• KCI Concrete Journal
• /
• 제14권1호
• /
• pp.36-42
• /
• 2002

Flexural behaviors of the two typical precast beam sections (inverted tee and rectangular) for buildings were investigated and compared. The height of web in the inverted tee beam was generally less than half of beam depth to be adapted to that of the nib in the ends of double-tee where the total building height limited considerably. The inverted-tee beams were designed for a parking live load - 500kgf/$m^2$ and a market - 1,200kgf/$m^2$ from the currently used typical shape of a domestic building site in Korea. The area and bottom dimension of rectangular beams were the same as those of inverted tee beams. These woo beams were also reinforced with a similar strength. following results were obtained from the studies above; 1) the rectangular beam is simpler in production, transportation, and erection, and more economic than the inverted tee beam in the construction test for these two beams with a same dimension and a similar strength, 2) all of the beams considered in the tests were generally failed in values close to those of the strength requirements in ACI Provisions. The ratios of test result to calculated value are averaged to 1.04. One rectangular and one inverted tee beams failed in a value only 2-3％ larger than the estimated volue of the Strength Design Methool the results of the Strain Compatibility Method wire slightly more accurate than those of the Strength Design Method, 4) the maximum deflections of all of the beams under the full service loads were less than those of the allowable limit in ACI Code Provisions. The rectangular beams experienced more deflection then inverted tee in the same loading condition and failed with more deflection, and 5) the rectangular and inverted tee beams showed good performances under the condition of service and ultimate loads. However, one inverted tee beams with fm span developed an initial flexural crackings under 88％ of the full service load even though they designed to satisfy the ACI tensile stress limit provisions.

• 콘크리트학회논문집
• /
• 제12권6호
• /
• pp.75-82
• /
• 2000

Flexural behaviors of two typical architectural precast beam sections ; inverted tee and rectangular - were compared and investigated. The heights of web in inverted tee beams are generally less than half of beam depth in building structures to accomodate the nib of double-tee where the total building height limited considerably. The inverted-tee beams are designed for parking live load - 500kgf/$\m^2$ and market - 1,200kgf/$\m^2$ according to the currently used typical shape in the domestic market building site in Korea. The bottom dimension and area of rectangular beams are same to those of inverted tee beams to compare the flexural behaviors of two beams. These two beams are also reinforced for similar strength. Four flexural tests are performed on two beams. Following results are obtained from the tests; 1) The rectangular beam is simpler in production, transportation, and election, and more economic than the inverted tee beam for these two beams with same dimension and similar strength. 1) The estimations of flexural strength of two beams by Strength Design Method and Strain Compatibility Method is fully complied with the result of tests. However, Strain Compatibility Method is slightly ore accurate than Strength Design Method. 2) Overall deflections of two type beam under the service loads are less than those of the allowable limit in ACI Code provision. 3) The rectangular beam is failed in large deflection (average 12.56mm large) than those of inverted tee beams. 4) The rectangular and inverted tee beams with 6m span develop initial flexural crackings under the 88% of full service loading even though they designed to satisfy the ACI tensile stress limit provisions.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
• /
• pp.190-193
• /
• 2003

Flexural-torsional behaviors of the typical architectural precast beam sections - inverted tee and rectangular - were compared. The inverted-tee beams were designed with a parking live load - 500kgf/$\textrm{m}^2$ and a market-1,200kgf/$\textrm{m}^2$ according to the currently used typical shape in the domestic market building site. The rectangular beams were also designed as the same bottom dimension and area, and reinforced for similar strength as in the cases of inverted tee beams. Two rectangular and two inverted precast pretensioned concrete beams were tested and analyzed

• 콘크리트학회논문집
• /
• 제16권6호
• /
• pp.733-740
• /
• 2004

본 논문에서는 휨과 비틀림을 함께 받는 전형적인 건축분야의 프리캐스트 프리스트레스트 콘크리트 역T형 보와 직사각형 보의 거동을 연구하였다. 연구 목적을 위하여 국내 건축시장에서 사용되고 있는 주차장 활하중 $5 kN/m^2$ 및 상가 활하중 $12 kN/m^2$ 의 역T형 프리캐스트 프리스트레스트 콘크리트 보를 제작하였다. 또한 같은 길이의 보 밑면과 면적을 갖는 두개의 직사각형 콘크리트 보도 제작하였다. 따라서 설계 활하중과 단면형상이 다른 네 개의 보를 휭과 비틀림의 동시 작용 하에서 실험하여 그 결과를 분석하고 비교하였다. 실험결과 비틀림의 영향으로 시험체 모두 초기 균열 및 극한 휨의 강도가 저하되었다. 그러나 단면형상에 따라 사용하중 및 극한 하중 하에서의 하중 지지력에는 커다란 차이가 없는 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
• /
• pp.71-74
• /
• 2005

The increasement in the floor hight may be one of the most significant problem in the use of precast concrete double slab in the multi-story buildings. The modified double-tees including duct space at the ends of slab were considered in this study. The length and thickness of nib of modified double tee was increased to receive the uniform reaction from rectangular beam, while the original PCI dapped one to receive the point load from inverted tee beam to the leg of double tee. Shear tests were performed on the ends of the modified double tees which were designed by strut-tie model. The modified double tees generally show more ductile flexural failure in the long thickened nib. It is concluded that they show superior failure patterns than that of original dapped one with shear failure.

• 콘크리트학회논문집
• /
• 제13권1호
• /
• pp.46-53
• /
• 2001

본 연구에서는 PCI 방법으로 설계한 직사각형보의 댑 전단거동을 구명키 위해 실물 크기의 두 개의 보 네 개의 댑단부에 대하여 실험하였다. 적용된 설계 활하중 500kgf/$m^2$은 주차장, 1,200kgf/$m^2$은 매장을 위한 국내설계기준이다. 보의 하단폭은 5층 정도의 매장 또는 주차장건물의 하부 기둥크기와 동일하게 60cm로 하였고, 댑의 깊이는 PCI에서 허용하는 최대치 내에서 하부 플랜지높이의 절반을 적용하였다. 대상 실물 실험체는 PCI 설계에 충분히 만족하도록 설계하였으나, 네 개의 실험체중 활하중 1200kgf/$m^2$를 위한 두 개의 실험체는 사용하중이전에 초기균열이 발생되었고 예측강도에 훨씬 못 미치는 하중에서 니브의 수직 전단파괴에 의하여 종국파괴되었다. 니브 수직전단파괴를 일으킨 활하중 1200kgf/$m^2$실험체의 최종 파괴강도는 77.22tonf과 78.36tonf으로 PCI의 81.9tonf과 ACI의 65.62tonf 사이 값으로 ACI의 예측식에 상회하나 PCI 제안 값에 미달하여 발생하였으므로 ACI제안 방식이 안전적인 측면을 고려할 때 더 합리적인 것으로 사료된다. 모든 하중-변형률곡선에서 걸이철근(Ash)의 변형률이 항복변형률에 도달할 정도로 가장 두드러졌다. 강도를 개선하기 위하여 추가적인 경사 걸이 철근이 필요한 것으로 판단된다.