Bangladesh National Building Code Research Articles

Effect of positioning of shear walls in a multi-storied building on response to earthquake

Seismic events are a matter of concern for structural engineers because of their devastating effects. These events are neither can be predicted. nor can be prevented. To mitigate its impacts on the structures several measures are taken. But none of them can be treated as 100% effective, there is a lot of scope for improvement. In this study, the dynamic behavior of structures under seismic loading was investigated, focusing on the combined influence of geometric shapes, different types of shear walls, and their position on lateral displacement and drift. Specifically, four different geometric shapes of plans of identical floor areas were taken for this study. Two types of shear walls, oupled shear walls, and core shear walls were placed in four different positions. The Static Equivalent Load method to assess the seismic response of structures is employed in this study, following the guidelines given in the Bangladesh National Building Code 2006 using ETABS software. Key findings of the study are the efficacy of shear walls in mitigating lateral displacement. The optimum results were achieved for central positions and core wall configurations. The study discloses the significance of different geometric shapes on seismic responses. This study provides a perception of effective seismic retrofitting strategies.

SEISMIC BEHAVIOR OF MULTI-STORIED RC BUILDING WITH RE-ENTRANT CORNER

Nowadays, buildings often feature irregular floor plans for functional, aesthetic, or economic reasons. Constructing earthquake-resistant structures in seismic areas, especially with irregular shapes like re-entrant corners, poses challenges. Such corners are common when maximizing limited space is a priority. In earthquakes, re-entrant corners in structures pose major vulnerabilities, causing stress concentration and torsion problems. The main aim of this paper is to develop finite element structural analysis models of 10, 12, and 15-storied L-shaped RC buildings with a re-entrant corner under different seismic zones using equivalent static analysis (ESA) and response spectrum analysis (RSA). This research also focuses on the overall behavior of analysis results (story drift, overturning moment, base shear, etc.) with the influence of re-entrant corner. It also investigates the performance of columns and beams near re-entrant corners as the number of stories increases in different seismic zones. For the current study, ETABS V19 is used. Models consider seismic, dead, and live loads. The Bangladesh National Building Code (BNBC) 2020 is used to examine the equivalent static analysis (ESA) and the response spectrum analysis (RSA) methods. It has been concluded from the study that re-entrant corner beams consistently exhibit the highest bending moments and torsion levels across all seismic zones. Similarly, re-entrant corner columns consistently demand the most axial force and rebar when compared to similar column types. Furthermore, the study identifies maximum stress levels in re-entrant corner slabs across all seismic zones.

Seismic Risk Assessment of Existing Buildings of HSTU Campus in Dinajpur

Bangladesh is at high risk of earthquakes due to its geographic location. Earthquakes can cause widespread damage to buildings and infrastructure, as well as significant loss of life, due to the sudden release of energy in the form of seismic waves. Therefore, identifying and assessing the vulnerability of existing buildings is crucial for earthquake risk reduction. Hajee Mohammad Danesh Science and Technology University (HSTU) is situated just 13 kilometers from Dinajpur, which falls under zone II, a medium-risk zone according to the Bangladesh National Building Code (BNBC, 1993). This study aims to evaluate the seismic vulnerability of HSTU's existing buildings. A widely used seismic assessment technique, the Turkish two-level assessment procedure, was employed in this study to identify seismically vulnerable buildings. A total of 79 buildings were surveyed at level I, considering vulnerability parameters such as soft storey, heavy overhanging, pounding effect, topographic effect, short column, shape of building, number of storeys, apparent quality of building, and soil type. Based on these parameters, performance scores were assigned to each building, and they were classified into damage categories of safe, moderate, and unsafe at level I. Digital photographs of each building from at least two directions were taken for easy identification. All 79 buildings on the HSTU campus were found to be safe after the level I survey. Level II assessment was conducted on only one building to validate the level I findings, and it was classified as a low-risk structure. A significant outcome of this study is the identification of damage categories and the potential to reduce seismic risk at HSTU by creating a comprehensive building inventory.

Lateral Load and Design Disparity between BNBC1993 and BNBC2020

Building codes are the minimal requirements for design and construction to assure a safe and resilient structure. A building code recognized as the Bangladesh National Building Code (BNBC) is existent in Bangladesh (BD), just like in other developing nations. It's now a difficult task to comply with the code because of the extensive update after two decades. The main goal of this work is to compare the analytical and design requirements for lateral loads between BNBC2020 and BNBC1993. To do so, a large number of structural models are assessed using ETABS following the considered code procedure at different locations in the country. It also compares the lateral load parameters such as zone coefficient, wind velocity, building period, story shear, base shear, drift, deflection, reinforcement ratio etc. The parametric comparison of the outcomes has demonstrated that BNBC2020 is more conservative and boosts the safety factor against lateral loads. Engineers will be able to comprehend the differences in lateral load between these codes after perusing this study.

