Search

The low yield point (LYP) steel components for energy dissipation generally experiences substantial plastic deformation at triaxial stress states before fracture failure. This paper presents experimental and theoretical studies on the ultra-low cyclic fatigue performance of LYP at triaxial stress states. The monotonic mechanical properties of LYP steel under triaxial stress states are established through 14 tensile tests on four types of specimens with different initial geometries. Subsequently, 10 ultra-low cyclic tests are conducted to investigate the ultra-low cycle fatigue behavior of LYP steel at various triaxial stress states. An optimization-based technique is employed to calibrate the constitutive model for LYP steel, incorporating both isotropic and kinematic hardening performances. A phase-field framework is established and used for fracture prediction of LYP steel loading at triaxial stress states. In this proposed framework, the critical fracture density representing the fracture toughness in phase-field theory is taken as a variable related to equivalent plastic strain and stress states rather than a constant to describe the variation of fracture ductility of material under cyclic loading. The calibrated constitutive model and proposed fracture prediction framework are both implemented in finite element model and validated by simulating experimental results. • Monotonic and cyclic tests on specimens with various geometries were conducted. • A combination hardening constitutive model of LYP225 was established by an optimization algorithm. • A phase-field framework for fracture failure prediction of LYP225 was established. [ABSTRACT FROM AUTHOR]

In order to evaluate the performance of the slip critical bolted connection of HSS members, 30 specimens fabricated from high strength steel (HSS) (Q550, Q690 and Q890), are tested to investigate the slip factors of shot-blasted surface and rusted surface after blasting. For comparison, a group of specimens fabricated from mild steel Q345 are tested as well. In order to investigate the effect of the steel strength grade on slip factor, the values of hardness, roughness and capacity of plastic deformation of steels with different strength grades are also tested and analyzed. Based on experimental results and friction theory, it is found that with the same blasting treatment, the surface roughness tends to decrease with the increase of steel hardness, which induces the decreasing of the slip factor. Based on the friction mechanism, the slip factor is not only decided by surface roughness, but also can be affected by the capacity of plastic deformation of the contacting materials. With the increasing of plastic deformation capacity of the steel, the slip factor tends to be higher. According to the test results, the suggested slip factor of HSS specimens with blasted surfaces is 0.40. Moreover, for the specimens with rusted surface after blasting, there may be an increment in the slip factor owing to the increased surface roughness by rusting. However, the positive influence of rusting on the slip factor is not recommended to be considered in the connection design due to its instability. Therefore, the recommended slip factor of the specimen with rusted surface after blasting takes the value of 0.40 as well. • The performance of the slip critical bolted connection of high strength steel members is investigated. • The slip factor is not only decided by surface roughness, but also can be affected by the capacity of plastic deformation of contacting materials. • The recommended values of slip factor of the specimen with shot-blasted surface and rusted surface after blasting are given. [ABSTRACT FROM AUTHOR]

Due to the sufficient toughness and high strength, the High Strength Structural (HSS) steels with nominal yield strength not less than 460 MPa are rapidly gaining popularity in steel construction worldwide. The failure point of steel elements in steel structures typically experiences significant plastic deformation at triaxial stress levels. In order to study the ultra-low cyclic behavior of HSS steels at various triaxial stress states, a series of cyclic tests on three typical HSS steels specimens with various initial geometrics are designed and conducted in the present study. The characteristics of HSS steels including Lode angle dependence of yield strength, combined hardening and three-stage strength softening are observed. Moreover, the strength softening laws of HSS steels are different at various stress states. However, the existing constitutive models fails to capture strength softening of HSS steels when subjected to a range of loading types in terms of various triaxial stress states. Based on ductile damage mechanism, a new cyclic constitutive model (HSS-3D) with consideration of damage accumulation and influence of triaxial stress states is proposed. The HSS-3D model is implemented into ABAQUS via user subroutine and its applicability to HSS steels is verified. The evolution and distribution of damage of HSS steels under various stress states are studied. • Monotonic and cyclic tests on specimens with various geometries were conducted. • Influences of stress states on strength deterioration of HSS steels were studied. • A 3D cyclic constitutive model of HSS steels was proposed. [ABSTRACT FROM AUTHOR]

In order to study the hysteretic behavior of the ultra-high strength steel (UHSS), cyclic tests on Q1100 UHSS with nominal yield strength equal to 1100 MPa are conducted in the present study. The strength softening, preserved strength, and energy dissipation capacity of Q1100 UHSS are analyzed. The influences of the loading scheme and initial residual strain on the hysteretic behavior of UHSS are investigated. It is found that Q1100 UHSS shows a significant softening behavior under cyclic loading. The strength decrease is relatively rapid at the beginning of the cyclic loading and then tends to stabilize. The decrease of the strength of UHSS with larger residual strain tends to be more slowly. The energy dissipation coefficient of Q1100 UHSS increases with the increase of strain amplitude. The sampling direction has a negligible effect on the hysteretic behavior of Q1100 UHSS. A nonlinear combined hardening constitutive model is calibrated for various cyclic loading schemes by using an automatic calibration method and the cyclic behavior of Q1100 UHSS is predicted well. • Monotonic tensile and cyclic loading tests were carried out on Q1100 UHSS. • Q1100 UHSS shows a significant softening behavior under cyclic loading. • The characteristics of Q1100 UHSS under cyclic loading are analyzed. • The Q1100 UHSS can be considered isotropic. • A nonlinear combined hardening constitutive model is calibrated. [ABSTRACT FROM AUTHOR]

