Seismic Performance Evolution of Tube-in-Tube Diagrid Structure Using Non Linear Static Analysis

Diagrid structures are evolved as one of the best structural system for high rise buildings. In this study seismic performance of 36 stories Tube-in-Tube Diagrid Structure with various diagonal slopes is evaluated by Non Linear Static Analysis. Tube-in-Tube diagrid structures are modified Diagrid structures in which gravity core is replaced with Diagrid core. Single tube diagrid structure is also studied for comparison. The structure is pushed gradually proportional to fundamental Mode shape. The analysis results shows that Tube-in-Tube structure possess higher stiffness and Lateral Load resisting capacity. The pushover analysis demonstrates that diagrid core can perform better by hardening the structure. According to analysis results, the Tube-in-Tube diagrid structure shows higher non-linear lateral displacement. It was observed that as the diagrid angle increases the stiffness and lateral load carrying strength decreases.

Effect of Aspect Ratio on High Rise Structures with Diagrid

Urbanization and population explosion in the present times has led to increase in demand for land and residencies but the availability of land is scare i.e reason a trend has evolved for construction of high rise structures in high rise structures major emphasis given to lateral load resisting systems. As diagrid structural system is lighter, stiffer and is effective in resisting the lateral loads, the present investigation carried out to study the performance diagrid on high rise structures varying aspect ratio. The study is carried out to observe the performance of diagrid structures ranging from 30 to 90 storeys. Diagrid structures are modelled with 3 storey module and performance of 7 models with different storeys i.e 30, 40, 50, 60, 70, 80, 90 (aspect ratio 3.67-10.86) and with fixed plan area. As a part 1 investigation to optimise the diagrid angle a 30 storey Diagrid structure performance is studied with 4 different diagrid angles one storey module angle 35°45’, Two storey module angle 55°13’, Three storey module 65°9’, Four storey module 70°51’. The optimized diagrid angle is used for different aspect ratio high rise structures to investigate the performance in terms of Storey displacement, Storey drift ratio, base shear and time period. For all the models plan area is fixed. Second part of investigation was a numerical study carried out by utilizing identified optimum angle of diagrid is applied on high rise buildings with aspect ratios 3.67, 4.86, 6.06, 7.26, 8.46, 9.67, 10.86 (Aspect ratio is the total height of the building to the width of the building). Behaviour of the Diagrid buildings due to change in aspect ratio is analysed based on parameters such as Storey displacements, Storey drift ratio, Base shear, Time period. As a part of investigation parameters such as Storey displacements and storey drift ratio were evaluated if they were within the limits as per IS code provisions. Percentage increase in storey displacements, maximum storey drift ratio,

Evaluation of R-Factor for 5 Storey RC Frame (IMRF) Building

According to IS 1893 part 1 (2016), the philosophy of earthquake resistant structures allows for some damages and inelastic lateral displacement in the structure for energy dissipation during an earthquake. The non-linear behaviour of elements in the structure plays a crucial role in earthquake resistance. There are three detailed classes for distinct seismic zones in different national codes. In India, the draught IS 13920 advocated the usage of IMRF (intermediate moment resisting frame) in zones II and III. The 5 story IMRF is designed and detailed as per IS 1893 (part 1) 2016, IS 13920 (2016), IS 1893 draft, IS 13920 draft, IS 456 (2000). In addition, nonlinear static pushover analysis was performed on IMRF and SMRF RC frame buildings in accordance with FEMA 356. (Displacement Coefficient method) During the analysis, two distinct load patterns (i) parabolic as per IS 1893 (part 1) 2016 (ii) fundamental mode shape are utilised, and the influence of p-delta is also taken into account when evaluating the response reduction factor. The analysed R-factor for studied frame building for fundamental mode shape loading was found to be near to the initial estimated R-factor during the design.

A Study on Mass Irregularity Limits of RC Structures for Various Seismic Zones of India

The performance of any structure under lateral loads depends on its structural configuration. Most of the codes worldwide mentioned the provisions for the lateral load analysis for regular structures. Structures may be irregular in practice due to uneven distributions in mass, stiffness and strength. In India, most common type of multi-storied apartments constructed varies from 5 to 15 storeys and many apartments are constructed with penthouse which creates mass irregularity in the structures. The present study investigates the performance of mass irregular structures which are created by providing penthouse and also modeled as a stepped setback structure. Total four structures, 5, 7, 11 and 16 storied with an aspect ratio (height to width of the structure) of 0.64, 0.88, 1.36 and 1.96 are considered. For each structure response spectrum analysis is carried and the response parameters like storey displacements, storey drift and base shear variation in 4 seismic zones of India is studied. The main focus of the investigation is to understand the acceptance of mass irregularity with respect to the aspect ratio of the structure. The acceptance limit of the mass irregularity is also investigated as per 4 seismic zones of India. The results are compared with Indian standard code limits and concluded the acceptance limit as per seismic zones of India.

Optimization of Diagrid Angle for High Rise Structure for Varying Bay Widths

The development of urban population, the lack of space and the high land costs has created the scope and necessity for the high-rise structures. In high rise structures, the design of lateral load resisting systems is more crucial than gravity load resisting system. There are many structural systems exists in literature to resist lateral loads. Diagrid structure is one among them which is proven to be both structurally and architecturally efficient structural system to resist lateral loads. The present study aims to investigate the best bay spacing for a particular high-rise structure and also optimizing the best diagrid angle to suit to the selected bay spacing. A numerical study is carried out with a 24 storied high-rise structure of plan area 36m x 36m considering with and without corner columns. The structure performance is checked with a bay width of 4m and with a bay width of 6m. Each structure is analyzed for four angles of inclinations of diagrid are formed by connecting 1, 2, 3, 4 stories respectively to optimize the diagrid angle. A comparative investigation is carried out for the structural responses like storey displacement, storey drift and base shear with different diagrid angles and with different bay width.