scholarly journals Axial Behaviour of Slender RC Circular Columns Strengthened with Circular CFST Jackets

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Yiyan Lu ◽  
Tao Zhu ◽  
Shan Li ◽  
Weijie Li ◽  
Na Li
Keyword(s):  
Bearing Capacity ◽  
Ductile Failure ◽  
Steel Tube ◽  
Experimental Results ◽  
Strengthening Effect ◽  
Load Bearing Capacity ◽  
Rc Columns ◽  
Load Bearing ◽  
Cfst Columns ◽  
Material Utilization

This paper investigates the axial behavior of slender reinforced concrete (RC) columns strengthened with concrete filled steel tube (CFST) jacketing technique. It is realized by pouring self-compacting concrete (SCC) into the gap between inner original slender RC columns and outer steel tubes. Nine specimens were prepared and tested to failure under axial compression: a control specimen without strengthening and eight specimens with heights ranging between 1240 and 2140 mm strengthened with CFST jacketing. Experimental variables included four different length-to-diameter (L/D) ratios, three different diameter-to-thickness (D/t) ratios, and three different SCC strengths. The experimental results showed that the outer steel tube provided confinement to the SCC and original slender RC columns and thus effectively improved the behavior of slender RC columns. The failure mode of slender RC columns was changed from brittle failure (concrete peel-off) into ductile failure (global bending) after strengthening. And, the load-bearing capacity, material utilization, and ductility of slender RC columns were significantly enhanced. The strengthening effect of CFST jacketing decreased with the increase of L/D ratio and D/t ratio but showed little variation with higher SCC strength. An existing expression of load-bearing capacity for traditional CFST columns was extended to propose a formula for the load-bearing capacity of CFST jacketed columns, and the predictions showed good agreement with the experimental results.

Experimental Research on the Strengthening of RC Columns by High Performance Ferrocement Laminates

2011 ◽  
Vol 243-249 ◽  
pp. 1409-1415 ◽  
Author(s):  
Long Min Jiang ◽  
Fan Hua Tang ◽  
Man Li Ou
Keyword(s):  
Bearing Capacity ◽  
High Performance ◽  
Ultimate Load ◽  
Strengthening Effect ◽  
Test Results ◽  
Load Bearing Capacity ◽  
Rc Columns ◽  
Cracking Behavior ◽  
Load Bearing ◽  
Better Than

Eleven approximate full-size specimens including nine eccentrically compressed columns of monotonic loading and two axially compressed columns of laterally cyclic loading were tested. By a series of comparison experiment of specimens strengthened by high performance ferrocement laminates (HPFL) and no strengthened specimens, it was found that the RC columns strengthened with attached HPFL demonstrated greater degree of improving in load-bearing capacity, in which the carrying capacity increment of the strengthened eccentrically compressed columns with lesser eccentricity was greater than that of the same type of columns with bigger eccentricity under the same strengthening conditions; the strengthening effects of the specimens with lower concrete grade are better than that of those ones with higher concrete grade; the ductility and energy dissipation ability of the strengthened columns were remarkably increased. In this paper, the test results is described, the principle and regularity that this category of strengthening laminate improved the ultimate load-bearing capacity, ductility, cracking behavior and mode of failure etc. of the RC columns are analyzed. The studying results proved that this strengthening measure for RC columns is superior to make the strengthening effect notable, working behavior of strengthened column excellent, strengthening construction easy and economical.

Axial behaviour of slender concrete-filled steel tube square columns strengthened with square concrete-filled steel tube jackets

2019 ◽  
Vol 23 (6) ◽  
pp. 1074-1086 ◽  
Author(s):  
Tao Zhu ◽  
Hongjun Liang ◽  
Yiyan Lu ◽  
Weijie Li ◽  
Hong Zhang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Bearing Capacity ◽  
Element Model ◽  
Steel Tube ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Concrete Filled Steel Tube ◽  
Experimental Parameters ◽  
Modified Formula

