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Copyright of e & i Elektrotechnik und Informationstechnik is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Testing the effectiveness of an inverse Wenner‐Schlumberger array On the Swabian Alb high plain, southwestern Germany, the new high‐speed railway line Wendlingen–Ulm of the German Railway Company (Deutsche Bahn AG) is under construction. 2.5D electrical resistivity tomography (ERT) measurements (meaning the use of parallel 2D lines) were performed at the excavation bottom level in addition to the investigation program of the construction company including microgravimetric and seismic methods. The aim was to test the effectiveness of an inverse Wenner‐Schlumberger array for exploring geological defective karst voids and other karstic features in a highly heterogeneous karstic environment. The 2.5D ERT survey provided resistivity values of marls and marlstones, a limestone bedrock, a collapse doline and of an air‐filled cavity. A clear demarcation between the marls and marlstones and the limestone bedrock was only possible outside the area of influence of the collapse doline; the latter could not be exactly delineated from the adjoining geological units. In addition, one of three air‐filled voids (open fractures, cavities) could be derived accurately in location and roughly in size and shape from the 2.5D ERT survey; the other two were not detected by means of ERT because of (i) its location beneath a high‐resistive anomaly and (ii) its comparatively small maximum horizontal opening width of only 1 time the used inter‐electrode spacing. [ABSTRACT FROM AUTHOR]

Test method to determine the impact sound insulation of thermal insulation elements of balconies The thermal insulation of balconies and access balconies from the façade is usually performed by using reinforced thermal insulation elements. These elements also affect the impact sound transmission and are therefore relevant for the acoustic planning of a building. In a research project at the University of applied sciences Stuttgart a laboratory test procedure to provide acoustic quantities of such elements was developed. The relatively compact test set‐up consists of a balcony that is connected to a ceiling by a thermal insulation element. The impact sound reduction in analogy to floor coverings and the impact sound difference as insertion loss with reference to a rigidly connected balcony can be determined using structure‐borne sound measurements. Both values can be used for product description and to predict the impact sound transmission in a building according to EN ISO 12354‐2. This article describes the test procedure and validates it by means of finite element simulations. [ABSTRACT FROM AUTHOR]

Rock stress determination by means of the overcoring method. Part 2: Borehole deformation gauges. Recommendation no. 14 (revised) of the Commission on Rock Testing of the DGGT The Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e. V. is compiling suggestions for rock mechanical laboratory and field tests as well as for monitoring rocks and geotechnical structures on‐site. The presented revision of recommendation No. 14 covers the determination of rock stresses by means of overcoring tests and considers the development of this method since the publication of recommendation No. 14 in 1990 [1]. Further, requirements for the measuring instruments and the procedures regarding the execution and evaluation of these tests are specified. Reference is made to the ISRM Suggested Methods in which overcoring tests are dealt with [2, 3]. Recommendation No. 14 is divided into two parts. The first part deals with overcoring tests using triaxial strain cells. This second part covers overcoring tests using borehole deformation gauges. [ABSTRACT FROM AUTHOR]

Horizontal stress state of non‐cohesive soils due to deep vibro compaction with depth vibrator – Experimental and numerical studies Vibratory compaction methods for deep‐reaching improvement of non‐cohesive soils have been used since the 1930s. Either depth vibrators or top vibrators can be applied. The design of the compaction process as well as the subsequent quality control is still based almost exclusively on empirical relationships. In this context, the use of indirect ground exploration methods like dynamic probing or cone penetration tests and the work‐integrated recording of process parameters has become established. This paper presents experimental investigations to assess the change in horizontal stress in the subsoil due to deep vibro compaction with depth vibrator. The aim is to provide a basis for a better understanding of the increase in stiffness and strength of improved non‐cohesive soils. Furthermore, results of a highly simplified numerical simulation for estimating the stress changes are discussed in abbreviated form. A large‐scale compaction experiment was realized. At two test fields with different compaction grid the inclinodeformeter was used the first time for this application. Additionally, conventional compaction control techniques (dynamic probing and cone penetration tests) were performed. Besides the qualitative development of the stress change over depth, the influence of the compaction grid spacing could be measured. [ABSTRACT FROM AUTHOR]

