Adjacent buildings with insufficient separation, having different dynamic characteristics may vibrate out of phase during earthquakes causing pounding between them. The pounding of structures may lead to severe damage and even result in complete collapse. Seismic pounding damage was found to be significant between adjacent buildings during the 1985 Mexico, 1994 Northridge, 1995 Kobe, 1999 Kocaeli and 2008 Sichuan earthquakes. The concentrated local damage and increased floor accelerations in buildings are some of the major consequences of seismic pounding.

The seismic pounding of structures is studied through numerical simulations, focusing on multi-story reinforced concrete (RC) buildings. The buildings are designed according to ACI-318-08. Three dimensional frame models of buildings are used where RC members are modeled as force-based elements with fiber-based section discretization. Material as well as geometric nonlinearities are considered (Fig. 1). Nonlinear transient analysis is carried out for different earthquake records, configurations of buildings and gap sizes. The response of buildings is compared in terms of damage, pounding scenarios, impact forces, shear amplification factors and inter-story drift demands. For example, number of pounding instances can be observed from the horizontal displacement time history at a typical impact level between adjacent buildings (Fig. 2). The impact forces at each impact level as shown in Fig. 3 can provide valuable insights into the significance of impact between the buildings. Recently, a modified Kelvin-Voigt (MKV) model is proposed for the contact-elements to simulate the pounding between buildings. The proposed model eliminates the serious drawbacks of conventional Kelvin-Voigt model (Fig. 1).

Future directions in the study include further development of contact-element models to capture the pounding phenomenon with greater accuracy, pounding analysis of base isolated tall buildings and non-structural loss estimation in the buildings.

Fig. 1. Building pounding simulation.

Fig. 2. Horizontal displacement time history at a typical impact level.

Fig. 3. Maximum impact force variation at each impact level for different earthquakes.

**Related Journal Papers:**

[1] Shakya, K. and Wijeyewickrema, A. C., 2009, "Mid-column pounding of multi-story reinforced concrete buildings considering soil effects", Advances in Structural Engineering, Vol. 12, No. 1, pp. 71-85. IF = 0.463 (2010)

[2] Pant, D. R. and Wijeyewickrema, A. C., 2011, "Structural performance of a base-isolated reinforced concrete building subjected to seismic pounding", Earthquake Engineering and Structural Dynamics, Vol. 41, Issue 12, pp. 1709-1716. IF = 1.778 (2011)

[3] Pant, D. R., Constantinou, M. C. and Wijeyewickrema, A. C., 2013, "Re-evaluation of equivalent lateral force procedure for prediction of displacement demand in seismically isolated structures", Engineering Structures, Vol. 52, pp. 455-465. IF = 1.713 (2013)

[4] Pant, D. R., Wijeyewickrema, A. C. and ElGawady M. A., 2013, "Appropriate viscous damping for nonlinear time-history analysis of base-isolated reinforced concrete buildings", Earthquake Engineering and Structural Dynamics, Vol. 42, Issue 15, pp. 2321-2339. IF = 1.898 (2013)

[5] Pant, D. R. and Wijeyewickrema, A. C., 2013, "Influence of near-fault ground motions on the response of base-isolated reinforced concrete buildings considering seismic pounding", Advances in Structural Engineering, Vol. 16, No. 12, pp. 1973-1988. IF = 0.489 (2012)

[6] Pant, D. R. and Wijeyewickrema, A. C., 2014, "Performance of base-isolated reinforced concrete buildings under bidirectional seismic excitation considering pounding with retaining walls including friction effects", Earthquake Engineering and Structural Dynamics, Vol. 43, Issue 10, pp. 1521-1541. IF = 1.898 ( 2013)

**Related Conference Papers:**

[1] Usui, K. and Wijeyewickrema, A. C., 2004, "Seismic pounding of adjacent buildings", Proceedings of the Sixth International Summer Symposium JSCE, July 31, Saitama, Japan, pp. 125-128.

