this PDF file - Archives of Mining Sciences

this PDF file - Archives of Mining Sciences

Arch. Min. Sci., Vol. 54 (2009), No 3, p. 467–479
467
Electronic version (in color) of this article is available: http://mining.archives.pl
KAROL FIREK*
PROPOSAL FOR CLASSIFICATION OF PREFABRICATED PANEL BUILDING DAMAGE INTENSITY
RATE IN MINING AREAS
PROPOZYCJA KLASYFIKACJI INTENSYWNOŚCI USZKODZEŃ BUDYNKÓW WIELKOPŁYTOWYCH
NA TERENACH GÓRNICZYCH
The paper presents a proposal for classification of intensity of damage to prefabricated panel building
elements in mining areas. The study was based on the data collected by the author of this paper, which
regarded technical condition as well as potential reasons for damages and accelerated wear of 74 building
objects located in the mining area of Legnica – Głogów Copper District. On the basis of the inspection
conducted for each of the buildings, an index wu, defined at work, of grading intensity of damages made
to its construction and non-construction elements, was specified. Then comparative studies of wu index
defined for buildings erected in WWP and Wk-70 systems were carried out, as well as its correlation with
indices defining the impact of mining tremors was examined.
Keywords: technical condition, prefabricated panel buildings, building damages, mining effects
Na stan techniczny budynku, oprócz zużycia naturalnego, składa się również intensywność, czyli
zakres i częstość uszkodzeń wszystkich jego elementów, zarówno konstrukcyjnych, wykończeniowych
jak i wyposażenia (instalacji). Wspólną cechą tych uszkodzeń jest fakt, iż przyczyn ich powstania szukać
należy w czynnikach w sensie statystycznym losowych, takich jak skutki błędów projektowych i wykonawczych, przeciążenia elementów konstrukcyjnych, drgania komunikacyjne lub od maszyn i urządzeń,
zmiany stosunków wodnych w podłożu fundamentowym, ruchy masowe, itp. Należą do nich również
wpływy górnicze, zarówno w postaci wstrząsów, jak i ciągłych deformacji powierzchni.
Na terenach górniczych mamy do czynienia z koniecznością okresowej oceny stanu technicznego
licznych grup budynków, zróżnicowanych pod względem funkcji, wieku, zastosowanych rozwiązań
konstrukcyjno-materiałowych oraz jakości utrzymania. Potrzeba określenia stanu technicznego zabudowy
jest związana z oceną bezpieczeństwa konstrukcji i użytkowników, z określeniem poziomu uciążliwości
użytkowania lub wyceną powstałych szkód. W tej sytuacji słusznym wydaje się poszukiwanie metodyki,
która może uprościć i przyspieszyć ocenę stanu budynków oraz zapewni w efekcie syntetyczne i porównywalne wyniki.
*
AGH UNIVERSITY OF SCIENCE AND TECHNOLOGY, FACULTY OF MINING SURVEYING AND ENVIRONMENTAL
ENGINEERING, AL. MICKIEWICZA 30, 30-059 KRAKÓW, POLAND
468
Podstawę prezentowanych w artykule badań stanowiła utworzona przez autora baza danych o stanie
technicznym oraz potencjalnych przyczynach uszkodzeń i przyspieszonego zużycia 74 budynków zlokalizowanych na terenie górniczym Legnicko-Głogowskiego Okręgu Miedziowego. W tym 32 budynki
o wysokości 5 kondygnacji wzniesiono w systemie Wk-70 oraz 42 o wysokości od 5 do 11 kondygnacji
wykonano w systemie WWP.
W pierwszej części pracy przedstawiono propozycję klasyfikacji intensywności uszkodzeń elementów wielkopłytowych budynków mieszkalnych usytuowanych na terenach górniczych. Do oceny
intensywności występowania uszkodzeń zaproponowano wskaźnik wu zdefiniowany w 6-stopniowej skali
(tab. 3.1). Intensywność uszkodzenia poszczególnych elementów konstrukcyjnych i niekonstrukcyjnych
każdego z badanych budynków została ustalona według szczegółowych kryteriów określonych przez
autora i zestawionych w tabeli 3.2.
Główną inspiracją przy definicji wskaźnika wu było podejście do oceny intensywności wstrząsów
sejsmicznych przedstawione w Europejskiej skali makrosejsmicznej (EMS, 1998; An advanced…, 2004).
