Využití UHPC pro moderní návrh progresivních spřažených dřevo-betonových mostních konstrukcí

This paper deals with the material properties of Ultra High Performance Fiber Reinforced Concrete (UHPFRC or UHPC) and especially focuses on bending tests executed for the development of bridge deck segments for an innovative timber-concrete composite bridge system. In the first step, the precast bridge deck segment is designed as a thin slab made of UHPC of a constant thickness, without any ribs and without any reinforcement. Only steel fibres are used as a scattered reinforcement. The bending tests for determining flexural strength of UHPC were executed on the slab strips under similar boundary conditions as by the bridge deck segments. The slab strips of various thickness of 40, 50, 60, 70 and 80 mm were tested in 4-point bending tests with span 1900 mm and in 3-point bending tests with span 600 mm. Half of the test specimens were tested in casting position, other half were tested upside down. The obtained values of the flexural strength were compared with values from reference bending tests of the beams 150 x 150 x 700 mm, 100 x 100 x 400 mm and 40 x 40 x 160 mm. Different size of the tested specimen is discussed. An influence of the positioning of the slab with respect to the direction of casting and the influence of the deck thickness on the flexural strength is evaluated

Detail

Článek je zaměřen na stanovení ohybové pevnosti tenkých desek z ultra-vysokohodnotného betonu vyztuženého ocelovými vlákny (UHPFRC). Únosnost prvků bez betonářské výztuže vyztužených pouze rozptýlenou výztuží v podobě drátků v ohybu je ovlivněna především orientací a distribucí vláken a projevuje se u nich size-effect. Speciální tělesa - deskové pruhy o různých tloušťkách 40, 50, 60, 70 a 80 mm byly testovány ve čtyřbodovém ohybu na rozpětí 1900 mm a ve tříbodovém ohybu na rozpětí 600 mm v poloze stejné jako při betonáži a obrácené dnem vzhůru. Vyhodnocené ohybové pevnosti byly porovnány s pevnostmi stanovenými referenčními ohybovými zkouškami na trámcích o velikostech 150 x 150 x 700 mm, 100 x 100 x 400 mm a 40 x 40 x 160 mm. Byly vyhodnoceny vlivy velikosti prvku, tloušťky desky, rozpětí a polohy vzhledem k betonáži na únosnost v ohybu. Experimenty byly dále podpořeny numerickou simulací.

Detail

This paper summarizes the results and evaluation of the push-out shear tests of the timber-precast concrete composite connection designed for lightweight pedestrian bridges. The timber-concrete composite bridge structure consists of glulam beams connected with precast segments made of UltraHigh Performance Fiber Reinforced Concrete (UHPFRC). A shear connection is carried out by notches made of steel plate embedded in the timber beams supplemented with welded shear dowels (headed studs) situated in the concrete part of cross-section. The precast slab is provided with slots for the shear dowels. After placing of the deck segments on the timber beams, the slots are poured with UHPFRC. The short-term push-out shear tests are carried out. The test specimens are composed of two identical precast UHPFRC slabs and timber beam placed in the middle between them. Some parameters of the shear connection are varied and their influence on the mechanical behaviour of the connection is discussed. The executed experiments are supplemented with numerical simulations. The results obtained from the experiments and numerical analysis are compared with analytical calculation.

Detail

This paper focuses on the determination of the flexural strength of thin slabs made of the Ultra High Performance Fiber Reinforced Concrete (UHPFRC). The load-bearing capacity in bending of elements reinforced only with steel fibers (used as a scattered reinforcement) is primarily influenced by the orientation and distribution of the fibers. A size-effect occurs by these elements. Some special bending tests were executed within the development of precast bridge deck segments for an innovative timber-concrete composite bridge system. The bending tests were executed on the slab strips under similar boundary conditions as by the bridge deck segments. The slab strips of various thickness of 40, 50, 60, 70 and 80 mm were tested in 4-point bending tests with span 1900 mm and in 3-point bending tests with span 600 mm. Half of the test specimens was tested in casting position, the other half was tested upside down. The obtained values of the flexural strength were compared to values from reference bending tests of the beams 150 x 150 x 700 mm, 100 x 100 x 400 mm and 40 x 40 x 160 mm. An influence of the different size of the tested specimen, of the slab thickness, of the span size and of the positioning of the slab with respect to the direction of casting on the flexural strength are evaluated. The experiments are further supported by numerical simulation.

