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

Risk management strategies for managing natural disaster risks: A case study in Shiraz City, Iran

Almost all parts of Iran are seismic hazard prone areas and due to the low quality of constructions as well the increase of exposure in urban areas, recent earthquake events caused unacceptable huge losses, both in human and economic terms. To assess the resilience of various risk bearers, including the government as well as private sector entities, the resources to cope with potential future events as well as possible interdependencies during the occurrence have to be analyzed in detail. Furthermore, to pro-actively act against possible future extremes with risk hedging instruments such as insurance, the underlying risk has to be determined in quantitative manner. This paper suggest how to combine both, the coping dimension as well as the risk dimension, to determine possible risk management strategies which may be feasible in the Iranian context. The focus is specifically on risk instruments, such as insurance, for the Shiraz region in Iran, where the newly produced probabilistic loss estimates are available which are subsequently used to analyze possible insurance schemes and for determining corresponding premium payments as well as affordability. The paper discusses how such risk instruments can be embedded within an integrated framework and which additional options, such as risk reduction or risk pooling, would be beneficial to lower premiums to affordable levels

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

Physical Resilience of the Electricity Transmission Grid against Earthquake: Analysis of a Prototype Model

Increasing number of power supply interruptions due to earthquakes leads to heavy direct and indirect economic losses and indicates the importance of resilience of electric power networks. The present study, focusing on seismic resilience of the electricity transmission grid, is looking to develop a basic framework for calculating power grid performance and resilience. This research, based on the network performance analysis and the graph theory, is using a prototype model of the electricity transmission grid to calculate the average performance of the system over recovery time, as the system resilience. This research distinguishes between the damaged facilities in the network by classifying damage levels to different degrees between zero and one and assigning performance values to each level to go beyond the binary statement of connectivity analysis, while having fast and simple calculations

Managing institutional fragmentation and time compression in post-disaster reconstruction - the case of Bam

Several studies have revealed the difficulties often found in defining stakeholders’ roles in post-disaster reconstruction projects. Insufficient and ill-timed collaboration are typically identified as the principal source of problems. Borrowing the concept of Institutional Fragmentation (IF) from the field of project management, this paper examines significant obstacles to collaboration and to sharing knowledge and experience in post-disaster reconstruction projects, revealing the causes and effects at four levels of fragmentation: the construction industry, project procurement, design and construction work. The case of the reconstruction program conducted after the 2003 earthquake in Bam (Iran), illustrates these different levels of fragmentation and their short and long-term impacts. Results show that three of the four levels of fragmentation caused unexpected outcomes during program implantation and afterwards; fragmentation increased the divergence between the many stakeholders with their interests and expectations, during and after their intervention. Conflict and confrontation between two controller organizations led to an excessive emphasis on technical requirements at the expense of heritage preservation. Results also explain how specific conditions after the disaster - such as lack of time coupled with socio-political pressures - increased fragmentation. Post-disaster reconstruction projects require systematic and comprehensive procurement to cover the interfaces that will enable tasks to be conducted effectively. The study proposes a conceptual approach to fragmentation that can help academics, practitioners, and decision-makers understand the origins and consequences of institutional fragmentation on the timely use of resources, and to develop governance structures and mechanisms that can help reduce it in post-disaster reconstruction initiatives