• Structural Monitoring and Maintenance
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• v.7 no.3
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• pp.215-231
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• 2020

In a reinforced concrete building different shapes of column are adopted depending on the structural orientation and the architectural aspect. When there is an increase in loading due to changes in usage or revision in the design codes these columns need to be strengthened for enhanced performance during their service life. Strengthening materials such as carbon fiber and glass fiber polymer has been successfully used however, due to high cost application other alternative materials need to be explore. Galvanized steel wire mesh (GSWM) is one of the suitable materials locally available. High tensile strength, low weight, corrosion resistance, easy installation, minimum change in dimensions of the sections and cost effectives are the advantages of GSWM. Therefore, in this paper, four different shapes of column such as circular, square, rectangular and L were wrapped with different layers GSWM and jacketed with mortar. All the specimens were tested under axial compression. The objective of the study is to investigate the effectiveness of GSWM as a confining material for strengthening of column having varying shape. Test results shows that the axial strength enhanced with wrapping of GSWM jacket and a circular column presented the highest load carrying capacity and ductility as compared to the others. From the study of 22 column specimens, it is found that axial load is increased upto 20% and 19% when circular and square column are strengthened with one wrap of GSWM respectively, while a rectangular and L column required a wraps of two and three layers respectively in order to achieved the same load capacity as that of a circular column. Based on the present study, it is concluded that GSWM can be effectively used for strengthening of different shapes of concrete columns economically.

• Korean Journal of Construction Engineering and Management
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• v.5 no.5 s.21
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• pp.183-192
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• 2004

Even in Korea the number of steel structure buildings that allow internal space and easy change of their layouts in accordance with the purpose of buildings and box-type steel bridges constructed with thick plates with thickness in a rage just from a few $\beta$AE to \$100\beta$AE is increasing these days and therefore, domestic fabrication and processing technology of members for steel structures is being improved at a pace faster than in the past to meet the growing requirements of consumers for high reliability on quality control on the related steel structures. However, most domestic fabricators os steel structures who are turning out their steel products in accordance with the designs prepared by engineering companies in their respective works for the sake of cost cut more than anything else, hesitating to introduce any advanced new technology into themselves. In the case of the steel structure design application for small and mid-size buildings in particular, it is quite meaningful not only for those who are involved in steel structure business, but also for the people working at construction work fields to review the result of the study on the connections of steel structure members deigned to obtain superb quality of steel structures within short period for steel fabrication and erection at fields in economical ways, as there is a glowing tendency seeking standardization of connection of steel structure members as well as whole structure together with the development on design of construction system of buildings including their exterior and interior decoration materials, manufacture of the related members and fabrication technique structure. This paper has been prepared with the aim to review the peculiar characteristics of buildings constructed with the main frames of steel structures and actual cases of the change made ing the connections between steel structure columns and between columns and girder members in order to reduce the work period necessary for fabrication and erection of steel structures at the maximum as well as the some examples of steel structures fabricated through automatic welding by robots for box-type columns in addition to the description of the problems found in the course of fabricating those steel structures, suggesting possible counter-measures to solve them.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.2
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• pp.125-133
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• 2007

External confinement by CFS (Carbon Fiber Sheet) is a very effective retrofit method for the reinforced concrete columns subject to either static or seismic loads. For the reliable and cost-effective design of CFS, an accurate stress-strain curve is required for CFS-confined concrete. In this paper, uniaxial compression test on short RC column with circular section was performed. To evaluate the effect of confinement on the stress-strain relationship of CFS-confined concrete, CFS area ratio, spiral area ratio, and concrete compressive strength are considered as the test variables. Experiment results indicate that CFS jacketing significantly enhances strength and ductility of concrete. In addition, the CFS-jacketed specimens with the spiral steel show the lower load increasement ratio than those without the spiral steel.

