• Earthquakes and Structures
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• v.4 no.3
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• pp.265-283
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• 2013

This research was prompted by the paucity of specific code provisions regarding the design of short columns for shear. The purpose of this paper was to investigate whether the use of the normal shear design procedure of various codes may or may not be applied to reliably calculate the shear strength of short columns. Provisions of the codes American ACI 318M-08, Canadian CSA A23.3-04, Japanese AIJ Guidelines, New Zealand NZS 3101, European EN 1998 (EC8) parts 1 and 3, combined with EN 1992-1-1 (EC2), and draft fib Model Code 2010, as well as a strut-and-tie model are applied on short columns tested under cyclic loading that failed in shear. Actual shear resistances are compared to predictions, and the resulting shortcomings of the codes are identified. EN1998-3 appears to be the only code among those considered that may be reliably applied to estimate the shear resistance of short columns. Further, the proposed strut-and tie model can be a useful tool for the detailed design and assessment of short columns.

• Steel and Composite Structures
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• v.21 no.2
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• pp.267-287
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• 2016

The seismic performance of the ordinary steel reinforced concrete (SRC) columns has no significant improvement compared to the reinforced concrete (RC) columns mainly because I, H or core cross-shaped steel cannot provide sufficient confinement for core concrete. Two improved SRC columns by constructing with new-type shaped steel were put forward on this background, and they were named as enlarging cross-shaped steel and diagonal cross-shaped steel for short. The seismic behavior and carrying capacity of new-type SRC columns have been researched theoretically and experimentally, while the shear behavior remains unclear when the new-type columns are joined onto SRC beams. This paper presents an experimental study to investigate the shear capacity of new-type SRC joints. For this purpose, four new-type and one ordinary SRC joints under low reversed cyclic loading were tested, and the failure patterns, load-displacement hysteretic curves, joint shear deformation and steel strain were also observed. The ultimate shear force of joint specimens was calculated according to the beam-end counterforce, and effects of steel shape, load angel and structural measures on shear capacity of joints were analyzed. The test results indicate that: (1) the new-type SRC joints display shear failure pattern and has higher shear capacity than the ordinary one; (2) the oblique specimens have good bearing capacity if designed reasonably; and (3) the two proposed construction measures have little effect on the shear capacity of SRC joints embedded with diagonal cross-shaped steel. Based on the mechanism observed from the test, the formulas for calculating ultimate shear capacity considering the main factors (steel web, stirrup and axial compression ratio) were derived, and the calculated results agreed well with the experimental and simulated data.

• Computers and Concrete
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• v.29 no.5
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• pp.323-334
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• 2022

In order to study the axial compression performance of basalt-fiber reinforced recycled concrete (BFRRC) filled circular steel tubular short columns, the axial compression performance tests of seven short column specimens were conducted to observe the mechanical whole-process and failure mode of the specimens, the load-displacement curves and the load-strain curves of the specimens were obtained, the influence of design parameters on the axial compression performance of BFRRC filled circular steel tubular short columns was analyzed, and a practical mathematical model of stiffness degradation and a feasible stress-strain curve equation for the whole process were suggested. The results show that under the axial compression, the steel tube buckled and the core BFRRC was crushed. The load-axial deformation curves of all specimens show a longer deformation flow amplitude. Compared with the recycled coarse aggregate (RCA) replacement ratio and the basalt fiber dosage, the BFRRC strength has a great influence on the peak bearing capacity of the specimen. The RCA replacement ratio and the BFRRC strength are detrimental to ductility, whereas the basalt fiber dosage is beneficial to ductility.

• 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.

• Earthquakes and Structures
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• v.9 no.2
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• pp.431-453
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• 2015

A destructive earthquake, the magnitude of this earthquake was 7.2, hit Van, Turkey on October 23, 2011. After this devastating earthquake, a moderate earthquake which had 5.7 magnitude on November 9, 2011 occurred in Edremit, Van. These earthquakes caused heavy damages and collapses in many reinforced concrete buildings with loss of lives. In this paper, characteristics of ground motions of these earthquakes were studied and, deficiencies in structural elements and engineering faults such as poor workmanship and quality of construction, soft and weak stories, strong beam-weak column, short column, large overhang, hammering and unconfined gable wall were investigated. According to the observations, it was seen that, low quality of structural materials, lack of engineering services, inappropriate design and construction with insufficient detailing of the structural elements were the main reasons of heavy damages.

