Mücip Tapan

Resistivity, ESR, and Radiation Shielding Properties of the Volcanic Rock Materials

Pumices have been used in cement, concrete, brick, and ceramic industries as an additive and aggregate material. It will be important to study pumice types by using a different tool as EPR which is a new technique for related material to be used for industrial aims. Electron spin resonance (ESR) spectra of the pumice types were taken by EMX-type spectrometer. Also, the current-voltage (I-V) and surface resistivity probe stand of the thin films was studied using a four-point probe measurements. The relationship between radiation shielding properties of the pumice samples and their surface resistivity, chemical, and electrokinetic properties was evaluated using simple regression analysis. Simple regression analysis indicated a strong correlation between surface resistivity and density and SiO2, Fe2O3, CaO, MgO, and TiO2 content of pumice samples in this study. It is found that a correlation between determined -factor by EPR spectroscopy and radiation shielding is established for pumice samples.

Alkali–silica reactivity of alkali volcanic rocks

The purpose of this study is to determine the alkali silica reactivity (ASR) of alkali volcanic rocks (from basalt to rhyolite) that have different mineralogical, chemical compositions and textures. For this purpose, nine different alkali volcanic samples, located in seismically active Lake Van region, were collected from five different volcanic area named as Etrüsk volcano, Girekol volcano, Timar, Yüksektepe and Bendimahi. Petrographical analysis, chemical method and accelerated mortar bar test results showed that intermediate and acidic alkali volcanic rocks are deleterious but basic alkali volcanic rocks are innocuous in terms of ASR. It is concluded that the products resulted from alteration processes, amount of volcanic glass in the aggregate and magma-mixing processes of the magma chamber in which rocks are formed may be effective in ASR of aggregates.

Performance Based Rapid Seismic Assessment Method (PERA) for Reinforced Concrete Frame Buildings

Recent destructive earthquakes have shown that many existing buildings, particularly in developing countries, are not safe against seismic actions. Since code-based seismic safety evaluation methods generally require detailed and complex structural analysis, the necessity for simplified, yet sufficiently accurate evaluation methods emerges for reducing cost and duration of assessment procedures. In this study, a performance based rapid seismic safety assessment method (PERA) is proposed for reinforced concrete buildings. The overall structural performance is determined based on the demand/capacity ratios of individual columns, as well as their failure modes (brittle/ductile), confinement characteristics, and levels of axial and shear stresses. The lateral drift of the critical story, calculated through a simplified approach, is also taken into account during determination of the global structural performance. The predictions of this method are compared with the results of conventional detailed seismic safety assessment analyses carried out for 672 different cases representing typical reinforced concrete frame buildings in Turkey. Good agreement is obtained between the predictions of the proposed algorithm and code-based structural performance assessment procedures. Finally, predictions of the proposed approach are compared with actual damages observed in 21 existing buildings in Turkey after destructive earthquakes that have occurred during the last two decades. These comparisons also point to an acceptable level of accuracy and sufficient conservatism for the methodology proposed.

Determining the site effects of 23 October 2011 earthquake (Van province, Turkey) on the rural areas using HVSR microtremor method

A magnitude of 7.1 Mw earthquake struck Van city on October 23, 2011. Although, construction practices of all rural housing units are similar in the region, the earthquake caused massive damage to villages located on soft soils in northern region of the city. In this study, the effects of soil conditions on damaged housing units were determined by conducting horizontal to vertical spectral ratios of microtremor (HVSR) measurements. The level of damage in the villages that are settled on lacustrine and stream sediments has verified that the damage correlates well with comparatively high HVSR peak period and HVSR peak amplitude values in the range of 0.2–1.6 s and 4–10, respectively. The HVSR peak period and HVSR peak amplitude levels on rock units are in the range of 0.1–0.2 s and 1.5–2, respectively. It is important to note that hillside effect is found to be another key factor that increased the level of damage to the housing units in some villages.