RC High-rise Buildings Research Articles

Stiffness Irregularity in RC High-rise Building

Stiffness Irregularity in RC High-rise Building

Seismic loss assessment of RC high-rise buildings designed according to Eurocode 8

Seismic loss assessment of RC high-rise buildings designed according to Eurocode 8

Design Demand of RC Building as per Soil Type

The RC-framed building is one of the most common construction techniques for seismic-resistant structures due to its ductile nature. But the seismic performance of the RC structure is affected by various factors among which site soil condition is vital. The sub-soil condition affects the time period of the structure which eventually impacts the earthquake force in the structure, thus making variations in seismic loadings. Although several studies have been performed and design elastic spectra have been defined as per soil types in the design codes, there are no studies quantifying the effect of design demand in the buildings due to variation of soil type in the context of Nepal and NBC 105:2020. Therefore, this study aims to present the variation in design demand for moderately high-rise RC buildings in different soil types. A representative sample building has been taken and analyzed in the Finite Element platform SAP 2000. Numerical analysis is performed using linear static and response spectrum methods. Based on the study, variation in the base shear, story displacement, inter-story drift, and section size to meet the limit state of strength are compared for soil types A, B, C, and D.

Enhancing the earthquake resistance of RC and steel high-rise buildings by bracings, shear walls and TMDs considering SSI

The increasing population, limited residential space, and scarcity of suitable land for construction have led to a rise in the construction of high-rise buildings (HRBs) as a means to provide additional housing. The increase in human activities (such as excavations for geothermal resources) has led to an increase in seismic activity, making HRBs more vulnerable to earthquakes. Structural analysis of HRBs that are exposed to seismic loadings depends on one of the most important factors that judge the stability and resistance to seismic waves which is the stiffness of the buildings. Various methods that reduce flexibility and enhance stiffness for HRBs are the subject of this numerical investigation, and they were applied to a high-rise building (HRB) of 20 floors, considering soil–structure interaction (SSI). The stiffening methods adopted herein are steel or concrete shear walls (SWs) in specific arrangements, and different bracings in specific arrangements. Moreover, in this study, tuned mass dampers (TMDs) are used, as a damping method of the HRB seismic response, also considering SSI, and the results are compared with the stiffening methods results to judge how the applied methods enhance the seismic resistance of HRBs. These methods, which were used to influence the stiffness or the damping of the building, had different positive effects on the seismic response of the HRBs, which appeared in the results through the base shears, the base moments, the maximum top displacement, and the fundamental period of the building.

Performance Based Seismic Design of Two RC High-Rise Buildings

Performance Based Seismic Design of Two RC High-Rise Buildings

施工者を対象とした高強度コンクリートの施工性向上に関するアンケート調査

High-strength concrete has been put into practical use by technological development of air-entraining and high-range water-reducing admixture and low-heat type cement, and has become widespread mainly in high-rise RC buildings. However, high-strength concrete with a low water-cement ratio and a large amount of cement has a high viscosity, so construction problems such as pumpability and finishability have emerged with its widespread use. Therefore, we conducted a questionnaire survey on the specific details of defects and how to improve them by modifying the mix-proportions, for construction problems such as transportation of high-strength concrete, placing and compaction, and finishing.

SHEAR STRENGTH OF HIGH STRENGTH STEEL FIBER REINFORCED CONCRETE COLUMNS

At present, the highest high-rise RC building in Japan is over 200 meters high. All columns from the first to the 13th floor of the building are applied high strength steel fiber reinforced concrete columns （HSFRC）to control damage under huge earthquake loading. The high strength steel fiber reinforced concrete columns are contain 1.0% steel fiber by volume. It is the first time to apply much steel fiber for high strength concrete columns. Nevertheless, there is no established design equation for high-strength SFRC columns. Therefore, authors have conducted an experimental study of HSFRC columns since 2020. A total of 15 specimens were conducted. In this research, 13 specimens’ experimental data are used. The shear strength equation based on truss arch theory with the volume ratio of steel fibers as a variable factor is proposed as a design equation for high-strength steel fiber reinforced concrete columns.

Sensitivity indices of RC beams considering construction sequence analysis for RC high-rise building

Sensitivity indices of RC beams considering construction sequence analysis for RC high-rise building

Seismic Analysis of RC High-Rise Buildings Rested on Cellular Raft

This paper includes the investigation of the soil–structure interaction (SSI) effect on the seismic response of 20 and 30-story reinforced concrete moment resisting frames (MRFs) rested on a piled raft foundation using the direct approach. After that, a study is conducted to show the impact of using a cellular raft instead of the designed solid raft on the dynamic response of the building. A study is introduced to select the best gap size for the cellular raft. The soil model is assumed as a single layer of sandy clay. Time history analysis by the direct integration method is performed under seven earthquake records (El-Centro, Northridge, Kobe, Chichi, Friuli, Kocaeli, and Loma), which are scaled to the Egyptian Code for Loads (ECP-201) response spectrum using a full 3D model by a finite element software named (Midas GTS NX). It is concluded that considering SSI significantly affects the dynamic response of high-rise buildings, and using cellular rafts generally leads to a decrease in their dynamic response.

