Drift design of steel‐frame shear‐wall systems for tall buildings

Drift design methods based on resizing algorithms are presented to control lateral displacements of steel‐frame shear‐wall systems for tall buildings. Three algorithms for resizing of structural members of the steel‐frame shear‐wall systems are derived by formulating the drift design process into an optimization problem that minimizes lateral displacement of the system without changing the weight of a structure. During the drift design process, cost‐effective displacement participation factors obtained by the energy method are used to determine the amount of material to be modified instead of calculating sensitivity coefficients. The overall structural design model with the drift design method for the steel‐frame shear‐wall systems is proposed and applied to the structural design of three examples. As demonstrated in the examples, the lateral displacement and interstorey drift of a frame shear‐wall system can be effectively designed by the drift design method without the time‐consuming trial‐and‐error process. Copyright © 2002 John Wiley & Sons, Ltd.     

Model‐Based Multi‐input,Multi‐output Supervisory Semi‐active Nonlinear Fuzzy Controller

Abstract: The authors recently proposed a new multi‐input, single‐output (MISO) semi‐active fuzzy controller for vibration control of seismically excited small‐scale buildings. In this article, the previously proposed MISO control system is advanced to a multi‐input, multi‐output (MIMO) control system through integration of a set of model‐based fuzzy controllers that are formulated in terms of linear matrix inequalities (LMIs) such that the global asymptotical stability is guaranteed and the performance on transient responses is also satisfied. The set of model‐based fuzzy controllers is divided into two groups: lower level controllers and a higher level coordinator. The lower level fuzzy controllers are designed using acceleration and drift responses; while velocity information is used for the higher level controller. To demonstrate the effectiveness of the proposed approach, an eight‐story building structure employing magnetorheological (MR) dampers is studied. It is demonstrated from comparison of the uncontrolled and semi‐active controlled responses that the proposed design framework is effective in vibration reduction of a building structure equipped with MR dampers.     

Fuzzy‐Valued Intensity Measures for Near‐Fault Pulse‐Like Ground Motions

Two fuzzy‐valued (FV) structure‐specific intensity measures (IMs), one based on squared spectral velocity and the other on inelastic spectral displacement, are presented to characterize near‐fault pulse‐like ground motions for performance‐based seismic design and assessment of concrete frame structures. The first IM is designed through fuzzying structural fundamental period to account for the period shift effect due to stiffness degradation, whereas the second IM is developed to take into account higher mode contribution in high‐rise buildings by employing a fuzzy combination of the first two or three modes for the lateral loading pattern in pushover analysis. A benchmark study of three example reinforced concrete frame structures shows that for moderate‐ to medium‐period structures, both of the proposed IMs improve prediction accuracy in comparison with the existing IMs. For short‐period structures, the FV inelastic spectral displacement is the best.     

Reduced order control for wind‐induced vibrations of tall buildings

The design of a structural control system for a tall building may not be easy owing to the large number of degrees of freedom involved. Obviously, it is much easier to design a structural control system for the reduced‐order system than for the full‐order system. Model reduction is thus useful when control systems are implemented in civil engineering structures. A reduced‐order modelling technology for vibration control of wind‐excited tall buildings is presented and its performance is studied. The important issues associated with wind‐induced vibrations, model condensations and reduced‐order control are addressed. Finally, a numerical example, a tall building with an active tuned mass damper or a passive tuned mass damper, is given to show the efficiency of the reduced‐order control technique. Copyright © 2003 John Wiley & Sons, Ltd.     

Ein prototypisches Kunststoff‐Faltwerk mit neuartiger Fügetechnologie

Prototypic plastic folded‐plate structure with custom designed detachable jointing technique. The class for structural design of the State Academy of Art and Design Stuttgart has designed and realized a prototype for a plastic folded‐plate structure. The special features of the spectacular experimental building are the high‐performance structure, an innovative high‐class material plus a custom designed detachable joining technique. The article describes the conceptual design, the structural design as well as production and assembly of the plastic structure.     

