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1
Khan, Kaffayatullah, Mudassir Iqbal, Muhammad Raheel, Muhammad Nasir Amin, Anas Abdulalim Alabdullah, Abdullah M. Abu-Arab und Fazal E. Jalal. „Prediction of Axial Capacity of Concrete Filled Steel Tubes Using Gene Expression Programming“. Materials 15, Nr. 19 (07.10.2022): 6969. http://dx.doi.org/10.3390/ma15196969.
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The safety and economy of an infrastructure project depends on the material and design equations used to simulate the performance of a particular member. A variety of materials can be used in conjunction to achieve a composite action, such as a hollow steel section filled with concrete, which can be successfully utilized in the form of an axially loaded member. This study aims to model the ultimate compressive strength (Pu) of concrete-filled hollow steel sections (CFSS) by formulating a mathematical expression using gene expression programming (GEP). A total of 149 datapoints were obtained from the literature, considering ten input parameters, including the outer diameter of steel tube (D), wall thickness of steel tube, compressive strength of concrete (fc’), elastic modulus of concrete (Ec), yield strength of steel (fv), elastic modulus of steel (Es), length of the column (L), confinement factor (ζ), ratio of D to thickness of column, and the ratio of length to D of column. The performance of the developed models was assessed using coefficient of regression R2, root mean squared error RMSE, mean absolute error MAE and comparison of regression slopes. It was found that the optimal GEP Model T3, having number of chromosomes Nc = 100, head size Hs = 8 and number of genes Ng = 3, outperformed all the other models. For this particular model, R2overall equaled 0.99, RMSE values were 133.4 and 162.2, and MAE = 92.4 and 108.7, for training (TR) and testing (TS) phases, respectively. Similarly, the comparison of regression slopes analysis revealed that the Model T3 exhibited the highest R2 of 0.99 with m = 1, in both the TR and TS stages, respectively. Finally, parametric analysis showed that the Pu of composite steel columns increased linearly with the value of D, t and fy.
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Rezvani Sharif, Mostafa, und Seyed Mohammad Reza Sadri Tabaei Zavareh. „Numerical analysis of the shear strength of circular reinforced concrete columns subjected to cyclic lateral loads using linear genetic programming“. Engineering Computations 37, Nr. 7 (18.03.2020): 2517–37. http://dx.doi.org/10.1108/ec-10-2018-0453.
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Purpose The shear strength of reinforced concrete (RC) columns under cyclic lateral loading is a crucial concern, particularly, in the seismic design of RC structures. Considering the costly procedure of testing methods for measuring the real value of the shear strength factor and the existence of several parameters impacting the system behavior, numerical modeling techniques have been very much appreciated by engineers and researchers. This study aims to propose a new model for estimation of the shear strength of cyclically loaded circular RC columns through a robust computational intelligence approach, namely, linear genetic programming (LGP). Design/methodology/approach LGP is a data-driven self-adaptive algorithm recently used for classification, pattern recognition and numerical modeling of engineering problems. A reliable database consisting of 64 experimental data is collected for the development of shear strength LGP models here. The obtained models are evaluated from both engineering and accuracy perspectives by means of several indicators and supplementary studies and the optimal model is presented for further purposes. Additionally, the capability of LGP is examined to be used as an alternative approach for the numerical analysis of engineering problems. Findings A new predictive model is proposed for the estimation of the shear strength of cyclically loaded circular RC columns using the LGP approach. To demonstrate the capability of the proposed model, the analysis results are compared to those obtained by some well-known models recommended in the existing literature. The results confirm the potential of the LGP approach for numerical analysis of engineering problems in addition to the fact that the obtained LGP model outperforms existing models in estimation and predictability. Originality/value This paper mainly represents the capability of the LGP approach as a robust alternative approach among existing analytical and numerical methods for modeling and analysis of relevant engineering approximation and estimation problems. The authors are confident that the shear strength model proposed can be used for design and pre-design aims. The authors also declare that they have no conflict of interest.
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Rashedi, Ahmad, Riadh Marzouki, Ali Raza, Khawar Ali, Niyi Gideon Olaiya und Mayandi Kalimuthu. „Glass FRP-Reinforced Geopolymer Based Columns Comprising Hybrid Fibres: Testing and FEA Modelling“. Polymers 14, Nr. 2 (13.01.2022): 324. http://dx.doi.org/10.3390/polym14020324.
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This study seeks to evaluate the effectiveness of glass-FRP-reinforced geopolymer concrete columns integrating hybrid fibres (GFGC columns) and steel bar-reinforced geopolymer concrete columns incorporating hybrid fibres (SFGC columns) under eccentric and concentric loadings. Steel fibre (SF) and polypropylene fibres (PF) are two types of fibres that are mixed into hybrid fibre-reinforced geopolymer concrete (HFRGC). Eighteen circular concrete columns with a cross-section of 300 mm × 1200 mm were cast and examined under axial loading up to failure. Nine columns were cast with glass-FRP rebars, whereas the other nine were cast with steel rebars. Using ABAQUS, a nonlinear finite element model was established for the GFGC and SFGC columns. The HFRGC material was modelled using a simplified concrete damage plasticity model, whereas the glass-FRP material was simulated as a linear elastic material. It was observed that GFGC columns had up to 20% lower axial strength (AST) and up to 24% higher ductility indices than SFGC columns. The failure modes of both GFGC and SFGC columns were analogous. Both GFGC and SFGC columns revealed the same effect of eccentricity in the form of a decline in AST. A novel statistical model was suggested for predicting the AST of GFGC columns. The outcomes of the experiments, finite element simulations, and theoretical results show that the models can accurately determine the AST of GFGC columns.
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Campione, Giuseppe. „The effects of fibers on the confinement models for concrete columns“. Canadian Journal of Civil Engineering 29, Nr. 5 (01.10.2002): 742–50. http://dx.doi.org/10.1139/l02-066.
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A mathematical model is developed to express the stressstrain relationships in compression of fiber-reinforced concrete (FRC) columns for both normal- and high-strength concrete, with and without conventional steel reinforcement. This model allows one to determine the maximum strength and strain capacity by determining the effective concrete core of the confining devices at rupture. Analytical expressions are also given for the ultimate load corresponding to the complete formation of the concrete failure plane. The proposed model incorporates the most relevant parameters of confinement, i.e., type of confinement, volumetric ratio, spacing, yielding strength, shape of the member cross section, type of fiber (length, diameter, shape), and fiber volume. The model has been verified against data obtained from concentric compressive tests on concrete specimens reinforced with transverse steel and fibers.Key words: high-strength concrete, fiber-reinforced concrete, lateral reinforcement, stressstrain curves.
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Lie, T. T., und D. C. Stringer. „Calculation of the fire resistance of steel hollow structural section columns filled with plain concrete“. Canadian Journal of Civil Engineering 21, Nr. 3 (01.06.1994): 382–85. http://dx.doi.org/10.1139/l94-041.
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Experimental studies were conducted to determine the fire resistance of circular and square hollow structural section columns filled with plain concrete. Mathematical models were developed and used to investigate the influence of important parameters that determine the fire resistance of these columns. The experimental and parametric studies provide information for the development of formulas for the calculation of the fire resistance of circular and square concentrically loaded columns filled with plain carbonate or siliceous aggregate concrete. Such formulas are suitable for incorporation into building codes. Key words: calculation, fire resistance, columns, concrete-filled, steel, hollow structural sections.
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Isleem, Haytham F., Muhammad Abid, Wesam Salah Alaloul, Muhammad Kamal Shah, Shayan Zeb, Muhammad Ali Musarat, Muhammad Faisal Javed, Fahid Aslam und Hisham Alabduljabbar. „Axial Compressive Strength Models of Eccentrically-Loaded Rectangular Reinforced Concrete Columns Confined with FRP“. Materials 14, Nr. 13 (23.06.2021): 3498. http://dx.doi.org/10.3390/ma14133498.
