Base‐isolated hospitals are frequently preferred to fixed‐base ones because of their improved seismic structural performance. Despite this, the question remains open on the advisability of using this ...modern seismic protection technology in preference to other conventional solutions, on the grounds of a holistic approach based on limiting non‐structural damage as well as continuity of service to the community in the aftermath of an earthquake. Two full‐scale four‐storey (fixed‐base) and three‐storey (base‐isolated) hospital buildings have been recently built and subjected to three‐dimensional shaking table tests at the National Research Institute for Earth Science and Disaster Prevention (Japan), with particular attention to evaluating and classifying functionality of non‐structural components and vital medical equipment. A two‐phase experimental campaign was carried out considering two earthquakes scaled at different intensity levels and applied along the horizontal and vertical directions. The current study aims to provide results of a numerical structural and non‐structural blind prediction of these hospital settings. A homemade numerical code is developed to account for lumped plasticity modelling of steel frame members and variability of the friction coefficient of spherical sliding bearings. Moreover, three non‐structural components are modelled in the fixed‐base structure: that is, elastic single degree of freedom systems representing two tanks filled with sand at the top floor; elastic beam elements for piping at the third floor; five‐element macro‐model for the in‐plane‐out‐of‐plane nonlinear response of partition walls at the first floor. The identification of predominant vibration periods of the fixed‐base structure is carried out using a homemade numerical code based on the continuous wavelet transforms in combination with the complex Morlet wavelet. Finally, the sliding and rocking motion of three items of medical equipment (i.e., incubator at third floor, dialysis machine at second floor and surgical bed at first floor) are analysed by means of a homemade numerical code, considering acceleration time histories of selected structural nodes of the fixed‐base structure.
•Natural agar was firstly introduced into intumescent fire-retardant coatings on steel substrates in this study.•Only 1 % of agar addition could notably enhance the fire resistance and smoke ...suppression.•Agar addition promoted the formation of a notably compact and consistent carbon layer and a possible mechanism was proposed.
To improve the fire resistance and smoke suppression performances of intumescent fire-retardant (IFR) coatings, natural agar was firstly introduced into IFR coatings on steel substrates in this study. It is found that the introduction of only small quantity of agar could notably enhance the fire resistance. The coating with 1.0 wt.% agar reduced the total heat release rate by 43.0 % and total smoke production of the coating by 57.3 % according to cone calorimetry test. It also exhibited significantly high water resistance. Observed through scanning electron microscopy, the forming char owns a notably compact and consistent carbon layer all through its heated process. Various analysis and characterization reveal that the agar introduction enhanced the char-forming ability of the coatings and significantly promoted the abundant CO2 release which should play a positive role in improving the function of vapor phase flame retardancy and the expansion ratio of the char. Further, the addition notably promoted the formation of the well cross-linked carbon layer and improved its graphitization degree. Benefited from these advantages, the coating with 1.0 wt.% agar obtained the excellent fire resistance and smoke suppression. This study provides a constructive and effective idea to improve the fire performances of IFR coating.
This paper presents an experimental study on a bolted joint for connecting H-section steel beams to square hollow structural steel (HSS) columns and connecting upper and lower HSS columns in a ...multi-storey prefabricated steel structure. The components within a module are welded together in the factory, and the modules are assembled on site using high-strength bolts. A rigid connection or a semi-rigid connection can be achieved by adjusting the number and size of bolts. The stiffness of semi-rigid bolted connection changes with the load. The connection is rigid during minor and moderate earthquakes, whereas during major earthquakes, the cover plate slips relative to the beam flange to dissipate energy. In this paper, model tests and finite element analysis (FEA) of the seismic performance under cyclic loads are conducted on six full-scale connections, and the results are compared with the results of a welded connection. The failure mode, slip behaviour, variation and distribution of the bolt tensions, and seismic performance of the connections, including the hysteretic behaviour, skeleton curve, ductility, rotational capacity and stiffness degradation, are obtained. The influences of the number of bolts and the thickness of cover plate on the mechanical and seismic properties are studied. The results show that a reasonable larger bolt hole can facilitate the installation and improve the ductility and energy dissipation capability without significantly affecting the load-carrying capacity of the connection. The results show that the proposed bolted connection has good hysteresis behaviour, energy dissipation and ductility. It is suitable for earthquake-resistant structures.
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•A new type of bolted beam-column joint for high-rise steel structures is presented.•Cover plate slips relative to beam flange to dissipate energy during an earthquake.•Connection stiffness can be controlled by adjusting the number or size of the bolts.•Bolted slip connection raises the joint's ductility and energy dissipation capacity.•Tests and FEA of seismic performance are conducted on 6 joints under cyclic loads.
riveted–adhesive hybrid joining technique is suitable for joining dissimilar material due to excellent performance and tightness of the joint. In this paper, electromagnetic self-piecing ...riveted–adhesive hybrid joining method was proposed to join Al/steel structure. The mechanical properties and failure behavior of electromagnetic self-piecing riveting, adhesive and its hybrid joints were compared. The shear tests were conducted, and digital image correlation (DIC) technique was employed to analyze the strain of the sheets. The typical failure fracture was observed to reveal the failure mechanism. The results showed that the peak load of the hybrid joint was 177.3% larger than that of the riveted joint, and the energy absorption of the hybrid joint was 360.0% and 47.9% higher than that of the riveted and bonded joint respectively. The failure process of electromagnetic self-piecing riveted–bonded hybrid joint could be divided into two parts: adhesive failure firstly and then rivet failure. The rivet in hybrid joint after adhesive failure could still suffer a certain amount of load, so that suddenly complete failure was not easy to happen. This indicated that the hybrid joint had better reliability and security. In general, the combination of electromagnetic self-piecing riveting and adhesive bonding could produce beneficial coupling effect.
