Wyniki wyszukiwania - BazTech

1

Wpływ technologii układania betonu samozagęszczalnego na nośność połączenia beton-beton oraz stal-beton w elementach wykonywanych warstwowo

Dybeł Piotr

Cement Wapno Beton

|

2023

|

R. 28, nr 4

210--224

PL

Artykuł przedstawia badania dotyczące technologii warstwowego wykonywania konstrukcji z betonu samozagęszczalnego. Badania przeprowadzono na elementach panelowych o wymiarach 800×480×160 mm, betonowanych w dwóch warstwach z jednego punktu podawania mieszanki. Założono trzy różne czasy opóźnienia podawania drugiej warstwy mieszanki: 15, 30 oraz 60 minut. Przeanalizowano dwa warianty technologiczne podawania mieszanki: od góry i od dołu formy. Analizowano wpływ technologii układania mieszanki na nośność połączenia warstw betonu oraz pręta zbrojeniowego z betonem. Nośność połączenia warstw betonu określono za pomocą badania wytrzymałości na rozciąganie przy rozłupywaniu, na próbkach rdzeniowych pobranych z elementów panelowych. W dotychczasowej literaturze badanie nośności połączenia warstw było badane na znacznie mniejszych elementach i nie uwzględniały one innej technologii podawania mieszanki niż tradycyjna. Badanie przyczepności pręt zbrojeniowy-beton na styku warstw wykonano metodą pull-out. Wykazano duże różnice w sposobie mieszania się warstw betonu, w zależności od zastosowanej technologii jego podawania. Betonowanie od góry formy powodowało spadek nośności zespolenia warstw jak i zmniejszenie sztywności i nośności połączenia pręt zbrojeniowy-beton wraz ze zwiększeniem czasu opóźnienia podawania drugiej warstwy. Z kolei betonowanie od dołu formy zapewniło uzyskanie nośności zespolenia warstw betonu na poziomie 90% wytrzymałości próbki monolitycznej w całym zakresie badań. Technologia betonowania od dołu została polecona do wykonywania elementów w technologii wielowarstwowej z betonu samozagęszczalnego.

EN

The article presents a study on the technology of layered execution in self-compacting concrete structures. The research focused on 800×480×160 mm panel elements, cast in two layers from a single mix casting point. Three different delay times for delivering the second layer of mix were considered: 15, 30 and 60 minutes. Two technological variants of mix application were analysed: from the top and from the bottom of the mould. The study investigated the influence of the placement technology on the load bearing capacity of the concrete layer-to-layer joint and the rebar-to-concrete joint. The load-bearing capacity of the concrete layer-to-layer joint was determined through a splitting tensile strength test on core specimens extracted from panel elements. Notably, existing literature has primarily explored the load-bearing capacity of the concrete layer-to-layer joint on smaller elements and has not accounted for mix placing technologies diverging from the traditional one. A test of the rebar-to-concrete bond at the layer interface was conducted using the pull-out method. Substantial differences were identified in the mixing pattern of concrete layers, contingent on the placing technology employed. Top-down casting led to a reduction in the load-bearing capacity of the concrete layer-to-layer interface, coupled with decreased stiffness and bond strength of the rebar-to-concrete connection as the delay time of the second layer increased. Conversely, bottom-up concreting maintained the load-bearing capacity of the combined concrete layers at 90% of the strength of the monolithic specimen throughout the entire test range. The article recommends the utilization of bottom-up placing technology for executing elements in the multilayer casting of self-compacting concrete.

2

Evaluation of Tunnel Contour Quality Index on the Basis of Terrestrial Laser Scanning Data

Dybeł Piotr, Dybeł Katarzyna, Cieślik Jerzy

Studia Geotechnica et Mechanica

|

2021

|

Vol. 43, nr 3

255--269

EN

The Tunnel Contour Quality Index (TCI) is an index established by Kim and Bruland for an effective management of a tunnel contour quality. It is estimated on a basis of measurements of two contour profiles within a single blasting round, using a laser profiler. However, the representativeness of measurement results obtained that way for the assessment of a contour quality of the entire blasting round is disputable. Terrestrial laser scanning (TLS) technology, combined with available numerical surface modeling tools, enables development of three-dimensional models of a monitored surface. The article reports results of TCI calculations based on TLS data. The presented TLS technique is based not only on selected cross-sections of the tunnel contour but also on the description of the morphology of the tunnel contour surface. The case study concerns measurements of the "Mały Luboń" tunnel niche, located in Naprawa, Poland. The TCI values for three blasting rounds were determined in accordance with Kim and Bruland’s guidelines and were compared to TCI values determined with the proposed TLS technique. On a basis of this comparison, it can be concluded that the results obtained with the TLS technique are more reliable and representative for description of the contour quality of the entire blasting round than results obtained with the laser profiling technique.

