Fragility assessment of high‐rise reinforced concrete buildings considering the effects of shear wall contributions

The effect of shear wall configurations on seismic responses of high‐rise RC buildings is investigated in this paper using fragility analysis method. Four lower high‐rise RC buildings that have the same plan dimensions and height but are different in configurations in lateral force resisting systems, were firstly designed following the standard code procedure. To consider uncertainties in earthquake motions, 16 real ground motion pairs were selected and scaled, then applied orthogonally to the four RC building models during the Incremental Dynamic Analysis (IDA). Fragility relationships were therefore derived based on the IDA results for the three limit states including slight damage, moderate damage and collapse to show the probabilistic comparison of seismic responses among the four buildings in both x and y‐directions. It was observed that generally adding shear walls will improve buildings' seismic performance at all limit states. However, shear wall configuration also plays a significant role in seismic behavior of the lower high‐rise regular RC buildings' and internal shear walls are generally more effective than external shear walls in improving building's seismic resistance. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

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.     

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.     

The effect of design drift limit on the seismic performance of RC dual high‐rise buildings

Current building codes aim to ensure the acceptable performance of structures implicitly. Because these provisions are empirically developed for low‐ to medium‐rise buildings, their applicability to high‐rise building warrants further investigation. In this paper, the effect of design drift limit on the seismic performance of reinforced concrete dual high‐rise buildings is considered. Nine buildings are designed for 3 drift limits: the code limit (i.e., 2%), one that is lower than the code limit (i.e., 1.5%), and one that is higher than the code limit (i.e., 3%). For each drift limit, buildings of 3 heights (20, 25, and 30 stories) are designed. Finite element models are constructed in OpenSees, and incremental dynamic analysis is performed. The results are used to develop probabilistic seismic demand models, where model parameters are determined using maximum likelihood estimation to incorporate equality and censored data. Reliability analysis using probabilistic demand models is conducted to derive seismic fragility and demand hazard curves. In addition, the collapse performance of the drift limits is evaluated using the Federal Emergency Management Agency (FEMA) P695 procedure. The study results show that the design drift limit affects the building's seismic performance, and the effect depends on the performance level considered. Moreover, from a structural integrity perspective, a larger design drift limit does not induce a significantly higher risk and might yield a more cost‐effective design.     

Seismic performance of high‐rise building with a rock‐slip isolation system with cables

To avoid the overturning hazard of high‐rise buildings with traditional isolation technology, a rock‐slip structure with cables (RSSC) was proposed to improve their seismic performance. The mechanical model was established, and the motion behaviour equation of the RSSC was derived. Shake‐table tests of the RSSC were performed, and the results were compared with the corresponding finite‐element model simulations. The influences of key structural parameters and earthquake motion characteristics were analysed. The study results showed that the RSSC could effectively reduce the internal seismic force response and interlayer deformation under a severe earthquake, as well as decrease the overturning probability. The seismic reduction effect was influenced by the prestressed force, the aspect ratio of the structure, and the friction coefficient between the superstructure and foundation as well as seismic site type. The motion equation derived in this paper can be used to theoretically predict the motion behaviour of RSSC.     

Investigation on seismic performance and shear strength of high‐strength concrete‐filled polyvinyl chloride tube short columns

This paper innovatively designs polyvinyl chloride tube (PVCT) with high‐strength concrete (HC) and presents the results of cyclic loading tests on new reinforced high‐strength concrete short columns, including three high‐strength concrete‐filled PVCT (HC‐PVCT) short columns, one high‐strength concrete‐filled steel tube short column and one HC short column. The main objective of this research was to evaluate the seismic behaviors of HC short columns based on the quasistatic test of the columns. The design parameters of the columns in the experiments were axial compression ratio, reinforcement measures, concrete strength, stirrups configuration, and the height‐diameter ratio of tubes. The crack distribution, failure modes, hysteresis loops, skeleton curves, energy dissipation capacity, strength degradation, stiffness degradation, and cumulative damage of the columns were presented and analyzed. The results showed that the HC‐PVCT column had a fuller hysteretic loop and a higher peak load than the HC column. Compared with HC column, the strength degradation of HC‐PVCT columns was slower, and the ductility increased significantly. With a larger axial compression ratio, the ductility of HC‐PVCT columns was decreased. Based on the test and analysis results, a modified HC‐PVCT design method was proposed to calculate the nominal shear strength of HC‐PVCT short columns.     

