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Pounding Between Adjacent Buildings: Comparison of Codal Provisions by Rajaram Chenna, Pradeep Kumar Ramancharla in Indian Concrete Journal Report No: IIIT/TR/2012/-1 Centre for Earthquake Engineering International Institute of Information Technology Hyderabad - 500 032, INDIA August 2012 Pounding between adjacent buildings: comparison of codal provisions Chenna Rajaram and Ramancharla Pradeep Kumar It is not uncommon to find buildings in seismically active regions built adjacent to each other without following the prescribed codal separation distance. If the separation distance is insufficient, in the event of an earthquake, pounding may cause severe architectural and structural damage, and may even lead to the collapse of the structure. Seismic design codes suggest minimum separation distance between two adjacent structures; however, the spacing has to be enough to withstand earthquake excitations. To understand the effect of codal provisions on pounding, two buildings were idealised as linear single degree of freedom oscillators. The separation distance between them was provided following the codal provisions of select countries. By subjecting the buildings to five different ground motions the first impact force due to collision was calculated and the results were analysed to compare the codal provisions. Keywords: Pounding, separation distance, ground motion, impact force, predominant frequency. Pounding describes collision between adjacent buildings or different parts of the same building during strong vibrations. It may cause either architectural or structural damage or both and may lead to partial or complete collapse of the structure. Some reported cases of pounding include Mexico City earthquake of 1985 that damaged more than 20% of the buildings in the city; Loma Prieta earthquake of 1989 (Mw7.1*) that affected over 200 structures and Chi-Chi earthquake of 1999 in central Taiwan that caused severe destruction in the towns and villages near the epicentre.1,2,3 In the case of the Loma Preita earthquake, a ten storey building 90 km away from the epicenter, experienced pounding with an adjacent five-storey building. The typical floor mass of the five-storey building was about eight times that of the ten-storey building. The distance separating them was about 4 centimeter. Pounding occurred at the 6th level in the ten-storey building and at the roof level in the five-storey building. The Taiwanese quake also left marks of pounding on many structures. Some other notable pounding cases include Sumatra earthquake [(Mw9.3) (2004) at the junctions at the top ends of piles of the approach jetty], Diglipur earthquake [(Mw6.5), (2002) at the junction of the approach segment and main berthing structure] and Sikkim earthquake [(Mw5.3) (2006) a nine storey masonry infill RC frame hostel building of Sikkim Manipal Institute of Medical Sciences].4,5 Figure shows the case of Sikkim involving two long wings of a building and the connecting corridors (Figure 1). *The moment magnitude scale denoted as Mw is used by seismologists to measure the size of earthquakes in terms of the energy released. The scale Mw was developed in the 1970s to succeed the 1930s-era Richter magnitude scale. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of the area that slipped ..... 2012 The Indian Concrete Journal Australia, Canada, France, India, Indonesia, Mexico, Taiwan and the USA take pounding into account by specifying a minimum separation distance between adjacent buildings. However, the procedure to determine the distance varies from country to country. In the USA, for example, Uniform Building Code 1997 or UBC-1997 says that it depends on the maximum displacements of each building.10 In Canadian and Israeli codes, the separation distance is a sum of the displacements of each building. The French find it using a quadratic combination of the maximum displacements. The Taiwanese code fixes it depending on the building height and the site soil conditions.3 The Argentinean code suggests a minimum gap of 2.5 cm. According to the International Building Code, IBC-2009 the separation distance between two adjacent buildings 