• Steel and Composite Structures
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• 제44권2호
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• pp.183-198
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• 2022

Plastic deformation of link beams in eccentrically braced frames is the primary dissipating source of seismic energy. Despite the excellent compatibility with the architectural designs, previous researches indicate the deficiency of flexural yielding links compared to the shear yielding ones because of their localized plastic deformation. Previous investigations have shown that implementing web openings in beams could be an efficient method to improve the seismic performance of moment-resisting connections. Accordingly, this research investigates the use of flexural links with stiffened and un-stiffened web openings to eliminate localized plasticity at the ends of the link. For this purpose, the numerical models are generated in finite element software "Abaqus" and verified against experimental data gathered from other studies. Models are subjected to cyclic displacement history to evaluate their behavior. Failure of the numerical models under cyclic loading is simulated using a micromechanical based damage model known as Cyclic Void Growth Model (CVGM). The elastic stiffness and the strength-based and CVGM-based inelastic rotation capacity of the links are compared to evaluate the studied models' seismic response. The results of this investigation indicate that some of the flexural links with edge stiffened web openings show increased inelastic rotation capacity compared to an un-perforated link.

• 국제초고층학회논문집
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• 제6권3호
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• pp.249-259
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• 2017

The use of high-strength steels in construction of highrise and mega building structures can bring about many technological advantages from fabrication to erection. However, key design criteria such as local and lateral stability in current steel design specifications were developed based on tests of ordinary steels which have stress-strain characteristics very different from that of high strength steels. A series of tests on 800 MPa tensile strength steel (HSA800) members are summarized in this paper which were conducted to investigate the appropriateness of extrapolating current ordinary-steel based design criteria to high strength steels. 800 MPa I-shape beam specimens designed according to flange local buckling (FLB) criteria of the AISC Specification developed a sufficient strength for elastic design and a marginal rotation capacity for plastic design. It is shown that, without introducing distinct and significant yield plateau to the stress-strain property of high-strength steel, it is inherently difficult to achieve a high rotation capacity even if all the current stability limits are met. 800 MPa I-shape beam specimens with both low and high warping rigidity exhibited sufficient lateral torsional buckling (LTB) strength. HSA800 short-column specimens with various edge restraint exhibited sufficient local buckling strength under uniform compression and generally outperformed ordinary steel specimens. The experimental P-M strength was much higher than the AISC nominal P-M strength. The measured residual stresses indicated that the impact of residual stress on inelastic buckling of high-strength steel is less. Cyclic seismic test results showed that HSA800 members have the potential to be used as non-ductile members or members with limited ductility demand in seismic load resisting systems. Finally, recent applications of 800 MPa high strength steel to highrise and mega building structures in Korea are briefly presented.

• Steel and Composite Structures
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• 제18권3호
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• pp.641-657
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• 2015

Application of reduced web beam section (RWBS) as a sacrificial fuse element has become a popular research field in recent years. Weakening of beam web in these connections may cause local web buckling around the opening area which can affect cyclic behavior of connection including: maximum load carrying capacity, strength degradation rate, dissipated energy, rotation capacity, etc. In this research, effect of local web buckling on the cyclic behavior of RWBS connections is investigated using finite element modeling (FEM). For this purpose, a T-shaped moment connection which has been tested under cyclic loading by another author is used as the reference model. Fracture initiation in models is simulated using Cyclic Void Growth Model (CVGM) which is based on micro-void growth and coalescence. Included in the results are: effect of opening corner radii, opening dimensions, beam web thickness and opening reinforcement. Based on the results, local web buckling around the opening area plays a significant role on the cyclic behavior of connection and hence any parameter affecting the local web buckling will affect entire connection behavior.

• Earthquakes and Structures
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• 제8권3호
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• pp.591-617
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• 2015

Standards for seismic assessment and retrofitting of buildings provide deformation limit states for structural members and connections. However, in order to perform fully consistent performance-based seismic analyses of soil-structure systems; deformation limit states must also be available for foundations that are vulnerable to nonlinear actions. Because such limit states have never been established in the past, a laboratory testing program was conducted to study the rotational capacity of small-scale foundation models under combined axial load and moment. Fourteen displacement-controlled monotonic and cyclic tests were performed using a cohesionless soil contained in a $2.0{\times}2.0{\times}1.2m$ container box. It was found that the foundation models exhibited a stable hysteretic behavior for imposed rotations exceeding 0.06 rad and that the measured foundation moment capacity complied well with Meyerhof's equivalent width concept. Simplified code-based soil-structure analyses of an 8-story building under an array of strong ground motions were also conducted to preliminary evaluate the implication of finite rotational capacity of vulnerable foundations. It was found that for the same soil as that of the experimental program foundations would have a deformation capacity that far exceeds the imposed rotational demands under the lateral load resisting members so yielding of the soil may constitute a reliable source of energy dissipation for the system.

• Steel and Composite Structures
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• 제18권5호
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• pp.1177-1195
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• 2015

Six specimens are tested to investigate the cyclic behavior of beam-to-column abnormal joints in steel moment-resisting frames, which are designed according to the principle of strong-member and weak-panel zone. Key parameters include the axial compression ratio of column and the section depth ratio of beams. Experimental results indicate that four types of failure patterns occurred during the loading process. The $P-{\Delta}$ hysteretic loops are stable and plentiful, but have different changing tendency at the positive and negative direction in the later of loading process due to mechanical behaviors of specimens. The ultimate strength tends to increase with the decrease of the section depth ratio of beams, but it is not apparent relationship to the axial compression ratio of column, which is less than 0.5. The top panel zone has good deformation capacity and the shear rotation can reach to 0.04 rad. The top panel zone and the bottom panel zone don't work as a whole. Based on the experimental results, the equation for shear strength of the abnormal joint panel zone is established by considering the restriction of the bottom panel zone to the top panel zone, which is suitable for the abnormal joint of H-shaped or box column and beams with different depths.

