A seismic‐resistant steel frame with energy‐dissipating, chevron‐type braces is proposed. The braces are equipped with replaceable hourglass‐shaped pins made of duplex stainless steel. Under design ...seismic loading, energy is dissipated through inelastic deformations confined in the replaceable pins while the other members remain essentially elastic. As a result, the frame exhibits high post‐yield stiffness due to the inherent properties of the stainless‐steel pins. A Eurocode‐8‐based design methodology is adopted for the frame and assessed following the Eurocode‐8‐compatible INNOSEIS approach. Specifically, the overstrength factor is evaluated through nonlinear pushover analysis while the behaviour factor is assessed through incremental dynamic analysis considering high and medium seismicity site‐specific ground motion suites. The determined behaviour factor satisfies the global collapse prevention and life safety objectives while also keeping the maximum residual inter‐storey drifts below 1/300 to permit an easy substitution of the damaged pins after the design level earthquake.
Structures may be subjected to earthquake sequences after major mainshock (MS) events in seismically active sites within a short time. As a result, they may be susceptible to damage accumulation, ...which may hinder their performance under consecutive seismic loading. This study evaluates the effects of earthquake sequences on the seismic performance of seismic‐resistant concentrically braced steel frames designed to Eurocode‐8. The frames under investigation have concentric chevron‐type braces with replaceable hourglass‐shaped pins made of duplex stainless steel. The seismic energy is dissipated through inelastic deformations concentrated in the pins while keeping the other members elastic. The stainless‐steel pins provide the frame with high‐post‐yield stiffness to reduce the residual drifts after a seismic event. The seismic behaviour of the frame is assessed using site hazard‐specific mainshock‐consistent‐aftershock (MS‐AS) sequences selected for a site in Terni, Central Italy. Nonlinear back‐to‐back dynamic analyses are performed at multiple intensity levels while adopting detailed numerical nonlinear models created in OpenSees. We show that the implemented behaviour factor satisfies the life safety assurance objective while keeping the maximum residual inter‐storey drifts below 1/300 to permit an easy substitution of the damaged pins after the design‐level earthquake without being curtailed by the potential following events. We then develop prediction models for the damage accumulation in the pins, considering different energy‐based intensity measures and we show that the cumulative absolute velocity‐based model is the most efficient predictor in this particular case. Finally, the damage accumulation in the pins is evaluated, confirming their superior low‐cycle fatigue capacity under earthquake sequences.
Visual damage inspection of steel frames by eyes alone is time-consuming and cumbersome; therefore, it produces inconsistent results. Existing computer vision-based methods for inspecting civil ...structures using deep learning algorithms have not reached full maturity in exactly locating the damage. This paper presents a deep convolutional neural network-based damage locating (DCNN-DL) method that classifies the steel frame images provided as inputs as damaged and undamaged. DenseNet, a DCNN architecture, was trained to classify the damage. The DenseNet output was upscaled and superimposed on the original image to locate the damaged part of the steel frame. The DCNN-DL method was validated using 144 training and 114 validation sets of steel frame images. DenseNet, with an accuracy of 99.3%, outperformed MobileNet and ResNet with accuracies of 96.2% and 95.4%, respectively. This case study confirms that the DCNN-DL method effectively facilitates the real-time inspection and location of steel frame damage.
•Deep learning approaches is proposed to locate the damaged part of the steel frame.•DenseNet based deep convolutional neural network is implemented and validated.•Data augmentation and Grad-CAM visualization techniques is implemented.•The proposed model accurately locates the damages in the steel structures.
In this study, to improve the collapse resistance of steel frame structures, corrugated steel plates are welded between the inner side of the flange of the I-shaped beams and the column to form novel ...steel frame joints with corrugated plates (reinforced joints). Collapse resistance tests of the novel reinforced joints under welded and bolt-welded connections are conducted. After a finite element model is validated, the effects of the circular arc length, thickness, and central angle of the corrugated plates on the collapse resistance of the novel reinforced joints are analyzed, and design recommendations are proposed. Results show that the failure modes of the tested specimens are the fracture failure of the beam flange outside the reinforced area and the sequential fracture of the tension flange of the joint region and corrugated plate. Compared with the original specimens, the bearing capacities and ductility of the reinforced specimens are significantly improved. A partial or complete out-shift plastic zone can be realized in the novel reinforced joints. The novel reinforced joints can effectively improve the collapse resistance of steel frame structures under welded and bolt-welded connections without affecting their seismic behavior. The corrugated plate even provides an additional resistance reserve for steel frame structures.
