a large correlation between the abutment rotation angle and the loading displacement. With the increase in the number of cycles, the abutment rotation angle first gradually increases and then tends to level off. Under the action of medium-long-term ambient temperature, the semi-integral abutment gradually presents the trend of deflection in its rear direction. The effect of day-night temperature change on the abutment rotation angle cannot be ignored. Under the same loading displacement, the test results of the abutment rotation angle considering the superimposed effect of seasonal temperature and day-night temperature are 94% higher than those when only the seasonal temperature effect is taken into account.More>

2022, 22(5): 131-144. doi: 10.19818/j.cnki.1671-1637.2022.05.007

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Quasi-static test on H-shaped steel-RC stepped pile-soil interaction of integral bridge

ZHUANG Yi-zhou, SONG Kun-sheng, SONG Yong-qing, CHEN Guo-dong, HUANG Fu-yun, CHEN Liang

Abstract: On the basis of H-shaped steel-RC stepped pile model tests, the quasi-static tests of 2 H-shaped steel-RC stepped piles (HS-RC-0.25, HS-RC-0.50) and an H-shaped steel (HS) pile under the low cyclic repeated loading were carried out. A horizontal displacement load was applied on the pile top, and the strain and soil pressure gauges were embedded, a specially designed test method for the horizontal displacement of the pile body was adopted, and the failure characteristics of the HS-RC stepped pile, the horizontal displacement and strain of the pile body along the pile depth, skeleton curve, and hysteretic behavior curve were obtained. The horizontal displacement abilities of the stepped pile top under free and fixed conditions were compared and analyzed by OpenSEES. The reduction coefficient and conversion coefficient of the horizontal bearing capacity of the stepped pile were obtained, and the calculated value obtained by the reduction coefficient and test value of horizontal bearing capacity of the model pile were compared. Test results show that the elastic deformation range of the pile top of the HS pile is 2-25 mm, and the pile has strong horizontal deformation ability, positive bearing capacity, full hysteresis loop during the whole loading process, and excellent energy consumption effect. The stiffness ratio has no significant effect on the failure mode of the stepped pile. The upper steel pile of the stepped pile has no apparent buckling failure, and the concrete at the variable section is seriously peeled off with the same failure position. With the increase in the stiffness ratio, the yield displacement and yield load of the stepped pile-soil system increase. Compared with that of HS-RC-0.50, the yield displacement of HS-RC-0.25 decreases by 29.15%, and the strain mutation of the pile body decreases. The hysteresis loop of the stepped pile is pinched at the initial loading stage due to slip and becomes spindle-shaped at the later loading stage. The energy consumption effect is positive, and the energy consumption of HS-RC-0.50 during the whole loading process is 25.4% more than that of HS-RC-0.25, which shows an excellent horizontal deformation ability. Compared with the experimental value, the calculation error of HS-RC-0.25 is -9.68%, while the calculation error of HS-RC-0.50 is -2.47%. The HS-RC stepped pile can meet the horizontal deformation requirements of the integral abutment bridge pile foundation, and the reduction coefficient can be used to better calculate the stepped pile's horizontal bearing capacity characteristic value.More>

2022, 22(5): 145-162. doi: 10.19818/j.cnki.1671-1637.2022.05.008

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Back analysis of build-up effect of earth pressure behind integral abutment

XU Ming, LIN Yong-zhi, ZHOU Wen-xuan

Abstract: To determine the ultimate earth pressure behind integral abutment subjected to horizontal cyclic displacements, the back analysis using the finite difference numerical simulation was performed on five sets of model tests of integral abutments. A soil constitutive model capable of reflecting the high modulus and highly non-linear stiffness property of soil within the small strain range was utilized, and the properties of the interface between the soil and the abutment were considered. Through the application of horizontal displacements at the abutment top. Earth pressures behind the abutments measured at different cycles were back-analyzed. The corresponding small strain stiffness parameter of soil was obtained, and the evolution laws of the small strain stiffness of soil behind the abutments in each set of model tests during the cyclic loading process were revealed. On the basis of the above findings, the formulas were proposed to estimate the increasing multiple of the small strain stiffness of soil behind the integral abutments with a hinged base and a spread base separately. Then, a method was proposed to design and calculate the ultimate earth pressure behind the integral abutments with the consideration of soil-abutment interaction. Research results show that for the abutment with a hinged base, the increasing multiple of the small strain stiffness of soil increases with the rise in the relative displacement at the abutment top before and after the cyclic loading, while it decreases with the increase in the relative density of soil behind the abutment. For the abutment with a spread base, the increasing multiple of the small strain stiffness of soil increases at a slower rate with the rise in the relative displacement at the abutment top compared with that in the case of a hinged base, but it is slightly influenced by the relative density of soil behind the abutment. Compared with the British design guidance PD 6694-1, the proposed formulas consider the influences of the above multi-factors and can make reasonable prediction on the increasing multiple of the small strain stiffness of soil obtained from the back analysis on different model tests. It can be a reference for the design of integral abutments.More>

