Flat Plate Frame Research Articles

Analysis of Dynamic Response of RC Flat Plate Frame’s Performance under Dynamic Loads

The progressive collapse of structures under accidental actions is a serious threat to the public safety. Numerical analysis of a 2x2-bay and single-story reinforced concrete flat plate frame model is done in this paper, the time of failure and the position of failure column are taken into account. It can be found that the Dynamic Amplification Factor (DAF) increases with the decrease of failure time, the DAF under compressive membrane action is less than the stage of the tensile membrane action and the compressive membrane action is more important to avoid progressive collapse. When the time of failure is not changed, the DAF is negatively correlated with the load under compressive membrane action and the DAF is positively correlated with the load under tensile membrane action.

Effective Structural System for the Affordable Housing Construction

This article falls within vital question in quickly builds construction – theoretical method for calculating the slabs and columns of such buildings. Calculation research of buildings with reinforced concrete frame slabs is described in the article. The features of work the collapsible flat plate ceiling in composition of reinforced concrete framework of building are analyzed. Problems in the design of framework building are considered in order to increase its reliability. The suggestions for directions of perfection the calculation of flat plate frame construction elements are proposed in the article. The novelty of this work is to get new theoretical data about bearing capacity and deformability of structural system for the affordable housing construction from reinforced concrete.

Seismic performance evaluation for gravity-designed flat plate frames

Most existing reinforced concrete (RC) buildings in regions of low and moderate seismicity have been designed only considering gravity loads. Gravity-designed RC flat plate frames may be more vulnerable than RC frames with beams and columns owing to the potential for abrupt and brittle punching shear failure at slab–column connections. This study evaluates the seismic performance of gravity-designed three- and seven-storey flat plate frames, which were assumed to be located at sites having low, moderate and high seismic risks. An analytic model for simulating the hysteretic behaviour of slab–column connections obtained from experiments was proposed. It was found that the level of gravity load as measured by the gravity shear ratio significantly affects the inelastic behaviour of flat plate frames. The frames satisfied the basic safety objective (BSO) specified in AISC 41 subjected to ground motions at the Boston site, but not at the Seattle and LA sites.

Effect of slab bottom reinforcement on seismic performance of post-tensioned flat plate frames

The purpose of this study is to evaluate the seismic performance of gravity-designed post-tensioned flat plate frames with and without slab bottom reinforcement passing through the column. In low and moderate seismic regions, the seismic demands may not control the design, and buildings are often designed considering only gravity loads. This study focuses on the seismic performance of gravity load designed post-tensioned flat plate frames. For this purpose, three-, six- and nine-storey post-tensioned flat plate frames are designed considering only gravity loads. For reinforced concrete flat plate frames, continuous slab bottom reinforcement (integrity reinforcement) passing through the column should be placed to prevent progressive collapse; however, for the post-tensioned flat plate frames, the slab bottom reinforcement is often omitted since the requirement for the slab bottom reinforcement for post-tensioned flat plates is not clearly specified in ACI 318-05. This study evaluates the seismic performance of the model frames by conducting non-linear static pushover analyses and non-linear response history analyses. For conducting non-linear response history analyses, six sets of ground motions are used as input ground motions, which represent two different hazard levels (return periods of 475 and 2475 years) and three different locations (Boston, Seattle and Los Angeles). An analytical model is developed for emulating the non-linear hysteretic behaviour and the failure mechanism of post-tensioned slab–column connections. This study shows that gravity-designed post-tensioned flat plate frames have some seismic resistance. In addition, the seismic performance of post-tensioned flat plate frames is significantly improved by placing slab bottom reinforcement to pass through the column.