• Advances in Computational Design
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• v.3 no.1
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• pp.49-69
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• 2018

This paper shows an optimal design for reinforced concrete rectangular combined footings based on a criterion of minimum cost. The classical design method for reinforced concrete rectangular combined footings is: First, a dimension is proposed that should comply with the allowable stresses (Minimum stress should be equal or greater than zero, and maximum stress must be equal or less than the allowable capacity withstand by the soil); subsequently, the effective depth is obtained due to the maximum moment and this effective depth is checked against the bending shear and the punching shear until, it complies with these conditions, and then the steel reinforcement is obtained, but this is not guaranteed that obtained cost is a minimum cost. A numerical experimentation shows the model capability to estimate the minimum cost design of the materials used for a rectangular combined footing that supports two columns under an axial load and moments in two directions at each column in accordance to the building code requirements for structural concrete and commentary (ACI 318S-14). Numerical experimentation is developed by modifying the values of the rectangular combined footing to from "d" (Effective depth), "b" (Short dimension), "a" (Greater dimension), "${\rho}_{P1}$" (Ratio of reinforcement steel under column 1), "${\rho}_{P2}$" (Ratio of reinforcement steel under column 2), "${\rho}_{yLB}$" (Ratio of longitudinal reinforcement steel in the bottom), "${\rho}_{yLT}$" (Ratio of longitudinal reinforcement steel at the top). Results show that the optimal design is more economical and more precise with respect to the classical design. Therefore, the optimal design presented in this paper should be used to obtain the minimum cost design for reinforced concrete rectangular combined footings.

• Computers and Concrete
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• v.19 no.5
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• pp.589-597
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• 2017

Strut-and-tie modeling method, which evolved on truss-model approach, has generally been preferred for the design of complex reinforced concrete structures and structural elements that have critical shear behavior. Some structural members having disturbed regions require exceptional detailing for all support and loading conditions, such as the beam-column connections, deep beams, short columns or corbels. Considering the general expectation of exhibiting brittle behavior, corbels are somewhat dissimilar to other shear critical structures. In this study, reinforcement layout of a corbel model was determined by the participation of structural optimization and strut-and-tie modeling methods, and an experimental comparison was performed against a conventionally designed model.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.423-430
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• 1998

Elastomeric bearings are frequently used as a means to isolate structural systems from earthquake loadings. The combination of rubber layers and reinforcing steel shims makes the bearings stiff axially but soft laterally The shear flexibility of these short columns can lead to relatively low buckling loads which may be further reduced when high shear strains are simultaneously imposed. The area reduction formula has been proposed to account for the reduction in buckling load due to shear. The result obtained from the formula is presumed to be conservative but the degree of conservatism is unknown. This paper describes a numerical study which aims at determining the effect of high shear strain on the critical load of rubber bearings. The results from the finite element analysis which accounts for both the material and geometric non-linearities are compared against the theoretical results in order to examine the validity of the theoretical formulas.

• Steel and Composite Structures
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• v.36 no.4
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• pp.383-398
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• 2020

This paper investigates the progressive collapse behavior of 3D steel-framed gravity buildings under fires with a cooling phase. The effect of fire protections and bracing systems on whether, how, and when a gravity building collapses is studied. It is found that whether a building collapses or not depends on the duration of the heating phase, and it may withstand a "short-hot" fire, but collapses under a mild fire or a "long-cool" fire. The collapse time can be conservatively determined by the time when the temperature of steel columns reaches a critical temperature of 550 ℃. It is also found that the application of a higher level of fire protection may prevent the collapse of a building, but may also lead to its collapse in the cooling phase due to the delayed temperature increment in the heated members. The tensile membrane action in a heated slab can be resisted by a tensile ring around its perimeter or by tensile yielding lines extended to the edge of the frame. It is recommended for practical design that hat bracing systems should be arranged on the whole top floor, and a combination of perimeter and internal vertical bracing systems be used to mitigate the fire-induced collapse of gravity buildings. It is also suggested that beam-to-column connections should be designed to resist high tensile forces (up to yielding force) during the cooling phase of a fire.

