Dynamic Response Of Buildings Research Articles

Long‐term building safety assessment from a series of earthquake excitations

AbstractStructural health monitoring is conducted to ensure the structural integrity of a building during earthquakes. This study aimed to improve our understanding of the dynamic response of buildings subjected to a series of earthquake excitations, focusing on interpreting structural dynamic characteristics and identifying potential seismic damage subjected to a series of earthquake excitations. To this end, a series of seismic response data of a 13‐story reinforced‐concrete/steel building were collected through long‐term monitoring over 2 years. A systematic approach for monitoring the health of the building was established by integrating several algorithms for vibration‐based (both output‐only and input–output parametric nonparametric feature‐discrimination algorithms) and model‐based feature extraction techniques. Furthermore, the time‐varying dynamic characteristics of the building were determined, including its modal frequency, mode shape, and stiffness, as extracted from features obtained over the monitoring period of 2 years. Safety assessment of this newly compound high‐rise building is investigated to explore the system dynamic characteristics through long‐term seismic monitoring.

A New Methodology for Optimal Design of Hybrid Vibration Control Systems (MR + TMD) for Buildings under Seismic Excitation

This study proposes a new methodology, based on the optimization procedure by a metaheuristic algorithm, for designing a hybrid vibration control system to mitigate the dynamic response of buildings under nonstationary artificial earthquakes (NSAEs). For illustration purposes, a 10-story shear building is studied. The hybrid control system involves the use of an MR damper (MR) and a tuned mass damper (TMD) located in different places of the structure. To describe the behavior of the MR, the modified Bouc–Wen model (MBW) was used. To calculate the damping force of the MR, the clipped optimal control associated with linear quadratic regulator (LQR), CO-LQR, was considered. The optimization was performed using the whale optimization algorithm (WOA) and seismic load generated by the Kanai–Tajimi spectrum. Different control scenarios were evaluated: MR-OFF, MR-ON, CO-LQR, STMD, and CO-LQR (MR + TMD) to determine the best control scenario that can effectively control the structure. Overall, the optimized hybrid control scenario (MR + TMD) was the only one able to adapt all story drifts to the control criterion of the consulted normative. Then, CO-LQR (MR + TMD), designed via the methodology proposed in this work, proved to be the best alternative to control the seismic response of this building.

Performance-based wind and earthquake design framework for tall steel buildings with ductile detailing

According to the Canadian building code, wind design relies on prescriptive static methods, which lead to a conservative design. In consequence, in moderate seismic regions where both winds and earthquakes are critical, the size of ductile members resulting from seismic design, and especially those of bottom floors, may not accommodate the elastic wind demand and larger member sizes are required. In general, this is the case of rectangular buildings, where in the direction perpendicular to the largest building dimension, the base shear due to elastic wind demand is critical, while in the orthogonal direction the seismic demand governs. Hence, in one direction, the allowable base shear increases above the seismic demand, which results in reduced energy dissipation and amplification of torsion. To mitigate the incoherence in the current building code, a refined code-based multi-hazard design approach, targeting performance of tall steel buildings in Eastern Canada, is proposed. Thus, accounting for the building’s overstrength and allowing limited controlled inelasticity under high-intensity wind, a wind-related reduction factor RW is proposed to reduce the design wind load. The method is implemented for the design of two identical 15-storey steel braced frame buildings, but of different occupancy, hospital and office, respectively. Nonlinear response history analyses are performed to verify the member sections of steel braced frames, while the parameters investigated are the interstorey drift, residual interstorey drift and floor acceleration. Then, seismic and wind incremental dynamic analyses provide insight into the multi-hazard dynamic response of buildings subjected to ground motions and winds of increasing intensity. The fragility concept is used to quantify the performance of studied buildings designed with RW = 2 versus the building designed with RW = 1. Comfort criteria, as well as, the drift acceptance criteria, commonly considered in research and practice, are used to verify the effectiveness of the proposed method. The nonlinear response of the studied buildings at the design level and beyond shows that using RW = 2 for wind design does not change the response at design level, but slightly decreases the collapse capacity within the acceptable range.