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The majority of experimental and analytical studies on fiber-reinforced polymer (FRP) confined concrete has largely concentrated on plain (unreinforced) small-scale concrete columns, on which the efficiency of strengthening is much higher compared with large-scale columns. Although reinforced concrete (RC) columns subjected to combined axial compression and flexural loads (i.e., eccentric compression) are the most common structural elements used in practice, research on eccentrically-loaded FRP-confined rectangular RC columns has been much more limited. More specifically, the limited research has generally been concerned with small-scale RC columns, and hence, the proposed eccentric-loading stress-strain models were mainly based on the existing concentric-loading models of FRP-confined concrete columns of small scale. In the light of such demand to date, this paper is aimed at developing a mathematical model to better predict the strength of FRP-confined rectangular RC columns. The strain distribution of FRP around the circumference of the rectangular sections was investigated to propose equations for the actual rupture strain of FRP wrapped in the horizontal and vertical directions. The model was accomplished using 230 results of 155 tested specimens compiled from 19 studies available in the technical literature. The test database covers an unconfined concrete strength ranging between 9.9 and 73.1 MPa, and section’s dimension ranging from 100–300 mm and 125–435 mm for the short and long sides, respectively. Other test parameters, such as aspect ratio, corner radius, internal hoop steel reinforcement, FRP wrapping layout, and number of FRP wraps were all considered in the model. The performance of the model shows a very good correlation with the test results.
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Abdallah, Wafaa, Jacqueline Saliba, Ziubir-Mehdi Sbartaï, Marwan Sadek, Fadi Hage Chehade und S. Mohammed ElAchachi. „Reliability analysis of non-destructive testing models within a probabilistic approach“. MATEC Web of Conferences 281 (2019): 04003. http://dx.doi.org/10.1051/matecconf/201928104003.
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The diagnosis of reinforced concrete is essential to detect the degradation and thus maintain the structural performance of civil engineering structures. This paper aims to establish a mathematical relationship between the ultrasonic pulse velocity UPV (considered as an observable variable) and two concrete properties indicators (compressive strength fc and water content W) within a probabilistic framework. Synthetic simulations are proposed to derive a conversion model between the statistical properties of the output and the input parameters for a reinforced concrete structure by taking into account spatial variability of concrete.
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Štefan, Radek, und Jaroslav Procházka. „Modelling of Hygro-Thermal Processes in Steel-Concrete Composite Columns Exposed to High Temperatures“. Solid State Phenomena 249 (April 2016): 246–52. http://dx.doi.org/10.4028/www.scientific.net/ssp.249.246.
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In the paper, transport processes in heated steel-concrete composite columns are analyzed. Mathematical models of heat transfer and coupled heat and mass transfer are described with respect to the specific parameters of composite structures. Numerical formulations of the models are implemented into MATLAB environment and the applicability of the models is depicted on an illustrative example. It is shown that not only the thermal distribution, but also the moisture migration as well as the pore pressure built-up are of particular interest.
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Anand, Praveen, und Ajay Kumar Sinha. „Effect of Reinforced Concrete Jacketing on Axial Load Capacity of Reinforced Concrete Column“. Civil Engineering Journal 6, Nr. 7 (01.07.2020): 1266–72. http://dx.doi.org/10.28991/cej-2020-03091546.
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Whenever a member of a structure becomes structurally deficient, it becomes vulnerable to the existing load and for the additional loads that it may be subjected to in the coming future. Since columns are the most important structural element, the structural retrofit of columns, relative to other structural elements is of prime importance. This study intends to investigate the performance and behaviour of an RC column jacketed with Reinforced Concrete columns under axial loads. The objective of this paper is to find out the efficiency of RC jacket in enhancing the strength of an existing RC column. A mathematical design based upon Indian Standards codes has been designed to identify the behaviour of jacketed RC columns. This has been followed by a finite element based numerical simulation using the same material properties as used in the process of designing. The simulation has been done in ABAQUS software with appropriate contact modelling. The analytical model considers that there is no bond slippage between the existing and new concrete surface i.e. the bond between the existing and new concrete is assumed to be perfect. This perfect bond between the surfaces has been modelled by using appropriate constraints in ABAQUS software. The finite element models show fair agreement with the designed values in terms of ultimate capacity and failure mode. The load bearing capacity enhancement of the RC jacketed column has been found to increase substantially. The enhancement capacity results obtained from the finite element software differs about 16-25% from the design values.
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Xing, Guo Hua, Yuan Pan, Guo Fu und Jian Ling Hou. „Cumulative Seismic Damage of Reinforced Concrete Columns: Variable Amplitude Tests“. Applied Mechanics and Materials 52-54 (März 2011): 740–44. http://dx.doi.org/10.4028/www.scientific.net/amm.52-54.740.
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The findings from an experimental study to investigate cumulative seismic damage in reinforced concrete columns are presented. Fourteen identical half-scale concrete columns were fabricated and tested to failure. Results from Phase I testing, which included constant amplitude tests to determine the low-cycle fatigue characteristics of the rectangular concrete column, were presented in a companion paper. This paper summarizes results of variable amplitude tests. The imposed displacement histories were obtained from analytical simulations of the model column subjected to a series of earthquakes. Test observations indicate that failure is generally initiated by confinement inadequacy and the rupture of the transverse hoop reinforcement. The tests also demonstrated the potential for low-cycle fatigue fracture of the main longitudinal steel when the specimen was subjected to relatively larger displacement amplitudes. A fatigue-based damage model, derived from the constant-amplitude tests completed in Phase I testing, was applied to the observed response of the three specimens tested in this phase. Findings from the study indicate that the energy capacity of members is ductility-dependent and that fatigue-based damage models offer a reliable means of assessing seismic structural performance.
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Anwar, Muhammad Kashif, Syyed Adnan Shah, Marc Azab, Ibrahim Shah, Muhammad Khalid Chauhan und Fahad Iqbal. „Structural Performance of GFRP Bars based High-Strength RC Columns: An Application of Advanced Decision-Making Mechanism for Experimental Profile Data“. Buildings 12, Nr. 5 (06.05.2022): 611. http://dx.doi.org/10.3390/buildings12050611.
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Several past studies have shown the use of glass fibre-reinforced polymer (GFRP) bars to alleviate the reinforced steel rusting issue in different concrete structures. However, the practise of GFRP bars in concrete columns has not yet achieved a sufficient confidence level due to the lack of a theoretical model found in the literature. The objective of the current study is to introduce a novel prediction model for the axial capability of concrete columns made with bars of GFRP. For this purpose, two different approaches, such as data envelopment analysis (DEA) and artificial neural networks (ANNs) modelling, are used on a collected dataset of 266 concrete column specimens made with GFRP bars from previous literature works. Eight parameters were used to predict the axial performance of GFRP-based RC columns. The proposed DEA and ANNs predictions demonstrated a good correlation with the testing dataset, having R2 values of 0.811 and 0.836, respectively. A comparative analysis of the DEA and ANNs models is undertaken, and it was found that the suggested models are capable of accurately forecasting the structural response of GFRP-made RC column structures. Then, a comprehensive parametric analysis of 266 GFRP-based columns was performed to study the effect of different materials and their geometrical shape.
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Ashteyat, Ahmed, Yasmeen T. Obaidat, Yasmin Z. Murad und Rami Haddad. „COMPRESSIVE STRENGTH PREDICTION OF LIGHTWEIGHT SHORT COLUMNS AT ELEVATED TEMPERATURE USING GENE EXPRESSION PROGRAMING AND ARTIFICIAL NEURAL NETWORK“. JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 26, Nr. 2 (10.02.2020): 189–99. http://dx.doi.org/10.3846/jcem.2020.11931.
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The experimental behavior of reinforced concrete elements exposed to fire is limited in the literature. Although there are few experimental programs that investigate the behavior of lightweight short columns, there is still a lack of formulation that can accurately predict their ultimate load at elevated temperature. Thus, new equations are proposed in this study to predict the compressive strength of the lightweight short column using Gene Expression Programming (GEP) and Artificial neural networks (ANN). A total of 83 data set is used to establish GEP and ANN models where 70% of the data are used for training and 30% of the data are used for validation and testing. The predicting variables are temperature, concrete compressive strength, steel yield strength, and spacing between stirrups. The developed models are compared with the ACI equation for short columns. The results have shown that the GEP and ANN models have a strong potential to predict the compressive strength of the lightweight short column. The predicted compressive strengths of short lightweight columns using the GEP and ANN models are closer to the experimental results than that obtained using the ACI equations.
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Khan, Kaffayatullah, Rahul Biswas, Jitendra Gudainiyan, Muhammad Nasir Amin, Hisham Jahangir Qureshi, Abdullah Mohammad Abu Arab und Mudassir Iqbal. „PCA-Based Hybrid Intelligence Models for Estimating the Ultimate Bearing Capacity of Axially Loaded Concrete-Filled Steel Tubes“. Materials 15, Nr. 18 (18.09.2022): 6477. http://dx.doi.org/10.3390/ma15186477.
