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Ensuring resilience through rapid buildings recovery in seismic zones has been placed at the forefront of recent studies. However, studies that compare the relative resilience of buildings constructed with different materials are lacking. This paper focuses on a comparative resilience analysis of concrete moment frames where beam-column connections are made with varying types of concrete mixtures. The connections are made with normal strength concrete (NSC), rubberized concrete (RbC), steel fiber rubberized concrete (STFRC), synthetic fiber rubberized concrete (SYFRC), and high strength concrete (HSC). Nonlinear static pushover and incremental dynamic analysis (IDA) are utilized to understand system response and the level of damage sustained following an earthquake. Subsequently, seismic fragility functions are constructed for the five considered frame types. The frames are subjected to different seismic scenarios, and the corresponding losses, recovery time, and resilience are quantified. A comparison between the five frame types is carried out to examine the optimal concrete mixture to be used to reduce damage probabilities, total direct losses, and recovery time and subsequently enhance resilience. The results show that rubberized concrete strengthened with steel and synthetic fibers can reduce economic losses by up to 19% and increase building resilience by up to 37% compared with the frames constructed with normal strength concrete. [ABSTRACT FROM AUTHOR]

This study aimed to present the effect of mixture proportions (including coarse-to-fine aggregate ratio and water-to-binder ratio) and mixture compositions (including the addition of different supplementary cementing materials and fibers) on the impact resistance and mechanical properties of concrete cured in cold temperatures. The impact resistance was evaluated using drop-weight and flexural impact tests conducted on concrete samples cured in different curing conditions. The studied parameters included coarse-to-fine aggregate (C/F) ratio (0.7 and 1.2), water-to-binder (w/b) ratio (0.4 and 0.55), type of supplementary cementing materials (SCMs) [20% metakaolin (MK) and 10% silica fume (SLF)], and the addition of steel fibers (0.35%) (SFs). The studied mixtures were cured under different curing conditions, including moisture condition at 23°C, air condition at 23°C, +5°C curing condition, and −10°C curing condition. The positive effect of using SFs and SCMs (MK and SLF) on enhancing the impact resistance and splitting tensile strength (STS) was more pronounced in samples cured at normal curing temperatures compared to samples cured at low temperatures. The mechanical properties and impact resistance of mixtures developed with higher C/F and w/b ratios were more affected by the low-temperature curing condition compared to the control mixture (with lower C/F and w/b ratios). The results also showed that low-temperature curing had a more pronounced negative effect on the impact resistance and STS than the compressive strength. [ABSTRACT FROM AUTHOR]