Rock stress determination by means of the overcoring method. Part 1: Triaxial strain cells – Recommendation No. 14 (revised) of the Commission on Rock Testing of the DGGT The Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e. V. (German Geotechnical Society) is compiling instructions for rock mechanical laboratory and field tests as well as for monitoring in rocks and geotechnical structures on‐site. The presented revision of recommendation No. 14 covers the determination of rock stresses by means of overcoring tests and considers the development of this method since the publication of recommendation No. 14 in 1990 [1]. Further, requirements for the measuring instruments and the procedures regarding the execution and evaluation of these tests are specified. Reference is made to the ISRM Suggested Method, in which overcoring tests are dealt with [2, 3]. Recommendation No. 14 is divided into two parts. This first part deals with overcoring tests using triaxial strain cells. The second part covers overcoring tests using borehole deformation gauges. [ABSTRACT FROM AUTHOR]

Decentral monitoring as a contribution towards improving indoor comfort and operation of commercial buildings Many existing non‐residential buildings offer potential for improving the indoor climate and energy performance through improved use and operational management. To do this, however, the conditions must first be measured and assessed so that recommendations for action can be developed. Existing building automation systems are often not sufficiently qualified for these activities. A corresponding expansion of the hardware and/or software is often economically disproportionate. Against this background, room climate measurements were carried out in exemplary buildings with decentralised data loggers of different designs over at least one year. The three buildings selected for this paper have very different ventilation concepts. The two buildings without air conditioning systems showed the influence of user behaviour on the achieved indoor climate level in different ways. The building with an air‐handling system exemplified the influence of an unfavourable set point on energy consumption. Decentralised measurement technology offers great potential for quality assurance in existing buildings. In new buildings, it is necessary to design building automation systems for quality assurance tasks and not only for function assurance. [ABSTRACT FROM AUTHOR]

Cutting release‐ and compensation‐method to measure compression stresses near the surface of geotechnical structures – Recommendation No. 22 of the Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e.V. The Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e. V. (German Geotechnical Society) is compiling suggestions for rock testing in laboratory and in‐situ and for performing monitoring of rock masses and civil engineering structures. Recommendation No. 22 deals with the measurement of peripheral compression stresses at the surface of geotechnical structures and of structural elements using the cutting release‐ and compensation‐method. The measurement principles, the required equipment, the practical application on site and the evaluation of the obtained data are described and an example is given. [ABSTRACT FROM AUTHOR]

Copyright of Tribologie und Schmierungstechnik is the property of Narr Francke Attempto Verlag GmbH & Co.KG and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The behaviour of granular materials, such as sands, is controlled by the interaction of particles. This interaction can be described geometrically by orientations and statically by forces. Using x‐ray μ‐tomography and image analysis, it is possible to determine the geometrical fabric at the grain‐scale, whereas the forces still remain inaccessible in natural granular materials. This article shows how the fabric can be accessed using standard and recently proposed advanced image analysis techniques and elaborates which problems arise when describing the fabric quantitatively. These techniques were applied to a triaxial compression test on Hostun sand. The results are described in terms of a fabric tensor, a coordination number and an anisotropy and then related to the macroscopic behaviour of the sample. [ABSTRACT FROM AUTHOR]

Impact sound level reduction, sound insulation dimensions and impact sound levels of prefabricated bathrooms Prefabricated bathrooms have been used in the construction industry for decades. They are assembled in the factory as closed elements with all installations, objects, wall cladding and accessories, and only have to be set up and connected on site. Prefabricated bathrooms are available as concrete cells but also as sheet steel structures that receive a cladding of plasterboard panels on site. DIN 4109 does not contain a component catalog for prefabricated bathrooms, so that manufacturers of such prefabricated bathrooms must submit test certificates on sound insulation. For the most part, these test certificates contain the weighted impact sound level reduction in order to be able to predict the weighted standard impact sound level on the basis of the reinforced concrete raw ceiling. However, there are also test results on the sound insulation dimensions of the partition walls and of the complete system on the building. The following is a summary of the findings on the sound insulation properties of prefabricated bathrooms obtained from a large number of measurements. [ABSTRACT FROM AUTHOR]