11 is computed by Equation 1: This paper reviews the separating distance codal provisions in select countries and estimates the impact force between structures by introducing stipulations from various codes. Literature review Pounding damages during earthquakes have aroused the interest of many researchers. Stavros A Anagnostopoulos (1987) studied the pounding damages of several buildings in a block, following strong earthquakes.6 He modelled each structure as a single degree of freedom (SDOF) system and simulated pounding using impact elements. The parametric investigation of this case showed that the end structures in the row housing he studied were displaced more than the interior structures. Maison and Kasai (1992) studied pounding between a 15storey building and an 8-storey building.7 They assessed the influence of building separation, relative mass, and contact location on the impact force. Van Jeng, Kazuhiko Kasai and B.F. Maison (1992) developed spectral difference method (Double Difference Combination rule) to estimate the required separation to preclude pounding.8 Their study was based on the response spectrum approach. This method is useful not only for the assessment of pounding but also for studying the relative displacement. Filiatrault and Wagner (1995) proposed pounding mitigation techniques.9 By introducing a separation distance their solutions dealt with pounding and included either filling the gaps between buildings with an elastomeric material or connecting them with collision or bumper walls. The literature review on the subject reveals that seismic design regulations of many countries such as Argentina, The Indian Concrete Journal .....2012 ......(1) where, δmax is the maximum elastic displacement that occurs anywhere in a floor by the application of the design base shear to the structure. Cd is the deflection amplification factor and ’I’ is the importance factor for seismic loading. According Indian Standard, IS 1893:2002 the separation between two adjacent units or buildings shall be equal to the response reduction factor (R) times the sum of the calculated storey displacements.12 However, when the two buildings are at the same elevation levels, the factor R may be replaced by R/2. This clause assumes only two dimensional behaviour of building, that is, only translational pounding, and ignores the torsional pounding. However, during real ground motions torsional pounding is also possible along with uni-directional pounding. According to the Federal Emergency Management Agency (FEMA: 273-1997) the separation distance between adjacent structures shall be more than 4% of the building height to avoid pounding.13 FEMA states that for meeting the enhanced design objective, the buildings shall be adequately separated from the adjacent structures to prevent pounding as the structures respond to earthquakes, except as indicated in section 2.11.10.2 of FEMA 273:1997. This section states that pounding is assumed not to occur when the buildings are separated at any level ‘i’ by a distance greater than or equal to si. The value of si need not exceed 0.04 times the height of the buildings above grade at the zone of potential impacts. Table 1. Building separation distance between two adjacent structures from different country code provisions S.No Country Formula for distance between two adjacent structures R times the sum of the calculated storey displacements using design seismic forces to avoid damage of the two structures when the two units deflect towards each other. When the two buildings are at the same elevation levels, the factor R may be replaced by R/2. (Clause 7.12.3) 1 INDIA (IS- 1893:2007 (Draft)) 2 IBC-2009 3 UBC 1997 4 FEMA:273-1997 Separation distance between adjacent structures shall be more than 4% of the building height to avoid pounding. 