Journal of the Structural Engineering and Geotechnics
Volume:4 Issue: 3, Summer 2014

The reservoir-induced seismicity (RIS) at the Karkheh dam site with a reservoir capacity of about 7.4x109 meters is investigated. Based on the assessment of the seismicity of the dam site in equal time periods before and after reservoir impoundment, it was found that the number of earthquakes have been tripled after impoundment, while their magnitudes and focal depths become smaller. The average earthquake depth before the impoundment was about 40 km whereas it decreased to about 23 km after that. Based on this study, it is concluded that RIS is happening in the Karkheh dam site and it is necessary to study the possible associated hazards.

Irregular buildings make up a large portion of urban infrastructure. Presence of irregularities can be due to architectural and user changes in building stories. Main objective of this article is evaluate seismic performance of structures with vertical irregularities. Seismic responses are obtained by enveloping peak inelastic responses resulting from pushover analyses according to provided pattern in ASCE/SEI 41-06 standard. To verify and appraise procedure, it is applied to 10, 15, and 20-storey models with irregular distribution of mass, stiffness and strength along height. Results from the pushover procedure are compared with results obtained by nonlinear response history analysis (NL-RHA). Results of research reveal that seismic response of building structures is more sensitive to stiffness irregularities than to mass irregularities and strength irregularities. Nonlinear static procedure that proposed in standard can predict to a reasonable accuracy peak inelastic responses, such as plastic rotations of hinges, story drifts and shear stories in vertically irregular structures.

When the out-of-plane stiffness of a beam is remarkably lower than the in-plane stiffness, the lateral-torsional buckling occurs. In this study, the behavior of mono-symmetric I-beams with discrete torsional and lateral bracings under the concentrated moment is investigated using the finite element analyses. Then, based on the numerical analyses, equation for the stiffness requirement is proposed. The results show that the location and the type of the bracing have an important role on the stiffness requirement and buckling strength.

Developing measure performance, especially in civil activities, is mainly based on economic or social approaches, regardless of its environmental effects. This matter has caused imbalances of human life and hazardous future for him. Modern human’s awareness of the imbalances in normal performance of the nature cycle, caused by technology, has led him to create some ideas such as sustainability and to consider its components in recent technology. This paper is to take the most appropriate soil improving and enhancing method out of the well-known ones, based on the sustainability framework (society, economy and environment). The methodology is descriptive-analytical. The data or questionnaire sheets were collected and the analysis hierarchical process (AHP) was used in order to achieve optimal analysis and determination of the best choice. The results showed that the soil stabling method is the most appropriate one among the existing methods of soil improvement and that it tends to show the most correspondence with sustainability principles. Regarding the results of this paper, all contractors and those who are involved in construction would be capable of choosing appropriate methods of increasing soil compaction and improving foundation loading, based on the sustainability indexes, which consequently causes remarkable decrease of the environmental damages for present and future generation.

The influences of nano-ZrO2 (NZ), nano-TiO2 (NT), nano-Fe2O3 (NF) and nano-Al2O3 (NA) additions on properties of the fresh and hardened cement paste in comparison with the fine cement paste were experimentally studied. Mini slump and flow cone tests were conducted on fresh cement pastes. Moreover the compressive and tensile strength of hardened cement paste were measured. SEM micrographs and XRD powder patterns of hardened cement paste were analyzed in order to evaluate the effects of Nano additives on the microstructure of cement pastes. The results of this study showed that Nano-particles can improve the compressive strength of cement paste. While NA has the most influence on compressive and tensile strength of the cement paste, NZ has the least effect on the compressive and tensile strength of the hardened cement paste. It was also shown that Nano particles can increase the viscosity of fresh cement paste. The results of this study seem to indicate that the most effective Nano-particle content on mechanical properties of hardened cement paste is about 1.5% to 2% for various kinds of Nano-particles.

Seismic safety of liquid storage tanks is of considerable importance due to its application in different industries. In Iran, most of these storage tanks are designed based on API650 code provisions. Despite designing tanks according to API standard, the lesson learned from previous earthquakes, shows different kind of damage occurring on them. This study is an investigation on evaluating different revisions of API650 seismic codes from years 2001 to 2013. The failure modes considered are Buckling, Overturning, Sliding and Shell Yielding. For this, three steel cylindrical tanks has been checked by different revisions of API650 under different PGA from 0.1 to 2 and various failure modes are taken into account respectively for each tank. According to these information, the fragility curves are derived and compared among all the revisions of API650 code.
According to the resultsit seems that API650 in edition of 2001, Presents buckling criteria as the main criterion.This criterioncompared to the overturning criteria even in unanchored tanks­determinedvery conservative.In these samplesthere were no overturning criteria prior.
In 2005, 2009 and 2013 editions of API650 for unanchored tanks, presented overturning criteria as the main criterion considering the sliding and total stress failure criteria but for anchored tanks total stress failure criteria controlled much more conservatively. Generally buckling criteria not reported in prior.