Bangladesh National Building Code Research Articles

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.

Accessibility of Public Buildings in Khulna, Bangladesh, for Wheelchair Users

Purpose : Physical accessibility is one of the fundamental rights of wheelchair users in order to ensure their integration into society. After Bangladesh ratified the UN Convention on the Rights of Persons with Disabilities (CRPD) on November 30, 2007, there has been a paradigm shift in the government’s approach to ensure the welfare and rights of persons with disabilities through legislative and policy actions. This study assesses how accommodative the public buildings are for wheelchair users in Khulna, Bangladesh. Method : All the public buildings in Khulna city - including government offices, public schools, colleges and universities, hospitals, libraries, post offices and court buildings - were visited to assess the presence and suitability of facilities for wheelchair users, such as accessible parking, ramps, elevators, doors, and essential interior facilities like water closets and drinking-water fountains. Bangladesh has no specific accessibility guidelines document, but accessibility requirements have been included in the Bangladesh National Building Code (BNBC) 2008. The study made its assessment using an abridged form of the Americans with Disabilities Act Accessibility Guidelines (ADAAG) and BNBC 2008. Results : Only 6.7% (5) of the 75 public buildings were found suitable for wheelchair users. There is scope for modifications to be made in 28% (21) of the buildings which are currently unsuitable for wheelchair users. Conclusion : The study revealed that public buildings are, in general, not very accommodative of wheelchair users. There is a need for modifications in infrastructure to ensure inclusive development of these individuals.

ANALYTICAL FRAGILITY CURVES FOR REINFORCED CONCRETE BUILDING USING SINGLE POINT SCALED SPECTRUM MATCHED GROUND MOTION ANALYSES

Seismic performance is obtained for a five-storied reinforced concrete frame building performing non-linear dynamic time history analyses. Performance of the building was obtained as a mean of fragility function of spectral acceleration. Earthquake ground motion records are selected from online source considering local earthquake faults scenario proposed in Comprehensive Disaster Management Program (CDMP) and then scaled to fit with Bangladesh National Building Code (BNBC) 1993 design response spectra. Since the structure is considered as typical reinforced concrete ordinary moment resisting frame located in Bangladesh, mechanical properties and other associated parameters are chosen according to Bangladeshi perspective. Each ground motion spectrum is matched with design code spectrum at fundamental time period of the building. Non-linear static pushover analysis is performed to determine damage states from pushover curve. Four damage states (from slight to collapse) are defined based on simplified assumptions. A set of dynamic time history analyses are carried out in order to obtain probability density function of the displacement demand correspond to different level of ground motions. Cumulative distribution of each associated damage states allows deriving fragility curves. Finally four fragility curves are obtained for four damge grades (slight, moderate, severe and collapse).

SEISMIC VULNERABILITY ASSESSMENT OF MEDICAL FACILITIES: A GIS BASED APPLICATION FOR CHITTAGONG, BANGLADESH

Medical facilities are one of the most important lifelines that need to remain functionalduring and after an earthquake. Bangladesh is a multi-hazard prone country located in thesouthern part of Asia where a significant number of natural disasters are recorded each year. Thesecond largest city and economic hub, Chittagong, is located in the south-eastern part of thecountry, falls in the seismically moderate zone as per Bangladesh National Building Code(BNBC 2017) with a seismic zoning coefficient of 0.28g based on 2 percent probability ofexceedance in 50 years. Most of the buildings were built before implementation of seismic codepracticed in Bangladesh. Based on growing need for developing disaster risk plan, seismicperformance is evaluated for existing important medical facilities by applying simple visual riskassessment procedure. The structural database is developed through field survey and result ofseismic performance is presented in Geographic Information System (GIS).

