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Predicting resilient modulus of recycled concrete and clay masonry blends for pavement applications using

Mosbeh R. KALOOP, Alaa R. GABR, Sherif M. EL-BADAWY, Ali ARISHA, Sayed SHWALLY, Jong WAN HU

《结构与土木工程前沿(英文)》 2019年 第13卷 第6期   页码 1379-1392 doi: 10.1007/s11709-019-0562-2

摘要: To date, very few researchers employed the Least Square Support Vector Machine (LSSVM) in predicting the resilient modulus ( ) of Unbound Granular Materials (UGMs). This paper focused on the development of a LSSVM model to predict the of recycled materials for pavement applications and comparison with other different models such as Regression, and Artificial Neural Network (ANN). Blends of Recycled Concrete Aggregate (RCA) with Recycled Clay Masonry (RCM) with proportions of 100/0, 90/10, 80/20, 70/30, 55/45, 40/60, 20/80, and 0/100 by the total aggregate mass were evaluated for use as UGMs. RCA/RCM materials were collected from dumps on the sides of roads around Mansoura city, Egypt. The investigated blends were evaluated experimentally by routine and advanced tests and the values were determined by Repeated Load Triaxial Test (RLTT). Regression, ANN, and LSSVM models were utilized and compared in predicting the of the investigated blends optimizing the best design model. Results showed that the ’s of the investigated RCA/RCM blends were generally increased with the decrease in RCM proportion. Statistical analyses were utilized for evaluating the performance of the developed models and the inputs sensitivity parameters. Eventually, the results approved that the LSSVM model can be used as a novel tool to estimate the of the investigated RCA/RCM blends.

关键词: Least Square Support Vector Machine     Artificial Neural Network     resilient modulus     Recycled Concrete Aggregate     Recycled Clay Masonry    

Confined masonry as practical seismic construction alternative–the experience from the 2014 Cephalonia

Fillitsa KARANTONI, Stavroula PANTAZOPOULOU, Athanasios GANAS

《结构与土木工程前沿(英文)》 2018年 第12卷 第3期   页码 270-290 doi: 10.1007/s11709-017-0390-1

摘要:

During August 1953 three strong earthquakes of magnitude ranging from 6.3 to 7.2 shook the Ionian Island of Cephalonia (Kefalonia), Greece, and destroyed almost the entire building stock of the Island which consisted primarily of traditional unreinforced masonry (URM) houses. The authorities went on to restructuring of the building stock, using a structural system that is most like what is known today as confined masonry. They designed about 14 types of one- to two-storey buildings providing the engineers with detailed construction plans. These buildings are known as “Arogi” buildings (Arogi in Greek meaning Aid). On the 24th of January and 3rd of February 2014, two earthquakes of magnitude 6.1 and 6.0 struck the island, causing significant soil damages, developing excessively high ground accelerations. Surprisingly, no damage was reported in the “Arogi” buildings. The seismic behavior of the buildings is examined by FEM linear analysis and it is compared to that of URM structures. Computed results illustrate that the displacements of identical URM buildings would be about twice the magnitudes observed in the corresponding “Arogi” ones, with the implication that the earthquake sequence of 2014 would have caused critical damage should the type of structure be of the URM type. Furthermore, it is illustrated that this low cost alternative method of construction is a very effective means of producing earthquake resilient structures, whereas further reduction of seismic displacement may be achieved in the order of 50% with commensurate effects on damage potential, when reinforced slabs are used to replace the timber roofs.

