Behaviour of lightweight concrete wall panel under axial loading: Experimental and numerical investigation toward sustainability in construction industry

Awareness of sustainability in construction has led to the utilization of waste material such as oil palm shell (OPS) in concrete production. The feasibility of OPS as alternative aggregates in concrete has been widely studied at the material level. Meanwhile, nonlinear concrete material properties are not taken into account in the conventional concrete wall design equations, resulting in underestimation of lightweight concrete’s wall axial capacity. Against these sustainability and technical contexts, this research investigated the buckling behavior of OPS-based lightweight self-compacting concrete (LWSCC) wall. Failure mode, load-deflection responses, and ultimate strength were assessed experimentally. Numerical models have been developed and validated against experimental results. Parametric studies were conducted to study the influence of parameters like slenderness ratio, eccentricity, compressive strength, and elastic modulus. The results showed that the axial strength of concrete wall was very much dependent on these parameters. A generalized semi-empirical design equation, based on equivalent concrete stress block and modified by mathe-matical regression, has been proposed. The ratio of average calculated results to test results of the proposed equation, when compared to ACI 318, AS 3600, and Eurocode 2 equations, are respectively improved from 0.36, 0.31, and 0.42 to 0.97. This research demonstrates that OPS-based LWSCC concrete can be used for structural axial components and that the equation developed can serve a good guideline for its design, which could encourage automation and promote sustainability in the construction industry

Experimental Investigation into the Behavior of Back-to-Back Gapped Built-up Cold-Formed Steel Channel Sections under Compression

Back-to-back gapped built-up cold-formed steel channel-sections are used as compression members in cold-formed steel structures, such as trusses, space frames and portal frames etc. Because of the complex and non-uniform cross section of the back-to-back gapped built- up cold-formed steel channel columns, it is difficult to calculate the strength of these sections accurately. Current guidance by the direct strength method in the AISI Specification and the Australian/New Zealand Standard doesn’t include the gap between the back-to-back channels, thus not being able to predict the axial capacities of these sections accurately. In the literature, very few results have been reported for such columns and specially investigated the effect of link-channel’s spacing on axial strength of such columns. This issue is addressed herein. Forty new experimental results are reported, conducted on back-to-back gapped built-up cold-formed steel channel-sections, covering stub to slender columns. Axial capacity of the columns, load-axial shortening, load-axial strain, failure modes and deformed shapes were observed and reported in this paper. Also, the effect of link-channel’s spacing on axial strength, is investigated. Test strengths are compared against the design strengths calculated in accordance with AISI and Australian/New Zealand standard for cold-formed steel structures. It is shown that the design standards can be conservative by as much as 53%, while predicting axial strength of such columns. Therefore, a modification to the non-dimensional slenderness, that considers the gap, is proposed which leads the design standards being within 5% conservative to the test results

Design Optimization of Long-Span Cold-Formed Steel Portal Frames Accounting for Effect of Knee Brace Joint Configuration

The application of cold-formed steel channel sections for portal frames becomes more popular for industrial and residential purposes. Experimental tests showed that such structures with long-span up to 20 m can be achieved when knee brace joints are included. In this paper, the influence of knee brace configuration on the optimum design of long-span cold-formed steel portal frames is investigated. The cold-formed steel portal frames are designed using Eurocode 3 under ultimate limit states. A novel method in handling design constraints integrated with genetic algorithm is proposed for searching the optimum design of cold-formed steel portal frames. The result showed that the proposed routine for design optimization effectively searched the near global optimum solution with the computational time is approximate 50% faster than methods being popularly used in literature. The optimum configuration for knee brace joint can reduce the section size of rafter and so the lighter frame could be obtained especially for long-span portal frame. The minimum weight of main frame obtained from optimization process is approximate 19.72% lighter than a Benchmark Frame used in the full-scale experimental test

<p>Evaluation of patients’ needs to design and assess a patient education program in cancer pain</p>

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