•An overview on dynamic properties of rubberised concrete and structural applications.•Rubber particles improve concrete material performance under impact and blast loads.•Rubberised concrete ...improves structural performance under cyclic and seismic loads.
Rubberised concrete is an eco-friendly material with reasonable mechanical strengths for potential civil engineering applications. Recent research has proved that rubberised concrete has superior properties at high strain rates such as dynamic compressive strength, dynamic splitting tensile strength, dynamic flexural strength, impact and collision resistance, repeated and reversed cyclic loads, and seismic loads. This paper presents in depth classification and summary of over ninety published articles on rubberised concrete dynamic properties and its structural applications where the dynamic properties are dominant and high strength of concrete is not necessary. The results show that structural applications such as reinforced concrete slabs, columns, beams, and walls with rubberised concrete exhibit better performance under high velocity impact and collision, bullet resistance, and blast loads compared with traditional concrete. In addition, rubberised concrete has high sensitivity to strain loading rates, high energy dissipation and ductile performance under dynamic loads compared to traditional concrete. A significant improvement in the behaviour of structural members under cyclic and seismic loads, including ductility, energy dissipation, stiffness degradation was observed. On the other hand, the reduction in load carrying capacity is significantly smaller than the reduction in the concrete strength of rubberised concrete compared with traditional concrete.
This paper develops a state-queueing model to analyze the price response of aggregated loads consisting of thermostatically controlled appliances (TCAs). Assuming a perfectly diversified load before ...the price response, we show that TCA setpoint changes in response to the market price will result in a redistribution of TCAs in on/off states and therefore change the probabilities for a unit to reside in each state. A randomly distributed load can be partially synchronized and the aggregated diversity lost. The loss of the load diversity can then create unexpected dynamics in the aggregated load profile. Raising issues such as restoring load diversity and damping the peak loads are also addressed in this paper.
For coordinated multipoint transmission in heterogeneous ultra dense networks (HUDN), clustering and multicell resource scheduling should be carried out jointly. Based on the α-fairness function, the ...joint optimization problem is formulated that is NP-hard. A two-step joint clustering and scheduling (TS-JCS) scheme is proposed. Considering the extremely imbalanced cell loads in HUDN, the impact of cell loads on resource availability must be concerned, and a novel load aware clustering (LAC) is designed at the first step and solved by game theory. Based on the clustering results, a fair graph-coloring based inter-cell resource scheduling can be employed at the second step to maximize the resource utilization. Simulations are carried out to evaluate the performance of TS-JCS in a three-layer HUDN. It is shown that the utility of TS-JCS is close to the optimal value, demonstrating the high effectiveness of TS-JCS to solve the joint optimization problem. Compared with non-joint schemes, when fairness is considered in TS-JCS with α = 1 and α = 2, the average throughput can be improved by about 30% while keeping similar performance in cell-edge throughput. Finally, it is also shown that in HUDN with imbalanced load, the performance gain of TS-JCS with α = 1 and α = 2 over the baseline scheme is obvious compared to that in regular hexagonal networks with uniformly distributed loads, demonstrating the importance of the load aware scheme LAC for HUDN.
•LWSCC Columns Reinforced with BFRP and GFRP bars.•Behavior under Concentric and Eccentric Loads.•Development of Axial Load–Moment Interaction Diagram.•Analysis Considering a Modification in the ...Rectangular Stress-Block Parameters.
No research has yet been reported on the behavior of lightweight-aggregate self-consolidating concrete (LWSCC) columns reinforced with fiber-reinforced polymer (FRP) bars. LWSCC can be of great interest for reducing dead loads, section dimensions, and project costs, especially for precast elements. This paper presents, for the first time, the test results of a study conducted on 12 circular LWSCC columns reinforced with two types of FRP bars: basalt FRP (BFRP) and glass FRP (GFRP). In addition, columns with steel reinforcement were introduced into the test matrix as references. A mix design for the LWSCC with an equilibrium density of 1,807 kg/m3 and compressive strength of 52 MPa was developed and used to cast the columns. The columns were tested under concentric and eccentric loading. The test variables were the eccentricity-to-diameter ratio, and the type of reinforcement (steel versus GFRP and BFRP). The study was conducted to investigate whether the type of concrete and reinforcement affect the column performance and to develop the experimental load–moment interaction diagram. The load–strain behavior for the concrete, bars, and spirals; the load-deformation curves (axial and lateral); and the experimental P–M interaction diagrams are presented. An analytical study was conducted to predict the axial–flexural capacity. The effect of concrete density was considered in the analysis based on parameters in the codes for conventional and modified rectangular stress blocks. The test results indicate that the LWSCC columns with BFRP and GFRP reinforcement had behavior and strength comparable to their steel-reinforced counterparts when tested under different levels of eccentricity. The analytical results show that the column capacity was sensitive to variations in the rectangular stress-block parameters. Lastly, this study demonstrated the effectiveness of integrating GFRP and BFRP reinforcement into lightweight-aggregate concrete would play a role in producing lighter and more durable concrete members for precast applications.
