Gianvittorio Rizzano

Experimental Analysis of Bolted Steel Beam-to-Column Connections: Component Identification

In this paper, the results of an experimental program dealing with the ultimate behavior of bolted beam-to-column connections under cyclic actions are presented. The design criteria adopted for tested specimens are discussed in detail, aiming to point out how the ultimate behavior can be governed by properly strengthening the components for which yielding has to be prevented. To this scope, the component approach is adopted as a design tool for component hierarchy criteria. The aim of the paper is the investigation of the actual possibility of extending the component approach to the prediction of the cyclic response of beam-to-column joints. To this scope, the attention has been focused on the possibility to evaluate the overall energy dissipation capacity starting from the energy dissipation of the single joint components, provided that they are properly identified and their cyclic behavior is properly measured.

Cyclic Modeling of Bolted Beam-to-Column Connections: Component Approach

The work is aimed at the prediction of the cyclic response of bolted beam-to-column joints starting from the knowledge of their geometrical and mechanical properties. To this scope a mechanical model is developed within the framework of the component approach already codified by Eurocode 3 for monotonic loadings. Accuracy of the developed mechanical model is investigated by means of the comparison between numerical and experimental results with reference to an experimental program carried out at Salerno University. The obtained results are encouraging about the possibility of extending the component approach to the prediction of the cyclic response of bolted connections.

Experimental Behavior and Mechanical Modeling of Dissipative T-Stub Connections

This work aims to enhance the energy-dissipation capacity of classical rectangular T-stubs by proposing an hourglass shape for the T-stub flange according to the approach usually adopted for added damping and stiffness (ADAS) devices. A new type of axial damper is developed. First, a mechanical model of the device is set up and a finite-element model is carried out in ABAQUS code. The accuracy of both models is verified through comparison with experimental results. Next, on the basis of cyclic tests, the improvement of the energy-dissipation capacity of classical T-stubs provided by the proposed approach is quantified, and the low-cycle fatigue curves are determined with reference to the case of both T-stubs on rigid support and of coupled T-stubs. The results of the work also represent a useful tool for designing a dissipative double split tee connection.

A new method to design extended end plate connections and semirigid braced frames

Abstract In this paper, the relations between the parameters representing the rotational behaviour of extended end plate connections are investigated and, by a wide number of numerical analyses, their dependence on the geometrical detail of the connection is shown. As a result of these analyses, powerful design tools are presented. In addition, a design procedure for braced frames is suggested. The originality of the proposed procedure consists of its ability to guide the designer up to the complete detailing of beam-to-column connections. Finally, with reference to braced frames, some examples are presented to show the economical convenience of semirigid joints.

Cyclic Behavior and Modeling of a Dissipative Connector for Cross-Laminated Timber Panel Buildings

This article aims to propose an innovative type of angle to be used in substitution of the hold-down in cross-laminated timber (CLT) panel buildings. The new connection, called XL-stub, applies a concept similar to the classical ADAS (added stiffness and damping) device. In order to characterize the force-displacement response under cyclic loads of the proposed XL-stub, an experimental campaign is presented. Successively, the effectiveness of the proposed angle is proved by analyzing the non-linear response under seismic loads of a single wall alternatively equipped with hold-downs or the XL-stub.

Local Buckling of Aluminum Alloy Angles under Uniform Compression

Metal members are able to exhibit plastic deformations whose amplitude depends on the local slenderness of the plate elements constituting the member section, provided that global instabilities are prevented. This local slenderness depends on the width-to-thickness ratios of the plate elements and governs the occurrence of local buckling which can be developed either in elastic or in plastic range. Aiming at the development of a ductile behavior, the occurrence of local buckling in elastic range has to be prevented to assure the development of ultimate behavior in plastic range. To this scope, the width-to-thickness ratios of the plate elements constituting the member section have to be properly limited. Wide experimental research dealing with the influence of width-to-thickness ratios on the local buckling of heat-treated aluminum alloys has been recently completed with the aim of providing Eurocode 9 with the background data necessary for setting up classification criteria specific to aluminum members. The aim of the developed experimental activity is evaluation of the relationship between the strain corresponding to the complete development of local buckling and the slenderness parameters of the plate elements composing the section. This relationship has been derived by analyzing the results obtained from a great number of stub column tests carried out on specimens having width-to-thickness ratios covering the whole range of variability of commonly extruded profiles. The whole experimental program has dealt with square hollow section, rectangular hollow section members, channels, and angles made of 6,000 series alloy, provided by the major European aluminum industries. This paper presents and discusses the results of the part of the experimental program regarding aluminum alloy angles subjected to local buckling under uniform compression. Sixty-four stub column tests have been carried out at the Material and Structure Laboratory of the Department of Civil Engineering of Salerno University. These experimental results and their interpretation are presented in this paper. In addition, a classification criterion accounting for the interaction between the two slenderness parameters of the cross-section is proposed.

