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CONTENTS
Volume 28, Number 1, January 2025
 

Abstract
Response Spectrum (RS) tools, commonly used in aseismic-design codes, exhibit a significant limitation due to their inability to address non-classically damped (NcD) systems. This research tackles this challenge with original design-oriented RS tools, specifically tailored to NcD systems, unveiling a new concept: the non-classical response spectrum (NcRS). For the first time, the non-classical damping (NcDing) effect is presented as a disturbance in the conventional RS, depending on a phase shift angle serving as a modal NcDing indicator. Then, a practical NcRS model, based on white noise (WN), is proposed allowing the generation of modified response spectra through effortless calibration of conventional ones. Further contribution involves introducing single-termed non-classical cross-correlation (Nc-Cc) coefficients, unique in their independence from structural properties. Afterwards, a random-vibrations-based exact non-classical response spectrum method (ENcRSM) is developed. The ENcRSM's novelty lies in its applicability to arbitrary frequency distributions inputs. Another contribution is the practical NcRSM, derived from the original WN-based Nc-Cc and NcRS tools, aligning with aseismic regulations. Validation of the NcRS models through artificial simulations involving stochastic seismic motions, demonstrates their excellent performance. Numerical implementations showcase the superior effectiveness of Nc-Cc coefficients, particularly in high NcDing scenarios. Applying these design tools to a benchmark equipment-structure system illustrates their outperformance over classical methods, revealing instances where the latter may lead to unsafe designs.

Key Words
artificial simulation of stationary processes; first-excursion statistics of peak response; modified response spectrum; new modal combination rules; non-classically damped systems; random-vibrations-based design tools; stochastic analysis

Address
Naima Lebib: 1) Civil Engineering Department, National Polytechnic School (ENP), 10 Rue des freres Ouadek, Hacen Badi, B.P.182, El Harrach, 16200, Algiers, Algeria, 2) Civil Engineering Faculty, University of Sciences and Technology Houari Boumediene (USTHB), El Alia, B.P. 32, Bab Ezzouar, 16111, Algiers, Algeria
Mounir K. Berrah and Nouredine Bourahla: Civil Engineering Department, National Polytechnic School (ENP), 10 Rue des freres Ouadek, Hacen Badi, B.P.182, El Harrach, 16200, Algiers, Algeria

Abstract
This paper presents selected results from the numerical investigation of the potential effect of soil deformability on the peak seismic response of base-isolated buildings of various numbers of floors, under both near-fault and far-fault earthquake excitations. The dynamic simulations are conducted parametrically with the SAP2000 Open Application Programming Interface, through a custom-made software developed using the Python programming language. The motivation is twofold: firstly, to examine whether the common assumption that the soil deformability can be ignored in dynamic analyses of base-isolated buildings, assuming that it would be always beneficial to the peak seismic response; and, secondly, to assess the abilities of the provided interface in combination with a modern programming language to effectively and efficiently perform parametric analyses of base isolated buildings. Specifically, three different soil types are considered in the parametric analyses: rock, sand, and clay, using simplified soil springs to model the deformability of the supporting soil. Base isolated buildings with various numbers of stories are considered, while two sets of strong seismic excitations, near-fault and far-fault, are used in the conducted dynamic analyses, to assess the influence of soil deformability, as well as the earthquake characteristics, on the peak seismic responses of the simulated base isolated multi-story buildings. The computed results indicate that neglecting the soil deformability may lead to underestimation of the peak seismic responses, particularly in case of near-fault seismic excitations. That would be very crucial especially for the proper estimation of the required minimum width of the seismic gap that should be provided as clearance around a base isolated building to accommodate the maximum relative displacements that are expected at the seismic isolation level.

Key Words
base/seismic isolation; NF vs. FF seismic excitations; SAP2000 OAPI; soil flexibility

Address
Department of Civil and Environmental Engineering, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus

Abstract
Ensuring the normal operation of liquid storage tanks after the earthquakes is of great significance, but the probability of seismic damage of the non-isolated liquid storage tanks is relatively high. In order to improve the seismic performance of liquid storage tanks, a new type of three-dimensional isolation suitable for the liquid storage tanks is obtained through improvement. Considering the material nonlinearity, the liquid-solid coupling, and the liquid sloshing characteristics, a refined calculation model of the new type three-dimensional isolated liquid storage tanks is established. The damping effects of the new type of three-dimensional isolation, the ordinary three-dimensional isolation and the lead rubber isolation are compared and analyzed. The dynamic responses of the liquid storage tank under the action of different types of seismic waves is discussed. Finally, the parameter influence analysis is conducted. The results show that the control effect of the new type three-dimensional isolation on the liquid sloshing wave height is significantly better than that of the ordinary three-dimensional isolation and the lead rubber isolation. Moreover, the new three-dimensional isolation has a remarkable effect on vertical earthquake control. The dynamic responses of the tank wall under the action of the near-field pulse-like seismic waves is larger, and the damping effect of the new type three-dimensional isolation is more significant. As the friction coefficient of the new type three-dimensional isolation increases, the damping effect becomes weaker, and as the liquid storage height increases, the damping effect of the new type three-dimensional isolation becomes more significant.

