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This study proposes a novel reduced beam section concrete‐filled double steel tube (RBS CFDST) beam‐to‐column joint and investigates the effect of RBS length and the beam moment of inertia on the plastic hinge formation in such joints. Therefore, a set of nine RBS CFDST connections were fabricated and cast with self‐consolidating concrete in the laboratory. Then, parameters including failure pattern, buckling mode, plastic hinge location, joint maximum load‐bearing capacity, and column rotation were inspected. The findings reveal that when the RBS length is equal to that of the beam dimension, the entire plastic hinge length is formed within the RBS zone. As such, the plastic hinge occurs away from the column face and brittle failure is avoided, while the joint column rotation is significantly reduced. It was also concluded that the maximum load‐bearing capacity is the highest when the RBS length is at its lowest. [ABSTRACT FROM AUTHOR]

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The results of experimental research involving nine one-way slabs are detailed in this report. The objective was to investigate the impact of different parameters on the structural performance of these slabs in their absence and with strengthening. Externally bonded CFRP sheets strengthened six of the nine slabs; the three remaining slabs served as control specimens. Before subjecting the specimens to monotonic loading, pre-fatigue damage of 50% and 70% repeated loading was induced. An exhaustive assessment was conducted on each slab, in which it was compared to its control slab. Several crucial elements were incorporated into the evaluation, including the ultimate load capacity, the reason for failure, crack patterns, and load-deflection curves. Examining these metrics was intended to provide insight into the efficacy and structural performance of the employed fortification technology. Compared to unenhanced reinforced concrete slabs (control slab), the highest stresses on slabs supported with bonded CFRP sheets are between 20 and 44% better. Compared to the control slab, an almost 70% reduction in deflection was observed. The flexural performance of compromised reinforced concrete slabs repaired with this technology can be brought up to date and enhanced.

Six (1000*1000 mm2) slab specimens were cast and tested as two-way simply supported slabs previously (three under monotonic loading and three under repeated loading) are used in this research. The tested specimens consist of one solid slab and two voided slabs with the following variables (type of slab (solid and voided), presence of steel fibers (0% and 1%), and the presence of GFRP layers). This paper presents the results of tested slabs and the 3D-Nonlinear finite element (ABAQUS program) is proposed to verify the tested slabs under monotonic and repeated loading. The process of modeling the structure components of the tested slabs will be discussed in detail, including the creation of the parts, model material properties, surface interaction, loading method, boundary conditions, and meshing. Then, the experimental findings will be compared to the proposed FE models. A parametric study with new variables has been investigated that affect the behavior of reinforced concrete slabs and is not implemented in the experimental part of this study. These specimens are divided into two groups according to the nature of loading as in the experimental work. The created finite element models can accurately reflect the test results with an acceptable degree of difference in deflection and ultimate load by 10%. The crack patterns obtained using finite element models for the investigated specimens under monotonic and repeated loading are extremely similar to the crack patterns observed in the experimental work.

During pumped energy storage using abandoned mines, coal pillars are not only affected by monotonic loads, but also suffer from frequent stress disturbances. The strength and deformation characteristics as well as the failure mode of the coal specimens under the influence of monotonic loading (stress path 1), multilevel constant-amplitude cyclic loading (stress path 2) and multilevel increasing cyclic loading (stress path 3) were studied using the coal samples from Hepan Coal Mine, Shaanxi Province, as the research object. The test results showed that the stress-strain curves of the coal specimens under cyclic loading formed obvious hysteresis loops, and the area of hysteresis loops increased significantly with the rise of stress level; compared with the axial strain, the circumstantial strain was more sensitive to the stress path; the peak strength and peak axial strain of the coal samples were the largest under monotonic loading, and the peak strength and axial strain of the specimens decreased by 22.12% and 18.35% (path 2) and 5.30% and 10.34% (path 3) under multi-level cyclic loading, respectively; the tangent modulus of the specimens under stress path 2 was significantly higher than the other stress paths; the stress paths had not changed the macroscopic failure mode of the coal specimens, but the cyclic loading caused the number and size of cracks on the specimen’s surface to become larger.