5 NBC Peru E030-2003 This minimum distance not be lower than 2/3 of the sum of the maximum displacement of adjacent blocks nor lower than S=3+0.004(h-500). (Clause 3.8.2) 6 ASCE:7-2010 (Adjacent Buildings located on the same property line) (Clause 1633.2.11) (Clause 12.12.3) S = Separation distance (in cms); h = Height of structure (in cms); R = Response reduction factor; δM = Separation distance between two structures; δM1 and δM2 = Peak Displacement response of adjacent structures 1 & 2 Cd = Total deflection amplification factor; δmax = Maximum elastic displacement that occurs anywhere in a floor from the application of design base shear to the structure; I = Importance factor for seismic loading National Building Code of Peru (NBC-PERU) states that every structure should be separated from other close structures by a minimum distance to avoid contact during strong ground motions. This minimum distance shall not be less than 2/3 of the sum of the maximum displacement of adjacent blocks.14 American Society of Civil Engineers ASCE 7-10 stipulates that all portions of a structure shall be designed and constructed to act as an integral unit resisting seismic forces unless separated by a distance sufficient to avoid damaging contact under total deflection as determined in section 12.12.3 of ASCE 7-10.15 According to this section the separations shall allow for the maximum inelastic response displacement (δM). δM shall be determined at critical locations with consideration for translational and torsional displacement of the structure including torsional amplification, where applicable. Table 1 summarises the key codal provision of select countries. From the table and above discussion, it is clear that the minimum separation distance not only depends on the response of the structure but also on the amplification factor and importance factor. To understand the effect of codal provisions on pounding, two buildings were idealised as linear single degree of freedom oscillators. The separation distance between them was provided following the codal provisions of select countries. By subjecting the buildings to five different ground motions the first impact force due to collision was calculated. The study in particular dealt with the collision force of first impact of the structure by using linear impact models. Only the translational response was considered and the torsional response was ignored. Minimum separation between buildings To carry out this numerical study, two adjacent buildings were idealised as two equivalent linear single degree of freedom (SDOF) systems (Figure 2). The buildings labelled as Building 1 and Building 2 and separated by a distance δ, were assumed to have lumped masses m1 = 11400kg, m2 = 6410kg, equal stiffness k = 45000kN/m and equal damping ratios ξ=0.05. u1(t) and u2(t) represent the responses of building 1 and building 2 respectively. Typical response of building subjected to El-Centro ground motion is shown in Figures 4 and 5. The governing differential equation of motion for SDOF system is expressed in equation (2). ......(2) Where, ‘i’ denotes the building under consideration. For the purpose of studying the collision between the buildings, the south-east component of El-Centro ground motion (Figure 3) with peak ground acceleration (PGA) of 0.348 g was considered. Also for finding out the response of building to earthquake ground motion, Newmark’s approach was used. This approach is an implicit method, to calculate the response of a structure under dynamic loading. ..... 2012 The Indian Concrete Journal Now if Building-2 is placed adjacent to Building-1, the minimum distance between the buildings can be checked by the following conditions. ......(3) Collision occurs if the above condition is satisfied For the purpose of finding the minimum gap between the buildings, different periods or the time taken by the wave to complete one cycle of motion of the earthquake wave for Building 2 were considered. These were: 0.075, 0.10, 0.125, 0.15, 0.175, 0.20, 0.225 and 0.25 sec. The peak relative response of the adjacent buildings gives the minimum separation distance between them. Figure 6 shows the minimum separation distance between the two adjacent structures. From this figure it can be observed that as the period of the structure increases the minimum distance also increases. When the two structures have the same natural period, there is no need to provide any separation distance. This is because these buildings will vibrate in phase and not collide at any point of time. However, this situation is not