Harbor Cay Condominium Collapse - Research Paper Example

Harbor Cay Condominium Collapse Abstract On March 27th 1981 the Harbour Cay Condominium collapsed while under construction. The result was loss of nine workers and 23 more injured in the site. The exact incidence that led to its collapse was pouring concrete cement on the fifth story which is said to be twice as heavy as dry concrete. The incidence attracted interest from various stakeholders such as the National Bureau of Standards (NBS), Occupational Safety and Health Administration and ACI. In their research, the groups identified various structural and engineering flaws carried out by the designers and engineers. On the design aspects the teams identified that the slabs were slim compared to the standards offered by ACI. The used slab had 8 inches whereas the minimum requirement is set at 11 inches. The process of punching shear was overlooked when designing the slabs. The structural engineer, who retired from NASA, also failed to make the necessary calculations on concrete requirements such as beam shear and column reinforcement spacing. Table of Contents Table of Contents 2 Introduction 3 1.Failure Causes 5 1.1Design errors 5 1.2 Construction Errors 7 2 Clashing Accounts of the Building’s Collapse 8 3 Avoiding Reoccurrence 9 4 Lessons Learned 10 5 Changes Made in the Engineering field 11 Conclusion 11 References 13 Introduction Harbour Cay Condominium was designed to be a medium sized building with a total height of 242 fees and 58 feet in width. The preassembled plywood was made from flying form where they constructed the floor slabs, 8 inches thick. The east side of the building hosted a detached elevator tower whereas the north and south ends were occupied by the stairwells. The building had both exterior and interior columns that measured 10 x 12 and 10 x 18 inches respectively. The structural engineer advocated for above-grade concrete to be used, with strengths of up to 4,000 psi. 11 There were pile caps supporting exterior slabs. Floor slabs were placed twice per week with the first session covering half the total space. The roof plan indicated it would be cast in one day. Harbour Cay Condominium was near completion when it collapsed. The concrete was already placed on the flying forms of the roof when things changed. The construction workers were pouring concrete on the roof slab when a loud crack was heard and it all fell like a house of cards. Witnesses reported that the fifth floor fall first. The upper floor fell on the lower ones leading to comprehensive total building collapse (Lew, Center for Building Technology, & United States, 1982). There reports indication that the workers had reported presence of web like cracks on the slabs with increased deflection of about 2 inches. The structural engineer was summoned to address the situation, but he insisted that it was not a big dal considering the progress made. Construction continued as usual until when the building came down. The cracks posed potential signings that could have been avoided (Lew et al. 1982). This is an engineering disaster caused by negligence and failure to abide by the engineering code of conduct. When the building collapsed, the first two floors had the exterior walls intact whereas the masonry structured was on the third floor. The walls to the northern side were already constructed and held on the third floor (Lew et al. 1982). The process increased the rate of constructing the walls and winding up the process within the shortest time possible. There was presence of restores on the first to the fourth floor stories. Their presence raised further questions on how the building was constructed. Fig.1. Location of workers (From the National Bureau of Standards) The building had 36 workers in different parts of the building. The figure above shows the position of all workers before its collapse. The two workers on the ground floor were installing windows; there was no activity in the second story where no one is present. The workers on the third story were winding up with the masonry walls. In the fourth floor, there was one workers cleaning debris while the other two were adjusting the formwork. The top floor had most of the workers that were overseeing the placement of the concrete slab on the North Bay. Survivors are on the record that there was no concrete delivered on the roof when the building collapsed. 1. Failure Causes 1.1 Design errors Design and construction errors have been attributed to the failure of Harbour Cay Condominium. The slab design failed to meet the set standard by ACI which places the standard requirement at 11 inches. The engineer to this project had advocated for 8 inches. The standard gives into consideration punching shear for specified load, column sizes and spans. The flat plate structures constitute to the higher failure in design of slabs whereas there were omissions from slab thickness calculation (Delatte, 2009). Surprisingly, the columns remained erect when the floor slabs fall on top of the other after the collapse. This was clear evidence for failure in punching shear. The teams carrying disaster assessment concluded that there was only gravity loads aligned to the building’s collapse. There was no presence of overturning or sideways movement from the pilled floor slabs. Punching shear failure is experienced from cracks on the concrete slabs and also when it breaks up from the column connection. The characteristics were reported to the structural engineer when they were construction the third floor. However, he assured them everything was ok as he had maintained the required standards (Delatte, 2009). This was a poor decision from a NASA retiree who knew it too well that there was more than what met the eye. Additionally, he is to blame for not acting accordingly despite of the warning signs reported. He assumed all will be well after it was finished and other components put in place (Delatte, 2009). The structural engineer ignored the necessity to calculate punching shear strength. The following is the formula of calculating the shear strength of an interior column: Vc = 4((f’c) ^ (1/2)) (b0) (d) f’c= a 28 days