Super-tall Buildings Research Articles

Automated operational modal analysis for supertall buildings based on a three-stage strategy and modified hierarchical clustering

Several automated operational modal analysis (AOMA) methods have been developed to evaluate the dynamic characteristics of large-scale structures in real-time under environmental and operational variations. Typically, these methods need to manually set some thresholds to achieve automatic identification. However, there is a lack of uniform standards for setting these thresholds, which may result in the adoption of inappropriate settings in AOMA, thereby introducing errors in modal identification. To address this issue, this paper proposes a novel AOMA framework to automatically identify modal parameters, which mainly involves three steps. Firstly, the covariance-driven stochastic subspace identification (Cov-SSI) algorithm is employed to perform modal estimation based on measured ambient vibration records. Then, a three-stage strategy, including hard validation criteria, Gaussian mixture model clustering-driven soft validation criteria, and the local outlier factor algorithm, is presented to remove spurious modes and determine real physical modes. Finally, a modified hierarchical clustering based on the k-nearest neighbor information is applied to group the determined physical modes to achieve automatic modal identification. The effectiveness of the proposed AOMA framework in automatically identifying modal parameters is validated through a numerical simulation study for a five-floor frame structure. Furthermore, the proposed framework is applied to evaluate the modal properties of a 600 m high supertall building based on long-term monitoring records. The results show that the AOMA framework can effectively remove spurious modes and group physical modes, thus identifying the modal parameters with high accuracy. In short, the proposed AOMA framework is an effective tool for modal identification applied in field measurements or structural health monitoring.

Modal identification with uncertainty quantification of large‐scale civil structures via a hybrid operation modal analysis framework

SummaryIn operational modal analysis (OMA), only structural responses are typically available. In this context, bias and variance (uncertainty) errors may exist in modal estimates (especially damping estimates), resulting in inaccurate determination of the modal properties of large‐scale structures under harsh excitations. To this end, a hybrid OMA framework based on the modal decoupling, the natural excitation technique, the random decrement technique (RDT), and improved eigensystem realization algorithm (ERA) with the automated stabilization diagram is presented to perform high‐accuracy modal estimates with uncertainty quantification for large‐scale structures under normal and severe ambient excitations. The accuracy and effectiveness of the hybrid framework for identifying the modal parameters are validated by numerical simulation study of a framework structural model. Furthermore, the hybrid framework is applied to analyze recorded acceleration responses of a supertall building with 600‐m height under normal excitations and typhoon condition to verify its applicability in field measurements. The numerical simulation and field measurement studies demonstrate that the hybrid framework can not only perform precise modal estimations with uncertainty quantification through a single ambient vibration measurement but also effectively reveal the variations of modal properties of supertall structures under harsh excitations from multiple perspectives. This paper aims to enhance the reliability and accuracy of modal estimation for engineering structures and further provide insight into the variations of dynamic properties of large‐scale civil structures under severe excitations.

High-rise building foundation design of the Lakhta Center

The foundation is the most significant element of buildings. The foundation structure closely relates to the general construction of the building frame and is largely determined by soil conditions. High-rise buildings are complex engineering structures with increased requirements for strength, stability and durability. Therefore, their safety and durability depend on strength, deformity and stability of foundation. These principles allow creating foundations of the higher quality, bearing capacity, reliability, and durability.Purpose: Optimization of production processes in the construction of foundation structures of super tall buildings and structures.Research findings: The structural design of the Lakhta Center 462 m high in Saint-Petersburg, which is the tallest building in Europe. A particular attention is paid to the design and construction of the foundation. Key results can prove operation and design of high-rise buildings designed for weak and unstable soils.Value: Determination of the most significant factors influencing the choice of production processes during the construction of super-tall buildings.

Full-scale measurements of mode coupling vibrations during super typhoons on a rectangular supertall building with limited sensors

Towards a complete and accurate assessment of the model parameters (i.e., frequency, damping ratio, and mode shape) of supertall buildings, this study proposes a new modal identification method named SCA-MBSDA based on the framework of sparse component analysis (SCA) and modified Bayesian spectral density approach (MBSDA). The feasibility and uncertainty of the SCA-MBSDA method are analyzed in an underdetermined case using a three-degree-of-freedom frame structure via numerical simulations. Through measurements from a wireless biaxial ultra-low frequency accelerometer atop the building, the variations in the first three modal parameters of a 125 m high rectangular supertall building with significant multi-mode coupling vibrations (maximum accelerations >15 cm/s2) are illustrated during typhoons Hato and Mangkhut. The results demonstrate the high effectiveness of the SCA-MBSDA method in identifying time-varying structural frequencies and mode shapes. During super typhoon conditions, the third mode of the monitored building exhibits a significant decrease in natural frequency and modal stiffness, with reduced rates of 9 % and 17 %, respectively. The averages of the first three mode directions obtained from the measurements agree well with the values obtained from the finite element model (FEM). This paper aims to provide a feasible identification method to enhance the understanding of the changes in the first three modal properties of supertall buildings during typhoons.

