Investigation of a testing approach for trapezoidal crest fastened metal cladding

Stephan, Hendrik Christoffel (2013-03)

Thesis (MscEng)--Stellenbosch University, 2013.

Thesis

ENGLISH ABSTRACT: Low-rise buildings with crest fastenedmetal cladding are susceptible to failures in the vicinity of the fasteners during strongwind uplift conditions. These localised failures often lead to the progressive removal of cladding, which can cause disastrous building damage. In South Africa, the current metal cladding design approach is inadequate, since it solely relies upon manufacturer design specifications. These specifications are typically designated as broad design guidelines for the maximum allowable cladding support spacings which are independent from any specified design loads. This research focuses on the investigation of 0.50 mm ISQ550 IBR cladding systems to understand basic cladding behaviour during static wind uplift conditions and to quantify the uplift performance of IBR systems. The research investigation also included the improvement and performance evaluation of a full-scale cladding test method which applies an air-bag loading method to simulate static wind uplift conditions according to the revised SANS 10237:201X code of practice. This thesis may serve as a basis for further cladding research, and the development of suitable standardised metal cladding test methods in South Africa. Several experimental investigation methods and limited finite element analyses (FEA) were used to investigate IBR and the performance of the test methods. Tensile testing was used to determine the material properties of the cladding metal. The full-scale cladding assembly testing was used to investigate the behaviour of IBR and to evaluate the performance of the air-bag test rig. The localised behaviour of the cladding around the fasteners was also investigated with a small cladding subassembly test method. The FEA served as a supplementary investigation for IBR performance evaluation. The experimental investigation confirmed that the static wind uplift resistances of IBR systems are mainly governed by localised deformations of their fastened crests and fastener pull-through failures. The behaviour and performance of IBR systems are heavily dependent on the crest fastening arrangement. IBR systems with every crest fastening demonstrated a considerably higher wind uplift resistance than IBR systems with the standard alternate crest fastening arrangement. The measured fastener loads were independent from span length, whereas the overall uplift resistance of IBR reduced with increased span lengths. Load-span resistance data for 0.50 mm ISQ550 IBR was derived from testing to provide a rational framework for design. The FEA provided a reasonable simulation of IBR subjected to static wind uplift and confirmed the presence of high stress and strain concentrations around the fastener holes which cause fastener pull-through failures. Therefore, FEA can be used as an effective tool to investigate the behaviour of IBR. In conclusion, the air-bag test method used in this research investigation provided an effective method for evaluating the uplift performance of crest fastened metal cladding. However, the air-bag load method is not capable of accurately simulating a true uniformly distributed uplift load. It is recommended that direct air pressure testing be adopted for any further research or commercial testing ofmetal cladding because direct air pressure testing is an effective and proven test method for accurate simulation of static and cyclic wind uplift conditions.

AFRIKAANSE OPSOMMING: Metaalbekleding met kruinvashegting op lae geboue is geneig om te faal by die vashegters tydens toestande van sterkwind-opheffing. As vashegters faal kan bekleding progressief verwyderwordomrampspoedige skade aan die gebou te veroorsaak. Die huidige ontwerpmetode vir metaalbekleding in Suid-Afrika is onvoldoende, aangesien dit slegs gegrond is op vervaardigers se ontwerpspesifikasies. Spesifikasies word gewoonlik verklaar as breë ontwerpriglyne vir die maksimum toelaatbare spasiërings van ondersteunings sonder enige oorwegings vir ontwerpbelastings. Hierdie navorsing fokus dus op 0.50mm ISQ550 IBR metaalbekleding omdie basiese gedrag van bekleding tydens wind-opheffing beter te verstaan en die ophefweerstand van IBR te kwantifiseer vir ontwerpdoeleindes. Verder ondersoek hierdie navorsing ook die verbetering en evaluasie van ’n volskaalse bekledingstoetsmetode wat statiese wind-opheffing naboots met verspreide lugsakbelasting volgens die hersiende SANS 10237:201X gebruikskode. Hierdie proefskrif kan dien as ’n grondslag vir verdere navorsing en die ontwikkeling van geskikte standaard-toetsmetodes vir metaalbekleding in Suid-Afrika. Verskeie eksperimentele toetsmetodes en beperkte eindige-element-analises (EEA) is gebruik om die gedrag van IBR en die toets-opstellings te ondersoek. Trektoetse is gebruik om die meganiese eienskappe van die bekledingsmetaal te bepaal. Volskaalse toets-opstellings is gebruik om die weerstand van IBR te ondersoek en die lugsaktoetsmetode te evalueer. Die gelokaliseerde gedrag van die bekleding rondom die vashegters was ook ondersoek met klein toets-opstellings. EEA het gedien as ’n aanvullende ondersoek om die gedrag van IBR te evalueer. Die eksperimentele ondersoek het bevestig dat die wind-ophefweerstande van IBR-stelsels hoofsaaklik bepaal word deur gelokaliseerde deformasies van die vasgehegde kruine en die vashegters se deurtrekweerstand. Die gedrag en weerstand van IBR-stelsels is ook grootliks afhanklik van die toegepaste vashegtingsmetode. IBR stelsels met vashegting deur elke kruin het ’n hoër ophefweerstand verskaf as IBR-stelsels met die standaard vashegtingsmetode deur elke tweede kruin. Die gemete vashegterbelastings was onafhanklik van die spanlengtes, terwyl die algehele ophefweerstand van IBR verminder het vir langer spanlengtes. Toetsdata is gebruik om ophefweerstande vir 0.50mm ISQ550 IBR oor verskeie spanlengtes af te lei sodat ’n rasionele raamwerk vir ontwerp bewerkstellig kan word. Die EEA het die gedrag van IBR tydens toestande van statiese wind-opheffing redelik goed nageboots en het ook die teenwoordigheid van hoë spannings- en vervormingskonsentrasies rondom die vashegtergate, wat vashegters laat deurtrek, bevestig. Daarom kan EEA as ’n effektiewe instrument gebruik word om die gedrag van IBR te ondersoek. Ten slotte word dit afgelei dat die lugsaktoetsmetode van hierdie navorsingsondersoek ’n effektiewe metode verskaf het vir die gedrag-evaluering van kruinvasgehegte bekleding tydens wind-opheffing. Die lugsaktoetsmetode kan egter nie ’n ware gelykverspreide ophefbelasting naboots nie. Daarom word dit voorgestel dat toetsmetodes wat direkte lugdruk aanwend gebruik moet word vir enige verdere navorsing of kommersiële toetse van metaalbekleding, aangesien dit ’n effektiewe en bevestigde toetsmetode is wat statiese en sikliese opheftoestande akkuraat kan naboots.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/80018
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