We develop assembled reinforcement structures(ARSs)composed of connection parts,connecting rods,and straight bolts to strengthen segmental joints in the lining of shield tunnels.Through full-scale bending experiments ...We develop assembled reinforcement structures(ARSs)composed of connection parts,connecting rods,and straight bolts to strengthen segmental joints in the lining of shield tunnels.Through full-scale bending experiments and numerical simulations,we investigate the deformation and failure characteristics of segmental joints strengthened by ARSs,and propose a novel optimization method for ARSs.The experimental results show that the ARSs can effectively limit the opening of a segmental joint,but also that separation can occur during loading if the connection between the ARSs and segments is not designed properly.Importantly,this connection can be improved by embedding anchor parts in the concrete.In numerical modeling,we investigate the failure modes of segmental joints strengthened by ARSs for both positive bending and negative bending loading cases.In the case of positive bending loading,first the concrete around the anchor parts cracks,and subsequently the concrete on the external side of the joint is crushed.The joint failure is caused by the crushing of concrete on the external side of the joint.While the un-strengthened segmental joint fails with an opening of 5.884 mm,the strengthened segmental joint only opens by 0.288 mm under the same loading,corresponding to a reduction of 95.1%.In the case of negative bending loading,the concrete around the anchor parts first cracks,and then the amount of joint opening exceeds a limiting value for waterproofing(6 mm),i.e.,the joint’s failure is caused by water leakage.While the opening of the un-strengthened segmental joint is 9.033 mm and experiences waterproofing failure,the opening of the strengthened segmental joint is only 2.793 mm under the same loading,corresponding to a reduction of 69.1%.When constructing a new shield tunnel,anchor parts could be embedded in the concrete segments in tandem with ARSs for improved resistance to joint opening.For existing shield tunnel linings,anchor parts cannot be embedded in the concrete segments;therefore,the connections between the ARSs and concrete need to be optimized to strengthen the segmental joint.展开更多
In this paper,a type of reinforcing structure for composite shell with single and through hole is presented.The experimental tests for the composite shells without hole,with single hole and reinforced structure,with t...In this paper,a type of reinforcing structure for composite shell with single and through hole is presented.The experimental tests for the composite shells without hole,with single hole and reinforced structure,with through hole and reinforced structure subjected to hydrostatic pressure were carried out by the designed experimental test system.The mechanical responses of the composite shells under hydrostatic pressure are obtained by the high-speed camera and strain measurement.The results show that the entire deformation process of the shell can be divided into three:uniform compression,"buckling mode formation"and buckling.The"buckling mode formation"process is captured and reported for the first time.For the composite shell with single hole,the proposed reinforcing structure has a significant reinforcement effect on the shell and the buckling capacity of the shell is not weaker than the complete composite shell.For the composite shell with through hole,sealing effect can be achieved by the proposed reinforcing structure,but the buckling capacity of the shell after reinforcement can only reach 77%of the original buckling capacity.展开更多
Metallic glass matrix composites(BMGCs)with compositions of[(Zr_(0.5)Cu_(0.5))_(0.925)Al_(0.07)Sn_(0.005)]_(100-x)Ta_(x)(atomic fraction,%,x=3,5,7)were successfully prepared via dealloying in metallic melt.The reinfor...Metallic glass matrix composites(BMGCs)with compositions of[(Zr_(0.5)Cu_(0.5))_(0.925)Al_(0.07)Sn_(0.005)]_(100-x)Ta_(x)(atomic fraction,%,x=3,5,7)were successfully prepared via dealloying in metallic melt.The reinforcing phase in these alloys has core-shell hybrid structure with Ta-rich particles as core and B2-CuZr as shell.In this method,the dealloyed Ta from Zr-Ta pre-alloys maintained in solid state and aggregated to form the fine Ta-rich phase in the final products.This effectively decreases the size of Ta-rich phase compared with that prepared via conventional arc-melting,where the Ta-rich phase was formed through dissolving and precipitation.Among the three compositions,[(Zr_(0.5)Cu_(0.5))_(0.925)Al_(0.07)Sn_(0.005)]_(95)Ta_(5) showed the highest plastic strain of 11.2%,much higher than that of the arc-melted counterparts(4.3%).Such improvement in mechanical properties was related with the refined core-shell hybrid reinforcing structure,which could hinder the rapid propagation of main shear band more efficiently and cause them to branch and proliferate at the interface.展开更多
The loop heat pipe with a flat evaporator is mainly divided into two forms:rectangular evaporator and disk-shaped evaporator.The rectangular evaporator has advantages such as low heat leakage,a thin shell,and a large ...The loop heat pipe with a flat evaporator is mainly divided into two forms:rectangular evaporator and disk-shaped evaporator.The rectangular evaporator has advantages such as low heat leakage,a thin shell,and a large contact area compared to the disk-shaped evaporator.However,most of the research on rectangular evaporators focuses onworking fluids such as water,methanol,and acetone,when theseworking fluids are in operation,the internal pressure of the evaporator is less than atmospheric pressure.Ammonia,propylene,and other working fluids can also be utilized in the loop heat pipe,these working fluids demonstrate better performance when operating within other temperature intervals,for example,the operating temperature range of ammonia is−20℃to 50℃,however,in an atmospheric pressure environment,it is very difficult for the shell of the rectangular evaporator to withstand the saturated vapor pressure of the working fluid.This paper designs a rectangular flat plate loop heat pipe that can use ammonia as the working fluid.The internal reinforcing structure is used to improve the pressure strength of the shell.The secondary wick connects the compensation chamber and the capillary wick hydraulically.The experiment indicates that this kind of rectangular evaporator is unaffected by the position,and the secondary wick can effectively supply liquid under different angles.The thermal resistance of the evaporator wall was analyzed,and it was found that the thermal resistance of the evaporator wall was the main component of the thermal resistance of the system.The heat transfer capacities of 460 W@0.5 m and 200W@10 m were tested.The test results indicate that by setting a reinforcing structure inside the flat plate evaporator,the evaporator can withstand internal pressure.Combined with the design of the secondary wick,the flat plate evaporator can use working fluids with different pressures,expanding the range of available working fluids.展开更多
