A robust analytical model of Eccentric Braced Frames (EBFs), as a well-known seismic resistance system, helps to comprehensive earthquake-induced risk assessment of buildings in different performance levels. Recently, the modeling parameters have been introduced to simulate the hysteretic behavior of shear links in EBFs with specific Coefficient of Variation associated with each parameter to consider the uncertainties. The main purpose of this paper is to assess the effect of these uncertainties in the seismic response of EBFs by combining different sources of aleatory and epistemic uncertainties while making a balance between the required computational effort and the accuracy of the responses. This assessment is carried out in multiple performance levels using Endurance Time (ET) method as an efficient Nonlinear Time History Analysis. To demonstrate the method, a 4-story EBF that considers behavioral parameters has been considered. First, a sensitivity analysis using One-Variable-At-a-Time procedure and the ET method has been utilized to sort the parameters with regard to their importance in seismic responses in two intensity levels. A sampling-based reliability method is first used to propagate the modeling uncertainties into the fragility curves of the structure. Radial Basis Function Networks are then utilized to estimate the structural responses, which makes it feasible to propagate the uncertainties with an affordable computational effort. The Design of Experiments technique is implemented to acquire the training data, reducing the required data. The results show that the mathematical relationships defined by Artificial Neural Networks and using the ET method can estimate the median Intensity Measures and shifts in dispersions with acceptable accuracy.

The excavated soil in the chamber of an earth pressure balance (EPB) shield is typically required to achieve a plastic flow state during tunneling to ensure a stable excavation face and the smooth discharge of soil. When EPB shield tunneling takes place in composite strata with gravelly sand above and moderately weathered argillaceous siltstone with high clay mineral content below, the changing sand–rock ratio on the excavation face leads to a greater risk of water spewing and clogging on the cutterhead, posing enormous challenges to soil conditioning. In the study reported here, we used foam and bentonite slurry as conditioning materials for mixed soil. A series of laboratory tests were performed on the conditioned soil with different sand–rock ratios and water contents to determine the optimal injection ratios of conditioning materials. A miniature EPB shield model test involving soil pressure balance, conditioning material injection, and tunneling control was conducted to simulate the continuous excavation process from full-face sand to full-face rock stratum. The model and field test results of thrust, torque, and soil pressure in the soil chamber and screw conveyor validate the effectiveness of the proposed soil conditioning schemes for composite strata with different sand–rock ratios. The test results indicate that the volume ratio 4:1 of foam to bentonite slurry achieves better performance of the conditioned gravelly sand at a lower total injection ratio (TIR < 10%). The bentonite slurry has a significant improvement effect on the flow plasticity of crushed moderately weathered argillaceous siltstone. The influence of bentonite slurry on the slump value of conditioned soil is greater than that of foam. Based on the optimal injection ratios of conditioning materials for full-face sand (ϕ = ∞) and full-face rock (ϕ = 0), the injection ratios for composite strata were obtained by weighted summation according to the area ratio of different strata on the tunnel face. This research provides valuable insights into soil conditioning and parameter determination methods for EPB shield tunneling in composite strata.

With 200 km of new lines and 68 new stations, the Grand Paris Express (GPE) project is currently the biggest transport project under construction in Europe. Starting in 2010, the GPE project involves an ambitious schedule with major milestones planned between 2022 and 2030. To meet these deadlines as well as the associated cost, quality and safety goals, intensive construction technology is needed in this once-in-a-century megaproject, but this project also provides ideal opportunities to apply this technology. This paper offers a review of the new and innovative construction technologies used during the GPE project’s design and construction stages. Such a large project certainly presents a range of complexities and poses many technical, material, human and environmental challenges. Due to its high-risk nature, the risk management plan that applies throughout the whole GPE project, along with the contractual and insurance conditions, is introduced first. Then, an overview is provided of the design principles and construction methods selected to overcome the engineering challenges and reduce the technical risks, all of which are accompanied by monitoring methods and digital approaches. In addition, several new and innovative construction technologies adopted in this project are illustrated. The paper concludes with the project’s environmental protection.

This study focuses on a reasonable lateral isolation system for a typical long-span single-tower cable-stayed bridge with a significantly asymmetric span arrangement that is particularly suitable for mountainous areas. Based on the Jinsha River Bridge, the significant structural asymmetry and its effects on structural seismic responses were analyzed. The significantly asymmetric characteristics could result in complex dynamic behavior in seismic conditions and the lateral seismic responses of the structure are governed by multiple modes. A multilinear model composed of an ideal elastoplastic element and a multilinear elastic element was used to simulate different hysteresis, and a parametric analysis was conducted to investigate the appropriate damping hysteresis for the lateral seismic isolation of such a bridge. It shows that the inverted S-shaped hysteresis has relatively smaller secant stiffness and could help to balance the great difference in the lateral stiffness of the tower/piers. Thus, the inverted S-shaped hysteresis could lead to more efficient damping effects and less base shear forces of the tower/piers. A correlation between the reasonable yield forces of the dampers in the lateral isolation system, determined through an influence matrix-based method, and the shear forces of the corresponding bearings in the lateral fixed system was also observed. Moreover, the influence of geological conditions including different terrain and site conditions on the reasonable lateral isolation system was further investigated. It suggests to use dampers at all tower/pier locations when the side span crosses a steep valley slope, while a lateral isolation system without using dampers at the auxiliary piers could be employed when the side span crosses a gentle valley slope. Soft sites require larger damper yield forces and cause greater seismic responses compared to hard sites.

This study proposes the use of three-dimensional (3D) printed artificial aggregates as phase change material (PCM) carriers and investigates its effects on alkali-activated slag concrete. The artificial aggregates were manufactured using Fused Deposition Modeling (FDM) and Stereolithography (SLA) techniques and PCM was injected into the artificial aggregates. Natural aggregates were replaced with FDM or SLA-type artificial aggregates by 15% and 30% by volume and alkali activated slag concrete specimens were produced. The characteristics of artificial aggregates and their impact on mechanical, physical, and thermal properties of concretes are examined. The results showed that 3D-printed artificial aggregates ameliorated the abrasion resistance of concrete specimens. The concrete samples had a minimum strength of 32 MPa after 28 d, with 15SLA concrete achieving 42.5 MPa, which is comparable to the reference concrete. Thermal test results demonstrated that the PCM helps maintain the concrete surface temperature 3.7 °C higher than the reference mix when the ambient temperature drops below zero and notably slows down the temperature decrease. The concrete mixes without PCM showed ice formation on their surfaces when the ambient temperature dropped to −5 °C, while no ice formation was observed on samples incorporating PCM. Furthermore, the inclusion of PCM improved the freeze–thaw resistance of concretes.