[2] Ohta, R, Wijeyewickrema, A. C. and Farahani, A., 2006, "Structural pounding between adjacent buildings in a row", 2006 Taiwan-Japan Symposium on the Advancement of Urban Earthquake Hazard Mitigation Technology, September 25-26, Chungli, Taiwan, Paper #: A12, 8 pages.

[3] Ohta, R, Wijeyewickrema, A. C. and Farahani, A., 2006, "End building pounding during earthquake", Proceedings of the Symposium on Infrastructure Development and the Environment (SIDE 2006), December 7-8, Diliman, Quezon City, Philippines, Paper #: STR-016, 10 pages.

[4] Shakya, K., Wijeyewickrema, A. C. and Madurapperuma, M. 2007, "Seismic pounding of reinforced concrete buildings with non-equal story heights considering effects of underlying soil", Proceedings of the Fourth International Conference on Urban Earthquake Engineering, March 5-6, Tokyo, Japan, pp. 715-722.

[5] Shakya, K. and Wijeyewickrema, A. C., 2007, "Structural pounding of reinforced concrete buildings in a row considering soil effects", NCU-KU-TIT Student Seminar, July 17, Kyoto University, Kyoto, Japan, Paper #4.

[6] Shakya, K. and Wijeyewickrema, A. C., 2007, "Structural pounding between adjacent multi-story buildings in a row considering soil effects", Proceedings of the Third International Conference on Structural Engineering, Mechanics and Computation, September 10-12, Cape Town, South Africa, pp. 155-156.

[7] Shakya, K. and Wijeyewickrema, A. C., 2007, "Effects on structural pounding between adjacent multi-story buildings with non-equal heights in a row under consideration of underlying soil", Proceedings of the 62nd JSCE Annual Meeting, September 12-14, Hiroshima, Japan, CD-ROM Paper No. I-484, pp. 963-964.

[8] Shakya, K. and Wijeyewickrema, A. C., 2007, "Mid column seismic pounding of multi-story RC buildings in a row considering underlying soil", Proceedings of the Ninth International Summer Symposium JSCE, September 18, Yokohama, Japan, pp. 47-50.

[9] Shakya, K. and Wijeyewickrema, A. C., 2007, "Effects of underlying soil on mid-column seismic pounding of reinforced concrete buildings in a row", 2007 Taiwan-Japan Symposium on the Advancement of Urban Earthquake Hazard Mitigation Technology, September 26-27, Chungli, Taiwan, pp. 9-16.

[10] Shakya. K and Wijyewickrema, A. C., 2008, "Eccentric building pounding considering effects of underlying soil", Proceedings of the Fifth International Conference on Urban Earthquake Engineering, March 4-5, Tokyo, Japan, pp. 375-380.

[11] Shakya, K. and Wijeyewickrema, A. C., 2008, "Seismic pounding of reinforced concrete buildings located eccentrically with different story heights considering soil effects", NCU-KU-TIT Student Seminar, March 10-11, National Central University, Chungli, Taiwan, Paper #10.

[12] Shakya, K, Wijeyewickrema, A. C. and Ohmachi, T., 2008, "Seismic pounding analysis of multi-story reinforced concrete buildings considering effects of underlying soil", Proceedings of the Symposium on Development of Practical Urban Earthquake Engineering Research for Mitigation of Mega Earthquakes in the Metropolitan Area, March 28, Suzukakedai, Yokohama, Japan, pp. 55-60.

[13] Shakya, K, Wijeyewickrema, A. C. and Ohmachi, T., 2008, "Mid-column pounding of eccentrically located multi-story reinforced concrete buildings considering soil effects", Proceedings of the 8th International Congress on Advances in Civil Engineering (ACE2008), September 15-17, Eastern Mediterranean University, Famagusta, North Cyprus, 465-472.

[14] Shakya, K, Wijeyewickrema, A. C. and Ohmachi, T., 2008, "Mid-column seismic pounding of reinforced concrete buildings in a row considering effects of soil", Proceedings of the 14thWorld Conference on Earthquake Engineering (14WCEE), October 12-17, Beijing, China, paper ID: 05-01-0056 (8 pgs).

