Assessment of time and mining exploitation effects on

GOSPODARKA Tom 24

SUROWCAMI

MINERALNYMI

2008

Zeszyt 3/1

ALEKSANDER WODYÑSKI*, KAROL FIREK*, JANUSZ RUSEK*

Assessment of time and mining exploitation effects on the technical wear of prefabricated panel buildings

Introduction Technical wear is one of basic factors deciding on the resistance of a building to the impact mining. This wear consists of natural wear and many other factors of a random character, including the impact of mining exploitation. The need to define the degree of technical wear of buildings situated in mining areas is also connected with the necessity to assess mining damage. Here we deal with technical wear understood in economic categories [4]. This is a material (physical) wear connected with changes in the building substance, interpreted as the diminishing the usability of the building or the values of its individual elements. Technical wear of the building is a function of the wear of all its elements of construction, decoration as well as facilities. The buildings in the area of the Legnica-G³ogów Copper Mining District (later called LGOM) have been subdued to mining impact for more than 40 years. At the beginning this impact was due to the formation of a subsidence trough over the workings and the formation of a large-surface trough connected with the draining of the rock mass. Since 1980s in the LGOM area also mining tremors occur. Lasting many years experiences indicate that they make a basic factor of mining impact on the surface buildings in the area of LGOM. Together width widely described in technical literature problems of the impact of these tremors on the construction safety, their influence on the acceleration of technical wear of the buildings is also important. The carried out in the latest years studies of the impact of mining tremors on technical wear of the built-up area in LGOM referred to the buildings of masonry construction * AGH University of Science and Technology, Kraków, Poland.

174 (e.g. [1, 2, 8, 9, 13, 14]). This paper presents the results of preliminary studies of these impacts on technical wear of buildings prefabricated panel buildings.

1. The description of the studied buildings The base for the studies was a database containing a group of 129 residential buildings of prefabricated panel construction, located within the range of the mining impact from the LGOM mines. The following can be differentiated: — 71 buildings of 5–11 storeys made in the Wk-70 system, including the majority in the Wk-70sg system, adjusted to mining areas, — 58 buildings of 5–11 storeys made in the WWP system. In both technologies buildings have usually a transverse system of bearing walls. The bearing system consists of vertical wall shields based on fundaments and joint on every storey with horizontal ceiling shields. Spatial stiffness of buildings is secured by transverse and longitudinal wall shields. Wall and ceiling shields make a monolithic structure due to the application of continuous monolithic beams and characteristic horizontal and vertical joints. The differences between systems included (among others) different size of prefabricated elements and joints construction.

2. The method of the assessment of the degree of buildings’ wear The data on the technical state and possible building interventions, were collected by the authors during the carried out in recent years detail inventory. This allowed the application of “the weighted average method” in the assessment of the degree of wear for individual buildings (e.g. [3, 7, 15]). The method consists of an individual assessment of the degree of wear of particular elements, assigning appropriate weights to those elements and then determining the average-weighted degree of wear of the entire building: n

u i × sei i =1 100

sz = å

[%]

(1)

where: ui – the percentage participation of the reconstruction costs for the elements in the structure of reconstruction cost of the object, serving as weight, sei – a degree of wear of a given elements, in percentage, n – the number of elements. At the determination of the percentage participation of the costs of the reconstruction of a given element win the structure of the reconstruction costs for the whole object; data included in [6] were used.

175 3. Establishing the course of technical wear of buildings in time Natural wear of buildings is a function of time. Technical wear is also influenced by many factors, in a statistical sense random. They can either accelerate the process of wear (among others the impact of mining) well as modify this process in a favourable way (e.g. renovations). The abundance of these factors of a difficult to establish individual to every object character, makes finding an accurate form of this dependence practically impossible. If the goal is to find the trend of the phenomenon – the analysis can be limited to simple forms of functions. The non-linear regression method was applied; at the selection of model parameters the smallest-squares method was applied. Such an approach allowed direct comparison of optimal models in different classes of the function, and consequently, the choice of the best solution (e.g. [10, 11, 12]). The studies were carried out for the whole group of 129 buildings and in the sets distinguished due to the construction system. The results were presented in figures 1–3 and table 1. The estimated based on the shown above data mean durability of the built-up area T is 90.4 years for buildings in Wk-70 system and 94.3 years for objects in WWP system. This does not exceed the margin given in the literature for this type of building.

