Turkish Earthquake Code Research Articles

FRP versus traditional strengthening on a typical mid-rise Turkish RC building

This paper investigates the limits and efficacies of the Fiber Reinforced Polymer (FRP) material for strengthening mid-rise RC buildings against seismic actions. Turkey, the region of the highest seismic risk in Europe, is chosen as the case-study country, the building stock of which consists in its vast majority of mid-rise RC residential and/or commercial buildings. Strengthening with traditional methods is usually applied in most projects, as ordinary construction materials and no specialized workmanship are required. However, in cases of tight time constraints, architectural limitations, durability issues or higher demand for ductile performance, FRP material is often opted for since the most recent Turkish Earthquake Code allows engineers to employ this advanced-technology product to overcome issues of inadequate ductility or shear capacity of existing RC buildings. The paper compares strengthening of a characteristically typical mid-rise Turkish RC building by two methods, i.e., traditional column jacketing and FRP strengthening, evaluating their effectiveness with respect to the requirements of the Turkish Earthquake Code. The effect of FRP confinement is explicitly taken into account in the numerical model, unlike the common procedure followed according to which the demand on un-strengthened members is established and then mere section analyses are employed to meet the additional demands.

Performance based assessment for existing residential buildings in Lake Van basin and seismicity of the region

Earthquake safety of existing buildings has gained considerable importance after earthquakes which have occurred in our country especially in the last 30 years. Performance based assessment methods have been widely used for existing reinforced concrete structures. This study aims to investigate the earthquake performances of the building stock located in Van Lake basin in Eastern Anatolia of Turkey. The case study of buildings has been modeled on and the structural performances have been determined by employing the non-linear methods described in the latest Turkish Earthquake Code published in 2007. The Van lake basin is located on the very seismically active in a region. On October 23, 2011, a magnitude of Mw 7.2 earthquake struck the Van province in eastern Turkey. The earthquake ground motion was recorded as about 0.1g in Bitlis province. Performance evaluations have been performed by taking samples from each district consisting urban building stocks of Bitlis. A total of 16 reinforced concrete buildings have been evaluated. Among them, 53% of those buildings were determined in the Fully Operational performance level; 13% of them in the Life Safety performance and 34% of them could not be evaluated because of the ratio of the effective mass of first mode to the total mass of the buildings was smaller than 0.70. Therefore, incremental equivalent seismic load methods, which are a part of Turkish Earthquake Code -2007, cannot be used.

The evaluation of structural properties of reinforced concrete building designed according to pre-modern code considering seismic performance

In this study, the structural properties of reinforced concrete buildings designed according to pre-modern code (1998 Turkish Earthquake Code (TEC)) are investigated considering seismic performance. These kinds of buildings reflect the majority of the existing building stock. As part of this study, 20 reinforced concrete buildings' projects are achieved from different municipalities. These reinforced concrete buildings designed and applied pre-modern code (1998 TEC) have different number of stories. Reinforced concrete projects are re-calculated by protecting structural systems' properties of available buildings in two ways: firstly by calculating in terms of only buildings' vertical load effects not considering the seismic loads; secondly by calculating the under seismic loads according to 1975 Turkish Earthquake Code which was built on the date of these buildings' designed. The obtained analysis results of reinforced concrete buildings re-designed according to different load cases are compared with existing application projects. In this way, it is tried to be defined which load cases have been used in the analysis of designed buildings before 1998 according to the realization rate. Furthermore, it is found that the relations between the internal forces occurring in the existing structural elements under seismic loads defined according to 2007 Turkish Earthquake Code and the shear and moment capacities of existing structural elements.

Non-linear performance analysis of existing and concentric braced steel structures

Since there are several places located in active seismic zones in the world, serious damages and losses have happened due to major scaled earthquakes. Especially, structures having different irregularities have been severely damaged or collapsed during these seismic events. Behavior of existing structures under several loading conditions is not completely determined due to some uncertainties. This situation reveals the importance of design and analysis of structures under seismic effects. Several non-linear static procedures have been developed in recent years. Determination of the seismic safety of the existing structures and strengthening techniques are significant civil engineering problems Non-linear methods are defined in codes to determine the performance levels of structures more accurately. However, displacement based ones give more realistic results. These methods provide more reliable evaluation possibilities for existing structures with developing computer technology. In this study, non-linear performance analysis of existing and strengthened steel structures by X shaped bracing members with 3, 5 and 7 stories which have soft story irregularity is performed according to FEMA-356 and Turkish Earthquake Code-2007. Damage ratios of the structural members and global performance levels are determined as well as modal properties and story drift ratios after non-linear finite elements analysis for each structure.

