scholarly journals Experimental Study on the Torsional Behaviour of Prestressed HSC Hollow Beams

2020 ◽  
Vol 10 (2) ◽  
pp. 642 ◽  
Author(s):  
Luís Bernardo ◽  
Sérgio Lopes ◽  
Mafalda Teixeira
Keyword(s):  
Experimental Study ◽  
High Strength Concrete ◽  
Concrete Beams ◽  
Concrete Strength ◽  
High Strength ◽  
Experimental Program ◽  
Pure Torsion ◽  
Strength Concrete ◽  
Hollow Beams

This article describes an experimental program developed to study the influence of longitudinal prestress on the behaviour of high-strength concrete hollow beams under pure torsion. The pre-cracking, the post-cracking and the ultimate behaviour are analysed. Three tests were carried out on large hollow high-strength concrete beams with similar concrete strength. The variable studied was the level of longitudinal uniform prestress. Some important conclusions on different aspects of the beams’ behaviour are presented. These conclusions, considered important for the design of box bridges, include the influence of the level of prestress in the cracking and ultimate behaviour.

Available plastic rotation in continuous high-strength concrete beams

2008 ◽  
Vol 35 (10) ◽  
pp. 1152-1162 ◽  
Author(s):  
Ricardo N.F. do Carmo ◽  
Sérgio M.R. Lopes
Keyword(s):  
High Strength Concrete ◽  
Concrete Beams ◽  
Concrete Strength ◽  
High Strength ◽  
Reinforcement Ratio ◽  
Experimental Program ◽  
Strength Concrete ◽  
Model Code ◽  
Moment Redistribution ◽  
Eurocode 2

An experimental program was formulated to study moment redistribution in continuous high-strength concrete beams. The evaluation of ductility is important for this type of beam as, for high-strength concrete, the ductility decreases as the concrete strength increases. It is therefore necessary to determine whether the critical sections are able to develop appreciable plastic rotations to justify the application of a linear elastic analysis with moment redistribution. This work specifically examined the influence of the tensile reinforcement ratio and the transverse reinforcement ratio on the rotation capacity of plastic hinges. The moment redistribution obtained experimentally is compared with the guidelines recommended in Eurocode 2, CEB-FIP Model Code 1990, and ACI 318. The results show that ACI 318 recommendations for linear analysis with moment redistribution are too conservative and that the predictions, according to Eurocode 2 and CEB-FIP Model Code 1990, agree with experimental evidence.

scholarly journals HIGH-STRENGTH CONCRETE HOLLOW BEAMS STRENGTHENED WITH EXTERNAL TRANSVERSAL STEEL REINFORCEMENT UNDER TORSION / SUKTINĖS STIPRIOJO BETONO DĖŽINIO SKERSPJŪVIO SIJOS, SUSTIPRINTOS IŠORINE PLIENINE SKERSINE ARMATŪRA

2011 ◽  
Vol 17 (3) ◽  
pp. 330-339 ◽  
Author(s):  
Luis F. A. Bernardo ◽  
Sergio M. R. Lopes
Keyword(s):  
High Strength Concrete ◽  
High Strength ◽  
Steel Reinforcement ◽  
Experimental Results ◽  
Pure Torsion ◽  
Strength Concrete ◽  
Box Beam ◽  
Torsion Moment ◽  
Hollow Beams ◽  
Transversal Reinforcement

Some bridges have to withstand high levels of torsion forces. As a consequence, box type beams are often the obvious solution. It could be possible that the balance of transversal to longitudinal torsion reinforcement is not fully reached. If the transversal reinforcement is somehow underestimated, the box beam needs to be transversally strengthened. From the various solutions, external transversal reinforcement is certainly one possibility. The investigation presented here aimed to study such solution. The authors tested four hollow beams under pure torsion. The level of the non balanced ratio between internal longitudinal and transversal torsion reinforcement was one of the parameters that were considered in this investigation. Other parameter was the existence or the no existence of external transversal strengthening reinforcement. The experimental results of the tests have shown the effectiveness of the use of the external transversal strengthening steel reinforcement to compensate the lack of balance of internal transversal to longitudinal torsion reinforcement with respect to various behaviour aspects, such as: increasing of torque strength, increasing of ductility, increasing of cracking torsion moment, and better distribution of cracking. Santrauka Kai kurie tiltai turi atlaikyti dideles sukimo jėgas. Tam tikslui dažnai naudojamos dėžinio skerspjūvio sijos. Gali būti, kad tarp sukimui atlaikyti naudojamos skersinės ir išilginės armatūros ne visada pasiekiamas tinkamas balansas. Jei skersinė sija armuota nepakankamai, dėžinio skerspjūvio sijas gali tekti papildomai stiprinti. Vienas iš įvairių galimų stiprinimo variantų – armavimas išorine skersine armatūra. Šiame straipsnyje pateikiama tokio stiprinimo analizė. Autoriai išbandė keturias grynojo sukimo veikiamas dėžinio skerspjūvio sijas. Vienas iš tyrimo parametrų – skersinės ir išilginės sukimo armatūrų santykio nesubalansuotumo lygis. Kitas parametras – išorinės skersinės stiprinimo armatūros buvimas arba nebuvimas. Eksperimentinių tyrimų rezultatai parodė stiprinti naudojamos išorinės plieninės skersinės armatūros veiksmingumą, kompensuojant vidinės skersinės ir išilginės suktinės armatūrų tarpusavio nesubalansuotumą. Efektyvumas buvo įrodytas tokias aspektais: padidėjusi sukamoji galia ir elastingumas, padidėjęs plyšių atsiradimo sukimo momentas bei geresnis plyšių pasiskirstymas.

