• 콘크리트학회논문집
• /
• 제14권4호
• /
• pp.615-622
• /
• 2002

철근콘크리트 무량판 구조의 내력 및 변위를 합리적으로 예측하기 위해서는 슬래브의 휨 강성을 고려한 해석모델이 필요하다. FEMA 273과 ACI 318-99에서는 횡 하중에 대한 슬래브의 해석모델들을 제시하고 있으나 실제적인 적용 방법론은 언급하고 있지 않다. 본 연구에서는 무량판 슬래브의 모델링 방법론을 정립하고 이를 내진설계에 어떻게 적용할 것인가에 대하여 연구하였다. 연구결과는 다음과 같다. 1) 무량판 구조의 3차원 해석시 슬래브의 휨 강성을 적절히 고려하기 위해서는 본 연구진이 제시하는 유효보폭 모델을 적용하는 것이 바람직하다. 2) 예제 무량판 건물 해석에서 슬래브의 균열효과를 고려한 유효보폭을 이용할 경우 해석결과는 횡변위에 대하여 상한값을 나타낸 반면 유효보폭 계수만을 고려한 모델은 접합부 불균형 모멘트에 대하여 상한값의 결과를 나타냈다.

• Steel and Composite Structures
• /
• 제39권4호
• /
• pp.435-451
• /
• 2021

Shear lag effect was a significant mechanical behavior of steel-concrete composite beams, and the effective flange width was needed to consider this effect. However, the effective flange width is mostly determined by static load test. The cyclic vehicle loading cases, which is more practical, was not well considered. This paper focuses on the study of shear lag effect of the concrete slab in the negative moment region under fatigue cyclic load. Two specimens of two-span steel-concrete composite beams were tested under fatigue load and static load respectively to compare the differences in the negative moment region. The reinforcement strain in the negative moment region was measured and the stress was also analyzed under different loads. Based on the OpenSees framework, finite element analysis model of steel-concrete composite beam is established, which is used to simulate transverse reinforcement stress distribution as well as the variation trends under fatigue cycles. With the established model, effects of fatigue stress amplitude, flange width to span ratio, concrete slab thickness and shear connector stiffness on the shear lag effect of concrete slab in negative moment area are analyzed, and the effective flange width ratio of concrete slab under different working conditions is calculated. The simulated results of effective flange width are compared with calculated results of the commonly used specifications, and it is found that the methods in the specifications can better estimate the shear lag effect in concrete slab under static load, but the effective flange width in the negative moment zone under fatigue load has a large deviation.

• 한국음향학회지
• /
• 제40권4호
• /
• pp.391-399
• /
• 2021

곡면 배열 센서는 빔의 지향 방위에 따라 부 배열이 구성된다. 여기서 부 배열의 센서 선택 방법에 따라 곡면 배열 센서의 성능이 달라질 수 있다. 또한, 곡면 배열 센 서는 형상의 특성으로 인해 빔 지향 방위에 따라 부 배열의 형상이 달라진다. 따라서 빔 지향 방위에 따라 지향지수, 빔 폭 등의 성능이 달라진다. 그러므로 센서 선택 방법을 선택할 때, 빔 지향 방위에 따라 달라지는 지향지수, 빔폭 등의 성능을 고려해야 한다. 본 논문에서는 각 단일 센서의 위치 벡터가 기준인 부 배열을 선택하는 방법과 센서 빔의 지향 벡터가 기준인 부 배열을 선택하는 방법을 사용하였다. 두 가지 방법에 대해 빔 지향 방위별 지향지수와 수평 및 수직 빔 폭의 평균과 분산을 비교 분석하였다. 또한, 두 방법에서 사용되는 센서 수를 고정 하여 비교 분석하였다. 센서 수를 고정하지 않았을 때는 센서 빔의 지향 벡터 기준 방법의 성능이 대부분 높았으나 수직 빔 폭의 성능은 낮거나 비슷하였다. 하지만 센서 수를 고정하였을 경우, 두 방법 모두 성능은 비슷하나 지향 방위별 성능 분산은 줄어들었다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
• /
• pp.312-316
• /
• 1995

Flat-plate buildings are commonly modeled as two-dimensional frames to calculate lateral drift, unbalanced moments, and shear at slab-column connections. For gravity loads. the slab-column frames are analyzed using equivalent column approach, while equivalent beam approach is typical for lateral loads. The equivalent beam approach is convenient for computer analysis, but no rational procedure exists for determining the effective width of foor slabs. At present, the determination of the equivalent slab width and its stiffness is a matter of engineering judgement. To account for cracking, overly conservative assumptions are made regarding the stiffness of the slab. A rational approach is therefore needed to realistically estimate the equivalent slab width and its stiffness for unbalanced moment and lateral drift calculations. Based on the test results of 8 interior slab-column connections, an equivalent beam model is proposed in which columns are modeled conventionally as a function of column and slab aspect ratios and the magnitude of the gravity load. the proposed approach is verified with selected experimental results and is founded to be practical and convenient for analyzing flat-plate buildings subjected to gravity and lateral loading.

