Journal of Structural Technology

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EISSN : 2581-950X
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Tulsiram Bhattarai, Rajan Suwal
Journal of Structural Technology, Volume 7, pp 24-32; https://doi.org/10.46610/jost.2022.v07i01.004

Abstract:
Beingan earthquake-prone country, Nepal has seen numerous high-magnitude earthquakes in recent years, resulting significant damage to the bridge and its components. Even after an earthquake, bridges should be able to be used for emergency and rescue operations. Fragility curves are an important technique for measuring the seismic vulnerability of bridges. Hence, this research is focused on the use of analytical method for development of fragility curve for generally used type of pier in Nepal which is hammerhead pier and multicolumn pier. Capacity of bridge is determined by non-linear static analysis and Demand parameter is estimated using non-linear time history analysis. The assumption of a log normal distribution is used to characterize fragility functions. The probability of exceedance of Slight, Moderate, Extensive and collapse damage states for hammerhead pier are 98.28%, 59.36%, 12.29%, 5.11% and 80.11%, 15.07%, 1.54%, 0.42% for MCE and DBE and those values for multicolumn pier are 97.79%, 37.91%, 5.49%, 2.01% and 72.35%, 4.22%, 0.33%, 0.08% for MCE and DBE respectively.
M. K. Laghate
Journal of Structural Technology, Volume 6; https://doi.org/10.46610/jost.2021.v06i03.006

Abstract:
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.
A. Vimala
Journal of Structural Technology, Volume 6; https://doi.org/10.46610/jost2021.v06i03.005

Abstract:
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,
Aditya Kushwah
Journal of Structural Technology, Volume 6; https://doi.org/10.46610/jost.2021.v06i03.002

Abstract:
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.
Kathi Lavanya, A. Vimala
Journal of Structural Technology, Volume 6; https://doi.org/10.46610/jost.2021.v06i02.006

Abstract:
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.
Mahammad Fayeemuddin, A. Vimala
Journal of Structural Technology, Volume 6; https://doi.org/10.46610/jost/.2021.v06i02.007

Abstract:
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.
Dharmesh N., V. Devaraj
Journal of Structural Technology, Volume 5, pp 42-52; https://doi.org/10.46610/jost.2020.v05i02.005

Abstract:
A seismic base isolation technique is used to resist damage against earthquakes and decreases seismic forces and accelerations for rigid structures. The main objective of this work is to design of base isolator. In the present study, four models were studied, namely square (with and without isolator) and C-shaped model (with and without isolator). Square-shaped model has 6 bays each in x-direction and y-direction, each bay spacing 6 m of plan size 36  36 m and 15storeys in the z-direction. The C-shaped model has 4  6 bays with 15 storeys having a plan dimension of 24  36 m that has been taken for seismic analysis. The equivalent static lateral force and response spectrum method are adopted for zone-V, soil type-II as per IS 1893:2016, part-1 using ETABS 2017 software.The building models were designed using IS: 456-2000. There is no specific IS codes for the design of isolators, hence the UBC 1997 code is adopted. Lead rubber bearing is designed manually for two models based on Design BasisEarthquake (DBE) and Maximum Considered Earthquake (MCE) and the following properties, namely vertical stiffness, initial stiffness for bearing, post-yield stiffness ratio were assessed and fed as an input to the isolator to analyse the frame with isolator. The following response quantities, namely mode period, base shear, storey displacement, and storey acceleration were assessed, and comparative study is made for the frame with and without isolator. A comparative study is made to assess the suitability of the model for structural response.
Dhiraj D Ahiwale, Rushikesh R Khartode
Journal of Structural Technology, Volume 5, pp 1-13; https://doi.org/10.46610/jost.2020.v05i02.001

Abstract:
Open ground construction is quite prevalent from last 25 years in metropolitan India. Buildings with open ground stories are to be particularly exposed to collapse, and severe damage under earthquake excitation. Although, many buildings constructed in recent times have been observed adverse effect during Bhuj earthquake. The study has been performed to work out the performance of RC building with open ground storey subjected to seismic loads. In present work, twelve storied building are taken into account and the performance of structure evaluated by using pushover analysis in SAP 2000 software. The analytical results discussed in the nature of capacity curve, structure performance point and plastic hinge development pattern. Result indicated that, there are formations of plastic hinges at ground storey column level. To counteract the total collapse of soft storey structures, there is need to retrofit the open storey. Therefore, the alternative measures are recommended to get better the reaction of soft storey like RC shear wall, steel bracing, and infill wall.
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