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Vortex-induced vibration (VIV) is a critical problem for high-rise buildings. Thus, accurate prediction of aerodynamic damping becomes a key problem in the wind-resistant design of high-rise buildings. A common feature of the existing aerodynamic damping models is that most of their model parameters are functions of wind velocity. Such a feature leads to the inconvenience of users because the parameters need to change from case to case. This paper proposes an aerodynamic damping model that is a function of structure responses only. That means it does not need to adjust its parameters in different wind speeds. A single-degree-of-freedom aeroelastic square section high-rise building model with different structural damping ratios is tested in a wind tunnel for the analytical modeling. According to the identified aerodynamic damping coefficients and its relation with response amplitudes, the nonlinear aerodynamic damping model is proposed. It is a polynomial-type function of the instantaneous velocity and displacement of the structure. The results show that predicted responses, by using one set of model parameters, are in good agreement with the experiment data in the whole tested wind speed range. These results suggest that the proposed aerodynamic model can be a generic model for prediction of wind-induced vibration. [ABSTRACT FROM AUTHOR]

This paper develops a horizontal displacement estimation framework for wind-excited high-rise buildings based on limited measurements of accelerations and strains and applies it to reconstruct the displacement responses of a 600-m-high skyscraper in Shenzhen, China, during Super Typhoon Mangkhut on September 16, 2018. A field measurement study was conducted to verify the reliability and effectiveness of the framework based on the acceleration and strain responses of the skyscraper during Typhoon Kompasu. Then, the horizontal displacements of the skyscraper during the passage of Mangkhut were reconstructed by the framework based on the measurements of accelerations at one floor and strain responses at four floors, and the accuracy of the reconstructed displacement responses was subsequently validated in both time and frequency domains. In the final, the along-wind and across-wind responses as well as the resonant and background components of the reconstructed displacements during the extreme typhoon event were investigated. This paper aims to provide useful information for structural health monitoring and wind-resistant design of supertall buildings in tropical cyclone-prone regions. [ABSTRACT FROM AUTHOR]

This study examined the accuracy of a reduced-order building model approach for inelastic response analysis of tall buildings under simultaneous actions of both alongwind and crosswind loadings. The reduced-order model was established following the modal pushover analysis procedure. The inelastic building response was represented by fundamental modes in principal directions. The hysteretic relationships of generalized restoring forces and displacements were determined by static modal pushover analysis using nonlinear finite element model with distributed plasticity. These relations were then represented by a biaxial hysteresis model, which leads to state-space equations of the building motion with a reduced-order building model that can be solved by response history analysis or by statistical linearization approach. A comprehensive analysis of response statistics of a 60-story building, including time-varying mean, standard deviation, kurtosis, and peak factors at different wind speeds was carried out using the reduced-order building model and computationally more demanding finite element model. The results demonstrate the accuracy of the reduced-order building model. The statistical linearization approach based on Gaussian response assumption can also offer quite accurate estimations, although it can be further improved by considering the non-Gaussian probability distribution of response caused by yielding. The interaction of inelastic alongwind and crosswind responses was addressed. The challenges faced in the estimation of time-varying mean component of inelastic response were also highlighted. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) structural walls are widely used in high-rise structures in earthquake-prone areas. Damaged by the earthquakes in the past decades, these buildings need retrofitting in order to increase the resilience of buildings with concrete shear walls. This study aimed to investigate the retrofitting of high-rise RC wall buildings using energy dissipation devices. To this end, a total of four buildings with 15, 20, 25, and 30 stories equipped with concrete shear walls as their lateral load-resisting system were retrofitted using passive seismic control systems. The buildings were subjected to the set of the far-field and near-field records presented in the FEMA standard (P-695), and an index was defined to relate the structural responses of the building, such as drift, acceleration, velocity, displacement, and base shear, to the earthquake records. For this purpose, numerical models, which have been validated with the experimental results, have been performed. The resulting index values were considered as the criteria, and the passive systems were ranked by the efficient Multicriteria Decision Making (MCDM) method. Based on the results from the MCDM method and using the considered criteria, friction damper was ranked first among the available energy dissipation devices for high-rise RC wall buildings. [ABSTRACT FROM AUTHOR]

