Design Tools for Bolted End-Plate Beam-to-Column Joints

Predicting the response of beam-to-column joints is essential to evaluate the response of moment frames. The well-known component method is based on a mechanical modelling of the joint, through joint subdivision into more elementary components subsequently reassembled together to obtain the whole joint characteristics. Significant advantages of the component method are the following: (i) the mechanics-based modelling approach; (ii) the easier general characteristics of components. However, the method is commonly perceived by practicing engineers as being too laborious for practical applications. Within this context, this paper summarizes the results of a theoretical study aiming to develop simplified analysis tools for bolted end-plate beam-to-column joints, based on the Eurocode 3 component method. The accuracy of the component method was first evaluated, by comparing theoretical predictions of the plastic resistance and initial stiffness with corresponding experimental data collected from the available literature. Subsequently, design/analysis charts were developed through a parametric application of the component method by means of automatic calculation tools. They are easy and quick tools to be used in the first phases of the design process, in order to identify joint configurations and geometrical properties satisfying specified joint structural performances. The parametric analysis allowed also identifying further simplified analytical tools, in the form of nondimensional equations for predicting quickly the joint structural properties. With reference to selected geometries, the approximate equations were verified to provide sufficiently accurate predictions of both the stiffness and the resistance of the examined beam-to-column joints

The prediction of collapse mechanisms for masonry structures affected by ground movements using Rigid Block Limit Analysis

Abstract Masonry structures belonged to the Cultural Heritage suffered severe damages in the last decays due to the action of the settlement-induced ground movements. The researchers have been developing numerical tools for the vulnerability analysis and assessment of masonry structures subjected to settlements. Continuous, discrete and rigid block models were proposed in literature. The analysis of both local or global failure modes due to settlement is a still debated topic, involving several questions related to the modelling techniques and to the investigation of the parameters which affect the masonry behaviour against foundation movements. In this framework, the paper focuses on a numerical approach for the settlement analysis based on the rigid block limit analysis. The Italian Code (NTC 2018) also suggests linear kinematic approach for the seismic-induced collapse mechanisms analysis. In such a formulation, the structure is modelled as a collection of polyhedral rigid blocks assuming frictional contact interfaces with infinite compressive strength and zero tensile strength and neglecting the mortar contribution. Originally formulated for the in-plane and out-of-plane mechanisms analysis, the numerical formulation was recently improved in order to analyze blocky-structures subjected to uniform settlement. Numerical case study of a monumental masonry church facade subjected to uniform settlement at the base was presented in this paper aiming at testing the numerical procedure. The results were discussed to evaluate the software capability and accuracy in the settlement-induced collapse mechanisms prediction

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Yield and ultimate rotations of beam-to-column end-plate connections

The deficiencies of traditional force-based design approaches and the recognition of the key-role of displacements and deformations as reliable and direct index of structural damage caused by earthquakes recently produced a shift in seismic design and assessment philosophy. In fact, new performance-based design requirements have strongly emerged internationally in seismic design and analysis. One design concept that was developed in response to these needs is currently known as “displacement-based” design (DBD). A large amount of work has already been undertaken in the field of displacement-based design especially for reinforced concrete structures. Recommendations for steel moment resisting frame (MRF) structures are few and the available proposals have not been fully confirmed. In this context, a research project – named DiSTEEL (Displacement based seismic design of STEEL moment resisting frame structures) and aiming to develop performance-based design guidelines for moment resisting steel frame structures – has been funded by the European Community. The DiSTEEL Project was the framework of the study presented in this thesis. In case of moment resisting steel frames, beam-to-column joints are essential structural components that significantly affect the overall seismic response. Therefore, a first step towards the development of DBD rules for MRFs is the analysis of response of beam-to-column joints with a focus on limit-state deformations. Within the context briefly outlined, the focus of this work is on the features of the inelastic response of beam-to-column end-plate joints. The efforts are addressed to the development of simple yet reliable design equations and tools to predict joint rotations associated with selected limit-states. After a review of some available experimental data, an assessment of existing analytical models for predicting joint rotational stiffness and strength is presented. Using these analytical models the geometrical and material parameters mostly affecting the joint yield rotations are highlighted. Analytical predictions of yield rotations of both flush and extended end-plate joints are subsequently evaluated by comparison with experimental data. Once validated by such a comparison, the analytical tools are further developed for design purposes, in the form of design charts to be obtained by an automated application of the analysis tools. Finally, discussion and preliminary evaluation of the rotation capacity of extended end-plate joints are presented

Cold-formed thin-walled steel structures as vertical addition and energetic retrofitting systems of existing masonry buildings

According to the current trend for sustainable constructions in urban areas, the present paper deals with the analysis of vertical addition systems for energetic retrofitting of existing masonry buildings. Starting from the current European (EN 1998-3:2005) and Italian (NTC 08) technical codes for the seismic assessment of existing structures, first a FEM model has been implemented to investigate the structural performances of masonry units with variable storeys (1, 2 and 3) and material strength (fk = 1, 3 and 6 MPa). Later on, traditional (reinforced concrete, masonry and steel) and innovative (glued laminated timber and cold-formed thin-walled steel) technologies have been proposed as a solution for vertical addition of the studied buildings. Therefore, a numerical campaign of linear dynamic analyses has been undertaken on the examined structures aiming at selecting the best vertical addition solution. The achieved numerical analysis results have provided cold-formed steel systems as the dominant solution for improving the energetic behaviour of the inspected existing masonry buildings. Finally, the achieved numerical results have been confirmed by a consistent and reliable multicriteria decision-making (MCDM) TOPSIS method, where the proposed vertical addition systems have been compared with each other in terms of structural, environmental and economic performance parameters