A Comparative Study on Dynamic Response of Buildings Resting on Coir and Rubber mat Reinforced Soil Bed

Geotechnical seismic isolation has emerged as an efficient technique for mitigating the severe effects of earthquakes by providing smooth synthetic liners beneath foundations or between soil layers for dissipating seismic energy through sliding. This study investigates the efficacy of using a rubber mat and a natural coir mat as reinforcement materials within the soil to act as a seismic soil-isolation medium. A three-dimensional finite element simulation of five-storey buildings resting on raft foundations in soft soil with and without the soil-isolation mechanism has been performed. The reinforced soil-structure system was exposed to two different earthquake motions, such as the ground motions corresponding to the elastic design spectrum for Zone III as per the Indian standard code (IS 1893 (Part 1): 2016) and the Northridge earthquake (1994). The proposed study deals with the analysis of dynamic responses of buildings when the soil is reinforced with a coir mat and rubber mat under earthquake motions. The findings show that the seismic responses of low-rise buildings are significantly reduced by a novel technique proposed in this work to reinforce the soil with isolation materials in their mat form to reduce the seismic responses under earthquake loads.

Dynamic certification and assessment of the buildings life cycle under regular explosive impacts

Today in Ukraine, there is no single legalized, generally accepted methodology (at the level of a Ukrainian building standard) for dynamic certification of buildings and structures. A unified approach is proposed as such a technique. It includes four components: visual inspection of buildings; experimental studies of the dynamic response of buildings or structures to explosive effects; mathematical modeling of the stress-strain state of the object under study; synthesis of the results of visual inspection; experimental studies and numerical simulation in order to generalize them systematically. As an approbation, the deterioration of the resource of reinforced concrete structures of residential buildings under the conditions of constant mass industrial explosions with a capacity of 500 to 700 tons in the quarry of Southern GZK (Mining and Processing Plant) in the city of Kryvyi Rih, Ukraine, has been studied. Based on the processing of numerous experimental data and the results of mathematical modeling, a probabilistic model for predicting the deterioration of the technical condition of reinforced concrete structures of the Center for Children and Youth Creativity “Mriya” has been obtained. Calculations of the risks of destruction of the building’s load-bearing elements for its vulnerable areas made it possible to clarify its service life. It decreased by ~ 30 years compared to the standard in 2012.

Prediction of the Influence of Higher Modes on the Dynamic Response of High-Rise Buildings Subjected to Narrow-Banded Ground Motions

This paper presents the results of a study aimed at assessing the effects of higher modes of vibration on the nonlinear dynamic response of tall framed-buildings subjected to narrow-banded motions. For this purpose, analytical models of a 20-story building were developed under the consideration of two types of hysteretic behavior and subjected to 20 seismic excitations having a dominant period of motion of 1[Formula: see text]s. While the fundamental period of vibration of the building equals 2.7[Formula: see text]s, its second period is close to 1[Formula: see text]s; as a result, the selected seismic excitations over-stimulate the participation of the second mode in the overall dynamic response of the building. The circumstances under which the contribution of higher modes gives place to an excessive response of the upper stories are identified, and quantitative measures are presented. From an engineering point of view, parameters that predict an excessive response of higher-level floors are proposed.

Seismic Analysis of RC High-Rise Buildings Rested on Cellular Raft

This paper includes the investigation of the soil–structure interaction (SSI) effect on the seismic response of 20 and 30-story reinforced concrete moment resisting frames (MRFs) rested on a piled raft foundation using the direct approach. After that, a study is conducted to show the impact of using a cellular raft instead of the designed solid raft on the dynamic response of the building. A study is introduced to select the best gap size for the cellular raft. The soil model is assumed as a single layer of sandy clay. Time history analysis by the direct integration method is performed under seven earthquake records (El-Centro, Northridge, Kobe, Chichi, Friuli, Kocaeli, and Loma), which are scaled to the Egyptian Code for Loads (ECP-201) response spectrum using a full 3D model by a finite element software named (Midas GTS NX). It is concluded that considering SSI significantly affects the dynamic response of high-rise buildings, and using cellular rafts generally leads to a decrease in their dynamic response.

The Use of SMAV Model for Computing Fragility Curves

Among the buildings with strategic role for civil protection purposes part of them were built before the introduction of modern seismic codes. Aiming to guarantee their operability in case of seismic events, they have to be assessed and, hopefully, seismically upgraded. This aspect arises the necessity of reliable low computational demanding numerical models and probabilistic strategies that can be easily adopted in case of the assessment of conspicuous building stock. Part of the authors proposed and validated, in previous works, a low-demanding seismic model calibrated on ambient vibrations (SMAV) that is engaged in this paper for calculating fragility curves. On the base of dynamic and geometric properties, the SMAV model simulates the dynamic response of buildings. The herein proposed procedure adopts the SMAV model and takes into account the direction of seismic input in a probabilistic manner. The use of the ASI scale as an Intensity Measure parameter is discussed and the results are compared to those obtained with others IM scales. Although SMAV implements an equivalent linear procedure the results are compared with those obtained by more sophisticated FEM models and nonlinear dynamic analyses with a satisfactory agreement. Finally, two real case studies are presented. The fragility curves for both the case studies are calculated and discussed. The results encourage the authors to the use of fragility curves based on SMAV model. Additionally, the fragility curves can be easily implemented in seismic risk assessment procedures at urban or territorial scale and, consequently, the proposed procedure may represent a key aspect in the reduction of seismic risk and rationalization of investments for the seismic upgrading of strategic buildings.