Investigation of the effect of weak-story on earthquake behavior and rough construction costs of RC buildings

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 Duzce (1999), Bingol (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.

Comparison of loads in Turkish earthquake code with those computed statistically

In this study, earthquake loads are investigated statistically and compared with the nominal earthquake loads calculated according to the Turkish Earthquake Code, namely: "Specifications for Structures to be Built in Earthquake Areas". For this purpose, the "actual" mean load values estimated from statistical methods and the nominal load values computed according the Seismic Code are compared, with respect to some variations in the basic parameters, such as the importance factor, building height, site coefficient, seismic zone and seismic load reduction factor. In addition to the data compiled from different regions of Turkey, the published data and information in the foreign literature are also used in the determination of the earthquake load statistics. Although the dead and live loads acting on a structure are independent of the geographical location of the structure, environmental loads, such as earthquake loads are highly dependent on the location of the structure. Accordingly, for the assessment of statistical parameters associated with earthquake loads, twelve different locations which can represent the different seismic zones of Turkey as accurately as possible are chosen. As a result of the code calibration procedure considered in this study, it is observed that the load values obtained from the Turkish Seismic Code may overestimate or underestimate the actual seismic loads in some of the seismic zones.

Investigation of blast-induced ground vibration effects on rural buildings

In this paper, blast-induced vibration effects on buildings located in rural areas were investigated. Damages to reinforced concrete, adobe and masonry buildings were evaluated in Çatakk<TEX>$\ddot{o}pr\ddot{u}$</TEX> and Susuz villages in Silvan district of Diyarbakir, Turkey. Blasting of stiff rocks to construct highway at vicinity of the villages damaged the buildings seriously. The most important reason of the damages is lack of engineering services and improper constructed buildings according to the current building design codes. Also, it is determined that, inappropriate blast method and soft soil class increased the damages to the buildings. The study focuses on four points: Blast effect on buildings, soil conditions in villages, building damages and evaluation of damage reasons according to the current Turkish Earthquake Code (TEC).

Structural repairing of damaged reinforced concrete beam-column assemblies with CFRPs

Depending on the damage type as well as the level of damage observed after the earthquake, certain measures should be taken for the damaged buildings. In this study, structural repairing of two different types of damaged RC beam-column assembly by carbon fiber-reinforced polymer sheets is investigated in detail as a member repairing technique. Two types of 1:1 scale test specimens, which represent the exterior RC beam-column connection taken from inflection points of the frame, are utilized. The first specimen is designed according to the current Turkish Earthquake Code, whereas the second one represents a deficient RC beam-column assembly. Both of the specimens were subjected to cyclic quasistatic loading in the laboratory and different levels of structural damage were observed. The first specimen displayed a ductile response with the damage concentrated in the beam. However, in the second specimen, the beam-column joint was severely damaged while the rest of the members did not attain their capacities. Depending on the damage type of the specimens, the damaged members were repaired by CFRP wrapping with different configurations. After testing the repaired specimens, it is found that former capacities of the damaged members were mostly recovered by the application of CFRPs on the damaged members.

Construction and design defects in the residential buildings and observed earthquake damage types in Turkey

Abstract. Turkey is situated in a very active earthquake region. In the last century, several earthquakes resulted in thousands of deaths and enormous economic losses. In 1999, the Kocaeli earthquake had an approximate death toll of more than 20 000, and in 2011 the Van earthquake killed 604 people. In general, Turkish residential buildings have reinforced concrete structural systems. These reinforced concrete structures have several deficiencies, such as low concrete quality, non-seismic steel detailing and inappropriate structural systems including several architectural irregularities. In this study, the general characteristics of Turkish building stock and the deficiencies observed in structural systems are explained, and illustrative figures are given with reference to the Turkish Earthquake Code 2007. The poor concrete quality, lack of lateral or transverse reinforcement in beam–column joints and column confinement zones, high stirrup spacings, under-reinforced columns and over-reinforced beams are the primary causes of failures. Other deficiencies include weak-column–stronger-beam formations, insufficient seismic joint separations, soft-story or weak-story irregularities and short columns. Similar construction and design mistakes are also observed in other countries situated on active earthquake belts. Existing buildings still have these undesirable characteristics, and so to prepare for future earthquakes they must be rehabilitated.

