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Passive dampers play a key role in the smart and reliable design of building structures under uncertain earthquake loading. Passive dampers enable structural designers to enhance the potential of their structural design techniques and acquire the powerful methodologies for more reliable structures under unpredictable uncertainties. While there exist many review articles on optimization of passive dampers, this review is aimed at introducing a new perspective that most passive damper algorithms can be classified based on the combination of several component approaches with different objectives. Mixed approaches considering input uncertainties are particularly highlighted. Research focused on comparison among different optimization methods is also investigated. [ABSTRACT FROM AUTHOR]

The editorial discusses Nature-based Solutions (NbS) in the built environment, emphasizing the importance of working with nature to address societal challenges effectively. NbS involve actions to protect, manage, and restore ecosystems while providing benefits for human wellbeing and biodiversity. The article highlights the role of green infrastructure in climate adaptation and the need for a holistic approach that integrates ecological engineering with traditional grey infrastructure. Various studies presented in the editorial explore the application of NbS at different scales, from mesocosms to regional systems, to address challenges such as disaster risk reduction and sustainable urban development. [Extracted from the article]

Basin presence is believed to affect the ground surface response due to earthquakes, particularly in areas around the basin edge. Previous studies showed that 1-D and 2-D wave propagation analyses resulted in significant differences in amplification at the basin edge. However, the link between 1-D and 2-D responses has not been studied for engineering practices. In practical application, seismic studies were commonly performed using 1-D analysis, for example, to develop a city micro-zonation map. Based on practical considerations, it is necessary to estimate the scaling factor for the 1-D analysis by considering the basin presence, particularly for one containing soft soil. There are three stages carried out in this study. The first stage: collecting data on some basin geometries for the 2-D modeling references and then defining selected site class and input motions. The second stage: modeling 1-D and 2-D wave propagation using D-MOD and Fast Lagrangian Analysis of Continua (FLAC), respectively. The third stage: comparing spectral acceleration resulting from the 1-D and 2-D analyses to obtain the scaling factors. This research studied and reported the relationship between PGA values varied as 0.2 g, 0.3 g, 0.4 g, and 0.5 g, basin geometry (e.g., the angle was set to 5°, 10°, 15°, 30°, and 45°, with depth and width variations of 0.0125, 0.025, 0.05, 0.075, 0.1, 0.2, and 0.4, while the basin width was adjusted to 500 m, 1 km, 2 km, and 4 km), and the spectral acceleration in several observation points on the ground surface. Based on this evaluation, a series of scaling factors are proposed. These factors can be used for spectral acceleration from available hazard maps, commonly developed based on 1-D analysis. The application example of this scaling factor is presented in this study, using the Bandung Basin case. [ABSTRACT FROM AUTHOR]

This paper proposes an accurate and efficient reliability evaluation method for robust design optimization using a probabilistic approach. First, the validity of this method is verified using two benchmark functions. This method is then applied to the robust design optimization problem of building‐connecting damper parameters, and the effect of robust design is verified. The variation in the natural period and structural damping ratio of buildings is considered, and the criteria satisfaction rate (CSR) are directly evaluated using the response value calculated by time history response analysis. [ABSTRACT FROM AUTHOR]

An explicit design procedure of cross‐sections of framed tube high‐rise buildings via an inverse problem approach is presented. In the formulation, interstory drift ratios and net deformations of beams are prescribed. The derived expressions clearly express the three‐dimensional effect (tube effect) from the orthogonal frame. The expressions are helpful for the preliminary design because cross‐sections are rationally and rapidly provided for a set of target deformations without trial‐and‐error repetition. In the proposed design method, a 2×2‐bay basic model under a set of static horizontal loads is designed at first. Then, this 2×2‐bay model is transformed into a multi‐bay model. The second moments of cross‐section of the multi‐bay model can be obtained based on the equivalence of the responses of those two models in the case where the elongation of columns is neglected. In addition, assumptions of axial strains of columns are introduced to obtain the equivalent parameters of cross‐sections of the 2×2‐bay model. It is demonstrated through numerical examples that the proposed method has reasonable accuracy. [ABSTRACT FROM AUTHOR]

