Conventional RC Research Articles

Determining potential passive islanding detection indicators for single-point single inverter, single-point multi-inverter and multi-point multi-inverter scenarios

Distributed Generation (DG) sources predominantly renewable energy-based like solar photovoltaic and wind energy sources are considerably penetrated in power system networks. This high penetration of DG sources may lead to the formation of unintentional islands which is hazardous to both the equipment and personnel, if sustained. In this paper, 46 passive parameters are considered to find out which candidate(s) are promising for detecting sustained unintentional islands and avoid false DG trips. These 46 parameters are derived from point of common coupling (PCC) voltage, DG output current, frequency, power factor angle, active and reactive powers. All these parameters are tested on standard IEEE 13 and 34 bus distribution networks integrated with inverter-interfaced DGs at different locations for different penetration levels in MATLAB/SIMULINK environment. The parameters are tested for different islanding events (comprising of various local loads such as conventional parallel RLC resonant load, R, RC, and RL loads) and for different non-islanding events. The parameters are then ranked accordingly by a suitable averaging approach based performance ranking technique. From this analysis, the best candidates are obtained for detecting inverter DG islands at single-point (or single PCC) location and multi-point (or multiple PCCs) locations. Multiple best passive candidates are obtained for different island scenarios from which a set of promising islanding detection indicators are proposed.

WITHDRAWN: An experimental and numerical investigation on flexural characteristics of wire mesh reinforced concrete beam blended with rice husk ash (RHA) and nano silica

The reinforced concrete beam is strengthened with an additional reinforcement namely Welded Wire Mesh (WWM) blended with RHA and Nano silica was investigated for its flexural behaviour. The flexural behaviour of modified beam provided with single and double layers of welded wire mesh was compared with the conventional RC beam. The paper also presents the benefits of using cement with rice husk ash with proportion of 20% in addition to 3% of Nano silica against the reference mixture of Portland cement (100%) i.e. partial replacement. The structural indicators namely first crack load, ultimate load, deflection at first crack load, deflection at ultimate load, crack pattern and ductility index were studied. The load deflection curve was further used to compare the structural characteristics. From experimental and numerical results concluded that, WWM2, WWM1 and WWM0 beam has high ultimate load comparatively 23%, 21.5% and 6.6% respectively higher than control beam and the crack found in the beam indicates that, beams has the capacity to carry higher bending stress with too lesser shear failure expect control beam. It is concluded that WWM2 beam has high ultimate load comparatively 23% higher than control beam and the crack found in the beam indicates that, WWM2 beam has the capacity to carry higher bending stress with too lesser shear failure.

Analogy of novel TRC crash barriers with RC crash barrier under impact load

The most popular crash barriers made so far are made up of steel-reinforced concrete (RC), which has high flexural rigidity but poor energy absorption. Consequently, when a vehicle collides with such crash barrier, the vehicle is seriously damaged and occupants may be fatally injured due to the severe impact of the collision. Hence, in order to enhance the safety of road users, a pre-fabricated textile-reinforced concrete (TRC) crash barrier prototype is developed using glass and basalt textile as reinforcement. The experimental investigations are carried out on both glass and basalt TRC crash barrier at the laboratory level under impact load to study the level of impact and deceleration rate. The performance of TRC crash barriers are also compared with RC crash barriers of equivalent calibrated reinforcement ratio. The lesser impact force and the lower rate of deceleration and higher energy absorption characteristics were experienced during the impact test for TRC crash barriers when compared to that of conventional RC barrier. Present study indicates that the application of TRC in crash barriers can improve the safety of the occupants and reduces damages to the impacting vehicles.

Structural Performance of PC Double Beam\u2013Column Connection Under Gravity and Seismic Loading

Recently, as a new precast concrete (PC) construction method for increasing economy and constructability, the PC double-beam system has been developed for factories or logistic centers, where construction duration is particularly important. In this study, half-scaled PC double beam–column connection was tested under gravity loading and cyclic lateral loading. The major test parameters included the use of the spliced PC column and the addition of reinforcement at the beam–column joint. In the gravity loading test, the flexural behavior of the PC double beam was investigated. The test results showed satisfactory flexural capacity at the PC double-beam section, validating the composite action between the PC and RC members. In the cyclic lateral loading test, the seismic performance of the PC double beam–column connection was investigated. Based on the test results, the failure mode, load-carrying capacity, deformation capacity, energy dissipation capacity, secant stiffness, and shear strength of the PC double-beam system were evaluated and compared with those of a conventional RC double beam–column connection. According to the test results, the structural performance of the PC double beam–column connection was comparable to that of the RC double beam–column connection and satisfied the acceptance criteria of moment frame in the ACI 374.1-05 provision.

