High-rise Reinforced Concrete Research Articles

Review of Using Shear Walls and Bracings for Seismic Strengthening of High-Rise RC Structures

This review explores the seismic resistance of high-rise buildings through the implementation of shear wall and steel bracing systems. The use of reinforced concrete (RC) buildings with shear wall systems and steel structures with concentrated steel bracing systems has become increasingly common to mitigate seismic effects. However, the response of these systems to seismic loads varies due to differences in structural design and response factor values. Additionally, the presence of asymmetrical building designs poses a potential risk during earthquakes, necessitating a thorough examination of both new and old structures. By analyzing the dynamic properties and influencing factors of irregular RCC buildings with shear walls, this research aims to assess the impact of shear walls on factors such as base shear, torsion, story displacement, and drift. Furthermore, the study investigates the effectiveness of steel bracing systems in enhancing the performance of high-rise buildings under wind and seismic loading conditions. Different bracing configurations are evaluated to determine their ability to reduce lateral displacements and improve structural strength and stiffness. The findings will provide valuable insights into optimizing the location and design of bracing systems for enhanced structural resilience against seismic and wind forces while considering both economic and effectiveness factors.

Residual design life-based evaluation of structural retrofitting on high-rise reinforced concrete buildings

The deteriorating structural performance of aging high-rise reinforced concrete (RC) buildings has brought increasing attention to the necessity of retrofitting in developed regions. In this context, the present paper introduces a novel approach by reversing the conventional service life-based structural design procedure. The proposed approach establishes a residual design life evaluation framework, enabling a comprehensive assessment of the performances of existing RC buildings both before and after retrofitting. This assessment framework takes into account various load scenarios, including wind and earthquake forces, etc., and yields an intuitive index based on design codes, termed "residual design life", which serves as valuable information for decision-makers. To exemplify the framework's application, a case study involving a high-rise RC building is presented. Initially, the influence of the adopted design codes on the residual life of the aging building is investigated. Subsequently, three commonly employed structural-level retrofit methods, namely steel bracing, RC wall addition, and exoskeleton, are examined. The findings reveal that the residual design life of the existing building decreases as the adopted design code transitions from an outdated version to the current one. However, the implementation of structural-level retrofit interventions proves highly effective in enhancing the building's residual life, particularly when failure is primarily governed by column capacities and storey drift. Nonetheless, it should be noted that certain structural-level interventions may increase the load on adjacent beams, potentially leading to a negative impact on the building's residual life when the condition of the beams becomes the predominant factor. Furthermore, the obtained residual life of the retrofitted building could be used to assist in conducting life-cycle analysis and further investigations and contribute to the understanding regarding structural performance and safety in the built environment.

Seismic collapse performance of high-rise RC dual system buildings in subduction zones

The satisfactory ‘collapse prevention’ performance level of reinforced concrete (RC) buildings has been widely recognized during recent earthquakes in Chile. However, there is limited research on the actual level of seismic collapse protection. In this study, the seismic collapse behavior of high-rise RC dual wall-frame buildings representative of the Chilean inventory is quantitatively evaluated. A suite of four 16-story structural archetypes was carefully selected and code-based designed assuming two different locations (i.e., high and moderate seismicity zones) and two different soil types (i.e., very stiff and moderately stiff soils). The archetypes were analyzed considering the latest developments in performance-based earthquake engineering implementing incremental dynamic analyses for 3D nonlinear models with sets of Chilean subduction ground motions. Results, expressed in terms of the probability of collapse conditioned on the Maximum Considered Earthquake (MCE) hazard level (<10%) and the collapse probability in 50 years (<1%), showed that all archetypes fully met the targets specified by ASCE 7 for an acceptable ‘life safety’ risk level. These results indeed explain why a very small number of RC building collapses was observed in the recent megathrust earthquakes (Mw>8.0) in Chile. Nevertheless, it was also found that the seismic collapse performance is not uniform, due mainly to the soil type. This observation suggests that the design spectra indicated by the Chilean seismic design code for buildings might need to be revised.

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.