Przy określaniu szczegółowych kryteriów oceny intensywności uszkodzeń dla poszczególnych elementów
korzystano z literatury traktującej o diagnostyce stanu technicznego budynków z uwzględnieniem specyfiki
budynków wielkopłytowych oraz oddziaływań górniczych (Hajdasz, 1992; Wodyński i Kocot, 1996;
Lewicki, 2002; Kawulok i Selańska-Herbich, 2002; Cholewicki, 2002; Instrukcja..., 2006). W przyjętej
skali wskaźnik wu = 0 oznacza, że uszkodzenia nie występują, wu = 1 – nieznaczne uszkodzenia, wu = 2
– umiarkowane uszkodzenia, itd. W praktyce zwykle znajdujemy się w zakresie wskaźnika wu od 0 do 3.
W niektórych jednak przypadkach, przy intensywnych uszkodzeniach elementów konstrukcyjnych lub
bardzo intensywnych uszkodzeniach elementów drugorzędnych może wystąpić konieczność wykonania
szczegółowej ekspertyzy w celu sprawdzenia bezpieczeństwa budynku.
W drugiej części pracy przedstawiono wyniki wstępnych analiz z udziałem określonego wcześniej
wskaźnika intensywność uszkodzeń wu. Badania przeprowadzono przy użyciu metod statystycznych.
W pierwszej kolejności polegały one na porównaniu średnich wartości wskaźnika wu poszczególnych
elementów w analizowanych grupach budynków. Pozwoliło to na wyciągnięcie wniosków o znaczeniu
jakościowym. Pomimo generalnie umiarkowanego zakresu uszkodzeń w 5 przypadkach stwierdzono
istotne statystycznie różnice w tym zakresie pomiędzy poszczególnymi elementami budynków w grupach Wk-70 i WWP. W 6 przypadkach wskaźnik wu był wyższy dla elementów budynków wzniesionych
w technologii WWP. W niektórych przypadkach różnice te mogły wynikać w pierwszym rzędzie z różnic
w jakości wykonawstwa oraz utrzymania obiektów.
Następnie przeprowadzono badania zależności między intensywnością uszkodzeń ścian nadziemia
analizowanych budynków, a oddziaływaniami górniczymi w postaci wstrząsów górniczych. Uzyskane
wyniki pozwalają na stwierdzenie, że w przypadku budynków wzniesionych w technologii WWP istnieje
istotna w sensie statystycznym korelacja między wskaźnikiem intensywności uszkodzeń ścian nośnych
nadziemia wu2, a wskaźnikiem amax opisującym wpływ wstrząsów górniczych. Najwyższy współczynnik
korelacji uzyskano w przypadku grupy budynków 11-kondygnacyjnych. Dla budynków wykonanych
w systemie Wk-70 stwierdzono wprawdzie nieistotną statystycznie zależność, jednak stosunkowo niska
wartość p, wskazuje na potrzebę dalszych badań na poszerzonym zbiorze obiektów.
Przedstawione wyżej analizy traktować należy jako wstępną propozycje opisu i oceny intensywności
uszkodzeń w budynkach wielkopłytowych. Zakres i częstość tych uszkodzeń zależy od wielu trudnych do
jednoznacznego opisu czynników. Wyniki wstępnych badań, pozwalają jednak przypuszczać, że przedstawiona w pracy metodyka, po szerszej weryfikacji, może uprościć i przyspieszyć ocenę stanu budynków
na terenach górniczych, zapewniając jednocześnie syntetyczne i porównywalne wyniki.
Słowa kluczowe: stan techniczny, budynki wielkopłytowe, uszkodzenia budynków, wpływy górnicze
469
1. Introduction
The technical condition of a building results from its natural wearing processes as
well as a number of other factors of randomized character. Random factors, which also
include mining exploitation effects, may cause emergence of damages which, in turn,
may result in increased technical wear rate, increased renovation costs, lowered durability
of a building and even safety hazard. Therefore the technical condition of a building is
a function of natural wear and a scope of damage of all its elements, both construction,
finishing and fitting (installation) ones.
In mining areas there is a necessity of periodical assessment of technical condition
of numerous groups of buildings, diversified according to their function, age, applied
construction and material solutions as well as maintenance quality. The necessity of defining specified technical condition of a building is closely associated with the evaluation
of both construction and users safety, with defining the level of exploitation nuisance, or
with the assessment of damages which emerged. In such a case it seems reasonable to
look for methodology which could simplify and accelerate the assessment of the building
condition and which, in turn, could guarantee synthetical and comparable results.
