• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.459-467
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• 2008

This paper describes a proposal for average crack width and immediate deflection calculation in structural concrete members. The model is mathematically derived from actual bond stressslip relationships and tension stiffening effect between reinforcement and the surrounding concrete, and the actual strains of steel and concrete are integrated respectively along the embedded length between the adjacent cracks so as to obtain the difference in the axial elongation. With these, a model for average crack width and immediate deflection in reinforced concrete flexural members are proposed utilizing difference in the axial elongation and average steel strain and moment-curvature relationship with taking account of bond characteristics. The model is applied to the test specimens available in literatures, and the crack width and deflections predicted by the proposal equation in this study are closed to the experimentally measured data compared the current code provisions.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.329-332
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• 2008

The member deflection is one of the most important considerations for the serviceability evaluation of reinforced concrete structures, and the concept of the effective moment of inertia has been generally used for the estimation of beam deflections. The KCI design code adopted Branson's equation for the calculation of the effective moment of inertia, which was formulated based on the results of beam tests subjected to uniformly distributed loads. Therefore, it is worthwhile to check the applicability of the code approach on the estimation of the effective moment of inertia for the cases of beams under different loading conditions. In this study, an experimental investigation has been conducted on six beams, where primary variables were concrete compressive strengths and loading distances from supports. The test results were compared with various approaches proposed by Branson and others as well. The test results indicated that the effective moment of inertia was somewhat influenced by the moment distribution shape. Despite the different moment distribution shapes for specimens, however, the effective moment of inertia of all test beams were closely predicted by the existing methods considered in this study.

• Journal of Korean Association for Spatial Structures
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• v.12 no.1
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• pp.87-98
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• 2012

In this study, mechanical role of edge beams in the gabled hyperbolic paraboloid shells was investigated through the comparisons of Finite element(FE) analysis results between the shells structures with and without edge beams. In addition, the effects of roof slope was studied. FE analysis showed that roof loads was directly transferred to the supports at corners by the arch action in the diagonal direction of the shells, thus, less member forces in the edge and ridge beams but higher stresses near supports were estimated than those from the membrane theory. When the edge beams were removed, stress concentration in the shells near the supports and the deflections along the shell edge were increased. Such phenomenon were intensified as the roof slope decrease. Thus, in gable hyperbolic paraboloid shell, the thickness of the shell near supports needs to be increased and careful investigation should be made in the cases when the roof height is low and/or the edge beams are removed.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.309-312
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• 2008

This paper describes ultimate load tests which were performed to show the effects of prestress loss and tendon corrosion on the flexural strength of post-tensioned concrete beams and the occurrence of wire fracture. Five test specimens were fabricated in laboratory with the variations of the prestress of tendons and the loss of tendon area. For two specimens, small area of tendon at the center of the beam was exposed by using diameter 25mm drill and the exposed tendon was corroded using accelerated corrosion equipment. During the tests, deflections, crack width, and strain changes were measured and acoustic events were monitored with two acoustic sensors. Tests results show that the ultimate flexural strength of test specimens with corroded tendons is smaller than the predicted flexural strength which is calculated considering the loss of tendon area. It is considered that estimation of flexural strength of PSC beams with corroded tendons is very complicated just based on the loss of tendon area obtained by one-side visual inspection.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.113-129
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• 1999

In this study, a total of 12 types of sequential model tests were conducted at the laboratory for small scale anchored walls. The sequential behavior for flexible wall embedded in sand was investigated by varying degrees of relative density of Joomoonjin sand and flexibility number of model wall. The model tests were carried out in a 1000mm width, 1500mm length, and 1000mm high steel box. Load cells, pressure cells, displacement transducer and dial gauges were used to measure the anchor forces, lateral wall deflections, lateral earth pressures and vertical displacements of ground surface, respectively. Limited model tests were performed to examine the parameters for soil-wall interaction model and the formulation of analytical method was revised in order to predict the behavior of anchored wall in sand. Based on the model tests and proposed analytical method, model simulations were performed and the predictions by the present approach were compared with measurements by the model tests and predictions by other commercial programs. It is shown that the prediction by the present approach simulates qualitatively well the general trend observed for model test.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.5
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• pp.429-437
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• 2008

In this study the progressive collapse potential of braced frames were investigated using the nonlinear static and dynamic analyses. All of nine different brace types were considered along with a special moment-resisting frame for comparison. According to the pushdown analysis results, most braced frames designed per current design codes satisfied the design guidelines for progressive collapse initiated by loss of a first story mid-column; however most model structures showed brittle failure mode. This was caused by buckling of columns after compressive braces buckled. Among the braced frames considered, the inverted- V type braced frames showed superior ductile behavior during progressive collapse. The nonlinear dynamic analysis results showed that all the braced frame model structures remained in stable condition after sudden removal of a column, and their deflections were less than that of the moment-resisting frame.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.525-532
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• 2014

The purpose of this study is to analyze the deflection for serviceability assessment of the prestressed concrete one-way slab using finite element program. Proposed finite element analysis method was verified comparing with existing experimental results, and it showed a good agreement. Also, a parametric study has been conducted to analyze the influence of concrete compressive strength, eccentricity, live load, and tendon profile. The finite element analysis results were compared with hand calculation results. Deflections were decreased as the concrete compressive strength increases, eccentricity increases, and the live load decreases. The deflection of straight tendon was smallest. And regression analysis has been conducted to analyze the correlation between parameters and camber.

