Collapse of Margalla Towers


OCT 10, 2005
Why Margalla Towers Collapsed OCT 10: On Saturday October 8, two blocks of the Margalla Towers - a posh building of luxury apartments in Islamabad � collapsed after a 7.6 Richter scale earthquake struck at 8:53 am and lasted for approx 6 minutes. Besides many killed, more than 250 people, including foreign nationals, were buried alive under the debris. The earthquake also left completely collapsed Aiwan-e-Wazir-e-Azam, Secretariat, CMH, Radio Colony, old campus of Islamabad University, parts of the central city, and at least 75 buildings in close vicinity of Chehla Bandi were razed to the ground. While rescue operations continue to retrieve survivors from the debris of these two Margalla Towers blocks, each comprising 10 stories and 60 apartments, questions are being raised as to why these two structures collapsed. Federal Minister for Religious Affairs, Ijazul Huque said that the Margalla Towers blocks destroyed were declared dangerous 10 months ago, but the residents were unwilling to vacate the building as they had bought these apartments at heavy prices. While visiting Margalla Towers, he told journalists that highly substandard materials were used in the construction, which culminated into the incident. Reports say these towers were designed by Islamabad based architect Afzal Qureshi and their structural design, engineering was done by Engr Dr Hafeez Shaikh. While it is possible that substandard construction materials may have been used in these buildings, a senior Pakistani journalist based in Washington now says he remembers these buildings remained unoccupied for almost a year or two because it was said then that it was built on a shaky rock and that geologists who surveyed the ground had asked the owners not to sell the apartments but the owners who built the buildings first and then did the survey later, ignored their warnings. "It remained empty for sometime. I know this, because I tried to buy a flat there", he added. A report in the highly respected Lahore-based newspaper Daily Times, said the two blocks that collapsed were constructed after amendments to the construction rules of the Capital Development Authority and that only iron bars were used to join the new blocks with the old ones in the towers, and that these bars were not strong enough to withstand the severe shocks, therefore both newly built blocks fell to the ground. According to a very senior Pakistani Structural-cum-Geotechnical Engineer Syed Faiz Ahmed, "I don't think the buildings collapsed because the old and new towers were connected with each other. Even if they were and let's say the connections were done very badly, the two buildings would separate and not crumble down." Mr Ahmed is Senior Structural Engineer with Saudi based internationally renowned consulting firm SAUDI OGER and was the only non-Saudi professional to have been appointed to formulate the Saudi Building Code and Design as it's Concrete Structural Design Committee member. When asked to give his technical opinion on why the two Margalla Towers buildings collapsed, this is what Mr Faiz Ahmed had to say: "Earth quake failures are basically two types. One is due to liquefaction of soil under the foundation. Due to strong waves due to ground motions, most soils (if it is not rock) would liquefy, that is sort of melt and loose bond/density and hence the compaction strengths wherefrom this bearing capacity (whatever the value may be) is derived. So when soils liquefy (and the density is lost) the soil underneath will no longer be able to sustain the impending loads and hence would yield. This will result in the structures: SINKING, TILTING and/or BOTH. But you should have noticed this has not HAPPENED. The other type of failure is: the JOINT FAILURE. The failure of the FRAMES, implying slabs, beams, columns and combination of all th above. And, in my opinion, this is exactly what has HAPPENED to these two towers. This is pure structural failure; that is the structural frame that was designed was simply NOT able to SUSTAIN the ground accelerations/ motions inflicted due to this earthquake." "Upon looking at the structural debris from TV footage, I can say for sure this is seismic failure," he added. According to Mr Ahmed, "In Islamabad things are governed by CDA (Capital Development Authority) which is an agency very much subservient to the people who sit in the parliament, that is the Choudhuries, Maliks, Generals, etc who are only interested in plots in and around Islamabad." "CDA is also responsible to manage all the HOUSES (Sindh House, Punjab House, Balochistan House, etc) and the clubs, the hostels for MNAs and so on. CDA is also responsible for the care taking and maintenance of the parliament buildings, the PM and President house, Secretariats, etc. A lot is put on the shoulder of CDA." "As far as I know there is no section within CDA to review the design and drawings submitted for construction in Islamabad. It admits architectural plans only," he added. When questioned whether CDA has any formal requirement for seismic design of buildings, Mr Ahmed said "as far as seismic design is concerned I don't think it has made it mandatory for designs to be submitted to cater for quake based lateral load design (as is