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OPTIMIZATION ALGORITHMS FOR CALCULATION OF THE JOINT DESIGN POINT IN PARALLEL SYSTEMS

structural OPTIMIZATION 1992年第2期4卷 121-127页

作者： ENEVOLDSEN, I SORENSEN, JD Department of Building Technology and Structural Engineering University of Aalborg Aalborg Denmark

In large structures it is often necessary to estimate the reliability of the system by use of parallel systems. Optimality criteria-based algorithms for calculation of the joint design point in a parallel system are described and efficient active set strategies are developed. Three possible algorithms are tested in two examples against well-known general non-linear optimization algorithms. Especially one of the suggested algorithms seems to be stable and fast.

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CO2 seepage behavior in coal under different stress and water content conditions

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Quarterly Journal of engineering Geology and Hydrogeology 2025年

作者： Wang, Chongyang Pan, Yisha Zhang, Dongming Liu, Chenxi Xiong, Ziyang State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing University Chongqing400030 China Department of Structural Geotechnical and Building Engineering Politecnico di Torino Turin10010 Italy School of Public Administration China University of Mining and Technology Jiangsu Xuzhou221116 China

Understanding CO₂ seepage behavior in coal beds is crucial for effective geological CO₂ storage. This study explores CO₂ seepage characteristics in coal samples under varying stress conditions (axial, confining, and gas pressures) and water content through laboratory tests, theoretical analysis, and mathematical modeling. Increasing axial and confining pressures compresses the original pores and cracks in the coal, leading to a gradual reduction in CO₂ seepage. At low gas pressures values, the slip effect impacts permeability;however, as gas pressures increases from 3 to 4 MPa, the higher pressure reduces this effect, increasing CO₂ permeability by approximately 300%. Water content also significantly influences permeability, with dry samples showing the highest and water-saturated samples the lowest permeability. The direction of confining pressure, perpendicular to the seepage flow, more effectively obstructs gas seepage channels, making confining pressure the most strongly correlated factor with seepage discharge (correlation coefficient of 0.72). Based on the regression fitting and neural network analysis of experimental data, a permeability model (R²=0.92) was developed, providing accurate predictions of CO₂ seepage behavior in coal under various conditions and serving as a valuable numerical reference for similar studies. © 2025 The Author(s). Published by The Geological Society of London. All rights, including for text and data mining (TDM), artificial intelligence (AI) training, and similar technologies, are reserved. For permissions: https://***/publishing-hub/permissions-policy. Publishing disclaimer: https://***/publishing-hub/publishing-ethics.

关键词： Hydrocarbon seepage

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DRAFT RISK FROM COLD VERTICAL SURFACES

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building AND ENVIRONMENT 1994年第3期29卷 297-301页

作者： HEISELBERG, P Department of Building Technology and Structural Engineering Aalborg University DK-9000 Aalborg Denmark

Cold, natural convective flows from glazed facades are in winter time often the cause of thermal discomfort and there is a need for research to improve design methods. The objective of the research is to develop expressions for the air flow beyond the floor area, which influences the thermal comfort in the occupied zone. Expressions for the rate of decrement of the maximum velocity with distance from the surface and for the maximum temperature difference between the cold airflow along the floor and the rest of the occupied zone have been developed. The percentage of dissatisfied persons in the occupied zone, due to cold downdraught from a vertical surface, has been estimated.

关键词： Aerodynamics

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Predicting compressive strength of fly ash and sugarcane bagasse ash-based geopolymer concrete using statistical techniques

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Journal of the Indian Chemical Society 2025年第7期102卷

作者： Rihan, Mohammed Ali M. Onchiri, Richard O. Gathimba, Naftary Sabuni, Bernadette Pratap, Bheem Pan African University Institute for Basic Sciences Technology and Innovation Hosted at the Jomo Kenyatta University of Agriculture and Technology P. O. Box 62000-00200 Nairobi Kenya Civil Engineering Department Faculty of Engineering University of Kordofan El Obeid 51111 Sudan Department of Building and Civil Engineering Technical University of Mombasa (TUM) P.O.BOX 90420-80100 Mombasa Kenya Department of Civil Construction and Environmental Engineering Jomo Kenyatta University of Agriculture and Technology Nairobi Kenya Department of Civil and Structural Engineering Masinde Muliro University of Science and Technology P.O. Box 190 50100 Kakamega Kenya Department of Civil Engineering Graphic Era (Deemed to be University) Uttarakhand Dehradun 248002 India