With the development of modern society,people put forward higher requirements for building safety,which makes the construction project face new challenges.Reinforced concrete frame structure as a common engineering ty...With the development of modern society,people put forward higher requirements for building safety,which makes the construction project face new challenges.Reinforced concrete frame structure as a common engineering type,although the construction technology has been relatively mature,but its earthquake collapse ability still needs to be strengthened.This paper analyzes the specific factors that affect the seismic collapse ability of reinforced concrete frame structure,summarizes the previous research results,and puts forward innovative application of fiber-reinforced polymer(FRP)composite materials,play the role of smart materials,improve the isolation and energy dissipation devices,etc.,to promote the continuous optimization of reinforced concrete frame structure design,and show better seismic performance.展开更多
With the continuous improvement of people's safety awareness, the attention of building structure reinforcement technology is also increasing. During the construction period of housing construction, we must combin...With the continuous improvement of people's safety awareness, the attention of building structure reinforcement technology is also increasing. During the construction period of housing construction, we must combine with the actual situation of the project, reasonably carry out the structural reinforcement design, and make targeted use of the reinforcement construction technology. But at present, in the construction period, due to the weak awareness of technical personnel and other factors, the structural reinforcement is often ignored, resulting in the durability and seismic resistance of the building structure cannot meet the standard, there are relatively many potential safety hazards, causing a greater threat to people's life safety. In the future housing construction process, we must strengthen the emphasis on structural reinforcement. In view of this, this paper mainly analyzes the application of building structure reinforcement design and reinforcement construction technology in order to provide reference for relevant personnel.展开更多
A numerical model using the coupled smoothed panicle hydrodynamics-finite element method （SPH-FEM） approach is presented for analysis of structures under blast loads. The analyses on two numerical cases, one for fre...A numerical model using the coupled smoothed panicle hydrodynamics-finite element method （SPH-FEM） approach is presented for analysis of structures under blast loads. The analyses on two numerical cases, one for free field explosive and the other for structural response under blast loads, are performed to model the whole processes from the propagation of the pressure wave to the response of structures. Based on the simulation, it is concluded that this model can be used for reasonably accurate explosive analysis of structures. The resulting information would be valuable for protecting structures under blast loads.展开更多
In this paper, the tensile properties of the MWK structures produced with different basic stitches for composite reinforcement were experimentally studied. The results show that the MWK structures with the double loop...In this paper, the tensile properties of the MWK structures produced with different basic stitches for composite reinforcement were experimentally studied. The results show that the MWK structures with the double loop pillar stitches have better mechanical properties.展开更多
The properties and tensile behaviors of polypropylene (PP) geogrids and geonets for reinforcement of soil structures are investigated.Mass per unit area of the geogrids and geonets was weighed using an electronic bala...The properties and tensile behaviors of polypropylene (PP) geogrids and geonets for reinforcement of soil structures are investigated.Mass per unit area of the geogrids and geonets was weighed using an electronic balance and aperture sizes of the geonets were exactly measured using a computer.Laboratory tests were performed using a small tensile machine capable of monitoring tensile force and displacement.Tensile failure behaviors were described,and tensile index properties such as tensile strength,maximum tensile strain,tensile forces corresponding to different strains in the geogrids and gronets were obtained.The characterization of these indexes is discussed.展开更多
The paper mainly summarized the developments on structural aseismic theory, aseismic analysis and design of reinforced concrete structure, lifeline system, several another kinds of structures, site and structure found...The paper mainly summarized the developments on structural aseismic theory, aseismic analysis and design of reinforced concrete structure, lifeline system, several another kinds of structures, site and structure foundation, structure mitigation and isolation of vibration in China in recent four years. This is the introduction of recent re-search results of Chinese professionals for international organizations and professionals. At the same time, it provides numerous abstract materials for colleagues to realize the trend of the structural aseismic theory and re-search range needing more study.展开更多
