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CONSTRUCTADD 101057957 "Resource-efficient steel CONSTRUCTion using ADDitive manufacturing"
No full textSecondary frame action in concentrically braced frames designed for moderate seismicity: a full scale experimental study
No full textEuropean seismic design codes do not take into account the strength and stiffness of the secondary frame action provided by bracing gusset plates of concentrically braced frames (CBFs). This is an attractive assumption for practicing engineers, as it provides simplifications during the analysis and design phases. However, when efficiency and economy are concerned, especially in low-to-moderate seismic regions, this normally neglected frame resource may be interesting to consider in design. Gusset plates can provide a certain degree of stiffness and strength following the bracing failure, and may even prevent global collapse. In particular, when the shear deformation demand of the braced cell remains limited, as in the case of low-to-moderate seismic actions, it may become reasonable to take this extra stiffness and strength into account. Ongoing research project RFSR-CT-2013-00022 MEAKADO investigated this phenomenon by means of experimental and numerical studies with the perspective of setting new inputs for the design rules of the future generation of Eurocodes. This paper presents the results of full scale tests performed inside this research project, which characterized resistance, stiffness, and ductility resources of CBF systems designed for moderate seismicity. The paper also quantifies the effective contribution of the frame action, provided by gusset plate connections, to the global performance of CBF frames
Role of compression diagonals in concentrically braced frames in moderate seismicity: A full scale experimental study
No full textAccording to European building code provisions, compression diagonals should be neglected during the analysis stage of concentrically braced frames (CBFs) with X and N type bracings, and the inelastic capacity of the tension bracings only should be considered in the design. This provides simplifications at analysis and design stages for practising engineers. Such an assumption can be rational in the high-seismicity context, where the compression bracings undergo buckling at the early stages of the seismic event, and the shear demand is very high. On the other hand, in moderate seismicity areas (that is estimated as the 90% of the seismic regions of the world), where the shear deformation demand for braced frames and the number of high-amplitude cycles are very limited, it may be reasonable to consider both tension and compression diagonals in the analysis. Accounting for compression diagonals at the analysis stage, and exploiting their post-buckling resistance and dissipative contribution in design, may allow using a higher behaviour factor, and increase the economic efficiency of CBF structures in moderate seismic regions. To understand the real seismic performance of braced frames in moderate seismicity areas, a sound characterization is needed, focusing on behaviour of compression diagonals. In the literature, many tests have been performed to analyse the behaviour of bracing elements, but they were mostly designed to meet high seismicity criteria with significant connection over-strengths.
The European research project RFSR-CT-2013-00022 MEAKADO investigated the influence of compression diagonals on the global performance of CBF structures, by means of experimental and numerical studies. This paper presents the results of full scale tests performed within this research project, focusing on the stiffness and post-buckling performances of double-angle bracings with bolted connections, which are the most common bracing configurations in the European construction market characterized by low-to-moderate seismicity. Experiments have shown that extra stiffness and strength provided by the contribution of the compression diagonals to the structural response are significant for moderate seismicity drift and shear demands, and may be worth considering in the analysis and design phases
Moderate ductility of the bracing joints with preloaded bolts
No full textIn Europe, concentrically braced frames (CBFs) with double angle bracings are the most frequent lateral-resistant structural systems. Although their standard bolted connections provide economic and robust solutions for the static loading, they are assumed to have almost zero ductility under strong earthquake actions. In order to avoid a brittle failure, the current seismic design requirements of European Code provisions require these joints to have sufficient over-strength, and to remain elastic for the design earthquake. While this is a safe approach for the high seismicity situations, it causes costly solutions for the buildings designed in the low-to-moderate seismicity context. Therefore, mainly for economy reasons, design engineers usually choose standard non-seismic approach (DCL) for the design of CBFs located in low-to-moderate seismic regions. However, such a choice may lead to unsafe solutions, since no effort is paid to control ductility. To combine safety and economy in this context, a new specific method has been studied in the recently concluded EU-RFCS MEAKADO project. To explore the inherent ductility provided by standard double-angle bracing joints with preloaded bolts and respecting new edge-spacing requirements, full scale tests have been performed as a project task. This article analyses the test results, and quantifies the ductility provided by the bolt hole ovalization and the slippage of preloaded bolts of the bracing joints not fulfilling the current over-strength design criteria. The test data has been analysed by means of LVDTs, strain gauges and thermal images. Such ductility and dissipation resources are traditionally not desired from a high seismicity design point of view, but may satisfy the low horizontal shear demand of the buildings designed for the low-to-moderate earthquake zones
Inelastic cyclic numerical analysis of steel struts using distributed plasticity approach
Full text linkRobustness‐oriented topology optimization for steel tubular joints mimicking bamboo structures
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Simplified numerical modeling of elevated silos for nonlinear dynamic analysis
No full textSilos are industrial facilities used for storing a huge range of different materials. They should be designed to resist several loading conditions, and their seismic behaviour strongly depends on the geometrical and mechanical behaviour of their supporting frame, and the nonlinear behaviour of the content (e.g. friction, content-silo wall interaction). Nonlinear dynamic simulation of such systems can be very time-consuming, and most of the time unfeasible. This study compares a finite element model made of bricks elements and a simpler model with distributed masses on the silo walls. While simplified models were not suitable to simulate local behaviour of the silo wall, they reasonably predicted the global response of the elevated silo system. Yet, the accuracy strongly depended on the rigidity of the supporting structure, and this should be investigated carefully during the calibration phase
Full Scale Experimental Assessment of Concentrically Braced Steel Frames Designed for Moderate Seismicity
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