How to Cite
Abstract
Economic and constructional considerations favour diversification of the strength of the concrete of columns and slabs of multi-storey structures. However, this raises a question to what extent large intersection of the slab with concrete can influence the decrease in load carrying capacity of the column. The aim of the research was to analyze the factors so far unconsidered in literature, the factors which could determine the load carrying capacity of columns made from highstrength concrete, intersected with weaker concrete of a slab.
Within the research project considered 10 elements made in half scale and divided into four test groups, were tested. The basic tested models were the columns with the cross section of 200 by 200 mm and the total height of 1320 mm, made from high-strength concrete. They were intersected with a 120 mm thick slab made from normal concrete or lightweight aggregate concrete. The basic elements were accompanied by benchmarking models, i.e. columns with the cross section of 200 by 200 mm and the height of 600 mm, made completely from high-strength concrete and reinforced like the columns of basic models. Their load carrying capacities was a benchmark for estimating the influence of intersection with weaker concrete of a slab on the load carrying capacity of the columns of basic models.
The first and the second series of the tests concerned the models of inner columns. The variable parameters were: the type of the concrete of a slab – normal ( the M series) or light aggregate (the ML series), as well as the value of the load on the slab: 50, 100 or 150 kN. The results of the tests showed that the load carrying capacity of the columns of the models with slabs made from light aggregate concrete was about 20% lower than the load carrying capacity of the benchmark models, independently of the value of the load on slabs, and, consequently, exhaustion of their punching shear capacity. At the same time, clear differences in the performance and load carrying capacity of the model with a slab made from lightweight aggregate concrete and the element with a slab made from normal concrete, despite the same load on both slabs, was observed.
The tests of the third series concerned three models of edge columns. The only variable parameter was the position of a column in relation to the edge of a slab. The distance was equal to the thickness of the slab or to half of it, and the column of one of the models was surfaced with the slab’s edge. The load carrying capacity of the model with the slab surfaced with the edge of the column was about 20 % lower than the load carrying capacity of the reference column. At the same time it was observed that slight overhanging of a slab beyond the edge of a column may result in significant increase of the load carrying capacity of the element, so, consequently, the factor deciding on the failure will be reaching the limit of the load carrying capacity of a column made from high-strength concrete, and not shredding of concrete in the joint zone.
The fourth series of the tests concerned three models of corner columns. The only variable parameter was the location of a column in relation to the edge of a slab. The observations were similar to the ones made in case of the tests of the third series. The load carrying capacity of the model with a column surfaced with both edges of a slab was about 25 % lower than the load carrying capacity of the reference column. What decided on the failure of the models with overhang slabs was running out of the load carrying capacity of the columns outside the joint zone.
Cracking of the lower surfaces of the slabs in the models with overhang slabs corresponded with the cracking of the slabs in the models of the internal column – slab connections.
The results of the tests showed significant influence of deformability of concrete of a slab on the load carrying capacity of the intersected columns made from high-strength concrete. What was observed at the same time was very beneficial influence of overhanging a slab beyond the edges of a column. In the tests described below it made it possible to increase the load carrying capacity by about 20 to 25% in comparison with the models of slabs surfaced with the edges of columns.