Cyclic behaviour of precast reinforced concrete sandwich slender walls

Experimental investigation on the performance of full scale precast RC sandwich slender walls under reversed cyclic loading is reported. Eight full scale precast 3D sandwich slender walls, with two different aspect ratios of 3.0 and 2.63, under in-plane lateral loading were tested. Four of them were designed with end stiffners, while the remaining were without stiffners. In each of four stiffened and four unstiffened walls, only two were provided with additional longitudinal reinforcement, consisting of 12 mm diameter HYSD steel rebars at 300 mm c/c spacing along on two vertical faces. All the sandwich walls were subjected to constant axial load in addition to the lateral incremental monotonic and cyclic loading using displacement control system. The performance of precast sandwich slender walls using lateral load vs. lateral displacement, pattern of cracking, displacement ductility, stiffness degradation and energy dissipation has been evaluated. The experimental results have been validated with the predicted lateral strength predicted by various codes of practice. The additional longitudinal reinforcement and end stiffeners significantly improved the lateral strength, cracking resistance, stiffness, ductility, and energy dissipation of the precast sandwich slender walls under lateral cyclic loading. The precast sandwich slender walls designed with additional longitudinal reinforcement and end stiffeners exhibited marginal improvement in the stiffness under lateral loading. The energy dissipation in the precast sandwich walls decreases in subsequent cycles of lateral displacements. The seismic base shear capacity of the precast sandwich slender walls seems to be better and comparable with the conventional RC walls.

A novel harmonic impedance compensator based on POHMR-type RC under gird voltage distortion

The LCL-type grid-connected inverter can suppress high-frequency current harmonics but the inject grid current of the inverter will be worse under grid voltage distortion, therefore harmonic impedance compensation technology is required for this condition. The proportional Multi Resonant (PMR) controller is a feasible method for this purpose, but this scheme needs a large calculation burden and complex design. To overcome these drawbacks, a novel Proportional Odd harmonic Multi Resonant-type Repetitive Controller (POHMR-type RC) is proposed to compensate for the harmonic impedance, which means the grid voltage distortion hardly influence injected grid current. Compared to the PMR controller, the proposed scheme omits the even harmonic resonant controllers and has much more odd harmonic resonant controllers, which also reduces the memory space consumption, calculation burden and controller complexity. The proposed scheme also has better dynamic performance than conventional RC. When the proposed scheme is proposed, the inject grid current is still sinusoidal under strong grid voltage distortion and the transient response is desired. Experimental results verify the feasibility of the POHMR-type RC.

Life-cycle seismic resilience assessment of highway bridges with fiber-reinforced concrete piers in the corrosive environment

The benefit of fiber-reinforced concrete (FRC) to the life-cycle seismic performance of the bridge has not yet been fully studied. A probabilistic methodology was proposed in this study for the life-cycle performance assessment of deteriorating bridges constructed with FRC piers. The effect of the corrosive environment on the seismic performance of FRC bridges was evaluated under uncertainty through the seismic resilience analysis. The time-variant seismic capacity from different limit states was employed to estimate the functionality loss before the occurrence of the seismic event in order to improve the estimate of seismic resilience. A method was proposed to improve the accuracy of Cloud Analysis for the seismic fragility analysis, which was validated by the results of Incremental Dynamic Analysis (IDA). Seismic fragility analysis was then conducted by the improved Cloud Analysis based on numerical finite element models for simulating the behavior of FRC to obtain the reliable fragility estimates. The whole methodology in this paper was illustrated using a two-span highway bridge with conventional RC and FRC piers considering both diffusion process and seismic hazards. It can be concluded from the results that the FRC can improve the life-cycle seismic performance and resilience of highway bridges by around 25%. The performance benefit from the FRC can be underestimated if not considering the life-cycle effect. The improved Cloud Analysis is proved to be efficient and reliable in the seismic fragility analysis of bridges.

