Joo-Hong Chung

One-Way Shear Strength of Donut Type Biaxial Hollow Slab Considered Hollow Shapes and Materials

Dept. of Architectural Engineering, College of Engineering, Hanyang University, Seoul 133-791, KoreaABSTRACT This paper presents the shear capacities of biaxial hollow slab with donut type hollow sphere. Recently, varioustypes of slab systems which can reduce self-weight of slabs have been studied for increasing constructions of taller and larger build-ing structures. A biaxial hollow slab system is widely known as one of the effective slab system, which can reduce self-weightof slab. According to previous studies, the hollow slab has low shear strength, compared to solid slab. Also, the shear capacitiesof biaxial hollow slab are influenced by the shapes and materials of hollow spheres. However, the current code does not providea clear computation method for the shear strength of hollow slab. To verify the shear capacities of this hollow slab, one-way sheartests were performed. Four test specimens were used for test parameters. One was conventional RC slab and others were hollowslabs. The test parameters included two different shapes and materials of plastic balls. The shape parameters were donut and non-donut forms and the material parameters were general plastic and glass fiber plastic. The results showed that the shear strengthsvaried depending on hollow shapes and materials used in the slab.Keywords : biaxial hollow slab, hollow sphere, shear strength, experimental study, flat plate slab

Flexural Strength and Stiffness of Biaxial Hollow Slab with Donut Type Hollow Sphere

This paper presents the flexural capacities of biaxial hollow slabs with donut type hollow shapes. Recently, various types of slab systems which can reduce self-weight of slabs have been studied as the height and width of building structures increase. A biaxial hollow slab system is widely known as one of the effective system which can reduce self-weight of slab. A biaxial hollow slab has hollow spheres within slabs in order to reduce self-weight of slabs. The capacities of biaxial hollow slab are influenced by the shapes, volume of hollow spheres. According to analytical studies, the hollow slab with donut type hollow sphere had good flexural capacities such as strength, stiffness and deflection. To verify the flexural capacities of this hollow slab such as strength and stiffness, flexural tests were performed. Three test specimens were planned to verify the effect of test parameters. One was conventional RC slab and others were donut type hollow slabs. The donut type hollow slabs have two different fixing methods of plastic balls. The one is used diagonal steel cage and the other is fixed with only its geometrical shapes without additional steel cage.

An Experimental Study for Bond Characteristics of Deformed Bar Embedded in Donut Type Biaxial Hollow Slab

This study investigated the bond characteristics of embedded deformed steel bar in donut type biaxial hollow slabs. The donut type hollow sphere make concrete inner cover formed between steel bar and hollow sphere due to the hollow shape and arrangement. Generally, inner cover was thinner than outer cover, and some part of donut type biaxial hollow slab has smaller inner cover thickness than . It was affected to the bond condition of deformed bar. Furthermore, inner cover thickness changes along the longitudinal deformed bar due to hollow shape. Therefore, donut type hollow slab was divided 3 regions according to the hollow shape such as insufficient region, transition region, sufficient region. Pull-out test were performed to find out the effect of bond condition by the region. Main parameters are inner cover thickness, embedded length and bond location. Bond characteristics of donut type biaxial hollow slab were confirmed through comparison of bond stress-slip relationship, maximum bond strength and bond stress distribution of each regions. And the calculation method of bond strength of donut type biaxial hollow slab was suggested based on the test results.

Experimental Study on Punching Shear Strength and Failure Behaviour of Donut type Biaxial Hollow slab

This paper presents the punching shear strength and failure behavior of biaxial hollow slab with donut type hollow-shaper. Until now, various types of slab systems which can reduce self-weight of slabs have been studied as the height and width of building structures rapidly increase. A biaxial hollow slab system is widely known as one of the effective slab system which can reduce self-weight of slab. According to previous studies, the biaxial hollow slab has weakness in slab-column connection compared with solid slab. And previous studies pointed out reduced cross-section area of concrete by hollows as the cause. It is assumed in this study that the shape of hollows and the location of hollow-shaper exert influence on the punching shear strength of biaxial hollow slabs. Therefore, donut type hollow-shaper which was suggested as the optimal hollow shape in previous study was used in this study. To verify the punching shear strength and failure behaviour of donut type biaxial hollow slab, punching shear tests were conducted. 4 test specimens were used for test parameters. One was conventional RC slab and 3 were hollow slabs. The test parameter was the area of critical section which were determined by the number of hollow-shaper around the column. The punching shear strength of the donut type biaxial hollow slabs are 87%~103% of solid slabs and superior to generic biaxial hollow slabs. And punching shear cracks occurred at the first perimeter line of donut type hollows.

Estimation Method of Residual Performance for Hollow Slab at Elevated Temperature

Generally, the reinforced concrete slab has great fire resistance performance because concrete has excellent thermal material properties under fire. But, in the case of hollow slab, it will be expected that hollow slabs have different temperature distribution and fire endurance performance compare to reinforced concrete slab. Because hollow slab has internal void space that occurs decreasing regenerative effect of concrete and formation of internal air layer. Evaluation method for fire resistance performance of hollow slabs was proposed using wickstroms method. For the casual use of evaluation, simplified method was proposed which was limited to solid slab and donut type hollow slab which was developed by authors of this research paper. Also, verification on proposed method was performed by comparing results of fire experiment for hollow slab and evaluation results. Proposed method of the results of this study was possible to predict the residual strength and temperature distribution of slabs under fire.