Search

• The compressive behaviour of square RACFSST stub columns after exposure to fire is investigated. • Twelve post-fire compression tests are conducted. • The influences of heating durations and RCA replacement ratios are discussed. • Thermal and mechanical FE models are validated against test results and then used to conduct parametric studies. • The relevant design codes are assessed against the test and FE data. Experimental and numerical studies on the cross-section compressive behaviour and residual resistances of square recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns after exposure to fire are reported in this paper. An experimental programme was firstly carried out on twelve stub column specimens with three recycled coarse aggregate replacement ratios (0%, 35% and 70%) after exposure to the ISO-834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The test results, including load–end shortening curves, failure loads and failure modes, were presented, with the initial compressive stiffness and confinement effect analysed. The experimental programme was followed by a numerical modelling programme, where thermal and mechanical finite element models were developed and validated against the test results and afterwards used to conduct parametric studies to generate additional numerical data over a wide range of cross-section dimensions. Based on the test and numerical data, the relevant design rules for square natural aggregate concrete-filled carbon steel tube stub columns at ambient temperature, as specified in the European code, Australia/New Zealand standard and American specification, were evaluated, using post-fire material properties, for their applicability to square RACFSST stub columns after exposure to fire. The evaluation results generally revealed that the European code and Australian/New Zealand standard led to a good level of design accuracy, while the American specification resulted in slightly conservative post-fire cross-section compression resistance predictions. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations into the post-fire cross-section compressive behaviour and resistances of circular recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns. Twelve stub column specimens, fabricated from concretes with three recycled coarse aggregate replacement ratios (0%, 35% and 70%), were tested after exposure to the ISO-834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The experimental investigation included heating and cooling of specimens, cylinder tests and post-fire tensile coupon tests and stub column tests. The test results, including load–end shortening curves, failure loads and failure modes, were fully reported and the initial compressive stiffnesses and confinement effect were discussed. The numerical investigation was subsequently conducted, where thermal and mechanical finite element models were developed and validated against the test results and then used to perform parametric studies to generate further numerical data. Given the absence of design codes for stainless steel–recycled aggregate concrete composite structures after exposure to fire, the relevant design rules for circular natural aggregate concrete-filled carbon steel tube stub columns at ambient temperature, as set out in the European code, Australia/New Zealand standard and American specification, were assessed, using post-fire material properties, for their applicability to circular RACFSST stub columns after exposure to fire, based on the test and numerical data. The assessment results generally revealed that the European code and the Australian/New Zealand standard led to an acceptable level of design accuracy and consistency, while the American specification resulted in rather conservative and scattered post-fire cross-section compression resistance predictions. • The compressive behaviour of circular RACFSST stub columns after exposure to fire is investigated. • Post-fire compression tests on twelve circular RACFSST stub column specimens are conducted. • The influences of heating durations and RCA replacement ratios are analysed. • Thermal and mechanical FE models are validated against test results and then used to conduct parametric studies. • The relevant design codes are assessed against the test and FE data. [ABSTRACT FROM AUTHOR]

This paper reports experimental and numerical investigations into the structural behaviour and resistances of high strength concrete-filled stainless steel tube (HCFSST) beam-columns under combined compression and bending. An experimental investigation was conducted on sixteen HCFSST beam-columns specimens fabricated from stainless steel tubes with two cross-section sizes and high strength concretes with four material grades, and included concrete cylinder tests, tensile coupon tests, initial global geometric imperfection measurements and eccentric compression tests. The test setups and procedures were fully reported and the experimental observations were discussed and analysed in detail. It was found that the plane cross-section assumption was valid for eccentrically loaded HCFSST sections and the lateral deflection distribution patterns for HCFSST beam-columns were approximately half-sine wave shapes. The test results were used in a subsequent numerical investigation for the validation of finite element models, which were then employed to conduct parametric studies to generate additional numerical data over a wide range of cross-section dimensions, member lengths and loading combinations. Based on the experimental and numerical results, the relevant design rules, as set out in the European code, American specification and Australian/New Zealand standard, were evaluated for their applicability to HCFSST beam-columns. The evaluation results revealed that the European code provided accurate but scattered failure load predictions when used for HCFSST beam-columns, while the American specification and Australian/New Zealand standard resulted in conservative and scattered failure load predictions. • The behaviour of high strength concrete-filled stainless steel tube (HCFSST) beam-columns is investigated. • Eccentric compression tests on sixteen HCFSST beam-column specimens are conducted. • The ductility, strength, longitudinal strain development and lateral deflection distribution are analysed. • FE models are developed to validate against the test results and then used to conduct parametric studies. • The applicability of relevant design codes is assessed against test and FE data. [ABSTRACT FROM AUTHOR]