Modeling of opening for realistic assessment of infilled RC frame buildings

Openings provided to meet functional requirements are often neglected in analytical assessment of Un-Reinforced Masonry (URM) infilled Reinforced Concrete (RC) frame buildings, mostly due to unavailability of simplified comprehensive model to simulate its effect. Ignoring presence of opening in infills results unrealistic assessment of seismic response for these popular building typologies, as opening reduces the strength and stiffness of the composite frame. Several reduction factor models have been developed over the years to account effect of opening in infills. In the present study efficacy of five such models of opening have been investigated which can be used by design practitioners for simulation of opening with sufficient accuracy in predicting the response of composite frame. Extensive analytical study has been conducted on a set of mid-rise and high-rise Indian infilled RC frame buildings considering various realistic combinations of openings by varying size, shape of doors and windows. The study revealed that increasing opening in infills significantly affects the seismic performance, and consequent fragility thereby reduces lateral strength, stiffness, ductility, while increasing fundamental time period, overall deformation capacity and damage probability.

Performance of RC cast-in-place buildings during the November 26, 2019 Albania earthquake

This paper documents performance of cast-in-place reinforced concrete (RC) buildings in the Durrës municipality during Albania earthquake of November 26, 2019 (MW 6.4). Both mid- and high-rise RC buildings were affected by the earthquake, experiencing structural and/or non-structural damage and even collapse in some cases. The authors performed a reconnaissance study after the earthquake and were involved in seismic assessment of buildings in the affected area. Besides the observations related to physical damage of RC buildings, the paper also presents results of a statistical analysis of damaged RC buildings in the Durrës municipality. The discussion in the paper is focused on damage patterns and failure mechanisms that are relevant for the seismic response of RC structures. Most common damage pattern observed after the earthquakes was related to masonry infill walls, which experienced damage and failure in some cases, and affected the performance of adjacent RC columns due to the infill/frame interaction. Taller RC framed buildings (10 storeys and higher) were expected to have RC shear walls; however, these walls were reportedly absent in the damaged buildings of this type. In some cases, masonry infill walls (instead of RC shear walls) were used in the elevator shaft areas, which resulted in inadequate seismic performance. A case study has been presented to illustrate seismic behaviour of mid-rise and high-rise cast-in-place RC buildings in the November 2019 earthquake, and is based on post-earthquake field observations and a detailed seismic assessment of two earthquake-damaged buildings. Finally, relevant lessons and recommendations are presented in light of the observed performance of RC buildings.

Multicriteria Decision-Making Methods in Selecting Seismic Upgrading Strategy of High-Rise RC Wall Buildings

Reinforced concrete (RC) structural walls are widely used in high-rise structures in earthquake-prone areas. Damaged by the earthquakes in the past decades, these buildings need retrofitting in order to increase the resilience of buildings with concrete shear walls. This study aimed to investigate the retrofitting of high-rise RC wall buildings using energy dissipation devices. To this end, a total of four buildings with 15, 20, 25, and 30 stories equipped with concrete shear walls as their lateral load-resisting system were retrofitted using passive seismic control systems. The buildings were subjected to the set of the far-field and near-field records presented in the FEMA standard (P-695), and an index was defined to relate the structural responses of the building, such as drift, acceleration, velocity, displacement, and base shear, to the earthquake records. For this purpose, numerical models, which have been validated with the experimental results, have been performed. The resulting index values were considered as the criteria, and the passive systems were ranked by the efficient Multicriteria Decision Making (MCDM) method. Based on the results from the MCDM method and using the considered criteria, friction damper was ranked first among the available energy dissipation devices for high-rise RC wall buildings.

Examining progressive collapse robustness of a high-rise reinforced concrete building

To examine high-rise building robustness to sudden column removal, progressive collapse studies of a 13-story flat-slab reinforced concrete (RC) core-wall building system were completed in this study. Two buildings on the University of Nebraska-Lincoln (UNL) campus, Cather and Pound Halls, were demolished in December of 2017. UNL researchers were given unique access to the building sites to assess their response before, during, and after the event. Prior to demolition, accelerometers were placed throughout both buildings, and ambient measurements were conducted to establish natural frequencies and mode shapes. The response of both buildings during controlled demolition was recorded and analyzed using time histories from the accelerometers. Controlled demolition initiated with sequential blast detonation at selected column sections that resulted in progressive collapse. A detailed 3D nonlinear numerical model of Pound Hall was developed using LS-DYNA to mimic the progressive collapse. The accuracy of the building model was evaluated via comparisons between (i) simulated and measured building ambient frequencies and modes; and (ii) displacement and video recorded during the full-scale demolition. The validated model was then used to further investigate damage scenario effects on the robustness of high-rise RC buildings caused by sudden removal of columns at various locations on the ground floor. The study results can be used to develop and calibrate the nonlinear numerical model for analyzing high-rise building progressive collapse behavior and can help provide information that may improve new and existing flat-slab RC core-wall building robustness against progressive collapse.