Different orientations of shear wall in a reinforced concrete structure to control drift and deflection

While Dhaka, the capital city of Bangladesh, adapts to more and more high-rise buildings and skyscrapers, concerns remain about their design efficiency and ability to withstand shear loads from seismic movements. In this study, several orientations and placements of shear walls in a regular G +15 story reinforced concrete building were assessed to observe the nature of the structure subjected to earthquake seismic loads by adopting the Equivalent Static Analysis. CSi ETABS 2019 was utilized to analyze the story shear, drift, displacement, stiffness, torsional irregularity and compared against eight separate models with different shear wall placements. The significance of this study lies in its contribution to the area of designing earthquake-resistant structures with appropriate shear wall locations following the recent Bangladesh National Building Code 2020 (Seismic criteria as per ASCE 7-05). Results reveal that shear walls placed symmetrically and along the shorter span for the selected structural plan have shown less lateral drift and displacement than structures with other shear wall orientations.

Comparison of Wind Load among Bangladesh National Building Code (BNBC) and Other International Codes

Comparison of Wind Load among Bangladesh National Building Code (BNBC) and Other International Codes

In-plane cyclic response of unreinforced masonry walls retrofitted with ferrocement

Unreinforced masonries are weak against seismic loads which necessitates their retrofitting. Ferrocement is widely used as it is cheaper than alternative methods of retrofitting. Some crucial parameters can significantly affect the performance of such retrofitted structures under cyclic loading conditions, such as: aspect ratio, difference of wire mesh arrangements & pattern of retrofitting. To quantify the impact of these parameters, this study has implemented two variations of each parameter. This study conducts experimental investigations of the ferrocement retrofitted unreinforced masonry walls (URM) and evaluation of their properties such as energy dissipation, stiffness degradation, hysteretic damping, ductility, and load deformation responses. Results show notable increase in strength after ferrocement retrofitting of URM walls. Retrofitting of URM walls with inexpensive material such as ferrocement is gaining popularity, our research is guided towards finding the in-plane cyclic load characteristics of such method of retrofitting. Sample walls were prepared in two categories: (1) Long walls (aspect ratio 0.57) and (2) Short walls (aspect ratio 1). A total of ten clay masonry walls (five for each category) were constructed with reinforced concrete base slab. The first variable parameter for the tests was ferrocement coating difference. Some sample walls were retrofitted completely even the base slab & wall panel connection point while on some walls the ferrocement lamination was only applied on the wall panels. Steel wire mesh’s opening size is another crucial variable test parameter. Two different wire mesh opening sizes: (1) 3.2 × 3.6 mm and (2) 8.5 × 8.5 mm were used on the walls. One control specimen with no retrofitting for both short and long walls were prepared for test comparison purpose. Laterally reversed cyclic loads and vertical loads both were applied to the sample walls during tests. Improvements in hysteretic damping, stiffness, energy dissipation and ductility were scrutinized in particular. Finally, a comparison was drawn between the test findings and allowable load provisions prescribed in the Bangladesh National Building Code (BNBC) 1993.

Proposal of Resilient Housing Features for the Disaster Affected Community of Bangladesh

Thinking resiliency in terms of housing features for post disaster housing reconstruction (PDHR) is a paramount initiative after a disaster. Therefore, the aim of this research is to ascertain the demands of the disaster victims and propose a wind-resistant, resilient housing prototype that would be affordable. Based on a three-month survey of the region severely damaged by Cyclone SIDR in Bangladesh, this research argues that PDHR’s planning features are significantly short of the victims’ choice, need, and demand, forcing them to quickly modify or transform the reconstructed houses. Based on the survey, a prototype covering an area of 37.21 sq. m (400 sq. ft) with a hybrid construction technique and a cost model are proposed that will be a resilient solution against cyclones and other natural hazards. Additionally, the proposed house was modeled using finite elements, and its findings are within the International Building Code’s allowable limits. In conclusion, this paper proposes some guidelines to strengthen Bangladesh National Building Code (BNBC) that would enable to build a resilient housing society in the disaster-prone areas.