In this study, a hypoplastic model is developed to describe the mechanical behaviors of cemented sand under both monotonic and cyclic loading conditions. A state variable is proposed to qualify the bonding strength, and it is incorporated into the model to reflect the influence of cementation on the strength, stiffness, and dilatancy of sand. To reflect the bonding degradation, this variable evolves during the shearing following a simple evolution rule and may vanish after large deformation. The critical void ratio and friction angle are related to the initial cemented content to consider the variation of the critical state induced by the cementation. The model is subsequently extended to account for cyclic loading by incorporating the intergranular strain, fabric change effect, and semifluidized state. The capability of the model is demonstrated by simulating the behavior of cemented sand under both monotonic and cyclic loading conditions. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC), a new cement-based material that offers high mechanical strength and good durability, has been widely applied in construction and rehabilitation projects in recent years. An optimum bending system is achieved by positioning the UHPC layer at the bottom tensile zone of the composite beam and placing the normal-strength concrete (NC) layer at the upper compression zone, which is described as the UHPC-NC composite beam. The fatigue behavior of reinforced UHPC-NC composite beams was described in this study, with an emphasis on the effects of UHPC layer thickness and fatigue load level on the fatigue life of the beam, deformation of the interface between UHPC and NC layers, as well as the bending stiffness of the beam. A total of 9 reinforced UHPC-NC composite beams were tested under cyclic loading. The test variables include UHPC layer thicknesses (zero, 200, and 360 mm), reinforcement ratios (1.184% and 1.786%), and the upper load levels (0.39~0.65). The results showed that good bonding had been achieved without delamination between UHPC and NC layers prior to the final fatigue failure of the beam, and the bending stiffness of the composite beam experienced a three-stage reduction under cyclic loading. Furthermore, an equation was proposed to predict the stiffness reduction coefficient of UHPC-NC composite beams under cyclic loading. [ABSTRACT FROM AUTHOR]

The study of fatigue of thin reinforced-concrete shells presents a complex modelling approach. This work is devoted to the numerical evaluation of the fatigue life of reinforced-concrete domes, with the concrete class of C25/30. For the formulation of a fatigue criterion under a symmetrically alternating load, with a very high number of cycles (106), the approach begins with the study of mechanical behavior under monotonic loading, related to the fatigue response. The numerical correlation results of the studied cases, based on a conservative fatigue limit of concrete in compression, enables to estimate the service life of these structures, knowing only the response under monotonic loading. The correlation formula proposed in this article can therefore directly estimate the service life of reinforced concrete domes, based on the maximum stress resulting from monotonic loading. [ABSTRACT FROM AUTHOR]

This paper aims to determine the effects of local corrosion at three different corrosion areas, the (1) entire area, (2) the constant moment area, and (3) the constant shear area, on the flexural performance of RC beams. To analyze this, an experimental study was carried out to prepare two series of RC beams (200 × 300 × 2800 mm) created with three different degrees of corrosion, inducing local rebar corrosion. Furthermore, two series of experimental tests were conducted under different loading types: monotonic and cyclic loading. It was observed that the strength capacity reduction grew in the RC specimens with induced corrosion in the order of the (1) entire area > (2) the constant moment area > (3) the constant shear area, as the average corrosion rate increased. Our test results further showed that the yield and ultimate strength were kept nearly equivalent to the uncorroded RC specimen, with average corrosion rates of 10% and 15%, respectively. Over these corrosion rates, the yield strength and ultimate strength dropped significantly. Compared to the test results under a monotonic loading condition, the structural capacity under a cyclic loading condition decreased, with a more pronounced tendency for each corrosion case as the corrosion rate increased. Longitudinal cracks developed throughout and adjacent to the corrosion areas as the corrosion rate increased. Thus, we can infer that strength reductions may be strongly influenced by these longitudinal cracks. [ABSTRACT FROM AUTHOR]

This study evaluated various mechanical responses that evolved as a function of gauge length for PGCL sutures. Gauge length dependency is important to be studied as it directly reflects the possible complications related to suture failure and inadequacy of mechanical properties, which could happen due to inappropriate suture lengths used in incision closure. The results show that the gauge length caused differences in monotonic and cyclic responses of the PGCL samples. However, the stress relaxation response is unaffected by the gauge length. In monotonic responses, most of the mechanical parameters, including elongation at break, load at break, ultimate tensile strength as well as initial modulus, improve with increasing gauge length. The overall stiffness and strain at break decrease as the gauge length increases. Both stress-softening and hysteresis loops are observed in all PGCL samples with varying gauge lengths. As the gauge length increases, the permanent set decreases, whereas the maximum stress level and hysteresis increase. Concerning crystallization behavior, the degree of crystallinity, lattice strain, and crystallite size are altered by the gauge length. As the gauge length increases, the lattice strain decreases, and the crystallite size decreases. [ABSTRACT FROM AUTHOR]

