• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.4
• /
• pp.169-178
• /
• 2010

In this study, the optimal strengthening by micro genetic algorithm(${\mu}$-GA) method is proposed for improvement of load-carrying capacity of RC hollow slab bridges using external prestressing. The Qeen-post type and King-post type are considered for the optimal strengthening. The type for optimal strengthening, deviator, areas of tendons and the number of anchor are calculated by ${\mu}$-GA. The objective function is constituted with dimensionless cost of tendon and steel for optimal strengthening. The constraints are formulated by design specification for bridges and anchors. The validity of this study is presented by analysis of the results after the optimal strengthening of the RC hollow slab bridge.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.13 no.6 s.58
• /
• pp.204-211
• /
• 2009

In this study, the optimal method is applied to strengthening of RC hollow slab bridges using external prestressing. The Queen-post and King-post shapes are considered to find the effective tendon configurations. In order to achieve the objective rating factor, the optimal configurations and tendon forces are obtained by using the Sequential Unconstrained Minimization Technique (SUMT). The object function for optimal strengthening is constituted with the dimensionless function of material costs. The constraints are formulated by design specification and the rating factor. The validity of this study is presented by the analysis of the results of strengthening of the RC hollow slab bridges.

• Journal of Korean Society of Steel Construction
• /
• v.16 no.5 s.72
• /
• pp.587-598
• /
• 2004

In this study, an experiment was conducted on the Slim Floor system, using a hollow core PC slab, which could reduce the over-all depth of a composite beam. The Slim Floor system is a method used in steel frame multi-story building construction, in which the structural depth of each floor is minimized after incorporating the steel floor beams within the depth of the concrete floor slab. This experimental study focused on the flexural behavior of the partially connected Slim Floor system with asymmetric steel beams encased in hollow core PC slabs. Ten full-scale specimens were constructed and tested in this study, with different steel beam heights, hollow core PC slabs, slab widths, and PC slab bearings. Observations made in line with the experiments indicated that the degree of shear connection without additional shear connection was 0.48-0.98 times more than that of the full shear connection, due to inherent mechanical and chemical bond stress.

• Journal of the Korea Concrete Institute
• /
• v.14 no.2
• /
• pp.156-163
• /
• 2002

Hollow core slabs generally have not been used for a bridge or a parking slab in Korea. In this study, high performance hollow core slabs, which have been the most thick one in domestic are re-designed and examined for practical use. Flexural tests were performed on four 315mm deep hollow core slabs to investigate adaptability for high vehicle live loadings and composite action with topping concrete. The precast slabs were pre-tensioned with ten strands of 1/2 inch diameter at the lower of slab and four strands of 1/2 inch diameter at the upper of slab, and cast with 80 mm deep topping concrete. Tested hollow core slabs showed ductile failure behaviors which were conformed to the current Ultimate Strength Design Method for a span of 10m up to the live load of 1,000 kgf/㎡. The rectangular md round shear cotters which were used for the composite action between precast and topping concrete, developed sufficient strengths because cracking, even micro had not been developed at the end of slabs up to the pure flexural tensile failure.

• Advances in concrete construction
• /
• v.11 no.4
• /
• pp.271-284
• /
• 2021

This study aims to trace the response of twelve one-way sustainable concrete hollow-core slabs made by reducing cement content and using replacement of coarse aggregate by plastic aggregate. The trial mixes comprise the 25, 50, 75, and 100% replacement of natural coarse aggregate. The compressive strength of the resulting lightweight concrete with full replacement of coarse aggregate by plastic aggregate was 28 MPa. These slabs are considered to have a reduced dead weight due to using lightweight aggregate and due to reducing cross-section through using voids. The samples are tested under two verticals line loads. Several parameters are varied in this study such as; nature of coarse aggregate (natural or recycled), slab line load location, the shape of the core, core diameter, flexural reinforcement ratio, and thickness of the slab. Strain gauges are used in the present study to measure the strain of steel in each slab. The test samples were fourteen one-way reinforced concrete slabs. The slab's dimensions are (1000 mm), (600 mm), (200 mm), (length, width, and thickness). The change in the shape of the core from circular to square and the use of (100 mm) side length led to reducing the weight by about (46%). The cracking and ultimate strength is reduced by about (5%-6%) respectively. With similar values of deflection. The mode of failure will remain flexural. It is recognized that when the thickness of the slab changed from (200 mm to 175 mm) the result shows a reduction in cracking and ultimate strength by about (6% and 7%) respectively.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.1
• /
• pp.1-8
• /
• 2023