Rockbolts are widely used in the tunnels and underground mining industry for support and reinforcement of the rock mass around the perimeter of the excavation. Better understanding of the load ...transfer mechanisms of rockbolts could improve rockbolt technology. Current rockbolt testing generally focuses on axial loading of the rockbolt, with shear loading of rockbolts only becoming more prevalent in the last 10–15 years. This research experimentally investigated the load-carrying capacity of five new rockbolts under axial and shear loadings, of which three were friction bolts and two were yielding bolts. Testing was undertaken using high strength concrete blocks to simulate a homogenous rock mass. The yielding style rockbolts provided considerably more tensile load capacity and deformation compared to the inflatable rockbolts; however, the inflatable rockbolts have the ability to deform significantly more in shear than in tension and have similar shear deformation as the yielding-style rockbolts. This research contributes to the understanding of the performance of the new inflatable and yielding rockbolts in different loading conditions and hence provided a benchmark for comparison with other existing friction and yielding bolts. Ultimately, the addition of these new rockbolts in the ground support community would give the site engineers more options to properly select the most suitable rockbolt under varying geotechnical conditions.
Highlights
The inflatable rockbolts (Hydrabolt) performed similarly and could hold peak loads of up to 82-107 kN
In shear loading situations the inflatable rockbolt can achieve peak shear loads up to 91-121 kN.
The MP1 Bolt could achieve a maximum tensile load of 273-308 kN while deforming up to 132-135 mm.
PAR1 Resin Bolt achieved maximum tensile load of 232-238 kN while deforming up to 148-176 mm.
The shear load capacity of the inflatable bolts is greater than the tensile load capacity.
•High-strength concrete filled box columns (CFBCs) are investigated.•Five column specimens are laterally and cyclically tested after axial compression (0.2–0.4Pn).•The addition of concrete infill ...inside a hollow column does not improve the ductility of CFBCs.•The b/t limit of the code cannot assure good seismic behavior of CFBCs under high axial load.
This paper presents an experimental study of the seismic performance of high-strength concrete-filled box columns (CFBCs) under combined axial and cyclic lateral loads. Specimens were made of high-strength SM 570 M steel (with yield strengths between 520 and 580 MPa), and concrete with compressive strength (fc') greater than 80 MPa. Three parameters that affect the seismic performance of CFBCs were investigated: the width-to-thickness (b/t) ratio of the steel column, magnitude of the axial load, and the addition of concrete infill. The specimens, which were 280–420 mm in width and 2000 mm in height, were tested under combined axial (4058–10,090 kN) and cyclic lateral loads. Experimental results indicated that the lateral displacement ductility decreases significantly with an increase in either the axial load or b/t ratio. The addition of concrete infill inside a hollow steel box column does not improve the lateral displacement ductility of CFBCs under high axial load. Although the CFBC specimens satisfied the b/t requirement of a highly ductile member, as per AISC Seismic Provisions (2016), specimens under high axial load (40%Pn) failed at 4% drift, indicating that the requirement does not guarantee that CFBCs will sustain high axial load under significant drift (i.e., >3%). The Eurocode 4 (2009), AISC Specification (2010), and Architectural Institute of Japan (2014) reasonably estimate the flexural strength of high-strength CFBCs under axial load; however, ACI 318 (2011) does not. The finite element analysis program ABAQUS can be used to estimate the hysteretic behavior of specimens before significant strength degradation.
