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Confined Concrete and Its Application in Structural Engineering
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Confined Concrete and Its Application in Structural Engineering

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Construction and Building Materials".

Deadline for manuscript submissions: closed (20 December 2022) | Viewed by 25973

Special Issue Editor

Prof. Dr. Faxing Ding

E-Mail Website
Guest Editor
1. School of Civil Engineering, Central South University, Changsha 410075, China
2. Engineering Technology Research Center for Prefabricated Construction Industrialization of Hunan Province, Changsha 410075, China
Interests: engineering structures; buliding engineering; civil engineering

Special Issue Information

Dear Colleagues,

Concrete is one of the most important materials in the building and infrastructures construction fields due to its versatility for structural applications depending on the density range, competitiveness in terms of durability and manufacturing costs, as well as ease in finding raw constituent elements. However, the high brittleness and low tensile strength hindered its application as structural members that were subjected to bending and seismic load. Hence, using structural and constructional measures to improve the mechanical behaviors of concrete has been a research theme tackled by many researchers through different approaches for years. Although there has been a good deal of studies and references in this field, in recent years, new technologies and structural measures continue to emerge with the development of materials science and the renewal of design concepts. The present Special Issue intends to provide a forum for researchers to present the current state within the field of experimental findings, numerical approaches, and analytical models of the enhanced concrete structures. Potential topics include, but are not limited to: 1) High-performance concrete and its applications in structural engineering, 2) Concrete-filled steel tube columns and structural systems, 3) CFRP and other composites confined concrete and its applications, 4) Reinforced and stirrups confined concrete.

Prof. Dr. Ding Faxing
Guest Editor

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Keywords

  • concrete
  • confinement
  • structural columns
  • seismic
  • composite structures
  • concrete-filled steel tube

Published Papers (15 papers)

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21 pages, 91441 KiB  
Article
Experimental and Theoretical Study on the Fatigue Crack Propagation in Stud Shear Connectors
by Yachuan Kuang, Yameng Wang, Ping Xiang, Li Tao, Kun Wang, Fan Fan and Jiahui Yang
Materials 2023, 16(2), 701; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16020701 - 11 Jan 2023
Cited by 2 | Viewed by 1219
Abstract
Steel-concrete composite girder bridges are subjected to reciprocal cyclic loading from vehicles, and the stud shear connectors are the key components for transmitting shear forces. Thus, it is necessary to study the fatigue performance of the stud shear connectors. At present, there are [...] Read more.
Steel-concrete composite girder bridges are subjected to reciprocal cyclic loading from vehicles, and the stud shear connectors are the key components for transmitting shear forces. Thus, it is necessary to study the fatigue performance of the stud shear connectors. At present, there are few studies on the fatigue crack propagation process of studs, and the variation curve of the crack depth of studs with the number of fatigue loading cycles is not clear. In this study, the degradation law of fatigue properties and the fatigue crack propagation law of stud shear connectors in steel-concrete composite structures are examined under fatigue loading. The fatigue properties, i.e., failure mode, the dynamic slip-fatigue number curve, cross-sectional characteristics, and the residual bearing capacity of the stud specimens, are first systematically studied through ten standard push-out specimen tests. The test results show that the relative value of the fatigue crack extension area increases, while the relative value of the residual bearing capacity of the studs decreases approximately linearly. Then, the expression of the relationship between the fatigue crack depth and the residual load-bearing capacity of the stud is proposed, based on the fatigue crack theory of fracture mechanics. Finally, combined with the ABAQUS and FRANC3D software, a fatigue crack propagation finite element analysis (FEA) model of the stud is established. The FEA results showed that the trends in the number of cyclic loads and the fatigue crack depth of studs are basically the same for the simulation curve, test curve and theoretical calculation curve. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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12 pages, 5732 KiB  
Article
Analyzing the Effects of Calcium Nitrate over White Portland Cement: A Multi-Scale Approach
by Mihai Marius Rusu, Adriana Vulpoi, Cristian Vilau, Cristian Mircea Dudescu, Petru Păşcuţă and Ioan Ardelean
Materials 2023, 16(1), 371; https://0-doi-org.brum.beds.ac.uk/10.3390/ma16010371 - 30 Dec 2022
Cited by 3 | Viewed by 1218
Abstract
Calcium nitrate is considered a promising accelerator in cement-based composites, with high potential in 3D printing and cold cement concreting. The effect induced by the composition of calcium nitrate tetrahydrate (CN) accelerator into white Portland cement is evaluated here from three perspectives: (1) [...] Read more.