Current tall building design to ultimate wind loads is based on a linear elastic design framework. The adoption of a performance-based wind design framework for tall buildings explicitly requires evaluation of building performance under various levels of wind hazards, including inelastic response. This study presents a comprehensive characterization of inelastic response of tall buildings under simultaneous actions of both alongwind and crosswind loads using a fiber-based three-dimensional (3D) nonlinear finite-element (FE) model of a 60-story high-rise steel building. The statistics of inelastic responses in terms of building displacement, acceleration, interstory drift, and base bending moment and member forces are quantified through response history analysis at different wind speeds. The inelastic building responses under alongwind and crosswind loads acting separately are also calculated and compared. The inelastic response is also compared to the elastic response of the corresponding linear building model. The yielding causes building drift in the alongwind direction that leads to increasing time-varying mean displacement. The development of drift is affected by fluctuating alongwind and crosswind responses. The steady-state value of drift is determined by the mean load and second stiffness in the alongwind direction. On the other hand, the fluctuating alongwind and crosswind responses can be quantified regardless of the mean load and time-varying mean response. The yielding leads to a reduction of fluctuating responses due to additional hysteretic damping. The second-order P-Delta effect on both elastic and inelastic responses is also examined. Finally, the influence of material yield stress is investigated, and the inelastic response is discussed in nondimensional quantities. The results of this study reveal the importance of consideration of simultaneous actions of both alongwind and crosswind loads for inelastic response analysis. The inelastic crosswind response affects the alongwind inelastic response. It particularly results in increased time-varying mean alongwind displacement, which contributes to building collapse when the second-order P-Delta effect is considered. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the effects of building geometry on tall-building aerodynamics, accompanying the analysis for low-rise buildings found in the companion paper. Aerodynamic data for total of 30 rectangular-plan buildings were obtained in wind tunnel experiments. This work tested building configurations with plan aspect ratios, L/B (where L is the horizontal dimension parallel to the wind and B is the across-wind dimension) ranging from 0.25 to 4 and height ratios, H/W (where H is roof height and W is the least horizontal dimension) ranging from 1 to 12. Additionally, this work made systematical comparisons with wind load provisions in Chapter 27 of ASCE 7-16. Buildings with ratios of H/W>∼4 have aerodynamic coefficients that are approximately constant, which means that this can be a practical aerodynamic definition of high-rise buildings. There is continuous variation of the aerodynamic coefficients for H/W<4 such that differentiation of mid-rise and low-rise buildings may be considered as arbitrary from an aerodynamics perspective. Wind load coefficients for mid-rise buildings are observed to be lower than for high-rise buildings. However, for both mid-rise and high-rise buildings, largest load coefficients are observed for L/B∼0.67. The plan ratio of L/B captures the variation of the load coefficients for high-rise buildings. For lower buildings, both L/B and H/W ratios are needed to define the wind loads. [ABSTRACT FROM AUTHOR]

This paper presents a case study of applying a new device termed deformation adjustor in piled raft foundations to support a highrise building. The deformation adjustors are mounted on a pile head to optimize load distribution of a piled raft foundation so that a relatively uniform foundation deformation can be achieved in complicated load, construction, and soil conditions. In this case study, the project site is located in a coastal city in China, featuring complicated subsurface soil conditions with abundant large boulders. The project was put on hold for a decade because in the complicated soil conditions the piles could not be installed to the required depths. The project resumed with introduction of deformation adjustors which helped to shift the applied loads from piles to subsoil below the raft and thus considerably reduced the pile lengths. This case study describes the preliminary design of pile-raft foundations with deformation adjustors, followed by a comprehensive monitoring program for settlements, earth pressures, and pile top reaction forces during and after building construction. Based on the long-term monitoring, subsoil below the raft was able to bear 83% of total applied loads, whereas the piles carried 17% of the loads. Based on this case study, deformation adjustors were proved to be an effective and economical solution for piled raft foundations to support high-rise buildings in complicated subsurface conditions. [ABSTRACT FROM AUTHOR]

Shear strains may have negligible influence on maximum displacements at the top of slender shear walls, but may significantly increase interstory drift ratios at lower levels where gravity-load columns are often less flexible. A nonlinear finite-element (FE) model calibrated with experimental results confirmed that large shear strains occur in flexural tension regions of concrete walls due to vertical tension strains in the presence of diagonal cracks and in the absence of demand on the horizontal shear reinforcement. A fan of diagonal cracks will form at the base of flexurally hinging walls independent of the shear stress level. A parametric study confirmed that a principal strain angle of 75° can be used to estimate shear strains from vertical tension strains. Thus interstory drift ratios due to shear strains can be estimated from the easily calculated flexural demands. A simple and safe estimate of interstory drift ratio due to shear strains is 60% of the global drift ratio. Interstory drift ratios from shear strains up to 0.8% have been measured in slender wall tests. [ABSTRACT FROM AUTHOR]

This paper introduces a framework for the performance-based design (PBD) of high-rise buildings with respect to the occupant comfort performance objective. The performance is expressed in terms of the probability--conditional on the wind event intensity--that the fraction of the building occupants on one floor that perceive the motion is greater than a chosen threshold value. The framework is fully probabilistic, and numerous uncertainties affecting both the structural response and the human perception threshold are considered in the assessment of the exceedance probability. In addition, a new database-enabled online analysis module based on the proposed PBD framework [Performance-Based Data-Enabled Design module for Occupant Comfort (PBDED-OC)] is presented. The PBDED-OC allows the assessment of the occupant comfort performance of a tall building by taking advantage of databases of high-frequency base balance measurements or by adopting specific user-supplied wind tunnel data and is envisaged to be particularly useful during the preliminary design phase. [ABSTRACT FROM AUTHOR]