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In order to forecast the axial load-carrying capacity of concrete-filled steel tubular (CFST) columns using principal component analysis (PCA), this work compares hybrid models of artificial neural networks (ANNs) and meta-heuristic optimization algorithms (MOAs). In order to create hybrid ANN models, a dataset of 149 experimental tests was initially gathered from the accessible literature. Eight PCA-based hybrid ANNs were created using eight MOAs, including artificial bee colony, ant lion optimization, biogeography-based optimization, differential evolution, genetic algorithm, grey wolf optimizer, moth flame optimization and particle swarm optimization. The created ANNs’ performance was then assessed. With R2 ranges between 0.7094 and 0.9667 in the training phase and between 0.6883 and 0.9634 in the testing phase, we discovered that the accuracy of the built hybrid models was good. Based on the outcomes of the experiments, the generated ANN-GWO (hybrid model of ANN and grey wolf optimizer) produced the most accurate predictions in the training and testing phases, respectively, with R2 = 0.9667 and 0.9634. The created ANN-GWO may be utilised as a substitute tool to estimate the load-carrying capacity of CFST columns in civil engineering projects according to the experimental findings.
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Gao, Feng, Gui Ling Liu und Qing Guo Huang. „Ultrasonic Non-Destruction Detecting Method for Concrete Compression Strength“. Advanced Materials Research 724-725 (August 2013): 1585–88. http://dx.doi.org/10.4028/www.scientific.net/amr.724-725.1585.
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Regional materials and mixing ratio of Datong area are used to make the concrete testing blocks. The rebounding and ultrasonic non-destruction detecting testing for concrete strength were done by using the six types of strength grades concrete standard specimens according to the technical regulation. On the basis of regression analysis with least squares technique, the mathematical models between rebounding values, ultrasonic velocity values, rebounding-ultrasonic method values and concrete compression strength were set up by three kinds of functions’ regression analysis. The error analysis showed that the rebounding-ultrasonic non-destruction detecting testing method has higher precision results and the practical value.
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Gao, Feng, Gui Ling Liu und Feng Xian Wang. „Concrete Compression Strength Non-Destruction Detecting with Rebounding and Ultrasonic Synthesis Method“. Applied Mechanics and Materials 357-360 (August 2013): 1488–91. http://dx.doi.org/10.4028/www.scientific.net/amm.357-360.1488.
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Regional materials and mixing ratio in Datong region are used to make the concrete testing blocks. The rebounding and ultrasonic non-destruction detecting testing for concrete compression strength were done by using the six types of strength grades concrete standard specimens according to the technical regulation. By using the common software Matlab7.0, the mathematical models between rebounding values, ultrasonic velocity values, rebounding- ultrasonic method values and concrete compression strength were set up by three kinds of functions’ regression analysis. The error analysis showed that the rebounding-ultrasonic non-destruction detecting testing method had higher precision results and was used firstly when the conditions were permitted, compared with the rebounding testing method or the ultrasonic testing method.
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Filatov, Valery, Zulfat Galyautdinov und Alexander Suvorov. „Elaboration of testing technique of flat slabs on punching shear strength using finite element modeling“. MATEC Web of Conferences 196 (2018): 02048. http://dx.doi.org/10.1051/matecconf/201819602048.
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The results of researches on finite-element models of stress-strain state of flat reinforced concrete slabs of beamless frame under punching by columns of square and rectangular cross-section are presented. The purpose of the study was to develop a technique for testing samples plates for punching in the presence of bending moments in a column. The results of the study of deflections of reinforced concrete slabs, the distribution of bending moments in the punching zone of the plate under various loading schemes are presented. Variable parameter was the ratio of the sides of the column cross-section. Comparative analysis of studies results on finite element models has made it possible to choose the optimal variant of applying the load to the test samples, depending on the aspect ratio of rectangular section of column. Results of the conducted research will allow simulating the stress-strain state in the punching zone of natural reinforced concrete slabs of monolithic beamless frame during the test of samples.
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Kwasniewski, L., E. Szmigiera und M. Siennicki. „Finite Element Modeling of Composite Concrete-Steel Columns / Numeryczne Modelowanie Zespolonych Słupów Stalowo-Betonowych“. Archives of Civil Engineering 57, Nr. 4 (01.12.2011): 373–88. http://dx.doi.org/10.2478/v.10169-011-0027-z.
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Abstract This paper presents the numerical part of the research program on concrete-filled steel columns. Nonlinear, three dimensional FE analysis of axial compression, was conducted using the finite element program ABAQUS. The numerical results were validated through comparison with experimental data in terms of ultimate loading and deformation modes. Modeling related problems such as the definition of boundary conditions, imperfections, concrete-steel interaction, material representation and others are investigated using a comprehensive parametric study. The developed FE models will be used for an enhanced interpretation of experiments and for the predictive study of cases not included in the experimental testing.
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Lazovic Radovanovic, Marija M., Jelena Z. Nikolic, Janko R. Radovanovic und Svetlana M. Kostic. „Structural Behaviour of Axially Loaded Concrete-Filled Steel Tube Columns during the Top-Down Construction Method“. Applied Sciences 12, Nr. 8 (08.04.2022): 3771. http://dx.doi.org/10.3390/app12083771.
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The paper discusses the structural behaviour of concrete-filled steel tube columns (CFT) when applied to the top-down construction method as temporary internal supports for ceilings. Their ultimate capacity to take into account the actual boundary conditions of the column is essential for successful application in construction. The paper presents the full-scale in situ testing of four slender specimens with variable D/t ratios under concentric axial loading. The CFT columns were supported on the previously jacked concrete piles. In addition, detailed finite element numerical models in ABAQUS and PLAXIS computer programs were developed. The models include the nonlinear behaviour of materials and the nonlinear behaviour of soil. The soil–pile–column interaction and impact of the CFT column–pile connection stiffness on global column stability were considered. The numerical model was validated by comparison with the experimental results. In conclusion, the coefficient for the effective buckling length of the studied columns is proposed. Finally, the experimental results of the critical buckling forces were compared with widely used international design codes Eurocode 4-EC4, American standard-ACI and the Australian standard-AS.
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Nguyen, Thi Tuyet Trinh, Van Bac Nguyen und Minh Quan Thai. „Flexural Strength of Partially Concrete-Filled Steel Tubes Subjected to Lateral Loads by Experimental Testing and Finite Element Modelling“. Buildings 13, Nr. 1 (12.01.2023): 216. http://dx.doi.org/10.3390/buildings13010216.
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In this paper, the flexural strength and buckling of the partially concrete-filled steel tubes (PCFST) under laterally repeated loads was investigated through three-point bending test configuration. Three-dimensional Finite Element (FE) models of the bending tests of the PCFST were developed, in which the concrete filling was modelled using elastic-plastic-fracture model capturing crack development and the tube steel was modelled using elastic-plasticity model. The bond between concrete and tube was considered as frictional touching contact. The validation showed the FE results including the ultimate flexural load and buckling failure mode of the steel tube were in excellent agreement with the experimental ones. A parametric study was then conducted using the verified FE models to investigate the effects of the tube diameter-to-thickness ratio, the concrete filling length ratio, the compressive strength of concrete, and the tube steel’s yield and tensile strengths on the PCFST’s ultimate flexural strength. Based on this study, buckling modes, the optimal concrete filling lengths, and the confined compressive strengths of concrete were determined considering the effects of all these parameters. The confined compressive stresses and strains in concrete predicted by the FE models were evaluated against those determined by theoretical models. The results revealed that the effects of concrete compressive strength to the PCFST’s flexural capacity was insignificant while increasing the tube diameter-to-thickness ratio or the tube steel’s yield and tensile strengths could significantly increase the PCFST’s flexural capacity and the confined compressive strength of concrete; and there was an optimal length of concrete filling at about 66% of the tube length. It demonstrated that the Finite Element analysis can therefore be used as a powerful method to the analysis and design the PCFST columns under lateral loads.
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Sarsam, Saad I. „Modeling the Thermal Behavior of the Viscoelastic Properties of Asphalt Concrete“. Britain International of Exact Sciences (BIoEx) Journal 4, Nr. 2 (02.09.2022): 79–91. http://dx.doi.org/10.33258/bioex.v4i2.729.
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The viscoelastic properties of asphalt concrete are susceptible to the variation in the pavement temperature. In the present work, asphalt concrete beam specimens were prepared at optimum binder content and tested under repeated flexural stresses for fatigue life. Three testing temperature were implemented (5, 20, and 30) ℃. The variation in the phase angle, dissipated energy, flexural stiffness, and permanent deformation due to the testing temperatures were monitored and modeled. It was concluded that the viscoelastic properties of asphalt concrete are highly sensitive to the variation in testing temperature. The phase angle and the permanent deformation increases sharply as the testing temperature rises. However, the dissipated energy and the flexural stiffness declines as the testing temperature rise. Mathematical models were obtained which can be implemented in identifying the thermal behavior of the viscoelastic properties of asphalt concrete.
