ETABS-Based Structural Analysis and Architectural Design of a 21-Story Multifunctional Building in Dhaka: Insights from Shanghai-Inspired Designs on Soft Soil ()
1. Introduction
The capital city of Bangladesh, Dhaka, is one of the fastest urbanizing cities in the world, with a rapidly increasing population and an ever-increasing economic activity [1]. Dhaka is one of the most populated cities in the world and this has posed a great challenge in terms of urban planning, infrastructure and housing [2]. The need to maximize the available urban space has led to an increased demand of multifunctional buildings that can effectively combine commercial and residential uses [3]. To address these issues, the suggested 21-story multifunctional building in Dhaka will combine commercial and residential areas in one building. This will be the best way to utilize the land and it has the potential to develop a dynamic and sustainable urban environment. This building will create a lively community by integrating various functions into a single building to meet the increasing demands of the city. The major goals of this project are:
Dual Functionality: The building will provide a large amount of commercial space (ground floor to 4th floor) and high-quality residential living space (5th to 21st floor) to provide a balanced combination of business and living space.
Sustainability: The project focuses on the environmentally friendly design features that comply with the international environmental standards [4]. The green building techniques such as energy efficient systems and sustainable materials are also included to minimize the environmental impact of the building and to make it viable in the long run [5].
Seismic Resilience: An important objective of this project is to make sure that the building meets the seismic requirements of Bangladesh and surpasses the local seismic safety requirements [6]. The architecture uses modern engineering methods to protect the building against earthquake hazards that are characteristic of the geography of Dhaka [7].
Community Enhancement: The building is not only a physical building but also a community center, where accessible facilities, public space, and social space are provided and they have a positive impact on the urban fabric of Dhaka.
2. Project Scope and Methodology
2.1. Project Scope
The project is a complex of architectural and structural design of a 21-story multifunctional building in Dhaka. The scope encompasses the whole lifecycle of the project starting with conceptualization to its economic viability considering different design criteria, load calculations, material selection and sustainability [8]. Particular topics are:
Architectural and Structural Design: An in-depth discussion of the architectural design features that emphasize on the aesthetic value and functionality [9]. The structural design makes the building safe and fits well in the urban environment.
Compliance and Standards: A detailed analysis of how the design is in accordance with the local and international building codes and especially structural safety, seismic resilience, and sustainability.
Technological Integration: The integration of the latest technologies, such as structural modeling and simulation software (ETABS and SAP2000) to increase the efficiency of operations and make the building more comfortable to occupants [10].
Financial Overview: Cost estimates of the construction and maintenance of the project and an economic analysis of the project, so that the building is financially viable throughout its life.
2.2. Methodology
The approach taken in the current project is a combination of theoretical research, empirical studies, and computational modeling in order to make the design innovative and practical. The main stages of the methodology are the following:
Literature Review: The study of the current trends and technologies in the design of high-rise buildings, paying attention to mixed-use buildings. This stage examines international best practices and benchmarks of cities that have similar urban issues such as Shanghai, which has been used to design this building.
Site Analysis: The site analysis is done in terms of environmental and geotechnical analysis to determine the site conditions in Dhaka in terms of soil properties, seismic activity, and climatic considerations [7]. This is important information in the determination of design parameters particularly in foundation design and load bearing capacity (Figure 1).
Design Simulation: The structural modeling is done in ETABS and SAP2000 to simulate the behavior of the building under different loading conditions, e.g. seismic loads, wind loads, and live loads [11]. This assists in identifying the most effective and safe design alternatives of the structural system of the building.
Stakeholder Consultations: Consultation with the local authorities, potential investors and future occupants will help to make sure that the building design will be in line with the practical needs and expectations of all stakeholders. This teamwork will assist in perfecting the design and making it practical and workable.
Evaluation and Revision: There are constant feedback loops with design team and stakeholders so that the design of the building can be revised to reflect the goals of the project and the compliance needs. Refinement and optimization of the design is done through iterative revisions (Table 13).
2.3. ETABS Modelling Assumptions
The 3D structural model was built in ETABS (version X.X) using shell elements as floor slabs and frame elements as beams/columns. Slabs of rigid diaphragms were assigned at each floor level to provide in-plane load distribution. Material models: concrete was modelled as linear elastic with M25 properties and HYSD415 reinforcement (E, rho and nu as shown in Table 10). According to BNBC load combinations, gravity loads and lateral loads (wind and BNBC 2020 seismic cases) were applied (see Table 8). To conduct dynamic analysis, we extracted eigenvalues (modal analysis) and Response Spectrum Analysis (RSA) with BNBC 2020 spectral parameters; P-Delta (geometric second-order) effects were considered in the analysis. A consistent meshing approach was used with element sizes selected so that the largest panel dimensions of the slab were not more than 4 m × 4 m (refinement around openings and irregular plan elements) (Table 4). Boundary conditions: piles/foundations and soil properties were modelled as fully fixed (zero displacement/rotation) at the base level in the ETABS model (no explicit soil-structure interaction) (Table 2). Damping of fundamental modes was 5% (Table 3). Spectral scaling was done using the modal period of the model unless otherwise stated; where empirical code period estimates were used to compare, the formula T = CtH m (BNBC Table 6.2.20 parameters) was used and differences are discussed. Edit element size, foundation modelling and ETABS version to suit our precise model (if not the same).