PROBABILISTIC SEISMIC HAZARD MAPS FOR ADANA PROVINCE IN TURKEY

Turkey is located in a highly seismic region, where Mw > 6.5 earthquakes take place in every 10 year. According to the seismic zonation map of Turkey, approximately 42 % of the Turkish territory is located in the most seismic prone zone, known as Zone I. The other seismic zones are termed as Zone II, III and IV from the second severe to the least severe one. In this paper, we investigated the seismicity of Adana Province that is situated on four different seismic zones (i.e. Zone I to IV). Accordingly, we developed probabilistic seismic hazard maps of Adana for 475 year return period for stiff and soft site conditions. The probabilistic seismic hazard maps are presented in terms of PGA. The comparative maps indicate remarkable differences between proposed PGA values and the current design PGA values provided by the seismic zonation map and Turkish Earthquake Code

Investigation of the soil amplification factor in the Adapazari region

Turkey is located on the highly active Eurasian plate. A very active strike slip fault, the North Anatolian Fault Zone (NAFZ), crosses Turkey from east to west; earthquakes occurred on this fault on August 17, 1999 (Kocaeli) and November 12, 1999 (Duzce). Regional geology and subsoil conditions can significantly change the characteristics of ground motion. For this reason, determining soil amplification during an earthquake, especially for soft soils, is a very important topic for researchers. In this study, one dimensional ground response analyses were performed for selected Adapazari sites using the August 17, 1999 Kocaeli earthquake strong ground motion record with SHAKE2000 software. Soil characteristics and depth to engineering bedrock at the selected sites are different and the observed level of structural damage at these sites during the Kocaeli earthquake was also different. Calculated soil surface response spectrums at these sites were compared with the recommended design spectra of the Turkish Earthquake Code and the Eurocode 8. According to one dimensional ground response analyses, the calculated response spectra of the selected sites exceed the recommended design spectra of the Turkish Earthquake Code and the Eurocode 8. Calculations show that higher amplification ratios occur at higher periods due to soil behaviour. Results of this study indicate that local geological conditions may amplify ground motion at some periods and, due to this amplification, the calculated response spectra may exceed the recommended design spectra. Therefore, it is clear that local site conditions must be considered for earthquake-resistant engineering designs on soft alluvial soil deposits.

Necessity and adequacy of near-source factors for not-so-tall fixed-base buildings

Nonlinear response history analyses and use of strong ground motion data including near-field effects has become a common practice in both performance based design of tall buildings and design of base-isolated buildings. On the other hand, ordinary buildings are commonly analysed via response spectrum analysis following the rules of conventional seismic codes, most of which do not take near-field effects into account. This study evaluates the necessity and the adequacy of near-source factors for ordinary fixed-base buildings that are not specifically classified as tall, by comparing dynamic responses of 3, 8, and 15-story benchmark buildings obtained via (1) linear time history analyses using 220 record components from 13 historical earthquakes and 45 synthetic earthquake records of different magnitudes and fault distances and (2) response spectrum analyses in accordance with the Turkish Earthquake Code 2007 -representing seismic codes not taking near-field effects into account- and the Uniform Building Code 1997 which takes near-field effects into account via near-source factors that amplify design response spectrum. It is shown that near-source factors are crucial for the safe design of not-so-tall ordinary fixed-base buildings but those defined in UBC97 may still not be adequate for those located in the vicinity of the fault.

Seismic behavior analysis of multi-story reinforced concrete buildings having torsional irregularity

