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18 pages, 4375 KiB

Open AccessArticle

Comparison of the Prediction of Effective Moment of Inertia of FRP Rebar-Reinforced Concrete by an Optimization Algorithm

by Nag-Seop Jang, Young-Hwan Kim and Hong-Seob Oh

Materials 2023, 16(2), 621; https://doi.org/10.3390/ma16020621 - 9 Jan 2023

Viewed by 1772

Abstract

FRP (fiber-reinforced polymer)-reinforced concrete members have larger deflection than reinforced concrete members because of the low modulus of elasticity of the FRP bar. In this paper, we proposed a new effective moment of inertia equation to predict the deflection of FRP-reinforced concrete members [...] Read more.

FRP (fiber-reinforced polymer)-reinforced concrete members have larger deflection than reinforced concrete members because of the low modulus of elasticity of the FRP bar. In this paper, we proposed a new effective moment of inertia equation to predict the deflection of FRP-reinforced concrete members based on the harmony search algorithm. The harmony search algorithm is used to optimize a function that minimizes the error between the deflection value of the experimental result and the deflection value expected from the specimen’s specifications. In the experimental part, four GFRP (Glass Fiber-Reinforced Polymer)- and BFRP (Basalt Fiber-Reinforced Polymer)-reinforced concrete slab specimens were manufactured and tested. FRP-reinforced concrete slabs were reinforced with GFRP and BFRP rebars on spiral rib surfaces. The effects of the FRP reinforcement ratio and balanced reinforcement ratio (

ρ_{f}

/

ρ_{f b}

), the moment of inertia of the transformed cracked section and the gross moment of inertia (

I_{c r}

/

I_{g}

), and the cracking moment and the maximum service load moment (

M_{c r}

/

M_{a}

) on the effective moment of inertia have been considered. The experimental results and predicted results of the flexural testing of concrete slabs reinforced with FRP rebars were compared, and the experimental results were in good agreement with the calculated values using the proposed effective moment of inertia equation. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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28 pages, 14171 KiB

Open AccessArticle

Punching Shear Behavior of Slabs Made from Different Types of Concrete Internally Reinforced with SHCC-Filled Steel Tubes

by Galal Elsamak, Ali Abdullah, Magdy I. Salama, Jong Wan Hu and Mahmoud A. El-Mandouh

Materials 2023, 16(1), 72; https://doi.org/10.3390/ma16010072 - 21 Dec 2022

Cited by 10 | Viewed by 2090

Abstract

The punching shear failure of reinforced concrete (RC) flat slabs is an undesirable type of failure, as it is sudden and brittle. This paper presents an experimental and numerical study to explore the behavior of flat slabs made of different types of concrete [...] Read more.

The punching shear failure of reinforced concrete (RC) flat slabs is an undesirable type of failure, as it is sudden and brittle. This paper presents an experimental and numerical study to explore the behavior of flat slabs made of different types of concrete under the influence of punching shear. Experimental tests were carried out on four groups of flat slabs, each group representing a different type of concrete: ordinary normal concrete (NC), high-strength concrete (HSC), strain-hardening cementitious composite concrete (SHCC), and ultra-high-performance fiber concrete (UHPFC). Each group consisted of six slabs, one representing an unreinforced control slab other than the reinforcement of the bottom mesh, and the others representing slabs internally reinforced with SHCC-filled steel tubes and high-strength bolts. An analytical equation was used to predict the punching shear capacity of slabs internally reinforced using steel assemblies. A numerical model was proposed using the ABAQUS program, and was validated by comparing its results with our experimental results. Finally, a case study was performed on large-scale slabs. The results showed that using steel assemblies inside NC slabs increased the slab’s punching shear capacity but does not completely prevent punching shear failure. Internally unreinforced slabs made of UHPFC and SHCC were able to avoid punching shear failure and collapse in a ductile bending pattern due to the high compressive and tensile strength of these types of concrete. The proposed analytical method succeeded in predicting the collapse load of slabs reinforced with steel assemblies with a difference not exceeding 9%. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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16 pages, 7608 KiB

Open AccessArticle

Printability, Thermal and Compressive Strength Properties of Cementitious Materials: A Comparative Study with Silica Fume and Limestone

by Dodda Srinivas, Dhrutiman Dey, Biranchi Panda and Thallak G. Sitharam

Materials 2022, 15(23), 8607; https://doi.org/10.3390/ma15238607 - 2 Dec 2022

Cited by 16 | Viewed by 2428

Abstract

Over the past decade, 3D printing in the construction industry has received worldwide attention and developed rapidly. The research and development of cement and concrete products has also become quite well-established over the years, while other sustainable materials receive considerably lower attention in [...] Read more.

