ECC Strength Research Articles

Comparative analysis of the seismic performance of ECC jacket reinforced columns with different cross-sectional forms subject to different load modes

Based on the high tensile strength and tensile strain of (engineered cementitious composites) ECC, it is applied to the weak link central columns of subway stations to enhance their seismic resilience. In this study, the effects of the column's cross-sectional shape, ECC jacket form, and the vertical gravity load and vertical dynamic load during seismic action on the hysteretic performance of the column were thoroughly analyzed. A constrained constitutive model for cementitious materials, a reinforced hysteresis constitute model, and a calculated damage factor for concrete were adopted to establish a three-dimensional refined column model with an experimentally verified error of less than 10 %. After that, the damage distribution and damage degree of the columns, as well as the changes in hysteretic performance such as hysteretic curve, skeleton curve, energy dissipation, and stiffness degradation were analyzed by the static model analysis. The results showed that the columns had higher damage levels under high frequency and high amplitude of dynamic axial compression ratio in the vertical direction compared to the constant high axial compression ratio, and the ECC jacket could effectively reduce the damage levels of the columns, but the use of the in-built ECC (IB-ECC) jacket was better than the out-sourced ECC (OS-ECC) jacket. In addition, the IB-ECC jacket did not significantly improve the peak bearing capacity of the columns, but significantly improved the ultimate bearing capacity and displacement ductility of the columns, while the OS-ECC jacket significantly improved the peak bearing capacity of the columns. The ECC jacket was also effective in slowing down the stiffness degradation of the columns. This study significantly contributes to the design strategies for enhancing the resilience of columns in subway stations.

Study on the relationship between the double-sided shear strength of ECC and the critical fracture toughness of mode II

To avoid the risk of Type II fracture failure in building structures under pure shear forces, which involves complex experimental elements and is difficult to effectively control. Therefore, studying the relationship between shear strength and type II critical fracture toughness has become particularly crucial. This article studied the uniaxial ultimate tensile strength, cubic compressive strength, double-sided shear strength, and type II critical fracture toughness of ECC using different mix proportions. The results showed that the initiation strength σfti and ultimate tensile strength σftu of ECC with different ratios were found to be M10 > M1 > M2 > M8 > M3 through tensile tests; The compressive strength of ECC cubes with different mix ratios was obtained as M10 > M1 > M8 > M2 > M3, and compared with Nissan fibers, it was found that the influence of fiber types on the compressive strength of ECC was not significant; Linear fitting was performed on the tensile strength, cubic compressive strength, and double-sided shear strength of ECC, and strong correlations were found. The linear fitting coefficient R2 between shear strength and critical fracture toughness is as high as 0.98, indicating that this fitting relationship curve can further understand the mutual influence between shear strength and critical fracture toughness of ECC at different stress levels, and estimate complex Type II fracture toughness through relatively simple shear strength fs, which helps predict the bearing capacity of the structure and provides theoretical support for the improvement and optimization design of ECC.

Prediction of compressive strength of nano-silica modified engineering cementitious composites exposed to high temperatures using hybrid deep learning models

