Abstract: These days the use of vehicular bombs to attack crowded areas has been a feature of campaigns by terrorist organizations around the world. Due to the threat from such extreme loading conditions, efforts have been made during the past three decades to develop methods of structural analysis and design to resist blast loads. This paper presents a comprehensive overview of the effects of explosion on buildings like building with shear wall and building with X bracing. An explanation of the nature of explosions and the mechanism of blast waves in Air Burst condition is given. A 3D model of RCC framed structures (G+6) is developed using SAP 2000 software by defining the geometric properties and material properties confirming to IS 456:2000. This paper shows that blast parameters mainly depend on Charge weight and Stand-off distance. The increase in blast load leads to increase in displacement and inter storey drift. Also from the comparison of building with and without Shear wall at the front face, the building with shear wall shows a gradual decrease in displacement along the height of the building. Whereas by optimizing the X bracing level-wise, it shows drastic decrease in displacement. However in both cases, the rate of reduction of displacement increases with the increase in height of the building.
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The above graph represents a maximum inter storey drift of 0.00176 for special shaped columns, whereas a storey drift of 0.001533 has been recorded for shear wall in G+15 storeyed structure which was subjected to seismic loads in the zone III.The storey drift of the building under seismic forces keeps on increasing with the height of the building up to some extent and then keeps on decreasing with increase in storey height. The storey height from around 20- 30m height, the drift is maximum in both cases, but the special shaped column shows maximum drift than shear walls representing better uniformity in structural stiffness of various floors. From graph the drift in structure with shear wall are reduced by 12.89% compare to structure with special shaped columns.
The displacement is reduced upto 15-25% for the models with the lift core shear wall compared to the bare frame model in the both X and Y direction for equivalent static method. There is a 15-17% reduction of inter storey drift for the buildings with lift core shear wall compared to the bare frame model in both X and Y direction in equivalent static method for all the soil types. In the response spectrum method it is observed that the parameters such as storey displacements and storey shear have been minimized compared to equivalent static method. Hence proves to be economical for the construction of high rise buildings .
Abstract: The construction industry is changing fast due to continuing invention of new technologies, construction equipments and materials. To keep pace with the advancement of technology it is required for the codes to be updated on a regular basis. Initiative has been taken to update BNBC (Bangladesh National Building Code) 1993, and a draft copy has already been prepared. Significant changes have been introduced in BNBC 2012 with regard to analysis for lateral loads. To identify the changes in design and analysis of various structures a comparative study is necessary to relook at the provisions of the present code and look for the feasibility of any change of the recent upgrading code. This study aims at the comparison of provisions of wind and earthquake analysis given in existing BNBC 1993 to that in proposed BNBC 2012. It is found that seismic base shear of the building calculated by BNBC 2012 varies significantly from seismic base shear calculated by BNBC 1993. Finally structural analysis and design of a typical apartment building situated in Dhaka City is conducted to demonstrate the changes regarding lateral load in proposed BNBC 2012 with respect to BNBC 1993. The basic differences in seismic base shear and maximum lateral displacement with varying number of stories using two codes are presented. The comparison in inter storey drift is also made for 6 storied and 12 storied building to show the effect in inter storey drift using two codes. Analysis is made to compare maximum reinforcement requirement for column design to provide guideline to the engineer for the most economic design.
The storey displacement and inter storey drift decreases in 10 storey for time history analysis, hence the time history is well performed for tall structures.Storey drift is increased in both the cases in middle storeys showing maximum drift, When SSI is considered there is a magnification of storey drift in the middle storeys. Due to decrease in frequency of the system , the local forces (shear force, bending moment) are increased. The response of the soil structure interation tall building founded on soft soil has shown significant increase
We observed lesser displacements in M1,M4 regular structures when compared to M2,M5 aground floor level floating structural systems and higher displacements in M3,M6 alternate floor level floating structural systems. This shows alternate floor floating column structural systems will effect much on global stiffness of the structure which results reduction in lateral load resisting capacity. Inter storey drift,in the structures varies with the size of the building as well as the bay size between the columns, M4, M5 & M6 with 4m bay size between columns is found having higher drift compared to M1, M2& M3 with 3m bay size building .We observed lower inter storey drift in M1,M4 regular structures when compared to M2,M5 floor level floating structural systems and higher inter storey drift in M3,M6 alternate floor level floating structural systems. This shows that alternate floor floating column structural systems will effect much on global stiffness of the structure which results in soft storey effect thus result in higher drift. Even though the stiffness and soft storey comes into effect here the mass distribution about the structure should be considered seriously structure with evenly distributed mass are less effected to drift than the structures unevenly architected or uneven mass distribution
4. Different variation of storey stiffness obtained from RSA over the number of storeys in both X and Y directions for all the developed RC building models. However, storey stiffness in X-direction are observed to be more than that in Y-direction in M1, M2, M3, M4, M5, M6 and M8 models. Further model M7 storey stiffness in Y-direction is observed to be more than that in X- direction.