Over the past decade, 3D printing in the construction industry has received worldwide attention and developed rapidly. The research and development of cement and concrete products has also become quite well-established over the years, while other sustainable materials receive considerably lower attention in comparison. This study aims to investigate the influence of the two most commonly used sustainable cementitious materials i.e., silica fume and limestone powder, on printability, thermal and mechanical properties of fly ash–Portland cement blends. Ternary blends containing Portland cement, fly ash and silica fume or limestone powder are prepared, whereas phase change material (PCM) is introduced to improve the thermal behavior. Based on the rheological properties and concurrent 3D concrete printing, improved buildability of the modified mixtures is linked to their static yield stress. Anisotropic mechanical properties are observed for 3D printed specimens, while cast specimens exhibit a maximum 41% higher compressive strength due to better material compaction. It is clear from the results that addition of silica fume and limestone powder ranged from 5% to 10%, reducing the anisotropic mechanical properties (maximum 71% and 68% reduction in anisotropic factor, respectively) in the printed specimens. The PCM addition ranged from 5% to 10% and improved thermal performance of the mixtures, as measured by a decrease in thermal conductivity (9% and 13%) and an increase in volumetric heat capacity (9% and 10%), respectively. However, the PCM-containing mixtures show around 29% reduction in compressive strength, compared to the control specimen, which necessitates new material design considering matrix strengthening methods. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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17 pages, 7747 KiB

Open AccessArticle

Accuracy of Seismic Response Evaluation of Two-Dimensional Analysis Model with Rigid Joints for RC Frame Buildings

by Jae-Do Kang, Takuya Nagae, Seong-Hoon Jeong and Koichi Kajiwara

Materials 2022, 15(22), 8027; https://doi.org/10.3390/ma15228027 - 14 Nov 2022

Cited by 1 | Viewed by 1564

Abstract

Three- or two-dimensional (2D) numerical models are used for the evaluation of the seismic performance of reinforced concrete (RC) buildings. This study examines a 2D numerical model for a specimen used in a full-scale four-story RC shaking-table test and evaluates the accuracy of [...] Read more.

Three- or two-dimensional (2D) numerical models are used for the evaluation of the seismic performance of reinforced concrete (RC) buildings. This study examines a 2D numerical model for a specimen used in a full-scale four-story RC shaking-table test and evaluates the accuracy of the seismic response of the 2D numerical model, which is composed of a square fiber section model for the columns, a T-shape fiber section model for the beam and slab, and a rigid joint model for the beam–column joint. A parametric analysis of the effective slab width is performed to analyze its effects on the modal shape and natural period. The results suggest that the primary natural period of the considered model is almost identical to that associated with the experimental results. The applicability of the 2D numerical model for estimating the seismic response of the structure is established. By comparing the results of the seismic analysis and the experiment in the 50% amplitude of the JMA-Kobe wave, which corresponds to slightly exceeding VII on the modified Mercalli intensity scale, the root-mean-square percentage error of the 2D numerical model is 1.03% for the floor acceleration and 4.7% for the inter-story drift. Thus, the analytical model used in this study has sufficient accuracy in evaluating the seismic performance of buildings constructed in regions with a maximum seismic intensity of VII. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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19 pages, 4334 KiB

Open AccessArticle

Assessment of Waste Marble Powder on the Mechanical Properties of High-Strength Concrete and Evaluation of Its Shear Strength

by Mahmoud A. El-Mandouh, Jong-Wan Hu, Ayman S. Mohamed and Ahmed S. Abd El-Maula

Materials 2022, 15(20), 7125; https://doi.org/10.3390/ma15207125 - 13 Oct 2022

Cited by 5 | Viewed by 2043

Abstract

Currently, the costs of building materials, especially cement, are increasing. Waste marble powder (WMP) could be used as a cement replacement material to produce environmentally friendly concrete to help preserve resources and reduce environmental pollution. The study’s goals are (1) to evaluate the [...] Read more.

