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Analysis on interstory drift of high-rise residential quasi-megastructure
Abstract
Based on the superior lateral resistant performance of mega-X layout pattern, the concept of quasi-megastructure was put forward to introduce quasi-mega mechanism in residential buildings, using normal members only, avoiding large architecture space occupation of mega members. Unlike the megastructures that are dominated by their primary structures, the quasi-megastructures mainly realize a synergistic mechanism between the frame structure and quasi-mega braces. In order to investigate its deformation mechanism and reduce the lateral stiffness irregularity, a simplified method for evaluating interstory drift of high-rise quasi-megastructure was proposed, based on three fundamental assumptions. Thus, the interstory drift formula for any specific layout scheme of quasi-megastructure can be deduced. The formula was validated by different layout schemes. By this method, the interstory drift proportion of quasi-megastructure was investigated, showing that the interstory drift of a target story mainly consists of drift due to rigid body rotation, pure shearing drift, and shear-lag added drift. And the vertical stiffness irregularity of the original scheme was due to great changes of shear-lag added drift in different neighboring stories. Thereafter, stiffened schemes were proposed, which effectively eliminate the interstory stiffness irregularity by complementing a quasi-mega cantilever wall of full height. Compared with mega frame structure, the original scheme has a similar overall deformation mechanism, while the properly stiffened quasi-megastructure scheme behaves quite close to mega braced frame structure, both in deformation mechanism and in structural efficiency.
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The paper demonstrates concepts for designing stiffer structures. They are: (a) the more direct the internal force path, the stiffer the structure; (b) the more uniform the internal force distribution, the stiffer the structure; and (c) the smaller the internal forces, the stiffer the structure. These concepts are applicable to the design of many structures. Two ways of implementing the concepts into practice are provided. Simple examples are given to illustrate the implementation and the efficiency of the concepts. Laboratory tests and the demonstration of two physical models further confirm the findings. Several practical designs are also provided to show the applicability and significance of these concepts. An alternative definition of structural stiffness is given which complements the existing definition and allows for designing stiffer structures. It is interesting to note that using the concepts may lead to not only stiffer but also more economical and elegant designs.
SUMMARY Irregular frame buildings with discontinuous columns in one or several stories have been vulnerable to collapses during strong earthquakes. This paper presents the investigation of the seismic response demands at irregular stories of such buildings in terms of story strength factor demand. In this study, a story strength factor was defined to represent the relative reserve strength against the formation of a story failure mechanism of the structure. In addition, a huge number of rigorous nonlinear inelastic dynamic time-history analyses of various analytical models of 7-story, 8-story and 15-story frame structures with discontinuous columns in one and two irregular stories were conducted under 29 strong earthquake records with various characteristics. The results show that the seismic response demands at irregular stories of the structures were well evaluated in terms of the story strength factor demand to avoid development of a story failure mechanism of the structures when subject to strong earthquakes. Copyright © 2011 John Wiley & Sons, Ltd.
In this study, the progressive collapse-resisting capacities of tilted or twisted buildings were evaluated by nonlinear static and dynamic analyses. For analysis models, 30-storey tilted buildings with braced cores and 30-storey twisted buildings with reinforced concrete cores were designed, and their performances were compared with those of the regular buildings. According to the analysis results, the progressive collapse potential of the tilted structures varied significantly, depending on the location of the removed column. It was also observed in the tilted structures that the plastic hinges formed not only in the bays from which a column was removed, but also in the nearby bays. Similar results were observed in the analysis of the twisted structures. The progressive collapse potentials of the tilted structure were high when a column was removed from the tilted side. However, the twisted structures considered in this study had progressive collapse potentials not very large compared with those of the corresponding regular structures, mainly because more structural elements were involved in resisting progressive collapse when a structural member was eliminated. Copyright © 2009 John Wiley & Sons, Ltd.
Buckling-restrained steel plate shear wall (BRSPSW) is a new type of lateral force resisting component suitable for high-rise steel structures. BRSPSW has a good plastic performance and stable hysteretic characteristics, and its bearing capacity and stiffness can be individually adjusted. Also, unlike braces, BRSPSWs can be applied at various locations of the structures without being limited by architectural functions. This paper presents an application of BRSPSW in a 34-story high-rise steel residential structure. Based on the elastic inter-story drift requirement, the force transfer is analyzed through six examples on D-shape arrangement of BRSPSW across the doorway. The concept of effective aspect ratio is proposed and design recommendations for BRSPSW system in overall design phase are proposed. © 2015, Progress in Steel Buiding Structures All right reserved.