Performance of concrete beams reinforced with GFRP bars under monotonic loading

The use of GFRP bars in concrete structures has emerged as an alternative to conventional RC due to the corrosion of steel in aggressive environments. Although many studies were reported on concrete beams reinforced with GFRP bars, still the full potentiality of GFRP reinforced concrete is yet to be known. This study reports experimental, analytical and numerical investigations carried out on concrete beams reinforced with TMT and GFRP bars under monotonic loading. Experimental studies were carried out on concrete beams of size 100 × 200 × 1500 mm reinforced with TMT (10 mm and 12 mm dia.) and GFRP bars (10 mm and 13 mm dia.). The deflection of GFRP reinforced concrete beams corresponding to service load is found to be 2.75 times the deflection of TMT reinforced concrete beams. Widely used analytical/empirical models were compiled to predict the load deflection behaviour of beams. The analytical models were primarily based on effective moment of inertia to account for beams stiffness after cracking. Nonlinear finite element (FE) analysis has been carried out on concrete beams reinforced with TMT and GFRP bars. FE models were developed by employing the appropriate constitutive relationship of concrete, TMT and GFRP bars. The integrity of all the elements has been ensured by applying the appropriate constraint conditions. Average load–deflection plots obtained from experiments were compared with computed load–deflection of analytical and numerical studies. From the load–deflection behaviour, it is observed that (i) numerical prediction is stiffer and (ii) the analytical models incorporated with tension stiffening aspects predicted the deflections close to experimental observations.

Seismic performance of a novel self-sustaining beam-column connection for precast concrete moment-resisting frames

In this paper, a novel prefabricated reinforced concrete (PC) self-sustaining beam-column connection for moment-resisting frames was developed to achieve the targets of short erection time, high construction efficiency, low-cost and satisfactory seismic performance. The connection design eliminates the need of temporary supports for the PC beams and slabs during the assembly process in site, and reduces the amount of lateral supports for PC multi-storey columns and formwork for cast-in-place concrete. As the designed thickness of PC U-shells at the beam ends was about 1/3 of the beam width, there could be a marked effect on the achieved integrity of such connections, especially under seismic loading. To investigate the seismic performance of this PC connection, five large-scale PC self-sustaining beam-column connections specimens and one reference conventional RC connection were designed and tested under reverse cyclic loading. The test parameters included the length and area of the flexural reinforcing bars placed at the bottom of PC U-shells, and the anchorage measures (stirrups) inside the PC U-shell. The five precast specimens exhibited similar crack distributions and failure patterns due to the gap-opening between the PC beams and column surface, which was attributed to the reduced effective width and depth of beam cross-section. The test results showed that the use of longer flexural reinforcing bars had little influence on the load-carrying capacity, but contributed to the initial stiffness and energy dissipation capacity. The load-carrying capacity increased by 24% when the area of flexural reinforcing bars increased by 50% in the U-shell region. The incorporation of stirrups in the overlapping region of beam flexural reinforcing bars and longitudinal rebars improved their bond-slip behaviour in specimen PC-S. Compared with specimen PC-C, the energy dissipation capacity of specimen PC-S was improved by 16.5%. Finally, the failure pattern and load-carrying capacity of the PC specimens were analysed and discussed using a simplified mechanical model.

Response of low-percentage FRC slabs under impact loading: Experimental, numerical, and soft computing methods

Application of fiber reinforced concrete (FRC) has been increased in the past decade due to its enhanced structural performance. Therefore, it is important to fully characterize its static and dynamic behavior under different loading scenarios. In this paper, the effects of low-percentage steel fibers with four different fiber volume is investigated on the dynamic responses of concrete slabs. First, a series of experimental tests are conducted. Next, the results are used to validate a nonlinear finite element model under impact loading. Finally, a large dataset of numerical simulations are developed using appropriate design of experiments, and four soft computing techniques are used to predict the target responses.The findings show that application of low-percentages fiber increases the acceleration response of the concrete slabs subjected to impact load, on the average of 102%. The slab’s stiffness increases with an increase in fiber percentage. The dominant frequency, the damping ratio, as well as the slab’s cracking pattern, and the failure modes indicate that FRC slabs are stiffer than conventional RC specimen. The numerical simulations reasonably estimate the maximum acceleration. Outcome of the predictive meta-models can be used to estimate the dynamic behavior of similar slabs with no additional experimental and numerical costs.