• Journal of Welding and Joining
• /
• 제7권4호
• /
• pp.12-21
• /
• 1989

Laser beam welding parameters have experimentally investigated, using a continuous wave 3kW $CO_2$ laser with the various travel speeds, beam mode and laser beam power in low carbon steels. An optimum position of focus and the effect of shielding gas on penetration depth with varying the flow range of 0.5 to 5.1m/min have been combined to investigate the effect of laser power and travel speed on penetration depth and bead width. It is found that the optimum position of focus in 3kW class laser is 0.5 to 1.5mm below the surface of the material. The flow rate of shielding gas affects the penetration depth and He is more effective than Ar. The penetration depth in laser welds of low carbon steels is between two and four times of the bead width. Laser beam welding of butt joints in 2mm thick carbon steel has been carried out to establish a weldability lobe. The lobe indicating acceptable welding conditions is introduced.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
• /
• pp.125-126
• /
• 2009

유효보폭 모델은 횡하중하의 포스트 텐션(PT) 플랫 플레이트 골조 해석에 사용된다. PT 플랫 플레이트의 정확한 해석을 위해서 슬래브의 강성감소는 정확하게 평가되어야 한다. 이 목적을 위하여 본 연구는 기존 연구자들의 PT 플랫 플레이트 실험체를 수집하였으며. 반복적인 작업으로 실험체 강성에 수렴하는 유효보폭모델의 강성을 찾기 위하여 슬래브 폭을 감소시켰다. 이러한 데이터를 수집하여 비선형 회귀분석을 통하여 PT 플랫 플레이트의 강성 감소 계수식을 제안하였다.

• Structural Engineering and Mechanics
• /
• 제21권3호
• /
• pp.295-313
• /
• 2005

This paper evaluates the effective width of composite steel beams with precast hollowcore slabs numerically using the finite element method. A parametric study, carried out on 27 beams with different steel cross sections, hollowcore unit depths and spans, is presented. The effective width of the slab is predicted for both the elastic and plastic ranges. 8-node three-dimensional solid elements are used to model the composite beam components. The material non-linearity of all the components is taken into consideration. The non-linear load-slip characteristics of the headed shear stud connectors are included in the analysis. The moment-deflection behaviour of the composite beams, the ultimate moment capacity and the modes of failure are also presented. Finally, the ultimate moment capacity of the beams evaluated using the present FE analysis was compared with the results calculated using the rigid - plastic method.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
• /
• pp.36-43
• /
• 2005

Stiffness reduction factor of slab in flat-plate structure is proposed in comparison with UCB test result. Then analysis of structural system of flat-plate apartment buildings is carried out by using effective beam width method and finite element method. Effective beam width method overestimates the lateral stiffness of the system where columns are arranged atypically and overestimates the stiffness of slab-wall joint.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
• /
• pp.337-340
• /
• 2006

The purpose of this study is to propose the stiffness reduction factor for flat plate slabs under lateral loads. Current design code (e.g., ACI 318-05) requires considering the effects of cracks for calculating slab stiffness under lateral loads. This study collected the test results of 20 interior slab-column connections, from which stiffness reduction in each test was estimated with respect to the ratio of applied moment to cracking moment ($M_a/M_{cr}$). Based on collected data, this study proposed equations for calculating stiffness reduction with respect to $M_a/M_{cr}$. To verify the proposed equations, this study conducted the experimental test of interior slab-column connections under quasi-static cyclic loading. From the test, load-deformation curve is compared to that obtained from effective beam width method with the proposed equation for the stiffness reduction. It is shown that the effective beam width method with the proposed equation for stiffness reduction predicts accurately the test results.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
• /
• pp.521-526
• /
• 2001

The flexural behavior of a strengthened beam that is a reinforced concrete beam with externally bonded carbon fiber sheets, is theoretically and experimentally investigated. A rectangular beam having a width of 20cm depth of 30cm and effective depth of 25cm is chosen. In order to have a variety of beams analyzed, three reinforcement ratios are chosen for the analysis: 1)$\frac{1}{2}$$\rho$$_{max}$, which is the most suitable reinforcement ratio for deflection consideration and the highest reinforcement ratio for practical designing beams as well; 2)$\rho$$_{max}$, which is the lowest reinforcement ratio for design purposes; and 3)the reinforcement ratio halfway from 1) and 2). Carbon fiber sheets with width of 15cm are externally bonded at the bottom fiber of the beam. The effect of the amount of carbon fiber sheets varying from 1 to 4 plies on the flexural capacity of the strengthened beam are also examined. Yield loads, ultimate loads, and flexural rigidities of the strengthened beam from the experimental results are composed with theoretical ones.nes.