Earthquakes are one of the most important and hazardous natural disasters in the world and in our country. They also have lots of characteristics from the point of effects caused by them. For this reason it requires special engineering approach to analyze those effects and to design earthquake resistant structures. Almost all of the life losses caused by the earthquakes are related with improperly designed buildings safety of which are not ensured against severe earthquakes. Structural damages and collapses cause very important economical losses. So, understanding of the characteristics of an earthquake and correct determination of the behavior of buildings under earthquake excitation turn out to be the most important requirement to build earthquake resistant buildings. When we take into consideration the destructive effects of severe earthquakes that happened especially in recent years (Kocaeli 1999, Duzce 1999) one can easily see the importance of knowing the behavior of buildings under earthquake loads. In this study torsional effects that occur during earthquake excitations are analyzed in multi-story reinforced concrete buildings. In that manner the behavior of reinforced concrete structures under earthquake loads are examined and by the way the behaviors of structures having torsional irregularities are enlightened and clarified. Moreover the effects of rigidity, ultimate capacity and ductility on the behavior of structures under ground motion are summarized. Torsional irregularity is a key irregularity in determination of the method to be used in earthquake analysis. Definition of the torsional irregularity of a multi-story reinforced concrete building is explained in accordance with Turkish Earthquake Code and the related principles of computations that have to be followed according to the code are given. Multi-story reinforced concrete buildings are classified according to their plan geometry and the effects of plan geometry on the torsional irregularity are explained. While in certain structures torsional irregularity may happen in very high levels in some structures it may happen so small that can be safely omitted. For that reason buildings forming torsional irregularity are classified and their characteristics and torsional irregularity parameters are given. Shear walls without causing any torsional irregularity on buildings having different plan geometries are shown.

Seismic performance evaluation of an existing school building in Turkey

A great part of existing RC structures built in Turkey is that they have been designed without considering seismic-induced actions and seismic criteria for strength and ductility design. In this context, after the recent devastating earthquakes in Turkey, there has been a concerted effort to address the seismic vulnerability of existing public buildings in Turkey. The need for the evaluation and strengthening of these public buildings have come into focus following the enormous loss of lives and property during the past earthquakes. This study aims to assess the seismic performance evaluation of a typical school building in accordance with the rules of Turkish Earthquake Code-2007. The performance analysis is carried out by using nonlinear static analysis. The analytical solutions show that the intended performance level has not been satisfied for this building and decided to retrofit the structural system. The proposed procedure is applied to the retrofitted system and the obtained results are tabulated and discussed.

Assessment the Effective Ground Motion Parameters on Seismic Performance of R/C Buildings Using Artificial Neural Network

Building damage level due to earthquake is widely related to the features of the record which consist of many parameters. Although it is difficult to realize the ground motion parameters that have high influence on building performance, the vital parameters that may cause building damage may be considered as PGA, PGV, PGD, PGA/PGV, PGA/PGD, PGV/PGD, frequency content, effective time duration, fault line distance of the earthquake. In this study, these parameters were selected in order to determine more effective parameter on the building performance. For this aim, a model of Artificial Neural Network (ANN) algorithm was used as an efficient tool consisting of the obtained results of nonlinear time history analysis of samples. The 200 records, produced by strike-slip fault mechanism, were selected for the soil type C (Z3) according to the Turkish Earthquake Code [1]. A six story R/C frame building, with three various spans were analyzed via IDARC-2D software. The Park and Ang damage index was used in order to evaluate the vulnerability of buildings. The results showed that the ANN can be able to determine the effective parameters of ground motions with sufficient correlation. Also the most and least significant parameters of earthquake are discussed based on the results of the analysis.

Assessment the Effective Ground Motion Parameters on Seismic Performance of R/C Buildings using Artificial Neural Network

Building damage level due to earthquake is widely related to the features of the record which consist of many parameters. Although it is difficult to realize the ground motion parameters that have high influence on building performance, the vital parameters that may cause building damage may be considered as PGA, PGV, PGD, PGA/PGV, PGA/PGD, PGV/PGD, frequency content, effective time duration, fault line distance of the earthquake. In this study, these parameters were selected in order to determine more effective parameter on the building performance. For this aim, a model of Artificial Neural Network (ANN) algorithm was used as an efficient tool consisting of the obtained results of nonlinear time history analysis of samples. The 200 records, produced by strike-slip fault mechanism, were selected for the soil type C (Z3) according to the Turkish Earthquake Code [1]. A six story R/C frame building, with three various spans were analyzed via IDARC-2D software. The Park and Ang damage index was used in order to evaluate the vulnerability of buildings. The results showed that the ANN can be able to determine the effective parameters of ground motions with sufficient correlation. Also the most and least significant parameters of earthquake are discussed based on the results of the analysis.