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Jong, Wan Hu, und Woong Park Ji. „Composite Joints Design - Migrating from Finite Element Models to Component Models“. Advanced Materials Research 716 (Juli 2013): 620–25. http://dx.doi.org/10.4028/www.scientific.net/amr.716.620.
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When developing innovative structural systems, designers are faced with a difficult problem when addressing connection design. While the provisions for the design of members and their failure modes are well understood and codified, the design and performance of the connections are not. Current specifications require designers to provide evidence, through either experiments or analysis and combinations thereof, that these connections will perform as intended. In this paper, the design of an innovative type of connection to concrete-filled tube columns is described. These connection are partially-restrained, contain a new type of material (shape memory alloys), and are geared for high seismic loads making their design a very challenging proposition without the aid of physical testing. The design is developed based on detailed finite element analyses of the connection region and elements which lead to simplified spring models suitable for design of entire frames. The results indicate that through careful and rigorous analyses, robust simplified connection models can be developed even for complex connections.
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Andjelkovic, Vladimir, Zarko Lazarevic und Velimir Nedovic. „Application of analogous models in civil engineering“. Facta universitatis - series: Architecture and Civil Engineering 9, Nr. 3 (2011): 395–405. http://dx.doi.org/10.2298/fuace1103395a.
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The paper describes the results of making the mathematical and physical models of the authors, by using analogous methods and materials. There is the mathematical rock mass deformability model as a base for foundation engineering a concrete arch dam and the physical rock slope model which was tested by loading until failure and the results were compared with the calculation procedure. In the first example the correlation is established between the static and the analogous dynamic in situ investigations for creating the mathematical rock mass deformability model. In the second example there is application of the analogous materials for the discontinuity shearing simulation on the physical slope model. The results of the geotechnical in situ investigations and laboratory testing carried out in the Institute for Development of Water Resources "Jaroslav Cerni" in Belgrade were used for making the models.
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Pang, Yingbo, Iftikhar Azim, Momina Rauf, Muhammad Farjad Iqbal, Xinguang Ge, Muhammad Ashraf, Muhammad Atiq Ur Rahman Tariq und Anne W. M. Ng. „Prediction of Bidirectional Shear Strength of Rectangular RC Columns Subjected to Multidirectional Earthquake Actions for Collapse Prevention“. Sustainability 14, Nr. 11 (02.06.2022): 6801. http://dx.doi.org/10.3390/su14116801.
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The understanding of the effects of multidirectional loadings imposed on major load bearing elements such as reinforced concrete (RC) columns by seismic actions for collapse prevention is of utmost importance, and a few simplified models are available in the literature. In this study, the distinguishing features of two machine-learning (ML) methods, namely, multi expression programming (MEP) and adaptive neuro-fuzzy inference system (ANFIS) are exploited for the first time to develop eight novel prediction models (M1-to M4-MEP and M1-to M4-ANFIS) with different combinations of input parameters to predict the biaxial shear strength of RC columns (V). The performance of the developed models was assessed using various statistical indicators and by comparing them with the experimental values. Based on the statistical analysis of the developed models, M1-ANFIS and M1-MEP performed very well and exhibited the best overall efficiency of the studied ML methods. Simple mathematical formulations were also provided by the MEP algorithm for the prediction of V, using which the M1-MEP model was finalized based on its performance, accuracy, and generalization capability. A parametric analysis was also performed for the model to show that the mathematical formulation provided by MEP accurately represents the system under consideration and is imperative for prediction purposes. Based on its performance, the model can thus be recommended to update the current code provisions and engineering practices.
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Wu, Yingxiong, Ning Liu und Ai Qi. „Seismic Performance of a New Structural Design Solution for First-Story Isolated RC Buildings with Coupled Beam-Column Connections“. Applied Sciences 9, Nr. 1 (06.01.2019): 177. http://dx.doi.org/10.3390/app9010177.
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This study proposes a new structural design of the first-story isolation system in reinforced concrete (RC) structures. Compared to the conditional buildings with independent columns, this new design integrates the independent columns with beams to increase the seismic capacity of the building by increasing the integrated stiffness of the coupled columns and the stability of the isolation system. The seismic responses of the proposed structure and the corresponding isolation effect were investigated by performing a series of numerical simulation and shaking table tests on a typical 7-story RC frame structure. The structure models were subjected to four earthquake waves with two PGAs (peak ground acceleration) of 0.30 g and 0.40 g for seismic analysis regarding the peak acceleration and inter-story displacement. Both simulation and testing results showed that the story acceleration and inter-story displacement of the superstructure in the isolated model decreased significantly. While the substructure below the isolation layer had a negligible decrease of acceleration. The connection of beams with concrete columns significantly increases the seismic capacity of the RC frame buildings compared to non-isolated frame buildings. The coupled beam-column connections could thus be potentially adopted in the practical first-story isolation system to avoid the requirements of large column stiffness and large column size.
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Zainal, S. M. Iqbal S., Farzad Hejazi, Farah N. A. Abd Aziz und Mohd Saleh Jaafar. „Constitutive Modeling of New Synthetic Hybrid Fibers Reinforced Concrete from Experimental Testing in Uniaxial Compression and Tension“. Crystals 10, Nr. 10 (01.10.2020): 885. http://dx.doi.org/10.3390/cryst10100885.
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Hybridization of fibers in concrete yields a variety of applications due to its benefits compared to conventional concrete or concrete with single type-fiber. However, the Finite Element (FE) modeling of these new materials for numerical analyses are very challenging due to the lack of analytical data for these specific materials. Therefore, an attempt has been made to develop Hybrid Fiber Reinforced Concrete (HyFRC) materials with High Range Water-Reducing Admixture (HRWRA) during the concrete mixing process and conduct experimental study to evaluate the behavior of the proposed materials. Constitutive models for each of the materials are formulated to be used as analytical models in numerical analyses. The acquired data are then used to formulate mathematical equations, governing the stress–strain behavior of the proposed HyFRC materials to measure the accuracy of the proposed models. The experimental testing indicated that the Ferro with Ferro mix-combination improved the performance of concrete in the elastic stage while the Ferro with Ultra-Net combination has the highest compressive strain surplus in the plastic stage. In tension, the Ferro with Ferro mix displayed the highest elastic behavior improvement while the Ferro with Ultra-Net designs proved superior in the plastic range, providing additional toughness to conventional concrete.
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Wang, Yingtao, und Shaohua Hu. „Experimental Investigation on the Response of Elliptical CFT Columns Subjected to Lateral Impact Loading“. Buildings 12, Nr. 11 (02.11.2022): 1847. http://dx.doi.org/10.3390/buildings12111847.
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This study reports an experimental investigation on the impact behavior of elliptical concrete-filled steel tubular (CFT) columns subjected to lateral loading. A total of five CFT columns, including one circular cross-section and four elliptical cross-sections, were tested using a horizontal-impact-testing system. The influences of the impact velocity, the impact times, and the cross-section geometry on the dynamic response of the elliptical CFT columns were analyzed. The experimental results have shown that the specimens withstood the global displacements without the buckling of the steel tubes. The strain rates of the steel tubes in this paper were small. The impact velocity had significant influences on the impact load-time histories and energy absorption. Meanwhile, the impact times had little influence on the impact force and displacement at the same impact velocity. Circular CFT columns have the highest ductility and impact-energy-absorption capacity. Based on the finite element analysis software ABAQUS, the finite element models of the elliptical CFT columns under impact loads were established. The simulation results were in good agreement with the experimental results. Finally, the mechanical mechanism of the elliptical CFT columns under lateral impact was analyzed by the finite element model.
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Ilyas, Israr, Adeel Zafar, Muhammad Talal Afzal, Muhammad Faisal Javed, Raid Alrowais, Fadi Althoey, Abdeliazim Mustafa Mohamed, Abdullah Mohamed und Nikolai Ivanovich Vatin. „Advanced Machine Learning Modeling Approach for Prediction of Compressive Strength of FRP Confined Concrete Using Multiphysics Genetic Expression Programming“. Polymers 14, Nr. 9 (27.04.2022): 1789. http://dx.doi.org/10.3390/polym14091789.