• Structural Engineering and Mechanics
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• v.73 no.5
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• pp.543-554
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• 2020

This paper aims to investigate the seismic performance of RC short columns and long columns with welding stirrups. Through the low-cyclic horizontal loading test of specimens, the seismic performance indexes such as failure modes, hysteretic curve, skeleton curve, ductility, energy dissipation capacity, stiffness degradation and strength degradation were emphatically analyzed. Furthermore, the effects of shear span ratio, stirrups ratio and axial compression ratio on the performance of specimens were studied. The results showed that the seismic performance of the RC short columns with welding stirrups were basically the same as that of the RC short columns with traditional stirrups, but the seismic performance of RC long columns with welding stirrups was better than that of RC long columns with traditional stirrups. The seismic performance of RC short columns and long columns with welding stirrups could be improved by increasing stirrup ratio and shear span ratio and reducing axial pressure ratio. Moreover, the welding stirrup have the advantages of steel saving, industrialization and standardization production, convenient construction, and reducing time, which indicated that the welding stirrups could be applied in practical engineering.

• Structural Engineering and Mechanics
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• v.68 no.3
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• pp.277-287
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• 2018

This paper presents the experimental study of nine pieces of reinforced concrete (RC) short columns. RC short columns were tested with cyclic loading with displacement control under the influence of constant axial load with load index of 0.2. Three columns within the tested nine columns are reference columns which have the details of the reinforcement given in the modern regulations and six of them are 150 mm and 100 mm externally collared columns. In addition to the parameter of the collar spacing, aspect ratio (as=2-1.5-1) is also considered as a parameter. The data obtained from experimental results have shown that externally collar contributes significantly to increasing the shear resistance of RC short columns and limiting the shear dominant behavior. It has been observed that the effectiveness of the externally collar increases with the decrease of the aspect ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.941-946
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• 2002

Short reinforced concrete bridge piers are particularly susceptible to shear failure as a consequence of the high shear/moment ratio and conservatism in the flexural strength design of existing RC bridge pier, which were constructed before 1992. In addition, shear failure is brittle and involves rapid strength degradation. Inelastic shear deformation is thus unsuitable for ductile seismic response. It is, however, believed that there are not many experimental research works for shear failure of the existing RC bridge pier in Korean peninsula subjected to earthquake motions. The object of this research is to evaluate the seismic performance of existing circular RC bridge piers by the quasi-static test. Existing RC bridge piers were moderate seismically designed in accordance with the conventional provisions of Korea Highway Design Specification. This study has been performed to verify the effect of aspect ratio (column height-diameter ratio). Quasi-static test has been done to investigate the physical seismic performance of RC bridge piers, such as lateral force-displacement hysteric curve, envelope curve etc.

• Structural Engineering and Mechanics
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• v.76 no.4
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• pp.513-528
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• 2020

This paper presents the results of an experimental study on the residual behavior of reinforced recycled aggregate concrete (RRAC) beam-columns after exposure to elevated temperatures. Two parameters were considered in this test: (a) recycled coarse aggregate (RCA) replacement percentages (i.e. 0, 30, 50, 70 and 100%); (b) high temperatures (i.e. 20, 200, 400, 600, and 800℃). A total of 25 RRAC short columns and 32 RRAC beams were conducted and subjected to different high temperatures for 1 h. After cooling down to ambient temperature, the following basic physical and mechanical properties were then tested and discussed: (a) surface change and mass loss ratio; (b) strength of recycled aggregate concrete (RAC) and steel subjected to elevated temperatures; (c) bearing capacity of beam-columns; (d) load-deformation curve. According to the test results, the law of performance degradation of RRAC beam-columns after exposure to high temperatures is analyzed. Finally, introducing the influence coefficient of RCA replacement percentage and high temperatures, respectively, to correct the calculation formulas of bearing capacity of beam-columns in Chinese Standard, and then the residual bearing capacity of RRAC beam-columns subjected elevated temperatures is calculated according to the modified formulas, the calculated results are in good agreement with the experimental results.

• 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.