practicable because it is very difficult to construct two structures with the same natural period. Also, it can be observed from this curve that the minimum separation distance is getting flat when natural period of building The Indian Concrete Journal .....2012 2 increases beyond 0.25 sec. However, to study this case, nonlinear analysis is necessary. In contrast, most of the code provisions are based on linear analysis, so the same was used in this study. Case study Impact force was estimated by providing the minimum separation distance between the buildings following the codal recommendations. This exercise considered Building 1 with 0.1 sec natural period and Building 2 with natural periods, ranging from 0.075 sec to 0.2 sec with an interval of 0.025 sec. Five earthquake records, namely Loma-Prieta earthquake, El centro earthquake, Parkfield earthquake, Petrolia earthquake and Northridge earthquake were selected for factoring in the ground motions characteristics (Table 2). Kelvin approach takes into account damping also. The calculation of collision force using this approach is as follows: ......(6) & (7) The damping co-efficient c k can be related to the coefficient restitution e by equating energy loss during impact. When subjected to ground motion, collision between buildings may take place transferring energy from one structure to the other. This results in the loss of energy from one and the gain of energy to the other with the two structures behaving differently. Impact force calculation uses models available on the subject. For example, Kelvin model are linear spring models.16 On the other hand, hertz model and hertz damp model are nonlinear models. In linear spring model, the energy loss during impact is not considered for calculating the impact force. The contact force during impact is taken as, ......(4) & (5) ..... 2012 The Indian Concrete Journal Table 2. Details of ground motion data S. No Earthquake Name Location Year Mw PGA, (g) Trifunac Duration (sec) Predominant Time Period Range, sec Energy, ergs 1 Lomaprieta Lomaprieta, California, USA 1989 6.9 0.220 9.58 0.41-1.61 1.41x1022 2 Elcentro Imperial Valley, California, USA 1940 7.1 0.348 24.44 0.45-0.87 2.81x1022 3 Parkfield Parkfield, California, USA 1966 6.0 0.430 6.76 0.30-1.20 6.31x1020 4 Petrolia Cape Mendocino, California, USA 1992 7.2 0.662 48.74 0.50-0.83 4.00x1022 5 Northridge Northridge, California, USA 1994 6.7 0.883 8.94 0.20-2.20 7.08x1021 Trifunac and Brady Duration: It is the time interval between the points at which 5% and 95% of the total energy has been recorded. Predominant period. The period (s) at which maximum spectral amplitudes is shown on response spectra. Normally, acceleration response spectra are used to determine the predominant period(s) of the earthquake ground motion. Ergs: Energy released by an earthquake (1 erg=1dyne.cm=1g.cm2/s2) ......(8) & (9) structure’s natural period increased, the response of the structure also increased for a given ground motion and damping. Subjecting the structure to Lomaprieta ground motion In this study, Kelvin model was used. k k was 4378 MN/m (assumed).16 The co-efficient of restitution, which is defined as the ratio of the relative velocities of the bodies after collision to the relative velocities of the bodies before collision, e = 0.6 (assumed). Results and discussion The minimum separation distances were calculated from the codal provisions listed in Table 3. As the Table 3. Minimum gap required between adjacent structures having time period T1 and T2 with respect to different codal provisions T1=0.10 sec No Code T2=0.075 T2=0.10 sec sec T2=0.15 sec T2=0.20 sec Gap(m) Gap(m) Gap(m) Gap(m) 1 IS:1893-2002 0.0005 0.001 0.004 0.01 2 UBC-1997 0.0001 0.0004 0.002 0.004 3 FEMA:273-1997 0.120 0.120 0.120 0.120 4 NBC-Peru:E0302003 0.022 0.022 0.022 0.022 5 ASCE:07-2010 and IBC-2009 0.0001 0.0003 0.001 0.003 The Indian Concrete Journal .....2012 The structures (T1=0.10 sec, T2 = 0.075 sec, 0.15 sec and 0.20 sec) were subjected to Lomaprieta ground motion. The predominant frequencies range present in the ground motion was 0.41-1.61 sec, which was far more than the fundamental period of the structures. All ground motion records