[15] Shakya, K, Wijeyewickrema, A. C. and Ohmachi, T., 2009, "Seismic pounding of eccentrically located reinforced concrete buildings considering soil flexibility effects", Proceedings of the Sixth Regional Symposium on Infrastructure Development (RSID6), January 12-13, Bangkok, Thailand,, paper ID: RSID6-STR.15 (6 pgs).

[16] Shakya. K and Wijyewickrema, A. C. and Ohmachi, T., 2009, "Mid-column pounding with heavy adjacent building considering soil-foundation interaction", Proceedings of the Sixth International Conference on Urban Earthquake Engineering, March 3-4, Tokyo, Japan, pp. 311-316.

[17] Shakya, K, Wijeyewickrema, A. C. and Ohmachi, T., 2009, "Performance of reinforced concrete buildings during seismic pounding considering soil-foundation interaction", Proceedings of the Symposium on Development of Practical Urban Earthquake Engineering Research for Mitigation of Mega Earthquakes in the Metropolitan Area, March 25, Suzukakedai, Yokohama, Japan, pp. 39-42.

[18] Pant, D. R., Wijeyewickrema, A. C. and Ohmachi, T., 2009, "Nonlinear Seismic Pounding Analysis of Taller Adjacent Reinforced Concrete Buildings", 2009 Taiwan-Japan Symposium on the Advancement of Urban Earthquake Hazard Mitigation Technology, September 21-22, Jhongli, Taoyuan, Taiwan, pp. 84-95.

[19] Pant, D. R., Wijeyewickrema, A. C. and Ohmachi, T., 2010, "Three dimensional nonlinear analysis of seismic pounding between multi-story reinforced concrete buildings", Proceedings of the Seventh International Conference on Urban Earthquake Engineering (7CUEE) and Fifth International Conference on Earthquake Engineering (5ICEE), March 3-5, Tokyo, Japan, pp. 1829-1840.

[20] Pant, D. R., Wijeyewickrema, A. C. and Ohmachi, T., 2010, "Nonlinear seismic pounding response of reinforced concrete buildings using a modified Kelvin-Voigt impact model", Proceedings of the Symposium on Development of Practical Urban Earthquake Engineering Research for Mitigation of Mega Earthquakes in the Metropolitan Area, March 24, Suzukakedai, Yokohama, Japan, pp. 45-50.

[21] Pant, D. R. and Wijeyewickrema, A. C., 2010, "Seismic pounding between base-isolated and fixed-base reinforced concrete buildings", Second Multidisciplinary International Student Workshop (2nd MISW), August 5-6, Tokyo Institute of Technology, Japan. pp. 25.

[22] Pant, D. R., Wijeyewickrema, A. C. and Ohmachi, T., 2010, "Seismic pounding between reinforced concrete buildings: a study using two recently proposed contact element models", Fourteenth European Conference on Earthquake Engineering, August 30-September 3, Ohrid, Republic of Macedonia, CD-ROM Paper No. 608, 7 pages.

[23] Pant, D. R. and Wijeyewickrema, A. C., 2010, "Analysis of seismic pounding of a base-isolated RC building using a modified Kelvin-Voigt impact force model", 2010 Taiwan-Japan Symposium on the Advancement of Urban Earthquake Hazard Mitigation Technology, September 20-21, Jhongli, Taoyuan, Taiwan, pp. 9-12.

[24] Pant, D. R. and Wijeyewickrema, A. C., 2010, "Seismic pounding analysis of base-isolated reinforced concrete buildings", Quake Summit 2010, NEES and PEER Annual Meeting, October 8-9, San Francisco, USA. Poster presentation.

[25] Pant, D. R. and Wijeyewickrema, A. C., 2010, "Seismic pounding of a base-isolated reinforced concrete building", The 5th AOTULE International Postgraduate Students Conference on Engineering, November 1-2, Bandung, Indonesia, pp. 33-36.

[26] Pant, D. R. and Wijeyewickrema, A. C., 2010, "Earthquake-induced interaction of base-isolated RC buildings with adjacent structures", The 3rd ASEAN Civil Engineering Conference, 3rd ASEAN Environmental Engineering Conference and 1st Annual Meeting of the JSPS Asian Core Program, November 11-12, Metro Manila, Philippines. Abstract No. DRM1_01.