This study estimated the compressive strength of nano-silica-modified engineering cementitious composites subjected to high temperatures using innovative hybrid deep learning models. The innovative hybrid models in this study were designed using autoencoder (AE)-decision tree (DT) and autoencoder (AE)-extreme learning machine (ELM). Additionally, ELM, DT, and deep AE models in this study were designed to compare the results of innovative hybrid deep learning models. The sensitivity analysis was used for the statistical assessment of the experimental results. The input variables of the models were selected as the cement amount, fly ash amount, sand amount, water amount, high-range water reducer amount, PVA (polyvinylalcohol) fiber amount, nano-silica amount, and the degree of exposure to high temperatures. The compressive strength was used as the output variable of the models. The mixture ratio in the experimental study was 583 kg/m3 cement, 467 kg/m3 sand, 700 kg/m3 fly ash, 187 kg/ m3 water, PVA fiber (0.5 %, 1 %, 1.5 % and 2 %) and nano silica (0 %, 1 %, 2 %, 3 % and 4 %) were used. The ELM, DT, and deep AE models estimated the compressive strength of nano-silica-modified engineering cementitious composites subjected to high temperatures with 93.86 %, 77.35 %, and 86.5 % accuracy, respectively. Also, the same compressive strength was estimated with 94.28 % and 98 % accuracy using the hybrid deep AE-DT and AE-ELM models. This study found that the innovative hybrid deep AE-ELM model predicted compressive strength with higher accuracy than the deep AE-DT, DT, ELM, and deep AE models. Additionally, the deep AE-DT model predicted compressive strength with higher accuracy than non-hybrid models. Thus, it can be stated that innovative hybrid deep models are more advantageous than other models in estimating the compressive strength of ECC. The sensitivity analysis obtained that the PVA fiber was the most significant variable affecting the compressive strength results of nano-silica-modified engineering cementitious composites subjected to high temperatures.

Development of engineered cementitious composite with moderate tensile properties using polyester fibers

In recent years, the use of reinforced cementitious composites has increased manifold for structural rehabilitation purposes. The present study concerns the development of a special variant of ECC, which is low-cost but has moderate tensile strength and ductility. Widely available polyester fiber was chosen, which was about ten times cheaper but about four times weaker than the preferred but expensive PVA fibers. Micromechanics-based mathematical model was used for fiber optimization to attain the multiple and strain hardening phenomena of the ECC. Different ECC mixes were prepared to investigate the effect of the matrix toughness on the tensile properties of ECC. ECC, with a strong matrix, failed to attain multiple cracking after 28-days of tensile testing because the fracture toughness exceeded the fiber bridging energy. The matrix was made weaker by increasing the amount of fly ash, and the desired strain hardening phenomena was achieved after 28-days of tensile testing. A low-cost ECC was developed, which used 3% polyester fiber by volume; the tensile strength and strain capacity of ECC was 2.17 MPa and 1.88%, respectively.

Numerical simulation and theoretical analysis on RECC ring beam joints for RECC-encased CFST composite columns

The failure mechanisms of reinforced engineered cementitious composite (RECC) ring beam joints were numerically analysed using finite element (FE) software of ATENA. The failure mode, load-carrying capacity, ductility, and distribution of the strain in the steel reinforcement were comprehensively investigated. The simulation results showed that the RECC ring beam significantly contributed to the mechanical property of the joint. Part of the circumferential reinforcement in the ring beam contributed to the shear strength and improved the strength of the core ECC by the restraint effect. A total of 46 specimens were subsequently investigated to examine the influences of the circumferential reinforcement ratio, stirrup ratio, axial compressive ratio, tensile properties and compressive strength of ECC on the seismic behaviour of RECC ring beam joints. Finally, a simplified softened strut-and-tie model was proposed to predict the shear-carrying capacity of the RECC ring beam joint.

Behavior of Pultruded Glass-Fiber-Reinforced Polymer Beam-Columns Infilled with Engineered Cementitious Composites under Cyclic Loading

Glass-fiber-reinforced polymer (GFRP) is an advanced material that has superior corrosion resistance, a high strength-to-weight ratio, low thermal conductivity, high stiffness, high fatigue strength, and the ability to resist chemical and microbiological compounds. Despite their many advantages compared with traditional materials, GFRP sections exhibit brittle behavior when subjected to severe loading conditions such as earthquakes, which could be overcome by infilling the GFRP sections with concrete. This paper presents the results of an experimental investigation carried out on the cyclic response of a GFRP beam-column infilled with high-volume fly ash engineered cementitious composites (HVFA-ECC) consisting of 60%, 70%, and 80% fly ash as a replacement for cement. Finite element analysis was also conducted using robot structural analysis software, and the results were compared with the experimental results. The mechanical properties of GFRP sections presented are the compressive strength of ECC, the direct tensile strength of ECC determined using a dog-bone-shaped ECC specimen, the hysteresis behavior of the beam-column, and the energy dissipation characteristics. The lateral load-carrying capacity of beam-column GFRP infilled with HVFA-ECC consisting of 60%, 70%, and 80% fly ash was found to be, respectively, 43%, 31%, and 20% higher than the capacity of GFRP beam-columns without any infill. Hence the GFRP sections infilled with HVFA-ECC could be used as lightweight structural components in buildings to be constructed in earthquake-prone areas. Also in the structural components, as 70% of cement could be replaced with fly ash, it can potentially lead to sustainable construction.

