Federal Highway Research Institute

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Analysis and Development of Pavement Structures

Investigation potential of point clouds for engineering geodetic purposes (02.0444)
In recent years, a large number of new methods for the generation of point clouds for engineering geodetic purposes have come onto the market. This concerns terrestrial as well as mobile and airborne laser scanning measurement systems and photogrammetric systems based on drones. Each of the different measurement systems has advantages and disadvantages or can only be used in combination with conventional methods. At the present time, it is unclear which system specifications are appropriate and economically viable for applications in road construction surveying. It is also unclear to what extent the use for subsequent work processes represents a gain, for example through georeferenced point clouds in the preparation of the design, in surveying-related construction supervision or in construction accounting. The aim of the project is to clarify for which applications point clouds can be used in road construction management, both from a technical and a qualitative point of view. Aspects of road safety and the reduction of traffic disruption should also be taken into account.

Adaptation of pavement design to climate change (04.0332)
All scientific forecasts on climate change as well as the experiences from the past years lead to the assumption that the weather will change with regard to the long-wave counter radiation and thus the prevailing temperatures. Furthermore, it is undisputed that this climate change will lead to changed stresses in asphalt and concrete road pavements and thus to earlier or later damage occurrence times. Climate change will therefore affect the design of road pavements, which is usually carried out for periods of use of at least 30 years. The aim of the research project is to develop a sustainable procedure for taking into account the effects of climate change in the structural design of road pavements and the associated updating of the input parameters. The procedure to be developed with the forest impact zone maps to be created and the maps of the KiST zones converts the entire pavement design to the consideration of climate change. The results are thus directly incorporated into the corresponding regulations.

Aspects of dimensioning and construction to ensure availability during temporary use of peripheral areas of federal highways (04.0327)
Road pavements, in particular motorways, are usually dimensioned and constructed under the assumption that the traffic loads are at a distance from the edge of the road. In exceptional cases, the guidelines for the construction of motorways (RAA 2008) provide for the temporary use of peripheral areas. Examples are the repeated exceeding of the capacity limit of the motorway section as well as traffic jams or severe traffic disturbances. The use of the peripheral areas can have an unfavourable effect on the service life, in particular due to the loads of heavy traffic, expressed by a reduced number of load cycles that can be sustained, and the necessary maintenance measures. Accordingly, the quantification of the reduced number of load cycles that can be absorbed as a result of roadside traffic is required in order to be able to take the necessary constructive measures in accordance with the planned duration of the traffic management due to the structural condition. Investigations shall be carried out which take into account the changing cross-sectional conditions, identify existing weak points and propose solutions to ensure the functionality of the design. The aim of this research work is to develop computational models based on realistic assumptions of heavy traffic and to carry out dimensioning which takes this marginal load into account.

Optimization of the applicability of probabilistics in dimensioning and substance evaluation of concrete roads (04.0313)
The aim of the research project is to combine existing research results on probabilistic dimensioning as well as on dimensioning with the finite element method of concrete roads and to demonstrate them in IT terms. The main task is to optimize the computing time. Restrictions regarding the applicable geometries and material properties may arise. The results form the basis for the new creation of RDO Concrete and the first creation of RSO Concrete.

Experience in using RSO Asphalt (3416002)
The current draft of the guidelines for the assessment of the structural substance of pavements of traffic areas executed in asphalt (RSO Asphalt) are to become FGSV standards and specifications. Within the scope of this project and working in collaboration with the regional road construction authorities, an empirical background for the use of the procedure described in the RSO Asphalt is to be created. For this purpose, different road sections in the federal trunk road network of different age are to be considered in accordance with the RSO Asphalt and the respective remaining useful lives determined by the regional road construction authorities, under the lead of the Federal Ministry of Transport, together with the Federal Highway Research Institute. The findings made on the theoretical and practical application of RSO Asphalt will be put up for discussion in the responsible committee in finalisation of the current draft.