•Collapse tests of the novel joints under welded and bolt-welded connections are conducted.•The effects of the parameters on the collapse resistance of the novel reinforced joints are analyzed.•Design recommendations of the novel joints under welded and bolt-welded connections are proposed.
To provide valuable insights into the seismic performance and self-centering behavior of self-centering braced systems, a 1/2-scale 3-story 1-bay steel frame equipped with disc spring self-centering ...energy dissipation braces (DS-SCBs) was designed, fabricated, and subjected to pseudo-dynamic testing. This testing encompassed various earthquake hazard levels, a doublet earthquake, and a mainshock-aftershock sequence. The experimental findings revealed the stable hysteretic response of the DS-SCB, with no observed degradation in stiffness or activation forces. Additionally, the test frame exhibited outstanding seismic performance, sustaining only confined damage under very rare earthquakes. Due to the presence of the DS-SCBs, the test frame performed commendable self-centering behavior, characterized by minimal residual deformations. Peak story drifts and floor accelerations under two earthquakes of the same hazard level were regarded as equivalent. Furthermore, the subsequent aftershocks exhibited no discernible impact on the seismic performance of the test frame. Floor acceleration spikes were observed at locations where the brace stiffness underwent changes or where adjacent stories moved in opposite directions. The steel frame equipped with DS-SCBs proved to be an attractive, low-damage alternative to conventional steel systems for the development of resilient urban areas.
•Pseudo-dynamic tests were conducted on a 1/2-scale steel frame with disc spring self-centering energy dissipation braces.•Seismic performance of the test frame under the doublet earthquake and mainshock-aftershock sequence was investigated.•The mechanism of floor acceleration spikes was analyzed under seismic loads.•The test frame exhibited satisfactory self-centering behavior and experienced confined damage under very rare earthquakes.
In this study, the hysteretic behaviour of shape memory alloy (SMA) plates under cyclic tension-release loadings was examined to promote their seismic applications, with an emphasis on large-size SMA ...plates with different geometries. Based on a series of SMA plate coupons extracted from base plates with different geometries, the thermal characteristics were investigated, and the phase transformation behaviour of the SMA plates was characterised. Subsequently, cyclic tension-release tests were conducted on the SMA plates in the laboratory, and the key mechanical performance indexes including the transformation strength, post-yield behaviour, self-centring capabilities, and energy dissipation abilities were carefully investigated. According to the results, SMA plates have a comparatively encouraging self-centring ability and moderate energy dissipation capabilities within a specified strain range. However, larger SMA plates show less satisfactory self-centring behaviour and are prone to brittle fracture at the edges. Based on the test programme, a numerical investigation was conducted to offer further insight into the potential applications of large-size SMA plates in the seismic field. A practical modelling procedure, namely the hybrid finite element (FE) modelling technique, was proposed and used to reproduce the degradation and cumulative residual deformation in the SMA plates. Moreover, nonlinear response history analyses (NL-RHAs) were performed on a prototype steel frame equipped with SMA plates in the connections to verify the feasibility of using large-size SMA plates in steel structures.
•Six large-size SMA plates with various geometric dimensions were fabricated and heat-treated.•The influence of plate size on the cyclic tension-release behaviour of SMA plates was examined.•A practical FE modelling strategy and flowchart procedure for the SMA plates were proposed and verified.•The feasibility of exploiting SMA plates in seismic-resistant steel frames was explored.
