Strength Of Concrete Increases Research Articles

Experimental and numerical investigation on seismic performance of SFRC shear walls with CFRP bars

In order to investigate the seismic performance of steel fiber reinforced concrete (SFRC) shear walls with CFRP bars, quasi-static tests were conducted on six full-scale shear walls with a shear span ratio of 2.0, including one steel bars reinforced ordinary concrete (RC) shear wall, one CFRP bars reinforced ordinary concrete (CRC) shear wall and four CFRP bars reinforced SFRC (CSFRC) shear walls. The variables included steel fiber volume fraction (SFVF), axial load ratio and concrete strength grade. The experimental results showed increasing the SFVF could significantly decrease the concrete damage level and improve repairability. Meanwhile, the bearing capacity, ductility, and energy dissipation capacity all improved, and the stiffness degradation slowed. Compared to RC shear wall, the peak load of the CSFRC shear wall with SFVFs of 0 %, 0.75 % and 1.5 % increased by 16.36 %, 30.06 % and 46.01 %, respectively. The residual drift ratio decreased by 54.75 %, 61.61 %, and 52.98 % at 2.2 % drift ratio, respectively. Compared to CRC shear wall, the cumulative energy dissipation of the CSFRC shear wall with SFVFs of 0.75 % and 1.5 % increased by 39.54 % and 94.10 %; and the ductility increased by 5.12 % and 18.06 %, respectively. These improvements indicated that applying SFRC with SFVFs of 0.75 % and 1.5 % to shear walls reinforced with CFRP bars could effectively improve the seismic performance and compensate for the shortcomings of resilient shear walls. In addition, increasing the axial load ratio improved the bearing capacity, but decreased deformation capacity and accelerated stiffness degradation. An increase in concrete strength significantly improved the bearing capacity, stiffness and energy dissipation but reduced ductility. Meanwhile, the stability of lateral loads at large drift ratios weakened. Additionally, a detailed finite element model (FEM) was established using DIANA and the accuracy was verified by comparing the simulation and experimental results. Subsequently, parametric analyses were carried out to study the effects of shear span ratio, CFRP bar ratio, and wall thickness on the seismic behaviour of CSFRC shear walls.

Bond properties of deformed steel bars coated with quartz sand modified enamel in concrete under both monotonic and reversed cyclic loading

Reinforced concrete structures located in seismic zones require significant ductility, which is affected by the bond properties between steel and concrete. The bond may be negatively impacted by anti-corrosion coatings. Quartz sand modified enamel (QSME) enhances the bond ductility for steel rebars in concrete under monotonic loading. This study investigates the bond properties of QSME-coated deformed steel rebars under monotonic and cyclic loading. For comparison, uncoated, fusion-bonded epoxy (FBE)-coated, and unmodified enamel-coated steel rebars are also studied. In addition to the coating type, the effects of steel rebar diameter, anchorage length, and concrete strength are considered. Acoustic emission (AE) technique was utilized to capture the AE energy released during the pull-out tests. Results showed that the bond stiffness and strength properties of QSME-coated steel rebars increase when concrete strength increases, while they decrease with rebar diameter under monotonic loading. The energy dissipation capacity of QSME-coated deformed rebar specimens is in average 1.43, 2.11, and 1.56 times greater than that of uncoated, FBE- and enamel-coated specimens, respectively. Among all coating types, the QSME-coated steel rebars exhibit the highest degradation index for the residual bond strength and the most AE activity, attributed to their improved chemical bonding and interfacial friction.

