İhsan Engin Bal

A Comparative Study of European Earthquake Loss Estimation Tools for a Scenario in Istanbul

A damage estimation exercise has been carried out using the building stock inventory and population database of the Istanbul Metropolitan Municipality and selected European earthquake loss estimation packages: KOERILOSS, SELENA, ESCENARIS, SIGE, and DBELA. The input ground-motions, common to all models, correspond to a “credible worst case scenario” involving the rupture of the four segments of the Main Marmara Fault closest to Istanbul in a Mw 7.5 earthquake. The aim of the exercise is to assess the applicability of the selected software packages to earthquake loss estimation in the context of rapid post-earthquake response in European urban centers. The results in terms of predicted building damage and social losses are critically compared amongst each other, as well as with the results of previous scenario-based earthquake loss assessments carried out for the study area. The key methodological aspects and data needs for European rapid post-earthquake loss estimation are thus identified.

Displacement-Based Earthquake Loss Assessment for an Earthquake Scenario in Istanbul

DBELA is a Displacement-Based Earthquake Loss Assessment methodology for urban areas which relates the displacement capacity of the building stock to the displacement demand from earthquake scenarios. The building stock is modeled as a random population of building classes with varying geometrical and material properties. The period of vibration of each building in the random population is calculated using a simplified equation based on the height of the building and building type, while the displacement capacity at different limit states is predicted using simple equations which are a function of the randomly simulated geometrical and material properties. The displacement capacity of each building is then compared to the displacement demand obtained from an over-damped displacement spectrum, using its period of vibration; the proportion of buildings where damage exceeds each specified threshold value can thus be estimated. DBELA has been applied using the Turkish building stock following the collection of a large database of structural characteristics of buildings from the northern Marmara region. The probabilistic distributions for each of the structural characteristics (e.g., story height, steel properties, etc.) have been defined using the aforementioned database. The methodology has then been applied to predict preliminary damage distributions and social losses for the Istanbul Metropolitan Municipality for a Mw 7.5 scenario earthquake.

The Influence of Geographical Resolution of Urban Exposure Data in an Earthquake Loss Model for Istanbul

Exposure data available to developers of earthquake loss models are often very crudely aggregated spatially, and in such cases very considerable effort can be required to refine the geographical resolution of the building stock inventory. The influence of the geographical resolution of the exposure data for the Sea of Marmara region in Turkey is explored using several different levels of spatial aggregation to estimate the losses due to a single earthquake scenario. The results show that the total damage over an urban area, expressed as a mean damage ratio (MDR), is rather insensitive to the spatial resolution of the exposure data if a sufficiently large number of ground-motion simulations are used. However, the variability of the MDR estimates does reduce as the spatial resolution becomes higher, reducing the number of simulations required, although there appears to be a law of diminishing returns in going to very high exposure data resolution. This is largely due to the inherent and irreducible spatial variability of ground motion, which suggests that if only mean MDR estimates are needed, the effort required to refine the spatial definition of exposure data is not justified.

Correlation Between Detailed and Preliminary Assessment Techniques in the Light of Real Damage States

Seismic risk assessment of two real RC multi-story buildings, located on similar soil profile in Kocaeli, is conducted in respect to code-based linear and nonlinear approaches, as well as to P25-v2 Method, a recently suggested method for risk evaluation and preliminary assessment of existing buildings against life-loss. Twenty-five different parameters and seven different collapse criteria are taken into consideration in the suggested P25-v2 Method, including soil and topographic conditions, earthquake demand, various structural irregularities, material and geometrical properties, and location of the buildings. After summarizing the different methodologies and describing the case study buildings, 3D linear-elastic and static nonlinear analyses are performed in parallel to the application of the P25 Method-v2. One of the two case study buildings totally collapsed during 1999 Kocaeli Earthquake, while the other survived with negligible damage, noting that both had legal construction and occupation permissions. SAP2000 and SeismoStruct software packages have been utilised for the analysis procedure to find out the damage states of the structural members at critical stories and to determine the performance levels of the case study buildings. The code-based performance levels and the final performance scores obtained by the preliminary assessment technique are compared in order to underline the existence of the correlation between the detailed procedure and the suggested preliminary assessment technique with the real damage state. Consequently, structural inadequacies, weak points of the buildings and failure reasons are also discussed in this paper.