Learning-curve theory has been applied to construction activities due to their labor-intensive and repetitive features. However, previous research argued that the effect of the learning curve does not exist in construction because it is not recognizable by the amount of repetition in construction labor. Although prior research implied that there is a need for the modified learning curve specifically tailored to construction, the studies may not fully investigate the reasons for the gap between theory and practice or fully consider the factors that affect the manifestation process of learning development. Moreover, they tend to underestimate the applicability of the learning-curve theory in construction. To address these issues, this paper clarifies factors that impact the manifestation process to suggest a more suitable learningcurve model for high-rise building construction activities as a subject. Specifically, three influence factors are selected--(1) task change, (2) work adaptation, and (3) vertical transportation time--and a hypothetical learning curve is proposed for the high-rise building construction. A case project in Korea is tested to validate the suggested factors. The quantitative data including labor performance (e.g., work hours, quantity, and number of workers) per floor are converted to the proposed learning curve and compared with actual data. The results show that the suggested learning curve is more suitable for representing the development of learning in high-rise construction than that of previous research. The proposed learning curve can also extend its applicability toward labor productivity issues for the high-rise building because its accuracy was improved considering the influence factors. Based on the results of this research, a project manager can improve labor productivity from the learning-curve effect by controlling influence factors in the construction phase. Further, this research may have implications for investigating hidden phenomenon through a quantitative approach, which is shown as tangible. [ABSTRACT FROM AUTHOR]

This paper describes an integrated topology optimization framework using discrete and continuum elements for buckling and stiffness optimization of high-rise buildings. The discrete (beam/truss) elements are optimized based on their cross-sectional areas, whereas the continuum (polygonal) elements are concurrently optimized using the commonly known density method. Emphasis is placed on linearized buckling and stability as objectives. Several practical examples are given to establish benchmarks and illustrate the proposed methodology for high-rise building design. [ABSTRACT FROM AUTHOR]

A new damping system, the viscoelastic coupling damper (VCD), has been developed to enhance the wind and seismic performance of coupled shear wall high-rise buildings by adding high damping elements in place of reinforced concrete coupling beams. VCDs replace structural members, such as outriggers or coupling beams, and therefore do not occupy any usable architectural space. When they are properly configured in high-rise buildings, they provide supplemental viscous damping to all lateral modes of vibration, which mitigates building tenant vibration perception problems and reduces both the wind and earthquake response. Experimental results from tests on five small-scale viscoelastic (VE) damper specimens of 5- and 10-mm thicknesses are first presented, followed by the results from six full-scale VCDs representing two alternative configurations. The first was designed for areas where moderate seismic ductility is required, and the second was designed with built-in ductile structural fuses for areas where high seismic ductility is required. The VE material tests exhibited stable hysteretic behavior under the loading conditions that are expected in high-rise buildings under wind and earthquake loading. The fullscale tests validated the overall system performance within a realistic coupled wall configuration, and confirmed the performance of the wall anchorages and all connecting elements as well as the VE material behavior. The full-scale test results also demonstrated the targeted viscoelastic response during wind and low level earthquake loading and the targeted viscoelastic-plastic response for extreme earthquakes, where the response is a combination of the VE response and the nonlinear behavior of the structural fuses. [ABSTRACT FROM AUTHOR]

The Palazzo Lombardia Tower, located at the heart of the city of Milan, Italy, recently was completed. At 161.30 m high, the new building is currently the tallest in Italy and one of the most prominent features of the city skyline for many years to come. Given the strategic importance and the strong impact of the new building, it was decided to perform a series of dynamic excitation tests, with special emphasis on the Tower. Thus, it was possible to estimate its basic modal features and then compare them to the numerical simulation predictions provided by the same finite-element (FE) numerical analysis used for design. This offered the chance to start an important and interesting model-updating procedure, taking advantage of both the actual material properties measured during the construction phase and dynamic measurements, the latter having added significant insight to the structural behavior. The mechanical engineering department of the Polytechnic University of Milan was in charge of the design and execution of the tests. Professor F. Mola served as the structural designer of the building and also supervised the design and interpretation of the tests, together with the staff of ECSD Engineering and CAD DataConsult, who created the analytical model of the complete structure to be used as a benchmark for the experimental results. The tests provided an experimental validation of the modeling assumptions accuracy and of the robustness and reliability of the FE model in predicting the structural behavior. Moreover, the experimental validation of the FE model of the Tower was meant as the initial part of an intended continuous monitoring activity. This paper describes the main structural features of the Palazzo Lombardia Tower and those of the experimental tests. Also, the FE model is presented and the comparison between the numerically predicted and the experimentally derived modal properties is discussed. [ABSTRACT FROM AUTHOR]

