• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.653-659
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• 2002

Recently, the failure case of the bridge deck slabs have been increasing in Korea and it was observed that the failure modes of most deck slabs collapsed were not caused by flexural moment but by local punching shear. The main reason of the failures was the punching shear failure of deck slabs under heavy truck traffics. This paper presents test results obtained from punching shear tests performed on prestressed precast deck specimens. Cracking patterns, failure modes, deflections, and stresses are included as well as discussion of the punching shear strength observed during punching shear tests. Static lest specimens had punching shear failures at loads much higher than predicted by the current codes. Tests results indicate that current code provisions appear to be conservative.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.523-530
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• 2008

In structural design provision, maximum punching shear stress of slabs is prescribed as combined stress in direct shear occurred by gravity load and eccentric shear occurred by unbalanced moment. This means that the effect of unbalanced moment is considered to decide the punching shear stress. However, from the resistance capacity standpoint, the effect of unbalanced moment strength is not considered for deciding punching shear strength. In this paper, a model considering interrelation between unbalanced moment and punching shear was proposed. In the model, the relation between load effect and resistance capacity in unbalanced moment and punching shear was two-dimensionally expressed. Using the interrelation model, a method how unbalanced moment strength should be considered to decide the punching shear strength was proposed. Additionally, effective width enlargement factors for deciding the unbalanced moment strength of flat plates with shear reinforcements were proposed. The interrelation model proposed in this paper is very effective for the prediction of the behavior of slab-column connection because not only punching shear and unbalanced moment strengths but also failure modes of flat plates can be accurately predicted.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.187-196
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• 2008

The punching shear strength of RC slabs is estimated analytically by the simple truss model. To avoid intrinsic difficulties in punching shear analysis of reinforced concrete slabs, the slabs were divided into three sub-structures as the punching cone and the remaining parts. The strength of the punching cone was evaluated by the stiffness of inclined strut. The stiffness of springs which control lateral displacement of the roller supports consists of the steel reinforcement which passed through the punching cone. Initial angle of struts was determined by curve fitting method of the experimental data with variable reinforcement ratio in order to compensate for uncertainties in the slab's punching shear, the simplification errors and the stiffness of the remaining sub-structures. The validity of computed punching shear strength by simple truss model was shown by comparing with experimental results. The punching shear strength, which was determined by snap-through critical load of shallow truss, can be used effectively to examine punching shear strength of RC slabs.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.33-36
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• 2009

현행 도로교설계기준의 바닥판에 대한 설계방법은 휨 이론에 따라 바닥판을 단위 폭의 보로 보고 강도설계법으로 설계하고 있다. 그러나 실제 교량 바닥판의 파괴 형태는 펀칭에 의한 파괴이므로 바닥판의 극한성능은 펀칭전단강도를 토대로 평가해야 할 것이다. 하지만 기존에 연구된 결과로는 초간편 강합성 바닥판의 펀칭전단강도를 산정하기 어려워 이에 대한 연구가 필요한 실정이다. 본 연구에서는 개발된 초간편 강합성 바닥판의 펀칭전단성능을 파악하기 위하여 초간편 강합성 바닥판과 RC바닥판에 대한 펀칭전단실험을 실시하여 비교하여 보았다.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.23-30
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• 2009

According to Korea Highway Bridge Design Code the bridge deck is designed by the strength design method and is regarded as a beam possessing the unit width based on the bending theory. By many researches it is revealed that the existing bridge deck is failed by punching shear. For evaluating the ultimate capacity of bridge deck it is important to estimate the behavior of bridge deck under the punching shear. For the punching strength it is difficult that the existing research results are applied to the simplified composite deck. In this study for comparing characteristics on punching shear the punching shear tests on simplified composite deck and RC deck are performed. The punching shear strength of simplified composite deck is compared with several bridge design codes.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.149-152
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• 2008