Capacity evaluation of the investigated residential build- ings is performed using damage limit states suggested by Calvi (1999). Pushover analysis data and criteria of Table 1 were used to determine inter-storey drift ratios of each build- ing in both directions. Identification of damage limit states and its representations on capacity curves for each building is given in Figs. 8–10b and d. Small displacement capacities at different performance levels are remarkable for the build- ings with greater openings in the respective directions due to failure of masonry elements. Also, TD-83/3 x-direction and TD-72/3 in both directions do not have the expected dis- placement capacity due to lack of continuous walls (window openings) and irregularity in plans and elevations. The re- ductions in wall thickness cause a jump in inter-storey drift ratios at the third floor as obviously seen below (Figs. 8–10).
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In order to prevent building from severe damage during an earthquake, it is necessary for a structural engineer to design a structure for dynamic analysis and also for static analysis. Various parameters like Storey displacement, storey drift, and Base shear are obtained. Analysis of the models are done by using SAP2000 v 20.2.0 for Plan regular, Plan irregular and vertical irregularity by having with and without Shear wall and infill wall.
Mohana H. S and Kavan M. R (2015), have performed a comparative study of flat slab and conventional slab building using ETabs for all the Seismic Zones. They considered G+5 multistoried commercial building having a flat slab and conventional slab. They have carried out the analyses for base shear, storey drift, axial force and displacement. On the basis of result obtained, it is observed that the storey shear will be maximum at the ground level and will be minimum at the top storey. The axial force intensity at Zone II, III in case of conventional slab will be more as compared to flat slab. Displacement depends on the height and slenderness of building. They also found out that the displacement of structure with flat slab is slightly more as compared to the conventional slab for all Earthquake Zone. The displacement variation was 4mm for each Seismic Zone for both flat slab and conventional slab.
The storey drift for various storey levels for various configurations of the shear wall panels are plotted in Fig.5. From Fig.5 and Table 1, for various configurations of shear wall panels, as in the previous case, we can see that the bare frame is having the maximum storey drift of 146.90mm. The conventional shear wall system, alternate arrangement of conventional shear wall system and the lift core wall is having almost same values of storey drift. The storey drift for the diagonal shear wall system and the zigzag shear wall system are 28.64mm and 25.80mm respectively, which are much lesser than the other four. The maximum values of storey drift and the percentage decrease when compared with the bare frame is given in Table1 and Table 2 respectively. The reduction in storey drift, when compared to bare frame, is the maximum for the zigzag shear wall system which is about 83 percent. The reduction in storey drift for the diagonal shear wall system is about 81 percent. The
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Tausif J. Shaikh (2017) studied about the wind analysis of high rise building having outrigger and diagrid. He compared different lateral load resisting systems such as outrigger and diagrid system provided in the high rise building of 108m. He performed wind analysis by using gust factor approach as per IS;875 (Part-3)-1987 and lateral wind load was calculated “along Wind” response. In this paper different models were analysed and compared by changing angle of inclination and location of outrigger. Comparison and analysis had been made in terms of top storey displacement, axial force, material consumption and time period. The study shows that material consumption in outrigger structural system is 17% higher than diagrid structural system. So it can be concluded that diagrid system is economical. Time period for diagrid structure is very less compared to outrigger which means diagrid system is stiffer than outrigger. Diagrid structural system is more feasible in architectural planning and provide higher structural efficiency for high rise buildings.