Adaptive fuzzy controller for active tuned mass damper of a benchmark tall building subjected to seismic and wind loads

Active tuned mass dampers (ATMDs) are one of the most effective solutions for mitigation of destructive effects of earthquakes and strong winds in tall buildings. In order to achieve optimal performance, these systems are designed and tuned to mitigate effect of either wind or earthquake excitation. However, due to different frequency contents and intensities of wind and earthquake excitations, which will cause contrasting structural modes stimulation, the ATMD designed for one of these disturbances may not work optimally for the other one. This paper addresses a methodological simulation approach for adaptive control design of ATMDs in tall buildings located in regions with high level of seismic activity and recurrent strong winds. For this purpose, a multi‐objective adaptive genetic‐fuzzy controller is proposed for the control of an ATMD of a benchmark 76‐story building subjected to wind load and earthquake disturbances. Simulation results reveal that the optimal ATMD designed for earthquake disturbance does not work adequately for wind load disturbance and vice versa. Furthermore, the proposed adaptive controller has superior performance in suppressing base shear and inter‐story drifts induced by wind load and earthquake excitations. Copyright © 2013 John Wiley & Sons, Ltd.     

Overstrength and force reduction factors of multistorey reinforced‐concrete buildings

This paper addresses the issue of horizontal overstrength in modern code‐designed reinforced‐concrete (RC) buildings. The relationship between the lateral capacity, the design force reduction factor, the ductility level and the overstrength factor are investigated. The lateral capacity and the overstrength factor are estimated by means of inelastic static pushover as well as time‐history collapse analysis for 12 buildings of various characteristics representing a wide range of contemporary RC buildings. The importance of employing the elongated periods of structures to obtain the design forces is emphasized. Predicting this period from free vibration analysis by employing ‘effective’ flexural stiffnesses is investigated. A direct relationship between the force reduction factor used in design and the lateral capacity of structures is confirmed in this study. Moreover, conservative overstrength of medium and low period RC buildings designed according to Eurocode 8 is proposed. Finally, the implication of the force reduction factor on the commonly utilized overstrength definition is highlighted. Advantages of using an additional measure of response alongside the overstrength factor are emphasized. This is the ratio between the overstrength factor and the force reduction factor and is termed the inherent overstrength (Ω _i). The suggested measure provides more meaningful results of reserve strength and structural response than overstrength and force reduction factors. Copyright © 2002 John Wiley & Sons, Ltd.     

Efficiency of active systems in controlling base‐isolated buildings subjected to near‐fault earthquakes

It has been pointed out that base‐isolated structures may be vulnerable during near‐fault earthquakes and special considerations are required in the design of isolated structures in near‐fault areas. This paper investigates the efficiency of active control systems in reducing the responses of base‐isolated structures with various isolation parameters. The design of hybrid control systems using base isolation and active systems are optimized in order to accomplish different design purposes. Also for some cases, equivalent passive control systems are introduced which result in comparable responses with respect to hybrid control systems. Copyright © 2009 John Wiley & Sons, Ltd.     

Robust control of civil structures with parametric uncertainties through D‐K iteration

Active control is an alternative method to suppress the civil structural vibration, which is more effective than the passive control or strengthening the structural components. The performance of active control is dependent on the control strategy and the accuracy of the structural model. However, there always exist some uncertainties in the model, such as mass, damping and stiffness uncertainties. This paper presents a robust H_∞ controller design for civil structures with consideration of the parametric uncertainties. The formulation to extract the parametric uncertainties from the structural model matrices is proposed through the linear fractional transformations approach. The robust H_∞ controller design for the civil structures with the parametric uncertainties is achieved through the D‐K iteration method. The linear matrix inequality is then used in the H_∞ optimization procedure of the D‐K iteration. The robustness of the controller is first numerically validated by a four‐story building example and then experimentally corroborated by a shaking table test of a two‐story frame with one active mass damper. The results show that the robust H_∞ controller can consider the parametric uncertainties in the civil structural model and achieve the robust performance. Copyright © 2015 John Wiley & Sons, Ltd.     