Key Words
base-isolation; fluid-structure interaction; liquid storage tank; seismic control; seismic response

Address
Wei Jing, Yixin Zhang, Jie Feng and Shushuang Song: 1) Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology, Lanzhou, 730050, PR China, 2) Western Engineering Research Center of Disaster Mitigation in Civil Engineering of Ministry of Education, Lanzhou University of Technology, Lanzhou, 730050, PR China

Abstract
This study aims to provide valuable insights into the significant effects of varying local soil conditions, particularly non-uniform distributions, on isolator displacements in bridge structures. To achieve this, earthquake-induced maximum displacements in lead-rubber isolators of a box-girder highway bridge are systematically examined through a comprehensive parametric analysis. The research employs nonlinear time history analyses, utilizing an optimal set of artificial spatially varying earthquake ground motions (SVEGMs) that match the response spectra of different local soil classes. Additionally, wave-passage and incoherency effects, as well as local soil conditions, are incorporated in the generation of SVEGMs to ensure robust modeling. A custom-developed code, seamlessly integrated with a bridge structural analysis program via an application programming interface (API), automates the parametric studies. The numerical results reveal that, while wave-passage and incoherency effects are negligible for relatively short bridges, local soil effects significantly influence isolator displacements. Maximum isolator displacements increase as much as 358% when weak soils are located at critical points, such as piers adjacent to abutments, with the most pronounced impacts occurring at the abutments. In contrast, assuming a uniform distribution of the weakest soil type for analysis can conservatively reduce displacement variations by up to 17%, though this approach often leads to over-conservative and economically inefficient isolator designs. Moreover, increasing the height of pier columns on weak soils decreases isolator displacements at that support by approximately 33%, while simultaneously increasing displacements at neighboring supports by around 22%. These results underscore the importance of considering non-uniform soil distributions to achieve both safety and cost efficiency in seismic isolation design.

Key Words
box-girder highway bridge; lead-rubber isolator; local site effect; spatially varying ground motion

Address
Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey

Abstract
This paper presents a simplified procedure for the seismic evaluation of structures based on the dynamic capacity curve; and its validity as a structural property associated with seismic demands. The proposed procedure calculates the performance of a structure subjected to seismic demands from a uniform hazard spectrum through an approximation of the dynamic capacity curve constructed from modal spectral analysis associated with increasing intensity demands. To account for stiffness reduction and energy dissipation due to hysteresis, a single-degree-of-freedom oscillator with the characteristics of the fundamental mode is analysed. The approximation of the dynamic capacity curve obtained from the proposed procedure is validated by comparing it with that obtained from nonlinear time-history analysis under increasing intensity demands for two reinforced concrete structures: a 12-storey plane frame irregular in elevation and a continuous viaduct-type bridge.

Key Words
approximate analysis; dynamic capacity curve; incremental dynamic analysis; seismic performance; seismic performance; spectral modal analysis

Address
Francisco Bañuelos-Garcia and Jesus Valdes-Gonzalez: Facultad de Ingeniería, Universidad Autónoma del Estado de México, Cerro de Coatepec S/N, Ciudad Universitaria, Toluca 50110, México
Marco Escamilla: Instituto de Ciencias Básicas e Ingeniería, Universidad Autónoma del Estado de Hidalgo, km 4.5 carretera Pachuca-Tulancingo S/N, Mineral de la Reforma 42184, Hidalgo, México
Gustavo Ayala: Instituto de Ingeniería, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 CDMX, México

Abstract
This study concentrates on the seismic resilience assessment and reinforcement schemes of the RC frame shear wall building. Firstly, the theory of the GB/T 38591-2020 is introduced and the comparison among the international commonly used methods is conducted. Secondly, the fragility analysis and seismic resilience assessment of the RC frame shear wall building are performed, in which the resilience indicators (restoration cost, repair time and casualties) are elaborately analyzed. Finally, the retrofit schemes of the viscous damper, SMA brace and the hybrid of the two are proposed according to the seismic resilience weakness of the building, and the comparison of the original building and retrofit schemes is conducted. This study aims to help to identify the weak links of the existing RC frame shear wall building and formulate effective reinforcement schemes to improve the seismic resilience, which can provide theoretical reference for the retrofit of the RC frame shear wall building.

Key Words
fragility analysis; RC frame shear wall building; seismic resilience; seismic retrofit; SMA braces; viscous dampers

Address
School of Civil Engineering and Architecture, Key Lab of Electric Power Infrastructure Safety Assessment and Disaster Prevention of Jilin Province, Northeast Electric Power University, No. 169 Changchun Road, Chuanying District, Jilin, Jilin Province 132012, China

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