Air well system of the Burgtheater Vienna: sustainable cooling strategies The Burgtheater Vienna was built at the end of the 19th century and it is one of the most important straight theatres in Europe. It is equipped with an air well system for the fresh air supply and conditioning of the auditorium. The air is drawn in at the Volksgarten nearby and led to the auditorium via an underground tunnel. Warm and used air is dissipated through the ceiling and the roof of the theatre. The original dimensions of the facilities are still apparent. In the framework of this study, temperature, humidity and air velocity sensors were positioned at significant places along the ventilation system and the data was evaluated over the summer 2019. As a result, optimization potentials regarding operation control and air cooling using water atomization were evaluated. Finally, it was shown that the air well system can be used to sustainably condition the theatre in a time of rising temperatures. [ABSTRACT FROM AUTHOR]

Urban thermal comfort maps based on a three‐dimensional sampling algorithm and UAV‐based radiometric measurements A new methodology and workflow to assess outdoor thermal comfort and thermal stress in urban areas is developed. The new methodology is applied to a case of an urban quarter in the city of Graz. The method recognizes the significance of detailed and accurate spatially resolved determination of mean radiant temperatures taking into account all relevant radiative components. The method relies on 3D‐data acquired from drone (unmanned aerial vehicles UAV) flights, pre‐existing city models and a Monte‐Carlo ray‐tracing algorithm using directional sampling curves based on a 3D‐model with human topology. The detailed three‐dimensionally determined mean radiation temperatures are used to calculate thermal comfort level maps using UTCI and PMV calculation. [ABSTRACT FROM AUTHOR]

Evaluation of software for the creation of soil models In the "Road Map for Digital Design and Construction" of the Federal Ministry of Transport and Digital Infrastructure (BMVI), public infrastructure projects are required to use the Building Information Modeling (BIM) method. As a result, the Federal Department of Foundation Engineering of the Federation of the German Construction Industry (Hauptverband der Deutschen Bauindustrie e. V.) demands a discipline‐specific model for foundation soil from the client in its technical position paper. The discipline‐specific model should consist of the earth's surface in the form of a digital terrain model (DTM), the soil layer model and also the subsoil data on which it is based (drillings, survey data, etc.), as well as layer information and soil characteristics of the subsoil on the basis of the geotechnical report. The location of the layer boundaries between the outcrops is to be derived by using interpolation methods and adjusted by manual post‐processing. In order to manage these challenges, different software is evaluated. [ABSTRACT FROM AUTHOR]

On the determination of water pressures on bank walls in tidal areas For the design of bank walls, the pressure and flow forces resulting from ground and surface water have to be considered. For tidal areas, the EAU 2012 contains approximation approaches which can be used to estimate the water levels for the individual design situations. The approximation approaches are universal, so that under certain hydraulic boundary and local conditions the water overpressures are too far on the safe side. In this context, it may be useful to determine the water overpressures on the basis of groundwater level measurements. By means of an example, it is shown which evaluation approaches are to be pursued for the conditions in the northern German tidal regions, in order to also capture the hydrogeological conditions more precisely. Here the water overpressures, which were determined by an evaluation of the groundwater levels and a groundwater modelling, are far below the values, which result from the EAU approximation approaches. Thus, groundwater level measurements and a specific evaluation enable a more economical dimensioning of bank walls in tidal areas, so that groundwater measurements are generally recommended for the northern German tidal areas. [ABSTRACT FROM AUTHOR]

Stress state in conveyor bridge dumps In the Lusatian lignite mining area in eastern Germany, extensive mine dumps have been created as a result of opencast lignite mining, where under certain conditions there is a risk of soil liquefaction. Spontaneous soil liquefaction can occur if a trigger disturbs the original equilibrium state. The required energy of the trigger is directly dependent on the stress state. Due to the dumping technology with inclined dumping discs, the stress state in the dumped soil can differ from the stress state of naturally deposited soils. In an active open pit mine, a comprehensive measurement program was implemented to record the stress state in the dumps during overburdening and progress of the open pit. For this purpose, 16 stress‐measuring stations were installed in four sensor positions and four measuring cross‐sections and covered by a conveyor bridge of type F 60. At each stress measuring station the horizontal stress in the direction of the stope σxx and perpendicular to the direction of the stope σyy as well as the vertical stress σzz were recorded. The measurement results were reproduced with numerical calculations. The measurement results and the results of the numerical calculations show that no homogeneous stress state prevails in the dumps, which can only be described by one earth pressure coefficient. [ABSTRACT FROM AUTHOR]