Fig. 1. Detected values of technical wear sz and the trend for the group of 129 buildings Rys. 1. Wartoœci wykrytego zu¿ycia technicznego sz oraz trendy dla grupy 129 budynków

176

Fig. 2. Detected values of technical wear sz and the trend for the group of 58 buildings built in Wk-70 system Rys. 2. Wartoœci wykrytego zu¿ycia technicznego sz oraz trendy dla grupy 58 budynków wybudowanych systemem typu Wk-70

Fig. 3. Detected values of technical wear sz for the group of 71 buildings built in WWP system Rys. 3. Wartoœci wykrytego zu¿ycia technicznego sz oraz trendy dla grupy 71 budynków wybudowanych systemem typu WWP

177 TABLE 1 The values of the parameters of the course model during the technical wear in the studied groups of buildings and adjustment coefficients TABELA 1 Wartoœci parametrów modelu przebiegu procesu zu¿ycia technicznego badanych budynków oraz wspó³czynniki regulacji Trend equation sz = b · t

Correlation coefficient R

Determination coefficient R2 [%]

Total (129)

sz = 0.0108 · t

0.8947

80.06

Buildings built in Wk-70 (58) system

sz = 0.0111 · t

0.9435

89.02

Buildings built in WWP (71) system

sz = 0.0106 · t

0.7817

61.11

The studies group of buildings (items)

4. The studies of the impact of mining tremors on technical wear of buildings 4.1. T h e m e t h o d o f s t u d y In the case of the analysis of the impact of mining tremors on the construction safety of buildings the parameters of the strongest tremor affecting the object are taken into account. Regarding a single (strongest) tremor does not allow the assessment of these impacts on technical wear. In this case the repetitiveness and individual intensities of the impacts of all the seismic impacts affecting the building over the whole period of its exploitation should be regarded. Due to this the repetitiveness of dynamic influence can be considered. Papers [8, 13, 14] present the concept of the assessment of the impact of mining tremors on technical wear of buildings in LGOM. In case of buildings of traditionally structured masonry construction, the concept was verified by the studies presented in (among others) [1, 2]. As the index of dynamic influence accelerating technical wear of building was the geometric sum of peak values of the acceleration of vibrations, caused by tremors in the place of their localization. Only the tremors that occurred during the period of the exploitation of building were taken into account and for which peak values in the place of its localization are bigger than a pre-determined threshold value ap: a sg ( x, y ) =

n

å a H , k ( x, y ) 2 ;

k =1

a H , k ( x, y ) ³ a p

(2)

178 where: (x,y) – object coordinates, aH,k(x,y) – calculated in point (x,y) peak value of the tremor-caused acceleration, n – number of tremors that occurred during the exploitation and for which the calculated peak value in point (x,y) was greater than threshold value ap. It was found that for the applied in LGOM relation of damping, optimal from the standpoint of the estimation of repetitive seismic index asg is the threshold value ap = 0.12 m/s2, while values aH refer to peak values of horizontal component of the acceleration of vibrations in the range of frequency up to 10 Hz. It should stressed that ap is a threshold value to be applied in the case of the analysis of the impact of mining tremors on technical wear of buildings, and not on the damage of the elements of their construction (the threshold value would be in this case much higher). In this paper, for the assessment of the impact of mining tremors on technical wear of buildings a new formula, regarding statistical uncertainty in the relation to the estimated relations of damping was applied [5]. This index for the object situated in the place of co-ordinates (x,y) is described as: a sg , prob ( x, y ) =

n

å {E k [a H ,k (x, y ) a H ,k ( x, y ) ³ a p ]}2

(3)

k =1

where: (x,y) – co-ordinates of the object, E k [ a H ,k ( x, y ) a H ,k ( x, y ) ³ a p ] – conditional expected value of the impact n

of kth tremor in point (x,y), provided threshold a H , ( x, y ) ³ a p is exceeded, – number of tremors that occurred in the exploitation period and for which calculated peak value in point (x,y) was higher than the threshold value ap.

The values of index asg,prob were calculated individually for every building, based on the database on tremors occurring in the LGOM area over the whole period of their existence [5]. 4.2. T h e s t u d i e s o f t h e c o r r e l a t i o n b e t w e e n t h e d e g r e e o f t e c h n i c a l w e a r o f b u i l d i n g s sz, a n d i n d e x asg,prob d e s c r i b i n g t h e i m p a c t o f m i n i n g t r e m o r s The purpose of the research was checking whether there is a statistically significant difference between the technical wear of the analysed building structure and mining impacts in the form of mining tremors. The test of Pearson linear correlation was applied. Apart from the correlation R, every time the significance level p of the obtained result was calculated at the critical level p = 0.05.

