Theses supervised by Yrd. Doç. Dr. Mehmet Tolga Göğüş
10 theses · Gaziantep University
Flexural performance of reinforced self-compacting concrete filled steel tube (Rsccfst) beams
Reinforced concrete filled steel tubular (RCFST) structures offer several structure benefits and has been increasingly used in civil engineering structures. In this study a total of 16 beam specimens were tested to investigate the flexural behavior of RCFT experimentally, 14 of them filled with reinforced self-compacting concrete, two filled with self-compacting concrete and two were hollow beams. The main parameters varied in this study were: (1) ratio of longitudinal reinforcement area to the concrete area 3%, 5% and 7%; (2) distribution of axial reinforcement (two layers and three layers); (3) spacing between stirrups (6cm and 12cm). It concluded that the internal reinforcement with different ratios has obvious effect on bending capacity and failure mode of beam specimens and insignificant effect on their ductility. The moment versus mid-span deflection curves and moment versus ultimate strains curves for specimens presented. Comparisons made with the predicted specimens capacity results using the existing methods, such as AISC 360-10 and Eurocode 4 and generally good agreement between predicted and experimental results achieved.
Investigation of design parameters effects performance of concrete filled steel composite rectangular members according to design codes
Rectangular Concrete Filled Steel Tube (RCFST) members are used widely around the world in various types of structures such as (building, bridges, and, towers etc.). RCFST members are classified according to AISC360-10 as compact, non-compact and slender based on the slenderness ratio (width-to-thickness b/t ratio) of the steel tube walls. In this thesis presents an investigation on a design which parameters affect the performance of RCFST members. There are several factors that affect the design of RCFST members. Other than the interaction between the steel and the concrete core, geometric and material properties like height of rectangular HSS member (H), width (B), thickness of the tube (t), yield strength of steel (f_y) and compressive strength of concrete (f_c^'). Since the goal of the parametric study is to evaluate the contribution of the concrete, steel and dimensions quantitatively, the relative area and strength proportions of concrete to steel constitute the main parameters. The axial compression, and, flexural strength calculation basis of the applied calculation formula specification according to American Institute of Steel Construction (AISC360-10) and Eurocode 4 (EC4-2004) codes for the design of which parameter effects performance of RCFST members. Keywords: Rectangular CFST members, Axial strength, Flexural strength, Design codes.
Investigation of design parameters effects performance of concrete filled steel composite circular beams according design to codes
The Concrete Filled Steel Tubular (CFST) members offer many structural features and have been widely used in civil engineering structures. Available in many different shapes, but most important circular, rectangular and square, etc. The CFST structures offers numerous structural benefits, including high strength, favorable ductility, and highly absorbable to withstand external shocks. They have proven to be economically as well as providing for the rapid construction and thus additional cost savings. The circular CFST members included normal strength concrete filled circular structural sections. In this study the parameters; diameter (D), thickness (t), yield stress 〖(f〗_y), and compressive strength of concrete 〖(f〗_c^') show their effect on the members and their comparison, according to calculation equations of the American (AISC 360-10) and European (Eurocode 4-2004) codes for the design of which parameter effects performance of CCFST members under axial compression and flexure. Keywords: Circular CFST members, Axial strength, Flexural strength, Design codes.
Concrete filled steel tube composite beams and improvement of flexural performance
Concrete-filled steel tube (CFST) beams represent one of the most promising composite members within the CFST family. CFST beams are widely utilized in different structural applications including, bridges of several typologies, offshore structures, and high-rise buildings. CFST beams display several advantages over the conventional tubular steel or reinforced concrete members, including high flexural capacity, high stiffness, significant ductility, and energy absorption ability. The superior performance of CFST beams is thanks to the composite action between the steel profile and the concrete core. The concrete core delays and even precludes local buckling of the confining steel tube, and this significantly increases strength and ductility. On the other hand, the steel section provides continuous longitudinal and lateral reinforcement for the concrete core in addition to effective confinement. The essential goal of this thesis is to experimentally investigate the flexural performance of concrete-filled steel tube beams subjected to a pure bending load. To achieve this aim three different typologies of CFST beams have been studied comprising lightweight-concrete filled steel tube (LWCFST) beams, self-compacting-concrete filled steel tube (SCCFST) beams, and finally, SCCFST beams retrofitted using external bolted steel plates, all with various parameters and configurations. Five international pioneering design codes have been adopted to assess the flexural capacities of the tested CFST beams, involving the AISC 360-16, EC4-2004, DBJ/T13-51-2010, AS 5100.6-2004, and AIJ-2001. Furthermore, a theoretical model was developed to predict the moment resistance of the retrofitted SCCFST beams.
