In beidseitig eingespannten kurzen Stahlstützen unter Querkrafteinwirkung entsteht gewöhnlich eher Schubfließen als Biegefließen. Im Beitrag werden Ergebnisse experimenteller und analytischer Untersuchungen zum Schubversagen beidseitig eingespannter kurzer Stahlstützen vorgestellt. Im Versuchsprogramm wurden unterschiedliche Schlankheitswerte für die Elemente Flansch und Steg des doppelsymmetrischen I-förmigen Stützenquerschnittes betrachtet. Es konnte ein eindeutiger Grenzschubschlankheitsgrad zwischen Schubfließen kürzerer Stahlstützen und Biegefließen längerer Stahlstützen bestimmt werden. In den Stützlängen dazwischen gibt es grundsätzlich große Unterschiede im Verhalten. Der Grenzschubschlankheitsgrad von Stahlprofilen wird hier analytisch hergeleitet und durch Versuch bestätigt.

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Keine Kurzfassung verfügbar.

Keine Kurzfassung verfügbar.

Der Zustand der Bauwerke einer Stadtstraße verschlechtert sich schnell unter ungünstigen Umweltbedingungen, dem Anwachsen des Schwerlastanteils und dem zunehmenden Lebensalter. Bei der Wartung dieser Bauwerke sind viele Probleme zu lösen: So reihen sich über die ganze Länge ältere und neuere Konstruktionen aneinander. Eine notwendige Komplettsanierung eines Straßenabschnitts wird damit schwierig, noch dazu unter dem gegenwärtigen langsamen Wachstum der japanischen Wirtschaft. Die Sperrung einer Fahrbahn aufgrund konstruktiver Schäden würde das Verkehrsnetz zum Erliegen bringen und zu länger andauernder wirtschaftlicher Stagnation in der Region führen. Unter diesen Umständen analysiert dieser Beitrag, inwieweit eine vernünftige Beurteilung der Schadstellen hinsichtlich ausgesuchter Schadensbilder möglich ist. Daneben werden effektive Reparatur- und Instandsetzungsmaßnahmen empfohlen, so daß wichtige Bauwerke dauerhaft in gutem Zustand bewahrt werden können.

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The seismic performance of a reinforced concrete pier structure depends greatly on the plastic hinge region at the base of the pier. To improve the plastic hinge region of the structure, we propose using ultra-high-strength fibre-reinforced concrete (UFC) formwork for the concrete cover at the base of the pier. This study describes the structural characteristics of a pier with a base cast using mortar-jointed UFC formwork.
To investigate the structural characteristics, a bilateral circular cyclic loading experiment and a simulation analysis using a fibre model were conducted. The results show that the flexural strength remained stable under a large rotation angle. Even at the rotation angle at the ultimate limit state, crushing failure of the mortar did not occur and the ultimate limit state did not result from mortar damage, because the tensile strength of mortar-filled joints is close to zero, and thus excellent flexural crack distribution performance can be achieved.

This study investigates the dynamic biaxial behaviour of concrete by testing more than 60 cubic specimens on a custom-designed, servo-hydraulic-controlled machine. Each specimen was axially loaded in compression at a constant strain rate of 10-5, 10-4, 10-3 or 10-2 s-1 while two opposite side faces were subjected to a constant confining pressure and the other two side faces were free. The confining pressure applied to each specimen was 0, 30.5, 61.0 or 91.5 % of its uniaxial compressive strength. Test results indicate that the biaxial strength of concrete increases with strain rate at a reduced slope as confining pressure increases. The failure mode of the concrete specimens was basically unaffected by the strain rate. An empirical relation for the ultimate strength of concrete in a biaxial stress state was developed taking into account the effects of both confinement and strain rate.

