Shear Behavior of Reinforced Post-Filling Coarse Aggregate Concrete Beams Produced by Creative Construction Process

Different from the traditional concrete mixing procedure, the innovative post-filling coarse aggregate concrete (PFCC) reduces the cost of pumping concrete by increasing the coarse aggregate content and reducing the usage of cement. Previous studies have shown that PFCC enhances the compressive strength, elastic modulus, and flexural strength of concrete. In this paper, the shear behavior of 13 post-filling coarse aggregate concrete beams and 3 control beams was tested to determine the relationships between the shear performance of the beam and the post-filling coarse aggregate ratio, concrete strength grade, shear span ratio and stirrup reinforcement ratio. The results showed that the ultimate shear capacity of beam specimen increases first and then decreases with the increase in post-filling coarse aggregate ratio, reaching the maximum at 15% post-filling ratio. The results also indicated that the ultimate shear capacity of the beam increases with the increase in concrete strength grade and stirrup ratio. However, experimental results exhibited that the ultimate shear capacity decreases as the shear span ratio increases. This study provides a reference for the application of post-filling coarse aggregate concrete in engineering practice

Interactive Effects of Admixtures on the Compressive Strength Development of Portland Cement Mortars

The interaction effects of four chlorine-free admixtures such as calcium formate (CF), triethanolamine, (TEA), triisopropanolamine (TIPA), and sodium sulfate (SS) on the compressive strength development of Portland cement mortars were investigated based on the design of experiment (DoE). The results showed that both the addition of CF and SS contributed significantly to the strength of cement mortars at early curing age. However, the interaction of CF and SS could hinder their respective positive effect on the strength of cement at 1 d. At later curing ages, CF was still beneficial in improving the late strength of cement, but SS had a negative effect on the strength of cement at 28 d. A negative effect of TIPA on the strength of cement was found at 3 d. However, the positive interactive effect of TIPA and CF was sufficient to offset the negative effect of TIPA on the strength of mortars at 3 d if the dosage of CF exceeded 2%. In addition, TEA had a positive influence on 7 d strength until a turning point was reached and the optimum dosage of TEA was approximately 0.013%

The Influence of Different Parameter on the Seismic Behavior of SRUHSC Frame

The seismic behaviors of steel reinforced ultrahigh strength concrete (SRUHSC) frames with different axial compression ratios and shear span ratios are experimentally studied through the reversed cyclic loading test of four specimens. The test results reveal that the seismic response of the frame is closely related to the failure process and failure mode of the columns. Based on the results, a systematic exploration is further conducted in terms of the characteristics of the skeleton curve, hysteresis curve, strength degradation, stiffness degradation, and energy dissipation capacity of the structure. The results indicate that as the axial compression ratio increases, and the shear span ratio decreases, the failure process of the entire structure and the weakening of the beam end are accelerated. Meanwhile, a change of the failure mode is also observed, accompanied by corresponding changes in the strength, stiffness, and energy dissipation capacity of the system

Effect of Fast Loading on the Seismic Performance of SRUHSC Frame Structures

Due to the high compressive strength and durability of ultra-high-strength concrete, SRUHSC (steel-reinforced ultra-high-strength concrete) frame structures have been used extensively in super-high-rise buildings. However, the SRUHSC showed obvious brittleness. Encasing structural steel in the material was recognized to be a good way of alleviating the problem of brittleness. The purpose of this study is to investigate the effect of the axial compression ratio on the seismic performance of a single-story, single-span SRUHSC frame structure under rapid loading. The failure mode, deformation, strength and stiffness degradation, energy dissipation capacity and residual displacement of the structure were compared and analyzed. The seismic performance of a single-story single-span SRUHSC frame structure is verified under the conditions of a fast loading rate and high axial compression ratio. The results suggest that the horizontal resistance capacity of structures can be significantly improved by fast loading in the elastic and elastic–plastic ranges. The ductility coefficient of the structure increases with the same axial compression ratio under fast loading. With an increase in loading rate, the secant stiffness of the structure is improved