Housing development in Legnica–Głogów Copper District has been exposed to
mining effects for over 40 years. Initially, these influences resulted from the formation
of a subsidence trough over mining excavations and a large surface trough associated
with the rock mass dehydration. Since 1980s on the territory of Legnica–Głogów Copper District there have also occurred mining tremors of significant strength. Long term
experience shows that they constitute a main factor of mining impact on building development in Legnica–Głogów Copper District.
Apart from issues of mining effects on construction safety measures, which are
widely described in technical literature, their influence on the scope and frequency of
damages to secondary elements and accelerated natural wear of a building is also significant (e.g. Ostrowski & Ćmiel, 2008). The research on mining effects on technical
condition of housing development in Legnica–Głogów Copper District, which, in the
past few years, has been carried out at the Faculty of Engineering Geodesy and Civil
Engineering of AGH University of Science and Technology, regarded masonry construction buildings (e.g. Firek, 2005; Wodyński, 2007). This study presented a proposal for
classification of damage intensity rates of residential building elements constructed in
industrialized prefabricated panel systems and then the results of introductory research
on dependence of damage intensity index on building technology as well as mining
tremor impacts were shown.
2. Description of analysed housing development
The study was based on the data comprising a group of 74 residential building objects
of prefabricated concrete slabs construction located within the impact range of mines in
470
the area of Legnica–Głogów Copper District. These building objects are located in the
area of maximum intensity of mining tremors for the built-up area of Legnica–Głogów
Copper District. They include:
− 32 five-storey buildings erected in Wk-70 system, most of which were erected
in Wk-70sg system adapted for mining areas,
− 42 five- to eleven-storey buildings erected in WWP system.
In both technologies the buildings mostly have crosswise construction of the load
bearing walls. Their bearing structure is composed of vertical wall shields based on
the foundation and connected by means of horizontal ceiling shields at each storey.
Monolithic structure of wall and ceiling shields is guaranteed by the application of
continuous monolithic tie beams as well as characteristic horizontal and vertical joints.
Spatial rigidity of the buildings is guaranteed by crosswise and lengthwise wall shields.
The differences between the systems regard, but are not limited to, dimensions of the
prefabricated elements and structure of the joints.
Data on the technical condition of the buildings in question has been gathered with
the author's contribution during detailed inspections carried out in the last few years.
3. Methodology of determining intensity index
for damages to prefabricated panel
building elements
Both intensity, i.e. the scope and frequency of damage to the construction, finishing
and fitting (installation) elements of a building as well as natural wear constitute to its
technical condition. The common feature of these types of damages is that their source
is constituted by factors statistically considered as randomized, such as effects of faulty
engineering design, faulty execution, overload of construction elements, traffic, vibrations of machinery or appliances, changes of water ratio in the foundation soil, mass
movements, etc. Mining influences, both in the form of tremors as well as continuous
surface deformation, are also included.
This paper presents a proposal for classification of intensity rate occurrence of damages to elements of prefabricated panel residential buildings. In order to evaluate the
intensity of damage occurrence, the index wu defined in a six-grade scale was introduced
(table 3.1). The intensity of damage to specific elements of each of the examined panel
buildings was determined in accordance with detailed criteria specified by the author
and presented in table 3.2.
The main inspiration while defining the damage intensity index wu was an approach
towards the estimate of seismic shocks intensity, as presented in European Macroseismic Scale (EMS, 1998; An advanced ..., 2004). Professional literature on diagnostics
of technical condition of buildings with respect to panel housing characteristics and
mining impacts was used to define detailed criteria for damage intensity grading for
471
particular elements (Hajdasz, 1992; Wodyński & Kocot, 1996; Lewicki, 2002; Kawulok
& Selańska-Herbich, 2002; Cholewicki, 2002; Instruction …, 2006).
In the adopted scale, damage intensity index wu = 0 means that damages do not
occur, wu = 1 means minor damages, wu = 2 – moderate damages, etc. In practice the
index wu usually ranges from 0 to 3. In some cases, with intensive damage to construction elements or very intensive damage to secondary elements, a necessity to carry out
a detailed expertise in order to inspect building safety features may occur.