The cultivation of engineering capabilities aims to equip engineering professionals with high-level expertise to meet the demands of society and industry development,thereby enhancing their competitiveness and career ...The cultivation of engineering capabilities aims to equip engineering professionals with high-level expertise to meet the demands of society and industry development,thereby enhancing their competitiveness and career potential.This article focuses on engineering capability development,exploring teaching strategies for the Reinforced Concrete Structure course.It aims to provide insights for educators in engineering programs at universities and vocational colleges in China.By doing so,teaching plans that meet the needs of engineering capability development,laying a solid educational foundation for the healthy growth of engineering professionals in the new era,and enhancing their application of knowledge and skills can be developed.展开更多
The aim of this study is to characterize soil/reinforcement interaction in reinforced earth structures. The study showed that the internal behavior of this type of structure depends on a number of factors, including t...The aim of this study is to characterize soil/reinforcement interaction in reinforced earth structures. The study showed that the internal behavior of this type of structure depends on a number of factors, including the engineering backfill, the reinforcement and the soil/reinforcement interaction. The study also showed that the soil-reinforcement interaction phenomenon is a fairly complex mechanism that depends on the applied load, the geometry of the structure, the characteristics of the soil and a set of parameters characterizing the nailing: density, number and length of reinforcements, inclination of the reinforcements in relation to the sliding surface, mechanical characteristics of the reinforcements and, in particular, the relative stiffness of the reinforcements and the soil. The results showed that the tensile forces developed in the reinforcement are not entirely reversible, and that the soil at the interface undergoes permanent deformation, leading to the appearance of irreversible tensile forces in the reinforcement.展开更多
This paper reviews the applications of the multi degree-of-freedom(MDOF)equivalent linear system in seismic analysis and design of planar steel and reinforced concrete framed structures.An equivalent MDOF linear struc...This paper reviews the applications of the multi degree-of-freedom(MDOF)equivalent linear system in seismic analysis and design of planar steel and reinforced concrete framed structures.An equivalent MDOF linear structure,analogous to the original MDOF nonlinear structure,is constructed,which has the same mass and elastic stiffness as the original structure and modal damping ratios that account for the effects of geometrical and material nonlinearities.The equivalence implies a balance between the viscous damping work of the equivalent linear structure and that of the nonlinearities in the original nonlinear structure.This work balance is established with the aid of a transfer function in the frequency domain.Thus,equivalent modal damping ratios can be explicitly determined in terms of the period and deformation levels of the structure as well as the soil types.Use of these equivalent modal damping ratios can help address a variety of seismic analysis and design problems associated with planar steel and reinforced concrete framed structures in a rational and accurate manner.These include force-based seismic design with the aid of acceleration response spectra characterized by high amounts of damping,improved direct displacement-based seismic design and the development of advanced seismic intensity measures.The equivalent modal damping ratios are also utilized in the context of linear modal analysis for the definition and construction of the MDOF response spectrum.Furthermore,the equivalent modal damping ratios are employed in a seismic retrofit method for steel-framed structures with viscous dampers.Finally,it is demonstrated that modal behavior(or strength reduction)factors can be easily constructed based on these modal damping ratios for a more rational and accurate force-based seismic design,including the determination of inelastic displacement profiles.展开更多
Seeking for innovative structures with higher mechanical performance is a continuous target in railway vehicle crashworthiness design.In the present study,three types of hexagonal reinforced honeycomb-like structures ...Seeking for innovative structures with higher mechanical performance is a continuous target in railway vehicle crashworthiness design.In the present study,three types of hexagonal reinforced honeycomb-like structures were developed and analyzed subjected to out-of-plane compression,namely triangular honeycomb(TH),double honeycomb(DH)and full inside honeycomb(FH).Theoretical formulas of average force and specific energy absorption(SEA)were constructed based on the energy minimization principle.To validate,corresponding numerical simulations were carried out by explicit finite element method.Good agreement has been observed between them.The results show that all these honeycomb-like structures maintain the same collapsed stages as conventional honeycomb;cell reinforcement can significantly promote the performance,both in the average force and SEA;full inside honeycomb performs better than the general,triangular and double schemes in average force;meanwhile,its SEA is close to that of double scheme;toroidal surface can dissipate higher plastic energy,so more toroidal surfaces should be considered in design of thin-walled structure.These achievements pave a way for designing high-performance cellular energy absorption devices.展开更多