3

Potential for tunnel technology in the development of hyperloop vacuum rail

Piotr Gospodarczyk, Stopka Grzegorz, Dybeł Piotr

New Trends in Production Engineering

|

2020

|

Vol. 3, Iss. 1

472--480

EN

Hyperloop is a new concept of transport system the main assumption of which is to use hermetic tunnels where air pressure is very low compared to atmospheric pressure. It enables significant reduction of traffic resistance and, as a result, energy consumption. One of the most important elements of this system is land infrastructure with transport tubes. This system component has a significant impact on the construction costs related to the whole system and affects its functional parameters (e.g. capsule travel speed). Appropriate configuration of the route of a new transport system will require the use of all possible ways of leading transport tubes, including tunneling. The paper presents the key premises that prove a large potential application of tunnel technologies in the development of a new transport system.

4

Wpływ położenia prętów zbrojeniowych na ich wiązanie z wysokowartościowym, samozagęszczającym się betonem

Dybeł Piotr

Cement Wapno Beton

|

2019

|

R. 22/84, nr 4

307--319

PL

W pracy przedstawiono wyniki badań wpływu położenia prętów zbrojeniowych na ich siłę wiązania z betonem. Badania przeprowadzono na próbkach wykonanych z czterech różnych mieszanek wysokowartościowego betonu samozagęszczającego się, do których stosowano różny dodatek pyłu krzemionkowego, wynoszący 5%, 10% i 15% masy zastępowanego cementu. Zbadano zmiany wiązania prętów na wysokości 480, 800 i 1600 mm, próbek betonowych. W elementach pręty zbrojeniowe zorientowane były prostopadle do kierunku betonowania. Otrzymane wyniki porównano z próbkami z betonu wysokowartościowego zagęszczanego wibracyjnie, wykonanymi z tych samych składników i o takim samym stosunku w/s. Przeprowadzone badania wykazały, że w betonach o wysokiej jakości, samozagęszczających się i BWW, obu zawierających pył krzemionkowy, siła wiązania pręta, wzdłuż wysokości próbki, jest prawie stała. Maksymalne różnice przyczepności między strefą „dobrych” i „słabych” warunków wiązania są znacznie mniejsze niż postuluje się w wytycznych normowych.

EN

In this work the effect of the reinforcing bars location on their bond with concrete was presented. The studies were performed on specimens made of four different High Performance Self-compacting concrete mixes with varying addition of silica fume 5%, 10% and 15% by mass of replaced cement. Since the specimens had heights of 160, 480, 800 and 1600 mm, it was possible to measure the changes of the bond at these levels. In these elements the reinforcing bars were oriented perpendicularly to the placing direction. The obtained results were compared with the specimens of HPC compacted by vibration and made from the same ingredients and with the same water/binder ratio. The performed tests have shown that in the case of the elements made of the HPC–Self Compacting Concrete and HPC, both containing silica fume, the quality of bond conditions, along the elements heights, was nearly constant. The maximum bond differences between the ‘good’ and ‘poor’ bond condition zones were much lower than those mentioned in the standard guidelines.

5

Jak zwiększyć przyczepność stal zbrojeniowa-beton?

Kucharska Milena, Dybeł Piotr

Builder

|

2019

|

R.23, nr 1

65--67

EN

The paper analyses the impact of casting direction of self-compacting concrete (SCC) on its bond quality to steel reinforcing bars. Tests were performed on high performance self-compacting concretes with different amount of silica fume to cement mass. Experiment was carried out on 480 mm height specimens, which allowed determining changes of bond condition along its height. The ribbed reinforcing bars have been placed perpendicularly to the direction of casting. Casting was performed from two points – from the bottom and the top of the form. Research has shown that casting from the bottom of the form improves bond strength and quality.

6

Experimental assessment of the casting position factor of reinforcing bars in high performance concretes (HPC, HPSCC)

Dybeł Piotr, Kucharska Milena

Archives of Civil and Mechanical Engineering

|

2019

|

Vol. 19, no. 1

127--136

EN

This paper concerns the problem of the experimental assessment of the casting position factor in comparison to the current normative guidelines. Our experiment was performed on three types of concrete: high-performance concrete (HPC), high-performance self-compacting concrete (HPSCC) and normal strength concrete (NSC) used as a reference. The HPC and the HPSCC were made in respectively, two and four different variants that differed in the content of silica fume. To assess the casting position factor, three types of elements with heights of 480, 800 and 1600 mm were used. In each element, a ribbed reinforcing bar with a diameter of 16 mm was embedded perpendicularly to the direction of concreting. The bond was examined using pull-out test. The test results showed that regardless of the type and composition of concrete, the linear change of the casting position factor with element's height was observed. No significant differences in the changes of the casting position factor with height were noted between the HPC and the HPSCC. The experiment revealed that the new generation concretes were characterized by a much lower value of the casting position factor in comparison to the current normative guidelines.