نشریه علوم و فنون سازندگی
سال چهارم شماره 1 (پیاپی 11، بهار 1402)

Cube-shaped armours are the first type of concrete armours used by humans. In the past, cubic blocks were used as a double-layers. The high consumption of concrete in double-layer cube-shaped armours made the idea of producing armours with an interlocking function that have corners and consume less concrete volume to be considered. For a long time, blocks with an interlocking were used in the armour layer, but due to some of their disadvantages, such as the possibility of breaking during transportation, the difficulty and complications of production, problems during installation, and difficulties related to the usage, caused renewed attention to cubic armours and other bulky armours. The use of cubic armours as a single layer has not been investigated much. Therefore, in this article, the behavior of single-layer cubic armours with regular and irregular placement and comparing its behavior with double-layer armours in low-crested/submerged breakwaters have been investigated. The results of the experiments showed that single-layer armours with regular placement perform relatively well and can be used instead of double-layer armours with irregular placement. While single-layer armour with irregular placement has a very poor performance against wave attact and the spread of damage in the armour layer occurs quickly in this case.

Current research is to use artificial intelligence computation to provide algorithms that meet all Mabhas-6, Mabhas-10, and Standard-2800 regulations of national building codes while minimizing the weight of structures. In previous studies, the control of boundary conditions and optimal design of steel moment frames was done in 2D and only with older algorithms. One of the most important tasks of this research is to perfect new constraint rules to control all constraints and to optimally design the common short and medium length steel structures. All the necessary regulations and controls for the three main types of steel structures widely used in the country: 1) braced frames and 2) frames with shear walls, and 3) a dual system of moment frames and shear walls are implemented. Finally, the results of this algorithm were validated in the Tabriz hospital project. One of the valuable results of this work is that it facilitates a safe design and control process for steel buildings by providing a graphical panel of model inputs and displaying all the key results of the structure in the form of text and diagrams. The work process is intelligently programmed to automatically run by simply inputting a standard ETABS file into the optimal seismic design process algorithm. In the ETABS file, each group sections are defined as a list to allowing artificial intelligence algorithms to choose the best placement. The hospital project demonstrated design safety as well as the ability to significantly reduce the total weight of the steel.

The wear of the disc cutter results in an increase in contact area with the rock, so when the wearing of the cutter exceeds its maximum limits, it should be replaced. However, this is not done on time because of cost concerns. Thus, this study will investigate the effects of disc cutter wear on tunnel boring machines (TBMs) operational parameters such as thrust force, torque, penetration rate, and specific energy as well as how it impacts advance rate and project time. for this goal, the hard rock TBM parameters of the Kani Sib water conveyance tunnel have been studied after the replacement of worn disc cutters. The results show that the average thrust force decreases by 11%, while the torque increases by 2%. Furthermore, an average increase of 25% in penetration rate can also be observed. The reduction of specific energy is also significant. This means that by changing worn disc cutters on time, excavation time is reduced, excavation efficiency is improved, and final costs are reduced significantly.

The use of fiber concrete technology in the form of flooring to remove thermal rebars and reduce the consumption of structural rebars is popular in the world today. Therefore, it is necessary to evaluate the properties of fibers such as their mechanical properties in concrete, to provide a fiber-concrete mixture design suitable for each project. The mechanical properties of fiber concrete are influenced by various parameters such as the type of fibers, the amount of fiber consumption, the dimensional characteristics, and the physical and mechanical characteristics of the fibers. The main parameter in determining the performance of fiber-reinforced concrete is the ability to provide bending strength after cracking. The purpose of this research is to investigate the effect of different amounts of macro synthetic fibers on the residual strength of concrete. For this purpose, eight concrete mix designs were used with amounts of 2, 4, and 6 kg per cubic meter and a control sample without fibers in two different compressive strengths of 25 and 35 MPa. The method of performing the test is based on the ASTM-C1609. Moreover,, to test the residual strength of fiber-reinforced concrete, the properties of fresh concrete and compressive strength testing were also done. The results of the residual strength test show that the use of macro synthetic fibers increases the load-carrying capacity after cracking, In the compressive strength test, the use of fibers, although it has no effect on the compressive strength value, changes the type of fracture from brittle to ductile.

Today, bridges play an important role in transportation networks, so that prestressed concrete bridges with post-tension tendon is one of the most common construction methods that have been prepared to meet the needs of infrastructure. These types of bridges are subject to various damages during operation, such as breakage in strands of tendons. Therefore, monitoring the status of their integrity during operation is of great importance. In this paper, a method based on axial strain changes in the wedge plate is used to identify strand breakage in post-tension tendons. Two wedge plate patterns, including 19- and 12-strand wedge plates, were modeled in ABAQUS software. Then, monitoring points were considered to identify the broken strand. Afterward, the performance of the damage detection framework based on axial strain changes was investigated by various wire breakage scenarios. The results show that the presence of breakage in strands of the tendon can be detected by observing distinct peaks at monitoring points. As the location of the damaged strand is closer to the monitoring points, the rate of axial strain changes will be more severe. Therefore, using the thresholds for each type of wedge plate, it is possible to identify the strand number that has been damaged in the post-tension tendon.