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Numerical modelling of innovative DST steel joint under cyclic loading

Lemos A., Da Silva L. S., Latour M., Rizzano G.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 3

687--701

EN

This paper addresses the numerical simulation of an innovative double split Tee beam-to-column joint fitted with a dissipative friction damper, recently proposed at the University of Salerno. The innovative connection prevents damage to all other structural components with the exception of one component of the connection that is specially designed to dissipate the input energy of a seismic hazard by means of the slippage of a friction material. The main topics herein presented are the development of a strategy for the numerical modelling of complex friction problems and a detailed numerical model of the overall beam-to-column joint equipped with the friction device. The joint is subjected to both monotonic and cyclic loading conditions. The numerical modelling was developed using the Finite Elements Method (FEM) with Abaqus Software. Sliding force–displacement curves are obtained for two damper materials and an estimation of their wearing is presented. To evaluate the accuracy of the numerical model, moment–rotation curves of the joint are compared with the experimental curves. The FE results show good correlations and confirm the potential interest of this novel joint typology to achieve easily replaceable details in case of a seismic event.

2

Seismic behavior of cross-laminated timber panel buildings equipped with traditional and innovative connectors

Latour M., Rizzano G.

Archives of Civil and Mechanical Engineering

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2017

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Vol. 17, no. 2

382--399

EN

The aim of this paper is to analyze the possibility to improve the seismic performance of cross-laminated timber (CLT) panel buildings introducing in the structure dissipative connectors in substitution of the classical hold-downs. In fact, as demonstrated by past experimental tests and numerical analyses, hold-downs exhibit a limited dissipation capacity. The proposed dissipative connector is called XL-stub and applies the concept usually adopted for ADAS devices. In order to prove the effectiveness of the proposed system the results of an experimental program devoted to characterize the force–displacement response under cyclic loads and low fatigue behavior of the XL-stub are presented and compared to the results of cyclic tests of hold-downs with same resistance. Afterwards, the comparison is extended at the level of the building, evaluating the influence of the connection on the seismic performance of the whole CLT panel building. To this scope, a FE model of the three-storey building tested within the SOFIE project is calibrated and multiple transient dynamic analyses are performed both for the building with the classical layout of connections and for the building equipped with XL-stubs. The obtained results are compared and the values of the behavior factor for the two solutions are calculated.

3

A Low-Resolution Spectroscopic Exploration of Puzzling OGLE Variable Stars

Pietrukowicz P., Latour M., Angeloni R., di Mille F., Soszyński I., Udalski A., Germanà C.

Acta Astronomica

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2015

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Vol. 65, No. 1

63--79

EN

We present the results of a spectroscopic follow-up of various puzzling variable objects detected in the OGLE-III Galactic disk and bulge fields. The sample includes mainly short-period multi-mode pulsating stars that could not have been unambiguously classified as either δ Sct or β Cep type stars based on photometric data only, also stars with irregular fluctuations mimicking cataclysmic variables and stars with dusty shells, and periodic variables displaying brightenings in their light curves that last for more than half of the period. The obtained low-resolution spectra show that all observed short-period pulsators are of δ Sct type, the stars with irregular fluctuations are young stellar objects, and the objects with regular brightenings are A type stars or very likely Ap stars with strong magnetic field responsible for the presence of bright caps around magnetic poles on their surface. We also took spectra of objects designated OGLE-GD-DSCT-0058 and OGLE-GD-CEP-0013. An estimated effective temperature of 33 000 K in OGLE-GD-DSCT-0058 indicates that it cannot be a δ Sct type variable. This very short-period (0.01962 d) high-amplitude (0.24 mag in the I-band) object remains a mystery. It may represent a new class of variable stars. The spectrum of OGLE-GD-CEP-0013 confirms that this is a classical Cepheid despite a peculiar shape of its light curve. The presented results will help in proper classification of variable objects in the OGLE Galaxy Variability Survey.