3. Design Codes, Structural Design and Requirements
The proposed 21-story multifunctional building in Dhaka will be designed structurally in accordance with the Bangladesh National Building Code (BNBC) 2020 (Table 1) which is a complete set of guidelines specifically designed to provide structural safety, material specifications, load calculations, and design methodologies of high-rise buildings in Bangladesh. The BNBC 2020 has the necessary requirements of constructing structures that can resist seismic forces, wind loads, and other environmental stresses (Table 1) that are common in the area given the fact that Dhaka is prone to seismic activity and high wind velocity [7] [12].
Table 1. Design code standard.
Category |
Code/Standard |
Details |
General Settings |
BNBC 2020 |
Bangladesh National Building Code |
Display Units |
Metric SI |
International System of Units |
Region for Materials |
User-Defined |
Based on project specifications |
Steel Database Section |
AISC14 |
American Institute of Steel Constructure (14th Edition) |
Steel Design Code |
AISC 360-10 |
Specification for Structural Steel Buildings |
Concrete Design Code |
ACl 318-08 |
Building Code Requirements for Structural Concrete |
Seismic Design |
BNBC 2020 |
Seismic provisions of BNBC |
Wind Load Design |
BNBC 2020 |
Wind load provisions of BNBC |
Load Combinations |
BNBC 2020 |
Load combination rules as per BNBC |
Table 2. Foundation and soil properties.
Parameter |
Value |
Soil Bearing Capacity |
250 kPa |
Soil Type |
In Between Loose to Medium Dense |
Foundation Type |
Pile Foundation |
Soil Factor (S) |
1.35 |
Time Period (T) |
4.000 s |
Seismic Zone (Z) |
2 |
Short Period Site Coefficient (Fa) |
1.35 |
Long Period Site Coefficient (Fv) |
2.70 |
Table 3. Seismic load parameters determination.
Parameter |
Value |
Building Height Above Base (H) |
66.5 m |
Length Along X Direction |
69.0 m |
Length Along Y Direction |
50.0 m |
Structure Type |
Concrete Moment
Resisting Frame |
Building Period Coefficient (Ct) |
0.0466 |
x or m |
0.90 |
Damping Ratio (ξ) |
5% |
Damping Correction Factor (η) |
1.0 |
Response Modification/Reduction Factor (R) |
6.5 |
Occupancy Category |
II |
Importance Factor (I) |
1.0 |
Location of the Building |
Dhaka |
Seismic Zone (Z) |
2 |
Soil Factor (S) |
1.35 |
Long-Period TL |
2.04 s |
Normalized Acceleration Response Spectrum (Cs) |
0.338 |
Coefficient used to calculate lower bound for Sa (β) |
0.11 |
Short Period Site Coefficient (Fa) |
1.35 |
Long Period Site Coefficient (Fv) |
2.70 |
Design Spectral Acceleration (Sa) |
0.0199 |
Distribution exponent for Building Height (K) |
2.000 |
Seismic Design Category (SDC) |
D |
Expected Horizontal Peak Ground Acceleration (ah) |
0.18 |
The vertical seismic load effect (Ev) |
0.09 D |
Concrete Unit Weight |
24 kN/m3 |
Table 4. Various load condition.
Element |
Level/Story |
Width (nm) |
Depth (nm) |
Beam |
1 - 5 |
350 |
700 |
Beam |
6 - 21 |
300 |
600 |
Column |
1 - 5 |
1200 |
1200 |
Column |
1 - 5 |
100 |
1000 |
Column |
6 - 21 |
600 |
800 |
Slab |
All |
190 |
N/A |
Share Wall |
All |
350 |
N/A |
4. Architectural Design
The architectural design of the multi-purpose high-rise building in Shanghai is a perfect combination of modern beauty and functionality (Figure 1). This is informed by the concept of vertical zoning whereby different functions are well planned on various levels to maximize land use and improve the overall functionality of the building (Figures 2-5).
Figure 1. Column layout.
Figure 2. Ground floor layout.
Figure 3. First floor shop layout.
Figure 4. 2nd-4th floor shop layout.
Figure 5. Residential floor (5th to 21st floor).
Figure 6. Details living space.
Figure 7. Stair, elevator and escalator details.
Figure 8. Washroom & toilet details.
Figure 9. Front elevation.
The design allows the efficient circulation and utility systems by vertically separating the commercial and residential functions, which reduces interference between the various uses (Figures 6-8). The facade of the building will be a mixture of high-performance glass and energy efficient materials which will effectively minimize the heat gain and maximize the amount of natural light entering the retail and residential spaces (Figure 9).