Stiffness reduction factor for post-tensioned flat plate slabs

The effective beam width model (EBWM) has been used for estimating force and drift demands on flat plate frames under lateral loads. The accuracy of this model depends strongly on how to estimate the effective stiffness of flat plate slabs. With an increase in slab moments due to lateral loads, slab cracks occur and propagate on the slab, which leads to a reduction in slab flexural stiffness. For post-tensioned (PT) flat plate slabs, the initiation and propagation of slab cracks can be delayed due to slab in-plane compressive stress induced by PT tendon forces. This study investigates the contribution of slab in-plane compressive stress to the slab stiffness reduction factor, which is defined as the ratio of slab stiffness obtained from a cracked slab section to that from the corresponding uncracked slab section. For this purpose, this study collected the test results of PT flat plate slab–column connection specimens and estimated the slab stiffness reduction factors (β) for those specimens with respect to a level of applied slab moment. Non-linear regression analysis is used to propose an empirical equation computing β for PT flat plate slabs using β estimated from the test results. The accuracy of the empirical equation for β is verified by comparing the lateral stiffness of a two-storey PT flat plate frame, obtained using the EBWM with the empirical equations for β, with that estimated from shaking table test results on the frame.

Modal Experiment on RC Flat Plate Frame and Identification of Interior Column Damage

Damage identification and health monitoring is an important aspect in the evaluation of structural safety recently. This paper presents a modal experiment and analysis of a 2×2 bay (6.128m×6.128m) 1 storey (1.4m) RC flat plate frame structure on rigid foundation. The displacement mode experiments were carried out by hammer-hitting excitation method in the age of frame concrete. The varieties of the modal parameters of the flat plate were obtained by dynamic testing along with the growth of elastic modulus of concrete and change of the environment temperature. it can be used to identify the location and form of the damage. Base on the missing of some specific structure modal shapes and reduction of the frame horizontal stiffness, it can be revealed that the interior slab-column connection cannot transfer the unbalance moment well. Further more, modal parameters of the RC flat plate with the interior column removed had been exhibited and discussed. A 3-D solid finite element models with the interior column fixed/hinged were constructed, they were validated to match the frame natural frequencies and mode shapes. The results demonstrate the effectiveness of modal parameters identification method in estimate the damage of column in RC flat plate frame. Additionally, the dynamic modulus of elastic is obtained by the comparison of experimental test and FEM simulation analysis.

Trailing-edge scalloping effect on flat-plate membrane wing performance

This investigation studies the effect of trailing-edge scalloping on the lift and drag force coefficients of flat, membrane wings that vibrate at low Reynolds numbers ( < 61 , 000 ). A series of rigid, flat plate frames with moderate aspect ratio and repeating membrane cell structure were studied and compared to a rigid plate and a rigid scalloped plate. Lift and drag measurements were acquired using an external force-balance; flow fluctuation measurements were captured with a hot-wire. Results showed that the size and aspect ratio of the latex cell had a greater impact on lift than scalloping and that scalloping had a greater effect on drag than the cell aspect ratio. Compared to the solid wings, the membrane wings exhibited higher lift and drag coefficients, likely due to both effective cambering and dynamic interaction with the free shear layer. While trailing-edge scalloping decreased both the lift and drag coefficients relative to no scalloping, the greater effect was on drag, thus, increasing aerodynamic efficiency. The maximum lift-to-drag ratio was attained for a 25% scallop with a repeating cell aspect ratio of one. A unique nondimensional scaling of the membrane vibration peak frequency is also presented.

Effective beam width for flat plate frames having edge beams

The effective beam width method has been widely used to predict lateral drifts and slab moments in flat plate frames subjected to lateral loads. However, the effective beam width method may not account for the contribution of the lateral stiffness provided by edge beams of the frames. This study examines the contribution of edge beams to the lateral stiffness of flat plate frames using the results of prior analytical and experimental research. It was observed that the lateral stiffness of flat plate frames with edge beams is larger than that of corresponding frames without edge beams. To account for the effect of the edge beam contribution on the effective beam width method, this study proposes a factor that modifies the effective beam width in the effective beam width method. To verify the accuracy of the effective beam width method with the proposed modification factor, this study estimated the lateral stiffness of the two-storey frames using the effective beam width method with the proposed modification factor, and compared that estimate with the lateral stiffness determined using experimental test results.