A novel bio-based water reducer for concrete application: Facile process and techno-economic analysis of xylonate bioproduction from lignocellulosic residues

The xylonate was bioproduced directly from lignocellulosic residues, and the application properties of crude xylonate powder were investigated with a promising potential as a bio-based concrete water reducer. The overall integrated process was evaluated on the view of mass balance and techno-economic analysis using Aspen Plus modeling. 56 g/L of calcium xylonate (XA-Ca) can be obtained within 8 h from acidic corncob hydrolysate (ACH) at a 100 % yield with the whole-cell catalysis of Gluconobacter oxydans. At the addition of 0.2 wt% in the dry concrete content, XA-Ca powder and sodium xylonate powder prepared from pure xylose and ACH could reduce water used in concrete by 15 %, 14 %, 13 %, and 13 %, respectively. XA-Ca from ACH led to a 33% increase in concrete compressive strength and a 24% increase in concrete flexural strength at day 7 compared to the blank group. The techno-economic analysis showed the minimum XA-Ca powder price to be $ 0.806/kg which can be economically feasible. This study provides a practical and economical process prototype for the industrial concrete water reducer application of novel bio-based xylonate produced from lignocellulosic residues.

Analysis of the influence of water qualities on the strength of concrete

Concrete is commonly employed in construction for its tremendous compressive strength, despite its low tensile strength. This study aimed at analyzing the strength of concrete when mixed with water of varying qualities. Before concrete is formulated, tests are done on the aggregates to ascertain the right proportions but not on water used. Dreux-Gorrise concrete formulation method was employed. CAMWATER (tap water), rain water and water from a free-flowing river was used to cast concrete samples after which it was crushed to obtain 7 and 28 day resistances. The water qualities varied were pH and hardness. Hydrochloric acid and sodium hydroxide were used to vary the pH of water. Results showed an increase in concrete strength as a function of increase in water pH. Water with a high pH resulted in concrete with an appreciable strength value while acidic water resulted in very low strength values. The usage of hard water for mixing concrete resulted in a strength value lower than with soft water. Conclusively, water quality has an effect on the strength of concrete. Therefore, it is advisable to use water with a high pH value for mixing concrete, preferring rainwater over tap water when mixing concrete due to hardness of water.

A Sustainable Steel-GFRP Composite Bars Reinforced Concrete Structure: Investigation of the Bonding Performance

Steel-fiber reinforced polymer (FRP) composite bars (SFCBs) can enhance the controllability of damage in concrete structures; thus, studying the interfacial bonding between them is fundamental and a prerequisite for achieving deformation coordination and collaboration. However, research on the interfacial bonding performance between SFCBs and concrete remains inadequate. This study conducted central pullout tests on SFCB-concrete specimens with different concrete strengths (C30, C50, and C70), bar diameters (12, 16 and 20 mm), and hoop reinforcement constraints, analyzing variations in failure modes, bond-slip curves, bond strength, etc. Additionally, finite element simulations were performed using ABAQUS software to further validate the bonding mechanism of SFCB-concrete. The results showed that the failure mode of the specimens was related to the confinement effect on the bars. Insufficient concrete cover and lack of hoop restraint led to splitting failure, whereas pullout failure occurred otherwise. For the specimens with pullout failure, the interfacial damage between the SFCB and concrete was mainly caused by the surface fibers wear of the bar and the shear of the concrete lugs, which indicated that the bond of the SFCB-concrete interface consisted mainly of mechanical interlocking forces. In addition, the variation of concrete strength as well as bar diameter did not affect the bond-slip relationship of SFCB-concrete. However, the bond strength of SFCB-concrete increased with the increase of concrete strength. For example, compared with C30 concrete, when the concrete strength was increased to C70, the bond strength of the specimens under the same conditions was increased to 50–101.6%. In contrast, the bond strength of the specimens decreased by 13.29–28.71% when the bar diameter was increased from 12 to 14 mm. These discoveries serve as valuable references for the implementation of sustainable SFCB-reinforced concrete structures.