Quantitative Energy Estimate: With the plan dimensions of Table 3 (69 m × 50 m floor plate) the gross floor area of the building is 72,450 m2 (21 floors × 3450 m2). The baseline annual energy demand would be 14.49 GWh/yr with a conservative mixed-use baseline EUI of 200 kWh/m2∙yr. Assuming that the proposed envelope and passive measures can reduce the energy demand by 20 percent (conservative early design passive measures), the estimated annual energy demand would be 11.59 GWh/yr (approximately 20 percent saving of 2.9 GWh/yr). To compare with a local office benchmark (SREDA reported 45 kWh/m2∙yr for government offices), the baseline would be 3.26 GWh/yr and the forecast demand after the same 20% savings 2.61 GWh/yr (savings 0.65 GWh/yr). These are conceptual estimates to measure the claim; a more detailed building energy simulation (EnergyPlus/IES/Green Building Studio) with precise program areas, internal gains and HVAC system specifications is suggested to substitute these estimates.
5. Structural Design, Load Analysis & Material Properties
5.1. Design Analysis
Column: To design a column according to BNBC, start by calculating all applicable loads (dead, live, wind, seismic) and determine the factored load combinations. Select a preliminary column size and check the slenderness ratio to ensure it is not too slender. Calculate the axial load capacity using the formula φPn = 0.65fc'Ag + 0.75fyAs, where φ is the strength reduction factor, fc' is the compressive strength of concrete, Ag is the gross area, fy is the yield strength of steel, and 𝐴𝑠 is the area of steel reinforcement (Figure 10). Verify the moment capacity using interaction diagrams to ensure φMn ≥ Mu. Calculate the required steel reinforcement and ensure it falls within the minimum and maximum reinforcement ratios (Figure 10). Design the transverse reinforcement (stirrups) to resist the shear force using Vs = Vu − Vc, where Vc is the shear capacity of concrete. Detail the longitudinal and transverse reinforcement according to BNBC requirements, ensuring proper cover, anchorage, and lap splices. Finally, verify the column design against BNBC requirements for stability and serviceability.
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Figure 10. Beam selection commercial.
Beam: For the beam design according to BNBC, start by calculating the loads including dead loads, live loads, and any additional loads such as wind or seismic forces. Determine the factored load combinations as per BNBC. Select a preliminary beam size based on span, load, and deflection criteria (Figure 11).
Figure 11. Beam selection residential.
Compute the bending moments, shear forces, and deflections for the beam under these load combinations using structural analysis methods. Ensure the reinforcement ratio is within the allowable limits. Determine the shear reinforcement by calculating the shear capacity of the concrete Vc and the required shear reinforcement Vs using Vu = φ(Vc + Vs), where Vu is the factored shear force. Check for deflection control to ensure the beam meets serviceability requirements. Finally, detail the reinforcement, ensuring proper spacing, cover, anchorage, and lap splices according to BNBC requirements (Figure 12). Verify the design for compliance with all BNBC provisions, ensuring safety and performance.
Slab: For the slab design according to BNBC, start by determining the loads, including dead loads, live loads, and any additional loads such as wind or seismic forces. Use these loads to calculate the factored load combinations as per BNBC.
a) Load Calculation: Determine the total load per unit area including the self-weight of the slab, live loads, and any superimposed dead loads (Tables 4-7).
b) Thickness Selection: Select a preliminary slab thickness based on span-to-depth ratios specified by BNBC to control deflection (Table 8).
c) Moment and Shear Calculation: Calculate the bending moments and shear forces for the slab. For one-way slabs, use the formulas for simply supported or continuous slabs. For two-way slabs, use methods like the direct design method or equivalent frame method.
d) Flexural Reinforcement: Calculate the required reinforcement for flexure. Use the moment capacity equation Mu = ϕMn where Mu is the factored moment, ϕ is the strength reduction factor, and Mn is the nominal moment capacity. Ensure the reinforcement ratio is within allowable limits.
e) Shear Reinforcement: Check for shear strength. For slabs, shear reinforcement is typically, not required unless the slab is very thick or carries high loads, as the concrete itself usually provides sufficient shear strength. Calculate the shear capacity of the slab and provide reinforcement if necessary (Table 9).
f) Deflection Check: Ensure that the slab meets deflection criteria. This can be done by verifying that the selected slab thickness and reinforcement comply with the serviceability requirements for deflection.
g) Detailing: Detail the reinforcement, ensuring proper spacing, cover, and anchorage. Follow BNBC guidelines for reinforcement detailing, including minimum and maximum reinforcement spacing, cover requirements, and lap splice lengths (Table 13).
h) Punching Shear Check: For flat slabs and slabs without beams, check for punching shear around columns. Calculate the punching shear stress and ensure it is within the limits specified by BNBC (Table 1).
i) Serviceability Checks: Finally, check for serviceability criteria such as crack control and deflection limits to ensure the slab performs well under service conditions.
The structural plan of the first four stories, which are to be used as commercial, consists of a grid structure with regularly spaced columns and beams to hold the commercial spaces (Figure 12). The plan makes the distribution of the load uniform and has a lot of open space to be used commercially activities (Figure 13). The design combines permanent service equipment and partitions where required, making sure that they are in line with the load bearing elements to ensure structural integrity.
