Mariana Zimbru

FINITE ELEMENT ANALYSES ON FREE FROM DAMAGE SEISMIC RESISTING BEAM-TO-COLUMN JOINTS

The seismic design strategy implemented in current codes is based on the capacity design principles that allow the formation of plastic hinges into predefined parts of the structure. Therefore, significant damage is expected at ultimate limit state, to which high repair costs are associated. Recently, new design strategies have been proposed in order to avoid the damage of the structure. The most of them are grouped into two categories, namely i) using special damping devices introduced in the structure as additional resisting element; ii) changing the dissipation mechanism of the structure by means of friction-based dissipative joints. The second possibility is promising and really effective because it guarantees no architectural interference if adopted for moment-resisting frames (MRFs), and low forces transferred to the foundations. The novelty of free from damage (FREEDAM) joints lays in the fact that the energy is dissipated by friction at the interface between plates in contact instead of the classical plastic deformation energy dissipation mechanism. In this paper, the seismic behaviour of FREEDAM joints is investigated by means of parametric finite element analyses carried out in order to examine the influence of geometric and mechanical feature of the friction device (e.g. position of friction plane, type of friction interface, bolt clamping, bolt strength). The accuracy of finite element models is also validated on the basis of some experimental tests. 802 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 802-814

Investigation on Friction Features of Dissipative Lap Shear Connections by Means of Experimental and Numerical Tests

RESEARCH ARTICLE Investigation on Friction Features of Dissipative Lap Shear Connections by Means of Experimental and Numerical Tests Mariana Zimbru, Mario D’Aniello, Attilio De Martino, Massimo Latour, Gianvittorio Rizzano and Vincenzo Piluso Department of Structures for Engineering and Architecture, University of Naples Federico II, Napoli, Italy Department of Civil Engineering, University of Salerno, Fisciano, Italy

Finite Element Analysis of Composite Replaceable Short Links

Eccentrically braced frames (EBF) with detachable short links are an efficient solution for buildings in seismic areas owing to their high energy dissipation capacity and ductility and ease of repair in the earthquake aftermath. Past studies revealed that short links can develop shear overstrength (i.e. Vu/Vp, where Vu is the ultimate shear strength and Vp the corresponding plastic resistance) larger than the value recommended in EC8 [1] (i.e. Vu/Vp =1.5). One of the factors causing the higher shear overstrength is the presence of axial restraints that leads to the development of tensile forces in the link at large levels of rotation. Another reason for higher shear overstrength is the composite slab that can resist the shear distortion together with the short link. Within the DUAREM project [2], full scale pseudo-dynamic experimental tests were carried out on 3D EBF allowing thus the investigation of replaceable links considering two arrangements: (i) steel solution – the link was uncoupled from the slab (ii) composite solution – the slab and link are connected. The aim of this paper is to present the results of finite element analyses (FEAs), based on calibrated models and the comparison between the obtained results and the experimental tests performed by [2]. The numerical investigation carried out aims to evaluate the shear overstrength and the level of axial force in the link for both tested configurations.

FINITE ELEMENT MODELLING OF DETACHABLE SHORT LINKS

Eccentrically braced frames with replaceable links are viable seismic resisting systems that guarantee large dissipative capacity and quick and easy replacement of the damaged dissipative zones after seismic events, thus reducing the repair costs. Experimental tests carried out within DUAREM research project [12] demonstrated the high effectiveness of this system and highlighted the importance of the bolted connections of the shear links on the system response at both global and local level. In order to investigate the behaviour of the tested detachable links, finite element analyses have been carried out. The finite element (FE) models are calibrated on the basis of the experimental response curves in terms of the shear force and link rotation. Once calibrated the finite element models, several parameters have been investigated such as the type of pre-loadable bolts (i.e. HR and HV), the level of bolt clamping force, the boundary conditions, the presence of constructional tolerances (e.g. initial gap between end-plate at both link ends). The results from the parametric study enables the characterization of the shear and axial force interaction on the link end connections. 790 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 790-801

Comparison Between Different Design Strategies For Freedam Frames: Push-Overs and Ida Analyses

Modern seismic code design rules are known to be based on capacity design principles. They try to assure the damage to occur in the ductile parts of the structure, such as beam ends while the other have to remain in elastic range. Therefore, in the aftermath of design earthquakes, plastic deformations at member or connection level will imply high repair costs. In the last decades, innovative structural solutions based on the so-called supplementary energy dissipation strategy allow increasing the dissipative capacity of structures through equipping it with special damping devices. In the case of substitution of dissipative zones with dissipative devices the strategy takes the name of substitutive strategy. This is the case of Moment Resisting Frames investigated in this paper, where traditional dissipa-tive zones, are equipped with innovative low damage frictional devices. However, the current version of codes does not provide any rules to design of MRFs equipped with this type of friction joints.

Preliminary Finite Element Analyses on Seismic Resistant FREE from DAMage Beam to Column Joints under Impact Loading

Nowadays, the interest on structural robustness is increasing because of the recent terroristic attacks. Although a large number of research projects have been carried out in this field, limited design guidelines as well as code recommendations are nowadays available. Leading to the fact that the design for robustness is far from being current practice. Conversely, the design for natural hazards as the earthquake is a well-consolidated practice and modern codes implement effective and well-recognized design rules. Even though seismic design philosophy based on the concept of hierarchy of resistance enables structural robustness for conventional structural systems, this is not demonstrated for structures equipped with anti-seismic devices as well as innovative dissipative systems. Recently, the use of friction based dissipative joints has been proved to be a promising solution for seismically design steel moment resisting frames. However, the robustness and the resistance against impact loading of this type of joints is not yet investigated. With the aim to develop an experimental campaign based on impact tests, preliminary finite element analyses have been carried out to identify the main criticisms and to drive the rational design of the joint specimens. With this regard, in the present paper, the results of a numerical parametric study on the preliminary push-down test are presented and discussed.