• Structural Engineering and Mechanics
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• v.34 no.5
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• pp.563-580
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• 2010

Composite beams using bolts to attach steel plates to the side faces of existing reinforced concrete (RC) coupling beams can enhance both their strength and deformability. The behavior of those composite beams differs substantially from the behavior of typical composite beams made up of steel beams and concrete slabs. The former are subjected to longitudinal, vertical and rotational slips, while the latter only involve longitudinal slip. In this study, a mixed analysis method was adopted to develop the fundamental equations for accurate prediction of the load-carrying capacity of steel plate strengthened RC coupling beams. Then, a rigid plastic analysis technique was used to cope with the full composite effect of the bolt group connections. Two theoretical models for the determination of the strength of medium-length plate strengthened coupling beams based on mixed analysis and rigid plastic methods are presented. The strength of the strengthened coupling beams is derived. The vertical and longitudinal slips of the steel plates and the shear strength of the anchor-bolt connection group is considered. The theoretical models are validated by the available experimental results presented in a companion paper. The strength of the specimens predicted from the mixed analysis model is found to be in good agreement with that from the experimental results.

• Restorative Dentistry and Endodontics
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• v.43 no.2
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• pp.22.1-22.9
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• 2018

Objectives: To evaluate and compare light-transmittance in dental tissues and dental composite restorations using the incremental double-layer technique with varying layer thickness. Materials and Methods: B1-colored natural teeth slabs were compared to dental restoration build-ups with A2D and B1E-colored nanofilled, supra-nanofilled, microfilled, and microhybrid composites. The enamel layer varied from 0.3, 0.5, or 1.2 mm thick, and the dentin layer was varied to provide a standardized 3.7 mm overall sample thickness (n = 10). All increments were light-cured to $16J/cm^2$ with a multi-wave LED (Valo, Ultradent). Using a spectrophotometer, the samples were irradiated by an RGB laser beam. A voltmeter recorded the light output signal to calculate the light-transmittance through the specimens. The data were analyzed using 1-way analysis of variance followed by the post hoc Tukey's test (p = 0.05). Results: Mean light-transmittance observed at thicker final layers of enamel were significantly lower than those observed at thinner final layers. Within 1.2 mm final enamel resin layer (FERL) thickness, all composites were similar to the dental tissues, with exception of the nanofilled composite. However, within 0.5 mm FERL thickness, only the suprananofilled composite showed no difference from the dental tissues. Within 0.3 mm FERL thickness, none of the composites were similar to the dental tissues. Conclusions: The supra-nanofilled composite had the most similar light-transmittance pattern when compared to the natural teeth. However, for other composites, thicker FERL have a greater chance to match the light-transmittance of natural dental tissues.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.433-445
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• 2009

The panels are used as a composite part of the completed deck. They replace the main bottom transverse deck reinforcement and also serve as a form surface for the cast-in-place concrete upper layer that contains the top of deck reinforcement. Research has also demonstrated that mechanical shear ties on the top of the panels are required. In a composite deck with precast panels, it is required to notice behavior of transverse joints between panels. In this paper, static tests of composite deck with shear ties and loop joints were conducted. From the results, the validity of loop joints for continuity of deck was observed. Also, a composite behavior was abserved between precast panel and slab concrete. Tested composite decks with shear ties have 140~164% ultimate strength than have no shear ties due to the increase of composite action. Therefore, the shear ties between the slabs were sufficient to enforce composite flexural behavior to failure.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.750-753
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• 2004

In this paper, experimental test on the full scale model of steel and concrete composite plate girder with prefabricated slabs under hogging moments was conducted cautiously and observed in order to study cracking in precast decks. Details of prefabricated slab transverse joints were determined from previous research. A test specimen was overhanging simple support beam, totally 28 meter length. Through the 4-point flexural test, the behaviour of the composite girder under hogging moments was observed. From the test results, crack development and crack widths were observed.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.518-523
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• 2003