Sectional Analysis of Reinforced Engineered Cementitious Composite Columns Subjected to Combined Lateral Load and Axial Compression

The ultra-high tensile ductility of ECC provides an alternative way to enhance the ductility of structural members by using high-ductile matrix material instead of simply increasing reinforcements. However, the application of ECC members is still limited due to the relatively short research time and the lack of design specifications. Being equivalent to eccentric compressive members, a sectional analysis of RECC columns subjected to combined lateral load and axial compression are proposed in this paper. Based on the design theory of load capacity of eccentric compression columns and the unique constitutive model of ECC, the calculation equations for the sectional load capacity of RECC columns are derived. The analytical prediction of the load capacity of RECC column is evaluated in comparison with that of experiments that confirm the capacity of the proposed calculation method to capture the behavior of the RECC column accurately. The strength-interaction diagrams showing the axial force-moment (N-M) interaction curves are then constructed for analysis using the proposed calculation equations. A parametric study is also carried out by using the proposed calculation equations, demonstrating the effects of ultimate tensile strain of ECC, compressive and tensile strength of ECC, yield strength of steel bar, and reinforcement ratio on the N-M interaction curves of RECC columns. The investigations exhibited in this paper are expected to provide insight into the design principles of RECC columns.

Effect of splitting bond on shear response of reinforced engineered cementitious composite short columns under cyclic loading

The effect of splitting bond on shear response of reinforced engineered cementitious composites (RECC) short columns under cyclic loading is experimentally investigated in this paper. Nine RECC short columns were designed to test the effect of axial load ratio, stirrup spacing and shear span-to-depth ratio on their cyclic response, and one reinforced concrete (RC) short column was prepared for comparison. The test results show that the RC short column failed in shear-splitting bond failure (shear accompanied by splitting bond) with poor plastic deformation and low energy dissipation. Splitting bond failure was effectively delayed in RECC short columns due to the high tensile strength and ductility of ECC, the RECC short columns failed in shear-splitting bond failure with ductile characteristics and thus exhibited improved cyclic response. In particular, the RECC short column corresponding to the control RC short column gained a 54.5% and a 60.7% improvement in ultimate drift ratio and cumulative energy dissipation, respectively. Additionally, a series of formulas based on truss-arch model was proposed to predict the shear strength of RECC short columns controlled by splitting bond, and the proposed model gives reasonable calculated results compared with the test results.

The Isometric And Eccentric Grip Strength In Athletes And Controls.

