Response Of Tall Buildings Research Articles

Analysis of Wind Response of Braced and Unbraced Tall Building

As high-rise buildings become increasingly prevalent worldwide, their complex structural components and the need for high stability pose challenges for safety and design requirements. The present study investigates the influence of bracing systems and plan aspect ratios on the ability of tall buildings to withstand wind loads. The study aims to analyze the effects of these variables on the wind-induced responses of tall buildings and improve bracing system design for structures with high aspect ratios. Numerical simulations using finite element analysis software are conducted, creating various building models with different aspect ratios and bracing systems. The displacement, drift, base shear responses and time period of each model are examined to evaluate the effectiveness of different bracing systems. The results highlight the significant impact of aspect ratio on the response to wind loads, with larger aspect ratios experiencing greater motion and stress. However, well-designed bracing systems prove effective in reducing wind-induced motion and stress. The study provides insights on best bracing system for different aspect ratios, offering valuable insights for creating safer and more resilient high-rise buildings.

An optimal nonlinear fractional order controller for passive/active base isolation building equipped with friction-tuned mass dampers

This paper presents an optimal nonlinear fractional-order controller (ONFOC) designed to reduce the seismic responses of tall buildings equipped with a base-isolation (BI) system and friction-tuned mass dampers (FTMDs). The parameters for the BI and FTMD systems, as well as their combinations (BI-FTMD and active BI-FTMD or ABI-FTMD), were optimized separately using a multi-objective quantum-inspired seagull optimization algorithm (MOQSOA). The seismic performances of the BI, FTMD, BI-FTMD, and ABI-FTMD systems for a 15-storey building subjected to two far-field (Loma Prieta and Landers) and two near-fields (Tabas and Northridge) earthquakes were evaluated. The results indicated that structures with BI, FTMD, BI-FTMD, and ABI-FTMD systems outperformed the uncontrolled structure in reducing structural responses during the design earthquakes (Loma Prieta and Tabas). However, under validation earthquakes (Landers and Northridge), the peak acceleration of the building with the FTMD system was worse than that of the uncontrolled structure during the near-field Tabas earthquake. To address this issue, we proposed a combination of the active BI system and the FTMD system. Time history analysis results demonstrated that for the building equipped with the ABI-FTMD system, the peak displacement, peak acceleration, and peak inter-storey drift were reduced by approximately 60%, 64%, and 78%, respectively, as compared to the uncontrolled structure.

The extended consecutive modal pushover (ECMP) procedure for the seismic assessment of tall dual steel concentrically braced-moment resisting systems and concentrically braced frame (CBF) buildings

The contribution of higher modes to the seismic responses of tall buildings is substantially significant. In recent years, enhanced pushover analyses, developed to account for the effects of higher modes in predicting the seismic demands of tall buildings, have been mostly conducted for moment-resisting (MR) frame buildings. The question is whether these methods can accurately estimate the seismic demands of tall concentrically braced frame (CBF) buildings. Hence, this paper aims to extend the consecutive modal pushover (CMP) procedure for estimating the seismic demands of tall dual concentrically braced-moment resisting systems (CB-MR dual systems) and CBF buildings. In the extended consecutive modal pushover (ECMP) procedure, single-stage and two-stage pushover analyses are performed. Also, the modal properties of the structure are used to modify the displacement increment during the stages of the two-stage pushover analysis. Enhanced pushover methods, including the modal pushover analysis (MPA), modified consecutive modal pushover (MCMP), Extended N2, single-run multi-mode pushover (SMP) and modified upper-bound pushover (MUB) methods as well as the first-mode pushover analysis are implemented for the purpose of comparison. The seismic demands obtained by the pushover methods are compared to those from the most accurate nonlinear response history analysis (NL-RHA). The results demonstrate that although the degree of contribution of higher modes to the seismic demands at the upper storeys of the CB-MR dual systems and CBF buildings is less than the MR frames, this effect should be considered in estimating the seismic demands of this type of mid-rise and high-rise buildings. Furthermore, the ECMP method provides accurate storey drifts for almost all of the CB-MR dual systems and CBF buildings.

