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Assessment of an alternative to deep foundations in compressible clays: the structural cell foundation

Sergio A. MARTÍNEZ-GALVÁN, Miguel P. ROMO

《结构与土木工程前沿(英文)》 2018年 第12卷 第1期   页码 67-80 doi: 10.1007/s11709-017-0399-5

摘要: The new type of deep foundation for buildings on saturated, compressible-low strength clayey soil deposits, branded structural cell essentially consists of a rigid concrete top slab, structurally connected to reinforced concrete peripheral walls (diaphragms) that enclose the natural soil. Accordingly, as the initial volume of the confined soft clays within the lateral stiff diaphragms will remain constant upon loading, the hollowed structural cell will be “transformed” into a very large cross-section pillar of unit weight slightly higher than that of the natural soft clayey soil. This type of foundation seems to be a highly competitive alternative to the friction pile-box foundations (widely used in Mexico City clays), due to its economic and environmental advantages. Economies result, for example, from the absence of huge excavations hence sparing the need of earth retaining structures. Further savings result from appreciably smaller concrete volumes required for building the structural cell than the friction pile-box foundation; moreover, the construction time of the former is much shorter than that of the latter. Regarding the impact to the environment, less air contamination follows from the fact that both traffic jams and soil excavation lessen appreciably. Considering these facts and others regarding scheduling, it was decided to replace 48-friction pile-box foundations specified in the master plan project by this new type of foundation. The overall behavior of these cell foundations over a five-year period is fared from close visual observations and their leveling during the first three years after their construction.

关键词: deep foundations     bearing capacity     resistant moment     structural cell     3D numerical modeling    

Effects of operational and structural parameters on cell voltage of industrial magnesium electrolysis

Ze Sun,Chenglin Liu,Guimin Lu,Xingfu Song,Jianguo Yu

《化学科学与工程前沿(英文)》 2015年 第9卷 第4期   页码 522-531 doi: 10.1007/s11705-015-1539-x

摘要: Electric field is the energy foundation of the electrolysis process and the source of the multiphysical fields in a magnesium electrolysis cell. In this study, a three-dimensional numerical model was developed and used to calculate electric field at the steady state through the finite element analysis. Based on the simulation of the electric field, the operational and structural parameters, such as the current intensity, anode thickness, cathode thickness, and anode-cathode distance (ACD), were investigated to obtain the minimum cell voltage. The optimization is to obtain the minimum resistance voltage which has a significant effect on the energy consumption in the magnesium electrolysis process. The results indicate that the effect of the current intensity on the voltage could be ignored and the effect of the ACD is obvious. Moreover, there is a linear decrease between the voltage and the thicknesses of the anode and cathode; and the anode-cathode working height also has a significant effect on the voltage.

关键词: finite element method     magnesium electrolysis cell     electric field    

Approximation of structural damping and input excitation force

Mohammad SALAVATI

《结构与土木工程前沿(英文)》 2017年 第11卷 第2期   页码 244-254 doi: 10.1007/s11709-016-0371-9

摘要: Structural dynamic characteristics are the most significant parameters that play a decisive role in structural damage assessment. The more sensitive parameter to the damage is the damping behavior of the structure. The complexity of structural damping mechanisms has made this parameter to be one of the ongoing research topics. Despite all the difficulties in the modeling of damping, there are some approaches like as linear and nonlinear models which are described as the energy dissipation throughout viscous, material or structural hysteretic and frictional damping mechanisms. In the presence of a mathematical model of the damping mechanisms, it is possible to estimate the damping ratio from the theoretical comparison of the damped and un-damped systems. On the other hand, solving the inverse problem of the input force estimation and its distribution to each SDOFs, from the measured structural responses plays an important role in structural identification process. In this paper model-based damping approximation method and a model-less structural input estimation are considered. The effectiveness of proposed methods has been carried out through analytical and numerical simulation of the lumped mass system and the results are compared with reference data. Consequently, high convergence of the comparison results illustrates the satisfactory of proposed approximation methods.

