• Steel and Composite Structures
• /
• v.1 no.3
• /
• pp.329-340
• /
• 2001

Cyclic response of "shear" connections between steel outrigger beams and reinforced concrete core walls is presented in this paper. The connections investigated in this paper consisted of a shear tab welded onto a plate that was connected to the core walls through multiple headed studs. The experimental data from six specimens point to a capacity larger than the design value. However, the mode of failure was through pullout of the embedded plate, or fracture of the weld between the studs and plate. Such brittle modes of failure need to be avoided through proper design. A capacity design method based on dissipating the input energy through yielding and fracture of the shear tab was developed. This approach requires a good understanding of the expected capacity of headed studs under combined gravity shear and cyclic axial load (tension and compression). A model was developed and verified against test results from six specimens. A specimen designed based on the proposed design methodology performed very well, and the connection did not fail until shear tab fractured after extensive yielding. The proposed design method is recommended for design of outrigger beam-wall connections.

• Steel and Composite Structures
• /
• v.46 no.6
• /
• pp.823-837
• /
• 2023

This paper presents the seismic performance of seven beam-column joints with an eccentricity between beam depths under cyclic loadings. The failure modes of the panel zone were divided into two types. One was the shear force failure that appeared in the entire panel zone (SFEPZ), the other was the shear force failure that appeared in the partial panel zone (SFPPZ). Seven finite element models were established using multi-scale methods. Compared with the experimental specimens, the hysteretic loops exhibited a similar trend. The multi-scale models could accurately simulate the experimental results. Furthermore, the calculation formulas of yield and plastic shear capacity of unequal-depth joints with outer annular stiffener were proposed.

• Journal of Korean Society of Steel Construction
• /
• v.14 no.3
• /
• pp.413-421
• /
• 2002

This study sought to understand the mechanical behavior according to the shape of the connecting part of the hybrid beam. This part is composed of central steel. with the end reinforced by concrete in the experiment of cyclic loading. The experimental result was compared and verified with the ultimate strength formula. Likewise, the composite effect and the effectiveness of seismic capacity and stress transmission were examined. The types of each setup were as follows: main bars by welding type, reinforcing by end-plate type, reinforcing by shear connector type, and shear connector type. Results showed that the reinforcing by end-plate type and the shear connector type had excellent strength and seismic capacity as well as better stress transmission. This was due to the unity between reinforced concrete and the steel's connecting part. However, the experimental result was somehow different from the previously established ultimate strength formula. Thus, a definite ultimate strength formula is required.

• Journal of Korean Society of Steel Construction
• /
• v.14 no.1
• /
• pp.51-58
• /
• 2002

To reduce the story height for high-rise buildings, the TEC Beam is developed as a new composite beam composed of structural tee, precast concrete, stirrup, and site-in-cast reinforced concrete slab. The preliminary test of the proposed system was performed for simple beams and it showed a good behavior. However, for the field application of the system, it is required to develope a steel moment resisting connection using steel brackets on which upper rebars of the TEC BEAM are anchored. In this paper, three types of the proposed system are experimentally investigated. The parameters of the test are as follows: (1) the spacing of transverse bars, (2) the ratio of width of rebar's layer to bracket length. Specimens were classified as semi-rigid full strength by the Eurocode 4. It could be concluded that the proposed moment resisting system shows a good structural behavior and may be applicable in the filed.

• Journal of Korean Society of Steel Construction
• /
• v.29 no.2
• /
• pp.111-122
• /
• 2017

In this paper, the applicability of a 1900mm-deep concrete-filled U-shaped composite beam to composite ordinary moment frames (C-OMFs) was investigated based on existing test results from smaller-sized specimens and supplemental numerical studies since full-scale seismic testing of such a huge sized beam is practically impossible. The key issue was the web local buckling of concrete-filled U section under negative bending. Based on 13 existing test results compiled, the relationship between web slenderness and story drift capacity was obtained. From this relationship, a 1900mm-deep mega beam, fabricated with 25mm-thick plate was expected to experience the web local buckling at 2% story drift and eventually reach a story drift over 3%, thus much exceeding the requirements of C-OMFs. The limiting width to thickness ratio according to the 2010 AISC Specification was shown to be conservative for U section webs of this study. The test-validated supplemental nonlinear finite element analysis was also conducted to further investigate the effects of the horizontal stiffeners (used to tie two webs of a U section) on web local buckling and flexural strength. First, it is shown that the nominal plastic moment under negative bending can be developed without using the horizontal stiffeners, although the presence of the stiffeners can delay the occurrence of web local buckling and restrain its propagation. Considering all these, it is concluded that the 1900mm-deep concrete-filled U-shaped composite beam investigated can be conservatively applied to C-OMFs. Finally, some useful recommendations for the arrangement and design of the horizontal stiffeners are also recommended based on the numerical results.

