civil engineering
Masoud Dehkhoda Rajabi; Ramazanali izadifard
Abstract
Concrete Damaging and reduction of durability characteristics under sulfate attack is one of the important matters. Compared to the situation where concrete is always immersed in sulfate environments, the damages caused in dry and wet conditions are more complex. The dry and wet cycle is a significant ...
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Concrete Damaging and reduction of durability characteristics under sulfate attack is one of the important matters. Compared to the situation where concrete is always immersed in sulfate environments, the damages caused in dry and wet conditions are more complex. The dry and wet cycle is a significant factor that affects on the sulfate attack of concrete. Some concrete structures such as piers, are subject to wet and dry cycles due to sea tides, which causes a continuous process of destructive ions entering to the concrete matrix during wetting, and increasing cracks during the drying process. Considering the wide using of high-strength concrete and the weaknesses of this concrete in the mentioned conditions, the present study has investigated the compressive strength, tensile strength, separation and shrinkage test of HS, FRHSC concrete reinforced with polypropylene (PP), steel (ST) and hybrid fibers under the conditions of dry and wet cycles in the environment containing magnesium sulfate for 6 months. The results of this study show that although dry and wet cycles reduce the strength of concrete containing steel fibers, the effect of these fibers in increasing the compressive and tensile strength of HS concrete is much greater compared to PP fibers. The use of steel fibers, polypropylene and a combination of steel fibers and polypropylene has reduced the shrinkage of high-strength concrete samples by 13, 24 and 33%, respectively (compared to HS concrete without fibers).
civil engineering
Firouz Karamshahi; ebrahim nohani; Mohammad Hossein Noorolah Dezfouli
Abstract
Concrete is one of the most widely used materials in construction, and the reason for that is its hardness, durability and high resistance. Pores are usually filled with fluid. So far, nanostructures with regular and irregular shapes have been made from different materials, which in total form one of ...
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Concrete is one of the most widely used materials in construction, and the reason for that is its hardness, durability and high resistance. Pores are usually filled with fluid. So far, nanostructures with regular and irregular shapes have been made from different materials, which in total form one of the most diverse categories of materials. In this regard, 30 samples were made and tested for compressive strength testing and 30 samples for tensile testing. The amount of nanosilica and nanoclay in three different ratios of 0.25, 0.50, and 0.75 of cement weight has been added to the concrete mixture. The obtained results show an increase in the compressive and tensile strength of concrete due to the addition of nanosilica and nanoclay
Civil Engineering
Javid Rezania; Massoud Hamian; Alireza Rasekhi
Abstract
In today's modern world, traces of artificial intelligence can be found in almost any field. In recent years, with the introduction of algorithms and machines, the fields of building engineering and construction project management have also experienced new challenges, from optimizing processes and improving ...
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In today's modern world, traces of artificial intelligence can be found in almost any field. In recent years, with the introduction of algorithms and machines, the fields of building engineering and construction project management have also experienced new challenges, from optimizing processes and improving product design to automating tasks and parametric design. Artificial intelligence in structural engineering involves the use of advanced algorithms and machine learning techniques to simplify and improve various aspects of the design and analysis process. Also, artificial intelligence software related to construction is a group of technological tools and solutions that use artificial intelligence to optimize various functions of this industry. On the other hand, one of the relatively new topics that artificial intelligence can enter into is the investigation of various types of damage, including progressive damage in the design and construction of structures. In this article, an attempt has been made to define artificial intelligence and machine learning, to explain the various functions of this technology, and practical algorithms, plus introduce useful and pioneering software in civil engineering, where artificial intelligence is the main origin. Also, the basic influencing parameters in the study of progressive collapse, such as critical path identification and extreme load patterns, have been investigated. According to the functions stated in this research, the importance of using artificial intelligence in theoretical studies and future applied projects is clearly known. Especially vital projects such as Spatial Structures or buildings with a special seismic bearing system such as Staggered Truss Systems and structures with high ductility requirements that need special analysis, design, and monitoring.
civil engineering
Reza Bazrgary; Arian Seilany; Saeideh Ziyadidegan; Seyed Arian Shojaei
Abstract
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, ...