2022, 22(5): 163-172. doi: 10.19818/j.cnki.1671-1637.2022.05.009

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Calculation method for earth pressure behind integral abutment under horizontal reciprocating large displacement

LI Lan, HUANG Fu-yun, ZHANG Feng, LIU Zheng-feng, CHEN Wei

Abstract: To analyze the effect of horizontal reciprocating large displacement generated by the abutment on the interaction between the abutment and the backfill behind the abutment under the actions of strong earthquake and temperature, a quasi-static test for the interaction among the integral abutment, H-shaped steel pile, and soil was carried out. On the basis of the test results, the distribution law of the earth pressure behind the integral abutment under the action of large displacement was studied. According to the distribution of the earth pressure behind the abutment, the relational expression between the action point location of the resultant earth pressure behind the abutment and the loading displacement was proposed, and an improved calculation method for the earth pressure behind the integral abutment was given based on the existing research. Research results indicate that when the abutment is loaded in the positive direction (the abutment squeezes the soil behind the abutment), the earth pressure behind the abutment first increases and then decreases as the loading displacement rises. Earth pressures at the abutment back and 20% of the abutment height behind the abutment are highly affected by the abutment displacement and has a trapezoidal distribution along the depth direction. In the earth pressure distribution at the abutment back, due to the constraint of H-shaped steel pile at the bottom of the abutment, the maximum earth pressure is located at a depth of 0.875 m, and the earth pressure at the bottom of the abutment decreases slightly. Earth pressures at 60% of the abutment height and 1.4 times the abutment height behind the abutment are less affected by the abutment displacement and is triangularly distributed along the depth direction. When the abutment is loaded in the negative direction (the abutment deviates from the soil behind the abutment), the earth pressure behind the abutment is triangularly distributed along the depth direction, and the earth pressure behind the abutment has no connection with the loading displacement, and its value can be neglected relative to the positive loading. Under the action of a horizontal reciprocating large displacement, the soil behind the integral abutment will face a void phenomenon, and the void range will exceed 37.5% of the abutment height. The earth pressure behind the abutment reduces exponentially along the longitudinal direction, and it reduces faster than that under the action of a small displacement. The action point location of the resultant earth pressure behind the abutment decreases gradually as the loading displacement increases, and the earth pressure coefficient behind the abutment has an obvious nonlinear relationship with the loading displacement, which is reflected by the law of first increasing and then decreasing. Existing earth pressure calculation methods do not take into account the effect of the abutment displacement or consider that the earth pressure behind the abutment rises with the increase in the abutment displacement when small displacements occur and remains basically unchanged when large displacements occur. The determination coefficient of the proposed earth pressure fitting formula is 0.92, and the relative error between the calculated value and the test value is 6.2%, which can be a useful supplement to the existing earth pressure calculation methods.More>

2022, 22(5): 173-183. doi: 10.19818/j.cnki.1671-1637.2022.05.010

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Flexural performance and capacity of embedded H-shaped steel pile-abutment joint

