Serviceability‐based damping optimization of randomly wind‐excited high‐rise buildings

Fluid viscous dampers are proved to be effective for reducing the response of high‐rise buildings subjected to wind excitations so as to enhance structural habitability, which serves as a critical performance in serviceability design. High‐rise buildings attached with fluid viscous dampers, however, exhibit nonlinearity and even act as stiff systems in most cases of wind‐induced vibration mitigation. The traditional equivalent linearization methods employed in practices often fail to obtain an accurate solution. Equivalent linearization methods, including the energy‐dissipation equivalent linearization method and the statistical linearization technique, are first studied and validated in this paper by the backward difference formula, which was verified to be of high accuracy through the nonlinear dynamic analysis. The damping optimization for habitability control is then proceeded. Two families of serviceability criteria, the minimization of standard deviation of roof acceleration employed in traditional habitability analysis and the minimization of failure probability of roof acceleration proposed in the present study, are addressed. For the logical treatment of randomness inherent in wind excitations and its influence upon structural reliability, the probability density evolution method is employed. Numerical results reveal that the criterion of minimizing failure probability of roof acceleration has better performance in habitability enhancement.     

Multiperformance optimization design of a hybrid vibration mitigation system for super high‐rise buildings to improve earthquake resistance

A structure must meet many performance requirements to survive an earthquake. For a super high‐rise structure, the dominant control performance metric is stiffness when considering earthquake resistance because the lateral displacement of the structure often does not meet the requirements of the code even if the structure meets strength requirements. For moderate and major earthquakes, stiffness and strength play a leading role jointly. Viscous damper (VD) and buckling restraint brace (BRB) are damping devices that are commonly used in modern engineering. The efficiencies of these devices are different for different situations, and combining them can yield improved structural vibration mitigation. In this study, the performances of VD and BRB are summarized. A kind of virtual VD model with an additional damping ratio is proposed on the basis of which a VD priority placement analysis method is developed, and an optimal design is proposed. A detailed analysis of various stress states of a BRB is also performed, and a BRB arrangement method based on brace stress level analysis is proposed. The two kinds of vibration damping equipment are combined in the structure, and a practical design method for a hybrid vibration damping system is proposed. The accuracy of the proposed method is verified by considering a 10‐story plane frame. Finally, a hybrid vibration mitigation design for different objective damping ratios is performed for a super tall building project, and the design results are compared. The analysis results show that a VD can effectively increase structural damping and reduce the seismic response of the structure. A BRB is used to replace supports that experience high stress and reduce their section size, thereby reducing costs. Therefore, the proposed hybrid vibration damping structure is cost effective while providing good energy dissipation and is thus promising for engineering applications.     

Seismic capacity of typical high‐rise buildings in Singapore

Pushover analysis is a simplified method to determine the lateral load capacity of buildings. However, recent studies have suggested that pushover analysis could underestimate the capacity by as much as 25%. Thus, this study uses dynamic collapse analysis to determine the overstrength of a 16‐storey and a 25‐storey building, which are typical in Singapore. The results are compared with previously performed pushover analyses to justify the adequacy of pushover analysis for determining the ultimate capacity of such buildings. It is found that the buildings in Singapore, which are not designed for earthquake loads, possess overstrength varying from 4 to 12 times the design strength depending on the type of building. Furthermore, the pushover analysis could underestimate the capacity of such buildings up to 14%. It is suggested that one may choose to adopt pushover analysis to evaluate the lateral load capacity of such high‐rise buildings to err on the conservative side. Copyright © 2012 John Wiley & Sons, Ltd.     

Seismic fragility relationships of reinforced concrete high‐rise buildings

A complete methodology is presented for the seismic fragility assessment of reinforced concrete high‐rise buildings. The key steps of the methodology are illustrated through an example of the fragility assessment of an existing 54‐story building with a dual core wall system. The set of rigorously derived probabilistic fragilities are the first published for high‐rise reinforced concrete buildings. The inelastic nonlinear dynamic analyses for the fragility assessments are made using a simplified lumped‐parameter model that was derived from highly detailed FE models using genetic algorithms. New definitions for performance limit states were based on the results of detailed pushover analyses of a distributed inelastic nonlinear finite element model that includes shear–flexure–axial interaction effects. To develop the fragility relationships, 1800 dynamic response history analyses were conducted. This study considered uncertainty in structural material values as well as in seismic demand. Thirty strong motion records were selected for use in the analyses that would produce an appropriate range in structural response characteristics due to variation in magnitude, distance and site condition. The overall approach is generic and can be applied to developing computationally efficient and probabilistically‐based seismic fragility relationships for reinforced concrete high‐rise buildings of different configurations. Copyright © 2007 John Wiley & Sons, Ltd.     