关键词: Cephalonia     confined masonry     comparative FEM analysis     unreinforced masonry     seismic damage    

Bearing and uplift capacities of under-reamed piles in soft clay underlaid by stiff clay using lower-bound

Mantu MAJUMDER, Debarghya CHAKRABORTY

《结构与土木工程前沿(英文)》 2021年 第15卷 第2期   页码 537-551 doi: 10.1007/s11709-021-0708-x

摘要: Ensuring a safe foundation design in soft clay is always a challenging task to engineers. In the present study, the effectiveness of under-reamed piles in soft clay underlaid by stiff clay is numerically studied using the lower-bound finite element limit analysis (LB FELA). The bearing and uplift capacities of under-reamed piles are estimated through non-dimensional factors and , respectively. These factors increased remarkably and marginally compared to and of the piles without bulbs when the bulb is placed in stiff and soft clay, respectively. For a given ratio of undrained cohesion of stiff to soft clay ( / ), the factors and moderately increased with the increase in the length-to-shaft-diameter ratio ( / ) and adhesion factors in soft clay ( ) and stiff clay ( ). The variation of radial stress along the pile–soil interface, distribution of axial force in the under-reamed piles, and state of plastic shear failure in the soil are also studied under axial compression and tension. The results of this study are expected to be useful for the estimation of the bearing and uplift capacities of under-reamed piles in uniform clay and soft clay underlaid by stiff clay.

关键词: bearing capacity     uplift capacity     under-reamed pile     clay     limit analysis    

Experimental study on the compressive performance of new sandwich masonry walls

Jianzhuang XIAO, Jie PU, Yongzhong HU

《结构与土木工程前沿(英文)》 2013年 第7卷 第2期   页码 154-163 doi: 10.1007/s11709-013-0203-0

摘要: Sandwich masonry wall, namely, multi-leaf masonry wall, is widely applied as energy-saving wall since the interlayer between the two outer leaves can act as insulation layer. New types of sandwich walls keep appearing in research and application, and due to their unique connection patterns, experimental studies should be performed to investigate the mechanical behavior, especially the compressive performance. 3 new types of sandwich masonry wall were investigated in this paper, and 3 different technical measures were considered to guarantee the cooperation between the two leaves of the walls. Based on the compression tests of 13 specimens, except for some damage patterns similar with the conventional masonry walls, several new failure patterns are found due to unique connection construction details. Comparisons were made between the tested compression capacity and the theoretical one which was calculated according to the Chinese Code for Design of Masonry Structures. The results indicate that the contributions of the 3 technical measures are different. The modification coefficient ( ) was suggested to evaluate the contribution of the technical measures on the compression capacity, and then a formula was proposed to evaluate the design compression capacity of the new sandwich masonry walls.

关键词: sandwich wall     insulation wall     connection     compressive performance     compression test    

Model testing of tripod caisson foundations in silty clay subjected to eccentric lateral loads

《结构与土木工程前沿(英文)》 2023年 第17卷 第3期   页码 467-476 doi: 10.1007/s11709-023-0933-6

摘要: In this study, model tests were conducted to investigate the bearing capacities of tripod caisson foundations subjected to eccentric lateral loads in silty clay. Lateral load–rotation curves of five eccentric-shaped tripod suction foundations were plotted to analyze the bearing capacities at different loading angles. It was observed that the loading angle significantly influenced the bearing capacity of the foundations, particularly for eccentric tripod caisson foundations. Compared with eccentric tripod caisson foundations, the traditional tripod foundation has a relatively high ultimate lateral capacity at the omnidirectional loading angle. By analyzing the displacement of the caissons, a formula for the rotational center of the tripod caisson foundation subjected to an eccentric lateral load was derived. The depth of the rotation center was 0.68–0.92 times the height of the caisson when the bearing capacity reached the limit. Under the undrained condition, suction was generated under the lid of the “up-lift” caisson, which helps resist lateral forces from the wind and waves.

关键词: tripod caisson foundation     silty clay     eccentric lateral capacity     model tests    

Behavior of compacted clay-concrete interface

R. R .SHAKIR, Jungao ZHU

《结构与土木工程前沿(英文)》 2009年 第3卷 第1期   页码 85-92 doi: 10.1007/s11709-009-0013-6

摘要: Tests of interface between compacted clay and concrete were conducted systematically using interface simple shear test apparatus. The samples, having same dry density with different water content ratio, were prepared. Two types of concrete with different surface roughness, i.e., relatively smooth and relatively rough surface roughness, were also prepared. The main objectives of this paper are to show the effect of water content, normal stress and rough surface on the shear stress-shear displacement relationship of clay-concrete interface. The following were concluded in this study: 1) the interface shear sliding dominates the interface shear displacement behavior for both cases of relatively rough and smooth concrete surface except when the clay water content is greater than 16% for the case of rough concrete surface where the shear failure occurs in the body of the clay sample; 2) the results of interface shear strength obtained by direct shear test were different from that of simple shear test for the case of rough concrete surface; 3) two types of interface failure mechanism may change each other with different water content ratio; 4) the interface shear strength increases with increasing water content ratio especially for the case of clay-rough concrete surface interface.