Comparison of various shear connectors for improved structural performance in CFS concrete composite slabs

Composite sections comprising of wisely selected materials has gained popularity in the construction industry, as it may result in utilizing the advantages of two different materials thus resulting in efficient sections, which will not only reduce the dead loads but also provide economical solutions. Cold-formed steel (CFS) concrete composites have been used extensively in building construction, as the inherent weakness of local buckling in the CFS sections under compressive loading is taken care of by the concrete, which has significant compressive strength. This study presents an experimental investigation performed on full-scale simply supported CFS concrete composite slabs under four-point monotonic loading, with an aim to evaluate the effectiveness of the different shear connectors being adopted. The shear connectors were so adopted that they could provide the least possible interaction (for representing the no-interaction condition), partial-interaction and full-interaction between the steel deck sheet and the concrete slab. The performance of the various shear connectors was assessed in terms of strength, stiffness and ductility ratio. Cracking as well as end slippage were also studied. The test results were compared with a conventional RC slab, in terms of structural performance as well as cost and strength-to-weight ratio. The flexural test strengths were compared with the design strength quantified using the Euro Code. The degree of shear interaction was also investigated. It was found that the CFS concrete composite slabs not only performed better structurally but economically as well, in addition to providing significant strength-to-weight ratio, when compared to a conventional RC slab.

The Behavior of Flat Slab and Conventional RC Slab for Multi-Storey Buildings with Passive Energy Dissipating Devices Situated in High Seismic Zone.

The disaster safe construction practice for an engineer is a most difficult job. Today we have witnessed these natural disasters at its peak. Even after all highly skilled techniques used for constructions these natural disasters-like floods, earthquake, landslides etc.… are not negotiable. However, we are learning lessons from these disasters and upgrading ourselves so that a resistant structure is constructed. Among these disasters, the less predictable the less comprehended and highly disastrous is an earthquake. Even after the development of technology this disaster is highly unpredictable. Conventional attempts to make a building earthquake resistance which do not collapse under strong seismic forces has proved to be satisfactory but these techniques will cause a damage to non-structural components such as glass, window, door etc.… (OR) even some times the failure of structural components which leads to non-functionality of a building, but it should be noted that building like corporate offices, call centers, hospitals etc.… must remain functional even after the earthquake. Hence special techniques are required to design the buildings to overcome above problem. Passive energy dissipating devices is the technique used to dissipate the energy incorporated in the building due to an earthquake.

Estimation and development of innovative hybrid coupled shear wall system using nonlinear dynamic and fragility analysis

The Innovative hybrid coupled shear wall system (HCW) is one of the most advanced economical structural systems which has already been conducted. It constitutes of RC shear wall connected to two side steel columns by mean of replaceable coupling steel links. The main design objective of this system is to withstand lateral loads with minimized or even no damage of non-replaceable components (i.e. RC wall and steel columns), while the replaceable coupling steel links could undergo severe damage. This system still highly lacks investigations and detailed estimation as well as being of low efficiency in low-rise buildings. In this research, the emphasis is upon the estimation of the most efficient current HCW systems which have been recommended in literature so far, to be thoroughly calibrated against equivalent conventional RC wall system. Furthermore, new recommendations are presented in intention of optimizing the performance of HCW system to efficiently achieve the design objective through multi-type modifications: links arrangement, internal wall structure and combined systems. The study implements an advanced modelling procedure and extensive nonlinear dynamic analyses with fragility assessment to obtain a highly reliable evaluation. The newly proposed methods reveal excellent efficiency, especially in low-rise buildings.

