• Earthquakes and Structures
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• v.11 no.5
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• pp.809-822
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• 2016

Reinforced concrete buildings constitute the majority of the building stock of Turkey and much of them, do not comply the earthquake codes. Recently there is a great tendency for strengthening to heal their earthquake performance. The performance evaluations are usually executed by the numerical investigations performed in computer packages. However, the numerical models are often far from representing the real behaviour of the existing buildings. In this condition, experimental modal analysis fills a gap to correct the numerical models to be used in further analysis. On the other hand, there have been a few dynamic tests performed on the existing reinforced concrete buildings. Especially forced vibration survey is not preferred due to the inherent difficulties, high cost and probable risk of damage. This study applies both ambient and forced vibration surveys to investigate the dynamic properties of a six-story residential building in Istanbul. Mode shapes, modal frequencies and damping ration were determined. Later on numerical analysis with finite element method was performed. Based on the first three modes of the building, a model updating strategy was employed. The study enabled to compare the results of ambient and forced vibration surveys and check the accuracy of the numerical models used for the performance evaluation of the reinforced concrete buildings.

• Structural Engineering and Mechanics
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• v.76 no.1
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• pp.83-99
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• 2020

Shear walls are structural members in buildings that are used extensively in reinforced concrete frame buildings, and almost exclusively in the UK, regardless of whether or not they are actually required. In recent years, the UK construction industry, led by the Concrete Centre, has questioned the need for such structural elements in low to mid-rise reinforced concrete frame buildings. In this context, a typical modern, 5-storey residential building is studied, and its existing shear walls are replaced with columns as used elsewhere in the building. The aim is to investigate the impact of several design variables, including concrete grade, column size, column shape and slab thickness, on the building's structural performance, considering two punching shear limits (V_Ed/V_Rd,c), lateral drift and accelerations, to evaluate its maximum possible height under wind actions without the inclusion of shear walls. To facilitate this study, a numerical model has been developed using the ETABS software. The results demonstrate that the building examined does not require shear walls in the design and has no lateral displacement or acceleration issues. In fact, with further analysis, it is shown that a similar building could be constructed up to 13 and 16 storeys high for 2 and 2.5 punching shear ratios (V_Ed/V_Rd,c), respectively, with adequate serviceability and strength, without the need for shear walls, albeit with thicker columns.

• Journal of the Korea Institute of Building Construction
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• v.11 no.5
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• pp.501-514
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• 2011

Recently, there have been many cases in which the difficulty of repair and replacement of principal elements in the bearing wall structure for apartment buildings, which is a major part of apartment buildings in Korea, has led to the reconstruction of buildings rather than their remodeling. To address this problem, the Korea government now allows a floor area ratio of up to 20 %, and has relaxed the building height limits to encourage the use of a rahmen structure instead of a bearing wall structure. However, since reinforced concrete rahmen structures have many problems, including higher floor height and greater construction cost, a great deal of research into rahmen composite precast concrete structures have been conducted. Green Frame, one of the developed prototypes, is expected to provide economic benefits through in-situ production for precast concrete column and beam. For in-situ production of composite precast concrete members, a detailed plan for production, curing, and installation is needed. However, it needs to be confirmed that the space is sufficient to produce the precast concrete members on-site before planning those activities. Therefore, this study proposes in-situ production analysis of composite precast concrete members of Green Frame with the evaluation of structural safety and available area on the parking structure. The result of this study shows that the in-situ production of precast concrete members is possible through a case study.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.6
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• pp.285-292
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• 2020

The methodology classifying structural types of concrete buildings in the existing seismic fragility functions is too simple to estimate the fragility of existing residential buildings and neighborhood living facilities, especially those below five stories. Their structural types are dependent on information contained in the building register such as main use, total floor area, story, permission date, and first story floor area of the individual building. All of this information is not considered for classifying types in the existing functions; therefore, the goal of this study was to suggest a methodology that classifies structural types of concrete buildings by utilizing such information. The results of this study showed that the suggested methodology can classify structural types better than the existing methodology. Nevertheless, there is still a need to simplify the methodology because fragility estimation demands quickness rather than accuracy.

• Earthquakes and Structures
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• v.5 no.5
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• pp.571-588
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• 2013

Many of the current buildings in Algeria were built in the past without any consideration to the requirements of the seismic code. Among these buildings, there are a large number of individual houses built in the 1980's by their owners. They are Reinforced Concrete (RC) frame structures with unreinforced hollow masonry infill walls. This buildings type experienced major damage in the 2003 (Algeria) earthquake, generated by deficiencies in the structural system. In the present study, special attention is placed upon examining the vulnerability of RC frame houses. Their situation and their general features are investigated. Observing their seismic behavior, structural deficiencies are identified. The seismic vulnerability of this type of buildings depends on several factors, such as; structural system, plan and vertical configuration, materials and workmanship. The results of the vulnerability assessment of a group of RC frame houses are presented. Using a method based on the European Macroseismic Scale EMS-98 definitions, presented in previous studies, distribution of damage is obtained.