Following is a continuation of the list of titles and authors of the papers presented: High Rise Construction in France. By Jean A. Roret. Steel Construction. By K. D. Cunningham. Steel Construction. By E. E. F. Taylor. Concrete Frame Construction. By W. S. Bellows Jr. Hybrid Frame Construction (Steel and Concrete). By J. F. Camellerie. Design of Compensated Foundations. By Leonardo Zeevaert. Distribution of Wind Loads to Soil. By S. V. DeSimone. Effects of Foundations on Adjacent Structures. By E. Horvat and Cornelius van der Veen. Deep Foundations - Piles and Caissons. By G. M. Cornfield. Precast Concrete Piles. By Bengt H. Fellenius. Soil-Structure Interaction for Tall Buildings. By John T. Christian. High-Rise Building Construction Design in Japan and Asia. By Kiyoo Matsushita and Yoshichika Uchida. Architectural Elements in European Practice. By Jean H. Polak.
The calculation of story drift and the specification of structural performance levels are major works to determine the target displacement in performance-based seismic design. Based on the characteristics of shear wall structures, the floor displacement is classified as destructive and nondestructive, and the story drift is classified as nominal and destructive considering the rigid body rotation of floor. The relationships among nominal story drift, destructive story drift and floor rotation are investigated, and the practical formulas to calculate the destructive story drift are derived. Based on the displacement profiles of shear wall structures, an improved method for calculating the story drift is presented. Next, the destructive story drift ratio is taken as the performance index of shear wall structures. Then, the performance levels of shear wall structure are quantified and the lateral deformation is controlled by two parameters: the destructive story drift ratio and the roof drift ratio. Finally, the determination method of target story drift of shear wall structures is presented, which can be used to estimate the target displacement profile in displacement-based seismic design.
A full-scale composite slit steel plate walls(CSSPW) specimen was tested, which further verified the cyclic strain hardening phenomenon. In the meanwhile, a unified model of equivalent cross brace(ECB) model and corresponding hysteretic models were proposed to simulate the hysteresis behavior of steel plate shear walls with slits and CSSPW. Numerical simulation was conducted for four specimens of steel plate shear walls and three specimens of CSSPWs, showing good accuracy of the proposed model.
This paper is concerned with the structural mechanics of pin-jointed structures and temporary grandstands. Particular attention is paid to horizontal stiffness which is one of the principal design checks for such structures. It is demonstrated that the stiffness of a pin-jointed structure can be increased by providing shorter or direct load paths between the loads and the supports and also by providing a uniform inner force distribution. Following these concepts, five simple criteria for arranging bracing members of temporary grandstands are obtained. Several bracing systems are examined and compared with equivalent systems obtained using these criteria. The results show that the criteria can be used to increase the lateral stiffness (or frequencies) without using extra bracing members. Then the structural characteristics of typical bracing systems of parts of two temporary grandstands are studied. Following the proposed criteria, the bracing systems can be rearranged to provide a significant increase in lateral stiffness. The effects of misalignment or omission of bracing members are also considered.
The cumulative problem of vertical deformation for super high-rise buildings during construction becomes more significant as the height of structure continue to increase nowadays, for which the investigation of the characteristics of the vertical deformation is worth conducting. First, the technique of simulation of the construction process for super high-rise buildings was developed systematically, with which simulation of construction of the three typical high-rise buildings was conducted. The effect of concrete creep, shrinkage and leveling during construction were investigated and the characteristics of the vertical deformation revealed. Furthermore, a method of pre-deformation for super high-rise buildings was presented with deformation compensation stepwise. The total vertical displacement and the relative deformation between the inner core tube and the outer steel frame were chosen as the control targets in the method, which can be used to address the cumulative problem of vertical deformation and to provide technical support for deformation control in construction of super high-rise buildings.