179 The relationships referring to the whole analysed built-up area and in the groups differentiated due to technical features of buildings were calculated. The studied buildings were located in two regions. In one of them there was the impact of mining tremors of maximal for LGOM built up areas intensity asg,prob = 2.5–3.5, and in the second the intensity was small asg,prob = 0.03–0.16. In this situation, this study group was a group of 74 buildings located in the first of the presented regions (table 2). Due to a significant difference in the stiffness of 5- and 11-storey buildings, in table 3 the results of the correlation for 5- and 11-storey buildings were presented separately. TABLE 2 The studies of correlation between the degree of wear sz and the index of the impact of mining tremors asg,prob – the group of 74 buildings situated in the region of the maximal for the built-up areas of LGOM tremor intensity TABELA 2 Badania nad zale¿noœci¹ pomiêdzy stopniem zu¿ycia sz oraz wskaŸnikiem oddzia³ywania wstrz¹sów podziemnych asg,prob – grupa 74 budynków znajduj¹cych siê na obszarze o maksymalnym natê¿eniu wstrz¹sów dla terenów zabudowanych LGOM

The examined group of buildings [items]

sz Correlation coefficient R

Significance level p

Total [74]

0.470

0.000

Buildings built in system Wk-70 [32]

0.352

0.048

Buildings built in system WWP [42]

0.777

0.000

TABLE 3 The studies correlation between the degree of wear sz and the of the impact of mining tremors asg,prob – group of 63 five-storey buildings situated in the region of maximal for the built-up areas of LGOM tremor intensity TABELA 3 Badania nad zale¿noœci¹ pomiêdzy stopniem zu¿ycia sz oraz wskaŸnikiem oddzia³ywania wstrz¹sów podziemnych asg,prob – grupa 63 piêciopiêtrowych budynków znajduj¹cych siê na obszarze o maksymalnym natê¿eniu wstrz¹sów dla terenów zabudowanych LGOM

The examined group of buildings [items]

sz Correlation coefficient R

Significance level p

5-storey buildings [63], including:

0.407

0.001

a) built in system Wk-70 [32]

0.352

0.048

b) built in system WWP [31]

0.727

0.000

0.928

0.000

11-storey buildings (all in system WWP) [11]

180 The obtained results allow the following conclusions: — in case of buildings built in Wk-70 technology much lower correlation coefficient of the degree of technical wear with the index describing the impact of mining tremors was found. It indicates a higher resistance of buildings built in system Wk-70 to this impact; — the highest correlation coefficient was obtained in case of the selected group of 11-storey buildings. This follows the logic of this phenomenon, because this confirms the influence of object stiffness on its resistance of a dynamic impact. These results are, however, not fully reliable, because the number of objects in this group was small.

5. Closing remarks The carried out in recent years studies of the impact of mining tremors on technical wear of buildings in the LGOM area referred to the buildings of masonry construction. The described in this paper studies are the first attempt to assess the impact of mining tremors on the wear of prefabricated panel buildings. The analysis of the course of the technical wear of the studied buildings in time showed that the mean durability T of the buildings ranges from 90.4 to 94.3 years, which corresponds the values given in literature for this type of buildings. The carried out studies showed that there is a statistically significant correlation between technical wear of buildings and the impact of mining tremors in the regions of their greatest intensity. The highest correlation coefficient between the degree of technical wear and the index describing the influence of mining tremors was obtained in case of 11-storey buildings. It was also found that the correlation coefficient for buildings made in system Wk-70 was much lower than the obtained for the objects built in system WWP. The given above results should be treated as preliminary assessment of the phenomenon, the course of which depends on many factors difficult to describe in a non-ambiguous way. Bearing in mind the number of these factors connected, for example, with the quality of the building maintenance, building interventions, scale of the occurring damage, etc., in further studies it is planned to apply the methods of artificial intelligence. For this reason artificial neural networks and the models of fuzzy inference system, which fulfil the role of universal approximators of the function of many variables can be applied to solve this problem. The article was prepared within the Research Project Badania Statutowe AGH No. 11.11.150.312

REFERENCES [1] F i r e k K., 2005 – Badanie wp³ywu czynników górniczych i budowlanych na zu¿ycie techniczne tradycyjnej zabudowy terenu górniczego LGOM. Rozprawa doktorska, Akademia Górniczo-Hutnicza, Wydzia³ Geodezji Górniczej i In¿ynierii Œrodowiska, Kraków.