This study analyzes wave propagation in a Timoshenko beam model of a high-rise building excited by base motion. This model accounts for wave dispersion caused by bending and is more realistic for analysis of wave propagation in high-rise buildings than shear beam and other discrete nondispersive models. The model transfer functions and impulse response functions are obtained from the analytical solution for a forced vibration response of the beam excited by base motion. The impulse response functions represent the model response to a virtual input pulse; a set of such functions at different levels is used to study pulse propagation in the beam. A parametric study of dispersion and its effects on the model transfer functions and impulse response functions is presented in terms of dimensionless parameters and in ranges corresponding to buildings. The model is validated for a 9-story full-scale RC building and smaller earthquake excitation. The results provide insight into dispersive wave propagation in buildings caused by bending, which is useful for the interpretation of impulse responses of buildings obtained from earthquake records and for the development and testing of wave methods for structural health monitoring. The results can also be used for testing numerical models for pulse propagation in buildings. [ABSTRACT FROM AUTHOR]

With a height of 52 stories and a steel structure visible from the exterior, the New York Times Building is the third-tallest building in the city of New York. Located on 8th Avenue between 40th and 41st Streets, it was designed by the Italian architect Renzo Piano. Two separate structures comprise the building: a 5-story podium rectangular in plan and a 52-story tower with a cruciform plan. Two interesting features of the structural system are the bracing system, located both on the perimeter and in the core, and the outrigger systems, located at the two mechanical floors. The effectiveness of these features, as well as the pretensioning of diagonals, is examined numerically in this paper by studying their influence on deflections due to wind, distribution of internal forces, and dynamic response of the building. [ABSTRACT FROM AUTHOR]

This paper discusses structural-architectural integration of vertical, double-layer space structures in tall buildings. It covers the integration of the structures with building facades, entrances, lobbies, and interior space. As double-layer space structures have not yet been used vertically, their application in tall buildings would be challenging for architects. This is because their structural components and compositions are different from those in other current tall structures. The double-structural layers, which consist of vertical, horizontal, and diagonal members, are located at the building perimeter. This condition requires high-level, structural-architectural integration with other building components. The research reviews structural-architectural integration in current tall buildings and investigates its possible applications in double-layer space structure buildings by showing various alternatives using computer models. Also discussed are view obstructions in double-layer space structure buildings as would normally occur in perimeter structure buildings. The study provides alternatives and guidance regarding the architectural designs of vertical, double-layer space structures in tall buildings. [ABSTRACT FROM AUTHOR]

The emergence of performance-based wind engineering calls for improved probabilistic modeling of wind effects on buildings. This paper focuses on the development of probabilistic models of the peak distribution and peak factor for non-Gaussian processes and explores the applications of this development in wind engineering. The closed-form expressions for the mean, SD, and fractile levels of extremes are derived for a random process whose peaks are modeled by the parametric Weibull distribution. A new translated-peak-process method is then developed for the estimation of the peak distribution, peak factor, and variability of extremes, based on the Weibull distribution and point-to-point mapping procedure. The proposed translated-peak-process method is validated by wind-tunnel pressure measurements on a standard tall building and is shown to be more robust and practical than many existing methods in analyzing non-Gaussian wind pressure data. [ABSTRACT FROM AUTHOR]

This study introduces a unique prototype system for structural health monitoring (SHM), SmartSync, which uses the building's existing Internet backbone as a system of virtual instrumentation cables to permit modular and largely plug-and-play deployments. Within this framework, data streams from distributed heterogeneous sensors are pushed through network interfaces in real time and seamlessly synchronized and aggregated by a centralized server, which performs basic data acquisition, event triggering, and database management while also providing an interface for data visualization and analysis that can be securely accessed. The system enables a scalable approach to monitoring tall and complex structures that can readily interface a variety of sensors and data formats (analog and digital) and can even accommodate variable sampling rates. This study overviews the SmartSync system, its installation/operation in the world's tallest building, Burj Khalifa, and proof-of-concept in triggering under dual excitations (wind and earthquake). [ABSTRACT FROM AUTHOR]

A low- and high-velocity based controller (LH controller) is developed to model the force-velocity relationship of a magnetorheological (MR) fluid damper that enables the controlling current to be calculated as a function of required control force. The proposed bilinear force-velocity model predicts the high-velocity region as well as the often neglected low-velocity region that corresponds to the damper responses in the postyield and preyield regions, respectively. The calculated current may then be supplied to an experimentally parameterized prototype small-capacity MR damper (50 kN) to control seismic responses at a lower cost. Numerical examples are used to demonstrate the ability of the LH controller to reduce structural displacements and accelerations in comparison with three other state-of-the-art controllers, namely, the clipped optimal controller, modified clipped optimal controller, and inverse model, which neglect the low-velocity region of the damper. After including this region, the LH controller significantly lowers peak accelerations by 57.7, 33.4, and 13.0%, respectively, over the three other common controllers and also lowers mean displacements by 85.9, 81.7, and 85.4%, respectively. Lastly, the LH controller is used to reduce the peak drifts and accelerations in comparison with those of a 20-story benchmark building. [ABSTRACT FROM AUTHOR]

