Shear Deformation Capacity Research Articles

Elongation of Reinforced Concrete Members Subjected to Cyclic Loading

Longitudinal elongation develops in reinforced concrete members that exhibit flexural yielding during cyclic loading. The longitudinal elongation can decrease the shear strength and deformation capacity of the members. In the present study, nonlinear truss model analysis was performed to study the elongation mechanism of reinforced concrete beams and the effects of various design variables on the elongation. The results showed that residual tensile plastic strain of the longitudinal reinforcement in the plastic hinge is the primary factor causing the member elongation and that the shear-force transfer mechanism of diagonal concrete struts has a substantial effect on the magnitude of the elongation. Based on the elongation mechanism found by truss model analysis, a simplified method for evaluating member elongation was developed. The proposed method was applied to test specimens with various design parameters and loading conditions.

Evaluation of Steel Fiber Reinforcement for Punching Shear Resistance in Slab-Column Connections - Part I: Monotonically Increased Load

Results from an experimental investigation aimed at evaluating the effectiveness of steel fiber reinforcement for increasing punching shear strength and ductility in slabs subjected to monotonically increased concentrated load are presented. Ten slab-column connections were tested to failure. The main test parameters evaluated were: 1) fiber geometry (hooked or twisted), 2) fiber strength (1100, 1800, or 2300 MPa [160, 260, or 334 ksi]), 3) fiber volume fraction (1% or 1.5%), and 4) slab tension reinforcement ratio (0.56% or 0.83% in each principal direction). Out of the fiber-reinforced concretes (or mortar) evaluated, those reinforced with a 1.5% volume fraction of either regular strength (1100 MPa [160 ksi]) or high-strength (2300 MPa [334 ksiJ) hooked steel fibers led to the best performance in terms of punching shear strength and deformation capacity. These two fiber-reinforced concretes (FRCs) were therefore selected for further evaluation in connections subjected to lateral displacement reversals, as described in the companion paper.

Evaluation of Steel Fiber Reinforcement for Punching Shear Resistance in Slab-Column Connections - Part II: Lateral Displacement Reversals

Results from an experimental investigation aimed at evaluating the seismic behavior of steel fiber-reinforced concrete slab-column connections are presented. Two approximately half scale slab-column subassemblies were tested under combined gravity load and lateral displacement reversals to evaluate the ability of fiber reinforcement to increase the connection punching shear strength and deformation capacity. The connection of one specimen featured high-strength (2300 MPa [334 ksi]) hooked steel fibers in a 1.5% volume fraction, while the other connection was reinforced with regular strength (1100 MPa [160 ksi]) hooked steel fibers, also in a 1.5% volume fraction. The two connection subassemblies were subjected to displacement cycles of up to 5% drift in combination with gravity shear ratios as large as 5/8. While the connection with regular strength hooked fibers exhibited substantial punching shear-related damage at the end of the test, no significant damage could be observed in the connection with high-strength fibers. A combined shear stress due to direct shear and unbalanced moment of (1/3) √f' c (MPa) (4 √f' c [psi]) represented a limit below which a rotation capacity of at least 0.05 rad can be expected in connections constructed with either of the two fiber-reinforced concretes evaluated. In terms of gravity shear ratio, the data suggest that a gravity shear ratio of 1/2 is a safe upper limit for ensuring a minimum drift capacity of 4% drift.

Joint shear behaviour of reinforced concrete beam–column connections

An extensive experimental database (341 cases in total) has been constructed for reinforced concrete (RC) beam–column connections subjected to quasi-static cyclic lateral loading. All cases within the database experienced joint shear failure, either in conjunction with or without yielding of beam reinforcement. RC joint shear strength models, which are applicable to both modern and older types of beam–column connections, have been developed using the constructed database in conjunction with a Bayesian parameter estimation method. Following this same procedure established to develop the strength models, joint shear deformation models (at maximum joint shear stress) have also been developed. The proposed quantitative RC joint shear strength and deformation models indicate that the following parameters are most important towards determining joint shear strength and deformation capacity–concrete compressive strength, beam reinforcement, joint transverse reinforcement, in-plane geometry, out-of-plane geometry and joint eccentricity. Finally, the influence of these six key parameters on the RC joint shear stress against joint shear strain behaviour at peak response has been assessed.