The critical penetration depth and failure displacement of vertically loaded anchor (VLA) have already been investigated. However, only few investigations focused on the double-plate VLA. Therefore, based on the finite element method, the critical penetration depth for the double-plate VLA was obtained, which is approximately 6.0 times the width of the upper fluke of the double-plate VLA. According to the reduced-scale model tests, the failure displacement of the double-plate VLA with different included angles and dimensions of the bottom fluke under shallow-embedded and deep-embedded conditions was obtained. Furthermore, the failure displacement of double-plate VLA with 30° included angle and the dimension of bottom fluke equal to that of upper fluke under shallow-embedded and deep-embedded condition is 0.29 and 0.67 times the width of upper fluke, respectively. Based on the empirical bearing capacity formula for VLA model, an improved bearing capacity formula for double-plate VLA model has been put forward; by means of the improved bearing capacity formula, the coefficient of bearing capacity for double-plate VLA under shallow-embedded and deep-embedded condition is obtained to be 5.013 and 4.106, respectively. [ABSTRACT FROM AUTHOR]

Experimental tests of a seven-bolted connection with an asymmetric contact area between the joined elements are presented. The research is divided into two stages. In the first one, the connection is preloaded in a three-pass cycle. In the second stage, the connection is loaded with a monotonic alternating force applied at an angle of 30 degrees to the contact surface of the joined elements to generate compressive and shear forces in the connection. The tests are carried out with the use of the INSTRON 8850 testing machine. As a result, the courses of forces in the bolts measured with the use of resistance strain gauges and the relative displacements between the joined elements measured with an extensometer are shown. In the second part, the modeling of the connection in the convention of the finite element method is presented. The joined elements are modeled with the use of spatial finite elements, and the fasteners, as the hybrid elements made of deformable beams, rigid heads, and rigid nuts. The paper is completed with a comparison of the results obtained from the measurements and calculations, based on which the conclusions important from the point of view of the FEM analysis are drawn. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the flexural behavior of composite Reinforced Concrete (RC) beams having a monolithic Engineered Cementitious Composites (ECC) layer at the tension face. Due to the brittle nature of normal concrete, clear cover on the tension side of beam cracks results in spalling and corrosion of reinforcement. The proposed technique overcomes the inherent brittle behavior of normal concrete with the incorporation of ECC on the tension face. This also helps in reducing bond-splitting, cover-spalling, and buckling of reinforcement in RC flexural members. For testing purposes, six full-scale beam specimens (225 mm x 300 mm x 2400 mm) with the same reinforcement were cast and tested. Out of six, two specimens were made of conventional concrete, whereas the remaining four (two each) had an ECC layer of 75 mm and 100 mm thick at the tension face respectively. Each specimen was installed with three strain gauges (one each at the midspan top & bottom surface of concrete and one midspan rebar on the tension face) and one LVDT at midspan. The samples were then subjected to simple monotonic loading under a third-point bending test as per ASTM C78. The load-displacement, stress-strain and momentcurvature curves were obtained for all the tested specimens. It was found that ECC-strengthened beam samples displayed an increased flexural performance at first crack, yield, and ultimate load-carrying capacity as compared to conventional RC specimens. Whereas a better crack arrest with even distribution of cracks and improvement in ductility was observed for the ECC-strengthened composite beams. [ABSTRACT FROM AUTHOR]

The numerical modeling of structures is a widely preferable approach to investigate the structural behavior of RC beams since it delivers inexpensive predictions for confirming the required goals concurrently with reducing casting, testing time, and effort. Shear-strengthening of reinforced concrete (RC) beams using externally bonded (EB) fiber-reinforced polymers (FRPs) has attracted much attention due to the fact that the FRP strengthening technique has the ability to alter the distribution of stresses between the structural elements and increase the load-carrying capacity. A significant number of experimental studies have been carried out to test the monotonic behavior of FRP shear-strengthened RC beams. Conversely, limited numerical research has been performed to investigate such performance. The VecTor2 software is developed based on the modified compression field theory (MCFT) and is directed to examine the monotonic behavior of retrofitted specimens using fiber-reinforced polymer (FRP) composites. To the authors' knowledge, the behavior of FRP shear-strengthened beams has not been explored in the literature using the MCFT modeling approach. The main objective of this study is to detect the software's capability of predicting the experimental outcomes of FRP shear-strengthened RC beams. This research study is carried out in two stages. Initially, the numerical study involves the development of an accurate finite element model to simulate the control specimens. The quality of this model is assessed by comparing the numerical results with the experimental outcomes. In the second phase of the numerical study, the control beam model is modified to accommodate the presence of external FRP composites. The accuracy of this model is again measured by comparing its predictions with the experimental measurements. The goal of these phases is to ensure that the numerical model captures the actual behavior of the tested beams. Additionally, two distinctive modeling approaches are investigated to represent the behavior of FRP composites. The accuracy of the numerical models is verified through comparisons of numerical predictions to experimental results in terms of ultimate loading capacity, load–deflection relationships, and failure modes. It can be stated that the validated numerical model provides alternate means for evaluating the monotonic behavior of both strengthened and non-strengthened RC beams. The predicted results compare very well with the test results of the control specimens when discrete truss elements are employed for the FRP composites. Furthermore, the numerical model provides useful information on the crack patterns and failure modes. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC), a new cement-based material that offers high mechanical strength and good durability, has been widely applied in construction and rehabilitation projects in recent years. An optimum bending system is achieved by positioning the UHPC layer at the bottom tensile zone of the composite beam and placing the normal-strength concrete (NC) layer at the upper compression zone, which is described as the UHPC-NC composite beam. The fatigue behavior of reinforced UHPC-NC composite beams was described in this study, with an emphasis on the effects of UHPC layer thickness and fatigue load level on the fatigue life of the beam, deformation of the interface between UHPC and NC layers, as well as the bending stiffness of the beam. A total of 9 reinforced UHPC-NC composite beams were tested under cyclic loading. The test variables include UHPC layer thicknesses (zero, 200, and 360 mm), reinforcement ratios (1.184% and 1.786%), and the upper load levels (0.39~0.65). The results showed that good bonding had been achieved without delamination between UHPC and NC layers prior to the final fatigue failure of the beam, and the bending stiffness of the composite beam experienced a three-stage reduction under cyclic loading. Furthermore, an equation was proposed to predict the stiffness reduction coefficient of UHPC-NC composite beams under cyclic loading.