Study on dynamic safety distance of multi-storey buildings on the top of loess slope

In view of the frequent occurrence of strong earthquakes and the actual characteristics of buildings built on the top of slopes in the loess region of Western China, the dynamic response and stability law of loess slope under the building load on the top of the slope are discussed by using the three-dimensional finite element numerical calculation method. Taking the slope safety factor, acceleration amplification coefficient, building permanent displacement and slope sliding range as evaluation indexes, the dynamic safety of buildings on the top of the slope under earthquake is analyzed, and the recommended value of dynamic safety distance between top building and slope shoulder is put forward. The results show that: firstly, affected by the amplification effect of slope elevation, the dynamic response of buildings on the top of slope is stronger than that of buildings under slope. At the same time, affected by the amplification effect of the free surface of the slope, the dynamic response amplitude of the building is negatively correlated with the distance from the slope shoulder. Secondly, the horizontal acceleration ratio between the top building and the under building is the largest at the height of 3–6 m, indicating that the multi-storey building with pile raft foundation is most prone to damage at this height. Thirdly, the dynamic safety distance of multi-storey buildings with pile raft foundation located on the top of loess slope with slope height H ≤ 30 m and slope gradient 25° ≤ α ≤ 70° can be 24 m.

Seismic Response of Buildings Resting on Soil Isolated With EPS Geofoam Buffer

The present study deals with analyzing the efficacy of EPS (epoxy polystyrene) geofoam buffer as a soil-isolation medium to reduce the seismic energy transferred and thereby to reduce the dynamic response of buildings under earthquake-induced loads. Finite element simulation of the transient response of an integrated soil isolation-building system in which buildings resting on raft foundation in medium dense sand beds with and without soil-isolation mechanism has been carried out using a recorded accelerogram of El Centro earthquake. Four sets of three-dimensional buildings (one, two, three, and four story) of single bay moment resisting concrete frames have been considered for the analysis. The EPS geofoam buffer of various thicknesses was placed at different depths below the raft foundation. The results under field-scale conditions indicate that soil isolation provided by the EPS geofoam buffer substantially reduces the earthquake energy transmission to the superstructure during a strong earthquake.

Comparative Study on Dynamic Response of Buildings with Floating Columns

High-rise buildings are essential for providing the necessary space for both residence and offices due to the lack of large areas in an urban setting. However, these multi-storey buildings are prone to lateral loads such as earthquake loads due to their large mass. Often, columns of such multi-storey buildings are truncated at some level either due to some obstructions or some architectural restrictions. Such columns that do not directly rest on the foundation are called floating columns. The floating columns are generally considered harmful, especially for buildings constructed in seismically active areas. Their existence creates a discontinuity in the path to transfer the load resulting in an inadequate structure performance. Hence, this study focuses on reducing the risk factor due to seismic effects by strengthening buildings with floating columns using the shear walls, bracings, and masonry infills. A typical building with floating columns located at two different seismic zones was considered for the study. This building was strengthened by considering various approaches such as diagonal bracings, shear walls and infill walls. The equivalent static method is used in the study to carry out the seismic analysis. The results indicate that using any strengthening methods mentioned above can significantly reduce storey displacements. However, providing a shear wall is found to be more effective in reducing the storey displacements in both the directions of earthquake forces when compared with other methods. Though infills and bracings can reduce storey drifts, it was also found that at lower storey levels, there is a considerable increase in the storey drifts when bracings and infill walls are considered. This is mainly attributed to the presence of the open first storey. However, the storey drift values reduce at the higher levels.

