| Summary: | Thesis (MscEng)--Stellenbosch University, 2013. === 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.
|
|---|