TABLE 3.1
Definition of damage intensity index wu
Damage intensity index wu
0
Definition
Description
Range [%]
Do not occur
0
1
Minor
2
Moderate
3
Intensive
4 (and 5)
Very intensive
Damages do not occur or they are not visible
Damages are insignificant, tiny, occurring
individually
Damages are moderate, occurring locally, in
some places
Damages are intensive, considerable, vast,
occurring locally or numerously
Damages are very intensive, considerable,
vast, occurring in large numbers (until devastated)
(0-10>
(10-30>
(30-50>
>50
4. Comparative studies of intensity rate damage
to particular elements of buildings erected
in wk-70 and wwp systems
The purpose of the studies was a comparative analysis of the type, scope and size
of damage to particular elements of buildings erected in prefabricated concrete slabs
industrialized systems. The analysis was carried out for selected groups of buildings
erected in Wk-70 (32 buildings) and WWP (42 buildings) technologies. In direct comparisons damage intensity indices wu specified for particular elements of the buildings
in question were employed.
The statistical test “significant differences between group means” (NIR) was applied. Significance level (p) of the obtained result was calculated each time. Statistical
significance informs about the representativeness of the result obtained from a sample in
respect to the whole population. The significance level complies with the probability of
making a mistake by groundlessly accepting the obtained result as true, i.e. representative. In most fields it is customary to accept p = 0.05 as critical level. It means, that only
at the level of p < 0,05 the obtained result may be considered as significant.
2
1
2.
Overground
level bearing
walls
Tight cracks
do not occur
or they are
not visible
(aperture up
to 0,1 mm)
Tight cracks occurring
numerously (tiny, microcracks), or locally
occurring cracks with
aperture up to 1 mm, or
individual cracks up to
3 mm, with the length
reaching the whole
height of a storey
Cracks occurring numerously with aperture up to
1 mm, or occurring locally
with aperture up to 3 mm,
or individual cracks exceeding 3-5 mm; possible
wall surface displacements
in splits; possible loosening
of concrete cover
6
(30-50>
Intensive
3
7
>50%
Very Intensive
4 (and 5)
TABLE 3.2
Cracks occurring in large numbers
with aperture up to 3 mm, aperture of
individual cracks exceeds 5 mm; possible loosening of concrete cover and
reinforcement deformation; aggregate
aperture exceeds 20 mm, possible wall
surface displacements; besides the size
of apertures the construction hazard
degree is significant (until emergency
condition)
Cracks occurring in large numbers
Tight cracks occurring Tight cracks occurring Cracks occurring numerwith aperture up to 3 mm, aperture
numerously (tiny, mi- ously with aperture up
locally; tiny, hairline
to 1 mm, or occurring
of individual cracks exceeds 5 mm;
cracks (microcracks)
crocracks), or locally
occurring cracks with locally with aperture up to aggregate aperture exceeds 20 mm;
or individual cracks
with aperture up to 1
aperture up to 1 mm, or 3 mm, or individual cracks besides the size of apertures the construction hazard degree is significant
mm and length reach- individual cracks up to exceeding 3-5 mm; local
ing 1.5 m
3 mm, with the length mortar losses in wall joints; (until emergency condition); numerous mortar losses in wall joints; steel
possible signs of steel
reaching the whole
corrosion in joints; possible loosening
corrosion in joints; posheight of a storey;
individual tiny mortar sible loosening of concrete of concrete cover as well as reinforcement deformation; rainwater leakage
cover; possible rainwater
losses in wall joints
leakage
Tight cracks occurring
locally; tiny, hairline
cracks (microcracks)
or individual cracks
with aperture up to 1
mm and length reaching 1.5 m
5
4
3
(10-30>
(0-10>
0%
Moderate
2
Minor
1
Do not occur
0
Construction elements
1. Cellar load
Tight cracks
bearing walls do not occur
or foundation or they are
walls
not visible
(aperture up
to 0,1 mm)
Elements of
buildings
No.
Damage intensity index (wu)
Detailed assessment criteria of damage intensity index wu in buildings erected in industrialized technologies
472
Balconies and
loggias
4.