Current Situation of Fire Safety Condition for Steel Structures in Dhaka: Exploring Fire Resilient Design

Steel framed building plays a vital role in construction sector with respect to Bangladesh’s socio-economic development due its long spanning capability and better flexibility. Yet there is very insufficient attention for the fire safety in steel buildings. Given the lack of fire risk assessment in steel building, this study intends to develop an understanding in fire safety condition in the sector. With the help of software analysis, this study presented the fire resistance capacity of steel at 816°C for minimum 30 minutes. Also, a field survey was conducted in 25 steel buildings situated at Dhaka city or near Dhaka like Gazipur, Savar, Narayngonj to picture the actual safety conditions in steel buildings. After analyzing the survey data, this study develops fire risk index for individual steel building with a scale 0 to 4, with average FRI 2.46 which indicates the poor fire safety condition in most of the buildings. The poor FRI values shows large deviations from standard fire safety requirements set by Bangladesh National Building Code (BNBC-2006). Stricter monitoring and enforcement of rules by the authority and increasing awareness is recommended to improve safety condition and practice among the users of steel buildings.

Fire Risk Situation Analysis in the Nimtoli Area of Old Dhaka

Assessment of the fire risk situation of Nimtali area by using eight indicators related to the fire source, fire spreading and evacuation during fire incidents was conducted. The results revealed that none of the buildings has emergency exits, fire protection measures, fire hydrant and provision of a fire drill. The area is densely populated. Most of the buildings are mixed-used and have no space in between. Electrical cables are haphazardly hanging from poles. Access roads are incredibly narrow. By analyzing eight indicators, it is found that the entire Nimtoli area is still at risk of fire hazard. Within Nimtoli, 32% area is at high risk, and 45% is at moderate risk of fire hazard. Proper fire safety measures and safety inspection, regular maintenance of utility lines, awareness about fire hazards among the dwellers, proper implementation of Bangladesh national building code (BNBC) and regulation of mixed-use of buildings can drastically reduce the fire risk in the urban area of Bangladesh.
 J. Asiat. Soc. Bangladesh, Sci. 46(1): 91-102, June 2020

An investigation on the impact of shading devices on energy consumption of commercial buildings in the contexts of subtropical climate

PurposeApplication of appropriate shading device strategies in buildings can reduce direct solar heat gain through windows as well as optimize cooling and artificial lighting load. This study investigates the impact of common shading devices such as overhangs, fins, horizontal blinds, vertical blinds and drapes on energy consumption of an office building and suggests energy efficient shading device strategies in the contexts of unique Bangladeshi subtropical monsoon climate.Design/methodology/approachThis research was performed through the energy simulation perspective of a prototype office building using a validated building energy simulation tool eQUEST. Around 100 simulation patterns were created considering various types of shading devices and building orientations. The simulation results were analysed comprehensively to find out energy-efficient shading device strategies.FindingsOptimum overhang and fin height is equal to half of the window height in the context of the subtropical climate of Bangladesh. South and West are the most vulnerable orientations, and application of shading devices on these two orientations shows the highest reduction of cooling load and the lowest increment of lighting load. An existing building was able to save approximately 7.05% annual energy consumption by applying the shading device strategies that were suggested by this study.Originality/valueThe shading device strategies of this study can be incorporated into the Bangladesh National Building Code (BNBC) as new energy-efficient building design strategies because the BNBC does not have any codes or regulations regarding energy-efficient shading device. It can also be used as energy-efficient shading device strategies to other Southeast Asian countries with similar climatic contexts of Bangladesh.

Seismic response of multi-span continuous irregular bridges using displacement-based and conventional force-based methods

In the recent years, the displacement-based seismic design (DBD) method of structures has been recognized as the alternative design method to the conventional force-based seismic design (FBD) method. The problems inherited in the FBD method are mostly overcome by the DBD method as it better correlates the structural damage with displacement-based quantities. In this study, the seismic response of multi-span bridges with varying number of spans and unequal pier heights was evaluated using the DBD method and compared with the conventional FBD method. Two approaches were employed in the DBD method, such as the traditional direct displacement-based seismic design (DDBD) approach and the proposed approach in this study entitled as alternative-to-direct displacement-based seismic design (ADBD). For seismic evaluation of the bridge structures with the FBD method, acceleration response spectra as suggested in the Bangladesh National Building Code were used; while in the DBD method, displacement response spectra for different damping ratios were developed keeping consistency with the above-mentioned design acceleration spectra. Five bridge models were used in the analysis to compare the seismic response in both the longitudinal and transverse directions taking into account the number of spans and height irregularity in the bridge models. Numerical analysis showed very obvious results that the base shear calculated by both approaches of the DBD method is found to be smaller than the FBD method indicating that an economic member section be attained for meeting the same design objective. More specifically, the ADBD approach provides the design professionals a more conservative design approach in compared with the DDBD approach keeping an economic design approach comparing with the FBD method.