The generalized plasticity theory has evolved in the last decades and attracts the attention of different research groups, because of characteristics like the absence of an explicit flow surface formulation. This paper presents a detailed inspection of two sophisticated constitutive models for granular soils under monotonic loading: the Pastor‐Zienkiewicz‐Chan (P‐Z‐C) model[1] and the Manzanal‐Merodo‐Pastor (M‐M‐P) model.[2] Even though they are similar in mathematical framework, the P‐Z‐C model requires only eight parameters compared to the M‐M‐P model which requires 18 parameters to describe the material behavior under monotonic loading. Parameters of both models were calibrated based on the extensive experimental database available for monotonic triaxial tests performed on Karlsruhe fine sand by Wichtmann et al.[3] An objective discussion addressing the strengths and weaknesses of each model is presented. Finally, a procedure to identify the most relevant parameters that control different elements in the model like the stiffness, the evolution of dilatancy or the hardening variables is introduced, using the Monte Carlo Toolbox (MCAT) for simulations. Some interesting inferences could be obtained, like the conclusion that the MCAT is a helpful tool for identifying material parameters and their interaction, but it cannot replace the human factor, the experience and objective judgement of the modeller for the calibration of constitutive models. [ABSTRACT FROM AUTHOR]

The axial compression behaviour of fibre-reinforced polymer (FRP)-confined concrete-core-encased rebar (FCCC-R) was investigated by performing monotonic axial compression tests on seven groups of FCCC-R specimens and three groups of pure rebar specimens. The research parameters considered were the FRP winding angle (0°, ±45°, and 90°), number of layers (2, 4, and 6 layers), and slenderness ratio of specimens (15.45, 20, and 22.73). The test results showed that FCCC-R's axial compression behaviour improved significantly compared with pure rebar. The axial load–displacement curves of the FCCC-R specimens had a second ascending branch, and their carrying capacity and ductility were enhanced substantially. The best buckling behaviour was observed for the FRP winding angle of 90°. The capacity and ductility of the specimens were positively related to the number of FRP-wrapped layers and inversely related to the slenderness ratio of the specimens. A finite element model of FCCC-R was constructed and agreed well with the test results. The finite element model was used for parametric analysis to reveal the effect of the area ratio, FRP confinement length, internal bar eccentricity, and mortar strength on the axial compression behaviour of FCCC-R. The numerical results showed that the area ratio had the most significant impact on the axial compression behaviour of FCCC-R. The confinement length of the FRP pipe and internal bar eccentricity had similar effects on the axial compression behaviour of FCCC-R. Both of them had a significant impact on the second ascending branch, with the post-peak behaviour exhibiting minimal differences. The influence of mortar strength on the axial compression behaviour of FCCC-R was observed to be minimal. [ABSTRACT FROM AUTHOR]

A plasticity model is proposed to simulate the monotonic and cyclic behaviour of cemented sand. The model is an extension of the critical state-based bounding surface plasticity model originally developed for clean sand by researchers Y. F. Dafalias and M. T. Manzari in 2004. The elastic parameters, state parameter, yield function, flow rule and plastic modulus of the base model are modified for cemented sand mainly by incorporating a bonding strength variable. In addition, the critical state variables, stress ratio and void ratio of cemented sand are linked to the initial cement content. The model formulation is presented first in the triaxial and then in generalised stress space. The capabilities of the model are illustrated by simulating the response in a series of monotonic and cyclic tests on cemented sand. This shows that the model can capture the main features of the mechanical behaviour of cemented sand well, including cement-induced enhancements of stiffness, strength, dilatancy and liquefaction resistance. [ABSTRACT FROM AUTHOR]