Tight cracks
do not occur
or they are
not visible
(aperture up
to 0,1 mm)
3
Tight cracks
do not occur
or they are
not visible
(aperture up
to 0,1 mm)
Damages (tight cracks
and losses of mortar in
wall joints, tight cracks
and plaster loosening) occurring locally
and visible individual
cracks (up to 3 mm) in
elevation layer of wall
slabs
5
Tight cracks on plaster
along the edge of
prefabricated floor
slabs occurring locally;
possible individual
microcracks in floor
slabs; possible individual plaster loosening and losses;
Damages (cracks and
losses of mortar in wall
joints, tight cracks as well
as loosening and losses of
plaster) occurring numerously; locally cracks or
individual splits (up to
5 mm) in elevation layer of
wall slabs; possible loosening of concrete cover
6
Tight cracks on plaster
along the edge of prefabricated floor slabs occurring
numerously; individual
cracks in floor slabs running perpendicularly or
obliquely to the main
reinforcement; possible
individual loosening and
losses of plaster as well as
concrete cover;
Tight cracks on plaster Tight cracks on plaster Tight cracks on plaster
along the edge of prefabrialong the edge of pre- along the edge of
cated floor slabs occurring
prefabricated floor
fabricated floor slabs
occurring individually, slabs occurring locally; numerously; individual
cracks in floor slabs runinsignificant (microc- possible individual
ning perpendicularly or
microcracks in floor
racks)
obliquely to the main
slabs; possible indireinforcement; possible
vidual plaster loosenindividual loosening and
ing and losses;
losses of plaster as well as
concrete cover;
4
Tight cracks on plaster
along the edge of prefabricated floor slabs
occurring individually,
insignificant (microcracks)
Non-construction elements (secondary)
5. Elevation
Damages do Damages (tight cracks
layers
not occur or
and losses of mortar
they are not
in wall joints, hairline
visible
cracks and plaster
loosening) occurring
individually, insignificant
2
Floor slabs
and stairs
1
3.
Damages (cracks, splits and losses of
mortar in wall joints, tight cracks as
well as loosening and losses of plaster)
occurring in large numbers; numerous
cracks or individual splits (exceeding
5 mm) in elevation layer of wall slabs;
possible loosening and losses of
concrete cover
7
Tight cracks on plaster along the edge
of prefabricated floor slabs occurring
in large numbers (in most rooms);
local cracks in floor slabs running
perpendicularly or obliquely to the
main reinforcement; numerous plaster
loosening and losses; possible loosening of concrete cover; besides the size
of apertures the construction hazard
degree is significant (until emergency
condition)
Tight cracks on plaster along the edge
of prefabricated floor slabs occurring
in large numbers (in most rooms);
local cracks in floor slabs running
perpendicularly or obliquely to the
main reinforcement; numerous plaster
loosening and losses; possible loosening of concrete cover; besides the size
of apertures the construction hazard
degree is significant (until emergency
condition)
473
Dampproof
insulation,
roofing, flashing, as well as
gutters and
rain water
pipes
Building
entrances,
landings and
trims
7.
8.
2
Partition
walls, interior
plasters and
ceramic wall
and floor cladding
1
6.
3
Damages do
not occur or
they are not
visible
Damages do
not occur or
they are not
visible
Damages do
not occur or
they are not
visible
5
Damages (tight cracks
along wall edges, plaster tight cracks, mortar
and cladding loosening
and plaster dampness)
occurring locally and
visibly; individual
cracks (up to 3 mm)
in walls, in plaster, in
wall cladding and in
floors; possible small
mortar and cladding
losses
Leakage occurring individually, a few cases
6
Damages (cracks along
wall edges, plaster tight
cracks, mortar and cladding
loosening and losses, plaster dampness) occurring
numerously; locally cracks
or individual splits (up to 5
mm) in walls, in plaster, in
wall cladding and in floors;
possible wall surface
displacements in splits; in
damp locations possible
plaster corrosion
Individual leakage
Leakage occurring locally;
in some places splits, loosening and losses of insulation or covering; in some
locations broken joints
and reversed inclination of
drainpipes
Tight cracks occurring Tight cracks occurring Cracks occurring numerously, possible individual
individually
numerously, possible
tiny plaster or concrete splits; possible local displacements as well as plasloosening occurring
locally; possible small ter or concrete loosening
displacements
4
Damages (microcracks
along wall edges,
hairline plaster cracks,
cladding loosening
and plaster dampness)
occurring individually,
insignificant
7
Cracks occurring in large numbers,
possible local splits; locally significant
displacements as well as plaster or
concrete loosening
Leakage occurring numerously; numerous splits, loosening and losses of
insulation or covering; local cases of
broken joints and reversed inclination
of drainpipes
Damages (cracks and splits along wall
edges, plaster tight cracks, mortar and
cladding loosening and losses, plaster
dampness) occurring in large numbers;
numerous cracks or individual splits
(exceeding 5 mm) in walls, in plaster,
in wall cladding and in floors; possible
wall demonolithization and its surface
displacements; in damp locations plaster and masonry wall corrosion
474
475
The results of the conducted analysis are compiled in table 4.1, where mean values
of damage intensity indices specified for particular elements of the buildings in study
groups, differences between these mean values as well as significant differences test
results were presented.