Experimental study on wind-induced vibration and aerodynamic mitigation measures of a building over 800 meters

The new-generation high-rise buildings are taller and more flexible than before. Rigid model and aeroelastic model tests of a proposed steel super high-rise building with a height of 838 m were carried out in two simulated typical wind fields defined in the Chinese code [1] and the ISO standard (ISO 4354) in an atmospheric boundary layer wind tunnel. The wind pressure distributions of the building were obtained through the rigid model tests and then the wind-induced vibration responses of the building were calculated. Through the aeroelastic model test, the vibration responses of the building, which naturally include the wind–structure coupling effects, were directly obtained. The test results shows that strong crosswind vortex-induced resonance may appear at high wind speeds. Based on these results, the crosswind aerodynamic damping of the building was then studied. Finally, seven aerodynamic measures for controlling the wind-induced vibrations of the building were proposed and tested. The results show that the seven proposed aerodynamic measures can reduce the dynamic responses of buildings in different degrees.

A comparative evaluation of semi-active control algorithms for real-time seismic protection of buildings via magnetorheological fluid dampers

Semi-active vibration control is considered a powerful method in reducing the dynamic responses of buildings by using additional smart damping devices. In this study, magnetorheological (MR) dampers have been proposed as one of the semi-active control devices to mitigate the structural vibrations and improve the seismic performance of the structures. The performance of the MR dampers strongly depends on implemented controllers. Hence, the main purpose of this paper is to evaluate the efficiency of several semi-active control algorithms related to MR dampers for seismic control of civil building structures. A 5-story test structure is manufactured, and an MR damper is installed between the ground and the first floor. The performance of the semi-active control approach is experimentally evaluated on a shaking table under historical earthquake records. A neural network-based modeling approach is adopted in the inverse MR damper model for the current control. Three different control algorithms, namely Proportional-Integral-Derivative (PID), Sliding Mode (SMC) and Energy-based controller (EBC), are applied to the system in real-time. The shaking tests are also carried out on the structures with different natural frequencies by increasing the number of stories without changing the geometry and material properties of the 5-story building model. The results indicate that the SMC controller is the most effective control algorithm among all controllers in reducing the base shear force by 51%.

Optimal design of tuned mass dampers through differential evolution method for reducing the dynamic response of structures subjected to earthquake loads

This paper introduces a methodology for the optimal design of passive Tuned Mass Dampers (TMDs) to control the dynamic response of buildings subjected to earthquake loads. The selection process of the optimal design parameters is carried out through a metaheuristic approach based on differential evolution (DE) which is a fast, efficient, and precise technique that does not require high computational efforts. The algorithm is aimed to reduce the maximum horizontal peak displacement of the structure and the root mean square (RMS) response of displacements as well. Furthermore, four more objective functions derived from multiple weighted linear combinations of the two previously mentioned parameters are also studied to obtain the most efficient TMD design configuration. A parallel process based on an exhaustive search (ES) with precision to 2 decimal positions is used to validate the optimization methodology based on DE. The proposed methodology is then applied to a 32-story case-study derived from an actual building structure and subjected to different ground acceleration registers. The best dynamic performance of the building is observed when the greatest weight is given to the RMS response of displacement in the optimization process. Finally, the numerical results reveal that the proposed methodology based on DE is effective in finding the optimal TMD design configuration by reducing the maximum floor displacement up to 4% and RMS values of displacement of up to 52% in the case-study building.

Experimental validation of a simplified soil-structure interaction approach for the prediction of vibrations in buildings due to railway traffic

The use of numerical tools to predict and analyze the dynamic response of buildings exposed to railway traffic is essential to face the continuous challenges motivated by the increasing demand for transportation infrastructures in urban context. Given the complexity of the entire system involved, their experimental validation is an essential step. The existence of a completely characterized experimental test site, where the whole system is considered, from the vibration source (the vehicle-track interaction) to the receiver (the building and its users), allows approaching the problem in a comprehensive and integrated way. Thus, this paper presents an extensive experimental characterization of a structure built next to a railway line, in an experimental test site near Carregado, in Portugal, for which a deep characterization of the geotechnical profile and of the railway track has already been developed and is here summarized. The construction of the structure, exclusively for experimental purposes, allows the in-situ validation of a simplified methodology to deal with soil-structure interaction problems in the context of vibrations induced by railway traffic.