•Electromagnetic self-piecing riveted–adhesive hybrid joining technique was proposed to join steel/Al structure.•The mechanical properties of the electromagnetic self-piecing riveting, adhesive and hybrid joints were compared.•The failure mechanism of the electromagnetic self-piecing riveting, adhesive and hybrid joints was analyzed.
The mechanical properties and failure behaviours of three different specimens of sinusoidal corrugated web girders with stiffened circular openings were investigated experimentally and numerically. ...The experimental outcomes showed similarities in the mechanical properties and failure model of the specimens, despite differences in the geometric dimensions. The numerical simulations further confirmed the buckling as well as post-buckling behaviours of the experimental results. The influence of initial geometric imperfections on the shear buckling load of the corrugated web girders was quantified and neglecting geometric imperfections led to an overestimation of the actual shear load capacity, emphasizing the importance of considering imperfections in the design of structural components. The investigation results showed that the shear load capacities of the girders were significantly affected by the thickness of the opening stiffeners, and that the presence of openings reduced the load carrying capacity and the overall stiffness of the beams, whereas the existence of opening stiffeners increased both the ultimate load bearing capacity and the global stiffness. However, the strengthening effect of the opening stiffener becomes less pronounced beyond a specific thickness. Besides, a comparison between hand calculations and numerical simulations show that the recently developed calculation method provided a more reliable prediction of the shear buckling resistance of corrugated web with stiffened openings. This investigation provides valuable guidance on the shear buckling behaviour of sinusoidal corrugated web girders with circular opening stiffeners, thus benefiting the design and analysis of steel structural components with sinusoidal corrugated web.
•Shear buckling behaviour of sinusoidal corrugated web girders with stiffened circular openings was investigated.•Parametric studies were conducted to reveal the effects of parameters on the buckling behaviour of corrugated web girders.•Two different failure modes, web buckling failure and reinforcement yielding failure, were discussed.•Shear capacity formulae were presented and design suggestions were proposed for two different types of failure.
Abstract
With the continuous maturity and improvement of BIM Tech, it has been more in-depth application in architectural design. However, the current application of Bim in prefabricated steel ...structure buildings still has some problems and shortcomings, such as the advantages of BIM Tech in improving the efficiency of building design, reducing the cost and reducing the workload. Based on this, this paper first analyzes the necessity of applying BIM Tech in steel structure prefabricated building, then studies the design of prefabricated steel structure building based on BIM, and finally gives the specific application of prefabricated steel structure building design based on BIM Tech.
Pitting corrosion poses a threat to plated steel structures serving in aggressive corrosion environments. This paper involves numerical studies on the structural behaviour and ultimate strength ...reduction of plated steel structures due to random pitting damage. Stochastic simulations were used to model the random nature of the pitting corrosion varying pitting shape, depth and distribution. A series of nonlinear analyses were performed on unstiffened plates and stiffened panels to understand the mechanisms of structural collapse due to random pitting damage. Empirical formulae were derived respectively for the prediction of ultimate strength reductions of unstiffened plates and stiffened panels in terms of regression analysis from the numerical results. Random pitting corrosion induces a variation and reduction in ultimate strength, and can lead to a transition in failure mode. The collapse of pitted structures under uniaxial compression has a feature that the onset of plasticity initiates in the areas close to the unloaded edge of the structure, and propagates into a continuous plasticity region linking the pits with highly concentrated stress. The pitted area with intensively stress-concentrated pits undergoes a locally amplified deformation that determines the failure mode, leading to structural failure.
•Develop a modeling method to simulate random pitting damage on unstiffened plates and stiffened panels•Clarify failure mechanism of structure due to random pitting damage•Study probabilistic characteristics of ultimate strengths of pitted plated structure•Regressive analysis of ultimate strength reduction due to actual pitting damage
The fire resistance performance of intumescent fireproofing materials for steel structure changes with time, as a result of exposure to environmental conditions especially temperature. The objective ...of this study is to investigate the impact of environmental conditions on fire protection properties (fire performance and char formation) of intumescent coating materials by using accelerated weathering technique. In this study a group of eight steel plates were coated with intumescent fireproofing of the same dry film thickness (DFT), the prepared samples were devided into two supgroups in which every supgroup of four specimens was exposed to ultraviolet radiation (UV) of wavelength (340 nm) for 0, 3, 6 and 9 years. The all intumescent coated samples were exposed to fire resistance tests in accordance with International test standard to evaluate their fire resistance performance. The formed char layers were characterized by using scanning electron microscopy (SEM). The results revealed insignificant change in the fire resistance for the 3 years aged samples. Increasing the accelerating aging over 3 years led to remarkable degradation of fire resistance. The SEM analysis revealed various foaming efficiencies as function of the exposure time.
•A method is proposed for the detection of weld surface porosity defects.•Defects are identified in weld images using computer vision techniques.•The actual defect size can be accurately ...measured.•The proposed method can accurately detect weld surface porosity defects.
Welding is the main connection type used in steel structure bridges. As the weld quality significantly affects the performance of a structure, weld defect detection is crucial in the performance evaluation of bridges. With the continuous development of computer vision (CV) techniques and image acquisition equipment, CV-based methods are being increasingly applied to weld defect detection. However, accurate identification of welding defects from several images is challenging. This paper proposes a CV-based method for detecting and quantifying surface porosity defects in welds. CV techniques were used to identify and extract weld defects, and the pixel-level sizes of the weld defects were obtained. The actual sizes of the weld defects were calculated based on a conversion between the image size and actual size. The results show that the proposed image processing method has low complexity and high accuracy in detecting weld defects, providing accurate measurement of the defect size. It is a fast and non-contact detection method for weld defect detection.
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