Different strategies can be used to perform reparations and reinforcements of ancient bolted and riveted metallic bridges. As the riveting process is not currently a common practice, it requires proper equipment and s...Different strategies can be used to perform reparations and reinforcements of ancient bolted and riveted metallic bridges. As the riveting process is not currently a common practice, it requires proper equipment and skilled workers. Another solution is the use of welding. However, the weldability of old steels is poor. Bolts are very attractive alternative solutions, and are most commonly used to repair old metallic bridges. Fitted bolts are expensive solutions; the alternative is the use of resin-injected bolts. The behavior of bolted joints with preloaded resin-injected bolts has been studied using quasi-static and creep tests; however, few studies on the slip and fatigue behavior of these joints can be found in the literature. This paper presents an overview of a few experimental programs that were carried out by several authors aiming at evaluating the fatigue behavior of single and double shear resin-injected bolted connections. A comparison between the experimental data of joints with preloaded standard bolts and preloaded resin- injected bolts shows a fatigue strength reduction in the latter. Since Eurocode 3 （EC3） suggests the same fatigue strength curve for joints made of resin-injected bolts and standard bolts, this may raise some con- cerns. Furthermore, research on the feasibility of using both bonded and bolted connections is shown. This last study was performed with high-strength low-alloy structural steel plates and an acrylic struc- tural adhesive for metal bonding. For both case studies, a statistical analysis is performed on fatigue experimental data using linearized boundaries and the Castillo and Fernandez-Canteli model. Fatigue design curves are proposed and compared with the design suggestions of several European and North American standards,展开更多
An anchorage reliability analysis approach for simply supported reinforced concrete beams under corrosion attack in the anchorage zone is developed.The first-order second-moment method is employed to analyze the effec...An anchorage reliability analysis approach for simply supported reinforced concrete beams under corrosion attack in the anchorage zone is developed.The first-order second-moment method is employed to analyze the effects of various factors on the anchorage reliability.These factors include both the length and width of cover cracking due to reinforcement corrosion,the cover thickness,the anchorage length,and the stirrup ratio.The results show that the effect of corrosion-induced crack length on the reliability index for anchorage,β0,is negligible when the crack on the concrete surface is just appearing,but with the crack widening,the β0 value is reduced significantly;the considerable changes in β0 result from a variation in cover depth and anchorage length;the effect of changes in the diameter or space of stirrups on the anchorage resistance is very limited,and the variation in β0 is also very low.展开更多
Implications of the differences in leaf life span are still subject to debate in the field of ecophysiology.Since leaf traits associated with these differences may be decisive for determining the distribution of tree ...Implications of the differences in leaf life span are still subject to debate in the field of ecophysiology.Since leaf traits associated with these differences may be decisive for determining the distribution of tree species,this topic is particularly relevant in the context of climate change.This study analyzes the effects of the differences in leaf life span on premature losses of leaf area owing to insect herbivory and to abiotic stress.Loss of leaf area may be an important determinant of total leaf carbon assimilation.Seven Mediterranean tree species,distributed on four sites with different climates were studied.The species exhibited strong differences in leaf life span and in leaf traits,especially leaf mass per unit area.Premature leaf area losses were estimated in response to insect herbivory and summer drought over two years.The results revealed that,despite having older leaf cohorts with more damage,species with longer leaf duration had lower area lost to herbivores and less damage due to accelerated senescence during the summer drought.With respect to the predicted increase in water stress,deciduous species are at a disadvantage due to their high premature loss of leaf area and thus loss of photosynthetic capacity.展开更多
in order to evaluate the capacity of reinforced concrete （RC） structures subjected to blast Ioadings, the damaged plasticity model for concrete was used in the analysis of the dynamic responses of blast-loaded RC st...in order to evaluate the capacity of reinforced concrete （RC） structures subjected to blast Ioadings, the damaged plasticity model for concrete was used in the analysis of the dynamic responses of blast-loaded RC structures, and all three failure modes were numerically simulated by the finite element software ABAQUS. Simulation results agree with the experimental observations. It is demonstrated that the damaged plasticity model for concrete in the finite element software ABAQUS can predict dynamic responses and typical flexure, flexure-shear and direct shear failure modes of the blast-loaded RC structures.展开更多
This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and min...This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose,an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters -the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio,peak acceleration ratio,energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake.展开更多
Earthquake simulator tests of a 1/6-scale nine-story reinforced concrete frame-wall model are described in the paper. The test results and associated numerical simulation are summarized and discussed. Based on the tes...Earthquake simulator tests of a 1/6-scale nine-story reinforced concrete frame-wall model are described in the paper. The test results and associated numerical simulation are summarized and discussed. Based on the test data, a relationship between maximum inter-story drift and damage state is established. Equations of variation of structural characteristics （natural frequency and equivalent stiffness） with overall drifts are derived by data fitting, which can be used to estimate structural damage state if structural characteristics can be measured. A comparison of the analytical and experimental results show that both the commonly used equivalent beam and fiber element models can simulate the nonlinear seismic response of structures very well. Finally, conclusions associated with seismic design and damage evaluation of RC structures are presented.展开更多
基金supported by the National Natural Science Foundation of China(No.52008308)the China Postdoctoral Science Foundation(Nos.BX20200247 and 2021M692447)the Research Project from Jinan Rail Transit Group Co.,Ltd.and China Railway No.5 Engineering Group Co.,Ltd.(No.R2-ZF-2019-039).