done by KDA & KBCA). They don't have bye laws which specifically delineates Islamabad to seismic zones for consideration for seismic design." "It's the consulting engineer who probably does this on his own discretion (and should also after all he/she is responsible for design) based on his/her experience, Mr Ahmed added about seismic design submission. Mr Faiz Ahmed was also asked several related questions, particularly as to how and why Islamabad is designated by Geological Survey of Pakistan(GSP) as belonging to Seismic Zone 2 when the United States Geological Survey designates Islamabad being in Zone 3. Following is the excerpt of our online chat with Mr Faiz Ahmed: DesPardes.com says: As a Senior Structural Design Engineer with a highly reputable Design firm Saudi Oger what do you think is the cause of the towers collapse? syed faiz says: Obviously it couldn't resist the lateral force and gave way. possibly design fault. was not designed to take such a high intensity of seismic force; 7.6 on Richter scale. However, having said that, it is interesting to note only a part or probably one of several towers collapsed, why? DesPardes.com says: did u look at the USGS map of Pak we sent you? *(See USGS map)* syed faiz says: you mean map of pak? yes i did DesPardes.com says: http://neic.usgs.gov/neis/world/pakistan/gshap.html syed faiz says: yes i went to this USGS site and there is a seismic map of Pak which probably shows Islamabad on zone-3 DesPardes.com says: so what is zone 3 ? syed faiz says: zone-3 as I said describes a region in terms of intensity of seismic it is expected to experience which is moderate to severe; zone-0 means no seismic activity that is the region will not experience seismic activity. and there is no need to design structures for seismic zone-o. DesPardes.com says: Zone 3 = major damage zone corresponding to intensity above VII on MM scale but GSP map shows Islamabad in zone 2? So is it possible the towers were inadequately designed? *(See GSP map)* DesPardes.com says: do u think it is possible that islamabd zone was initially zone 2 and may have been changed to zone 3 later? syed faiz says: yes I think it does fall in zone-3 Despardes.com says: can zone 3 include quakes up to 7.6 Richter scale (Major earthquake. Can cause serious damage over larger areas) ? syed faiz says: In pak the seismic maps are flawed; it has never been taken seriously. There is no seismic code in Pak; we still use UBC (Uniform Building Code) an American code. We still don't have a building design code )( for gravity load design) so what to talk about a national code for seismic design. we still use ACI 318 (an American code) and/or BS8112 a British code which are not based on pak conditions but based on the local condition os USA and/or UK. syed faiz says: I am making a correlation with what we have in the USGS map about Karachi. I measure karachi as Zone-2; so as corollary Islamabad should be Zone 3 and not zone-2; based on its ground acceleration value in the map. DesPardes.com says: but GSP map shows ISL zone 2 also. that is bothering us. syed faiz says: As you said earlier there isa confusion also whether ISL is in Zone-2 oer zone-3. DesPardes.com says: it is in zone 2 according to GSP. but we have been told ISL bldgs are designed for 2B. syed faiz says: CDA has a poor infrastructure for review of submittals. This is evident from the buildings that it has allowed to be constructed in and around the famous Blue Area. CDA has internal arrangement and the architectural plans are reviewed by their internal team and for structural, they probably send it to outside consultants. This is how more or less practiced by KDA also but KDA is more organized and stringent and CDA is not. DesPardes.com says: why did only 2 bldgs fall down and not all? DesPardes.com says: if it is seismic failure all bldgs shud have failed no? syed faiz says: u should know when seismic forces are acting they act as base shears at the colum nodes; that is joints of beam-columns. Almost all TV footage I saw was clearly showing huge pieces of column-beam joint failures. syed faiz says: Now coming to the question why two towers failed and not all? Well there could be several reasons for this. I will describe all for you and one or all could be valid for this case. First is the geometry of the tower; meaning its length and depth in foot print and its height. The forces attracted on the structure are very much dependent on its geometry of its foot print and of course the height. syed faiz says: There is a possibility the geometry of these two towers were more SLENDER than the rest. If the geometry is slender its stiffness would be far less than those whose geometry are are better and not as slender. The stiffness of the structure is very important in resisting forces. The stiffness is two: in minor axis and major axis (X and Y). So, if any or both the axes has weak stiffness the structure. the structure will not be as strong as the others who have larger stiffness. syed faiz says: Daily times theory is weak technically as such. They are talking about building more floor areas. This could have been a VALID argument if the structure had failed in gravity loads meaning the loads on the soil transferred was greater than what the soil was able to