Study on Empirical Formulas and Distribution Ranges of Vibration Periods in High-Rise Reinforced Concrete Constructions

ABSTRACT China is now undergoing the largest and fastest urbanization process in the world, developing various reinforced concrete high-rise buildings during this process. Most high-rise structures are constructed in densely populated and economically active areas and earthquakes pose a potential possibility of serious economic loss and casualties, which cannot be ignored. This paper conducts on-site dynamic tests on 129 high-rise RC buildings in eastern China by utilizing ambient vibration measurement. Fundamental vibration periods, second vibration periods, and third vibration periods are statistically analyzed in translational directions based on two high-rise building types: shear wall slab building and shear wall tower building (including framed shear wall structures and framed tube structures). After fully considering building usage conditions and comparing the fitting formulas in existing codes, fitting empirical formulas of the vibration periods in two translational directions based on the above structural types are given. The ratio distribution ranges of vibration periods are calculated by utilizing the vertex displacement method, concentrated mass method, and Rayleigh-Ritz energy method. In addition, by analyzing the vibration period ratio in horizontal directions of 543 high-rise RC buildings, different ranges are distinguished as well as suggested boundaries are given. The conclusion of this paper provides a reference and convenient method for future on-site dynamic testing and a new proposal is provided to the empirical formula of vibration period in the current building seismic design code.

Seismic vulnerability assessment of RC high-rise building considering soil–structure interaction effects

Seismic vulnerability assessment of RC high-rise building considering soil–structure interaction effects

The Effects of Differential Axial Shortening on RC High-rise Buildings with Outrigger or Mega Structure Systems

초고층 건물에서 수평변위 제어와 수직부재에서 발생하는 부등축소에 대한 검토가 필수적이다. 수평변위 제어를 위해 근래에 아웃리거 구조시스템과 메가 구조시스템을 횡력저항시스템으로 사용한 초고층 건물이 증가하고 있다. 또한, 부등축소로 인한 구조적 문제를 해결하기 위해 부등축소량 예측과 예측결과를 통한 시공단계에서의 보정방법이 연구되어 왔으나 부등축소에 대한 횡력저항시스템의 영향 비교는 드문 편이다. 따라서, 본 논문에서는 수평변위 제어를 위해 아웃리거 구조시스템과 메가 구조시스템을 사용한 60층 규모의 철근콘크리트 주거용 초고층 건물에 대해 시공단계해석을 통한 부등축소를 비교하고 그 영향을 분석하고자 한다. 또한, 부등축소는 비구조요소의 파손 및 구조요소에 부가하중을 유발하기도 하며 부등축소가 야기한 문제는 초고층 건물에서 중요한 부재를 손상시킬 수 있으므로 각 횡력저항시스템별로 수직부재의 부등축소에 대한 영향을 분석하였다.

Comparative Study of Conventional Steel Braces and Buckling Restrained Braces in a High-Rise RC Building

A study was carried out on a reinforced concrete building with conventional steel braces and buckling restrained braces (BRB) for seismic analysis with dissimilar type of bracing system ( V type, inverted V type, X type, Zig-Zag bracing) is considered. The bracing is providing for outer exterior columns. A twenty-five storey (G+25) building is located at earthquake zone 2 & 4. The structure models are examined by response spectrum method using ETABS2016 program. The parameters which are consider in this research to equate the seismic investigation of buildings are storey displacement, storey drift, storey shear(forces). These parameters are compared in both type of bracing systems and effective bracing is selected with respect to different zones.

Estimation of inter-story drifts at onset of damage statesfor RC high-rise buildings

In this paper, a detailed probabilistic seismic damage analysis of RC high-rise buildings was performed and as a result, the damage states (DSs) and appropriate performance levels (PLs) were defined in a quantitative manner. DSs were quantified using inter-story drift, where the drifts were determined at the onset of each DS. The analysis was performed on three RC high-rise buildings: 20-story, 30-story and 40-story with core wall structural system. Probabilistic seismic damage analysis was performed for 60 earthquake records, recorded on rock and stiff soil, and scaled to two intensity levels associated with probability of exceedance, 10 % in 50 years - 475-year return period (10%/50) and probability of exceedance, 2 % in 50 years - 2475-year return period (2%/50). In addition to these analyses for estimation the damage index, nonlinear static pushover analyses (NSPAs) were performed using different modal combination patterns. Large deviations among the pushover curves for individual considered modal combination patterns were observed. In order to adequately select the parameters for calculating damage index, an analysis of drifts and shear forces for individual modal combination patterns was performed. The functional dependencies between inter-story drifts and damage index were derived using the regression analysis. Based on the derived dependencies, the values of inter-story drifts at the onset of considered DSs for high-rise buildings were proposed.