A hybrid output-only scheme for precise modal estimation and uncertainty quantification of large-scale structure through vibration-based measurements

In structural health monitoring or operational modal analysis, owing to unknown or unmeasured ambient excitation information, only structural responses are typically available for modal identification. In this context, bias and variance (uncertainty) errors inevitably exist in modal estimates (especially damping estimates), resulting in inaccurate determinations of structural dynamic properties. To this end, a hybrid output-only scheme based on the second-order blind identification, block bootstrap, and enhanced covariance-driven stochastic subspace identification algorithm with first-order perturbation is presented in this paper to perform precise modal estimation and uncertainty quantification. The accuracy and effectiveness of the hybrid scheme in performing modal identification are verified by numerical simulation study of a framework structure. Furthermore, the hybrid method is applied to analyze recorded acceleration responses of a supertall building with 600 m height during Typhoon Kompasu by considering different sensor setups to verify its applicability and robustness in practical applications, and further investigates the dynamic properties of the skyscraper and their variations during the typhoon. The numerical simulation and field measurement studies demonstrate that the hybrid scheme can effectively reduce the bias errors and quantify the variance errors in modal estimates through a single ambient vibration test, thereby improving the confidence and accuracy of modal identification. Notably, the hybrid method is an effective tool to perform high-accuracy modal estimation and uncertainty quantification for large-scale structures under ambient excitations.

Exploring Key Issues in the Structural Design of Supertall Buildings

Exploring Key Issues in the Structural Design of Supertall Buildings

Examining Space Efficiency in Supertall Towers through an Analysis of 135 Case Studies

This study addresses the critical need for a comprehensive exploration of space efficiency in supertall buildings, a crucial aspect of skyscraper architecture with profound implications for sustainability. Despite the paramount importance of spatial utilization, the existing literature lacks a thorough investigation into this domain. This research aims to fill this significant gap by conducting an exhaustive analysis based on data from 135 case studies. The proposed model for evaluating space efficiency yielded compelling technical insights. The key metrics employed in this examination include: (1) average space efficiency: the findings revealed an average space efficiency of about 72%. This metric provides a quantitative measure of how effectively space is utilized in supertall buildings. (2) core area proportion: on average, the proportion of core area to the gross floor area was around 24%. This metric sheds light on the distribution of core areas within the overall structure, impacting both functionality and spatial optimization. This study also highlighted notable trends and characteristics observed in the examined cases: (3) central core design: the majority of skyscrapers featured a central core design tailored primarily for mixed-use purposes. This architectural choice reflects a strategic approach to maximize functionality and versatility in supertall structures. (4) structural systems: The outriggered frame system emerged as the prevailing structural system, with composite materials commonly used for the structural components. This insight into prevalent structural choices contributes to the understanding of the technical aspects influencing space utilization in skyscraper design.

Research on Wind Effects of Super Tall Buildings with Rounded Arcs, Triangles and Retracted Platforms

Research on Wind Effects of Super Tall Buildings with Rounded Arcs, Triangles and Retracted Platforms

Exploring the natural ventilation potential for supertall buildings considering vertical meteorology: A case study in Harbin, China

The natural ventilation strategy is gaining increasing attention from architects due to its advantages in reducing energy consumption and maintaining a healthy indoor environment. For supertall buildings, the vertical variation in outdoor meteorology has inspired us to explore the energy-saving potential by adopting natural ventilation strategy. This study investigates the impact of vertical variation in urban meteorology on the natural ventilation potential (NVP) of supertall buildings based on numerical simulation and field observation. Firstly, the Weather Research and Forecasting (WRF) model is used to simulate the urban meteorology of the study region by integrating the local climate zone (LCZ) map. Next, meteorological data from sounding experiments by unmanned aerial vehicle (UAV) and monitoring stations are used to validate the simulated result, and thereby to explore the vertical meteorology in urban area. Finally, the vertical NVP in supertall buildings is quantitatively assessed considering the impact of LCZ in urban areas based on thermal comfort models. The findings reveal that atmospheric temperature decreases approximately linearly with increasing altitude, with a maximum temperature gradient of up to −0.82 °C/100 m. Static models underestimated the annual natural ventilation hours (NVHs) by at least 348 h compared to the adaptive thermal comfort model. Compared to low-density building regions, the higher NVP is indicated in high-density building regions. This study aims to illustrate the importance of considering the vertical variations of urban meteorology, and is expected to assist architects and policy makers in quantifying the energy saving potential of natural ventilation in supertalls.