In domestic composite bridges, it has been reported that most failure is occurred in deck and the type of failure was mainly punching shear failure. Therefore to increase a life of bridges and reduce maintenance costs, an improvement of a durability of slabs is needed. In these respects, precast deck can be very useful. In a composite bridge with precast decks, it is required to notice behavior of transverse joints between decks. In this paper, bending tests of precast deck with loop joints were conducted. From the results, the validity of loop joints for continuity of deck was observed and especially an interval of loop joint, diameter of loop and reinforcement were checked.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.126-133
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• 1997

For each construction material used, there is certain theoretical limit in sizes. For tall building construction, the reduction in slab weight is the first step to take in order to break such size limits. In this paper, the feasibility of such objective is proven and given by numerical analysis result. For a typical building slab, both concrete and advanced composite sandwich panels are considered. The concrete slab is treated as a special orthotropic plate to obtain more accurate result. For each panel, the deflection under the dead and live loads is compared, since both tensile and compressive strengths of the composites are far more higher than those of concrete. All types of sandwich panels considered, except one case, have weights less than one tenth of that of reinforced concrete slab, with deflections less than that of the concrete slab. The cost analysis result and manufacturing methods will be reported later.

• Journal of Industrial Technology
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• v.18
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• pp.97-105
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• 1998

The most of the design engineers for construction has academic background of bachelors degree. Theories for advanced composite structures are too difficult for such engineers and some simple but accurate enough methods are necessary. The senior author has reported that some laminate orientations have decreasing values of $D_{16}$, $B_{16}$, $D_{26}$ and $B_{26}$ stiffnesses as the ply number increases. Such plates behave as special orthotropic plates and simple formulas developed by the author can be used. Most of the bridge and building slabs on girders have large aspect ratios. For such cases further simplification is possible by neglecting the effect of the longitudinal moment terms($M_x$) on the relevant partial differential equations of equilibrium. In this paper, the result of the study on the subject problem is presented.

• Steel and Composite Structures
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• v.1 no.2
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• pp.159-170
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• 2001

The Millennium Tower is situated to the north of the center of Vienna. With a height of 202 m it is the highest building in Austria. Realization was improved by new methods. The tower is a typical example of mixed building technology, combining composite frames with a concrete core. Special attention has been paid to the moment connections between the slim floors and the column tubes resulting in a drastically reduced construction time and thin slabs. The semi-continuity has been considered in the design at ultimate and serviceability limit states.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.2
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• pp.131-137
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• 2000

In order to evaluate the design shear strength of composite slabs with truss-shaped shear connectors(TSC), a series of push-out tests on several types of specimens was carried out. The test results for the two parameters of bearing area and solid angle of the connector were compared to obtain the design shear force of the truss-shaped connectors. The results obtained from this study are as follows: (1) The slip-coefficients of TSC ranges from 0.87 to 3.12(${\times}10^6kgf/cm$). (2) The slip stiffness and the shear strength of TSC with $60.6cm^2$ bearing area are greater than those with $14.6cm^2$. (3) For estimating the allowable shear force of TSC, a design equation that is based on the bearing strength of the connector is suggested. (4) The mean safety factors of the critical force and the ultimate force are 2.38 and 4.62. respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.80-86
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• 2020

In the fabrication process of inverted multi-tee (IMT) slabs, concrete has to be poured twice due to its shape, which is a huge disadvantage as a precast member. To overcome this, a new technique for manufacturing IMT slabs using a slipform method has been recently developed. In this study, flexural and shear tests were carried out to investigate the structural performances of inverted multi-tee (IMT) slabs manufactured using slipform method. To this end, one flexural specimen and two shear specimens with topping concrete were fabricated, and their failure modes and crack patterns, and the slips that occurred between the precast slab and topping concrete were measured and analyzed in detail. In addition, the flexural and shear strengths of the specimens were evaluated by utilizing the structural design code, and a shear strength estimation method, which is suitable for composite IMT slabs with different concrete properties, was proposed for practical design. The IMT slab satisfied the nominal flexural strength calculated by the current design code, and the proposed method provided a good estimation of the shear strength of the specimens.