The influence of source concrete (SC) with different compression strengths on the workability and mechanical properties of recycled mortar made with river sand substituted by 100% fine recycled concrete aggregates (FR...The influence of source concrete (SC) with different compression strengths on the workability and mechanical properties of recycled mortar made with river sand substituted by 100% fine recycled concrete aggregates (FRCA) is experimentally investigated. The basic physical performance test shows that with the increase in SC strength, FRCA exhibit lower water absorption and crushing index, meanwhile keeping higher densities. Mechanical property tests, including compressive strength, flexural strength and uniaxial compressive stress-strain tests, show that compressive strength,flexural strength and elasticity modulus of recycled sand mortars increase roughly with the increase in SC strength. The proposed mixture design method demonstrates that all of the components can be kept as the same as those in natural mortar mixture design and FRCA must be pre-wetted before making mortar mixture. Meanwhile, the reuse of higher strength SC can ensure that recycled mortar mixtures are able to achieve similar mechanical performance when compared to natural mortar designs.展开更多
To promote the visualisation and informatisation of the construction process of precast foamed lightweight concrete wallboards(PFLCWs),from the analysis of the construction requirements of PFLCWs,three key constructio...To promote the visualisation and informatisation of the construction process of precast foamed lightweight concrete wallboards(PFLCWs),from the analysis of the construction requirements of PFLCWs,three key construction technologies based on building information modelling(BIM),namely,parameterised modelling for the PFLCW layout design,drawing generation to draw the PFLCW layout and quantity statistics for extracting PFLCW quantities,are proposed.Then,a reinforced concrete(RC)frame infilled with PFLCW is considered the test model to verify the feasibility of the aforementioned technologies.The results show that PFLCW layout design can be accomplished rapidly and visually using parameterised modelling technology.The PFLCW layout diagram can be generated directly using drawing generation technology.The proposed quantity statistics technology enables the automatic export of PFLCW bills of quantities.The built parameterised model helps construction workers rapidly and intuitively understand the specific layout details of PFLCWs.Moreover,the generated layout drawing and the bills of quantities based on the parameterised model can guide the production and on-site installation of PFLCWs.The research conclusions can serve as a practical guide and technical support for PFLCW engineering applications.展开更多
The road traffic network contains a large number of bridges,and calculating bridge damage using refined models demands significant time and resources.Therefore,developing a rapid evaluation method for the seismic capa...The road traffic network contains a large number of bridges,and calculating bridge damage using refined models demands significant time and resources.Therefore,developing a rapid evaluation method for the seismic capacity of regular bridges has become a crucial scientific challenge.This study presents an approach in which the ductile column is represented by a single degree-of-freedom model with elastic-plastic constitutive characteristics.Utilizing an uncoupled multivariate power function model and a plastic hinge model,a multidimensional power function model for section hierarchical curvature is constructed.Subsequently,the seismic multistage damage constitutive model(SMSD-CM)of member hierarchy is deduced and calibrated through theoretical methods.This model efficiently derives the trilinear constitutive model of components by inputting several crucial parameters.The SMSD-CM accurately simulates the hysteretic curve and displacement time-history under actual seismic conditions and aligns well with pushover analysis results from tests.The efficiency,ease of operation,and accuracy make the model suitable for rapid evaluation of the seismic capacity of regular bridges within the road traffic network.展开更多
The key points to consider in determining the effectiveness of using structural isolation with shape memory alloys （SMA） are the constitutive model, the SMA isolation device and the analysis method. In this paper, a...The key points to consider in determining the effectiveness of using structural isolation with shape memory alloys （SMA） are the constitutive model, the SMA isolation device and the analysis method. In this paper, a simplified constitutive model based on the classic theory of plasticity is proposed to simulate the behavior of the superelasticity of the SMA, in which the martensite volume fraction is considered as one of the state variables. Comparisons between simulation results and experimental results are made and indicate that the proposed constitutive model yields stress-strain curves that are in good agreement with the experimental ones. Thus, the proposed model can correctly simulate the yield mechanism and energy dissipation capacity of the SMA. Next, in order to make full use of the superelasticity of SMA, a new SMA isolator composed of pre-tensioned SMA bars is presented. Then, a finite element analytical model is established to simulate the behavior of the SMA isolator according to its configuration and simplified constitutive model. Finally, a simplified design method for long-span structures installed with SMA isolators is proposed, which is further used to investigate the isolation effects of a space grid structure. Results show that the SMA isolator can reduce the seismic responses of the structure effectively, which indicates the effectiveness of the proposed SMA isolation method.展开更多
In order to improve the seismic performance, deformation ability and ultimate load-carrying capacity of columns with rectangular cross section, engineered cementitious composite （ECC） is introduced to partially subs...In order to improve the seismic performance, deformation ability and ultimate load-carrying capacity of columns with rectangular cross section, engineered cementitious composite （ECC） is introduced to partially substitute concrete in the edge zone of reinforced concrete columns and form reinforced ECC/concrete composite columns. Firstly, based on the assumption of plane remaining plane and the simplified constitutive models, the calculation method of the load-carrying capacity of reinforced ECC/concrete columns is proposed. The stress and strain distribu- tions and crack propagation of the composite columns in different states of eccentric compressive loading are ana- lyzed. Then, nonlinear finite element analysis is conducted to study the mechanical performance of reinforced ECC/concrete composite columns with rectangular cross section. It is found that the simulation results are in good agreement with the theoretical results, indicating that the proposed method for calculating the load-carrying capacity of concrete/ECC composite columns is valid. Finally, based on the proposed method, the effects of ECC thickness, com- pressive strength of concrete and longitudinal reinforcement ratio on the mechanical performance of reinforced ECC/ concrete composite columns are analyzed. Calculation results indicate that increasing the thickness of ECC layer or longitudinal reinforcement ratio can effectively increase the ultimate load-carrying capacity of the composite column with both small and large eccentricity, but increasing the strength of concrete can only increase the ultimate Ioad- carrying capacity of the composite column with small eccentricity.展开更多
