Seismic design of space steel frames using advanced static inelastic (pushover) analysis

A rational and efficient seismic design method for regular space steel frames using inelastic (pushover) analysis (PA) is presented. This method employs an advanced static finite element analysis that takes into account geometrical and material non-linearities and member and frame imperfections. Resistances (strengths) are computed according to Eurocodes 3. The PA is employed with multimodal lateral loads along the height of the building combining the first few modes. The design starts with assumed member sections, continues with deformation and damage check at three performance levels with the aid of PAs and ends with the adjustment of member sizes. Thus, it can sufficiently capture the limit states of displacements, strength, stability and damage of the structure and its individual members so that separate member capacity checks through the interaction equations of Eurocode 3 or the use of the behavior factor q suggested in Eurocode 8 are not required. One numerical example dealing with the seismic design of a one bay in both horizontal directions and three storey steel moment resisting frame is presented to illustrate the method and demonstrate its advantages. © 2020 Elsevier Lt

The unusual behavior of the young X-ray pulsar SXP 1062 during the 2019 outburst

We present the results of the first dedicated observation of the young X-ray pulsar SXP 1062 in the broad X-ray energy band obtained during its 2019 outburst with the NuSTAR and XMM-Newton observatories. The analysis of the pulse-phase averaged and phase-resolved spectra in the energy band from 0.5 to 70 keV did not reveal any evidence for the presence of a cyclotron line. The spin period of the pulsar was found to have decreased to 979.48 +/- 0.06 s implying a similar to 10% reduction compared to the last measured period during the monitoring campaign conducted about five years ago, and is puzzling considering that the system apparently has not shown major outbursts ever since. The switch of the pulsar to the spin-up regime supports the common assumption that torques acting on the accreting neutron star are nearly balanced and thus SXP 1062 likely also spins with a period close to the equilibrium value for this system. The current monitoring of the source also revealed a sharp drop in its soft X-ray flux right after the outburst, which is in drastic contrast to the behavior during the previous outburst when the pulsar remained observable for years with only a minor flux decrease after the end of the outburst. This unexpected off state of the source lasted for at most 20 days after which SXP 1062 returned to the level observed during previous campaigns. We discuss this and other findings in context of the modern models of accretion onto strongly magnetized neutron stars

Direct damage controlled seismic design of plane steel degrading frames

A new method for seismic design of plane steel moment resisting framed structures is developed. This method is able to control damage at all levels of performance in a direct manner. More specifically, the method: (a) can determine damage in any member or the whole of a designed structure under any given seismic load, (b) can dimension a structure for a given seismic load and desired level of damage and (c) can determine the maximum seismic load a designed structure can sustain in order to exhibit a desired level of damage. In order to accomplish these things, an appropriate seismic damage index is used that takes into account the interaction between axial force and bending moment at a section, strength and stiffness degradation as well as low cycle fatigue. Then, damage scales are constructed on the basis of extensive parametric studies involving a large number of frames exhibiting cyclic strength and stiffness degradation and a large number of seismic motions and using the above damage index for damage determination. Some numerical examples are presented to illustrate the proposed method and demonstrate its advantages against other methods of seismic design. © 2014, Springer Science+Business Media Dordrecht

Demographic, clinical and antibody characteristics of patients with digital ulcers in systemic sclerosis: data from the DUO Registry

OBJECTIVES: The Digital Ulcers Outcome (DUO) Registry was designed to describe the clinical and antibody characteristics, disease course and outcomes of patients with digital ulcers associated with systemic sclerosis (SSc). METHODS: The DUO Registry is a European, prospective, multicentre, observational, registry of SSc patients with ongoing digital ulcer disease, irrespective of treatment regimen. Data collected included demographics, SSc duration, SSc subset, internal organ manifestations, autoantibodies, previous and ongoing interventions and complications related to digital ulcers. RESULTS: Up to 19 November 2010 a total of 2439 patients had enrolled into the registry. Most were classified as either limited cutaneous SSc (lcSSc; 52.2%) or diffuse cutaneous SSc (dcSSc; 36.9%). Digital ulcers developed earlier in patients with dcSSc compared with lcSSc. Almost all patients (95.7%) tested positive for antinuclear antibodies, 45.2% for anti-scleroderma-70 and 43.6% for anticentromere antibodies (ACA). The first digital ulcer in the anti-scleroderma-70-positive patient cohort occurred approximately 5 years earlier than the ACA-positive patient group. CONCLUSIONS: This study provides data from a large cohort of SSc patients with a history of digital ulcers. The early occurrence and high frequency of digital ulcer complications are especially seen in patients with dcSSc and/or anti-scleroderma-70 antibodies

Analysis of nonlinear dynamic second-order effect of a large-scale container crane under seismic excitations

Under seismic excitations, the second-order effect (P-Delta effect) exists in deformed structure under vertical loading even in linear-elastic system. For the vulnerability of the large-scale container crane, the effect is particularly remarkable in the slender structure, especially under large deformations. The current research on the rule of the static P-Delta effect has gained tremendous achievements, through systematic, reliable and simplified calculation methods. This paper however proposes the nonlinear dynamic second-order effect of the large-scale container crane. The aim of this paper is to analyze the influence of P-Delta effect on nonlinear dynamic seismic responses owing to different seismic conditions and seismic excitations. Meanwhile, by comparing with the methods of numerical FEM simulations, the simplified theoretical calculation conclusions of the dynamic second-order effect for the bending-type structure on portal frame can be verified. This research reveals clearly the regular pattern of P-Delta effect and influencing factors. The results have great significance on the seismic design of large-scale container crane. The main findings are presented in the paper