Summary: A pseudo‐multi impulse (PMI) is proposed as an extension of the ordinary base‐input multi impulse substituting a long‐duration, long‐period ground motion which can often be simulated by a multi‐cycle sine wave (MSW). PMI is treated as a multitude of impulsive lateral forces and hardly excites the higher‐mode responses of elastic multi‐degree‐of‐freedom (MDOF) models because the undamped fundamental participation vector is adopted as the influence coefficient vector. It is shown that the critical time interval of PMI can be obtained without any repetition. This enables a smart derivation of the critical response. The displacement transfer functions are derived for elastic MDOF models, where two kinds of the influence coefficient vectors are adopted: (1) one at every component (conventional one) and (2) the undamped fundamental‐mode participation vector. It is demonstrated that the critical PMI can efficiently and accurately evaluate the maximum responses under MSW and the critical input period of MSW for elastic–plastic MDOF models. Furthermore, PMI is extended to treat the critical case for the second eigenmode. Finally, the critical PMI is applied to high‐rise buildings for the investigation into the input energy and the cumulative plastic deformation ductility demand. [ABSTRACT FROM AUTHOR]

A new model reduction method is presented for moment‐resisting frames with viscous dampers. The proposed method considers (1) the interactive effect of added damping between the horizontal‐vertical directions and (2) the direct effect with regard to the vertical direction different from the conventional static condensation method. When brace‐type dampers are treated, these effects cannot be neglected originally. The proposed method gives a better correspondence of the fundamental eigenmode with that of the non‐reduced moment frame than the static condensation method. In addition, the proposed reduced model can accurately evaluate the maximum interstory drifts of the non‐reduced moment frame. The proposed model reduction method is formulated in the frequency domain. The frequency dependency of the stiffness matrix and the damping matrix of the reduced model is investigated. The influences of the added damping matrix by viscous dampers on the natural circular frequencies, the damping ratios and the participation vectors are also investigated. Finally, it is demonstrated through a numerical example that the displacement‐based optimization of the damper allocation can be accurately and rapidly conducted by using the reduced models throughout the optimization process. [ABSTRACT FROM AUTHOR]

A simple evaluation method of building resilience is proposed, and the resilience of elastic‐plastic high‐rise buildings is evaluated under resonant long‐duration ground motions. The concept of availability is incorporated into the evaluation model of the building resilience, which was proposed in the previous paper. Not only in‐building components but also external factors such as lifelines and redundancy of facility systems are considered in the evaluation model. Based on the evaluation model, the following probabilistic indices are formulated: (1) the expected value of the total recovery time, (2) the expected values of the availability of the structural frame, facilities, and non‐structural components just after an earthquake event, and (3) the maximum likelihood recovery curves (MLRCs) of the structural frame, facilities, and non‐structural components. Numerical examples are presented for evaluating the resilience of elastic‐plastic high‐rise building models under a pseudo‐multi impulse (PMI), which substitutes for resonant long‐duration ground motions. Finally, the influences of the passive viscous dampers, the redundancy of facility systems, and the uncertainty of manpower to repair the components on the building resilience are clarified through the results of numerical examples. [ABSTRACT FROM AUTHOR]

Summary: A new concept of a "lower‐bound transfer function (LBTF)" and a new frequency‐domain optimal damper design method are presented. LBTF expresses an ideal performance for response control in the frequency domain under a constant sum of added damping coefficients (or the total cost of dampers). The effectiveness of the damper design for each mode can be captured visually through plotting the transfer function amplitudes of the model and the LBTF. An efficient generation method of LBTFs is also proposed. The proposed design method provides designs with multimodal adaptability (effective for multimodes). It does not require much computational load to implement the method since the optimization is conducted in the frequency domain, and the first‐order or second‐order sensitivities of the objective function can be derived analytically. The proposed design and the fundamental mode optimal damper placement are compared for shear‐mass systems and moment‐resisting frames through the transfer functions and the incremental dynamic analysis (IDA). It is demonstrated that the proposed designs effectively reduce the floor acceleration responses and the elastic deformation responses. Moreover, it is shown that the proposed designs can effectively reduce the elastic–plastic responses although the optimization is conducted for linear elastic models. [ABSTRACT FROM AUTHOR]