关键词: soil structure interaction     simple shear test     interface     friction     compacted clay     interface modeling    

Mechanical properties characterization of different types of masonry infill walls

André FURTADO, Hugo RODRIGUES, António ARÊDE, Humberto VARUM

《结构与土木工程前沿(英文)》 2020年 第14卷 第2期   页码 411-434 doi: 10.1007/s11709-019-0602-y

摘要: It is remarkable, the recent advances concerning the development of numerical modeling frameworks to simulate the infill panels’ seismic behavior. However, there is a lack of experimental data of their mechanical properties, which are of full importance to calibrate the numerical models. The primary objective of this paper is to present an extensive experimental campaign of mechanical characterization tests of infill masonry walls made with three different types of masonry units: lightweight vertical hollow concrete blocks and hollow clay bricks. Four different types of experimental tests were carried out, namely: compression strength tests, diagonal tensile strength tests, and flexural strength tests parallel and perpendicular to the horizontal bed joints. A total amount of 80 tests were carried out and are reported in the present paper. The second objective of this study was to compare the mechanical properties of as-built and existing infill walls. The results presented and discussed herein, will be in terms of strain-stress curves and damages observed within the tests. It was observed a fragile behavior in the panels made with hollow clay horizontal bricks, without propagation of cracks. The plaster increased the flexural strength by 57%.

关键词: masonry infill walls     experimental characterization     compression strength     shear diagonal strength     flexural strength    

Experimental research on seismic behavior of recycled concrete frame under varying cyclic loading

SUN Yuedong, XIAO Jianzhuang, ZHOU Deyuan

《结构与土木工程前沿(英文)》 2008年 第2卷 第4期   页码 302-308 doi: 10.1007/s11709-008-0050-6

摘要: A study is conducted on the seismic behavior of one natural concrete frame and two recycled concrete frames with 100% recycled coarse aggregate whose scales are 1:2 entirely, and a comparative study is conducted under low-reversed cyclic lateral loading and different vertical loading. This work aims to estimate the failure mechanism, hysteresis loops, displacement ductility, deterioration of strength and stiffness and energy dissipation of recycled concrete frames under low-reversed cyclic loading as well as the influence of different vertical loading. Analysis on the basis of the experiment proves that it is entirely feasible to apply recycled concrete to practical engineering for the sake of its good seismic behaviors. Theoretical base is provided for further study and practical application of recycled concrete structure.

关键词: different     aggregate     stiffness     practical application     % recycled    

Chloride diffusion in concrete with carbonated recycled coarse aggregates under biaxial compression

《结构与土木工程前沿(英文)》 2023年 第17卷 第4期   页码 637-648 doi: 10.1007/s11709-023-0902-0

摘要: Chloride attack on concrete structures is affected by the complex stress state inside concrete, and the effect of recycled aggregates renders this process more complex. Enhancing the chloride resistance of recycled concrete in a complex environment via carbonization facilitates the popularization and application of recycled concrete and alleviates the greenhouse effect. In this study, the chloride ion diffusion and deformation properties of recycled concrete after carbonization are investigated using a chloride salt load-coupling device. The results obtained demonstrate that the chloride ion diffusivity of recycled concrete first decreases and then increases as the compressive load increases, which is consistent with the behavior of concrete, in that it first undergoes compressive deformation, followed by crack propagation. Carbonation enhances the performance of the recycled aggregates and reduces their porosity, thereby reducing the chloride diffusion coefficient of the recycled concrete under different compressive load combinations. The variation in the chloride ion diffusivity of the carbonized recycled aggregate concrete with the load is consistent with a theoretical formula.

