Article

Frame property of unequal storey height with specially shaped columns under cyclic loading

Authors:
Article

Frame property of unequal storey height with specially shaped columns under cyclic loading

If you want to read the PDF, try requesting it from the authors.

Abstract

A 1/3-scale reinfored concrete (RC) frame of unequal storey height with specially shaped columns was tested under low frequency cyclic loading. The damage characteristic, bearing capacity, deformation capacity and ductility were analyzed. The restoring force model of the frame was obtained based on the study of the hysteresis curve measured in experiment, and the stiffness degeneration characteristics of every storey of the frame were analyzed. Finally the accumulated damage was analyzed with the damage assessment model. It is shown that the seismic behavior of this frame of unequal storey height with specially shaped columns is generally good, but the bottom of first floor column is a weak part, which should be paid more attention in design, and the restoring force model derived from this experiment can be seen as a valuable guide for design and non-linear finite element analysis for this kind of structure.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Owing to these advantages, this kind of structure is widely used in multi-story and high-rise buildings in China. Experiments on specially shaped reinforced concrete frames and components have been carried out in recent years to study their seismic performance [22,23]. However, studies on progressive collapse performance of structures are mainly concentrated on frame structures with rectangular columns and rarely involve frame structures with specially shaped columns. ...
Article
Full-text available
RC frame structures with specially shaped columns and RC frame structures with rectangular columns are different types of structures with different column sections. A progressive collapse analysis model of RC frames was proposed using the beam-column element and joint element based on the program OpenSees. Progressive collapse performance of the experimental frame was simulated and the calculation results were in good agreement with the experimental results. The characteristics of progressive collapse performance of frames with specially shaped columns were studied by comparing the progressive collapse resistance of one frame with specially shaped columns with that of three frames with rectangular columns which were designed in accordance with three different principles. It was observed from the results that the progressive collapse resistance of frame with specially shaped columns and frames with rectangular columns with the same reinforcement under the same seismic fortification, design and application conditions were equivalent. The frame with specially shaped columns had a superior performance to resist progressive collapse.
... However, specially shaped columns are weak at bearing capacity and seismic performance owing to the relatively smaller cross section area. Experiments on reinforced concrete frames with specially shaped columns and components had been carried out in recent years to study their seismic performance [13,14]. However, studies on progressive collapse performance of structures are mainly concentrated on frame structures with rectangular columns and rarely involve frame structures with specially shaped columns. ...
Article
Full-text available
A static collapse experiment was carried out to study the progressive collapse resistance and failure mechanisms and modes of a 1/3-scale, 2 × 3 -bay, and 2-story reinforced concrete frame with specially shaped columns subjected to middle column removal. A vertical concentrated load was applied to the top of the middle column to simulate the gravity load of the upper floors and the applied load was statically transmitted to the adjacent columns through the frame beams and slabs during the collapse process. The frame collapsed when the vertical displacement of the joint on the top of the failed column reached 170 mm due to the failure of beam-column joints. Based on the experimental phenomena and results, the progressive collapse-resistant behavior of the model frame is analyzed and the redistribution and transition of the load resisting mechanisms are discussed. It is concluded that the redistribution of internal force was mainly realized via the beam resisting mechanism and the compressive arch action in beams played an important role to improve the collapse-resistant capacity.
... In addition, it can be seen from Table 5 that the fi nal h e values of specimens confi gured with solid-web steel are over 0.4, and the fi nal h e values of specimens confi gured with empty-web steel are almost more than 0.2. A large number of previous studies (Wang et al., 2007(Wang et al., , 2010 have shown that the energy dissipation of RC special shaped columns is much worse than that of RC rectangular columns (h e ≈ 0.2), which means that the h e values of RC special shaped columns are smaller Table 4 Interlayer lateral angle of specimens Code T1 T2 T3 T4 T5 T6 T7 T8 T9 Δ cr /L Positive ...
Article
Full-text available
This paper describes a series of experimental investigations on seventeen specimens of steel reinforced concrete special shaped (SRCSS) columns under low cyclic reversed loading using parallel crosshead equipment. Nine T-shaped SRC columns, four L-shaped SRC columns and four +-shaped SRC columns were tested to examine the effects of shape steel configuration, loading angle, axial compressive ratio and shear-span ratio on the behavior (strength, stiffness, energy dissipation, ductility, etc.) of SRCSS column specimens. The failure modes and hysteretic performance of all the specimens were obtained in the tests. Test results demonstrate that the shear-span ratio is the main parameter affecting the failure modes of SRCSS columns. The specimens with small shear-span ratio are prone to shear failure, and the primary failure planes in SRCSS columns are parallel to the loading direction. As a result, there is a symmetry between positive and negative loading directions in the hysteretic curves of the SRCSS columns. The majority of displacement ductility coefficients for all the specimens are over 3.0, so that the SRCSS columns demonstrate a better deformation capacity. In addition, the equivalent viscous damping coefficients of all the specimens are greater than 0.2, indicating that the seismic behavior of SRCSS columns is adequate. Finally, the superposition theory was used to calculate the limits of axial compressive ratio for the specimens, and it is found that the test axial compressive ratio is close to or smaller than the calculated axial compressive ratio limit. © 2015, Institute of Engineering Mechanics, China Earthquake Administration and Springer-Verlag Berlin Heidelberg.