This study proposed a novel rocking component, namely self-centring hybrid rocking columns (SCR). Cyclic loading tests are conducted on a substructure consisting of the SCR and a frame beam-to-SCR connection to investigate its hysteretic performance. A numerical model of the SCR substructure is built and validated against the test results. Finally, the seismic performance of steel frames equipped with the SCR is demonstrated through the nonlinear time history analysis. It shows that the proposed self-centring hybrid rocking column has acceptable lateral resisting, energy dissipation and self-centring capability. The simplified numerical model of the SCR can reasonably well capture the hysteretic behaviour of the SCR substructure no matter with or without the steel damper and tension braces. The system-level analysis of steel frames with the SCRs verifies the effectiveness of the proposed SCR in mitigating maximum and residual drift responses of steel frames under earthquakes. After equipping the SCRs, the inter-storey drift concentration is also mitigated under earthquakes. • A novel rocking component, namely self-centring hybrid rocking columns (SCR), is proposed. • Cyclic loading tests are conducted on a substructure consisting of the SCR and a frame beam-to-SCR connection. • A numerical model of the SCR substructure is built and validated against the test results. • The system-level analysis of steel frames with the SCRs verifies the effectiveness of the proposed SCR. [ABSTRACT FROM AUTHOR]

The Energy Dissipative Rocking Column is a novel seismic mitigation device that could effectively mitigate maximum inter-storey drift and drift concentration of low-rise buildings under earthquakes. This study proposed a beam-through configuration for the connections between steel frames and Energy Dissipative Rocking Columns (EDRCs) to reduce the necessary workload in the application of EDRCs. The study commenced with a cyclic loading test on a substructure composed of the beam-through EDRC and frame beam-to-EDRC connections. Following the cyclic loading test, a simplified numerical model of the beam-through EDRC was built and validated against the test results. Finally, parametric studies were conducted to determine the seismic demand on the beam-to-EDRC connections. The results showed that the beam-through EDRCs have acceptable lateral resisting and energy dissipation capacity. The simplified numerical model could reasonably well predict the hysteretic behaviour of the specimens with and without the steel damper. The parametric study results, based on hundreds of nonlinear time history analyses, indicated that increasing connection stiffness in the range of 0 to 1.5 is most effective in mitigating both maximum drift and drift concentration. Moreover, the beam-through EDRC has very close effectiveness with the conventional column-through EDRC when the connection stiffness ratio is close to or larger than 4. • The Energy-Dissipative Rocking Column (EDRC) with beam-through configuration is proposed. • The beam-through configuration could effectively reduce the necessary workload in the practical application of EDRCs. • Feasibility of the configuration is verified by cyclic loading test. • Effectiveness of the EDRC in mitigating maximum drift and drift concentration is verified by nonlinear time history analysis. [ABSTRACT FROM AUTHOR]

Skeletal muscle atrophy is a debilitating condition that occurs with aging and disease, but the underlying mechanisms are incompletely understood. Previous work determined that common transcriptional changes occur in muscle during atrophy induced by different stimuli. However, whether this holds true at the proteome level remains largely unexplored. Here, we find that, contrary to this earlier model, distinct atrophic stimuli (corticosteroids, cancer cachexia, and aging) induce largely different mRNA and protein changes during muscle atrophy in mice. Moreover, there is widespread transcriptome-proteome disconnect. Consequently, atrophy markers (atrogenes) identified in earlier microarray-based studies do not emerge from proteomics as generally induced by atrophy. Rather, we identify proteins that are distinctly modulated by different types of atrophy (herein defined as "atroproteins") such as the myokine CCN1/Cyr61, which regulates myofiber type switching during sarcopenia. Altogether, these integrated analyses indicate that different catabolic stimuli induce muscle atrophy via largely distinct mechanisms. [Display omitted] • Deep-coverage proteomics reveal molecular changes responsible for muscle wasting • Different catabolic stimuli induce muscle atrophy via largely distinct mechanisms • Transcriptome-proteome disconnect occurs during muscle wasting • Atroproteins are proteins modulated by atrophic stimuli Skeletal muscle wasting is caused by many catabolic stimuli, which were thought to act via shared mechanisms. Hunt et al. now show that distinct catabolic stimuli induce muscle wasting via largely different molecular changes. The authors identify atrophy-associated proteins ("atroproteins") that may represent diagnostic biomarkers and/or therapeutic targets. [ABSTRACT FROM AUTHOR]

