نشریه عمران و پروژه
سال پنجم شماره 7 (پیاپی 53، مهر 1402)

Today, controlling of structures’ progressive collapse decreases damages while natural and unnatural events happen. This issue requires deliberation and consideration for cable-stayed bridges which their utilization in the country is going to increase, so by taking previous surveys into consideration, the best design for the cable-stayed bridge is gained. In this study, the structure’s progressive collapse is investigated by alternative load path method. In this method there is an effort to make certitude about the appropriate joint between vertical and horizontal components, in a way that the structure has the ability of load transfer with the elimination of any components of the structure. In order to control this phenomenon in the potential state, destruction of the bridge’s elements is evaluated by linear and non-linear static and dynamic processes. In this survey, first the mentioned cable-stayed bridge with assumed geometrical characteristics and materials is designed two-dimensional by relevant regulations. This study and design is performed by SAP2000 computer program and then the designed system’s response to the progressive collapse is controlled by static and dynamic methods. But the ultimate purpose of this research is to study geometrical changes of the design such as changes in horizontal distances of cables and changes in pylon altitude or altitude-to-span ratio and the effects of these factors in the mentioned progressive collapse and to compare them. By investigating this research models under dead load, we came to the conclusion that when two cables of the structure are destroyed as a result of breaking away, force redistribution occurs and forces in all the cables are increased. This increase can be up to 1.5 times more and causes forces to exceed the limit which the cables are designed for and therefore it causes destruction of the cable and the structure. But in general the structure is less likely to proceed to the progressive collapse as a result of gravity loads. ***All authors have contributed equally to this work.

The present paper studies experimental research on the effects of fiber on the strain and the Poisson's ratio of self-compacting concrete (SCC). The experiment was carried out on 48 cubic concrete samples and 68 standard cylindrical samples of 4 different mixes with compressive strengths of 25, 28, 30, and 33 MPa. The percentage of fiber in the mixes increases from 0 to 12. Axial and lateral strains of the samples were calculated simultaneously, with respect to the stress exerted by uniaxial compressive loading. Having compared the stress-strain curves for axial and lateral strain, Poisson's ratios were calculated by taking the number of the loadings into account. One of the implications of the results was that the ratio of the inner area in lateral stress-strain curve to those in axial stress-strain curve relate to the square of Poisson's ratio in the same percent of fiber. At the end, with respect to the concrete's compressive strength and percentage of fibers, an integrated model was formulated for Poisson's ratio of fiber SCC under compressive loading. The results show that an increase in fiber (only 2%) causes a significant increase in Poisson's ratio (more than 5%) after the second compressive loading. Also, the third lateral strain provides maximum strength in all self-compacting concrete mixes.

The soil-structure interaction is one of the most important challenges in structural design that can significantly change the seismic response of structures. . During an earthquake, the behavior of the soil under the structure plays an important role in the response of the structure and affects the dynamic characteristics of the structure. Therefore, there is a need for more accurate modeling of the soil environment in special structures. In engineering applications, the soil is often not modeled and its important effects are neglected, due to the unlimited nature of the soil environment and its modeling is more complicated than the structure modeling. There are different methods for modeling the soil-structure interaction phenomenon. One of the most popular methods is the method of beam on the elastic foundation. This method is based on the Winkler model, which is widely used in the design codes, but does not accurately show the changes in soil stiffness along the length of the foundation. Therefore, in the present article, the reaction of the soil under the foundation is investigated, and finally, a suitable and simplified model is presented for modeling the soil-structure interaction in engineering applications.To achieve this goal, several structures were modeled in 3D in the OpenSees environment. Then, the output of the reaction of the soil environment and the foundation of the structure has been used to estimate the hardness of the soil environment and foundation and extract simplified engineering relations

This study explores the impact of modernizing water distribution systems on the efficiency of agricultural water distribution from surface water resources. While previous studies have focused on technical and hydraulic evaluations of modernization options for irrigation networks, this research uses the life cycle assessment (LCA) method to compare selected modernization options regarding environmental performance. This is crucial given the increasing global focus on the environment and the importance of addressing environmental issues related to irrigation. The modernization options in this study were selected from structural and non-structural methods proposed in previous studies and were evaluated in terms of environmental impact over a 30-year lifespan. The environmental model of each option was developed in SimaPro v.9 software to use the LCA method. The results showed that the highest environmental impacts in all three scenarios were related to global warming potential, particulate matter formation, and human toxicity, respectively. However, environmental emissions were found to be lower in the structural scenario than in the current situation, while the non-structural scenario showed greater reduction. Further analysis revealed that carbon dioxide emissions equivalent had decreased by 9% in the structural scenario compared to the current situation. This is due to the decrease in electricity consumption caused by pumping wells by farmers. Over 99% of carbon dioxide production is due to electricity consumption, so using the structural modernization method during its service life could significantly reduce environmental pollution. Using non-structural methods could also reduce carbon dioxide emissions by up to 22%. Given these findings, the non-structural modernization scenario was found to be the most environmentally friendly among the scenarios examined in this study. The authors recommend that future research use the life cycle sustainability assessment (LCSA) method, which includes evaluating LCA as an environmental criterion, LCC as an economic criterion, and social life cycle assessment (S-LCA) as a social criterion.