The structural layout changes to suit residential purposes starting with the fifth story. This plan is an extension of the grid system and can have more load-bearing walls and partition walls to hold the residential units (Figure 14). The plan guarantees the vertical and lateral load paths are in line with the lower commercial floors, which gives structural continuity in general and stability (Figure 14).
Figure 12. From first floor to top floor.
Figure 13. Commercial floor grid.
Figure 14. Residential floors grid.
The ETABS software was used to analyze and design the 21-story building in terms of its structure employed. ETABS is a powerful, easy to use and flexible software that is popular in the building industry in structural analysis and design. It combines different calculation design codes, such as those of the Bangladesh National Building Code (BNBC).
5.2. Load Analysis
The Bangladesh National Building Code (BNBC) provides the following procedure of determining loads in building structures (Table 8). First, enumerate all the loads that are connected in each room, flat or office per floor and the whole building, including the equipment like lifts, water pumps and ventilation systems (Table 7). Use suitable diversity factors to cover the differences in the use of loads (Table 8). Based on these diversity factors, determine the maximum demand using the guidelines of BNBC on commonly used equipment. Design loads should be estimated in watts or kilowatts and track load growth with time. Compute current to select breakers, fuses and cables based on kVA and power factor.
Specific loads considerations are designing roofs to support loads of accumulated rainwater in case drainage systems are undersized or blocked, and calculating loads caused by hydrostatic and hydrodynamic effects on structures in flood-prone regions (Table 6 & Table 7). Loads that are miscellaneous should be followed as per BNBC procedures or consult an expert where not specified. Exceptions to load reduction are roof uniform dead and live loads, and the reduction is permitted on the basis of the tributary area (Table 5). Live loads greater than 4.80 kN/m2 are not to be reduced, and there are particular restrictions on the reduction of loads in some occupancies such as public assembly areas and cyclone shelters (Table 6).
The site class definitions categorize the type of soil at a construction site based on its properties, significantly influencing the seismic design parameters. The BNBC 2020 references similar categories to those in ASCE 7-16 (Table 8). Below are the site class definitions and their corresponding parameters (Table 9). The seismic load calculations are based on the BNBC seismic zoning map of Bangladesh, which divides the country into four seismic zones with different spectral response acceleration parameters (Ss and S1). The design response spectrum is used to determine the maximum seismic response of structures at different periods (Table 13). This ensures that the structural design adheres to the seismic performance criteria specified by the BNBC, providing safety and resilience against earthquakes.
Table 5. Dead loads.
Component |
Dead Load (kN/m2) |
Details |
Concrete Floor Slabs |
5.0 |
Assuming 200 mm thickness |
Partition Walls |
2.4 |
120 mm thick brick walls |
Fixed Equipment |
0.5 |
HVAC systems, plumbing |
Table 6. Live loads.
Area |
Live Load (kN/m2) |
Details |
Residential Floors |
2.0 |
Per Square Meter |
Office Floors |
2.5 |
Per Square Meter |
Shops |
4.0 |
Per Square Meter |
Roof |
1.5 |
Per Square Meter |
Table 7. Special loads.
Load Type |
Description |
Load (kN/m2 or kN/m) |
Lift Load |
Loads due to lift equipment and operation |
Varies |
Equipment Load |
Loads due to heavy equipment |
Varies |
Light Shop |
Loads due to light shop equipment |
3.5 |
Heavy Shop |
Loads due to heavy shop equipment |
7.5 |
Storage Load |
Loads due to storage materials |
5.0 |
Vehicle Load |
Loads due to vehicles in parking garages |
2.5 |
Wind Load |
Loads due to wind pressure |
Varies |
Seismic Load |
Loads due to seismic activity |
Varies |
Table 8. Load table for ETABS according to BNBC 2020.
Load Case |
Load Type |
Occupancy /Category |
Load Description |
Value (kN/m2) |
Dead Load |
Self-Weight |
Structural |
-- |
-- |
Dead Load |
Floor Finish |
All |
Floor finishes like tiles, marble |
1.5 |
Dead Load |
Partition Wall |
All |
Non-structural walls |
1.0 |
Dead Load |
Ceiling |
All |
Suspended ceilings |
0.5 |
Dead Load |
Roofing |
Roof |
Roofing materials |
1.0 |
Live Load |
Residential |
Residential |
Residential occupancy |
2.0 |
Live Load |
Office |
Office |
Office occupancy |
2.5 |
Live Load |
Classroom |
Educational |
Educational occupancy |
3.0 |
Live Load |
Corridor/Stairs |
High Traffic |
High foot traffic areas |
4.0 |
Live Load |
Storage |
Storage |
Storage areas |
5.0 |
Live Load |
Retail/Shop |
Commercial |
Retail spaces |
4.0 |
Live Load |
Assembly Areas |
Assembly |
Assembly spaces |
4.5 |
Live Load |
Industrial |
Industrial |
Machinery and equipment |
7.5 |
Live Load |
Roof Live |
Roof |
Typical roof live load |
1.5 |
Live Load |
Roof Garden |
Roof |
Landscaping and gardens |
3.0 |
Special Load |
Lift Load |
All |
Lift equipment and operation |
Varies |
Special Load |
Equipment Load |
All |
Heavy equipment |
Varies |
Special Load |
Light Shop |
Commercial |
Light shop equipment |
3.5 |
Special Load |
Heavy Shop |
Industrial |
Heavy shop equipment |
7.5 |
Special Load |
Storage Load |
Storage |
Storage materials |
5.0 |
Special Load |
Vehicle Load |
Parking |
Parking garages |
2.5 |
Special Load |
Wind Load |
All |
Wind pressure |
Varies |
Special Load |
Seismic Load |
All |
Seismic activity |
Varies |
Table 9. Site class definitions (Earthquake).