considered in this analysis and their Fourier spectrua are shown in Figures 7 to 11. These Figures show the predominant frequency of an earthquake. The left side diagrams are the ground motions, which were applied to the structure and the right side diagrams are the Fourier amplitude spectra for corresponding ground motions. From the Fourier amplitude spectra one can find the predominant frequency of ground motion. Using the separation distances from the codal provisions and Kelvin model approach, the initial impact forces were calculated (Table 4). According to UBC-1997, ASCE and IBC, the initial collision force generated between T 1=0.1 sec and T 2=0.075 s was 137 kN when the structures were subjected to Lomaprieta ground motion. It may be noted that the separation distance was the least at 0.0001 m (Table 3) in these codes. Table 4 summarises the impact forces for all structures and codes. For structures ..... 2012 The Indian Concrete Journal T1=0.1 s and T2=0.15 s, the impact force was 800 kN following the ASCE and IBC codal provisions. Subjecting the structure to El centro ground motion The impact force between the buildings with periods (T1=0.10 and T2=0.075 s) was 389 kN as per IS 1893:2002 (Table 5) when subjected to El centro ground motion. For other buildings (T2=0.1, 0.15 and 0.2 s) it was zero. For the structures having the same time period, there is no need to provide separation distance between them, because they will vibrate with same amplitude and phase. The Indian Concrete Journal .....2012 The impact force for the structures having time period 0.1 and 0.075 s was 26.57 kN according to UBC-1997 even though the separation distance in this code was less than that in the IS 1893 2002 (Table 3). The amount of impact depends on the response of the structures at a particular time, minimum space between the structures and the velocity response of the structures. The velocity response of structures with time period 0.1 sec and 0.075 sec in UBC code is less than that in IS code. As the minimum separation distance between the Table 4. Initial impact forces : Structures subjected to Lomaprieta ground motion Table 6. Initial impact forces : structures subjected to Parkfield ground motion T1=0.10 sec No Code T2=0.075 sec T2=0.10 sec T2=0.15 sec T1=0.10 sec T2=0.20 sec No Code Force(kN) Force(kN) Force(kN) Force(kN) 1 IS:1893-2002 0 0 0 0 2 UBC-1997 137 0 0 0 3 FEMA:2731997 0 0 0 0 4 NBC-Peru: E030-2003 0 0 0 0 5 ASCE:072010 and IBC-2009 137 0 800 0 structures decreases, the impact force also increases. However, the time of impact does not change. If the separation distance between these buildings is say 0.01 m. The impact may occur at 15 sec. (If the separation distance is less than 0.01 m, the force of impact increases. But this impact may not occur at 15 sec. It may occur at either before or after 15 sec.) The separation distance and impact forces are the same in ASCE:07-2010 and IBC-2009. According to UBC-1997, the impact force is 1170 kN for the structures having period of 0.1 and 0.15 s, however ASCE: 07-2010 and IBC-2009 give an impact force of 6052 kN for the same structures. Between the former and the duo of the latter, the separation distance decreases Table 5. Initial impact forces: structures subjected to Elcentro ground motion T1=0.10 sec No Code T2=0.075 sec T2=0.10 sec T2=0.15 sec T2=0.20 sec Force(kN) Force(kN) Force(kN) Force(kN) 1 IS:18932002 2 UBC-1997 3 FEMA:2731997 0 0 0 4 NBC-Peru: E030-2003 0 0 5 ASCE:072010 and IBC-2009 26.57 0 389 0 0 0 26.57 0 1170 460 T2=0.075 sec Force(kN) T2=0.10 sec T2=0.15 sec T2=0.20 sec Force(kN) Force(kN) Force(kN) 1 IS:18932002 150 0 0 0 2 UBC-1997 248 0 2442 3757 3 FEMA:2731997 0 0 0 0 4 NBC-Peru: E030-2003 0 0 0 0 5 ASCE:072010 and IBC-2009 248 0 412 2236 from 0.002 m to 0.001 m and the time of impact does not change. For structures with periods T1=0.10 and T2=0.2 s, the impact forces are 460 and 5762 kN as per UBC and ASCE/IBC respectively. In this case the impact force reduces as the separation distance increases because the time of impact does not change. Subjecting the structures to Parkfield ground motion. According to IS 1893:2002, the impact force between structures with periods T1=0.1 s and T2=0.075 s is 150 kN (Table 6). But UBC and ASCE/IBC give 248 kN. Here the impact occurs at the same time. For structures having same period, there is no need to provide separation distance, because they will vibrate with same amplitude and phase. Table 7. Initial impact forces: structures subjected to Petrolia ground motion T1=0.10 sec No Code T2=0.075 sec T2=0.10 sec T2=0.15 sec T2=0.20 sec Force(kN) Force(kN) Force(kN) Force(kN) 1 IS:1893-2002 326 0 2032 0 2 UBC-1997 72 0 598 911 0 3 FEMA:2731997 0 0 0 0 0 0 4 NBC-Peru: E030-2003 0 0 0 0 6052 5762 5 ASCE:072010 and IBC-2009 72 0 1582 3466 ..... 