To study the effect of slenderness ratio on the ultimate bearing capacity of UHPC (ultra-high performance concrete)-encased concrete-filled steel tubular (UC-CFST) columns, a total of nine specimens under axial compression were tested. A finite element model, considering the effects of material nonlinearity and interaction between concrete and steel tube, was developed. A full-range analysis was carried out on the typical load–deformation response of the UC-CFST medium-long columns. The experimental and numerical analysis results showed that with the increase in slenderness ratio, the deformation capacity of the UC-CFST columns increased, the ultimate bearing capacity decreased, and the failure mode changed from exceedance of compressive strength to loss of stability. The internal forces and stress distributions at the mid-height section of the columns at different stages were also investigated. Finally, the applicability of various methods for calculating the ultimate bearing capacity of ordinary concrete-encased CFST (OC-CFST) columns to UC-CFST columns was discussed, including the methods recommended by Chinese standard T/CECS 188-2019, European standard Eurocode 4, Australian/New Zealand joint standard AS/NZS 5100.6 : 2017 and American standard ANSI/AISC 360-16. It was found that the method recommended in AS/NZS 5100.6 : 2017 was suitable for calculating the ultimate bearing capacity of UC-CFST medium-long columns. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study of eccentrically loaded circular recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns. The testing programme was conducted on twelve specimens designed with different stainless steel tube section sizes and recycled coarse aggregate replacement ratios, and included tensile coupon tests, concrete cylinder tests and eccentric compression tests. The test results, including the failure loads and modes, load–mid-height lateral deflection curves and evolution of neutral axis, were reported and discussed. Following the testing programme, a numerical modelling programme was conducted, with finite element models developed and validated against the test results and then employed to perform parametric studies to generate further numerical data. The confinement effects were analysed based on the numerical data. The relevant design interaction curves, as set out in the European code, American specification and Australian/New Zealand standard, were assessed for their applicability to circular RACFSST stub columns under combined compression and bending. On the basis of the quantitative and graphical assessments, it has been found that (i) each set of codified design interaction curve leads to similar assessment results for eccentrically loaded circular RACFSST stub columns with different recycled coarse aggregate replacement ratios and (ii) the failure load predictions from the codified design interaction curves are conservative. • The structural behaviour and resistance of circular RACFSST stub columns under combined loading are investigated. • Twelve eccentric compression tests are conducted. • FE models are developed to validate against the test results and then used to conduct parametric studies. • The confinement effects of different types of RACFSST composite sections are discussed. • The applicability of the relevant codified N–M interaction curves is evaluated. [ABSTRACT FROM AUTHOR]

