Frost resistance research is one of the important subject of concrete durability, however strength criteria is an important part of the study of mechanical behavior of concrete. So far, about concrete failure criteria are almost for normal concrete, which the domestic and overseas scholars have comparative detailed research in every respect to it, and to freeze-thaw damage of concrete but few research. Based on the summary of the existing ordinary concrete strength and failure criteria in normal state and after freeze-thaw damage,this paper have a brief comment of failure criteria on concrete after freeze-thaw damage. For later research about concrete strength and failure criteria under freezing and thawing cycle provide the reference.
Traditional transmission line poles and towers have many problems, such as higher corrosion, heavy weight, poor durability and maintenance cost is high. Use of fiber reinforced polymer composites (FRP), based on the theory of poles and towers design, 110 kV FRP pole structure size parameters are calculated, designed the 110 kV FRP pole structure, cross section form and wire grounding scheme. Design results show that compared with traditional pole, 110 kV FRP pole has the characteristics of compact structure, small occupied line corridors.
Based on numerical simulation of the seepage field of earth rockfill cofferdam using nonlinear Finite Element Method under the action of flood during construction period, the stability of the cofferdam slope with nonlinear shear strength is studied. The effectiveness and applicability of the method introduced in the paper is certified through computation in the study on the practical project. The paper provides an effective analysis method for the study on the stability of dam slope of earth rockfill cofferdam.
Straw has relatively high tensile strength, as a kind of aggregate, combined with cement, gypsum and other bonding materials, which can improve the strength of the benchmark materials and control the initiation and propagation of microcracks. The physical and mechanical properties of straw-mortar composite materials are determined by the property of straw itself, the bonding capacity of matrix materials, the environment and other factors. In this study, three-factor and three-level regression analysis experiment was carried out by using Design-Expert software to obtain the optimal physical and mechanical properties and mix ratio of rice straw-mortar composite materials. The highest compressive strength, dry density and the lowest water absorption rate of rice straw-mortar composite materials were 3.06 MPa, 1.340 g·cm-3 and 20.8%, respectively, and the corresponding gypsum content, straw length, and straw content were 15%, 20 mm, and 15%, respectively. After 15 times freeze-thaw (F-T) between − 20 ℃ and 20 ℃, the strength loss rate, mass loss rate and water absorption rate of rice straw-mortar composites produced in different conditions varied from 32.2–47.3%, from 2.1–4.5%, and from 22.6–42.2%, respectively. The above experimental results indicated that the rice straw-mortar composite materials could meet the actual using demand of self-bearing wall whether to experience F-T, which laid a certain foundation for the popularization and application of rice straw-mortar composite materials in non-bearing wall.
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