International Concrete Abstracts Portal

For the assessment of existing reinforced concrete slab bridges, the shear capacity under concentrated loads and transition to flexural failure are under discussion. Previous research showed an increased shear capacity for slabs under concentrated loads close to the support, so that for assessment, positions farther from the support became governing. This experimental research studies the flexural and shear capacity of reinforced concrete slabs under concentrated loads. For this purpose, six slabs representing 1:2 scale continuous slab bridges were tested at various positions from the support and along the width. The results show two main failure modes: flexural failure (onset of yielding of the reinforcement), and shear failure. Secondary punching was observed as well. The comparison between the test results and calculations methods shows that all considered methods perform reasonably well when both shear and flexure are considered, and the effective width in shear is included, with average tested-to-predicted capacities between 0.92 (Regan’s method) and 1.39 (Extended Strip Model) and coefficients of variation between 15% (Regan’s method) and 25% (ACI 318-19 and Eurocode 2). These insights can be used for the assessment of existing reinforced concrete slab bridges.

This study uses six large-scale experimental tests to investigate the seismic behavior of external socket connections for reinforced concrete columns. The tests evaluated the effects of key design parameters, including socket height and grout strength, on the performance of these connections under reverse cyclic lateral loads. The results indicate that socket height significantly affects whether the plastic hinge forms in the column above the connection or inside the socket and influences the required strength of the structural components. Shorter socket heights required higher grout strengths and increased shear capacity to avoid undesirable failure modes. Three primary failure modes were observed: grout crushing, shear failure, and flexural failure above the socket. Regardless of socket height, all tests showed that external socket connections effectively protect adjoining structural members by limiting plastic strain demands. These findings provide valuable insights into optimizing the design and performance of external socket connections in seismic regions.

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.

The challenges of deterioration and increasing maintenance costs in steel-reinforced concrete railway sleepers emphasize the urgent need for innovative, durable, and sustainable alternatives. This study evaluated the shear strength of precast concrete sleepers prestressed with basalt fiber-reinforced polymer (BFRP) rods, using normal self-consolidating concrete (NSCC) and fiber-reinforced self-consolidating concrete (FSCC). Seven full-scale specimens, each 2590 mm (8 ft, 6 in.) in length and prestressed to 30% of the tensile strength of BFRP rods in accordance with the Canadian Highway Bridge Design Code (CHBDC), were tested to assess cracking loads, ultimate strength, bond behavior, and failure mechanisms. All tests were conducted in accordance with the American Railway Engineering and Maintenance-of-Way Association (AREMA) guidelines. The results indicate that all specimens met AREMA design load requirements without visible cracks or slippage based on a train speed of 64 km/h (40 mph), annual traffic of 40 MGT (million gross tons), and sleeper spacing of 610 mm (24 in.). Comparative analysis using CSA S806-12 (R2021) design standard and ACI 440.4R-04 (R2011) design guide revealed that predictions based on CSA S806-12 (R2021) were less conservative than those from ACI 440.4R-04 (R2011) for the shear strength of BFRP prestressed sleepers. The BFRP rods exhibited excellent tensile performance, with minimal prestress losses, and their sand-coated surface ensured efficient load transfer by preventing slippage and enhancing the bond strength. FSCC specimens demonstrated delayed cracking, enhanced crack control, and ductility compared to NSCC specimens. These findings highlight the potential of BFRP prestressed concrete sleepers, particularly when combined with FSCC, as a sustainable solution for railway infrastructure, emphasizing the need for a design code refinement for BFRP applications.