Rigid Wall Structure Research Articles

Sandbox Testing for Structural Assessment of Plastic Manholes

Structural behavior of flexible plastic manholes is very different from rigid concrete products. Although this is state-of-the-art knowledge, no international or EN standard exists on structural design of these products. Therefore, traditional soil models and soil pressure coefficients are usually applied if calculations for design checks are required. These models are based on rigid wall structures and pipe design methods and do not adequately account for the flexibility and soil interaction of the manholes in the subsurface 3D-space. Recently a working group was established in Germany to develop a design standard for concrete and plastic manholes. In order to calibrate the design equations for the flexible manholes on experimental data and field experience, an extensive in-situ testing of a PP manhole (DN 1000) in a sandbox was conducted. The comparison of deflection readings and calculation result reveals a great difference. Evidently, the assumption of horizontal soil pressure on plastic manholes is wrong. Only soil pressure coefficients of less than 0.1 give realistic results. This is significantly less than the coefficient for active soil pressure, which is widely used today. Short Summary: The paper presents results from sandbox testing of plastic manholes. It focuses on horizontal deflections resulting from wheel loads at the surface. Explanation is given on why most part of vertical point loads adjacent to flexible manholes is not acting on these products. Theoretical background for this specific behaviour is the load distribution of vertical soil pressure in the subsurface 3D-space. Based on these findings, a range for realistic soil pressure coefficients for actions on plastic manholes is presented.

Sandbox Testing for Structural Assessment of Plastic Manholes

Structural behavior of flexible plastic manholes is very different from rigid concrete products. Although this is state-of-the-art knowledge, no international or EN standard exists on structural design of these products. Therefore, traditional soil models and soil pressure coefficients are usually applied if calculations for design checks are required. These models are based on rigid wall structures and pipe design methods and do not adequately account for the flexibility and soil interaction of the manholes in the subsurface 3D-space. Recently a working group was established in Germany to develop a design standard for concrete and plastic manholes. In order to calibrate the design equations for the flexible manholes on experimental data and field experience, an extensive in-situ testing of a PP manhole (DN 1000) in a sandbox was conducted. The comparison of deflection readings and calculation result reveals a great difference. Evidently, the assumption of horizontal soil pressure on plastic manholes is wrong. Only soil pressure coefficients of less than 0.1 give realistic results. This is significantly less than the coefficient for active soil pressure, which is widely used today. Short Summary: The paper presents results from sandbox testing of plastic manholes. It focuses on horizontal deflections resulting from wheel loads at the surface. Explanation is given on why most part of vertical point loads adjacent to flexible manholes is not acting on these products. Theoretical background for this specific behaviour is the load distribution of vertical soil pressure in the subsurface 3D-space. Based on these findings, a range for realistic soil pressure coefficients for actions on plastic manholes is presented

Assessment of Non-Lethal Projectile Head Impacts

Anti-personnel NLW (Non-Lethal Weapons) are used to impart sufficient effect onto a person in order to deter uncivil, suspect or hazardous behaviour with a low probability of permanent or fatal injury. In many situations of conflict, where the army and law-enforcement units are involved, the use of such weapons can ensure a minimal risk of collateral damage. The most used NLW are Kinetic Energy Non-Lethal Weapons (KENLW) that involve the shooting of a deformable or breakable projectile. Since their first use, real cases indicate that the injuries inflicted by such projectiles may be irreversible and sometimes lead to death, especially for the head impacts. Therefore, there is a necessity to assess the head impacts in order to allow a safer use of such projectiles. This article concludes a 4-year study where three methods, independently developed, are considered to be applicable for the head risk assessment. The first method links force measurements on rigid wall structure with cadaveric and animal impact test results. Lesional thresholds, in terms of the maximum impact force and intracranial pressure, are proposed for unconsciousness, meningeal damages and bone damages, respectively. The second one is based on direct impact force measurements on a specific mechanical surrogate. The third method makes use of numerical simulations using a validated finite element head model. The numerical model allows the prediction of different kind of injuries. Firstly, the necessity of the assessment of the non-lethal head impacts is highlighted through some examples taken from literature. Secondly, the three different methods are detailed and illustrated for different projectiles. Outstanding results are given and a comparison between the different methods is proposed including some correlations between different criteria. Finally, some discussions and remarks conclude the present article.