Site Class |
Shear Wave Velocity Vs (ft/s) |
Standard Penetration Resistance N (blows/ft) |
Undrained Shear Strength Su 9psf) |
A. Hard rock |
>5000 |
NA |
NA |
B. Rock |
2500 to 5000 |
NA |
NA |
C. Very dense soil and soft rock |
1200 to 2500 |
>50 |
>2000 |
D. Stiff soil |
600 to 1200 |
15 to 50 |
1000 to 2000 |
E. Soft clay soil |
<600 |
<15 |
<1000 |
F. Soils requiring site response analysis |
BNBC Section 21.1 |
BNBC Section 21.1 |
BNBC Section 21.1 |
5.3. Material Properties and Parameters
Materials and their properties are very important in the structural integrity and performance of the building. The material properties and parameters applied in the ETABS model were specified and determined based on the specifications and guidelines of the BNBC. The structural performance requirements of the 21-story building are established to provide safety, serviceability, and durability of the building under different loading conditions as per the Bangladesh National Building Code (BNBC) (Table 10).
The material properties defined for the building include M25 grade concrete and HYSD415 steel reinforcement (Table 10). For M25 concrete, the specified compressive strength is 25 MPa with a modulus of elasticity of 25,000 MPa. HYSD415 steel reinforcement is defined with a minimum yield strength of 415 MPa and a tensile strength up to 533.5 MPa. This material accurate lateral load application for seismic analysis (Table 10). These load definitions cover all essential load types acting on the structure, ensuring comprehensive analysis and design.
Table 10. Material properties and parameters.
Material |
Property |
Value |
Concrete (M25) |
Grade |
M25 (fc' = 25 MPa) |
Density |
24 kN/m3 |
Young’s Modulus (E) |
25,000 MPa |
Poisson’s Ratio (ν) |
0.2 |
Steel |
Grade |
Fe500 (fy = 500 MPa) |
Density |
78.5 kN/m3 |
Young’s Modulus (E) |
200,000 MPa |
Poisson’s Ratio (ν) |
0.3 |
Reinforcement Bars |
Yield Strength (fy) |
500 MPa |
Ultimate Strength (fu) |
600 MPa |
Other Parameters |
Live Load Reduction Factor |
As per BNBC |
Damping Ratio |
5% |
Seismic Zone Factors |
As per BNBC |
Site Class |
As per BNBC |
5.4. Story Drift
The story drift results for seismic effects along the X direction show that all levels of the structure are within the allowable drift limits as per BNBC 2020. The maximum calculated story drift (Δx) at each level is compared against the allowable drift (Δa), Table 11 which is 0.06 for most stories and 0.08 for the lower levels. All drift values fall within the permissible limits, ensuring the building’s compliance with the code requirements for seismic safety and structural stability.
Table 11. For seismic effect along X direction.
