Most design codes evaluate the non-linear seismic performance of structures using the response reduction/modification factor (R). The value of R is sensitive to a variety of factors in terms of overall ductility and over-strength. In this work, actual R values were assessed for vertical irregularity cases for reinforced concrete bare buildings with moment-resisting frames (MRFs). A significant relationship between R and the vertical irregularity index, calculated from the relative stiffness between adjacent storeys, was derived. Three-dimensional numerical modelling was carried out for soft storey and setback irregularity scenarios using Etabs. Modal pushover analysis was used to obtain the inelastic seismic capacity. It was found that vertically irregular buildings have weak inelastic seismic capacities compared with regular buildings. So, before the design stage, R should be scaled down by 15–40% for single and combined vertical irregularity scenarios. Structures with a combined asymmetric setback with a soft ground storey were found to have the worst R value and R was sensitive to the vertical irregularity index (Vtm) that has R-squared of 80%. So, the vertical irregularity index can be used to specify the allowable vertical irregularity ratio, location and combination of vertical irregularities for each seismic zone. 

Keywords: concrete structures/ductility/dynamics/earthquake/modal non-linear pushover analysis/modification factor (R)/over-strength/response reduction/seismic engineering/structural analysis/vertical geometric irregularity

Structural damage identification has recently become one of the most important topics for engineering structures due to its benefits in enhancing safety, reducing life-cycle cost, and providing guidance for system construction and maintenance. This research studies the accuracy of using displacement influence lines (DIL) and their derivatives (first and second derivative) for detecting structural damage characteristics (location and severity). The study includes analytical and numerical studies to investigate the sensitivity of displacement influence lines and their derivatives (first and second derivative) as a main parameter for damage identification. The results illustrate that the method can locate and quantify damage in both simply supported and continuous beams without the need for an optimization algorithm. Although, for simply supported beam, the optimal location of the displacement measurement point is at the middle of span. While, for continuous beam, one displacement sensor at the middle of each span enables locating the damages reliably. The advantages and disadvantages of using this index are also discussed.

Glass fiber-reinforced polymer (GFRP) bars have emerged as an attractive economic reinforcement due to their corrosion performance in aggressive environmental conditions. The current study aims to investigate the creep rupture strength of GFRP bars exposed to high alkaline water-saturated concrete (pH > 13.0) at an elevated temperature of 60 ℃ under high sustained loads. The test involves a new generation of GFRP bars, including three different products produced by two different manufacturers, while two products were fabricated with different types of resin chemicals. Three sustained load levels were implemented in the study, corresponding to 83%, 80%, and 75% of the guaranteed tensile strength (GTS). Five GFRP bars were tested at each load level. Creep rupture testing in the current study was achieved using an innovative loading frame, which maintained the required sustained load values on the bars. The strain evaluation of each bar was recorded using a data acquisition system, which enabled recording the accurate time to failure of the tested bars. The 100-year creep rupture endurance time was then calculated using the obtained results. The results show that the recommended stress limit under sustained load by the ACI 440.11 and AASHTO is conservative. Additionally, the stress limit stipulated by the current Eurocode 2 draft to account for the long-term tensile strength, the influence of temperature, service life, and environmental attack is significantly over-conservative and leads to uneconomical design.

The design of glass fiber-reinforced polymer (GFRP) reinforced concrete (RC) members is often governed by the crack width and deflection serviceability limits due to the low elastic modulus of GFRP material compared to steel. The available formulations in the current standards and guidelines control the crack widths of the GFRP-RC elements by considering the bond interaction between the GFRP reinforcement and surrounding concrete through bond-dependent coefficient, k_b. This study investigates the effect of different parameters, including the concrete compressive strength, clear concrete cover to GFRP reinforcement, and the number of GFRP reinforcement layers on the moment capacity, cracking progression, deflection behavior, and the variation of k_b values at different crack widths. The study involves experimentally testing 11 full-scale GFRP-RC beams. Moreover, a numerical parametric model was developed to investigate the effect of varying the concrete strength on the deflection performance of the GFRP-RC beams. The experimental results provided insights into how the investigated parameters impact the crack width and deflection values at the service stage. Moreover, the numerical model simulated the experimental behavior of the beams with high accuracy. It was also found that the ACI 440.1R-15 deflection formulation underestimates the deflection values at the service stage, particularly at high concrete strengths.

A control approach for aircraft Starter/Generator (S/G) with Permanent Magnet Machine (PMM) operating in Flux Weakening (FW) mode is presented. The proposed strategy helps the previous approaches which are adopted for the Variable Voltage Bus (VVB) or Voltage Wild Bus (VWB) concept for an aircraft Electric Power System (EPS), to cover a wide speed range in motoring and generation modes. Compared to prior works, the proposed control approach adjusts the q-axis reference voltage with a single current regulator, and the maximum available voltage provided by the converter is used to evaluate the d-axis voltage. By adopting the proposed approach, the DC bus voltage can be fully utilized, increasing aircraft efficiency by allowing the S/G system to operate at a wide range of speeds. The results of the analytical design and the performance of the system were verified by time-domain simulations using MATLAB/Simulink and experiments and compared to the conventional method.

This paper deals with innovative multi-function battery controller with seamless transition between controllers for future MEA platforms. The battery controller performs different functions i.e. providing DC power, maintaining DC bus voltage, controlling battery voltage and battery current for charging and discharging process purposes. Due to its superiority and simplicity of implementation, the constant current-constant voltage technique is chosen for battery charging. Furthermore, the study provides a detailed analysis of the proposed approach and control challenges then proposes the corresponding solutions. The PI controller is adopted for all controllers and it was designed to provide a robust control system behaviour. Therefore, the battery terminal voltage and charging current are efficiently limited by the corresponding battery controllers. A robust Energy Management Strategy (EMS) to supervise the charging and

this paper proposes a control scheme for permanent magnet machine (PMM) based aircraft starter/generator (S/G) operated in flux weakening (FW) mode. In contrast to previous publications, the proposed control scheme uses a single current regulator to adjust the q-axis reference voltage, and the d- axis voltage is calculated considering the maximum available voltage from the converter. This allows the full utilization of DC bus voltage and improves the machine efficiency. Furthermore, it is more robust against with regards to machine parameters variation. The analytical design results and the system performance are confirmed by time domain simulation and compared against traditional approach.

Most of the existing methods used to estimate the cable resistance require the use of many hardware devices and the injection of perturbations to the system. Therefore, they are time-consuming, costly and prone to errors. In addition, the injection of perturbations has the potential of degrading the power quality of the system. In this paper, a new artificial neural network (ANN) aided cable resistance estimation approach is proposed. The ANN model is trained by simulation data. The trained ANN model can quickly and effectively map the current sharing ratios between the converters to the droop coefficients of the converters. In this way, the optimal droop coefficient combination that will yield the desired accurate current sharing ratio between the converters can be predicted by the trained ANN model. Subsequently, the optimal droop coefficient combination can be used in the estimation of the corresponding subsystem