Response of innovative high strength reinforced concrete encased-composite corbels

This work is devoted to discuss experimentally the behavior of high strength reinforced concrete (R.C.) encased corbels using the available commercial W-shape rolled steel. Eight specimens are tested and two shear slenderness ratio are considered, namely 0.70 and 1.00. The tested specimens are categorized in two groups according to (a/d) ratio. Each group included one conventional RC corbel and three composite corbels. Three configurations of composition are discussed, W-shape, WT shape and Tapered WT shape. Besides, two steel corbels have been tested, one W-shape while the other was WT-shape to get more understanding about the failure of composite corbels. The comparison between specimens is based on load-deflection curves, ductility, toughness, failure load, pattern of cracking propagation, failure mode and history of crack width development.Results revealed that the low properties commercial rolled steel can be used in composite corbels and such corbels could be adopted as a convenient alternative to the conventional RRC. In addition, it was found that the tested composite corbels yielded better behavior than the conventional ones, the composite corbels yielded toughness ranged from 120% to 170% from that of the RC conventional corbels with similar capacity for those composed using full W-shape with opening in webs. More ductile behavior is observed for corbels especially when shear force is dominant and low a/d ratio is adopted. Furthermore, Its found that that increasing a/d ratio from 0.7 to 1.0 for the control specimens, composite W-shaped and Tee-shaped encased beam result in reduction of capacity by 29%, 27% and 21%. Respectively. Moreover, a simple equation is suggested to estimate the composite corbels based on toughness and failure loads.

Seismic design of three damage-resistant reinforced concrete shear walls detailed with self-centering reinforcement

Recent studies have shown that the innovative shear walls detailed with a type of self-centering reinforcement and fiber reinforced concrete are effective in reducing the permanent displacement and concrete damage compared to conventional concrete (RC) shear walls. However, more investigation is required into the seismic design parameters, such as the inelastic rotational capacity and plastic hinge length of innovative shear walls. This paper investigates the response of three innovative walls cast with fiber-reinforced composites and reinforced with steel rebars and a type of self-centering reinforcement consisting of shape memory alloy (SMA) bars, glass fiber reinforced polymer (GFRP) bars, or high-strength steel strands. The response of each innovative wall is compared to that of a conventional RC shear wall called the control wall. Then, the inelastic rotational capacity, plastic hinge length, and self-centering of the innovative walls are discussed within the framework of the seismic design codes of North America.It is shown that innovative walls can undergo significant inelastic rotational deformations due to the use of ductile reinforcements in their boundary elements – SMA bars in the boundaries of steel-SMA reinforced wall and steel rebars in the steel-GFRP and the partially post-tensioned walls. The reinforcement with lower tensile strain capacities, such as PT strands and GFRP bars, were placed away from the boundaries of the steel-GFRP and the partially post-tensioned walls. It is also shown that the crack opening at the base of each innovative wall was greater in comparison to that of the control wall. This was due to the use of fiber-reinforced composites and self-centering reinforcements with low bonding stresses in the walls, which increased the rocking in the response of the innovative walls. It is shown that the plastic hinge in the steel-GFRP reinforced and post-tensioned walls was shorter than in the control wall since plastic strains were more concentration in steel rebars adjacent to the bases of the walls. In the steel-SMA reinforced wall, the plastic hinge length was longer than in the control wall due to the low bonding properties of the SMA bars compared to the control wall. The self-centering capacity of the innovative walls at different seismic performance levels is also discussed, and three improved self-centering objectives for the design of innovative walls are introduced.

Seismic Behaviour of Flat Slabs in High Rise Building

In the modern era, the growth of population has influenced the construction of high rise buildings day by day. The construction of the building structures with conventional RC slabs are in the public eye since many decades. Although it has more stiffness and minimizes the large moments occurred due to the applied loads, it does not have the advantages in terms of architectural flexibility, easier formwork and shorter construction period compared to the flat slabs. This developing technique of flat slabs construction improves aesthetical and structural aspect of tall building, offices, hospitals, shopping malls etc. As this is considered to be beamless slab, it has less shear strength and less stiffness compared to the conventional slabs. Due to its huge advantages, it is common in both the construction of regular and irregular buildings nowadays. From Structural engineer’s point of view, the flat slabs should be adopted with other structural component like shear walls and bracings for better results. The main motive of the present work is to compare and observe the seismic behaviour of regular and different configuration of irregular building in zone V by using different types of flat slabs. The considered G+13 storied buildings were analyzed with flat plate, drop panel, column head and combination of column head & drop panel by using E-tabs 17.0.1 software. The nonlinear time history method was carried out to observe the different parameters like storey displacement, storey drift, storey shear, base shear and time period following the guidelines of IS 1893 (Part 1): 2016