|
Floor Height Below the X |
Elastic Displacement = Diaphragm Center of Mass Disp (For EQx) |
|
Story Drift Analysis |
Allowable Drift |
|
Level ID |
(m) |
(m) |
|
|
|
Condition |
Story21 |
3 |
0.096341 |
0.431705 |
0.02864 |
0.06 |
Without Limit |
Story20 |
3 |
0.080613 |
0.403065 |
0.028495 |
0.06 |
Without Limit |
Story19 |
3 |
0.074916 |
0.374570 |
0.029165 |
0.06 |
Without Limit |
Story18 |
3 |
0.069081 |
0.345405 |
0.029605 |
0.06 |
Without Limit |
Story17 |
3 |
0.063160 |
0.315800 |
0.030005 |
0.06 |
Without Limit |
Story16 |
3 |
0.057159 |
0.285795 |
0.030285 |
0.06 |
Without Limit |
Story15 |
3 |
0.051102 |
0.255510 |
0.030375 |
0.06 |
Without Limit |
Story14 |
3 |
0.045027 |
0.225135 |
0.030250 |
0.06 |
Without Limit |
Story13 |
3 |
0.038977 |
0.194885 |
0.029485 |
0.06 |
Without Limit |
Story12 |
3 |
0.033008 |
0.165040 |
0.029120 |
0.06 |
Without Limit |
Story11 |
3 |
0.027184 |
0.135920 |
0.028040 |
0.06 |
Without Limit |
Story10 |
3 |
0.021576 |
0.107880 |
0.026645 |
0.06 |
Without Limit |
Story09 |
3 |
0.016265 |
0.081325 |
0.024620 |
0.06 |
Without Limit |
Story08 |
3 |
0.011341 |
0.056705 |
0.022175 |
0.06 |
Without Limit |
Story07 |
3 |
0.006906 |
0.034530 |
0.019250 |
0.06 |
Without Limit |
Story06 |
3 |
0.003056 |
0.015280 |
0.015280 |
0.06 |
Without Limit |
Story05 |
3 |
0.000000 |
0.000000 |
0.004425 |
0.06 |
Without Limit |
Story04 |
4 |
−0.000850 |
−0.004425 |
0.001565 |
0.08 |
Without Limit |
Story03 |
4 |
−0.001197 |
−0.005985 |
−0.000860 |
0.08 |
Without Limit |
Story02 |
4 |
−0.001025 |
−0.005125 |
−0.002430 |
0.08 |
Without Limit |
Story01 |
4.5 |
−0.000539 |
−0.002695 |
|
|
Without Limit |
The story drift results for seismic effects along the Y direction indicate that all levels of the structure are within the allowable drift limits as specified by BNBC 2020. The maximum story drift (Δy) at each level is compared with the allowable drift (Δa), Table 12 which is 0.06 for most stories and 0.08 for the lower levels. All calculated drift values are within the permissible limits, ensuring the building’s compliance with seismic safety and structural stability requirements.
Table 12. For seismic effect along Y direction.
|
Floor Height Below the X |
Elastic Displacement = Diaphragm Center of Mass Disp (For EQx) |
|
Story Drift Analysis |
Allowable Drift |
|
Level ID |
(m) |
(m) |
|
|
|
Condition |
Story21 |
3 |
0.076800 |
0.384000 |
0.020550 |
0.06 |
Within Limit |
Story20 |
3 |
0.072789 |
0.363945 |
0.020300 |
0.06 |
Within Limit |
Story19 |
3 |
0.068729 |
0.343645 |
0.021555 |
0.06 |
Within Limit |
Story18 |
3 |
0.064418 |
0.322090 |
0.022755 |
0.06 |
Within Limit |
Story17 |
3 |
0.059867 |
0.299335 |
0.024015 |
0.06 |
Within Limit |
Story16 |
3 |
0.055064 |
0.275320 |
0.025210 |
0.06 |
Within Limit |
Story15 |
3 |
0.050022 |
0.250110 |
0.026265 |
0.06 |
Within Limit |
Story14 |
3 |
0.044769 |
0.223845 |
0.027155 |
0.06 |
Within Limit |
Story13 |
3 |
0.039338 |
0.196690 |
0.027685 |
0.06 |
Within Limit |
Story12 |
3 |
0.033801 |
0.169005 |
0.027910 |
0.06 |
Within Limit |
Story11 |
3 |
0.028219 |
0.141095 |
0.027715 |
0.06 |
Within Limit |
Story10 |
3 |
0.022676 |
0.113380 |
0.027030 |
0.06 |
Within Limit |
Story09 |
3 |
0.017270 |
0.086350 |
0.025725 |
0.06 |
Within Limit |
Story08 |
3 |
0.012125 |
0.060625 |
0.023685 |
0.06 |
Within Limit |
Story07 |
3 |
0.007388 |
0.036940 |
0.020720 |
0.06 |
Within Limit |
Story06 |
3 |
0.003244 |
0.016220 |
0.016220 |
0.06 |
Within Limit |
Story05 |
3 |
0.000000 |
0.000000 |
0.002730 |
0.06 |
Within Limit |
Story04 |
4 |
−0.000546 |
−0.002730 |
0.000880 |
0.08 |
Within Limit |
Story03 |
4 |
−0.000722 |
−0.003610 |
−0.000680 |
0.08 |
Within Limit |
Story02 |
4 |
−0.000586 |
−0.002930 |
−0.001440 |
0.08 |
Within Limit |
Story01 |
4.5 |
−0.000298 |
−0.001490 |
|
|
Within Limit |
6. Design Results (Vibration Periods & Mode Shapes)
The dynamic analysis of the building indicates the vibration of the building during an earthquake. The first mode is the most significant vibration, which occurs with the period of approximately 1.301 seconds (Table 13). This implies that it vibrates once in slightly more than one second. The frequency for this mode is 0.768 cycles per second. The higher the mode the shorter the period and the higher the frequency (Table 13). This implies that the building shakes more quickly in these higher modes. As an example, the second mode has a period of 1.252 seconds and the third mode has a period of 0.91 seconds (Table 13). The significance of these results is that they will enable us to know how the building will move in case of an earthquake. With the knowledge of the vibration periods and frequencies, engineers will be able to design the building in a way that it will be able to resist seismic forces more effectively and minimize the chances of damage (Table 13). The analysis assists in making the building safe and effective in case of an earthquake.