Seismic response analysis of super-high-rise building structures with three-layer isolation systems

This paper proposes a triple-layer isolation device based on the single-story isolation and double-layer isolation. By establishing dynamic equilibrium equations and conducting earthquake response comparative analyses on the same super-tall building structure using three different forms of isolation: single-story isolation, double-layer isolation, and triple-layer isolation, it is found that the triple-layer isolation device, which adds an isolation layer on the basis of the double-layer isolation device, exhibits many different characteristics in terms of its damping mechanism, seismic response rules, etc., due to the differences in the position and quantity of the isolation layer. Rare earthquakes are equivalent to ASCE maximum considered earthquake or annual occurrence probability of 2%. The research shows that, under rare earthquake conditions, the isolation effect of the triple-layer isolation device in the super-tall frame-shear structure is better than that of the single-story isolation and double-layer isolation devices. Particularly, as the number of floors increases, the triple-layer isolation device can significantly reduce the seismic isolation support tension and compression stresses, inter-story displacement, single-story shear force, overturning moment, and floor acceleration of the high-rise building structure, and concentrate the lateral displacement of the structure on the three isolation layers, dissipating most of the seismic input energy.

Automatic Identification of the Working State of High-Rise Building Machine Based on Machine Learning

High-rise building machines (HBMs) play a crucial role in the construction of super-tall buildings, with their working states directly impacting safety, quality, and progress. Given their extensive floor coverage and complex internal structures, monitoring priorities should shift according to specific workflows. However, existing research has primarily focused on monitoring key HBM components during specific stages, neglecting the automated recognition of HBM workflows, which hinders adaptive monitoring strategies. This study investigates the critical states of HBM construction across various structural layers and proposes a method rooted in vibration signal analysis to determine the HBM’s working state. The method involves collecting vibration signals with a triaxial accelerometer, extracting five distinct vibration signal features, classifying these signals using a k-Nearest Neighbors (kNN) classifier, and finally, outputting the results through a classification rule that aligns with the actual workflow of the HBM. The method was implemented in super-high-rise buildings exceeding 350 m, achieving a measured accuracy of 97.4% in HBM working state recognition. This demonstrates its proficiency in accurately determining the construction state and facilitating timely feedback. Utilizing vibration signal analysis can enhance the efficiency and safety, with potential applications in monitoring large-scale formwork equipment construction processes. This approach provides a versatile solution for a wide range of climbing equipment used in the construction of super-tall buildings and towering structures.

CFD simulation of wind loads of kilometer‐scale super tall buildings with typical configurations in veering wind field

SummaryThe atmospheric boundary layer (ABL), whose total height is about 1–1.5 km, is composed of the atmospheric surface layer (ASL) and the Ekman layer, which typically account for the lower 10% and the upper 90% of the ABL, respectively. The wind veering angle in the Ekman layer can be between 10° and 30°, which may be an important influence factor for the wind‐resistant design of kilometer‐scale super‐tall buildings. Unfortunately, there is very little research on this issue so far due to the difficulty in simulations of veering wind in wind tunnels and computational fluid dynamics (CFD) simulation platforms. In this study, the simulations of non‐veering and veering wind fields are presented, and furthermore, the wind loads of kilometer‐scale super tall buildings with several typical configurations in veering wind fields are numerically investigated. Specifically, the large eddy simulations (LES) of unsteady flow around three buildings, namely, a square building, a tapered building (tapering ratio: 6.6%), and a 4‐layer setback building with the same height and the same aspect ratio of 9:1, are systematically performed for the cases of veering wind and non‐veering wind. The wind pressures and wind forces on these buildings are obtained and comprehensively analyzed. The differences in the wind loads among the building configurations are highlighted, and the mechanisms are discussed based on the time‐averaged and instantaneous flow fields.