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The purpose of this article is to demonstrate the potential of gene expression programming (GEP) in anticipating the compressive strength of circular CFRP confined concrete columns. A new GEP model has been developed based on a credible and extensive database of 828 data points to date. Numerous analyses were carried out to evaluate and validate the presented model by comparing them with those presented previously by different researchers along with external validation comparison. In comparison to other artificial intelligence (AI) techniques, such as Artificial Neural Networks (ANN) and the adaptive neuro-fuzzy interface system (ANFIS), only GEP has the capability and robustness to provide output in the form of a simple mathematical relationship that is easy to use. The developed GEP model is also compared with linear and nonlinear regression models to evaluate the performance. Afterwards, a detailed parametric and sensitivity analysis confirms the generalized nature of the newly established model. Sensitivity analysis results indicate the performance of the model by evaluating the relative contribution of explanatory variables involved in development. Moreover, the Taylor diagram is also established to visualize how the proposed model outperformed other existing models in terms of accuracy, efficiency, and being closer to the target. Lastly, the criteria of external validation were also fulfilled by the GEP model much better than other conventional models. These findings show that the presented model effectively forecasts the confined strength of circular concrete columns significantly better than the previously established conventional regression-based models.
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Bouaanani, Najib, Patrick Paultre und Jean Proulx. „Dynamic response of a concrete dam impounding an ice-covered reservoir: Part I. Mathematical modelling“. Canadian Journal of Civil Engineering 31, Nr. 6 (01.12.2004): 956–64. http://dx.doi.org/10.1139/l04-075.
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This paper examines the dynamic response of a concrete dam impounding an ice-covered reservoir and subjected to forced-vibration testing. The analytical research presented is a follow-up to an extensive dynamic testing program carried out on a 84-m high concrete gravity dam located in northeastern Quebec, Canada, under harsh winter conditions, including a 1.0- to 1.5-m-thick ice sheet covering the reservoir. One of the major challenges encountered when analyzing ice-dam-reservoir-foundation interaction is modelling the complex nature of the ice and the boundary conditions governing reservoir motion. The problem is further complicated because there are little or no appropriate experimental data and observational evidence relevant to ice-dam interaction processes. Some of these challenges are addressed herein using a two-dimensional analytical approach, which investigates the effects due to ice cover, water compressibility, and reservoir bottom absorption. A frequency-domain substructure method technique is used and a new boundary condition along the ice-cover-reservoir interface is proposed. The technique developed is implemented in a finite element code specialized in the seismic analysis of concrete dams. Numerical results are discussed in the companion paper in this issue. Key words: gravity dams, concrete dams, ice, reservoirs, mathematical models, ice-structure interaction, fluid-structure interaction, forced-vibration testing, finite elements modelling.
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Allouzi, Rabab A., Hatem H. Almasaeid, Donia G. Salman, Raed M. Abendeh und Hesham S. Rabayah. „Prediction of Bond-Slip Behavior of Circular/Squared Concrete-Filled Steel Tubes“. Buildings 12, Nr. 4 (07.04.2022): 456. http://dx.doi.org/10.3390/buildings12040456.
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Numerous existing formulas predicted the ultimate interfacial bond strength in concrete-filled steel tubes (CFST) between steel tubes and concrete core without investigating the whole response under push-out load. In this research, four models are proposed to predict the interfacial behavior in CFST including the post-peak branch under the push-out loading test based on 157 circular specimens and 105 squared specimens from the literature. Two models (one for circular and one for squared CFST) are developed and calibrated using artificial neural network (ANN) and two models (one for circular and one for squared CFST) are developed based on multivariable regression analysis, analysis of variance (ANOVA). The shape of the specimen (circular or squared), diameter of the tube, thickness of the tube, concrete compressive strength, age at the time of testing, and length of the specimen are the main factors considered. These models are then compared to other existing formulas to verify their capability to better predict the ultimate interfacial bond strength. It is found that the ANN model gives better results for most of the considered data. It is also found that ANN models can predict the overall bond-slip response for the considered dataset. In order to simulate the response of any CFST column using finite element (FE) method, it is vital to have sufficient input data on the overall bond-slip behavior between the interior face of the steel tube and the exterior surface of the concrete core including the post-peak branch. Accordingly, the suggested ANN model is used to generate the required input data related to the cohesive behavior and damage along the interface in ABAQUS model to simulate the response of two circular and two squared CFST columns under concentric compressive load. The results are in good agreement with experimental outcomes. The cohesive criterion and damage interface that are used based on ANN models in FE are found to be sufficient and can be adopted to model CFST columns.
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Dmytrenko, Tetiana, Oleksandr Semko, Andrii Dmytrenko, Tetiana Derkach und Olena Voskobiinyk. „Development and implementation of algorithms of building structure engineering calculations for shear fraction under pressing-through.“ MATEC Web of Conferences 230 (2018): 02004. http://dx.doi.org/10.1051/matecconf/201823002004.
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Development of calculating algorithms for designed and patented constructive solutions for beamless monolithic slab and concrete reinforced column connection in the form of software program is presented in this article. Also a mathematical model for the constructive solutions was created using finite elements method. A theoretical part of the research includes engineering technique for the connection nodes between monolithic concrete slab and reinforced concrete column in stress strain state. A technical goal is simplifying and reliability increasing of loading capacity of the junction and assembly work facilitation along with reducing building frame costs. To perform testing of connection nodes between monolithic reinforced concrete beamless non-bearing slab and reinforced concrete column for shear existing calculating algorithm was improved using the designed formula. A connection node for a shear along the column body calculation according to the technique was also implemented as a software program. A technique for calculating a connection node between monolithic beamless non-capital concrete reinforced slab and concrete reinforced columns was developed. Visual Basic for Applications was used to automate calculating of the connection nodes for shear. The research results have been implemented into practical design and calculation during extension of manufacturing building of Skvira confectionary shop in Skvira settlement.
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Amin, Muhammad Nasir, Kaffayatullah Khan, Fahid Aslam, Muhammad Izhar Shah, Muhammad Faisal Javed, Muhammad Ali Musarat und Kseniia Usanova. „Multigene Expression Programming Based Forecasting the Hardened Properties of Sustainable Bagasse Ash Concrete“. Materials 14, Nr. 19 (28.09.2021): 5659. http://dx.doi.org/10.3390/ma14195659.
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The application of multiphysics models and soft computing techniques is gaining enormous attention in the construction sector due to the development of various types of concrete. In this research, an improved form of supervised machine learning, i.e., multigene expression programming (MEP), has been used to propose models for the compressive strength (fc′), splitting tensile strength (fSTS), and flexural strength (fFS) of sustainable bagasse ash concrete (BAC). The training and testing of the proposed models have been accomplished by developing a reliable and comprehensive database from published literature. Concrete specimens with varying proportions of sugarcane bagasse ash (BA), as a partial replacement of cement, were prepared, and the developed models were validated by utilizing the results obtained from the tested BAC. Different statistical tests evaluated the accurateness of the models, and the results were cross-validated employing a k-fold algorithm. The modeling results achieve correlation coefficient (R) and Nash-Sutcliffe efficiency (NSE) above 0.8 each with relative root mean squared error (RRMSE) and objective function (OF) less than 10 and 0.2, respectively. The MEP model leads in providing reliable mathematical expression for the estimation of fc′, fSTS and fFS of BA concrete, which can reduce the experimental workload in assessing the strength properties. The study’s findings indicated that MEP-based modeling integrated with experimental testing of BA concrete and further cross-validation is effective in predicting the strength parameters of BA concrete.
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Toma, Ionut Ovidiu, Daniel Covatariu, Irina Lungu und Mihai Budescu. „Evaluation of the Load Carrying Capacity of Short RC Columns Strengthened with a Novel Cementitious Material by Using FEA“. Advanced Engineering Forum 8-9 (Juni 2013): 343–52. http://dx.doi.org/10.4028/www.scientific.net/aef.8-9.343.
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Numerical simulations based on the Finite Element Method (FEM) have become an important tool in studying various phenomena of interest to both researchers and practitioners alike. The recent advances in computational power coupled with accurate mathematical models have made FEM an indispensable tool for investigating complex loading states and material behavior that are frequently met in civil engineering. Strengthening of existing RC columns is becoming a pressing issue in the field of civil engineering due to the necessity of meeting new safety requirements for the buildings located in active seismic areas. Jacketing is a widely used method for strengthening of reinforced concrete columns showing good results in terms of increased strength and stiffness but with the addition of some unwanted effects amongst which the added dead weight is of primary importance in case of an earthquake. The paper presents the results obtained by means of Finite Element Analysis (FEA) on the load carrying capacity of short RC columns strengthened with a novel Cementitious material that may be the solution to lighter structures and lower added costs compared to other existing methods.