Dedicated to Prof. Dr. Eng. Akimitsu Kurita on his 70th birthday, in honour of his scientific achievements, guidance and the education of his students.
Fire safety in bridge design is not as developed as fire safety in building design, even though a bridge failure can cause significant economic damage impacting on an area. This paper addresses an unanswered question with regard to fire safety, i.e. the capability to identify the governing failure mode of a bridge subjected to severe fire loading and ranking the regions of greatest fire exposure risk. Hence, this proposed methodology is also expected to support forensic work identifying the failure mode where a bridge has failed due to a severe fire, as will be shown using the 9-Mile Road Overpass collapse as an example. In an effort to mitigate fire damage, the fire protection panel (FFP) is introduced, which is part of a sacrificial structure shielding the bridge superstructure from exposure to fire from underneath.

There are several methods available to decide appropriate design recommendations to prevent corrosion of reinforcing steel in prestressed concrete bridge girders. With respect to chloride-induced corrosion, in the present study two methods are considered. The first one is based on the target probability of corrosion initiation and the initial cost. The other method is based on the life-cycle cost that includes the initial cost, maintenance cost, and expected failure cost. This paper deals with the development of recommendations for durability design of structures in marine environments from the reliability point of view, taking into consideration the life-cycle cost of a structure. In order to address the problem, the chloride diffusion coefficient of a cracked area under service load is obtained considering opening and closing motion of cracks. Utilizing the diffusion coefficient of a cracked area, the development over time of the chloride concentration at the surface of reinforcement can be predicted. This information is used to quantify the probability of initiation of corrosion of prestressing steel as well as the distribution of life-cycle cost. Based on the findings, recommendations for durability design in various exposure environments are developed.

Das Stadtbild von New York im 20. Jahrhundert ist von Hochhäusern und Großbrücken aus Stahl geprägt. Zwar hält die Stadt heute in keiner der beiden Kategorien den Höhen bzw. Längenrekord, aber der überwiegende Teil der ehemaligen Rekordinhaber leistet weiterhin seinen Dienst. Die Priorität liegt inzwischen nicht mehr auf dem Brechen von Rekorden des Höher und Weiter, sondern auf der unter anspruchsvollen städtischen Bedingungen angepaßten optimierten Leistungsfähigkeit. Dichte, Bedeutung und Alter des Netzwerks an Brücken stellt unter den heutigen Verkehrsverhältnissen einzigartige Herausforderungen in bezug auf Design und Management, auf die in diesem Artikel näher eingegangen wird.

This paper presents a new theory for the shear capacity of reinforced concrete members without shear reinforcement. While recognizing that there are multiple failure mechanisms, the theory attributes the opening of a critical flexural shear crack as the lower bound of the shear capacity. It proposes that the shear displacement of an existing flexural crack can be used as the criterion for the unstable opening of the critical flexural shear crack. Based on the theory, the paper presents a simplified shear evaluation model. Compared with the current shear provisions in the design codes, the model is characterized by good accuracy and a solid physical background. It demonstrates a great flexibility for dealing with complex design conditions. As an example, the paper discusses the possibility of extending the theory to the shear resistance of higher-strength concrete. The suggested method provides a more logical and fluent transition from normal- to high-strength concrete and shows good agreement with experimental observations.

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In this article, the cyclic performance of an innovative precast beam-to-column connection is evaluated experimentally and numerically. Two full-scale beam-column cross-shape interior connection specimens named PF-1 and PF-2 are tested. By adding extra nuts to the connecting bolts, specimen PF-2 behaves in a more shear-dominant pattern and shows less pinching. Comparison of performance of these specimens with the numerical monolithic model in terms of stiffness, strength, ductility and energy dissipation capacity indicates the proposed system can provide conditions close to the monolithic connection. However, to reduce the pinching drawback, a minor modification was made leading to performance improvements in strength and equivalent viscous damping ratio up to 51 % and 29 % respectively. The results of this study have direct industrial relevance and may be used for the development of reliable seismic guidelines for precast concrete structures.