Calcium nitrate is considered a promising accelerator in cement-based composites, with high potential in 3D printing and cold cement concreting. The effect induced by the composition of calcium nitrate tetrahydrate (CN) accelerator into white Portland cement is evaluated here from three perspectives: (1) Fresh cement paste properties in terms of setting time and slump, (2) mechanical properties of hardened cement samples at 7 and 28 days and (3) material characteristics in terms of structure and porosity that further link the presence of the accelerator with the macroscopic performances. The compressive and flexural strength of the hardened samples, evaluated after 7 and 28 days of hydration, indicate a non-monotonous trend with CN concentration. Crystalline phase composition is investigated using X-ray diffraction (XRD). The morphology and texture are analyzed at the flexure interface by visual inspection and electron microscopy. Complementary, the porous features are investigated by NMR-relaxometry on dry and cyclohexane-filled samples. The studies confirm that CN promotes changes in the composition and morphology of hydrates, while a trend of increase in capillary porosity is outlined as well. This competition between multiscale effects may be quantified by NMR and complementary techniques to further clarify the mechanical behavior of such composites. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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19 pages, 19906 KiB  
Article
Research on Confinement Effect of the Outer Steel Tube in Notched Square CFST Columns
by Biao Li, Faxing Ding, Yujie Yu, Jingke Zhang, Qiong Huang, Chenjie Gong and Haibo Wang
Materials 2022, 15(15), 5161; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15155161 - 25 Jul 2022
Cited by 1 | Viewed by 1088
Abstract
The outer steel tube in a concrete-filled steel tubular (CFST) column confines the core concrete and improves the compressive strength of the core concrete. When there is a notch damage in the tube, the confinement effect may be affected. The confinement effects of [...] Read more.
The outer steel tube in a concrete-filled steel tubular (CFST) column confines the core concrete and improves the compressive strength of the core concrete. When there is a notch damage in the tube, the confinement effect may be affected. The confinement effects of the notched steel tube in rectangular CFST columns were systematically investigated by using numerical approaches. Refined three-dimensional finite element models with advanced concrete constitutive relations were established. With the verified finite element modeling method, full-sized square CFST columns with horizontal, vertical, or diagonal notches at different locations of the steel tube were simulated. Stress distributions and deformation modes of the steel tube and core concrete were analyzed. Columns with a horizontal notch at the plate center location displayed a higher axial strength reduction than those with vertical notches. A parametric study was performed to investigate the influences of concrete strengths, steel strengths, steel ratios, notch length to column width ratios, and notch angles on the compressive strengths of the rectangular CFST columns. A practical design formula was proposed based on the obtained results. The proposed formula could effectively predict the influences of different notches on the confinement effect in the notched CFST columns. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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15 pages, 16201 KiB  
Article
Effect of Using Steel Bar Reinforcement on Concrete Quality by Ultrasonic Pulse Velocity Measurements
by Ominda Nanayakkara, Hadee Mohammed Najm and Mohanad Muayad Sabri Sabri
Materials 2022, 15(13), 4565; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15134565 - 29 Jun 2022
Cited by 5 | Viewed by 1560
Abstract
Non-destructive tests (NDTs) represent one of the solutions that aid engineers in evaluating the strength of materials. However, the results obtained using such tests are still questionable as they may be affected by different factors. One of these factors is the presence of [...] Read more.