Construction schedules are uncertain in nature; therefore, predicting construction duration is a difficult task. Extensive research has proposed mathematical models to predict construction duration based on regression analysis, Monte Carlo method (MCM), and so on. Yet regression analysis cannot capture duration uncertainties. Studies normally use Monte Carlo methods to simulate hundreds to thousands of activities in a project schedule. This can be complicated, time-consuming, and unrealistic because the statistical properties of all the activities cannot be readily determined in practice. Typical construction sequences in condominium building construction were first identified, and then the statistical distributions of controlling activities on the sequences were surveyed. Two-stage questionnaire surveys and goodness-of-fit statistical tests were conducted to achieve the mentioned objectives. Subsequently, a model for predicting the duration of building construction was proposed and applied to a high-rise building project. The results showed that the proposed model reasonably predicted the construction duration for this apartment building. The model fills the gap in knowledge of construction time forecast by introducing the concept of controlling activities to simplify the evaluation of the schedule uncertainty in multistory building construction. This research is beneficial for practitioners to estimate an overall construction schedule of building projects, especially in preconstruction phases. [ABSTRACT FROM AUTHOR]

Zoning has been a powerful force in shaping the three-dimensional landscape of the urban built environment. Although market forces and private interests have historically controlled the decision-making process, land-use regulations have been used to counter market failures and to collectively guide the growth of the American city. During the second half of the nineteenth century, advancements in construction and building technologies, including the steel structural frame, internal pneumatic and telegraphic communications, efficient mechanical systems, and improved fireproofing materials and techniques, allowed for the construction of structures of increasing height. As tall building construction flourished in major U.S. cities, issues of light, ventilation, and public health, as well as encroachment of incompatible uses, began to capture the public's attention. Where tenement reform laws had addressed residential overcrowding, owners, architects, and public officials viewed building regulations as a means to minimize the negative impacts of increasingly massive structures on surrounding property values and public space. This article discusses the evolution of zoning and its implications for the form of cities and suburbs by tracing the history of New York's first comprehensive zoning law. It first presents the economic, social, and technological forces leading to calls for regulation of the built environment and then examines the passage of the 1916 Zoning Resolution as it related to issues of public health, separation of uses, and real estate economics. Finally, the article explores the effect of zoning on the growth of the New York region, focusing on its impact on urban form and the spatial patterns of development and its relationship to emerging issues of environmental sustainability and urban resilience. [ABSTRACT FROM AUTHOR]

A structural health monitoring (SHM) network was installed during the construction of a 56-story frame-wall concrete building with a height of 196 m. The SHM network recorded the vibrations produced by ambient, construction, and earthquake excitations. The vibrations were used to identify the natural periods, mode shapes, and damping ratios of the structure every 10 min for 6 consecutive months and at five specific stages of the construction process over a two-year period. The identified modal parameters were used to validate the construction process and the computer design model by comparing different adaptive computer models that correspond to the progress in construction. Maximum differences of 14% between measured and analytical model natural period were obtained, and correlation to modal shapes were close to 95%, which indicates a good approximation of the predictive design computer model. The experimental techniques also allowed for the direct measurement of the energy dissipation properties of the building. For the low amplitude vibrations, the modal damping ratio ranges from 0.7 to 1.6% for the largest natural periods. The occurrence of the 2010 Central-South Chile earthquake (magnitude ) also allowed for the comparison of the dynamic properties before and after an extreme loading event. A visual inspection of the building indicates an acceptable correlation between the minor damage observed and changes in the modal parameter values. The continuous monitoring of the dynamic properties of this permanently changing building proves to be an excellent tool for the verification of design models and quality assurance in construction control. [ABSTRACT FROM AUTHOR]

This case study presents the horizontal translocation of the Hongxing Mansion, a high-rise building in China, which was moved transversally for 26 m because of modifications in urban planning. The 13-story RC frame-wall structure was built in 2002 with a total height of 63.2 m and a total weight of 109,881 kN, making the project unique as compared with other similar cases. The executive process of this project is introduced, including the initial planning, design, and construction procedures. A load underpinning system was proposed that can transfer the vertical loads uniformly to the rails and distribute the propelling loads from the loaded end to the other end of the building. Anchor-jacked piles were used at the original foundation from the limited indoor clear height so that rails in the original basement can be well supported without the need of large piling machines. A special moving system was proposed and successfully applied, which combined the advantages of pull and push, so that the efficiency and stability of moving were guaranteed. The removable reaction frames were used to alleviate the energy accumulation in tendons and the sudden energy release when the building started to move. Finally, the columns and walls were connected with the new foundation without diminishing their seismic capacities. The design and construction methods in this project provide references to buildings in need of translocation. [ABSTRACT FROM AUTHOR]