Reliability analysis of concrete filled steel tube for quadrilateral and circular cross sections
Concrete filled steel tube beams is a structural composition that brings the advantages of the combination of the surrounding steel with the core concrete, this structural member had been investigated under different conditions but still, there is a significant difference among the well-known design codes provisions and limitations. Assessing the limit states of the codes can be conducted based on structural reliability analysis. Bending capacity of the beams can be characterized by the reliability index in terms that can be readily understood by structural engineers with only a basic knowledge of probability theory. In this study, First-order Reliability Method was used in assessing the selected tested specimens. More than 2000 concrete filled steel tube members of different shapes cross-section had been collected from recently introduced literature (from 2000 up to 2018); moreover, the selected specimens were compared with the provisions of many codes. The judgment was based on the convergences between the calculated beams load capacity in term of bending strength according to mentioned codes and the recorded load capacity that obtained from the experimental work. Different parameters were evaluated from the selected beams, while the geometry of the beams were the main parameters, the tube thickness is ranging between, the width of the members. The material properties are also altered in order to evaluate its effect on the beam strength, where the concrete compressive strength was ranging between 10 to 154 MPa, and the steel yield strength was less than 762 MPa. The results show that both codes (EC4-2004 and AISC360-10) have percentages of error within the unsafe zone, and EC4 is less conservative than the AISC.
Performance evaluation of double skin steel tube filled by concrete as composite beam
This study is presented in order to show how Concrete-Filled Double Skin Steel Tube (CFDSST) beams behave under pure bending. Laboratory investigations were made on thirteen test specimens that involved twelve units of the CFDST specimens and one unit of Concrete-Filled Steel Tube (CFST) beam as a control. Six of the CFDSST specimens were having a square and rectangular inner tube in the bottom side of the outer tubes, while the other six CFDSST specimens had a centric square and centric rectangular inner tubes. Two major and important parameters relied on this study, namely, the inner tube position and inner tube cross-section. Based on these parameters, bending moment against mid-span deflection, deflection curves, flexural stiffness, flexural capacity, ductility and self-weight differences were investigated. The results of laboratory work showed clear improvement in moment capacity and strength for the CFDSST beams with inner tubes in the bottom side compared to those with centric inner tubes, in addition to showing the advantages of CFDSST beams to CFST beams. Also, this study confirmed that the effect of inner tube cross-section (square to rectangular and vice versa) for the same section area was slight.
Investigation of flexural performance of double skin concrete filled steel tube beams
Concrete Double Skin Steel Tube (CFDSST) beams are consist of two skins of steel filled with concrete between them. CFDSST member is lighter than Concrete Filled Steel Tube (CFST) members, which has a solid cross-section. Therefore, by lessening seismic force against the structures during an earthquake, the CFDST members can be effectively applied to the seismic resistance structures such as the high-rise buildings, bridge piers, etc. This thesis deals with are an experimental investigation of the effect of cross-section and the position of the inner tube on the flexural performance of CFDST beams. A total 13 CFDST beams specimens filled with self-compacted concrete was tested. The parameters examined in the test: (a) inner tube cross-section (square and rectangular) (b) the position of inner tube (center and bottom). Comparisons are presented between the examined specimens according to the flexural strength, failure modes, ductility and flexural stiffness.