文摘We develop assembled reinforcement structures(ARSs)composed of connection parts,connecting rods,and straight bolts to strengthen segmental joints in the lining of shield tunnels.Through full-scale bending experiments and numerical simulations,we investigate the deformation and failure characteristics of segmental joints strengthened by ARSs,and propose a novel optimization method for ARSs.The experimental results show that the ARSs can effectively limit the opening of a segmental joint,but also that separation can occur during loading if the connection between the ARSs and segments is not designed properly.Importantly,this connection can be improved by embedding anchor parts in the concrete.In numerical modeling,we investigate the failure modes of segmental joints strengthened by ARSs for both positive bending and negative bending loading cases.In the case of positive bending loading,first the concrete around the anchor parts cracks,and subsequently the concrete on the external side of the joint is crushed.The joint failure is caused by the crushing of concrete on the external side of the joint.While the un-strengthened segmental joint fails with an opening of 5.884 mm,the strengthened segmental joint only opens by 0.288 mm under the same loading,corresponding to a reduction of 95.1%.In the case of negative bending loading,the concrete around the anchor parts first cracks,and then the amount of joint opening exceeds a limiting value for waterproofing(6 mm),i.e.,the joint’s failure is caused by water leakage.While the opening of the un-strengthened segmental joint is 9.033 mm and experiences waterproofing failure,the opening of the strengthened segmental joint is only 2.793 mm under the same loading,corresponding to a reduction of 69.1%.When constructing a new shield tunnel,anchor parts could be embedded in the concrete segments in tandem with ARSs for improved resistance to joint opening.For existing shield tunnel linings,anchor parts cannot be embedded in the concrete segments;therefore,the connections between the ARSs and concrete need to be optimized to strengthen the segmental joint.
基金supported by the Ningbo Major Research and Development Plan Project(Grant No.2024Z135)the Natural Science Basic Research Program of Shaanxi Province(Grant No.2024JC-YBMS-322)+1 种基金China Postdoctoral Science Foundation(Grant No.2020M673492)National Natural Science Foundation of China(Grant No.51909219)。
文摘In this paper,a type of reinforcing structure for composite shell with single and through hole is presented.The experimental tests for the composite shells without hole,with single hole and reinforced structure,with through hole and reinforced structure subjected to hydrostatic pressure were carried out by the designed experimental test system.The mechanical responses of the composite shells under hydrostatic pressure are obtained by the high-speed camera and strain measurement.The results show that the entire deformation process of the shell can be divided into three:uniform compression,"buckling mode formation"and buckling.The"buckling mode formation"process is captured and reported for the first time.For the composite shell with single hole,the proposed reinforcing structure has a significant reinforcement effect on the shell and the buckling capacity of the shell is not weaker than the complete composite shell.For the composite shell with through hole,sealing effect can be achieved by the proposed reinforcing structure,but the buckling capacity of the shell after reinforcement can only reach 77%of the original buckling capacity.
基金supported by the National Natural Science Foundation of China(Nos.52101138,52201075)Natural Science Foundation of Hubei Province,China(Nos.2023AFB798,2022CFB614)+3 种基金Shenzhen Science and Technology Program,China(No.JCYJ20220530160813032)State Key Laboratory of Solidification Processing in NWPU,China(Nos.SKLSP202309,SKLSP202308)Guangdong Basic and Applied Basic Research Foundation,China(No.2022A1515011227)State Key Laboratory of Powder Metallurgy of Central South University,China(No.Sklpm-KF-05).
文摘Metallic glass matrix composites(BMGCs)with compositions of[(Zr_(0.5)Cu_(0.5))_(0.925)Al_(0.07)Sn_(0.005)]_(100-x)Ta_(x)(atomic fraction,%,x=3,5,7)were successfully prepared via dealloying in metallic melt.The reinforcing phase in these alloys has core-shell hybrid structure with Ta-rich particles as core and B2-CuZr as shell.In this method,the dealloyed Ta from Zr-Ta pre-alloys maintained in solid state and aggregated to form the fine Ta-rich phase in the final products.This effectively decreases the size of Ta-rich phase compared with that prepared via conventional arc-melting,where the Ta-rich phase was formed through dissolving and precipitation.Among the three compositions,[(Zr_(0.5)Cu_(0.5))_(0.925)Al_(0.07)Sn_(0.005)]_(95)Ta_(5) showed the highest plastic strain of 11.2%,much higher than that of the arc-melted counterparts(4.3%).Such improvement in mechanical properties was related with the refined core-shell hybrid reinforcing structure,which could hinder the rapid propagation of main shear band more efficiently and cause them to branch and proliferate at the interface.
