Jeung-Hwan Doh

Ultimate Load Formula for Reinforced Concrete Wall Panels with Openings

Reinforced concrete walls with openings are tested in both one-way and two-way action. The test panels, with a slenderness ratio of 30 or 40, were subjected to a uniformly distributed axial load with an eccentricity of tw/6. Apart from highlighting the experimental set-up; typical crack patterns, failure modes, and load-deflection behaviour are also reported. Utilising these and other published test results, a formula predicting the ultimate load of walls with openings was derived. A comparative study of predicted to test results indicates that the new formula is accurate and reliable.

Evaluation of experimental work on concrete walls in one and two-way action

Abstract Currently, the design of reinforced concrete wall panels under eccentric axial loading only is carried out using empirical or semi-empirical methods. These methods involve approximations, which are not always reliable and being empirical, their scope of application is limited. In particular walls supported on all sides (i.e. two-way action behaviour), made of high strength concrete strength or high slenderness ratios have been given little treatment in research. In view of this, the authors have undertaken an extensive investigation on the development of a more reliable and accurate wall design equation. This paper initially presents a brief overview of an experimental program undertaken. The experimental results are compared to the proposed design equation. Also the proposed design equation is compared to results from previous studies on this topic, confirming that the new equation is accurate and reliable.

Development of Strut-and-Tie Models in Deep Beams with Web Openings

The strut-and-tie models of a total of fourteen (14) concrete deep beams with varying size and location of web openings are developed herein using a topology optimisation approach. By systematically eliminating inefficient materials from an over-designed discretized domain, the load transfer mechanism in deep beams is progressively characterised by the residual part of the structure. Both von Mises stress and displacement sensitivity number are used as deletion criteria with the aim of maximising the material efficiency and overall stiffness of the structural beam. The performance indices in terms of von Mises stress and nodal displacement are evaluated to monitor the optimisation process and to determine the optimal topology which is transformed to the strut-and-tie model. The relationship between the strut-and-tie models and the ultimate load-carrying capacity of the beams are discussed in some detail. A series of comparisons offer insight into the varying characteristics of the strut-and-tie models influenced by the size and location of web openings. To demonstrate the effectiveness of the resulting strut-and-tie model in aiding the design of deep beams, a worked design example of a representative beam is also presented where the practical layout of main steel reinforcement is determined.

Behavior of Axially Loaded Concrete Wall Panels with Openings: An Experimental Study:

Forty seven reinforced concrete walls with various opening configurations are tested in both one-way and two-way action. The test panels, with a slenderness ratio of 30, 35 or 40, were subjected to a uniformly distributed axial load at an eccentricity of one sixth of the wall thickness (tw/6). Apart from highlighting the experimental set-up; typical crack patterns, failure modes, and load-deflection behaviour of test panels are also reported. Actual test failure loads are compared to ultimate load predictions using the Australian standard wall design equation and also a recently derived formula specifically for walls with openings. The code equation is found to be inadequate for the many cases investigated whereas the derived formula was verified as being adequate in predicting failure load of walls with openings.

Incorporating Sustainable Development Principles into Building Design

The main aim of this research is to utilise the focus of sustainable design to compare the material and subsequent environmental impacts of multi‐storey structures situated in Australia. The structure types under investigation were characterised by post‐tensioned and conventionally reinforced floor and roof flat plate slab systems. The foundation designs are undertaken for isolated spread footings on 32 structural model types with constant external dimensions which were composed of floor and roof slabs of varying concrete strength, span length and construction method, with all footing designs providing equivalent structural performance. The results from this study have reinforced the evidence that post‐tensioned construction can have significant effects in reducing material requirements and provide increased structural and environmental efficiency. Through reducing the frame mass, the footing systems were able to be designed using significantly less embodied energy when compared to the reinforced concrete structures. It is also noted that further investigation in the foundational requirements of these models is warranted, with the need to investigate the use of mat foundations for cases where isolated spread footings have required more than 50% of the structural plan area and for the footings that have required excessively thick sections to resist large shearing actions for larger spanned cases at 10 and 13.33 m.

