Effect of sleeve length on deformation properties of grouted splices
Tests on 12 grouted splices were performed to investigate their deformation properties under tensile loading. Test variables included diameter and type of spliced bars and the size of splicing sleeves. Finite element method based models of the splices were built, verified and used to investigate the effect of sleeve length on the deformation properties of the grouted splices. The sleeve length significantly affected the failure modes and further affected the splices’ deformation properties. A recommendation was proposed to maximize deformation properties of a specific splice by using a critical sleeve length associated with failure mode of bar fracture.
Mechanical Analysis of Grouted Sleeve Lapping Connector
Compared to grouted splice connectors that have been widely used in constructing precast concrete structures, grouted sleeve lapping connectors have the advantages of a large sleeve interior diameter and low manufacturing cost. In this study, 16 grouted sleeve lapping connectors and three grouted splice connectors were tested under an incremental tensile load. The differences in their tensile capacities and failure modes, especially the mechanical properties of the grouted sleeve lapping connectors, were investigated. It was found that the tensile capacities of the grouted sleeve lapping connectors were up to 2.45 times that of the grouted splice connectors when the sleeve inner surfaces were smooth. All of the grouted sleeve lapping connectors failed by a bar tensile fracture or bar-grout slip, whereas the only failure mode of the grouted splice connectors was grout-sleeve failure. The bond stress distribution around the inserted bar in the grouted sleeve lapping connector was similar to the bond stress distribution around a single bar anchored in concrete. The ultimate hoop compressive strain of the sleeve and the corresponding load increase with greater lap length. In addition, an approximate mechanical model with high reliability was put forward to describe the mechanical properties of the grouted sleeve lapping connector.
Bond of cement grouted reinforcing bars under constant radial pressure
Abstract A ribbed rebar or rock bolt, grouted with Portland cement is the most common type of reinforcement in geomechanical projects such as tunnels, rock slopes and foundations. Due to the frictional nature of the bond slip the normal stress acting on the rebar is the most important parameter controlling the bond capacity of the reinforcement. The more the confining stress, the higher would be the mobilized load bearing capacity of the system. To quantify this effect, series of laboratory tests were designed to study the effect of confining pressure on the bond capacity. A modified triaxial Hoek cell (usually used for testing the strength of rock samples under radial confining pressure) was used to facilitate application of a “constant radial confining pressure” to the grouted sample while pulling the bolt axially through the cement annulus. During test, axial load and displacement of the bolt as well as the radial dilation of the grout was recorded and stored in computer using a data acquisition system. The results show a non-linear relation between the increase of bond capacity and confining pressure. The radial dilation is quantified also as a function of confining pressure. A peak-residual behaviour is also a characteristic of these results which shows the importance of limiting the deformation of rock blocks to avoid entering into the post peak range of the reinforcement with low values of bond.