scholarly journals Cyclical Behavior of Concrete-Encased Composite Frame Joints with High Strength Concrete

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Lei Zeng ◽  
Zhenkun Cui ◽  
Yunfeng Xiao ◽  
Siqian Jin ◽  
Yuanyuan Wu
Keyword(s):  
Cyclic Loading ◽  
High Strength Concrete ◽  
Joint Strength ◽  
Concrete Strength ◽  
Outer Part ◽  
High Strength ◽  
Crack Pattern ◽  
Experimental Program ◽  
Strength Concrete ◽  
Composite Frame

This paper presents an application of high strength concrete to concrete-encased composite frame building based on an experimental program. The work emphasized joints behavior under reverse cyclic loading caused by earthquakes to provide information for seismic design. To investigate the internal mechanisms and seismic performance, cyclic loading tests were carried out on five half-scale interior joints. Two design variables were addressed in the research: concrete strength and axial column load. Frame joints performance including crack pattern, failure mode, deformation, ductility, strain distribution, and energy dissipation capacity was investigated. It was found that all joint specimens behaved in a manner with joint panel shear failure. Using high strength concrete increased the joint strength and had relatively little effect on the stiffness and ductility. The axial column load helped the joint strength by better mobilizing the outer part of the joint, but it had an obvious influence on the ductility and energy-dissipating capacity, which can be improved by providing enough transverse reinforcement. A typical crack pattern was also provided which can well reflect mechanical character and damage process. This research should contribute to the future engineering applications of high strength concrete to concrete-encased composite structure.

An Experimental Study on the Compressive Behavior of CFRP-Confined High- and Ultra High-Strength Concrete

2013 ◽  
Vol 671-674 ◽  
pp. 1860-1864 ◽  
Author(s):  
Thomas Vincent ◽  
Togay Ozbakkloglu
Keyword(s):  
Experimental Study ◽  
High Strength Concrete ◽  
Axial Stress ◽  
Concrete Strength ◽  
Experimental Studies ◽  
High Strength ◽  
Compressive Behavior ◽  
Stress Strain ◽  
Strength Concrete ◽  
Ductile Behavior

It is well established that external confinement of concrete with fiber reinforced polymer (FRP) sheets results in significant improvements on the axial compressive behavior of concrete. This understanding has led to a large number of experimental studies being conducted over the last two decades. However, the majority of these studies have focused on normal strength concretes (NSC) with compressive strengths lower than 55 MPa, and studies on higher strength concretes have been very limited. This paper presents the results of an experimental study on the compressive behavior of FRP confined high- and ultra high-strength concrete (HSC and UHSC) with average compressive strengths of 65 and 100 MPa. A total of 29 specimens were tested under axial compression to investigate the influence of key parameters such as concrete strength and method of confinement. All specimens were cylindrical, confined with carbon FRP and were 305 mm in height and 152 mm in diameter. Results obtained from the laboratory testing were graphically presented in the form of axial stress-strain relationships and key experimental outcomes are discussed. The results of this experimental study indicate that above a certain confinement threshold, FRP-confined HSC and UHSC exhibit highly ductile behavior. The results also indicate that FRP-wrapped specimens perform similar to concrete-filled FRP tube (CFFT) specimens at ultimate condition, however notable differences are evident at the transition region when comparing stress-strain curves.

scholarly journals Influence of steel tube thickness and concrete strength on the axial capacity of stub CFST columns

2018 ◽  
Author(s):  
Carmen Ibáñez Usach ◽  
David Hernández-Figueirido ◽  
Ana Piquer Vicent
Keyword(s):  
High Strength Concrete ◽  
Concrete Strength ◽  
High Strength ◽  
Steel Tube ◽  
Experimental Program ◽  
Ultimate Capacity ◽  
Strength Concrete ◽  
Axial Capacity ◽  
Thin Walled ◽  
Cfst Columns

In order to study the mechanical response of concrete-filled steel tubular (CFST) columns, several experimental and theoretical studies have been conducted in the last years. However, the influence of thin-walled steel tubes on the axial capacity of these composite columns is not completely stablished, especially when it is combined with high-strength concrete as infill. In this paper, the results of an experimental campaign on 9 concrete-filled steel tubular stub columns subjected to concentric load are presented. Different cross-section shapes are considered in this campaign, i.e. circular, square and rectangular. The influence of the steel tube wall thickness is analysed by including in the tests specimens with thin-walled tubes, whose behaviour needs to be studied in depth given the issues arising when working under compression. The experimental program is designed so the analysis of the results permits to drawn consistent conclusions. For each series, the steel tube thickness is the only geometric parameter modified in order to properly study its effect. Besides, two different concrete strengths were considered for the concrete infill, i.e. normal and high- strength concrete, to observe their effect on the ultimate capacity of the columns. During the tests, the specimens are subjected to axial load and the evolution of the axial displacement with the load is registered. The ultimate capacity of each specimen is obtained and an analysis of the steel tube thickness and concrete strength influence is accomplished. Finally, the study of the dependency of the failure mode on these parameters is carried out.

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