Table 13. Modal periods and frequencies.
Case |
Mode |
Period |
Frequency |
CircFreq |
Eigenvalue |
|
|
sec |
Cyc/sec |
Rad/sec |
Rad2/sec2 |
ModalH |
1 |
1.301 |
0.768 |
4.8278 |
23.3077 |
ModalH |
2 |
1.252 |
0.799 |
5.0186 |
25.1865 |
ModalH |
3 |
0.91 |
1.099 |
6.9081 |
47.7215 |
ModalH |
4 |
0.31 |
3.224 |
20.2601 |
410.4703 |
ModalH |
5 |
0.271 |
3.696 |
23.2253 |
539.4158 |
ModalH |
6 |
0.268 |
3.735 |
23.4663 |
550.6679 |
ModalH |
7 |
0.26 |
3.851 |
24.1942 |
585.3608 |
ModalH |
8 |
0.166 |
6.016 |
37.7979 |
1425.6803 |
ModalH |
9 |
0.144 |
6.959 |
43.7227 |
1911.6704 |
ModalH |
10 |
0.139 |
73174 |
45.0783 |
2032.0521 |
ModalH |
11 |
0.132 |
7.595 |
47.718 |
3060.2062 |
ModalH |
12 |
0.114 |
8.804 |
55.3191 |
3247.8102 |
ModalH |
13 |
0.11 |
9.07 |
56.9896 |
3247.8102 |
ModalH |
14 |
0.094 |
10.593 |
66.5547 |
4429.5226 |
ModalH |
15 |
0.092 |
10.86 |
68.2363 |
4656.1955 |
ModalH |
16 |
0.086 |
11.63 |
73.0757 |
5340.0569 |
ModalH |
17 |
0.074 |
13.439 |
84.4424 |
7130.514 |
ModalH |
18 |
0.071 |
14.123 |
88.74 |
7874.792 |
ModalH |
19 |
0.07 |
14.252 |
89.5487 |
8018.9723 |
ModalH |
20 |
0.068 |
14.667 |
92.1544 |
8492.4248 |
ModalH |
21 |
0.062 |
16.072 |
100.9814 |
10197.2333 |
ModalH |
22 |
0.06 |
16.663 |
104.6985 |
10961.7668 |
ModalH |
23 |
0.054 |
18.466 |
116.0282 |
13462.5526 |
ModalH |
24 |
0.054 |
18.685 |
117.3994 |
13782.618 |
ModalH |
25 |
0.051 |
19.775 |
124.2479 |
15437.5438 |
ModalH |
26 |
0.049 |
20.276 |
127.3995 |
16230.6397 |
ModalH |
27 |
0.048 |
20.829 |
130.8753 |
17128.3318 |
ModalH |
28 |
0.046 |
21.661 |
136.0998 |
18523.1684 |
ModalH |
29 |
0.045 |
22.272 |
22.272 |
19582.293 |
ModalH |
30 |
0.041 |
24.235 |
152.2733 |
23187.169 |
ModalH |
31 |
0.04 |
24.807 |
155.869 |
24295.1341 |
ModalH |
32 |
0.04 |
25.212 |
158.4118 |
25094.2948 |
ModalH |
33 |
0.038 |
26.049 |
163.6699 |
26787.8265 |
ModalH |
34 |
0.037 |
26.711 |
167.8323 |
28167.6684 |
ModalH |
35 |
0.034 |
29.201 |
183.4731 |
33662.3624 |
ModalH |
36 |
0.034 |
29.809 |
187.295 |
35079.429 |
ModalH |
37 |
0.033 |
30.374 |
190.8454 |
36421.9622 |
ModalH |
38 |
0.032 |
31.583 |
198.4417 |
39379.0993 |
ModalH |
39 |
0.03 |
33.49 |
210.4211 |
44277.0232 |
ModalH |
40 |
0.028 |
35.263 |
221.5655 |
49091.2681 |
ModalH |
41 |
0.028 |
36.183 |
227.3451 |
51685.8055 |
ModalH |
42 |
0.027 |
37.04 |
232.7277 |
54162.1925 |
ModalH |
43 |
0.025 |
39.857 |
250.4301 |
62715.2126 |
ModalH |
44 |
0.025 |
40.307 |
253.2592 |
64140.2099 |
ModalH |
45 |
0.025 |
40.442 |
254.1058 |
64569.7642 |
ModalH |
46 |
0.023 |
43.193 |
271.3893 |
73652.1523 |
ModalH |
47 |
0.023 |
44.105 |
277.1199 |
76795.4362 |
ModalH |
48 |
0.023 |
44.262 |
278.1055 |
77342.6839 |
ModalH |
49 |
0.022 |
45.433 |
285.4611 |
81488.0234 |
ModalH |
50 |
0.021 |
46.887 |
294.5967 |
86787.2126 |
ModalH |
51 |
0.021 |
47.544 |
298.7253 |
89236.7979 |
ModalH |
52 |
0.021 |
47.953 |
301.2953 |
90778.8493 |
ModalH |
53 |
0.02 |
50.23 |
315.606 |
99607.1474 |
ModalH |
54 |
0.02 |
51.24 |
321.9497 |
103651.6293 |
ModalH |
55 |
0.019 |
52.292 |
328.5625 |
107953.3074 |
ModalH |
56 |
0.019 |
53.799 |
338.026 |
114261.6086 |
ModalH |
57 |
0.019 |
53.811 |
338.1062 |
114315.7835 |
ModalH |
58 |
0.018 |
54.805 |
344.347 |
118574.8309 |
ModalH |
59 |
0.018 |
55.756 |
350.3259 |
122728.2054 |
ModalH |
60 |
0.017 |
57.457 |
361.0148 |
130331.6931 |
7. Discussion
The 21-story multifunctional building proposed in Dhaka is a modern solution to the development of the city, as it is a solution to the architectural and structural problems of high-rise construction in a densely populated city. The combination of commercial and residential areas in one building is a sign of the current trends in urban planning to make the best use of the land, particularly in such cities as Dhaka, where space is a luxury [13]. The paper identifies some of the major aspects that make the building viable in general, including the architectural design and the structural analysis with the help of the advanced software such as ETABS.
