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Showing 83 results for Rajabi
Volume 25, Issue 2 (7-2025)
Abstract
In the seismic active areas, strong ground motions usually consist of the numerous successive shocks (Foreshock-mainshock or mainshock-aftershock), which have the significant potential to increase the structural response and cumulative damage. This phenomenon (as called seismic sequence) can affect on the behavior of structures, control the seismic performace of buildings. Multiple earthquakes which have been recorded in all parts of the world are proven that the structures located in the mentioned areas are not only experienced a single event, but also they withstand a series of shocks. Due to the high importance of consecutive earthquakes, application of buckling restrained braces (BRB) and shape memory alloy (SMA) materials as smart materials in engineering sciences in the past decades, this paper tries to evaluate the seismic performance of steel frames equipped with buckling restrained brace by determination of the optimal percentage of shape memory alloy under successive earthquakes. Because SMA has unique advantages and characteristics such as no need to replace after an earthquake, high resistance to corrosion and fatigue, the ability to absorb high energy, the ability to return to the original state by applying temperature, tolerating strain up to about 10% without leaving residual strain after an earthquake, and tolerating multiple cycles of loading and unloading, various applications can be found separately and combined in controlling the behavior of structures. It should be noted that despite the high damage potential of successive earthquakes, they are neglected in the seismic codes and design earthquake is still proposed without successive shocks.
Hence, the acceptance of new methods for improving the seismic performance of structures under consecutive shocks seems necessary by the engineering community. Therefore, in this regard, 4 and 7 story steel frames with diagonal buckling restrained braces representing short and mid rise structures were designed based on Iranian codes in ETABS software and then implemented in OpenSees software. After selecting the reference model, the performance of the studied models is verified for the linear and non-linear region through comparison of periods and pushover curve of reference and implemented model. In the following, different percentages of shape memory alloys including 20, 40, 60, 80 and 100% for the 4 story steel frames and 5, 10, 15, 20 and 25% for 7 story steel structure has been considered. The studied models are analyzed with/without shape memory alloys under seismic scenarios with and without seismic sequence in Opensees software. For this purpose, critical successive shocks are selected based on effective peak acceleration (EPA) from PEER center. For compatibility aspects between the seismic analysis and seismic design, the selected records should be scaled by designing spectrum for each fundamental period of studied structure in order to have identical spectral acceleration. The results of nonlinear dynamic analysis show that with the increase in the percentage of shape memory alloy in the 4 story steel frame, the response ratio of steel frames under single and consecutive earthquakes increased, but in the 7 story steel frame, it almost decreased, and this reduction is better felt in the higher stories under the single earthquake. Finally, the optimal percentage of shape memory alloy among the selected percentages in the present study is suggested to be 20% for 4 story steel frame and 15% for 7 story steel frame.
Volume 25, Issue 4 (Winter 2021)
Abstract
Extended abstract
introduction
Tourism has significant implications for sustainability. Tourism can make full use of tourism resources in different regions to adjust and optimize industrial structures, expand the agricultural industrial chain, develop tourism services, promote non-agricultural employment, increase farmers' incomes and create a better economic base for construction. Thus, tourism has become a strong pillar for sustainable development in developed and emerging countries. Coastal cities can play an effective role in the development of these areas, and consequently, in the development and growth of the national economy by proper and appropriate planning and identification of capabilities in coastal tourism. Given the unemployment that exists among the various strata of these cities and the main features of job creation in tourism, which includes a wide range of forces, both in terms of education, is an issue that along with effects in this industry, cannot be ignored. Because, tourism as an intelligent and humane element and as important inputs of an urban system can have positive effects in spatial-spatial dimensions and pave the way for sustainable urban development for the studied cities. On the other hand, the lack of careful planning by city managers in the field of tourism to achieve sustainable development in these coastal cities will create problems for both tourists and current and future citizens. Considering that the coastal cities under study are among the tourist cities of the province and the country, and also have the ability to achieve sustainable tourism development, the study of the role that tourism can play in these cities in the field of sustainable development is a significant issue.
