Journal of the Structural Engineering and Geotechnics
Volume:11 Issue: 2, Summer and Autumn 2021

Determination of equivalent viscous damping (EVD) is an important step in the direct displacement-based design (DDBD) method. This study aims to investigate whether the proposed method used in the equivalent lateral force (ELF) procedure, according to ASCE/SEI 7, for the calculation of effective damping in steel structures equipped with fluid viscous dampers (FVDs) can be used in the DDBD method. In order to evaluate the accuracy of this method, modified Jacobsen’s method and the approach used in Pennucci et al.’s study are applied to determine the EVD. At first, a set of steel structures with different heights and bays are designed for 0.75, 0.85 and 1.0 of the design base shears based on the primary calculation of the ELF procedure and then nonlinear time history analyses are carried out to determine the dampers constants and the EVD at two seismic hazard levels, i.e., design earthquake (DE) and maximum considered earthquake (MCE). According to the obtained results for the EVD, it is found that the obtained results in the ELF procedure has acceptably matched with Pennucci et al.’s approach. On the other hand, there are some differences between the obtained results and those obtained from modified Jacobsen’s method. Therefore, the ELF proposed equation for calculating EVD can be used in the DDBD method in mid-rise steel structures equipped with FVDs to accurately determine the EVD.

Presenting a model specific to the city of Tabriz to estimate the liquefaction potential due to the region's seismicity and the high groundwater level can be effective in dealing with and predicting solutions to deal with this phenomenon. In recent years, the accumulation energy ratio (AER) as a parameter for estimating the liquefaction potential in the energy-based method proposed by Kokusho (2013) has been considered by many researchers. In this research, using perceptron multilayer (MLP) and radial base function (RBF) methods in artificial neural network (ANN) and genetic expression programming (GEP), the accumulation energy ratio using seismic and geotechnical data is modeled for the city of Tabriz. These modeling’s performed by all three methods are well consistent with the outputs. Still, the modeling performed using the Perceptron Multilayer (MLP) method is very compatible with the outputs and can estimate the results with an acceptable percentage. The relationship presented by genetic expression programming (GEP), which is trained with local data, can also yield satisfactory results from estimating the rate of accumulated energy in the study area and provided an independent and accessible relationship trained. With data specific to the study area, there is another advantage.

One of the major impacts of near-field earthquakes is a concentration of rupture on the limited number of stories and structural elements beyond the expected. Therefore, predicting the distribution of quantitative parameters of earthquake response at structural height can help to estimate the destructive potency of near-field earthquakes. In near-fault regions, directivity cause fling-step in the velocity time-history records, imposing more resistance and ductility requirements on the structure perpendicular to the fault line. The Endurance Time (ET) method is an innovative and straightforward method for dynamic loading and analysis of structures, apprehensible for the standard level of seismic engineering knowledge. The collapse performance and the accuracy of the ET in the seismic assessment of steel moment-resisting frames are discussed. Results of ET and IDA compared to observe the ET method’s potential benefits and drawbacks in the seismic evaluation of this category of frames. To model the semi-rigid connection to reduce flexural stiffness, the width of the upper and lower beam flanges were reduced and the results were analyzed. According to the obtained results, the reduction in rigidity percentage decreases the median of collapse capacities and increases the dispersion of IDA curves and seismic vulnerability of the building. Also, it was observed that the ET method overestimates the median of collapse capacity and leads to unsafe design.

In order to control seepage from the dam, various methods are used to reduce water seepage. One of the methods of reducing the permeability of the water according to its material is building cut-off walls and filling them with plastic concrete materials. In this study, it has been tried to study the mixing plan of the plastic concrete in the main body of the Nargesi dam’s cutoff wall and to determine the results of compressive strength and elasticity modulus of 108 panels of cut-off wall in different ages in this project. Due to the individual concreting of each panel from the cutoff wall, the results of the plastic concrete panels at runtime are somewhat different. Due to the sensitivity of the plastic concrete to the dispersion of the results, considering that the cutoff wall should have a seamless function as well as the sensitivity of the concrete over time, it seems necessary to address this issue in an operational project. The results indicate that the growth rate of elastic modulus in a period of time is less than the growth rate of the compressive strength, and in other words, the plasticity of the concrete is changed less over time.

Existing reinforced concrete (RC) columns may be structurally deficient due to variety of reasons such as improper transverse reinforcement, flaws in structural design, insufficient load carrying capacity, etc. Fiber reinforced polymer (FRP) is a new generation of materials which illustrates in order to enhance concrete compressive strength and ductility. Among the FRP types, Carbon fiber reinforced polymer (CFRP) is more common. CFRP can be effectively used for strengthening and confinement the deficient RC columns. This research conducts to evaluate the behavior of this fiber in improvement of aforementioned quantities. In this investigation, three categories of compressive strength of concrete were selected. The samples were warped with 0, 1, 3, and 5 layers of CFRP were subjected under stress-strain tests. The results display that carbon fiber is more effective in enhancing the compressive strength and ductility. Fiber performance is more effective on low-strength concretes, and its effective role decreases with increasing the number of layers.

For selecting the appropriate structural concrete prefabricated system, construction managers have to identify and extract the most important and most effective features. This paper addresses how the best system can be selected using Analytic Hierarchy Process (AHP) method. This method has been utilized for selecting the appropriate structural system among three pre-fabricated concrete construction system, including Large Panels, 3D Panels and Insulating Concrete Formwork (ICF). These systems considered to examine the importance of the criteria of efficient construction including cost and time, technical specifications and performance facilities. In this paper expert choice program has been used to approach the best system.The result of this study shows that the cost of production the pre-construction percentage, and the weight of elements and moreover the less need for heavy machinery and modularity of components have the maximum rank among the performance criteria. In addition, 3D Panel has been selected as the most appropriate structural system, and then ICF system and Large Panel have been selected as the second and third choice, respectively.