Cement production and other industrial activities are major contributors to environmental and health concerns, primarily due to the substantial amounts of carbon dioxide (CO₂) emitted into the atmosphere. The use of supplementary cementitious materials can reduce the quantity of cement required, thus lowering CO₂ emissions. One such material, sugarcane bagasse ash, improves the mechanical properties of concrete by promoting a denser mix, which is crucial for achieving higher strength. This study proposes three predictive models’ linear regression (LR), nonlinear regression (NLR), and artificial neural networks (ANN) to estimate the compressive strength of high-strength fly ash geopolymer concrete modified with sugarcane bagasse ash. These models present a practical and cost-effective method for predicting compressive strength, offering a more efficient alternative to traditional approaches that require extended testing. The study utilizes 54 experimental data points from geopolymer concrete mixtures containing sugarcane bagasse ash, collected through experimental work, to develop and assess the prediction models. The models are evaluated using various metrics, including the coefficient of determination (R²), root means squared error (RMSE), scatter plot analysis, and mean absolute error (MAE). Among the models tested, the ANN model proves to be the most effective, achieving R², RMSE, and MAE values of 0.905, 2.5004 MPa, and 1.9604, respectively. © 2025 Indian Chemical Society

关键词： ANN Geopolymer concrete LR NLR Sugarcane bagasse ash

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OPTIMAL RELIABILITY-BASED CODE CALIBRATION

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structural SAFETY 1994年第3期15卷 197-208页

作者： SORENSEN, JD KROON, IB FABER, MH Department of Building Technology and Structural Engineering University of Aalborg Sohngaardslholmsvej 57 DK-9000 Aalborg Denmark

Calibration of partial safety factors is considered in general, including classes of structures where no code exists beforehand. The partial safety factors are determined such that the difference between the reliability for the different structures in the class considered and a target reliability level is minimized. Code calibration on a decision theoretical basis is also considered and it is shown how target reliability indices can be calibrated. Results from code calibration for rubble mound breakwater designs are shown.

关键词： CODE CALIBRATION OPTIMIZATION FORM RELIABILITY BREAKWATERS

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Sensitivities in structural maintenance planning

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RELIABILITY engineering & SYSTEM SAFETY 1996年第3期51卷 317-329页

作者： Faber, MH Kroon, IB Sorensen, JD Department of Building Technology and Structural Engineering University of Aalborg Sohngaardsholmsvej 57 DK-9000 Aalborg Denmark

A general description of optimal inspection and maintenance planning based on the classical decision theory and the modern reliability theory is given. A number of simplifications to this description is given leading to more appropriate formulations for practical applications. Sensitivities of both optimal inspection and maintenance plans as well as the associated costs are given with respect to the assumptions on which the planning has been performed. These sensitivities indicate the significance of the individual assumptions and may be used as a decision tool to reject particular optimal inspection and maintenance plans showing too large sensitivity. An example from the offshore industry is given to indicate how the methodologies can be used in practical applications. (C) 1996 Elsevier Science Limited.

关键词： Maintenance

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SENSITIVITY WEAKNESSES IN APPLICATION OF SOME STATISTICAL DISTRIBUTIONS IN 1ST-ORDER RELIABILITY METHODS

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structural SAFETY 1993年第4期12卷 315-325页

作者： SORENSEN, JD ENEVOLDSEN, I Department of Building Technology and Structural Engineering University of Aalborg Sohngaardsholmsvej 57 DK-9000 Aalborg Denmark

It has been observed and shown that in some examples a sensitivity analysis of the first order reliability index results in increasing reliability index, when the standard deviation for a stochastic variable is increased while the expected value is fixed. This unfortunate behaviour can occur when a stochastic variable is modelled by an asymmetrical density function. For lognormally, Gumbel and Weibull distributed stochastic variables it is shown for which combinations of the beta-point, the expected value and standard deviation the weakness can occur. In relation to practical application the behaviour is probably rather infrequent. A simple example is shown as illustration and to exemplify that for second order reliability methods and for exact calculations of the probability of failure this behaviour is much more infrequent.