Optimal compensation of differential column shortening in high‐rise buildings

To avoid unexpected damage in structural and nonstructural elements, differential shortening between vertical members resulting from differing stress levels, loading histories, volume‐to‐surface ratios and other factors in a high‐rise building must be properly considered in the design process. While research activity has been reported in the literature on the development of estimation algorithms or prediction procedures for the elastic and inelastic shortenings of vertical members, no algorithms or systematic methods for the compensation of the differential shortenings have been reported. In this paper, a compensation method for the differential column shortening in a high‐rise building is formulated into an optimization problem. A simulated annealing algorithm is used to find optimal solutions. The proposed method is applied to the compensation of the differential shortening of the vertical members in two high‐rise buildings, including one verifying example of a 70‐storey building and a practical example of a 63‐storey building. As demonstrated in the examples, the differential shortenings of the examples are effectively controlled by the optimal compensation method. Copyright © 2003 John Wiley & Sons, Ltd.     

Estimation of floor acceleration demands in high‐rise buildings during earthquakes

A simplified method to estimate lateral acceleration demands in high‐rise buildings subjected to earthquakes is presented. In the proposed method acceleration demands are obtained by approximating the dynamic characteristics of the building with those of a continuous model consisting of a combination of a flexural cantilever beam and a shear cantilever beam. Closed‐form solutions for mode shapes, period ratios and modal participation factors for the first six modes of vibration are presented. The method is evaluated by comparing peak floor acceleration demands and acceleration time histories computed with the proposed method to those recorded during earthquakes in six instrumented high‐rise buildings. A comparison of floor spectra computed with the approximate method and spectra computed with recorded motions is also presented. Results indicate that the proposed method produces relatively good results with a very small computational effort and requires only a small amount of information about the building. Variations of accelerations demands along the height are closely examined in each building for each component. It is shown that the variation of acceleration demands along the height of high‐rise buildings can differ significantly from that currently recommended in US seismic provisions for anchoring building nonstructural components. Copyright © 2005 John Wiley & Sons, Ltd.     

Steady suction for controlling across‐wind loading of high‐rise buildings

To reduce across‐wind effects on high‐rise buildings, this paper introduces a new active aerodynamic control named steady suction. To test its effect, the control mechanism of steady suction is discussed first, and then, a synchronization pressure test was conducted in a wind tunnel to measure the across‐wind loading on a high‐rise model (Commonwealth Advisory Aeronautical Research Council standard high‐rise building model). A series of analytical methods were used to compare the different effects on across‐wind aerodynamic forces caused by different parameters. The results show that when the wind blows straight on the wide side of the model, steady suction arranged on the narrow side close to the leading edge can effectively reduce the fluctuating base moment. When the wind blows straight on the narrow side, steady suction arranged on the middle of the wide side effectively reduces the fluctuating base moment. Copyright © 2016 John Wiley & Sons, Ltd.     

A simplified analysis and vibration control to super‐high‐rise buildings

This paper clarifies the following four points on the dynamic behavior of super‐high‐rise buildings of 700m high consisting of doubly symmetric frame‐tubes with or without braces. A simple and accurate analytical method presented by Takabatake (1996) is shown to be very useful for the preliminary design of such a mega‐structure. The building is replaced by an equivalent rod which may allow the main deformation field composed of longitudinal deformation, bending, transverse shear deformation, and shear‐lag. It is pointed out originally that, after the horizontal component of earthquake ground motion fades away, noticeable swell breaks out for a long time and that phenomenon is undamping. The serious phenomenon of swell increases remarkably in addition to the action of the horizontal component of an earthquake wave having a long period. The effect of soil–structure interaction on such a structure is discussed using a general analytical method proposed here. An epochal method both to reduce the dynamic response and to leave out the undamping swell after earthquake action is proposed and its effectiveness as a device for vibration control is demonstrated through the numerical computation. Copyright © 2006 John Wiley & Sons, Ltd.     

Comparative study of structural material quantities of high‐rise residential buildings

A major factor in the selection of the structural system for a high‐rise building is the initial construction cost of candidate structural systems. In Korea, composite steel and concrete construction, and cast‐in‐place concrete flat plate construction are the most commonly used structural systems. However, there is a lack of data related to the relative construction costs of these two structure types. This paper compares material quantities for representative building models up to 80 stories in height using both types of structural system. Based on a typical floor plan, six models are developed and the buildings are designed for gravity and lateral loading. Quantities of materials for each model are calculated and compared. The information presented can be used with appropriate cost data to compare construction costs for the two structural system types. Copyright © 2007 John Wiley & Sons, Ltd.     

