This research aims to experimentally investigate the ductile fracture characteristics and the level of anisotropy of four plates, 400 mm × 150 mm × 3.72 mm, made by Wire Arc Additive Manufacturing (WAAM) technology with 1 mm thick layers. Relatively small roughness is measured, expressed in maximum peak-to-valley height, measured by scanning, of 98 μm. Calibrated parameters for an advanced computational material model are derived for a finite element mesh size of 0.5 mm. The experimental campaign is based on eight types of short coupon specimens, analysed to explore fracture behaviour exposed to various stress conditions. Sixty-five coupon specimens, 51 milled and 14 tested in as printed conditions, cut out in three directions relative to the printing direction, are examined. The assumption of isotropic mechanical characteristics is confirmed. The mesoscale critical equivalent plastic strain (MCEPS) methodology is used to predict experimental results numerically. Three stages are considered: elastic, plastic, and couple plastic-damaged stages. The accuracy of the calibrated parameters is validated by comparing the engineering stress-strain relationships obtained from experimental tests and finite element (FE) analysis, reaching very good agreement. A list of all material parameters for ductile fracture modelling at various triaxiality levels and Lode parameters is provided for a mesh size of 0.5 mm.

Bolted connections are one of the key connection configurations in steel structures. The ductile fracture prediction is one of the challenges in the structural integrity evaluating of steel structures. To guarantee the safety of steel bridge in connections, an accurate assessment of the ultimate resistance of high-strength bolts under combined tensile-shear loads is necessary. However, the impacts of various parameters on high-strength bolts under combined tensile-shear loads are not sufficiently analysed in the existing references. Hence, in this paper, the validated mesoscale critical equivalent plastic strain (MCEPS) method is used to evaluate the ultimate resistance of high-strength bolts with different bolt grades, bolt diameters, bolt types, hole clearance, and preload force when the bolts are exposed to combined tensile-shear loading. The simulation results are compared to existing design specifications. Finally, the formula modifications in the existing design standards are proposed based on statistical analysis on numerical parametric results.

Wire arc additive manufacturing (WAAM) has increasingly attracted attention in the construction sector because of its ability to produce large metallic structural parts in short times. In this paper, Coffin-Manson and Morrow (CMM) equation is employed to compare the fatigue life of WAAM stainless steel with the structural steels S355 and S690. The results showed that the fatigue performance of structural steel is better than the WAAM stainless steel, the fatigue performance vertical to printing direction (WAAM-900) is better than it along the printing direction (WAAM-00). In addition, the fatigue cycle of the transition reversals of structural steel is much less than it of WAAM stainless. With the increasing the fatigue cycle, the maximum density of the strain amplitude ratio is gradually increased to 1.0. The probabilistic parameters of CMM equation were obtained by a stochastic analysis using Latin hypercube sampling strategies. The probabilistic strain-fatigue life behaviour obtained from the constant exponent sampling strategy is higher when compared with the varied exponent sampling strategy for both WAAM stainless and structural steels.

The development of numerical simulation for Ultra-high-performance concrete (UHPC) and Ultra-high-performance fiber-reinforced concretes (UHPFRC) is fundamental for the design and construction of related structures. The simplified engineering stress-strain relationship and the input values are necessary in the finite element modeling. Four-linear curves and modified Kent–Park model were proposed to describe the engineering tensile and compressive stress-strain relationship, respectively. An attempt was made to simulate the fracture of UHPC and UHPFRC using concrete damaged plasticity model and element deletion strategies. The predicted tensile and compressive behaviors of UHPC and UHPFRC were successfully validated by the test results in the literature. For a better understanding of the mechanical behavior of UHPC and UHPFRC exposed to biaxial loadings, mixed-mode crack propagation simulation on the double-notched specimens exposed to combined shear-tensile and shear-compressive forces was discussed.