Measurement monitoring of the installation of a king pile with vibration and impact ramming The installation of combined sheet steel pile walls is still a challenge. Distorted king piles can lead to a failure in the connection between the king pile and the sheet pile. There is only little of rules how to choose the driving hammer and guiding which is suitable for the soil and installed pile. Currently the proof for combined walls is only done for the final state. Hence a proof for the combined walls is required which takes the installation process in account and a guideline for choosing the correct guiding for the installation of king piles is required. Unfortunately, the dynamics of the installation process of king piles is not well known. That's why the installation of a big king pile is investigated on a construction site at the harbor of Rostock. It's possible to measure the acceleration, change in length and inclination at the king pile. Further the dynamics and movements of the installation devices, which are influenced by the ram guide, can be investigated. The following change in the position of the foot of the king pile can be derived. [ABSTRACT FROM AUTHOR]

Duration of the Pressure Build‐up for Pressurization Tests of Very Airtight Buildings: During an airtightness test of a usual house the target indoor‐outdoor pressure difference is attained nearly at once. But the behaviour of very airtight buildings is different: it can take some minutes until the pressure difference practically does not vary any more. Because of pressure fluctuations induced by wind the operator is not able to recognise, when this state is achieved. Therefore this article describes the pressure difference as a function of time. An idealised fan with a constant volume flow independent of the pressure difference is assumed. The most important result: the air change rate at 50 Pa, n50, has a major effect on the necessary waiting time. The waiting time is reciprocally proportional to the air change rate at 50 Pa. Divide 7 by the air change rate at 50 Pa (in h–1) to get the necessary waiting time in seconds. Also the air flow exponent and the target pressure difference are affecting the waiting time. [ABSTRACT FROM AUTHOR]

Investigation of the heat transfer of cyclic loaded concrete cylinders Periodic load cycles, such as those that occur on bridges or wind turbines, are of great importance for dynamic long‐term considerations of concrete. Within the life span of such structures, up to 109 load changes can be expected. To determine the fatigue strength, the resistance to periodic loads can be determined in a short time in laboratory tests by increasing the load frequency. As a result of this increased load frequency, however, the concrete test specimens heat up, which can lead to an earlier, unrealistic time of failure, which is why the heating must be limited. Therefore, tests and simulations were carried out to investigate the heat release in the sample. In this article, the analytical analysis and measurements of the heat release of heated concrete cylinders are presented. As a conclusion, a possibility of reducing the temperature of dynamically stressed concrete cylinders is introduced. [ABSTRACT FROM AUTHOR]

Tamping process in railway engineering Mechanical model of the tamping unit‐ballast matrix interaction. Condition of the ballast bed is one of the most important parameters for safe and economical operation of railway systems. In order to define the optimum time for ballast bed cleaning or renewal as well as to improve ballast serviceability and track life cycle performance, better knowledge of the ballast bed condition, i.e. definition of the degree of ballast fouling is of crucial importance. As a core maintenance activity in ballasted track, the tamping process influences the economical service life of the track to a great extent and is essential in restoring the track geometry for safe train operations. During the tamping process, the tamping tines interact with the ballast matrix, transferring the displacement caused by the dynamic excitation overlapped with the extension in the hydraulic cylinder to the ballast, compacting it under the sleeper. This interaction is observed and measured in‐situ in several locations in Austria. Serving as a mean of comparison and confirmation with the conducted in‐situ measurements, a semi‐analytical model of the tamping unit – ballast matrix interaction has been developed. Conclusions regarding the differences in response and resistance to compaction of both new and fouled ballast material are made and presented in this paper. [ABSTRACT FROM AUTHOR]