Non-destructive tests (NDTs) represent one of the solutions that aid engineers in evaluating the strength of materials. However, the results obtained using such tests are still questionable as they may be affected by different factors. One of these factors is the presence of steel reinforcement in concrete. An experimental investigation is presented in this study to investigate the effect of the single reinforcement steel bar on ultrasonic pulse velocity (UPV). Seven concrete beams, one containing no steel and the other six beams containing varying bar diameter and cover thicknesses, were tested. UPV measurements were obtained using the indirect method and then modified to eliminate the effect of the steel bar. To provide the scientific evidence to give a reliable and reasonable solution, a statistical analysis was also conducted. The results show that a large bar diameter and a small cover thickness significantly influence the measured UPV. Measured UPV with a spacing between transducers up to 500 mm can effectively be used to predict the compressive strength of concrete after the modification of the initial UPV. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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21 pages, 3738 KiB  
Article
Finite Element Analysis of the Mechanical Properties of Axially Compressed Square High-Strength Concrete-Filled Steel Tube Stub Columns Based on a Constitutive Model for High-Strength Materials
by Biao Li, Faxing Ding, Deren Lu, Fei Lyu, Shijian Huang, Zheya Cao and Haibo Wang
Materials 2022, 15(12), 4313; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15124313 - 18 Jun 2022
Cited by 6 | Viewed by 1571
Abstract
With the development of new concrete technology, high-strength concrete has been used worldwide. In particular, more economic benefits can be achieved by applying high-strength concrete-filled steel tube (HSCFST) columns in the concrete core walls of super high-rise buildings. A constitutive relation with high [...] Read more.
With the development of new concrete technology, high-strength concrete has been used worldwide. In particular, more economic benefits can be achieved by applying high-strength concrete-filled steel tube (HSCFST) columns in the concrete core walls of super high-rise buildings. A constitutive relation with high applicability for high-strength materials with different strength grades is proposed. Based on this constitutive model, a brick element model of 181 sets of axially compressed square HSCFST members is established and experimentally verified. The effects of the concrete strength, diameter-to-thickness ratio, and steel yield strength on the axial compressive capacities of these members were investigated based on finite element calculation results. The results showed that with an increase in the concrete strength, the ultimate bearing capacities of CS-CC, HS-HC, HS-CC, and CS-HC stub column members increased by 60%, 24%, 44%, and 21% at most, respectively. Additionally, as the steel yield strength increased, the ultimate bearing capacities of CS-CC, HS-HC, HS-CC, and CS-HC stub column members increased by 8.8%, 5.1%, 8.5%, and 5.2%, respectively, Hence, material strength has the greatest impact on CS-CC and HS-CC. The confinement effect of the square steel tube on the concrete weakens as the strength grade of steel or concrete increases. Notably, the confinement effect of steel tube on the concrete is strongest in CS-CC and weakest in the CS-HC. In addition, the confinement coefficients of square HSCFST stub columns with different combinations of concrete and steel strengths were analyzed. Based on the superposition principle in the ultimate state, a practical axial compressive capacity calculation formula for three types of square HSCFSTs is established. Compared with existing major design code formulas, the proposed formula is more accurate and concise and has a clear physical meaning. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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23 pages, 10226 KiB  
Article
Stiffening Performance of Cold-Formed C-Section Beam Filled with Lightweight-Recycled Concrete Mixture
by Ahmed W. Al Zand, Mustafa Farooq Alghaaeb, Mohammed Chyad Liejy, Azrul A. Mutalib and Riyadh Al-Ameri
Materials 2022, 15(9), 2982; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15092982 - 20 Apr 2022
Cited by 6 | Viewed by 2078
Abstract
The aim of this paper is to investigate the flexural performance of a new steel–concrete composite beam system, which is required to carry higher loads when applied in flooring systems with less self-weight and cost compared with conventional composite beams. This new composite [...] Read more.