Reinforced Concrete Slab Shear Prediction Competition: Experiments

This paper describes 28 large-scale tests that were conducted to investigate the shear strength and deformation capacity of orthogonally reinforced concrete slabs. Test parameters included the slab thickness, the in-plane and the transverse reinforcement ratios, and the deviation of the principal shear (and moment) direction from the direction of the in-plane reinforcement. Eight of the 28 tests were used for an international competition to predict the expected load-deformation response. Information on the test concept, the test specimens, and the test procedures is given. Findings show that with a sufficient transverse reinforcement, ductile flexural failures instead of brittle shear failures occurred. Contrary to the specimens without transverse reinforcement, the shear strength of thick slabs was not reduced compared to thin slabs; that is, no size effect was observed for the specimens with transverse reinforcement. Results also indicate that a deviation of 45 degrees of the principal moment direction from the reinforcement direction resulted in a significant decrease of the cracked slab stiffness of the orthogonally reinforced concrete slabs. The tests with transverse reinforcement showed no reduction in strength, while the tests without transverse reinforcement did show a strength reduction.

주기하중을 받는 세장한 철근콘크리트 보의 길이방향 인장변형

초록·키워드 목차 오류제보하기 등록된 정보가 없습니다. ABSTRACT1. 서론2. 해석연구3. 길이방향 인장변형의 평가4. 검증5. 결론참고문헌요약

Structural performance of corrosion-damaged concrete beams

This paper describes experimental work to investigate the effect of reinforcement corrosion on the behaviour of concrete beams reinforced with plain round bars. Particular attention is paid to the bond between reinforcement and concrete. Four groups of beam specimens were tested, each designed to investigate specific aspects of structural performance including stiffness and deflection under service loads, ultimate flexural and shear strengths and deformation capacity at failure. Beams were conditioned to induce loss of cross-sectional reinforcement of up to 10% owing to corrosion, equivalent to 0·3 mm corrosion penetration, and longitudinal crack widths of 1·0 mm. Flexural stiffness of specimens detailed for a flexural mode of failure was not impaired by corrosion. Strength of beams with corroded bars equalled or exceeded that of companion non-corroded specimens in all cases, despite loss of bar section. It is concluded that an enhancement of anchorage capacity, believed to be associated principally with increased radial stresses on the bar–concrete interface in the vicinity of the end reactions, was able to offset loss of bar section.

PROPOSAL AND VERIFICATION OF EVALUATION METHOD FOR SHEAR STRENGTH AND DEFORMATION CAPACITY OF DAMPER USING HIGH PERFORMANCE FIBER REINFORCED CEMENTITIOUS COMPOSITE

The influence of ultimate tensile strain (ePSH) fluctuation during the Pseudo Strain Hardening (PSH) behavior on the shear strength and deformation capacity after the flexural yielding of damper with High Performance Fiber Reinforced Cementitious Composite was examined by FEM parametrical analysis. Subsequently, the evaluation methods for shear strength and deformation capacity after flexural yielding, which can give proper consideration to fluctuation of ePSH, were proposed, and their applicability was verified. As a result of comparing the applicability of these evaluation methods with parametric analysis, it was shown that the improvement of the deformation capacity after the shear strength along with the increase of ePSH and flexural yielding could be well evaluated. Furthermore, as a result based on comparison between the test results in the past research and the evaluated value, this proposal equation evaluated all the test results in the past research to be safe.

Life-Safety and Near-Collapse Capacity Models for Seismic Shear Behavior of Reinforced Concrete Columns

In seismic assessment of existing reinforced concrete (RC) structures, it is important to reliably predict potential column shear failure. Shear strength and deformation capacities can be used to evaluate this failure. This paper evaluates the reliability of three available strength models for estimating the shear strength of RC columns using existing experimental test results. Deformation capacity models are developed for life-safety and near-collapse performance levels. The models account for the difference between the deformation of double-curvature and double-ended columns, in which damage can concentrate on one end of the specimen, and that of cantilever columns. The models include the effects of the transverse reinforcement, axial load, and the aspect ratio of columns on their deformation capacities. Using shear force transfer mechanics, a shear strength capacity model is also developed for RC columns that can estimate column shear strength significantly better than the currently available models. In addition to the section and material characteristics, the shear strength capacity model accounts for the effects of the aspect ratio, compressive load, and displacement ductility on the column strength.