Currently, the costs of building materials, especially cement, are increasing. Waste marble powder (WMP) could be used as a cement replacement material to produce environmentally friendly concrete to help preserve resources and reduce environmental pollution. The study’s goals are (1) to evaluate the effects of using marble powder in place of cement in high-strength concrete (HSC) on the material’s mechanical properties and durability characteristics. (2) The study is expanded to assess the effect of using partial WMP on the shear behavior of HSC beams under static loads. Eight half-scale simply supported reinforced beams with and without WMP have been tested. Each beam’s cross-section was 120 × 200 mm, and each beam had a total length of 1000 mm. The ratios of the used WMP were 0%, 2.5%, 5%, 7.5% by weight, and two different stirrup ratios, 0% and 0.47%, were used. When applied to HSC beams with and without WMP, the shear strength provisions of two of the most used codes, such as the locally used Egyptian Code (ECP 207) and the internationally used American Concrete Institute’s (ACI-2019), were examined. Using the ABAQUS software, the experimental results were compared to the findings of the nonlinear finite element analysis. The results established that partial replacement of cement by WMP led to increases in the concrete’s compressive and tensile strengths of about 15% and 16%, respectively. When tested specimens were exposed to acid attack, there were slight losses in weight and compressive strength (1.25% to 2.47%) for both with and without the addition of WMP. Both the concrete with and without WMP showed the same level of water absorption. Additionally, WMP led to an enhancement in the shear capacities for all beams. Increasing the WMP ratio from 0% to 2.5%, 5%, and 7.5% increased the shear capacity by about 13%, 20%, and 28%, respectively, for beams without stirrups, while for beams with stirrups, the shear capacity improved by 12%, 19%, and 25%, respectively. The enhancement in the beams’ shear capacities could be attributed to the advanced concrete matrix produced by WMP’s extremely small particle size. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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19 pages, 3819 KiB

Open AccessArticle

Shear Strength of Nano Silica High-Strength Reinforced Concrete Beams

by Mahmoud A. El-Mandouh, Mosbeh R. Kaloop, Jong-Wan Hu and Ahmed S. Abd El-Maula

Materials 2022, 15(11), 3755; https://doi.org/10.3390/ma15113755 - 24 May 2022

Cited by 3 | Viewed by 1812

Abstract

In this study, the shear strength of sixteen full-scale over-reinforced concrete beams with and without nano silica (NS), constructed from high-strength concrete (HSC), was investigated both experimentally and analytically. Nano silica was used as a partial replacement for Portland cement. According to the [...] Read more.

In this study, the shear strength of sixteen full-scale over-reinforced concrete beams with and without nano silica (NS), constructed from high-strength concrete (HSC), was investigated both experimentally and analytically. Nano silica was used as a partial replacement for Portland cement. According to the NS ratio, the tested beams were divided into four groups: 0%, 1%, 2%, and 3%. Shear span to effective depth (a/d) ratios of 1.5 and 2.5 were used in each group, and two different stirrups ratios (ρ_v) were employed as 0% and 0.38%. The shear strength provisions used by some international codes, such as the American Concrete Institute (ACI-2019), the Eurocode 2 (EC-2), and the Egyptian Code (ECP 207), were examined when applied to HSC beams with and without NS. The most important factors to consider were the effect of using NS on the shear span to effective depth (a/d) ratio and the shear strength of the beams with and without stirrups. The experimental results were validated using a nonlinear finite element analysis using the computer program ABAQUS. The experimental results showed that increasing the NS ratio reduced the number of cracks, and increased the cracks spacing, as well as reducing crack width. In specimens without stirrups, these effects were more obvious. A rise in the (a/d) ratio increased the number of cracks along the beam length, notably in the mid-span region. For specimens without stirrups and with an (a/d) of 1.5, raising NS from 0% to 1%, 2%, and 3% increased the ultimate load by 13%, 30%, and 39%, respectively, whereas for specimens with an (a/d) of 2.5, the ultimate load increased with approximately the same increase as that in beams with an (a/d) of 1.5 due to using NS. Additionally, the addition of NS to concrete boosted the contribution of the concrete to the shear strength, as shown by the results of beams without stirrups. For specimens with stirrups and an (a/d) of 1.5, raising NS from 0% to 1%, 2%, and 3% increased the ultimate load by 8%, 21%, and 30%, respectively. Additionally, for specimens with stirrups and an (a/d) of 2.5, the ultimate load increased with approximately the same increase as that in beams with stirrups and an (a/d) of 1.5 due to using NS. The test findings indicate that the shear strength calculated using the equations of the ACI 318-19 is more conservative than EC-2 and ECP 207 for NS concrete beams. The finite element program ABAQUS may be successfully used to predict the shear strength of NS concrete beams. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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26 pages, 10651 KiB

