فصلنامه رویکردهای نوین در مهندسی عمران
سال ششم شماره 2 (تابستان 1401)

The characteristics of earthquakes vary both in terms of amplitude and frequency of content for sites at distances close to the seismic spring and far from it. However, the 2800 standard, which is used as the basis for the seismic design of the country, does not exclude the effects of the near-fault field on loading, and therefore the necessity of studying and comparing such effects on the response of structures is very necessary. Studies on the behavior of structures under the influence of near-field earthquakes have shown that the tracing of these types of earthquakes has more effects on structures (including permanent displacement and directional effects) than accelerations far from faults. Therefore, in order to estimate the near-active faults of earthquakes, the features of the near-earthquakes should be considered in the analysis and design of structures. Accordingly, in this research, we tried to study the effect of directional earthquakes near the seismic response of mid concrete structure using time histories analysis. For this purpose, firstly, the records of the various stations of the quake were determined as the basis for the selection of accelerometers, and then using the analytical methods, the response spectrum of this acceleration, taking into account the directional effect and without it, as well as the pulse isolated from these records In two directions north-south and east-west. Then, according to the time history analysis on two mid concrete structures with the number of stories 10, for 7 station records of the Taiwan Chichi earthquake, the drainage (relative displacement) of floors in structure was investigated. The results of this study showed that, due to the unpredictable nature of the earthquake, in mide structure, in many cases, the availability of earthquake records has little effect on the response of the structures of the structures, and the effect of the earthquake record on the response of the structure has increased.

Today, reinforced concrete structures have a special place in the construction industry. To retrofitting some existing concrete buildings, steel braces are used with direct connection to concrete frame. The important issue here is what the details of the connection of the brace to the concrete structure should be. The connections in concrete structures always have the most damage during an earthquake. Therefore, the performance of the connections and the type of steel braces connection to the concrete frames will affect the seismic behavior of them. For this purpose, in this study, three methods of steel brace connection to the concrete frame have been investigated. Models are created as one-story single-span and two-story single-span frames using the finite element method in the Abaqus software. The results indicate that the change in the type of connection causes changes in energy absorption, stress distribution and maximum lateral displacement of the frame. Meanwhile, by applying bilateral loads, first the bolt planting model and then the metal jacket method are considered as selected models. Concerning the performance, which is represented by plasticity and damage of elements, the maximum difference between connection methods is 10 percent and all of them are considered acceptable.

According to the American Building Loading Code, progressive failure is defined as the spread of failure in a structure from one element to another, which ultimately leads to the failure of the entire structure or a large part of it. Lead to this type of failure are: car impact, gas explosion, aircraft collision, construction error, fire, accidental overloading of members, explosion, etc. Most of these accidents have a short impact time that in The result leads to dynamic responses. In this research, 100 types of models will be considered and the progressive collapse reference codes will be used for analysis and the application software will be used to achieve the answer under nonlinear static analysis by removing the column and performing nonlinear static analysis. The behavior of structural members against this phenomenon will be evaluated and finally the results will be controlled by the rules in the regulations and the final behavior of the structure against this phenomenon will be examined. Artificial neural networks have been used as a powerful tool in various fields of engineering and their use is increasing. Civil engineering and the study of the behavior of structures are no exception to this rule and neural methods have been used in it. In this study, three types of neural networks have been used to investigate the phenomenon of progressive collapse. Input and output parameters are selected and modeled with the help of evaluation indicators of this phenomenon. Finally, by comparing the performance of artificial neural networks, the most successful type of neural network has been proposed.

In this study, we investigated the effect of silica fume with ratios of 10, 20, 30, 40, 50, 60% of the total weight of sulfur dry concrete. After melting at 175 ° C, sulfur powder was mixed with preheated microsilica that reached the level of molten sulfur powder and then poured into molds. In this paper, 189 samples in different forms, including a 10 cm cube for compressive strength test, a 5 cm cube for acid resistance, melting and freezing tests, and a 16 x 4 x 16 cm sample for flexural strength have been prepared. The samples were tested 1, 24 and 72 hours after concreting according to the pre-tests. All samples are stored in the laboratory and poured into molds. An oven in the laboratory was used to bring the sulfur powder to the melting point. Sulfuric acid has been used to test its.

The present study was carried out to investigate the quantitative and qualitative status of water resources in Varamin plain and to provide suitable management strategies for sustainability and outflow from current and future challenges in this area. Therefore, statistics and the necessary data were gathered and used WEAP software to provide appropriate management solutions for the impact of the continuation of current water resources policies in the region over the next20 years, by considering the population growth. The results showed that if the current status of water resources continues, we have to harvest more of the surface water resources to cover the increased drinking water demand, based on the increasing population of this area. So that this overdrawn would reach about a 10.8Million cubic meters in 2035. Also, the average annual no coverage of agricultural and industrial demand in the year 2035was 76 and 23 million cubic meters, respectively, 16/2 and 27/4 percent. This overdrawn could reflect the adverse effects on the Mamlu dam, increase in the ground subsidence and increase other economic- social issues. So that, it causes to reduce the average annual volume of the aquifer to around 35 million cubic meters and a 1centimeter daily average drop in the aquifer during the 20-year period. Therefore, due to the high evaporation rate in the region, using artificial feeding methods, such as reducing the amount of evaporation, is a solution to compensate for some of the water shortages in some areas. Therefore, collecting surface water, feeding water underground, and proper water management, using modern water management practices is some of the most important factors in water resource management.