关键词: structural modal parameters     damping identification method     input excitation force identification     Inverse problem    

Effects of green roof damping and configuration on structural seismic response

《结构与土木工程前沿(英文)》   页码 1133-1144 doi: 10.1007/s11709-023-0959-9

摘要: Sustainable structures are critical for addressing global climate change. Hence, their structural resilience or ability to recover from natural events must be considered comprehensively. Green roofs are a widely used sustainable feature that improve the environment while providing excellent occupant amenity. To expand their usage, their inherent damping and layout sensitivity to seismic performance are investigated in this study. The soil of a green roof can serve as a damper to dissipate the energy generated by earthquakes or other dynamic events. Results of preliminary analysis show that a green roof soil can increase localized damping by 2.5% under both dry and saturated conditions. Based on these findings, nonlinear time-history analyses are conducted on a three-story building in SAP2000 to monitor the structural behavior with and without a green roof. The increased damping in the green roof soil is beneficial to the structural performance, i.e., it reduces the building displacement and acceleration by 10% and 12%, respectively. Additionally, certain configurations are more effective and beneficial to the structural response than others, which suggests the possibility of design optimization. Based on the findings of this study, new methods of modeling and considering green roofs in structural design are established.

关键词: green infrastructure     green roof     structural resilience     seismic design    

Development of an integrated structural health monitoring system for bridge structures in operational

Xinqun ZHU, Hong HAO

《结构与土木工程前沿(英文)》 2012年 第6卷 第3期   页码 321-333 doi: 10.1007/s11709-012-0161-y

摘要: This paper presents an overview of development of an integrated structural health monitoring system. The integrated system includes vibration and guided-wave based structural health monitoring. It integrates the real-time heterogeneous sensor data acquiring system, data analysis and interpretation, physical-based numerical simulation of complex structural system under operational conditions and structural evaluation. The study is mainly focused on developing: integrated sensor technology, integrated structural damage identification with operational loads monitoring, and integrated structural evaluation with results from system identification. Numerical simulation and its implementation in laboratory show that the system is effective and reliable to detect local damage and global conditions of bridge structures.

关键词: integrated structural health monitoring     operational conditions     vibration and guided wave    

Digital image correlation-based structural state detection through deep learning

《结构与土木工程前沿(英文)》 2022年 第16卷 第1期   页码 45-56 doi: 10.1007/s11709-021-0777-x

摘要: This paper presents a new approach for automatical classification of structural state through deep learning. In this work, a Convolutional Neural Network (CNN) was designed to fuse both the feature extraction and classification blocks into an intelligent and compact learning system and detect the structural state of a steel frame; the input was a series of vibration signals, and the output was a structural state. The digital image correlation (DIC) technology was utilized to collect vibration information of an actual steel frame, and subsequently, the raw signals, without further pre-processing, were directly utilized as the CNN samples. The results show that CNN can achieve 99% classification accuracy for the research model. Besides, compared with the backpropagation neural network (BPNN), the CNN had an accuracy similar to that of the BPNN, but it only consumes 19% of the training time. The outputs of the convolution and pooling layers were visually displayed and discussed as well. It is demonstrated that: 1) the CNN can extract the structural state information from the vibration signals and classify them; 2) the detection and computational performance of the CNN for the incomplete data are better than that of the BPNN; 3) the CNN has better anti-noise ability.

关键词: structural state detection     deep learning     digital image correlation     vibration signal     steel frame    

Identification of structural parameters and boundary conditions using a minimum number of measurement

Ali KARIMPOUR, Salam RAHMATALLA

《结构与土木工程前沿(英文)》 2020年 第14卷 第6期   页码 1331-1348 doi: 10.1007/s11709-020-0686-4

摘要: This article proposes a novel methodology that uses mathematical and numerical models of a structure to build a data set and determine crucial nodes that possess the highest sensitivity. Regression surfaces between the structural parameters and structural output features, represented by the natural frequencies of the structure and local transmissibility, are built using the numerical data set. A description of a possible experimental application is provided, where sensors are mounted at crucial nodes, and the natural frequencies and local transmissibility at each natural frequency are determined from the power spectral density and the power spectral density ratios of the sensor responses, respectively. An inverse iterative process is then applied to identify the structural parameters by matching the experimental features with the available parameters in the myriad numerical data set. Three examples are presented to demonstrate the feasibility and efficacy of the proposed methodology. The results reveal that the method was able to accurately identify the boundary coefficients and physical parameters of the Euler-Bernoulli beam as well as a highway bridge model with elastic foundations using only two measurement points. It is expected that the proposed method will have practical applications in the identification and analysis of restored structural systems with unknown parameters and boundary coefficients.