Open AccessArticle

Seismic Performance Evaluation According to HSS and CFST Columns of 3D Frame Buildings with Rubber Friction Bearing (RFB)

by Young-chan Kim, Hasan Shahriyer and Jong-wan Hu

Materials 2022, 15(4), 1281; https://doi.org/10.3390/ma15041281 - 9 Feb 2022

Cited by 12 | Viewed by 2344

Abstract

This study has been conducted to observe nonlinear time history analysis of a 3D-office building frame where performance has been examined in the presence of base isolation and a bracing system. This steel structure has an underground story surrounded by stiff well-graded sand [...] Read more.

This study has been conducted to observe nonlinear time history analysis of a 3D-office building frame where performance has been examined in the presence of base isolation and a bracing system. This steel structure has an underground story surrounded by stiff well-graded sand and is assumed to be located in an intense seismic area. The static and dynamic experimental performance of a Rubber Friction Bearing (RFB) has been considered, and an equivalent numerical model has been used in finite element software, which provides a satisfactory relationship between experimental and numerical prediction. The results show that the story drift and post-earthquake damage of the frame reduced significantly due to the presence of RFB devices. These isolators are most effective in moderate earthquakes. The presence of a minimum number of Steel Buckling Restrained Braces (BRBs) systems improve structural performance under moderate and strong ground motions by reducing story drift and residual damage. Hollow Steel Section (HSS) and Concrete-Filled Steel Tube (CFST) sections have been used in the simulation process, and it was found that the HSS system is susceptible to damage even if both seismic protection systems have been considered. The findings provide important conclusions to select suitable seismic protection for this type of structure, which is limited by simulation study due to the absence of experimental observation. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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19 pages, 16835 KiB

Open AccessEditor’s ChoiceArticle

Image-Based vs. Parametric Modelling of Concrete Meso-Structures

by Jiaming Wang, Andrey P. Jivkov, Dirk L. Engelberg and Qingming Li

Materials 2022, 15(3), 704; https://doi.org/10.3390/ma15030704 - 18 Jan 2022

Cited by 8 | Viewed by 2102

Abstract

Damage initiation and crack propagation in concrete are associated with localisation of energy dissipation by the concrete meso-structure. Meso-scale models are, therefore, required for realistic analysis of concrete non-linear behaviour. Such models are constructed either from X-ray Computed Tomography images (image-based modelling) or [...] Read more.

Damage initiation and crack propagation in concrete are associated with localisation of energy dissipation by the concrete meso-structure. Meso-scale models are, therefore, required for realistic analysis of concrete non-linear behaviour. Such models are constructed either from X-ray Computed Tomography images (image-based modelling) or by in silico meso-structure generation (parametric modelling), while both approaches are widely used and their advantages and disadvantages are recognised, little work is done on comparing their performance in predicting measured macroscopic behaviour with equivalent constitutive relations for meso-structural features. This work uses microstructure characterisation and mechanical behaviour data to construct, validate and compare the two modelling approaches. The macroscopic behaviour obtained with both meso-structural models is found to be in good agreement with experimental data. Differences are observed only between the predicted distributions of damage within specimens. These outcomes suggest that the computationally simpler parametric meso-structures are sufficient to derive stress–strain behaviour for engineering-scale models in the absence of other environmental factors. The observed differences in damage distribution could be important for analysis of coupled behaviour, e.g., mass transport and chemical reactions affecting local mechanical properties and being affected by local damage. Establishing the importance of damage distribution is such cases requires further research. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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20 pages, 11133 KiB

Open AccessArticle

A Study on Tensile Behavior According to the Design Method for the CFRP/GFRP Grid for Reinforced Concrete

by Jin Sung Kim, Seong Jong Kim, Kyoung Jae Min, Jung Chul Choi, Hwa Seong Eun and Bhum Keun Song

Materials 2022, 15(1), 357; https://doi.org/10.3390/ma15010357 - 4 Jan 2022

Cited by 4 | Viewed by 2455

Abstract

In the present study, fiber-reinforced plastics (FRP) grid-reinforced concrete with very rapid hardening polymer (VRHP) mortar composites were fabricated using three types of design methods for the FRP grid (hand lay-up method, resin infusion method, and prepreg oven vacuum bagging method), along with [...] Read more.

