• Structural Engineering and Mechanics
• /
• 제61권4호
• /
• pp.527-538
• /
• 2017

The evaluation of the loss-of-support conditions of frictional beam-to-column connections using simplified numerical models describing the transverse response of a portal-like structure is presented in this paper considering the effects of the seismic-hazard disaggregation. Real earthquake time histories selected from European Strong-motion Database (ESD) are used to show the effects of the seismic-hazard disaggregation on the beam loss-of-support conditions. Seismic events are classified according to different values of magnitudes, epicentral distances and soil conditions (stiff or soft soil) highlighting the importance of considering the characteristics of the seismic input in the assessment of the loss-of-support conditions of frictional beam-to-column connections. A rigid and an elastic model of a frame of a precast industrial building (2-DoF portal-like model) are presented and adopted to find the minimum required friction coefficient to avoid sliding. Then, the mean value of the minimum required friction coefficient with an epicentral distance bin of 10 km is calculated and fitted with a linear function depending on the logarithm of the epicentral distance. A complete parametric analysis varying the horizontal and vertical period of vibration of the structure is performed. Results show that the loss-of-support condition is strongly influenced by magnitude, epicentral distance and soil conditions determining the frequency content of the earthquake time histories and the correlation between the maxima of the horizontal and vertical components. Moreover, as expected, dynamic characteristics of the structure have also a strong influence. Finally, the effect of the column nonlinear behavior (i.e. formation of plastic hinges at the base) is analyzed showing that the connection and the column are a series system where the maximum force is limited by the element having the minimum strength. Two different longitudinal reinforcement ratios are analyzed demonstrating that the column strength variation changes the system response.

• Structural Engineering and Mechanics
• /
• 제85권1호
• /
• pp.65-80
• /
• 2023

To explore the effect of Engineered Cementitious Composite (ECC) on improving the progressive collapse resistance of reinforced concrete frames under a middle column removal scenario, six beam-column substructures were tested by quasistatic vertical loading. Among the six specimens, four were ECC-concrete composite specimens consisting of different depth of ECC at the bottom or top of the beam and concrete in the rest of the beam, while the other two are ordinary reinforced concrete specimens with different concrete strength grades for comparison. The experimental results demonstrated that ECC-concrete composite specimens can improve the bearing capacity of a beam-column substructure at the stages of compressive arch action (CAA) and catenary action in comparison with ordinary concrete specimen. Under the same depth of ECC, the progressive collapse resistance of a specimen with ECC at the beam bottom was superior to that at the beam top. With the increase of the proportion of ECC arranged at the beam bottom, the bearing capacity of a composite substructure was increased, but the increase rate slows down with the proportion. Meanwhile, the nonlinear numerical analysis software MSC Marc was used to simulate the whole loading process of the six specimens. Theoretical formulas to calculate the capacities of ECC-concrete composite specimens at the stages of flexural action, CAA and catenary action are proposed. Based on the research results, this study suggests that ECC should be laid out at the beam bottom and the layout depth should be within 25% of the total beam depth.

• 한국산업융합학회 논문집
• /
• 제23권2_2호
• /
• pp.361-374
• /
• 2020

Recently, small and medium-sized rahmen-type bridges have been developed as a technology that ensures the stability of structural behavior and the safety of use at the same time by using efficient and economical materials that make up the convergence section of reinforced bar, structural steel and concrete. This study is about a rahmen-type structure applied with the installation and dismantling of the strut. It improves the serviceability of the structure by forming multi-points and efficiently applies the convergence section of structural steel and concrete materials to the structural system changes to induce the displacement improvement effect additionally. By constructing mock-up models for the beam-column joint, the displacement was calculated and compared, and this was compared and analyzed by numerical analysis. The final displacement showed an improvement effect of 13.46% to 36.28% based on the vertical displacement of the existing structure without struts through the experiment of the mock-up models. As a result of analysis by numerical analysis method, the displacement improvement effect of 42.89% could be derived.

• Structural Engineering and Mechanics
• /
• 제26권5호
• /
• pp.569-589
• /
• 2007

This paper presents an analytical model for RC beam-column connections that takes into account bond deterioration between reinforcing steel and concrete. The model is based on the Lumped Damage Mechanics (LDM) theory which allows for the characterization of cracking, degradation and yielding, and is extended in this paper by the inclusion of the slip effect as observed in those connections. Slip is assumed to be lumped at inelastic hinges. Thus, the concept of "slip hinge", based on the Coulomb friction plasticity theory, is formulated. The influence of cracking on the slip behavior is taken into account by using two concepts of LDM: the effective moment on an inelastic hinge and the strain equivalence hypothesis. The model is particularly suitable for wide beam-column connections for which bond deterioration dominates the hysteretic response. The model was evaluated by the numerical simulation of five tests reported in the literature. It is found that the model reproduces closely the observed behavior.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
• /
• pp.53-56
• /
• 2008

대부분의 철근콘크리트 라멘 구조물은 지진하중 작용 시 가장 취약한 부분인 보-기둥 접합부 영역에서 큰 피해를 유발할 수 있다. 이러한 피해를 방지하기 위하여 보수 및 보강에 관한 연구가 이루어지고 있으며, 전 세계적으로 내진규정이 강화되고 구조물의 내진성능이 중요시되면서 지진에 효율적으로 저항할 수 있는 성능을 확보한 재료 개발이 증가되고 있다. 변형경화형 시멘트 복합체(Strain-hardening cementitious composite, SHCC)는 연성능력이 우수하여 보-기둥 접합부 영역에서 상당한 보강효과가 기대된다. 따라서 본 연구에서는 SHCC로 접합부를 보강한 철근콘크리트 보의 보강특성을 평가하고자 총 3개의 실험체를 제작하였다. 실험을 통하여 균열 및 파괴양상에 대하여 휨거동 특성을 평가하고 섬유 혼입률에 따른 SHCC의 보강효과에 대한 강도를 비교하였다.