SEISMIC VULNERABILITY ASSESSMENT OF MEDICAL FACILITIES: A GIS BASED APPLICATION FOR CHITTAGONG, BANGLADESH

Medical facilities are one of the most important lifelines that need to remain functionalduring and after an earthquake. Bangladesh is a multi-hazard prone country located in thesouthern part of Asia where a significant number of natural disasters are recorded each year. Thesecond largest city and economic hub, Chittagong, is located in the south-eastern part of thecountry, falls in the seismically moderate zone as per Bangladesh National Building Code(BNBC 2017) with a seismic zoning coefficient of 0.28g based on 2 percent probability ofexceedance in 50 years. Most of the buildings were built before implementation of seismic codepracticed in Bangladesh. Based on growing need for developing disaster risk plan, seismicperformance is evaluated for existing important medical facilities by applying simple visual riskassessment procedure. The structural database is developed through field survey and result ofseismic performance is presented in Geographic Information System (GIS).

SEISMIC FRAGILITY ASSESSMENT AND RETROFIT OF A GOVERNMENT HOSPITAL BUILDING IN CHITTAGONG, BANGLADESH

Chittagong Medical College Hospital (CMCH) is one of the most important government hospitals in Bangladesh. It is located in the heart of Chittagong city, the only port city of Bangladesh. Bangladesh National Building Code (BNBC) is the only official document, which has been used since 1993 as guidelines for seismic design of buildings. As per the guidelines of BNBC, the CMCH building was designed for an earthquake ground motion having a return period of 200 years. However, the revised version of BNBC has suggested that the building structures shall be designed for an earthquake ground motion having a return period of 2475 years. It is mentioned that a single seismic performance objective, the life safety, of the building is considered in both versions of BNBC. Considering the significant importance of CMCH building in providing the emergency facilities during and after the earthquake, it is indispensable to evaluate its seismic vulnerability for the two types of earthquake ground motion records having return period of 200 (Type-I) and 2475 (Type-II) years. In this regard, this paper deals with the seismic vulnerability assessment of the existing ancillary building (AB) of CMCH. The seismic vulnerability of building is usually expressed in the form of fragility curves, which display the conditional probability that the structural demand (structural response) caused by various levels of ground shaking exceeds the structural capacity defined by a damage state. The analytical method based on elastic response spectrum analyses results is used in evaluating the seismic fragility curves of the building. To the end, 3-D finite element model of the building subjected to 18 ground motion records having PGA of 0.325g to 0.785g has been used in theresponse spectrum analysis in order to evaluate its inter-story-drift ratio (IDR), an engineeringdemand parameter (EDP) for developing fragility curves. The analytical results have shown thatstructural deficiencies exist in the existing ancillary building (AB) for the Type-II earthquakeground motion record, which requires the building to be retrofitted to ensure that the existingancillary building (AB) becomes functional during and after the Type-II earthquake groundmotion record.

SEISMIC FRAGILITY ASSESSMENT AND RETROFIT OF A GOVERNMENT HOSPITAL BUILDING IN CHITTAGONG, BANGLADESH

Chittagong Medical College Hospital (CMCH) is one of the most important government hospitals in Bangladesh. It is located in the heart of Chittagong city, the only port city of Bangladesh. Bangladesh National Building Code (BNBC) is the only official document, which has been used since 1993 as guidelines for seismic design of buildings. As per the guidelines of BNBC, the CMCH building was designed for an earthquake ground motion having a return period of 200 years. However, the revised version of BNBC has suggested that the building structures shall be designed for an earthquake ground motion having a return period of 2475 years. It is mentioned that a single seismic performance objective, the life safety, of the building is considered in both versions of BNBC. Considering the significant importance of CMCH building in providing the emergency facilities during and after the earthquake, it is indispensable to evaluate its seismic vulnerability for the two types of earthquake ground motion records having return period of 200 (Type-I) and 2475 (Type-II) years. In this regard, this paper deals with the seismic vulnerability assessment of the existing ancillary building (AB) of CMCH. The seismic vulnerability of building is usually expressed in the form of fragility curves, which display the conditional probability that the structural demand (structural response) caused by various levels of ground shaking exceeds the structural capacity defined by a damage state. The analytical method based on elastic response spectrum analyses results is used in evaluating the seismic fragility curves of the building. To the end, 3-D finite element model of the building subjected to 18 ground motion records having PGA of 0.325g to 0.785g has been used in theresponse spectrum analysis in order to evaluate its inter-story-drift ratio (IDR), an engineeringdemand parameter (EDP) for developing fragility curves. The analytical results have shown thatstructural deficiencies exist in the existing ancillary building (AB) for the Type-II earthquakeground motion record, which requires the building to be retrofitted to ensure that the existingancillary building (AB) becomes functional during and after the Type-II earthquake groundmotion record.