This article investigates the behaviour of slender concrete-filled steel tube square columns strengthened by concrete-filled steel tube jacketing. The columns were realised by placing a square outer steel tube around the original slender concrete-filled steel tube column and pouring strengthening concrete into the gap between the inner and outer steel tubes. Three concrete-filled steel tube square columns and seven retrofitted columns ranging from 1200 to 2000 mm were tested to failure under axial compression. The experimental parameters included three length-to-width ( L/ B1) ratios, three width-to-thickness ( B1/ t1) ratios and three strengths of concrete jacket (C50-grade, C60-grade and C70-grade). Experimentally, the retrofitted columns failed in a similar manner to traditional slender concrete-filled steel tube columns. After strengthening, the retrofitted columns benefitted greatly from the component materials, with their load-bearing capacity and ductility notably enhanced. These enhancements were mainly brought about by sectional enlargement and good confinement of concrete. A finite element model was developed using ABAQUS to better understand the axial behaviour of the retrofitted specimens. A parametric study was conducted, with parameters including the length of the column, thickness of the outer steel tube, strength of the concrete jacket, yield strength of the outer steel tube, thickness of the inner steel tube and strength of the inner concrete. Furthermore, the finite element model was adopted to study the behaviour of rust-damaged and post-fire slender concrete-filled steel tube square columns strengthened by square concrete-filled steel tube jacketing. A modified formula was proposed to predict the load-bearing capacity of retrofitted specimens, and the numerical results agreed well with the experiments and the finite element results of undamaged, rust-damaged and post-fire specimens. It could be used as a reference for practical application.

Effect of Concrete-Filled in Chord Tubes on Mechanical Behavior of RHS Steel Tube Trusses

2010 ◽  
Vol 163-167 ◽  
pp. 2171-2175 ◽  
Author(s):  
Jun Ping Liu ◽  
Yong Jian Liu ◽  
Jian Yang
Keyword(s):  
Bearing Capacity ◽  
Failure Modes ◽  
Steel Tube ◽  
Structural Stiffness ◽  
Static Behavior ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Compression Load ◽  
Hollow Section ◽  
Joint Deformation

Based on the experimental results, this paper presents the effects of concrete-filled in chord on the static behavior of rectangular hollow section (RHS) steel tubular trusses, including failure modes, load bearing capacity and structural stiffness. Failure of RHS trusses occurs at joints wether concrete-filled in chord or not, concrete-filled in chord changed the failure mode. Load bearing capacity and stiffness of joints subjected to compression load increased significantly, while it is limited to the tension joints. Concrete-filled in the compression chord tube can increase its stiffness significantly, while tension chord tube, it is not that obvious. Finally, based on the results discussed, failure modes and their formulas of calculating the load bearing capacity are discussed. Meanwhile, two methods, that is, amplified factor method and stiffness discounting method, which calculate the structural displacement when considering the joint deformation effects are presented.

Experimental Study on the Axial Loading Tests of RC Columns Strengthened with Steel Tube

2012 ◽  
Vol 204-208 ◽  
pp. 2878-2882 ◽  
Author(s):  
Miao Zhou ◽  
Jian Wei Li ◽  
Jing Min Duan
Keyword(s):  
Experimental Study ◽  
Bearing Capacity ◽  
Axial Loading ◽  
Steel Tube ◽  
Experimental Results ◽  
Engineering Practice ◽  
Rc Columns ◽  
Short Columns ◽  
Loading Tests ◽  
Engineering Staff

This paper carries out a series of experimental study on 6 column specimens, analyses and compares with the different parameters on the axial loading tests of RC columns and RC columns strengthened with steel tube. The experimental results show that the RC columns strengthened with steel tube take full advantage of loading properties of both materials, thus greatly improve the bearing capacity of specimens. With the same wall thickness steel tube, the improving degree of bearing capacity of long columns is bigger than the short columns, and the reinforcement effect is more obvious. The experimental results can offer reference for scientific research and engineering staff, and promote this reinforcement method to be widely used in engineering practice.

LOAD-BEARING CAPACITY OF CONCRETE-FILLED STEEL COLUMNS

2009 ◽  
Vol 15 (1) ◽  
pp. 21-33 ◽  
Author(s):  
Artiomas Kuranovas ◽  
Douglas Goode ◽  
Audronis Kazimieras Kvedaras ◽  
Shantong Zhong
Keyword(s):  
Bearing Capacity ◽  
Cross Section ◽  
Cross Sections ◽  
Rectangular Cross Section ◽  
Circular Cross Section ◽  
Steel Tube ◽  
Sustained Load ◽  
Load Bearing Capacity ◽  
Concrete Core ◽  
Load Bearing