• KIEAE Journal
• /
• 제10권6호
• /
• pp.145-151
• /
• 2010

Bearing wall system was used extensively in most multi-residential apartment buildings in Korea. However, bearing wall apartments have the lack of architectural plan flexibility, remodelling-incompatible, causing serious economic losses in terms of construction waste. Recently, many researchers have studied the use of Rahmen structure as a potential alternative. The beam-column connection in the paper for long-life apartment housing forms connection of a Rahmen structure utilizing the advantages of steel and reinforced concrete. In addition, reduction of cast-in place concrete and construction schedule is expected by using precast concrete. Reduction effect of quantity decreased construction costs and $CO_2$ emission of key construction materials. However, verifying the feasibility of new construction method entails numerous challenges. Accordingly, the purpose of this study is to analyze the construction feasibility of sleeve, coupler, and pressure welding connections for long-life apartment building structure. A 3D modeling software was used to perform the analysis, and a real scale model was created to verify the results of construction feasibility. By verifying the construction feasibility of beam-column connections, this study will contribute to the efficient application of these methods on construction sites.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
• /
• pp.185-190
• /
• 1992

ACI318-89 Recommended that when the specified compressive strength of concrete in a column is greater than1.4 times that specified for a floor system, top surface of the column concrete shall extend 2ft(600mm)into the slab from the face of column to avoid unexpected brittle failure. The major variables are extension distance, flexural strength ratio(Mr), and shear reinforcement ratio(Vs). Test results are as follows ; (1) The failure modes of specimens under cyclic loading were concentrated at critical region from beam-column joint face. (2) Ductility index($\mu$f) were increased with increasing of shear confinement ratio and flexural strength ratio. (3)The specimens with 2ft extension distance showed more ductility than the specimens with 1ft extension distance.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1992년도 봄 학술발표회 논문집
• /
• pp.90-94
• /
• 1992

ACI318-89 Recommened that when the specified compressive strength of concrete in a column is greater than 1.4 times that specified for a floor system, top surface of the column concrete shall extend 2ft (600mm) into the slab from the face of column to avoid unexpected brittle failure. The major variables are extension distance, compressive strength of concrete (f'c), shear confinement ratio(Vs), and loading types. The test results showed that the load capacity of the specimen subjected to monotonic loading had more than that of the specimen subjected to one way cyclic loadings. The failure models of specimens under cyclic loading were concentrated at 5∼20cm apart region from beam-column joint face. Ducility index(μf) are increased with increasing of shear confinement ratio. The specimen with 2ft extension distance shows more ductility than specimen with lft extension distance.

• 한국강구조학회 논문집
• /
• 제29권2호
• /
• pp.169-180
• /
• 2017

본 연구에서는 국내 소규모 철골조 건축물에서 실제 시공된 보-기둥 약축 접합부에 대한 현황조사를 바탕으로 시공성을 향상시킨 약축접합부 상세를 제안하였으며, 제안된 약축접합부에 대한 반복가력 실험을 통해 접합부 내진성능을 평가하였다. 실험변수는 보-기둥 접합부에 사용된 볼트의 개수이다. 실험결과, 본 연구에서 제안하고 있는 보-기둥 약축 접합부의 거동은 수평 스티프너에 연결되는 고력볼트의 개수의 의해 결정되는 것으로 나타났다. 접합부에 4개 이상의 볼트접합이 사용될 경우 현행 기준에서 요구하는 부분 강접합 요구조건을 만족시키는 것으로 나타났다. 모든 실험체는 플랜지 연결플레이트의 연단쪽 보 플랜지 볼트 구멍 주위에서 국부적인 지압파괴와 파단 등이 발생하였다. 하지만, 웨브 높이와 플랜지 폭이 작은 기둥을 사용할 경우, 접합부에 사용되는 고력볼트의 개수가 제한적으로 사용되어야 할 것으로 판단되므로 향후 이 부분에 대한 추가적인 연구가 필요하다.

• Earthquakes and Structures
• /
• 제12권6호
• /
• pp.603-617
• /
• 2017

This paper presents investigation into the behavior of beam-column joints, with the joint region concrete being replaced by steel fiber reinforced concrete (SFRC) and by ultra-high performance concrete (UHPC). A total of ten beam-column joint specimens (BCJ) were tested experimentally to failure under monotonic and cyclic loading, with the beam section being subjected to flexural loading and the column to combined flexural and axial loading. The joint region essentially transferred shear and axial stresses as received from the column. Steel fiber reinforced concrete (SFRC) and ultra-high performance concrete (UHPC) were used as an innovative construction and/or strengthening scheme for some of the BCJ specimens. The reinforced concrete specimens were reinforced with longitudinal steel rebar, 18 mm, and some specimens were reinforced with an additional two ties in the joint region. The results showed that using SFRC and UHPC as a replacement concrete for the BCJ improved the joint shear strength and the load carrying capacity of the hybrid specimens. The mode of failure was also converted from a non-desirable joint shear failure to a preferred beam flexural failure. The effect of the ties in the SFRC and UHPC joint regions could not be observed due to the beam flexural failure. Several models were used in estimating the joint shear strength for different BCJ specimens. The results showed that the existing models yielded wide-ranging values. A new concept to take into account the influence of column axial load on the shear strength of beam-column joints is also presented, which demonstrates that the recommended values for concrete tensile strength for determination of joint shear strength need to be amended for joints subject to moderate to high axial loads. Furthermore, finite element model (FEM) simulation to predict the behaviour of the hybrid BCJ specimens was also carried out in an ABAQUS environment. The result of the FEM modelling showed good agreement with experimental results.