• Journal of Korean Society of Steel Construction
• /
• v.26 no.5
• /
• pp.431-439
• /
• 2014

Concrete filled tubular columns are widely used because the mutual reaction between the concrete and the tube improves strength and ductility of the columns. In an attempt to secure efficient use of members, built-up square columns featuring large width-thickness ratio and the use of thin steel plates are suggested in this study. In order to evaluate the structural characteristics and seismic performance of the column-to-beam connections of the new shape columns, cyclic load test of T-shaped column-to-beam connections was conducted with variables of diaphragms and concrete-filling. Moment-rotational angle relationship, dissipated energy and failure behavior were compared to evaluate stress transfer mechanism of the new shape built-up square column-to-beam connections associated with the variables.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.1
• /
• pp.39-46
• /
• 2017

In this paper, a model updating procedure based on the response surface method combined with the multi-objective optimization was proposed and applied for updating of the FE models representing a low-rise reinforced concrete building before and after the seismic retrofit. The dynamic properties to be matched were obtained from vibration tests using a small shaker system. By varying the structural parameters according to the central composite design, analysis results from the initial FE model using a commercial software were collected and used to produce two regression functions each of which representing the errors in the natural frequencies and mode shapes. The two functions were used as the objective functions for multi-objective optimization. Final solution was determined by examining the Pareto solutions with one iteration. The parameters representing the stiffnesses of existing concrete, masonry, connection stiffness in expansion joint, new concrete, retrofitted members with steel section jacketing were selected and identified.

• Steel and Composite Structures
• /
• v.27 no.6
• /
• pp.727-745
• /
• 2018

The design criteria and the corresponding performance levels characterize the response of extended stiffened end-plate beam-to-column joints. In order to guarantee a ductile behavior, hierarchy criteria should be adopted to enforce the plastic deformations in the ductile components of the joint. However, the effectiveness of thesecriteria can be impaired if the actual resistance of the end-plate material largely differs from the design value due to the potential activation of brittle failure modes of the bolt rows (e.g., occurrence of failure mode 3 in the place of mode 1 per bolt row). Also the number and the position of bolt rows directly affect the joint response. The presence of a bolt row in the center of the connection does not improve the strength of the joint under both gravity, wind and seismic loading, but it can modify the damage pattern of ductile connections, reducing the gap opening between the end-plate and the column face. On the other hand, the presence of a central bolt row can influence the capacity of the joint to resist the catenary actions developing under a column loss scenario, thus improving the joint robustness. Aiming at investigating the influence of these features on both the cyclic behavior and the response under column loss, a wide range of finite element analyses (FEAs) were performed and the main results are described and discussed in this paper.

• Steel and Composite Structures
• /
• v.22 no.2
• /
• pp.323-352
• /
• 2016

The results of a series of finite element (FE) simulations and experimental studies are used to develop strength and stiffness models that predict the failure capacity and response characteristics of unstiffened extended endplate connections with circular and rectangular bolt configurations associated with deep girders. The proposed stiffness models are composed of multi-linear springs which model the overall extended endplate/column flange system deformation and strength of key-components. Comparison of model predictions with FE and experimental results available in the literature show that the proposed models accurately predict the strength and the response of extended endplate/column system with circular and rectangular bolt configurations. The effect of the bolt configuration (circular and rectangular) on the prying phenomenon encountered in the unstiffened extended endplate/column system was investigated. Based on FE results, extended endplate with circular bolt configuration has a more ductile behavior and exhibits higher total prying forces. The proposed models can be used to design connections that cover all possible failure modes for extended endplate with circular bolt configuration. This study provides guidelines for engineers to account for the additional forces induced in the tension bolts and for the maximum rotational capacity demand in the connection which are required for seismic analysis and design.

• Steel and Composite Structures
• /
• v.20 no.6
• /
• pp.1193-1203
• /
• 2016

This paper focuses on the analytical behavior of modular circular concrete-filled tubular (CFT) column with enhanced bracing details. To design a full-scale bridge pier of multiple circular concrete-filled tubes, numerical analysis was used to evaluate structural performance according to load directivity. In previous research (Ma et al. 2012, Shim et al. 2014), low cycle fatigue failure at bracing joints was observed, so enhanced bracing details to prevent premature failure are proposed in this analysis. The main purpose of this research is to investigate seismic performance for the diagonal direction load without premature failure at the joints when the structure reaches the ultimate load. The ABAQUS finite-element software is used to evaluate experimental performance. A quasi-static loading condition on a modular bridge pier is introduced to investigate structural performance. The results obtained from the analysis are evaluated by comparing with load-displacement responses from experiments. The concrete-filled tubes with enhanced bracing details showed higher energy dissipation capacity and proper performance without connection failure for a diagonal load.