This paper represents the analysis of 1303 specimens of CFST experimental data. Test results are compared with EC4 provided method for determining the load‐bearing capacity of these composite elements. Several types of CFSTs were tested: both circular and rectangular cross‐sections with solid and hollow concrete core with axial load applied without and with moment, with sustained load and preloading. For circular cross‐section columns there is a good agreement between the test failure load and the EC4 calculation for both short and long columns with and without moment. For rectangular cross‐section columns the agreement is good except when the concrete cylinder strength was greater than 75 MPa, when many tests failed below the strength predicted by EC4. Preloading the steel tube before filling with concrete seems to have no effect on the strength. This paper also presents the stress distribution, confinement distribution and complete average longitudinal stress‐strain curves for concrete‐filled steel tubular elements. Based on the definition of the “Unified Theory”, the CFST is looked upon as an entity of a new composite material. In this paper, the research achievement of the strength and stability for centrifugal‐hollow and solid concrete filled steel tube are introduced. These behaviours relate to the hollowness ratio and the confining indexes of corresponding solid CFST. If the hollow ratio equals to 0,4–0,5 and over, the N‐ϵ relationship exists in steady descending stage. The critical stress of CFST elements stability is determined as an eccentric member with the initial eccentricity by use of finite element method. Santrauka Straipsnyje analizuojami 1303 betonšerdžių plieninių strypų bandinių eksperimentiniai duomenys. Duomenys lyginami su eurokode 4 pateiktais kompozitinių elementų laikomosios galios nustatymo metodais. Analizuojami šie betonšerdžių plieninių strypų bandinių tipai: pilnaviduriai ir tuščiaviduriai, apskrito ir stačiakampio skerspjūvio kolonos, kurių galuose veikia arba neveikia momentas, su iš anksto pridėta arba ilgalaike apkrova. Apskrito skerspjūvio kolonų laikomosios galios bandymų rezultatai atitinka skaičiavimų reikšmes, apskaičiuotas pagal eurokode 4 pateiktu metodu. Stačiakampio skerspjūvio elementų laikomosios galios reikšmių bandymo rezultatai puikiai atitinka teorines reikšmes, kai betono ritininis stipris nesiekia 75 MPa. Išankstinis elementų apkrovimas poveikio elementų laikomajai galiai beveik neturi. Taip pat nagrinėjami betonšerdžių elementų įtempių būvių pasiskirstymas, betono apspaudimo poveikis ir išilginių deformacijų ir įtempių kreivės. Pateikiama S. T. Zhong „Unifikuota teorija“, kuri nagrinėja kompozitinį elementą kaip visumą. Straipsnyje nagrinėjamos kompozitinio plieninio ir betoninio elemento stiprumo ir pastovumo sąlygos. Tokių elementų reikšmėmis. Jeigu tuštumos santykis lygus 0,4–0,5 ir daugiau, N-ε sąryšis yra kritimo stadijoje. Elgsenos stadijos keičiasi pagal tuštumos koeficientą.

Research on Hysteretic Behavior of the Concrete Filled Square CFRP-Steel Tubular (S-CFRP-CFST) Beam-Columns (I): Experimental Study

2010 ◽  
Vol 163-167 ◽  
pp. 3580-3585
Author(s):  
Yuan Che ◽  
Qing Li Wang ◽  
Yong Bo Shao ◽  
Hai Tao Mu
Keyword(s):  
Experimental Study ◽  
Bearing Capacity ◽  
Local Buckling ◽  
Steel Tube ◽  
Hysteretic Behavior ◽  
Strengthening Effect ◽  
Test Results ◽  
Load Bearing Capacity ◽  
Beam Columns ◽  
Hysteretic Performance

Overall 12 specimens were experimentally investigated in this paper to study the hysteretic behaviors of the concrete-filled square CFRP-steel tubular (S-CFRP-CFST) beam-columns. The test results indicated that CFRP can provide transverse confinement effect and longitudinal strengthening effect for the concrete filled square steel tubular (S-CFST) beam-columns effectively and the local buckling of the steel tube is deferred. The hysteretic load-deflection curves and the hysteretic moment-curvature curves at the mid-span of all the specimens are generally plump, and it shows these specimens have good hysteretic performance. In the later loading period, the load bearing capacity drops.

The assessment of the level of local strengthening of pipe steel welded connections

2020 ◽  
Vol 10 (3) ◽  
pp. 252-262
Author(s):  
Marat Z. Yamilev ◽  
◽  
Egor А. Tigulev ◽  
Andrey А. Raspopov ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Numerical Model ◽  
Bearing Capacity ◽  
Pipe Steel ◽  
Carbon Steels ◽  
Strengthening Effect ◽  
Low Carbon ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Welded Connection