Research on the Crushing of Reinforced Concrete Two-Way Slabs by Pulse Power Discharge Technology

The application of pulse power discharge (PPD) technology in the crushing and dismantling of concrete structures has characteristics related to both green and environmental protection, as well as safety and reliability, with broad application prospects in the construction and municipal engineering fields in dense urban areas. Nevertheless, the research into using this technology to break reinforced concrete (RC) slabs is very limited, while the influence of key parameters on the crushing effect of reinforced concrete slabs is not clear. To solve this problem, a finite element model of an RC slab was established by ABAQUS. The effect of a shock wave generated by PPD on the surrounding concrete was simulated by an explosion-load equivalent, and the development process of concrete crack was simulated by a cohesive force model. Based on the results of the model analysis, the effects of reinforcement spacing, as well as diameter and concrete strength on the crushing effect of RC slabs were investigated. The results show that the increase in reinforcement diameter and the decrease in reinforcement spacing have a significant effect on limiting the development of cracks. According to the development of cracks, they can be divided into three types: edge cracks, cracks between central holes, and cracks between edge holes. The influence of reinforcement spacing and diameter on the first two crack widths is the most obvious. The increase in concrete strength also reduces the width of cracks. Based on the analysis results, the calculation expressions of the crushing effect of the PPD technique on RC slabs were established, which provides theoretical support for the popularization and application of this technique.

Experimental and simulation study on seismic performance of steel‐PVA hybrid fiber cementitious composites‐encased CFST

AbstractSix hybrid steel and PVA fiber cementitious composite (S&PFCC)‐encased concrete‐filled steel tube (CFST) columns were designed and fabricated, and the effects of axial compression ratio, core concrete strength grade and steel tube thickness on the seismic performance of composite columns were studied. The test results show that the increase of core concrete strength can obviously improve the bearing capacity and energy dissipation capacity of composite column and can restrain the strain growth rate of steel tube after yielding. Low axial compression ratio and thicker steel tube thickness can improve the overall seismic performance of composite columns. Three calculation methods are modified, and the modified An method can predict the lateral bearing capacity of composite column well. Finally, based on the OpenSees finite element software, the seismic performance of the CFST column wrapped in S&PFCC is simulated to verify the test, and the numerical study shows that the seismic performance of the composite column can be optimized by increasing the steel fiber content, while PVA fiber has a weak effect in the elastic stage, and can effectively improve the ductility of the composite column in the plastic stage.

An experimental study of the relationship between modulus of elasticity, Poisson's ratio, and the mechanical properties of high-performance concrete

This study investigated the mechanical properties of high-performance concrete (HPC) with the percentage of mineral admixtures. HPC is a good choice for multi-story buildings because it has many advantages. As HPC becomes more popular, it is important to research its properties. This study used the P.C. Aitcin method to design HPC mixes with compressive strengths of 60 to 80 MPa. Fly ash is used for M60 and M70 grade HPC and Silica Fume is used for M80 grade HPC is used as mineral admixture as a 20% replacement for cement. In this research paper, the study of properties of the different ingredients used to make HPC is carried out. The testing of three concrete mixes for mechanical properties such as compressive strength, split tensile strength, modulus of elasticity, and flexural strength, as well as other important properties is done. This study explores High-Performance Concrete (HPC) by precisely controlling the water-to-cement ratio and incorporating mineral and chemical admixtures, achieving strengths from 60 to 80 MPa. It investigates key mechanical properties, establishes empirical equations, and compares findings with codes and literature. The results showed that a lower water-to-binder ratio (w/b) led to better mechanical properties. The experimental program includes the casting of 39 cubes, 39 cylinders, 39 beams and 81 columns to test the physical properties of different concrete grades. The use of a compression testing machine with a load capacity of 3000 kN to test the HPC cubes and a loading frame with a load capacity of 2000 kN to test the columns. The average compressive strength for HPC M60 to M80 was 65.40 MPa, 73.45 MPa, and 82.64 MPa respectively. The modulus of elasticity values ranged from 40 to 50 GPa. The findings of the study showed that an increase in concrete strength correlated with a decrease in the average value of Poisson's ratio. Overall, the study suggests that HPC is a good choice for high-rise buildings because it has many advantages. As HPC becomes more popular, it is important to research its mechanical properties. This study provides valuable results about the mechanical properties of HPC in comparison with IS 456:2000. From the experimental results of tested columns, it was observed that as the load increased, the deflection decreased for both uniaxially and biaxially loaded columns, highlighting the novelty of this finding. Additionally, the columns subjected to biaxial loading displayed greater sensitivity compared to their axial and uniaxial loading.