Design criteria for the folding implosion of high-rise RC buildings

Blasting is an efficient method for demolishing high-rise buildings and structures. If the collapse scope of a building to be blasted is insufficient controlled building implosion technology is preferred. However, for the conventional implosion, there is a lot of pre-weakening work that has to be done, and it is almost impossible to demolish the high-rise thin wall structures such as reinforced concrete (RC) chimneys. Therefore, a folding implosion method is proposed. In this method, several wedge-shaped notches should be blasted out in the high-rise building or structure, then these notches will turn to “plastic hinges”, meanwhile, the building or structure will turn to a folding kinematic chain, and the segments will overlap each other after falling down. For this method, some design criteria for the main parameters such as the position, initiation sequence, and initiation time delay of blast notches are proposed. The multi-body dynamics models for bi-folding implosion and tri-folding implosion are deduced to analyze the folding motions and rationality of the blasting plans. In two implosion cases, the design criteria and kinematics models are validated.

Evaluation of energy-dissipating devices in high-rise RC core wall buildings

Energy-dissipating devices (EDDs) are used to control the dynamic response of high-rise buildings in moderate to severe seismic risk areas. These systems can be effectively analysed using a rigorous non-linear response history analysis (NLRHA) procedure. However, expertise and time is required to perform and interpret the results from this procedure since several trials are required to select the most effective size and location of the dampers. In this study, the validity of the modal strain energy (MSE) method and the logarithmic decrement (LD) method was checked using a case study of a 40-storey reinforced concrete (RC) core wall building equipped with buckling-restrained braces (BRBs) and fluid viscous dampers (FVDs). Linear and non-linear models of the building including dampers were prepared. The elastic dominant modes and their target displacements were then determined using a response-spectrum analysis procedure. The MSE and LD methods were used to determine the equivalent damping ratio and the time period for BRBs and FVDs, respectively. The base shear and roof displacement, determined using modal and spectral parameters against these damping and time = period values, were found to match those determined using NLRHA with an accuracy of 5–10% and 20–30%, respectively. This study is helpful for the preliminary sizing of EDDs.

Seismic fragility assessment for post-1977 high-rise reinforced concrete structures in Romania

This study deals with the seismic fragility assessment of high-rise reinforced concrete (RC) structures in Romania designed after the major Vrancea intermediate-depth earthquake of March 4, 1977. Firstly, the evolution of Romanian seismic design codes employed before (P13-63 and P13-70) and after (P100-78/81) the Vrancea 1977 seismic event is presented. The influence of the above-mentioned seismic event on the seismic zonation of Romania is also discussed in the context of seismic design codes. Secondly, the damage information of pre-1977 high-rise RC structures during the March 4, 1977 Vrancea earthquake is presented and discussed. The seismic fragility assessment is performed by employing incremental dynamic analyses for both high-rise RC frames structures, as well as for high-rise RC shear walls structures which were widely used for residential purposes. For incremental dynamic analyses, ground motion datasets characteristic for the seismic conditions of Romania are selected and further employed. The results of the analyses show an increase of 30–40% of the median peak ground acceleration corresponding to various damage states for post-1977 RC frames and RC shear walls structures, as compared to the pre-1977 ones.

Yüksek Katlı Betonarme Binalarda Yanal Yük Dayanım Sistemleri

Verimli ve ekonomik bir yüksek bina, yapısal sistemin seçimini etkileyen önemli faktörler tam olarak anlaşılmadan ve bu sistemin mimari, mekanik ve diğer yönlerle nasıl bir ilişki içinde olacağı bilgisi olmadan tasarlanamaz. Bu çalışmada, farklı tipteki yanal yük dirençli sistemlerin (moment çerçeve sistem, perde duvarlı sistem, perdeli-çerçeveli sistem ve tüplü çerçeve sistemler) sismik yükler ve rüzgâr yükleri altında yapısal tepkilerini karşılaştırmak için bir yapısal analiz programı olan ETABS kullanılarak yapısal analizler yapılmıştır. Bina 625m² (25m x 25m) alana sahip 28 kattan oluşmaktadır. Tüm yanal yük dirençli sistemler için kat deplasmanları hesaplanmıştır. Yanal yük dirençli sistem tipleri arasında perdeli-çerçeveli sistem, bu yükseklik için çok uygun bir yapısal tepki göstermiş ve sınır değerlerini aşmamıştır.