• Structural Engineering and Mechanics
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• v.53 no.2
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• pp.311-324
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• 2015

The purpose of this study was to investigate experimentally the fatigue performance of reinforced concrete (RC) beams with hot-rolled ribbed fine-grained steel bars of yielding strength 500MPa (HRBF500). Three rectangular and three T-section RC beams with HRBF500 bars were constructed and tested under static and constant-amplitude cyclic loading. Prior to the application of repeated loading, all beams were initially cracked under static loading. The major test variables were the steel ratio, cross-sectional shape and stress range. The stress evolution of HRBF500 bars, the information about crack growth and the deflection developments of test beams were presented and analyzed. Rapid increases in deflections and tension steel stress occured in the early stages of fatigue loading, and were followed by a relatively stable period. Test results indicate that, the concrete beams reinforced with appropriate amount of HRBF500 bars can survive 2.5 million cycles of constant-amplitude cyclic loading with no apparent signs of damage, on condition that the initial extreme tensile stress in HRBF500 steel bars was controlled less than 150 MPa. It was also found that, the initial extreme tension steel stress, stress range, and steel ratio were the main factors that affected the fatigue properties of RC beams with HRBF500 bars, whose effects on fatigue properties were fully discussed in this paper, while the cross-sectional shape had no significant influence in fatigue properties. The results provide important guidance for the fatigue design of concrete beams reinforced with HRBF500 steel bars.

• Structural Engineering and Mechanics
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• v.39 no.2
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• pp.241-266
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• 2011

The Self Compacting Concrete, SCC is the new generation type of concrete which is not needed to be compacted by vibrator and it will be compacted by its own weight. Since SCC is a new innovation and also the high strength self compacting concrete, HSSCC behavior is like a brittle material, therefore, understanding the strength effect on the serviceability performance of reinforced self compacting concretes is critical. For this aim, first the normal and high strength self compacting concrete, NSSCC and HSSCC was designed. Then, the serviceability performance of reinforced connections consisting of NSSCC and HSSCC were investigated. Twelve reinforced concrete connections (L = 3 m, b = 0.15 m, h = 0.3 m) were simulated, by this concretes, the maximum and minimum reinforcement ratios ${\rho}$ and ${\rho}^{\prime}$ (percentage of tensile and compressive steel reinforcement) are in accordance with the provision of the ACI-05 for conventional RC structures. This study was limited to the case of bending without axial load, utilizing simple connections loaded at mid span through a stub (b = 0.15 m, h = 0.3 m, L = 0.3 m) to simulate a beam-column connection. During the test, concrete and steel strains, deflections and crack widths were measured at different locations along each member. Based on the experimental readings and observations, the cracked moment of inertia ($I_{cr}$) of members was determined and the results were compared with some selective theoretical methods. Also, the flexural crack widths of the members were measured and the applicability for conventional vibrated concrete, as for ACI, BS and CSA code, was verified for SCCs members tested. A comparison between two Codes (ACI and CSA) for the theoretical values cracking moment is indicate that, irrespective of the concrete strength, for the specimens reported, the prediction values of two codes are almost equale. The experimental cracked moment of inertia $(I_{cr})_{\exp}$ is lower than its theoretical $(I_{cr})_{th}$ values, and therefore theoretically it is overestimated. Also, a general conclusion is that, by increasing the percentage of ${\rho}$, the value of $I_{cr}$ is increased.

• Structural Engineering and Mechanics
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• v.31 no.2
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• pp.163-180
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• 2009

In the design of tall reinforced concrete (R/C) buildings, the serviceability stiffness criteria in terms of maximum lateral displacement and inter-story drift must be satisfied to prevent large second-order P-delta effects. To accurately assess the lateral deflection and stiffness of tall R/C structures, cracked members in these structures need to be identified and their effective member flexural stiffness determined. In addition, the implementation of the geometric nonlinearity in the analysis can be significant for an accurate prediction of lateral deflection of the structure, particularly in the case of tall R/C building under lateral loading. It can therefore be important to consider the cracking effect together with the geometric nonlinearity in the analysis in order to obtain more accurate results. In the present study, a computer program based on the iterative procedure has been developed for the three dimensional analysis of reinforced concrete frames with cracked beam and column elements. Probability-based effective stiffness model is used for the effective flexural stiffness of a cracked member. In the analysis, the geometric nonlinearity due to the interaction of axial force and bending moment and the displacements of joints are also taken into account. The analytical procedure has been demonstrated through the application of R/C frame examples in which its accuracy and efficiency in comparison with experimental and other analytical results are verified. The effectiveness of the analytical procedure is also illustrated through a practical four story R/C frame example. The iterative procedure provides equally good and consistent prediction of lateral deflection and effective flexural member stiffness. The proposed analytical procedure is efficient from the viewpoints of computational effort and convergence rate.