A new high-chromium grade EN 1.4420 stainless steel, which possesses higher material strength and better corrosion resistance but lower material price than the currently most commonly used grade EN 1.4301 stainless steel, has been recently developed, with a good potential in engineering practice. The present paper reports experimental and numerical investigations into the structural behaviour and resistance of concrete-filled high-chromium stainless steel tube (CFHSST) stub columns under combined compression and bending. The experimental investigation was conducted on twelve CFHSST stub column specimens fabricated from high-chromium grade EN 1.4420 stainless steel tubes with three cross-section sizes and concretes with two grades. The failure loads, mid-height lateral deflections, evolution of neutral axis and confinement effect were analysed and discussed. Numerical modelling was subsequently carried out, where finite element models were developed to simulate the test results and then employed to conduct parametric studies to generate further numerical data. The relevant design interaction curves, as set out in the European code, American specification and Australian/New Zealand standard, were assessed for their applicability to CFHSST stub columns under combined compression and bending, based on test and numerical data. The assessment results revealed that the European code and Australian/New Zealand standard provide overall accurate failure load predictions, while the American specification underestimates the failure loads for CFHSST stub columns under combined compression and bending, due to the conservative shape of the design interaction curve. • The structural behaviour of CFHSST stub columns under combined compression and bending is studied. • Twelve eccentric compression tests on CFHSST stub columns are conducted. • The test results, including the neutral axis and the confinement effect, are discussed. • FE models are developed to validate against the test results and then used to conduct parametric studies. • The relevant codied design interaction curves are assessed against the test and FE data. [ABSTRACT FROM AUTHOR]

• The structural behavior and capacity of RACFSST stub columns under combined loading are studied. • Twelve eccentric compression tests on RACFSST stub columns are conducted. • The evolution of neutral axis in RACFSST composite section as well as the confinement effect are discussed. • FE models are developed to validate against the test results and then used to conduct parametric studies. • The relevant design codes are assessed against the test and FE data. This paper reports experimental and numerical investigations into the behaviour and resistance of recycled aggregate concrete-filled stainless steel tube stub columns under combined compression and bending. Eccentric compression tests were conducted on twelve stub column specimens fabricated from austenitic stainless steel tubes with two cross-section sizes and concretes with three recycled coarse aggregate replacement ratios (0%, 35% and 70%). The test results, including the failure loads, load–mid-height lateral deflection curves, evolution of neutral axis and confinement effect, were discussed in detail. The testing programme was followed by a numerical modelling programme, where finite element models were developed and validated against the test results and then used to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and loading combinations. Given that there are no existing design codes for recycled aggregate concrete–stainless steel composite structures, the relevant codified design rules for natural aggregate concrete filled-carbon steel tube stub columns under combined compression and bending, as set out in the European code, American specification and Australian/New Zealand standard, were evaluated for their applicability to recycled aggregate concrete filled-stainless steel tube stub columns, based on the test and numerical data. The evaluation results revealed that the European code and Australian/New Zealand standard generally provide an acceptable level of design accuracy, while the American specification yields unduly conservative failure load predictions. [ABSTRACT FROM AUTHOR]

This paper reports experimental and numerical investigations into the structural behaviour and residual capacity of concrete-filled high strength steel tube (CFHST) stub columns after exposure to fire. The experimental investigation was conducted on twelve square CFHST stub column specimens after exposure to the ISO-834 standard fire for 15 min, 30 min and 45 min and four reference specimens at ambient temperature. The test results, including failure loads, load–end shortening curves, initial compressive stiffnesses and failure modes, were fully reported and discussed. A numerical investigation was subsequently conducted, where thermal and mechanical finite element models were developed and validated against the test results, and afterwards used to performed parametric studies to generate further numerical data over a wide range of cross-section dimensions. Owing to the absence of design codes for composite structures after exposure to fire, the relevant ambient temperature design rules, as set out in European code, American specification and Australian/New Zealand standard, were evaluated, using post-fire material properties, for their applicability to post-fire CFHST stub columns, based on the test and numerical data. The evaluation results revealed that all the three design codes generally yield accurate failure load predictions for CFHST stub columns after exposure to fire. • Post-fire tests on concrete-filled high strength steel tube (CFHST) stub columns were conducted. • The behaviour and residual resistance of CFHST stub columns after exposure to fire were analysed. • FE models were validated against the test results and then used to conduct parametric studies. • The applicability of the ambient temperature design codes to post-fire CFHST stub columns was demonstrated. [ABSTRACT FROM AUTHOR]