Behavior of Low, Medium and High Rise Reinforced Concrete Frame with Infill Using ATENA 2D

The Low, Medium and High rise reinforced concrete (RC) buildings are common in all cities in all countries. Unreinforced masonry wall (URW) is commonly used in low, medium and high rise building as a partition wall both in interior and exterior of building. But structural designers are not considered URW in analysis and design of buildings. This URM wall as an infill plays a very important role in structure subjected to lateral load. So it is very essential to know the nonlinear behavior of low, medium and high rise frame with and without infill. To conduct experiment for understanding the nonlinear behaviour of low, medium and high rise RC frame is very expensive and need good sophisticated testing facilities. With the available many finite element softwares, it is easy to create model and to know the performance of structure. So in this study, a finite element software ATENA 2D (2003) were used to conduct nonlinear analysis for capture nonlinear behaviour of low, medium and high rise RC frame with infill and without infill. Load versus displacement graphs, magnitude of principal compressive stresses, magnitude principal tensile stresses, stress contours, and cracks pattern are used to know the performance of low, medium and high rise RC frame with infill.

Seismic fragility assessment of existing reinforced concrete buildings in Patna, India

Assessment of seismic fragility of reinforced concrete (RC) buildings requires appropriate consideration of uncertainty in aleatory and epistemic sources. Aleatory uncertainty is typically attributed to randomness in ground motion records, while epistemic is due to the uncertainties in structural modelling. The present work focuses on obtaining the variability functions and fragility curves by considering those uncertainties for low, mid and high rise RC buildings in Patna, India, which is a region of high seismicity.Modelling uncertainties requires consideration of material, geometrical, and design as random parameters. These parameters mainly comprise material strength, storey height, plan, typology, design provisions, and various irregularities. In this study, the selection of the random parameters is purely based on the investigation of buildings in the Patna region. Considering the multiple combinations of random parameters, the buildings are modelled and analysed using nonlinear static (NLS) pushover analysis. The monotonic load in a triangular pattern is applied for NLS analysis to get pushover curves. The pushover curves are subsequently converted into capacity curves considering the dynamic characteristic of the first mode of vibration. The obtained capacity curves are utilised to derive the variability in the capacity spectrum for different categories of RC buildings. Subsequently, variability due to randomness in ground motion records is determined by generating several artificial (comprising near field and far field) ground motions considering the seismotectonic map of the region.Thence, by accounting for both the uncertainties, lognormal variability functions are determined, and seismic fragility assessment is performed for different building categories in Patna, India. Furthermore, the seismic vulnerability of existing buildings can be determined based on the obtained fragility curve.

Damping and Natural Period Evaluation of Tall RC Buildings Using Full-Scale Data in Korea

In recent years, the main usage of reinforced concrete (RC) structures in Korea has shifted from low-rise residential and commercial buildings to high-rise buildings. Because an increasing number of high-rise RC buildings are being built, especially in coastal cities, which are periodically hit by typhoons, wind-induced motion and the corresponding serviceability issues have attracted considerable attention. Natural period and damping ratio are the most important factors for estimating the design wind load and wind-induced response in the design of tall buildings. However, the Korean Building Code (KBC 2009) does not specify empirical formulae for estimating the natural period and damping ratio for wind design, unlike seismic design. In this study, the damping ratio and natural period of existing concrete buildings in Korea are measured and compared to those obtained using the formulae provided in various codes and research works. Furthermore, design formulae for estimating natural frequency and damping ratio for wind design are proposed based on the measured data. For this purpose, ambient vibration measurement is performed for 58 RC buildings with heights of 24.2–305 m.

Evaluation of Simplified Analysis Procedures for a High-Rise Reinforced Concrete Core Wall Structure

Nonlinear response history analysis (NLRHA) procedure is one of the most precise and accurate numerical method to compute the seismic demands of high-rise structures but is complex, rigorous, and time-consuming and requires a lot of expertise for nonlinear modelling and results interpretation. Therefore, practicing engineers in developing countries like Pakistan still use the simplified analysis procedures to compute the seismic demands. Among the simplified analysis procedures, equivalent lateral force and response spectrum analysis procedures are widely used for the design purpose. However, other procedures have also been proposed in the recent past to accurately capture the higher mode effects in mid-to-high-rise structures. In the current study, results of a forty-story core wall building are used to check the relative accuracy and ease of application of different simplified analysis procedures. Furthermore, a modal decomposition technique is used to separate the modal responses from the NLRHA results, and a mode wise comparison of different demand parameters for different simplified procedures is performed. The current study has been used to clearly identify the reasons of inaccuracies in different simplified procedures. Furthermore, a simplified analysis procedure is proposed to accurately estimate the seismic demands of high-rise buildings and the possible solutions to improve their predictions.