The aim of this paper is to investigate the flexural performance of a new steel–concrete composite beam system, which is required to carry higher loads when applied in flooring systems with less self-weight and cost compared with conventional composite beams. This new composite member is prepared by filling a single cold-formed steel C-section with concrete material that has varied lightweight-recycled aggregates. In addition, varied stiffening scenarios are suggested to improve the composite behavior of this member, since these cold-formed C-sections are of a slender cross-section and more likely to buckle and twist under high bending loads than those of hot-rolled C-sections. The influence of using four different lightweight-recycled aggregates that combine together in the infill concrete material was investigated. These recycled aggregates are recycled concrete aggregate (RCA), expanded polystyrene (EPS) beads, crumb rubber aggregates (CRA) and fine glass aggregates (FGA). For this purpose, 14 samples of cold-formed galvanized steel C-purlin were filled with concrete material (containing 0 to 100% recycled aggregates) which are experimentally tested under pure bending load, and 1 additional sample was tested without the filling material. Further numerical models were prepared and analyzed using finite element analysis software to investigate the effects of additional parameters that were not experimentally examined. Generally, the results confirm that filling the C-sections with concrete material that contains varied percentages of recycled aggregates offer significantly improved the flexural stiffness, bending capacity, and ductility performances. For example, using infill concrete materials with 0% and 100% recycled aggregate replacement increased the bending capacity of hollow C-section by about 11.4 and 8.6 times, respectively. Furthermore, stiffening of the concrete-filled C-sections with steel strips or screw connectors eventually improved the composite behavior of the specimens which led to an increase in their bending capacities accordingly, and this improvement enhanced more with an increased number of these strips and connectors. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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23 pages, 5451 KiB  
Article
Experimental Study on Seismic Behavior of PC Walls with Alveolar-Type Horizontal Joint under Pseudo-Static Loading
by Junfeng Cheng, Xiaoyong Luo, Laixiu Cheng, Qian Cheng and Linsong Chen
Materials 2022, 15(6), 2301; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15062301 - 20 Mar 2022
Cited by 5 | Viewed by 1405
Abstract
There are many horizontal joints on precast concrete (PC) wall panel structures, which certainly has a significant impact on the seismic behavior of structures. This paper proposes a novel alveolar-type horizontal joint, which has advantages of convenient and rapid assembly. Six precast concrete [...] Read more.
There are many horizontal joints on precast concrete (PC) wall panel structures, which certainly has a significant impact on the seismic behavior of structures. This paper proposes a novel alveolar-type horizontal joint, which has advantages of convenient and rapid assembly. Six precast concrete wall specimens with alveolar-type joints were designed and constructed, and they were weakly connected by spliced rebars anchored into grouted sleeves to meet the requirements of structural performance. The pseudo-static loading tests on these specimens were conducted to investigate the effects of influencing factors, such as the axial compression ratio, the thickness of wall (interface contact area), and the addition of a vertical grouted sleeve connection at the horizontal joint, on the seismic performance of PC walls. Analyses and comparisons were conducted in terms of the cracking propagation pattern, failure modes, force–displacement hysteretic curves, skeleton curves, bearing capacity, ductility factors, and energy dissipation of PC walls. It was concluded that the axial compression ratio and adding grouted sleeve connection had a significant influence on the cracking mode of PC walls, whereas the impact of the wall thickness was slight. The shear capacity and energy dissipation capacity of specimen dramatically enhanced by increasing the axial compression ratio or adding grouted sleeve connection. The PC wall exhibits good ductility after adding the vertical grouted sleeve connection at a horizontal joint. However, the ductility factor increases firstly and then decreases in the enhancement of the axial compression ratio. The reduction in wall thickness has remarkable impacts on the shear strength and energy dissipation capacity of specimens, but the influences on ductility were not significant. The prediction method for calculating the shear capacity of PC walls with alveolar-type horizontal joints was proposed based on the experimental data, and these calculated results are in good agreement with the experimental results. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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23 pages, 9566 KiB  
Article
Analysis on Seismic Performance of Steel-Reinforced Concrete-Filled Circular Steel Tubular (SRCFST) Members Subjected to Post-Fire
by Yi Han and Yanhong Bao
Materials 2022, 15(6), 2294; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15062294 - 20 Mar 2022
Cited by 2 | Viewed by 1355
Abstract
Steel-reinforced concrete-filled steel tubular (SRCFST) columns have a great development prospect in engineering practice due to their high load-bearing capacity, good ductility, and energy consumption capacity. This paper established the post-fire seismic analysis model of SRCFST with a circular-cased H section using the [...] Read more.