EARTHQUAKE RESPONSE ANALYSIS OF A MULTISTORIED RC BUILDING UNDER EQUIVALENT STATIC AND DYNAMIC LOADING AS PER BANGLADESH NATIONAL BUILDING CODE 2006

In the history of civil engineering, the structures were usually designed considering only static load factor. Later due to research in the civil engineering field, it was explored that the structures are also acted upon by several other loads which included seismic loads, wind loads, snow loads and many others depending upon the dimensions of the structure, location of the structure, type of the ground profile, etc. Hence this brought in the process of analyzing a structure for different types of loads and designing the structure for the critical load case of which dynamic load is considered as one of the important load for which the structure should be analyzed and designed. The main aim of this research work is to investigate the seismic performance of a multistoried reinforced concrete moment resisting framed building under static and dynamic loading as per Bangladesh National Building Code (BNBC, 2006). Static seismic load has been applied to the structure according to Equivalent static force (ESF) method. On the other hand, response spectrum (RS) method has been performed for the application of dynamic loading. The present study focuses on investigating the variation of storey-displacement and storey drift for each storey, base shear, bending moments and shear forces in columns at different storey level. Finally, a comparative study has been carried out between static and dynamic analysis. Based on computing modeling output data, it has been found that the base shear obtained from RS analysis is less compared to ESF method. Maximum storey-displacement obtained from dynamic RS analysis is about 78% of that of static analysis. At the same time, in case of maximum bending moment in an interior column, the dynamic value is approximately 87% of the static value.

Study of the Behavior of Beam due to the Variation in Strength of Concrete and Steel Bars

RCC structures are primarily based with beams and columns. In general, the compressive strength of concrete and the yield strength of steel are specified in the design process. Compressive strength of concrete depends on a number of factors and generally shows some degree of variation from the desired strength. On the other hand, reinforcing bars with higher yield strength than that recommended in the Bangladesh National Building Code is available in the market and being used in construction. So, in practical cases, after casting the compressive strength as well as the tensile strength are not generally achieved as desired. Therefore, increase in yield strength of steel and decrease in compressive strength of concrete may have adverse effects on the flexural behavior of beams. This study includes the behavior of reinforced concrete beam due to this variation in strengths. This study shows that how certain beam behaves due to the variation of strength. Besides, reduction in ductility is also observed due to strength variation in the properties of the major constituent materials. A complete theoretical analysis along with some experimental investigation is presented in this paper.

Assessment of Structural and Functional Status in High-rise Building in Tangail Pourashava

Today, most of the cities in the world encounter the phenomenon of high rise building. The growth of high rise building in Tangail pourashava has been considerably increased since the last few years. Though high-rise buildings helped in solving the problem of shortage of land and housing, it also caused many problems in different environmental, structural, spatial, functional, socio-economical, and demographic aspects of the city. Our study was to identify the location of high-rise buildings, to classify these buildings by their uses and to investigate the Structural and functional characteristics of high-rise buildings in Tangail Pourashava. For the study both primary and secondary data were collected, primary data has been collected from field survey and secondary data has been collected from different journals and published and unpublished publications. The study also focused on the existing high-rise buildings safety and security system available in those buildings and made recommendation that the buildings should follow the Bangladesh National Building Code (BNBC) guidance strictly to ensure all safety aspects.J. Environ. Sci. & Natural Resources, 10(1): 125-132 2017

Seismic Performance Analysis of RCC Multi-Storied Buildings with Plan Irregularity