Seismic performance analysis of steel-brace RC frame using topology optimization

Seismic performance analysis of steel-brace reinforced concrete (RC) frame using topology optimization in highly seismic region was discussed in this research. Topology optimization based on truss-like material model was used, which was to minimum volume in full-stress method. Optimized bracing systems of low-rise, mid-rise and high-rise RC frames were established, and optimized bracing systems of substructure were also gained under different constraint conditions. Thereafter, different structure models based on optimized bracing systems were proposed and applied. Last, structural strength, structural stiffness, structural ductility, collapse resistant capacity, collapse probability and demolition probability were studied. Moreover, the brace buckling was discussed. The results show that bracing system of RC frame could be derived using topology optimization, and bracing system based on truss-like model could help to resolve numerical instabilities. Bracing system of topology optimization was more effective to enhance structural stiffness and strength, especially in mid-rise and high-rise frames. Moreover, bracing system of topology optimization contributes to increase collapse resistant capacity, as well as reduces collapse probability and accumulated demolition probability. However, brace buckling might weaken beneficial effects.

Seismic collapse safety of high-rise RC moment framessupported on two ground levels

Reinforced concrete (RC) moment frames supported on two ground levels have been widely constructed in mountainous areas with medium to high seismicity in China. In order to investigate the seismic collapse behavior and risk, a scaled frame model was tested under constant axial load and reversed cyclic lateral load. Test results show that the failure can be induced by the development of story yielding at the first story above the upper ground. The strong column and weak beam mechanism can be well realized at stories below the upper ground. Numerical analysis model was developed and calibrated with the test results. Three pairs of six case study buildings considering various structural configurations were designed and analyzed, showing similar dynamic characteristics between frames on two ground levels and flat ground of each pair. Incremental dynamic analyses (IDA) were then conducted to obtain the seismic collapse fragility curves and collapse margin ratios of nine analysis cases designated based on the case study buildings, considering amplification of earthquake effect and strengthening measures. Analysis results indicate that the seismic collapse safety is mainly determined by the stories above the upper ground. The most probable collapse mechanism may be induced by the story yielding of the bottom story on the upper ground level. The use of tie beam and column strengthening can effectively enhance the seismic collapse safety of frames on two ground levels.

Seismic Behavior of Hybrid Coupled Wall System

Reinforced concrete (RC) couple wall systems, where RC beams couple two or more RC walls in series, are frequently used in high-rise buildings. Generally, coupling beams are made of RC materials. Steel coupling beam is an alternative for RC coupling beam which has a complex and and unefficient detailing construction. This paper presents a study on the use of Hybrid Coupled Wall System (HCWS) in seismic resistant high-rise RC structures. In the study, 25 storey office buildings with three types of coupling beams and three types of walls distributed over the height of the structure and located in a region with high seismicity are designed. Applying a performance-based design approach, this study developed an efficient design for RC structures having Coupling Ratio (CR) values 64.55% and affect the behavior of the wall pier in the upper region of the structure where widespread plastification and earlier crushing failure happen. Based on this findings, steel coupling beams can be used as an alternative with statisfying all performance criteria and perform at Life Safety(LS).

Seismic Performance of High-Rise RC Shear Wall Buildings Subjected to Ground Motions with Various Frequency Contents

Construction of tall buildings in societies is rising up for the increased population and limitation in horizontal expansion of cities. Therefore, behavior of these structures against earthquake essentially requires investigation. Recent research has shown that frequency content parameter of an earthquake has remarkable impacts on seismic response of buildings. This study aimed to investigate direct effects of frequency content on high – rise buildings. Thus, six Reinforced Concrete (RC) central core 10, 15, 20, 25, 30, and 35- story buildings were built in open source software OpenSees, and their seismic behavior under seismic records with various frequency contents were investigated. In this research, non – linear dynamic Time – History was carried out and also behavior of buildings was compared in drift, shear force of stories, and maximum displacement of stories. Results of Time – History analysis showed that low – frequency content records have the highest effects on buildings. Most of the responses of drift and displacement of stories pertained to low – frequency contents in low – rise 10 and 15-story buildings. Although the most shear force of stories was related to low – frequency contents, with increasing height of buildings, shear force of stories increased, too. So that under Kobe Japan record which has the lowest frequency content among all records in this paper. Maximum shear force of stories was 6840 ton in 10-story building, whereas it was 12332 ton in 35- story building.