Seismic collapse analysis of high‐rise reinforced concrete frames under long‐period ground motions

Structural damages associated with buckling of longitudinal reinforcing steel and crushing of concrete induce strength and stiffness degradation in reinforced concrete (RC) beams and columns. This paper presents a numerical investigation on earthquake‐induced damages and collapse of typical high‐rise RC buildings model incorporating strength degradation (SD) effects. In a simple finite‐element analysis program with the generalized stress fiber discretization, hysteretic constitutive models primarily dominate the inelastic behavior. Buckling of reinforcing steel and crushing of confined concrete are taken into accounted to the stress–strain relationship of fiber elements. The SD effect in components with small hoop ratio tends to amplify the seismic responses high‐rise RC moment‐resisting frames when the intensity of ground motions exceeds the design level. Buckling of steel rebar and crushing of concrete should be fully considered together with the P‐Δ effect for collapse simulations.     

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.     

Deformability design of high‐performance concrete beams

The use of high‐performance materials (HPMs) such as high‐strength concrete (HSC) and high‐strength steel (HSS) is becoming more popular in the construction of beams and columns of tall buildings. These HPMs not only increase the stiffness and decrease the strength‐to‐weight ratio, but also provide a more sustainable construction method by minimising the construction materials needed. However, HSC and HSS are more brittle than normal‐strength concrete and steel, respectively. Therefore, it will adversely affect the deformability of concrete beams. To evaluate the pros and cons of adopting HPM in beam design, the author will investigate the flexural strength and deformability of concrete beams made of HPMs. The deformability in this study is expressed in normalised rotation capacity and investigated by a parametric study using nonlinear moment–curvature analysis taking into account the degree of reinforcement, confining pressure, concrete and steel yield strength. From the results, it is evident that the deformability of concrete beams increases as the degree of reinforcement decreases or confining pressure increases. However, the effects of concrete and steel yield strength depend on other factors. For practical design purpose, charts and formulas are produced for designing high‐performance concrete beams to meet with specified flexural strength and deformability requirement. Copyright © 2011 John Wiley & Sons, Ltd.     

Shaking table test and numerical analysis of a high‐rise building with steel reinforce concrete column and reinforce concrete core tube

This paper assesses the seismic performance of a high‐rise building with steel reinforce concrete column and reinforce concrete core tube in Shanghai, China. This building has 54 floors above the ground and 4 basements, and it has two strengthened layers, which are composed of outrigger truss and belt truss. In order to validate the reliability and the safety of this structure, besides the conventional analysis, shaking table test of scale model was conducted. In the test, the maximum responses of acceleration and deformation were measured and evaluated, as well as the dynamic characteristics, crack pattern, and failure mechanism of the building. Meanwhile, elastic‐plastic time‐history analysis for prototype structure was carried out by the finite element analysis program, and the experimental data were compared with the analytical results to gain a better understanding of the seismic performance of the building. The conclusions are summarized below:

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Seismic partitioned fragility analysis for high‐rise RC chimney considering multidimensional ground motion

In order to identify the vulnerable parts and areas of the high‐rise reinforced concrete chimney, this paper presents an effective method, which called partitioned fragility analysis. One 240‐m‐high reinforced concrete chimney was selected as the practical project, and its analytical model was created with ABAQUS software. The selected high‐rise chimney structure was divided into 17 parts, and then the damage probability of each part in different damage states was obtained with the fragility analysis considering multidimensional ground motions. Twenty ground motion records were taken from the Next Generation Attenuation database as the input motions, and the peak ground acceleration was selected as the intensity measure. The response of the chimney structure under multidimensional ground motions was obtained based on incremental dynamic analysis. The maximum strains of concrete and steel bars were defined as the damage limit states of the chimney structure. The fragility curves and surfaces obtained from this analysis showed that the vulnerable areas of the chimney structure appear at 0–20 m, 90–130 m, and 150–200 m along the height of the chimney respectively. Based analytical results, these vulnerable parts can be retrofitted to enhance the seismic resistance of existing chimney structures. And the partitioned fragility analysis method can also be used to improve the design of new chimney structures.     

Behavior of coupled shear walls with buckling‐restrained steel plates in high‐rise buildings under lateral actions

Traditional coupling beams in coupled shear walls (CSWs) may be lack of required ductility or inconvenient to be fully repaired or replaceable after earthquake damage. To improve the CSW seismic performance, a type of new structural system, which is referred to as coupled shear walls with buckling‐restrained steel plates (CSW–BRSP), is proposed and thoroughly studied. In the system, a pair of individual concrete wall is coupled through buckling‐restrained steel plates instead of traditional concrete coupling beams. Based on the continuous medium method (CMM), stiffness and strength design formulas are developed for the seismic design of this system. Intensive investigations have been conducted to assess the undesirable axial forces in the buckling‐restrained steel plates induced by lateral loads. In order to facilitate the application of this system, a detailed design procedure is also explicitly stated. Finally, an example of typical high‐rise building is presented to illustrate the design procedure as well as demonstrate the excellent seismic performance of the proposed system by means of nonlinear time‐history analysis. Copyright © 2015 John Wiley & Sons, Ltd.     