Directional alongwind and crosswind effects on the performance of a 15-storey steel braced frame building in seismic environment

The effect of crosswind loads on buildings has been studied since the 1980s, but only a few researchers reported on the nonlinear response of tall buildings under ultimate crosswind loads. Performance-based wind design procedures provide a structurally efficient and economical alternative to prescriptive code based design, however their establishment necessitates further research in the following areas: i) development of a straightforward procedure for the derivation of reliable wind time-history loadings from wind tunnel data; ii) assessment of the dynamic behavior of tall buildings excited by wind in the full range of response: linear-nonlinear-near collapse; and iii) quantification of the effect of directionality on building performance in the full range of response. Herein, local aerodynamic data are used to produce reliable estimations of the directional alongwind and crosswind time-history loadings for a 15-storey steel braced frame hospital building, in Montreal, Canada. The case study is designed to withstand the code-based wind and earthquake loads, as independent load combination cases. Then, advanced finite element models are employed to assess the effect of directional alongwind and crosswind loads on the building performance under increasing levels of input wind motion. Ten excitation angles from 0° to 90° are considered. Incremental dynamic analysis is employed to assess the building performance under recurring winds, including the wind directionality effect. To monitor fatigue failure, the rainflow counting method is used to approximate the number and amplitude of loading cycles exhibited by ductile brace members of the lateral force resisting system.

EFFECTIVE POSITION OF SHEAR WALL FOR HIGHER RISE FOR TIME HISTORY ANALYSIS

The abstract of the study that is titled "Effective Position of Shear Wall for Higher Rise for Time History Analysis" focuses on the investigation of the best placement of shear walls in tall buildings in order to improve the seismic performance of these buildings via the use of time history analysis. By doing this research, the researchers hope to find a solution to the essential problem of establishing the most effective location of shear walls in high-rise structures in order to reduce the effects of seismic forces. Evaluating the dynamic response of tall buildings under earthquake loading circumstances is the purpose of this work. This evaluation is accomplished through the utilisation of sophisticated numerical simulations and time history analytic methodologies. In order to conduct a full analysis of the structural behaviour, the investigation takes into account a number of parameters, including the height of the building, the configuration of the shear wall, and the seismic intensity. Additionally, the study analyses the influence of varied shear wall placements on key performance measures including base shear, story drift, and acceleration responses. The purpose of this research is to determine the ideal position and configuration of shear walls for higher buildings by means of systematic analysis and comparison of the results. This will help to reduce the structural vulnerability of the building and increase its seismic resilience. Those structural engineers and designers who are involved in the seismic design of high-rise structures will find the findings of this study to have significant implications. These findings provide valuable insights into effective strategies for improving the earthquake resistance of tall buildings through optimized shear wall placement. Keywords: Shear walls, High-rise buildings, Seismic analysis, Time history analysis, Structural optimization, Finite element analysis, Seismic performance, Building dynamics, Structural stability, Optimal placement.

Beneficial and detrimental impacts of soil-structure interaction on seismic response of high-rise buildings

In the traditional design method, structures are usually assumed as rigid base structures without considering soil-structure interaction (SSI). However, whether the effect of SSI on the seismic performance of structures is beneficial or detrimental is far from consensus among researchers. Moreover, previous literature mostly concentrated on the seismic behaviour of mid-rise buildings and moment-resisting frames. Therefore, it is in real need to comprehensively investigate the seismic response of tall buildings considering SSI. In this study, a soil-foundation-structure model developed in finite element software and verified by shaking table tests is used to critically explore the effects of SSI on high-rise buildings with a series of superstructure and substructure parameters. The beneficial and detrimental impacts of SSI are identified and discussed. Numerical simulation results indicate the rise in the stiffness of subsoil can dramatically amplify the base shear of structures. As the foundation rotation increases, inter-storey drifts are increased, and base shears are reduced. In general, SSI amplifies the inter-storey drifts showing detrimental effects of SSI. However, as for the base shear, SSI exerts detrimental effects on most piled foundation cases as well as classical compensated foundation structures resting on Ce soil, whereas, for compensated foundation structures resting on soil types De and Ee, effects of SSI are beneficial since the base shear is reduced. Moreover, regarding buildings with different structural systems and foundation types, minimum base shear ratios considering the SSI reduction effect are presented.