Steel-reinforced concrete-filled steel tubular (SRCFST) columns have a great development prospect in engineering practice due to their high load-bearing capacity, good ductility, and energy consumption capacity. This paper established the post-fire seismic analysis model of SRCFST with a circular-cased H section using the sequential coupled thermal-stress method by ABAQUS. The P-Δ curve, stiffness, ductility, and energy dissipation were calculated. Then, the post-fire seismic performance of CFST members was compared while keeping the total steel ratio constant, and it revealed that the SRCFST had superior ductility to CFST. Finally, the ductility coefficient and skeleton curve were parametrically evaluated. The results of the study showed that the effects of heating time (th), axial compression ratio (n), slenderness ratio (λ), and steel tube ratio (αt) on the skeleton line of SRCFST columns are more significant; the axial compression ratio (n), slenderness ratio (λ), and steel tube ratio (αt) have a negative influence on the ductility subjected to post-fire. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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12 pages, 4577 KiB  
Article
Blast Resistance of 240 mm Building Wall Coated with Polyurea Elastomer
by Long Ji, Ping Wang, Youer Cai, Wei Shang and Xudong Zu
Materials 2022, 15(3), 850; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15030850 - 23 Jan 2022
Cited by 11 | Viewed by 2227
Abstract
Enhancing the blast resistance of building walls is a research hotspot in the field of anti-terrorism and explosion protection. In this study, numerical simulation and experimental verification were combined to analyze the failure phenomenon of brick masonry wall and sprayed polyurea-reinforced brick wall [...] Read more.
Enhancing the blast resistance of building walls is a research hotspot in the field of anti-terrorism and explosion protection. In this study, numerical simulation and experimental verification were combined to analyze the failure phenomenon of brick masonry wall and sprayed polyurea-reinforced brick wall under contact explosion and determine the failure response parameters of the wall. The failure limit, mode, and mechanism of a 240 mm wall without reinforcement and strengthened with polyurea elastomer under different strength loads were investigated. Under contact explosion, the increase in the size of the blasting pit of the 240 mm wall gradually slowed down after the dose was increased to higher than 0.5 kg. Thereafter, the energy of the explosive load was released by splashing wall fragments as well as by deflecting and movement of the wall. The results show that the 240 mm walls sprayed with polyurea elastomer had outstanding anti-explosion performance because it wraps the damaged area and fragments of masonry wall inside the polyurea layer. When the thickness of the polyurea layer increases to 8 mm, the damaged area of the masonry wall decreases by 55.6% compared with that without reinforcement. The numerical simulation results were in good agreement with the experimental results. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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18 pages, 5830 KiB  
Article
Confinement Effect and Efficiency of Concentrically Loaded RACFCST Stub Columns
by En Wang, Yicen Liu, Fei Lyu, Faxing Ding and Yunlong Xu
Materials 2022, 15(1), 154; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15010154 - 26 Dec 2021
Cited by 5 | Viewed by 2012
Abstract
Recycled aggregate concrete-filled steel tubular (RACFST) columns are widely recognized as efficient structural members that can reduce the environmental impact of the building industry and improve the mechanical behavior of recycled aggregate concrete (RAC). The objective of this study is to investigate the [...] Read more.