ZHU Wei-qing, SHI Hao-hui, ZHANG Guan-hua, LIU Yong-jian, LIU Jia-tong

Abstract: In order to investigate the flexural performance of embedded H-shaped steel pile-abutment joint for integral abutment bridges, the finite element model of the joint was established, and the effects of abutment thickness, concrete strength, steel pile orientation, buried depth ratio, steel strength, and axial load ratio on the flexural capacity and failure mode of the joint were analyzed. Based on the parameter research, the flexural model and the calculation formulae of bearing capacity were proposed for different failure modes. Analysis results show that the joint where the moment is around the strong axis of steel pile fails as compressive failure of abutment concrete when the buried depth ratio is less than 2.0. Increasing the buried depth ratio of steel pile and the strength of concrete can effectively enhance the flexural capacity of the joint. When the buried depth ratio is more than 2.0 for the joint where the moment is around strong axis of steel pile, or the buried depth ratio is more than 1.0 for the joint where the moment is around weak axis of steel pile, the failure behaves as the yielding of steel pile. Improving the material strength of steel pile will enhance the flexural capacity of the joint. With the increase of axial load ratio, the flexural capacity of the joint failing as the yielding of steel pile around the strong axis decreases significantly. While the effect of axial load ratio on the flexural capacity of the joint behaving as compressive failure or punching failure of abutment concrete can be ignored. The method proposed for calculating the flexural capacity of the joint can predicts the flexural capacity of embedded steel pile-concrete abutment joints with different failure modes accurately, and the average ratio of calculated values to simulated values is 0.981, and the average ratio of calculated values to experimental values is 0.941. So, it can be used to predict the flexural capacity and analyze the failure mode of the joint. It is suggested that the buried depth ratio is larger than 2.0 and the thickness of abutment is greater than 2.4 times the width of pile, so that the adverse compressive failure and punching failure of abutment concrete will be avoided.More>

2022, 22(5): 184-199. doi: 10.19818/j.cnki.1671-1637.2022.05.011

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Fatigue performance of composite girder bridge with corrugated steel webs-concrete filled steel tubular truss chords

CHEN Kang-ming, HUANG Han-hui, WU Qing-xiong, CHEN Bao-chun

Abstract: To study the distribution laws of hot-spot stress, fatigue performance evolution, and fatigue failure mode of the composite girder with corrugated steel webs-concrete filled steel tubular (CSW-CFST) truss chords, the fatigue performance test and finite element analysis on the composite girder with CSW-CFST truss chords and the composite girder with corrugated steel webs-steel tubular (CSW-ST) truss chords were carried out separately. The differences and similarites between the fatigue performance between composite girders with CSW-CFST truss chords and CSW-ST truss chords were explored. The essential reason for the improved fatigue performance of the composite girder with concrete-filled chords was analyzed, and the evaluation method for the fatigue life of the composite girder with CSW-CFST truss chords was discussed. Moreover, the test result was compared with the calculated fatigue life for the composite girder with CSW-CFST truss chords according to the design standards of the American Petroleum Institute (API), Comité International pour le Développement et l'Etude de la Construction Tubulaire (CIDECT), and Det Norske Veritas (DNV) separately. Research results show that the hot-spot stress of the composite girder with CSW-CFST truss chords acquired by the linear extrapolation is 1.036 times that acquired by the quadratic extrapolation. Therefore, For safety, the hot-spot stress of the composite girder with CSW-CFST truss chords shall be acquired by the linear extrapolation. The hot-spot stress is significantly larger in the inclined web segment than that in the straight web segment, and the maximum hot-spot stress is distributed near the intersection of the inclined web and the arc transition segment. Compared with the situation of the composite girder with CSW-ST truss chords, the hot-spot stress of the composite girder with CSW-CFST truss chords can be reduced by 26.8% by concrete-filled chords, but the distribution laws of hot-spot stress remain changed. It is recommended that the repeated loading times at the initial moment of the fatigue crack should be defined as the fatigue life of the composite girder with CSW-CFST truss chords. The concrete-filled chords can delay the fatigue crack propagation rate along the directions of the thickness and length of chords, and can improve the fatigue life of the composite girder with CSW-CFST truss chords by 61.5%, with the fatigue failure mode and fatigue crack type of the composite girder unchanged. The minimum difference between the test result and the calculated fatigue life of the composite girder with CSW-CFST truss chords by DNV is achieved, which is less than 26.4%. Thus, it is recommended that the fatigue design stress (S)-fatigue life (N) curve of steel tubular intersecting joints provided by DNV should be adopted to preliminarily calculate the fatigue life of the composite girder with CSW-CFST truss chords.More>

2022, 22(5): 200-216. doi: 10.19818/j.cnki.1671-1637.2022.05.012

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Analytical solution and calculation method of reasonable arch axis of through arch bridge