• 한국강구조학회 논문집
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• 제22권4호
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• pp.305-312
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• 2010

본 연구의 목적은 모멘트 접합 골조에서 각형강관 기둥-H 형강 보 접합부의 내진성능평가이다. 각형강관은 H형강에 비해서 효율적이고 많은 장점이 있음에도 불구하고, 아직 접합 디테일의 부족과 경험 부족 등의 이유로 현장에서 적용이 제한적이다. 각형강관을 사용한 기존의 모멘트 접합부는 주로 관통형 다이아프램 형식을 사용하고 있는데 이는 시공과정이 복잡하여 현장에서의 적용을 어렵게 한다. 그러므로 이 연구에서는 각형강관 기둥을 절단하지 않는 접합상세에 대하여 구조성능 및 내진성능을 평가하고자 하였다. 엔드플레이트와 헌치를 이용한 용접접합의 접합상세에 대하여 내력 및 강성, 에너지흡수능력을 비교분석하였다.

• 한국지진공학회논문집
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• 제18권1호
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• pp.63-71
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• 2014

This study presents an experimental study of the structural behavior for steel plate-concrete column-to-steel girder connections. Experiments were carried out to investigate the moment-rotation characteristics, failure behavior and ultimate moment capacity of these connections. The results of this experimental study involving three welded moment-resisting connections subjected to cyclic loading are presented. The specimens were fabricated at full scale to evaluate their hysteretic behavior. A description of the test specimens, the details of the joint, the test system and the testing methods are described. The test results showed that the structural behavior of these composite connections was influenced by the connection details.

• Structural Engineering and Mechanics
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• 제13권1호
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• pp.35-52
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• 2002

It was shown in the previous study (Lee and Bertero 1993) that incremental collapse can lead to the exhaustion of the plastic rotation capacity at critical regions in a structure when subjected to the number of load cycles and load intensities as expected during maximum credible earthquakes and that this type of collapse can be predicted using the shakedown analysis technique. In this study, a minimum-weight design methodology, which takes into account not only the prevention of this incremental collapse but also the requirements of the serviceability limit states, is proposed by using the shakedown analysis technique and a nonlinear programming algorithm (gradient projection method).

• Steel and Composite Structures
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• 제23권2호
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• pp.143-152
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• 2017

This paper focuses on the seismic performance of pallet-type steel storage rack structures in their down aisle direction. As evidenced by experimental research, the seismic response of storage racks in the down-aisle direction is strongly affected by the nonlinear moment-rotation response of the beam-to-column connections. In their down-aisle direction, rack structures are designed to resist lateral seismic loads with typical moment frames utilizing proprietary beam-to-column moment-resisting connections. These connections are mostly boltless hooked type connections and they exhibit significantly large rotations resulting in large lateral frame displacements when subjected to strong ground motions. In this paper, typical hooked boltless beam-to-column connections are studied experimentally to obtain their non-linear reversed cyclic moment-rotation response. Additionally, a compound type connection involving the standard hooks and additional bolts were also tested under similar conditions. The simple introduction of the additional bolts within the hooked connection is considered to be a practical way of structural upgrade in the connection. The experimentally evaluated characteristics of the connections are compared in terms of some important performance indicators such as maximum moment and rotation capacity, change in stiffness and accumulated energy levels within the cyclic loading protocol. Finally, the obtained characteristics were used to carry out seismic performance assessment of rack frames incorporating the tested beam-to-column connections. The assessment involves a displacement based approach that utilizes a simple analytical model that captures the seismic behavior of racks in their down-aisle direction. The results of the study indicate that the proposed method of upgrading appears to be a very practical and effective way of increasing the seismic performance of hooked connections and hence the rack frames in their down-aisle direction.

• Steel and Composite Structures
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• 제37권3호
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• pp.307-321
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• 2020

The slim-floor solution provides an efficient alternative to the classic slab-over-beam configuration due to architectural and structural benefits. Two deficiencies can be identified in the current state-of-art: (i) the technique is limited to nonseismic applications and (ii) the lack of information on moment-resisting slim-floor beam-to-column joints. In the seismic design of framed structures, continuous beam-to-column joints are required for plastic hinges to form at the ends of the beams. The present paper proposes a slim-floor technical solution capable of expanding the current application of slim-floor joints to seismic-resistant composite construction. The proposed solution relies on a moment-resisting connection with a thick end-plate and large-diameter bolts, which are used to fulfill the required strength and stiffness characteristics of continuous connections, while maintaining a reduced height of the configuration. Considering the proposed novel solution and the variety of parameters that could affect the behavior of the joint, experimental and numerical validations are compulsory. Consequently, the current paper presents the experimental and numerical investigation of two slim-floor beam-to-column joint assemblies. The results are discussed in terms of moment-rotation curves, available rotational capacity and failure modes. The study focuses on developing reliable slim-floor beam joints that are applicable to steel building frame structures located in seismic regions.