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The concrete-filled-steel-tube (CFST) column has been widely used in construction due to the benefit of composite action between inner concrete and exterior steel tube. Under axial compression, the steel tube is subjected to biaxial stress state in the hoop and axial direction, and the hoop stress component provides confinement for the inner concrete. However, the existence of axial stress component accelerates the buckling of steel tube, which hinders its confinement effect to inner concrete and accordingly column's axial compressive strength and ductility. This paper aims to enhance the axial compressive strength and ductility of CFST stub columns by improving its confinement effect provided by the steel tube. CFST stub columns axially loaded/unloaded were experimentally studied for different cases: a) varying concrete strength, b) lubrication on the contact between steel tube and concrete and c) corrugations in the steel tube that are introduced to intentionally weaken the tube vertically. It was found that axial compressive strength of CFST stub columns was effectively enhanced by reducing the axial stress in the steel tube. The introduction of corrugations in the steel tube led to largely concentrated axial deformation which reduced axial stress in other portions of the steel tube and consequently resulted in “tighter” hoop confinement to the inner concrete; both axial compressive strength and ductility were enhanced. [ABSTRACT FROM AUTHOR]

To improve the seismic resilience of steel moment-resisting frames, a new type of self-centering (SC) beam-column joint equipped with inclined tapered steel plate dampers is introduced in the current study. Firstly, the mechanical property of the SC beam-column joint is theoretically analyzed. Then, four SC joint assembly specimens, with study parameters of dimension and number of the tapered steel plates, are experimentally investigated under incremental cyclic loading tests. The proposed joint exhibits stable flag-shaped hysteresis curves and negligible residual deformation after unloading, which indicates that the joint can dissipate seismic energy well and at the same time have SC capability under earthquakes, thus reducing the cost of post-earthquake restoration. A comprehensive numerical simulation method is proposed to reproduce the hysteretic responses of the new SC beam-column joint. Subsequently, a series of parametric analyses are conducted to investigate the contributing factors affecting the seismic behaviors of the joint in terms of hysteresis, moment bearing capacity, energy dissipation, and SC capability. [Display omitted] • A new self-centering beam-column joint with steel plate dampers is proposed. • Mechanical properties of the joint are theoretically and experimentally analyzed. • Refined numerical modeling of the proposed joint is built and validated. • Affecting factors for the joint are investigated through parametric analysis. [ABSTRACT FROM AUTHOR]

• Contributing factors influencing the shear hysteretic behavior are summarized. • User-defined macro models are developed to capture different shear hysteresis. • Efficiency of SSSWs in enhancing structural fragility performance is investigated. The steel slit shear wall (SSSW) dissipates seismic energy through the developed plasticity at steel plate links separated by cutting slits. Its shear hysteretic behavior is influenced by parameters such as link configuration, amplitude of out-of-plane deformation and steel property. To investigate the contributing factors for different types of shear hysteretic behavior, four SSSW specimens with design parameters of link configuration (flat or twisted) and steel property (common carbon steel or low yield steel with significant strain hardening) are designed and tested under quasi-static cyclic loading. Four types of shear hysteretic behaviors are obtained: pinched, pinched without cyclic degradation, plump and combined (plump first and pinched later). Though pinching also occurs in the SSSW with twisted links, there is no strength and stiffness degradation in the hysteresis. Thanks to the strain hardening of low yield steel, the low yield SSSW presents plump hysteresis. These different shear hysteretic behaviors are successfully simulated using macro models firstly, including user-defined models for the pinched type without cyclic degradation and the combined type. Then moment resisting steel frame (MRSF) models equipped with these SSSWs are built respectively to study their influence on the overall structural performance. Results of fragility analysis show that four types of SSSWs enhance the seismic performance of MRSF structures at both small and moderate damage states nearly in the same degree. At extensive and collapse damage states, the SSSW with twisted links performs the best, followed by the low yield SSSW. [ABSTRACT FROM AUTHOR]