Compressive performance of eccentrically double-cell concrete-filled circular steel tubular columns

This paper presents a series of tests conducted on axial compression of concrete-filled steel tubes with double inner circular steel tubes (DIC-CFST) stub columns. The DIC-CFST stub columns are composed of four elements: an outer circular steel tube, two inner hollow circular steel tubes arranged symmetrically along the diameter of the outer tube, and concrete filling the space between the three steel tubes. A total of 27 specimens with varying eccentricity ratio (e), hollow ratio (ψ), and concrete strength (C) were subjected to the tests. The results indicate that under axial compression, noticeable local buckling failures occur in both the inner and outer steel tubes. Concrete failure manifests as vertical through cracks and circumferential crushing zones. The load-deformation curve of the specimens remains essentially the same as that of a full-section concrete-filled steel tube. A general positive correlation exists between the ultimate bearing capacity and the strength of concrete, and the range of eccentricity ratio and hollow ratio significantly influences the relationship between these two parameters and the ultimate bearing capacity of the specimens. As the concrete strength increases, the initial stiffness exhibits a noticeable increase. Conversely, the initial stiffness experiences a significant reduction with an increase in the hollow ratio. The ductility decreases with increasing concrete strength and eccentricity ratio. Furthermore, in comparison to the AISC 360–10 Specification, Eurocode 4, and Han's method, the calculation formula proposed in this paper for determining the ultimate bearing capacity of DIC-CFST stub columns has exhibited superior accuracy.

Finite Element Analysis of Axial Compression Behavior of L-Shaped Concrete-Filled Steel Tubular Columns with Different Combinations

L-shaped concrete-filled steel tubular (CFST) columns, a kind of structural member appropriate for high-rise buildings, not only avoid the defect of conventional square columns protruding from the wall but also have the green and low-carbon properties of steel structures appropriate for fabricated construction. To learn more about their axial compression behavior, refined 3D finite element models were established using the general finite element software ABAQUS. The reliability of the models was subsequently verified based on failure tests and load–displacement relation tests on eight L-shaped specimens. The axial compression mechanism of L-shaped CFST columns was investigated using the verified finite element models. Further systematic parameter analysis was carried out to investigate the influence of parameters such as steel strength, concrete strength, length ratio of long limb to short limb, the angle between the two limbs, and combination methods on the axial compression behavior of L-shaped CFST columns. The results demonstrate that the angle between the two limbs has a significant impact on the stress distribution of concrete and steel pipes. The corner effect increases as the angle between the two limbs decreases. The combination of F-type specimens can better exert the constraint effect of steel pipes on concrete, while the triangular cavity of unequal-limb specimens and specimens with an included angle of 60° cannot effectively trigger the interaction between steel pipes and concrete. The initial stiffness of L-shaped CFST columns increases with an increase in concrete strength and a decrease in limb length ratio, which is not sensitive to changes in steel strength and the included angle. The peak bearing capacity of the specimens increases with increases in steel strength and concrete strength and a decrease in the limb length ratio. Compared to C-type and Z-type specimens, the initial stiffness of F-type specimens is slightly higher, and the peak bearing capacity is significantly increased.