... However, specially shaped columns are weak at bearing capacity and seismic performance owing to the relatively smaller cross-section area. The column root is the key part controlling the failure of the total structure according to previous test results of the frames [3,4]. Lshaped columns are the corner columns in specially shaped concrete structures with asymmetric sections so the internal forced state is even more complex [5]. ...
Article
Full-text available
Based on tests on six L-shaped RC columns with 500 MPa steel bars, the effect of axial compression ratios and stirrup spacing on failure mode, bearing capacity, displacement, and curvature ductility of the specimens is investigated. Test results show that specimens with lower axial load and large stirrup characteristic value (larger than about 0.35) are better at ductility and seismic performance, while specimens under high axial load or with a small stirrup characteristic value (less than about 0.35) are poorer at ductility; L-shaped columns with 500 MPa steel bars show better bearing capacity and ductility in comparison with specimens with HRB400 steel bars.
Article
Full-text available
Structural engineers have used V-shaped columns based on technical requirements. The inclination of the V-shaped column underlines the individual purpose of the base floor. However, there is no any specification or guidance on the design of V-shaped columns to date. The aim of this study is to investigate the behavior of V-shaped reinforced concrete columns with three angles between columns (30, 60, and 90°) in order for the results to be used in the design and analysis of the V-shaped column. The impact of using a 1.5% dosage of micro-straight-steel fiber (MSSF) in the concrete mixture was also studied. The results showed that the V-shaped column with 30°, regardless of the concrete type (with and without MSSFs), exhibited crushing at legends when the sample reached the ultimate load, while no cracks occurred at the legends during the test for the other V-shaped columns. Upon increasing the angle of inclination of the V-shaped columns, the ultimate load capacity was decreased by 24, 23, and 20% for V-shaped columns with 30, 60, and 90° angles of inclination, respectively. The addition of MSSFs in the concrete significantly improved the ultimate axial load and the bending moment compared to the reference specimens with the normal reinforced concrete (NRC). The steel-fiber-reinforced concrete (SFRC) vertical column specimen demonstrated the highest increase in axial load, and the other SFRC V-shaped and flexural specimens showed a minor increase compared to the NRC specimens.
Article
A specially shaped column joint with T-shaped steel reinforcement in joint core range was proposed in this paper to solve problems of joint weakness. Four joints of specially shaped columns with or without T-shaped steel reinforcement were tested with low cyclic loading. Damage performance, loading, displacement, hysteretic curve, ductility and cumulated damage were compared with etcher. It is shown that the hysteretic characteristic of joint with T-shaped steel reinforcement is improved. The bearing capacity, deformation capacity and ductility are also enhanced. The stiffness degradation is delayed and the degree of cumulated damage is lightened. It concludes that the seismic behavior of the specially shaped column joint can be improved significantly by T-shaped steel reinforcement.
Article
Dynamic effects caused by sudden failure of the vertical load-bearing component are an important factor affecting the progressive collapse of building. In order to study the influence of dynamic effects on structure, a collapse experiment of a 1/3-scale, 2×3-bay and 2-story reinforced concrete frame with specially shaped columns with sudden column removal were carried out. The displacement response, reinforcement and concrete strains during the collapse of the frame were studied to reveal the dynamic response of structure such as deformation and internal force redistribution. Experimental results show that the influence of dynamic effects on structure at the moment of component failure was not significant. The structure was still in the elastic stage and collapse did not occur, indicating that reinforced concrete frame designed according to Chinese codes has a good behavior against progressive collapse caused by sudden loss of a first floor column. A progressive collapse dynamic analysis model was established using the alternate path method based on the test frame, and the relationship between the dynamic amplification factors and failure time were derived. Transient time history analysis was carried out on the finite element model of experimental frame using OpenSees to obtain the variation of dynamic amplification factor with the failure time.