关键词: recycled concrete     carbonated recycled coarse aggregate     biaxial compression     chloride diffusion     stress level    

Long term performance of recycled concrete beams with different water–cement ratio and recycled aggregate

Jingwei YING; Feiming SU; Shuangren CHEN

《结构与土木工程前沿(英文)》 2022年 第16卷 第3期   页码 302-315 doi: 10.1007/s11709-022-0803-7

摘要: The purpose of this study is to reveal the service performance of recycled aggregate concrete (RAC) components for different values of water−cement ratio and replacement rate of recycled coarse aggregate (RCA). Generally, the concrete strength decreases with the increase of the replacement rate of RCA, in order to meet the strength requirements when changing the replacement rate of RCA, it is necessary to change the water−cement ratio at the same time. Therefore, the axial compressive strengths of prism with 25 mix proportions, the short-term mechanical properties and long-term deformation properties of reinforced concrete beams were tested respectively by changing water−cement ratio and RCA replacement rate. The bearing capacity and the strain nephogram of samples under different loads were obtained using the Digital Image Correlation (DIC) method, and a self-made gravity loading experimental device was used for long-term deformation investigation. Results showed that the damage pattern of RAC was the same as that of natural aggregate concrete (NAC), but the brittleness was more pronounced. The brittleness of concrete before failure can be reduced more effectively by adjusting the replacement rate of RCA than by adjusting the water−cement ratio. The water−cement ratio has an evident influence on the axial compressive strength and early creep of concrete, while the replacement rate of RCA has a remarkable effect on the long-term deformation of the concrete beams.

关键词: recycled concrete     beam     the replacement rate of recycled coarse aggregate     water–cement ratio     digital image correlation    

Seismic safety evaluation methodology for masonry building and retrofitting using splint and bandage

Pravin Kumar Venkat Rao PADALU; Yogendra SINGH

《结构与土木工程前沿(英文)》 2022年 第16卷 第4期   页码 478-505 doi: 10.1007/s11709-022-0817-1

摘要: The paper presents a seismic safety assessment of unreinforced masonry (URM) building using two approaches. The first approach uses the ‘Pier Analysis’ method, based on the concept of equivalent lateral stiffness, where in-plane and out-of-plane actions are considered independently. The second approach is developed with the program SAP2000, where the linear response is evaluated using continuum ‘finite element modelling’ (FEM). Both methods are compared to evaluate the safety of wall piers and the differences in the outcomes under combined gravitational and lateral seismic forces. The analysis results showed that few wall elements are unsafe in in-plane and out-of-plane tension. It is also observed that the pier analysis method is conservative compared to FEM, but can be used as a simplified and quick tool in design offices for safety assessment, with reasonable accuracy. To safeguard the URM wall piers under lateral loads, a retrofitting technique is adopted by providing vertical and horizontal belts called splints and bandages, respectively, using welded wire mesh (WWM) reinforcement. The study using the ‘Pier Analysis’ shows that the lateral load capacity of unsafe URM piers can be enhanced up to 3.67 times and made safe using the applied retrofitting technique. Further, the retrofitting design methodology and recommendations for application procedures to on-site URM buildings are discussed in detail.

关键词: unreinforced masonry     seismic in-plane and out-of-plane forces     pier analysis     finite element modelling     splint and bandage technique with wire mesh    

