International Concrete Abstracts Portal

This research aims to provide a theoretical foundation for the structural design of magnesium phosphate cement (MPC) in high-temperature environments and facilitate the recycling of municipal solid waste incineration bottom ash (BA). Uniaxial compression tests of BA–MPC after exposure to temperatures from 20°C to 1000°C were carried out. Subsequently, the stress-strain curve, peak stress, peak strain, and deformation modulus are examined. The peak stress, peak strain, and deformation modulus, considering the influence of temperature factors, are proposed using regression analysis. Based on the continuum damage mechanics, the axial compression damage constitutive model of MPC is developed, accompanied by an analysis of its temperature damage characteristics. The results show that BA improves MPC strength and helps stabilize its deformation after exposure to high temperatures. The peak stress of MPC decreases after exposure to high temperatures, and the peak stress of BA–MPC is higher at the same temperature. At 1000°C, the peak stress of MPC ranges between 15.86 MPa and 28.38 MPa. After high thermal exposure, the peak strain fluctuation of the MPC with BA stays small, and the deformation modulus is higher than that of the MPC without BA. The developed MPC axial compression damage constitutive model can accurately describe the stress-strain relationship of MPC under axial compression following high-temperature exposure, with a correlation coefficient greater than 0.86. The temperature damage variable of MPC rapidly accumulates in the range of 20°C to 200°C. At 600°C, the temperature damage variable and the total damage variable without BA attained the maximum values of 0.656 and 0.751, respectively. BA can reduce the total damage and temperature damage of MPC to a certain extent.

Analysis of reinforced-concrete damage (RC) under nonuniform corrosion has mostly been performed by adopting the two-dimensional (2-D) plane strain assumption to reduce the computational efforts compared with three-dimensional (3-D) models. This paper aims to compare results obtained from the 2-D plane strain formulation with 3-D analysis in the context of nonuniform corrosion, highlighting differences and similarities to gain valuable insights into the structural response and damage prediction. The findings indicate that both the 2-D and 3-D models yield reasonably similar damage patterns with minor discrepancies in crack orientation and predict comparable hairline crack widths on the concrete surface. During initial corrosion stages, both models exhibit similar stress and strain distributions. However, as corrosion progresses, distinct variations in stress and strain patterns emerge. Interestingly, despite these differences, the extent of damage converges as corrosion advances, suggesting a critical stage beyond which the RC response remains consistent regardless of the modeling approach. The study emphasizes stress and strain variations over time for accurate RC behavior representation.

This study examines the lateral cyclic response of a repaired damaged bridge pier originally reinforced with fiber-reinforced polymer (FRP) bars, particularly glass FRP (GFRP), as a corrosion-resistant and durable alternative to traditional steel. An as-built large-scale hybrid (GFRP-steel) reinforced concrete (RC) column had an outer cage reinforced with GFRP bars and an inner cage reinforced with steel reinforcing bars. The columns were first tested under cyclic lateral loading, where the hybrid specimen demonstrated ductility and energy dissipation capacity comparable to the conventional single-layer steel RC column. Following these initial tests, both specimens were repaired using FRP wraps and retested under the same loading protocol, resulting in a total of four tests. Enhanced structural integrity and energy dissipation demonstrate the effectiveness of innovative repair techniques in seismic engineering. These findings provide a blueprint for resilient infrastructure in earthquake-prone areas and contribute to advancements in bridge design and repair strategies.

Integrating real-time sensor data with physics-based models enhances the accuracy and efficiency of structural simulation and prognosis. In this study, a sensing-based simulation method is introduced to compute bending moments in reinforced concrete bridge columns subjected to seismic motions, based on the measured strains continuously fed to plasticity models. The experimental program included hybrid testing of scaled reinforced concrete bridges under consecutive seismic events. The experimental columns were instrumented with embedded as well as surface-adhered fiber-optic Bragg grating (FBG) sensors for real-time monitoring of strains reflecting degradation of the columns during the formation of damage. The fundamental assumption of strain compatibility in reinforced concrete members was investigated for the successive progression of damage in the cross sections of the columns. The stress distributions within the concrete core and cover were computed through the confined and unconfined concrete stress-strain relations for loading, unloading, and reloading scenarios. The bending moments in the cross-section were computed and compared with the corresponding experimental values calculated based on direct measurements of forces. The results from this study revealed that the cross-sectional strains exhibit three primary features during the seismic events that need to be considered for the accurate calculation of bending moments. Computation of the bending moments requires considering the shifts in cyclic reference, post-event residual strains, and the real steel strains. By using these features, the computed bending moments during the column tests mimicked the experimental results based on the measured seismic forces on the columns.

This paper presents the interface shear between ordinary concrete and ultra-high-performance concrete (UHPC) connected with glass fiber-reinforced polymer (GFRP) reinforcing bars. Following ancillary tests on reinforcing bar fracture under in-plane shear loading, concrete-reinforcing bar assemblies are loaded to examine capacities and failure modes as influenced by the size, spacing, and number of the reinforcing bars. While the shear behavior of bare reinforcing bars is primarily governed by the orientation of the load-resisting axes in the glass fibers and their volume, the size and spacing of the reinforcement largely control the interface capacity by affecting the load-transfer mechanism from the reinforcing bar to the concrete. The degree of stress distribution affects the load-displacement response of the interface, which is characterized in terms of quasi-steady, kinetic, and failure regions. The primary failure modes of the interface comprise rebar rupture and concrete splitting. The formation of cracks between the ordinary concrete and UHPC results from interfacial deformations, leading to spalling damage when applied loads exceed service levels. An analytical model is formulated alongside an optimization technique. The capacities of the interface in relation to the reinforcing bar rupture and concrete splitting failure modes are predicted. Furthermore, a machine learning algorithm is used to define a failure envelope and propose practice guidelines through parametric investigations.