Experimental study on flexural strengthening of reinforced concrete beams with U-shaped steel under secondary load

This study proposes a new method to strengthen reinforced concrete (RC) beams with U-shaped steel, which can achieve rapid construction and great improvement in the flexural performance of RC beams. To investigate the influence of secondary load defined as newly applied loads after strengthening on the strengthening effect, a total of nine specimens were tested under four-point bending, including a reference beam, a strengthened beam under initial load, and seven strengthened beams under secondary load. The initial loading degree, the thickness of the bottom plate, and the height of the steel box were the main variables considered in this study. Testing results showed that compared with the reference beam, the flexural performance of strengthened beams was significantly enhanced, indicating the good joint performance of the U-shaped steel and the RC beams. Among the three main variables, the initial loading degree was found to have a minimal effect on the flexural performance while the thickness of the bottom plate and the height of the steel box had considerable influence, with the latter having a more pronounced effect. Testing results also showed that most of the strengthened beams experienced flexural failures, which were reflected by steel web peeling and buckling, and concrete crushing. Moreover, a formula was derived for calculating the flexural capacity of strengthened beams under secondary load. The results from the derived formula were found to be in good agreement with those from experiments.

Concept Designing of a Solar Photovoltaic UPS System with Sunlight Tracker

This paper defines the design of UPS system with the help of sun tracking system, as a source for chargingthe battery to provide the backup power when the regular power source fails. This authentication is provided by obtaining the theoretical calculation of output power, output current and output voltage which are developed due to solar radiations. In this system, if the primary load is not in use, then the power is automatically switching over to secondary load. Basically, an UPS is electrical equipment that is used at the time of emergency. The battery bank is charged with the help of solar photovoltaic cell. This paper proposed an approach to understand the peak power point of the sun based on analysis of the open-circuit voltage of the PV panel. This project provides the power supply to a load which is uninterruptible, by automatically selecting the supply from the main source or inverter.

Study on the flexural performance of RC beams anchored with CFRP plates under secondary load

In order to explore the influence of length and width of CFRP as well as anchor spacing on the reinforcement effectiveness of CFRP plates on reinforcement concrete beams (RC beams) under secondary load, 7 anchored damaged FRP reinforced concrete beams are used as test beams, 1 unanchored beam is used as a control beam, and structural indicators such as ultimate load and bending strength are analyzed in the result. The conclusion is that composite CFRP plate can effectively prevent the early peeling and failure of carbon plates and improve the ultimate bearing capacity of the beam. When the width of the CFRP plate decreases, the thickness increases and the steel plate anchor spacing increases appropriately, the ultimate bearing capacity and ductility of the beam are significantly improved.

Multidimensional load-bearing behaviour of timber-concrete composite road bridges with consideration of flexibility of connections

<p>Timber-concrete-composite structures for road bridges could be much more often used in the field of medium-span road bridges due to their good ecological and structural performance. Therefore, an appropriate consideration of the punctual connections usually used for such bridges is necessary. Those connectors have a large load-bearing capacity and stiffness. While there are established methods for determining the stiffness and load-bearing capacity in the main longitudinal load- bearing direction, the secondary load-bearing behaviour in transverse and vertical direction is usually not determined for those bridges. By assessing test results and evaluation of FE simulations, this article presents an approach of how a calculation method can be derived that makes the structural design of timber-concrete-composite bridges safely even in more demanding application scenarios.</p>

Experimental Study on the Mechanics Characteristics of CFRP Strengthening of Highway Tunnels at Different Damage States

Cracks and other diseases may occur in the long-term operation of highway tunnels and reduce the structural load-carrying capacity. Strengthening using carbon fiber reinforced polymer (CFRP) sheets and other materials could extend the service time of the tunnels. However, the process of strengthening tunnels is remarkably different from the process of strengthening aboveground structures because of the secondary load. In order to understand the development of stress and deformation of strengthened tunnels under secondary load, a 1 : 10 scaled model was tested to simulate the tunnel strengthened with CFRP under different damage states. The test results show that CFRP strengthening improved the stiffness of the structure and inhibited the propagation of the existing cracks. The peeling of the CFRP sheets made the strengthened structure quickly lose its load-carrying capacity, causing the instability of the structure. The failure loads of the structures strengthened at different damage states were essentially the same, with an average value of 184% of the original failure load. Nevertheless, the early strengthening helped control the structural deformation. The test results also demonstrate that the bonding strength between the CFRP and the lining is essential for strengthening effectiveness. This study provides a theoretical basis for similar engineering reinforcement designs.

Research on Hierarchical Control Strategy of AC/DC Hybrid Microgrid Based on Power Coordination Control

The AC/DC hybrid microgrid has a large-scale and complex control process. It is of great significance and value to design a reasonable power coordination control strategy to maintain the power balance of the system. Based on hierarchical control, this paper designs a reasonable power coordination control strategy for AC/DC hybrid microgrid. For lower control, this paper designs a variety of control modes for each converter in different application scenarios. For the higher control, this paper analyzes the working mode of the system and designs the power coordination control strategy under the grid-connected and isolated island mode. In grid-connected operation, the DC bus voltage can be stabilized by adjusting the operation mode of the DC energy storage and the on-off of the secondary load. In isolated island operation, the DC sub-microgrid is the main microgrid, and the DC energy storage is the main power regulating equipment. This is based on the principle of “energy is in short supply in the system, DC energy storage finally discharge, energy supply exceeds demand in the system, DC energy storage gives priority to charging” of DC energy storage. By adjusting the control strategy of the micro-source, the reference power, and the on-off of the secondary load, the overall power balance is maintained. The Matlab/Simulink simulation software was used to build the AC/DC hybrid microgrid simulation model, which verified the effectiveness and stability of the proposed power coordination control strategy under various operating conditions.