[27] Pant, D. and Wijeyewickrema, A. C. 2010, "Seismic pounding simulation of base-isolated reinforced concrete buildings", The 3rd ASIA Conference on Earthquake Engineering (ACEE-2010), December 1-3, Bangkok, Thailand, CD-ROM Paper No. ACEE-P-088.

[28] Pant, D. R. and Wijeyewickrema, A. C., 2011, "Nonlinear seismic response of base-isolated buildings considering pounding", The Eighth International Conference on Urban Earthquake Engineering (8CUEE), March 7-8, Tokyo, Japan, pp. 1277-1283.

[29] Pant, D. R. and Wijeyewickrema, A. C., 2011, "Seismic pounding of a base-isolated building with a fixed-base building", The Professor LEE SENG LIP Symposium, March 21-22, Singapore, pp. 159-168.

[30] Pant, D. R. and Wijeyewickrema, A. C., 2011, "Finite element analysis of seismic pounding of base-isolated reinforced concrete buildings", Sixth M.I.T. Conference on Computational Fluid and Solid Mechanics, June 15-17, Cambridge, MA. pp. 102.

[31] Pant, D. R. and Wijeyewickrema, A. C., 2011, "Pounding between base-isolated and fixed-base RC buildings during earthquakes", Eighth International Conference on Structural Dynamics (EURODYN2011), July 04-06, Leuven, Belgium, pp. 404-410.

[32] Pant, D. R. and Wijeyewickrema, A. C., 2011, "Seismic pounding of base-isolated reinforced concrete buildings", 11th Taiwan-Japan Joint Student Seminar on Earthquake Engineering, July 19-20, Miyagi, Japan.

[33] Pant, D. R. and Wijeyewickrema, A. C., 2011, "Selection of appropriate viscous damping for nonlinear dynamic analysis of base-isolated reinforced concrete buildings", 2011 PEER Annual Meeting, Sept. 30-Oct. 1, Berkeley, CA, USA. Poster presentation.

[34] Pant, D. R. and Wijeyewickrema, A. C., 2012, "Influence of near-fault ground motions and seismic pounding on the response of base-isolated reinforced concrete buildings", Proceedings of the Ninth International Conference on Urban Earthquake Engineering (9CUEE) and Fourth Asia Conference on Earthquake Engineering (4ACEE), March 6-8, Tokyo, Japan, pp. 1615-1624.

[35] Pant, D. R. and Wijeyewickrema, A. C. , 2012, "Influence of near-fault ground motions and seismic pounding on the response of base-isolated reinforced concrete buildings", Quake Summit 2012, NEES Annual Meeting, July 9-12, Boston, MA, USA. Poster presentation.

[36] Pant, D. R. and Wijeyewickrema, A. C., 2012, "Base-isolated structures under bidirectional excitation of near-fault earthquakes", Fourth Multidisciplinary International Student Workshop (MISW2012), August 9-10, Tokyo, Japan, pp. 18.

[37] Pant, D. R. and Wijeyewickrema, A. C., 2012, "Pounding of seismically isolated reinforced concrete buildings subjected to near-fault ground motions", Fifteenth World Conference on Earthquake Engineering (15WCEE), September 24-28, Lisbon, Portugal, paper 3376, 9 pgs

[38] Pant, D. R. and Wijeyewickrema, A. C., 2013, "Seismic pounding of base-isolated buildings under bidirectional excitation", Tenth International Conference on Urban Earthquake Engineering (10CUEE), March 1-2, Tokyo, Japan, pp. 1389-1398

[39] Pant, D. R. and Wijeyewickrema, A. C., 2013, "Response of Base-Isolated Buildings Subject to Near-Fault Ground Motion considering Seismic Pounding", Proceedings of the Thirteenth East Asia-Pacific Conference on Structural Engineering and Construction (EASEC-13), September 11-13, Sapporo, Japan, Paper B-1-5.