The increasing strength of new structural materials and the span of new structures, accompanied by aesthetic requirements for greater slenderness, are resulting in more applications of long-span structures. In this pa...The increasing strength of new structural materials and the span of new structures, accompanied by aesthetic requirements for greater slenderness, are resulting in more applications of long-span structures. In this paper, serviceability control technology and its design theory are studied. First, a novel tuned mass damper （TMD） with controllable stiffness is developed. Second, methods for modeling human-induced loads are proposed, including standing up, walking, jumping and running, and an analysis method for long-span floor response is proposed based on a finite element model. Third, a design method for long-span floors installed with a multiple TMD （MTMD） system considering human comfort is introduced, largely based on a study of existing literature. Finally, a design, analysis and field test is conducted using several large scale buildings in China including the Beijing Olympic Park National Conference Center, Changsha New Railway Station and the Xi＇an Northern Railway Station. The analytical and field test results show that the MTMD system designed using the proposed method is capable of effectively mitigating the vertical vibration of long-span floor structures. The study presented in this paper provides an important reference for the analysis of vibration serviceability of similar long-span floors and design of control system for these structures.展开更多
Bamboo is a green construction material in line with sustainable development strategies.The use of raw bamboo in architecture has existed since ancient times.In the long development years of original bamboo buildings,...Bamboo is a green construction material in line with sustainable development strategies.The use of raw bamboo in architecture has existed since ancient times.In the long development years of original bamboo buildings,many areas in the world gradually formed unique bamboo buildings,which have become an important local cultural feature.For building structures,joints are the key to ensure structural load transfer.Because of hollow and thin-walled material property of bamboo,the connection in raw bamboo buildings has always been a major difficulty and problem in the application of bamboo,which seriously hinders the development of original bamboo structures.In order to promote the use of raw bamboo,two traditional connection methods in raw bamboo structures are described in this paper firstly,with the advantages and disadvantages of the two methods pointed out.Also,research progress on four categories of raw bamboo building joints is described namely,bolt joints,steel member joints,filler reinforced joints and other types of joints.This work can provide a reference for future research and engineering applications.展开更多
The objective of this paper is to study the influence of repeated variable action on long-term behavior of concrete structural elements using quasi-permanent combination of actions, for the assessment of long-term eff...The objective of this paper is to study the influence of repeated variable action on long-term behavior of concrete structural elements using quasi-permanent combination of actions, for the assessment of long-term effects （e.g., effects due to creep and shrinkage in concrete structures）, as it is proposed in Eurocodes. Extensive experimental program and analytical research using model B3 and AAEM （age adjusted effective modulus） method was performed in order to define quasi-permanent factor ψ2, for two specific loading histories. These loading histories were consist of long-term permanent action ＂G＂ and repeated variable action ＂Q＂. The variable load was applied in cycles of loading/unloading for 24 h and 48 h in period of 400 days appropriately for one series of concrete elements. 24 reinforced concrete beams, dimensions 150 mm × 280 mm × 3,000 mm, were tested. Twelve beams were made of concrete class C30/37 and 12 of concrete class C60/75.展开更多
In this paper,recycled bricks and recycled concrete were applied to prepare eco-friendly recycled mixed powder(RMP)cementitious material,as a supplementary to replace conventional cement for improve the recycling of c...In this paper,recycled bricks and recycled concrete were applied to prepare eco-friendly recycled mixed powder(RMP)cementitious material,as a supplementary to replace conventional cement for improve the recycling of construction and demolition waste.Based on the effect of cementitious materials on the hydration of silicate cement,the effects of RMP on the workability,mechanical properties and microstructure of recycled mixed powder concrete(RMPC)with the different replacement ratios and the 8:4 and 6:4 mixing ratio of recycled brick powder(RBP)and recycled concrete powder(RCP)were investigated.The results showed that the fluidity of the mix decreased with increasing of the replacement ratio and the mixing ratio of RBP and RCP,but the influence of the fluidity was smaller within 15%replacement ratio.As the replacement ratio increases,the internal pore structure of RMPC tends to be loose and porous,which exhibits a significant pore volume distribution characteristic.The number of large capillaries was considerably increased at replacement ratio of 45%.The 7 d compressive strength of RMPC was slightly lower than that of ordinary concrete.The compressive and splitting tensile strengths of RMPC at 28 d increased by 4.2%and 10.1%,respectively,with increasing curing age at 15%replacement ratio and 6:4 mixing ratio.The RMPC mechanical strengths with RBP and RCP at the mixing ratio of 6:4 was higher than those of 8:2.Finally,a basis for the recycling of RBP and RCP in the construction industry can be provided by the results of this study.展开更多
To investigate the effect of higher modes on the displacement and inner forces in HWBB(hinged wall with buckling-restrained braces in base)-frame structure,distributed parameter models for both the HWBB-hinged frame s...To investigate the effect of higher modes on the displacement and inner forces in HWBB(hinged wall with buckling-restrained braces in base)-frame structure,distributed parameter models for both the HWBB-hinged frame structure and the HWBB-MRF(moment resisting frame)structure are built.The hinged wall is simplified as a flexural beam.BRBs(bucking-restrained braces)are simplified to a rotational spring.MRF is simplified to a shear beam.Vibration equations of distributed parameter models are derived.Natural periods,natural modes of vibration,inner forces and displacements of the distributed parameter models are derived based on the vibration equations using numerical methods.The effect of the relative stiffness ratio and the rotational stiffness ratio on the higher mode effects is investigated.For elastic structures,the global displacement and shear in MRF are predominantly controlled by the first mode,while the shear and bending moment in the wall are significantly affected by higher mode effects.The effect of the yielding of BRB on the inner forces distribution in the HWBB-hinged frame is investigated.The results indicate that the first mode will no longer contribute to the inner forces and the contribution from higher modes to inner forces increases after the BRBs yield.Displacement is not sensitive to higher mode effects and it is controlled by the first mode after the BRBs yield.Parameter analysis demonstrates that the displacement amplitudes are reduced with the increase in the flexural stiffness of the wall before the flexural stiffness reaches a certain value.The first three periods decrease with the increase in the rotational stiffness.With the increase in the rotational stiffness ratio,the contribution from the first mode decreases while contributions from both the second mode and third mode increase.展开更多