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Xiao, Congzhen, Baojuan Qiao, Jianhui Li, Zhiyong Yang und Jiannan Ding. „Prediction of Transverse Reinforcement of RC Columns Using Machine Learning Techniques“. Advances in Civil Engineering 2022 (22.11.2022): 1–15. http://dx.doi.org/10.1155/2022/2923069.
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Transverse reinforcement of reinforced concrete (RC) columns contributes greatly to the ductility deformation capacity of RC structures. The existing models to predict the amount of transverse reinforcement required are all empirical models with low accuracy and large dispersion and have not considered the real ductility demand of individual components. This paper proposes a ductility design method of RC structure based on component drift ratio demand obtained from nonlinear structural dynamic analysis. To establish the best transverse reinforcement ratio prediction model for RC columns, based on an experimental database consisting of 498 columns, 12 machine learning (ML) models are trained. To solve the over-fitting problem caused by the current situation of “few samples and big errors” of the experimental database, feature engineering aiming at dimension reduction is systematically carried out through an iterative process. Through comprehensive performance evaluation on the testing set, an XGBoost model is selected. To interpret the “black box” ML model, the SHAP method and partial dependence plots are used to analyse the correlation between the input parameters and the transverse reinforcement ratio. The interpretation results are consistent with mechanical laws and engineering experience, which prove the reliability of the selected ML model. Compared with two existing empirical models, the proposed XGBoost model shows higher accuracy and smaller deviation. After safety probability analysis, the trained XGBoost model is transformed into C code and integrated into seismic design software for productive practice. An open-source data-driven model to predict the transverse reinforcement ratio required for RC columns is provided worldwide, with the flexibility to account for additional experimental results.
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Souza, L. A. F. de, und R. D. Machado. „Numerical-computational analysis of reinforced concrete structures considering the damage, fracture and failure criterion“. Revista IBRACON de Estruturas e Materiais 6, Nr. 1 (Februar 2013): 101–20. http://dx.doi.org/10.1590/s1983-41952013000100006.
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The experimental results of testing structures or structural parts are limited and, sometimes, difficult to interpret. Thus, the development of mathematical-numerical models is needed to complement the experimental analysis and allow the generalization of results for different structures and types of loading. This article makes two computational studies of reinforced concrete structures problems found in the literature, using the Finite Element Method. In these analyses, the concrete is simulated with the damage classical model proposed by Mazars and the steel by a bilinear elastoplastic constitutive model. Numerical results show the validity of the application of constitutive models which consider the coupling of theories with the technique of finite element discretization in the simulation of linear and two-dimensional reinforced concrete structures.
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Chepurnenko, V., K. Hashhozhev, S. Yazyev und Arthur Avakov. „IMPROVING THE CALCULATION OF FLEXIBLE CFST-COLUMNS, TAKING INTO ACCOUNT STRESSES IN THE SECTION PLANES“. Construction Materials and Products 4, Nr. 3 (12.08.2021): 41–53. http://dx.doi.org/10.34031/2618-7183-2021-4-3-41-53.
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the article is devoted to a newly developed complex finite element that allows modeling concrete-filled steel tubular columns taking into account the compression of the concrete core from the steel tube, as well as ge-ometric nonlinearity. The derivation of the resolving equations, as well as expressions for the elements of the stiffness matrix, is based on the hypothesis of plane sections. The complex testing of the finite element was performed using the program code written by the authors in the MATLAB language and the ANSYS software, as well as the analysis of the effectiveness of the new FE in comparison with the classical methods of modeling CFST-columns in modern software systems. A significant decrease in the order of the system of FEM equations is demonstrated in comparison with the modeling of CFST-structures in a volumetric formu-lation in existing design complexes using SOLID elements for a concrete core with 3 degrees of freedom in each of the nodes, and SHELL elements for a steel tube with 6 degrees of freedom in each of the nodes, with a comparable accuracy in determining the stress-strain state. The behavior of steel and concrete in the presented work is assumed to be linearly elastic, however, the described calculation method can be generalized to the case of using nonlinear deformation models of materials.
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Meruane, Viviana, Sergio J. Yanez, Leonel Quinteros und Erick I. Saavedra Flores. „Damage Detection in Steel–Concrete Composite Structures by Impact Hammer Modal Testing and Experimental Validation“. Sensors 22, Nr. 10 (20.05.2022): 3874. http://dx.doi.org/10.3390/s22103874.
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Steel–concrete composite systems are an efficient alternative to mid- and high-rise building structures because of their high strength-to-weight ratio when compared to traditional concrete or steel constructive systems. Nevertheless, composite structural systems are susceptible to damage due to, for example, deficient construction processes, errors in design and detailing, steel corrosion, and the drying shrinkage of concrete. As a consequence, the overall strength of the structure may be significantly decreased. In view of the relevance of this subject, the present paper addresses the damage detection problem in a steel–concrete composite structure with an impact-hammer-based modal testing procedure. The mathematical formulation adopted in this work allows for the identification of regions where stiffness varies with respect to an initial virgin state without the need for theoretical models of the undamaged structure (such as finite element models). Since mode shape curvatures change due to the loss of stiffness at the presence of cracks, a change in curvature was adopted as a criterion to quantify stiffness reduction. A stiffness variability index based on two-dimensional mode shape curvatures is generated for several points on the structure, resulting in a damage distribution pattern. Our numerical predictions were compared with experimentally measured data in a full-scale steel–concrete composite beam subjected to bending and were successfully validated. The present damage detection strategy provides further insight into the failure mechanisms of steel–concrete composite structures, and promotes the future development of safer and more reliable infrastructures.
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Tahmasebinia, Faham, Linda Zhang, Sangwoo Park und Samad Sepasgozar. „Numerically Evaluation of FRP-Strengthened Members under Dynamic Impact Loading“. Buildings 11, Nr. 1 (31.12.2020): 14. http://dx.doi.org/10.3390/buildings11010014.
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Reinforced concrete (RC) members in critical structures, such as bridge piers, high-rise buildings, and offshore facilities, are vulnerable to impact loads throughout their service life. For example, vehicle collisions, accidental loading, or unpredicted attacks could occur. The numerical models presented in this paper are shown to adequately replicate the impact behaviour and damage process of fibre-reinforced polymer (FRP)-strengthened concrete-filled steel tube (CFST) columns and Reinforced Concrete slabs. Validated models are developed using Abaqus/Explicit by reproducing the results obtained from experimental testing on bare CFST and RC slab members. Parameters relating to the FRP and material components are investigated to determine the influence on structural behaviour. The innovative method of using the dissipated energy approach for structural evaluation provides an assessment of the effective use of FRP and material properties to enhance the dynamic response. The outcome of the evaluation, including the geometrical, material, and contact properties modelling, shows that there is an agreement between the numerical and experimental behaviour of the selected concrete members. The experimentation shows that the calibration of the models is a crucial task, which was considered and resulted in matching the force–displacement behaviour and achieving the same maximum impact force and displacement values. Different novel and complicated Finite Element Models were comprehensively developed. The developed numerical models could precisely predict both local and global structural responses in the different reinforced concrete members. The application of the current numerical techniques can be extended to design structural members where there are no reliable practical guidelines on both national and international levels.
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Hu, Jong Wan, und Ga Lam Choi. „Towards an Application of PBD Principles for Innovative Recentering Beam-to-Column Connections“. Advanced Materials Research 716 (Juli 2013): 569–74. http://dx.doi.org/10.4028/www.scientific.net/amr.716.569.
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An unintended consequence is that some freedom in the introduction of innovative composite connections has been removed. The innovative aspects of this connection are in the use of partial restraint connections between steel beams and concrete-filled tube columns that utilize a combination of low-carbon steel and shape memory alloy components. A refined finite element model with sophisticated three dimensional solid elements was developed to conduct numerical experiments on the proposed joints to obtain the global behavior of the connection and develop simplified models. The paper argues that careful analytical studies can replace the requirement for physical testing present in current steel codes.
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Dey, Alinda, Akshay Vijay Vastrad, Mattia Francesco Bado, Aleksandr Sokolov und Gintaris Kaklauskas. „Long-Term Concrete Shrinkage Influence on the Performance of Reinforced Concrete Structures“. Materials 14, Nr. 2 (06.01.2021): 254. http://dx.doi.org/10.3390/ma14020254.
