Structural system design and earthquake response analysis of prefabricated pile-plate bridge

With the advancement of building technology, the pile-plate structure, which originated in railway engineering, has been adopted into highway engineering. This study presents a new pile-plate structure connecting node. The addition of energy-dissipating components at the nodes and the use of non-shrinkage concrete at the joints demonstrate its novelty. The node’s ability to enter the plastic stage is enhanced, resulting in increased seismic performance. In this study, the seismic performance and energy consumption capacity of the pile plate joint were studied by numerical model, and the results showed that the stagnation curve of the pipe pile under low cycle reciprocating load was full and had good energy consumption capacity. Under the action of random seismic vibration, the displacement of the pile plate structure in one direction is up to 0.023 m, which meets the requirements of the specification. The innovative pile-plate joints are used in a nonlinear dynamic time-history analysis of the constructed bridge structure

Analysis of the behavior of ultra high performance concrete at early age

Ultra high performance concretes (UHPCs) are cementitious composite materials with high level of perfor- mance characterized by high compressive strength, high tensile strength and superior durability, reached by low water-to-binder ratio, optimized aggregate size distribution, thermal activation, and fiber reinforcement. In the past couple of decades, more and more UHPCs have been developed and found their ways into practice. Thus, the demand for computational models capable of describing and predicting relevant aging phenomena to assist design and planning is increasing. This paper presents the early age experimental characterization as well as the results of subsequent simulations of a typical UHPC matrix. Performed and simulated tests include unconfined compression, splitting (Brazilian), and three-point-bending tests. The computational framework is formulated by coupling a hygro-thermo-chemical (HTC) theory and a comprehensive mesoscale discrete model with formulated aging functions. The HTC component allows taking into account various types of curing conditions with varying temperature and relative humidity and predicting the level of concrete aging. The mechanical component, the Lattice Discrete Particle Model (LDPM), permits the simulation of the failure behavior of concrete at the length scale of major heterogeneities. The aging functions relate the mesoscale LDPM mechanical properties in terms of aging degree, defined in this work as the ratio between the quasi-static elastic modulus at a certain age and its asymptotic value. The obtained results provide insights in both UHPC early age mechanisms and a computational model for the analysis of aging UHPC structures.Comment: Cement and Concrete Composites, 201

Research status and development trend of mechanism and simulation test of coal and gas outburst

Theoretical research status of mechanism of coal and gas outburst was summarized. Typical examples of similar materials of gas-bearing coal and simulation experiment device of coal and gas outburst were analyzed. Deficiency of the research of mechanism of coal and gas outburst and simulation experiment was pointed out，namely, theory research results of mechanism of coal and gas outburst are more qualitative description, lack quantitative, unified and complete theoretical system; the existing outburst simulation test systems and devices can not accurately simulate the outburst phenomena under the influence factors of geological structure, ground stress, coal strength, gas content and construction process, and the accuracy of the mechanical loading system, gas filling system and testing system of the test equipment needs to be further improved; the experimental operation and convenience of the test instrument are not enough, and the reproducibility of the test needs to be improved; the data analysis system of test instruments is not perfect. The development trend of mechanism research of coal and gas outburst and simulation experiment was prospected: the simulation experiment of coal and gas outburst must conform to the similarity theory, and the research of simulation test instrument of coal and gas outburst is an urgent demand for the breakthrough of mechanism research

Thigmotropic responses of Oryza sativa L. to external rubbing stimulation

Our aim was to study the morphological and physiological responses of rice to rubbing stimulation. Rice was subjected to rubbing 30 times/day (R30), 60 times/day (R60), 90 times/day (R90) and 0 times/day (control) for 35 days. The height, elongation rates and second internode length were significantly decreased by the three treatments, whereas stem width increased significantly. The tiller number and chlorophyll contents of the top third and top fifth of leaves increased significantly after R30 and R60. In R90, the aboveground biomass was significantly decreased and dead leaf biomass was increased. In R30 and R60, the transpiration rates were 16% and 13% higher than in the control, whereas photosynthetic rates increased 25% and 23%, respectively. Root biomass was significantly increased in R30, and root/aboveground was enhanced in R90. Stomatal conductance and root triphenyltetrazolium chloride-deoxidizing ability was significantly increased by the three treatments. The SOD activities in all treatments and the control were similar after stimulation. POD and CAT activities increased significantly in R30 and R60, and malondialdehyde increased by 42% in R90. Membrane permeability in R30 and R60 decreased 26% and 15%, respectively. The calcium content and soluble protein content increased in R30, whereas the magnesium content decreased. The nitrogen content increased significantly in R30 and R60. The silicon content in the whole plant and the size of stomata increased significantly in the three treatments. Thus, rubbing stimulation had complex effects on rice growth