One of the problems encountered in the estimation of wind effects on high-rise structures is the development of combinations of wind-induced translational responses in possible conjunction with rotational responses and/or of forces and moments that contribute to the wind-induced demand at various cross sections of individual structural members. In current wind engineering practice such combinations are developed in large part intuitively because phase information on the effects being combined is not readily available from frequency domain analyses. In contrast, full time series analyses can produce estimates of combined wind effects because they preserve phase information; however, such analyses can be overly time-consuming. In current wind engineering practice it is common to use the empirical point-in-time (PIT) procedure for the estimation of peaks of combined stationary stochastic processes. The procedure is applied to pairs of such processes, and consists of adding an estimate of the peak value of one of the processes to the estimated value of the second process at the time of the occurrence of that peak. Even if the full time histories of the two stochastic processes are used, errors inherent in PIT can be in some cases as high as 20% on the unconservative side. The purpose of this paper is to present the empirical multiple points-in-time (MPIT) procedure, which improves significantly upon the PIT approach. The MPIT procedure is illustrated by an application to a 60-story reinforced concrete structure. Results show that the MPIT approach produces remarkably accurate estimates of the peak combined wind effects by using a limited number of peaks from the time histories of the individual wind effects being combined. Those estimates are obtained far more economically in terms of computational time than conventional time domain estimates that use full time histories. [ABSTRACT FROM AUTHOR]

A Rayleigh quotient is developed to calculate estimates of the fundamental frequencies of tall slender buildings. The quotient provides simple analytical frequency estimates that agree well with results reported using a more detailed beam model and finite-element analyses. It is also shown that the fundamental frequency varies inversely with the height of the building being modeled, and that the additional stiffening provided by one model of an outrigger appears not to appreciably alter the fundamental frequency. [ABSTRACT FROM AUTHOR]

Tianjin Jinta Tower is the first high-rise building built with steel plate shear walls in China. The main lateral force resisting system is the composite core tube composed of steel plate shear walls and concrete-filled steel tubular columns. To investigate the seismic performance of this structural system and to provide design instructions, two specimens of 2-bay and 5-story steel plate shear walls were tested under low-cycle reverse loading. The unstiffened steel plates of the first specimen were connected to the boundary beam and column frame by high-strength bolts. The steel plates of the second specimen were connected to the boundary frame by welding, and the steel panels were stiffened by channels. Both specimens showed satisfactory energy dissipation mechanisms during the loading process. For the unstiffened specimen with bolted connections, the considerable postbuckling strength generated excellent ductility and energy dissipation performance, but a slip at the bolted connections and the buckling of steel panels decreased the stiffness in the serviceability condition. The stiffened and welded specimen showed higher stiffness in the elastic range and excellent energy dissipation capacity, but the cost of stiffeners would decrease the economy of the steel plate shear walls. [ABSTRACT FROM AUTHOR]

The mechanism of collapse of tall steel moment-frame buildings is explored through three-dimensional nonlinear analyses of two 18-story steel moment-frame buildings under earthquake excitation. Both fracture-susceptible and perfect-connection conditions are investigated. Classical energy-balance analysis shows that only long-period excitation imparts energy to tall buildings large enough to cause collapse. Under such long-period motion, the shear-beam analogy alludes to the existence of a characteristic mechanism of collapse or a few preferred mechanisms of collapse for these buildings. Numerical evidence from parametric analyses of the buildings under a suite of idealized sawtooth-like ground-motion time histories, with varying period (), amplitude (peak ground velocity, PGV), and duration (number of cycles, ), is presented to support this hypothesis. Damage localizes to form a quasi-shear band over a few stories. When the band is destabilized, sidesway collapse is initiated, and gravity takes over. Only one to five collapse mechanisms occur out of a possible 153 mechanisms in either principal direction of the buildings considered. Where two or more preferred mechanisms do exist, they have significant story-overlap, typically separated by just 1 story. It is shown that a simple work-energy relation applied to all possible quasi-shear bands combined with plastic analysis principles can systematically identify all the preferred collapse mechanisms. [ABSTRACT FROM AUTHOR]

A wind-tunnel study has been carried out to investigate the effects of the barrier wall and surface roughness on the simulated atmospheric boundary-layer (ABL) flow generated using the Counihan method, (i.e., the castellated barrier wall, vortex generators, and surface roughness elements). Experimental results indicate that changing the basic barrier height does not influence the mean-velocity profiles. However, turbulence intensity and absolute values of the Reynolds stress increase with an increase in the barrier height, and simultaneously the integral length scales of turbulence decrease. Variations in the height of the barrier castellation influence the simulated ABL flow similarly to the changes in the basic barrier height. Empirical relations were derived to quantify effects of the surface roughness height on the simulated ABL flows. Increasing the height of surface roughness elements results in a larger velocity defect and stronger turbulence in the near-ground region. [ABSTRACT FROM AUTHOR]