To Study the Strength Characteristics of Concrete Using Mineral Admixture

Aside from the combustion of fossil fuels, the cement making business emits carbon dioxide. The global cement industry accounts for around 7% of greenhouse gas emissions into the earth's atmosphere. To address the environmental impacts connected with cement manufacturing, alternative concrete binders must be developed. Another important environmental concern is the extraction of natural resources such as sand from river bottoms. As a result, substantial study into the use of cement substitutes, including several waste materials and industrial byproducts, is continuing. Bamboo leaf ash was utilised as a partial replacement for cement and fenugreek as an addition in this study, and it was compared to standard concrete. The considered bamboo leaf ash was 5%, 10%, 15% by weight of cement for M25 grade concrete and 5% of fenugreek powder as additive for every mix [1]. Additionally, an experimental investigation of the effects of using bamboo leaf ash in place of some of the cement and fenugreek powder as an additive on the performance of concrete in terms of compressive strength and flexure strength. Concrete is cast for the experimental study, and cement is partially substituted with bamboo leaf ash by weight of cement and fenugreek powder as an addition. Because the inclusion of bamboo leaf ash and fenugreek powder works as a binding ingredient in the concrete, the compressive and flexural strength increases. Finally, the compressive and flexural strengths for the combination of bamboo leaf ash as a partial replacement and fenugreek powder as an addition powder in concrete are investigated for the best results obtained from the aforementioned experiment.

Experimental Study On Strength of Concrete Using Nano silica

The test on hardened concrete were destructive test on cube for size (150×150×150 mm) at 7, 14, 28 days of curing as per IS: 516-1959, flexural strength test on beam (100×100×500 mm) at 7, 14, 28 days of curing as per IS: 516-1959 and split tensile strength test on cylinder (100mmφ×200mm) at7, 14, 28 days of curing as per IS: 5816-1999. The primary aim of this study is to assess the effectiveness of silica fume as a pozzolanic material for replacing cement in concrete. It is anticipated that incorporating silica fume into concrete will enhance its strength properties. In this study, the combination of 5% nanosilica and 10%metakaolin which replaced part of the cement had the best results in the Mechanical properties of concrete with a 15% increase in the compressive strength and a 40%increase in the flexural and tensile strength of concrete.

The effect on punching shear failure in centrally loaded ground-supported concrete slabs for different aspects like slab thickness, size and the position of reinforcement bar, and the strength of concrete using a validated FE model

The effect of slab thickness, presence of reinforcement and concrete strength on punching shear capacity of the ground-supported concrete slabs (GSCS) is an important issue in Industrial Ground-supported slab construction. In this study, a three-dimensional nonlinear finite element (FE) model for GSCS was validated with three experimental results from literature and used to assess those effects. A Concrete damaged plasticity model in ABAQUS2020 software with a suitable simulation technique and the theory-based material property was adopted. The results of FE models and predictions of the Technical Report34 (TR34) of the Concrete Society were compared with the experimental results. The average FE predicted/Experimental punching shear capacity ratio was 0.93 with a 0.06 standard deviation and the average TR34 predicted/Experimental punching shear capacity ratio was 1.01 with 0.06 standard deviation. However, the average TR34 predicted/FE predicted punching shear capacity ratio was 1.08 with a 0.13 standard deviation. TR34 prediction was little bit liberal. The results of 72 FE models were compared with the TR34 prediction. The average TR34 predicted/FE predicted punching shear capacity ratio is 1.17 with a 0.21 standard deviation. TR34 prediction was liberal compared to FE prediction. The study showed that the effects of an increase of Slab thickness, Concrete strength, and reinforcement were positive in both FE and TR34 predictions, whereas TR34 predictions were conservative up to a certain slab thickness around 115–130mm for concrete grade 20–40 MPa. As concrete strength and thickness increase, TR34 predictions become more liberal. The bottom layer reinforcement provides greater strength, however, TR34 was unable to predict that.

Static performance of precast concrete arches with carbon fiber reinforced polymer reinforcement

In this paper, static performances of a new precast concrete arch system with carbon fiber reinforced polymer (CFRP) reinforcement were investigated. Varied concrete strengths and segment types of precast concrete arches were tested. The results show that the increase of concrete strength can improve the bearing capacity of the precast arches with CFRP reinforcement. The ultimate bearing capacity of the precast arches segmented at the arch vault with CFRP reinforcement can reach or even exceed that of complete arches, while the precast arch segmented at the shoulder had lower ultimate load. A theoretical analysis method was proposed to predict the failure and bearing capacity of the precast concrete arches with CFRP reinforcement, which were found to be in close agreement with the experimental result.