Compressive Stress Sensor CANopen (3415000)
A variety of instrumentation is used to provide information on ways in which a road reacts to the stresses of heavy goods traffic. Compressive stress and strain are the two most important physical variables in this context. The type of sensor used to measure these variables previously could not be calibrated following its installation, something that proved to be a significant shortcoming which also led to high default rates in the strain sensors. The intention is now to develop a production-ready compressive stress sensor. Besides updating the interface, the project seeks to develop the multi-sensor by integrating environmental sensors (for temperature and humidity); this process is to be supported by the inclusion of considerations in the “Feasibility Study on the Development of Sensors for the Recording of Structural Condition” published by the Fraunhofer Institute for Physical Measurement Techniques IPM in 2012.

Regular investigation of a test track with cold-recycling layer (3410002)
The cold-recycling method can be used to produce base courses at a building site by adding binder to bound and/or unbound layers of the superstructure. This allows complete use of road-building materials according to the Recycling Economy and Waste Act. The information sheet for cold recycling in situ for road superstructures , Version 2005, states that pavements with cold-recycling layers are only planned up to Building Class III as specified in the RStO 01 (Code of Practice for Road and Pavement Construction). During the general renovation of the B 52, sub-sections were implemented as test sections for the use of cold-recycling layers, although the traffic load exceeded Building Class III. Initial experiences with other road sections of this kind look promising. The main purpose of the test section is to extend the experience with cold recycling layers in pavements to traffic loads above Building Class III. The test section will also provide information concerning the effect of different bituminous binders, the share of the cold-recycling layer in the total carrying capacity of the pavement and a possible comparison of the capacities of the asphalt base courses and the cold-recycling layer. The current project also includes non-destructive measurements with a falling weight deflectometer and geo-radar as well as an evaluation of the data. Experience concerning the computational dimensioning of cold-recycling layers is to be gained as well.

Pilot application of a temperature-controlled road on the duraBASt (04.0325)
The aim of the research project is the development of a procedure for the computational dimensioning of temperature-controlled road pavements via the implementation in a large-scale test on the duraBASt. For this large-scale test, 5 construction variants of the temperature-controlled road and an energy system for temperature control will be set up, with which the mode of action and the efficiency of the temperature control will be investigated via corresponding sensor data in the system control and the construction variants. By limiting the temperature stress on the road pavement - both through low and high temperatures - a longer service life and trafficability of the road pavement can be expected. By avoiding icy roads, a seasonally independent high transport performance can be expected, road safety increases and the economic damage caused by icy road accidents is reduced. Furthermore, the reduction in the use of road salt significantly reduces the strain on road pavements and structures as well as environmental pollution. The tempering of road pavements can thus make a significant contribution to ecological and economic benefits on selected stretches of road.

Verification of the mix design of cold bound bituminous base courses and derivation of dimensioning principles (04.0329)
Large quantities of recycled asphalt pavements are stored at the mixing plants and will probably not be able to be reused completely in hot-mixed asphalt layers in a high-quality way. Another possibility is to use the RAP in cold-bound base layers. Requirements regarding the properties of the construction material mix and the performance are specified in the information sheets for the recycling of road construction materials containing pitch and of RAP in bitumen-bound base layers by cold processing in mixing plants (M VB-K, 2007 edition) and for cold recycling in situ in the road pavement (M KRC, 2005 edition). Information on the dimensioning of such cold bound base layers is given in the these guidelines. The aim of the research project is to check the performance of existing roads with cold bound bituminous base layers and to determine the relevant properties of these layers as a basis for the revision of the guidelines and for design guidelines for construction types with cold bound base layers.

The Seelow Test Road (3215101)
The Seelow test road was set up in 2007 by the Land of Brandenburg with a projected operational life span of ten years. The test road will therefore reach the end of its operational life within the foreseeable future. On the one hand, this project seeks to continue taking measurements with temperature and moisture sensors in the layers without binding agents for the various analysis variants beyond the end of the test road’s projected operational life. Secondly, the measurements of load-bearing capacity are to continue twice a year using the FWD in order to continue the observation and description of the analysis variants consisting of recycled concrete with varying amounts of brick rubble. Comparative FWD measurements and geo-radar measurements are also envisaged using the measurement instruments belonging to the Federal Highway Research Institute.