Stanislav Řeháček

Repeated Diagnostics of Maintained Prestressed Bridge Structure, Interpretation of Changes in Relation to Durability

General refurbishment of prestressed reinforced concrete bridge of Pavel Wonka in Pardubice was done in 2006. Within the preparation of refurbishment a full diagnostics of the structure was performed with the assistance of Klokner Institute, including diagnostics of longitudinal prestressed loose cables located in bridge boxes and the real condition of the corrosion was found. New inspection, including water-insulation system and condition of repaired concrete structures was held in 2015. Some of the findings and comparison of the condition before refurbishment and condition after about 10 years of operation are introduced in this article.

Quality Control of the Concrete of the Supporting Structure of Bridge Reg. No. 333-003 over the Elbe in Přelouč

This paper is introducing results of diagnostic survey of bridge reg. No. 333-003 over the Elbe in Přelouč [1], which included an evaluation of the previous reconstruction carried out in the 1990s [2, 3] and the quality control of the concrete used in the construction after more than 90 years of operation. Visual inspection, comparison of depth of concrete carbonation and thickness of top layer of reinforcement concrete and concrete compression strength are presented in this paper. This paper come into existence with cooperation with the state-funded organization Road Administration and Maintenance of the Pardubice Region.

Prefabrication of the Thin-Walled U-Profile UHPFRC Footbridge

This article presents a mix design, preparation and production of thin-walled footbridge made from UHPFRC. Optimization of UHPFRC matrix and parameters of this material leads to the design of very thin structures. In this case an experimental pedestrian bridge was designed and prepared. Single-span bridge with span of 10 m and the clear width of 1.50 m with the total thickness of shell structure 30 - 45 mm was cast as a prefabricated element in one piece. Self-compacting character of UHPFRC with high flowability allows the production of the final structure. Extensive research was done before production of footbridge. Two versions of large scale mock-ups were casted and tested. According to the complexity of whole experiment a casting technology and production of formwork were tested and optimized many times. Experimental reached data were compared with extensive numerical analysis and the final design of structure and UHPFRC matrix were optimized in many details.

Concrete Cover Effect on Bond Behaviour of UHPC

New materials require extensive research. Ultra high performance concrete is relatively modern cementitious material with favourable material properties. In previous research a lot of different mixtures of UHPC and many important properties were developed and tested as a basis for upcoming numerical analysis. Especially bond behaviour between steel and UHPC and comparison to bond behaviour of ordinary concrete were examined. UHPC has significant better material properties, especially bond behaviour, and represent an alternative material for some steel structures which can satisfy in some cases the requirements on construction dimension and economy. The function of the constructions details using small anchorage length was experimentally verified too. For reliable transfer of the forces the reinforcement need to be protected by sufficient concrete cover. This article deals with bond behaviour of embedded steel ribbed reinforcement in UHPC with small concrete cover and summarizes previous research results in field of the bond of UHPC.

UHPC Footbridge over the Opatovický Canal

Article deals with design of footbridge made from ultra high performance concrete (UHPC). UHPC is relatively new type of cementitious material with high compressive strength and high durability. For reliable design of construction from this material an extensive experimental research and verification of material properties are needed. Skanska and Pontex company with cooperation with Klokner institute developed matrix of UHPC used for footbridge construction. Material properties were verified during whole developing and producing process. Footbridge was casted in precast plant Skanska – Steti in December 2014. It was installed over Opatovický canal in October 2015. Contribution describes design, production and installation of footbridge. Material properties of used UHPC are also included.

Investigation of the Bond Behavior of UHPC

Ultra High Performance Concrete - UHPC has become increasingly used. Its outstanding features are generally known. It is a fact that the bond of the reinfocement in UHPC is better than that in ordinary concrete, but this bond needs to be quantified .The aim of the experimental research was to determine the average bond stress between prestressing strands and different types of UHPC and to show very significant increase in the average shear stress in bond with UHPC compared to ordinary concrete. In order to determine the bond capacity, an experimental research was carried out. Experimental details of the models in real structures – parts of prestressed girders made from UHPC, were tested in the laboratory and the results were compared with specimens prepared according to standard. The influence of different material properties and different anchorage length of prestressing strands to bond behavior of UHPC was examined in pull out tests. Test results of bond test led to the conclusion that the application of UHPC can significantly reduce the anchorage length of reinforcement compared with the ordinary concrete.

Impact Resistance of Thin-Walled Shell Structures

Fibre-reinforced composite materials are becoming important in many areas of technological application. In addition to the static load, such structures may be stressed with short-term dynamic loads or even dynamic impact loads during their lifespan. Dynamic effects can be significant especially for thin-walled shell structures and barrier constructions. Impact loading of construction components produces a complex process, where both the characteristics of the design itself and the material parameters influence the resultant behavior. It is clear that reinforced concrete with fibers has a positive impact on increasing the resistance to impact loads. Results of impact load tests carried out on drop-weight test machine are presented in this paper. The results are supplemented by compression strength test.

Bridge Pavla Wonky in Pardubice. Diagnostics of Corrosion Condition of External Cables and Use of Special Materials for Proposal of Treatment

Annotation: Complete reconstruction of the reinforced prestressed bridge Pavla Wonky in Pardubice was carried out in 2006. During this reconstruction specialists of the Klokners Institute made complete revision of linear free external cables in bridge chambers, namely from the aspect of corrosion. Some of the findings obtained during this revision are presented in this article.