The influence of cyclic temperature and humidity effects on the compressive strength of heavy concrete

The paper presents the results of experimental studies of the effect of cyclic exposure to elevated temperatures up to 90оС and 150оС and moistening to full water saturation on the strength of heavy concrete. Quantitative data on the change of concrete strength properties depending on the influence factors are obtained. Proposals are formulated to take into account in calculations the influence of heating and moistening modes on the strength of concrete in axial compression. Under cyclic exposure to elevated temperatures and subsequent moistening at normal temperature, there are significant changes in the compressive strength of concrete at different stages of each cycle. At the short-term heating stage, the reduction in the prismatic strength of the concrete amounted to 15 - 22% of the concrete strength before heating. Prolonged isothermal heating results in a 13 - 25% increase in concrete strength. At the stage of subsequent moistening of concrete after heating, there is a decrease in strength by 25 - 27%, while the relative magnitude of strength reduction does not significantly depend on the number of previous cycles. In the investigated interval of up to twenty-five cycles of exposure to elevated temperatures and moistening, the greatest reduction in concrete strength was observed in the first and last cycles. For cycles with heating temperature up to 90⁰C at short-term heating at the beginning of the second cycle the concrete strength drop was 45.5%, and the concrete strength drop at short-term heating for the 25th cycle was 9.7%. For cycles with heating temperature of 150⁰C the strength drop was 45.9% and 52.5%, respectively. The accepted experimental mode according to the formula of cycle (6+1) + (6+1) is the most unfavorable for the strength of concrete under cyclic effects of elevated temperatures and subsequent moistening.

EXPERIMENTAL STUDY ON STRENGTH OF CONCRETE USING NANO SILICA

Thetestonhardenedconcreteweredestructivetestoncubeforsize(150×150×150 mm) at 7, 14, 28 days of curing as per IS: 516-1959, flexural strength test on beam (100×100×500 mm) at 7, 14, 28 days of curing as per IS:516-1959 and split tensile strength test on cylinder (100mmφ×200mm) at 7,14,28 days of curing as per IS: 5816-1999.The main objective of this work is to study the suitability of the silica fume as a pozzolonic material for cement in concrete. However it is expected that the use of silica fume in concrete improve the strength properties of concrete. In this study the combination of 5% nano silica and 10%metakaolin which replaced part of the cement had the best results in the mechanical properties of concrete with a 15%increase in the compressive strength and 40%increase in the flexural and tensile strength of concrete.

PENGARUH SERAT BUAH PINANG TERHADAP KUAT TEKAN BETON

Concrete material innovations are no emerging more and more and are something that is really needed, one of which is material innovation with the addition of fiber. Fiber concrete is a mixture of concrete plus fiber. The fiber material can be asbestos fiber, plastic fiber (poly-propyline), or pieces of steel wire, plant fibers (hemp, coconut fiber, bamboo, palm fiber). The purpose of adding fiber is to improve or increase the mechanical properties of concrete in the form of tensile strength, compressive strength and flexural strength. This research uses areca nut skin fiber, the skin and seeds are separated, then the betel nut fiber is spread apart so that it does not clump when mixing, then the betel nut fiber is mixed little by little into the concrete mixture. This research aims to determine the effect of adding Areca nut fiber on the compressive strength of concrete aged 7, 14 and 28 days. The percentage of areca nut shell fiber used in this research as 1.6%, 2.4% and 4%. The research used test objects in the form of cubes measuring 15 x 15 x15 cm, with a sample of 12 pieces of concrete, including 9 pieces of concrete with a mixture of betel nut fiber according to each type of concrete aged 7, 14 and 28 days, and 3 pieces of concrete without mixed/normal. The test carried out on the concrete mixture is the compressive strength of the concrete. From the research results obtained, the results of testing the compressive strength of fiber concrete with a percentage of Areca fruit fiber of 1.6% at concrete ages of 7, 14, and 28 days obtained an average compressive strength result of 7.65 MPa, for testing the compressive strength of concrete with a percentage 2.4% for concrete ages of 7, 14 and 28 days experienced a decrease in average compressive strength of 5.88 MPa and for concrete compressive strength testing with a percentage of 4% for concrete ages of 7, 14 and 28 days there as an increase in average concrete compressive strength. The average is 11.43 MPa.

