**About the Editor**

#### **Maria Favvata**

Maria Favvata is an Assistant Professor at the Civil Engineering Department, University of Patras, Greece. Her primary research concerns the field of the seismic assessment and design of structures: nonlinear FE modelling; nonlinear static and dynamic analysis; seismic codes; building damage; performance-based earthquake engineering; structural pounding; and the morphological effects on structures. She has authored or co-authored 41 papers published in international journals and conference proceedings (one Keynote address, and two invited address) and one book chapter, while her published work has been referred by more than 1000 papers, h-index 15.

**Maria Favvata**

Department of Civil Engineering, School of Engineering, University of Patras, 26504 Rio, Greece; mfavvata@upatras.gr

#### **Introduction**

This Special Issue gathers 29 scientific papers that capture various open and challenging issues in earthquake engineering for the assessment and design of structures. Advanced computational, analytical, numerical, and experimental studies have provided novel results and interesting discussions.

Six papers are focused on evaluating the seismic performance of structures, considering key parameters that still have not been fully understood. Thus, the first paper authored by J. Valdés-Vázquez, A. García-Soto, and M. Jaimes [1] is focused on studying the effect of the vertical seismic component in the assessment and design of a steel frame structure. The paper authored by W. An, and G. Song [2] provides an insight into the influence of near-fault vertical seismic excitation amplitude on bridge pier failure. The paper authored by M. Srbi´c, A. Mandi´c Ivankovi´c, A. Vlaši´c, and G. Hrelja Kovaˇcevi´c [3] is focused on the seismic performance of existing bridge columns with an atypical cross-section, without seismic details and with smooth reinforcement. The vertical irregularity setback in a reinforced concrete (RC) building subjected to earthquake ground motions is the topic of interest in the paper authored by T. Maulana, B. Enkhtengis, and T. Saito [4]. A review of the methodologies regarding the effect of the seismic action's incidence angle on the performance of the structures is presented in the paper authored by I. Bugueño, J. Carvallo, and J. Vielma [5]. The sixth paper authored by A. Marchisella and G. Muciaccia [6] is focused on the evaluation of bi-axial shear demand for RC beam–column joints by comparing different numerical methods for seismic analysis.

Four papers are focused on providing new results to improve the effectiveness of dampers on the seismic mitigation performance of structures. In the first paper authored by M. Shih, and W. Sung [7] a new impulsive semi-active mass damper to mitigate the damage to facilities in high-rise buildings is presented. In the paper authored by J. You, Y. Yang, Y. Fan, and X. Zhang [8] a magnetorheological damper is proposed to analyze the multi-dimensional seismic mitigation performance and the torsional vibration characteristic of L-shaped frame structure. In the third paper authored by C. Mrad, M. Titirla, and W. Larbi [9] three types of passive energy dissipation systems tuned mass dampers, viscous dampers, and friction dampers are evaluated as strengthening solutions for RC symmetric buildings. Finally, the structural performance of a 10-story steel building with passive control systems using a single type of damper or a combination of different types of dampers is evaluated in the paper authored by A.K. Karimi, E. Moscoso Alcantara, and T. Saito [10].

The next four papers introduce new approaches for the seismic fragility assessment of structures. In the paper authored by M. Flenga, and M. Favvata [11] the seismic performance of RC structures subjected to structural pounding is assessed through displacementbased and curvature-based fragility curves. Different methodologies for developing the fragility curves of the pounding risk are evaluated, while linear and bilinear probabilistic seismic demand models are introduced. C. Contiguglia, A. Pelle, B. Briseghella, and C. Nuti [12] study the accuracy and the effectiveness of different analysis methods to assess the vulnerability of structures. For this purpose, fragility curves derived by MPA-based

**Citation:** Favvata, M. Special Issue on Seismic Assessment and Design of Structures. *Appl. Sci.* **2023**, *13*, 505. https://doi.org/10.3390/app13010505

Received: 23 December 2022 Accepted: 23 December 2022 Published: 30 December 2022

**Copyright:** © 2022 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

cloud analysis, IMPA, and cloud analysis are compared against IDA. J. Vielma, R. Aguiar, C. Frau, and A. Zambrano review the effect of masonry infill panels on the seismic response of RC structures with characteristics similar to the typology and the mechanical and the geometric characteristics of the corner buildings of Portoviejo [13]. Fragility curves have been developed based on IDAs, and a new damage measure based on floor rotations is proposed. In the paper authored by Q. Liu, and C. Yang a copula technique for developing seismic fragility curves for an RC-isolated continuous girder bridge, is presented taking into account different damage indicators [14].