A corner protrusion strategy for the aerodynamic response mitigation of tall buildings with the aim of using non-structural components

Side protrusion, i.e., the addition of material on the side of a tall building, has been demonstrated as an effective strategy to mitigate the aerodynamic responses under a broad range of design wind speeds. This study investigates the possibility of producing similar behavior of side protrusion via a corner protrusion strategy. The proposed strategy is evaluated using two parameters, which are the gap ratio (GR) and the protrusion ratio (PR). High-frequency force balance (HFFB) wind tunnel testing was carried out to examine the aerodynamic performance of ten models under different wind angles. The results demonstrate that the corner protrusion strategy can achieve similar performance as the side protrusion strategy using nonstructural components (NCs). The reductions of base overturning moment (OTM) for model CP-14–86 are 33%, 39%, 33%, and 24% at the mean hourly design wind speeds (cities) of 42 m/s (San Francisco), 53 m/s (New York), 62 m/s (Houston), and 77 m/s (Miami), respectively. The effectiveness of the corner protrusion strategy occurs when the PR is larger than 6%. The benefits of using NCs to reduce wind responses of tall buildings are discussed, which is expected to be a competitive aerodynamic strategy not only for new buildings but also for retrofitting existing buildings.

Methodology to minimize the dynamic response of tall buildings under wind load controlled through semi-active magneto-rheological dampers

This paper proposes a methodology to evaluate and optimize the dynamic response of tall buildings under wind loading, controlled through semi-active Magneto-Rheological dampers (MR dampers). For this, a tall building, modeled as a 2D frame, is taken as case study and three structural control configurations are proposed. The original structural configuration of the building is the first configuration analyzed, called Uncontrolled Original (C1). In the second configuration, called Uncontrolled Optimized (C2), the fundamental frequency of the building is optimized via PSO algorithm as a function of its mass. Then, in the third configuration, Controlled Optimized (C3), a set of MR dampers with behavior formulated via the modified Bouc-Wen rheological model and controlled through the Linear Quadratic Regulator associated with the Clipped Optimal control strategy (LQR-CO) is applied to the structure. Finally, the dynamic response of the three scenarios under wind action is analyzed and compared to performance criteria established in the literature. The results demonstrate that the C3 configuration is the only one able of satisfying all the established performance criteria, proving that the proposed methodology y that combines structural optimization with MR dampers is a powerful tool for vibration control.

Performance comparison of linear and nonlinear compliant liquid dampers-inerter in controlling across-wind response of benchmark tall building

The potential of compliant liquid dampers-inerter (CLDI) for response control of tall buildings, capitalizing on the mass amplification property of the inerter, has been explored. However, the influence of the compliance connection on the damper displacement, energy dissipation, and inerter force is never addressed. The present work introduces a nonlinear compliant liquid damper-inerter (NCLDI), in which the compliance connection is achieved by joining the tank with the building through nonlinear spring and linear dashpot elements. The nonlinear mechanism (restoring force) is generated by connecting two linear springs in series. The effectiveness of NCLDI in reducing the across-wind response of tall buildings is examined and compared with that of a CLDI. For numerical demonstration, the 76-storey benchmark tall building is considered and subjected to across-wind loading. With the building's available mass, damping, and stiffness matrices, the uncontrolled and controlled structural responses are obtained using the Newmark–Beta method in the MATLAB environment. Iterations are executed at each time step to address the nonlinear stiffness term incorporating the Newton-Raphson method. Optimization is performed to estimate the optimum damper parameters utilizing MATLAB's multi-objective genetic algorithm solver, ‘gamultiobj’. The four selected objective functions are the peak and root-mean-square values of the roof displacement and acceleration. The performance of both the dampers is investigated for different inerter topologies with variable inertance ratios. The CLDI is found to be efficient when the inertance ratio and topology are less. However, an enhanced mitigation effect of the NCLDI compared to the CLDI is observed for higher inertance with a large topology. In addition, the stroke length of the damper is reduced significantly in case of NCLDI, which is a notable advantage for any passive damping device.