In this study, a model for the evaluation of a building's resilience and recovery time is proposed, and a new method is developed for the optimal viscous damper placement for a targeted resilience. The features of this model are as follows: 1) building components are categorized into systems in view of their functionality, 2) recovery time is regarded as a function of the damage to building components and human resources for repairing the components, 3) the model is applicable to structural design. This design method uses a type of real‐coded genetic algorithm (GA). The effective use of a constraint on the sum of the added damper damping coefficients enables an efficient search for the solution. [ABSTRACT FROM AUTHOR]

An input velocity adjustment method of the critical double impulse (DI) is presented for efficient design of viscous dampers for elastic‐plastic moment frames. The input velocity is adjusted so that the input energy to the lowest eigenmode under the critical DI is equal to those under the selected recorded ground motions. This adjustment makes the critical DI work as the active earthquake. The response bounding property of the critical DI is supported by, (1) the multi‐modal property of the critical DI, (2) the usual excitation of the lowest mode response under recorded ground motions, (3) the large proportion of the instantaneous input energy to the total input energy in the critical DI. The proposed method can treat not only pulse‐like near‐fault ground motions but also ground motions of random nature. To validate the proposed method, the input energies and the maximum interstory drifts under the recorded ground motions and the critical DI with the adjusted input velocity are investigated for elastic single‐degree‐of‐freedom (SDOF) models, elastic proportionally damped MDOF models, and elastic‐plastic proportionally damped MDOF models. The optimization method presented in the previous paper is extended so that the critical DI can be treated for the design of viscous dampers for elastic‐plastic moment frames. [ABSTRACT FROM AUTHOR]

Summary: Knowledge of the camera motion is important in the applications of structural dynamic response measurement using a vision‐based approach because in most of the field measurements, such motion can be non‐trivial and the accuracy of dynamic response measurements is strongly affected by the camera motion. This paper presents a new framework for camera motion estimation and vision‐based displacement measurement, which greatly lowers the barriers to the application of generally positioned cameras from strictly stationary cameras. The contributions in this paper are twofold. First, camera motion as well as reconstructed structural displacement are calculated based on reference planar structures visible in a given scene. In this case, a homography is more effective at describing view changes and planar geometric constraints can be incorporated early in the reconstruction process, thereby improving the quality and effectiveness of the estimates. The second contribution is that the homography of the planar structure is estimated by a newly proposed tracking algorithm that combines RANSAC algorithm and Efficient Second‐order Minimization (ESM) technique, which refines the final estimates to sub‐pixel accuracy and avoids tracking drift and non‐smoothness effectively. Experimental results indicate that the quality of the camera motion estimation and displacement reconstruction can be significantly improved by the judgmatical use of the proposed algorithm for planar structure homography estimation. Furthermore, nonlinear structural system identification is carried out to additionally verify the proposed algorithm using unscented Kalman filter. [ABSTRACT FROM AUTHOR]

A novel static identification approach to beam damage is presented. It is based on the minimum constitutive relation error (CRE) principle where the exact stiffness, the exact displacement and the exact bending moment are shown to make the CRE functional minimal. For practical implementation, two cases regarding full-field displacement measurements and finite-point displacement data, respectively, are considered. For full-field displacement measurements, the CRE functional is directly treated as the objective functional while in case of finite-point measurement data, the CRE functional along with additional penalty terms for treatment of the finite-point displacement measurements is defined as the objective functional. Multiple loads and associated sets of measurements are also considered to improve the identifiability and robustness of the procedure. Convergence is finally verified through numerical examples. [ABSTRACT FROM AUTHOR]