The metal welding is accompanied by the formation of mechanically non-homogenous sections of welded connection. The pipeline welded connections also have sections, which are different in structure, chemical composition and mechanical properties. The mechanical inhomogeneity affects the load bearing capacity of welded connection and the structure as a whole, which is necessary to take into consideration when performing calculation analysis. So far, the specialists have established the dependencies in assessment of welded connection strength with various types of heterogeneous sections. However, this phenomenon has received little attention in case of pipeline welded connections made of low carbon steels. The existing theoretical models do not reflect actual anisotropy of mechanical properties of the welded connections and weld adjacent zone. The present study considers the model of welded connections of K56 pipe steels with various strength characteristics of sections of welded seam and weld adjacent zone, without defects. The assessment of mechanical inhomogeneity influence on load bearing capacity of welded connections was performed by applying the finite-element modelling of its stress-strain state. The developed numerical model helps to determine and optimize the criteria of testing of full scale samples of pipe steel welded connections with regards to the implementation of local strengthening effect. The research results demonstrated that the degree of contact strengthening in welded connections with X-shape grooving is higher than in welded connections with V-shaped grooving by 8 % at similar relative thickness of soft interlayer. The suggested numerical model can be applied for detailed calculations of pipelines with regards to the mechanical inhomogeneity of its welded connections.

Parameters Survey and Experiment on Steel Scaffold Components

2011 ◽  
Vol 368-373 ◽  
pp. 1513-1516
Author(s):  
Chuan Li Chang ◽  
Jian Xue Song
Keyword(s):  
Bearing Capacity ◽  
Wall Thickness ◽  
Steel Tube ◽  
Construction Sites ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
The Right

Ten construction sites are chosen as survey places, and several parameters for scaffold designing are collected, such as the wall thickness of steel tube, the weight of three kinds of couplers, the working tighten-moment on belts of couplers. Corresponding to different tighten-moment of the right angle coupler and anti-slipping tests are carried out. Reliability of 97% and wall thickness of 2.7mm should be considered in scaffold designing only about 10% of the practical used couplers comply with the National Code. The working tighten-moment of couplers should be 40 ～ 50N • m, which is up to the load bearing capacity of coupler.

Load-Bearing Capacity of CFDST Based on the Unified Strength Theory

2012 ◽  
Vol 204-208 ◽  
pp. 4031-4037
Author(s):  
Gui Yun Xia ◽  
Jia Jun Li ◽  
Mei Liang Yang
Keyword(s):  
Bearing Capacity ◽  
Steel Tube ◽  
Strength Theory ◽  
Load Bearing Capacity ◽  
Unified Strength Theory ◽  
Load Bearing

Based on the unified strength theory presented by Maohong Yu, the calculating formula for the load-bearing capacity of concrete-filled double steel tube was derived. Through tests, the calculating load-bearing capacity results were compared with testing results, which agreed well. The change of load-bearing capacities with parameter k of the unified strength theory was discussed. It can be drawn that the load-bearing capacity of CFDST will increase with the increase of parameter b, but the increase is not obvious.

scholarly journals FLEXURAL CAPACITY OF CORRODED POST-TENSIONED CONCRETE BEAMS: LARGE SCALE TESTS AND NUMERICAL SIMULATION

2020 ◽  
Author(s):  
Antonino Recupero ◽  
Nino Spinella ◽  
Antonio Marì ◽  
Jesús Miguel Bairan
Keyword(s):  
Numerical Model ◽  
Bearing Capacity ◽  
Large Scale ◽  
Concrete Beams ◽  
Structural Response ◽  
Experimental Results ◽  
Analysis Model ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Post Tensioned

An experimental campaign on corroded post-tensioned concrete beams is being carried out at the University of Messina (Italy). The main goal of the research project is to study the influence of the tendon corrosion on the response behaviour of post-tensioned concrete beams subjected to a transversal load. In 2006, six beams were cast with a tendon placed at the centroid of the cross-section. Corrosion of the tendons was artificially induced in each specimen by injecting a chemical solution or an acid in some parts of the duct. The experimental results have showed how external causes, reproduced by artificial defects, can induce several critical issues, and undermine both the durability and the load bearing capacity of the beams. The load bearing capacity of the beam with defects was reduced until half of the one recorded for the specimen with not corroded tendon. In addition, a non-linear and time dependent analysis model, developed at UPC in Barcelona, was used to simulate the response of the tested beams, with the purpose of experimentally verifying the capacity of the model to capture the effects of corrosion along the time. A parametric study was performed with the numerical model to capture the influence of the degree of corrosion, (defined as the % loss of steel mass) on the serviceability response and on the ultimate capacity. By comparing the theoretical and the experimental results, the degree of corrosion was estimated and compared with that observed subsequently on the tested beams. Good correlation was obtained, thus allowing the numerical model to be used as a “virtual lab” to study the influence of several parameters on the structural response of corroded post-tensioned beams.

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