In the present study, fiber-reinforced plastics (FRP) grid-reinforced concrete with very rapid hardening polymer (VRHP) mortar composites were fabricated using three types of design methods for the FRP grid (hand lay-up method, resin infusion method, and prepreg oven vacuum bagging method), along with two types of fibers (carbon fiber and glass fiber) and two types of sheets (fabric and prepreg). The FRP grid was prepared by cutting the FRP laminates into a 10 mm thick, 50 mm × 50 mm grid. The tensile behavior of the FRP grid embedded in composites was systematically analyzed in terms of the load extension, fracture mode, partial tensile strain, and load-bearing rate. The CFRP grid manufactured by the prepreg OVB method showed the best tensile behavior compared to the CFRP grid manufactured by the hand lay-up and resin infusion methods. The load-bearing of each grid point was proportional to the height from the load-bearing part when reaching the maximum tensile load. In addition, finite element analysis was conducted to compare the experimental and analysis results. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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26 pages, 8358 KiB

Open AccessArticle

Performance Evaluation of Cementitious Composites Incorporating Nano Graphite Platelets as Additive Carbon Material

by Farhan Ahmad, Arshad Jamal, Mudassir Iqbal, Muwaffaq Alqurashi, Meshal Almoshaogeh, Hassan M. Al-Ahmadi and Enas E. Hussein

Materials 2022, 15(1), 290; https://doi.org/10.3390/ma15010290 - 31 Dec 2021

Cited by 8 | Viewed by 3167

Abstract

Nano graphite platelets (NGPs) belong to the carbon family and have a huge impact on the construction industry. NGPs are used as multi-functional fillers and have the potential to develop reinforcing within cementitious composites. In this paper, NGPs were incorporated in cementitious composites [...] Read more.

Nano graphite platelets (NGPs) belong to the carbon family and have a huge impact on the construction industry. NGPs are used as multi-functional fillers and have the potential to develop reinforcing within cementitious composites. In this paper, NGPs were incorporated in cementitious composites to investigate the effects of NGPs on the fresh, mechanical, durability, and microstructural properties of concrete. Five mixes were prepared with intrusion of NGPs (0%, 0.5%, 1.5%, 3%, and 5% by weight of cement). The properties studied involved workability, air content, hardened density, compressive strength, tensile strength, flexural strength, sorptivity, ultrasonic pulse velocity (UPV), water absorption, and external sulfate attack. The workability and percent air content decrease by 22.5% and 33.8%, respectively, for concrete with 5% NGPs compared to the control mix. The specimens containing 5% of NGPs revealed the hardened density, compressive, tensile, and flexural strength to increase by 11.4%, 38.5%, 31.6%, and 44.34%, respectively, compared to the control mix. The results revealed that the incorporation of 5%NGPs in cementitious composites reduces the sorptivity and water absorption by 32.2% and 73.9%, respectively, whereas, it increases the UPV value by 7.5% compared to the control mix. Furthermore, the incorporation of NGPs provided better resistance against external sulfate attacks. SEM–EDX spectroscopy was carried out to investigate its microstructural analysis. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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15 pages, 3338 KiB

Open AccessArticle

Structural Retrofitting of Corroded Reinforced Concrete Beams Using Bamboo Fiber Laminate

by Paul Oluwaseun Awoyera, Tobechukwu Austin Nworgu, Balaji Shanmugam, Krishna Prakash Arunachalam, Iman Mansouri, Lenin Miguel Bendezu Romero and Jong-Wan Hu

Materials 2021, 14(21), 6711; https://doi.org/10.3390/ma14216711 - 8 Nov 2021

Cited by 15 | Viewed by 3487

Abstract

Corrosion creates a significant degradation mechanism in reinforced concrete (RC) structures, which would require a high cost of maintenance and repair in affected buildings. However, as the cost of repairing corrosion-damaged structures is high, it is therefore pertinent to develop alternative eco-friendly and [...] Read more.

