A new elastomeric-sliding seismic isolation system

A new seismic isolation system is introduced in this study that utilizes a combination of confined rubber for vertical loading and sliding rings for energy absorption. In this new system, a central elastomeric core is contained between the steel sliding rings. In laboratory testing of the proposed system, it was shown that the steel rings maintained the required vertical stiffness of the system by controlling the lateral deformation of the rubber core. In the lateral motion, the steel rings dissipated energy by sliding on each other under a friction force limited by their small share of the gravity loads. The advantages of the proposed system as compared with the conventional laminated-rubber bearing include increased vertical stiffness and energy absorption capacity as well as ease of manufacturing at a lowered cost

Interaction of Connected Single-Degree-of-Freedom Systems

AbstractIn most industrial complexes many structures are connected to each other by secondary elements, since the connections between main structures are carried out by these secondary elements, modeling of links is relinquished in primary and also sometimes main seismic analysis, so their effects on the main structures and elements are not considered. While this negligence will be associated with some errors, modeling a whole set of adjacent-connected structures seems to be impractical in any case. This research investigates the interaction effect between two adjacent and connected singledegree-of-freedom systems through a study of basic parameters and shows the limitations and range of errors in current disconnected analysis practice. As a result of this study engineers can identify when their current analysis with separating structures would be reliable and when accurate analysis should be used. Also, practical graphs are presented making possible to do the analysis separately for each structure and modifying the maximum response using the correction factors given

Investigating the Effect of the Number of End-Panel Studs on the Seismic Properties of Cold-Formed Light-Steel Shear-Panel Braces

Detailed investigation of the effect of the number of end-panel studs on the seismic properties of light-steel shear-panel braces in cold-formed steel frames and in particular the associated response modification coefficients (R) factor, are presented in this paper. A total of 6 full-scale 1200×2400 mm specimens are considered, and the responses investigated under a standard cyclic loading regime. Of particular interest are the specimens’ maximum lateral load capacity and deformation behavior as well as a rational estimation of the seismic response modification factor. The study also looks at the failure modes of the system and investigates the main factors contributing to the ductile response of the tested shear-panel braces in order to suggest improvements so that braces respond plastically with a significant drift and without any risk of brittle failure, such as connection failure or stud buckling

Cyclic behaviour of elliptical-shaped reduced web section connection

In this paper, an RWS connection with an elliptic opening in the web is proposed, and its performance is investigated through an experimental and numerical study. A full-scale elliptical RWS connection was experimentally tested under cyclic loading, to evaluate the performance of the connection and to use for verifying the validity of numerical models. In order to determine the optimum ranges for geometrical parameters of the elliptical cut, a parametric study was carried out using the verified FE models. Based on the results, the appropriate ranges for the cut parameters were recommended. Then, the cyclic behaviour of the connection with optimum parameters was compared with the conventional RBS and with different types of RWS connections. The results emphasised that the elliptical RWS connections according to the present recommendations provide appropriate cyclic performance in terms of ductility, rupture index, buckling stability, and ability to prevent the formation of plastic hinge near the column face. In addition, the flexural capacity of the proposed connection satisfied the requirements of the codes for special moment-resisting frames

Cyclic behavior of welded elliptical-shaped RWS moment frame

One of the disadvantages of the reduced beam section (RBS) connection is the possibility of lateral-torsional buckling in the beam. Based on previous researches, reducing the cross-section along the web rather than the flange is one of the effective ways to prevent this phenomenon. The authors, in some part of their study on reduced web section (RWS) connections reported in references, have proposed new details about RWS connections by creating an elliptical opening in the beam web and presented recommendations for optimum ranges of the geometrical parameters. The main aim of this paper is to investigate the cyclic performance of an eight-story three-bay welded moment frame having elliptical-shaped RWS (E-RWS) and to compare it with that of the frames having the conventional full- or reduced-beam sections. For this purpose, at first, two connections with the E-RWS and with the common radial-cut (R-RBS) were experimentally tested under the cyclic loading and their performances were examined. The results showed the priority of the E-RWS over the R-RBS in terms of strength, stiffness, ductility, and lateral-torsional stability. Following that, a step-by-step design process for the E-RWS connection was presented. At last, by using an FEM analysis verified by the experimental data, the cyclic performance of an E-RWS frame was compared with that of the full- and RBS frames. According to the results of this study, the creation of an elliptic opening in the beam web can replace the reduced-beam section connections as a suitable method, which can improve the seismic behaviors of MRFs

Cyclic performance of bolted end-plate RWS connection with vertical-slits

The reduced beam section (RBS) connections are widely used in construction buildings due to their desirable ductility and strength. The current reduced web section (RWS) connections are produced by a reduction in the beam web as circular or rectangular cuts or as horizontal slits. This article has proposed a new detail for the RWS bolted connection by creating vertical-slits in the beam web. The aim of this investigation is the evaluation of its cyclic performance in comparison with the conventional RBS connection. Two specimens, one with vertical-slits in the web (VS-RWS) and the other one with a radial-cut in the flange (RC-RBS), were experimentally tested and the results were compared. Moreover, numerical models were employed to evaluate the behavior of connections in detail. These two connections were able to move the plastic hinge region away from the column face, exhibit good hysteresis behavior, and satisfy the AISC requirements for special moment-resisting frames. The results also showed that the flexural capacity of the proposed VS-RWS connection is 10% higher than that of the conventional RC-RBS one, while their ductility and energy dissipation were almost the same. An important advantage of VS-RWS over RC-RBS is its ability to prevent the lateral-torsional instability. Besides, a numerical study was conducted to investigate the performances of various cut shapes RWS connections with certain overall dimensions and location of the cutting region in terms of hysteresis curves, rupture index and end-plate deformations

An experimental investigation on the seismic behavior of cold-formed steel walls sheathed by thin steel plates

The use of cold-formed steel (CFS) frames has grown extensively in recent years, particularly in the earthquake-prone regions. However, the behavior of lateral resisting systems in CFS structures under seismic loads has not been scrutinized in detail. Towards this, an experimental investigation has been conducted on cold formed steel frames sheathed by thin galvanized steel plates, the results of which are presented here. The experiments involve 24 full-scale steel plated walls tested under cyclic loading with different configurations of studs and screws. Of particular interest were the specimens