Robust optimum design of tuned mass dampers for high‐rise buildings under moderate earthquakes

In the present study the optimum design of tuned‐mass‐damper (TMD) devices used for the vibration control of high‐rise buildings subject to moderate earthquakes is developed. For these structures a large acceleration demand can produce damage in equipment and contents: therefore, the performance of TMD will be based on the capacity of reducing this structural response. In order to maximize the performance and the efficiency of the TMD strategy, the ratio between the absolute accelerations of the protected and of the unprotected systems is assumed as objective function in the optimum design. The method is carried out in a stochastic way and a stationary‐filtered stochastic process is assumed to model the seismic action. Since the main disadvantage of using a single TMD is the mistuning related to errors in the evaluation of the natural frequency of the main structure, an uncertainty is introduced for this structural parameter, which is modelled as a random variable. Uncertainties in other structural mechanical properties and in TMD are neglected. Copyright © 2008 John Wiley & Sons, Ltd.     

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.     

A new control algorithm to protect nonlinear base‐isolated structures against earthquakes

Currently, nonlinear base isolation systems are widely used in the construction of earthquake resistant structures. However, they are found to be vulnerable in near‐fault regions as a result of long‐period pulses that may exist in near‐source ground motions. Various control strategies including passive, active and semi‐active control systems have been studied in order to handle this issue. In this study, a semi‐active control algorithm based on the different performance levels anticipated from an isolated building during different levels of ground shaking was developed. The proposed performance‐based algorithm is based on a modified version of the well‐known semi‐active skyhook control algorithm. A series of analyses were performed on the base‐isolated benchmark building, suggested by the American Society of Civil Engineers committee, subject to seven pairs of scaled ground‐motion records. The results proved that the new control algorithm is successful in improving structural and nonstructural performance of isolated buildings under near‐fault earthquakes. Copyright © 2012 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.     

Holz‐Beton‐Verbunddecken (HBV) – Neue Deckensanierungssysteme mit Vollgewindeschrauben,Stahlfaserbeton und Online‐Bemessungstools

Composite timber‐concrete structures – new floor renovation systems with fully threaded shear connectors, steel fibre concrete and online design tools. Composite timber‐concrete structures – efficiently static, oscillation‐technical and sound‐technical improvement of old timber joist floor systems. New products, design codes, approvals and investigation results are ready for online using in planning and structural design calculation.     

Life‐cycle cost assessment of mid‐rise and high‐rise steel and steel–reinforced concrete composite minimum cost building designs

The traditional trial‐and‐error design approach is inefficient to determine an economical design satisfying also the safety criteria. Structural design optimization, on the other hand, provides a numerical procedure that can replace the traditional design approach with an automated one. The objective of this work is to propose a performance‐based seismic design procedure, formulated as a structural design optimization problem, for designing steel and steel–reinforced concrete composite buildings subject to interstorey drift limitations. For this purpose, eight test examples are considered, in particular four steel and four steel–reinforced concrete composite buildings are optimally designed with minimum initial cost. Life‐cycle cost analysis (LCCA) is considered as a reliable tool for measuring the damage cost due to future earthquakes that will occur during the design life of a structure. In this study, LCCA is employed for assessing the optimum designs obtained for steel and steel–reinforced concrete composite design practices. Copyright © 2011 John Wiley & Sons, Ltd.     

Evaluation of deflection amplification factor in steel moment‐resisting frames

Steel moment‐resisting frames (SMRFs) are the most common type of structural systems used in steel structures. The first step of structural design for SMRFs starts with the selection of the structural sections on the basis of story drift limitation. ASCE 7 (2010) requires that the inelastic story drifts be obtained by multiplying the deflections determined by elastic analysis under design earthquake forces with a deflection amplification factor (C_d). For special moment‐resisting frames, C_d is given as 5.5 in ASCE 7 (2010). Lower C_d values will increase the overall inelastic response of the structure. On the other hand, the inelastic response of the structure is expected to be less severe when designed for higher C_d values. The performance objective is that the structure should sustain the inelastic deformation demand imposed due to design earthquake ground motions. This study aims at investigating the inelastic seismic response that low‐rise, medium‐rise and high‐rise SMRFs can experience under design earthquake ground motions and maximum considered earthquake (MCE) level ground motions and evaluating the deflection amplification factors (C_d) for SMRFs in a rational way. For this purpose, nonlinear dynamic time history and pushover analyses will be carried out on SMRFs with 4, 9 and 20 stories. The results indicate that the current practice for computing the inelastic story drifts for SMRFs is rational and the frames designed complying with the current code requirements can sustain the inelastic deformations imposed during design earthquake ground motions when seismically designed and detailed. Copyright © 2013 John Wiley & Sons, Ltd.     

