Buildings

Grouted sleeve connections (GSCs) are widely used in precast concrete (PC) bridge piers due to their convenience in construction and reliable structural performance. Corrosion-induced damage significantly compromises the seismic integrity of PC bridge piers with GSCs, making effective rehabilitation urgent. However, there is a scarcity of research addressing this specific retrofit need. To bridge this gap, this work systematically investigates the efficacy of ultra-high-performance concrete (UHPC) encasement in retrofitting the quasi-static seismic resilience of corroded GSC piers. Numerical analyses were conducted using OpenSEES, in which the GSCs were equivalently modeled by determining their yield strength and cross-sectional area. Three corrosion ratios of the GSCs (20%, 40%, and 60%) were considered. The effects of UHPC compressive strength (100 MPa, 120 MPa, 150 MPa) and different retrofit heights on the quasi-static seismic performance of the bridge piers were systematically investigated. The results reveal that corrosion of the GSCs markedly compromises the quasi-static seismic behavior of PC bridge piers, notably reducing both the bearing capacity and energy dissipation capacity. Retrofitting with UHPC shells effectively enhances the yield force, peak force, yield stiffness, and energy dissipation capacity of the piers. These improvements become more substantial with higher UHPC strength and greater retrofit height. Overall, the results underscore the significant detrimental effect of sleeve corrosion on quasi-static seismic performance and confirm UHPC retrofitting as a viable and effective mitigation approach.

To address the challenge that traditional dam model materials are difficult to simultaneously meet the requirements of microstructural similarity, dynamic damage simulation, and environmental friendliness, a novel microparticle mortar simulated concrete was developed. This new material consists of cement, sand, gypsum, mineral oil, water, and baryte sand. Through systematic material mechanical tests, the effects of each component on the material’s strength, density, and elastic modulus were revealed, and the optimal mix ratio was determined. This enabled precise control of low elastic modulus and had a high density, while the material is environmentally friendly, non-toxic, and compatible with direct contact with natural water. Its mechanical properties are highly similar to those of the prototype concrete. Based on a 1:70 geometric scale, a shaking table model test of the concrete gravity dam-reservoir system was conducted. The dynamic response and damage evolution under empty and full reservoir conditions were compared and analyzed. The study shows that this material can accurately simulate the stress-strain relationship and failure mode of prototype concrete. Under the full reservoir condition, the dam’s fundamental frequency showed only a 2.72% deviation from the numerical simulation, and as the seismic excitation amplitude increased, the changes in the fundamental frequency effectively reflected the accumulation of damage. Under the design seismic motion, the measured accelerations and stress responses for both empty and full reservoir conditions were in good agreement with numerical calculations. Under overload conditions, the acceleration amplification factor at the dam crest decreased with damage accumulation, and the dam neck was identified as the seismic weak zone. As the peak ground acceleration (PGA) increased from 0.15 g to 0.70 g, the fundamental frequency changes effectively reflected the damage accumulation process in the dam, while the hydrodynamic pressure at the dam heel showed a linear increase (457% increase). The experimentally measured hydrodynamic pressure distribution was between the rigid dam and elastic dam hydrodynamic pressures, reflecting the real fluid-structure interaction effect. This study provides a reliable material solution and data support for dam seismic physical model testing.

As a low-carbon and lightweight material, glulam is increasingly being used in spatial gridshells. However, these glulam gridshells are prone to instability owing to the material properties of glulam. In this study, to enhance the overall stability behaviour, a prestressed cable system was introduced to the ordinary glulam gridshell to form a novel prestressed cable-braced glulam gridshell. Extensive finite element simulations were conducted to examine the mechanical performance of these novel gridshells. This paper analyses how variations in structural parameters impact the stability performance of the shell. Furthermore, an approximate formula is developed to assess the load carrying capacity. This formula is established by integrating theoretical derivations with numerical simulations. We have thus demonstrated that the stability behaviour of traditional glulam gridshells can be significantly improved by the introduction of prestressed cable systems, and the proposed evaluation formula is accurate enough for the load carrying capacity prediction of prestressed cable-braced glulam gridshell.