• Composites Research
• /
• v.34 no.2
• /
• pp.96-100
• /
• 2021

The lightweight industry continuously demands reliable near-net-shape fabrication where the preform just out-of-machine is close to the final shape. In this study, different half-finished preforms are made π-beams. Then the preforms are unfolded to make a 3D shape with integrated structure of fibers, providing easier handling in the further processing of composites. Several 3D textile preforms are made using weaving technique and are examined after resin infusion for mechanical properties such as inter-laminar shear strength, compressive strength and tensile strength. Considering that the time and labor are important parameters in modern production, 3D weaving technique reduces the manufacturing steps and therefore the costs, such as hand-lay up of textile layers, cutting, and converting into preform shape. Hence this 3D weaving technique offers many possibilities for new applications with efficient composite production.

• Structural Engineering and Mechanics
• /
• v.24 no.1
• /
• pp.1-18
• /
• 2006

Strengthening of existing old structures has traditionally been accomplished by using conventional materials and techniques, viz., externally bonded steel plates, steel or concrete jackets, etc. Alternatively, fibre reinforced polymer composite (FRPC) products started being used to overcome problems associated with conventional materials in the mid 1950s because of their favourable engineering properties. Effectiveness of FRPC materials has been demonstrated through extensive experimental research throughout the world in the last two decades. However there is a need to use refined analytical tools to simulate response of strengthened system. In this paper, an attempt has been made to develop a numerical model of strengthened reinforced concrete (RC) beams with FRPC laminates. Material models for RC beams strengthened with FRPC laminates are described and verified through a nonlinear finite element (FE) commercial code, with the help of available experimental data. Three dimensional (3D) FE analysis has been performed by assuming perfect bonding between concrete and FRPC laminate. A parametric study has also been performed to examine effects of various parameters like fibre type, stirrup's spacing, etc. on the strengthening system. Through numerical simulation, it has been shown that it is possible to predict accurately the flexural response of RC beams strengthened with FRPC laminates by selecting an appropriate material constitutive model. Comparisons are made between the available experimental results in literature and FE analysis results obtained by the present investigators using load-deflection and load-strain plots as well as ultimate load of the strengthened beams. Furthermore, evaluation of crack patterns from FE analysis and experimental failure modes are discussed at the end.

• Steel and Composite Structures
• /
• v.1 no.4
• /
• pp.427-440
• /
• 2001

The growing use of unprotected or partially protected steelwork in buildings has caused a lively debate regarding the safety of this form of construction. A good deal of recent research has indicated that steel members have a substantial inherent ability to resist fire so that additional fire protection can be either reduced or eliminated completely. A performance based philosophy also extends the study into the effect of structural continuity and the performance of the whole structural totality. As part of the structural system, thermal expansion during the heating phase or contraction during the cooling phase in most beams is likely to be restrained by adjacent parts of the whole system or sub-frame assembly due to compartmentation. This has not been properly addressed before. This paper describes an experimental programme in which unprotected steel beams were tested under load while it is restrained between two columns and additional horizontal restraints with particular concern on the effect of catenary action in the beams when subjected to large deflection at very high temperature. This paper also presents a three-dimensional mathematical modelling, based on the finite element method, of the series of fire tests on the part-frame. The complete analysis starts with an evaluation of temperature distribution in the structure at various time levels. It is followed by a detail 3-D finite element analysis on its structural response as a result of the changing temperature distribution. The principal part of the analysis makes use of an existing finite element package FEAST. The effect of columns being fire-protected and the beam being axially restrained has been modelled adequately in terms of their thermal and structural responses. The consequence of the beam being restrained is that the axial force in the restrained beam starts as a compression, which increases gradually up to a point when the material has deteriorated to such a level that the beam deflects excessively. The axial compression force drops rapidly and changes into a tension force leading to a catenary action, which slows down the beam deflection from running away. Design engineers will be benefited with the consideration of the catenary action.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.4 s.37
• /
• pp.577-587
• /
• 1998

The influences of high speed train on the dynamic responses of steel composite railway bridges are investigated. The bridge system which has two I-girder and several cross beams is modeled with plate and frame elements. With assumption of concrete slabs are fully connected with steel girders, the offset between slabs and girders is modeled using constraint equation. The track system is modeled using beams on elastic foundation theory. And, the TGV train model is developed in 2-dimension considering bouncing and pitching motion. And braking action of vehicle is considered using speed dependent braking function. To investigate the behavior of bridges due to moving trains, parametric studies on the variation of natural frequency of bridge, speed parameter, vehicle modeling method, braking action of train, etc are performed.

• Journal of Korean Society of Steel Construction
• /
• v.20 no.6
• /
• pp.731-740
• /
• 2008

This paper deals with the fatigue behavior and strength of a new-type of steel-concrete composite bridge deck. The new-type composite bridge deck consists of corrugated steel plate, welded T-beams, stud-type shear connectors and reinforced concrete filler. A total of eight composite bridge deck specimens were fabricated, the fatigue tests were conducted under four-point bending test with three different stress ranges in constant amplitude. According to the test results, the fatigue crack generated at the welding part of the corrugated steel plate, progressed down to the bottom of the steel plate and encountered the crack, which came out from the opposite side at the same position. After the two cracks were connected at the bottom of the steel plate, the lower flange was cut off and the fatigue crack developed up to the T-beam. And the displacements and strains of fatigue test specimens were increasing with cyclic loading number, these were changed sharply at the fatigue failure. The fatigue results are compared with the design S-N curves specified in the Korea Highway Bridge Design Specifications and data in NCHRP 102 and NCHRP 147 report. The new-type composite bridge deck has a stress category of C, which means that new-type composite bridge deck can be designed by the current fatigue design specifications provided for steel members.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.11a
• /
• pp.695-698
• /
• 2004

