Effect of epsilon-based record selection on fragility curves of typical irregular steel frames with concrete shear walls in Mashhad city

In this paper, the seismic vulnerability of Mashhad city, as the second largest city in Iran, has been investigated using analytical fragility curves. Disaggregation analysis is first performed in order to identify the target epsilon at different hazard levels. The disaggregation results revealed different epsilon values at the first mode period of two representative structures, in the case of 72-, 475-, and 2,475-year return periods. Nonlinear incremental dynamic analyses are then performed for two representative models of a typical steel frame with a concrete shear wall, using independent suites of acceleration time histories that are selected based on the target epsilons. Structural limit states are defined on each incremental dynamic analysis curve, and the corresponding damage measures are estimated. The results show that if ϵ is neglected in the considered simulations, then the predicted median structural capacities is decreased by around 10%, 15%, and 18%, respectively, for the three abovementioned hazard levels

Tehran Geotechnical Microzonation Project

Megacity of Tehran with a population of more than 8 million is located in a very active region, both in terms of tectonic and seismicity. Due to socio-economic and political importance of Tehran, in 1994 IIEES has initiated a comprehensive geotechnical hazard study in Tehran. The geotechnical microzonation part of the program was composed of two parts: site effect and liquefaction potential microzonation. Site effect microzonation was started for south of Tehran using one dimensional site response analysis and microtremor measurement. The results of these studies were compiled and presented in three microzonation maps for south of Tehran including: natural site period map, dynamic site period map and the PGA distribution map. Based on the preliminary result, comprehensive studies for south as well as for north of Tehran have been started. Liquefaction potential study of Tehran alluvium was started in 1995. Considering that the northern part of the Tehran is located on coarse grain clayey alluvium and deep water table the liquefaction study was concentrated in the south of Tehran. The liquefaction potential was evaluated and the microzonation maps were developed. A more detailed investigation is now underway to assess more accurately the liquefaction potential for the south of Tehran

Innovative method for incremental dynamic analysis curves in semi-isolated bridges

U radu se predlaže inovativna metoda za određivanje krivulje koja prikazuje približnu inkrementalnu dinamičku analizu djelomično izoliranih mostova uključujući izvod statističkih matematičkih izraza. U konačnici, inovativna je metoda osmišljena na temelju vrijednosti primarne tangencijalne krutosti i granične tangencijalne krutosti djelomično izoliranih mostova. U ovom istraživanju su odabrana dva armiranobetonska mosta autoceste u Sjedinjenim Američkim Državama koji su optimizirani primjenom gumenih ležajeva s olovnom jezgrom. Prikazani postupak može se primijeniti u budućim istraživanjima kako bi se izdvojili probabilistički odzivi djelomično izoliranih mostova uz pomoć jednostavne i učinkovite metode.This paper proposes an innovative method for determining the approximate incremental dynamic analysis curves of semi-isolated bridges, including the derivation of statistical mathematical formulas. Ultimately, an innovative method is devised based on the primary and limit state tangential stiffness values of semi-isolated bridges. The bridges selected for this study are two reinforced concrete highway bridges in the United States, which have been optimally re-designed using lead rubber bearing isolators. The established procedure can be used in future studies to extract the probabilistic responses of semi-isolated bridges via a simplified and efficient method

Detecting structural damage in Timoshenko beams based on optimization via simulation (OVS)

Considering easy determination of natural frequency in structures leads researchers to focus on detecting the damage through the dynamic parameters using combination of various artificial intelligence algorithms. The main contribution of this research is to detect damage in structures (including its depth and location) for the deep beams with Timoshenko behavior using optimization via simulation (OVS). This method is established based on the first three natural frequencies of the deep or semi-deep beams. The finite element method (FEM) is conducted to obtain essential inputs parameters for OVS. The exact location and depth of the structural damage are determined, using combination of multi-objective optimization algorithms, multi-objective genetic algorithm (MOGA), and modified multi-objective genetic algorithm (MMOGA). This research also remarkably concerns about detecting the location of the defect in the beams with several cracks. In order to verify the results obtained from numerical analysis, several experimental specimens are presented. The dynamics parameters of the beams are experimentally identified using modal hammer. The responses obtained from the numerical method, proposed in this research, are also compared with the results obtained from previous studies. Practically, a beam with real dimensions is examined for different boundary conditions. In addition, the results obtained from MOGA and MMOGA are compared with the other researchers’ achievements. Finally, it was observed that the proposed method, (OVS), can be satisfyingly determined the exact location and depth of damage with the high accuracy

Sensitivity of beam-column element stiffness matrix to the crack parameters

In this article, a new cracked beam-column element stiffness matrix is proposed through static condensation method. Seven dimensionless coefficients are introduced and applied for a sensitivity analysis in different damage scenarios. The accuracy of this proposed stiffness matrix is verified, and compared to the other available methods. The variation of each stiffness component due to the conversion of crack parameters is assessed and shown in different graphs. This study reveals that cracking has a maximum stiffness reduction of 30 % in the beam-column elements with rectangular cross sections and the damaged elements remain stable until the crack depth is below 80 % of the section depth

Multi-objective optimization approach to define risk layer for seismic mitigation

Earthquakes have caused more than 50,000 lives and $4,000 million economic losses over a period of 20 years in Iran. Having accurate risk assessment and effective future plans can significantly reduce these losses. In this paper, two key parameters, which are effective in both human and economic loss reduction, have been defined, one of which is the number of saved lives before and after taking mitigation measures and the other one is the household expense ratio related to the cost of earthquake mitigation measures. For this reason, Shiraz city, located in the southwest of Iran, has been selected for evaluation. Detailed building taxonomy is performed, and for seismic vulnerability evaluation, vulnerability curves exclusively derived for Iranian buildings are used. Multi-objective genetic algorithm optimization method is conducted to find a balance between the costs of seismic mitigation measures and number of casualties. This balance proposes the extent of mitigation actions which is representative of a specific layer of risk and is identified as a set of Pareto Front for all types of buildings. The optimal risk layer can play a vital role in shaping management policies for decision-makers in order to reduce the inherent risk of country