关键词: structural model validation     eigenvalue problem     response surface     inverse problems    

Advanced analysis for structural steel building design

CHEN Wai Fah

《结构与土木工程前沿(英文)》 2008年 第2卷 第3期   页码 189-196 doi: 10.1007/s11709-008-0024-8

摘要: The 2005 AISC LRFD Specifications for Structural Steel Buildings are making it possible for designers to recognize explicitly the structural resistance provided within the elastic and inelastic ranges of behavior and up to the maximum load limit state. There is an increasing awareness of the need for practical second-order analysis approaches for a direct determination of overall structural system response. This paper attempts to present a simple, concise and reasonably comprehensive introduction to some of the theoretical and practical approaches which have been used in the traditional and modern processes of design of steel building structures.

关键词: building     Specifications     comprehensive introduction     structural resistance     traditional    

Estimation of optimum design of structural systems via machine learning

《结构与土木工程前沿(英文)》 2021年 第15卷 第6期   页码 1441-1452 doi: 10.1007/s11709-021-0774-0

摘要: Three different structural engineering designs were investigated to determine optimum design variables, and then to estimate design parameters and the main objective function of designs directly, speedily, and effectively. Two different optimization operations were carried out: One used the harmony search (HS) algorithm, combining different ranges of both HS parameters and iteration with population numbers. The other used an estimation application that was done via artificial neural networks (ANN) to find out the estimated values of parameters. To explore the estimation success of ANN models, different test cases were proposed for the three structural designs. Outcomes of the study suggest that ANN estimation for structures is an effective, successful, and speedy tool to forecast and determine the real optimum results for any design model.

关键词: optimization     metaheuristic algorithms     harmony search     structural designs     machine learning     artificial neural networks    

Proposal of a probabilistic assessment of structural collapse concomitantly subject to earthquake and

Gholamreza ABDOLLAHZADEH, Hadi FAGHIHMALEKI

《结构与土木工程前沿(英文)》 2018年 第12卷 第3期   页码 425-437 doi: 10.1007/s11709-017-0427-5

摘要:

In recent decades, many public buildings, located in seismic-prone residential areas, had to grapple with abnormal loads against which the structures were unguarded. In this piece of research, an ordinary three dimensional reinforced concrete building is selected as case study. The building is located in an earthquake-prone region; however, it is designed according to seismic building codes. Yet, it is not shielded against abnormal loads, such as blasts. It is assumed that the building suffers a blast load, due to mechanical/thermal installation failure during or after intense seismic oscillations. These two critical incidents are regarded codependent and compatible. So the researchers developed scenarios and tried to assess different probabilities for each scenario and carried out an analysis to ensure if progressive collapse had set in or not. In the first step, two analysis models were used for each scenario; a non-linear dynamic time history analysis and a blast local dynamic analysis. In the second step, having the structural destructions of the first step in view, a pushdown analysis was carried out to determine the severity of progressive collapse and assess building robustness. Finally, the annual probability of structural collapse under simultaneous earthquake and blast loads was estimated and offered.