References
ACI 318-14 Building Code Requirements for Structural Concrete (ACI 318-14) Commentary on Building Code Requirements. American Concrete Institute, Farmington Hills (2015), 203-204;
AS 3600-2001 Australian Standard. Concrete Structures. Council of Standards Australia, Sydney (2001), 119;
Bianchini A., Woods, R., and Kesler, C. Effect of Floor Concrete Strength on Column Strength. ACI Journal Proceedings, 56, 5 (May 1960), 1149-1170;
CSA A23.3-04 Canadian Standard. Design of conrete structures. Canadian Standards Association, Mississauga (2004), 46;
Cyllok, M. Bemessung der Lastdurchleitung hochfester Stahlbetonstützen durch normalfeste Flachdecken nach EN 1992-1-1. Beton- und Stahlbetonbau, 106, 10 (Oktober 2011), 672–684;
DIN 1045-2:2014 Tragwerke aus Beton, Stahlbeton und Spannbeton - Teil 2: Beton - Festlegung, Eigenschaften, Herstellung und Konformität - Anwendungsregeln zu DIN EN 206. Deutsches Institut für Normung, Berlin (2014);
EN 1992-1-1:2004 Eurocode 2: Design of concrete structures - Part 1-1: General rules and rules for buildings. European Committee for Standarization, Brussels (2004);
Freire, L. Resistência De Pilares De Concreto De Alta Resistência Interceptados Por Elementos De Concreto De Menor Resistência. Universidade Federal de Rio de Janeiro, Rio de Janeiro (2003), Praca magisterska;
Gamble, W. and Klinar, J. Tests of High – Strength Concrete Columns with Intervening Floor Slabs. Journal of Structural Engineering, 117, 5 (Maj 1991), 1462–1476;
Gołdyn, M. Wpływ różnych betonów płyty stropowej i słupa na nośność monolitycznych połączeń płytowo–słupowych, Politechnika Łódzka, Łódź (Kwiecień 2016), Rozprawa doktorska;
Gołdyn, M., Krawczyk, Ł., and Urban, T. Carrying Capacity of Axially Loaded HSC Concrete Columns Intersected by NSC Slab. ACEE Journal, 8, 3 (September 2015), 51-60;
Gołdyn, M. and Urban, T. Behaviour of Eccentrically Loaded High Strngth Concrete Columns Intersected by Lower Strength Concrete Slabs. Structural Concrete, 16, 4 (December 2015), 480-495;
Guidotti, R., Fernández Ruiz, M., and Muttoni, A. Crushing and flexural strength of slab–column joints. Engineering Structures, 33, 3 (March 2011), 855–867;
Helene, P., Tula, L., and Diaz, N. Resistência à Compressão do Concreto Confinado. In IBRACON 42º Congresso Brasileiro do Concreto (Fortaleza 2000);
Hobbs, D. W. Strength and Deformation Properties of Plain Concrete Subject to Combined Stress. Part 3: Strength results obtained on one concrete. Cement Concrete Association, London, 1974;
Kayani, M. Load transfer from high-strength concrete columns through lower strength concrete slabs. University of Illinois, Urbana-Champaign, 1992, Rozprawa doktorska;
Lee, S. and Mendis, P. Behavior of High-Strength Concrete Corner Columns Intersected by Weaker Slabs with Different Thicknesses. ACI Structural Journal, 101, 1 (January 2004), 11-18;
Lee, J. and Yoon, Y. Prediction of strength of interior HSC column- NSC slab joints. Magazine of Concrete Research, 62, 7 (July 2010), 507-518;
Lee, J., Yoon, Y., Cook, W., and Mitchell, D. Benefits of Using Puddled HSC with Fibers in Slabs to Transmit HSC Column Loads. Journal of Structural Engineering, 133, 12 (December 2007), 1843-1847;
Lee, J. and Yoon, Y. Prediction of effective compressive strength of corner columns comprising weaker slab–column joint. Magazine of Concrete Research, 64, 12 (December 2012), 1113-1121;
McHarg, P., William, D., Mitchell, D., and Young-Soo, Y. Improved Transmission of High-Strength Concrete Column Loads through Normal Strength Concrete Slabs. ACI Structural Journal, 97, 1 (January 2000), 157-165;
Neville, A. Właściwości Betonu. Stowarzyszenie Producentów Cementu, Kraków, 2012;
NZS 3101-1 Concrete structures standard - Part 1: The design of concrete structures. Standards Council, Wellington (2006), 10-5;
Ospina C. and Alexander, S. Transmission of Interior Concrete Column Loads through Floors. Journal of Structural Engineering, 124, 6 (June 1998), 602–610;
Ospina, C. and Alexander, S. Transmission of high strength concrete column loads through concrete slabs.
Department of Civil and Environmental Engineering, University of Alberta, Edmonton, 1997;
Shah, A., Dietz, J., Tue, N., and König, G. Experimental Investigation of Column-Slab Joints. ACI Structural Journal, 102, 1 (January 2005), 103-113;
Shu, C. and Hawkins, N. Behavior of columns continuous through concrete floors. ACI Structural Journal, 89, 4 (April 1992), 405-414;
Siao, W. Reinforced Concrete Column Strength at Beam/Slab and Column Intersection. ACI Structural Journal, 91, 1 (January 1994), 3-9;
Tue, N., Dietz, J., and Shah, A. Vorschlag für die Bemessung der Deckenknoten mit Stützen aus hochfestem Beton. Beton- und Stahlbetonbau, 100, 2 (Februar 2005), 132-138;
Yoon, Y., Lee, J., and Yang, J. Strategic slab–column joint details for improved transmission of HSC column loads. Magazine of Concrete Research, 60, 2 (March 2008), 85-91;