Bioinspired High-Strength Montmorillonite-Alginate Hybrid Film: The Effect of Different Divalent Metal Cation Crosslinking

The natural nacre has a regular ordered layered structure of calcium carbonate tablets and ion crosslinking proteins stacked alternately, showing outstanding mechanical properties. Inspired by nacre, we fabricated different divalent metal cation-crosslinked montmorillonite-alginate hybrid films (MMT-ALG-X2+; X2+ = Cu2+, Cd2+, Ba2+, Ca2+, Ni2+, Co2+ or Mn2+). The effect of ionic crosslinking strength and hydrogen bond interaction on the mechanical properties of the nacre-mimetics was studied. With the cations affinities with ALG being increased (Mn2+ < Co2+ = Ni2+ < Ca2+ < Ba2+ < Cd2+ < Cu2+), the tensile strength of nacre-mimetics showed two opposite influence trends: Weak ionic crosslinking (Mn2+, Co2+, Ni2+ and Ca2+) can synergize with hydrogen bonds to greatly increase the tensile properties of the sample; Strong ionic crosslinking (Ba2+, Cd2+, Cu2+) and hydrogen bonding form a competitive relationship, resulting in a rapid decrease in mechanical properties. Mn2+ crosslinking generates optimal strength of 288.0 ± 15.2 MPa with an ultimate strain of 5.35 ± 0.6%, obviously superior to natural nacre (135 MPa and 2%). These excellent mechanical properties arise from the optimum synergy of ion crosslinking and interfacial hydrogen bonds between crosslinked ALG and MMT nanosheets. In addition, these metal ion-crosslinked composite films show different colors, high visible transparency, and excellent UV shielding properties

Bioinspired Nacre-like Heparin/Layered Double Hydroxide Film with Superior Mechanical, Fire-Shielding, and UV-Blocking Properties

The combination of two or more seemingly distinct properties into a unique composite is an exciting direction for the fabrication of novel multifunctional materials. A vacuum-filtration method was used to fabricate strong and multifunctional heparin/layered double hydroxide (HEP/LDH) films mimicking nacre. The experimental results confirm that the prepared films show a layered nano/microscale-hierarchical structure, in which the LDHs are aligned, with a very high loading amount of LDHs closely comparable to that in the natural nacre, up to 87.5 wt %. Both the modulus (<i>E</i>_r ≈ 23.4 GPa) and hardness (<i>H</i> ≈ 0.27 GPa) of the HEP/LDH films are remarkably high. Furthermore, the hybrid films show a combination of outstanding properties of UV-blocking and fire-resistance properties. Therefore, this work provides a way of fabricating multifunctional organic–inorganic hybrid films, which have potential applications in the areas of optical applications, transportation, and construction

Ca²⁺ Enhanced Nacre-Inspired Montmorillonite–Alginate Film with Superior Mechanical, Transparent, Fire Retardancy, and Shape Memory Properties

Inspired by nacre, this is the first time that using the cross-linking of alginate with Ca ions to fabricate organic–inorganic nacre-inspired films we have successfully prepared a new class of Ca²⁺ ion enhanced montmorillonite (MMT)–alginate (ALG) composites, realizing an optimum combination of high strength (∼280 MPa) and high toughness (∼7.2 MJ m^–3) compared with other MMT based artificial nacre. Furthermore, high temperature performance of the composites (with a maximum strength of ∼170 MPa at 100 °C) along with excellent transmittance, fire retardancy, and unique shape memory response to alcohols could greatly expand the application of the mutilfunctional composites, which are believed to show competitive advantages in transportion, construction, and insulations, protection of a flammable biological material, etc