Corrosion creates a significant degradation mechanism in reinforced concrete (RC) structures, which would require a high cost of maintenance and repair in affected buildings. However, as the cost of repairing corrosion-damaged structures is high, it is therefore pertinent to develop alternative eco-friendly and sustainable methods. In this study, structural retrofitting of corroded reinforced concrete beams was performed using bamboo fiber laminate. Three reinforced normal weight concrete beams were produced, two of which were exposed to laboratory simulated corrosion medium, and the remaining one sample served as control. Upon completion of the corrosion cycle, one of the two corroded beams was retrofitted externally with a prefabricated bamboo fiber laminate by bonding the laminate to the beam surface with the aid of an epoxy resin. The three beams were subjected to loading on a four-point ultimate testing machine, and the loads with corresponding deflections were recorded through the entire load cycle of the beams. Finally, the mass loss of embedded steel reinforcements was determined to measure the effect of corrosion on the beams and the steel. The result showed that corroded beams strengthened with bamboo laminates increase the bearing capacity. Using a single bamboo laminate in the tensile region of the corroded beam increased the ultimate load capacity of the beam up to 21.1% than the corroded beam without retrofit. It was demonstrated in this study that the use of bamboo fiber polymer for strengthening destressed RC beams is a more sustainable approach than the conventional synthetic fibers. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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13 pages, 2099 KiB

Open AccessArticle

Comparison between Multiple Regression Analysis, Polynomial Regression Analysis, and an Artificial Neural Network for Tensile Strength Prediction of BFRP and GFRP

by Younghwan Kim and Hongseob Oh

Materials 2021, 14(17), 4861; https://doi.org/10.3390/ma14174861 - 26 Aug 2021

Cited by 20 | Viewed by 3107

Abstract

In this study, multiple regression analysis (MRA) and polynomial regression analysis (PRA), which are traditional statistical methods, were applied to analyze factors affecting the tensile strength of basalt and glass fiber-reinforced polymers (FRPs) exposed to alkaline environments and predict the tensile strength degradation. [...] Read more.

In this study, multiple regression analysis (MRA) and polynomial regression analysis (PRA), which are traditional statistical methods, were applied to analyze factors affecting the tensile strength of basalt and glass fiber-reinforced polymers (FRPs) exposed to alkaline environments and predict the tensile strength degradation. The MRA and PRA are methods of estimating functions using statistical techniques, but there are disadvantages in the scalability of the model because they are limited by experimental results. Therefore, recently, highly scalable artificial neural networks (ANN) have been studied to analyze complex relationships. In this study, the prediction performance was evaluated in comparison to the MRA, PRA, and ANN. Tensile strength tests were conducted after exposure for 50, 100, and 200 days in alkaline environments at 20, 40, and 60 °C. The tensile strength was set as the dependent variable, with the temperature (TP), the exposure day (ED), and the diameter (D) as independent variables. The MRA and PRA results showed that the TP was the most influential factor in the tensile strength degradation of FRPs, followed by the exposure time (ED) and diameter (D). The ANN method provided the best correlation between predictions and experimental values, with the lowest error and error rate. The PRA method applied to the response surface method outperformed the MRA method, which is most commonly used. These results demonstrate that ANN can be the most efficient model for predicting the durability of FRPs. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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13 pages, 1666 KiB

Open AccessArticle

A Prediction Model for the Calculation of Effective Stiffness Ratios of Reinforced Concrete Columns

by Sourav Das, Iman Mansouri, Satyabrata Choudhury, Amir H. Gandomi and Jong Wan Hu

Materials 2021, 14(7), 1792; https://doi.org/10.3390/ma14071792 - 5 Apr 2021

Cited by 10 | Viewed by 3011

Abstract

Nonlinear dynamic analyses of reinforced concrete (RC) frame buildings require the use of effective stiffness of members to capture the effect of cracked section stiffness. In the design codes and practices, the effective stiffness of RC sections is given as an empirical fraction [...] Read more.

Nonlinear dynamic analyses of reinforced concrete (RC) frame buildings require the use of effective stiffness of members to capture the effect of cracked section stiffness. In the design codes and practices, the effective stiffness of RC sections is given as an empirical fraction of the gross stiffness. However, a more precise estimation of the effective stiffness is important as it affects the distribution of forces and various demands and response parameters in nonlinear dynamic analyses. In this study, an evolutionary computation method called gene expression programming (GEP) was used to predict the effective stiffness ratios of RC columns. Constitutive relationships were obtained by correlating the effective stiffness ratio with the four mechanical and geometrical parameters. The model was developed using a database of 226 samples of nonlinear dynamic analysis results collected from another study by the author. Subsequent parametric and sensitivity analyses were performed and the trends of the results were confirmed. The results indicate that the GEP model provides precise estimations of the effective stiffness ratios of the RC frames. Full article

(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior)

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