In view of the poor robustness of fully welded connections, energy dissipation cover-plates (EDCs) were proposed in this study with the aim of improving their anti-progressive collapse capacity. ...First, the stress law and failure modes of the EDCs were revealed through the study of 13 uniaxial tensile test specimens, and the calculation formulas for the collapse resistance and corresponding deformation of the EDC were determined by theoretical analysis. Then, a design method for a fully welded connection with EDCs was proposed according to the forming principle of the double plastic regions and the deformation coordination principle of the EDC and beam flange. The analysis results show that the design method verified by analyzing three series of numerical examples is reasonable. The collapse resistance and deformation of the substructures with EDCs were increased by 78%–120% and 140%–182%, respectively, compared with those of substructures without EDCs. Moreover, the substructures with EDCs formed an obvious resistance improvement stage. The beam members in the substructure with EDCs can yield completely before connection failure, which enhances the catenary mechanism and delays the failure of the connection. The energy generated by the vertical load dissipation in the structure with EDCs can be increased to approximately twice that of the original structure. Therefore, adding EDCs is conducive to the dissipation of the energy generated by vertical loads and to the improvement of the collapse resistance of a fully welded connection.
•A fully welded connection with energy dissipation cover-plates was proposed.•Stress law and failure modes of energy dissipation cover-plates were revealed.•Design method for fully welded connection with energy dissipation cover-plates was proposed.•Substructures with energy dissipation cover-plates formed a resistance improvement stage.•Adding energy dissipation cover-plates is conducive to the dissipation of the energy generated by vertical loads.
This work calculates the collapse load and collapse mechanism of 2D frames with slender structural members and uniformly distributed loads. The search for the collapse mechanism and the collapse load ...is carried out using step by step method: the load factor is increased and at each step the balance and compatibility equations must be satisfied that the value of the plastic moment is not exceeded in any section. It is verified that the results are different in the cases of point loads and uniform distributed loads, both from a qualitative and quantitative point of view.
•Systematic Method.•2D frame limit analysis.•Step by step plastic method.•Collapse mechanism process.•Virtual Works Principle (VWP•Uniform distributed loads.
In current composite floors, the strength of the deck connections restraining the profiled steel decks to the floor beams or to the neighboring steel decks are much weaker compared with the sectional ...strength of the steel deck, which would limit the load-carrying capacity of the composite floors under progressive collapse scenarios. Given this, this study proposed two novel types of enhanced deck connections for improving the load-carrying behavior of the deck-to-beam connection and deck-to-deck connection. Based on a 5-story steel prototype building, the feasibility of the proposed deck connections in improving the progressive collapse resistance was validated by comparing with the common practice of the deck connections via a reduced-order (RO) modeling approach. The structural robustness of the prototype building in the case of sudden column removal was evaluated and discussed. Compared with the commonly used deck connections, the enhanced deck connections could improve the structural robustness of the prototype building by 27%.
•Novel enhanced profiled deck connections are proposed.•The structural configurations are designed using high-fidelity analysis results.•Verified reduced-order models are developed.•Enhanced deck connections can improve the structural robustness of steel frame building.
With the development of artificial intelligence (AI), it gains in popularity to use AI to solve problems in civil engineering. However, the research on AI is mainly focused on the field of structural ...health monitoring, and less on the field of structural design. As one new direction in the AI domain, the generative adversarial network (GAN) method has developed rapidly, which is able to synthesize high-quality images based on demand. Therefore, it opens a new window for AI-aided automatic structure design. In this paper, a novel GAN-based method, namely FrameGAN, is proposed to realize automated component layout design of steel frame-brace structures. By collecting and processing drawings designed by senior structural engineers, FrameGAN and two mainstream GAN models (pix2pix and pix2pixHD) are tested and compared, which demonstrates the superiority of the proposed FrameGAN. In addition, the design results of FrameGAN are compared and analyzed with those of senior structural engineers based on two unique evaluation metrics, i.e., expert grading and objective comparison. The results show that the design of FrameGAN is close to that of structural engineers, which indicates the availability of FrameGAN in the component layout design of steel frame-brace structures.
•A dual GAN model is proposed for the layout design of steel frame-brace structures.•Two GANs determine the layout of columns and braces respectively.•A dataset of steel frame-brace structures is established.•Two evaluation metrics are introduced to evaluate GAN performance in layout design.