Seismic isolation columns for earthquake‐resistant structures

Seismic isolation is a well‐known trend in earthquake design of structures. It enables a reduction in structural response to earthquakes and minimizes possible damage to buildings. This paper deals with a new constructive solution for seismic isolation, adapted to a structural scheme traditionally used in the Mediterranean region; it is usually presented as an open ground floor with a system of reinforced‐concrete columns, supported on single bases. The best‐known base isolation systems, implemented in existing structures, are elastomeric bearings and friction pendulums. The proposed solution is based on the idea of pendulum suspension brackets installed in seismic isolation columns. The main differences between existing solutions and the proposed one are that the latter requires no additional space for its installation, its lifetime corresponds to that of the structure, and no service is required during the entire period. The proposed solution provides additional damping and, like other base isolation systems, shifts the vibration period of the structure, reducing its spectral response. Since its size is compact, the ground‐floor columns of existing structures with low seismic capacity may easily be replaced by the proposed ones. It yields significant improvement in structural seismic response. Numerical simulation shows that buildings where the proposed system is installed are likely to sustain minimal damage, or none at all, whereas traditionally designed ones may suffer major damage or even collapse due to the same earthquake. Copyright © 2007 John Wiley & Sons, Ltd.     

An inter‐story drift‐based parameter analysis of the optimal location of outriggers in tall buildings

Outriggers are usually added in structural systems of tall buildings to collaborate central shear walls with peripheral columns. With outriggers, the structural overturning moment can be balanced, and the inter‐story drift can be controlled under horizontal loads. Therefore, the optimal location of outriggers plays a very important role in controlling the behavior of the whole building. Existing research has focused on the optimal position of outriggers on the base of the structural roof deflection. In the engineering practice, however, inter‐story drift is the most important target to control the design of tall building structures. This paper investigates the theoretical method of inter‐story drift‐based optimal location of outriggers. A Matlab program is written to perform the parameter analysis of optimal location of outriggers. Take a 240‐m tall building for a target building, the optimal location of one to three sets of outriggers under wind and earthquakes is obtained and can be utilized for the structural preliminary design of tall buildings. Copyright © 2015 John Wiley & Sons, Ltd.     

Direct displacement‐based design of steel‐braced reinforced concrete frames

This study investigates a direct displacement‐based design procedure for dual system structures composed of reinforced concrete frames and steel bracings. In this procedure, in order to establish the design displacement profile before any analysis, strength proportions between bracings and frames are assigned. By using the displacement profile and damping characteristics of the structural components, the structure can be represented as an equivalent single‐degree‐of‐freedom system. The effective period and secant stiffness of the structure are then calculated, and finally, after the base shear was computed, the design process can be implemented. Structures with 4, 8 and 12 stories have been designed using this methodology, and in order to validate it, seven accelerograms have been used for nonlinear time‐history analysis of the above structures. The results demonstrate the efficiency of this procedure. Copyright © 2012 John Wiley & Sons, Ltd.     

A variable gain state‐feedback technique for an AMD control system with stroke limit and its application to a high‐rise building

As the auxiliary mass of an active mass damper/driver (AMD) control system in a high‐rise building has excessive strokes and its relative velocities are in the same direction with the strokes, the auxiliary mass probably collides with its anti‐collision device. As a result, the structural responses increase and even the structural safety is endangered. In this paper, a variable gain state‐feedback control system is proposed to limit the strokes and relative velocities of the auxiliary mass, so as to ensure the safety of the system. Firstly, the limited state of the auxiliary mass is defined, and a regional pole assignment algorithm that utilizes only a damping factor is realized as a control gain. Then the relationship between the control gain corresponding to the stroke and its threshold limit value is deduced. A suitable threshold limit value is chosen to reduce the strokes and the relative velocities. Finally, the performance characteristics of the control systems with or without stroke limit are analyzed. The results demonstrate that the controller limits the strokes effectively on the premise of guaranteeing the control effects and the AMD parameters. To verify its effectiveness, the proposed methodology is also applied to an experiment of a four‐storey frame.