Generally, cement composites like high-performance concrete (HPC) are very brittle. The resistance to the impact loading of the HPFRC and the HPFRC reinforced by the textile reinforcement are compared in this article. The samples (0.56 × 0.1 × 0.1 m) were experimentally tested in three-point bending, by using horizontal impact machine. The better resistance of the textile reinforced HPFRC is obvious from the collected data (impact force, acceleration of hammer and acceleration of the tested sample).
The aim of this work is to analyse the mechanical and durability properties of Recycled Ultra High Performance Concretes (RUHPC) containing different amounts of recycled fine aggregate obtained from crushing Ultra High Performance Concretes (UHPC). This paper summarizes and compares the results from different experimental campaigns carried out in the framework of the ReSHEALience project (Rethinking coastal defence and Green-energy service infrastructures through enhanced-durAbiLity high-performance cement-based materials) which has received funding from the European Union's Horizon 2020 programme (GA 760824). Mechanical performance was evaluated by means of compressive and flexural tests, whereas durability was evaluated by means of chloride penetration, chloride migration and water absorption capillary tests. The results indicated that replacing 50% or 100% of natural aggregates with recycled aggregates did not significantly affect neither compressive strength nor flexural strength. In the case of high replacement rates, a slight decrease in workability was detected, but the mix retained its self-compacting properties. RUHPC had similar durability performance as UHPC. In conclusion, the results have shown that it is feasible to produce RUHPC; the recycled fine aggregate has shown great potential to be used in the production of new UHPC. Scalability of the recycling procedure to industrial level was also addressed in order to pave the way towards the uptake from the different value chain actors of the construction industry of the innovation potential demonstrated by the research.
One of the top ten goals by the European Union's White Paper on Transport is to reduce road fatalities. With the most vulnerable road users, motorcyclists, suffering frequent fatalities in crashes involving road barriers, the European Road Assessment has indicated the critical need to adopt improved barrier designs. While both steel guardrail and concrete barriers are encountered nowadays as road safety measures, accident statistics reveal lower numbers of motorist deaths when collisions involve concrete rather than steel. Aiming to reduce road fatality rates further by increasing the energy absorption of concrete barriers significantly, this paper investigates the incorporation of End-of-life tyre materials (e.g. steel wires and rubber particles) into concrete and the formulation of a suitable fibre-reinforced rubberised concrete mixture. The compressive strength of various rubberised concrete mixtures using cement replacements such as fly ash and silica fume was assessed experimentally, and an optimised mixture was selected. A numerical material model was calibrated based on the selected mixture. A case study barrier was simulated on LS-DYNA using the calibrated material and its performance under impact loading was investigated through numerical simulations. The scope of the paper is to present the experimental work and the resulting calibrated numerical model, and illustrate the preliminary results of the numerical study.
Thesis (Master)--Izmir Institute of Technology, Civil Engineering, Izmir, 2015 ; Includes bibliographical references (leaves: 97-100) ; Text in English; Abstract: Turkish and English ; xiv, 100 leaves ; As rare as it may seem, impact loads can act on a structure in its lifespan. For structures such as nuclear energy facilities, industrial facilities, and military buildings design for impact loads may be required. Steel fibers are increasingly used in the design and construction of such reinforced concrete structures. However, studies on the effect of steel fibers on the impact resistance of reinforced concrete structures are rare in the literature. This study investigates the global behavior of reinforced concrete slabs with different ratios of steel fibers under static and impact loading. 