• Structural Engineering and Mechanics
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• v.59 no.3
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• pp.387-401
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• 2016

This paper takes a half-through steel truss arch bridge as an example. A seismic analysis is conducted with nonlinear finite element method. Contrast models are established to discuss the effect of simplified method for main girder on the accuracy of the result. The influence of seismic wave direction and wave-passage on seismic behaviors are analysed as well as the superstructure and arch ring interaction which is mostly related with the supported bearings and wind resistant springs. In the end, the application of cable-sliding aseismic devices is discussed to put forward a layout principle. The main conclusions include: (1) The seismic response isn't too distinctive with the simplified method of main girder. Generally speaking, the grillage method is recommended. (2) Under seismic input from different directions, arch foot is usually the mostly dangerous section. (3) Vertical wave input and horizontal wave-passage greatly influence the seismic responses of arch ring, significantly increasing that of midspan. (4) The superstructure interaction has an obvious impact on the seismic performance. Half-through arch bridges with long spandrel columns fixed has a less response than those with short ones fixed. And a large stiffness of wind resistant spring makes the the seismic responses of arch ring larger. (5) A good isolation effectiveness for half-through arch bridge can be achieved by a reasonable arrangement of CSFABs.

• Structural Engineering and Mechanics
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• v.69 no.3
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• pp.257-268
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• 2019

Infills are as important members in structural design as beams, columns and braces. They have significant effect on structural behavior. Because of lots of variables in infills like material non-linear behavior, the interaction between frames and infill, etc., the infills performance during an earthquake is complicated, so have led designers do not consider the effect of infills in designing the structure. However, the experimental studies revealed that the infills have the remarkable effect on structure behavior. As if these effects ignored, it might occur soft-story phenomena, torsion or short-column effects on the structures. One simple and appropriate method for considering the infills effects in analyzing, is replacing the infills with diagonal compression strut with the same performance of real infill, instead of designing the whole infill. Because of too many uncertainties, codes and researchers gave many expressions that were not as the same as the others. The major intent of this paper is calculation the width of this diagonal strut, which has the most characteristics of infill. This paper by comprehensive on different parameters like the modulus of young or moment of inertia of columns presents a new formula for achieving the equivalent strut width. In fact, this new formula is extracted from about 60 FEM analyses models. It can be said that this formula is very efficient and accurate in estimating the equivalent strut width, considering the large number of effective parameters relative to similar relationships provided by other researchers. In most cases, the results are so close to the values obtained by the FEM. In this formula, the effect of out of plane buckling is neglected and this formula is used just in steel structures. Also, the thickness of infill panel, and the lateral force applied to frame are constant. In addition, this new formula is just for modeling the lateral stiffness. Obtaining the nearest response in analyzing is important to the designers, so this new formula can help them to reach more accurate response among a lot of experimental equations proposed by researchers.

• Structural Engineering and Mechanics
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• v.51 no.1
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• pp.89-110
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• 2014

In this study, two beam-column elements based on the Elasto-Fiber element theory for reinforced concrete (RC) element have been developed and compared with each other. The first element is based on Elasto Fiber Approach (EFA) was initially developed for steel structures and this theory was applied for RC element in there and the second element is called as Fiber & Bernoulli-Euler element approach (FBEA). In this element, Cubic Hermitian polynomials are used for obtaining stiffness matrix. The beams or columns element in both approaches are divided into a sub-element called the segment for obtaining element stiffness matrix. The internal freedoms of this segment are dynamically condensed to the external freedoms at the ends of the element by using a dynamic substructure technique. Thus, nonlinear dynamic analysis of high RC building can be obtained within short times. In addition to, external loads of the segment are assumed to be distributed along to element. Therefore, damages can be taken account of along to element and redistributions of the loading for solutions. Bossak-${\alpha}$ integration with predicted-corrected method is used for the nonlinear seismic analysis of RC frames. For numerical application, seismic damage analyses for a 4-story frame and an 8-story RC frame with soft-story are obtained to comparisons of RC element according to both approaches. Damages evaluation and propagation in the frame elements are studied and response quantities from obtained both approaches are investigated in the detail.