Settlement performance of vibratory compacted granular soil. Vibratory compaction is widely used to reduce settlement in granular soils. The cone penetrometer CPT and the Dilatometer DMT are particularly suited for the planning and execution of compaction projects, as the soil stiffness as well as the increase in horizontal stress can be measured. The stress path during vibratory compaction is described, which explains the permanent increase of horizontal stresses and the resulting preloading effect. The settlement behaviour of normally consolidated soils is discussed. The application of the tangent modulus method for settlement analysis before and after compaction is presented. The modulus number as well as the overconsolidation ratio can be derived, from field tests (CPT and DMT). Compaction criteria for settlement reduction can be chosen based on CPT and DMT investigations. The practical application of the proposed method of settlement analysis is described by a case history, where a silty sand was compacted using the VibroWing method, followed by surface treatment using a vibratory plate. [ABSTRACT FROM AUTHOR]

Work‐integrated quality control during deep vibro compaction. Deep vibro compaction (vibroflotation) is a ground improvement method, which is used worldwide for compaction of granular soil. An appropriate compaction procedure results in a homogenous soil body and in reduced settlements. Despite the long tradition of this technique, the specification of process parameters and the control and quality assurance of the compaction works are still based on the experience of the contractors. This paper discusses a proposal for a work‐integrated compaction control, based on the motion behaviour of the compaction device. The dynamic interaction between the deep vibrator and the compacted soil was observed and recorded in large‐scale experiments, with well‐known ground conditions. A complementary theoretical investigation of the soil‐vibrator interaction system allowed the quantification of the compaction success by a parameter, which was derived directly from the monitored vibrator movement. This parameter allowed a work‐integrated compaction control covering the depth of the compacted soil. Moreover, the homogeneity of the compacted soil body could be controlled. Thus, a three‐dimensional quality control of the compaction works was made possible. [ABSTRACT FROM AUTHOR]

Ein knapp 150 Jahre altes Bauernhaus im oberbayrischen Landkreis Altötting wurde bereits 2011 in einzelnen Räumen mit einer kapillaraktiven und trotzdem sehr schlanken Innendämmung ausgestattet. Bei dieser Dämmung handelt es sich um einen Hybridbaustoff aus Kalziumsilikat und einer Hochleistungsdämmung (Fa. Evonik). Beide Komponenten sind rein mineralisch und dampfdiffusionsoffen. Bereits im zweiten Jahr nach der Applikation konnte im Rahmen eines angepassten Bauteilmonitorings nachgewiesen werden, dass diese spezielle Form der Dämmung nicht nur ein angenehmes Raumklima unterstützt, sondern auch das Austrocknen der Baufeuchte begünstigt. [ABSTRACT FROM AUTHOR]

Evaluation of clogging and wear of tools in loose rock based on model tests. The occurrence of clogging of the cutting wheel and in the mixing chamber as well as the wear of cutting tools still represent a problem in mechanized tunneling with earth pressure balanced shield drives (EPB) and hydroshield drives. Despite different procedures for prognosis based on the plasticity and consistency indices, still massive delays of tunnel excavation occur due to clogging because interruptions are needed for cleaning of the cutting wheel and the mixing chamber. Besides the clogging problems, also abrasiveness of the subsoil frequently represents a problem, because strongly abrasive soil leads to the frequent need for changing the cutting tools. A correct assessment of clogging potential as well as of abrasiveness, especially in loose rock and mixed soils still represents a difficult task for the employer and his ideally all‐embracing request for bids as well as for the contractor who has to consider the clogging potential and abrasiveness as exactly as possible in his offer. In this contribution, a new cutting wheel model test is presented, which is, in contrast to existing methods, supposed to consider the interaction of human influence, machine and subsoil in a harmonic way for the prognosis of clogging problems and problems of cutting tool wear in mechanized tunneling. [ABSTRACT FROM AUTHOR]

Comfort monitoring – comprehensive and cost‐effective with the sensor station CoMoS. The Comfort Monitoring Station CoMoS has been developed to record ambient conditions in indoor environments. The aim of the development was a cost‐effective yet accurate system for comprehensive use in buildings. The requirement was met through a design based on compact, integrated sensors for air temperature, relative humidity, globe temperature, and air velocity. An individual calibration of all sensors in relation to a reference device resulted in a minimization of measurement deviations and thus a high comparability of individual sensor stations. Calibration and evaluation measurements showed very good results for the readings of air temperature, relative humidity, and globe temperature, whereas the air velocity can only be measured with adequate accuracy for the application. After calibration and evaluation, the functionality of the system was proven under actual environmental conditions in a field test. In addition to this article, the results of the development have been published online in the form of detailed assembly instructions including source code and calibration functions, see Living Lab smart. [ABSTRACT FROM AUTHOR]