To study the contributing factors for the hysteretic behavior of the steel slit shear wall (SSSW), four SSSW specimens are designed, with design parameters of link configuration (flat and twisted) and steel property (mild carbon steel and low yield steel). Subjected to quasi-static cyclic loading, four patterns of shear force-drift curves are obtained: pinched, pinched but without cyclic degradation, plump and combined. Macro models are developed to simulate their different hysteretic behaviors, which agree well with the tested data. Finally, to investigate the influence of hysteretic pattern on the overall structural response, steel frame structure models equipped with SSSWs having different patterns of hysteretic behavior respectively are built. Structural responses in terms of maximum inter-story drift, residual inter-story drift and story shear force distribution are comparatively investigated. • Contributing parameters for hysteretic behavior of SSSWs are experimentally studied. • Four patterns of hysteretic behavior are successfully simulated by uniaxial macro models. • Efficiency of different SSSWs in reducing structural response is investigated. [ABSTRACT FROM AUTHOR]

Previous study has suggested that the stress paths of confined concrete in concrete-filled steel tube (CFT) stub columns influence the compressive strengths of the concrete, which, however, is based on the test of concrete-loaded CFT columns. In this paper, to fully understand the compressive strength of confined concrete in CFT column, the stress paths of confined concrete in the whole-section-loaded CFT columns are investigated. A detailed parametric study is conducted on the stress paths and their corresponding effects on compressive strength. Test results suggest that the lateral stress of the concrete in a whole-section-loaded CFT column generally occurred in a later stage and less significant than that in a concrete-loaded CFT column. The compressive strength of confined concrete in the whole-section-loaded CFT column with a small confinement coefficient is path-dependent, and the confinement effect of the concrete is generally weaker than that in concrete-loaded CFT column. With the increase of the confinement coefficient, the compressive strengths of confined concrete in whole-section-loaded CFT columns become path-independent. Based on the test results, a compressive strength model incorporating the stress path effect is developed for confined concrete in both whole-section-loaded and the concrete-loaded CFT columns. Good agreement between the experimental results and the ones predicted by the model is found, indicating a high performance of the proposed model. [ABSTRACT FROM AUTHOR]

For reinforced concrete (RC) structures located in seismic zones, reinforcement corrosion over time may have adverse effects on their seismic performance. Therefore, it is necessary to evaluate the effect of reinforcement corrosion on the seismic behavior of RC structures. In this study, an experimental study on corroded RC moment-resisting frames was carried out to investigate the effect of longitudinal reinforcement corrosion on the seismic behavior of RC frames. Six frame specimens, including five corroded frames and one frame without corrosion, were tested under quasi-static cyclic loading. The corrosion ratio of longitudinal reinforcement and the axial compression ratio were the main variable parameters. It was found that with the increase of corrosion ratio, the lateral load carrying capacity as well as the deformation capacity of RC frames decreased roughly linearly, and the energy dissipation capacity reduced approximately exponentially. For corroded frames with low axial compressive load level, the lateral strength and energy dissipation capacity were enhanced with the increase of the axial compression ratio, and the effect of axial compression ratio on the deformation capacity was insignificant. For frames with larger corrosion ratio or higher axial compression ratio, damages at beam ends developed more significantly during the loading process. In comparison with the beam, the damage evolution of columns was less affected by the corrosion ratio and axial compression ratio. [ABSTRACT FROM AUTHOR]

• Seismic behavior of damage-control steel plate fuses is experimentally investigated. • Parametric study on influence of fuse dimension and loading protocol is presented. • Buckling is made full use of for better strength control and visible damage indicator. • A method to estimate the fuse's compressive strength is proposed. Adoption of replaceable damage-control steel plate fuses at the intended location of beam-to-column connection is a potential solution for achieving seismic resilient steel structures. Different from the previous design concept, in this study, buckling of the plate fuse is made full use of to avoid excessive strength increase and also works as a visible damage indicator. Seismic behavior of the proposed damage-control fuses for the beam-to-column connection is studied in detail. Six fuse specimens are designed and experimentally investigated for various fuse dimensions and different loading protocols. Buckling under compression and eventual fracture under tension is the typical failure pattern. The obtained hysteretic curve of the fuse exhibits the feature of asymmetry, with tensile strength larger than compressive strength and the difference becoming larger with the increase of loading amplitude. Different cyclic loading protocols have a greater influence on the ductility than the maximum strength. The compressive strength of the fuse is theoretically estimated, which gives fairly good agreement with the test results. All the fuse specimens can reach the loading amplitude of 5% effective length without fracture. The maximum strength of the fuse degrades with the progress of out-of-plane deformation. The out-of-plane deformation of the fuses could be treated as a visible indicator for determining whether or not to replace the damaged fuse. [ABSTRACT FROM AUTHOR]