Article
To investigate the seismic behavior of specially shaped column joints with X-shaped reinforcement, two groups of specimens with or without X-shaped reinforcement in joint core region were tested under constant axial compression load and low reversed cyclic loading, which imitated low to moderate earthquake force. The seismic behavior of specially shaped column joints with X-shaped reinforcement in terms of bearing capacity, displacement, ductility, hysteretic curve, stiffness degradation and energy dissipation was studied and compared to that without Xshaped reinforcement in joint core region. With the damage estimation model, the accumulated damage was analyzed. The shearing capacity formula of specially shaped column joints reinforced by X-shaped reinforcement was proposed with a simple form. The test results show that X-shaped reinforcement is an effective measure for improving the seismic behavior of specially shaped column joints including deformation behavior, ductility and hysteretic characteristic. All specimens were damaged with gradual stiffness degeneration. In addition, X-shaped reinforcement in the joint core region is an effective way to lighten the degree of cumulated damage. The good seismic performance obtained from the specially shaped column joint with X-shaped reinforcement can be used in engineering applications. The test value is higher than the calculated value, which indicates that the formula is safe for the design of specially shaped column joints.
Article
In order to study the seismic behavior of frame with specially shaped columns, the hysteretic curve was analyzed based on a quasi-static test of a two-span, three-story frame with specially shaped columns. The top layer framework curve and the corresponding resilience model were obtained from the hysteretic curve. And the stiffness and strength degeneration were also investigated. The results indicated that the stiffness degeneration is not obvious, thus the frame with specially shaped columns has high earthquake-resistant behavior. The resilience model calculated from the test can provide reference for design and nonlinear finite element analysis.
Article
Based on the experimental study on a frame with specially shaped columns reinforced by fiber in weak position and a frame with specially shaped columns not reinforced, the authors compared failure characteristic and failure mechanism, bearing capacity and duttility, hysteresis property, energy dissipation and rigidity degeneracy of the two specimens It is shown that the bearing capacity and integral ngidity of the frame reinforced by fiber increase significantly, the damage to the weak position diminishes and the energy dissipation enhances It is proved that the frame with specially shaped columns can be reinforced by fiber.
Article
Based on experimental research on the seismic behaviors of two frames, one with specially shaped columns, and the other with wide flange specially shaped columns on the first floor, the failure characteristics, bearing capacity, ductility, hysteresis properties, subsequence of hinge occurrence and rigidity degeneracy of the two specimens were compared. The results show that the adoption of wide flange improves the rigidity of the columms on the first floor and correspondingly some other seismic behaviors of frame with normal specially shaped columns to resist the earthquake effectively.
Article
During the procedure of manufacturing structural steel profiles the considerable temperature changes cause residual stresses in the material. These stresses can have a significant effect on the stability resistance of structures consisting of such profiles. Therefore engineers have paid special attention to the consideration and modelling of residual stresses in the comprehensive research into column buckling. They developed several stress distribution forms based on experimental and/or theoretical results, which worked well in column buckling problems. However, when the member has twisting displacements–e.g. in the case of lateral–torsional buckling–these stress distributions can lead to malfunction, because they do not satisfy certain equilibrium equations connected with torsion and warping of the profile. In order to avoid this problem a new stress pattern is proposed which satisfies all the equilibrium equations, thus being applicable in stability problems including torsional and warping effects.
Article
There have been many studies performed on steel beam–column connections, and many connection details that can improve seismic performance and connection strength have been developed and are in use. However, the conventional type of connection with a bracket is preferred in Korea’s construction market. This study develops, by experiment and theoretical analysis, an easy-to-construct beam–column connection that also ensures the flexural behaviour of the weak axis connection so that the steel structure system can be used in constructing low-rise buildings. This study also proposes basic data for structural design and construction of the beam–column connection of the H-shaped column’s weak axis.
Article
Most of the previous investigations studied the structural behavior of concrete columns with ‘+’-shaped cross section at room temperature, but the behavior of such columns during a fire and the effect of boundary conditions on the mechanical properties of the heated columns have seldom been examined. In this paper, the influence of axial-and-rotational restraint on the behavior of heated concrete columns with ‘+’-shaped cross section is investigated. A self-developed finite element program RCSSCF is applied in this study. The development of column internal forces as well as deflections at the mid-height of concrete columns are discussed. Simulation results show that: (1) axial restraint can induce significant additional axial forces in concrete columns with ‘+’-shaped cross section and subjected to fire, and the additional axial forces in strongly restrained concrete columns during a fire can reach approximately 65–70% of the axial forces in columns at room temperature; (2) the fire resistance of concrete columns without rotational restraint decreases significantly with an increase of load eccentricity ratio, but that with rotational restraint is influenced lightly by load eccentricity ratio; and (3) for columns with different non-zero rotational restraint ratios, the internal axial forces, and the internal moments and deflections at the mid-height of these columns appear to follow common trends.
