Keywords: finite element analysis, concrete walls, openings, restraint conditions, slenderness ratio, eccentric load, code methods.

Available studies have illustrated the conservative nature of empirical wall design equations provided in major codes of practice such as AS3600 [1] and ACI-318 [2]. Furthermore these equations fail to recognise walls that are supported on all four sides, walls with slenderness ratios greater than 30 and walls that require openings for doors, windows or services. The recognition of such factors in design codes would result in improved designs through more efficient material use and subsequent savings in construction costs.

The objective of this study is to investigate the effect of side restraints and the presence of openings for reinforced concrete wall panels loaded axially where an eccentricity indices secondary bending. A numerical analysis of such walls is undertaken using the non-linear Layered Finite Element Method (LFEM) [3,4]. The LFEM takes into account all bending, membrane and shear deformations of structures and is capable of modelling vertically oriented structural elements such as walls.

Eight half scale wall panels tested previously at Griffith University [5,6] form the basis of a comparative study. These walls have one or two openings, are supported either at the top and bottom or on all four sides, and have slenderness ratios of 30 and 40. Minimum reinforcement is placed centrally and panels are loaded axially with an eccentricity of tw/6. The accuracy of the LFEM in predicting the failure loads, the load-deflection responses, the deformed shapes and the crack patterns of the tested wall panels is demonstrated. The establishment of a benchmark model enabled parametric studies on a total of 24 new wall panels investigating the effects of eccentricity on the ultimate load capacity of one-way and two-way reinforced concrete walls with openings. Relationships of failure load with eccentricity are subsequently established.

Numerical analysis of reinforced concrete walls has been successfully carried out and findings from this preliminary study offer an insight into the complex behaviour of one and two-way slender wall panels with openings. The study has illustrated the effect of openings, side restraints and eccentricity on the performance of concrete wall panels. Further work in this area will lead to improved design methods being eventually accepted by major codes of practice leading to significant cost savings for the building industry.

1

Standards Association of Australia, "AS3600-2001: Concrete Structures", Sydney, Australia, 2001.

2

American Concrete Institute (ACI), "Building Code Requirements for Reinforced Concrete (ACI 318-89) and Commentary - ACI318R-92", Detroit, Michigan, 1992.

3

H. Guan, "Comparative and Parametric Studies of Slab-Edge Column Connections with Varying Locations of Opening", Proceedings of the 6th World Congress on Computational Mechanics (WCCM VI) in conjunction with Asia-Pacific Congress on Computational Mechanics (APCOM'04), Beijing, China, RS03-137, 2004.

4

D.J. Lee, H. Guan, S. Fragomeni, J.H. Doh, "Preliminary Analysis of Normal Strength Concrete Walls with Openings using Layered Finite Element Method", Proceedings of the International Conference on Computational Methods (ICCM 2004), Singapore, 2004.

5

J.H. Doh, S. Fragomeni, "Evaluation of Experimental Work on Concrete Walls in One and Two-way Action", Australian Journal of Structural Engineering, 2004. (Accepted for publication.)

6

J.H. Doh, S. Fragomeni, Y.C. Loo, "Evaluation of Experimental Analysis on Reinforced Concrete Walls with Openings", Proceedings of the 4th International Conference on Concrete under Severe Conditions of Environment and Loading (4th CONSEC), Seoul, Korea, 1216-1223, 2004.

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