فصلنامه رویکردهای نوین در مهندسی عمران
سال ششم شماره 1 (بهار 1401)

Demolition is mainly related to environmental sustainability, and since demolition creates a new life cycle for materials, the demolition of dilapidated and old buildings helps reduce the need to use new resources. Demolition engineering is a science in which we destroy structures with the necessary planning and supervision and ensuring safety, also called demolition engineering, reverse construction. Sometimes, due to the reverse engineering science that comes from the answer to the question, it is possible to make a technological discovery of a system that is obtained through the analysis of its structure and function. In this paper, we have investigated the process of demolition of a post tensional segmental bridge using reverse engineering, in which we find the exact application of reverse engineering in the demolition of such structures. Despite the importance of the demolition issue, no regulations have been drafted for it in the country to date, and some foreign regulations have paid more attention to protection and safety during the demolition and have given less talk about the plan, details and methods of demolition. In this research, we have tried to collect some of the relevant regulations in the world in this field and one of the best ways of demolition base on data gathered will proposed.

Usually the vibrations caused by the movement of the train on the line are divided into two categories: ground and air. Ground vibrations propagate around the line, inside the ground, and vibrate in any object they reach. These vibrations in the body are converted to other types of vibrations and displacements or heat, or changes in the environment. In some areas, there are buildings near the line, where the vibrations cause secondary vibrations, structural problems, and annoying noise. Several factors affect the transmission of vibrations due to the movement of the train to the surrounding buildings. One of these factors is the length of the transmission path, which is inversely proportional to the level of vibration created in the body. In order to reduce ground vibrations caused by the movement of trains in buildings, first, the background of the technical literature on the subject has been studied. In the following, some solutions have been developed in the path of vibration transmission and then these solutions have been expanded by the brainstorming method and new solutions have been presented. There are suggestions for construction that are mentioned in the results for the most critical situation, namely the construction of a high-speed railway station with an iron wheel on an iron railway.

Seismic collapse of buildings is the level of structural performance in which the amount of damage reaches its maximum, so this event can be the worst happening in the construction industry. Due to the seismicity of Iran, more accurate assessment of the collapse of structures under earthquakes is one of the important challenges of structural engineering. In this paper, the effect of the number of bays on the seismic response of three sets of short steel frames is investigated. In all three sets, moment frame, an eccentric braced frame and the concentric braced frame are considered in the regular state. Then, the number of bays in all three sets of frames are 2, 3 and finally 4, respectively. Nonlinear static analysis is conducted based on base shear and roof displacement to determine the possible failure mechanisms of these frames and incremental nonlinear dynamic analysis is performed with intensity parameter (IM) corresponding to maximum relative displacement between stories and damage measure parameter (DM) corresponding to the spectral acceleration of the first mode Sa (T1, 5%) were considered. In addition, the collapse-preventing performance level of CP was analyzed. The results of the fragility curves in the limit state (CP) indicate that with increasing the number of bays, the probability of failure of ten percent for all studied frames has increased and consequently their vulnerability has decreased.

Did you know that due to its geographical location, Iran has a varied climate? As a matter of fact, this can be seen in the country's various heights, distances from the sea, different extents, and the long-distance between north and south (spanning from 30-degrees to 60-degrees North latitude). The most common climate state in the country is the hot and dry climate (the climate in the central part of Iran). It means that the humidity conditions in this region range from hyper-arid lands (deserts) to very humid lands (plains). It appears that the rapid increase in greenhouse gases, as well as human interference in the natural cycle of the environment, is among those factors that affect the rate of climate change. Compared to Brazil, Russia, China, and some other countries, Iran has neither large and watery rivers nor many renewable water resources. A vital factor in optimal use of water resources and coping with the drought consequences in the long term is the reasonable and planned use of water resources, as well as water resources management. The study aims to remove various water pollutants by recognizing their characteristics and origin and by optimal management. Furthermore, the study addresses the concept of natural stability of rivers, water-related standards, water pollution effects, along with some plans for the pursuit of sustainable water resource management and evaluating the potential environmental impacts of chemicals.

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 short 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 short 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 short structure, in many cases, the availability of earthquake records has little effect on the response of the structures of the structures, and in some cases, it has reduced the structure response.