Recycled aggregate concrete-filled steel tubular (RACFST) columns are widely recognized as efficient structural members that can reduce the environmental impact of the building industry and improve the mechanical behavior of recycled aggregate concrete (RAC). The objective of this study is to investigate the behavior of recycled aggregate concrete-filled circular steel tubular (RACFCST) stub columns subjected to the axial loading. Three-dimensional finite element (FE) models were established using a triaxial plastic-damage constitutive model of RAC considering the replacement ratio of recycled aggregates. The FE analytical results revealed that the decreased ultimate bearing capacity of RACFCST stub columns compared with conventional concrete infilled steel tubular (CFST) columns was mainly due to the weakened confinement effect and efficiency. This trend will become more apparent with the larger replacement ratio of recycled aggregates. A practical design formula of the ultimate bearing capacity of RACFCST stub columns subjected to axial load was proposed on the basis of the reasonably simplified cross-sectional stress nephogram at the ultimate state. The derivation process incorporated the equilibrium condition and the superposition theory. The proposed equation was evaluated by comparing its accuracy and accessibility to some well-known design formulae proposed by other researchers and some widely used design codes. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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20 pages, 11801 KiB  
Article
Study on Road Performance of Cement Fly Ash Stabilized Steel Slag—Concrete Recycled Macadam
by Hongbo Li, Yufei Tong, Hubiao Zhang, Xuanshuo Zhang and Junku Duan
Materials 2021, 14(24), 7530; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14247530 - 08 Dec 2021
Cited by 10 | Viewed by 2305
Abstract
In order to promote the application of steel slag in road engineering, improve its utilization rate and solve the environmental problems caused by its large accumulation, unconfined compressive strength (UCS) test, indirect tensile strength (ITS) test, freeze-thaw cycle test, dry shrinkage and temperature [...] Read more.
In order to promote the application of steel slag in road engineering, improve its utilization rate and solve the environmental problems caused by its large accumulation, unconfined compressive strength (UCS) test, indirect tensile strength (ITS) test, freeze-thaw cycle test, dry shrinkage and temperature shrinkage test tests with different steel slag contents were carried out. And the strength formation mechanism of steel slag in base material was revealed by SEM. The results show that the strength of the mixture initially increased and then decreased with increasing steel slag content. The frost resistance increased with increasing steel slag content, which should be limited to no more than 75%. Increasing the steel slag content improved the drying shrinkage resistance but was not conducive to the temperature shrinkage resistance. Microscopic analysis shows that adding a suitable amount of steel slag generated a gel material that was distributed inside the pores. This increased the density of the hardened slurry structure, which improved the strength. The research can provide scientific basis for the application and promotion of steel slag in road base. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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24 pages, 4836 KiB  
Article
Study on Mechanical and Frost Resistance Properties of Slag and Macadam Stabilized with Cement and Fly Ash
by Hongbo Li, Pengfei Yan, Juncang Tian, Hao Sun and Jianguang Yin
Materials 2021, 14(23), 7241; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14237241 - 26 Nov 2021
Cited by 5 | Viewed by 1579
Abstract
China is a large country in terms of coal production and consumption. The fly ash and slag produced by thermal power plants pose a great threat to the environment. To reduce the adverse effects of fly ash and slag on the environment, a [...] Read more.