For a braced frame it is important to understand the relationships between the lateral stiffnesses, internal forces and bracing patterns in order to achieve an efficient design. This paper studies these relationships based on a four-bay and four-storey braced frame using both hand and computer analyses. Assuming that two bracing members can be placed arbitrarily in each of the four stories, there are 331,776 possible bracing arrangements. The best and the worst patterns of the total patterns are reviewed, with their characteristics summarized. All possible 256 symmetrically braced frames are further studied, allowing a more detailed examination of these relationships. Criteria for selecting bracing panels and bracing orientations are suggested based on the findings of this study and basic concepts, which may be applicable to the design of other braced frames. It is also found that the mega X brace or the double inversed V brace is the stiffest brace pattern, dependent on the aspect ratio of the braced panel and the size ratio of the columns to beams. This finding is confirmed using evolutionary structural optimization.
This paper presents simple methods of analysis for preliminary design of high-rise structures comprising reinforced concrete shear walls or steel trussed frames with a perimeter belt bracing structure consisting of steel trusses, subjected to horizontal loading. The methods are based on the analysis of facade rigger braced structures where horizontal steel trusses (web riggers), located in the two end facades (web frames), are positioned in a direction parallel to the lateral loading on the building. Perpendicular to the horizontal load additional horizontal steel trusses in the wind and lee sides of the building, "flange trusses", complete the belt bracing structure. The method is focused on the contribution of the flange trusses to the lateral stiffness of the structure. The shear-lag due to differential strain in the flange frame columns along the wind and leeward facades is caused by bending and racking shear deformations in the flange trusses and is taken into account. In an approximate method the flange columns are replaced by a continuous medium of equivalent axial stiffness, i.e. a beam on an elastic foundation. The proposed methods of analysis, for use in the initial stages of the structural design of proposed tall buildings, offer simple and rapid means of establishing the influence of belt structures on horizontal deformations of the high-rise structure and internal forces.
Fundamentals of Earthquake Engineering combines aspects of engineering seismology, structural and geotechnical earthquake engineering to assemble the vital components required for a deep understanding of response of structures to earthquake ground motion, from the seismic source to the evaluation of actions and deformation required for design. The nature of earthquake risk assessment is inherently multi-disciplinary. Whereas Fundamentals of Earthquake Engineering addresses only structural safety assessment and design, the problem is cast in its appropriate context by relating structural damage states to societal consequences and expectations, through the fundamental response quantities of stiffness, strength and ductility. The book is designed to support graduate teaching and learning, introduce practicing structural and geotechnical engineers to earthquake analysis and design problems, as well as being a reference book for further studies. Fundamentals of Earthquake Engineering includes material on the nature of earthquake sources and mechanisms, various methods for the characterization of earthquake input motion, damage observed in reconnaissance missions, modeling of structures for the purposes of response simulation, definition of performance limit states, structural and architectural systems for optimal seismic response, and action and deformation quantities suitable for design. The accompanying website at www.wiley.com/go/elnashai contains a comprehensive set of slides illustrating the chapters and appendices. A set of problems with solutions and worked-through examples is available from the Wley Editorial team. The book, slides and problem set constitute a tried and tested system for a single-semester graduate course. The approach taken avoids tying the book to a specific regional seismic design code of practice and ensures its global appeal to graduate students and practicing engineers.
SUMMARY Irregular buildings behave differently as compared with regular buildings. Seismic design codes have quantified the irregularities in terms of magnitude only ignoring the effect of irregularity location. In the present study, a single parameter to quantify mass, stiffness and strength irregularity in terms of both magnitude and location is proposed on the basis of the dynamic characteristics of the building. Furthermore, building models with different types of irregularity with variation in magnitude and location of irregularity are analyzed by subjecting them to an ensemble of 27 ground motions to create a seismic response databank. In the analysis, the torsional effects generated due to irregularities in the building systems (as per EC 8:2004 provisions) are included. On the basis of regression analysis conducted on this seismic response databank, equations to estimate seismic response parameters such as fundamental period, maximum roof displacement and maximum inter-story drift ratio etc. are proposed for the irregular buildings in terms of the proposed irregularity index. Finally, applicability of the proposed equations is discussed in brief, and these equations are validated for 2D and 3D building models. Copyright © 2012 John Wiley & Sons, Ltd.