Backgrounds for demonstrating the glowing behaviour of certain building materials. One of the key points of the ECJ ruling of October 2014 was the national general building approval required for certain mineral wool insulating materials to prove that the insulating material shows "no glowing combustion". In the meantime, a European test method for smouldering and glowing combustion behaviour has been developed. According to DIBt's list of priorities, this can be used to prove that a building product does not smoulder. The article explains the background of the glow detection, the European test method, the expected future development and the consequences for planners and users of construction products. [ABSTRACT FROM AUTHOR]

Researchers in building science require detailed high‐quality detailed data to systematically support building design and operation applications. Such data are required, amongst other things, to develop and verify models of people's presence and behavior in buildings that can be deployed in building performance simulation. Toward this end, open access data is of essential importance. An important prerequisite of pervasive data sharing is the availability of a systematic ontology and standardized data formats. To address this need, we previously introduced an ontology for the representation and incorporation of multiple layers of occupancy–related data obtained via building monitoring. In the present contribution, we use this ontology as a starting point toward identification and illustration of a hierarchical data format, suitable for managing data collections of different sizes and complexity. [ABSTRACT FROM AUTHOR]

Evaluation of 3D in situ stresses for the Brenner Base Tunnel project. The article present results of in situ stress analyses in the area of three exploration boreholes for the Brenner Base Tunnel. This includes direct determinations of the complete 3D stresses with Racos (Rock anisotropy characterisation on rock samples) and the minimum stress component with hydraulic fracs plus additional analytical and numerical calculations. The determined local stress at the northern part of the tunnel illustrates a strikeslip tectonic state with the maximum stress in N-S orientation. In the central tunnel area, the in situ stresses (markedly different from vertical-horizontal) correspond to a transition between tectonic strikeslip and normal fault conditions with a strong N-S compression. Further to the south, a tectonic reverse fault configuration with an approximately verticalhorizontal stress orientation and NS aligned maximum component was determined. The orientations of all maximum horizontal stresses correlate to a largescale tectonic stress field with an N-S to NNW-SSE orientation perpendicular to the Alpine arc (corresponding to the World Stress Map). The small differences between total and effective in situ stresses indicate negligible mechanical pore pressure effects in the analyzed areas. Overall, the in situ stresses determined by different methods show (with accurate consideration of the respective spatial orientations) a good agreement. [ABSTRACT FROM AUTHOR]

Tensile testing of geomembranes: Characteristic values, influences, testing procedure. The tensile test is an important method for the quality assurance of geomembranes, which are used in geotechnical engineering (landfill lining, tunnel etc.). The method has to be standardised for the comparability and evaluation of the testing results. The characteristic values as well as their significance and meaning for construction purposes are discussed with the focus on the viscoelastic behaviour of plastics, which differs fundamentally from the mechanical behaviour of other constructions materials. The possibilities and limits of the use of extensometers are explained. The difficulties in the standardisation work are demonstrated in case of this testing method: starting from the influence of different standardisation organisations, committees and geomembrane producers on the formation process up to mistranslation. Against this background it seems reasonable to develop special tensile testing standards for certain types of products, such as HDPE geomembranes. [ABSTRACT FROM AUTHOR]

