دانلود رایگان ترجمه مقاله تایید مدل دستگاه مبتنی بر HDR بر روی چارچوب کامپوزیت فولادی بتن – 2008

اعتبار مدل دستگاه HDR – مبتنی بر آزمونهای تجربی بر روی یک چارچوب کامپوزیت فولادی بتن

VALIDATION OF A HDR-BASED DEVICE MODEL BY EXPERIMENTAL TESTS ON A STEEL-CONCRETE COMPOSITE FRAME

Abstract

High Damping Rubber (HDR), commonly used for seismic isolation devices, may also be used to produce passive dissipation devices. HDR-based devices have a number of advantages: they are recentering, they can withstanding a large number of cycle and moreover they can dissipate energy even under low excitations, such in the case of frequent earthquakes or wind actions. This paper presents a validation of a nonlinear viscoelastic model for HDR-based dampers already proposed by the same authors, by means of comparisons with experimental tests carried out on a full scale steel-concrete composite mock-up. The paper firstly describes the real scale mock-up and its characterization, in the elastic displacement range, carried out by means of free vibration tests. HDR devices were introduced in the frame by means of chevron-type braces and dynamic free vibration tests, force-controlled tests and displacement-controlled tests were performed. The coupled system is modelled as a nonlinear SDOF system consisting of an linear elastic element placed in parallel with HDR dampers. All experimental tests were numerically simulated with satisfactory results.

2. THE MOCK-UP

The mock up is a steel-concrete composite structure, consisting of a pair of one-storey two-bay moment resisting frames with a height of 3.00 m and spans of 4.20 m. The six columns are obtained with HE160A hot rolled grade S355 steel profiles. The composite beams are also obtained with HE160A grade S355 steel profiles and a 120 mm thick slab realised with C30/37 concrete cast on a collaborating EGB210 steel sheet. The composite slab is directly supported by the main beams and connected with Nelson studs in order to ensure full shear connection (Figs.1). The composite beam-to-column connections are partial-strength and are obtained by means of beam end-plates bolted to the column flange and by placing suitable reinforcements in the slab (Dezi et al. 2007). An additional mass of 12.4 t was placed on the slab thank to nine concrete blocks suitably linked to the structure in order to avoid undesired slides. The characterization of the bare frame, in the range of the elastic behaviour, was carried out by performing a series of snap back tests (Fig.2). Five levels of displacements were imposed below the elastic limit estimated for the frame. Table in Fig. 2 reports the values of frequencies, stiffness and damping ratios obtained for the bare frame. Both quasi-static (ks) and dynamic (kd) stiffness are reported, the first is deduced from the initial load path while the second is deduced from the frequency (assuming the total mass is known and equal to 26,6t). The damping coefficient ξ was deduced from the snap back tests by means of the classic logarithmic decrement method (Chopra 2000).