This paper presents the outcome of an experimental study carried out by the authors on the performance of a connection between an I-beam and a square hollow section (SHS) column. In the light of practical and economic bolted field applications and transportation without damage by leaving the column exterior without projections, an appropriate joint type composed of T-stub connecting elements was studied. These connecting elements were bolted with long partially threaded studs passing through the SHS column. In order to observe the performance of the joint, four full-scale beam-column tee-joint specimens were tested under monotonic and cyclic loading in two groups. As a parameter, the rear face of the SHS column in the area of the connection was reinforced by backing plates in the second group of specimens. The results obtained are provided in terms of moment-rotation relationship and energy dissipation capacity. All specimens reached beam plastic load level at high deformation levels. Reinforcing the SHS column rear face with a backing plate resulted in an increase in strength and initial stiffness but a reduction in the energy dissipation capacity of the joint. Considering the overall cyclic performances, both joints maintained high plastic rotations in adequate resistance levels with acceptable energy dissipation capacities; consequently, they are suitable for use as semi-rigid partial strength joints in simply designed, braced steel frames in seismic regions or in unbraced steel frames in regions with less seismic activity. Additional component tests were carried out to understand better the component behaviour of the hollow section face in bending and to try to design component modelling parameters. The influence of bolt spacing and the distance between bolt rows on the resistance of the square hollow section face in bending was examined. As expected, when the bolts were closer to the sidewall, the resistance of the face increased.

Für die Bestimmung der Lagerungsdichte gemischtkörniger plastischer Böden, deren Grösstkorn im Feinkiesbereich liegt, ist ein Alternativggerät zum Proctorgerät entwickelt worden. Mit dem neuen Gerätetyp VFG sind die Nachteile des Proctorgeräts ausgeschlossen, wie: Wassergehaltveränderung durch Abdampfen während des Versuchs, Klebenbleiben der Stampfvorrichtung auf der Bodenoberfläche sowie seitliches Ausweichen und Auswurf des Bodens durch das Stampfen.

Ein Großteil der Schäden an Ingenieurbauwerken wird durch Korrosion verursacht. In der vorliegenden Arbeit wurden repräsentative Erhaltungsprojekte von Ingenieurbauwerken in der Schweiz detailliert analysiert. In den untersuchten Fällen zeigte sich, dass 56 % der Instandsetzungskosten (± 11 %) direkt durch die Korrosion verursacht werden. Bei Ingenieurbauwerken im Straßennetz der Schweiz liegen die direkt durch Korrosion versursachten Kosten somit schätzungsweise bei 260 bis 510 Mio. CHF pro Jahr, also gegen 1 000 CHF pro Minute. Dies entspricht 0,08 % des Bruttoinlandprodukts. Nebst dem Straßennetz werden Korrosionskosten auch an anderen Ingenieurbauwerken erwartet, etwa an der Bahninfrastruktur, im Energiesektor oder bei Wohn- und Bürobauten. Diese wurden hier nicht berücksichtigt; ebenso wurden die indirekten Kosten (Staus, Umweltbelastung, etc.) nicht quantifiziert. Die hier ermittelten direkten Kosten durch Korrosion an Ingenieurbauwerken im Straßennetz der Schweiz stimmen in der Größenordnung mit den für die USA vorliegenden Daten überein und können daher möglicherweise auch auf andere industrialisierte Länder angewandt werden. Aufgrund dieser volkswirtschaftlichen Bedeutung ist es zentral, das Korrosionsphänomen bestmöglich unter Kontrolle zu haben. Dies bedingt dringend technologische Innovationen und eine zeitgemäße Ausbildung von Fachkräften im Bauwesen.

Corrosion Caused Costs on Civil Engineering Structures of the Swiss Road Networks
The degradation of traffic infrastructure is to a large extent caused by corrosion. For this study, selected representative maintenance projects of Swiss civil engineering structures were analysed in detail. These analyses revealed that on average 56 % of the maintenance costs (± 11 %) are directly related to corrosion. The direct costs of corrosion of civil engineering structures in the Swiss road network amounts to approximately 260-510 million Swiss francs per year, i.e. almost 1 000 Swiss francs per minute. This corresponds to 0.08 % of the GDP. Apart from civil engineering structures of the road network, corrosion also generates costs for other engineering structures, i.e. structures of rail operators, of the energy sector, or residential and office buildings and industrial plants. These structures were here not taken into account. Additionally, indirect costs (traffic jams, environmental pollution, etc.) were here not quantified. The direct costs of corrosion of civil engineering structures of the Swiss road network estimated in this study are in agreement with the available data from the U.S. and therefore might be applied to other industrialised countries.

