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This paper presents an experimental study on the determination of the mechanical behaviors of Grade 8.8 and 10.9 high-strength bolts at elevated temperatures. Strength reduction coefficients are obtained based on test results at temperatures ranging from 20°C to 900°C, for both yield and ultimate stresses. Simplified expressions are presented to identify the strength reduction factors at considered temperatures. At 400°C, the yield and ultimate strengths of bolts decrease by 30%–35% for both grades compared to those in ambient temperature. Yield strengths are 30% and 20% of yield strengths of Grade 8.8 and 10.9 bolts at ambient temperature, respectively, when the temperature exceeds 500°C. The ultimate strength decreases slightly slower than the yield strength at high temperatures. Although the decrease in ultimate strength follows the decrease in yield strength at elevated temperatures, it is slightly slower. About 3%–6% of yield and ultimate strengths at ambient temperature remain for both grades at 700°C. Moreover, a series of expressions are provided to obtain the full range stress–strain curve of high-strength bolts at elevated temperatures. Comprehensive literature studies are taken into consideration to propose a more generalized description of the stress–strain curves. The proposed model can be fully drawn by only using elastic modulus, yield, and ultimate stresses at ambient temperature. It is shown that the proposed model has enough efficiency to describe the general material behavior at elevated temperatures. [ABSTRACT FROM AUTHOR]

Concrete can be regarded as a composite material comprising aggregates, cement mortar, and an interfacial transition zone (ITZ) at the mesoscale. The mechanical properties and durability of concrete are influenced by the properties of these three phases. The establishment of a mesoscale model of concrete and the execution of numerical simulations constitute an efficacious research method. It is an efficacious method to research concrete by establishing the mesoscale model of concrete and executing numerical simulations. By this method, the influence of an aggregate shape on concrete performance can be studied. This paper presents a systematic review of mesoscale modeling methods for concrete, with a focus on three aspects: the aggregate modeling method, the collision detection algorithm, and the particle-packing algorithm. The principal processes, advantages, and disadvantages of various methods are discussed for each aspect. The paper concludes by highlighting current challenges in the mesoscale modeling of concrete. [ABSTRACT FROM AUTHOR]

The square cap is a typical semi-submersible component of sea-crossing bridges, which connects piers and pile-group foundations. As the cap size is large, it usually has a non-negligible influence on the wave motion around the pile-group foundation, so it is not considered in the relevant specification. However, neglecting this influence may have adverse effects on the structure. In this paper, the wave forces on capped pile groups are simulated by a numerical wave flume. Firstly, the numerical flume used in this paper is validated by an experiment in the previous literature. Then, capped pile groups with different arrangements and different water levels are modeled to study the interference effect of the square cap on the wave force, and the variation law of the interference effect coefficient K c p of the cap is given. Next, we introduce K c p into the theoretical formula of wave forces on pile groups and obtain a modified formula that considers the cap effect. To verify the feasibility of the modified formula in practical engineering, we use the formula to calculate the wave forces acting on capped pile groups of a sea-crossing bridge. The results of the modified theoretical formula are compared with that of the numerical water flume and recommended values in the specification. It is found that the theoretical values are relatively close to the numerical results, while the specification values tend to be conservative. The modified theoretical formula proposed in this paper and the obtained parameter distribution law can provide a reference for engineering design. [ABSTRACT FROM AUTHOR]