[Display omitted] • The heat exchange factors were summarized and analyzed in the tunnel construction. • Theoretical analysis and numerical simulation were used to analyze temperature field. • Factors were examined for the effect of the radius of the heat regulating circle. • Proposed a method for estimating the cooling requirement at the tunnel excavation face. In the construction of a geothermally active tunnel, ventilation cooling is a key strategy for controlling environmental temperatures, substantially affecting the mechanical properties of the surrounding rock and tunnel lining. This study develops formulas to estimate the required ventilation volume at the working face, accounting for heat dissipation from equivalent heat source and the cooling impact of airflow. Subsequently, it deduces a formula for calculating the radius of the heat regulating circle (HRC). Theoretical calculations are validated by a finite element analysis model. Simulations under various working conditions examine the effects of different surrounding rock temperatures, inlet air temperatures, and ventilation volumes on tunnel environment, surrounding rock thermal field, and the evolution of the HRC. The results indicate that airflow temperature at the working face, influenced by initial inlet air temperature, varies over time; significant variations in the growth rate of the HRC radius are observed after six months of ventilation. The HRC radius is positively correlated with the initial geothermal rock temperature and ventilation volume and negatively correlated with inlet air temperature. The HRC radius increased by 0.44 m for every approximately 10 °C increase in the surrounding rock temperature. For every 5 °C increase in inlet air temperature and every 10 m3/s increase in ventilation volume, the HRC radius decreased by 0.63 m and 0.29 m, respectively, after three years of ventilation. [ABSTRACT FROM AUTHOR]

High Strength Structural (HSS) steels, with nominal yield strength greater than 450 MPa exhibit phenomena including Lode angle dependence of yield, and accelerated cyclic softening at large strains that cannot be conveniently simulated by existing constitutive models that are developed primarily for conventional strength structural steels. This paper presents an experimental study consisting of 25 coupon scale tests (monotonic and cyclic) as well as 2 large scale cantilever column tests. According to experimental results, a classical combined isotropic and kinematic hardening constitutive model, the Armstrong and Frederick (A-F) model is identified by using the particle swarm optimization (PSO) algorithm. However, the yield plateau region and full-range softening behavior of HSSs under cyclic loading are difficult to be captured by the A-F model. A new constitutive model, termed the HSS-TD model with consideration of the yield plateau and three-stage strength softening, is formulated to simulate the response of HSS steels. The HSS-TD model shows significantly lower errors relative to the conventional A-F model, when assessed relative to test data. Moreover, the limitations of the HSS-TD model including influence of strain history and nonproportional loading are discussed. [Display omitted] • 25 coupon scale with various loading protocols tests were conducted. • A new constitutive model for high strength structural steels was proposed. • Particle Swarm Optimization algorithm is used for model calibration. [ABSTRACT FROM AUTHOR]

The relationship between von Mises equivalent stress σ ¯ and equivalent plastic strain ε ¯ (PEEQ), termed as von Mises stress-strain, plays an important role in numerical simulations for ductile fracture of structural metallic materials with large plastic strain. The standard uniaxial tensile test on cylindrical specimens is the most straightforward method to derive the (σ ¯ − ε ¯) data. However, the distribution of the stress and strain along the necking section of the tensile specimen is no longer uniform in the post-necking process, which induces difficulty in acquiring the (σ ¯ − ε ¯) data. The existing correction methods to identify von Mises stress-strain in the post-necking regime need instantaneous geometry of the notched region and ignore influence of the initial geometry of the specimen, which induces these methods are inconvenient for application and inapplicable for circumferentially notched tensile specimens to determine (σ ¯ − ε ¯) of each individual material zone in a hybrid coupon (e.g. weldment). In the present study, influences of initial geometry of the specimen and plastic hardening property of material on necking process are investigated firstly. It is found that the shrinking behavior of the minimum cross-section of the specimen is determined by the geometric parameter of specimen and plastic hardening exponent of materials. Based on an extensive parametric study a modified power law function to characterize the von Mises stress-strain curve from tensile tests on circumferentially notched specimens without measuring instantaneous geometry of cross-section is proposed. [Display omitted] • Effects of initial geometry and hardening property on necking process are studied. • A method is proposed to identify the full von Mises stress-strain curve. • The proposed method is applicable to circumferentially notched tensile specimens. • No instantaneous geometry is needed. • The proposed method is verified by using test results of structural steels. [ABSTRACT FROM AUTHOR]

• Triaxial compression tests with confining pressure on UHSC/UHPC are conducted. • Strength & ductility of UHSC/UHPC are higher with increasing of confining pressure. • Failure modes of UHSC/UHPC under various stress states are analyzed. • Failure surfaces for UHSC/UHPC are calibrated according to the test data. Ultra-high strength concrete (UHSC) and Ultra-high performance concrete (UHPC) with high compressive strength and good durability have been increasingly used in engineering structures. In the present study, uniaxial and triaxial compression tests on UHSC and UHPC are carried out by using servo-hydraulic actuators to investigate the mechanical properties of UHSC and UHPC under various stress states. In triaxial compression tests, the confining pressure ranging from 0 to 50 MPa is applied on UHSC and UHPC specimens. The mechanical responses of UHSC and UHPC specimens under various confining pressures, including peak strength, axial and circumferential strain are recorded in the loading process. According to the elastoplastic behavior of UHSC and UHPC specimens in tests, the influence of confining pressure on the compressive strength and plastic deformation performances of UHSC and UHPC are studied. It is found that the compressive strength and plastic deformation capacity of UHSC and UHPC tend to be higher with the increasing of confining pressure. The enhancement of compressive strength of UHPC is slightly lower than that of UHSC However, due to the lateral restraint effect of the confining pressure and the tensile action of the steel fibers inside the UHPC specimen, failure of the cylindrical specimen are delayed more significantly with increasing of confining pressure. Failure surfaces based on Ottosen's criterion for UHSC and UHPC are identified accroding to test data. By comparing and analyzing the tests results on UHSC, UHPC and previously tested C200, it is concluded the effect of confining pressure on the enhancement of compressive strength of concretes has a negative relationship with the uniaxial compressive strength of concretes. [ABSTRACT FROM AUTHOR]