关键词： RELIABILITY FORM SENSITIVITY ANALYSIS

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RESPONSE ANALYSIS OF REINFORCED-CONCRETE STRUCTURES UNDER SEISMIC EXCITATION

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EARTHQUAKE engineering & structural DYNAMICS 1994年第1期23卷 33-48页

作者： MORK, KJ Department of Building Technology and Structural Engineering University of Aalborg Sohngaardsholmsvej 57 DK-9000 Aalborg Denmark

The theoretical background and capabilities of a program for response analysis of reinforced concrete structures under seismic excitation are presented. The emphasis is on the analysis of stiffness and strength degradation due to severe plastic deformations. An extended version of the model of Roufaiel-Meyer is utilized as the constitutive moment-curvature relation. This takes into account the transition from uncracked to cracked sections, including a mechanism for strength deterioration. The finite length of plastic end zones is taken into account by controlling the plasticity in certain sections and at internal cross sections of the members. Incremental bending stiffness corresponding to the local bending axes of the elements between these control sections is determined by linear interpolation. The stochastic earthquake excitation may be specified either as a standardized acceleration time-series applied at the earth surface and scaled with stochastically varying maximum acceleration and duration, or as an intensity modulated Gaussian white noise process filtered through a Kanai-Tajimi filter. Based on Monte-Carlo simulation, the program calculates the mean values and standard deviations of storey displacements, bending moments in critical sections and maximum softening damage indicators, defined from the lower time-averaged eigenperiods. An adaptive system reduction scheme has been implemented based on a truncated expansion of external nodal point degrees-of-freedom in the linear eigenmodes of the initial undamaged structure. A full description of the internal degrees-of-freedom controlling the hysteresis is maintained. In order to demonstrate the ability of the program to predict the actual seismic response of reinforced concrete structures, computed results were compared to the experimentally recorded results of a 10-storey 4-bay reinforced concrete model.

关键词： structural analysis

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ENERGY-RELEASE RATE OF SYMMETRICAL ADHESIVE JOINTS

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engineering FRACTURE MECHANICS 1992年第4期43卷 549-559页

作者： KRENK, S Department of Building Technology and Structural Engineering University of Aalborg Sohngaardsholmsvej 57 DK-9000 Aalborg Denmark

A formula is derived for the mixed mode energy release rate of adhesive joints in terms of local stress concentrations sigma(max) and tau(max) determined by beam theory. The formula G = 1/2 t/E(a)' sigma(max)2 + 1/2 t/G(a) tau(max)2 is equivalent to a similar expression from two-dimensional elasticity theory in terms of the stress intensity factors K(I) and K(II). The equivalence permits explicit determination of the two stress intensity factors K(I) and K(II) in terms of the finite stress concentrations sigma(max) and tau(max) determined by technical beam theory. The reinterpretation of the stress concentration from beam theory in terms of stress intensity factors enables the use of simple beam-type calculations for fracture predictions without the need for a detailed three-dimensional analysis. While the stress concentrations sigma(max) and tau(max) increase with decreasing thickness t of the adhesive layer, the energy release rate G is nearly independent of t. The centrally loaded symmetric lap joint is analysed in detail and explicit results for the mixed mode energy release rate g and the corresponding load phase angle psi = tan-1(K(II)/K(I)) are given. For long joints psi = 49-degrees, independent of adhesive properties, increasing for shorter joints.

关键词： Adhesive joints

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RELIABILITY-BASED OPTIMIZATION IN structural-engineering

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structural SAFETY 1994年第3期15卷 169-196页

作者： ENEVOLDSEN, I SORENSEN, JD Department of Building Technology and Structural Engineering University of Aalborg Sohngaardshobnsvej 57 DK-9000 Aalborg Denmark

In this paper reliability-based optimization problems in structural engineering are formulated on the basis of the classical decision theory. Several formulations are presented: Reliability-based optimal design of structural systems with component or systems reliability constraints, reliability-based optimal inspection planning and reliability-based experiment planning. It is explained how these optimization problems can be solved by application of similar techniques. The reliability estimation is limited to first order reliability methods (FORM) for both component and systems reliability evaluation. The solution strategies applying first order non-linear optimization algorithms are described in detail with special attention to sensitivity analysis and stability of the optimization process. Furthermore, several practical aspects are treated as: Development of the reliability-based optimization model, inclusion of the finite element method as the response evaluation tool and how the size of the problem can be made practicable. Finally, the important task of model evaluation and sensitivity analysis;of the optimal solution is treated including a strategy for model-making with both pre and post-analysis.

关键词： RELIABILITY-BASED DESIGN OPTIMUM DESIGN RELIABILITY-BASED OPTIMIZATION OPTIMIZATION MODELS

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