Experimental behaviour of high‐strength concrete deep beams with web openings

This paper focuses on an experimental study undertaken on high‐strength concrete (HSC) deep beams with various opening sizes and locations on the web. The test covers a wide scope of variables that have not been investigated in previous research. Apart from highlighting the experimental setup, failure loads and typical crack patterns of the test specimens are also reported. Experimental results are then compared with predictions using currently available design methods. The comparison indicates that the predictions using current design methods can overly underestimate or sometimes overestimate the ultimate strength of these HSC deep beams. Further, the reduction of ultimate strengths due to the existence of web openings is not considered adequately in these design methods. To rectify the shortcomings of current design formulae, a new design equation is proposed and compared with the experimental results and those from previous studies on the related topics. The accuracy and reliability of the proposed new equation is subsequently confirmed. With the outcome of this work, more experimental tests with various opening configurations including shape and location of web openings are recommended for future study. Copyright © 2011 John Wiley & Sons, Ltd.     

Optimal design and seismic performance of Multi‐Tuned Mass Damper Inerter (MTMDI) applied to adjacent high‐rise buildings

The tuned mass damper inerter (TMDI) is an enhanced variant of the tuned mass damper (TMD) that benefits from the mass‐amplification effect of the inerter. Here, a multi‐TMDI (MTMDI) system (comprising more than one TMDI) linking two adjacent high‐rise buildings is presented as an unconventional seismic protection strategy. The relative acceleration response of the adjacent structures triggers large reaction forces of the inerter devices in the MTMDI, which in turn efficiently improve the seismic performance of the two buildings. By addressing a real project of two adjacent high‐rise buildings connected by two corridors equipped with the proposed MTMDI system, the displacement‐, interstory drift‐, and acceleration‐based parametric optimizations are separately performed by employing Nondominated Sorting Genetic Algorithm II (NSGA‐II) under 44 ground motions from the FEMA P695 far‐field record set. It is found that the frequency content of the seismic input has strong impact on the MTMDI mitigation performance. Adopting realistic mass ratio constraints, the optimally designed MTMDI outperforms both conventional MTMD and single TMDI in acceleration control, while it is not much effective in mitigating the displacement response due to the highly flexible nature of the high‐rise buildings, in contrast to other literature studies generally focused on low‐to‐medium rise buildings.     

Seismic performance of Y‐type eccentrically braced frames combined with high‐strength steel based on performance‐based seismic design

In the Y‐type eccentrically braced frame structures, the links as fuses are generally located outside the beams; the links can be easily repairable or replaceable after earthquake without obvious damage in the slab and beam. The non‐dissipative member (beams, braces, and columns) in the Y‐type eccentrically braced frames are overestimated designed to ensure adequate plastic deformation of links with dissipating sufficient energy. However, the traditionally code design not only wastes steel but also limits the application of eccentrically braced frames. In this paper, Y‐type eccentrically braced steel frames with high‐strength steel is proposed; links and braces are fabricated with Q345 steel (the nominal yield stress is 345 MPa); the beams and columns are fabricated with high‐strength steel. The usage of high‐strength steel effectively decreases the cross sections of structural members as well as reduces the construction cost. The performance‐based seismic design of eccentrically braced frames was proposed to achieve the ideal failure mode and the same objective. Based on this method, four groups Y‐type eccentrically braced frames of 5‐story, 10‐story, 15‐story, and 20‐story models with ideal failure modes were designed, and each group includes Y‐type eccentrically braced frames with ordinary steel and Y‐type eccentrically braced frames with high‐strength steel. Nonlinear pushover and nonlinear dynamic analyses were performed on all prototypes, and the near‐fault and far‐fault ground motions are considered. The bearing capacity, lateral stiffness, story drift, link rotations, and failure modes were compared. The results indicated that Y‐type eccentrically braced frames with high‐strength steel have a similar bearing capacity to ordinary steel; however, the lateral stiffness of Y‐type eccentrically braced frames with high‐strength steel is smaller. Similar failure modes and story drift distribution of the prototype structures designed using the performance‐based seismic design method are performed under rare earthquake conditions.     

Moving average correction method for compensation of differential column shortenings in high‐rise buildings

The differential length changes of vertical members in a high‐rise building due to elastic, creep and shrinkage shortenings are of primary concern since the differential shortening of the vertical members causes unexpected damages on structural and nonstructural members. In contrast to researches on prediction methods for calculation of the amount of the shortenings, only few methods or algorithms of compensation of the differential column shortenings have been reported. In this paper, a practical compensation method using moving average correction is presented. The proposed method is applied to the compensation of the differential shortenings of the vertical members in a 70‐story high‐rise building. The performance of the moving average correction method is compared with the optimal compensation method based on simulated annealing algorithm. It is demonstrated that the magnitude of the differential shortening or the degree of the slab tilt due to the length changes in the vertical members can be controlled without using structural optimization techniques. Copyright © 2011 John Wiley & Sons, Ltd.