The paper describes the formulation and simulative potential of a constitutive model for monotonic and cyclic shearing of sands. It is a SANISAND-type model that does not consider a (small) yield surface and employs the last stress reversal point for defining both the elastic and the plastic strain rates. Emphasis is put on the updating of the stress reversal point to avoid stress-strain overshooting. It incorporates a fabric evolution index that scales the plastic modulus targeting strain accumulation with cycles and a post-liquefaction formulation affecting the dilatancy function. The paper includes the calibration process of the 14 model parameters. Model performance is verified against a large database of monotonic and cyclic shearing tests on Toyoura and Ottawa-F65 sands. To complement sand-specific data, empirical relations are used for validating the shear modulus at small strains, its degradation with cyclic shear strain, the corresponding increase in hysteretic damping, the evolving rates of volumetric and shear strain accumulation with cycles and the effect of relative density and stress level on liquefaction resistance. Model verification shows that a single set of sand-specific parameters may be used for both monotonic and cyclic shearing of any strain level, irrespective of stress level and relative density. [ABSTRACT FROM AUTHOR]

This paper proposes a new simplified restoring force characteristic model of the bending moment–rotation angle relationship for square concrete‐filled steel tube (CFT) beam‐columns to estimate the elastoplastic flexural‐shear behavior from short to slender beam‐columns. The square CFT beam‐column model incorporates a reduction in strength after the ultimate strength. The proposed simplified model is multilinear and involves a cracking strength point, a yield strength point, an ultimate strength point, and strength reduction points. In the proposed model, each flexural strength is calculated by a general superposed strength method, and new empirical expressions for each rotation angle are proposed from the results of previous experimental cyclic and monotonic loading tests. The proposed model for the bending moment–rotation angle relation is found to agree approximately with experimental results up to large rotation angles. [ABSTRACT FROM AUTHOR]

The reservoir landslide in the Three Gorges Reservoir Area (TGRA) often suffers from local cyclic loading scenarios produced by surge waves, groundwater level fluctuation, traffic loading, and seismic activity. However, the effects of local cyclic loading on the shear resistance of the shear-zone of the reservoir landslide are poorly understood. This study experimentally investigates the effects of local cyclic loading on the shear strength and the deformation of shear-zone material using cyclic direct shear tests. A series of cyclic direct shear tests are performed with different normal stresses, cyclic periods, and numbers of cycles. The experimental results indicate that: (1) Compared with monotonic loading, local cyclic loading can significantly decrease the shear stress of shear-zone soil. (2) Shear-zone soil exhibits greater volumetric contraction under local cyclic loading conditions than that under monotonic loading. (3) Under different vertical stresses, the differentiation of shear deformation after 40 cycles of loading was slight and virtually insignificant. The research results reveal the weakening law of the mechanical strength of shear-zone soil under local cyclic loading, which provides a foundation for investigating the mechanism of the reservoir landslide under the fluctuation of water levels. [ABSTRACT FROM AUTHOR]

The most susceptible area of a structural member, where the most inelastic rotation would take place, is the plastic hinge. At this stage, flexural elements in particular achieve their maximal bending flexibility. This study uses finite element analysis (FEA) and experimental inquiry to analyze and test the effects of carbon fiber mesh jacketing and steel fiber reinforcement at the concrete beam's plastic hinge length subjected to a vertical monotonic load. The compressive strength, split tensile strength, and flexural strength tests are used to evaluate the mechanical qualities, such as compressive strength and tensile strength, of M25 grade concrete that is used to cast specimens. While conducting this analysis, seven different parameters are taken into account. After the conventional concrete beam has been cast, the steel-fiber reinforced beam is cast. Several empirical formulas drawn from Baker, Sawyer, Corley, Mattock, Paulay, Priestley, and Park's methods were used to calculate the length of the beam's plastic hinge. Finally, the steel fiber was inserted independently at 150 mm into the concrete beam's plastic hinge length mechanism using the techniques described by Paulay and Priestley. The analytical and experimental results are compared. The results obtained from the investigations by applying monotonic loads to the beam show that fibers used at specific plastic hinge lengths show a 41 kN ultimate load with 11.63 mm displacement, which is similar to that of conventional beam displacement, and performance. Meanwhile, the carbon fiber mesh wrapped throughout the beam behaves better than other members, showing an ultimate load of 64 kN with a 15.95 mm deflection. The fibers provided at the plastic hinge length of the beam perform similarly to those of a conventional beam; eventually, they become economical without sacrificing strength. [ABSTRACT FROM AUTHOR]