Detail

Článek je zaměřen na stanovení ohybové pevnosti tenkých desek z ultra-vysokohodnotného betonu vyztuženého ocelovými vlákny (UHPFRC). Únosnost prvků bez betonářské výztuže vyztužených pouze rozptýlenou výztuží v podobě drátků v ohybu je ovlivněna především orientací a distribucí vláken a projevuje se u nich size-effect. Speciální tělesa - deskové pruhy o různých tloušťkách 40, 50, 60, 70 a 80 mm byly testovány ve čtyřbodovém ohybu na rozpětí 1900 mm a ve tříbodovém ohybu na rozpětí 600 mm v poloze stejné jako při betonáži a obrácené dnem vzhůru. Vyhodnocené ohybové pevnosti byly porovnány s pevnostmi stanovenými referenčními ohybovými zkouškami na trámcích o velikostech 150 x 150 x 700 mm, 100 x 100 x 400 mm a 40 x 40 x 160 mm. Byly vyhodnoceny vlivy velikosti prvku, tloušťky desky, rozpětí a polohy vzhledem k betonáži na únosnost v ohybu. Experimenty byly dále podpořeny numerickou simulací.

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Článek prezentuje výsledky experimentálního vývoje inovativního mostního systému tvořeného trámy z lepeného lamelového dřeva spřaženými s mostovkou z prefabrikovaných panelů z ultra-vysokohodnotného betonu (UHPC). Článek se věnuje výrobě prototypu zkušební dřevo-betonové konstrukce v měřítku 1:1 a následnému provedení zatěžovací zkoušky. Zkušební konstrukce šířky 3,30 m a délky 10,24 m byla navržena jako dva dřevěné trámy spřažené se subtilními panely mostovky z UHPC tloušťky pouze 60 mm s typickou skladebnou délkou 1,50 m. Cílem výroby zkušební konstrukce bylo verifikovat výrobní detaily a postupy a následně ověřit chování spřažené konstrukce při zatížení pomocí zatěžovací zkoušky. Zatěžovací zkouška byla provedena čtyřbodovým ohybem s teoretickým rozpětím 9,5 m do porušení. Následně byly z lávky vyřezány segmenty šířky 1 m, na kterých bylo ověřeno chování a únosnost prefabrikátů mostovky z UHPC v příčném směru.

Detail

This paper describes the development of an innovative timber–concrete composite bridge system and especially focuses on the evaluation of the load tests of an experimental bridge structure. The load-bearing structure was designed as glue-laminated timber beams connected with only 60-mm-thick precast bridge deck segments made of ultra-high-performance concrete (UHPC). To verify the production details and behavior of the designed structure, we built a full-scale experimental structure and performed a load test. The load test was arranged as a four-point bending test. First, we performed the overall load test until failure. Some bridge deck segments were consequently cut from the structure in order to run further load tests of the bridge deck in the transversal direction. The results of the experiments were evaluated in detail and compared with analytical calculations.

Detail

This article presents the results of the experimental development of a unique bridge system consisting of timber beams connected with bridge deck segments made of Ultra-High Performance Concrete (UHPC). The article deals with the production of a full-scale prototype of the timber-concrete composite structure and with an execution of a subsequent load test. The test structure was 3.30 m wide and 10.24 m long and was designed as two beams made of glue laminated timber connected with subtle bridge deck segments with a thickness only 60 mm and with a typical length of 1.50 m. The aim of the production of the test structure was to check some production details and procedures and subsequently to verify the behavior of the composite structure under load by the load test. The load test was performed with a theoretical span of 9.50 m as a four-point bending test to failure. After the overall load test was done, some bridge deck segments were cut from the structure and a load test of the bridge deck in transversal direction were executed to verify the behavior and the load-bearing capacity of the bridge deck segments made of UHPC.

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This article presents the results of research on composite timber-UHPFRC structures. The findings relate to the proposed method of coupling these materials with regard to the maximum degree of prefabrication. The article contains a proposal of a special method of coupling, specification of used materials, experimental testing and numerical analysis. The results obtained experimentally, by numerical non-linear analysis and the predicted load capacity according to the applicable European standards were compared with each other. The results confirmed the possibility of replacing the experiments by non-linear numerical analysis. It also points out the reserves of TCC assessments of structures according to valid European standards, especially when using UHPFRC.

Detail

This paper describes the development of an innovative timber-concrete composite (TCC) bridge system. The optimization of TCC bridge structures using the application of a precast bridge deck made of ultra-high-performance concrete (UHPC) was studied in this research program. The first part of research program was focused on the verification of mechanical characteristics of the proposed shear connection system. Another part of the experiments was focused on the verification of the load-bearing capacity of thin slabs made of a local mixture of UHPC. Finally, a full-scale experimental structure was built. The load-bearing structure was designed as glue-laminated timber beams connected with only 60-mm-thick precast bridge deck segments made of UHPC. The overall load test of experimental structure until failure was performed. The results of the experiments were evaluated in detail and compared with analytical calculations and numerical simulations.

Detail