• International Journal of High-Rise Buildings
• /
• v.7 no.3
• /
• pp.223-232
• /
• 2018

Two novel types of construction detailings, including using the distributive beam and the inner ring diaphragm in the joint between large-section CFT columns and outrigger truss to enhance the transferring efficiency of huge vertical load, and using the T-shaped stiffeners in the steel tube of large-section CFT columns to promote the local buckling capacity of steel tubes, were tested to investigate their working mechanism and design methods. Experimental results show that the co-working performance between steel tube and inner concrete could be significantly improved by setting the distributive beam and the inner ring diaphragm which can transfer the vertical load directly in the large-section CFT columns. Meanwhile, the T-shaped stiffeners are very helpful to improve the local bulking performance of steel tubes in the column components by the composite action of T-shaped stiffeners together with the core concrete under the range of flange of T-shaped stiffeners. These two approaches can result in a lower steel cost in comparison to normal steel reinforced concrete columns. Finally, a practical engineering case was introduced to illustrate the economy benefits achieved by using the two typical detailings.

• Steel and Composite Structures
• /
• v.30 no.2
• /
• pp.149-169
• /
• 2019

A new form of composite column, concrete-filled round-ended steel tubes (CFRTs), has been proposed as piers or columns in bridges and high-rise building and has great potential to be used in civil engineering. Hence, the objective of this paper presents an experimental and numerical investigation on the flexural behavior of CFRTs through combined experimental results and ABAQUS standard solver. The failure mode was discussed in detail and the specimens all behaved in a very ductile manner. The effect of different parameters, including the steel ratio and aspect ratio, on the flexural behavior of CFRTs was further investigated. Furthermore, the feasibility and accuracy of the numerical method was verified by comparing the FE and experimental results. The moment vs. curvature curves of CFRTs during the loading process were analyzed in detail. The development of the stress and strain distributions in the core concrete and steel tube was investigated based on FE models. The composite action between the core concrete and steel tube was discussed and clarified. In addition, the load transfer mechanism of CFRT under bending was introduced comprehensively. Finally, the predicted ultimate moment according to corresponding designed formula is in good agreement with the experimental results.

• Structural Engineering and Mechanics
• /
• v.77 no.6
• /
• pp.745-751
• /
• 2021

Concrete filled double skin tubular members (CFDST) consist of double concentric circular or square steel tubes with concrete filled between the two steel tubes. The CFDST members, having a hollow section inside the internal tube, are generally lighter than ordinary concrete filled steel tubular members (CFT) which have a solid cross-section. Therefore, when the CFDST members are applied to bridge piers, reduction of seismic action can be expected. The present study aims to investigate, experimentally, the behavior of CFDST stub columns with double concentric square steel tubes filled with concrete (SS-CFDST) when working under centric compression. Two test parameters, namely, inner-to-outer width ratio and outer square steel tube's width-to-thickness were selected and outer steel tube's width-to-thickness ratio ranging from 70 to 160 were considered. In the results, shear failure of the concrete fill and local buckling of the double skin tubes having largest inner-to-outer width ratio were observed. A method to predict axial loading capacity of SS-CFDST is also proposed. In addition, the load capacity in the axial direction of stub column test on SS-CFDST is compared with that of double circular CFDST. Finally, the biaxial stress behavior of both steel tubes under plane stress is discussed.

• Steel and Composite Structures
• /
• v.38 no.2
• /
• pp.165-176
• /
• 2021

Existing research on confined concrete filled steel tubular (CCFT) columns has been mainly focused on static or cyclic loading. In this paper, square section CCFT and CFT columns were tested under both static and impact loading, using a 10,000 kN capacity compression test machine and a drop weight testing equipment. Research parameters included bonded and unbonded fiber reinforced polymer (FRP) wraps, with carbon, basalt and glass FRPs (or CFRP, BFRP, and GFRP), respectively. Time history curves for impact force and steel strain observed are discussed in detail. Experimental results show that the failure modes of specimens under impact testing were characterized by local buckling of the steel tube and cracking at the corners, for both CCFT and CFT columns, similar to those under static loading. For both static and impact loading, the FRP wraps could improve the behavior and increase the loading capacity. To analyze the dynamic behavior of the composite columns, a finite element, FE, model was established in LS-DYNA. A simplified method that is compared favorably with test results is also proposed to predict the impact load capacity of square CCFT columns.

