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

Optimization of shape memory alloy braces for concentrically braced steel braced frames

Expanding the use of smart braced frames to govern the seismic response of structures by providing ductility and elasticity has been hampered and delayed by cost indexes. The braces in frames comprise two segments of expensive shape memory alloys (SMAs) and high-strength steel with high stiffness. These smart materials can reduce seismic damage by providing stiffness, yielding, and phase shifting. In this study, the length of the SMA segments in three- and six-story frames (applied either at all floors or as part of a dual system) was increased to determine the optimal length at a constant period. Performance levels and fragility curves were obtained to evaluate the seismic behavior of the optimized frame. The response modification factor determined based on the static pushover, incremental nonlinear dynamic analysis, and linear dynamic analysis suggests the ductility and over-strength of the optimized frame. The probability of being in or exceeding each damage state was determined with a Monte Carlo analysis and was acceptable and in accordance with previous deterministic analysis results

Investigating laboratory parameters of the resistance of different mixtures of soil – lime – fume using the curing and administrative method

Soils treatment is affected by various factors such as density, moisture content and mineral composition of soil and different percentages of materials in soil. Lime soil as a suitable and inexpensive material has been used for decades to stabilize in civil engineering projects; however, the effect of adding fume and curing temperature on strength and stability parameters of the mixture seldom been studied. In this study, soil and water has been studied from Dokhtar Borji in Hosseinieh city in Iran. Based on a laboratory study, we dealt with evaluating the physical and mechanical properties of soils and chemical properties of soil and water. The cylindrical samples of different mixtures of soil- lime- fume were modified using the AASHTO method and compressive strength testing of 7-, 14- and 28-day samples were conducted according to ASTM standards at 27 °C. Analysis was conducted in SAS (Statistical Analysis System) software. Results indicated that the increase in average compressive strength from 7 to 14 and from 14 to 28 days were 62 and 53.57%, respectively. Therefore, by increasing the number of curing days from 7 to 14, the percentage of the compressive strength is at its highest. The study also provided a linear regression equation that determines compressive strength with an accuracy of 95.1%