Towards estimating higher-mode effects on the seismic response of tall-buildings

Towards estimating higher-mode effects on the seismic response of tall-buildings

Uncertainty in the dynamic properties of tall buildings and propagation to the wind‐induced response

SummaryThe response of tall buildings to wind actions is commonly assessed through the quasi‐static approach considering mean, background, and resonant components of the action. The latter accounts for the amplification due to resonance and depends on the dynamic properties of the buildings, that is, modal mass, frequency, and damping ratio. Selecting appropriate values of the modal parameters of tall buildings is not immediate and is usually done using predictive models. These contain uncertainty, which eventually propagates to the dynamic response. The main aim of the paper is the assessment of uncertainty in the dynamic response of flexible buildings to wind action arising from a not perfect knowledge of their dynamic properties. The paper explicitly refers to the dynamic models given by Eurocode 1, but the approach is general, and the analyses can be repeated selecting any other model. It is found that the bias in the dynamic factor is always less than one, with values on average between 0.86 and 0.98. This indicates that the approach of Eurocode 1 is conservative. The only exception is that of the acrosswind response of steel buildings with an high aspect ratio, in which case the bias can be as large as 1.16. As to randomness, the coefficient of variation of the alongwind dynamic factor is very seldom found to exceed 10%, with average values around 5%. Such values are much lower than those of the coefficient of variation of damping, which is in the order of 50% or more. This indicates that uncertainty attenuates when it propagates to the response. On the other hand, the coefficient of variation of the acrosswind and torsional dynamic factors reaches values of 20% or more, indicating that such attenuation is much lower in that case.

Predicting crosswind response of tall buildings: Base isolation and nonlinear aeroelastic effects

This study introduces an analysis framework to evaluate the crosswind response of tall buildings under the influence of base isolation and nonlinear aeroelastic effect near the vortex lock-in wind speed. The motion-induced and buffeting forces are determined based on those in a building with a fixed base. The primary focus is on modeling the motion-induced force in tall buildings with base isolation, where no pre-existing model exists. The fundamental modal displacement is used to describe the building motion relative to the base. The Bouc-Wen model is employed to capture the hysteresis in the relation of shear force and displacement of the isolation system. Through response history analysis, the response statistics of a 65-story building with a square cross-section are determined and compared with those of a fixed-base building. An investigation is conducted to examine the impact of different isolation layer parameters on building response. Additionally, this study explores how the motion-induced force model influences the building response. The findings indicate that base isolation effectively mitigates nonlinear aeroelastic effects, leading to a significant reduction in crosswind response.

Machine learning techniques for diagrid building design: Architectural–Structural correlations with feature selection and data augmentation

Artificial intelligence (AI) and machine learning (ML) techniques are transforming building engineering. This work goes through the critical role of architectural parameters in influencing the structural responses of tall buildings, with a special focus on diagrid structures. The main aim of this study is to demonstrate how ML can improve the early design phase of diagrid buildings. Using a small, initially collected data set, enhanced through data augmentation, the classification of diagrid buildings in terms of design feasibility is investigated. This study identifies key architectural and structural parameters, employing various filter and wrapper methods for feature selection. The results show that our methods are effective in producing high-quality synthetic data, maintaining stable learning accuracies, and establishing accurate and robust relationships between architectural parameters and structural responses in diagrid buildings. These insights are crucial for facilitating more effective design processes in the realm of high-rise diagrid building design.