Variation of dynamic elasticity modulus with experimentally determined concrete compressive strength

In reinforced concrete structures, one of the most important factors for structural safety is the quality of concrete. The first thing that comes to mind for concrete quality is the compressive strength of concrete. However, properties such as elasticity modulus are also among the properties that determine concrete quality. Since concrete is a brittle material, different methods are used to determine dynamic elasticity modulus. In practice, dynamic elasticity modulus of concrete can be identified by utilizing concrete compressive strength value. In this context; compressive strength tests were performed on a series of concretes accordingly relevant standards. Since it is difficult to determine elasticity modulus from the stress and strain relationship, the dynamic elasticity modulus values in this study was calculated using empirical formulas according to TS 500-2000, ACI 318-95 and CEB-FIP 1978 on the basis of experimental data in this study. The relationship between the calculated dynamic elasticity modulus values and concrete compressive strength was analyzed. From the study, it is concluded that as concrete compressive strength increases, dynamic elasticity modulus increases for the concrete specimens.

Failure assessment of concrete shear walls under close-in blast based on viscous damage model

In this research, failure of reinforced concrete shear walls under close-in blast is evaluated based on numerical analysis. By introducing the Duvaut–Lions type damage driving stress rate, a dynamic viscous damage evolution law for concrete materials is constructed under the framework of elastoplastic damage theory. The rate effect-induced increase in concrete strength is well captured by the suggested model. For validation, the response of reinforced concrete slabs in blast tests and their mechanical behaviors after explosion were calculated, and the results are in good agreement with the experimental findings. Under blast loads at various scaled distances, the failure of a series of reinforced concrete shear walls with different axial load ratios is simulated, and the post-blast residual bearing capacity is calculated using a three-step loading analysis process. The ratio of the residual axial strength is defined to assess the performance degradation of the shear walls after blast, and the effect of different factors on the failure of structures under blast is examined.

Experimental investigation of the dynamic mechanical properties of concrete under different strain rates and cyclic loading

To investigate the effects of strain rate and cyclic loading on the mechanical parameters of concrete compressive strength, residual strain, peak strain and elastic modulus, a series of cyclic loading tests over concrete were conducted by setting different numbers of cycles, magnitude factors, and cycle frequencies/periods based on the FST-1000 alpine geotechnical dynamic and static triaxial test system. The quantitative relationships between the mechanical parameters of concrete and the parameters of cyclic loading as well as the strain rate were also proposed. The results show that as the strain rate increases, the concrete compressive strength and elastic modulus increase linearly, while the residual strength and peak strain show a decreasing trend. Under cyclic loading, the compressive strength was quadratically related to each cyclic loading parameter, and the elastic modulus was quadratically related to the cyclic number and magnitude factor. The trend of the concrete compressive strength rate sensitivity undergoes a change at the specific thresholds of 0.145 for the magnitude factor and 1.93 Hz for the frequency. The minimum value of the peak strain rate sensitivity corresponds to the specific thresholds of 6023 for the number of cycles, 0.14 for the magnitude factor, and 1.38 Hz for the frequency thresholds, respectively. Additionally, the enhancement of the elastic modulus rate sensitivity occurs when the number of cycles exceeds 918 or when the magnitude factor surpasses 0.33. The results can provide a theoretical basis for the design of concrete structures and seismic engineering.