ZHANG Guo-jing, LIU Yong-jian, LIU Jiang

Abstract: To obtain the analytical solution and calculation method of the reasonable arch axis of through arch bridge, the dead load action mode and differential equation of the reasonable arch axis were established, and the analytical solution of the reasonable arch axis was determined. Based on the analytical solution, the dead load ratio of main arch was defined. Based on the rise-span ratio and dead load ratio of main arch, a quick calculation method of the reasonable arch axis was obtained. The reliability of the proposed method was confirmed by arch bridge design specifications, engineering cases, and related research achievements. Research results show that the dead load action mode of through arch bridge can be equivalent to the combination of continuous uniform dead load and arch dead load, the reasonable arch axis is catenary, and the corresponding arch axis coefficient is determined by the rise-span ratio and dead load ratio of main arch. The fitted functional relationships between the arch axis coefficients and dead load ratios of main arch under different rise-span ratios are a linear correlation, and the determination coefficients are greater than 0.99, indicating that the fitted equations are accurate. The rise-span ratio of through arch bridge is between 1/3 and 1/8 in engineerings, and the range of the corresponding arch axis coefficient is between 1.000 and 1.792. The common rise-span ratio ranges from 1/4 to 1/5, and the corresponding arch axis coefficient ranges from 1.000 to 1.465. The calculation results are in good agreement with the statistical results of arch axis coefficients of engineering cases, indicating that the calculation results are reliable. The common dead load ratio of main arch ranges from 0.1 to 0.5, and the corresponding arch axis coefficient ranges from 1.102 to 1.364. The calculation results are close to the value ranges in the arch bridge design specification, which proves the rationality of value range in the arch bridge design specification. When the dead load ratio of main arch is less than 0.5 and the rise-span ratio is less than 1/7, or the dead load ratio of main arch is less than 0.1, the arch axis coefficient is close to 1.000. As a result, the quadratic parabola can be used as reasonable arch axis. The reasonable arch axis equation can be obtained quickly by the look-up table method and simplified formula method. Compared with the mature research achievements, the deviations of bending moments, eccentricities and sums of squared eccentricities of main arch cross-section are within 5%, which proves the correctness of the solution method.More>

2022, 22(5): 217-230. doi: 10.19818/j.cnki.1671-1637.2022.05.013

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Experiment on mechanical property degradation of Q345 steel after strong corrosion

QIAO Wen-jing, YANG Fan, HU Qi-han, ZHANG Hao, JIAO Xue-feng

Abstract: The influences of surface morphology and corrosion time of Q345 steel after strong corrosion on its mechanical property degradation were systematically studied. A rapid corrosion method based on the industrial hydrochloric acid with a concentration of 36% at room temperature was adopted, and nine groups of steel specimens with the corrosion time of 0, 1, 2, 4, 8, 12, 24, 48, and 72 h respectively were designed. A 3D non-contact laser scanner and an electron microscope were adopted to scan the corroded steel, and the width and height of the largest corrosion pit and the thicknesses of corroded specimens were measured. The influence coefficient of the largest corrosion pit was calculated. A tensile test was carried out, and the mechanical property degradation mechanism of Q345 steel after strong corrosion was explained according to the scanning morphology and microstructure morphology. The corrosion kinetics curve and constitutive relation model of Q345 steel after strong corrosion by the industrial hydrochloric acid with a concentration of 36% were established at room temperature, and the mechanical property degradation law of Q345 steel after strong corrosion was revealed. Research results show that as the corrosion time increases, the corrosion kinetics curve of Q345 steel demonstrates the change law of corrosion rate. When the corrosion time is less than 1 h, the influence coefficient of the largest corrosion pit increases obviously, and the nominal yield strength, nominal tensile strength, nominal elastic modulus and elongation of the steel degrade significantly, reaching 3.00%, 0.69%, 1.99%, and 4.88% of the uncorroded steel respectively. When the corrosion time exceeds 12 h, the influence coefficient of the largest corrosion pit increases slowly, and the nominal yield strength, nominal tensile strength, nominal elastic modulus and elongation of steel degrade slowly, reaching 7.58%, 4.02%, 10.27%, and 26.64% of the uncorroded steel respectively. The change of the yield-strength ratio is slight as the influence coefficient of the largest corrosion pit and the corrosion time increase. In the stress-strain constitutive relation curves of the corroded specimens, as the corrosion time increases, the yield platform of steel gradually shortens or even disappears, and the steel changes from ductile failure to brittle failure.More>

2022, 22(5): 231-246. doi: 10.19818/j.cnki.1671-1637.2022.05.014

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