Isolation by ConA binding of haustoria from different rust fungi and comparison of their surface qualities

Rust haustoria isolated from infected leaf tissue strongly bind to ConA. This property was exploited to purify them by affinity chromatography on a ConA-Sepharose macrobead column. Haustoria were obtained with more than 90% purity and yields of up to 50%. Binding of haustoria to the column was partially inhibited by a ConA-specific sugar, methyl α-D-mannopyranoside. Compared to ConA,Lens culinaris agglutinin and wheat germ agglutinin were less efficient affinity ligands. Using ConA-Sepharose, rust haustoria from a variety of sources could be isolated with equal efficiency, indicating that they have similar carbohydrate surface properties. The haustoria maintained their typical shape after the isolation procedure, which suggests a rather rigid wall structure. The morphology of haustoria was characteristic both for a given species and the nuclear condition of the rust mycelium. Electron microscopy of isolated haustoria revealed an intact haustorial wall surrounded by a fibrillar layer presumably derived from the extrahaustorial matrix. The matrix thus appears to represent a layer with gel-like properties which is rich in ConA-binding carbohydrates and connected to the haustorial wall but not to the host-derived extrahaustorial membrane.

Numerical investigation of controlled yielding of soil-retaining wall structures

Geosynthetic materials used as compressible layers against rigid wall structures can be employed to induce controlled yielding of the retained soil backfill during construction, and thereby ensure minimum lateral earth pressures on the structure. This paper describes two sets of numerical simulations that were carried out to model the controlled yielding concept. The simulations used a finite-element method together with a hyperbolic constitutive soil model. The first set of simulations was used to validate the FEM approach by comparing in the literature. The second of simulations was carried out to generate preliminary design charts for the selection of stiffness and thickness of compressible layers placed against rigid walls retaining well-graded sand backfills compacted to a range of densities.

Snow–Avalanche Impact on Structures

AbstractTwo–dimensional hydrodynamic equations for laminar, viscous flow, and admitting a frictional slip-plane lower boundary are applied to the modeling of snow-avalanche impact on rigid wall structures. Predicted maximum pressures and pressures versus time are compared with published experimental results, and general correspondence is established. Impact pressure versus time is found to depend upon the shape of the avalanche leading edge, for which general information is lacking. Computer modeling of more complex structural configurations is feasible using the methodology reported.

Snow–Avalanche Impact on Structures

AbstractTwo–dimensional hydrodynamic equations for laminar, viscous flow, and admitting a frictional slip-plane lower boundary are applied to the modeling of snow-avalanche impact on rigid wall structures. Predicted maximum pressures and pressures versus time are compared with published experimental results, and general correspondence is established. Impact pressure versus time is found to depend upon the shape of the avalanche leading edge, for which general information is lacking. Computer modeling of more complex structural configurations is feasible using the methodology reported.

Earthquake induced pressures on a rigid wall structure

This paper describes the application of linear elastic theory to estimate the earthquake-induced soil pressures on a wall forming part of the structure of a power station founded on rock.
 Analyses showed that the Mononobe-Okabe assumptions would not be applicable for this relatively rigid wall structure and it was found that elasticity theory gave greater forces and moments than would be obtained by using the Mononobe-Okabe method. The extent to which deformations of the structure and its foundations influence the wall pressures was investigated. It was found that even for this relatively rigid structure and foundation, the displacements resulting from the inertia of the wall structure can produce a significant increase in the total forces acting on the wall.