ICE - Institution of Civil Engineers - Virtual Library

A new model for simulating cracks in cementitious composites using embedded planes with local plasticity is presented. In the model it is assumed that the embedded planes of degradation (PODs) can not only undergo separation but can also regain contact, with the state of contact being controlled by a local contact model. A local plasticity model is included to capture permanent relative displacements associated with rough contact between the surfaces of embedded cracks. This model is a significant development of the Craft model developed by the second author, which allows shear contact, or aggregate interlock, behaviour, as well as crack opening/closing behaviour, to be simulated more accurately. A fully consistent tangent stiffness matrix and stress recovery algorithm is derived. The model has been implemented in a constitutive driver program and also in the finite–element program Lusas. The model is assessed against a series of single-point stress–strain paths, and against data from normal-shear and cyclic tests. It is shown that the inclusion of local plasticity significantly improves the accuracy of the predictions of the model when judged against experimental data.

Hydraulic engineers and researchers deal with the scientific challenges presented by turbulent flow and its interactions with the surroundings. Turbulent flows are characterised by unpredictable behaviour, and, as yet, little systematic research has been conducted in natural systems. This paper discusses the implications of recent developments in affordable instrumentation, which was previously characterised by intrinsic weaknesses that adversely affected the quality of the signal outputs. A challenging application is the unsteady turbulence field in tidal bores. The interactions between open channel flows and movable boundaries and the atmosphere illustrate another aspect of our limited knowledge. Rapid siltation of reservoirs and air entrainment in turbulent freesurface flows are discussed. In both applications, hydraulic engineers require some broad-based expertise. In turn, the education of future hydraulic engineers is of vital importance.

This work deals with the modelling of the dynamic effects of anchor head assemblies of mine bolts and their interfaces with the rock and other components. The load of the anchorage installed in the laboratory was assessed by a non-destructive technique initially using a system based on the application of the impulse load and observation of the frequency response. An anchor head assembly, different from that commonly used, was then deployed as part of tests to assess the load of the anchorages. A dynamic model, developed previously, was used, to replicate the results obtained from the experiments. It was shown that the anchor head model required enhancement in order to obtain the range of frequencies found from the experiments. A set of tests with the more complex anchor head set-up was undertaken in order to obtain the characteristics, in this case stiffnesses, of the anchor assembly interfaces. The sensitivity of different components within the anchor head assembly is discussed showing the influence of the complexity of the head.

In the present study, experimental data for bend pressure drop were collected from a pilot plant test loop with a pipe diameter of 53 mm. The experiments were performed at three different efflux volumetric concentrations (0%, 3·94% and 8·82%) of 448·5μm silica sand particles and for each concentration the flow velocity was varied from 1·78 to 3·56 m/s. Pressure drops were measured using a multi-tube inverted U-tube manometer assembly, with separation chambers to prevent blockage of the connecting tubes. It was observed that pressure drop along the pipe bend increases with flow velocity and particle concentration. The experimental data for bend pressure drop collected in the present study have been compared with threedimensional computational fluid dynamics (CFD) modelling by running the commercial CFD code Fluent, and show good agreement (within a percentage deviation of ±10%). Modelling results indicate that the velocity and concentration distribution of solids become more uniform downstream, and the pressure at the outer wall is greater than that at the inner wall in the bend.