Experimental tests for improving buildability of construction methods for high‐strength concrete columns in high‐rise buildings

High‐strength concrete columns have the advantage of increasing the amount of usable area in the building because the cross‐section of the columns takes up less space compared with columns using normal strength concrete. However, it is difficult to weld the steel reinforcement and steel members because of the narrow column width due to a decrease in the cross‐section of the column, thereby causing construction delay in many cases. In this paper, five construction methods with different details for high‐strength reinforced concrete columns are tested to improve the buildability of the columns. Five specimens with different construction details were tested and analyzed based on four aspects: (a) the relationship between load and displacements, (b) strain distributions, (c) axial stiffness, and (d) crack patterns. Specimens were constructed using concrete with a compressive strength of 55 MPa, and the design strength of all five specimens were set to about 10,740 kN. From results of the experiment, the specimen with a reduced number of vertical reinforcements from 24 of HD22 (SD400, Fy = 400 MPa) to 16 of UD22 (SD600, Fy = 600 MPa) was the most effective specimen to improve the buildability of the column without deteriorating the structural performance of the reference specimen.     

Robustness of base‐isolated high‐rise buildings under code‐specified ground motions

The robustness of base‐isolated high‐rise buildings is investigated under code‐specified ground motions. Friction‐type bearings are often used in base‐isolated high‐rise buildings to make the natural period of those buildings much longer. While additional damping can be incorporated into every story in passive controlled structures with inter‐story type passive members, that can be incorporated into the base‐isolation story only in the base‐isolated building. This fact leads to the property that, as the number of stories of the building becomes larger, the damping ratio reduces. This characteristic may cause some issues in the evaluation of robustness of base‐isolated high‐rise buildings. The purpose of this paper is to reveal the robustness of base‐isolated high‐rise buildings. A kind of inverse problem for the target drift in the base‐isolation story is formulated in order to determine the required quantity of additional viscous damping. It is demonstrated numerically that, as the base‐isolated building becomes taller, the damping ratio becomes smaller and the ratio of the friction‐type bearings in the total damping becomes larger. This may lead to the conclusion that base‐isolated high‐rise buildings have smaller robustness than base‐isolated low‐rise buildings. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of infills on high‐rise buildings: a case study

In this study, the effects of infill walls to the response of a selected building under earthquake loading were investigated. Although various suggestions have been offered, designers usually neglect the effect of infill walls on building behaviour when designing a building. In this study, the effects of infill walls on a building, which consists of two storeys of basement, one storey of ground floor, one storey of mezzanine floor and 10 storeys of flats, were investigated. Three‐dimensional models of the building with and without infill walls were modelled in SAP2000. Then, nonlinear time history analysis was performed on the models with and without infill walls. Infill walls were modelled both as mass and structural elements. The results of two analyses were compared. Consequently, the effect of infill walls on the behaviour of buildings such as period, maximum roof displacement, base columns end‐forces and soft‐storey formation coefficient was determined. Addition of infill wall to the structures caused changes in maximum roof displacement, modal periods, maximum base column end‐forces, shear force and soft‐storey formation coefficient. Copyright © 2008 John Wiley & Sons, Ltd.     

Peak factor estimation of non‐Gaussian wind pressure on high‐rise buildings

A vast quantity of measurements of wind‐induced non‐Gaussian effects on buildings call for the burgeoning development of more advanced extrema estimation approaches for non‐Gaussian processes. In this study, a well‐directed method for estimating the peak factor and modeling the extrema distribution for non‐Gaussian processes is proposed. This method is characterized by using two fitted probability distributions of the parent non‐Gaussian process to separately fulfill the estimations of the extrema on long‐tail and short‐tail sides. In this method, the Johnson transformation is adopted to be the probabilistic model for fitting the parent distribution of the non‐Gaussian process due to its superior fitting goodness and universality. For each dataset, two Johnson transformations will be established by two parameter estimation methods to individually estimate the extrema on two sides. Then a Gumbel assumption is applied for conveniently determining the non‐Gaussian peak factor. This method is validated through long‐duration wind pressure records measured on the model surfaces of a high‐rise building in wind tunnel test. The results show that the proposed method is more accurate and robust than many existing ones in estimating peak factors for non‐Gaussian wind pressures.     

Seismic performance analysis of viscous damping outrigger in super high‐rise buildings

This paper introduces a seismic energy dissipation technology—viscous damping outrigger (VDO)—which is composed of outrigger truss and viscous damper. The viscous damper is set up vertically at the end of outrigger truss, which is an innovative and high‐efficiency arrangement. VDO can fully utilize the characteristic of structural lateral deformation of super high‐rise buildings to increase the efficiency of viscous dampers for enhancing structural security, improving seismic performance, and reducing construction expenditure. In this paper, working principle and seismic energy dissipating mechanism of VDO are explained firstly. Then, the influence of viscous damper parameters on energy dissipation efficiency is studied. Next, the optimal position of VDO in a super high‐rise building is analyzed in detail. Lastly, the application of VDO in structural seismic design of a super high‐rise building in China will be clearly verified based on their feasibility, economy, and safety.     