PURPOSE: To compare the characteristics of eccentric grip strength among athletes, elite climbers, and normal healthy subjects. METHODS: A total of 17 male subjects, including 8 athletes (age, 23.3 ± 3.1 years; height, 173.7 ± 3.6 cm; weight 71.4 ± 5.6 kg), 3 elite climbers (age, 19.3 ± 1.2 years; height, 162.8 ± 4.3 cm; weight 58.3 ± 3.1 kg), and 6male healthy control subjects (age, 26.0 ± 5.8 years; height, 172.3 ± 3.3 cm; weight, 64.0 ± 7.0 kg), participated in this study. They performed two maximal voluntary contraction tests (i.e., isometric [ISO], and eccentric [ECC] contraction) using a handgrip dynamometer (Takei, Co., Ltd, Tokyo, Japan) and original device utilized an AC servo motor (60 W class) to generate eccentric force at a constant speed of 32.67 mm/s. These tests were performed using the right hand. The values were calculated relative to body mass. RESULTS: ECC grip strength relative to body mass in athletes was higher than that in control subjects (p = 0.02, 1.15 ± 0.2 kg vs. 0.90 ± 0.2 kg). In particular, elite climbers showed higher ECC grip strength compared to athletes and control subjects (1.35 ± 0.1 kg, 1.08 ± 0.1 kg, and 0.88 ± 0.2 kg, respectively). There was no significant difference in ISO grip strength between athletes and control subjects. However, ISO grip strength relative to body mass in climbers was higher than those in athletes and control subjects (0.82 ± 0.1 kg, 0.69 ± 0.1 kg, and 0.67 ± 0.1 kg, respectively). The effect sizes of ECC and ISO grip strength relative to body mass between athletes and control subjects were 1.5 and 0.5, respectively. CONCLUSIONS: Our results suggest that eccentric grip strength might be more effectively manifested in athletes rather than isometric grip strength, especially in climbers.

Evaluation of novel jointless engineered cementitious composite ultrathin whitetopping (ECC-UTW) overlay

The objective of this study was to evaluate the construction, material characterization, initial structural assessment, and cost of a novel jointless Engineered Cementitious Composite Ultra-Thin Whitetopping (ECC-UTW) overlay. After construction, early-age cracks (from less than 0.25 mm to up to 2.54 mm width) were observed in the 101.6-mm (4 in.) jointless ECC-UTW section; yet, the majority of the cracks coincided with areas where fiber clumps were observed during construction and places of heavy instrumentation. On the other hand, no cracks were observed in the 63.5-mm (2.5 in.) jointless ECC-UTW at early ages; yet, when winter arrived, micro-cracks (<0.25 mm in width) developed. These micro-cracks were attributed to the normal functioning of the ductile pseudo strain-hardening (PSH) mechanism of ECC materials. Falling Weight Deflectometer (FWD) evaluation conducted before and after the construction of the UTWs showed a significant reduction in pavement deflection after construction. This deflection reduction was much more substantial for thicker 101.6-mm UTWs; yet, no major difference in deflection reduction was found between the 101.6-mm ECC and the 101.6-mm regular concrete UTW sections. The 28-day compressive and flexural strength of ECC evaluated from field specimens underperformed that of previous studies by 9.6% and 14.8%, respectively; however, deflection capacity slightly outperformed that of previous studies by 4.1%. The flexural performance of the ECC material was vastly superior to that of regular concrete exceeding the flexural strength by 92%. All specimens evaluated in uniaxial tension exhibited a PSH behavior after first-cracking; however, the tensile strength and tensile ductility values obtained underperformed expected values for ECC M3-15% and exhibited substantial variability. Uniaxial tensile test results from field specimens were deemed unreliable. Cost analysis results showed that a cost reduction of 14.8% per lane kilometer is expected by implementing the proposed jointless ECC-UTW system compared to that of the regular jointed concrete UTW. The greatest construction cost savings for utilizing ECC originates from its potential jointless attribute and its reduced thickness.