Nonlinear Dynamic Analysis for Safety Assessment of Heritage Buildings: Church of Santa Maria de Belém

Despite the remarkable longevity of heritage constructions, they typically present several structural fragilities inherent to their own material and constructive features. This fact is particularly relevant when seismic loads are concerned, because a very significant portion of such constructions lack adequate seismic resistance and require retrofitting interventions in order to mitigate their vulnerability. However, to guarantee the success of the interventions, the interventions should be carefully selected based on a full understanding of the dynamic response of the building and, particularly, its most vulnerable structural elements. Due to many reasons, the issues associated with this kind of analysis are still difficult to address; therefore, research on this subject should be encouraged. Taking this into account, the church of Santa Maria de Belém, one of the most emblematic buildings of the monastery of Jerónimos complex in Lisbon, is used in this work as a case study to discuss the nonlinear dynamic response of cultural heritage buildings. The nonlinear dynamic behavior of the church was numerically simulated with a three-dimensional (3D) model using artificially generated seismic acceleration time histories, in agreement with seismic hazard scenarios for return periods of 475, 975, and 5,000 years. The dynamic response of the church is discussed and a comparison against results derived from a pushover analysis is also presented. Finally, a modal analysis is presented, estimating the damage level that would be present in the church after the occurrence of such seismic scenarios.

Simulation analysis of TMD controlled building subjected to far- and near-fault records considering soil-structure interaction

This study aims to investigate the performance of a tuned mass damper (TMD) in mitigating the dynamic response of buildings to far- and near-fault earthquake records including soil–structure interaction (SSI) effects. The selected records ensure near-fault with forward directivity (FD) and near-fault with fling. The effects of certain parameters of the installed TMD, such as the mass, the frequency and the damping ratios have been investigated using a developed MATLAB code. Displacement, velocity, acceleration, and energy responses from the analysis of the building model subjected to each of the considered faults were numerically calculated. The obtained numerical simulation results for the cases without and with including the SSI effects are comparatively presented and evaluated for the building model with a TMD damper. The presented results clearly show that there is a more seismic demand on an induced response for buildings excited by near fault records with fling. In addition, the inclusion of SSI increases the induced responses and alters the role of TMD in reducing the superstructure responses.

Uncertainties in dynamic response of buildings with non-linear base-isolators

Dynamic response of base-isolated buildings under uni-directional sinusoidal base excitation is numerically investigated considering uncertainties in the isolation and excitation parameters. The buildings are idealized as single degree of freedom (SDOF) system and multi-degrees of freedom (MDOF) system with one lateral degree of freedom at each floor level. The isolation system is modeled using two different mathematical models such as: (i) code-recommended equivalent linear elastic-viscous damping model and (ii) bi-linear hysteretic model. The uncertain parameters of the isolator considered are time period, damping ratio, and yield displacement. Moreover, the amplitude and frequency of the sinusoidal base excitation function are considered uncertain. The uncertainty propagation is investigated using generalized polynomial chaos (gPC) expansion technique. The unknown gPC expansion coefficients are obtained by non-intrusive sparse grid collocation scheme. Efficiency of the technique is compared with the sampling method of Monte Carlo (MC) simulation. The stochastic response quantities of interest considered are bearing displacement and top floor acceleration of the building. Effects of individual uncertain parameters on the building response are quantified using sensitivity analyses. Effect of various uncertainty levels of the input parameters on the dynamic response of the building is also investigated. The peak bearing displacement and top floor acceleration are more influenced by the amplitude and frequency of the sinusoidal base excitation function. The effective time period of the isolation system also produces a considerable influence. However, in the presence of similar uncertainty level in the time period, amplitude and frequency of the sinusoidal forcing function, the effect of uncertainties in the other parameters of the isolator (e.g., damping ratio and yield displacement) is comparatively less. Interestingly, the mean values of the response quantities are found to be higher than the deterministic values in several instances, indicating the need of conducting stochastic analysis. The gPC expansion technique presented here is found to be a computationally efficient yet accurate alternative to the MC simulation for numerically modeling the uncertainty propagation in the dynamic response analyses of the base-isolated buildings.

Effect of pounding on nonlinear seismic response of torsionally coupled steel structures resting on flexible soil

The effects of earthquake induced pounding on the nonlinear response of torsionally coupled buildings resting on flexible soil are investigated in the current study. Three steel moment-resisting frame buildings with the same symmetric plan having 4, 7 and 10 stories are considered. Three-dimensional nonlinear models with different eccentricity ratios are created. The soil-structure interaction phenomenon is taken into account using the Winkler beam on nonlinear springs. The pair of adjacent structures spaced at different clear distances resting on a flexible soil are analyzed under a consistent set of ground motion records and the effects of seismic pounding, torsional eccentricity and soil-structure interaction are studied by comparison of nonlinear dynamic responses of buildings. The results show that the peripheral frames experienced the most critical conditions during earthquake-induced pounding and the combined effect of soil-structure interaction, torsional eccentricity and pounding results in the most severe nonlinear responses of the studied buildings in certain cases.

Non-structural elements and the dynamic response of buildings: A review

Non-structural elements and the dynamic response of buildings: A review