This study investigates the change in the acoustic emission (AE) parameters emitted in rubberized concrete under abrasion action at a sub-freezing temperature (−20°C). Seven concrete mixtures were developed with two coarse-to-fine aggregate ratios (C/F) (2.0 and 0.7), various crumb rubber (CR) content (0%, 10%, 20%, and 30%), and different rubber particle sizes [4.5 mm CR and 0.4 mm powder rubber (PR)]. Rotating cutter tests were conducted on three 100 mm cubic samples from each mixture at −20°C and 25°C while monitored via an AE system. AE parameters such as amplitude, number of hits, and signal strength were collected and underwent two parameter-based analyses: b -value and intensity analysis approaches, resulting in three additional parameters: b -value, severity (Sr), and the historic index [ H(t) ]. Results showed that testing concrete samples under abrasion at cold temperature, −20°C , resulted in a decrease in the emitted number of hits, cumulative signal strength (CSS), Sr , H(t) , and an increase in b -values compared to testing at 25°C. Furthermore, incorporating rubber particles was found to decrease the AE signals' amplitudes significantly at 25°C and slightly at −20°C , which manifested the higher wave attenuation occurrence at ambient temperature compared to cold temperature. AE analysis also showed a decrease in the abrasion resistance for mixtures with higher C/F, higher CR content, and larger rubber particle size. These decreases were more noticeable at 25°C compared to −20°C. Finally, the study developed two damage classification charts to estimate the ranges of abrasion mass loss percentage and wear depth in terms of the intensity analysis parameters: Sr and H(t). [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of different curing conditions/ temperatures on the compressive strength, flexural strength (FS), modulus of elasticity (ME), and abrasion resistance of concrete developed with different mixture compositions. The studied parameters included different water-binder ratios (w/b) (0.4 and 0.55), different coarse-to-fine aggregate ratios (C/F) (0.7 and 1.2), addition of steel fibers (SFs), and different supplementary cementitious materials (SCMs) (metakaolin [MK] and silica fume [SLF]). The developed mixtures were cured at four different curing conditions: moist curing (C1); air curing (C2); and cold curing, including +5°C curing (C3) and --10°C curing conditions (C4). The results indicated that the effect of curing concrete samples at cold curing conditions was more pronounced on FS results compared to all other mechanical properties results, in which the FS reduced by 23% and 41% at +5°C and --10°C curing conditions, respectively, compared to at the moist-curing condition. Despite the considerable enhancement in the mechanical properties and abrasion resistance when SFs or SCMs were used in the mixtures, cold curing of mixtures with SCMs or SFs significantly reduced this enhancement. The results also revealed that the rotating-cutter test results of the mixture with SFs were more affected by cold curing conditions than the sandblasting test results. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of cold temperatures on the abrasion resistance and mechanical properties of fiber-reinforced concrete mixtures with different saturation conditions. The studied variables included types of steel fibers (SFs) (needle fibers, single hooked ends, and double hooked ends), volumes of SFs (0, 0.35, and 1%), lengths of SFs, coarse-to-fine aggregate ratios (C/F) (0.7 and 2), coarse aggregate sizes (10 and 20 mm [0.39 and 0.79 in.]), and cement content (300 and 550 kg/m3 [18.73 and 34.34 lb/ft3]). The results indicated that decreasing the temperature below room temperature generally enhanced the abrasion resistance of concrete. On the other hand, all saturated samples showed a better enhancement in the abrasion resistance and mechanical properties under cold temperatures compared to unsaturated samples. The behavior of saturated samples compared to unsaturated samples under cold temperatures was obviously affected by C/F and cement content. Among all mixtures reinforced with different types, lengths, and volumes of SFs, using 1% 60 mm (2.36 in.) single hooked-end SFs showed the highest improvement in the mechanical properties and abrasion resistance under cold temperatures. Meanwhile, the lowest enhancement was recorded when 0.35% 35 mm (1.37 in.) SFs were used. [ABSTRACT FROM AUTHOR]

This study investigates the structural behavior of rubberized engineered cementitious composite (ECC) beam-column joints under cyclic loading. The effect of using different supplementary cementitious materials (SCMs) and different sand types on the cyclic behavior of ECC joints is also investigated. The main parameters were the percentage of crumb rubber (CR) (0%, 5%, 10%, and 15% by volume of sand), type of SCMs (metakaolin [MK], silica fume [SLF], and fly ash [FA]), and type of sand used (silica sand and natural sand). The investigation also tested a conventional normal concrete with 10 mm (0.39 in.) coarse aggregate size for comparison. The beam-column joint in this study was designed according to strong-column/weak-beam concept to put more focus on the ductile failure rather than brittle failure. The structural performance of tested beam-column joints was evaluated based on the load-deflection envelope response, hysteresis behavior, initial stiffness, deformability, cracking behavior, displacement ductility, brittleness index, energy dissipation, first cracking load, and ultimate load. The results indicated that increasing the percentage of CR up to 15% significantly increased the joint deformability, cracking behavior, ductility, and energy dissipation, while the initial stiffness, first crack load, and ultimate load were decreased. Replacement of FA (commonly used in standard ECC) with MK/SLF slightly reduced the beamcolumn joints' deformability, ductility, and energy dissipation while the first cracking load, initial stiffness, and ultimate load significantly increased. The results also revealed that although replacing silica sand with natural sand had an insignificant effect on the compressive and splitting tensile strengths of ECC, it showed a negative effect on the deformability, ductility, energy absorption, first cracking load, initial stiffness, and ultimate load of beam-column joints. [ABSTRACT FROM AUTHOR]