The design of the building employs vertical zoning to divide the commercial and residential activities so that each area has its own space and the interference between the two areas is minimal. This segregation enables effective circulation and utility systems, which is essential in smooth running of mixed-use buildings. Also, the architecture emphasis on sustainability, including the employment of energy-efficient materials, renewable energy, and the maximization of natural light, is consistent with the worldwide trend toward greener and more sustainable architecture. The emphasis on seismic resilience, which is a critical factor considering that Dhaka is located in a seismic zone, will make the building comply with the structural safety standards and be effective in case of an earthquake [14].
Structural analysis of the building using ETABS software gives useful information on how the building will perform under various loading conditions [15]. The major results of the analysis such as the displacement patterns, inter-story drifts and reinforcement details show that the building can resist the high loads and environmental forces that Dhaka is likely to experience including wind and seismic forces. The robustness of the design is further increased by the detailed analysis of the load combinations, material properties and soil conditions, which makes the design efficient and durable [7].
Although the outcomes of the structural analysis and architectural design are encouraging, there are a number of aspects that should be investigated in future projects. Among them is the incorporation of high-tech sustainable solutions such as smart building systems, which may further increase energy efficiency, lower operational expenses, and the overall experience of building occupants [16]. Also, with the growing urbanization in Dhaka, it is necessary to explore the adaptive reuse approach in future projects, so that the buildings can be adaptable to the changing needs in the future. More advanced seismic resilience methods could also be studied in the future, given the growing number of seismic events in the area and the introduction of new technologies such as base isolators or energy dissipative devices to reduce the risks of earthquakes even further.
Regarding the architectural aspects, additional focus on the green roofs, rainwater harvesting systems, and larger landscaping elements may help to make the building more sustainable [17]. These characteristics do not only enhance the environmental performance of the building but also the quality of life of the occupants of the building by offering green spaces within an urban setting. Finally, the integration of the building into a smart city, in which the systems of the building are linked to a larger urban infrastructure network, may also optimize the use of resources, so that the building becomes not only a sustainable object, but also a component of a smarter, more connected city [18].
8. Conclusions
The structural analysis and design of the 21-story multifunctional building that is proposed to be constructed in Dhaka shows that it can become a new standard of urban development in the rapidly growing cities. The building combines commercial and residential areas in one building, which makes the best use of the land and provides a dynamic and sustainable environment that responds to the issues of urbanization. The project is in line with the Bangladesh National Building Code (BNBC 2020) [19] and best practices in architectural design, structural engineering, and sustainability, which will make the building last long and offer a safe and comfortable environment to its occupants.
The structural analysis, which is carried out with the help of ETABS, confirms the capacity of the building to resist seismic forces, wind loads, and other environmental stresses, which proves its resilience and safety once again [20]. The project is also environmentally sustainable, as the energy-efficient materials and systems and the emphasis on green building practices are used [6] [21]. As technology and construction methods continue to evolve, the building can be used as a prototype of future high-rise buildings in Dhaka and other cities with such urban settings.
To sum up, the project does not only solve the existing problems of urban development in Dhaka but also opens the door to future innovations in building design, sustainability, and resilience. It establishes a standard in the combination of mixed-use areas, structural security, and environmental awareness, which can be of great use to architects, engineers, and urban planners.
Acknowledgements
I would like to thank all people and organizations that helped and assisted in the completion of this research. I would also wish to offer my heartfelt gratitude to the structural engineers and architects who offered their services during the design and analysis stages so that the project was in line with the best standards of safety, functionality, and aesthetics. Special thanks are due to the professionals that assisted in the use of ETABS in the structural analysis, and those that assisted in the assessment of seismic, wind and load conditions, which were essential to this project.
Conflicts of Interest
The authors declare no conflicts of interest.