Building codes and regulations for disaster resilience in Bangladesh: the case of Dhaka

Purpose The paper deals with the challenges and opportunities of enabling resilience of the built environment through building regulations and codes in a developing country context. The purpose of this paper is to explore how voluntary compliance can be achieved, drawing from the views of key stakeholders in this field. Design/methodology/approach Dhaka, the capital city of Bangladesh, is a central hub of more than 20 million people. The city is growing rapidly in an unplanned manner to host the increasing population, creating vulnerability to different hazards including earthquakes, fires and building collapses. The Bangladesh National Building Code (BNBC) and the building and planning regulations of the Capital Development Authority are the key instruments for ensuring safety, but lack of compliance is widespread. The views of relevant stakeholders on issues relating to compliance of safe building codes for ensuring disaster resilience were documented and analysed. Findings It was found that those involved in construction activities are in most cases not aware of the BNBC; landowners were reluctant to follow regulations and codes to avoid extra cost; and construction workers were not interested in compliance as there were no incentives. While enforced deterrence is required, it has its limitations in a context such as Dhaka. Raising awareness and building capacity at all levels can offer a way forward for voluntary compliance. Incorporation of knowledge on regulations and codes for disaster resilience into university and technical education curricula are likely to allow developing the capacity of built environment professionals and widespread awareness can be raised through training, media and public events. Originality/value There are many publications on building regulations and codes, but few specifically focussing on disaster resilience. Also, much of the discussion on regulations and codes deals with compliance through enforcement, but hardly any deal with the idea of voluntary compliance. There are also a lot of publications on disasters in the case study city, Dhaka, but comparatively few on building codes and regulations specifically for disaster resilience.

Numerical computation of natural ventilation system at the top floor of a multistory building in Dhaka city

urban environment studies have become more and more critical in the past decades because of the rapid development of urbanization in industrial countries. Temperature, velocity, average mass flow, etc. at different unit on the top floor of a multistory building are discussed here. For the numerical computation of the air flow inside the building rooms, the k−ε turbulence model is used. ANSYS CFX software is used to solve the governing equations. For modeling the building, Bangladesh's national building code is applied. The turbulence model is also validated by comparing the result with an experimental result and a numerical result. Satisfactory ventilation rate is also ensured by comparing the result with ANSI/ASHRAE Standard 62.1-2004.
 Journal of Bangladesh Academy of Sciences, Vol. 44, No. 2, 161-178, 2020

A Comparative Study of Lateral Load Analysis Considering Two BNBC Codes Using ETABS Software

The Bangladesh National Building Code (BNBC) specifies and regulates the general specifications for structural, architecture and design parameters in Bangladesh. In the last three decades, Civil Engineering techniques, knowledge and materials as well as design parameters have been modified as per requirement. As a consequence, BNBC 2010 was written to reflect the transition. In this study, a systematic and parametric structural analysis of a ten-story residential building was analyzed (ETABS 16.0.2 software) by using BNBC 1993 and BNBC 2020 for four different locations (Patuakhali, Chandpur, Rangpur and Moulovibazar) suited in several zones to demonstrate how lateral load affects structural analysis and design of high rise infrastructure. The decision making parameters for structural analysis and design are tremor and wind forces, story drift, wind and seismic shear, moment of unique beams and columns, and base shear for seismic forces according to BNBC 2020 vary significantly compared to BNBC 1993. In this study, the earthquake load varies from 7.42% to 59.78%, while wind force ranges from 19.16% to 36.14% in the x-direction and 49.51% to 63.78% for y-direction, and story drift for earthquake load ranges from 47.96% to 51.27% and for wind load ranges from 29.89% to 34.45%. The comparison of the aforesaid design parameters is depicted graphically, and relevant tables are presented in this research article. In comparison to BNBC 1993, the requirements of BNBC 2020 usually result in a less cost-effective design with a higher safety margin.

Design Water Level Calculation And Analysis Of Chittagong Power Plant Project In Bangladesh

The design water level calculation methods in the Chinese and foreign codes are different. The design high and low water levels and extreme high and low water levels in the Chinese norms are calculated using historical cumulative frequencies with tide level data of not less than 1 year and 20 years, respectively. In foreign norms, the average high and low tide levels of spring tides are mostly used as the design high and low water levels, and for the sea areas lacking long-term measured data, the water level combination method is mostly used to determine the extreme water levels. This paper compares the results of different methods used to calculate the design water level using the Chittagong Power Plant in Bangladesh as an example. The calculations show that it is safer to use the tidal eigenvalue method to determine the design high and low water levels, and that the Water Level Combination Method is more suitable for extreme water level determination than Bangladesh National Building Code.