Integral Lifting of Steel Structure Corridor between Two Super High-Rise Buildings under Wind Load

This paper explores the lifting project of a steel structure corridor in the Haiyue Center, Quanzhou City, with a focus on mechanical response, safety, stability, and construction guidance under wind load conditions. The investigation attends to safety apprehensions stemming from the absence of horizontal constraints within the corridor, rendering it vulnerable to wind-induced loads. Measures are implemented to prevent collisions with nearby buildings during lifting. Stability challenges, including beam displacement and excessive stress, are examined. Anti-deformation trusses and inclined web rods are employed to ensure stability, prevent potential instabilities, and promote uniform deformation. The study also analyzes stress during asynchronous lifting. Through the enforcement of stringent parameters, where asynchronous displacement is confined to a maximum of 25 mm and asynchronous lifting load is limited to 20%, the structural integrity of the corridor is meticulously upheld. This judicious approach serves to not only avert deformation but also to forestall structural impairment. Therefore, the significance of stress distribution and deformation is emphasized when conducting the integral lifting of steel structure corridor between two super-tall buildings under wind load conditions. Simultaneously, relevant construction control measures have been devised, along with offering scientific recommendations for similar cases involving lifting construction processes under the influence of wind.

Amplitude dependence of natural frequency and damping ratio for 5 supertall buildings with moderate-to-strong typhoon-induced vibrations

Modal parameters play a significant role in the wind-resistant design and vibration control of high-rise buildings. Results from previous studies demonstrate that the natural frequency and damping ratio of high-rise buildings usually exhibit nonlinear variation characteristics with the increase of structural amplitude. However, due to lacking relevant field measurements, the features of natural frequency and damping ratio for super-tall buildings under large wind-induced amplitudes have been less explored. This paper presents a field study on typhoon-induced structural responses of five supertall buildings whose structural heights all exceed 300 m. The peak acceleration responses at the measurement height of most buildings exceeded 10 cm/s2 (gal), with the maximum response reaching 20 gal. Two frequently used methods, i.e., the stochastic subspace identification (SSI) and random decrement technique (RDT) methods are utilized to compare and analyze the amplitude-dependent characteristics of target modal parameters. It is found that with the increase of wind-induced structural vibration amplitude, the fundamental natural frequency generally first decreased and then leveled off, while the damping ratio for the first-order mode of the buildings except the one equipped with a tuned mass damper (TMD) system first increased while then tended to decrease. More interestingly, the critical normalized structural vibration amplitude associated with the maximum damping ratio is found to be in the range of 10−4∼10−5, which agrees well with the theory of “critical tip drift ratio”. Potential explanations for the above phenomena are presented. Furthermore, the obtained results are further compared with existing statistical models, and associated discrepancies suggest the complexities of the dynamic features of supertall buildings.

Reliable modal estimation of high-rise structures via synergistic usage of multiple stabilization diagram-based operational modal analysis techniques

In operational modal analysis, typically only structural responses are available. Errors and uncertainties may exist in modal estimates, thereby leading to discrepancies in the results by different modal identification approaches even analyzing the same data set. To this end, a synergistic usage of multiple stabilization diagram-based modal identification techniques is presented in this paper to reduce the errors and uncertainties in modal estimates associated with modal identification techniques or modeling ideas. The effectiveness and noise robustness of the synergistic strategy are validated via numerical simulation study of a frame structure. Additionally, the synergistic strategy is further utilized to evaluate the dynamic characteristics of a supertall building with 600 m height during a typhoon event. The application of the synergistic strategy to field measurements reveal that the building natural frequencies varied during the typhoon and exhibited significant amplitude-dependent features. Meanwhile, the damping ratios of the skyscraper for all concerned modes remained roughly stable within a range of [0.16%, 0.94%]. This paper aims to provide a practical way or effective tool to enhance the accuracy and confidence in modal estimation of high-rise buildings, thus further revealing the dynamic characteristics of large-scale structures under severe wind excitations.

Investigation of the Aerodynamic Forces on a 600-m-High Supertall Building by Field Measurements and Wind Tunnel Test

This paper investigates the aerodynamic forces on a 600-m-high supertall building based on field measurements during Super Typhoon Mangkhut and wind tunnel test on a 1∶500 scaled model of the monitored building. The local wind force coefficients and their power spectral densities obtained by the full-scale measurements and the model experiment are compared and discussed. The comparative study shows that the wind tunnel test provides conservative mean local drag coefficients and root-mean-square (RMS) local lift coefficients, whereas for the RMS local drag coefficients, the model experiment reproduces smaller predictions at higher levels than those from the onsite measurements. Moreover, to explore the deviations between the full-scale and model-scale results, the Reynolds number effects in the range of 5.5×104 to 1.8×108 on the local wind forces and the Strouhal number are investigated. It is found that the Reynolds number has evident effects on the local wind force coefficients, although its influence on the Strouhal number is negligible. This combined study of field measurements and wind tunnel test aims to enhance the understanding of the aerodynamic forces on high-rise buildings during strong windstorms and provide useful information for the wind-resistant design of supertall buildings.

