Abstract

Glass fibers were used to investigate the impact of loose fiber reinforcement on the performance characteristics of"br" asphalt mixtures. For the laboratory tests on asphalt mixes a fiber content of 0.5 mass.-% was chosen. This paper"br" presents selected results of fatigue, stiffness (both cyclic indirect tensile tests) and rutting / plastic deformation"br" tests (cyclic uniaxial compression test) on different asphalt mixes. An asphalt base course mix AC 22 T S, an"br" asphalt binder course mix AC 16 B S and an asphalt concrete AC 8 D S were chosen to determine the effect of"br" glass fiber reinforcement. Furthermore, the fiber length was varied for the AC 16 B S. The content of reclaimed"br" asphalt (RA) was varied for the AC 22 T S. Depending on the mix design the bitumen content was increased up"br" to 0.3 mass.-%.

Abstract

EuroNCAP tests are carried out since 1997. The test procedure in general is comparable to the EC Directive 96/79 with a test speed of 64 km/h. This increased test speed implies a higher frontal stiffness for new vehicle designs in order to achieve a high ranking. This frontal stiffness is one of the major factors for compatibility in car to car collisions. To support the European 4th framework compatibility research activity, load cell barriers are used in ENCAP tests carried out at the TNO Crash Safety Centre and TRL. In this paper global force displacement characteristics of a number of different vehicle classes are compared and analysed. It will be made clear that small vehicles in the past known not to be strong can produce comparable force levels as large cars. For compatibility this means that in small car against large car collisions the small car's passenger compartment can stay stable and can offer better protection to the occupants, since from accident analyses it is known that serious injury often is caused by high intrusion into the passenger compartment. For frontal impacts this means that ENCAP tests have driven small cars to increased compatibility for one aspect of compatibility (cabin integrety) at higher speed. MPV's with high masses and little crushable space show more aggressive force displacement characteristics. This car category is expected to behave less compatible hitting small cars or medium size passenger cars. A longer crushable space for this category is desired, which is in conflict with the special look for these vehicles. This trend in stiffer vehicle fronts might result in future modifications of the European side impact barrier, which is currently based on average vehicle fronts of old vehicles. This item is only mentioned and will not be further discussed

Abstract

At the state of art, current simulative methods modelling joint properties as fixed interaction between components or concentrate on the characterization of the joint stiffness and damping of coupled metallic structures. In the current work, the developed thin layer interaction (TLI) method was applied to study the influence of the joint stiffness and damping of plastic components coupled with metallic structures. The joint stiffness and damping of different coupled metallic-plastic joint structures was characterized experimentally and was used to fill the reduced transverse shear stiffness and damping tensors of the numerical TLI model. The TLI model was used to determine the structural dynamics behavior of a short glass fiber reinforced plastic engine bracket mounted to a steel block. The comparison of experimental and simulative results shows a better correlation under the usage of the TLI model compared to a fixed modeled joint behavior. As result, the TLI model allows a better prediction of the structural dynamics of coupled plastic components. Further researches focus on the accurate experimental estimation of the boundary conditions regarding excitation and mounting of the plastic components. Thus, a more realistic modelling of the numerical joint boundary conditions is possible for an improved simulation of the structural dynamics of plastic components.

Abstract

The weathering profile in mudstone outcrops can range from weathered clay to unweathered mudstone. The strength and small-strain stiffness of these materials, and of stiff clays and weak rocks in general, is critical to the design of geotechnical structures. Monitoring data and ground investigation data were gathered during the construction of a trial embankment founded on weathered, Jurassic-aged mudstone, for the HS2 high-speed railway project (UK). These data included outputs from in-situ downhole geophysical tests and extensometers at the embankment location. These were compared to ground investigation data from the wider mudstone outcrop over an 18.2 km stretch of the route. The installation of extensometers prior to loading by the embankment construction enabled the measurement of in-situ strains for a range of small and medium strains. It was therefore possible to characterise the stress-strain behaviour of the individual layers within the ground profile. The results showed that stiff clays derived from weathered mudstone at shallow depth (<10 mbgl) are characterised by low undrained shear strength (<300 kPa) and by maximum stiffness values that are comparable to laboratory measurements from fine-grained soils. However, the unweathered mudstone at greater depth (>15 mbgl) showed higher strength (>300 kPa) and higher maximum stiffness than the overlying clay. Both the strength and stiffness profiles showed a transition zone between the weathered clay and the unweathered mudstone. This zone included a partially weathered mudstone that had the visual appearance and index properties of a mudstone, but the strength of a stiff clay (i.e. τu < 300 kPa).

Abstract

Field and laboratory testing was carried out for the construction of a 100 m long cable stayed bridge situated in the foothills of the Alps in the south of Germany, a region dominated by deep post-glacial, fine-grained sediments. Due to the sensitivity and associated challenges with retrieving undisturbed soil samples in situ tests and their evaluation proved to be essential for the geotechnical design of the bridge foundation. This contribution focuses on the analytical and numerical interpretation of Cone Pressuremeter Tests (CPM). The non-linear 𝐺-𝛾 relationship and undrained shear strength (using both the limit pressure and reverse plasticity contraction analysis) were determined analytically. Numerical investigations were carried out as verification using both the Finite Element method (FEM) using both 1D (cavity expansion) and 2D simulations (where the penetration of the probe was modelled) as well as using the Finite Difference (FD) method. 2D simulations demonstrated that the assumption of the cylindrical cavity expansion is appropriate for modelling the CPM tests. The interpreted undrained shear strength showed good agreement with other field tests, including CPTu, vane shear (FVT) and seismic cone penetration (SCPT) tests, as well as with the results of laboratory tests on disturbed samples. CPM tests with strain rate jumps were conducted during pressuremeter expansion, wherewith it was possible to quantify the viscous response of the soil. Based on the holistic interpretation of the field and laboratory results involving both numerical simulations and analytical methods the parameters for the material model Viscohypoplasticity were calibrated.

Abstract

The small strain shear modulus of soils is an important design geotechnical parameter for a wide range of civil infrastructure applications. The small strain shear modulus can be determined by using elastic theory as a relationship between the soil density, which is expressed as a function of void ratio, and the measured shear wave velocity. Thus, the void ratio has a fundamental impact on the accuracy of the result. Laboratory testing involving resonant column apparatus allows for determining the changes in stiffness of soils with varying void ratios. Standard of-the-shelf resonant column apparatus works well for clayey soils but presents a number of limitations for coarse soils that makes accurate and reliable void ratio measurement difficult due to both pore fluid and (often) sample loss during removal from the equipment. This paper presents the development of a modular set-up which allows for complete specimen sealing at the end of shear wave velocity testing. The modular set-up along with the specimen can be removed from the resonant column apparatus and the void ratio can be determined by means of end-of-test-freezing similar to triaxial testing. From this, reliable small strain stiffness at well-determined void ratio can be computed. The void ratio measurements using the new modular set-up were compared to those from triaxial tests performed on identically prepared specimens. The difference in void ratio at any given isotropic confining stress was between 0.001 and 0.011.