The obtained results allow for drawing the following conclusions:
a) in the adopted intensity scale, the scope and frequency of the identified damages is moderate in most cases. It refers both to the buildings erected in Wk-70
and in WWP systems. Insignificant damages with average intensity index
wue ≤ 1.0 were identified in two groups of elements of buildings erected in both
technologies. Only in the case of non-construction interior elements (partition
walls, interior plaster, ceramic wall and floor cladding) in buildings in WWP
technology, a result wue > 2.0 was obtained, which represents intensive damages,
b) comparing differences in values of the intensity rate index of damages made to
specific elements of buildings it must be emphasized that, with moderate damage
intensity, in six cases it is higher for the buildings erected in WWP technology,
with five cases the difference being significant in the statistical sense.
TABLE 4.1
Mean values of intensity rate index wue of damages made to specific elements of analysed buildings
and results of significant differences between mean values test
No.
Elements of building
1
Cellar load bearing walls
Overground level bearing
walls
Floor slabs and stairs
Balconies and loggias
Elevation layers
Partition walls, interior
plasters and ceramic wall
and floor cladding
Dampproof insulation,
roofing, flashing, as well as
gutters and rain water pipes
Building entrances, landings
and trims
2
3
4
5
6
7
8
Mean values of element
damage intensity indices
wue
Wk-70
WWP
Indices
value differences
Δwue
Significance of differences between mean
values test results (NIR)
p
1.656
1.976
–0.320
0.0084
1.375
1.643
–0.268
0.067 > 0.05
1.219
0.156
1.656
1.214
0.690
2.000
0.005
–0.534
–0.344
0.971 > 0.05
0.0001
0.0453
1.813
2.286
–0.473
0.00004
0.125
0.500
–0.375
0.0011
1.313
1.167
0.146
0.521 > 0.05
c) It must be emphasized, however, that in some cases the differences between damage range might derive from differences in execution and maintenance quality,
in the first place.
476
5. Analysis of relation between intensity rate index of
damage to overground walls and parameter defining
impact of mining tremors
The purpose of the study was to analyse if there exists a significant, in a statistical
sense, relation between the damage intensity rate of the analysed buildings and mining
impacts in the form of mining tremors.
In the case of impact analysis of mining tremors on building construction safety
features, the parameters of the strongest tremor affecting the object must be considered.
In this paper, index amax was adopted to define the effect of the tremors on damage to
building elements. It must be emphasized, however, that taking into consideration a single
(the strongest) tremor does not allow for the estimate of such impacts on the technical
wear. In this case, multiplicity and individual intensity of impacts of all seismic phenomena which affect the building in a significant manner throughout its whole period of
being used, must be taken into account. Owing to it, recurrence of dynamic effects may
be considered. The analysis of influence of mining tremors on technical wear of building structures located in Legnica–Głogów Copper District with reference to traditional
masonry construction building, was presented and verified by research included in the
works of (Firek, 2005, Wodyński, 2007). With respect to prefabricated panel buildings
the results of preliminary studies were presented in the paper (Wodyński et al., 2008).
The amax index values were calculated separately for individual buildings based on
data regarding tremors occurring on the territory of Legnica–Głogów Copper District
throughout the whole period of their existence. A maximum effect for a given object
was determined according to the following formula:
amax = max{aH k (x, y)} ; k = 1, ..., n
(5.1)
where:
(x, y) — object coefficients,
aH k (x, y) — peak value of horizontal component of acceleration of vibrations in frequency band up to 10 Hz for k – of this tremor,
n — number of tremors which occurred in the period ranging from the erection
of the object to the point of its inspection.
Pearson’s linear correlation coefficient test was applied in the analysis. Besides the
correlation coefficient R, the significance level p of the obtained result was also calculated each time at the critical level p = 0.05. The dependence studies comprised a group
of 74 buildings divided according to the Wk-70 and WWP technologies, which were
applied. Then, taking into consideration significant differences in building rigidity, the
research was carried out which selected 5 and 11-storey buildings. In tables 5.1 and 5.2
the results for overground bearing walls damage intensity index wu2 were presented.