China is a large country in terms of coal production and consumption. The fly ash and slag produced by thermal power plants pose a great threat to the environment. To reduce the adverse effects of fly ash and slag on the environment, a mixture of slag and macadam stabilized with cement and fly ash was prepared as pavement base material. Compaction tests, unconfined compressive strength tests, splitting strength tests, frost resistance tests, and ultrasonic tests were performed on the mixture. The results show that with an increase in slag replacement rate, the unconfined compressive strength and splitting strength decreased. However, the adverse influence of the slag replacement rate on unconfined compressive strength and splitting strength of specimens gradually weakened with increasing curing time. The frost resistance of the mixture first increased and then decreased with an increase in the slag replacement rate. When cement content was 5% and the slag replacement rate was 50%, the frost resistance of the mixture was the best. Regression analysis of the ultrasonic test showed that the ultrasonic test can effectively characterize the strength of the mixture and the internal damage degree under freeze–thaw cycles. In conclusion, the slag replacement rate of the mixture is recommended to be ~50%, which has preferable mechanical and frost resistance performance. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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25 pages, 48504 KiB  
Article
Mechanical Properties of Furnace Slag and Coal Gangue Mixtures Stabilized by Cement and Fly Ash
by Hongbo Li, Hubiao Zhang, Pengfei Yan, Changyu Yan and Yufei Tong
Materials 2021, 14(22), 7103; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14227103 - 22 Nov 2021
Cited by 8 | Viewed by 1698
Abstract
The mechanical properties and strength formation mechanism of cement–fly-ash-stabilized slag–coal gangue mixture were examined using an unconfined compressive strength test, splitting strength test, triaxial test, and scanning electron microscopy to solve the limitations of land occupation and environmental pollution that is caused by [...] Read more.
The mechanical properties and strength formation mechanism of cement–fly-ash-stabilized slag–coal gangue mixture were examined using an unconfined compressive strength test, splitting strength test, triaxial test, and scanning electron microscopy to solve the limitations of land occupation and environmental pollution that is caused by fly ash from the Xixia District thermal power plant in Yinchuan, slag from the Ningdong slag yard, and washed coal gangue. Its performance as a pavement base mixture on the road was investigated. The results demonstrated that as the slag replacement rate increased, the maximum water content increased while the maximum dry density decreased. The addition of slag reduced the unconfined compressive strength and splitting strength of the specimens; furthermore, the higher the slag substitution rate, the lower the unconfined compressive strength and splitting strength of the specimens. As the cement content increased, the specimen’s unconfined compressive strength increased. Based on the principle of considering the mechanical properties and economic concerns, the slag replacement rate in the actual construction should be ~50% and should not exceed 75%. Based on the relationship between the compressive strength and splitting strength of ordinary concrete, the relationship model between the unconfined compressive strength and splitting strength of cement–fly-ash-stabilized slag–coal gangue was established. The failure mode, stress–strain curve, peak stress, and failure criterion of these specimens were analyzed based on the triaxial test results, and the relationship formulas between the slag substitution rate, cement content, peak stress, and confining pressure were fitted. As per the SEM results, the mixture’s hydration products primarily included amorphous colloidal C-S-H, needle rod ettringite AFt, unhydrated cement clinker particles, and fly ash particles. The analysis of the mixture’s strength formation mechanism showed that the mixture’s strength was the comprehensive embodiment of all factors, such as the microaggregate effect, secondary hydration reaction, and material characteristics. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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19 pages, 37885 KiB  
Article
Numerical Investigation of Composite Behavior and Strength of Rectangular Concrete-Filled Cold-Formed Steel Tubular Stub Columns
by Liping Wang, Yanan An, Faxing Ding, Yachuan Kuang, Qing Ma, Sui Tan, Weizhen Zhang, Pengzhou Zhao and Enhui Ren
Materials 2021, 14(20), 6221; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14206221 - 19 Oct 2021
Cited by 3 | Viewed by 1849
Abstract
The objective of this study was to investigate the composite behavior of rectangular concrete-filled cold-formed steel (CFS) tubular stub columns under axial compression. A fine finite 3D solid element model of rectangular concrete-filled cold-formed steel tubular stub column was established by ABAQUS, which [...] Read more.