In order to evaluate the slip performance of hybrid connections between high strength steel and mild steel, 30 hybrid connection specimens between high strength steel (Q550, Q690 and Q890) and mild steel (Q235 and Q345) with shot-blasted surface are designed to measure slip factors. The test results are compared with the slip factors measured from the connections with the same grade of high strength steel. According to the test results, the slip factors of hybrid connections are lower than the slip factor of 0.5 for mild steel specified in existing design code. Furthermore, the influence of steel strength grade on slip factor is investigated based on friction mechanism. It can be concluded that with the increase of steel grade, the slip factor of hybrid connection tends to decrease due to the reduction of surface roughness and the reduced potential increase in contact surface by plastic deformation. The slip factor of 0.45 is recommended for hybrid connections between Q550 or Q690 and Q235 mild steel. The slip factor of 0.40 is recommended for hybrid connections between Q550 or Q690 and Q345 mild steel. For hybrid connections between Q890 and mild steel Q235 or Q345, slip factor of 0.40 is recommended. • 30 hybrid connection specimens are tested to investigate the influences of steel grades on the slip factor. • The slip factors of hybrid connections are lower than those of mild steel connections. • For hybrid connections, the higher strength difference, the lower slip deformation before slip failure and lower slip factor. • Recommended values of slip factor for hybrid connections are given. [ABSTRACT FROM AUTHOR]

• Tests of six types of specimens of high strength steels are conducted. • Influences of stress triaxiality and Lode angle on ductility of HSS are studied. • The applicability of three typical ductile fracture models is investigated. • The BWM can give the most accurate prediction of all tests for HSSs. • Elongation at fracture fails to describe ductility of HSS in complex stress state. The high strength steel (HSS) with a nominal yield stress not less than 460 N/mm2 has been increasingly used in engineering structures. Compared with mild steels, HSSs have higher strength but lower ductility. This paper is concerned with the ductile fracture prediction of the HSS in a wide range of stress triaxiality and Lode angle. Experimental investigation is conducted to study the influence of stress triaxiality and Lode angle on fracture ductility of three different HSSs (Q550, Q690 and Q890). The experimental results are used to calibrate three typical fracture criteria: Void Growth Model (VGM), Combined Fracture Model (CFM) and Bai-Wierzbicki Model (BWM). It is found that without of consideration of Lode angle, the VGM fails to give an accurate prediction of fracture responses of all types of experiments. Compared with VGM, the CFM gives better fitting results. However, because the stress triaxiality dependence and Lode angle dependence are separated in CFM, there still exists discrepancy between prediction and real responses. The BWM gives the most accurate fitting results and prediction for all tests on three different HSSs. Moreover, it is found that elongation at fracture fails to describe the fracture ductility of HSS in a wide range of stress states. Based on parametric study results, it is found that with increasing Lode angle dependence of plasticity, the Lode angle dependence of fracture ductility of HSSs tend to decrease. [ABSTRACT FROM AUTHOR]

The loading resistance of slip critical steel connection is determined by the slip factor between faying surfaces and pretension force in bolts. The shot-blasting treatment is a commonly used and simple type of surface treatments. In order to avoid the risk of rusting of shot-blasted surfaces which threatens the structure safety, shot-blasted surfaces are generally coated with aluminum or zinc-based product. In this study, the slip factors of high strength steels (Q550, Q690 and Q890) with inorganic zinc-rich coating are investigated. Two values of coating thickness (60 μ m and 80 μ m) are selected and the influence of thickness of coating on slip factor is studied. Based on classical friction mechanism theory, compared with slip factor of shot-blasted surface, the decreasing of slip factor of surface with inorganic zinc-rich coating is analyzed. Moreover, the coating thickness effect on slip factor is also investigated. Because the difference between the measured slip displacement at 5 min (short-term tests) and 3 h (long-term tests) exceed 2 μ m , corresponding creep tests are carried out to evaluate long-term effects. Based on tests results, the recommended values of slip factor of high strength steel surface with inorganic zinc-rich coating is 0.30. • Slip factors of HSSs with inorganic zinc-rich coating are tested. • Steel strength effect on slip factor of steel surface with coating can be ignored. • Creep tests are carried out to study the long-term effect on slip resistance. • Suggested slip factors of HSS surface with inorganic zinc-rich coating are given. [ABSTRACT FROM AUTHOR]

Ectomycorrhizal (ECM) fungi are closely related to vegetation compositions, edaphic properties, and site-specific processes. However, the coevolutionary mechanisms underlying the spatial distributions in floristic and ECM fungal composition in the context of biotic adaptations and abiotic variances remain unclear. We combine a total of 25 ECM fungus-associated environmental variables to impose three types of composite scores and then quantify the environmental gradients of geographical site, soil chemical property and vegetation functional trait across 122 grids of 20 m × 20 m in a 25-hm2 forest plot. Significant dissimilarities in vegetational and ECM fungal abundance and composition existed along the above environmental gradients. Specifically, a contrasting floristic distribution (e.g., Betula platyphylla vs. Tilia mandshurica) existed between the northeastern and southwestern areas and was closely related to the nutrient and moisture gradients (with high levels in the west and low levels in the east). Furthermore, the ECM fungal communities were more abundant in the nutrient-poor and low-moisture environments than in the nutrient-rich and high-moisture environments, and the mixed-forest in the middle-gradient sites between the northeastern and southwestern areas harbored the highest ECM fungal diversity. These findings suggest that predictable within-site vegetation succession is closely related to ECM-associated determinants and the natural spatial heterogeneity of edaphic properties at a local scale. Unlabelled Image • Geographic, edaphic and floristic gradients are separately determined by composite scores. • Tree and ECM fungal species show significant dissimilarities along environmental gradients. • Environmental gradients interactively influence floristic and ECM fungal life strategies. • ECM-associated determinants jointly reflect local-scale ecological processes. [ABSTRACT FROM AUTHOR]

