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Low-rise buildings with columns supporting transfer beams (Soni and Mistry 2006).
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In many high-rise buildings, architectural requirements may result in a variable configuration for the vertical structural elements between the stories of the building. To accommodate such vertical elements’ discontinui-ty, a “transfer” floor conveying vertical and lateral loads between upper and lower stories must be intro-duced. A drawback of the...
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Citations
... Shaking table experiments of scaled models of such buildings were carried out [3,6]. A review of previous research on buildings with transfer floors was summarized by Y.M. Abdlebasset et al and R.K.L. Su [7,2]. The following points of interest were the main points discussed in previous studies. ...
... UBC97 and ASCE7-10 specify a maximum story drift ratio between two successive stories of 1.3 so that the vertical irregularity can be ignored. All storey drift ratios obtained from table 2 are within UBC97 limitation except for the upper storey [7]. It is noted also that the deformation takes the shape of a shear deformation due to the presence of the stiff core walls and ground floor columns. ...
Transfer floors in multi-storey buildings are mainly used to have widely spaced columns below transfer floors to accommodate business areas or other similar purposes, while upper floors, with more suitable spacing of columns or walls, are used for hotels, offices or residence apartments. Transfer floors may take several structural forms most common of which are thick slabs and deep girders. The design of transfer structures is currently outside the codes guidance and require special treatment and engineering judgment. Planted columns or walls on thick plates or deep girders are the usual method of construction of this type of buildings. Transfer slabs were often modelled by designers as rigid diaphragms. Similarly, transfer deep girders were often considered rigid, and as such planted columns and walls on the transfer floors are considered fixed at the bottom. Previous research has recommended that transfer slabs or girders be considered as flexible shells or beam elements not as rigid diaphragms in order to include the effect of the flexibility of transfer floor and capture the true structural behaviour of the transfer floor building. The purpose of this paper is to investigate the behaviour of transfer floor buildings under seismic excitation by modelling transfer slabs as thick shells, rectangular 8-node finite solid elements and as rigid diaphragms. The considered 3-D reinforced concrete building was analysed for gravity and seismic loading using response spectrum and linear time history analysis utilising SAP2000 software. Results of the investigation were summarized, and conclusions were drawn out. It was found that modelling transfer floors by thick shell or rigid diaphragm elements show similar structural results, which are different from 8-node rectangular finite solid elements. Such differences are manifested in longer periods of vibration ((more flexible behaviour), and less vertical displacements of the transfer slab. In all cases, designers have to check punching shear stress in the transfer slab under planted columns.
... A transfer floor is identified to support and transfer the vertical and lateral load to a changed beneath structural system that resisting elements straining actions. Girders or slabs can be considered forms of the transfer systems [1][2][3]. ...
In numerous buildings in KSA, one of the architectural demands to increase the areas of external rooms is shifting the corner columns to the floor edges. The shifted columns (SCs) of the repeated floors (RF) are rested directly on a slab, cantilever, or overhang beam in the ground floor (GF) which considered a fatal mistake in the structural solutions. It is worth noting that, the loads may be transmitted from the shifted columns to the carrying member based on the concept of displacement control rather than load control. Therefore, depending on the rigidity of the cantilever or overhang beam and the slab in RF, the load of SC is transferred to the GF columns. To study the load value and distribution on the GF columns, the 3-D finite element analysis (FEA) was used to simulate the behavior of the existing buildings in KSA under gravity and earthquake loads. The results showed that, the load carried by the shifted column (SC) was based on the rigidity/stiffness of its foundation (the carrying element in the GF) and that of the RF. The rigidity/stiffness of GF, and RF slabs played a vital role in distributing the loads on the adjacent columns. On the other hand, the lower value of drift in the two directions x and y was for soil class A and reignited case. Moreover, the designated building shows the lowest value of drift in both x and y directions while the case of eccentric columns without beams (EN) showed the highest value.
... The limit identifying setback irregularity of frames at the lower 15% of the total height of the frame gives poor results and it is proposed to change this limit to become 30% of the total height of the frame. Abdlebasset et al. presented a state of the art review on recent publications dealing with the seismic behavior of high rise buildings with transfer floor [2]. The transfer system deformation is still ignored and assumption of rigid diaphragm is adopted in design, this concept is not quite correct and simulation in 3-D model should be done using solid element which will lead to stiff transfer system with high shear and flexural stiffness which reduces the deformation of the transfer system under lateral loads. ...
In multifunctional high rise buildings; the transfer systems are introduced to redistribute vertical and lateral loads from the discontinued columns in the upper floors to the lower levels of the building. Only high-rise buildings with single level of transfer floor were mostly studied. However, in some cases the architect may require two or more levels of transfer and it is expected to vary the building response; therefore further studies must be focused on these cases. A number of buildings with different altitudes of double transfer floors were analyzed using nonlinear time history technique using 3D finite element models. The global seismic responses of the buildings were evaluated. In addition, the optimum vertical position of the double transfer was investigated to minimize the bad effect of the transfer floor existence. It can be concluded that the worst seismic performance is in case of buildings with the lower altitude and nearer spacing of the double transfer floors also the irregularity arising from the soft story phenomenon is more pronounced. Additionally, as the distance between the double transfer floors increased, the building stiffness was reduced and therefore the soft story irregularity probability was increased.
