Federico M. Mazzolani

Theory and design of seismic resistant steel frames

Preface. Notation. Basic seismic design criteria. Global ductility of MR-frames. Local ductility of steel beams and beam-columns. Evaluation of the q-factor. Overall stability effects. Behaviour of connections. Seismic behaviour of semirigid frames. Structural regularity. Influence of random material variability. Influence of claddings. Index.

PLASTIC DESIGN OF SEISMIC RESISTANT STEEL FRAMES

A new method for designing moment resisting steel frames failing in a global mode is presented in this paper. Starting from the analysis of the typical collapse mechanisms of frames subjected to horizontal forces, the method is based on the application of the kinematic theorem of plastic collapse. The beam section properties are assumed to be known quantities, because they are designed to resist vertical loads. As a consequence, the unknowns of the design problem are the column sections. They are determined by means of design conditions expressing that the kinematically admissible multiplier of the horizontal forces corresponding to the global mechanism has to be the smallest among all kinematically admissible multipliers. In addition, the proposed design method includes both the influence of distributed loads acting on the beams and the influence of second-order effects. In particular, the influence of second-order effects, which can play an important role in the seismic design of steel frames, is accounted for by the mechanism equilibrium curves of the analysed collapse mechanisms. Moreover, in order to show the practical application of the proposed design procedure, a worked example is presented. Finally, the inelastic behaviour of the designed frame is compared to that obtained when the simple member hierarchy criterion or a similar rule is applied.

Ductility of Seismic-Resistant Steel Structures

Preface. Notations. 1. Why Ductility Control? 2. Learning from Earthquakes. Seismic Decade 1985-1995. 3. Basic Design Philosophy. 4. Material and Element Ductilities. 5. Section and Stub Ductilities. 6. Member Ductility Evaluation. 7. Advances in Member Ductility. 8. Comprehensive Methodology for Ductility Design. Appendix. DUCTROT computer program.

Post-earthquake fire resistance of moment resisting steel frames

Fires following earthquakes are considered one major threat in seismic regions. In fact, according to modern seismic codes, ordinary structures are designed to suffer damage to some extent during strong earthquakes, exploiting the structure own ductility to avoid collapse and safeguard human lives. Then, a fire coming soon after an earthquake will find a different, more vulnerable, structure with respect to the initial, undamaged, one. Depending on the extent of damage, the fire resistance rating of the structure could be significantly reduced. This paper is devoted to obtaining some quantitative information about this topic, with reference to steel moment-resisting frames, even if the adopted methodology could also be extended to either different structural types or structural materials. As a first step, a simplified modelling of earthquake-induced structural damage, based on the superposition of geometrical and mechanical effects, is proposed. Then, a wide numerical analysis is performed with reference to a single-bay single-storey frame structure, allowing the main parameters affecting the problem to be identified. Finally, two multi-storey plane frames, designed in accordance with methods specified by Eurocodes, are analysed as a case study.

Experimental analysis of steel dissipative bracing systems for seismic upgrading

Abstract Energy dissipating devices, such as metallic ductile dampers, could represent one reliable system for seismic performance upgrading of reinforced concrete (RC) structures. This paper illustrates the significant improvement to the seismic response of RC structures equipped with dissipative bracing systems, such as eccentric braces (EBs) and buckling restrained braces (BRBs). In fact, the results of experimental tests carried out on two similar two‐storey one‐bay RC structures, respectively equipped with EBs and BRBs, are described. Referring to EBs, 3 lateral loading tests have been performed. Each test is characterized by shear links with bolted end‐plate connections. Different design criteria have been applied in the design of the connections. In the first test, capacity design criteria have not been considered. In the second test, a capacity design criterion has been applied, with a link shear over‐strength factor equal to 1.5. In the third test, a design criterion similar to the one adopted fo...

Seismic response of MR steel frames with low-yield steel shear panels

Non-linear dynamic analyses examining the seismic response of moment resisting (MR) steel frames enhanced with low-yield steel shear panels are presented. Shear panels, which act as damping and stiffening devices, are schematised as equivalent bracing elements having a suitable hysteretic behaviour. For this purpose, an analytical model is set up and calibrated on the basis of available experimental tests. A parametric analysis is therefore carried out varying several parameters of shear panels, namely strength, stiffness, ductility and hysteretic behaviour, aiming at determining those factors having the major impact on the seismic response of the frame. Obtained results show that the considered design procedure is really effective and convenient, low-yield steel shear panels providing an apparent reduction of storey deflection and damage level of the primary structure.

T-stub aluminium joints: influence of behavioural parameters

Abstract This paper is focused on the behaviour of aluminium alloy T-stub joints. The analysis is developed by means of finite element method simulation carried out with the non-linear code ABAQUS. The procedure has been accurately calibrated on the basis of some existing experimental results. The analysis, which has been referred to several behavioural parameters, has shown that, contrary to steel joints, the collapse mechanisms cannot be clearly defined, owing to a more gradual transition observed between each other. This is mainly a consequence of the stronger influence of the alloy hardening features.

Earthquake engineering for structural design

Living with Earthquakes Learning from Earthquakes Engineering Seismology and Earthquake Engineering Advances in Conception About Earthquakes Tectonic Plates and Faults Faults and Earthquakes Earthquakes and Structures New Design Philosophies Progress and Challenges in Codifications

Modern trends in the use of special metals for the improvement of historical and monumental structures

The basic features of advanced metal materials and metal-based technologies, including innovative strategies for seismic protection based on the dissipation of seismic input energy, are shown and discussed in this paper, with particular emphasis on their application in the field of structural rehabilitation. The use of very advanced solutions relying on shape memory alloys, presently under experimentation in the world, is addressed in the paper as well. In the context, some outstanding cases of structural rehabilitation of historical and monumental works are presented and discussed. The aim is to illustrate the potential of these new materials and technologies in the restoration and preservation of cultural heritage.

Numerical calibration of an easy method for seismic behaviour assessment on large scale of masonry building aggregates

The paper deals with the numerical calibration of a speedy procedure for large scale seismic vulnerability assessment of masonry building aggregates, which are typical building compounds diffused within historical centres of many Italian towns. First of all, based on several numerical analyses developed with the 3MURI calculation program, this simplified assessment procedure has been implemented, it being derived from the well known vulnerability form for masonry buildings integrated by five parameters accounting for the aggregate conditions among adjacent units. Later on, the set-up procedure has been validated through an application to a single building aggregate in the Vesuvius area. Since the results previously achieved have been again confirmed, subsequently the procedure has been used to investigate a wide area of the historical centre of Torre del Greco, allowing for the knowledge of the buildings most at risk under earthquake.Finally, the methodology has been applied to the historical centre of Poggio Picenze (AQ), damaged by the recent Italian earthquake (2009), in order to prove its effectiveness to foresee the damage level experienced by other types of masonry aggregates under seismic actions.