Podium Structure Research Articles

Estimation of Shrinkage Effects on Reinforced Concrete Podiums

The shrinkage of concrete often creates cracking problems in large podium structures. The long-term effects of shrinkage and creep in a concrete structure may be estimated by analysing it as a plane stress problem with the supporting walls and columns modelled as springs having suitable stiffnesses. The variation of stresses and strains may be obtained by time integration based on the conventional creep coefficient, time-dependent concrete modulus and shrinkage strain. Using a simplified one-dimensional model, the effects of structure size, support stiffness and stage construction on the induced stresses are investigated. Results show that the magnitude of induced stress normally increases with the member length and support stiffness. The rate of stress increase also depends on the support stiffness. An extensive parametric study is carried out to investigate the use of stage construction in controlling shrinkage stresses particularly focusing on the effect of time-lag and size of late-cast strip. Design ...

Semiactive Seismic Response Control of Buildings with Podium Structure

A multistory building with a large podium structure under earthquake excitation may suffer from whipping effect due to the sudden change of building lateral stiffness and mass at the top of the podium structure. An experimental investigation was carried out in this paper to explore the possibility of using magnetorheological (MR) dampers to connect the podium structure to the multistory building to prevent the whipping effect. The multistory building was constructed as a slender 12-story building model, whereas the podium structure was built as a relatively stiff three-story building model. A MR damper together with a current controller was used to link the three-story building to the 12-story building. The dynamic characteristics of the two buildings without any connection and with a rigid connection were first identified. The two building models without any connection and with the rigid connection were then tested under the scaled El Centro 1940 north–south ground motion. Finally, the two building model...

Seismic response control of a complex structure using multiple MR dampers: experimental investigation

This paper presents an experimental investigation on semi-active seismic response control of a multistory building with a podium structure using multiple magnetorheological (MR) dampers manipulated by a logic control algorithm. The experiments are performed in three phases on a seismic simulator with a slender 12-story building model representing a multi-story building and a relatively stiff 3-story building model typifying a podium structure. The first phase of the investigation is to assess control performance of using three MR dampers to link the 3-story building to the 12-story building, in which seismic responses of the controlled two buildings are compared with those of the two buildings without any connection and with rigid connection. The second phase is to investigate reliability of the semi-active control system and robustness of the logic control algorithm when 2 out of 3 MR dampers fail and when the electricity supply to MR dampers is completely stopped. The last phase is to examine sensitivity of semi-active control performance of two buildings to change in ground excitation. The experimental results show that multiple MR dampers with the logic control algorithm can achieve a significant reduction in seismic responses of both buildings. The proposed semi-active control system is of high reliability and good robustness.

Innovative Technology for Seismic Response Reduction of Tall Buildings with Podium Structures

Structural controf technology offers many new ways to proted structures from naturol hazards. A comprehensive experimental Investigation was carried out in The Hong Kong Polytechnic University to apply multiple magnetorheological (MR) dampers to connect podium structures to tall buildingsfar preventing seismic damage due to sudden change of lateral stiffness and mass. A slender 12-storey building madel and a relatively stiff 3-storey bUilding model were construded to represent a tall building and a podium strudure respectively. MR dampers were used to link the 3-storey building to the 12storey building at each of the bottom three storeys. The two buildings without any connedlon and with a rigid connedian weref/rst tested under scaled EI Centro 1940 N-S ground motion. A test was then performed on the two buildings connected by MR dampers manipulated by a semi-adive logic control algorithm. Finally, reliability of the seml-adive cantrol system and robustness of the semi-adive logic control algorithm were ex...

Semi‐active control of seismic response of tall buildings with podium structure using ER/MR dampers

AbstractA tall building with a large podium structure under earthquake excitation may suffer from a whipping effect due to the sudden change of building lateral stiffness at the top of the podium structure. This paper thus explores the possibility of using electrorheological (ER) dampers or magnetorheological (MR) dampers to connect the podium structure to the tower structure to prevent this whipping effect and to reduce the seismic response of both structures. A set of governing equations of motion for the tower–damper–podium system is first derived, in which the stiffness of the member connecting the ER/MR damper to the structures is taken into consideration. Based on the principle of instantaneous sub‐optimal active control, a semi‐active sub‐optimal displacement control algorithm is then proposed. To demonstrate the effectiveness of semi‐active control of the system under consideration, a 20‐storey tower structure with a 5‐storey podium structure subjected to earthquake excitation is finally selected as a numerical example. The results from the numerical example imply that, as a kind of intelligent control device, ER/MR dampers can significantly mitigate the seismic whipping effect on the tower structure and reduce the seismic responses of both the tower structure and the podium structure. Copyright © 2001 John Wiley & Sons, Ltd.

Scope Twin-Tower Complex, Delhi

The twin-tower office complex under construction at Laxmi Nagar, Delhi is a part of the District Centre being developed by the Delhi Development Authority. The structure is in the form of two high-rise curvilinear tower blocks, rising above a four-storey circular podium block and includes two basements for parking and a central mushroom. Both towers are of different heights, the taller tower with a total of 22 storeys and the other tower with a total of 17 storeys, including provision of a heliport over the terrace. The total built-up area in both the towers, the four-storeyed low level structure and the two basements, is over 100,000 square meters. The diameter of podium structure at its base is about 110 m, which gives an idea of the large size of the structure.