Formulation of justifiable wind loading distributions up tall buildings derived from HFFB measurements

For the general case of non-linear and combined sway and twist mode shapes, analysis of HFFB measurements gives rise to serious challenges and various techniques have been developed using significant assumptions. This is because it is not possible to directly obtain the distribution of varying fluctuating wind loads throughout the height of tall buildings. This paper proposes a straightforward HFFB-based wind load/twist distribution approach in the time domain to predict the wind-induced dynamic response of tall buildings. Using this framework, it is possible to overcome the deficiencies of mode shape correction factor approach, and the complexity and impracticality of alternative approaches for tall buildings. Two 1:300 scale rigid models of benchmark tall buildings, IAWE Buildings A and B, have been selected to perform a detailed wind tunnel investigation as subjects to evaluate this proposed HFFB approach study. Building A has complex 3D mode shapes combining sway and twist, whereas the simpler Building B has uncoupled linear mode shapes in sway and twist. The high frequency pressure integration (HFPI) wind tunnel technique was utilised to measure surface pressure information in separate tests to obtain the reference wind loading for validation of the HFFB predictions. Furthermore, a commonly used HFFB mode shape correction factor approach was used to estimate the dynamic wind responses which were compared to those from the proposed approach. From the comparison between the aerodynamic and dynamic wind results from proposed HFFB approach and reference HFPI results, it is found that the proposed HFFB approach can predict the vertical distributions of the wind forces and torque (wind loads) with acceptable accuracy for carrying out the conceptual stage of tall building design.

Wind-induced torsional loads and responses of tall buildings

High-rise structures are prone to wind-induced forces. Wind load can be resolved into three parts: along-wind load, across-wind load, and torsional wind load. There are well-developed and reliable methods for calculating wind-induced loads in the along-wind direction for tall buildings. Numerous methods are also available to estimate the across-wind load, but this is not the case for the wind-induced torsional load. Researchers have extensively investigated the torsional behavior of tall buildings using wind tunnel experiments and full-scale investigations. This paper attempts to compile the current understanding of the wind-induced torsional response of tall buildings. The present study contributes to realizing the effects of wind-induced torsional loads on tall buildings and gives an in-depth understanding through a comparison of past studies.

Prospect of LES for predicting wind loads and responses of tall buildings: A validation study

Wind load evaluation on buildings using large-eddy simulation (LES) poses several critical challenges. The most notable ones include accurately reproducing the approaching atmospheric boundary layer flow conditions and modeling massively separated flows around buildings. This study investigates the capability of LES for predicting cladding and overall loads on a tall building by addressing these key challenges. The results from LES are systematically validated against boundary layer wind tunnel measurements. The validation process unfolds in three key stages. Firstly, the approaching wind profiles were reproduced in LES by integrating a recently developed synthetic inflow turbulence generator with an implicit ground roughness modeling technique. Then, the statistics of the cladding and global loads were compared with the experiment for representative wind directions. Finally, the performance of the LES for predicting wind-induced response is examined, assuming typical structural properties for the building. Overall, the results obtained from each validation step showed encouraging agreement with the experimental measurement. In light of the findings from the current study, it is evident that LES is progressively realizing its potential to be a practical wind load evaluation tool. Selected simulation cases used in this study are available at .