For reinforced concrete structures located along the seaside, the penetration of chloride ions into concrete may be a threat to the durability of the structures. Experimental investigations were carried out to study t...For reinforced concrete structures located along the seaside, the penetration of chloride ions into concrete may be a threat to the durability of the structures. Experimental investigations were carried out to study the effect of chloride content on the bond behavior between concrete and fiber reinforced polymer (FRP) plates. Direct shear tests were conducted on the FRP strengthened concrete members. Before testing, the specimens were immersed in NaCl solutions with concentrations ranging from 3%—15% for di...展开更多
In this paper,mercury intrusion porosimetry(MIP)is used to test the pore structure of non-dispersible underwater concrete so as to study the influence of pouring and curing environment,age and slag powder on the pore ...In this paper,mercury intrusion porosimetry(MIP)is used to test the pore structure of non-dispersible underwater concrete so as to study the influence of pouring and curing environment,age and slag powder on the pore characteristics of concrete,analyze the pore characteristics,porosity and pore distribution of concrete in different hydration stages,and reveal the relationship between pore structure and permeability of concrete.The results show that the pore-size distribution of concrete in fresh water condition is better than that in sulfate environment and mixed salt environment,and therefore,sulfate as well as mixed salt are not conducive to the development of pore structure of non-dispersible underwater concrete;chlorine salt has little effect on the pore structure of nondispersible underwater concrete;under the three conditions of sulfate,chlorine and mixed salt,the porosity of concrete mixed with slag powder is lower than that of concrete without slag powder.The results indicate that the addition of slag powder can ameliorate the pore size distribution of non-dispersed underwater concrete,reduce the porosity,and make the concrete structure more compact,which is beneficial to improve the permeability resistance of concrete at the macro level.展开更多
External bonding of fiber reinforced polymer （FRP） composites on the concrete structures has been proved to be an effective and efficient way to strengthen concrete structures. For a FRP strengthened concrete beam, ...External bonding of fiber reinforced polymer （FRP） composites on the concrete structures has been proved to be an effective and efficient way to strengthen concrete structures. For a FRP strengthened concrete beam, it is usually observed that the failure occurs in the concrete and a thin layer of concrete is attached on the surface of the debonded FRP plate. To study the debond behavior between concrete and FRP composites, an analytical model based on the three-parameter model is developed to study the debonding behavior for the FRP-to-concrete joint under pure shearing. Then, nonlinear FEM analysis is conducted to verify the PrOposed analytical model. The FEM results shows good agreement with the results from the model. Finally, with the analytical model, sensitivity analyses are performed to study the effect of the interracial parameters or the ~eometric parameters on the debondin~ behavior.展开更多
A resilience-incorporated risk assessment framework is proposed and demonstrated in this study to manifest the advantageous seismic resilience of precast concrete frame(PCF)structures with“dry”connections in terms o...A resilience-incorporated risk assessment framework is proposed and demonstrated in this study to manifest the advantageous seismic resilience of precast concrete frame(PCF)structures with“dry”connections in terms of their low damage and rapid recovery.The framework integrates various uncertainties in the seismic hazard,fragility,capacity,demand,loss functions,and post-earthquake recovery.In this study,the PCF structures are distinguished from ordinary reinforced concrete frame(RCF)structures by characterizing multiple limit states for the PCF based on its unique damage mechanisms.Accordingly,probabilistic story-wise pushover analyses are performed to yield story-wise capacities for the predefined limit states.In the seismic resilience analysis,a step-wise recovery model is proposed to idealize the functionality recovery process,with separate considerations of the repair and non-repair events.The recovery model leverages the economic loss and downtime to delineate the stochastic post-earthquake recovery curves for the resilience loss estimation.As such,contingencies in the probabilistic post-earthquake repairs are incorporated and the empirical judgments on the recovery parameters are largely circumvented.The proposed framework is demonstrated through a comparative study between two“dry”connected PCFs and one RCF designed as alternative structural systems for a prototype building.The results from the risk quantification indicate that the PCFs show reduced loss hazards and lower expected losses relative to the RCF.Particularly,the PCF equipped with energy dissipation devices at the“dry”connections largely reduces the expected economic loss,downtime,and resilience loss by 29%,56%,and 60%,respectively,compared to the RCF.展开更多
Taking advantage of heat absorbing and releasing capability of phase change material(PCM),Paraffin wax-based concrete was prepared to assess its automatic temperature control performance.The mechanical properties of P...Taking advantage of heat absorbing and releasing capability of phase change material(PCM),Paraffin wax-based concrete was prepared to assess its automatic temperature control performance.The mechanical properties of PCM concrete with eight different Paraffin wax contents were tested by the cube compression test and four-point bending test.The more Paraffin wax incorporated,the greater loss of the compressive strength and bending strength.Based on the mechanical results,four contents of Paraffin wax were chosen for studying PCM concrete's thermal properties,including thermal conductivity,thermal diffusivity,specific heat capacity,thermal expansion coefficient and adiabatic temperature rise.When the Paraffin wax content increases from 10%to 20%,the thermal conductivity and the thermal diffusivity decrease from 7.31 kJ/(m·h·°C)to 7.10 kJ/(m·h·°C)and from 3.03×10−3 m2/h to 2.44×10−3 m2/h,respectively.Meanwhile the specific heat capacity and thermal expansion coefficient rise from 5.38×10−1 kJ/(kg·°C)to 5.76×10−1 kJ/(kg·°C)and from 9.63×10−6/°C to 14.02×10−6/°C,respectively.The adiabatic temperature rise is found to decrease with an increasing Paraffin wax content.Considering both the mechanical and thermal properties,15%of Paraffin wax was elected for the mass concrete model test,and the model test results confirm the effect of Paraffin wax in automatic mass concrete temperature control.展开更多
In saline soil areas,there are a large number of ions in soil or water environments,such as Cl^(-)and SO_(4)^(2-),which have strong corrosive interactions with buildings.To study the deterioration of non-dispersible u...In saline soil areas,there are a large number of ions in soil or water environments,such as Cl^(-)and SO_(4)^(2-),which have strong corrosive interactions with buildings.To study the deterioration of non-dispersible underwater concrete in sulfate,chloride,and mixed salt environments,the compressive strength and deterioration resistance coefficient of the studied concrete mixed with different amounts of ground granulated blast-furnace slag(GGBS)were analyzed in this paper.At the same time,the micro morphology and corrosion products distribution of the studied concrete were observed by means of SEM,plus XRD diffraction,TG-DTG and FT-IR analyses to explore the influence of corrosive solutions on the hydration products of concrete.We also analyzed the mechanism of improving the deterioration resistance of the studied concrete by adding GGBS in a saline soil environment.The results show that the compressive strength of the studied concrete in a chloride environment was close to that in a fresh water environment,which means that chloride has no adverse effect on compressive strength.The deterioration of the studied concrete was most serious in a sulfate environment,followed by mixed salt environment,and the lowest in a chloride environment.In addition,by adding GGBS,the compressive strength and deterioration resistance of the studied concrete could be effectively improved.展开更多