cylinder strength for used concrete. d= overall depth of the used slab b0= perimeter of the surface around the column (Delatte, 2009). Larger columns are used to increase punching shear strength. Additionally, the punching shear cases should be connected to the top steel slabs to lower the negative moment tension. The decision to hire a retired NASA engineer to be the structural engineer was met with criticisms from various stakeholders (Delatte, 2009). Structural engineering is complicated and it needs someone who has a thorough knowledge of all the components involved and also the experience. In this case the engineer is retired and has spent most of his career in NASA (Delatte, 2009). This is a completely different area of specialization. Many critics claim that the engineering disaster would have been avoided if the job was given to the right person. Even though disasters happen all the time, it is probable that this one would have been avoided if the design standards were adhered. An experienced and disciplined structural engineer would have given the correct design for the slabs and properly calculated the shear strength. 1.2 Construction Errors The reinforcing steel on top was placed too low. The top fortification bars were put on seats that were just 4 ½" high, which diminished the successful slab depth "d" from 6.3 inches to 5.3 inches. Consequently, the top spread was expanded to 1 5/8 inches while it was intended to be 0.75 inches. The NBS examination additionally found that base slab bars were not put through numerous segments and that the sections split far from the segments where the pieces and segments met (Lew et al. 1982). Additionally, some vertical fortification was found to have been seriously twisted amid creation. Research center cured test chambers were utilized rather than field-cured test barrels to focus the genuine quality of pieces preceding the stripping of formwork. The NBS report additionally included interview with workers and witnesses who were available at the breakdown's season. Numerous differences exist as to the area and measure of reshores present in the structure when it crumpled. A few laborers said they saw bowed reshores, and others even said they saw reshores break when cement was being set on the rooftop. Because of the various disparities in the laborers' records, it is fundamentally difficult to focus the precise design of reshores at the collapse. Numerous laborers expressed that the cobweb sort breaks were seen once the flying structures were uprooted (Lew et al. 1982). Most splits were situated close middle points and around segments, and some were said to have stretched out 4 to 5 inches into the floor sections. Intemperate avoidances were accounted for once the structures collapsed. A 1 ¾ inch redirection was noted at last loft on the north side of the expanding on the second floor. Laborers likewise noticed that a solid's portion from the on location bunch plant had a non-uniform consistency and was hard to wrap up. One specialist expressed, "Twenty-two years I've been pouring cement and they've never pulled the structures in two days as they did here. A few agents asked why the structure had not caved in before. The shoring and reshoring strategies utilized gave the answer. Shores and reshores at first upheld the dead heaps of the structure and exchanged the heaps to the ground (Lew et al. 1982).. Once the reshores beneath the first floor level were uprooted, the solid slabs were compelled to bring the structure's heaviness through their punching shear limit at the segments. 2 Clashing Accounts of the Building’s Collapse There were not so much any real clashing records of the disappointment or contradicting assessments of the reason for the disappointment. Most agents concur that the primary driver of the Harbor Cay Condominium breakdown was a punching shear disappointment which prompted a dynamic breakdown of the whole structure (Nawy, 1997). Since a hefty portion of the sections were all the while remaining after the breakdown, it was an unmistakable sign that the structure caved in because of a punching shear disappointment. Examiners concur that punching shear was not represented in the structure's design, and that fortifying bars were put too low in the piece. One little contention identifies with the idea of design blunder versus structural slip. The National Bureau of Standards presumed that both the design mistake of the 8-inch section and the structural mistake of the deficient viable profundity of strengthening steel contributed reasonably just as to the structure's breakdown (Delatte, 2009). The NBS established that the structure would have presumably not fallen had one and only of these blunders been made. Feld and Carper, be that as it may, express Some structural inadequacies were noted, yet the configuration slip identified with punching shear alone was adequate to achieve the breakdown". Essentially, Feld and Carper claim that the punching shear design lapse would have created the breakdown itself, though the NBS expressed that the building would have stayed standing had just the configuration slip happened. Likewise, as beforehand talked about, observer accounts additionally offer a few contradicting feelings as to the area and number of re-shores in the building at the season of breakdown and whether the fourth floor or fifth floor descended first. 3 Avoiding Reoccurrence It is apparent that the disappointment could have effectively been avoided. Had the straightforward routine solid design checks for punching shear and least section thickness been made, the punching shear disappointment could have been maintained a strategic distance from (Meyer & Reniers, 2013). The most conservative approach to expand the punching shear limit of the slabs would have been to build the sections' extent. This would likewise have made more space for throwing cement between the vertical section fortification bars. Expanding the section's thickness would have required substantially more concrete than expanding the segments' span (Schlager, 1994). Consequently, expanding the section sizes would have gave a more prudent arrangement. What's more, paying consideration on notice indications of a potential breakdown is basic. All work on the building ought to have ceased after the unnecessary redirections and bug catching network sort splits had framed (Meyer & Reniers, 2013). Rather, chip away at the building proceeded without appropriately tending to these conspicuous indications of conceivable disappointment. As specified over, the NBS agents found that if just the primary configuration blunder or the fundamental structural lapse had been made, the structure would likely not have fell (Meyer & Reniers, 2013). Subsequently, had one of the real lapses included with the structure been disposed of, the building may perhaps still be upright. 