Bangladesh is one of the most earthquake prone areas in South-Asia and Sylhet is the most seismic vulnerable region in Bangladesh. Seismic performance analysis is highly recommended to ensure safe and sound building structures for this region. To get better performance from reinforced concrete (RCC) structure, new seismic design provisions require structural engineers to perform both static and dynamic analysis for the design of structures. The objective of the this study is to carry out static and dynamic analysis i.e. equivalent static analysis, response spectrum analysis (RSA) and time history analysis (THA) over different regular and irregular shaped RCC building frame considering the equal span of each frame as per Bangladesh National Building Code (BNBC)- 2006. In this study, four different shaped (W-shape, L-shape, Rectangle, Square) ten storied RCC building frames are analysed using ETABS v9.7.1 and SAP 2000 v14.0.0 for seismic zone 3 (Sylhet) in Bangladesh. Comparative study on the maximum displacement of different shaped buildings due to static loading and dynamic response spectrum has been explored. From the analyzed results it has been found that, for static load analysis, effects of earthquake force approximately same to all models except model-1(W-shape).W-shape has been found most vulnerable for earthquake load case. It is also found from the response spectrum analysis that the displacements for irregular shaped building frames are more than that of regular shaped building. The overall performance of regular structures is found better than irregular structures.

Seismic Vulnerability Assessment of Existing Building Stocks at Chandgaon in Chittagong City, Bangladesh

The draft of Bangladesh National Building Code (BNBC)-2012 has been updated the seismic coefficient of 0.28g (with Zone III) for Chittagong region, which is larger than the previous of 0.15g (with Zone II). Chittagong is the largest port city and commercial capital of Bangladesh, which has many development activities as like of planned residential areas. Although BNBC code is up-to-date with earthquake provisions since 1993 with interpreting several new clauses and provisions, but in case of pre-code revision structures it is quite unsafe. Thus it is quite impossible to reduce earthquake damage without considering the safety of pre-code revision structures. In this regards earthquake vulnerability of Chandgaon Residential Area(R/A) has been assessed on the basis of potential structural vulnerability of more than 300 buildings. Initial results reveal that there have large varieties of construction practices, however, predominantly RCC structures were found. RVS score of these structures reveal that in general buildings are of minimum quality and further evaluation and strengthening of buildings is recommended. Walk down evaluation encountered several factors which were responsible for comparatively lower range of vulnerability scores.

A Comparative Study on Seismic Analysis of Bangladesh National Building Code (BNBC) with Other Building Codes

Tectonic framework of Bangladesh and adjoining areas indicate that Bangladesh lies well within an active seismic zone. The after effect of earthquake is more severe in an underdeveloped and a densely populated country like ours than any other developed countries. Bangladesh National Building Code (BNBC) was first established in 1993 to provide guidelines for design and construction of new structure subject to earthquake ground motions in order to minimize the risk to life for all structures. A revision of BNBC 1993 is undergoing to make this up to date with other international building codes. This paper aims at the comparison of various provisions of seismic analysis as given in building codes of different countries. This comparison will give an idea regarding where our country stands when it comes to safety against earth quake. Primarily, various seismic parameters in BNBC 2010 (draft) have been studied and compared with that of BNBC 1993. Later, both 1993 and 2010 edition of BNBC codes have been compared graphically with building codes of other countries such as National Building Code of India 2005 (NBC-India 2005), American Society of Civil Engineering 7-05 (ASCE 7-05). The base shear/weight ratios have been plotted against the height of the building. The investigation in this paper reveals that BNBC 1993 has the least base shear among all the codes. Factored Base shear values of BNBC 2010 are found to have increased significantly than that of BNBC 1993 for low rise buildings (≤20 m) around the country than its predecessor. Despite revision of the code, BNBC 2010 (draft) still suggests less base shear values when compared to the Indian and American code. Therefore, this increase in factor of safety against the earthquake imposed by the proposed BNBC 2010 code by suggesting higher values of base shear is appreciable.