Vibratory driving is a common method for installing or extracting piles and sheet piles as well as for deep vibratory compaction. The most important parameters are vibration frequency, vibration amplitude and eccentric moment. These parameters govern vibratory driving and, in particular, the soil resistance at the toe and along the shaft of a pile. Pile driving causes oscillating horizontal ground vibrations in coarse-grained soils. It can be shown that these horizontal vibrations reduce the shaft resistance during driving. The process results in a permanent increase in the horizontal effective stress, which causes arching around the vibrated pile. The increase in horizontal effective stress is also important for deep vibratory compaction. The resonance frequency of the vibrator-pile-soil system significantly affects pile penetration and the emission of ground vibrations. At resonance, the vertical vibration velocity in the soil reaches a maximum and pile penetration becomes very slow, whereas beyond resonance, the vibration velocity decreases and the pile penetration speed is high. Field monitoring of the vibratory driving process can be used to optimize vibratory pile driving, as examples have shown. A new concept is proposed in which the driveability can be determined from a correlation between penetration resistance measurements (blows/depth) and penetration speed. The validity of the concept is demonstrated by a case history and project references. [ABSTRACT FROM AUTHOR]

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Der Zweck der im vorliegenden Beitrag beschriebenen Untersuchung bestand darin, die Betonstahlbewehrung und nach Möglichkeit auch die Spannglieder auf einer Fläche von insgesamt 8 000 m2 der oberen Brückenfahrbahn des Viadukts 'Viadotto Colle Isarco' an der Brennerautobahn mittels Potentialfeldmessungen auf Korrosionserscheinungen zu untersuchen. So wurden Zonen mit hoher Korrosionswahrscheinlichkeit ermittelt und anschließend durch Öffnen und Sandstrahlen inspiziert. Auf der Grundlage dieser Prüfungen konnte abgeschätzt werden, dass auf etwa 9 % der Gesamtfläche eine hohe Korrosionswahrscheinlichkeit in den Spanngliedern gegeben ist. Bei früheren Inspektionen sind bereits gebrochene Spannglieder festgestellt worden. Sämtliche Brüche wurden dabei im Gewindebereich der Verbindungsgelenke festgestellt. In den korrodierten Spanngliedern, die in den 'aktiven' Zonen abseits der Verbindungsgelenke lagen, wurden dagegen keine Brüche gefunden. Von den gebrochenen Spanngliedern wurden Proben genommen und zur metallurgischen Analyse ins Labor geschickt. Dabei wurden keine Anzeichen für eine Wasserstoffversprödung des verwendeten Stahls festgestellt. Die Brüche, die in den Spanngliedern bei früheren Inspektionen festgestellt worden sind, wurden höchstwahrscheinlich durch Zyklen mit höherer Belastungsermüdung durch Verkehrslasten in Kombination mit Korrosion aufgrund belastungsempfindlicher Verbindungsgelenke verursacht. Corrosion survey of the bridge deck 'Viadotto Colle Isarco'/'Autobahnbrücke Gossensaß' on the Motorway called 'Autostrada del Brennero' in North-Italy The scope of this corrosion survey was to detect and quantify zones with high corrosion probability of the normal reinforcement and if possible the prestressed tendons of a total of 8 000 m2 surface area of the upper bridge deck of the 'Viadotto Colle Isarco'. This viaduct is part of the A22 Motorway called 'Autostrada del Brennero' and lays 10 km's south of the Austrian-Italian border in Italian territory approximately 1 200 m high in the Alps. In case serious problems were found no recommendations were requested at this point of the survey due to the size and the structural complexity of the concrete structure. Zones with high probability of corrosion were identified by the potentials measured and inspected through scarification and sandblasting. Based on this verification it was estimated an approximate 9 % of the total surface area with high probability of corrosion in the prestressed tendons. This amount is based on adding up all measuring points with a potential being more negative than -450 mV divided by the total amount of measuring points. During previous inspections fractured prestressed tendons were found. All the fractures were found in the threaded region of the coupler joints but no fractures were found in corroded tendons laying in the 'active' zones away from the coupler joints. Samples taken from the fractured tendons were sent to the lab for metallurgical analysis and revealed no susceptibility for hydrogen embrittlement of the steel used which has a perlitic microstructure. Fractures found in the tendons in previous inspections are most probably caused by major stress fatigue cycles from traffic loads in combination with corrosion due to the stress-sensitive couplings. Exactly similar cases (Heerdter crossing in Düsseldorf in 1976) were found in old reports, e.g. published in the technical report 26 'Influence of material and processing on Stress Corrosion Cracking of prestressing steel - case studies' by the International Federation for Structural Concrete (fib) in Lausanne. [ABSTRACT FROM AUTHOR]