• Computers and Concrete
• /
• v.11 no.1
• /
• pp.1-20
• /
• 2013

There is an abundance of research on the strengthening of reinforced concrete (RC) structural elements such as beams, columns and slabs with fibre reinforced polymer (FRP) composites. Less research by comparison has been conducted on the strengthening of RC beam-column connections and the majority of such research has been predominantly experimental to date. Few existing experimental studies have reported extensive instrumentation of test specimens which in turn makes understanding the behavior of the connections and especially the contributions made by the FRP difficult to ascertain. In addition, there has been even more limited research on the analytical and numerical modelling of FRP-strengthened connections. In this paper, detailed descriptions of key strategies to model FRP-strengthened RC connections with finite elements are provided. An extensively instrumented and comprehensively documented set of experiments on FRP-strengthened connections is firstly presented and finite element models are then constructed using ANSYS. The study shows that the finite element approach is able to capture the overall behavior of the test specimens including the failure mode as well as the behavior of the FRP which will most importantly lead to a detailed understanding of the FRP and the future development of rational analytical models. The finite element models are, however, unable to model the stiffness of the connections with accuracy in the ultimate load range of response.

• Structural Engineering and Mechanics
• /
• v.48 no.5
• /
• pp.737-755
• /
• 2013

This paper aims to develop a practical approach to modeling of fiber reinforced polymers (FRP) strengthened masonry panels. The main objective is to provide suitable relations for the material characterization of the masonry constituents so that the finite element applications of elasto-plastic theory achieves a close fit to the experimental load-displacement diagrams of the walls subjected to in-plane shear and compression. Two relations proposed for masonry columns confined with FRP are adjusted for the cohesion and the internal friction angle of both units and mortar. Relating the mechanical parameters to the uniaxial compression strength and the hydrostatic pressure acting over the wall surface, the effects of major and intermediate principal stresses ${\sigma}_1$ and ${\sigma}_2$ on the yielding and the shape of the deviatoric section are then reflected into the analyses. Performing nonlinear finite element analyses (NLFEA) for the three walls tested in two different studies, their stress-strain response and failure modes are eventually evaluated through the comparisons with the experimental behavior.

• Structural Engineering and Mechanics
• /
• v.1 no.1
• /
• pp.75-86
• /
• 1993

The punching shear strength of concrete flat plates is one of the topics of intensive research in recent years by various concrete structures researchers. This paper reviews four current methods of analysing the punching shear strength at the corner-and edge-column positions of reinforced concrete flat plates. They include those recommended in the Australian Standard AS3600-1988, the American Concrete Institute ACI318-89 and the British Standard on Concrete Practices (BS8110) as well as the approach developed at the University of Wollongong, Australia. Based on half-scale model test results, a comparative study of these four analysis methods is made with regard to their limitation, accuracy and reliability. It is found that the Wollongong approach in general gives the best performance in predicting the punching shear strength of flat plates with torsion strips and those with spandrel beams. The Australian Standard procedure performs just as satisfactorily for flat plates with torsion strips but tends to be unsafe for those with spandrel beams. Both the ACI and the British methods are applicable only to flat plates with torsion strips; they also tend to give unsafe predictions for the punching shear strength.

• Advances in Computational Design
• /
• v.1 no.1
• /
• pp.105-117
• /
• 2016

The objective of this work is to study the restraining effect in fire resistance of framed structures and to evaluate the global response of reinforced concrete frames when exposed to fire based on advanced finite element method. To study the response a single portal frame is analyzed. The effect of floor slab on this frame is studied by modeling a beam-column-slab assembly. The evolution of temperature distribution, internal stresses and deformations of the frame subjected to ISO 834 standard fire curve for both the frames are studied. The thermal and structural responses are evaluated and a comparison of results of individual members and entire structure is done. From the study it can be seen that restraining forces has significant influence on both stresses and deflection and overall response of the structure when compared to individual structural member. Among the various structural elements, columns are the critical members in fire and failure of column causes the failure of entire structure. The fire rating of various structural elements of the frame is determined by various failure criteria and is compared with IS456 2000 tabulated fire rating.

• Steel and Composite Structures
• /
• v.28 no.4
• /
• pp.471-482
• /
• 2018

The composite reinforced concrete and steel (RCS) structural systems have larger structural lateral stiffness, higher inherent structural damping, and faster construction speed than either traditional reinforcement concrete or steel structures. In this paper, four RCS subassemblies with or without the RC slab designed following a strong column-weak beam philosophy were constructed and tested under reversed-cyclic loading. Parameters including the width of slab and composite effect of the RC slab and beam were explored. The test results showed that all specimens performed in a ductile manner with plastic hinges formed in the beam ends near the column faces. The seismic responses of composite connections are influenced significantly by different width of slabs. Compared with that of the steel beam without the RC slab, it was found that the load carrying capacity of composite connections with the RC slab increased by 30% on average, and strength degradation, energy dissipation also had better performance, while the ductility of that were almost the same. Furthermore, the contribution of connection deformation to the overall specimen displacement was analyzed and compared. It decreased approximately 10% due to the coupling effect in the columns and beams with the RC slab. Based on the test result, some suggestions are presented for the design of composite RCS joints.