• Journal of Korean Association for Spatial Structures
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• v.3 no.1 s.7
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• pp.47-55
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• 2003

This paper is concerned with the dynamic characteristics of buildings, especially with the measurement of the natural frequencies(natural periods) and the damping. Process of ambient vibration and synchronized human excitation tests for natural period and damping are given. Data from measurement on 16 reinforced concrete buildings in Seoul and Seoul national university of technology are given. 16 Low-rise Reinforced concrete buildings are measured for ambient vibration to obtain the vibrations characteristics. The natural periods obtained by ambient vibration measurements are compared with those of forecast model suggested by standards and foreign researchers. The natural periods show a clear dependence on building height. On the other hand, the damping ration scatter under the influence of various factors, for example, building height and natural frequency.

• Computers and Concrete
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• v.16 no.1
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• pp.141-161
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• 2015

A significant portion of residential areas of Turkey is located in active earthquake zones. In Turkey occurred major earthquakes in last twenty years, such as Erzincan (1992), Kocaeli and $D{\ddot{u}}zce$ (1999), $Bing{\ddot{o}}l$ (2003), Van (2011). These earthquakes have demonstrated that reinforced concrete (RC) buildings having horizontal and vertical irregularities are significantly damaged, which in turn most of them are collapsed. Architectural design and arrangement of load-bearing system have important effect on RC building since architectural design criteria in design process provide opportunity to make this type of buildings safer and economical under earthquake loads. This study aims to investigate comparatively the effects of weak story irregularity on earthquake behavior and rough construction costs of RC buildings by considering different soil-conditions given in the Turkish Earthquake Code. With this aim, Sta4-CAD program based on matrix displacement method is utilized. Considering that different story height and compressive strength of concrete, and infill walls or their locations are the variables, a set of structural models are developed to determine the effect of them on earthquake behavior and rough construction costs of RC buildings. In conclusion, some recommendations and results related to making RC buildings safer and more economical are presented by comparing results obtained from structural analyses.

• Earthquakes and Structures
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• v.5 no.3
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• pp.297-319
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• 2013

Two destructive earthquakes occurred on October 23 and November 9, 2011 in Van province of Turkey. The damage in residential units shows significant deviation from the expectation of decreasing damage with increasing distance to epicenter. The most damaged settlement Ercis has the same distance to the epicenter with Muradiye, where no damage occurred while relatively less damage observed in Van having half distance. These three cities seem to have resembling soil conditions. If the damages are evaluated: joint failures and insufficient lap splice lengths are observed to be the main causes of the total collapses in RC buildings. Additionally, low concrete strength, reinforcement detailing mistakes, soft story, heavy overhang, pounding and short columns are among other damage reasons. Examples of damages due to non-structural elements are also given. Remarkable points about seismic damages are: collapsed buildings with shear-walls, heavily damaged buildings despite adequate concrete strength due to detailing mistakes, undamaged two-story adobe buildings close to totally collapsed RC ones and undamaged structural system in buildings with heavily damaged non-structural elements. On the contrary of the common belief that buildings with shear-walls are immune to total collapse among civil engineers, collapse of Gedikbulak primary school is a noteworthy example.

• Earthquakes and Structures
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• v.18 no.6
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• pp.709-718
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• 2020

Fragility curves are useful tools to estimate the damage probability of buildings owing to seismic actions. The purpose of this study is to investigate seismic vulnerability of reinforced concrete (RC) buildings, according to the 2007 and 2018 Turkish Seismic Codes, using fragility curves. For the numerical analyses, typical five- and seven-storey RC buildings were selected and incremental dynamic analyses (IDA) were performed. To complete the IDAs, eleven earthquake acceleration records multiplied by various scaling factors from 0.2g to 0.8g were used. To predict nonlinearity, a distributed hinge model that involves material and geometric nonlinearity of the structural members was used. Damages to confined concrete and reinforcement bar of structural members were obtained by considering the unit deformation demands of the 2007 Turkish Seismic Code (TSC-2007) and the 2018 Turkey Building Earthquake Code (TBEC-2018). Vulnerability evaluation of these buildings was performed using fragility curves based on the results of incremental dynamic analyses. Fragility curves were generated in terms of damage levels occurring in confined concrete and reinforcement bar of structural members with a lognormal distribution assumption. The fragility curves show that the probability of damage occurring is more according to TBEC-2018 than according to TSC-2007 for selected buildings.

• Wind and Structures
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• v.29 no.3
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• pp.209-223
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• 2019

The assessment of wind-induced vibration for tall reinforced concrete (RC) buildings requires the accurate estimation of their dynamic properties, e.g., the fundamental vibration periods and damping ratios. In this study, RC frame-shear wall systems designed under gravity and wind loadings have been evaluated by utilising 3D FE modelling incorporating eigen-analysis to obtain the elastic periods of vibration. The conducted parameters consist of the number of storeys, the plan aspect ratio (AR) of buildings, the core dimensions, the space efficiency (SE), and the leasing depth (LD) between the internal central core and outer frames. This analysis provides a reliable basis for further investigating the effects of these parameters and establishing new formulas for predicting the fundamental vibration periods by using regression analyses on the obtained results. The proposed constrained numerically based formula for vibration periods of tall RC frame-shear wall office buildings in terms of the height of buildings reasonably agrees with some cited formulas for vibration period from design codes and standards. However, the same proposed formula has a high discrepancy with other cited formulas from the rest of design codes and standards. Also, the proposed formula agrees well with some cited experimentally based formulas.