Earthquake Resistant Design and Construction Practices in India

This paper examines the earthquake resistant design and construction practices prevailing in India. Results of a set of studies conducted to estimate the seismic performance of Indian housing stock, are presented. A field survey was conducted in the National Capital Region to assess the expected seismic performance of multistorey buildings, as these are so-called ‘engineered’ buildings and the area represents the best design and construction practices prevailing in India. Common deficiencies found in the buildings are presented along with the preliminary assessment as per FEMA-310 simplified analysis methodology. Regularity of building plans and elevations and adequacy of building structures in shear and overturning is examined. It is observed that a majority of the buildings is inadequate for the ground shaking hazard expected in the area as per Indian seismic design code, indicating a very poor enforcement of code. An investigation of the construction practices prevailing in the area also reveals that the ductile detailing practices as per Indian code of practice are not being followed. The details at beam-column joints are particularly poor. Results of analytical studies performed to assess the seismic performance of buildings designed and constructed with and without following the code provisions are also presented. Indian code, similar to other national codes, is a prescriptive code exercising control over strength, ductility and drift. ASCE-41 methodology has been used for assessment of building performance and HAZUS methodology has been used for assessing the seismic fragility of buildings. Relative influence of different code provisions on seismic performance of code designed buildings has been studied and some important conclusions about adequacy of code provisions are drawn. The RC buildings designed as per Indian Standard, have Overstrength Ratio of the order of 2, which results in significant reserve strength. The buildings designed as OMRF or as SMRF, as per Indian Standard satisfy Immediate Occupancy performance level, even for the Maximum Considered Earthquake. Interestingly, performance of OMRF design is marginally better than that of SMRF. The current provision for limiting the interstorey drift, at design load, is responsible for this discrepancy. Capping on the design period, as specified by the code, is the most crucial provision for controlling the expected performance of the buildings. This results in more than two times increase in the design base shear. The current form of Indian Standard provision for control of interstorey drift leads to many discrepancies. It governs the design, only when capping on design period is applied, although the buildings designed with period capping are generally stiffer than the buildings designed without capping. Further, it is generally not a governing criterion in case of SMRF, in spite of the fact that SMRF design results in more flexible buildings. In probabilistic terms, it results in higher probability of damage in case of SMRF design, as compared to OMRF design. This discrepancy is due to the specification of interstorey drift limit at design loads, which results in different effective limits on inelastic drifts in case of OMRF and SMRF. Construction Techniques: A Case Study of Earthquake Resistant Construction in State of Uttaranchal Girish Chandra Joshi Senior Executive (Earthquake Engineering), Disaster Mitigation and Management Centre, Department of Disaster Management (Government of Uttaranchal), Uttaranchal Secretariat, 4 Subash Road, DEHRADUN248 001, Uttaranchal Email: [email protected] Evaluation of new construction techniques together with increasing understanding of the seismic forces and the building response has certainly contributed positively to decrease seismic vulnerability. The up-gradation of the seismic standards has resulted in accurate and appropriate calculation of seismic forces that would act upon any structure. It is always easy to set standards but to comply with these is a Herculean task. Even after immense progress in earthquake engineering overwhelming large proportion of the building stock still has lower standards of earthquake safety and these would give way in case of earthquake loading. The common people, at present, do not adhere to correct design and construction methodology while using modern seismic design methods or even the use of our indigenous practices. Case study of Uttarartchal State clearly brings forth deterioration of time tested indigenous construction practices and proliferation of nonscientific and improper use of concrete. This adds to the vulnerability of the region that is at present much higher than what it was a decade before when the region last experienced a major quake. The case study highlights three inter-related aspects. First, these bring forth key features of local traditional knowledge and capacity of rural communities for mitigation, preparedness and recovery from earthquakes. The traditional knowledge is embodied in physical planning and building, skillfully using local resources, mutual support systems and informal livelihood mechanisms. Second, these provide an in-depth understanding of the transformation processes (pertaining to changes in built form, land use and ownership, occupational structure and social and economic structure) and their impact on traditional knowledge and capacity and resulting enhanced earthquake vulnerability. Third, these show the implications of post earthquake rehabilitation on disaster vulnerability in the long run. These show how certain decisions during rehabilitation not only reinforce pre-disaster vulnerabilities but also create new ones. Proposed Rapid Visual Screening Procedure for Seismic Evaluation of RC Frame Buildings in India Keya Mitra 1 , Sudhir K Jain 2 , Mehul R Shah 3 1 Department of Architecture, T & RP, Bengal Engineering and Science University, Shibpur, Howrah-711103 email: [email protected] 2 Director, Indian Institute of Technology Gandhinagar, Ahmedabad – 382424. email: [email protected] 3 Faculty, School of Building Science & Technology, CEPT University, Kasturbhai Lalbhai Campus, Navarangpura, Ahmedabad 380 009. email: [email protected]