Conical origami structures are characterized by their substantial out-of-plane stiffness and energy-absorptioncapacity.Previous investigations have commonly focused on the static characteristics of these lightweight s...Conical origami structures are characterized by their substantial out-of-plane stiffness and energy-absorptioncapacity.Previous investigations have commonly focused on the static characteristics of these lightweight struc-tures.However,the efficient analysis of the natural vibrations of these structures is pivotal for designing conicalorigami structures with programmable stiffness and mass.In this paper,we propose a novel method to analyzethe natural vibrations of such structures by combining a symmetric substructuring method(SSM)and a gener-alized eigenvalue analysis.SSM exploits the inherent symmetry of the structure to decompose it into a finiteset of repetitive substructures.In doing so,we reduce the dimensions of matrices and improve computationalefficiency by adopting the stiffness and mass matrices of the substructures in the generalized eigenvalue analysis.Finite element simulations of pin-jointed models are used to validate the computational results of the proposedapproach.Moreover,the parametric analysis of the structures demonstrates the influences of the number of seg-ments along the circumference and the radius of the cone on the structural mass and natural frequencies of thestructures.Furthermore,we present a comparison between six-fold and four-fold conical origami structures anddiscuss the influence of various geometric parameters on their natural frequencies.This study provides a strategyfor efficiently analyzing the natural vibration of symmetric origami structures and has the potential to contributeto the efficient design and customization of origami metastructures with programmable stiffness.展开更多
The research object was high 120 m concrete gravity dam of the Angara Bratsk hydroelectric power plant. The state of the concrete dam is estimated based on the results of continuous supervision performed by site perso...The research object was high 120 m concrete gravity dam of the Angara Bratsk hydroelectric power plant. The state of the concrete dam is estimated based on the results of continuous supervision performed by site personnel as well as periodic monitoring. According to the classification of the interrelations in the system ＂concrete-environment＂, there were selected some important parts of dams and a comprehensive analysis of concrete was executed on these parts. Concerning the complex research of concrete, a combination of full-scale tests with core-sampling has been proposed. Core samples tests had an object to study the deep concrete layers and to determine the specific indicators such as strength, density, porosity, comparative diameter of capillary pores, CaO content in cement stone and others. Obtained findings and recommended criteria can be applied when selecting technologies for constructing dams that guarantee their durability in the north.展开更多
The fuzzy comfortability of a wind-sensitive super-high tower crane is critical to guarantee occupant health and improve construction efficiency.Therefore,the wind-resistant fuzzy comfortability of a super-high tower ...The fuzzy comfortability of a wind-sensitive super-high tower crane is critical to guarantee occupant health and improve construction efficiency.Therefore,the wind-resistant fuzzy comfortability of a super-high tower crane in the Ma’anshan Yangtze River(MYR)Bridge site is analyzed in this paper.First,the membership function model that represents fuzzy comfortability is introduced in the probability density evolution method(PDEM).Second,based on Fechner’s law,the membership function curves are constructed according to three acceleration thresholds in ISO 2631.Then,the fuzzy comfortability for the super-high tower crane under stochastic wind loads is assessed on the basis of different cut-set levelsλ.Results show that the comfortability is over 0.9 under the required maximum operating wind velocity.The low sensitivity toλcan be observed in the reliability curves of ISOⅡandⅢmembership functions.The reliability of the ISOⅠmembership function is not sensitive toλwhenλ<0.7,whereas it becomes sensitive toλwhenλ>0.7.展开更多
To investigate the wind⁃induced vibration re⁃sponse characteristics of multispan double⁃layer cable photo⁃voltaic(PV)support structures,wind tunnel tests using an aeroelastic model were carried out to obtain the wind⁃...To investigate the wind⁃induced vibration re⁃sponse characteristics of multispan double⁃layer cable photo⁃voltaic(PV)support structures,wind tunnel tests using an aeroelastic model were carried out to obtain the wind⁃induced vibration response data of a three⁃span four⁃row double⁃layer cable PV support system.The wind⁃induced vibration characteristics with different PV module tilt angles,wind speeds,and wind direction angles were analyzed.The results showed that the double⁃layer cable large⁃span flexible PV support can effectively control the wind⁃induced vibration response and prevent the occur⁃rence of flutter under strong wind conditions.The maxi⁃mum value of the wind⁃induced vibration displacement of the flexible PV support system occurs in the windward first row.The upstream module has a significant shading effect on the downstream module,with a maximum effect of 23%.The most unfavorable wind direction angles of the structure are 0°and 180°.The change of the wind direction angle in the range of 0°to 30°has little effect on the wind vi⁃bration response.The change in the tilt angle of the PV modules has a greater impact on the wind vibration in the downwind direction and a smaller impact in the upwind di⁃rection.Special attention should be paid to the structural wind⁃resistant design of such systems in the upwind side span.展开更多
基金The National Key Research and Development Programm of China(No.2018YFD1100402-05)the National Natural Science Foundation of China(No.6505000184)
文摘The influence of source concrete (SC) with different compression strengths on the workability and mechanical properties of recycled mortar made with river sand substituted by 100% fine recycled concrete aggregates (FRCA) is experimentally investigated. The basic physical performance test shows that with the increase in SC strength, FRCA exhibit lower water absorption and crushing index, meanwhile keeping higher densities. Mechanical property tests, including compressive strength, flexural strength and uniaxial compressive stress-strain tests, show that compressive strength,flexural strength and elasticity modulus of recycled sand mortars increase roughly with the increase in SC strength. The proposed mixture design method demonstrates that all of the components can be kept as the same as those in natural mortar mixture design and FRCA must be pre-wetted before making mortar mixture. Meanwhile, the reuse of higher strength SC can ensure that recycled mortar mixtures are able to achieve similar mechanical performance when compared to natural mortar designs.