take. If this was true the structure would NOT BE STANDING that long; it would have failed immediately when it was occupied. The actual design loads was imposed on the same. This structure did not fail in GRAVITY loads it FAILED immediately after it was SUBJECTED to a SEVERE SEISMIC FORCE. syed faiz says: About this rebar connection b/w old and new blocks; yes it is a connection/joint failure. But this is not the reason. In this case both old and new would have separated from each other as we saw in some of structures in Lahore. DesPardes.com says: so that is not the cause of failure at all ? syed faiz says: No I don't agree. This can be a cause of structural damage but not collapse. DesPardes.com says: which papers did you read in USA in 2004? syed faiz says: 1. Foundatin Design over Expansive Soil - A Saudi Arabian case History. syed faiz says: 2. Managing Sink Holes at Project Site - a Saudi Arabian case History. Both papers were read in the 5th Int'l Conference in Geotechnical Case Histories held in New York from 13th thru 17th April 2004. This was organized by University of Missouri - Rolla. My 2nd paper was acclaimed one of the best papers presented. As a resulted it was also accepted for a Journal on geotech case Histories. and, I am now invited also for the 6th Conf on geotech case histories due to be held in Washington DC in 2008. DesPardes.com says: so give your recommendation now. syed faiz says: first of all we should have our seismic map made up to date and revised professionally taking recent earth quake data into account. second: it is high time we develop our own Code of Practice for Building Design. Every country with little sovereignty and self-respect has strived to develop one of its own. India did this long time ago, in the 60s. Even KSA has developed one of its own and I also served one of its committee. I served the Concrete Structural Design Committee and was selected to coordinate on of the sub-committees. 3rd. We must enforce the bye laws and the Code provisions (after it is developed) very strictly. 4th: we should involve the research institutions and the academics to continuously do research on seismicity for various regions in Pakistan. DesPardes.com says: Thank you Sir.

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Art Janklow, South Dakota, USA An excellent interview with Syed Faiz Ahmed. Hopefully the insights of your interview will benefit future generations throughout the region where construction, planning and review committees ignore the benefits of today's professional and modern technology. Congratulations to you for finding one such as Syed Faiz Ahmed who is truly a highly respected professional of international standing. *Shakoor Ahmed, Jeddah, Saudi Arabia* I totally agree with the analysis of Mr Faiz Ahmed concerning the collapse of Margalla towers. As per my experience and the TV coverage, it is quite obvious that the collapse could be due to weak supervision, faulty construction and negligence of the contractor. It is almost impossible to find professional honesty in our society. It is a common practice in Pakistan to employ non-qualified technical personnel or sub-contractors for construction of the buildings and if there isn't a good supervision either from the consultant or from the authorized agency (provided that the structural design have been reviewed by some qualified structural engineer) it can result in disasters as we have seen. I have personally experienced these problems when i was running my own consulting business in 1982 in Karachi. First of all the contractor wants the most economical design and after having approval of this they never follow the approved structural design, changes are made as it suits them. Nisar Khan, USA I completely agree that we lack national design standards and building codes. And whatever standards there are, they are flagrantly violated by those who only believe in making a fast buck. Just one correction for the record. We do have a Pakistan Seismic Code. Late Engineer Umar Munshi prepared and presented it to PEC/Council of Structural Engineers in 1981. Shujaat, Safdar and myself made our own little contributions in the code preparation, helping Munshi Saheb prepare the draft, proofreading it and checking the figures, tables and exhibits included in the code. In fact if I remember, it was right after the introduction of that seismic code that Karachi Building Control Authority started requiring the builders to submit seismic design calculations as part of the permitting process. One last point - failures may still happen despite following all standards, codes and regulations. We can only make the structures Earthquake Resistant. Nothing is Earthquake Proof. Amin Vahidy, *Alberta, Canada* Very good investigative reporting. Faiz has given excellent feedback. I wish one of our leading newspapers would reprint this verbatim. For sure, political considerations have to do with the inadequate design and construction, anywhere in Pakistan. Cheaply constructed buildings make more profits for the owners. This should be a wake up call, especially in Karachi, where despite of better management by Building Control Authority, not all buildings conform to the strict earthquake standards, some still fall through the cracks.