基金Science Foundation for Distinguished Young Scholars 2020-JCJQ-ZQ-042.
文摘The loop heat pipe with a flat evaporator is mainly divided into two forms:rectangular evaporator and disk-shaped evaporator.The rectangular evaporator has advantages such as low heat leakage,a thin shell,and a large contact area compared to the disk-shaped evaporator.However,most of the research on rectangular evaporators focuses onworking fluids such as water,methanol,and acetone,when theseworking fluids are in operation,the internal pressure of the evaporator is less than atmospheric pressure.Ammonia,propylene,and other working fluids can also be utilized in the loop heat pipe,these working fluids demonstrate better performance when operating within other temperature intervals,for example,the operating temperature range of ammonia is−20℃to 50℃,however,in an atmospheric pressure environment,it is very difficult for the shell of the rectangular evaporator to withstand the saturated vapor pressure of the working fluid.This paper designs a rectangular flat plate loop heat pipe that can use ammonia as the working fluid.The internal reinforcing structure is used to improve the pressure strength of the shell.The secondary wick connects the compensation chamber and the capillary wick hydraulically.The experiment indicates that this kind of rectangular evaporator is unaffected by the position,and the secondary wick can effectively supply liquid under different angles.The thermal resistance of the evaporator wall was analyzed,and it was found that the thermal resistance of the evaporator wall was the main component of the thermal resistance of the system.The heat transfer capacities of 460 W@0.5 m and 200W@10 m were tested.The test results indicate that by setting a reinforcing structure inside the flat plate evaporator,the evaporator can withstand internal pressure.Combined with the design of the secondary wick,the flat plate evaporator can use working fluids with different pressures,expanding the range of available working fluids.
文摘With the development of modern society,people put forward higher requirements for building safety,which makes the construction project face new challenges.Reinforced concrete frame structure as a common engineering type,although the construction technology has been relatively mature,but its earthquake collapse ability still needs to be strengthened.This paper analyzes the specific factors that affect the seismic collapse ability of reinforced concrete frame structure,summarizes the previous research results,and puts forward innovative application of fiber-reinforced polymer(FRP)composite materials,play the role of smart materials,improve the isolation and energy dissipation devices,etc.,to promote the continuous optimization of reinforced concrete frame structure design,and show better seismic performance.
文摘With the continuous improvement of people's safety awareness, the attention of building structure reinforcement technology is also increasing. During the construction period of housing construction, we must combine with the actual situation of the project, reasonably carry out the structural reinforcement design, and make targeted use of the reinforcement construction technology. But at present, in the construction period, due to the weak awareness of technical personnel and other factors, the structural reinforcement is often ignored, resulting in the durability and seismic resistance of the building structure cannot meet the standard, there are relatively many potential safety hazards, causing a greater threat to people's life safety. In the future housing construction process, we must strengthen the emphasis on structural reinforcement. In view of this, this paper mainly analyzes the application of building structure reinforcement design and reinforcement construction technology in order to provide reference for relevant personnel.
基金National Basic Research Program (973) of China (No. 2002CB412709)the National Natural Science Foun-dation of China (No. 50378054)
文摘A numerical model using the coupled smoothed panicle hydrodynamics-finite element method （SPH-FEM） approach is presented for analysis of structures under blast loads. The analyses on two numerical cases, one for free field explosive and the other for structural response under blast loads, are performed to model the whole processes from the propagation of the pressure wave to the response of structures. Based on the simulation, it is concluded that this model can be used for reasonably accurate explosive analysis of structures. The resulting information would be valuable for protecting structures under blast loads.
文摘In this paper, the tensile properties of the MWK structures produced with different basic stitches for composite reinforcement were experimentally studied. The results show that the MWK structures with the double loop pillar stitches have better mechanical properties.
文摘The properties and tensile behaviors of polypropylene (PP) geogrids and geonets for reinforcement of soil structures are investigated.Mass per unit area of the geogrids and geonets was weighed using an electronic balance and aperture sizes of the geonets were exactly measured using a computer.Laboratory tests were performed using a small tensile machine capable of monitoring tensile force and displacement.Tensile failure behaviors were described,and tensile index properties such as tensile strength,maximum tensile strain,tensile forces corresponding to different strains in the geogrids and gronets were obtained.The characterization of these indexes is discussed.