Shear Behavior of Reinforced Post-Filling Coarse Aggregate Concrete Beams Produced by Creative Construction Process

Different from the traditional concrete mixing procedure, the innovative post-filling coarse aggregate concrete (PFCC) reduces the cost of pumping concrete by increasing the coarse aggregate content and reducing the usage of cement. Previous studies have shown that PFCC enhances the compressive strength, elastic modulus, and flexural strength of concrete. In this paper, the shear behavior of 13 post-filling coarse aggregate concrete beams and 3 control beams was tested to determine the relationships between the shear performance of the beam and the post-filling coarse aggregate ratio, concrete strength grade, shear span ratio and stirrup reinforcement ratio. The results showed that the ultimate shear capacity of beam specimen increases first and then decreases with the increase in post-filling coarse aggregate ratio, reaching the maximum at 15% post-filling ratio. The results also indicated that the ultimate shear capacity of the beam increases with the increase in concrete strength grade and stirrup ratio. However, experimental results exhibited that the ultimate shear capacity decreases as the shear span ratio increases. This study provides a reference for the application of post-filling coarse aggregate concrete in engineering practice

A New Prestress Loss Calculation Model of Anchor Cable in Pile–Anchor Structure

Pile–anchor structures are widely used in foundation excavation and slope reinforcement due to their safety and reliability. However, the pile–anchor structures have the common problem of the prestress loss of anchor cables, which may reduce the stability of the structures. To accurately predict the prestress loss of anchor cables, a new prestress loss calculation model was established, and the availability of the prestress loss calculation model was verified through engineering cases. Meanwhile, aiming at the long-term prestress loss of anchor cables, the coupled creep behavior of anchor cable–rock and soil was studied and an anchor cable–rock and soil coupled creep model suitable for pile–anchor structures is proposed. The model test confirms that the coupled creep model could accurately describe the coupled creep behavior of the anchor cable and the rock and soil mass. The models provide a theoretical basis for the study of the prestress of anchor cables in pile–anchor structures, and have a guiding significance for the design and construction in foundation excavation and slope engineering

Optimization and economic analysis of distributed photovoltaic-energy storage system under dynamic electricity price

This paper investigated the influence of different dynamic electricity pricing schemes, energy storage capacity and unit capacity cost on the economics of PV-storage systems. The energy storage control stratety of improving the photovoltaic micro-grid self-consumption was adopted in this study. Taking an office building in Changsha as an example, the dynamic planning method was used to solve the system\u27s best operating strategy and calculated the system\u27 life cycle economy and PV self-consumption rate. The results showed that the system profitable area was increased by 87% for every 41.5% increase of dynamic electricity price. Moreover, the impact of energy storage capacity on system economics is greater than unit cost. The increase of dynamic electricity price is beneficial to increase the self-consumption of photovoltaic power generation, and the storage capacity and unit cost dominate the self-consumption of photovoltaic energy in different intervals

Preparation and Heat Dissipation Performance of Vertical Graphene Nanosheets/Carbon Fibers Composite Film

High-efficient heat dissipation materials are urgently required in advanced electronic packaging technology because effectively releasing the internal heat flow density of electronic devices is a key factor during their operation. In this work, a novel vertical graphene nanosheets/carbon fibers (VGNs/CF) composite film, with a vertically oriented structure and excellent heat dissipation properties, is fabricated on the stainless steel substrate by a facile thermochemical growth method. The preparation of composite film is green, safe, and highly efficient. CF is used as a thermally conductive filler to provide thermal conductivity channels for VGNs, and both of them construct a continuous thermally conductive network. The through-plane thermal conductivity of the VGNs/CF composite film could reach 17.7 W/(m·K), and the addition of CF significantly improved the heat dissipation performance of the composite film compared with the pure VGNs film (13.9 W/(m·K)). Conclusively, the simple preparation method and outstanding thermal conductivity capacity of the VGNs/CF composite film are expected to meet the application requirements of the electronics industry