Wire rope isolators (WRI) are devices that dissipate vibrational energy. They are used in various industrial applications to protect equipment and machinery. Heavy machinery and limited space are still some of the constraints engineers face when designing the WRI system. Heavy equipment requires increased vertical stiffness; however, using larger WRIs decreases their lateral flexibility, which is the target property in the first place. Using several small-sized WRIs is not possible in the case of limited space. Therefore, the present study proposes two improvements to WRIs to overcome the challenges caused by heavy-weight equipment and a lack of the space required to insert the appropriate number and size of WRIs. Two new configurations for WRIs are proposed, Spring-WRI (S-WRI) and Double-WRI (D-WRI), to improve the stiffness and damping properties in order to expand their applications. Monotonic and quasi-static cyclic loading tests were performed on the conventional and proposed WRI variants. Exploratory tests showed that the WRI's stiffness greatly depends on the wire rope diameter. Adding springs inside a conventional WRI (S-WRI) can improve vertical stiffness while maintaining the required lateral flexibility. The D-WRI was found to preserve the necessary flexibility and to be capable of solving the problem of limited space. The hysteresis behavior of the D-WRI can be expressed as the sum of the hysteresis of each WRI. The proposed configurations effectively improve the stiffness and damping properties of WRIs and expand their applicability for the vibration isolation of heavy equipment and in limited space. [ABSTRACT FROM AUTHOR]

Ultra-High Performance Concrete Filled Stainless Steel Tubular (UHPCFSST) column is a novel type of composite columns appealing to be adopted in corrosive and marine environment. To explore the axial performance of UHPCFSST columns, this paper initiates an experimental program containing 14 UHPCFSST columns subjected to either monotonic or cyclical axial compressive loading. The test variables in this program mainly include the column dimension, tube thickness and the loading schemes. Based on the test results, the damage evolution process, ultimate failure mode, load-deformation response and the typical mechanical performance indexes inclusive of loading-carrying capacity, stiffness degradation, as well as ductility coefficient are thoroughly examined. After that, theoretical analysis is carried out to explore the interaction behavior between UHPC and stainless-steel tube and hence judge the degree of confinement effect. To assess the applicability of the code equations stipulated in current international design guidelines and the empirical formulas proposed by other researchers, a small-scale dataset containing 41 UHPCFSST columns was compiled to make comparison of axial capacity between test results and analytical predictions. In view of the limited accuracy or the burdensome calculation process, a new formula considering actual loading carrying mechanism was proposed to calculate the axial capacity of UHPCFSST columns, which exhibits enhanced accuracy and efficiency than the current formulas. • 14 UHPCFSST columns were test under monotonic or cyclic axial loading. • The failure mode and performance indexes UHPCFSST columns were analyzed. • The confinement effect of UHPCFSST columns were discussed. • The prediction performance of current design formulas was evaluated. [ABSTRACT FROM AUTHOR]

• The experimental results for pre-fissured sandstone were well replicated based on an improved PSC model. • The crack evolution of fractured sandstone under monotonic and fatigue loading was analysed. • The impact of load type and rock bridge angle on AE hits, displacement and stress fields of sandstone was investigated. This study employed an improved stress corrosion model within a three-dimensional particle flow program to investigate the mechanical and cracking behavior of fractured sandstone samples with varying rock bridge angles under both monotonic loading and multilevel cyclic loading. Firstly, using the experimental results from intact sandstone under uniaxial compression, we calibrated the microscopic mechanical parameters of the parallel bond model. Then, the model was validated using the experimental results of fractured sandstone under monotonic and cyclic loading. Finally, the initiation, propagation, and coalescence behavior of cracks in fractured sandstone samples under the above two loading paths, as well as the evolution process of the stress field, displacement field, and force chain distribution, were discussed in detail. The results show that the stress–strain curves, strength, deformation parameters, and macroscopic failure modes obtained from numerical simulations are consistent with those from laboratory mechanical tests. The mechanical behavior of fractured sandstone is influenced by both the rock bridge angle and the loading path. As the rock bridge angle decreases, the mechanical parameters of the sample show an increasing trend, and the influence of rock bridge angle on the failure mode is reduced. Cracks in the samples all initiate at the tips of pre-existing flaws, and the rock bridge angle affects the crack propagation and coalescence process: for sandstones with smaller rock bridge angles, cracks gradually extend to the sample's ends; for sandstones with larger rock bridge angles, direct coalescence of cracks at the rock bridge is observed, then extending to the sample's ends. Compared with monotonic loading, the damage degree of sandstone samples under multilevel cyclic loading is more severe, and even obvious block spalling is observed. The experimental and numerical simulation results are expected to improve the understanding of the mechanical behavior and fracture behavior of fractured rocks under monotonic and multilevel cyclic loading. [ABSTRACT FROM AUTHOR]