基金National Naturel Science Foundation of China (59678048 and 50178055).
文摘The paper mainly summarized the developments on structural aseismic theory, aseismic analysis and design of reinforced concrete structure, lifeline system, several another kinds of structures, site and structure foundation, structure mitigation and isolation of vibration in China in recent four years. This is the introduction of recent re-search results of Chinese professionals for international organizations and professionals. At the same time, it provides numerous abstract materials for colleagues to realize the trend of the structural aseismic theory and re-search range needing more study.
文摘The cultivation of engineering capabilities aims to equip engineering professionals with high-level expertise to meet the demands of society and industry development,thereby enhancing their competitiveness and career potential.This article focuses on engineering capability development,exploring teaching strategies for the Reinforced Concrete Structure course.It aims to provide insights for educators in engineering programs at universities and vocational colleges in China.By doing so,teaching plans that meet the needs of engineering capability development,laying a solid educational foundation for the healthy growth of engineering professionals in the new era,and enhancing their application of knowledge and skills can be developed.
文摘The aim of this study is to characterize soil/reinforcement interaction in reinforced earth structures. The study showed that the internal behavior of this type of structure depends on a number of factors, including the engineering backfill, the reinforcement and the soil/reinforcement interaction. The study also showed that the soil-reinforcement interaction phenomenon is a fairly complex mechanism that depends on the applied load, the geometry of the structure, the characteristics of the soil and a set of parameters characterizing the nailing: density, number and length of reinforcements, inclination of the reinforcements in relation to the sliding surface, mechanical characteristics of the reinforcements and, in particular, the relative stiffness of the reinforcements and the soil. The results showed that the tensile forces developed in the reinforcement are not entirely reversible, and that the soil at the interface undergoes permanent deformation, leading to the appearance of irreversible tensile forces in the reinforcement.
文摘This paper reviews the applications of the multi degree-of-freedom(MDOF)equivalent linear system in seismic analysis and design of planar steel and reinforced concrete framed structures.An equivalent MDOF linear structure,analogous to the original MDOF nonlinear structure,is constructed,which has the same mass and elastic stiffness as the original structure and modal damping ratios that account for the effects of geometrical and material nonlinearities.The equivalence implies a balance between the viscous damping work of the equivalent linear structure and that of the nonlinearities in the original nonlinear structure.This work balance is established with the aid of a transfer function in the frequency domain.Thus,equivalent modal damping ratios can be explicitly determined in terms of the period and deformation levels of the structure as well as the soil types.Use of these equivalent modal damping ratios can help address a variety of seismic analysis and design problems associated with planar steel and reinforced concrete framed structures in a rational and accurate manner.These include force-based seismic design with the aid of acceleration response spectra characterized by high amounts of damping,improved direct displacement-based seismic design and the development of advanced seismic intensity measures.The equivalent modal damping ratios are also utilized in the context of linear modal analysis for the definition and construction of the MDOF response spectrum.Furthermore,the equivalent modal damping ratios are employed in a seismic retrofit method for steel-framed structures with viscous dampers.Finally,it is demonstrated that modal behavior(or strength reduction)factors can be easily constructed based on these modal damping ratios for a more rational and accurate force-based seismic design,including the determination of inelastic displacement profiles.
基金Projects(51875581,51505502)supported by the National Natural Science Foundation of ChinaProjects(2017M620358,2018T110707)supported by China Postdoctoral Science FoundationProject(kq1905057)supported by the Training Program for Excellent Young Innovators of Changsha,China
文摘Seeking for innovative structures with higher mechanical performance is a continuous target in railway vehicle crashworthiness design.In the present study,three types of hexagonal reinforced honeycomb-like structures were developed and analyzed subjected to out-of-plane compression,namely triangular honeycomb(TH),double honeycomb(DH)and full inside honeycomb(FH).Theoretical formulas of average force and specific energy absorption(SEA)were constructed based on the energy minimization principle.To validate,corresponding numerical simulations were carried out by explicit finite element method.Good agreement has been observed between them.The results show that all these honeycomb-like structures maintain the same collapsed stages as conventional honeycomb;cell reinforcement can significantly promote the performance,both in the average force and SEA;full inside honeycomb performs better than the general,triangular and double schemes in average force;meanwhile,its SEA is close to that of double scheme;toroidal surface can dissipate higher plastic energy,so more toroidal surfaces should be considered in design of thin-walled structure.These achievements pave a way for designing high-performance cellular energy absorption devices.