• Steel and Composite Structures
• /
• v.42 no.3
• /
• pp.325-351
• /
• 2022

This paper studies the lateral impact behavior of ultra-high performance fiber-reinforced concrete (UHPFRC) filled double-skin steel tubular (UHPFRCFDST) columns. The impact force, midspan deflection, and strain histories were recorded. Based on the test results, the influences of drop height, axial load, concrete type, and steel tube wall thickness on the impact resistance of UHPFRCFDST members were analyzed. LS-DYNA software was used to establish a finite element (FE) model of UHPFRC filled steel tubular members. The failure modes and histories of impact force and midspan deflection of specimens were obtained. The simulation results were compared to the test results, which demonstrated the accuracy of the finite element analysis (FEA) model. Finally, the effects of the steel tube thickness, impact energy, type of concrete and impact indenter shape, and void ratio on the lateral impact performances of the UHPFRCFDST columns were analyzed.

• Steel and Composite Structures
• /
• v.47 no.1
• /
• pp.37-50
• /
• 2023

This paper presented an investigation into steel tubes encased high-strength concrete (STHC) composite walls, wherein steel tubes were embedded at the boundary elements of high-strength concrete walls. A series of cyclic loading tests was conducted to evaluate the failure pattern, hysteresis characteristics, load-bearing capacity, deformability, and strain distribution of STHC composite walls. The test results demonstrated that the bearing capacity and ductility of the STHC composite walls improved with the embedding of steel tubes at the boundary elements. An analytical method was then established to predict the flexural bearing capacity of the STHC composite walls, and the calculated results agreed well with the experimental values, with errors of less than 10%. Finally, a finite element modeling (FEM) was developed via the OpenSees program to analyze the mechanical performance of the STHC composite wall. The FEM was validated through test results; additionally, the influences of the axial load ratio, steel tube strength, and shear-span ratio on the mechanical properties of STHC composite walls were comprehensively investigated.

• Proceedings of the KSR Conference
• /
• 2004.06a
• /
• pp.1211-1220
• /
• 2004

The confined concrete subjected multi-axial stresses have been known as the strength of concrete increases significantly. Many researchers have studied in confining effects of concrete, and now are studying in many fields. However, there are few passive confinements by steel tube. Although Mander et al. studied the concrete confined by transverse reinforcements, the confinement by steel tube differs from confining of reinforcements. To investigate the influence of concrete strength increased by confining conditions in steel, 51 specimens confined by different shapes and thicknesses of steel tube were tested and compared.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2012.05a
• /
• pp.213-214
• /
• 2012

This paper presents basic study to develop high performance concrete for concrete filled tube with addition content of steel fiber. In this study, all mixtures was added to nylon fiber (1.5 kg/㎥) and steel fiber was mixed by 0, 20 and 40 kg/㎥ respectively. To evaluate the property of high performance concrete was used to various test methods which were slump flow, air content, U-box test, O-lot test and L-flow(to 300 mm, 500 mm). Also, compressive strength test was measured by ages.

• Structural Engineering and Mechanics
• /
• v.37 no.3
• /
• pp.321-330
• /
• 2011

Long-term properties of concrete affect structures in many respects, not excepting dynamic behaviors. This paper investigates the influence of concrete creep on the dynamic behaviors of concrete filled steel tube (CFT) arch bridges, by means of combining the analytical method for the creep of axially compressed CFT members, which is based on Model B3 for concrete creep, with the finite element model of CFT arch bridges. By this approach, the changes of the stress and strain of each element in the bridge with time can be obtained and then transformed into damping and stiffness matrices in the dynamic equation involved in the finite element model at different times. A numerical example of a long-span half-through CFT arch bridge shows that creep influences the natural vibration characteristics and seismic responses of the bridge considerably, especially in the early age. In addition, parameter analysis demonstrates that concrete composition, compressive strength and steel ratio have an obvious effect on the seismic response of the CFT arch bridge.

• Steel and Composite Structures
• /
• v.32 no.1
• /
• pp.37-57
• /
• 2019

This paper presents experimental and analytical studies to evaluate the cyclic behaviour of Circular Reinforced Concrete column Steel beam (CRCS) connections. Two 3/4-scale CRCS specimens are tested under quasi-static reversed cyclic loading. Specimens were strengthened with a tube plate (TP) and a steel doubler plate (SDP). Furthermore; nine interior beam-through type RCS connections are simulated using nonlinear three-dimensional finite element method using ABAQUS software and are verified with experimental results. The results revealed that using the TP improves the performance of the panel zone by providing better confinement to the concrete. Utilizing the TP at the panel zone may absorb and distribute stress in this region. Results demonstrate that TP can be used instead of SDP. Test records indicate that specimens with TP, with and without SDP maintained their maximum strength up to 4% drift angle, satisfying the recommendation given by AISC341-2016 for composite special moment-resisting frames.