The double-impulse input is introduced as a substitute for the fling-step near-fault ground motion, and a closed-form solution for the approximate elastic-plastic response of a structure with viscous damping under the "critical double impulse" is derived. Since only the free vibration appears under such a double impulse, the energy approach plays an important role in the derivation of the closed-form solution for a complicated elastic-plastic response with viscous damping. The quadratic function approximation for the damping force-deformation relationship is introduced. The validity and accuracy of the proposed theory are investigated through comparison of the results of the response analysis to the corresponding one-cycle sinusoidal input and actual recorded ground motions. [ABSTRACT FROM AUTHOR]

When we encounter a devastating earthquake disaster, we have upgraded the earthquake resistant design codes in the long history of earthquake structural engineering. However the repetition of this action does never resolve the essential problem. This is because building structures and input ground motions have various complex uncertainties and unexpected phenomena often occur. The 2011 off the Pacific coast of Tohoku earthquake also provided some unexpected phenomena. This review paper discusses how to narrow unexpected issues in future earthquakes by referring to several concepts. Critical excitation methods, info-gap theories for uncertainty representation and interval analysis methods are the principal concepts. [ABSTRACT FROM AUTHOR]

A new vibration control system including viscoelastic or viscoplastic rubber dampers is proposed for residential houses. This system consists of braces and a damper unit including a high-hardness rubber damper or a linear rubber damper. The high-hardness rubber damper possesses many unprecedented properties such as large stiffness, small temperature and frequency dependencies compared to most of usual viscoelastic dampers. Post tensioning forces are introduced into the braces to reduce small gap in joint parts and this system has high damping performance for micro-vibration. The control system can absorb sufficient energy through the high-rubber damper and post tensioning braces. A concept is introduced called an effective deformation ratio, i.e. the ratio of the actual damper deformation to the interstory drift of the frame, as a criterion to measure the damping performance and effectiveness of this system. To find out principal parameters that affect greatly the effective deformation ratio of the proposed new vibration control system, an incremental analysis method taking into account the geometrical and material nonlinearities is developed to simulate the main characteristics of this vibration control system. The accuracy of the analysis method is investigated through the comparison with the results by two simple analysis methods. The comparison with the experimental result is also conducted for further investigation. [ABSTRACT FROM AUTHOR]

The input energy and energy input rate to a base-isolated (BI) building during an earthquake are considered and formulated in the frequency domain. The frequency-domain approach for computation of input energy and energy input rate has different remarkable advantages compared with the conventional time-domain approach. It is demonstrated that the input energy can be of a compact form via the frequency integration of the product between the input component (squared Fourier amplitude spectrum of acceleration) and the structural model component (so-called energy transfer function). Furthermore, the energy input rate can also be of a similar form via the frequency integration of the product between the instantaneous power spectrum and the energy transfer function. With the help of this compact form, it is shown that the formulation in the frequency domain is essential for deriving arbitrary-order closed-form sensitivities of the input energy and energy input rate with respect to uncertain stiffness and damping coefficients in the BI storey. The closed-form sensitivity expressions provide us with information on the most unfavourable variation of the uncertain parameters that leads to the maximum input energy and input rate. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The specification of earthquake loads as inputs to engineering structures is a crucial task in earthquake engineering. There are cases, however, where the site under consideration has limited or scarce seismic data, making this process a difficult task. Meanwhile, structural engineers are often concerned with the worst-case scenario that can happen to the structure during its service-life under possible future earthquakes. Repeated ground-motion sequences occurring after short intervals of time, resulting from mainshock-aftershock earthquakes, have been observed in many parts of the world. Such ground motion is capable of creating severe damage in the structure due to accumulation of inelastic deformations from multiple sequences before any structural repair is possible. This paper models ground motions of multiple sequences that produce the maximum damage in the structure. The ground acceleration is represented as Fourier series, with unknown amplitudes and phase angles, modulated by envelope functions. The unknown parameters are optimized to produce the maximum damage in the structure while the ground motion is constrained to the available seismic data at the site. The resulting inverse nonlinear dynamic problem is tackled using optimization techniques, nonlinear time-history analysis and damage indices. Numerical illustrations on modeling critical earthquake sequences for inelastic frame structures are provided. It is shown that critical repeated acceleration sequences produce larger structural damage compared to single critical earthquakes. [ABSTRACT FROM AUTHOR]