It is updated by panel of expert in related fields. This code is very much similar to ASCE Practicing civil engineers, architects, electrical engineers, fire protection designers, plumbing engineers, mechanical engineers and planners who want to practice in Bangladesh need BNBC for design and construction of infrastructures. BNBC , though have some errors, is very useful and informative for professional engineers practicing in Bangladesh. Earthquake load and wind load have revised significantly if compared with BNBC So, civil engineers should study BNBC with utmost importance.
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We'd like to understand how you use our websites in order to improve them. Register your interest. 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 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 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. The investigation in this paper reveals that BNBC has the least base shear among all the codes. Despite revision of the code, BNBC 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 code by suggesting higher values of base shear is appreciable.
Bangladesh lies well within an active seismic zone and is prone to earthquakes. To determine earthquake forces on a structure, static analysis has gained popularity in the country and also in many other countries because of the simplicity of the method.
This calls for the use of an established and tested building code so as to ensure the safety of the structure and its occupants against the natural hazard. As the number of high rise buildings is increasing, the international codes followed for building design, detailing and construction is revised quite frequently to adopt the new practices. A total change at wind load and earthquake provisions in the proposed code can be noticed [ 1 , 2 ].
This paper is aimed to review and compare the current and proposed seismic design provisions dealing with the specification of seismic design forces among the existing and recently proposed BNBC codes as well as other codes of different countries. The main objective of this work is to compare the current seismic provision with the coming one as well as well known seismic provisions of other countries. In detail, the objectives are:. Both these codes consider the earthquake force as a lateral force.
The forces are determined on the basis of a base shear by Equivalent Lateral Force procedure. Base shear is calculated on the basis of seismic zone factor, structural importance factor and response reduction factor which is a function of structural system. Time period and soil type as a function of acceleration spectrum C s defined by BNBC and as a function of numerical coefficient C defined by BNBC are used in the expression of base shear Table 1. NBC-India code also follows somewhat similar approach [ 3 ].
On the basis of distribution of earthquake epicenters, ground motion attenuation, geophysical and tectonic data available from within as well as outside of the country [ 7 ], Bangladesh was mapped dividing into three generalized seismic zones in BNBC The seismic zoning map is revised in the proposed BNBC with provisions for four seismic zones with different level of ground motion.
Therefore, northern east areas of the country are given highest priority in the both existing and proposed edition of BNBC. Seismic zone factor is increased considerably in BNBC In BNBC , structure importance co-efficient is different for structural and non-structural components and equipment and denoted by I.
The descriptions of the cases in old and new codes are completely different. This is termed as site coefficient in BNBC The amount of ground motion amplification depends on wave-propagation characteristics of soils, which can be estimated from the measurements of shear wave velocity.
Soft soils with slower shear wave velocities generally produce greater amplification than stiff soils with faster shear wave velocities. The site classes are defined mainly in terms of soil profile depth and shear wave velocity in the existing code. BNBC includes additional two procedures to determine the site classes as measuring shear wave velocity adds cost to a geotechnical investigation.
In BNBC , it is known as response modification coefficient. It is the factor by which the actual base shear force that would develop if the structure behaved truly elastic during earth quake is reduced to obtain design base shear. This reduction is allowed to account for the beneficial effects of inelastic deformation that can occur in a structure during a major earthquake. Buildings with shorter fundamental periods attract higher seismic forces as the code-based design spectrum exhibits higher accelerations at shorter periods.
Code-based response spectrum is similar to Numerical coefficient of BNBC in a sense that both are functions of time period T and site characteristics S. But edition of the code introduces an additional parameter Damping Factor as a function of response spectrum. Damping factor is the effect of inherent energy dissipation mechanisms in a structure due to sliding, friction, etc. BNBC introduces four equations each operating within a range of time period to determine C s.
Seismic weight is the total dead load of building or structure, including partition walls, and applicable portions of other imposed loads. Total weights of permanent equipments are considered in both codes. In Indian code seismic weight is the total dead load plus appropriate amounts of specified imposed load. A comparison of base shear is the simplest way to compare the final result. Only RC ductile moment resisting framed buildings have been dealt with, because of the wide use of this structure in Bangladesh.
The zones with similar seismic activity are considered and loose soil condition has been assumed. For simplicity, building with no horizontal and vertical irregularities has been considered. Sylhet being the region of the highest seismicity in Bangladesh is considered as the location for the mapped zone factor in Fig. In Ultimate Strength Design method, the nominal earthquake loads are multiplied by a factor called Load Factor. They remain in combination with other loads and termed as Factored Load.
Also, it can be realised that at higher altitude, the difference between the two codes becomes very small. The above plots will alter amplitude for the different locations, site classes and structural systems of the building in question but the nature of the curve remains the same. For intermediate periods, one may use a linear interpolation between a linear and a parabolic distribution, or a parabolic distribution which is more conservative.
For longer-period structures, a portion of the design base shear 0. Northern part of Bangladesh is surrounded by the regions of high seismicity which includes the Shillong plateau having possessed by multiple faults. Since these parts of Bangladesh and India can be characterized by the same tectonic features, computation of base shear for those zones following respective codes will highlight the design standards of these two countries against earthquake.
Consideration of Soil with identical geotechnical features is important in comparing the base shear values as different types of soil subject to different sorts of ground motion. The maximum load factors of 1. Figure 3 is a plot of factored base shear for the maximum seismic loading that is governed by each of the respective codes and it shows proposed BNBC code exceeds the Indian code by some margins. Another graph Fig.
Soil type is assumed as before. Kolkata is found higher in terms of factored base shear. This indicates buildings in Bangladesh will collapse form an earthquake that is 1. The ASCE 7 05 code is the basis of most state seismic codes. ASCE 7 05 code provides seismic ground motion parameters as spectral acceleration coefficients S s and S 1 spectral response accelerations at 0. Worldwide seismic design maps web application provides earthquake shaking parameters, more specifically, S s and S 1 values worldwide that are needed for seismic design of structures using the ASCE 7 05 code and similar standards e.
This application is used here as a tool to gather a preliminary assessment of the seismic design parameters for Bangladesh to make a comparison with the ASCE 7 05 standard. BNBC suggests the least base shear values among the current codes compared in this paper. While developed countries are going for more conservative design, this contradiction of BNBC could be suicidal. Some modifications are needed to be made in this respect.
Proposed BNBC will surely be a more conservative approach in the seismic design of buildings in Bangladesh. Because the ASCE 7 05 code design parameters are generic, they also generally impose higher base shear values. As India is the closest neighbor to Bangladesh and shares the same tectonic zone, comparison with the Indian standard will be of more significance. Looking at the Indian standard, the design seismic loading set by BNBC seems to be well justified as the nominal base shears in the proposed standard are relatively closer to that of NBC-India But remarkably higher reinforcement requirement in ground floor column of low storied buildings than before might be a concern for building design in Bangladesh by the proposed code.
Further studies need to be made in this aspect. Atique, Z. Bureau of Indian Standards, New Delhi, Accessed 12 Aug Ali, Earthquake database and seismic zoning of Bangladesh Accessed 10 Aug Download references.
This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author s and the source are credited. Correspondence to Md. Reprints and Permissions. Bari, M. India Ser. A 94, — Download citation. Received : 08 September Accepted : 17 February Published : 15 March Issue Date : September Search SpringerLink Search.
Download PDF. Abstract Tectonic framework of Bangladesh and adjoining areas indicate that Bangladesh lies well within an active seismic zone.
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