Surface morphology significantly influences the fatigue life of the metallic materials. Therefore, improving surface performance is important for economic and safety applications. Silica-based coatings are anticipated to protect the metallic materials under synergistic operating conditions, such as fatigue and corrosion. However, pure inorganic silica-based coatings are brittle and fail to protect metallic materials. The properties of the sol–gel coatings can be determined by optimizing synthesis factors, such as synthesis steps, precursors, solvents, and catalysts. Organically modified silica-based sol–gel coatings were synthesized using 3-glycidoxypropyl trimethoxysilane and 3-aminopropyltriethoxysilane as precursors, with ethanol as the solvent. The resulting coating was named EtOH. This coating was applied on the surface of stable austenitic stainless steel AISI 904L with the dip coating method. The fracture behavior of the coating during monotonic loading has been studied by interrupted tensile tests at different load steps and examined closely with scanning electron microscopy. On the other hand, very high cycle fatigue experiments were conducted using an ultrasonic fatigue testing system at load frequency of 20 kHz on coated specimens to investigate the fracture behavior of the coating during cyclic loading. Three different kinds of fracture due to stress relaxation in the coating and at its interface with substrate were observed in monotonic loading. The same kinds of stress relaxation were observed in cyclic loading with the difference being that the range of experienced elongation in cyclic tests was significantly smaller. Therefore, the fracture in cyclic loading were concentrated in the vicinity of macro crack. The application of organically modified coatings could suppress the persistent slip bands and result in increased fatigue life for coated specimens. [ABSTRACT FROM AUTHOR]

This paper aims to determine the effects of local corrosion at three different corrosion areas, the (1) entire area, (2) the constant moment area, and (3) the constant shear area, on the flexural performance of RC beams. To analyze this, an experimental study was carried out to prepare two series of RC beams (200 × 300 × 2800 mm) created with three different degrees of corrosion, inducing local rebar corrosion. Furthermore, two series of experimental tests were conducted under different loading types: monotonic and cyclic loading. It was observed that the strength capacity reduction grew in the RC specimens with induced corrosion in the order of the (1) entire area > (2) the constant moment area > (3) the constant shear area, as the average corrosion rate increased. Our test results further showed that the yield and ultimate strength were kept nearly equivalent to the uncorroded RC specimen, with average corrosion rates of 10% and 15%, respectively. Over these corrosion rates, the yield strength and ultimate strength dropped significantly. Compared to the test results under a monotonic loading condition, the structural capacity under a cyclic loading condition decreased, with a more pronounced tendency for each corrosion case as the corrosion rate increased. Longitudinal cracks developed throughout and adjacent to the corrosion areas as the corrosion rate increased. Thus, we can infer that strength reductions may be strongly influenced by these longitudinal cracks.

Abstract This paper proposes a new simplified restoring force characteristic model of the bending moment–rotation angle relationship for square concrete‐filled steel tube (CFT) beam‐columns to estimate the elastoplastic flexural‐shear behavior from short to slender beam‐columns. The square CFT beam‐column model incorporates a reduction in strength after the ultimate strength. The proposed simplified model is multilinear and involves a cracking strength point, a yield strength point, an ultimate strength point, and strength reduction points. In the proposed model, each flexural strength is calculated by a general superposed strength method, and new empirical expressions for each rotation angle are proposed from the results of previous experimental cyclic and monotonic loading tests. The proposed model for the bending moment–rotation angle relation is found to agree approximately with experimental results up to large rotation angles.

In Australian domestic structures, steel framing and sheathing panels are usually connected using screws. The ceiling diaphragm plays an important role in distributing lateral loads to the bracing walls. Shear connection tests could be used to observe the ceiling diaphragm performance without the complexity of testing full-scale isolated diaphragms. In this research, numerous inexpensive tests have been conducted to replicate representative tests to determine the parameters outlining the load-displacement behaviour for the screw connections between cold-formed steel framing members and plasterboard sheathing. All investigations of shear connection tests have focused on monotonic loading testing. These tests are aimed to determine the lower and upper bounds of the load-displacement curves for typical cold-formed steel framing-to-plasterboard screw connections in ceiling diaphragms. Finally, finite element (FE) models were developed by utilising these test results and predicted the performance of full-sized plasterboard-clad cold-formed steel framed ceiling diaphragms under lateral loading. [ABSTRACT FROM AUTHOR]