The poor stiffness and strength of traditional U-shaped dampers is an issue that is addressed in the present work by the development of a new form of T-section metallic damper, termed as the TSMD. Theoretical and experimental studies are carried out to evaluate the seismic performances of TSMD. Based on the principle of virtual work and Castigliano's second theorem, theoretical formulas of yield strength and initial stiffness of TSMD are derived and verified. Stiffness, strength and energy dissipation capacity of TSMD are significantly higher than those of the U-shaped damper with the same size of flange. A finite element model which can capture the cyclic responses and fracture failures of TSMD is established. Based on the numerical simulation and parametric study, the effects of geometrical dimensions and material properties on the seismic performances of TSMD are quantified. The mechanical characteristics of the damper are significantly affected by the web width, height, flange width, and thickness of the T-section of TSMD. Shape memory alloy-made TSMD shows stronger strength hardening and fracture resistance capacities than traditional steel-made TSMD and decreases damper residual displacement after cyclic loading. This study aims to provide valuable insights into the behavior and potential applications of the TSMD. • A new form of T-section metallic damper (TSMD) was proposed. • Theoretical formulas of yield strength and stiffness of TSMD are derived. • The cyclic responses and fracture failures of TSMD were studied. [ABSTRACT FROM AUTHOR]

The fire resistance of beam-to-column connections affects the safety of clad racks under fire conditions. However, existing research lacks studies on the behavior of these special connections at high temperatures. This study investigates the fire resistance of clad rack beam-to-column bolted connections (CRBCs). Firstly, single cantilever tests of CRBCs at temperatures of 20 °C, 300 °C, 400 °C, 500 °C, 600 °C, and 700 °C are carried out. The failure modes of the CRBCs at 600 °C and below are identical to that at ambient temperature, while the failure mode at 700 °C is different. The stiffness and strength of the CRBCs decrease with the increasing temperature. Subsequently, an FE model considering the high-temperature metal fracture is established, which can accurately simulate the typical failure mechanisms and satisfactorily predict the full range moment-rotation behavior of CRBCs. Furthermore, parametric analyses are conducted to investigate the influences of related parameters on the failure mechanism, initial rotational stiffness, and flexural capacity of CRBCs. Finally, theoretical models based on the component method are established for calculating the initial rotational stiffness and flexural capacity of CRBCs at high temperatures, respectively. The comparison of the theoretical model, experimental results, and numerical results indicates that the theoretical model can accurately calculate the mechanical properties of CRBCs at high temperatures. The findings of this study can provide a reference for the analysis and design of the fire resistance of clad rack structures. • High-temperature flexural tests were conducted on CRBCs. • Failure modes and moment-rotation curves of CRBCs at 6 temperatures were obtained. • FE model considering metal fracture can simulate the experiment well. • Theoretical model for estimating mechanical properties of CRBCs is proposed. [ABSTRACT FROM AUTHOR]

Due to the huge property difference between high strength structural (HSS) steels and mild steels after welding, mechanical behavior and failure mode of fillet welded joints of HSS steels should be studied further. Numerical simulations can provide increased insight into this topic. This paper concerns finite element simulations of component tests of two types transverse fillet welded joints of HSS steels: lap-welded transverse fillet welds and cruciform type transverse fillet welds. In order to investigate the influences of triaxial stress states on fracture ductility of weld metals, a series of tests on specimens with various initial geometries are carried out. By comparing three typical uncoupled fracture models (stress triaxiality-dependent ductile fracture model (VGM), Lode angle-dependent ductile fracture model (MSSM) and combination of stress triaxiality and Lode angle ductile fracture model (BWM)), BWM gives precious prediction of ductile fracture of weld metals. The behaviors in terms of load-displacement and failure modes of transverse fillet welds are all well captured by the numerical simulations with calibrated ductile fracture models. Specifically, the location of fracture initiation and propagation of cracks obtained from simulations are both identical with real responses. [Display omitted] • Effects of triaxial stress states on fracture ductility of weld metals are studied. • An uncoupled ductile fracture model for weld metals is adopted and calibrated. • Mechanical behavior of transverse fillet welded joints are simulated. [ABSTRACT FROM AUTHOR]