• Journal of Korean Association for Spatial Structures
• /
• v.20 no.3
• /
• pp.81-89
• /
• 2020

As the damage caused by earthquakes gradually increases, seismic retrofitting for existing public facilities has been implemented in Korea. Several types of structural analysis methods can be used to evaluate the seismic performance of structures. Among them, for nonlinear dynamic analysis, the hysteresis model must be carefully applied because it can significantly affect the behavior. In order to find a hysteresis model that predicts rational behavior, this study compared the experimental results and analysis results of the existing non-seismic reinforced concrete frames. For energy dissipation, the results were close to the experimental values in the order of Pivot, Concrete, Degrading, and Takeda models. The Concrete model underestimated the energy dissipation due to excessive pinching. In contrast, the other ones except the Pivot model showed the opposite results with relatively little pinching. In the load-displacement curves, the experimental and analysis results tended to be more similar when the column axial force was applied to columns.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.457-460
• /
• 2008

This study evaluated fire resistance performance for polypropylene/steel fiber reinforced high strength concrete column. Full-size columns were constructed and tested with or without fibers using ISO-834 fire curve. As the result of test, non-fiber high strength concrete column specimen occurred serious spalling and indicated rapidly internal temperature increase. Specimen with polypropylene fiber occurred not spalling. Specimen with hybrid fiber occurred not spalling as well as does not propagated temperature propagation. Therefore, hybrid fiber reinforced column specimen indicated a good fire resistance performance than other cases.

• Advances in concrete construction
• /
• v.2 no.4
• /
• pp.261-280
• /
• 2014

In many parts of the world, reinforced concrete (RC) buildings, designed and built in accordance with older codes, have suffered severe damage or even collapse as a result of recent near-fault earthquakes. This is particularly due to the deficiencies of most of the older (and even some of the recent) codes in dealing with near fault events. In this study, a tested three-storey frame designed for gravity loads only was selected to represent those deficient buildings. Nonlinear time history analyses were performed, followed by damage assessment procedures. The results were compared with experimental observation of the same frame showing a good match. Damage and fragility analyses of the frame subjected to 204 pulse-type motions were then performed using a selected damage model and inter-storey drifts. The results showed that the frame located in near-fault regions is extremely vulnerable to ground motions. The results also showed that the damage model better captures the damage distribution in the frame than inter-storey drifts. The first storey was identified as the most fragile and the inner columns of the first storey suffered most damage as indicated by the damage index. The findings would be helpful in the decision making process prior to the strengthening of buildings in near-fault regions.

• Journal of the Korea Concrete Institute
• /
• v.11 no.4
• /
• pp.147-156
• /
• 1999

Current design code states that the strength reduction factor shall be permitted to be increased linearly from that for axial compression to that for flexure as the design axial load strength $\Phi$cPn decrease from 0.1fckAg to zero. Since this empirically adopted axial load level of $\Phi$cPn=0.1fckAg considers only sectional area and concrete strength, the other variables such as steel ratio, steel yielding strength, and steel arrangement can not be considered. This research is performed to investigate the consistency and the rationality of the code requirement for determination of column design strength. A nonlinear axial force-moment-curvature analysis was conducted in order to investigate the ductility of reinforced concrete column sections. As the result of ductility analysis, it was found that the ductility at the axial force of $\Phi$cPn=0.1fckAg represented a lock of consistency for the various variable contained sections. Therefore, a more reasonable application method of strength reduction factor is proposed, that is based on the strain ductility index.

• Computers and Concrete
• /
• v.4 no.5
• /
• pp.331-346
• /
• 2007

A computer program was developed to analyze the non-linear, cyclic flexural performance of reinforced concrete structural members under various types of loading paths including non-sequential variations in axial load. This performance is significantly affected by the loading history. Different monotonic material models as well as hysteresis rules for confined and unconfined concrete and steel, some developed and calibrated against test results on material samples, were implemented in a fiber-based moment-curvature and in turn force-deflection analysis. One of the assumptions on curvature distribution along the member was based on a method developed to address the variation of the plastic hinge length as a result of loading pattern. Functionality of the program was verified by reproduction of analytical results obtained by others for several cases, and accuracy of the analytical process and the implemented models were evaluated against the experimental results from large-scale reinforced concrete columns tested under the analyzed loading cases. While the program can be used to predict the response of a member under a certain loading pattern, it can also be used to examine various analytical models and methods or refine a custom material model against test data.