Net Section Fracture Assessment of Welded Rectangular Hollow Structural Sections

Rectangular Hollow Sections (RHS) because of their high resistance to tension, as well as compression, are commonly used as a bracing member with slotted gusset plate connections in steel structures. Since in this type of connection only part of the section contributes in transferring the tensile load to the gusset plate, shear lag failure may occur in the connection. The AISC specification decreases the effective section net area by a factor to consider the effect of shear lag for a limited connection configuration. This study investigates the effective parameters on the shear lag phenomenon for rectangular hollow section members connected at corners using a single concentric gusset plate. The results of the numerical analysis show that the connection length and connection eccentricity are the only effective parameters in the shear lag, and the effect of gusset plate thickness is negligible because of the symmetric connection. The ultimate tensile capacity of the suggested connection in this study were compared to the typical RHS connection presented in the AISC and the similar double angle sections connected at both legs. The comparison indicates that tensile performance of the suggested connection in this study because of its lower connection eccentricity is much higher than the typical slotted connection and double angle connections. Therefore, a new equation is suggested based on the finite element analyses to modify the AISC equation for these connections

Comparative detection and fault location in underground cables using Fourier and modal transforms

In this research, we create a single-phase to ground synthetic fault by the simulation of a three-phase cable system and identify the location using mathematical techniques of Fourier and modal transforms. Current and voltage signals are measured and analyzed for fault location by the reflection of the waves between the measured point and the fault location. By simulating the network and line modeling using alternative transient programs (ATP) and MATLAB software, two single-phase to ground faults are generated at different points of the line at times of 0.3 and 0.305 s. First, the fault waveforms are displayed in the ATP software, and then this waveform is transmitted to MATLAB and presented along with its phasor view over time. In addition to the waveforms, the detection and fault location indicators are presented in different states of fault. Fault resistances of 1, 100, and 1,000 ohms are considered for fault creation and modeling with low arch strength. The results show that the proposed method has an average fault of less than 0.25% to determine the fault location, which is perfectly correct. It is varied due to changing the conditions of time, resistance, location, and type of error but does not exceed the above value

Synthesis, microstructure, magnetic and electromagnetic behavior of graphene oxide/hexagonal barium ferrite aerogel nanocomposites within the frequency range of 1–18 GHz

The fabrication of lightweight graphene oxide aerogel (GOA) composites with barium ferrite (BF) nanoparticles is investigated in this study as a method of shielding electronic and telecommunication equipment from electromagnetic radiation. The effects of various weight percentages of barium ferrite nanoparticles on the microstructure, phase, magnetic characteristics, and wave absorption were investigated. The XRD, FTIR, Raman spectroscopy, X-ray Photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), FESEM, and vibrational magnetometry (VSM) and the vector network analyzer (VNA) were used to characterize the sample.Results show that barium ferrite nanoparticles had a saturation magnetization of 42.94 emu/g, whereas graphene oxide aerogel composite containing 67 wt% of barium ferrite nanoparticles had a saturation magnetization of 29 emu/g. The Coercivity of the composite rose when the amount of barium ferrite nanoparticles was reduced. Within the matched frequency of 12.1 GHz and an effective absorption bandwidth (RL < −10 dB) of 2.6 GHz, the graphene aerogel nanocomposite sample with a thickness of 4 mm and 40 wt% of barium ferrite nanoparticles had the highest level of reflection loss (−43 dB)