TREND OF SEISMIC RESPONSES OF EXISTING HIGH-RISE RC BUILDINGS

This report presents studies on the seismic response of high-rise RC buildings in Japan. Data concerning the seismic response of approximately 600 high-rise RC buildings constructed from 1972 to 2015 were collected. Seismic response characteristics were analyzed by focusing on differences in seismic resistant structures, seismic response control structures, and seismic isolation structures. The results indicated that the maximum story drift ratio response under the level 1 study seismic ground motion (R) and the level 2 study seismic ground motion (R) criteria is smaller for seismic isolation structures than that of the seismic resistant structure and seismic response control structures. In addition, focusing on the R-R relationship, the correlation is low in the seismic resistant and seismic response control structures, but is almost linear in the seismic isolation structure. This is because the seismic isolation structure is designed such that the superstructure does not become plastic even with level 2 seismic ground motion.

Assessment of a High Rise RC Building with and without Opening of Shear Wall: A Review

Assessment of a High Rise RC Building with and without Opening of Shear Wall: A Review

Evaluation of Shear Lag Index in High-Rise RC Buildings Having Exo-skeleton Structural System

Although framed tube system has been found to be the most efficient system for high-rise buildings, they could experience the shear lag effects which will result in nonlinear distribution of axial stress along the flange and the web of the cross-section of the tall building plan. Exoskeleton structure is generally found to be a self-supporting structural system set outside and suitably connected to a primary inner structure, the latter being enhanced or protected. In this article, by studying three types of concrete structures having 20, 30, and 40 stories with elevations of 80, 120, and 160 m, respectively, the effects of change in the location of openings on Exo-Skeleton structures on the shear lag phenomenon are investigated. The shear lag of the compression wing of the structural models, which are perpendicular to the lateral force application, was studied. Among the index related to the shear lag, two indexes of the shear lag index including the axial stress ratio of each element in the axis to the axial stress of the middle element and the axial stress ratio of the corner element to the tensile stress of the middle element derived from the structural analysis under load side effects were studied. It could be concluded that the most effective opening configuration with the greatest reduction in shear lag is proposed for structures with different aspect ratios.

Rigorous versus less-demanding fragility relations for RC high-rise buildings

Analytical seismic scenario-based probabilistic fragility relations form the spine of earthquake risk assessment and mitigation of RC high-rise wall buildings. In this study, a framework is proposed to develop both rigorous (refined) and less-demanding (cheaper) fragility relations for such structures. Multi-record incremental dynamic analysis is employed using a new scalar intensity measure and net inter-storey drift as a consistent global damage measure for varying heights of buildings. To illustrate the framework, a 30-storey wall building located in a multiple-scenario earthquake-prone region is analysed. The refined fragility sets are derived using 40 real earthquake records representing two seismic scenarios, while the proposed methodology to develop less-demanding seismic scenario-based fragility relations employs a considerably lower number of earthquake records. In this methodology, a new record selection criterion and a fragility curve tolerance factor are introduced. Finally, the two fragility relation sets for the reference structure are developed, assessed, and compared to provide insights into their features and accuracy. Using the proposed methodology, the study revealed that fairly reliable seismic scenario-based fragility sets can be developed for RC high-rise buildings with a significant reduction in computational time and efforts. The proposed framework is generic and can be implemented to deriving refined and less-demanding fragility relations for RC high-rise buildings of different configurations and structural systems.

The effect of base isolation and tuned mass dampers on the seismic response of RC high-rise buildings considering soil-structure interaction

The most effective passive vibration control and seismic resistance options in a reinforced concrete (RC) high-rise building (HRB) are the base isolation and the tuned mass damper (TMD) system. Many options, which may be suitable or not for different soil types, with different types of bearing systems, like rubber isolator, friction pendulum isolator and tension/compression isolator, are investigated to resist the base straining actions under five different earthquakes. TMD resists the seismic response, as a control system, by reducing top displacement or the total movement of the structure. Base isolation and TMDs work under seismic load in a different way, so the combination between base isolation and TMDs will reduce the harmful effect of the earthquakes in an effective and systematic way. In this paper, a comprehensive study of the combination of TMDs with three different base-isolator types for three different soil types and under five different earthquakes is conducted. The seismic response results under five different earthquakes of the studied nine RC HRB models (depicted by the top displacement, base shear force and base bending moment) are compared to show the most suitable hybrid passive vibration control system for three different soil types.

Assessment of engineering demand parameters through SHM for RC-structures

Almost all in service and structures need some form of maintenance for monitoring their reliability and health conditions to extend their lifespans or to avoid cataclysmic failure. Structural health monitoring (SHM) is an advanced topic in the field of structural engineering that enables to monitor the structures for future safety. Considering this importance, the current research carries out SHM algorithm for RC high-rise building structures with shear walls. In this study, an approach applicable to real-time has been presented enabling decision-makers to assess the structural condition during the extreme cases. The parametric study has been done on ten stories RC residential building located in Walnut Creek, in the California State USA by considering four major recent earthquakes in the region. For algorithmic examination, general engineering demand parameters (EDPs) have been introduced. The EDPs such as spectral displacement (Sd), Inter-story drift ratio (∆s), Arias intensity (Ia) and spectral acceleration (Sa) limits have been investigated.