Methodology
This research is an applied research in terms of nature, and in terms of data analysis method, it is a descriptive-correlational and causal-relationship that has been evaluated using field and survey methods and a questionnaire. The statistical population of the group of experts including professors and experts and the sample size was determined based on the available method of 20 people. The research tool of the questionnaire and its validity has been done formally by a group of experts who have studied in this field so far and its reliability with Cronbach's alpha test and coefficient of 0.890 indicates the acceptable reliability of the questionnaire for research. Pls software has been used to analyze the data.
Results and discussion
According to the designed model, institutional-managerial indicators have an impact on economic, social-cultural, physical and environmental indicators, and economic indicators have a direct impact on the environment and socio-cultural and physical indicators on the environment. These relationships have been examined internally and indirectly on the main variable, namely sustainable development. Finally, all five indicators studied in the study were directly evaluated on sustainable development, which showed that the managerial-institutional index with a path coefficient of 0.803 plays the most important role in sustainable development. Then the economic index with a coefficient of 0.776 and socio-cultural index with a coefficient of 0.734 and physical and environmental indicators each with coefficients of 0.665 and 0.514, respectively, have the greatest impact on achieving sustainable tourism development. They will have a beach. It should be noted that all relationships and path coefficients, both endogenously and exogenously, have positive and directional effects and the intensity of relationships are evaluated as very high and significant. These indicators are good predictors for the sustainable development of coastal tourism. Due to environmental issues and problems due to the arrival of tourists and the resulting pollution, the environmental behavior of citizens is almost necessary.
Conclusion
According to these results, the main duties of the government are to support and develop maritime activities at the technological, environmental and social levels to meet the needs of the tourist community, make full use of the region's coastal potential and diverse water resources and their basic infrastructure, as well as the establishment of maritime and river transport networks and tourism in many areas. However, tourism and economic potential have not been fully utilized. After the managerial-institutional variable, the economic index and the socio-cultural index have the highest score in the role of coastal tourism on sustainable development. After that, the impact of the physical index and finally the environmental index is in the last rank in terms of impact on sustainable development. According to the analysis of the indicators of this study, it can be said that tourism is the main engine of development for this region and accelerates its sustainable development because, economically, it has a positive effect on income growth, job opportunities and job creation. Gross income and production will increase the motivation of investors to invest in the region. Socially, it causes interaction between residents and tourism, preserving the customs and culture of the region, getting acquainted with other cultures, increasing the presence of women in society, and so on. Physically, it will provide the development of infrastructure, the development of accommodation and catering facilities, the beautification of the environment, the inclusion of recreational and beach uses in plans and planning, and so on. But from the environmental point of view, it causes adverse effects on the cleanliness and cleanliness of the beaches, a negative role on the waste disposal system and increasing pollution and destruction of ecosystems, reducing animal species and changing land uses, and reducing agricultural lands, etc. This will harm the environment of the beaches.
Keywords: Coastal tourism, Sustainable development, Royan, Babolsar and Noor coastal cities.
introduction
Tourism has significant implications for sustainability. Tourism can make full use of tourism resources in different regions to adjust and optimize industrial structures, expand the agricultural industrial chain, develop tourism services, promote non-agricultural employment, increase farmers' incomes and create a better economic base for construction. Thus, tourism has become a strong pillar for sustainable development in developed and emerging countries. Coastal cities can play an effective role in the development of these areas, and consequently, in the development and growth of the national economy by proper and appropriate planning and identification of capabilities in coastal tourism. Given the unemployment that exists among the various strata of these cities and the main features of job creation in tourism, which includes a wide range of forces, both in terms of education, is an issue that along with effects in this industry, cannot be ignored. Because, tourism as an intelligent and humane element and as important inputs of an urban system can have positive effects in spatial-spatial dimensions and pave the way for sustainable urban development for the studied cities. On the other hand, the lack of careful planning by city managers in the field of tourism to achieve sustainable development in these coastal cities will create problems for both tourists and current and future citizens. Considering that the coastal cities under study are among the tourist cities of the province and the country, and also have the ability to achieve sustainable tourism development, the study of the role that tourism can play in these cities in the field of sustainable development is a significant issue.