181 [2] F i r e k K., 2006 – Assessment of mining tremor impacts on technical wear of masonry buildings located in the Legnica-G³ogów Copper District. 7. Geokinematischer Tag des Institutes für Markscheidewesen und Geodäsie an der Technischen Universität Bergakademie Freiberg, Heft 1. [3] H a j d a s z H., 1992 – Sposoby ustalania zu¿ycia technicznego budynków i budowli. Katowice. [4] K u c h a r s k a -S t a s i a k E., 1994 – Kategoria zu¿ycia obiektów budowlanych. Przegl¹d Budowlany nr 10. [5] L a s o c k i S., 2007 – Wyznaczanie dynamicznych wp³ywów wstrz¹sów na obiekty budowlane. Praca niepublikowana, Kraków. [6] Scalone normatywy do wyceny budynków i budowli, 2007. Warszawskie Centrum WACETOB. [7] W i n n i c z e k W., 1993 – Wycena budynków i budowli podejœciem odtworzeniowym. Wroc³aw, CUTOB-PZITB. [8] W o d y ñ s k i A., 2002 – Wp³yw wstrz¹sów górniczych na zu¿ycie techniczne budynków. Przegl¹d Górniczy nr 11, pp. 7–11. [9] W o d y ñ s k i A., 2007 – Zu¿ycie techniczne budynków na terenach górniczych. Uczelniane Wydawnictwa Naukowo Dydaktyczne AGH, Kraków. [10] W o d y ñ s k i A., F i r e k K., 2002 – Analiza przebiegu w czasie zu¿ycia technicznego tradycyjnej zabudowy Legnicko-G³ogowskiego Okrêgu Miedziowego. In¿ynieria Œrodowiska (pó³rocznik AGH), t. 7, z. 2. [11] W o d y ñ s k i A., F i r e k K., K o c o t W., 2006 – Ocena wp³ywu remontów oraz zabezpieczeñ profilaktycznych na trwa³oœæ budynków murowanych w LGOM. In¿ynieria Œrodowiska (pó³rocznik AGH), t. 11. [12] W o d y ñ s k i A., K o c o t W., 1996 – Metodyka oceny stanu technicznego budynków o tradycyjnej konstrukcji zlokalizowanych na terenach górniczych. Przegl¹d Górniczy nr 7–8. [13] W o d y ñ s k i A., L a s o c k i S., 2002 – Conception of assessment of mining tremor effects on technical wear of buildings. Acta Montana Serie A, No. 21 (125), Praha. [14] W o d y ñ s k i A., L a s o c k i S., 2004 – Assessment Of Mining Tremor Influence On The Technical Wear Of Building. Acta Geodynamica Et Geomaterialia vol.1 , No 2 (134), Praha. [15] Zu¿ycie nieruchomoœci zabudowanych. Poradnik Doradcy Maj¹tkowego, 2003 – Praca pod red. W. Baranowskiego i M. Cyrana Warszawa, Wyd. Instytut Doradztwa Maj¹tkowego.

OCENA WP£YWU CZASU ORAZ EKSPLOATACJI GÓRNICZEJ NA TECHNICZNE ZU¯YCIE SIÊ BUDYNKÓW Z P£YT PREFABRYKOWANYCH

S³owa kluczowe Zu¿ycie techniczne, budynki z p³yt prefabrykowanych, uszkodzenia budynków, skutki górnictwa, wstrz¹sy podziemne wywo³ane eksploatacj¹ górnicz¹ Streszczenie Niniejszy artyku³ przedstawia analizê przebiegu procesu technicznego zu¿ywania siê w czasie konstrukcji budynków z p³yt prefabrykowanych oraz badañ dotycz¹cych zale¿noœci pomiêdzy tym procesem a wstrz¹sami podziemnymi wywo³anymi górnictwem, na podstawie budynków znajduj¹cych siê w Legnicko-G³ogowskim Okrêgu Miedziowym (LGOM). Podstawê badañ stanowi³a autorska baza danych dotycz¹ca 129 obiektów, zawieraj¹ca informacje o ich stanie technicznym oraz potencjalnych przyczynach ich przyspieszonego zu¿ywania siê. Zbadany zosta³ trend czasowy technicznego zu¿ywania siê budynków oraz wp³yw jaki wywieraj¹ na niego wstrz¹sy podziemne wywo³ane górnictwem.

182 ASSESSMENT OF TIME AND MINING EXPLOITATION EFFECTS ON THE TECHNICAL WEAR OF PREFABRICATED PANEL BUILDINGS

Key words Technical wear, prefabricated panel buildings, building damage, mining effects, mining tremors Abstract The paper presents the results of the analysis of the course of technical wear in time and the studies of the relationships between mining tremors and the technical wear of prefabricated panel buildings localized in the mining area of Legnica-G³ogów Copper District (LGOM). The base for the studies was the authors-made database on the technical state and potential causes of the accelerated wear, containing the data on 129 objects. The temporal trend of technical wear of buildings and the impact of mining tremors on this wear was studied.