Behaviour of steel cushions subjected to combined actions

Mild steel is relatively low-cost and easily accessible material to fabricate some structural members. It would be a significant advantage if seismic energy dissipaters that are used in structures constructed in the earthquake prone areas, could also be produced on site. In this paper, a promising seismic energy dissipater made of mild steel, so-called steel cushion (SC) is presented. It is provided experimental and analytical responses of SCs subjected to bi-axial loadings. SC rolls under the lateral loading that allows relocation of the plasticized cross-section. Henceforth, SC dissipates considerable amount of seismic energy. A series of tests were performed to achieve experimentally the behavior of SC subjected to longitudinal and transversal loading. Finite Element Models (FEMs) were also generated to reproduce the experimental backbone curves and to predict the bi-directional response properties for discrete transversal forces and plate thicknesses. Closed-form equations were derived to determine yield and ultimate forces and the corresponding displacements as well as location of the plasticized sections. The behavior of SC could either be projected by the FEMs with the exhibited parameters or by means of the proposed closed-form equations and the normalized design chart.

Save the Tabique Construction

The main goal of this chapter consists in revising technical building aspects concerning the tabique construction. Tabique is a traditional building technique which applies raw building materials such as timber and earth, for example. External and partition walls are the main tabique building components, which may have a relevant structural performance in the overall stability of a building. In general, the traditional tabique buildings are facing high levels of degradation. This problem is mainly due to the lack of maintenance and technical knowledge. Therefore, reconstruction processes of this type of buildings also require accurate and updated technical information related to materials, to building details, to the main likely pathologies, to the knowledge of the physical and mechanical behaviour of the building components, to the reinforcement solutions, among other aspects. This research work intends to give some guidance in this context and to make a parallel analysis between the Portuguese and the Turkish tabique constructions.

External jacketing of unreinforced historical masonry piers with open-grid basalt-reinforced mortar

AbstractExisting unreinforced masonry buildings in seismically active regions are in urgent need of consolidation and preservation against seismic action to prevent damage and loss of financial res...

Review on the macro-modeling alternatives and a proposal for modeling coupling beams in tall buildings

Coupling beams between shear walls are one of the key elements for energy dissipation in tall buildings. A representative mathematical model of coupling beam should represent flexure, shear and interface slip/extension mechanisms simultaneously. This goal can be achieved by using either detailed finite element models or by using macro models. This paper presents a review of various macro model alternatives for diagonally reinforced coupling beams in the literature. Three distinct methods have been reviewed in terms of their modeling techniques, the cyclic response overlap and the amount of cumulative plastic energy dissipated based on the results of previously performed tests. Through an analytical study, adequately accurate results can be captured by using macro models, although they are simpler in practice compared to sophisticated micro models. This study shows that, by modifying ultimate shear capacities where concrete material between diagonal bundles is adequately confined, it is possible to capture a more realistic result and a better approximation to the actual responses. It is also concluded that a simpler numerical model for diagonally reinforced coupling beams can be achieved by introducing linear part of slip/extension behavior into elastic part of the beam. It is observed, as a result of this study, that the ratio of effective stiffness to that of the gross cross-sectional one ranges from 0.04 to 0.14 in diagonally reinforced coupling beams depending on the aspect ratio and the beam strength parameters.

Discussion on the response of unreinforced masonry to low-amplitude recursive loads: case of Groningen gas field

Unreinforced masonry (URM) is a fragile material that responds to cyclic load reversals in a non-ductile way, unless special measures are taken. Damage occurs in large amplitude loads causing partial or total collapse in some cases, as it was observed in the past earthquakes. Response of URM to recursive, frequent but low-amplitude seismic loads, on the other hand, is a relatively new topic that needs experimental and analytical validation. This paper focuses on Groningen URM buildings that have been subjected to low-amplitude load reversals in the last decades, especially in the very last decade, due to the induced seismicity caused by gas extraction. In the paper, previous experimental findings are reviewed mostly focusing on the range of low amplitudes. An exercise with existing hysteresis rules, trying to find residuals after recursive seismic actions, has been presented. Dimitrios Dais, Ihsan E. Bal, and Eleni Smyrou

P25 scoring method for the collapse vulnerability assessment of R/C buildings

It is historically a fact that Turkey experiences frequent earthquakes, on the order of one damaging earthquake of magnitude 6–7 approximately every 2 years, causing extensive losses to economy, life and limb. Every strong earthquake leaves behind poverty and tens of thousands of homeless people. In order to mitigate especially the losses of life due to earthquakes, a rapid scoring technique called the P25 – Preliminary Assessment Method is proposed herein. The purpose of the method is to determine, for a reinforced concrete-framed building, whether there is any vulnerability to collapse during a strong earthquake. By identifying those buildings, which are most likely susceptible to collapse inside a particular building stock, and consequently strengthening or demolishing them, practically no loss of life will occur. In this presentation, details of P25 – Preliminary Assessment Method are discussed and the high degree of prediction reliability of the method is demonstrated on 323 case study buildings, which experienced wide ranges of damage during past earthquakes.