基金The National Key Research and Development Program of China(No.2020YFD1100404-4)the National Natural Science Foundation for Young Scientists of China(No.52108120)the National Natural Science Foundation for Young Scientists of Jiangsu Province(No.BK20210258)。
文摘To promote the visualisation and informatisation of the construction process of precast foamed lightweight concrete wallboards(PFLCWs),from the analysis of the construction requirements of PFLCWs,three key construction technologies based on building information modelling(BIM),namely,parameterised modelling for the PFLCW layout design,drawing generation to draw the PFLCW layout and quantity statistics for extracting PFLCW quantities,are proposed.Then,a reinforced concrete(RC)frame infilled with PFLCW is considered the test model to verify the feasibility of the aforementioned technologies.The results show that PFLCW layout design can be accomplished rapidly and visually using parameterised modelling technology.The PFLCW layout diagram can be generated directly using drawing generation technology.The proposed quantity statistics technology enables the automatic export of PFLCW bills of quantities.The built parameterised model helps construction workers rapidly and intuitively understand the specific layout details of PFLCWs.Moreover,the generated layout drawing and the bills of quantities based on the parameterised model can guide the production and on-site installation of PFLCWs.The research conclusions can serve as a practical guide and technical support for PFLCW engineering applications.
基金The National Natural Science Foundation of China(No.52208468,52178125)Fundamental Research Funds for Central Universities(No.2242023S20004).
文摘The road traffic network contains a large number of bridges,and calculating bridge damage using refined models demands significant time and resources.Therefore,developing a rapid evaluation method for the seismic capacity of regular bridges has become a crucial scientific challenge.This study presents an approach in which the ductile column is represented by a single degree-of-freedom model with elastic-plastic constitutive characteristics.Utilizing an uncoupled multivariate power function model and a plastic hinge model,a multidimensional power function model for section hierarchical curvature is constructed.Subsequently,the seismic multistage damage constitutive model(SMSD-CM)of member hierarchy is deduced and calibrated through theoretical methods.This model efficiently derives the trilinear constitutive model of components by inputting several crucial parameters.The SMSD-CM accurately simulates the hysteretic curve and displacement time-history under actual seismic conditions and aligns well with pushover analysis results from tests.The efficiency,ease of operation,and accuracy make the model suitable for rapid evaluation of the seismic capacity of regular bridges within the road traffic network.
基金National Natural Science Foundation of China Under Grant No. 50725828 & No. 50808041Scientific Research Foundation of Graduate School of Southeast University Under Grant No. YBJJ1006Teaching and Research Foundation for Excellent Young Teacher of Southeast University
文摘The key points to consider in determining the effectiveness of using structural isolation with shape memory alloys （SMA） are the constitutive model, the SMA isolation device and the analysis method. In this paper, a simplified constitutive model based on the classic theory of plasticity is proposed to simulate the behavior of the superelasticity of the SMA, in which the martensite volume fraction is considered as one of the state variables. Comparisons between simulation results and experimental results are made and indicate that the proposed constitutive model yields stress-strain curves that are in good agreement with the experimental ones. Thus, the proposed model can correctly simulate the yield mechanism and energy dissipation capacity of the SMA. Next, in order to make full use of the superelasticity of SMA, a new SMA isolator composed of pre-tensioned SMA bars is presented. Then, a finite element analytical model is established to simulate the behavior of the SMA isolator according to its configuration and simplified constitutive model. Finally, a simplified design method for long-span structures installed with SMA isolators is proposed, which is further used to investigate the isolation effects of a space grid structure. Results show that the SMA isolator can reduce the seismic responses of the structure effectively, which indicates the effectiveness of the proposed SMA isolation method.
基金Supported by the National Natural Science Foundation of China(No.51278118)the Program for Special Talent in Six Fields of Jiangsu Province(No.2011JZ010)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK2012756)the Undergraduate Innovation Program(No.T13052007)
文摘In order to improve the seismic performance, deformation ability and ultimate load-carrying capacity of columns with rectangular cross section, engineered cementitious composite （ECC） is introduced to partially substitute concrete in the edge zone of reinforced concrete columns and form reinforced ECC/concrete composite columns. Firstly, based on the assumption of plane remaining plane and the simplified constitutive models, the calculation method of the load-carrying capacity of reinforced ECC/concrete columns is proposed. The stress and strain distribu- tions and crack propagation of the composite columns in different states of eccentric compressive loading are ana- lyzed. Then, nonlinear finite element analysis is conducted to study the mechanical performance of reinforced ECC/concrete composite columns with rectangular cross section. It is found that the simulation results are in good agreement with the theoretical results, indicating that the proposed method for calculating the load-carrying capacity of concrete/ECC composite columns is valid. Finally, based on the proposed method, the effects of ECC thickness, com- pressive strength of concrete and longitudinal reinforcement ratio on the mechanical performance of reinforced ECC/ concrete composite columns are analyzed. Calculation results indicate that increasing the thickness of ECC layer or longitudinal reinforcement ratio can effectively increase the ultimate load-carrying capacity of the composite column with both small and large eccentricity, but increasing the strength of concrete can only increase the ultimate Ioad- carrying capacity of the composite column with small eccentricity.