The use of nanomaterials improves the performance of reinforced concrete (RC) beams in terms of cracking load, failure load, and deflection. To further evaluate this improvement, the behavior of RC beams subjected to cyclic loading has to be experimentally investigated. In the present study, the effect of adding nanomaterials to RC beams was studied experimentally under monotonic and cyclic loadings. Eight RC beams with the dimensions of 2200 mm × 350 mm × 120 mm were prepared and divided into two groups. Both groups were tested under three-point bending, but one group was tested monotonously whereas the other group was tested cyclically. Each group consisted of four beams. The first beam in each group was tested without adding any nanomaterials. Nanotitanium, nanoaluminum, and nanosilica were added to the concrete mixes of the remaining three to replace 1% of the cement content. The performances of the tested beams were compared in terms of load-deflection curves, failure mode, cracking load, failure load, bending stiffness, toughness, and residual strength ratio (RSR). The results from both monotonic and cyclic loadings indicated better performances when nanotitanium was used. [ABSTRACT FROM AUTHOR]

Stainless steel alloys exhibit a nonlinear stress‐strain behaviour which can be precisely described by the Ramberg‐Osgood material model up to the ultimate stress. However, there is no consensus on the ductile fracture model under monotonic loading, which affects the post‐necking stress‐strain behaviour, to be adopted for stainless steels, even though the fracture model may have clear applications in structural design, such as in predicting joint failure in direct design approaches. This study presents the calibration of the fracture parameters for two of the most common ductile fracture models: the modified critical stress model and the Lee and Wierzbicki model. The calibrations are based on experimental results from tensile coupons tests on austenitic, ferritic and duplex stainless steel, extracted from cold‐formed tubes and sheet material, and on advanced finite element simulations. The calibrated values show a low dispersion for each of the analysed materials, indicating that the fracture parameters are an inherent property of the material, and which have been found to be slightly higher for the more ductile alloys. Average values of the fracture parameters for different stainless steels are also preliminarily proposed for their direct application in finite element simulations. [ABSTRACT FROM AUTHOR]

This study presents the comparison of soil behaviour under undrained monotonic and cyclic loading for both dry and saturated conditions. An experimental study has been carried out on cyclic triaxial for medium dense Solani sand. These experimental evaluations are numerically simulated using finite element software PLAXIS-3D for similar properties of Solani sand. Before this, some of the results presented are verified by comparing with those published in literature. The validations have been done both for laboratory tests and numerical simulations for monotonic and cyclic loadings. Since, tests were carried out under undrained condition, major focus of study are on pore pressure generation for saturated samples and on particle re-arrangement for dry samples. The novelty of the paper lies in the finding that the behaviour of sandy soil in saturated state is different under monotonic and cyclic loadings. [ABSTRACT FROM AUTHOR]

The need to reduce carbon emissions has recently become prevalent in light of concerns related to climate change. Since the cement industry causes approximately 8% of global CO2 emissions, it might be an urgent necessity to include cement replacement materials within the concrete industry. An important question arises about if such replacement negatively affects the cyclic or seismic behavior of reinforced concrete (RC) elements. This research presents an experimental investigation of the effect of using different percentages of metakaolin replacement on the monotonic and cyclic behavior of RC beams. The investigated parameters include the flexural strength, ductility and energy dissipation capacity of the tested beams. The current paper also aims to study the effect of using the CFRP-strengthening technique with 15% metakaolin replacement on the behavior of RC beams under the same loading protocols. The experimental results reveal that metakaolin can be used as a partial substitute for cement up to 20% without negative effect on the concrete behavior under both loading protocols. For cyclic loading, the percentage of replacement did not negatively affect the ductility; rather, it provided some improvement. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative internal configuration for the reinforced concrete masonry shear wall to improve seismic performance. A cyclic loading and monotonic loading test were carried out on reinforced concrete masonry shear walls with large cross-section core columns to study the in-plane response. The test walls' crack patterns, deformation characteristics, and failure characteristics were similar to those of a slit shear wall, which indicated a dislocation between core columns. The cyclic loading test results showed that the test walls' lateral bearing capacity was between 400 and 500 kN, the ultimate drift generally around 3%, and the equivalent viscous damping ratio with a non-linear response was found around 12%. Therefore, the test walls had ideal energy dissipation capacity as well as the lateral bearing capacity. According to the similarity phenomenon between the cyclic loading test and the monotonic loading test, three resistance mechanisms were proposed to explain the in-plane response of the wall, namely the core column-rotation mechanism, wall-rotation mechanism, and connector-shear mechanism. Based on the failure sequence of these resistance mechanisms, the intact wall was divided into two functional parts. One part was the masonry part, and the other part was the inner frame. The masonry part maintained integrity and required stiffness, and the inner frame dominated the in-plane response. [ABSTRACT FROM AUTHOR]