Impact assessment of window to wall ratio on energy consumption of an office building of subtropical monsoon climatic country Bangladesh

Building’s window-to-wall ratio (WWR) plays a significant role for predicting energy consumption in tropical climate because huge amount of solar heat gain occurs through the exterior windows for having high solar radiation intensity and annual average temperature in tropical climatic regions. This study investigates the impact of WWR on energy consumption of air-conditioned office buildings in subtropical monsoon climatic country Bangladesh. This research was conducted through rigorous energy simulation perspective by developing a two storey prototype office building in a validated energy simulation tool eQUEST. Around 216 design alternatives were developed for simulation considering eight major cities of Bangladesh, WWR percentage from 10% to 80%, wall thickness, thermal insulation thickness, shading height and window orientations. A comprehensive data analysis was performed to predict the optimum range of WWR percentage for the air-conditioned office buildings. This research suggests a range of WWR that 30% to 40% is the optimum range for the air-conditioned office buildings in Bangladesh. An existing office building was able to save about 9.40% percent of electricity by incorporating optimum percentage of WWR. The output of this work can be incorporated into Bangladesh National Building Code as energy efficient strategies for designing an air-conditioned office building.

Requirement of expansion joint for temperature load for RCC structures

Concrete is the most commonly used material in building construction. Concrete structures are subjected to seasonal and daily temperature changes due to their interaction with the surrounding environment, in addition to live and dead loads. Significant change of temperature can impose large amount of stress in a structure. These thermal stress values can even exceed the stress values induced by the live and dead loading in case of no or little thermal insulation and could lead to severe damages if not considered during the design. One way of minimizing the temperature stress is to limit lengths of building. In Bangladesh National Building Code and many other national codes, there is no specific guideline for length limits or provision for considering stresses due to temperature load. This paper is aimed to determine the maximum permissible length of a structure without providing an expansion joint so that temperature changes do not create undue stresses. Parametric study involving thermal effect on RCC structures was performed for varying dimensions, conditions and story levels. If temperature effect for structures with significant length is considered, it has been found that top deflection and rebar percentage exceeds limiting values. The finding could become useful in guiding to set the permissible building length without expansion gap.

Myths, Safety and Awareness of Lightning Protection in Bangladesh

Bangladesh, being a tropical country, experiences relatively high density of lightning each year. Lightning has been identified as one the major causes of weather-related deaths and injuries in Bangladesh. The government of Bangladesh has declared lightning as natural disaster when 81 people have lost their lives in just two days due to lightning in 2016. Lightning is a source of fearfulness, inquisitiveness, inspiration and panic. As number of death has increased in Bangladesh in lightning, so the safety rules for the installation of lightning prevention system which is a mandatory provision under Bangladesh National Building Code, to be followed for building construction. People of low literacy rate have the tendency to violate more, the basic lightning safety guidelines. Hence, awareness program has started to educate the people especially the rural one. However, a survey has been conducted to find out the common myths, beliefs, misconceptions in Bangladesh and its impact on lightning safety. It summarizes the prevailing lightning safety awareness and education around the world. Finally, it puts forward some ray of light about the suggestions about lightning protection, safety and awareness for Bangladeshi people to curb the myths and misconceptions.

A Comparative Study of Behavior of Multi-Storied Regular and Irregular Buildings under Static and Dynamic Loading

One of the major challenges of constructing any high rise building for civil engineers is to make it earthquake resistant. This resistance largely depends on the building’s shape and structural system. A comparative study has been done in this paper about the seismic behavior and response of buildings having a regular plan and plan irregularity (re-entrant corners). The 5 building models considered in this study are 15 stories each, the same area and identical weight. Among the 5 building models, 2 are with a regular plan (square, rectangle) and the other 3 building models are with plan irregularity (re-entrant corners). All of them are modeled using ETABS 2015 program for Dhaka, Bangladesh (seismic zone 2). Static loads, wind loads and seismic loads are considered for each model and dynamic response under Bangladesh National Building Code (BNBC) 2006 response spectrum has been meticulously analyzed. A comparison for story displacement, base shear, story drift and time period has been established and explored for dynamic response spectrum among the models. The results show that buildings with irregularity have a greater value of time period, drift and displacement and hereby are more susceptible to damage during an earthquake or disaster.