A closed loop inductorless equalizer with a modified analysis of power comparator behaviour

SummaryInductorless circuits are gaining advantage in radio frequency (RF) and high‐speed serial link circuits due to the reduced silicon area. This paper presents an inductorless adaptive analog equalizer using an adaptive hybrid filter comprising integrated low pass and high pass filter. The equalizer, designed and fabricated in 180‐nm CMOS technology, is able to adjust the high‐frequency boost (HFB) and cutoff frequency of the internal filters depending on the data rate and the channel loss. The presented equalizer operates at data rates more than 4 Gbps in post‐layout simulation without electrostatic discharge (ESD) and package parasitics. For the test purposes, the equalizer has been packaged in QFN 64 pin package and hence the measurement results are up to 3.125 Gbps. The measurement results show that the equalizer is able to adapt the HFB for the channel losses as high as 5 dB. Average dissipated power of the equalizer at 3.125 Gbps is 18 mW with 1.8‐V supply. After reading this chapter you should be able to understand the merits of the proposed hybrid filter compared with the conventional RC filters in the adaptive equalizer using spectrum balancing technique; theoretical analysis and the impact of short channel effects on the performance of the power comparator; and test results of the adaptive equalizer using the proposed hybrid filter in the spectrum balancing technique.

New rocking column with control of negative stiffness displacement range and its application to RC frames

This paper investigates the use of rocking columns with central steel bars in RC building frames. Motivated by the adverse effects of conventional steel bars anchored at both ends, a new rocking column is proposed that allows the slippage of the steel bar at the bottom end within a controlled range of displacements (gap). A numerical model of the new rocking column is developed and implemented in Opensees. A parametric study is conducted to investigate the overall response of several RC frames featuring the proposed rocking columns in the first story. It was found that the response is controlled by (i) the maximum restoring force provided by the rocking columns, (ii) the lateral strength provided by the dampers, and (iii) the dimensions of the gap. In comparison with conventional RC frames, the proposed solution reduces the maximum inter-story drifts in the upper stories by about 3 times, the story accelerations about 1.5 times and the energy dissipation demand about 20 times. The results of this research are expected to enhance the use of rocking columns for seismic isolation of RC frame structures, through a new solution that takes full advantage of the negative stiffness and prevents collapse.

Analysis of composite hollow RC beam strengthened with mild steel sections

The Advancements in Construction in terms of aesthetics and appeal has led to a need of creating spaces with more compact and convenient designs. There is a hierarchy of load transfer for a building. The changes in weight of any preceding member will change the dimensions of succeeding members in the hierarchy. The reduction in the self-weight of beam due to introduction of a hollow section changes the flexural behaviour and the shear behaviour of the beam and also makes it economical section. There is also the advantage of reduction in the depth of beam giving more floor space to user. This paper focuses on Comparative study of Conventional beam and RC beam strengthened with Mild Steel Pipe Section/Mild Steel Box Section. The Composite Section is obtained by embedding Reinforced Concrete beam with MS Pipe/Box Section in Longitudinal Direction. Load – deflection behaviour of conventional beam and RC beam with MS hollow sections are modelled in ABAQUS Software and their performance studies are conducted with stiffness as parameter. The Hollow RC beam strengthened with MS pipe Section showed more stiffness than the MS box section and conventional beam for 1P, 2P and UD loadings making it the most economical section.

A Design Method of High Order Repetitive Controllers

It turns out that higher-order RC is useful for improving the robustness of the entire control system, and its importance is only increasing. In this paper, we propose a new high-order RC design method. The proposed high-order RC design method includes more design parameters than the same order conventional high-order RC, which increases design flexibility. Further improvement of robustness can be expected. It will also prove useful for improving time response. Further, it is possible to suppress a disturbance having a frequency different from the frequency of the target periodic signal. This is not possible with conventional high-order RC.