Methodology
This research is an applied research in terms of nature, and in terms of data analysis method, it is a descriptive-correlational and causal-relationship that has been evaluated using field and survey methods and a questionnaire. The statistical population of the group of experts including professors and experts and the sample size was determined based on the available method of 20 people. The research tool of the questionnaire and its validity has been done formally by a group of experts who have studied in this field so far and its reliability with Cronbach's alpha test and coefficient of 0.890 indicates the acceptable reliability of the questionnaire for research. Pls software has been used to analyze the data.
Results and discussion
According to the designed model, institutional-managerial indicators have an impact on economic, social-cultural, physical and environmental indicators, and economic indicators have a direct impact on the environment and socio-cultural and physical indicators on the environment. These relationships have been examined internally and indirectly on the main variable, namely sustainable development. Finally, all five indicators studied in the study were directly evaluated on sustainable development, which showed that the managerial-institutional index with a path coefficient of 0.803 plays the most important role in sustainable development. Then the economic index with a coefficient of 0.776 and socio-cultural index with a coefficient of 0.734 and physical and environmental indicators each with coefficients of 0.665 and 0.514, respectively, have the greatest impact on achieving sustainable tourism development. They will have a beach. It should be noted that all relationships and path coefficients, both endogenously and exogenously, have positive and directional effects and the intensity of relationships are evaluated as very high and significant. These indicators are good predictors for the sustainable development of coastal tourism. Due to environmental issues and problems due to the arrival of tourists and the resulting pollution, the environmental behavior of citizens is almost necessary.
Conclusion
According to these results, the main duties of the government are to support and develop maritime activities at the technological, environmental and social levels to meet the needs of the tourist community, make full use of the region's coastal potential and diverse water resources and their basic infrastructure, as well as the establishment of maritime and river transport networks and tourism in many areas. However, tourism and economic potential have not been fully utilized. After the managerial-institutional variable, the economic index and the socio-cultural index have the highest score in the role of coastal tourism on sustainable development. After that, the impact of the physical index and finally the environmental index is in the last rank in terms of impact on sustainable development. According to the analysis of the indicators of this study, it can be said that tourism is the main engine of development for this region and accelerates its sustainable development because, economically, it has a positive effect on income growth, job opportunities and job creation. Gross income and production will increase the motivation of investors to invest in the region. Socially, it causes interaction between residents and tourism, preserving the customs and culture of the region, getting acquainted with other cultures, increasing the presence of women in society, and so on. Physically, it will provide the development of infrastructure, the development of accommodation and catering facilities, the beautification of the environment, the inclusion of recreational and beach uses in plans and planning, and so on. But from the environmental point of view, it causes adverse effects on the cleanliness and cleanliness of the beaches, a negative role on the waste disposal system and increasing pollution and destruction of ecosystems, reducing animal species and changing land uses, and reducing agricultural lands, etc. This will harm the environment of the beaches.
Keywords: Coastal tourism, Sustainable development, Royan, Babolsar and Noor coastal cities.
Volume 28, Issue 2 (8-2024)
Abstract
In concluding a contract, sometimes we need to leave some of its provisions to the future and agree on the basic elements of the contract. Many lawyers consider this contract vague and even invalid. However, due to the connection that certain conditions have with the public policy of the society, such invalidity does not come from jurisprudence, civil code and commercial practice. So, the question is what are the criteria for resolving the ambiguity of the provisions of the contract? By examining legal provisions, the ambiguity of an incomplete contract may be subject to an objective criterion or the will of the parties to the contract or one of the parties or a third party may prevail. If these criteria are not in the contract, the court can enter and resolve the ambiguity of the contract. All of this kind of Contracts is valid if one can evaluate by an objective criterion or by a personal decision or a court decision. Otherwise, the contract would be a void entity in law.