중력하중으로 설계된 포스트텐션 플랫플레이트 골조의 내진성능

The purpose of this study is to evaluate the seismic performance of gravity-designed post tensioned (PT) flat plate frames with and without slab bottom reinforcement passing through the column. In low and moderate seismic regions, buildings are often designed considering only gravity loads. This study focuses on the seismic performance of gravity load designed PT flat plate frames. For this purpose, 3-, 6- and 9-story PT flat plate frames are designed considering only gravity loads. For reinforced concrete flat plate frames, continuous slab bottom reinforcement (integrity reinforcement) passing through the column should be placed to prevent progressive collapse; however, for the PT flat plate frames, the slab bottom reinforcement is often omitted since the requirement for the slab bottom reinforcement for PT flat plates is not clearly specified in ACI 318-08. This study evaluates the seismic performance of the model frames, which was evaluated by conducting nonlinear time history analyses. For conducting nonlinear time history analyses, six sets of ground motions are used as input ground motions, which represent two different hazard levels (return periods of 475 and 2475 years) and three different locations (Boston, Seattle, and L.A.). This study shows that gravity designed PT flat plate frames have some seismic resistance. In addition, the seismic performance of PT flat plate frames is significantly improved by the placement of slab bottom reinforcement passing through the column.

중력전단비에 따른 철근콘크리트 플랫 플레이트 골조의 내진 성능 평가

Dept. of Architectural Engineering, Hanyang University, Seoul 133-791, KoreaABSTRACT This study evaluates the seismic performance of reinforced concrete (RC) flat plate structures relation to the gravity shearratio. For this purpose, 3 and 7 story framed buildings were designed for gravity loads only. Subsequently, a nonlinear static pushover anal-ysis and a nonlinear time history analysis for the prototype buildings were carried out. In the nonlinear analysis, newly propose analyticalslab-column joint model was utilized to capture punching shear failure and fracture mechanism in the analysis. The analytical resultsshowed that seismic performance of RC flat plate frame is strongly influenced by the gravity shear ratio. In particularly, in the RC flatplate frame with a large gravity shear ratio the lateral strength and maximum drift capacity decreased significantly.Keywords : reinforced concrete flat plate, gravity shear ratio, static pushover analysis, lateral strength, maximum drift capacity

한계상태모델을 이용한 철근콘크리트와 포스트텐션 무량판의 통합해석

2층 규모의 철근콘트리트조 및 포스트텐션조 무량판구조를 1/3 스케일로 축소하여 제작한 실험체의 진동대 실험 결과를 바탕으로 무량판구조의 모델링 기법을 향상하고자 하는 연구를 수행하였다. 이 연구에서 적용한 모델링 방법은 슬래브의 휨모멘트에 의한 휨파괴, 불균형모멘트의 전달에 의한 휨파괴 및 펀칭전단파괴에 의한 슬래브-기둥 접합부의 모멘트 전달능력 상실등의 영향을 반영하는 매우 포괄적인 구조해석 방식이다. 펀칭전단파괴에 대해서는 중력비와 층간변위각에 기초한 한계상태 모델이 적용되었다. 이 논문에서 제안된 비선형 모델은 무량판구조의 진동대 실험 결과와 잘 부합하는 것으로 나타났다.

횡하중하의 포스트 텐션 플랫 플레이트 해석을 위한 강성감소계수

횡하중을 받는 포스트 텐션(PT) 플랫 플레이트 슬래브 골조의 해석은 일반적으로 유효보폭모델을 많이 사용한다. 횡 변위비와 불균형 모멘트을 예측하기 위한 유효보폭모델의 정확성은 PT 플랫 플레이트 슬래브의 유효강성을 어떻게 평가하느냐에 달려 있다. 슬래브 강성은 횡하중에 의한 작용모멘트의 증가와 함께 감소되기 때문에, 슬래브의 강성 감소현상은 플랫 플레이트 골조의 해석에 반영되어야 하며 균열의 영향 또한 고려되어야 한다. 횡하중을 받는 PT 플랫 플레이트 슬래브 구조의 정확한 해석을 위해 슬래브 강성감소는 유효보폭모델이 정확하게 되어야 한다. 이 목적을 위해 이 연구는 기존 연구자들에 의해 실시된 PT 플랫 플레이트 내부 및 외부 접합부의 실험 결과를 수집하였다. 그리고 이 연구는 시행착오를 통해 각 실험체의 횡강성에 유효보폭모델의 강성이 수렴하도록 슬래브의 폭을 감소시켰다. 슬래브의 모멘트 크기에 따라 비선형 회귀 분석을 수행함으로서 슬래브에 대한 강성감소계수 계산식을 제안하였다. 이 연구에서는 제안된 식의 정확성을 검증하기 위해서 PT 플랫 플레이트 골조의 실험 결과와 비교하였다. 제안된 식을 적용한 유효보폭모델은 작용하중의 크기에 따라 변화하여 PT 실험체의 실제 강성을 잘 예측하는 것으로 나타났다.