2012 The Indian Concrete Journal Table 8. Initial impact forces : Structures subjected to Northridge ground motion T1=0.10 sec No Code T2=0.075 sec T2=0.10 sec T2=0.15 sec T2=0.20 sec Force(kN) Force(kN) Force(kN) Force(kN) 1 IS:1893-2002 1130 0 348 20878 2 UBC-1997 51 0 2204 88 3 FEMA:2731997 0 0 0 0 4 NBC-Peru: E030-2003 0 0 0 10700 5 ASCE:072010 and IBC-2009 51 0 1505 245 For structures having periods T1=0.1 and T2=0.15 s, the impact force is 2442 kN as per UBC1997. However, according to ASCE/IBC, impact force is 412kN, much less than that by UBC even though the separation distance is less. This means the time of impact changed under these conditions. Subjecting the structures to Northridge ground motion. The structure having period 0.2 s was matched with ground motion frequency. At predominant frequencies, the response of structure will be more and may lead to a high impact force. This effect can be clearly seen in Table 8 for structures with periods T1=0.10 s and T2=0.20 s. The impact force initially increases and then decreases with increasing eparation distance. With the same separation distance between two structures, the initial impact force will be same in both linear and nonlinear analysis before yielding starts. The impact values between structures having period 0.1 s and 0.2 s, are 20878 kN, 88 kN, 10700 kN and 245 kN as per IS:1893-2002, UBC-1997, NBC-PERU and ASCE/IBC respectively ( Table 8) . A comparison of codal provisions suggest, FEMA:273-1997 and NBC-PERU codes have no collisions in most ground motions except Northridge ground motion. It is noteworthy that the calculated separation distances are high in FEMA and NBC-PERU. Also the clauses on pounding in these codes are based on height of the structure only. Conclusions The case with the structure having period T2=0.2 s is similar. Even though the ground motion is same, the time of impact did not change for structure 0.075 s but not so for structures with period 0.15 and 0.2 s. The following conclusions may be drawn from this study: These data clearly show that the impact is dependent on the velocity response of the structure The structure is not affected by the amplitude of ground motion but by the frequency of ground motion. • In general as the separation distance between the two structures decreases, the force of impact increases; except when they vibrate out of phase. Subjecting the structures to Petrolia ground motion. For structures with periods 0.10 s and 0.075 s, the initial impact force is 326 kN as per IS: 1893-2002 (Table 7). However, according to UBC and ASCE/IBC it is 72 kN, even though the separation distance decreases from 0.0005 m in UBC to 0.0001 m in ASCE/IBC. This means that the time of impact changed under these conditions. The impact force between structures having periods 0.1 s and 0.15 s is 2032 kN as per IS 1893:2002. But it is less as per UBC and ASCE/IBC even though the separation distances in these codes are small compared to IS 1893:2002. Here, the impact force initially increases and then decreases. For structures with periods 0.1 s and 0.2 s, the impact values are 911 kN and 3466 kN as per UBC and ASCE/IBC respectively. Here, the impact force decreases as the separation distance increases. 