基金National Natural Science Foundation of China Under Grant No.51178100Foundation of the Priority Sciences Development Program of Higher Education Institutions of Jiangsu Province Under Grant No.1105007001+1 种基金Teaching and Research Foundation for Excellent Young Teachers of Southeast University Under Grant No.3205001205Scientific Research Foundation the Scientific Research Foundation of Graduate School of Southeast University Under Grant No.YBJJ1006
文摘The increasing strength of new structural materials and the span of new structures, accompanied by aesthetic requirements for greater slenderness, are resulting in more applications of long-span structures. In this paper, serviceability control technology and its design theory are studied. First, a novel tuned mass damper （TMD） with controllable stiffness is developed. Second, methods for modeling human-induced loads are proposed, including standing up, walking, jumping and running, and an analysis method for long-span floor response is proposed based on a finite element model. Third, a design method for long-span floors installed with a multiple TMD （MTMD） system considering human comfort is introduced, largely based on a study of existing literature. Finally, a design, analysis and field test is conducted using several large scale buildings in China including the Beijing Olympic Park National Conference Center, Changsha New Railway Station and the Xi＇an Northern Railway Station. The analytical and field test results show that the MTMD system designed using the proposed method is capable of effectively mitigating the vertical vibration of long-span floor structures. The study presented in this paper provides an important reference for the analysis of vibration serviceability of similar long-span floors and design of control system for these structures.
基金supported by the Natural Science Foundation of Jiang-su Province(No.BK20181402)the National Natural Science Foundation of China(51878354)+2 种基金National Key R&D Program of China,the Open Fund Project from Key Laboratory of Concrete and Pre-stressed Concrete Structure of Ministry of Education(Southeast university)the China Postdoctoral Science Foundation(2015M580382)Jiangsu Postdoctoral Science Foundation Project(1501037A),Qing Lan Project,and a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Bamboo is a green construction material in line with sustainable development strategies.The use of raw bamboo in architecture has existed since ancient times.In the long development years of original bamboo buildings,many areas in the world gradually formed unique bamboo buildings,which have become an important local cultural feature.For building structures,joints are the key to ensure structural load transfer.Because of hollow and thin-walled material property of bamboo,the connection in raw bamboo buildings has always been a major difficulty and problem in the application of bamboo,which seriously hinders the development of original bamboo structures.In order to promote the use of raw bamboo,two traditional connection methods in raw bamboo structures are described in this paper firstly,with the advantages and disadvantages of the two methods pointed out.Also,research progress on four categories of raw bamboo building joints is described namely,bolt joints,steel member joints,filler reinforced joints and other types of joints.This work can provide a reference for future research and engineering applications.
文摘The objective of this paper is to study the influence of repeated variable action on long-term behavior of concrete structural elements using quasi-permanent combination of actions, for the assessment of long-term effects （e.g., effects due to creep and shrinkage in concrete structures）, as it is proposed in Eurocodes. Extensive experimental program and analytical research using model B3 and AAEM （age adjusted effective modulus） method was performed in order to define quasi-permanent factor ψ2, for two specific loading histories. These loading histories were consist of long-term permanent action ＂G＂ and repeated variable action ＂Q＂. The variable load was applied in cycles of loading/unloading for 24 h and 48 h in period of 400 days appropriately for one series of concrete elements. 24 reinforced concrete beams, dimensions 150 mm × 280 mm × 3,000 mm, were tested. Twelve beams were made of concrete class C30/37 and 12 of concrete class C60/75.
基金The authors gratefully acknowledge the support of the Shaanxi Provincial Key Laboratory of Concrete Structure Safety and Durability Open Fund Project(XJKFJJ201904)National Natural Science Foundation of China(51878546).
文摘In this paper,recycled bricks and recycled concrete were applied to prepare eco-friendly recycled mixed powder(RMP)cementitious material,as a supplementary to replace conventional cement for improve the recycling of construction and demolition waste.Based on the effect of cementitious materials on the hydration of silicate cement,the effects of RMP on the workability,mechanical properties and microstructure of recycled mixed powder concrete(RMPC)with the different replacement ratios and the 8:4 and 6:4 mixing ratio of recycled brick powder(RBP)and recycled concrete powder(RCP)were investigated.The results showed that the fluidity of the mix decreased with increasing of the replacement ratio and the mixing ratio of RBP and RCP,but the influence of the fluidity was smaller within 15%replacement ratio.As the replacement ratio increases,the internal pore structure of RMPC tends to be loose and porous,which exhibits a significant pore volume distribution characteristic.The number of large capillaries was considerably increased at replacement ratio of 45%.The 7 d compressive strength of RMPC was slightly lower than that of ordinary concrete.The compressive and splitting tensile strengths of RMPC at 28 d increased by 4.2%and 10.1%,respectively,with increasing curing age at 15%replacement ratio and 6:4 mixing ratio.The RMPC mechanical strengths with RBP and RCP at the mixing ratio of 6:4 was higher than those of 8:2.Finally,a basis for the recycling of RBP and RCP in the construction industry can be provided by the results of this study.
基金The National Key Research and Development Program of China(No.2018YFC0705802)the National Natural Science Foundation of China(No.51978165)+1 种基金the Fundamental Research Funds for the Central Universities(No.3205007720)Postgraduate Research and Practice Innovation Program of Jiangsu Province(No.3205007720).
文摘To investigate the effect of higher modes on the displacement and inner forces in HWBB(hinged wall with buckling-restrained braces in base)-frame structure,distributed parameter models for both the HWBB-hinged frame structure and the HWBB-MRF(moment resisting frame)structure are built.The hinged wall is simplified as a flexural beam.BRBs(bucking-restrained braces)are simplified to a rotational spring.MRF is simplified to a shear beam.Vibration equations of distributed parameter models are derived.Natural periods,natural modes of vibration,inner forces and displacements of the distributed parameter models are derived based on the vibration equations using numerical methods.The effect of the relative stiffness ratio and the rotational stiffness ratio on the higher mode effects is investigated.For elastic structures,the global displacement and shear in MRF are predominantly controlled by the first mode,while the shear and bending moment in the wall are significantly affected by higher mode effects.The effect of the yielding of BRB on the inner forces distribution in the HWBB-hinged frame is investigated.The results indicate that the first mode will no longer contribute to the inner forces and the contribution from higher modes to inner forces increases after the BRBs yield.Displacement is not sensitive to higher mode effects and it is controlled by the first mode after the BRBs yield.Parameter analysis demonstrates that the displacement amplitudes are reduced with the increase in the flexural stiffness of the wall before the flexural stiffness reaches a certain value.The first three periods decrease with the increase in the rotational stiffness.With the increase in the rotational stiffness ratio,the contribution from the first mode decreases while contributions from both the second mode and third mode increase.