Effects of different load-bearing systems for multi-story reinforced concrete buildings
An efficient and economical tall building cannot be designed without a thorough understanding of the significant factors affecting the selection of the structural system and knowledge of how the structural system will interrelate with architectural, structural aspects. Usually two to three different structural systems will be selected for comparison. The selection of ETABS In this study, among the much commercial software goes back to the many reasons, the previous studies show that programs internationally approved, More specialized and accuracy in the design of shear walls, The possibility of using more than one code in a single program, all these reasons and more lead to use ETABS in this study. Religious and monumental architecture was first started in high structures, with the growing technology of today has taken shape. High structures, especially in densely populated, so as much as possible on the smaller areas are located in large urban centers and the establishment required more housing solutions. The construction of high rise building is seen to increase in the coming years. High structures, building design, horizontal loads and withstand the vertical loads to be effective, relocation and operation of structures designed according to the criteria defined. Due to the effectiveness of horizontal loads, structural load bearing system selection and placement of structures is very important. Load bearing system is the important factor affecting the behavior of structure. In this study, the effect of different load bearing system systems studied the behavior of the structure of different heights.
Performance evaluation of reinforced lightweight concrete filled steel tubular beams
This study presents an experimental research to evaluate the flexural performance of Reinforced Lightweight Concrete Filled Steel Tubular beams. 16 beam specimens were tested, 12 specimens as Reinforced Lightweight Concrete Filled Steel Tubular (RLWCFST) beams, two specimens as Lightweight Concrete Filled Steel Tubular (LWCFST) beams and two specimens as Square Hollow Steel Tubular (SHS) beams. The major experimental parameters in the study are: (1) ratio of longitudinal steel reinforcement (ρ) from 3% to 7%; (2) arrangement of longitudinal steel reinforcement (in two or three layers), and (3) the spacing of stirrups (6cm or 12 cm). Based on the test results, the flexural strength, failure modes, ductility, moment-deflection relationships andmoment-strain relationships were studied and their impact on the flexural performance of LWCFST and RLWCFST beams was discussed. The results indicated that the longitudinal reinforcement has important effect on bending performance of RLWCFST beams and provided obvious increasing in bending strength, ductility and stiffness of LWCFST beam and helped the steel tube and concrete to improve their performance. The experimental ultimate moments are compared to theoretical moments calculated by two international design codes namely the AISC-2010 code and the EC4-2004. The two design codes predicted good estimate and safe design moment capacitiesfor RLWCFST beams especially EC4 that limited the maximum ρ with 6%. However, test results showed that exceeding this ratio (6%) up to 7% is possible and EC4 design method is applicable, even if the limitation of ρ was increased up to 7%. Keywords: Lightweight Concrete (LWC), Reinforced LightweightConcrete Filled Steel Tubes (RLWCFST) beams, flexural strength, performance indices, ductility.
Structural performance assessment of concrete filled steel strengthened beams with steel plates
Composite members consist of rectangular, circular and square steel tubes filled with concrete are extensively used in the construction of modern buildings, bridges, and particularly in zones of high earthquake risk. A very large number of structures have arrived the finale of their service life either caused by the change in the functional usage or degradation caused by environmental factors or due to a need of an increase in applied loads. Therefore, the strengthening techniques become essential to combat these problems. This study experimentally investigates the behavior of external strengthening of the square and rectangular Self-Compacted Concrete Filled Steel Tube (SCCFST) beams by attaching various steel plate thicknesses by bolts under flexural loading. A total of eighteen specimens which consist of 12 strengthened SCCFST beams, 3 control SCCFST beams, and 3 hollow steel tubes. The main parameters of this study are the width-to-depth ratio (B/H), rectangular and square sections and strengthening steel plates with two different thickness 3mm and 1.5mm fixed by bolts with four different arrangements. The flexural behavior of the strengthening SCCFST beams had been studied in terms of flexural strength, ductility and failure modes. Experimental results detected that the moment carrying capacity of the strengthened SCCFST beam is increased with the increasing thickness of steel plate and width to depth ratio. And also, ductility of strengthened SCCFST beams are decreased significantly with increase the width-to-depth ratio of the steel tube and the thickness of the steel plates. In addition, the B/H=1 is more ductile than the B/H=0.5 and 1.5.