At construction sites, interest in the production of precast materials is increasing due to off-site conditions due to changes in construction site conditions due to increased labor costs and the Act on the Punishment of Serious Accidents. In particular, the precast prestressed hollow slab has a hollow shape in the cross section, so structural performance is secured by reducing weight and controlling deflection through stranded wires. With the application of structural standards, the urgency of securing fire resistance performance is emerging. In this study, a fire-resistance cross section was developed by reducing the concrete filling rate in the cross section and improving the upper and lower flange shapes by optimizing the hollow shape in the cross section of the slab to have the same or better structural performance and economic efficiency compared to the existing hollow slab. The PC hollow slab to which this was applied was subjected to a two-hour fire resistance test using the cross-sectional thickness as a variable, and as a result of the test, fire resistance performance (load bearing capacity, heat shielding property, flame retardance property) was secured. Based on the experimental results, it is determined that fire resistance modeling can be established through numerical analysis simulation, and prediction of fire resistance analysis is possible according to the change of the cross-sectional shape in the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.955-960
• /
• 2000

This paper evaluates the serviceability of vibration that is induced by people's walking and running when the long span hollow core slab is used. The dynamic characteristics like a natural frequency and a ramping ratio are found by impact loading test on the mock-up structures. Also, the human induced loading test output is evaluated by the various serviceability criteria. As the various serviceability criteria satisfy with this result, the vibration problem of relevant slab caused by people's behavior does not matter.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2016.05a
• /
• pp.101-102
• /
• 2016

Through the story height reducing method, cost saving can be implemented in many aspects. Recently, as one of PC floor system, HCS(Hollow Core Slab) has been applied in many project, and it is proved that it is excellent in productivity, economic efficiency, and workability as well. We developed a new composite beam(ANI Girder) which can be associated with HCS and reinforced with a truss-shape rebar and angle. As a result of actual application on underground parking building with HCS, it is confirmed that this system is effective in workability and story height reducing.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.6
• /
• pp.91-97
• /
• 2017

The purpose of this study is to get a more precise frequency of hollow core slabs by comparing the observed values from the actual free vibration tests and the predicted values based on the analysis model. The actual free vibration tests were carried out in the construction field using ${\Omega}$ shaped hollow core slabs. Modal analysis is conducted based on the analysis model that takes into account the differences in section properties due to void parts of slab. The differences between the predicted values based on the modal analysis with analysis model and the measured data from the actual tests range from 2~7%. This study demonstrates that the analysis model that incorporates void parts of slab could be used in evaluating serviceability of hollow core slabs with reasonable accuracies.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.5
• /
• pp.182-189
• /
• 2021

VPS(Void Plywood Slab System, VPS) has optimized the shape of the hollow material. In addition, it has a function to prevent the floating of the hollow material and the separation due to the working load. In this study, the punching shear capacity of flat plate was performed using Void Plywood Slab System with form work panel proposed in the previous study. As a result of the test, the strength of the VSPS specimen in which the hollow material was placed beyond 2.0 times the column width from the loading point was reduced by 9.4% compared to the reference specimen. However, the strength value was about 1.57 times higher than the design value suggested by KBC 2016. It was found that there was no change in stiffness compared to the reference specimen until shear failure occurred in the VSPS specimen in which the hollow material was placed. It can be seen that this experiment is being destroyed by shear as the flexural reinforcing bars are sufficiently reinforced.