A modified equivalent frame method for lateral load analysis

The equivalent frame method (EFM) was developed for two-way slabs as a simple approximate method. Current design codes (ACI 318-05, Eurocode 2 and BS 8110) permit the EFM for the analysis of two-way slab systems under gravity loads, as well as lateral loads such as seismic loads. The EFM, however, was developed based on a semi-empirical formula, derived from the behaviour of two-way slab systems under gravity loads. This study shows that the EFM is not appropriate in accurately predicting the response of two-way slab systems under lateral loads. To improve the EFM under lateral loads, this study proposes a modified equivalent frame method (MEFM). To verify the MEFM, an idealised two-storey flat plate frame is considered and analysed by both the MEFM and elastic finite-element (FE) analysis for estimating slab moments and lateral drifts. Analysis results obtained from the conventional EFM and effective beam width method (EBWM) are also compared. The lateral stiffness, based on the proposed MEFM, was also compared with experimental data.

하부 철근 유무에 따른 포스트 텐션 플랫 플레이트 골조의 내진성능 평가

This study evaluates the seismic performance of post-tensioned flat plate structures with or without slab bottom reinforcement. For this purpose, 3 and 9 story frames were designed only considering gravity loads. This study conducts a nonlinear static pushover analysis. This study was an analytical model that is able to represent punching shear failure and fracture mechanism. The analytical results showed that the seismic performance of a post-tension flat plate is strongly influenced by the existence of slab bottom reinforcement through column. By placing slab bottom reinforcement in a PT flat plate frame, lateral strength and max drift capacity are significantly increased.

Fracture Model for PT Flat Plate Connections under Seismic Loading

Post-tensioned (PT) flat plate frames are commonly used to support gravity load in connections in high seismic regions. But test results of many studies indicated that PT flat plate connections were possessed of later-resisting capacity for lateral load though this capacity is not enough to be used by itself in high seismic regions. So this study evaluated the cyclic behavior of PT flat plate connections and developed an analytical model for predicting nonlinear behavior of those to estimate the seismic performance of PT flat plate frames accurately. For this purpose, the test results of static pushover test and shaking table test of 2 story PT flat plate frame were used to evaluate the characters of failure mode for PT flat plate connections and to compare with analysis results. The test results indicated two failure modes which are classified the shear failure mode or the moment failure mode as for shear strength of PT connections to resist lateral loads acted on the specimens. So the analytical model was designed to consider these failure modes of PT connections and the results of comparing with test results predict the nonlinear behavior of PT connections.

Seismic design of concrete slabs for punching shear: a critical review of Canadian standard CSA A23.3-04

Unbalanced moments, transferred between concrete flat plates and columns due to earthquakes, produce shear stresses that increase the vulnerability to brittle punching failure. Appropriate design and detailing of the slab–column joints are essential to prevent such failure. Because of the high flexibility of flat plate structures, lateral-force-resisting systems, e.g., bracings, frames or shear walls, are necessary to limit the interstorey drift ratio to specified values. The slab–column joints must have the strength and the ductility to undergo, without punching failure, the lateral displacement of the structure. In the 2004 version of the Canadian standard, CSA A23.3-04, clause 21.12.3 is added, specifying the punching shear design of slab–column connections subjected to earthquakes. The provisions of the clause are critically reviewed using a design example. It is shown that the new clause permits absence of shear reinforcement in cases that lack strength and when it requires shear reinforcement, it specifies excessive amount. Changes to the standard are proposed.