高靱性セメント系複合材料を用いたダンパー部材のせん断耐力と変形能に影響を及ぼす要因に関する実験および解析的検討 : 高靱性セメント系複合材料を用いたダンパー部材のせん断耐力と変形能に関する研究(その1)

High performance fiber reinforced cementitious composite (HPFRCC) shows pseudo strain hardening (PSH) behavior under tensile stress. The purpose of this study is to verify the influencing factors on shear strength and deformation capacity of dampers using HPFRCC. In this study, the structural tests using HPFRCC dampers are conducted to obtain the basic data on shear behavior and investigate the application of FEM analysis to these experiments. On that basis, the shear resistance properties of dampers using HPFRCC are examined based on the results of experiments and analysis. It is concluded that the resistance force of the shear reinforcement and the tensile resistance force of the HPFRCC independently activate in the shear resistance properties of dampers using HPFRCC. In addition, the boundary point between PSH zone and strain softening zone in HPFRCC tensile stress-strain relationship is an important factor to control the brittle failure.

Shear strength of reinforced concrete beams with a fiber concrete matrix

The purpose of this study was to investigate the influence of fiber reinforcement on the shear capacity of reinforced concrete (RC) beams. Both steel and synthetic fibers at variable volume fractions were investigated. Two series of tests were performed: structural tests, where RC beams were tested to failure under an applied four-point load; and materials tests, where companion fiber-reinforced concrete (FRC) prisms were tested under direct shear to obtain material properties such as shear strength and shear toughness. FRC test results indicated an almost linear increase in the shear strength of concrete with an increase in the fiber volume fraction. Fiber reinforcement enhanced the shear load capacity and shear deformation capacity of RC beams, but 1% fiber volume fraction was seen as optimal; no benefits were noted when the fiber volume fraction was increased beyond 1%. Finally, an equation is proposed to predict the shear capacity of RC beams.Key words: shear strength, fiber-reinforced concrete, RC beam, stirrups, energy absorption capacity, steel fiber, synthetic fiber.

高強度材料を用いたコンクリート充填鋼管柱 : 鉄骨梁接合部の構造性能

As a part of the U.S.-Japan Cooperative Earthquake Engineering Research Program on Composite and Hybrid Structures, ten concrete filled steel tubular column (CFT) to structural steel beam connections were tested under reversed cyclic loading to investigate the effects of high material strength, configuration and geometry of connections, column axial load and loading direction on the shear strengths and deformation capacity. This paper presents the test results and discusses the shear behavior of CFT connections. All the specimens reached their ultimate panel shear strengths at least to be 1.3 times of the design panel ultimate strengths by AIJ-SRC (1987) formula, whose scope of application is for medium to low material strengths and not for high material strengths tested in this study. This means that the current AIJ-SRC formula can be conservatively used for high material strengths. The deformation capacity of the connections was also verified to have enough ductility.

耐震性能の多様化に対応した耐震設計

Previous earthquake resistant design method has mainly pursued the structural safety by providing structures with the strength and inelastic deformation capacity, neglecting other performance such as the reduction of acceleration responses and the avoidance of interruption of daily activities. On the other hand, newly developing base-isolated structures have made it possible to satisfy these additional performance by applying rubber bearings with extremely large vertical bearing capacity and shear-deformation capacity. In this paper, whether such a diversified structural performance can be realized or not within the framework of ordinary earthquake resistant design method is discussed. As a conclusion, it is made clear that flexible-stiff mixed structures can be a general solution to the problem.

Experimental observations on the seismic shear performance of RC beam‐to‐column connections subjected to varying axial column force

AbstractThe paper presents results from the first series of an ongoing experimental study aimed at quantifying the effect of axial column load on the shear capacity of beam‐to‐column connections. This is deemed important due to the recent evidence showing that vertical earthquake ground motion, when combined with high overturning moments, may cause reduced column compression or even tension. In which case, the concrete contribution to shear resistance in the panel zone is diminished, which may lead to failure prior to the attainment of the full resisting capacity of the beam section. The results first show that the failure mode of the models was, as intended, shear failure of the panel zone. It is further observed that the axial column load has a marked effect on the shear deformation capacity, yield point, cracking pattern, ultimate capacity and ductility of the panel zone. Differences in the range of 30 per cent in capacity and 50 per cent in deformability were recorded. The preliminary results are useful in providing design guidance for structures located in areas of potential high vertical ground motion component. Also, for high‐rise structures, where there are large overturning moments, the results may be of use in ensuring a uniform safety factor (or overstrength) in various non‐dissipative parts of the structure.

Beam-to-Column Connection Research in Japan

Present status of the research on the beam-to-column connection in Japan is reviewed. The design philosophy of beam-to-column moment connections of steel building frames under the unique situation that the earthquake loading dominates the structural design is discussed. The importance of the contribution of the excellent shear deformation capacity of joint-panels to the overall ductility of the frames which should be developed against the extreme earthquake is emphasized. Some design criteria for the beam-to-column moment connections suitable for seismic design are suggested.