• Function loss is quantified by assembling with fuzzy theory and logic trees. • A general repair scheme is developed to get time-varying function recovery. • Seismic resilience of buildings is assessed by quantifying an integrated index. Seismic resilience assessment of buildings is an important aspect in developing resilient buildings. To evaluate seismic resilience of general buildings directly and quickly using a comprehensive index, a new framework of seismic resilience assessment for buildings by assembly-based function loss quantification is developed. Considering the fuzziness uncertainty in evaluation, a new method quantifying function loss of buildings is firstly proposed by consequence analysis of components, logic trees connected with fuzzy operators, and logic system of buildings including relevance between stories. Then the repair scheme of buildings is proposed to compute the time-varying function loss of buildings during the whole recovery process. The proposed method is embedded in probabilistic performance-based earthquake engineering (PBEE), in which uncertainty factors during the whole life cycle of buildings can be considered. Case study on a ten-story RC moment-resisting frame building is provided to demonstrate the applicability of the proposed method. Results show that the case building's resilience index can be easily and reasonably computed by the proposed framework at different earthquake intensity levels. Compared with the existing assembly-based function methods and resilience assessment methods, the proposed method avoids subjectivity during evaluation greatly. The proposed resilience assessment method can help to develop resilient buildings. [ABSTRACT FROM AUTHOR]

The cable tray system, one type of non-structural components, may suffer severe damage and even fall in case of earthquakes, causing interruptions to post-earthquake operations and even injuries or casualties. This paper introduces a toggle-brace damper (TBD) into the cable tray system to control its seismic response and damage. However, owing to the large deformation/rotation effect in the TBD equipped cable tray system, the traditional design method based on small deformation assumption is no longer applicable. The new deformation calculations of suspension frame and TBD subjected to displacement loading are established combining the optimization technique and the geometry relationship, respectively. After then, an optimization design method for connecting location of the damper brace is proposed, considering the installation errors, deformation constraints, and loading process. With the aid of numerical analysis, it is found that the large deformation effect and in-plane installation errors have considerable influence on the damping magnification function. Compared with typical seismic resistant elements such as the steel brace, diagonal- and chevron-brace damper, the proposed optimal TBD can dissipate more energy and effectively suppress the vibration of cable tray system. [Display omitted] • Deformation calculation method for suspension frame and TBD is developed. • Optimization for brace connecting point location of TBD is established. • Influence of installation error of brace connecting point is investigated. • Seismic responses of cable tray systems with different dampers are compared. [ABSTRACT FROM AUTHOR]

So far, the loading path effect on the compressive strength of confined concrete has been poorly investigated. To clarify the compressive strength of confined concrete in concrete-filled steel tube (CFT) columns, experimental tests with a total of 18 specimens are conducted to investigate the loading paths of confined concrete in concrete loaded CFT stub columns. The parameters that are varied in the experiment include the steel strength, the unconfined concrete strength and the D / t ratio. Two evaluation indices, namely the laterally dominant index and the effect index, are proposed to characterize the loading path and its effect on the compressive strength of confined concrete, respectively. A detailed parametric study is conducted on the loading paths and the corresponding effects on compressive strength. The results suggest that the loading paths of confined concrete in CFT column are affected by the column parameters. Depending on the loading paths by which the concretes are confined, the loading path effects on the compressive strength of the confined concrete in CFT columns could be totally different. Based on the test results, a compressive strength model incorporating the loading path effect is developed and good performance was found in comparison with the experimental results. [ABSTRACT FROM AUTHOR]