Steel Bracket Connection on Modular Buildings

Modular construction methods have been adapted globally for the past few decades and are becoming more common due to their ease of use and flexibility. Structural connections between modules are required for integrity and robustness but details vary depending on the form of the module and the particular application. The behaviour of connections in analysis and design of modular buildings should particularly be taken into account in detail because of their effects on the distribution of internal forces and on structural deformations. The purpose of this paper is to present and analyse the behaviours of an innovative steel bracket connection. Experiments, including shear loading and simply supported tests, were carried out to establish directly the ultimate resistance as well as failure modes of the connections. The finite element software, Strand7, was subsequently utilised to produce models for comparison with test results. A parametric study has been carried out to investigate the effects of varying bolthole dimension and bolthole spacing on the structural behaviours of the steel bracket connection using linear analysis. The model presented in this paper was formed as a baseline for future in-depth investigations to ensure design optimisation of the steel bracket connection.

Evaluation of the Simplified Concrete Wall Design Equation in AS3600-2009

Summary The recently-released Australian Concrete Standard, AS3600–2009, has been extensively revised with particular emphasis on the inclusion of design rules for high-strength concrete. For the simplified design of axially-loaded concrete walls, the guidelines have been changed to include new effective height factors for different support conditions and to allow for higher concrete strengths. Initially the updated guidelines and scope of the simplified equation are provided. Load capacity predictions using the simplified method are then evaluated against a number of test results obtained from recent research. Finally, a typical case study is presented to illustrate the extended scope of the new rules.

PRELIMINARY ANALYSIS OF NORMAL STRENGTH CONCRETE WALLS WITH OPENINGS USING LAYERED FINITE ELEMENT METHOD

A nonlinear Layered Finite Element Method (LFEM) is applied to investigate the structural behaviour of reinforced concrete walls with openings. Four half-scale concrete walls with openings, tested recently in the laboratory, are analysed. The test variables are the wall slenderness ratio and the size and location of openings. The walls are axially loaded at an eccentricity of one-sixth of the wall thickness. The ultimate loads, the load–deflection responses and the crack patterns predicted by the LFEM are compared with the experimental results. The comparison shows that the LFEM is effective and accurate.

Variability in Embodied Energy and Carbon Intensities of Building Materials Using Hybrid LCA: Malaysian Experience

This paper empirically investigates the variations of embodied energy (EE) and carbon (EC) intensities of materials and identifies their parameter variations in hybrid life cycle assessment (LCA). These parameters include energy tariff, primary energy factor, disaggregation constant, emission factor, and price fluctuation. Hybrid LCA has been conducted to expand the system boundary by filling the gaps in traditional LCA data inventories. The Malaysian Input-Output (I-O) tables are used to derive indirect energy and carbon intensities which are then combined to take advantages of detailed process LCA. The results revealed that maximum increase in energy tariffs and material price fluctuations were the key parameters and issues leading to higher variations in EE and EC intensity values. Other parameters – such as maximum increase in primary energy factor, emission factor and excluding disaggregation constant – have a slight impact upon EE and EC intensity variations. Building materials with high indirect energy in the upstream boundary of materials production have high influence on hybrid LCA variation. Therefore, any decision relating to these materials should be considered carefully.

Experimental and numerical study for the shaping formation of SCST structures by cable-tensioning

This paper discusses the behaviour characteristics of the shaping formation of Single-Chorded Space Truss (SCST) structures by means of cable-tensioning of bottom chords. The innovative technique is fast and economical and issued in many types of space structures. The small-scale test models presented herein consist of uniform pyramids with multi-directional ball type joints which are erected into their final shape by cable-tensioning. Since the joint behaviour is very significant in studying the shaping of SCST structures, basic tests for beam and pyramidal units were performed. The feasibility of the proposed cable-tensioning technique and the reliability of the established geometric model were con- firmed by finite element analysis. The proposed cable-tensioning technique indicates that the behaviour characteristic of joints is very important in the shaping formation of SCST structures. More specifically in situations where heavy cranes are inaccessible, the cable-tensioning construction technique has proven to be an easy and reasonable method compared to conventional construction methods that typically include heavy cranes and scaffolding.