Application of GPS to monitoring of wind‐induced responses of high‐rise buildings

A new monitoring system using GPS is introduced to measure wind‐induced responses of high‐rise buildings. In this paper, wind‐induced responses of a long‐period structure include relative lateral displacements, acceleration records, and torsional displacements at the top of a building. After comparing responses of a test model measured by GPS with responses obtained by the most commonly used laser displacement meters and accelerometers, the wind‐induced responses of a 66‐story high‐rise building subject to the yellow dust storm were measured by the GPS‐based monitoring system. Based on the field measurement, it is concluded that the complete motion history of a high‐rise building can be monitored by GPS. Copyright © 2007 John Wiley & Sons, Ltd.     

Approximate method of estimating seismic performance of high‐rise buildings with oil‐dampers

When subjected to long‐period ground motions, many existing high‐rise buildings constructed on plains with soft, deep sediment layers experience severe lateral deflection, caused by the resonance between the long‐period natural frequency of the building and the long‐period ground motions, even if they are far from the epicenter. This was the case for a number of buildings in Tokyo, Nagoya, and Osaka affected by the ground motions produced by the 2011 off the Pacific coast of Tohoku earthquake in Japan. Oil‐dampers are commonly used to improve the seismic performance of existing high‐rise buildings subjected to long‐period ground motion. This paper proposes a simple but accurate analytical method of predicting the seismic performance of high‐rise buildings retrofitted with oil‐dampers installed inside and/or outside of the frames. The method extends the authors' previous one‐dimensional theory to a more general method that is applicable to buildings with internal and external oil‐dampers installed in an arbitrary story. The accuracy of the proposed method is demonstrated through numerical calculations using a model of a high‐rise building with and without internal and external oil‐dampers. The proposed method is effective in the preliminary stages of improving the seismic performance of high‐rise buildings.     

Seismic performance and cost‐effectiveness of high‐rise buildings with increasing concrete strength

The relationship between the seismic performance and economics of high‐rise buildings when designed to different material strengths is investigated in this paper. To represent the modern high‐rise construction, five 60‐story reinforced concrete buildings with varying concrete strengths, ranging from 45 MPa to 110 MPa, are designed and detailed to fine accuracy keeping almost equal periods of vibration. Detailed fiber‐based simulation models are developed to assess the relative seismic performance of the reference structures using incremental dynamic analyses and fragility functions. It is concluded that a considerable saving in construction cost and gain in useable area are attained with increasing concrete strength. The safety margins of high‐strength concrete in tall structures may exceed those of normal‐strength concrete buildings, particularly at high ground motion intensity levels. The recommendations of this systematic study may help designers to arrive at cost‐effective designs for high‐rise buildings in earthquake‐prone regions without jeopardizing safety at different performance levels. Copyright © 2014 John Wiley & Sons, Ltd.     

Experimental study on wind load characteristics of high‐rise buildings with opening

For investigation of the wind load characteristics on high‐rise buildings with opening, a series of rigid rectangular high‐rise building models with opening were tested by synchronous multi‐pressure sensing system (SMPSS) in a boundary wind tunnel. Influence parameters including different opening heights, opening rates, opening patterns, and terrain categories are studied in detail. Based on the test results, the local wind force coefficients, base moment coefficients, and power spectral densities were discussed. The results indicated that the opening could affect the wind loads acting on high‐rise buildings to different extent. The distinct reduction of wind loads on high‐rise buildings was found at along‐wind direction, which could be evaluated by a proposed simplified expression accordingly. This study aims to provide useful information for the wind‐resistant design of high‐rise buildings with opening.     

Resonant behaviour of base‐isolated high‐rise buildings under long‐period ground motions

The resonant behaviour of base‐isolated high‐rise buildings under long‐period ground motions is investigated. The long‐period ground motions are known to be induced by surface waves. While the acceleration amplitude of such long‐period ground motion is small, the velocity amplitude is fairly large. It is expected that high‐rise buildings and base‐isolated buildings with long fundamental natural periods are greatly influenced by these long‐period ground motions. Especially base‐isolated high‐rise buildings with friction‐type bearings may have remarkable mechanical characteristics unfavourable for these long‐period ground motions. The purpose of this paper is to reveal that the long‐period ground motions recorded in Japan have the intensity to make base‐isolated high‐rise buildings in resonance with long‐period components and that careful treatment is inevitable in the structural design of these base‐isolated high‐rise buildings. It is pointed out that the friction‐type bearings are effective in general in avoiding the resonance with ground motions with a narrow‐range frequency characteristic, but are dangerous for ground motions with a wide‐range frequency characteristic in the long period range. Copyright © 2006 John Wiley & Sons, Ltd.