... Many high-rise buildings are currently constructed with this kind of vertical irregularity where a "transfer" tool is provided to account for the discontinuous columns and or shear walls. Transfer Structure is a structure, comprising of horizontal deep beams, trusses or thick slabs which transfers load actions and which supports vertical elements above to vertical elements below that are not aligned with each other, through flexure and shear actions [1]. ...
This paper investigates the seismic performance of the buildings with transfer plate provided in two different building models, which further divided into two conditions in which the height of the building and the height of transfer floor itself is taken as variable. Different buildings with storey conditions as G+3+transfer floor+15; G+3+transfer floor+20; G+5+transfer floor+18 are modelled, analysed, designed and finally subjected to nonlinear static or pushover analysis (POA) using computer program CSI SAP 2000. various response factors such base shear, storey drift, roof displacement, inter-storey drift, time period is determined. Transfer Plates with depths ranging from 1m to 3m are used Owing to the irregularity in the elevation in turn, leads to the need for utilizing structural transfer system to transmit the heavy loads from towers vertical structural elements to podium vertical structural elements. One of these transfer systems that are recently becoming common and sometimes even inevitable in modern building developments is the Transfer Plate or slab system. Depending upon the architectural requirements the location of the Transfer Plate is located along the height of the building at the optimum position in the building to attain maximum performance characteristics with thickness of transfer plates ranging from 1m to 3m.
... This type of wall is considered to exhibit poor ductile behavior due to the premature shear failure. Squat walls have been widely used in practical engineering, especially in walls that directly connected with foundation, that located on the upper part of the conversion layer, and that used in the nuclear engineering buildings [1,2]. Because of the requirement for practical applications, many research works were carried out on the following related squat walls. ...
In order to investigate the seismic behaviour of the high strength concrete squat wall with distributed steel tubes, Three squat walls with steel tubes and one RC squat wall were tested. The strength, shear deformation, and energy dissipation capacity of these specimens were analyzed. The test results showed that the load-carrying capacity of the high strength concrete squat wall can be decreased after inserting steel tubes. However, the deformation capacity and the energy dissipation capacity of the squat wall can be improved dramatically when steel tubes are inserted into the section of the wall, especially the squat wall with steel tubes evenly distributed in the section, and as a result, it can be concluded that they are very suitable for application in the conversion layer to improve the collapse resistant capability of structures.
... A transfer floor is known to be the floor system which supports the vertical and lateral load resisting elements and transfer their straining actions to a different underneath structural system. The transfer system itself may take the form of a transfer girders or slabs [1][2][3]. A major drawback of any transfer floor is the abrupt change in the building's lateral stiffness in the vicinity of its level; a direct consequence of such irregularity is that the deformation of a soft-storey mechanism under moderate to severe earthquakes or lateral wind loads imposes high ductility demands on the elements in the vicinity of the transfer floors. ...
... Comprehensive literature review on seismic performance of high-rise buildings with transfer floors is presented elsewhere (Abdelbasset et al. 2016) which also includes a comparative study between different provisions of the most commonly used codes of practice dealing with design of high-rise building with the vertical irregularity resulting from transfer floors. ...
In many high-rise buildings, architectural requirements may result in a variable configuration for the vertical structural elements between the stories of the building. To accommodate such vertical elements’ discontinui-ty, a "transfer" floor conveying vertical and lateral loads between upper and lower stories must be intro-duced. A drawback of the transfer floor is the sudden change in the building's lateral stiffness at its level: the structure becomes susceptible to the formation of a soft-storey mechanism under moderate to severe earth-quakes. These buildings generally showed conventional elastic behaviour for frequent earthquake but suffer extensive crack in the vicinity of the transfer floors for rare earthquake. For design purposes, current numeri-cal modelling of high-rise building adopts reduced stiffness for the vertical elements for strength analysis and full stiffness for serviceability and drift analysis: a tradition that needs to be verified. A 3-D numerical model is built-up for a high-rise building with such vertical irregularities and analysed using elastic response spectrum and nonlinear time-history analysis techniques. The effect of the transfer floors on the buildings’ drift and seismic-generated internal forces is investigated where judgment for adopting a full or reduced stiffness for the vertical elements is scrutinized.
This paper is mainly composed of a comprehensive evaluation and discussion on the progressive collapse performances of outrigger braced reinforced concrete structures with transfer floor. The effects of transfer floor existence, combined use of transfer floor and outriggers, outrigger locations on load redistribution, plasticity development and robustness of structural systems under the sudden failure of the element(s) are the fundamental issues that shape the content of this study. Within this scope, six reinforced concrete systems with transfer floor and differently located outriggers are modelled in SAP2000 finite element program. The pushdown curves are compared through the nonlinear static analysis. For external and corner column cases, the maximum load factors versus vertical drift ratios are obtained in systems with outriggers located at the midheight (0.5H) and top level (H), especially. The differences in deformation characteristics of transfer floor-element interface can be properly limited by modifying outrigger locations and combinations. The hinging development can be much more effectively controlled with outriggers close to the transfer floor. The same tendency is also observed while the vertical spacing between outriggers is decreased, particularly until 0.65H. The results support that the optimized outrigger use develops an efficient alternate load paths under the abrupt element failure.