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The contribution of concrete to the tensile stiffness (tension stiffening) of a reinforced concrete (RC) member is a key governing factor for structural serviceability analyses. However, among the current tension stiffening models, few consider the effect brought forth by concrete shrinkage, and none studies take account of the effect for very long-term shrinkage. The present work intends to tackle this exact issue by testing multiple RC tensile elements (with different bar diameters and reinforcement ratios) after a five-year shrinking time period. The experimental deformative and tension stiffening responses were subjected to a mathematical process of shrinkage removal aimed at assessing its effect on the former. The results showed shrinkage distinctly lowered the cracking load of the RC members and caused an apparent tension stiffening reduction. Furthermore, both of these effects were exacerbated in the members with higher reinforcement ratios. The experimental and shrinkage-free behaviors of the RC elements were finally compared to the values predicted by the CEB-fib Model Code 2010 and the Euro Code 2. Interestingly, as a consequence of the long-term shrinkage, the codes expressed a smaller relative error when compared to the shrinkage-free curves versus the experimental ones.
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Sococol, Ion, Petru Mihai, Ionuţ-Ovidiu Toma, Ioana Olteanudonţov und Vasile-Mircea Venghiac. „Stress-Strain Relation Laws for Concrete and Steel Reinforcement Used in Non-Linear Static Analytical Studies of the Moment Resisting Reinforced Concrete (RC) Frame Models“. Bulletin of the Polytechnic Institute of Iași. Construction. Architecture Section 67, Nr. 1 (01.03.2021): 17–29. http://dx.doi.org/10.2478/bipca-2021-0002.
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Abstract Following the previous analytical studies performed with ATENA software for a series of RC moment resisting frame models, it were used in the pre-processing stage the stress-strain relation laws for concrete and steel reinforcement. These mathematical and graphical relations represent a necessity in the current conditions of numerical analysis and imply a correct knowledge of the deformation mode of the „reinforced concrete” which is a composite material. Thus, it is desired through this research paper the theoretical exposition of: equivalent uniaxial law for concrete, biaxial compressive failure and tensile failure consideration laws for concrete, bilinear with hardening law for steel reinforcement, cycling steel reinforcement model and steel reinforcement bond model. Finally, it will be possible to validate the correctness of the analytical RC frame systems through the experimental results of the optimal RC frame model after seismic platform testing.
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Benzaid, Riad, und Habib-Abdelhak Mesbah. „THE CONFINEMENT OF CONCRETE IN COMPRESSION USING CFRP COMPOSITES – EFFECTIVE DESIGN EQUATIONS“. JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 20, Nr. 5 (20.10.2014): 632–48. http://dx.doi.org/10.3846/13923730.2013.801911.
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This paper presents the results of an experimental study on the behaviour of axially loaded short concrete columns, with different cross sections that have been externally strengthened with carbon fibre-reinforced polymer (CFRP) sheets. Six series, forming the total of 60 specimens, were subjected to axial compression. All the test specimens were loaded to failure in axial compression and investigated in both axial and transverse directions. According to the obtained test results, FRP-confined specimen failure occurs before the FRP reached the ultimate strain capacities. Thus, the failure occurs prematurely and the circumferential failure strain is lower than the ultimate strain obtained from the standard tensile testing of the FRP composite. In existing models for FRP-confined concrete, it is commonly assumed that the FRP ruptures when the hoop stress in the FRP jacket reaches its tensile strength from either flat coupon tests, which is herein referred to as the FRP material tensile strength. This phenomenon considerably affects the accuracy of the existing models for FRP-confined concrete. On the basis of the effective lateral confining pressure of the composite jacket and the effective circumferential FRP failure strain, new equations were proposed to predict the strength of FRP-confined concrete and corresponding strain for each of the cross section geometry used, circular and square. The estimations given by these equations were compared with the experimental ones and general conclusions were drawn.
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Buchta, Vojtech. „Experimental Testing the Interaction of Fiber-Concrete Foundation Slab and Subsoil and Compare the Results with Numerical Models“. Advanced Materials Research 1020 (Oktober 2014): 227–32. http://dx.doi.org/10.4028/www.scientific.net/amr.1020.227.
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We solve interaction between the foundation base and the subsoil in civil engineering quite often. For the determination of stress in foundation structure is needed to determine the influence of the stiffness respectively pliability of subsoil to structural internal forces, and vice versa, how the stiffness of the foundation structure affects the resulting subsidence. It is necessary to compare the mathematical models with the actual behavior of the real structure. In 2013 was realised static load on testing equipment in the campus of Faculty of Civil Engineering, VSB–TU Ostrava. Dimensions of test element was 2000 x 2000 x 170 mm and the concrete slab was reinforced with steel fiber type DRAMIX 3D 65/60B6. During measurements were performed and recorded: tensometrical measurement on the surface of the slab, tensometrical measurement inside the slab, measuring the vertical load, measurement of the vertical deformation, measuring the stress on the interface of the slab and soil. Were also developed numerical models of this test in program Nexis. Comparison the test results with numerical models are presented in this paper. [1,9]
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Amin, Muhammad Nasir, Mudassir Iqbal, Arshad Jamal, Shahid Ullah, Kaffayatullah Khan, Abdullah M. Abu-Arab, Qasem M. S. Al-Ahmad und Sikandar Khan. „GEP Tree-Based Prediction Model for Interfacial Bond Strength of Externally Bonded FRP Laminates on Grooves with Concrete Prism“. Polymers 14, Nr. 10 (16.05.2022): 2016. http://dx.doi.org/10.3390/polym14102016.
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Reinforced concrete structures are subjected to frequent maintenance and repairs due to steel reinforcement corrosion. Fiber-reinforced polymer (FRP) laminates are widely used for retrofitting beams, columns, joints, and slabs. This study investigated the non-linear capability of artificial intelligence (AI)-based gene expression programming (GEP) modelling to develop a mathematical relationship for estimating the interfacial bond strength (IBS) of FRP laminates on a concrete prism with grooves. The model was based on five input parameters, namely axial stiffness (Eftf), width of FRP plate (bf), concrete compressive strength (fc′), width of groove (bg), and depth of the groove (hg), and IBS was considered the target variable. Ten trials were conducted based on varying genetic parameters, namely the number of chromosomes, head size, and number of genes. The performance of the models was evaluated using the correlation coefficient (R), mean absolute error (MAE), and root mean square error (RMSE). The genetic variation revealed that optimum performance was obtained for 30 chromosomes, 11 head sizes, and 4 genes. The values of R, MAE, and RMSE were observed as 0.967, 0.782 kN, and 1.049 kN for training and 0.961, 1.027 kN, and 1.354 kN. The developed model reflected close agreement between experimental and predicted results. This implies that the developed mathematical equation was reliable in estimating IBS based on the available properties of FRPs. The sensitivity and parametric analysis showed that the axial stiffness and width of FRP are the most influential parameters in contributing to IBS.
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Lin, Huang-bin, Shou-gao Tang und Cheng Lan. „Control Parametric Analysis on Improving Park Restoring Force Model and Damage Evaluation of High-Strength Structure“. Advances in Materials Science and Engineering 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/3696418.
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In the dynamic time-history analysis of structural elastoplasticity, it is important to develop a universal mathematical model that can describe the force-displacement characteristics for restoring force. By defining three control parameters (stiffness degradation, slip closureγ, energy degradationβ), the Park restoring force mathematical model can simulate various components. In this study, the Park restoring force has been improved by adding two control parameters (energy-based strength degradationβeand ductility-based strength degradationβd). Based on the testing data, the constitutive model is input and 55 numerical models are developed to analyze the effects of various parameters on structural behavior.Conclusion. (1)βhas determinative effect on structural behavior; the effect ofβeis basically consistent with that ofβ;αhas significant effect on shear forces and bending moments;γhas significant effect on displacements and accelerations;βdhas significant effect on shearing forces, acceleration, and total energy consumptions. (2) Based on the classification of four types of damage level, the recommended values forα,γ,β,βe, andβdare presented. (3) Based on the testing data of high-strength columns, the recommended values for the five control parameters of the improved Park restoring force model are presented.
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Murashkin, Vasily G. „Features of Nonlinear Deformation of Concrete“. Scientific journal “ACADEMIA. ARCHITECTURE AND CONSTRUCTION”, Nr. 1 (18.03.2019): 128–32. http://dx.doi.org/10.22337/2077-9038-2019-1-128-132.