The objective of this study was to investigate the composite behavior of rectangular concrete-filled cold-formed steel (CFS) tubular stub columns under axial compression. A fine finite 3D solid element model of rectangular concrete-filled cold-formed steel tubular stub column was established by ABAQUS, which utilized a constitutive model of cold-formed steel considering the cold-forming effect and a triaxial plastic-damage constitutive model of the infilled concrete. Good agreement was achieved and the average discrepancy between the experimental and FE results was less than 5%. Based on the verified models, a further parametric analysis was carried out to reveal the influence of various factors on the strength and behavior of the concrete-filled rectangular cold-formed steel tubular stub columns. The factors included constitutive models adopted for cold-formed steel, length over width ratio of the rectangular section, wall-thickness and width, and concrete strength and yield strength of the cold-formed steel. A total of 144 FE models were analyzed. The stress nephogram was reasonably simplified in accordance with the limit state and a theoretical formula considering confinement coefficient was proposed to estimate the ultimate bearing capacity of concrete-filled rectangular cold-formed steel tubular stub columns using the superposition method. The calculated results showed satisfactory agreement with both the experimental and FE results, which proved the validity and accuracy of the formula proposed in this paper. In the proposed formula, the confinement coefficient of square concrete-filled cold-formed steel tubular stub columns is larger than that of hot-rolled steel counterparts but smaller than that of the stainless steel counterparts. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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Review

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25 pages, 6255 KiB  
Review
Review of Modeling Techniques for Analysis and Assessment of RC Beam–Column Joints Subjected to Seismic Loads
by Muhammad Ilyas, Awais Ahmad, Abdullah Riaz, Fayaz Ahmad Khan, Sadaf Sher, Muhammad Waseem, Syeda Zunaira Ali, Yasir Irfan Badrashi, Hafiz Ahmed Waqas, Hermann Seitz, Khan Shahzada and Megersa Kebede Leta
Materials 2022, 15(21), 7448; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15217448 - 24 Oct 2022
Cited by 2 | Viewed by 1423
Abstract
Beam–column connections are the most critical components of reinforced concrete (RC) structures. They serve as a load transfer path and take a significant portion of the overall shear. Joints in RC structures constructed with no seismic provisions have an insufficient capacity and ductility [...] Read more.
Beam–column connections are the most critical components of reinforced concrete (RC) structures. They serve as a load transfer path and take a significant portion of the overall shear. Joints in RC structures constructed with no seismic provisions have an insufficient capacity and ductility under lateral loading and can cause the progressive failure of the entire structure. The joint may fail in the shear prior to the connecting beam and column elements. Therefore, several modeling techniques have been devised in the past to capture the non-linear response of such joints. Modeling techniques used to capture the non-linear response of reinforced-concrete-beam–column joints range from simplified lumped plasticity models to detailed fiber-based finite element (FE) models. The macro-modeling technique for joint modeling is highly efficient in terms of the computational effort, analysis time, and computer memory requirements, and is one of the most widely used modeling techniques. The non-linear shear response of the joint panel and interface bond–slip mechanism are concentrated in zero-length linear and rotational springs while the connecting elements are modeled through elastic elements. The shear response of joint panels has also been captured through rigid panel boundary elements with rotational springs. The computational efficiency of these models is significantly high compared to continuum models, as each joint act as a separate supe-element. This paper aims to provide an up-to-date review of macro-modeling techniques for the analysis and assessment of RC-beam–column connections subjected to lateral loads. A thorough understanding of existing models is necessary for developing new mechanically adequate and computationally efficient joint models for the analysis and assessment of deficient RC connections. This paper will provide a basis for further research on the topic and will assist in the modification and optimization of existing models. As each model is critically evaluated, and their respective capabilities and limitations are explored, it should help researchers to improve and build on modeling techniques both in terms of accuracy and computational efficiency. Full article
(This article belongs to the Special Issue Confined Concrete and Its Application in Structural Engineering)
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