• Tests of six types of specimens of high strength steels are conducted. • The von Mises yield function is no longer applicable well for HSS. • The plasticity model of HSS should considers the effect of Lode angle. • A new yield function with consideration of Lode angle effect of HSS is proposed. The high strength steel (HSS) with a nominal yield stress not less than 460 N/mm2 has been increasingly used in engineering structures. An accurate yield criterion which describes the elastoplastic behavior of high strength steels under complex stress states, is significant for the analysis and design of high strength steel structures. For ductile metal materials, the most generally used the von Mises yield criterion neglects the effects of stress triaxiality and Lode angle on the metal plasticity. However, due to the reduce ductility with the increase in strength, such yield criterion may not applicable to HSSs. In the present paper, the tests of six types of specimens are carried out to evaluate effects of stress triaxiality and Lode angle on the plastic behavior of HSSs (Q550, Q690 and Q890). The applicability of von Mises yield criterion is examined firstly using experimental results and finite element analyses. It demonstrates that an appropriate yield function of HSSs should consider effects of the Lode angle while the influence of stress triaxiality is negligible. Based on the experimental and numerical results, a yield function for HSSs is proposed, to essentially simulate the elastoplastic behavior of high strength steel under complex stress states. [ABSTRACT FROM AUTHOR]

• Despite single-cell antileukemic activity, DOT1L and EZH2 (PRC2) inhibition is not consistently synergistic in KMT2A- rearranged cell lines. • PRC2 does not control one of its best validated canonical targets, the HOXA cluster, in KMT2A -rearranged leukemias. • DOT1L and EZH2 oppose each other on ribosomal genes. • DOT1L inhibition affects protein translation in KMT2A -rearranged leukemias via transcriptional effects on ribosomal genes. • DOT1L inhibition is synergistic with the protein translation inhibitor homoharringtonine. Inhibition of the H3K79 histone methyltransferase DOT1L has exhibited encouraging preclinical and early clinical activity in KMT2A (MLL) -rearranged leukemia, supporting the development of combinatorial therapies. Here, we investigated two novel combinations: dual inhibition of the histone methyltransferases DOT1L and EZH2, and the combination with a protein synthesis inhibitor. EZH2 is the catalytic subunit in the polycomb repressive complex 2 (PRC2), and inhibition of EZH2 has been reported to have preclinical activity in KMT2A - r leukemia. When combined with DOT1L inhibition, however, we observed both synergistic and antagonistic effects. Interestingly, antagonistic effects were not due to PRC2-mediated de-repression of HOXA9. HOXA cluster genes are key canonical targets of both KMT2A and the PRC2 complex. The independence of the HOXA cluster from PRC2 repression in KMT2A-r leukemia thus affords important insights into leukemia biology. Further studies revealed that EZH2 inhibition counteracted the effect of DOT1L inhibition on ribosomal gene expression. We thus identified a previously unrecognized role of DOT1L in regulating protein production. Decreased translation was one of the earliest effects measurable after DOT1L inhibition and specific to KMT2A -rearranged cell lines. H3K79me2 chromatin immunoprecipitation sequencing patterns over ribosomal genes were similar to those of the canonical KMT2A-fusion target genes in primary AML patient samples. The effects of DOT1L inhibition on ribosomal gene expression prompted us to evaluate the combination of EPZ5676 with a protein translation inhibitor. EPZ5676 was synergistic with the protein translation inhibitor homoharringtonine (omacetaxine), supporting further preclinical/clinical development of this combination. In summary, we discovered a novel epigenetic regulation of a metabolic process—protein synthesis—that plays a role in leukemogenesis and affords a combinatorial therapeutic opportunity. [ABSTRACT FROM AUTHOR]

To research the mechanical properties and low cycle fatigue performance of Q355B structural steel and Q355GNHB weathering steel, this study performs monotonic and cyclic tests on the base metal, welded metal and heat-affected zone (HAZ) of Q355GNHB welded connections and Q355B. The monotone and cyclic constitutive model parameters are calibrated using the true stress-strain relationship and the Chaboche hybrid strengthening model, and their accuracy is verified by ABAQUS. To streamline the calibration process, a simplified calibration method is established for the Chaboche combined hardening model. Compared to the traditional calibration method, the proposed method uses the stress-strain data obtained from the monotonic tests. The applicability of the calibrated model is verified by simulating the tests via ABAQUS. The research results show that both Q355B structural steel and Q355GNHB weathering steel have excellent bearing capacity and plastic deformation capacity. The Q355GNHB weathering steel has better ductility, while the Q355B structural steel has higher bearing capacity and stronger strength reserve capacity. The strength of Q355GNHB varies according to different zones: the yield strength of the base metal material is the lowest, while the tensile strength and the plastic deformation capacity of the welded metal material is the lowest. Besides, the Chaboche combined hardening model and simplified combined hardening model can capture the cyclic fatigue performance of Q355B and Q355GNHB steel. The research results provide effective data support for the in-depth study of the constitutive relations and mechanical properties of weathering steel materials and the accurate simulation of the properties of weathering steel structures. • Real stress-strain relationships of 30 stainless steel specimens are obtained. • Base metal, welded metal and the heat-affected zone of Q355GNHB are considered. • A simplified calibration method of cyclic constitutive model is built for Q355GNHB. • The applicability of the calibrated model is verified by ABAQUS. [ABSTRACT FROM AUTHOR]