Survey of Eccentric-Based Strength and Conditioning Practices in Sport

McNeill, C, Beaven, CM, McMaster, DT, and Gill, N. Survey of eccentric-based strength and conditioning practices in sport. J Strength Cond Res 34(10): 2769-2775, 2020-Eccentric-based training (ECC) has been shown to be an effective training strategy in athletes; however, despite the theoretical benefits, the uptake by practitioners is currently unknown. This study investigated the current ECC strength and conditioning practices that are implemented in the training of athletes. Two hundred twenty-four practitioners were electronically surveyed anonymously with 98 responses available for analysis. Nearly all respondents (96%) had prescribed ECC in the last 24 months. Sport performance (64%), injury prevention (24%), and rehabilitation (8%) were the top-ranked reasons to include ECC. Respondents programmed ECC for strength (35%), hypertrophy (19%), and power (18%). A majority of respondents did not monitor ECC load (58%) or use eccentric-specific testing (75%). Seventeen respondents commented that high-intensity training such as sprinting and change of direction, were avoided during ECC blocks. Eccentric-based training intensity was prescribed as percentage of 1 repetition maximum (34%), rate of perceived exertion (20%), or velocity (16%). Respondents indicated muscle soreness and concurrent high-intensity activities were concerns during ECC but reported not using eccentric monitoring or testing. The efficacy of ECC is well supported, yet there seems to be a lack of defined protocol for integrating ECC research into practice. A greater understanding of eccentric contribution to sport performance and injury prevention may help define testing and monitoring procedures for the prescription of ECC interventions. Practitioners should consider factors such as periodization, soreness, and monitoring when designing ECC programs. The findings of this survey indicate that no uniform strategies exist for the prescription of ECC among experienced practitioners.

Investigation on interface fracture properties and nonlinear fracture model between ECC and concrete subjected to salt freeze-thaw cycles

The work aims at investigating on interface fracture properties and nonlinear fracture model between ECC and concrete under salt freeze-thaw cycles. Based on the interface nonlinear fracture mechanism, a three-parameter nonlinear fracture model was proposed to comprehensive and accurately reflect the degradation law of interface fracture properties under salt freeze-thaw cycles. The experimental results showed that the salt freeze-thaw erosion had a very negative effect on interface fracture properties. Moreover, the occurrence of interface fracture under salt freeze-thaw cycles was affected remarkably by ECC strength grade, and the higher ECC strength always leads to later occurrences of interface fracture. Regardless of cycles, the fracture propagation process of all specimens included three phases: initial crack, stable crack propagation, and instability failure. Moreover, the three phases all occurred at the interface, and the crack did not extend to ECC or concrete substrate. Meanwhile, the fibers bridging effect was very significant at the phases of crack stable propagation and instability failure. Only one kind of wedge-splitting load-crack mouth opening displacement (CMOD) curve was observed. As number of cycles increased, slope of rising section curve and ultimate wedge-splitting loads all gradually decreased, while the CMOD corresponding to ultimate splitting load had little change. The salt freeze-thaw erosion had a very negative effect on three fracture parameters. Moreover, the three fracture parameters all decreased continuously with the increasing number of cycles.

Flexural Performance of Steel Reinforced ECC-Concrete Composite Beams Subjected to Freeze\u2013Thaw Cycles

Experimental and theoretical investigations on the flexural performance of steel reinforced ECC-concrete composite beams subjected to freeze–thaw cycles are presented in this paper. Four groups of reinforced composite beams with different ECC height replacement ratios subject to 0, 50, 100 and 150 cycles of freeze–thaw were physically tested to failure. Experimental results show that the bending capacity decreases with the increase of freeze–thaw cycles regardless of ECC height replacement ratios. However, the ultimate moment, stiffness and durability of ECC specimens and ECC-concrete composite specimens are greater than those of traditional concrete specimens, owing to the excellent tensile performance of ECC materials. With the increase of ECC height, the crack width and average crack spacing gradually decrease. According to materials’ constitutive models, compatibility and equilibrium conditions, three failure modes with two boundary failure conditions are proposed. Simplified formulas for the moment capacity are also developed. The results predicted by the simplified formulas show good agreement with the experimental moment capacity and failure modes. A parametric analysis is conducted to study the influence of strength and height of ECC, amount of reinforcement, concrete strength and cycles of freeze–thaw on moment capacity and curvature ductility of ECC-concrete composite beams.