4 Lessons Learned A few lessons can be found out from the breakdown of Harbor Cay Condominium. In the first place, punching shear quality must be checked when outlining level pieces, for punching shear is the most well-known method of disappointment for solid level sections. Second, least profundity of a level section much be checked to represent redirection and quality necessities. Next, it is significant to place fortifying bars specifically inside of the section outskirts to help forestall dynamic failure (Meyer & Reniers, 2013). This should be possible at no extra cost. Moreover, legitimate configuration of formwork, shoring and re-shoring arranges and calendars, and systems to confirm least stripping quality of the solid by experts is key for effective field structural control. Another vital lesson is that all work on a task must be ceased if cautioning indications of potential disappointment are experienced (Schlager, 1994). Specialists ought to empty the building promptly, and expert assessment of the issues must be performed before work can be continued. At long last, it is imperative to utilize legitimate test systems to focus the set up quality of solid in frosty climate. Field-cured test chambers ought to be utilized rather than research center cured test barrels. The building business can likewise take in the results of a disaster disappointment like the Harbor Cay Condominium breakdown (Schlager, 1994). The essential basic architect on the undertaking, Harold Meeler, surrendered his permit and said he would never practice again. Meeler said he would pay the most extreme fine of more than $2,000 to avoid a hearing on the structure's breakdown. The other auxiliary architect additionally surrendered his permit and will never hone in the condition of Florida again (Lew et al. 1982). The Florida Department of Professional Regulation charged five of the gatherings included in the undertaking with carelessness. Moreover, two temporary workers were taught, and the designer was suspended from practicing in Florida for a long time. We must recollect that significant disappointments in low-ascent tasks are still conceivable regardless of the learning's majority accessible to keep away from them. 5 Changes Made in the Engineering field The condition of Florida reinforced its security laws after the Harbor Cay Condominium breakdown, requiring more on location examinations by architects and more investigation of structural arrangements (Delatte, 2009). The disappointment additionally brought issues to light that punching shear disappointments are the most widely recognized kind of disappointment of solid level slabs, and representing punching shear despite the configuration stage is pivotal (Schlager, 1994). The breakdown additionally showed that significant calamities can at present happen with low-ascent structures and not simply tall building structures. Conclusion The Harbor Cay Condominium breakdown shows the results of inappropriate design and structure structural systems. A punching shear disappointment on the fifth floor started a dynamic breakdown of the whole structure. Punching shear computations were excluded by the auxiliary specialist when the structure was composed. Fortification bars were set too low in the solid pieces, which lessened the compelling profundity of the sections and consequently decreased the general quality of the slabs too. Cautioning indications of a potential disappointment were conveyed to the consideration of chiefs and the engineer, however, was fundamentally overlooked. The Harbor Cay catastrophe could have effortlessly been anticipated had straightforward configuration checks and watchful structural methods been performed. Basic designing is an advanced procedure. Each configuration that an auxiliary architect does includes life security. Hence, auxiliary specialists should be sufficiently instructed, all around experienced, and inspected in basic configuration. Slips, oversights and botches can't be avoided altogether. Be that as it may, in the breakdown of Harbor Cay Condominium, the mishap was avoidable. The architects included were authorized and trusted they were working inside of their territories of skill. They had not been prepared or inspected in the range of basic solid design. Hence, they didn't know they were insufficient in information expected to secure people in general. In the event that Florida had required basic designers to have a basic building training, get four years of auxiliary building background and pass the16-hour basic exam, the Harbor Cay architects would have known not for shear quality. The breakdown would not have happened if the structure had been intended for shear. Separate licensure of auxiliary specialists in Florida would have kept this lethal mishap. References Delatte, N. J. (2009). Beyond failure: Forensic case studies for civil engineers. Reston, VA: ASCE Press. Lew, H. S., Center for Building Technology, & United States. (1982). Investigation of construction failure of Harbour Cay Condominium in Cocoa Beach, Florida. Washington, DC: U.S. Dept. of Commerce, National Bureau of Standards. Meyer, T., & Reniers, G. L. (2013). Engineering risk management. Berlin: De Gruyter. Nawy, E. G. (1997). Concrete construction engineering handbook. Boca Raton: CRC Press. Schlager, N. (1994). When technology fails: Significant technological disasters, accidents, and failures of the twentieth century. Detroit: Gale Research. Read More