• Ultra-low cycle fatigue life of steel rod energy dissipaters is accurately predicted. • Constitutive model considering strain amplitude effect is incorporated in FE model. • Ductile fracture model is calibrated and validated against experiments. • Fatigue failure mechanism of steel rod dissipaters is scrutinized. • Configuration of steel rod energy dissipater is improved. • Key factors in predicting fatigue life of steel rod energy dissipaters are clarified. In recent decades, various bar-typed miniature energy dissipaters with buckling restrained mechanisms have been proposed for seismic mitigation of engineering structures. The recently proposed assembled steel rod energy dissipater (ASRED), incorporating equally divided tubes as filler components, have shown plump hysteretic loops and remarkable fatigue performance. For such miniature dissipaters with varied dimensions, its ultra-low-cycle fatigue (ULCF) life is correlated with the geometrical dimensions. However, no research concerning this issue has been found. To enable the fracture prediction of ASREDs under various loading situations, numerical models integrated with the ductile fracture model were established in this paper. A newly proposed constitutive model and the famous combined hardening model were both employed in the numerical models to comparatively investigate the key factors affecting the accuracy of the fracture prediction. Moreover, the possible influence of Lode angle was also investigated by employing two different ductile fracture models, namely, the cyclic Bai-Wierzbicki model (CBWM) and the cyclic void growth model (CVGM). Seven specimens with different lengths and loading protocols were simulated, and the results show that the strain amplitude distributes unevenly in the ASRED and increases cycle by cycle at the fixed ends, which leads to the necking-induced failure mode. Using the fracture model of CBWM, numerical simulations that considers the influence of strain amplitude could successfully predict the fracture of all specimens. The dissipaters behaved approximately in an axially loaded state throughout the entire fatigue life, therefore the influence of the Lode angle was negligible, and the fracture predictions given by the CVGM are same with that by the CBWM. Based on a comprehensive analysis of the extended numerical investigations, an improved configuration for ASRED is proposed. [ABSTRACT FROM AUTHOR]

This paper numerically studies the anti-collapse behavior of the modular steel building (MSB) in the scenario of interior module removal and corner module removal. The vertical displacement, lateral displacement and internal force of a six-storey MSB in a sudden module loss are studied. The reasonability by using rigid body assumption in collapse analysis of the MSB is examined. A refined fracture model of the steel is incorporated into ABAQUS via user subroutine, in which the effects of both stress triaxiality and Lode angle on the fracture ductility of the steel are considered. In the pushover analyses, the effects of the horizontal connection, opening of the wall panel and thickness of the wall panel on the collapse resistance and failure mode of the MSB are studied. The dynamic amplification factor (DAF) of the MSB at the collapse limit state is also obtained. It is found that the rigid body assumption may significantly underestimate the displacement and maximum shear force in the horizontal connection of the MSB. Two types of failure modes of the structure are observed, namely, connection failure-induced collapse and module unit failure-induced collapse. Among the studied parameters, the effect of the opening size of the wall panel on the behavior of the structure is the most significant. In the scenario of the interior module removal and corner module removal, the DAFs of the structure at the collapse limit state range from 1.20–1.29 and 1.27–1.50, respectively. • Anti-collapse behavior of modular steel building (MSB) was studied. • The reasonability of rigid body assumption in collapse analysis of MSB was studied. • Effects of connection and wall panel on collapse resistance of MSB were studied. • Dynamic amplification factor of the MSB at the collapse limit state was obtained. [ABSTRACT FROM AUTHOR]

• Improved test methodology for connection with bolt pre-tension was presented. • Full-range distribution of triaxial stress field near bolt hole was analyzed. • Proportions of friction force and bearing force were investigated. • A trade-off between ultimate resistance and bearing resistance was discovered. • Comparisons with current codes were presented. Bolt pre-tension is regularly used in the practical case of bearing-type connection. Due to confinement of lap plates, complicate triaxial stress field can be observed near bolt hole, which may affect bearing behavior of the whole connection. Currently, investigations on the related issues are limited. To fill this research gap, this paper presents a combined experimental and numerical study on high strength steel single-bolt connections with bolt pre-tension. Results reveal several meaningful recognitions on the bearing behavior of connection with bolt pre-tension. Firstly, the effect of bolt pre-tension on the final tearout failure mode is negligible. Secondly, distribution of triaxial stress field initiates with a circular pattern and gradually shrinks to a localized pattern between shear fracture lines at ultimate resistance of the connection. Thirdly, out-plane confinement will limit the piling-up of plate material in front of bolt, which will reduce the related bearing resistance. However, increasing bolt grade is still beneficial to the whole connection due to a trade-off between ultimate resistance of the connection and related bearing resistance. Comparison with current code is further conducted. It is found that current Eurocode3 has adequate design safety for connection with bolt pre-tension while extra safety is needed for current AISC 360-16. [ABSTRACT FROM AUTHOR]

• Seismic performance of Q690D steel H-section beam-column bending about weak axis is experimentally studied. • Finite element model incorporated with ductile damage for Q690 high strength steel beam-column is established and verified. • Parametric study on Q690 high strength steel beam-column is conducted using numerical simulation results. Recently structural members fabricated of high strength constructional steels in civil and building engineering has been widely explored. However, their usage in earthquake zones is still restricted by seismic standards worldwide due to its poor ductility. In order to attain potential seismic application, this paper conducted five cyclic lateral loading experiments on H-shaped beam-columns fabricated of Q690D high strength structural steel. The tested members were cyclically bent about the weak axis. It was recognized that the low-fatigue fracture of edge fiber around bottom cross-section was the main failure mode. Besides, the hysteretic curves, cyclic backbones and energy dissipation characteristics were thoroughly discussed. The ultimate inter-storey drift was greater than the limitation of 1/50. All tested beam-columns exhibit favorable cyclic deformability and energy dissipated ability. To further study the influence of several factors, a series of FEA simulations were performed through verified numerical models. Ductile damage behaviors and advanced cyclic constitutive relationships were considered to improve the simulation performance. The influences of plate component slenderness and axial load ratio on seismic performance of steel beam-columns were thoroughly discussed. It is concluded that there exist interdependence characteristics between different influential factors on seismic performance. [ABSTRACT FROM AUTHOR]

