BULLETIN OF EARTHQUAKE SCIENCE AND ENGINEERING
Year:2017 | Volume:13 | Issue:4|Papers Count:7

Today, the wastes remaining from concrete degradation is considered as an environmental problem and is one of the biggest challenges in the building industry. Accordingly, many researchers have decided to re-use the materials of aggregates from degradation in concrete production cycles. In this paper, attempts were made to assess and if possible to promote the mechanical and durability characteristics after the addition of nano-silica and micro-silica to self-compacting concrete containing recycled aggregates (obtained from worn concrete degradation). One of the points to be considered in this paper was the attempt to use tests such as half-pole testing and concrete wave velocity. In this regard, 72 mixture designs were studied in 8 collections. In these mixture designs, with respect to the content of recycled aggregates, the nano- and micro-contents were changed. Then, the samples underwent mechanical tests including compressive strength and tensile strength, and durability tests including corrosion potential, concrete wave velocity (ultrasonic) and electrical strength. After the tests, with an increase in the use of nano-silica and micro-silica, the efficiency and fluidity of the fresh concrete were reduced, and compressive strength and tensile strength were increased. Also, at fixed strength, nano-silica caused less efficiency and fluidity than micro-silica and also, with an increase in the content of recycled aggregates in concrete, efficiency and fluidity as well as compressive strength and tensile strength of concrete were reduced.

Steel composite columns with parallel girth are one of the common types of columns used in steel structures in the country (IRAN). Despite many studies on the behavior of these columns, the impact dimensions and spacing of girth on the buckling load of these columns have been less considered. In addition to resistance criteria, in designing of pressure members, the stability criteria must also be considered. In other words, the pressure members of a structure will be defeated effectively by local buckling before reaching maximum compressive strength or influence of buckling phenomenon. The local buckling is one of the common instability of structural members and is an important factor in design of the Built-up columns, so the buckling phenomenon of these columns must be strongly controlled. In this research, 10 columns by double I sections and 6 columns by double C sections were analyzed by different intervals of girths. All column sections are double IPE140 or UNP140. Dimensions of the girth in double I sections are 100×180 mm, with thickness of 4, 6 and 8 mm, by intervals axes to axes 400, 600 and 800 mm in both side. Dimensions of the girth in double C sections are 100×140 mm, with thickness of 4 and 6 mm, by intervals axes to axes 400, 600 and 800 mm in both side. Finally, the elastic buckling load of these columns was obtained by using the Abacus finite element software and compared with the relationships in the tenth chapter of the National Building Regulations.

Progressive Collaps is a phenomenon in which a partial damage or local breakdown or initial local failure from one element to another causes a collapse in the whole structure or a large part of the structure. Due to the fact that the behavior of structures in the progressive failure can be related to various factors, such as how the loads are transferred to the nodes, the type of connections and their behavior can be very effective in the progressive Collaps of the structure.Therefore, the study of the effect of the type of connection in the progressive Collaps of the structures can demonstrate the performance of the Resistant systems of the structural steel well. To investigate this issue, steel structures, structures with a number of floors 5, 8, 10, 15 with a folding backrest system whose fittings are tight and fitted with a simple frame system whose joints are articulated, loaded and designed based on SAP2000 software. By analyzing the time history of the models, it is determined that the number of seismic responses, including the amount of lateral displacement of the classes, the base cut, the internal force of the columns, and the expansion of the failure in the structures in the use of the bending frame and the bracing frame relative to Different. It should be noted that the axial, shear and flexural forces of the elements in the frames are more than the frames, and based on the position of the column removal, it is different. Therefore, it can be said that the values of internal forces in the bending frame are more than the bracing and the amount of vertical displacement and less than the bracing frame.

Recent earthquakes have shown that torsional irregularity of buildings is a factor caused collapse of buildings. In previous edition of standard 2800, Iranian code of practice for seismic resistant design of buildings, there was no discussion on torsional irregularity. In the fourth edition, the regulations about this type of irregularity are also included. The aim of this study is to validate the regulations using analytical results and comparison of results with those regulations of other seismic codes. Parameters studied are location of shear walls in the plan, number of stories and number of axes. To study torsional irregularity in the Y plane, shear walls are considered symmetrical and asymmetrical about X and Y axis. Analyzing 96 analytical models, specified that maximum value for torsional irregularity coefficient increases by reducing the number of stories of the building. The upper stories have less torsional irregularity coefficient than the lower stories. The results of rotation angle of floor contrasts to that of torsional irregularity coefficient. A direct relationship proposed to relate the torsional irregularity coefficient and rotation angle of floor.

As a key point in main roads and railways of country, Andimeshk city has always have strategic situation in Khuzestan province and even Iran. On the other hand, most evidences indicate that this city is located in seismic area and the incidence of a massive earthquake could impose huge losses on Iran economy. Considering this background, the aim of this study is to perform seismic hazard analysis in Andimeshk territory and precisely evaluate the vulnerability of the buildings and structures in this city. To this end, the extreme risk curve was obtained using probability analysis, then the buildings were investigated in four types in order to identify the vulnerability curves in three levels. By the combination of risk curve and vulnerability curves the rate of vulnerability of Andimeshk buildings can be evaluated quantitatively. The results of this study show that the seismic hazard level in Andimeshk city is relatively high and the base acceleration is equal to 0/325g and even more than the proposed rate in the standard 2800. Although there is no considerable concern regarding concrete buildings, the collapse of ancient and traditional buildings which are calculated 80 to 155 years is very challenging. In conclusion, the results indicate that a 20-year period might be suggested as a short chance to preserve the city.

The basic purpose of applying the prestressing technique in steel structures is section weight decrease via increaseing their load-carrying capacity, eventually led to the technical and economical advantages of such structures. In this paper, prestressing method in steel I-beams, as post-tensioning of the external tendons installed in various samples of steel beams to determine the increase of flexural strength and improve load capacity, analysed and evaluated by ABAQUS finite element software. Considering suitable corresponding between the existence of experimental results and analysis done for each sample indicate that applying the prestressing technique, improve Flexural behavior of beams in terms of bending stress, strain and mid span deflection.

The performance of a BRBs is highly dependent on the geometric characteristics of sections. Steel core components play highly role in the absorption of energy and the other members only prevent buckling, Therefore the proper performance of BRBs are dependent on suitable steel core sections. There is an example of a recreant steel core of 40mm*20mm with total length of 2660mm selected in accordance to the Zsarnoczay Laboratory and modeled in the finite element software. Then compared with laboratory and accuracy results in the Abacus software three other models of 40mm*30mm, 40mm*40mm, 60mm*20mm with overall length of 2660mm in accordance with the necessary invariant bracket factors taken from the Pedro Romero laboratory paper were introduced, modeled and verified with the same physical specification. Then the cross section of 40mm*30mm was selected as the appropriate cross section for the recreant steel core in terms of software output based on parameters such as hysteresis curve comparison, sample hardness comparisons, proper ratios of compressive force to tensile strength. Then for accuracy of suitable cross section for different model, by retaining the proportions of the bracing components, recreant core 40mm*40mm with a total length of 3600mm were modeled.