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In most studies, when the problem of determining a nonlinear model of deformation of structural concrete in normal environment, or experienced a variety of destructive (aggressive, temperature, etc.) exposure, using individual mathematical apparatus and software. The main criterion in these works for the construction of the deformation model of concrete was a unique relationship "strength - modulus of elasticity". Apply the developed model for another type of concrete or experienced a destructive impact was erroneous. However, not all features of concrete deformation in the construction of models were taken into account. In particular, the gentle nature of deformation in the initial stage of loading was not taken into account. Similarly, models of nonlinear deformation of concrete in normative materials of different countries are constructed. Especially there are problems in the inspection of structures operated for along time. It is not rational to create individual models based on the algorithm created earlier. In recent studies, a number of works have noted the need to take into account the features of the initial stage ofloading of concrete and the fact that concrete from the beginning ofloading has macro and micro cracks and structural defects. But even in these works the possibility of creating a nonlinear deformation model based on experimentally obtained data when testing prototypes of generalized model was not considered. This article discusses the possibility of constructing a concrete extracted from the structure. The possibility of replacing the individual deformation models with the proposed one is shown. In the generalized model of deformation "strength and modulus of elasticity" may not coincide with the normative characteristics and it can serve as a basis for determining the stress state in the survey of operated structures and, if necessary, for the design of new ones.
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Su, Jizhi, Boquan Liu, Guohua Xing, Yudong Ma und Jiao Huang. „Influence of Beam-to-Column Linear Stiffness Ratio on Failure Mechanism of Reinforced Concrete Moment-Resisting Frame Structures“. Advances in Civil Engineering 2020 (10.01.2020): 1–24. http://dx.doi.org/10.1155/2020/9216798.
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The design philosophy of a strong-column weak-beam (SCWB), commonly used in seismic design codes for reinforced concrete (RC) moment-resisting frame structures, permits plastic deformation in beams while keeping columns elastic. SCWB frames are designed according to beam-to-column flexural capacity ratio requirements in order to ensure the beam-hinge mechanism during large earthquakes and without considering the influence of the beam-to-column stiffness ratio on the failure modes of global structures. The beam-to-column linear stiffness ratio is a comprehensive indicator of flexural stiffness, story height, and span. This study proposes limit values for different aseismic grades based on a governing equation deduced from the perspective of member ductility. The mathematical expression shows that the structural yielding mechanism strongly depends on parameters such as material strength, section size, reinforcement ratio, and axial compression ratio. The beam-hinge mechanism can be achieved if the actual beam-to-column linear stiffness ratio is smaller than the recommended limit values. Two 1/3-scale models of 3-bay, 3-story RC frames were constructed and tested under low reversed cyclic loading to verify the theoretical analysis and investigate the influence of the beam-to-column linear stiffness ratio on the structural failure patterns. A series of nonlinear dynamic analyses were conducted on the numerical models, both nonconforming and conforming to the beam-to-column linear stiffness ratio limit values. The test results indicated that seismic damage tends to occur at the columns in structures with larger beam-to-column linear stiffness ratios, which inhibits the energy dissipation. The dynamic analysis suggests that considering the beam-to-column linear stiffness ratio during the design of structures leads to a transition from a column-hinge mechanism to a beam-hinge mechanism.
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Zambon, Ivan, Anja Vidović und Alfred Strauss. „Reliability of Existing Concrete Structures Determined with Physical Models - Carbonation Induced Corrosion“. Solid State Phenomena 259 (Mai 2017): 255–60. http://dx.doi.org/10.4028/www.scientific.net/ssp.259.255.
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The main goal of transportation infrastructure management is to optimize the use of infrastructure in the most beneficiary way while respecting the predefined requirements. One of the crucial parts in management strategy is the prediction of behaviour of vital transportation elements. Used prediction models should accurately describe the process of degradation and allow forecasting of structural condition by considering environment, usage and maintenance actions. Deterioration models can be divided into mathematical (statistical), physical and empirical models. Statistical models are based on data that describe condition of structure, such as for example condition rating. Physical models describe damage-causing processes and empirical models are experience based. The focus of this paper is to present the physical model of carbonation in assessment of performance of existing reinforced concrete structures in transportation networks. Assessment is done through determining the probability of limit state of depassivation. In order to determine the carbonation without testing, a special attention has to be given to environmental and material parameter identification. Herein, the identification takes into account weather specifics and construction practice in Austria. Finally, the reliability of existing reinforced concrete structures for combination of different exposure classes and material characteristics is analysed. Based on the analysis of reliability, the carbonation nomogram for engineering use is presented, showing the reliability indices β for the service life of 50 years.
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Lechman, Marek. „Cross-Sectional Analysis of the Resistance of RC Members Subjected to Bending with/without Axial Force“. Materials 15, Nr. 5 (06.03.2022): 1957. http://dx.doi.org/10.3390/ma15051957.
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This paper deals with the cross-sectional analysis of the resistance of RC members subjected to a bending moment with or without axial forces. To determine section resistance, the nonlinear material law for concrete in compression is assumed according to Eurocode 2, taking into account the effect of concrete softening. It adequately describes the concrete behavior of RC members up to failure. The idealized stress–strain relation for the reinforcing steel is assumed. For the ring cross-section subjected to bending with axial force and for areas weakened by an opening, normalized resistances have been derived by integrating corresponding equilibrium equations. They are presented in the form of interaction curves and compared with the results of testing conducted on RC eccentrically loaded columns. Furthermore, the ultimate normalized bending moment has been derived for the RC rectangle subjected to bending without axial force. It was applied to the cross-sectional analysis of steel and concrete composite beams consisting of the RC rectangular core located inside a reversed TT-welded profile. Comparative analysis indicated good agreements between the proposed section models and experimental data. The objective of the paper is the dimensioning optimization of the considered cross-sections with the fulfillment of structural safety requirements.
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Bolborea, Bogdan, Sorin Dan, Cornelia Baeră, Aurelian Gruin, Felicia Enache und Ion Aurel Perianu. „Study Regarding the Evaluation of Prediction Models for Determining the Concrete Compressive Strength Using Non-Destructive Testing (NDT) Data: Validation Stage“. Solid State Phenomena 332 (30.05.2022): 173–81. http://dx.doi.org/10.4028/p-5w046c.
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In the evaluation of an existing reinforced concrete structure, a fundamental issue is determining the concrete compressive strength as accurately as possible. This process can be conducted by using destructive and non-destructive methods. The destructive method presumes a limited number of cores extracted from the concrete structure. A higher number of cores would affect the structural safety and is time and resource consuming. Therefore, the conclusions drawn using exclusively this method can also generate errors in correctly estimating the load bearing capacity of a structure, thus leading to the possibility of implementing deficient measures in order to ensure a structural safety. Data obtained via non-destructive methods are more comprehensive. Due to their non-destructive nature, there are no limitations regarding the number of elements investigated and are fast in delivering results. One of the main concerns of researchers in this field is developing a direct relationship between the measured indicators through non-destructive testing (NDT) methods and concrete compressive strength. Over the years different equations with different mathematical structure (linear, polynomial, power, exponential and logarithmic) were developed with the main purpose of delivering fast and accurate results concerning concrete compressive strength by the means of NDT. The aim of this paper is to validate some of the most important prediction models using an original set of data. The database consists in a number of 96 concrete cores that were subjected to Ultrasonic Pulse Velocity (UPV) and Schmidt Rebound Hammer (SRH) testing. The accuracy of the results was determined by using two statistical parameters the mean absolute error (MAE) and mean absolute percentage error (MAPE). The proposed equations have been analyzed in terms of prediction and dispersion of values. It was noticed that some of the formulations predict values that are higher than the ones obtained destructively, others provide a larger dissipation of values, while some equations deliver a compact distribution of results with higher rate in terms of accuracy. This study proposes a data validation of some of the most popular empirical equations, used for the estimation of the concrete compressive strength, elaborated through the years, using a new set of data.
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Ďurinová, Michaela, und Matúš Kozel. „Non-Destructive Evaluation of Asphalt Concrete Materials Performance During their Life Cycle Based on Accelerated Pavement Testing“. Civil and Environmental Engineering 17, Nr. 2 (01.12.2021): 621–28. http://dx.doi.org/10.2478/cee-2021-0062.
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Abstract The characteristics of asphalt concrete materials (ACM) composing the surfacing layer of a bituminous pavement must fulfil a requirement to maintain a level of operational capability demanded by national standards of a given country. ACM’s are a subject to significant stress caused by traffic load and climate conditions, this leads to changes in their physico-mechanical properties. The loss of physico-mechanical properties causes deterioration of road surface characteristics. Since these changes occur throughout the ACM’s life cycle, it is necessary to know the deterioration curves related to loading and time in mathematical terms, i.e. functions describing the initiation and progression of pavement’s defect in time. Pavement Performance Models (PPM) ascertained by non-destructive testing are used to objectively express the surface properties of pavements and their deterioration. The methodology consists of an analytical method to ascertain physico-mechanical characteristics of ACM’s and the use of experimental accelerated pavement testing (APT) facilities.