Analysis of Sydney’s recycled water schemes

Zhuo CHEN, Huu Hao NGO, Wenshan GUO, Xiaochang WANG

《环境科学与工程前沿(英文)》 2013年 第7卷 第4期   页码 608-615 doi: 10.1007/s11783-012-0468-x

摘要: Recycled water provides a viable opportunity to partially supplement fresh water supplies as well as substantially alleviate environmental loads. Currently, thousands of recycled water schemes have been successfully conducted in a number of countries and Sydney is one of the leading cities, which has made massive effort to apply water reclamation, recycling and reuse. This study aims to make a comprehensive analysis of recycled water schemes in Sydney for a wide range of end uses such as landscape irrigation, industrial process uses and residential uses (e.g., golf course irrigation, industrial cooling water reuse, toilet flushing and clothes washing etc.). For each representative recycled water scheme, this study investigates the involved wastewater treatment technologies, the effluent quality compared with specified guideline values and public attitudes toward different end uses. Based on these obtained data, multi criteria analysis (MCA) in terms of risk, cost-benefit, environmental and social aspects can be performed. Consequently, from the analytical results, the good prospects of further expansion and exploration of current and new end uses were identified toward the integrated water planning and management. The analyses could also help decision makers in making a sound judgment for future recycled water projects.

关键词: recycled water schemes     end use     water quality     public attitudes     integrated water planning and management    

Punching shear behavior of recycled aggregate concrete slabs with and without steel fibres

Jianzhuang XIAO, Wan WANG, Zhengjiu ZHOU, Mathews M. TAWANA

《结构与土木工程前沿(英文)》 2019年 第13卷 第3期   页码 725-740 doi: 10.1007/s11709-018-0510-6

摘要: A study on the punching shear behavior of 8 slabs with recycled aggregate concrete (RAC) was carried out. The two main factors considered were the recycled coarse aggregate (RCA) replacement percentage and the steel fibre volumetric ratio. The failure pattern, load-displacement curves, energy consumption and the punching shear capacity of the slabs were intensively investigated. It was concluded that the punching shear capacity, ductility and energy consumption decreased with the increase of RCA replacement percentage. Research findings indicated that the incorporation of steel fibres could not only improve the energy dissipation capacity and the punching shear capacity of the slab, but also effectively improve the integrity of the slab tension surface and thereby changing the trend from typical punching failure pattern to bending-punching failure pattern. On the basis of the test, the punching shear capacity formula of RAC slabs with and without steel fibres was proposed and discussed.

关键词: recycled aggregate concrete     steel fibres     slab     punching shear     recycled coarse aggregates replacement percentage    

Axial compression tests and numerical simulation of steel reinforced recycled concrete short columns

Hui MA; Fangda LIU; Yanan WU; Xin A; Yanli ZHAO

《结构与土木工程前沿(英文)》 2022年 第16卷 第7期   页码 817-842 doi: 10.1007/s11709-022-0844-y

摘要: To research the axial compression behavior of steel reinforced recycled concrete (SRRC) short columns confined by carbon fiber reinforced plastics (CFRP) strips, nine scaled specimens of SRRC short columns were fabricated and tested under axial compression loading. Subsequently, the failure process and failure modes were observed, and load-displacement curves as well as the strain of various materials were analyzed. The effects on the substitution percentage of recycled coarse aggregate (RCA), width of CFRP strips, spacing of CFRP strips and strength of recycled aggregate concrete (RAC) on the axial compression properties of columns were also analyzed in the experimental investigation. Furthermore, the finite element model of columns which can consider the adverse influence of RCA and the constraint effect of CFRP strips was founded by ABAQUS software and the nonlinear parameter analysis of columns was also implemented in this study. The results show that the first to reach the yield state was the profile steel in the columns, then the longitudinal rebars and stirrups yielded successively, and finally RAC was crushed as well as the CFRP strips was also broken. The replacement rate of RCA has little effect on the columns, and with the substitution rate of RCA from 0 to 100%, the bearing capacity of columns decreased by only 4.8%. Increasing the CFRP strips width or decreasing the CFRP strips spacing could enhance the axial bearing capacity of columns, the maximum increase was 10.5% or 11.4%, and the ductility of columns was significantly enhanced. Obviously, CFRP strips are conducive to enhance the axial bearing capacity and deformation capacity of columns. On this basis, considering the restraint effect of CFRP strips and the adverse effects of RCA, the revised formulas for calculating the axial bearing capacity of SRRC short columns confined by CFRP strips were proposed.