10 The Indian Concrete Journal .....2012 • The duration of strong motion increases with the the magnitude of ground motion. • The response of structure with period 0.2 sec and subjected to Northridge ground motion, which has 0.2 sec predominant frequency suggest that at predominant frequencies, the structure may collapse • Among the codal provisions discussed, FEMA: 273-1997 and NBC PeruE030-2003 give a higher separation distance than other codes. The separation distance in these two codes depends on the height of the structure. • For structures having same period, there is no need to provide separation distance, because they will vibrate with same amplitude and phase. • The strength of impact depends on velocity response of the structures at a particular time and minimum space between the structures. References 1. J. Aguilar, H. Juárez, R. Ortega, and J. Iglesias., The Mexico Earthquake of September 19, 1985—Statistics of Damage and of Retrofitting Techniques in Reinforced Concrete Buildings Affected by the 1985 Earthquake, Earthquake Spectra, February 1989, Vol. 5, Issue 1, pp. 145-151. 2. Kazuhiko kasai and B.F Maison., Building pounding damage during the 1989 Lomaprieta earthquake, Engineering Structures, 1997, Vol. 19, No. 3, pp. 195-207. 3. Jeng-Hsiang Lin and Cheng Chiang Weng., A study on seismic pounding probability of buildings in Taipei metropolitan area, Journal of the Chinese Institute of Engineers, 2002, Vol. 25, No. 2, pp. 123-135. 4. Durgesh C Rai and C V R Murthy., Engineering lessons not learnt from 2002 Diglipur earthquake-A review after 2004 sumatra earthquake, Current Science, November 2005, Vol. 89, No. 10, pp. 1681-1689. 5. Hemant B Kaushik, Kastubh Dasgupta, Dipti R Sahoo and Gayatri Kharel., Performance of structures during the Sikkim earthquake of 14 feb.06, Current Science, August 2006, Vol. 91, No. 4, pp. 449-455. 6. Stavros A. Anagnostopoulos., Pounding of buildings in series during earthquakes, Earthquake Engineering and Structural Dynamics, 1988, Vol. 16, pp. 443456. 7. Bruce F. Maison and Kazuhiko Kasai., Dynamics of pounding when two buildings collide, Earthquake Engineering and Structural Dynamics, 1992, Vol. 21, Issue 9, pp. 771-786. 8. Van Jeng, Kazuhiko Kasai and Bruce F. Maison., A Spectral Difference Method to Estimate Building Separations to Avoid Pounding, Earthquake Spectra, May 1992, Vol. 8, Issue 2, pp. 201-223. Mr. Chenna Rajaram received his MS by Research degree in Computer Aided Structural Engineering (CASE) from IIIT-H and is currently pursuing his PhD under the guidance of Dr. Ramancharla Pradeep Kumar at Earthquake Engineering Research Centre (EERC), International Institute of Information Technology, Hyderabad (IIIT-H). He has published 4 papers in journals and conferences. His areas of interests are Earthquake engineering and structural dynamics, analysis and design of RC structures. Dr. Ramancharla Pradeep Kumar, holds a PhD degree in civil engineering from University of Tokyo, Japan. He is an Associate Professor and Head of Earthquake Engineering Research Centre (EERC) at IIIT Hyderabad. His research interests are numerical modelling of faults and tectonic plates, collapse simulation of buildings, seismic evaluation and strengthening of buildings and concrete codes in India. Presently he is a panel member of CED 2: IS 456 and IS 1343. 9. Andre Filiatrault and Pierre Wagner., Analytical prediction of experimental building pounding, Earthquake Engineering and Structural Dynamics, August 1995, Vol. 24, Issue 8, pp. 1131-1154. 10. ______Uniform Building Code, UBC-1997, Volume-2, Structural Engineering Design Provisions, International Conference of Building Officials, California. 11. ______ International Building Code, IBC-2009, International Code Council. INC. 12. ______ Indian standard criteria for earthquake resistant design of structures, part1 general provisions and buildings, IS:1893-2002, Bureau of Indian standards, New Delhi. 13. ______ Federal Emergency Management Agency (FEMA), NEHRP Guidelines for the seismic rehabilitation of buildings, FEMA: 273-1997, Washington D.C., USA. 14. ______National Building Code- PERU, Technical Standard of Building E.030, Earthquake Resistant Design. 15. ______American Society of Civil Engineers for Minimum Design Loads for Buildings and Other Structures, ASCE/SEI 7-10, USA 16. Susender Muthukumar and Reginald Desroches., Evaluation of impact models for seismic pounding, Proceedings of Thirteenth World Conference on Earthquake Engineering, August 2004, paper No.235. ..... 2012 The Indian Concrete Journal 11