포스트 텐션 플랫 플레이트 골조의 해석모델

본 연구에서는 PT 플랫 플레이트 골조의 내진성능을 평가하기 위하여 비선형 거동을 예측할 수 있는 해석모델을 개발하였다. 특히 본 연구에서 개발한 해석 모델은PT 플랫 플레이트 슬래브-기둥 접합부에서 기둥을 관통하는 철근이 있는 경우와 없는 경우의 접합부 거동을 정확하게 예측할 수 있도록 개발하였다. 또한 본 연구에서 개발한 접합부 해석 모델은PT 플랫 플레이트 슬래브-기둥 접합부에서 뚫림 전단 파괴가 발생하는 때를 정확하게 예측하도록 하였다. 개발한 해석 모델의 타당성을 검증하기 위하여PT 플랫 플레이트 슬래브-기둥 접합부 실험결과와 해석 결과를 비교하였다. 또한 2층 PT 플랫 플레이트 골조의 진동대 실험결과와 해석결과를 비교하였다. 본 연구에서는 기둥을 관통하는 철근이 있는 접합부와 없는 접합부를 갖는 2층 PT 플랫 플레이트 골조를 세 가지의 크기로 조정한El Centro 지진에 대하여 비선형 동적 해석을 수행하였다. 지진의 크기가 커지면 하부 철근이 없는 골조의 요구 변위와 잔류 변형이 하부 철근이 있는 골조에 비하여 더욱 커지는 것으로 나타났다. This study developed an analytical model for predicting nonlinear behavior of PT flat plate frames having slab-column connections with and without slab bottom reinforcement passing through the column. The developed model can predict the failure sequence until punching failure occurs. For verifying the analytical model, the test results of PT flat plate slab-column connections were compared with the results of the analysis. Moreover, the results of static pushover test and shaking table test of 2 story PT flat plate frame were compared with analysis results. For evaluating seismic performance of PT flat plate frame, this study conducted nonlinear response history analysis of the 2 story PT flat plate frame with and without slab bottom reinforcement passing through the column under 1940 El Centro ground motion scaled to have pseudo spectral acceleration of 0.3, 0.5, and 0.7g at the fundamental period of the frame. This study observed that as ground motion is more intense, seismic demands for the frame having the connections without slab bottom reinforcement passing through the column are larger than those without slab bottom reinforcement.

Lateral Load Response of Flat‐Plate Frame

Lateral‐load response of a flat‐plate frame under simulated earthquake base motions is examined. The test structure is a three‐tenths scale model of a two‐story, three‐bay flat plate frame, which was designed and detailed according to current procedures for beamless slabs in regions of moderate seismic risk. Overall resistance to low, moderate, and high intensity base motions is examined, and design‐oriented methods to evaluate lateral‐load stiffness and strength are examined. It is concluded that the design resulted in a flexible but reasonably tough structural system. Relatively simple procedures to evaluate stiffness and strength are presented and found to be acceptably accurate for the test structure.

Lateral Load Resistance of Unbonded Post-Tensioned Flat Plate Construction

Two-way post-tensioned flat plate construction is commonly used for both highand low-rise structures such as parking garages, apartments, offices and industrial buildings. Two forms of construction are used: slabs cast monolithically with columns and lift slabs. For both forms, economics and speed of construction considerations usually dictate that slabs be post-tensioned with unbonded tendons. For moderate earthquakes and high winds, the response of a structure should be essentially elastic. For that condition, accurate information is needed on the lateral load stiffness of the flat plate frame and its attachments. For severe earthquakes or extremely high winds, the structure should be able to absorb and ultimately dissipate large amounts of energy. Under the deformations and moments caused by that condition, punching failures should not occur at plate-to-column connections. The main objective of this study was to determine the factors dictating the strength and stiffness of prestressed concrete plate-to-column connections transferring moments. Frequently, in order to make the