477
TABLE 5.1
Correlation analysis between overground bearing walls damage intensity index wu2 and mining tremors
impact index amax – a group of 74 buildings located in the area of maximum intensity of mining tremors
for the built-up area of Legnica–Głogów Copper District
Analysed group of buildings
(units)
Total (74)
Buildings erected in Wk-70
system (32)
Buildings erected in WWP
system (42)
wu2
Correlation coefficient
R
Significance level
p
0,186
0,112 > 0,05
0,257
0,155 > 0,05
0,541
0,000
TABLE 5.2
Correlation analysis between overground bearing walls damage intensity index wu2 and mining tremors
impact index amax – a group of 63 5-storey buildings located in the area of maximum intensity of mining
tremors for the built-up area of Legnica–Głogów Copper District
Analysed group of buildings
(units)
5-storey buildings (63), including:
a) buildings erected in Wk-70
system (32)
b) buildings erected in WWP
system (31)
11-storey buildings, all erected in
WWP system (11)
wu2
Correlation coefficient
Significance level
R
p
0,146
0,253 > 0,05
0,257
0,155 > 0,05
0,483
0,006
0,599
0,052
The obtained results lead to the following conclusions:
a) in the case of buildings erected in Wk-70 technology, in statistical sense, no
significant correlations between damage intensity index wu2 and mining tremors
impact index amax was obtained,
b) in the case of buildings erected in WWP technology, a significant correlation with
relatively high R coefficient value was identified. It shows that buildings erected
in WWP system have lower resistance to mining tremor impacts,
c) the highest correlation coefficient was obtained in the case of a selected group of
11-storey buildings. It is in accordance with the logical aspect of the phenomenon
as it confirms the influence of the object rigidity on its resistance to dynamic
effects. The results, however, are not fully reliable taking into account a small
number of the objects in this particular group.
478
6. Summary
The research on mining effects on the technical condition of buildings, carried out
at the Faculty of Engineering Geodesy and Civil Engineering of AGH University of
Science and Technology over the last few years, has regarded masonry construction
buildings. This paper presents the results of analysis carried out for prefabricated panel
buildings.
Pursuant to literature studies as well as author’s own experiments, a six-grade classification of damage rate to prefabricated panel residential buildings located in mining
areas was proposed. Then, for specific elements of buildings erected in industrialized
technologies, a detailed description of damage scope referring to consecutive intensity
grades was presented.
The study also comprises the results of introductory analysis with the use of damage
intensity index specified for particular elements of 74 prefabricated panel residential
buildings (32 of which were erected in Wk-70 system and 42 were erected in WWP
system) located in the mining area of Legnica–Głogów Copper District.
The research was carried out with the use of statistical methods. These included
a comparison of the mean values of damage intensity index for specific elements in the
analysed group of buildings. It made it possible to draw conclusions of quality significance. Despite a generally moderate scope of damage, in five cases essential statistical
differences between specific elements of buildings in Wk-70 and WWP groups were
identified. In six cases the damage intensity index was higher for the elements of buildings erected in WWP technology. In some cases, however, the differences between
damage scope might derive from differences in execution and maintenance quality, in
the first place.
Then, dependence analysis between overground bearing walls damage rate in the
analysed buildings and mining impacts in the form of mining tremors was conducted.
The obtained results allowed to determine that in the case of buildings erected in the
WWP system, there is a significant, in a statistical sense, correlation between the overground bearing walls damage intensity index and mining tremor impacts. The highest
correlation coefficient of damage intensity index and indices defining mining tremor
impacts was obtained in the case of a group of 11-storey buildings. In the case of buildings executed in the Wk-70 system, an insignificant, in a statistical sense, dependence
was identified; however, a relatively low value of p indicates a need for further research
on an extended group of objects.
The above-mentioned analysis should be perceived as introductory proposal of
description and assessment of damage intensity in prefabricated panel buildings, whose
scope as well as frequency depends on numerous, difficult to define in an evident manner, factors. The results of introductory research, however, make it possible to assume
that methodology of defining damage intensity, as presented in this paper, after extended
479
verification, is able to simplify as well as accelerate the assessment of the condition of the
buildings located in the mining areas to guarantee synthetical and comparable results.
The article was prepared within the Research Project Badania Własne AGH
No. 10.10.150. 964
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Received: 07 July 2009