This paper presents work on validating the dynamic wind load predicted by a wind tunnel model with the values identified from full-scale field vibration data of a super-tall building in Hong Kong. Dynamic wind load in this work refers to the power spectral density (PSD) of the modal force near the natural frequency of a particular mode of the building, in the context of random vibration with stationary loading and response. This quantity reflects the turbulence characteristics integrated over the building body and is of importance in wind engineering design. This study presents a method to predict the modal PSD of wind load of the first two translational modes of a tall building. The method combines wind tunnel test information and mean wind data available in the free field; the latter taken to be at the Waglan Island station maintained by the Hong Kong Observatory. On the full-scale side, although the modal PSD is not directly observable, it is identified from field vibration data measured at the building top during strong wind events. A Bayesian modal identification method is used for determining the most probable value and the uncertainty of the modal parameters including the natural frequency, damping ratio, and the modal PSD. A number of recent strong wind events are analyzed. Reasonable agreement is observed between the wind tunnel model predictions and the values identified from field data. Factors that can potentially lead to discrepancy are discussed. As the same random vibration modeling consistent with conventional wind engineering design has been used in the wind tunnel prediction model and field identification model, the results are directly transferable among these three disciplines. [ABSTRACT FROM AUTHOR]

The air pressure in a drainage stack of a high-rise building test platform (HBTP) is mathematically modeled by unsteady one-dimensional () partial differential equations, in which an additional term is introduced to reflect the gas-liquid interphase interaction, the stack top-base effect. This model is crucial for understanding the characteristics of air pressure variation, which is significant for the recognition of the HBTP's operational performance. A time-splitting based characteristic line method is used to solve the type governing equations, with the model parameters being calibrated by the measured data obtained on the HBTP. It is concluded that the generally used Saint-Venant equations should be extended appropriately so that the stack air pressure can be satisfactorily predicted. [ABSTRACT FROM AUTHOR]

Distributed mass damper (DMD) systems are discussed as a method of suppressing lateral motions of superstructures during wind storms and earthquakes. Potentially, DMD systems are a technology that is economical enough for widespread application to buildings or other structures. Focus is placed on lightweight superstructures as a reflection of the trend toward the use of ultra-lightweight floor slabs in high-rise buildings. Results of model-scale experiments are presented that show that tuned mass damper (TMD) systems that add between 1.3 and 2% to the total superstructure gravitational mass are effective methods of increasing damping in superstructures and reducing peak lateral accelerations during forced vibration events. In those experiments, tuned sloshing dampers (TSDs) were employed in conjunction with floor and roof plates that simulated ultra-lightweight slabs constructed from cross-laminated timber (CLT), which is a new material option in North America. The use of TSDs was a surrogate for TMDs in general, but such devices are expected to be economic and can easily be tuned to match free vibration frequencies of superstructures. A concept for incorporating DMD arrays as parts of multimaterial ultra-lightweight floor slabs is presented in the context of high-rise building superstructures having moment-resisting frameworks made of steel, reinforced concrete, or other materials that work in conjunction with the slabs and shear walls to form superstructures. The main conclusion is that DMDs are a practical and potentially economic approach for suppressing undesirable motions of lightweight high-rise superstructures. Continuing work is focused on developing and optimizing low-cost TMDs and design of DMD systems for specific buildings or other structures. [ABSTRACT FROM AUTHOR]

This paper presents finite-element analysis (FEA) and experimental study on the seismic behavior of joints between steel K-style outrigger truss and concrete core in tall buildings. Two new joint types with different details, including the joints with outside steel plates and encased steel plates, were conceived and intensively compared. Elaborate FEA models of the joints were developed, and a preliminary finite-element study was first conducted to evaluate the failure modes and hysteretic behavior of the joints to support the preparation of the laboratory test program. Then two specimens with different joint details were tested under cyclic loads. Several indexes that could reflect the seismic performance of the joints, such as the strength degradation, the rigidity degradation, the ductility, and the energy dissipation capacity, were analyzed. The mechanism of the joints was also revealed based on the stress distributions obtained by further FEA and test results, and a simplified FEA model was finally proposed for a more general purpose in routine design practice, and could provide a powerful tool for future research in design methods of the joints. The FEA and experimental results indicated that the joints exhibited favorable seismic performance which could transfer the loads reliably, and the joint with outside steel plates was better than that with encased steel plates, with more construction convenience, higher buckling load, and less concrete cracks. [ABSTRACT FROM AUTHOR]

In tall-building construction, the equipment-driven table formwork method is a useful alternative for improving productivity of horizontal formwork with less skilled labor. The lifting system significantly affects the productivity and costs of table formwork operation. This study proposes a new system integrated with the construction hoists for automating the lifting process of table formwork. The system targets crane-independent transportation for productivity improvements while overcoming the limitations of the existing independent lifting system, which include high initial cost and extra work for assembly and operation. In a case study, the proposed system showed 49.4% improved productivity over a tower crane, and equipment costs were 73.8% lower than those of the existing independent system. The simplified structure of the system through integration with the hoist could minimize the additional time and cost inputs for its assembly and operation. The proposed system could provide more flexible and stable scheduling at a lower cost in tall-building construction with short cycle times and excessive lifting loads. [ABSTRACT FROM AUTHOR]