SEISMIC DESIGN OF STEEL FRAMES WITH PARTIAL STRENGTH JOINTS

In the seismic design of steel frames, beam-to-column joints can be designed either as full strength joints, forcing the location of the plastic hinges at the beam ends, or as partial strength joints which have to dissipate the seismic input energy. Seismic codes provide specific design criteria for full strength joints, but there are no detailed recommendations dealing with partial strength connections. Therefore, in this paper, by means of a simplified model, such as a SDOF system, the requirements which partial strength joints have to possess, for designing steel frames characterised by seismic performances equivalent to those of steel frames with rigid full strength joints, are pointed out. Successively, starting from the above requirements, a new method for designing seismic resistant steel frames with extended end plate connections leading to the complete definition of the geometrical and mechanical parameters of the joints is proposed.

Experimental Analysis on the Cyclic Response of Beam to Column Joints:State-of-the-Art at Salerno University

Aiming to provide a contribution to the codification of design rules for dissipative joints to be applied to MRFs, in last five years, a comprehensive experimental and analytical work dealing with the cyclic behaviour of beam-to-column joints has been developed by the research group of the University of Salerno. In particular, the activity has regarded the study of both classical and innovative typologies characterized by the same initial stiffness and resistance but by different hysteretic behaviours due to the different source of energy dissipation supply imposed in the design process. In this paper, the main results of such a study, performed at the laboratory of materials and structures of the University of Salerno, are reported in order to provide an overview on the main mechanisms involved in the energy dissipation of partial-strength connections. A particular attention is given to the design issues by presenting the procedures aimed at providing to the joints adequate characteristics in terms of stiffness, resistance and ductility supply by hierarchically controlling the behaviour of the single joint components. Furthermore, the results of tested joints (classical and innovative) are compared in terms of hysteretic behaviour and energy dissipation supply in order to point out the advantages of the different connecting systems.

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 Bolted T-Stubs Undergoing Large Displacement: A Preliminary Study

To properly assess the robustness of steel Moment Resisting Frames (MRFs), the non-linear response of structural members and connections would need to be quantified. Under the influence of extreme load cases, structural joints are subjected to both material and geometric nonlinearities, known commonly as second-order effects. These effects cannot be disregarded if catenary actions develop in the connecting beam member. The rotational capacity of bolted joints is directly dependent on the deformation capacity of its components in bending which are typically represented by the equivalent T-stub. A T-stub is composed of a single T-section bolted to a support whose stiffness may be equivalent or greater than that of the T-element. To accurately characterise the response of a T-stub undergoing large displacement, the non-linear behaviour of its flange will need to be thoroughly investigated. In the flange, second order effects are caused by the development of axial (or membrane) forces which can be significant for those T-stubs connected to a rigid support. Hitherto, little information exists on the influence of second-order effects on the response of bolted T-stubs and, consequently, there are no existing guidelines on how to include these effects in design. In this paper, we present the results of a parametric investigation, using finite element (FE) analysis, to assess the influence of second-order effects in T-stubs bolted to a rigid support. Both material and geometrical non-linearities were considered since they are known to have a critical impact upon the performance of T-stubs. A benchmark FE model is first generated and validated against experimental data; it is then used to carry out a parametric investigation, by alternately considering and neglecting geometric non-linearity, to identify the geometric configurations that experience significant second order effects. A method to assess the contributions of membrane forces to the overall deformation response of a T-stub is also proposed