The SSI effects are obvious for soil type 1 than the soil type 2. As the storey number of the structures decrease, the increase in the SSI effects is obtained. Because of the SSI effects, the acceleration response of the 3- and 6-storey structures attenuated significantly. The same kind of decrease is observed for the displacement and basement storey drift ratios of the structures but at a less level. The response of the 12-storey structure change in a small amount when the differences are compared with that of the other structures. It should be pointed out that, the fundamental period of the 12-storey structure is close to the fundamental period of the site for soil type 2. For this reason, the response of the 12-storey structure is exaggerated for the analyses of soil type 1. The same kind of amplification is observed for both of the FB and SSI cases. The form of the SSI effects is slightly different from that of other structures. The acceleration response, displacement response and basement storey drift ratios of the 12-storey structure increase for soil type 2.
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In present work, Forty storey buildings (120m) have been modeled using software ETABS by dynamic analysis. All the analyses has been carried out as per the Indian Standard code books. Based on the literature of previous studies most effective positioning of shear walls has been chosen. This study is done on RC framed multistory building with RC shear walls with fixed support conditions. The usefulness of shear walls in the structural planning of multistory buildings has long been recognized. When walls are situated in advantageous positions in a building, they can be very efficient in resisting lateral loads originating from wind or earthquakes. Incorporation of shear wall has become inevitable in multi-storey building to resist lateral forces. This paper aims to study the behaviour of reinforced concrete building by conducting dynamic analysis for most suited positions and location of shear wall. Estimation of structural response such as, storey displacements, base shear, storey drift is carried out. Dynamic responses under zone V earthquake as per IS 1893 (part 1): 2002 have been carried out. In dynamic analysis, Response Spectrum method is used.
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Fig 11 shows the plots of storey displacement of structure in X and Y direction from Model 1 to Model 3 v/s Storey numbers. The above values are obtained by Response spectrum analysis for seismic zone 5. The highest displacement found to be 53.529mm in Model 1(Regular bare frame) in X direction and 40.62mm in Model 2 (Regular frame with shear wall) in Y direction.
Muhammed Asim Khan et al  had made study on a total of 9 models, with L shape for analysis to cover a broader spectrum of low, medium and high rise buildings for seismic control using pushover analysis. Different techniques adopted in the study include lead rubber bearing and masonry infill wall and analysis were carried out using SAP 2000 software. The study gave conclusion that the presence of isolators increases time period and thus flexibility. Also a five storey asymmetric RC framed building with lead rubber bearing isolator show better performance and maximum reduction of torsional moment.
replaceable link beams are designed as concrete structures connected to the columns through bolted joints. Response spectrum analysis is used to investigate the performance of multi storey multi bay RC building using SAP 2000. According to the study linked column frame system are good in reducing the storey displacement, storey drift and base shear than a normal building frame. Linked column provided at X and Y / -X and –Y direction shows considerable reduction in storey displacement and storey drift values. Linked column with infill shows better results than linked column provided without infill. So, the Linked Column Frame (LCF) system is a better option for a seismic resistant structures and strengthening of structures.
. Md. Arman Chowdhury1, Wahid Hassan,(2013) “Comparative study of the Dynamic Analysis of Multi- storey Irregular building with or without Base Isolator”. . Ms. Minal Ashok Somwanshi and Mrs. Rina N. Pantawane(2015) “Seismic Analysis of Fixed Based and Base Isolated Building Structures”.
0.3m. following data is used in the analysis of the RC frame building models. Density of Reinforced Concrete 25kN/m³ , Modulus of elasticity of brick masonry 4.33x10^3 KN/m², Density of brick masonry 20kN/m³, Poisson’s Ratio of concrete 0.2, Floor finishes 1.0kN/m², Imposed loads 4KN/ m², Roof live 1.5 KN/ m² , Thickness of wall 0.3m, Zone –V, Zone factor, Z (Table2 of IS 1893-2002) – 0.33, Importance factor, I (Table 3 of IS 1893-2002) – 1.5, Response reduction factor, R (Table 7 of IS 1893-2002) – 5.00, Soil type (figure 2 of IS 1893-2002) – Type II (Medium soil),Storey heights: Bottom storey = 8m, 2 to 11th storey = 3.7mTop storey =2.7m
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This paper deals with the comparative study of a normal multistoried building with the building containing the floating column. In this study, a ten storey building is considered for analysis purpose. For a building with floating column, some columns at the base is removed and the analysis is done. The various structural responses such as Storey Displacement, Storey Drift and Storey Shear and Time period have been evaluated and compared. The dynamic analysis is done using Response Spectrum Method for the multistoried building. For analysis purpose, ETABS software has been used.
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