Nach der Aki-Brücke mit einer Spannweite von 110 m im Jahre 1968, ist eine große Anzahl von Nielsen-Bogenbücken in Japan gebaut worden. Dazu gehört die Shinhamadera-Brücke mit eine Spannweite von 254 m, die 1991 als Nielsen-Lohse-Brücke konstruiert wurde und deren Bögen in der Art von Korbhenkeln geformt sind. Die Bemessung dieser Brücke erfolgte auf der Grundlage von elastoplastischen und Finite-Displacement-Berechnungsverfahren. Außerdem wurden Grenzfestigkeits-Modellversuche durchgeführt, um die effektive Knicklänge der Bögen zu bestimmen. Aus ästhetischen Gründen wurden für die oberen Querstäbe ovale und Kreisquerschnitte gewählt, deren Festigkeit im Modellversuch nachgewiesen wurde. Aufgrund der örtlichen Gegebenheiten der Baustelle zu beiden Seiten der Osaka-Bucht wurde die Brücke an einer anderen Stelle vollständig vorgefertigt und dann mit der Pontonmethode an Ort und Stelle montiert. Durch dieses Bauverfahren konnte die Brücke in kürzester Zeit fertiggestellt werden.

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Keine Kurzfassung verfügbar.

In recent decades, energy efficiency has been the priority for masonry buildings in order to keep up with ever more stringent requirements. For the evaluation of the sustainability of building solutions, however, the embodied energy to produce a building and finally to dispose of it at the end of its lifecycle are also important. The energy used for the disposal of a building and the processing of the residues are also important for the overall energy balance since the handling of natural resources is increasingly the centre point of thought and action. A research team at the Chair of Structural Design of TU Dresden has thus been working since 2012 on demountable solutions in masonry, which can be dismantled at the end of a building lifetime and sorted for recycling, which fully complies with the requirement for the reduction of rubbish and waste products. The high precision of block production today permits us to omit the levelling effect of mortar and to build dry buildings in the future, i.e. to do without the bonding principle. The associated strength reductions can be suffered without problems. The appropriate basics of such a dry building method have been researched in a collaboration between the ILEK in Stuttgart and the Xella Technologie- und Forschungsgesellschaft mbH in Emstal. In this research project with the abbreviation “REMOMAB”, the basics of an energy-efficient dry building method suitable for recycling were collected and made available for practical application. In a follow-up project, these basics are being implemented and tested on an experimental building. Cost aspects are also to be taken into account and if possible, construction solutions available on the market will be used - modified if necessary. Another aim is for the first time to dismantle such a building and to rebuild it at another location. This is intended to demonstrate that a reuse is possible after dismantling and such a building method can react to changing demands in the housing market.

This paper presents a critical comparison of the existing code provisions for the shear strength of concrete beams. The comparison is based on the computerized filtering-out of the inevitable statistical bias from the available multivariate database on shear strength, on an examination of the predicted size effects on shear strength and their underlying hypotheses and on the results of recent high-fidelity numerical simulations of shear failure. In addition to examining the existing models, the present comparison also provides several key considerations for testing the scientific soundness of any model of shear failure in concrete beams, which is necessary for future revisions to the design code provisions.

Concrete structures can suffer from water permeating under stresses. This paper investigates the surface water permeability of reinforced concrete elements subjected to uniaxial tension. A testing system was developed to combine a conventional loading machine with a surface permeameter. To eliminate the effect of initial absorption of water, calibration tests were conducted on plain concrete samples with different surface saturated states. The experiment presented is designed to test the surface water permeability of a structural member under uniaxial tension. Specimens were reinforced centrally with different sizes of steel bar and fabricated with normal-strength and high-strength concrete. A uniaxial tensile load was applied from 0.10 to 0.80 of estimated ultimate cracking load in 0.10 increments. At the same time, water permeability was measured at each load step. Test results give the relationship between water permeability of concrete member and tensile load levels.

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