基金the financial support of the Portuguese Foundation for Science and Technology (FCT) through the postdoctoral grant (SFRH/BPD/107825/2015)the funding of Pro-Life-Prolonging the Lifetime of Old Steel and Steel-Concrete Bridges (RFSR-CT-2015-00025) by the Research Fund for Coal and Steel (RFCS)
文摘Different strategies can be used to perform reparations and reinforcements of ancient bolted and riveted metallic bridges. As the riveting process is not currently a common practice, it requires proper equipment and skilled workers. Another solution is the use of welding. However, the weldability of old steels is poor. Bolts are very attractive alternative solutions, and are most commonly used to repair old metallic bridges. Fitted bolts are expensive solutions; the alternative is the use of resin-injected bolts. The behavior of bolted joints with preloaded resin-injected bolts has been studied using quasi-static and creep tests; however, few studies on the slip and fatigue behavior of these joints can be found in the literature. This paper presents an overview of a few experimental programs that were carried out by several authors aiming at evaluating the fatigue behavior of single and double shear resin-injected bolted connections. A comparison between the experimental data of joints with preloaded standard bolts and preloaded resin- injected bolts shows a fatigue strength reduction in the latter. Since Eurocode 3 （EC3） suggests the same fatigue strength curve for joints made of resin-injected bolts and standard bolts, this may raise some con- cerns. Furthermore, research on the feasibility of using both bonded and bolted connections is shown. This last study was performed with high-strength low-alloy structural steel plates and an acrylic struc- tural adhesive for metal bonding. For both case studies, a statistical analysis is performed on fatigue experimental data using linearized boundaries and the Castillo and Fernandez-Canteli model. Fatigue design curves are proposed and compared with the design suggestions of several European and North American standards,
基金The Key Science Foundation of Liaoning ProvincialCommunications Department (No.0101).
文摘An anchorage reliability analysis approach for simply supported reinforced concrete beams under corrosion attack in the anchorage zone is developed.The first-order second-moment method is employed to analyze the effects of various factors on the anchorage reliability.These factors include both the length and width of cover cracking due to reinforcement corrosion,the cover thickness,the anchorage length,and the stirrup ratio.The results show that the effect of corrosion-induced crack length on the reliability index for anchorage,β0,is negligible when the crack on the concrete surface is just appearing,but with the crack widening,the β0 value is reduced significantly;the considerable changes in β0 result from a variation in cover depth and anchorage length;the effect of changes in the diameter or space of stirrups on the anchorage resistance is very limited,and the variation in β0 is also very low.
基金financial support from the Regional Government of Castilla-León(Project No.SA126G18)。
文摘Implications of the differences in leaf life span are still subject to debate in the field of ecophysiology.Since leaf traits associated with these differences may be decisive for determining the distribution of tree species,this topic is particularly relevant in the context of climate change.This study analyzes the effects of the differences in leaf life span on premature losses of leaf area owing to insect herbivory and to abiotic stress.Loss of leaf area may be an important determinant of total leaf carbon assimilation.Seven Mediterranean tree species,distributed on four sites with different climates were studied.The species exhibited strong differences in leaf life span and in leaf traits,especially leaf mass per unit area.Premature leaf area losses were estimated in response to insect herbivory and summer drought over two years.The results revealed that,despite having older leaf cohorts with more damage,species with longer leaf duration had lower area lost to herbivores and less damage due to accelerated senescence during the summer drought.With respect to the predicted increase in water stress,deciduous species are at a disadvantage due to their high premature loss of leaf area and thus loss of photosynthetic capacity.
基金Supported by National Natural Science Foundation of China (No.50638030 and 50525825)National Science and Technology Support Program (No.2006BAJ13B02).
文摘in order to evaluate the capacity of reinforced concrete （RC） structures subjected to blast Ioadings, the damaged plasticity model for concrete was used in the analysis of the dynamic responses of blast-loaded RC structures, and all three failure modes were numerically simulated by the finite element software ABAQUS. Simulation results agree with the experimental observations. It is demonstrated that the damaged plasticity model for concrete in the finite element software ABAQUS can predict dynamic responses and typical flexure, flexure-shear and direct shear failure modes of the blast-loaded RC structures.
基金Univeristy of Maryland,Start-up Grant to the First Author
文摘This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose,an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters -the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio,peak acceleration ratio,energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake.
基金Basic Research Fund of Institute of Engineering Mechanics, China Earthquake Administration for Special Project Under Grant No.2007A02Joint Earthquake Science Foundation of China Under Grant No.95-07-443
文摘Earthquake simulator tests of a 1/6-scale nine-story reinforced concrete frame-wall model are described in the paper. The test results and associated numerical simulation are summarized and discussed. Based on the test data, a relationship between maximum inter-story drift and damage state is established. Equations of variation of structural characteristics （natural frequency and equivalent stiffness） with overall drifts are derived by data fitting, which can be used to estimate structural damage state if structural characteristics can be measured. A comparison of the analytical and experimental results show that both the commonly used equivalent beam and fiber element models can simulate the nonlinear seismic response of structures very well. Finally, conclusions associated with seismic design and damage evaluation of RC structures are presented.