Research on a surrogate model updating-based efficient multi-objective optimization framework for supertall buildings

Research on a surrogate model updating-based efficient multi-objective optimization framework for supertall buildings

The Influence of Aeroelastic Effects on Wind Load and Wind-Induced Response of a Super-Tall Building: An Experimental Study

To investigate the wind-induced response and equivalent wind load of a super-tall building, an aeroelastic model of the building was designed to measure aerodynamic interference in wind tunnel tests. Experiments on pressure and vibration measurements were conducted in both uniform and turbulent wind fields, and the displacement response and surface wind pressure at different locations of the model were recorded. The displacement time-history response spectrum and aerodynamic spectrum in both fields were compared and analyzed. The research showed that the mean displacement responses of the model in the across-wind and along-wind directions gradually increased with velocity under different wind attack angles. The mean displacement response of torsion moment in a uniform wind field changed very little, and the mean and fluctuating wind pressures in each layer were significantly stratified, making it is easy to generate a coupled vortex-induced resonance. On the other hand, the mean displacement response of torsion moment in a turbulent field increased with wind velocity. Strong turbulence made the fluctuating wind pressure at the top and bottom of the model slightly more significant than in a uniform field. The resistance of super-tall buildings came from turbulence excitation in the along-wind direction and the self-excited resistance generated by the across-wind direction. The test methods and main research conclusions may provide a reference for glass curtain walls and the structural wind-resistant design of super-tall buildings.

Automatic modal identification via eigensystem realization algorithm with improved stabilization diagram technique

Efficient and automatic identification of modal parameters becomes increasingly important for real-time structural health monitoring (SHM) of civil structures. As spurious modes usually exist as a key problem for most output-based identification methods, great efforts have been made to eliminate them typically via stabilization-diagram techniques. However, the quality of traditional stabilization diagrams depends on preset parameters whose values usually vary from one case to another, which makes the method to be less objective and low efficient. This article proposes an improved stabilization-diagram technique, through combined usage of Monte-Carlo sampling simulation, as well as fuzzy C-means (FCM) clustering and three-stage sifting manipulations. While the Monte-Carlo simulation aims to generate more robust stable-axis, the sifting and clustering manipulations can further remove outliers and discriminate true modal results. The improved stabilization-diagram technique is then applied to two mainstream modal identification methods, i.e., eigensystem realization algorithm (ERA) and stochastic subspace identification (SSI) under the context of both a simulation study on a dynamic system and a field research about a super-tall building. Results through comparison demonstrate that the improved stabilization-diagram technique can facilitate ERA and SSI to identify modal parameters automatically and effectively at a comparably good accuracy. However, ERA outperforms SSI evidently in terms of computational efficiency (upmost 15 times faster), which is attractive for real-time SHM. Parametric analysis has been also conducted to examine detailed performance of ERA aided by the proposed stabilization-diagram technique. Overall, the aforementioned method can be adopted to achieve a good balance between identification effectiveness and computational efficiency in an automatic working pattern, and has application prospect for real-time SHM of civil structures.

Enhance the Resilience of Steel Outrigger by Equipping GFRP Tendons and Viscoelastic Material

ABSTRACT Seismic resilience has emerged as a trend in the seismic design of buildings, with self-centering components or systems used as an effective method to improve seismic resilience. The outrigger is an essential component for resisting the lateral load in super-tall buildings. However, the diagonal member of the traditional outrigger is prone to buckling, resulting in excessive residual deformation and repair difficulties after earthquakes. A novel self-centering outrigger (SCO) with desirable energy dissipation and self-centering capacity is proposed in this paper. In the SCO, the traditional steel diagonal member is replaced with a new self-centering viscoelastic brace (SCVB). The seismic performance of the SCVB with a total length of 2.2 m is investigated using the low cyclic loading test, with results demonstrating that the SCVB exhibits a flag-shaped hysteretic response. Based on the experiment results of SCVB, a refined finite element model of the proposed SCO is developed to evaluate the seismic performance, then the hysteretic responses of the traditional outrigger and SCO under different load conditions are compared. Results show that the hysteretic curve of the proposed SCO is flag shaped, with stable stiffness and desirable energy dissipation and self-centering capacities. Even at a large loading displacement, a small amount of residual deformation will occur, but it is reduced by 75.52% compared to a traditional outrigger, while the strength is increased by 14.37%. Finally, the influence of the key parameters of SCVB on the hysteretic behavior of SCO are discussed, providing reference for future seismic design of the SCO.