Search Results (4)

This study presents a collaborative sensing approach that integrates the pre-embedded sensor method and the impact-echo technique to enhance the accuracy of grout filling quality assessment for precast concrete sleeve connections. The pre-embedded sensor method, which relies on vibration energy attenuation, enables continuous monitoring of the grout filling process; however, its accuracy is limited at low filling degrees, as vibration energy values remain constant at approximately 255 when the filling degree is below 70%. In contrast, the impact-echo technique, based on the principle of impact elastic wave propagation, demonstrates high accuracy in evaluating grout filling degrees across various levels, with reflected waveform amplitude increasing accordingly. This collaborative approach establishes a functional relationship between vibration energy values from the pre-embedded sensor method and grout filling degree, allowing for a comprehensive assessment of grout filling quality. In field demonstrations, the calculated grout filling degree values deviated by less than 5% from the set values. Practical guidelines for implementing the collaborative sensing approach are also provided. The method developed in this study offers a reliable solution for assessing grout filling quality in precast concrete sleeve connections, addressing the limitations of individual testing methods. Full article

For continuous steel–concrete composite girder bridges based on the post-combined method, the conventional rectangular group studs contribute to the isolation of the steel girder and the concrete slab before prestressing, leading to the majority of prestress forces being introduced to the concrete slab. However, rectangular-group stud holes cause the prestress forces to be unevenly distributed. In this study, a new type of bellow-sleeved stud (BSS) was developed to mitigate the weakening effects of rectangular group stud holes on the slab. A steel corrugated sleeve with a diameter of 60 mm was employed to cover the stud, which served as an internal formwork to prevent the concrete from bonding with the root of the stud. After prestressing was complete, the steel sleeve was filled with ultra-high-performance concrete (UHPC) to create a reliable combination between the concrete slab and the steel girder. To investigate the shear performance of this new type of connection, eight push-out test specimens were designed, and finite-element models were built. This study drew a comparison between the BSS and the ordinary headed stud (OHS). The research findings suggested that the BSS is subjected to less bending–shear coupling and offers a 4.5% increase in shear strength and a 31.9% increase in shear stiffness compared with the OHS. The study also analyzed the structural parameters influencing the shear performance of the BSS. It is found that the steel sleeve of the BSS has a negative effect on shear performance, but this can be mitigated by infusing high-strength material into the sleeve. Furthermore, the study examined the effect of construction quality on shear performance and suggested that sleeve deviation and grout leakage considerably reduced the shear performance of the BSS. Accordingly, strict control over the construction quality of the BSS is necessary. Full article

To study the performance and failure mechanisms of concrete-filled steel tube (CFST) column sleeve grouting connections, theoretical analysis and finite element simulation were performed for the structure in the connection. In this paper, a theoretical strut-and-tie model suitable for calculation of the axial compression capacity of sleeve grouting connections was proposed. High-precision numerical models were established to verify the applicability of the strut-and-tie model and the rationality of parameter selection in the sleeve grouting connection. The parameters include the shear key height, shear key shape, shear key distance, and grouting material strength. The results showed that the prediction values of the strut-and-tie model accorded well with the experimental values and simulated values. The average ratio of the calculated values based on the ACI and EC2 codes to experimental values were 1.07 and 1.09, respectively. An increase in the shear key height can improve the axial compression capacity of the sleeve grouting connection, and it was suggested that the range of the shear key height was reasonable at 2~3 mm. The shear key shapes of semicircular, rectangular vertical and trapezoidal were recommended, which can meet the requirements of sleeve grouting connections of CFST columns. The load-transmitting behavior of rectangular vertical shear keys was better due to the insignificant stress concentration. The rectangular horizontal form of shear keys is not recommended since it has the worst load transmission. The shear key height-to-distance ratios were recommended to be 0.044~0.1, the amplitude of the strength attenuation was different only after failure, and all models showed good ductility and compression capacity. With the increase in grouting material strength, the axial compression capacity of the sleeve grouting connection increased. It is reasonable to use grouting material strengths C50 to C90 for the sleeve grouting connection. Full article

Two groups of grouted sleeve splices for steel profile were tested to investigate their tensile behavior, serving as pilot studies for novel prefabricated reinforced concrete shear wall structures. In the first group, four splice specimens with different embedded lengths of steel profile were monotonic tensile loaded to determine an appropriate anchorage length. In the second group, three splice specimens with a conservative anchorage length of steel profile were tested under repeated tensile loading, cyclic loading at high stress, and cyclic loading at large strain, respectively. Parametric studies were then conducted on sleeve thickness, grout strength, offset of steel profile, and misalignment of steel profile using finite element method (FEM)-based models. The results show that the splices in the second group behaved well with minor residential deformation and almost no pinching effect. The optimized sleeve thickness could be appropriately determined using FEM models. The compressive strengths of the grout exceeding a threshold value and the offset of steel profile had minor influence on splice behavior, while the misalignment of steel profile had a pronounced effect. Full article