Compressive behaviour of engineered cementitious composites and concrete encased steel composite columns

This paper presents the results of an experimental study on the compressive behaviour of engineered cementitious composites and concrete encased steel (ECC-CES) composite columns. Two configurations of ECC-CES composite columns based on fully and partially concrete encasement were considered. A total of eleven short columns with different ECC and concrete encasing configurations were tested under pure compression. The effects of ECC strength, concrete strength and column configuration on the column compressive behaviour were investigated and reported in terms of failure modes, load-deformation curves, ductility and toughness. In addition, in order to study the confinement effect of different thickness ECC covers on high strength concrete (HSC), three ECC encased HSC short columns without encased steel section were also tested. The experimental results were compared with the ultimate strength predictions from different design codes for the tested columns. It was found that current design guidelines were generally conservative. Therefore, new equations with modified factors to predict the ultimate strength of ECC-CES columns were proposed. Finally, a comparison of performance of ECC-CES with conventional CES columns suggested that the ECC encasement could provide an alternative way to confine concrete core in columns applications.

Investigation of damage behaviors of ECC-to-concrete interface and damage prediction model under salt freeze-thaw cycles

This paper reveals an investigation of damage behaviors of ECC-to-concrete interface with various ECC strength grades and interface roughness of concrete substrate subjected to salt freeze-thaw cycles. The test results showed that salt freeze-thaw cycles had significant negative influences on bonding behaviors of ECC-to-concrete interface. The occurrence of interface fracture and degradation of interface shear strength under salt freeze-thaw cycles could be significantly influenced by ECC strength grade and interface roughness of substrate concrete. The lower ECC strength and the smoother interface always caused earlier occurrences of interface fracture under salt freeze-thaw cycles. Besides, the lower ECC strength and the smoother interface always caused earlier occurrences of a sharp decline of interface shear strength and more decrease of interface shear strength. The area erosion rate of interface under salt freeze-thaw cycles could be significantly influenced by interface roughness of substrate concrete, and the smoother interface always caused more area erosion rate of interface. Based on the micro-damage mechanism of ECC-to-concrete interface under salt freeze-thaw cycles, a damage prediction model of ECC-to-concrete interface was proposed in this paper. The model is expected to be used to predict the damage degree of ECC-to-concrete interface subjected to salt freeze-thaw cycles.

Investigation of interface shear properties and mechanical model between ECC and concrete

This paper reveals an investigation of the influences of ECC mixture construction method (i.e., common casting and spraying ECC), ECC strength grade, interface roughness of concrete substrate, and polyvinyl alcohol (PVA) fiber type on shear properties of ECC-to-concrete interface. The test results show that two failure modes of interface shear failure and ECC failure were observed. The roughness degree of concrete substrate had a strong effect on the failure mode, while ECC strength grade, ECC mixture construction method, and PVA fiber type had almost no influence on the failure mode. The shear load-slip curves of all specimens were basically similar. Compared to the casting ECC, the spraying ECC had an obvious decreasing effect on interface shear strength. The ECC strength grade and roughness degree of concrete substrate had a significant influence on interface shear strength, and higher ECC compressive strength and coarser interface could cause higher interface shear strength. On the contrary, PVA fiber type had a slight influence on interface shear strength. Based on the micro-bonding mechanism and test results of shear load-slip curves, a shear strength mechanical model and a shear stress-slip model of ECC-to-concrete interface were proposed to predict interface shear strength and shear stress-slip curve, respectively.

Design of rapid hardening engineered cementitious composites for sustainable construction

Abstract This paper deals with design of environmentally friendly Rapid Hardening Engineered Cementitious Composite (RHECC) nanomodified with ultrafine mineral additives, polycarboxylate ether based superplasticizer, calcium hydrosilicate nanoparticles and dispersal reinforced by fibers. The incremental coefficient of surface activity was proposed in order to estimation of ultrafine supplementary materials (fly ash, methakaolin, microsilica) efficiency. A characterization of RHECC’s compressive and flexural properties at different ages is reported in this paper. Early compressive strength of ECC is 45-50 MPa, standard strength – 84-95 MPa and parameter Rc2/Rc28 – 65–70%. The microstructure of the cement matrix and RHECC was investigated. The use of ultrafine mineral supplementary materials provides reinforcement of structure on micro- and nanoscale level (cementing matrix) due to formation of sub-microreinforcing hydrate phase as AFt- and C-S-H phases in unclinker part of cement matrix, resulting in the phenomena of “self-reinforcement” on the microstructure level. Designed RHECC may be regarded as lower brittle since the crack resistance coefficient is higher comparison to conventional fine grain concrete.