A high-rise building with pile-raft foundation suddenly experienced extraordinary settlements and seriously tilted after 6 years of use in Wenzhou, a city in southeastern China. Some investigations were conducted and several potential causal factors were analyzed to determine the cause of the distress. The results indicated that the inadequate bearing capacity of the pile foundation was the reason for the extraordinary settlement. Inappropriate structure type selection and structural arrangement made the building sensitive to earthquake-triggered loading and prone to tilt. Remedial measures were applied to address the causal factors identified. Because of the low bearing capacity of the pile foundation, unloading was first performed and then the pile foundation was strengthened using steel pipe piles driven by anchor bolts. To address the inappropriate structure type and arrangement, the building was retrofitted to resist earthquakes. Observation results showed that the remedial measures took effect and the settlement (and tilt) of the building was completely controlled. [ABSTRACT FROM AUTHOR]

Nonlinear response history analysis is an important tool for accurately determining the performance of tall buildings under severe earthquake loading. When a standard genetic algorithm is used in conjunction with nonlinear response history analysis, it is desirable to use smaller generation sizes because of the computational effort to analyze individual designs. A study was conducted to evaluate how different genetic algorithm techniques influence the reliability and efficiency of the algorithm when used with nonlinear response history analysis and small generation sizes. The system used in the study was a nine-story buckling restrained braced frame that was optimized to minimize brace areas under individual earthquake records. A baseline study showed that a typical genetic algorithm did not converge to the same best design for different random number sequences (seed numbers). Forced diversity improved the reliability of the algorithm such that it converged to the same optimum, regardless of initial seed number. Adaptive mutation decreased the required number of generations when coupled with a noncrossover constraint. Consecutive identical generations were found to predict convergence and provide a basis for an exit criterion. [ABSTRACT FROM AUTHOR]

Modern tall buildings are characterized by their slenderness and sensitivity to resonant wind effects. This is especially true considering the acceleration-based motion perception criteria under which they must be designed. In light of the significance of the resonant response, damping plays an important role in the design of tall buildings. Unfortunately, unlike other mechanical characteristics of structures, damping is far more difficult to estimate. This is due to the inherent complexity and high number of mechanisms responsible for damping. For this reason, the experimental determination of damping levels for tall buildings from full-scale data collected during monitoring programs has obtained a tremendous amount of interest over the past years. This paper firstly reviews the predictive damping models that are available in the literature highlighting their merits and shortcomings in light of the extensive experimental damping data collected over the past few years. A novel amplitude-dependent data-driven model is then proposed based on a fully probabilistic description of the mechanisms that are hypothesized to generate the majority of damping in tall buildings. Finally, the proposed model is calibrated to a number of specific buildings demonstrating its robustness. [ABSTRACT FROM AUTHOR]

Mean recurrence intervals (MRIs) of wind effects for the strength design (SD) of flexible buildings by the wind-tunnel method are based on estimates of total uncertainties that do not account for uncertainties in the dynamic parameters. This paper presents a procedure for assessing this practice. The procedure accounts for the probability distributions of total uncertainties in basic wind effects corresponding to MRIs of 50 or 100 years. The total uncertainties are estimated for two cases. For Case 1, only uncertainties in the wind loading are taken into account. For Case 2, uncertainties in both the wind loading and the dynamic parameters are considered. Cumulative distribution functions (CDFs) of the total uncertainties in the basic wind effects are determined by Monte Carlo simulation. To assure risk consistency, the MRIs of wind effects considered for SD correspond in both cases to the same upper confidence bound of the basic wind effects. For a 305-m-tall symmetrical steel building, the requisite MRIs are larger for Case 2 than for Case 1 by at most 80%. These increases corresponded to wind effects considered for SD larger for Case 2 than for Case 1 by at most 6%. [ABSTRACT FROM AUTHOR]

The continuum model constitutes a simple and efficient tool to analyze high-rise wall-frame buildings. It has been commonly used in recent decades to analyze the behavior of these structures. The related equations are revisited to study the effect of the calculation precision on the determination of the optimum level of wall curtailment. The results obtained illustrate the influence of calculation precision in specifying the optimum level of wall curtailment. The relationship between the curtailment level and the resulting internal forces is investigated. The level of curtailment which results in the minimum top deflection of the structure eliminates, at the same time, the negative moments and negative shear forces in the wall. [ABSTRACT FROM AUTHOR]

The customization of apartments can add value and increase clients' satisfaction. However, companies offering such a strategy often face problems in managing the construction process. Delayed product differentiation-postponing the tasks that customize a product as much as possible-is a principle applied in manufacturing that enables companies to better cope with customization. Yet, it has not been widely explored in the building industry. This paper proposes a method to implement this principle in the construction of high-rise apartment building projects using the line-of-balance technique. First, the method is described, followed by its application in a project developed by a construction company. A comparison between the long-term plan devised using the proposed method and the initial plan shows a postponement of the decoupling point (namely, the first task that customizes an apartment) of approximately 42 weeks. At the end, the potential benefits and difficulties in creating such postponement and adopting the proposed method are discussed. [ABSTRACT FROM AUTHOR]