关键词: steel reinforced recycled concrete     CFRP strips     short columns     axial compression behavior     recycled aggregate concrete    

Analysis of cement-treated clay behavior by micromechanical approach

Dong-Mei ZHANG, Zhen-Yu YIN, Pierre-Yves HICHER, Hong-Wei HUANG

《结构与土木工程前沿(英文)》 2013年 第7卷 第2期   页码 137-153 doi: 10.1007/s11709-013-0204-z

摘要: Experimental results show the significant influence of cement content on the mechanical properties of cement-treated clays. Cementation is produced by mixing a certain amount of cement with the saturated clay. The purpose of this paper is to model the cementation effect on the mechanical behavior of cement-treated clay. A micromechanical stress-strain model is developed considering explicitly the cementation at inter-cluster contacts. The inter-cluster bonding and debonding during mechanical loading are introduced in two ways: an additional cohesion in the shear sliding and a higher yield stress in normal compression. The model is used to simulate isotropic compression and undrained triaxial tests under various confining stresses on cement-treated Ariake clay and Singapore clay with various cement contents. The applicability of the present model is evaluated through comparisons between numerical and experimental results. The evolution of local stresses and local strains in inter-cluster planes are discussed in order to explain the induced anisotropy due to debonding at contact level under the applied loads. The numerical simulations demonstrate that the proposed micromechanical approach is well adapted for taking into account the main physical properties of cement-treated clay, including damage and induced anisotropy under mechanical loading.

关键词: microstructure     cementation     clay     micromechanics     anisotropy     debonding    

标题 作者 时间 类型 操作

Predicting resilient modulus of recycled concrete and clay masonry blends for pavement applications using

Mosbeh R. KALOOP, Alaa R. GABR, Sherif M. EL-BADAWY, Ali ARISHA, Sayed SHWALLY, Jong WAN HU

期刊论文

Confined masonry as practical seismic construction alternative–the experience from the 2014 Cephalonia

Fillitsa KARANTONI, Stavroula PANTAZOPOULOU, Athanasios GANAS

期刊论文

Bearing and uplift capacities of under-reamed piles in soft clay underlaid by stiff clay using lower-bound

Mantu MAJUMDER, Debarghya CHAKRABORTY

期刊论文

Experimental study on the compressive performance of new sandwich masonry walls

Jianzhuang XIAO, Jie PU, Yongzhong HU

期刊论文

Model testing of tripod caisson foundations in silty clay subjected to eccentric lateral loads

期刊论文

Behavior of compacted clay-concrete interface

R. R .SHAKIR, Jungao ZHU

期刊论文

Mechanical properties characterization of different types of masonry infill walls

André FURTADO, Hugo RODRIGUES, António ARÊDE, Humberto VARUM

期刊论文

Experimental research on seismic behavior of recycled concrete frame under varying cyclic loading

SUN Yuedong, XIAO Jianzhuang, ZHOU Deyuan

期刊论文

Chloride diffusion in concrete with carbonated recycled coarse aggregates under biaxial compression

期刊论文

Long term performance of recycled concrete beams with different water–cement ratio and recycled aggregate

Jingwei YING; Feiming SU; Shuangren CHEN

期刊论文

Seismic safety evaluation methodology for masonry building and retrofitting using splint and bandage

Pravin Kumar Venkat Rao PADALU; Yogendra SINGH

期刊论文

Analysis of Sydney’s recycled water schemes

Zhuo CHEN, Huu Hao NGO, Wenshan GUO, Xiaochang WANG

期刊论文

Punching shear behavior of recycled aggregate concrete slabs with and without steel fibres

Jianzhuang XIAO, Wan WANG, Zhengjiu ZHOU, Mathews M. TAWANA

期刊论文

Axial compression tests and numerical simulation of steel reinforced recycled concrete short columns

Hui MA; Fangda LIU; Yanan WU; Xin A; Yanli ZHAO

期刊论文

Analysis of cement-treated clay behavior by micromechanical approach

Dong-Mei ZHANG, Zhen-Yu YIN, Pierre-Yves HICHER, Hong-Wei HUANG

期刊论文