关键词: gas blast     pushdown analysis     progressive collapse     annual probability of structural collapse     3D model of structure    

Stress-strain relationship with soil structural parameters of collapse loess

SHAO Shengjun, LONG Jiyong, YU Qinggao

《结构与土木工程前沿(英文)》 2008年 第2卷 第2期   页码 151-160 doi: 10.1007/s11709-008-0020-z

摘要: Through the tri-axial shearing tests of unsaturated intact loess and based on the concept of comprehensive soil structural potential, this paper reveals the changing laws of soil structural property under the tri-axial stress conditions and establishes a mathematical expression equation of structural parameters, whereby reflecting the effects of unsaturated loess water content, stress and strain states, which is introduced into the shearing stress and shearing strain relation to obtain the structural stress-strain relation. The tests reveal that the loess dilatancy is of shearing contraction and shearing expansion, whereby indicating that there is a good linear relation between the stress ratio and shearing expansion strain ratio. The larger consolidation confining pressure is, the larger the stress of shearing contraction and expansion critical point is; and the larger water content is, the smaller the strain ratio of shearing contraction and expansion critical point is. Finally, the constitutive model is established to reflect the variation in loess structure, stress-strain softening and hardening, and shearing contraction and shearing expansion features. Through the comparative analysis, the stress-strain curves described by the constitutive relationship are found to be in good conformity with test results, whereby testing the rationality of the model in this paper.

关键词: hardening     shearing expansion     unsaturated     structural property     mathematical expression    

XFEM schemes for level set based structural optimization

Li LI, Michael Yu WANG, Peng WEI

《机械工程前沿(英文)》 2012年 第7卷 第4期   页码 335-356 doi: 10.1007/s11465-012-0351-2

摘要:

In this paper, some elegant extended finite element method (XFEM) schemes for level set method structural optimization are proposed. Firstly, two- dimension (2D) and three-dimension (3D) XFEM schemes with partition integral method are developed and numerical examples are employed to evaluate their accuracy, which indicate that an accurate analysis result can be obtained on the structural boundary. Furthermore, the methods for improving the computational accuracy and efficiency of XFEM are studied, which include the XFEM integral scheme without quadrature sub-cells and higher order element XFEM scheme. Numerical examples show that the XFEM scheme without quadrature sub-cells can yield similar accuracy of structural analysis while prominently reducing the time cost and that higher order XFEM elements can improve the computational accuracy of structural analysis in the boundary elements, but the time cost is increasing. Therefore, the balance of time cost between FE system scale and the order of element needs to be discussed. Finally, the reliability and advantages of the proposed XFEM schemes are illustrated with several 2D and 3D mean compliance minimization examples that are widely used in the recent literature of structural topology optimization. All numerical results demonstrate that the proposed XFEM is a promising structural analysis approach for structural optimization with the level set method.

关键词: structural optimization     level set method     extended finite element method (XFEM)     computational accuracy and efficiency    

Shear assessment of compression flanges of structural concrete T-beams

Bj?rn SCHüTTE,Viktor SIGRIST

《结构与土木工程前沿(英文)》 2014年 第8卷 第4期   页码 354-361 doi: 10.1007/s11709-014-0082-z

摘要: In T-beams the force transfer from the web into the flange has to be studied. The general design procedure is based on a strut-and-tie (or a stress field) model which comprises spreading compressive and transverse tensile forces. As is known, strut-and-tie models represent the force flow within a structural member at ultimate. This procedure is sufficient for design purposes and in general, leads to safe results. For the assessment of a structure it may be worthwhile to improve the accuracy. For this purpose both web and flange have to be looked at more in detail. An advanced method for the analysis of webs in shear is the Generalized Stress Field Approach [ ]. This approach can be utilized for treating flanges, where the classical assumptions have to be adapted; in particular by considering the strain dependence of the concrete compressive strength and thus, defining a representative strain value. In the present contribution background and details of these aspects are given, and the corresponding calculation procedure is described. Theoretical results are compared with experimental data and show a reasonably good agreement. However, as the number of sufficiently documented tests is very limited no concluding findings are attained.

关键词: concrete structures     structural assessment     stress field analysis     shear    

Implementation of an optimum algorithm for structural reliability analysis based on FEM

CHENG Ying, TU Hong-mao, FAN Hong-li

《机械工程前沿(英文)》 2006年 第1卷 第4期   页码 468-471 doi: 10.1007/s11465-006-0061-8

摘要: To analyze structural reliability by the stochastic FE (finite element) method rapidly and efficiently, a method combined with the FE method and gradient optimum algorithm based on ANSYS was presented when referring to the geometric interpretation of structural reliability index. ANSYS-based development was adopted to implement it. Results of an example demonstrate that the method requires fewer FE calculations compared with the design point method and Monte-Carlo simulation, and achieves satisfactory accuracy.