Flexural behavior of ECC-concrete composite beams reinforced with steel bars

This paper presents analytical technique and simplified formulas for the calculations of cracking, yield and ultimate moments of different cases as well as deflections of ECC-concrete composite beams reinforced with steel bars. The technique is based on the simplified constitutive models of materials, strain compatibility, perforce bond of materials and equilibrium of internal forces and moment. Experimental testing of eleven ECC-concrete composite beams reinforced with steel bars is also presented. All beams tested had the same geometrical dimensions but different steel reinforcement strength and ECC thickness. The proposed formulas showed good agreement with the experimental results of various moment values and deflections. A parametric analysis shows that yield and ultimate moments increase with the increase of concrete strength in case of compression failure but, essentially, remain unchanged in case of tensile failure. With increasing the tensile resistance, for example by increasing ECC height replacement ratio, reinforcement ratio, strength of steel reinforcement and ECC, ultimate curvature and energy dissipation increase in case of tensile failure and decrease in case of compressive failure. On the other hand, ductility and energy dissipation ratio decrease with the increase of reinforcement ratio and strength, but, essentially, remain unchanged with increasing the height replacement ratio and strength of ECC.

Hybrid-fiber reinforced engineered cementitious composite under tensile and impact loading

The behavior under impact loading of an innovative hybrid fiber-reinforced engineered cementitious composite incorporating short randomly dispersed shape memory alloy (HECC-SMAF) and PVA fibers was explored using a drop weight impact test. Test specimens were also heat-treated to investigate possible pre-stressing effects of SMA fibers on the impact resistance of the ECC. Uniaxial tensile testing on ECC coupon specimens was also conducted. A two-parameter Weibull distribution was used to analyze variations in experimental results in terms of reliability function. Results indicate that SMA fibers significantly enhanced the tensile and impact performance of the ECC. Adding fibers beyond a certain dosage led to fiber clustering, thus, no further gain in tensile and impact performance was measured. The impact resistance of HECC-SMAF specimens was further improved after exposure to heat treatment. This highlights the significant contribution imparted by the local pre-stressing effect of SMA fibers to the impact resistance of the composite. The Weibull distribution was adequate to predict the impact failure strength of ECC, allowing to avert additional costly experiments. This research underscores the potential to engineer new cementitious composites with superior tensile properties and impact resistance for the protection of critical infrastructure in the event of explosive or impact loading.

Theoretical modeling of steel reinforced ECC column under eccentric compressive loading

Fiber reinforced cementitious composites (ECC) are a class of advanced composites with strain hardening and multiple cracking behaviors. Substitution of concrete with ECC can significantly improve the seismic resistance and durability of the infrastructures. In this paper, it is proposed to use ECC as the matrix of frame columns for improving its load carrying capacity, ductility, and avoiding the brittleness of concrete. Based on the assumption of plane remaining plane and constitutive models of materials, theoretical models for calculating the load-carrying capacity of the steel reinforced ECC columns under small and large eccentric compression are proposed. With the parameters of the constitutive models from the existing experimental data, the relationship between ultimate axial load and moment capacities is also derived with the proposed models. To verify the validity of the proposed theoretical models, finite element analysis with the software of ATENA is conducted to simulate the mechanical behavior of the steel reinforced ECC columns under eccentric compressive loading. The calculation results from the theoretical models show good consistency with the simulated results, indicating that the proposed models are feasible and reliable for design. Finally, based on the theoretical models, the effect of the ultimate tensile strain and compressive strength of ECC, longitudinal reinforcement ratio on the load carrying capacity of the steel reinforced ECC column are comprehensively studied.