In two papers, new types of reinforcing steel for the seismic design and assessment of RC structures are presented and discussed. The first paper authored by J. Žižmond, and M. Dolšek [15] introduces an insight into the seismic performance of RC frame buildings designed by Eurocode 8 and reinforced by a recently developed dual-phase reinforcing steel (DPD2). The DPD2 is a new type of reinforcing steel that increases corrosion resistance. The seismic performance of DPD2 buildings was found to be improved compared to those designed with conventional reinforcing steel. The other paper authored by V. Kytinou, P. Kosmidou, and C. Chalioris [16] evaluates the seismic behavior of RC external beamcolumn joints with CFRP longitudinal bars in the beam. Experimental tests followed by FE analyses were performed. The results of the FE analyses reveal useful insights into replacing conventional reinforcement with CFRP bars.

In the next four papers, experimental results are used to evaluate and/or validate the structural performance of components such as anchors, connectors, and nuclear components. So, in the paper authored by S. Lee, and W. Jung static and dynamic experiments on the anchorages of non-structural elements are conducted using the seismic performance evaluation criteria of anchorages in accordance with the standards of the United States and Europe [17]. In the paper authored by G. Koo, T. Shin, and S. Ma the seismic isolation performance, and the dynamic characteristics of full-scale laminated rubber bearings (LRBs) are investigated through a well-established test matrix [18]. Results of shaking table tests are used by G. Koo, S. Ahn, J. Hwang, and J. Kim to validate the inelastic seismic analysis method applicable to pressure-retaining metal components in nuclear power plants [19]. An external ALC panel connector is proposed by K. Ding, D. Zong, Y. Liu, S. He, and W. Shen [20]. In this paper, experimental and numerical results between the external hooked bolt connector and the pendulous Z-panel connector are analyzed and discussed.

Also, an interesting topic that is addressed in this Special Issue is the seismic performance of retrofitted structures. In the paper authored by Y. Sonoda, H. Tamai, and H. Ikeda the effectiveness of the SRS method as a seismic retrofitting method on existing dam piers is studied using FEM analyses [21]. The practical difficulties in upgrading the structural performance of existing RC structures when retrofitting structural members by conventional RC jacketing are discussed in the paper authored by G. Manos, and K. Katakalos [22]. In this paper, an effective procedure for the shear upgrade of under-designed RC T-beams is presented. The tensile capacity of CFRP strips with or without anchors can be found by using a simple, novel laboratory test set-up devised by the authors.

Some other studies are motivated by the need for analytical modeling tools that can effectively capture the seismic behavior of substandard RC structural elements. Thus, in the paper authored by S. Pardalopoulos, S. Pantazopoulou, and G. Manolis a new assessment framework is proposed aiming to determine whether the estimated local drift demands can be tolerated without failure developing along the load resistance path of substandard RC buildings [23]. The paper authored by C. Lu, and Y. Sonoda [24] presents an analysis model that can produce crack development during the pull-out process and evaluate concrete fracture, bolt fracture, and steel–concrete bond fracture in the SPH method.

A modification of the modal-based ground motion selection method is presented in the next paper authored by Y. Liu [25]. The proposed modified method aims on improving the reliability of the nonlinear response time history analysis of RC shear wall structures. On the other hand, the paper authored by R. Zhang, D. Ye, J. Zhou, and D. Quan [26] presents a modified displacement-based method for the seismic analysis of an underground structure in the loess area. Nevertheless, in the paper authored by A. Naqi, T. Roy, and T. Saito a method for evaluating the cumulative damage of buckling-restrained braces under multihazard events that are expected to occur during the service life of a high-rise building, is introduced [27]. The paper authored by E. Diaz-Segura [28] provides a review on the methodologies for seismic site classification according to the Chilean regulations from their implementation in the 1930s to the most recent proposal in 2018–2021.

In the last paper authored by F. Fuentes, S. Lozano, M. Gomez, J. Vielma, and A. Lopez the dynamic characteristics of a multistory RC buildings are estimated, considering two different identification techniques [29]. Data based on earthquake acceleration time histories recorded by accelerometers placed throughout the building are used.

**Funding:** This research received no external funding.

**Data Availability Statement:** Data sharing is not applicable.

**Acknowledgments:** I am grateful to all contributors who made this Special Issue a success. My thanks and congratulations to all the authors for submitting their work. My sincere gratefulness to all reviewers for their effort and time spent to help authors improving their papers. Finally, I want to express my gratitude to the editorial team of Applied Sciences for their effective and friendly collaboration. I wish this collection to serve as an inspiration for future research in seismic engineering of structures.

**Conflicts of Interest:** The author declares no conflict of interest.

#### **References**


**Disclaimer/Publisher's Note:** The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.