关键词: satisfactory     interpretation     algorithm     structural reliability     stochastic FE    

Temperature and structural responses of a single-section utility tunnel throughout fire exposure

Yanmin YANG; Ying XIONG; Yongqing LI; Xiangkun MENG; Peng WANG; Tianyuan CAI

《结构与土木工程前沿(英文)》 2022年 第16卷 第10期   页码 1351-1364 doi: 10.1007/s11709-022-0857-6

摘要: In this study, fire tests of four single-section scaled-down utility tunnels were conducted. By analyzing temperature and structural responses of the utility tunnel throughout the fire exposure, the effects on the fire behavior of two different construction methods, cast-in-situ and prefabricated, and of two different materials, ordinary concrete and full lightweight concrete, were explored. The results of the study showed that the shear failure of the cast-in-situ utility tunnel occurred at the end of the top or bottom plate, and the failure of the prefabricated utility tunnel occurred at the junction of the prefabricated member and post-cast concrete. As the temperature increased, the temperature gradient along the thickness direction of the tunnel became apparent. The maximum temperature difference between the inner and outer wall surfaces was 531.7 °C. The highest temperature occurred in the cooling stage after stopping the heating, which provided a reference for the fire protection design and rescue of the utility tunnel. The displacement of the top plate of the prefabricated utility tunnel was 16.8 mm, which was 41.8% larger than that of the cast-in-situ utility tunnel. The bearing capacities of the ordinary concrete utility tunnel and full lightweight concrete utility tunnel after the fire loss were 27% and 16.8%, respectively. The full lightweight concrete utility tunnel exhibited good ductility and fire resistance and high collapse resistance.

关键词: full lightweight concrete     construction methods     temperature response     structural response     fire test    

标题 作者 时间 类型 操作

Assessment of an alternative to deep foundations in compressible clays: the structural cell foundation

Sergio A. MARTÍNEZ-GALVÁN, Miguel P. ROMO

期刊论文

Effects of operational and structural parameters on cell voltage of industrial magnesium electrolysis

Ze Sun,Chenglin Liu,Guimin Lu,Xingfu Song,Jianguo Yu

期刊论文

Approximation of structural damping and input excitation force

Mohammad SALAVATI

期刊论文

Effects of green roof damping and configuration on structural seismic response

期刊论文

Development of an integrated structural health monitoring system for bridge structures in operational

Xinqun ZHU, Hong HAO

期刊论文

Digital image correlation-based structural state detection through deep learning

期刊论文

Identification of structural parameters and boundary conditions using a minimum number of measurement

Ali KARIMPOUR, Salam RAHMATALLA

期刊论文

Advanced analysis for structural steel building design

CHEN Wai Fah

期刊论文

Estimation of optimum design of structural systems via machine learning

期刊论文

Proposal of a probabilistic assessment of structural collapse concomitantly subject to earthquake and

Gholamreza ABDOLLAHZADEH, Hadi FAGHIHMALEKI

期刊论文

Stress-strain relationship with soil structural parameters of collapse loess

SHAO Shengjun, LONG Jiyong, YU Qinggao

期刊论文

XFEM schemes for level set based structural optimization

Li LI, Michael Yu WANG, Peng WEI

期刊论文

Shear assessment of compression flanges of structural concrete T-beams

Bj?rn SCHüTTE,Viktor SIGRIST

期刊论文

Implementation of an optimum algorithm for structural reliability analysis based on FEM

CHENG Ying, TU Hong-mao, FAN Hong-li

期刊论文

Temperature and structural responses of a single-section utility tunnel throughout fire exposure

Yanmin YANG; Ying XIONG; Yongqing LI; Xiangkun MENG; Peng WANG; Tianyuan CAI

期刊论文