In structural design provision, maximum punching shear stress of slabs is prescribed as combined stress of direct shear occurred by balanced gravity load and eccentric shear occurred by unbalanced moment. This means that the effect of unbalanced moment is considered to decide the punching shear stress. However, from the resistance capacity standpoint, the effect of unbalanced moment strength is not considered for deciding punching shear strength. For this problem, a model to show unbalanced moment-punching shear interrelation was proposed. In the model, the relation between load effect and resistance capacity in unbalanced moment-punching shear was two-dimensionally expressed. Using the interrelation model, a method how unbalanced moment strength should be considered to decide the punching shear strength was proposed. Additionally, a effective width enlargement factor for deciding the unbalanced moment strength of flat plates with shear reinforcements was proposed. The interrelation model proposed in this paper is very effective for the design because not only punching shear and unbalanced moment strengths but also failure modes of flat plates can be accurately predicted.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.361-367
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• 2014

This paper investigates the punching shear strength of lightweight aggregate concrete (LWAC) slabs through a series of experimental study. Five full scale slabs were constructed using normal concrete and four different types of LWAC. Each lightweight aggregate (LWA) used in this study had different sources (clay, shale, or slate) and shapes (crushed or spherical shape). Based on the test results, the effect of the lightweight aggregates (LWA) on the punching shear behavior was investigated. From the test results, it was found that the punching shear failure surface of LWAC slab with spherical shape coarse aggregate was less inclined than that with crushed shape coarse aggregate, which resulted in an increase of the area of the shear failure surface. As a result, it leads to the increased punching shear strength of the slab. On the other hand, the failure surfaces of LWAC slab with crushed shape coarse aggregate and normal coarse aggregate were inclined similarly. Finally, the test results of this study were compared with the punching shear strength obtained from current design models, such as ACI and CEB-FIP, to examine the validation of current design model to predict the punching shear strength of the LWAC slab.

• Journal of Korean Society of Steel Construction
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• v.24 no.4
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• pp.423-433
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• 2012

This paper summarizes full-scale gravity-load test results on CFT column-to-RC flat plate connections reinforced with shearhead. CFT construction has many structural and constructional advantages over conventional steel and RC column construction and is gaining wide acceptance. Meanwhile the use of RC flat plate system in the basement and residential floors of tall buildings is often mandatory to reduce story height and enable rapid construction in domestic practice. Combining CFT column and flat plate floor is expected to result in further rapid construction. However, the issues related to connecting CFT column to RC flat plate have not been fully addressed yet. Several promising connecting schemes by using steel shearhead were proposed and tested in this study. Test results showed that the proposed connection can exhibit the punching shear strength higher than RC flat plate counterparts. An empirical formula that can reasonably predicts the punching shear strength of the proposed connection was also proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.219-228
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• 2006

Because of the advantage of light weight, lightweight concrete is frequently applied to long-span bridges and high-rise buildings. In the country, there is not enough experience for the long-span bridges using lightweight concrete. This paper presents results of an experimental study on the punching shear strength of high-strength lightweight concrete slabs. Four test slabs are fabricated using high-strength lightweight concrete and normalweight concrete and at the center of the test slabs, simulated wheel load is applied until failure. The compressive strengths of lightweight concrete and normalweight concrete are 47MPa and 32MPa, respectively. The test results show the failure mode of all specimens are punching shear and the behaviors of high-strength lightweight concrete slabs are very similar to that of normalweight concrete slabs. Based on the test results, it is discussed the safety and serviceability of high-strength lightweight concrete bridge decks.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.185-188
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• 2008

Flat plate system has structural weakness such as punching shear. Punching shear resistance can be increase by using a lager column section and effective depth, higer concrete compressive strength, and more flexural reinforcement ratio. But using a shear reinforcement is most economical, enable, workable solution in flat plate. The slab with thickness smaller than 250mm can not perform effectively due to insufficient development length of shear reinforcement in the slab. In case of proposed reinforcements, since the shear reinforcements were installed between the top bar and the bottom bar, shear elements generated slip failure before they reached yield. strength. effect of anchorage strength were effective anchorage length, concrete strength, diameter of shear element and anchorage detail. considering effect of slab thickness and concrete strength, formula of K factor propose in thin flat plate slab. by considering effect of anchorage length and concrete strength, strength of shear reinforcement will be computed correctly in thin flat plate slab.