基金Supported by National Natural Science Foundation of China (No. 50538086)National Key Basic Research and Development Program of China ("973" Program, No.2009CB623200)the Excellent Young Teachers Program of Southeast University
文摘For reinforced concrete structures located along the seaside, the penetration of chloride ions into concrete may be a threat to the durability of the structures. Experimental investigations were carried out to study the effect of chloride content on the bond behavior between concrete and fiber reinforced polymer (FRP) plates. Direct shear tests were conducted on the FRP strengthened concrete members. Before testing, the specimens were immersed in NaCl solutions with concentrations ranging from 3%—15% for di...
基金This work is supported by the National Natural Science Foundation of China(51878116 and 51902270)Liaoning Province Key Project of Research and Development Plan(2020JH2/10100016)+1 种基金Dalian Science and Technology Innovation Fund Project(2020JJ26SN060)the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basins(China Institute of Water Resources and Hydropower Research),Grant No.IWHR-SKL-201910.
文摘In this paper,mercury intrusion porosimetry(MIP)is used to test the pore structure of non-dispersible underwater concrete so as to study the influence of pouring and curing environment,age and slag powder on the pore characteristics of concrete,analyze the pore characteristics,porosity and pore distribution of concrete in different hydration stages,and reveal the relationship between pore structure and permeability of concrete.The results show that the pore-size distribution of concrete in fresh water condition is better than that in sulfate environment and mixed salt environment,and therefore,sulfate as well as mixed salt are not conducive to the development of pore structure of non-dispersible underwater concrete;chlorine salt has little effect on the pore structure of nondispersible underwater concrete;under the three conditions of sulfate,chlorine and mixed salt,the porosity of concrete mixed with slag powder is lower than that of concrete without slag powder.The results indicate that the addition of slag powder can ameliorate the pore size distribution of non-dispersed underwater concrete,reduce the porosity,and make the concrete structure more compact,which is beneficial to improve the permeability resistance of concrete at the macro level.
基金the National Basic Research Program of China (973 Project) (No. 2009CB623200)National Natural Science Foundation of China (No. 50808043)+1 种基金the Doctoral Program of Higher Education of China (No. 20070286024)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘External bonding of fiber reinforced polymer （FRP） composites on the concrete structures has been proved to be an effective and efficient way to strengthen concrete structures. For a FRP strengthened concrete beam, it is usually observed that the failure occurs in the concrete and a thin layer of concrete is attached on the surface of the debonded FRP plate. To study the debond behavior between concrete and FRP composites, an analytical model based on the three-parameter model is developed to study the debonding behavior for the FRP-to-concrete joint under pure shearing. Then, nonlinear FEM analysis is conducted to verify the PrOposed analytical model. The FEM results shows good agreement with the results from the model. Finally, with the analytical model, sensitivity analyses are performed to study the effect of the interracial parameters or the ~eometric parameters on the debondin~ behavior.
基金National Key Research and Development Program of China under Grant No.2022YFC3803004Postgraduate Research&Practice Innovation Program of Jiangsu Province under Grant No.SJCX20_0031Fundamental Research Funds for the Central Universities under Grant No.3205002108D。
文摘A resilience-incorporated risk assessment framework is proposed and demonstrated in this study to manifest the advantageous seismic resilience of precast concrete frame(PCF)structures with“dry”connections in terms of their low damage and rapid recovery.The framework integrates various uncertainties in the seismic hazard,fragility,capacity,demand,loss functions,and post-earthquake recovery.In this study,the PCF structures are distinguished from ordinary reinforced concrete frame(RCF)structures by characterizing multiple limit states for the PCF based on its unique damage mechanisms.Accordingly,probabilistic story-wise pushover analyses are performed to yield story-wise capacities for the predefined limit states.In the seismic resilience analysis,a step-wise recovery model is proposed to idealize the functionality recovery process,with separate considerations of the repair and non-repair events.The recovery model leverages the economic loss and downtime to delineate the stochastic post-earthquake recovery curves for the resilience loss estimation.As such,contingencies in the probabilistic post-earthquake repairs are incorporated and the empirical judgments on the recovery parameters are largely circumvented.The proposed framework is demonstrated through a comparative study between two“dry”connected PCFs and one RCF designed as alternative structural systems for a prototype building.The results from the risk quantification indicate that the PCFs show reduced loss hazards and lower expected losses relative to the RCF.Particularly,the PCF equipped with energy dissipation devices at the“dry”connections largely reduces the expected economic loss,downtime,and resilience loss by 29%,56%,and 60%,respectively,compared to the RCF.
基金This work is jointly supported by the National Natural Science Foundation of China(Grant Nos.51909223,51902270)the National Science Fund for Distinguished Young Scholars(Grant No.41825015)+2 种基金the Natural Science Basic Research Program of Shaanxi(Grant No.2019JQ-921)the Special research project of the Education Department of Shaanxi Provincial Government(Grant No.19JK0913)the Special Fund for the Launch of Scientific Research in Xijing University(Grant No.XJ18T02).
文摘Taking advantage of heat absorbing and releasing capability of phase change material(PCM),Paraffin wax-based concrete was prepared to assess its automatic temperature control performance.The mechanical properties of PCM concrete with eight different Paraffin wax contents were tested by the cube compression test and four-point bending test.The more Paraffin wax incorporated,the greater loss of the compressive strength and bending strength.Based on the mechanical results,four contents of Paraffin wax were chosen for studying PCM concrete's thermal properties,including thermal conductivity,thermal diffusivity,specific heat capacity,thermal expansion coefficient and adiabatic temperature rise.When the Paraffin wax content increases from 10%to 20%,the thermal conductivity and the thermal diffusivity decrease from 7.31 kJ/(m·h·°C)to 7.10 kJ/(m·h·°C)and from 3.03×10−3 m2/h to 2.44×10−3 m2/h,respectively.Meanwhile the specific heat capacity and thermal expansion coefficient rise from 5.38×10−1 kJ/(kg·°C)to 5.76×10−1 kJ/(kg·°C)and from 9.63×10−6/°C to 14.02×10−6/°C,respectively.The adiabatic temperature rise is found to decrease with an increasing Paraffin wax content.Considering both the mechanical and thermal properties,15%of Paraffin wax was elected for the mass concrete model test,and the model test results confirm the effect of Paraffin wax in automatic mass concrete temperature control.