• Full-scale corner-supported modular building was tested and simulated. • Stages of connection behavior in transfer of vertical load was analyzed. • Full-range variation of bolt pre-tension force in the bolt group was revealed. • Tolerance of splice connection for extreme initial imperfections was studied. • A transitional initial imperfection for modular building was found. Splice connection, comprised of splice plates and slip-critical high strength bolts, is an efficient and convenient connecting technique for modular buildings. Previous investigations on this splice connection were mainly conducted based on tests of substructures, which may not reveal the real connection behavior in the whole modular building. To fill this research gap, this paper presents a comprehensive research on a full-scale corner-supported modular building assembled with splice connections. Behavior of the splice connection during the transfer of vertical load in the full-scale modular building is analyzed in details with combined experimental and numerical techniques. Test results showed that no unfavorable phenomenon was caused by the proposed splice connection before the global buckling of the module column. Based on the validated numerical model, a three-stage behavior during the entire loading process is found for the splice connection. The involvement of splice connection in the transfer of vertical load is negligible in the first stage while the splice connection provides sufficient constraint for the second-order moment at the bottom of module column in the second stage. The localized deformation and obvious formation of gap are found in the third stage. However, the analysis on the full-range bolt pre-tension force of the bolt group indicates that the origin of such negative phenomenon is located after the global buckling, which will not affect design on the vertical-load transfer performance of the module column. The sensitivity of connection behavior to the values of initial imperfections are also investigated by the parametric study. It is found that the proposed splice connection has a satisfactory tolerance for extreme initial imperfections. A transitional initial imperfection is further proposed, which may be used as an important reference for the practical control on the initial imperfection. [ABSTRACT FROM AUTHOR]

• Multi-bolt high strength steel connections in tandem were tested and simulated. • Full-range load-distribution pattern were analyzed. • Bearing behavior of an individual bolt among the bolt group was investigated. • A nonlinear ultimate bearing resistance model was proposed. • Suggestions related to current design codes were given. This paper presents an experimental and numerical investigation on the bearing behavior of multi-bolt high strength steel connections in single bolt line. Three grades of high strength steel with nominal yield stress of 550 MPa, 690 MPa and 890 MPa were used to fabricate thirty lap connections with two or three bolts. It is found that the deformation capability of high strength steel plate near bolt hole is sufficient to meet the deformation demand of compatibility in multi-bolt connection even with an intended bolt hole misalignment of 2 mm for M24 high strength bolt. The comparison with Eurocode3 and AISC 360-16 is conducted. When no partial or safety factors are considered, the original formulae of Eurocode3 already has sufficient safety while AISC 360-16 gives unsafe predictions. Numerical models were established and verified by test results. With the obtained results, the full-range distribution of internal load among different bolts can be divided into four stages. Features for each stage are summarized and the effect of bolt hole misalignment on the distribution pattern is evaluated. Numerical analysis results indicate that, behavior of an individual bolt in multi-bolt connection may be influenced by surrounding bolts. The formation of critical yielding band between different bolts may explain this influence. Based on the experimental and numerical analyses, this paper proposed a new ultimate bearing resistance model for multi-bolt connections. The proposed model is capable of describing the nonlinearity in the ultimate bearing resistance of multi-bolt connection and achieves improved predicting accuracy compared to classical models. [ABSTRACT FROM AUTHOR]

It has been well-recognized that high strength steels possess worse ductility and deformability compared to normal strength steels, leading to greater risk of low-cycle failure. In addition, high strength steels generally exhibit prominent cyclic softening behavior rather than cyclic hardening behavior. These characteristics should be properly implemented into finite element model to gain exclusive numerical simulation on cyclic behavior of high strength steel beam columns. In this paper, finite element models which not only consider the initial imperfection but also incorporate the ductile fracture behavior as well as cyclic softening behavior were established and used to simulate cyclic loading experiments on high strength steel beam-columns bending about strong axis. The simulation results including hysteretic curves and failure modes both provide good agreement with experimental results, verifying the capability of finite element models proposed. Accordingly, a parametric study was conducted to investigate the effects of axial load ratio, flange width-to-thickness ratio and web height-to-thickness ratio on cyclic behaviors of Q690 high strength steel beam-columns. It can be concluded that the increase in flange width-to-thickness ratio and axial load ratio will change the damage mechanism and consequently present different cyclic deterioration characteristics. Furthermore, the increase in flange and web slenderness and axial load ratio results in decrease in deformability and sectional plasticity development ability. • Finite element model for simulating cyclic behavior of Q690 high strength steel beam-columns was established. • Finite element model was verified using experimental results. • Parametric study on effects of axial load ratio and plate slenderness ratio on cyclic behavior was conducted. [ABSTRACT FROM AUTHOR]