There are significant unprecedented structural damages at Ashiyahama residential high-rise steel building complex due to the Hyogo-ken Nanbu Earthquake (Kobe Earthquake), which occurred on January 17, 1995. This paper is concerned with two issues of steel fracture observed in the mega-structure that have been attracting the special attention of structural engineers. These are fracture propagating through very thick-plated steel column and brace, and brittle-type fracture at column–column welded connections. The cause of the former damage is first examined using numerical computation with recourse to an explicit method of dynamic analysis based on a continuous medium model. By taking account of the complexity of the mega-structure, and of the limitation of numerical computation, the analysis is carried out in two distinct steps. In the first approach, the global frame is dynamically analysed on the basis of beam element modelling; the second approach calls for an analysis, based on shell element modelling, of a partial frame that is composed of the joint and the adjacent brace, beam and columns. It turns out that the axial breakage is initiated from the brace and propagates through the column. The second issue of the fracture at column–column welded connections is investigated with consideration to energy balance, or the difference in the total energy across the boundary between the two elements connected at the weld. The paper concludes from a practical point of view with recommendations to enhance earthquake-resistant capability in the structural design. Copyright © 2004 John Wiley & Sons, Ltd.
In the present paper, the seismic upgrading of existing reinforced concrete (RC) structures by means of steel and pure aluminium shear panels is examined. After a preliminary experimental evaluation of the performance of the bare RC structure, a design approach based on the capacity spectrum method has been developed according to the procedure provided in the ATC 40 American guidelines. First, the geometrical configuration of the applied shear panels has been defined according to simplified analytical relationships, while appropriate steel members have been designed to allow the insertion of shear panels in the existing RC structure. Then, complex finite element models have been implemented in order to check the reliability of the proposed design procedure. Also, a numerical evaluation of the global response of the upgraded structure has been processed aiming at evaluating the interaction between the RC structure and the metal devices. Finally, the effectiveness of the applied shear panels has been proven by means of full-scale experimental tests, which confirmed the significant improvement of the RC structure performance, in terms of strength, stiffness and deformation capacity. Copyright © 2008 John Wiley & Sons, Ltd.
Tall building developments have been rapidly increasing worldwide. This paper reviews the evolution of tall building's structural systems and the technological driving force behind tall building developments. For the primary structural systems, a new classification – interior structures and exterior structures – is presented. While most representative structural systems for tall buildings are discussed, the emphasis in this review paper is on current trends such as outrigger systems and diagrid structures. Auxiliary damping systems controlling building motion are also discussed. Further, contemporary "out-of-the-box" architectural design trends, such as aerodynamic and twisted forms, which directly or indirectly affect the structural performance of tall buildings, are reviewed. Finally, the future of structural developments in tall buildings is envisioned briefly.
The present study assesses the seismic performance of steel moment resisting frames (MRFs) retrofitted with different bracing systems. Three structural configurations were utilized: special concentrically braces (SCBFs), buckling-restrained braces (BRBFs) and mega-braces (MBFs). A 9-storey steel perimeter MRF was designed with lateral stiffness insufficient to satisfy code drift limitations in zones with high seismic hazard. The frame was then retrofitted with SCBFs, BRBFs and MBFs. Inelastic time-history analyses were carried out to assess the structural performance under earthquake ground motions. Local (member rotations) and global (interstorey and roof drifts) deformations were employed to compare the inelastic response of the retrofitted frames. It is shown that MBFs are the most cost-effective bracing systems. Maximum storey drifts of MBFs are 70% lower than MRFs and about 50% lower than SCBFs. The lateral drift reductions are, however, function of the characteristics of earthquake ground motions, especially frequency content. Configurations with buckling-restrained mega-braces possess seismic performance marginally superior to MBFs despite their greater weight. The amount of steel for structural elements and their connections in configurations with mega-braces is 20% lower than in SCBFs. This reduces the cost of construction and renders MBFs attractive for seismic retrofitting applications.
This paper describes new concepts for the structural design of high-rise buildings, in which a system is introduced to increase the dependable structural damping by a factor of 5–10. By so doing the dynamic response of the building to wind effects (buffeting and vortex shedding) is virtually eliminated, leading to substantially reduced lateral design forces and assured occupant comfort. Substantial reductions in structural member size and construction cost savings can be realized in many cases. This may significantly improve the economic viability and sustainability of a development. The paper describes some means by which high levels of damping may be achieved and is illustrated by an implementation on a building, currently under construction, subjected to wind and seismic excitation. Copyright © 2007 John Wiley & Sons, Ltd.
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