基金supported by the National Natural Science Foundation of China(51878116 and 51902270)Liaoning Province Key Project of Research and Development Plan(2020JH2/10100016)+3 种基金Dalian Science and Technology Innovation Fund Project(2020JJ26 SN060)the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basins(China Institute of Water Resources and Hydropower Research),Grant No.IWHR-SKL-201910the Special Fund for the Launch of Scientific Research in Xijing University(XJ21T01)the Youth Innovation Team of Shaanxi Universities
文摘In saline soil areas,there are a large number of ions in soil or water environments,such as Cl^(-)and SO_(4)^(2-),which have strong corrosive interactions with buildings.To study the deterioration of non-dispersible underwater concrete in sulfate,chloride,and mixed salt environments,the compressive strength and deterioration resistance coefficient of the studied concrete mixed with different amounts of ground granulated blast-furnace slag(GGBS)were analyzed in this paper.At the same time,the micro morphology and corrosion products distribution of the studied concrete were observed by means of SEM,plus XRD diffraction,TG-DTG and FT-IR analyses to explore the influence of corrosive solutions on the hydration products of concrete.We also analyzed the mechanism of improving the deterioration resistance of the studied concrete by adding GGBS in a saline soil environment.The results show that the compressive strength of the studied concrete in a chloride environment was close to that in a fresh water environment,which means that chloride has no adverse effect on compressive strength.The deterioration of the studied concrete was most serious in a sulfate environment,followed by mixed salt environment,and the lowest in a chloride environment.In addition,by adding GGBS,the compressive strength and deterioration resistance of the studied concrete could be effectively improved.
基金supported by the National Natural Science Foundation of China(Grants Nos.51978150 and 52050410334)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grants No.SJCX23_0069)the Fundamental Research Funds for the Central Universities.
文摘Conical origami structures are characterized by their substantial out-of-plane stiffness and energy-absorptioncapacity.Previous investigations have commonly focused on the static characteristics of these lightweight struc-tures.However,the efficient analysis of the natural vibrations of these structures is pivotal for designing conicalorigami structures with programmable stiffness and mass.In this paper,we propose a novel method to analyzethe natural vibrations of such structures by combining a symmetric substructuring method(SSM)and a gener-alized eigenvalue analysis.SSM exploits the inherent symmetry of the structure to decompose it into a finiteset of repetitive substructures.In doing so,we reduce the dimensions of matrices and improve computationalefficiency by adopting the stiffness and mass matrices of the substructures in the generalized eigenvalue analysis.Finite element simulations of pin-jointed models are used to validate the computational results of the proposedapproach.Moreover,the parametric analysis of the structures demonstrates the influences of the number of seg-ments along the circumference and the radius of the cone on the structural mass and natural frequencies of thestructures.Furthermore,we present a comparison between six-fold and four-fold conical origami structures anddiscuss the influence of various geometric parameters on their natural frequencies.This study provides a strategyfor efficiently analyzing the natural vibration of symmetric origami structures and has the potential to contributeto the efficient design and customization of origami metastructures with programmable stiffness.
文摘The research object was high 120 m concrete gravity dam of the Angara Bratsk hydroelectric power plant. The state of the concrete dam is estimated based on the results of continuous supervision performed by site personnel as well as periodic monitoring. According to the classification of the interrelations in the system ＂concrete-environment＂, there were selected some important parts of dams and a comprehensive analysis of concrete was executed on these parts. Concerning the complex research of concrete, a combination of full-scale tests with core-sampling has been proposed. Core samples tests had an object to study the deep concrete layers and to determine the specific indicators such as strength, density, porosity, comparative diameter of capillary pores, CaO content in cement stone and others. Obtained findings and recommended criteria can be applied when selecting technologies for constructing dams that guarantee their durability in the north.
基金The National Natural Science Foundation of China(No.52108274,52208481,52338011)State Scholarship Fund of China Scholarship Council(No.202306090285).
文摘The fuzzy comfortability of a wind-sensitive super-high tower crane is critical to guarantee occupant health and improve construction efficiency.Therefore,the wind-resistant fuzzy comfortability of a super-high tower crane in the Ma’anshan Yangtze River(MYR)Bridge site is analyzed in this paper.First,the membership function model that represents fuzzy comfortability is introduced in the probability density evolution method(PDEM).Second,based on Fechner’s law,the membership function curves are constructed according to three acceleration thresholds in ISO 2631.Then,the fuzzy comfortability for the super-high tower crane under stochastic wind loads is assessed on the basis of different cut-set levelsλ.Results show that the comfortability is over 0.9 under the required maximum operating wind velocity.The low sensitivity toλcan be observed in the reliability curves of ISOⅡandⅢmembership functions.The reliability of the ISOⅠmembership function is not sensitive toλwhenλ<0.7,whereas it becomes sensitive toλwhenλ>0.7.
基金The National Natural Science Foundation of China(No.52338011).
文摘To investigate the wind⁃induced vibration re⁃sponse characteristics of multispan double⁃layer cable photo⁃voltaic(PV)support structures,wind tunnel tests using an aeroelastic model were carried out to obtain the wind⁃induced vibration response data of a three⁃span four⁃row double⁃layer cable PV support system.The wind⁃induced vibration characteristics with different PV module tilt angles,wind speeds,and wind direction angles were analyzed.The results showed that the double⁃layer cable large⁃span flexible PV support can effectively control the wind⁃induced vibration response and prevent the occur⁃rence of flutter under strong wind conditions.The maxi⁃mum value of the wind⁃induced vibration displacement of the flexible PV support system occurs in the windward first row.The upstream module has a significant shading effect on the downstream module,with a maximum effect of 23%.The most unfavorable wind direction angles of the structure are 0°and 180°.The change of the wind direction angle in the range of 0°to 30°has little effect on the wind vi⁃bration response.The change in the tilt angle of the PV modules has a greater impact on the wind vibration in the downwind direction and a smaller impact in the upwind di⁃rection.Special attention should be paid to the structural wind⁃resistant design of such systems in the upwind side span.