10 steel fiber reinforced concrete slabs with dimensions of 2150x2150x150 mm were tested with varying steel fiber volume ratios of 0.5 %, 1.0 % and 1.5 %. Specimens were manufactured as twins, as one to be tested under static loading and one to be tested under impact loading. Static tests were carried out by applying a static load at the midpoint with a hydraulic jack, whereas impact tests were applied through free falling drop-weights. Observed behavior and collected data were compared with companion studies of Batarlar (2013) and Arsan (2014), as they have used the same test setup with different parameters. As a result, it was seen that even steel a fiber addition of 0.5 % in volume was sufficient to provide a ductile behavior both under static and impact loading. Steel fibers significantly enhanced the impact behavior by increasing the strength and resiliency of the specimens. ; Her ne kadar ender görülse de yapılar kullanım ömürleri boyunca darbe yüklerine maruz kalabilirler. Nükleer enerji tesisleri, endüstriyel tesisler ve askeri binalar gibi yapıların darbe yüklerine karşı tasarımları gerekebilir. Bu tür betonarme yapıların tasarım ve inşalarında çelik fiberler artan oranda kullanılmaktadır. Ancak literatürde çelik fiberlerin betonarme yapıların darbe dayanımı üzerine olan etkilerini inceleyen çalışmalar çok azdır. Bu çalışma değişen çelik fiber oranına sahip betonarme döşemelerin statik ve darbe yükleri altındaki global davranışını incelemektedir. 2150x2150x150 mm boyutlarında 10 adet betonarme döşeme,% 0.5, % 1.0 ve % 1.5 oranlarında çelik fiber katkısı ile imal edilmiş ve test edilmişlerdir. Numuneler biri statik yük diğeri darbe yükü altında test edilmek üzere ikiz olarak imal edilmişlerdir. Statik yük orta noktaya hidrolik kriko yardımıyla uygulanırken darbe yükü serbest düşen darbe kütleleri vasıtasıyla uygulanmıştır. Testler sırasında oluşan mesnet reaksiyonları, donatılar üzerinde oluşan gerinimler, yerdeğiştirmeler ve ivmeler yüksek hızlı bir veri toplama cihazıyla kaydedilmiştir.Test düzeneği kenarlarda basit mesnet koşulları oluşturacak şekilde imal edilmiştir. Gözlemlenen davranış ve elde edilen veriler aynı test düzeneğini farklı numunelerle kullanan Batarlar (2013) ve Arsan'ın (2014) tamamlayıcı nitelikteki çalışmaları ile karşılaştırılmıştır. Sonuç olarak hacimce %0.5 oranındaki çelik fiber katkısının dahi hem statik hem darbe yükleri altında sünek bir davranış sağladığı görülmüştür. Çelik fiberler numunelerin darbe davranışını hem dayanımlarını hem de eski durumunu alma yeteneklerini geliştirerek önemli ölçüde iyileştirmiştir. Ayrıca çelik fiber oranının arttırılmasının darbe davranışını iyileştirmekle birlikte elde edilen faydanın aynı oranda olmadığı da gözlemlenmiştir.
This paper considers the problem of transverselongitudinal bending of multilayered concrete rods with a constant cross-section under the impact of quasistatic loading and volume forces. The research is aimed to establish general relations between the distribution topology of materials in the construction and the required types of permissible operating conditions, such as permissible ultimate elastic deformations, permissible pre-destruction deformations, and maximum permissible deformations at the start of local destructions. This study demonstrates the importance of volume forces and the possibility of increasing the bearing capacity using the redistribution of materials of the investigated constructions. The given problems are solved by the Bubnov- Galerkin method. Each of the numerically calculated cases is illustrated by the graphs of the distribution of longitudinal displacement and deflections of the rods and the values of maximum and minimum deformations in each layer of the considered rods.
Self-compacting concrete has constructive advantages over conventional concrete, such as reducing labor and construction time, mainly because of its fluidity in the fresh state. However, in the hardened state, it maintains low performance when tensioned, and the fibers can be added to the mixture, maintaining a portion of the resistance after cracking. Steel fibers are usually added to concrete, but recently synthetic fibers have been used, due to their lower cost and non-corrosive nature, but with lower tensile strength. Thus, by combining the two types of fibers, the benefits of each material can be used. This work presents the results of an experimental program to evaluate the effect of the hybridization of metallic and synthetic fibers on the shear strength of self-compacting concrete beams without stirrups. The results demonstrate that both steel and hybrid fibers result in greater shear strength compared with the reference concrete without fibers before shear crack formation; however, the greatest advantages are attributed to post-cracking residual strength. The experimental results were compared with estimates calculated using equations published in the literature, demonstrating the feasibility of using some existing equations for concretes with the addition of hybrid fibers.
