Discussion on “Seismic instability of free-standing statues atop multispondyle columns: A heuristic very stable system of ancient technology”, by A.N. Kounadiis [Soil Dyn Earthq Eng 119 (2019)253–264]

[No abstract available

Suspension bridges under blast loads: a preliminary linearized approach

This paper investigates the influence of an explosive (blast) load on the behavior of a suspension bridge, after studying the explosion characteristics (force, distance and height of explosion) and their effect on the bridge. More specifically, the influence of these characteristics on the three basic deformations of the bridge, namely the vertical, the lateral and the torsional ones, is sought. In doing this, the bridge model used is simple, and does not include secondary factors, that do not decisively affect the response of the bridge. The theoretical formulation is based on a continuum approach that has been used in the literature to analyze such suspension bridges. The analysis is carried out using the modal superposition method, and the resulting differential systems are solved using the Laplace transformation and the Duhamel’s integral. The present work is preliminary and will be followed by a more accurate and thorough one under preparation. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature

Investigation of the seismic performance of a single story – Single bay special truss moment frame with SMAs incorporated

The present work deals with the improvement of the seismic performance of a Single Story-Single Bay Special Truss Moment Frame (STMF) by incorporating Shape Memory Alloys (SMAs) as dissipation devices in the special segment, which can recover their initial geometry after mechanical distortion by unloading through the phase transformation (martensitic-austenitic phase). STMFs were initially designed with a special segment located in the middle of the truss to dissipate the input energy through the formation of plastic hinges at the four corners of the chord members. This mechanism is replaced with the input energy dissipation through the SMA deformation in a pin-ended special segment. In what follows, the frame at hand is examined incorporating SMA bars per diagonal of either 0.025 m or 0.035 m in diameter, restrained against buckling, simulated via a 4-DOF mechanical model consisting of two lumped masses, under selected ground motions. To further evaluate the performance of the frame with SMAs incorporated and at the same time verify the model, a non-linear dynamic time-history analysis is conducted using SeismoStruct Finite Element software. The response of the proposed system is compared with the one of the conventional one. Results show that the proposed system leads to a decrease of the maximum displacement and potentially allows a much lighter construction. © 2021 Institution of Structural Engineer

A new rate-dependent constitutive model of superelastic shape memory alloys and its simple application in a special truss moment frame simulation

In this work, a new constitutive model of the behavior of shape-memory alloys is presented, based on earlier models, showing a very good agreement with the existing experimental results. A simple approximate application concerning the use of these alloys modelled as dissipation devices in a special truss-moment frame is demonstrated. The results obtained are considered sufficiently encouraging as a motivation for the ongoing work. © 2018 Maria I. Ntina and Dimitrios S. Sophianopoulos

Steel beam-to-column RBS connections with European profiles: I. Static optimization

In this work we present an optimization procedure for achieving best beam-to-column reduced beam section connections in steel moment frames under static loading. The whole scheme is based on selecting European I-profiles for beams and columns, using the component method of Eurocode 3 for evaluating the design moment resistance of the joint, regression analysis to correlate the geometrical and inertial characteristics of the various components and elementary principles of Mechanics. In doing this, were are led to a constraint optimization problem, which is formed according to the design restrictions of European and North American Standards for RBS connections, regarding expected seismic behavior. Adopting advanced numerical procedures, optimum results are obtained, regarding either combinations of connection components or existing steel frames, a fact validating the flexibility and applicability of the proposed method. The calibration, verification and validation of the excellent seismic performance of the results obtained will be demonstrated in a companion paper, via FE analyses under cyclic loading. Hopefully, this work will contribute in adopting RBS connections in the design of steel moment frames in European engineering practice, as well as in the relevant codes. © 2017 Elsevier Lt

Static and dynamic responses of suspended arch bridges due to failure of cables

A mathematical model is proposed to investigate the behavior of a suspended arch bridge, subjected to sudden failure of cables. The main aim of this study is to analyze the effects produced by potential cables failure scenarios on the deformations and stresses of the bridge. The studied suspended arch bridge has a dense arrangement of cables, but the method described herein may be easily extended to the case of a sparse arrangement of cables. The theoretical formulation is based on a continuum approach, which has been used in the literature to analyze such bridges. Finally, the equations obtained are solved using the Duhamel’s integrals and the Laplace transform. For an exemplary bridge, results are obtained for the cases of failure of one, two and five cables, and important conclusions for structural design purposes are drawn. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature

STRUCTURAL APPLICATIONS OF SHAPE MEMORY ALLOYS FOR SEISMIC RESILIENCE ENHANCEMENT

Shape Memory Alloys (SMAs) are metallic materials with advanced properties enabling them to recover their initial geometry by the application of heat or by unloading which indicates the shape memory and the superelastic effect respectively, through the phase change (austenitic-martensitic). The discovery of their special nature was made in the 1960s. It was noticed that they possessed a shape recovery capability, apart from their good mechanical properties, a characteristic that since then has made SMAs popular in a wide range of industrial fields. As far as engineering applications are concerned, research studies of implementations of the SMAs have increased in recent years. In the present paper a comprehensive and thorough look is attempted to familiarize with their use for structural engineering purposes while particular emphasis is shown to their deployment towards improving buildings’ seismic resilience. In this framework, recent advances in scientific research are summarized and presented aiming to provide an up-to-date scientific knowledge, highlighting thus also the SMA potential in construction sector. © 2022, Jordan University of Science and Technology. All rights reserved

Dynamic response of cable-stayed bridges due to sudden failure of stays: the 3D problem

This paper studies analytically the problem of the sudden failure of a number of stays through a suitable mathematical model, based on the analytical method exposed by authors in previous publications and extended in this study through a 3D analysis. The analysis is carried out by the modal superposition method, and the gathered equations of the problem are solved through the Galerkin procedure and the Duhamel’s Integrals. Characteristic examples are solved and useful diagrams and plots are drawn, while interesting results are obtained. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature

Fire resistance prediction of slim-floor asymmetric steel beams using single hidden layer ANN models that employ multiple activation functions

In this paper a mathematical model for the prediction of the fire resistance of slim-floor steel beams based on an Artificial Neural Network modeling procedure is presented. The artificial neural network models are trained and tested using an analytical database compiled for this purpose from analytical results based on FEM. The proposed model was selected as the optimum from a plethora of alternatives, employing different activation functions in the context of Artificial Neural Network technique. The performance of the developed model was compared against analytical results, employing several performance indices. It was found that the proposed model achieves remarkably improved predictions of the fire resistance of slim-floor steel beams. Moreover, based on the optimum developed AN model a closed-form equation for the estimation of fire resistance is derived, which can prove a useful tool for researchers and engineers, while at the same time can effectively support the teaching of this subject at an academic level. Copyright © 2022 Techno-Press, Ltd