Article
Four full-scale reinforced concrete (RC) columns with L-shaped cross-sections, four full-scale RC columns with T-shaped cross-sections, three full-scale RC columns with +-shaped cross-sections, and one full-scale RC column with a square cross-section were experimentally investigated for fire resistance following the ISO834 standard heating process. The effects of axial load ratio and fire exposure condition on failure mode, axial deformation and fire resistance of the columns were analyzed. The experimental results showed that: (a) when the axial load ratio is 0.55, the fire resistances of the columns with L-, T-, and +-shaped cross-sections subjected to fire on all sides were 60–73% that of the column with the square cross-section. (b) In the case of samples subjected to fire on all sides, the fire resistance of columns with differently-shaped cross-sections increased in the following order: L-shaped cross-section <T-shaped cross-section <+-shaped cross-section. A computer program RCSSCF was developed to calculate temperature, deformation, and fire resistance of the loaded columns with L-, T-, and +-shaped cross-sections. The results of the numerical simulation were compared with those of the full-scale fire resistance tests.
Article
A plastic–damage model for reinforced concrete frames is developed in this article, based on the classical plastic model and the continuum damage model. The plastic–damage constitutive law is implemented into a beam model for framed structures, in which these are described by elastic beams and columns with two inelastic hinges at their ends. A numerical procedure for predicting the member and global damage in framed structures using the matrix analysis is developed. Additionally, the article introduces a damage index useful in evaluating the state of structural members and a meaningful global damage index for whole structure. The plastic–damage model, together with the member and global damage indices, are adequate for the computation of the limit load of reinforced concrete frames subjected to seismic actions. Examples of applications of the methodology to the non-linear analysis of reinforced concrete framed structures are finally given.
Article
Experimental research was conducted to investigate the structural behaviour of concrete-encased composite beam–columns with T-shaped steel section. Specimens were tested under lateral cyclic loading and axial compression. The test parameters included the distribution of longitudinal reinforcement, the spacing of transverse reinforcement, the presence of cross ties, and the axial compressive load level. The test results indicate that the cyclic behaviour and failure modes of the beam–columns are greatly affected by the direction of the bending moment owing to the unsymmetrical cross section. The concrete-encased composite beam–columns can develop stable hysteretic response and large energy absorption capacity by providing cross ties and decreased spacing of transverse ties. The current ACI and AISC-LRFD design provisions were also evaluated by comparing predicted strengths with the test results.
Article
This paper develops a sensitivity-based updating method to identify the damage in a tested reinforced concrete (RC) frame modeled with a two-dimensional planar finite element (FE) by minimizing the discrepancies of modal frequencies and mode shapes. In order to reduce the number of unknown variables, a bidimensional damage (element) function is proposed, resulting in a considerable improvement of the optimization performance. For damage identification, a reference FE model of the undamaged frame divided into a few damage functions is firstly obtained and then a rough identification is carried out to detect possible damage locations, which are subsequently refined with new damage functions to accurately identify the damage. From a design point of view, it would be useful to evaluate, in a simplified way, the remaining bending stiffness of cracked beam sections or segments. Hence, an RC damage model based on a static mechanism is proposed to estimate the remnant stiffness of a cracked RC beam segment. The damage model is based on the assumption that the damage effect spreads over a region and the stiffness in the segment changes linearly. Furthermore, the stiffness reduction evaluated using this damage model is compared with the FE updating result. It is shown that the proposed bidimensional damage function is useful in producing a well-conditioned optimization problem and the aforementioned damage model can be used for an approximate stiffness estimation of a cracked beam segment.
Technical specification for concrete structure with specially shaped columns [S]
  • Jgj 149—
JGJ 149—2006. Technical specification for concrete structure with specially shaped columns [S]. Beijing: China Architectural Industry Press, 2006.
Experimental research of square-steel tube concrete columns subjected to cyclic loading
  • L U Lü Xi-Lin
  • Wei-Dong
  • X.-l. Lü
Analysis and experiment of cumulated damage of RC structures with special columns under cyclic loading
  • Diao
  • Bo
  • Y E Shu-Chun
  • Ying-Hua
  • B. Diao
Experimental comparison of seismic behavior of two RC frames with specially shaped columns
  • Wang Tie-Cheng
  • Kang Zhang Xue-Hui
  • Gu-Yi
  • T.-c. Wang
Seismic behavior of frame with specially shaped columns subjected to cyclic load
  • Wang Tie-Cheng
  • Zhao Li Xin-Hua
  • Shao-Wei
  • T.-c. Wang
Research of resilience model of steel high strength concrete frame node
  • Xu Ya-Feng
  • Chen Hong
  • Wang Zhao-Cai
  • Lian-Guang
  • Y.-f. Xu
Research on limit values of axial compression ratios of specially shaped RC columns in case of 4th seismic grade
  • L I Zhao Yan-Jing
  • Chen Zhong-Xian
  • Yun-Xia
  • Y.-j. Zhao