Comparative investigation of the costs and performances of torsional irregularity structures under seismic loading according to TEC

The poor seismic performance of reinforced concrete buildings during the latest earthquakes has become a serious issue in the building industry in Turkey. This case, designing new buildings without structural irregularities against earthquake loads reveals to be quite significant. This study mainly is focused on the effects of different torsional irregularities on construction costs and earthquakes performance of reinforced concrete buildings. In that respect, structural torsional irregularities are investigated based on the Turkish Earthquake Code. The study consists of major eight main parametric models. In this models consist of totally 49 models together with the variations in the number of storey. With this purpose, the earthquake performances and construction costs (especially steel quantities) of reinforced concrete buildings which having different structural torsional irregularities were obtained with the help of Sta4-CAD program. Each model has been analyzed by both the methods of equivalent earthquake loading and dynamic analysis. The obtained results reveal that the model-1 which has lower torsional irregularity coefficient shows the best earthquake performance owing to its regular plan geometry. Also, economical comparisons on costs of the torsional irregularity are performed, and results-recommendations are given.

The effect of architectural form on the earthquake behavior of symmetric RC frame systems

In this study, structural irregularities in plan, which has a considerable effect on earthquake behavior of buildings, have been investigated in detail based on Turkish Earthquake Code 2007. The study consists of six main parametric models and a total of 144 sub-models that are grouped based on RC structural systems such as frame, frame + rigid core, frame with shear wall, and frame with shear wall + rigid core. All models are designed to have both symmetrical plan geometry and regular rigidity distribution. Changes in the earthquake behavior of buildings were evaluated according to the number of storeys, number of axes and the configuration of structural elements. Many findings are obtained and assessed as a result of the analysis for each structural irregularity. The study shows that structural irregularities can be observed in completely symmetric buildings in terms of plan geometry and rigidity distribution.

Comparison of Performance Based Static Methods In Turkish Earthquake Code For Frames With Vertical Stiffness Irregularity

Seismic performance evaluation of existing RC buildings have commonly been performed by using Equivalent Seismic Load Method (ESLM) and Incremental Equivalent Seismic Load Method (IESLM), since Turkish Earthquake Code 2007 (TEC) including significant improvements have come into force. Although the significant deficiencies are available in ESLM with respect to IESLM, ESLM possess the area of usage same with IESLM according to TEC without any limitation. Therefore, investigation of consistency in results of these methods has importance. In this study, ESLM and IESLM are assessed comparatively on three RC building frames with vertical stiffness irregularity (soft story) and on a regular (reference) frame. Section damage levels, story drift ratios and frame (global) performance levels are compared in the assessment. In addition, the effect of confinement is investigated. The results show that, the consistency of the methods show large diversities according level of stiffness irregularity in frames. IESLM results in more damage levels for frames with higher irregularity. However, ESLM results in more damage levels for frames with lesser irregularity and regular frame. In addition, it has seen that the confinement in members was very effective on section damage regions and frame performance levels.

PARALLEL STEEL FRAME TECHNIQUE FOR SEISMIC STRENGTHENING OF RC STRUCTURES: CASE STUDY

To strengthen reinforced concrete (RC) structures against possible future earthquakes, several techniques are used in practice such as adding new RC shear walls, column jacketing using steel or RC or carbon fibers, adding steel bracing, and using seismic isolation and dampers. To apply these techniques, the whole building or part of it should be evacuated for several months and if this building is a school or a factory it means that the building will lose its function for several months during the strengthening construction. In this paper, parallel braced steel frame strengthening technique is proposed to strengthen the low or middle raise RC structures in which all the construction works are applied from outside of the building and do not affect the building function. The main features of this technique are ensuring the view, ventilation, and sunlight from windows after the retrofitting work is done. Furthermore, using the construction steel members lead to shortening the construction term, improve in quality, and reduce costs. The idea of this technique is to reduce the earthquake displacement demand on the nonductile existing RC structures by attaching steel frames to the building floors. These frames are parallel to the structural system of the building and their foundations are connected to the existing building's foundation. In doing so, it is expected that during an earthquake the building's interstory drifts will reduce in half and prevent building collapse. The parallel steel frames can be designed to the desired limit states using performance-based design method in FEMA or Turkish earthquake code. A study case of a factory building in Turkey is presented. The seismic performance of the building before and after the strengthening was evaluated according to the Turkish earthquake code TERDC-2007. Analysis results indicate the effectiveness of the proposed technique.