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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.
civil engineering
Reza Bazrgary; Saeideh Ziyadidegan; Mehdi Bahmanzadeh
Abstract
Today, the role of concrete as the most widely used building material in the development of the civil and economic infrastructure of societies is undeniable. On the other hand, the production of cement requires the consumption of natural resources and the release of a significant amount of carbon dioxide ...
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Today, the role of concrete as the most widely used building material in the development of the civil and economic infrastructure of societies is undeniable. On the other hand, the production of cement requires the consumption of natural resources and the release of a significant amount of carbon dioxide into the environment, so the need to revise and change the ingredients of concrete in such a way as to meet the needs of construction and to minimize risks and damage to the environment. It is necessary that pozzolans are among the materials that can be used to improve this.Iran is one of the countries that can be a leader in this matter due to its diverse geographical areas and the availability of various mines. Therefore, this research presents the effect of using nano-silica (NS) and micro-silica (SF) of Hamadan city on the mechanical properties of ultra-high-strength concrete (UHPCs).For this purpose, two groups of concrete with and without silica fume (SF) were made. Also, nano silica (NS) was used as an additive to cement in amounts of 0%, 0.5%, 1%, 2% and 3%. In general, the results show the appropriate effect of pozzolanic materials produced in Iran in improving the properties of concrete in a way that gives that among the different contents of NS, UHPC containing 2% NS has the best results in terms of compressive strength, tensile strength, modulus of elasticity, and bending strength. Showed in 90 days. Also, UHPC samples containing dual cement materials (NS and SF) showed better results than concretes containing only NS
civil engineering
Hossein Khosravi; Atefeh Adelian Haghighi
Abstract
The concrete-filled double skin steel tubular columns (CFDST) are regarded as one of the composite columns consisting of double steel tubes with square or circular hollow sections and the space between two skins is filled with concrete. These columns possess several advantages, including a proper performance ...
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The concrete-filled double skin steel tubular columns (CFDST) are regarded as one of the composite columns consisting of double steel tubes with square or circular hollow sections and the space between two skins is filled with concrete. These columns possess several advantages, including a proper performance during loading, smaller dimensions, cost-effectiveness, protection of the concrete surface against the damage, others compared to conventional columns. In this paper, the buckling of the concrete-filled double skin steel tubular columns subjected to the axial compression was assessed using finite element software, ANSYS. For further investigation of the various types of this novel column system, the nonlinear behaviors of the 3D model of the double skin sections with various cross-section shapes of the section were compared and the influence of the support condition was studied Moreover the buckling of the columns filled with self-compacting concrete, which is required due to the difficulty in the pouring in the confined space, was scrutinized. The results for the short CFDST columns indicate that the column with square-outer-section and circular-inner-section tubes exhibited high buckling critical load and better ductility. Variations in the support conditions do not have significant influence on the columns.
civil engineering
HAMOON FATHI; Mohammad Yousefinezhad
Abstract
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, ...
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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.
civil engineering
Mohammad Memar Eftekhari; Mohammad amin Kadivar; Mohammad Rezaei
Abstract
Blast load is a load with a dynamic nature similar to an earthquake, with the difference that its effects take much less time than an earthquake, are more intense, and directly affect the structure itself. Therefore, in this case, in addition to carrying out the usual retrofitting, it is necessary to ...
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Blast load is a load with a dynamic nature similar to an earthquake, with the difference that its effects take much less time than an earthquake, are more intense, and directly affect the structure itself. Therefore, in this case, in addition to carrying out the usual retrofitting, it is necessary to reduce this explosive effect by changing the architecture of the structure. One of the solutions for this problem is the dual-purpose use of seismic elements such as shear walls, which can not only resist earthquakes but also resist explosive loads. Meanwhile, concrete structures have shown good resistance to explosion compared to steel structures, and one of the design methods in these types of structures is the use of concrete shear walls. One of the solutions to reduce the dimensions of the columns is to use a concrete shear wall. One of the capabilities of this method is the possibility of creating an opening in it, and it reduces the limitations created in the architectural discussion. In this research, the performance of arched concrete shear wall with opening against explosive load has been investigated, and the considered samples with and without opening have been compared. Also, the effect of compressive strength of concrete has been investigated. Finally, it was determined that when creating the opening, full care and inspection should be done and the area around the opening should be reinforced. Arched concrete shear wall with 10 cm thick opening has performed best against explosive load.