Recently, the usage of polymer concrete mortar gathering an interest as a new construction material rapidly increases inside and outside of the country because it is an environment-friendly and endurable material. However, up to these days, the researches about the polymer composite have not been satisfactorily conducted. The polymer concrete is superior to the general cement materials in the properties of strength and durability while it is inferior in elastic modulus. Because that the members using the polymer concrete have therefore higher strength and ductility than the members of general cement concrete, an analysis equation of high-strength cement concrete can be referenced but it is not applied for the researches about the polymer concrete members. In this study, the flexural properties of T-shaped beam of the steel- and GFRP-reinforced polymer concrete are analyzed to examine the suggested analysis equation. Results of this experimental researches are to be used as the basic data in a structural design of the polymer concrete.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.5
• /
• pp.111-118
• /
• 2020

The U-shaped composite beam used in this study consist of a reinforced concrete structure, a beam steel structure supporting the slab, a reinforced concrete structure, and a U-shaped steel plate. The U-shaped composite beam was developed for the purpose of using it as a parking lot because it is highly constructible and has low floor height and long span. For the improvement of constructivity, the U-shaped composite beam ends are planned with standardized H-shaped steel and connected directly to the columns, and the middle of the U-shaped composite beam consists of U-shaped steel plates folded in U-shaped form using thin steel plates (t=6) instead of H-shaped steel. In the middle of the composite beam, where U-shaped steel plates are located, the depth of U-shaped beam may be planned to be small so as to satisfy the height limit of the parking lot. It is important to grasp the structural performance according to the change of depth because low beam depth is advantageous for the reduction of the floor height, but it is a inhibitor to the structural behaviors of U-shaped composite beam. In addition, since U-shaped composite beams are a mixture of steel frame structures, reinforced concrete structures and U-shaped steel plates, securing unity has a great influence on securing structural performance. Therefore, in this study, a structural experiment was conducted to understand the structural performance according to the depth change for U-shaped composite beam. A total of three specimens were planned, including two specimens that changed the depth using a criteria specimen planned for a general parking lot. The results of the experiment showed that the specimens who planned the depth greatly had better structural performance such as yield strength, maximum strength, and energy than the standard specimen.

• Steel and Composite Structures
• /
• v.22 no.1
• /
• pp.25-43
• /
• 2016

This paper presents the results of an experimental study investigating the effects of anchorage systems used in externally bonded steel plates on the strength and ductility of reinforced concrete structures. In the literature, diagonal steel plates bonded to frames were designed to be more flexible than the connections to eliminate the possible effect of the connection flexibility. However, to better evaluate the performance of the strengthened structures, the strength and behavior of connections should also be considered. The purpose of this study was to experimentally investigate the effects of different connection types of steel plates bonded to the frame using anchors on the strengthened RC structures. For this purpose, eleven specimens were designed to simulate the interior and exterior connection behavior. Two of these were used as the control beams and remaining nine for the investigation of the functionality of the end steel plates. Experimental results show that the load carrying capacity of the strengthened beams is directly related to the connection types of the steel plates. For the interior connections, L-shaped end plates that were strengthened using steel anchors must have adequate stiffness to prevent its shape. While, for the exterior connections, the connection with three anchors carried more load than the other exterior connections.

• Steel and Composite Structures
• /
• v.19 no.6
• /
• pp.1403-1419
• /
• 2015

When precast concrete infill panels are connected to steel frames at discrete locations, interaction at the structural interface is neither complete nor absent. The contribution of precast concrete infill panels to the lateral stiffness and strength of steel frames can be significant depending on the quality, quantity and location of the discrete interface connections. This paper presents preliminary experimental and finite element results of an investigation into the composite behaviour of a square steel frame with a precast concrete infill panel subject to lateral loading. The panel is connected at the corners to the ends of the top and bottom beams. The Frame-to-Panel-Connection, FPC4 between steel beam and concrete panel consists of two parts. A T-section with five achor bars welded to the top of the flange is cast in at the panel corner at a forty five degree angle. The triangularly shaped web of the T-section is reinforced against local buckling with a stiffener plate. The second part consists of a triangular gusset plate which is welded to the beam flange. Two bolts acting in shear connect the gusset plate to the web of the T-section. This way the connection can act in tension or compression. Experimental pull-out tests on individual connections allowed their load deflection characteristics to be established. A full scale experiment was performed on a one-storey one-bay 3 by 3 m infilled frame structure which was horizontally loaded at the top. With the characteristics of the frame-to-panel connections obtained from the experiments on individual connections, finite element analyses were performed on the infilled frame structures taking geometric and material non-linear behaviour of the structural components into account. The finite element model yields reasonably accurate results. This allows the model to be used for further parametric studies.

• KIEAE Journal
• /
• v.8 no.1
• /
• pp.87-92
• /
• 2008

Sheathing work used for excavation in a crowded downtown is generally a temporary strut method using H-piles and sheathing wall includes lagging, CIP, SCW or slurry wall. A temporary strut serving the support for sheathing wall acts to resist the earth pressure, but it shall be removed when installing the underground structure members. A traditional temporary strut might cause the stress imbalance of the sheathing wall when it is demolished, resulting in time extension and the risk of collapse. A traditional temporary strut method thus needs to be improved for schedule and cost reduction, risk mitigation and for preparation for potential civic complaint. A permanent strut method doesn't require installing and demolishing the temporary structure that will lead to reducing the time and cost and the structural risk during the demolition process. And given the girder, the part of the underground structure, serves the role of strut, it can secure the wider interval compared to the traditional method, which enables to secure the wider space for the convenience of excavation as well as enhance the constructability and efficient site management. The thesis was intended to study the composite girder designed to use the strut as permanent structure so as to reduce the excavation and floor height.