SESMIC ANALYSIS OF VERTICALLY REGULAR AND IRREGULAR BUILDING

Earthquake damage results from several key factors, including irregularities in building design, soft stories, inadequate lateral strength, and structural interactions between the building and the ground. Within contemporary urban infrastructure, tall irregular structures play a significant role, representing a prominent feature that significantly impacts a building's response to seismic activity. Irregular structures are characterized by variations in geometry, mass distribution, and stiffness, making them susceptible to earthquake-induced damage. This study focuses on the analytical examination of vertical irregularities, encompassing stiffness irregularities, mass irregularities, and vertical geometry irregularities. The study comprises a total of 10 models, including an 11-story moment- resisting frame (MRF) building, along with additional models derived from the initial one to investigate stiffness, mass, and vertical geometry irregularities. Response spectrum analysis considering the design response spectrum provided by NBC 105:2020 is performed in each model and various responses of building are compared. From the study, it is concluded that there is significant variation in the responses of tall building with introduction of different vertical irregularities. Among the different kinds, the vertical geometry irregularity has comparatively more effect in responses in comparison to mass and stiffness irregularity in a particular storey.

Methodology & Impact of Vertical Irregularities on Seismic Responses in Tall Buildings: A Comparative Analysis

The vulnerability of tall buildings to earthquake damage is influenced by numerous factors, including irregularities in their design and construction. Irregular structures, characterized by variations in geometry, mass distribution, and stiffness, are particularly susceptible to seismic- induced damage. In this study, we conduct an in- depth analytical examination of vertical irregularities, encompassing stiffness, mass, and vertical geometry variations. Ten structural models are considered, including an 11-story moment-resisting frame (MRF) building and its derivative models, to investigate the effects of these irregularities. Response spectrum analysis, based on the design response spectrum from NBC 105:2020, is performed on each model, and the building's responses are compared. Our findings reveal significant variations in the responses of tall buildings when different vertical irregularities are introduced. Notably, vertical geometry irregularities have a more pronounced effect on responses compared to mass and stiffness irregularities in specific storeys. This research provides valuable insights into the seismic behavior of tall buildings and their vulnerability to vertical irregularities.

Seismic Behavior of an Inter-story Hinged Lateral Resistance Braced Frame

Based on the deflection behavior of structural components occurring at the lateral deformation of moment frames, a new lateral force-resisting system, the R-BRACE Frame (RBF) system, was proposed. This system is capable of effectively limiting the inter-story drift response of tall buildings. An evaluation was conducted using the finite element method program SAP2000 to simulate the internal force distribution and deformation of the system. The equivalent lateral force procedure (ELFP), the capacity spectrum method (CSM), a linear time-history analysis and the pushover method were applied to assess the yielding mechanism of the structure under different earthquake intensity levels. The findings revealed that the sub-unit, referred to as an R-BRACE, had a major impact on improving a structure's lateral stiffness. The placement of R-BRACE units could guarantee controllable stiffness degradation and enhanced seismic ductility, but would not alter the vertical load transfer path of the initial structure, which makes the RBF system an ideal option for seismic retrofitting. KEYWORDS: Lateral force-resisting system, R-BRACE frame, Enhanced lateral stiffness resistance, Seismic ductility

Improving aerodynamic response of tall buildings using smart morphing facades

Slender buildings are prone to vortex-induced vibrations and turbulence-induced buffeting. Usually, vortex-induced vibrations govern the strength and serviceability design criteria. The building's shape determines the aerodynamics of it; therefore, optimizing building shape can greatly reduce wind-induced vibrations. With a growing industry in adaptive and double-skin facades—mainly for energy saving purposes—there is an opportunity to innovate and implement smart, morphing facade modules (which we refer as Smorphacades) that actively modify their aerodynamic shape to alleviate flow-induced vibrations during high winds. This paper evaluates the performance of a 44-story tall building with the different configurations of the developed Smorphacade module system in mitigating building vibrations. Dynamic nonlinear time history analysis of the building under varying wind speeds ranging between 35 and 75 m/s are performed to evaluate the performance of building equipped with Smorphacade at low and high wind speeds. The performance measures chosen in the study are displacements and accelerations. Structural responses of building equipped with Smorphacade are compared against the bare building model responses to evaluate improvements in performance. Acceleration response comparisons at lower wind speeds provide insights into Smorphacade contributions to improving occupant comfort. Displacement comparisons at high wind speeds help understand the improvements in overall structural performance by reducing nonlinear response.