Comparative Analysis of a 15 Story Flat Plate Building with and Without Shear Wall and Diagonal Bracing Under Wind and Seismic Loads

A flat plate is a reinforced concrete slab supported directly by concrete columns without the use of beams, column flares or drop panels. Flat plate system has been adopted in many buildings constructed recently taking advantage of the reduced floor height to meet the economical and architectural demands. However, In Multistoried structures the flat plate floor system has week resistance to lateral loads like wind and earthquake hence this paper is concerned to increase lateral stiffness of flat plate structure and to minimize the displacement of the structure under lateral loading. This paper is also concerned about column axial load and to review our structure with special features like shear walls & diagonal bracing. In present work, a 15 storied flat plate garments building have been modeled using software package STAAD Pro for earthquake zone II in Bangladesh .This model is considered in most vulnerable situation where we took wind speed as 260 kmph and Earthquake load has been taken as per Bangladesh National Building Code(BNBC)

Simplified design guidelines for seismic base isolation in multi-storey buildings for Bangladesh National Building Code (BNBC)

Seismic base isolation is now a days moving towards a very efficient tool in seismic design of structure. Increasing flexibility of structure is well achieved by the insertion of these additional elements between upper structure and foundation as they absorb larger part of seismic energy. However in Bangladesh, this research is still young for building structures. Therefore, this is a burning question to design isolation device in context of Bangladesh. Effort has been made in this study to establish an innovative simplified design procedure for isolators incorporated in multi-storey building structures. Isolation systems namely lead rubber bearing (LRB) and high damping rubber bearing (HDRB) have been selected for the present schoolwork. Numerical formulation and limiting criteria for design of each element have been engendered. The suitability to incorporate isolation device for seismic control has been sight seen in details. The study reveals simplified design procedures for LRB and HDRB for multi-storey buildings in Bangladesh. The detail design progression has been proposed to be included in Bangladesh National Building Code (BNBC). Key words: Seismic base isolation, simplified design, building structures, rubber bearing, response modification, base shear, yield force, shear modulus, damping.

Earthquake time history for Dhaka, Bangladesh as competent seismic record

The time varying forces in the ground generates earthquake loads and the pattern of load specified as a time history of ground excitation is the most accurate means of representing earthquake actions. The difficulty with carrying out analysis procedures to compute the responses of a structure for this type of load is that the form of the acceleration time history is to be clearly known. As there is lack of earthquake data for Dhaka, Bangladesh, which is in risk of attack by severe earthquakes, the engendering earthquake time history data of this region for precise dynamic analysis is of utmost importance. So, the objective of this research is to develop the reliable Dhaka earthquake time history, functioning as a competent seismic record. Seismic data have been measured in-situ with proper seismographic instruments at the recently occurred local earthquake near the Dhaka vicinity. Choosing the nearby seismic record, probable acceleration time history of Dhaka has been properly scaled as per the seismicity and ground acceleration characteristics of its own, following the widely accepted Bangladesh National Building Code (BNBC). Generated EQ time history is then evaluated with the prominent seismic records available in literature. This seismic data essentially yield the responses at every little incremental state of numerous time extents. The research acquaints us with suitable Dhaka earthquake time history data which can be reliably exploited as advance future seismic record. Key words: Earthquake data, competent seismic record, peak ground acceleration, time history, scaling, seismic source, earthquake record, time varying forces, BNBC, seismographic instrumentation.

Design Provisions for Stair Slabs in the Bangladesh Building Code

This paper deals with the current state of the building code provisions for the structural design of concrete stair slabs in general and those proposed for the Bangladesh National Building Code (BNBC) in particular. The design of stairs has not received due attention in most building codes. As a result, stairs, as they occur with a variety of support conditions, are designed based on the individual designer's judgment. This results in considerable overdesign with some particular types of support arrangements, since their behavior is not readily understood. The recently proposed draft of the Bangladesh National Building Code provides categorical recommendations for the design of different types of stair slabs. Some of these provisions have for the first time been included in a building code. The background of the design provisions as proposed in the BNBC is presented. A critical review of the relevant provisions of BNBC as well as the American, British, and Indian codes of practice are also highlighted in this paper.