This paper describes the development of a unique rolling load simulator (ROLLS) for testing bridge superstructure with a footprint up to 4 m ×17 m, and its first application to test a full-scale 1220 ...mm ×900 mm ×16000 mm B900 prestressed concrete box girder. This facility at Queen’s University in Kingston, Ontario, is the first of its kind in Canada. ROLLS can apply cyclic loading in a controlled laboratory environment, under realistic highway scale ‘rolling wheel loads’, in lieu of the conventional ‘pulsating stationary loads’. It has two half-axles of a large tandem, each comprising a dual 1140 mm diameter air-inflated tires spaced at either 1.2 or 2.4 m. Each half-axle can apply up to 125 kN, representing the heaviest half-axle load of the CL-625 design truck of the Canadian Highway Bridge Design Code (CHBDC). The maximum travel range and speed are 14.9 m and 6 m/s, respectively. A case study involving analysis of a bridge with eight adjacent B900 box girders of 27.6 m span was carried out prior to experimentally testing one of the girders using ROLLS. Load distribution analyses were conducted using both (i) a finite element model of the full bridge under various CL-625 truck loading configurations and (ii) the CHBDC load distribution method, and both agreed well. Scaling analysis of the girder load share was then conducted to account for shortening it to 16 m to fit in the laboratory, resulting in two-115 kN ROLLS design loads, 1.2 m apart. Multiple passes were conducted at various loads of 40%–100% of the design load, at speeds of 1–5 m/s to examine the machine and girder behaviours. It was found that the applied load fluctuates by less than 10% of full capacity and a 0.13 s/cycle time lag occurs. The measured girder deflection and elastic strains were 11%–20% lower than predicted theoretically. With the two half-axles assembly spaced at 1.2 m, the apparatus has the ability to complete three million cycles in approximately 4.5 months if ran continuously at 5 m/s.
The Internet of Things (IoT) connects electric devices to a network in order to realize virtual control. Demand-side loads can provide ancillary services that optimize energy structures and promote ...supply-demand balance. For load management, this article proposes Internet of Electric Loads (IoEL) as a service-centric network, and the edge subcloud is introduced in the distributed computing system. The intelligent thermostatically controlled loads constitute the physical perceptual layer of the IoEL. Each subcloud controls a type of loads under the same regional distribution grid to form a stable and controllable aggregation system. The subclouds interact with the load cloud to form a platform layer. Through the interaction between the platform and physical perceptual layers, loads are controlled to realize the load transfer and provide ancillary services for the application layer. IoEL utilizes computing resources from different layers to form a distributed computing system made up of cloud, edge, and end devices. The load management is divided into four steps, namely, load aggregation in the edge-end interface, evaluation of load capacity in the edge, task allocation in the cloud-edge interface, and load control in the edge-end interface. The loads upload the physical properties to the subclouds and are then aggregated according to similarities of properties. The subclouds then evaluate schedulable capacity and upload these evaluations to the cloud, which then allocates tasks to each subcloud accordingly. The edge is responsible for receiving tasks from the cloud and controlling loads. The effectiveness of the method was verified by providing clean energy output tracking.
In this paper, a novel direct load control (DLC) planning based on providing free energy credits to residential end-users for their heating, ventilation, and air conditioning load during demand ...response (DR) events is proposed. The obtained credit can then be used by the end-users during relatively higher price periods free-of-cost to enable them lowering their energy procurement costs. Furthermore, the resulting reduction in the total household energy consumption considerably decreases the critical load demands in power systems, which is of vital importance for load-serving entities in maintaining the balance between supply and demand during peak load periods. In this regard, the aforementioned energy credits-based incentive mechanism is proposed for end-users enrolled in the DLC-based DR program, as a new contribution to the existing literature, testing it in a stochastic day-ahead planning context.
Reinforced concretes (RC) have been widely used in constructions. In construction, one of the critical elements carrying a high percentage of the weight is columns which were not used to design to ...absorb large dynamic load like surface bursts. This study focuses on investigating blast load parameters to design of RC columns to withstand blast detonation. The numerical model is based on finite element analysis using LS-DYNA. Numerical results are validated against blast field tests available in the literature. Couples of simulations are performed with changing blast parameters to study effects of various scaled distances on the nonlinear behavior of RC columns. According to simulation results, the scaled distance has a substantial influence on the blast response of RC columns. With lower scaled distance, higher peak pressure and larger pressure impulse are applied on the RC column. Eventually, keeping the scaled distance unchanged, increasing the charge weight or shorter standoff distance cause more damage to the RC column. Intensive studies are carried out to investigate the effects of scaled distance and charge weight on the damage degree and residual axial load carrying capacity of RC columns with various column width, longitudinal reinforcement ratio and concrete strength. Results of this research will be used to assessment the effect of an explosion on the dynamic behavior of RC columns.
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