Department of Construction

This study quantifies how beam-to-column joint damage alters the axial resistance and failure modes of cold-formed steel (CFS) uprights used in industrial storage rack systems. Current design-oriented assessments typically neglect the reduction of joint rotational stiffness and moment resistance caused by prior cyclic joint deterioration, which can compromise subsequent compression performance. To address this gap, six commercial perforated upright sections are tested under axial compression in intact and joint-damaged conditions. A unified framework combines experiments, nonlinear finite element analysis (FEA; ANSYS), and machine learning (ML) prediction using geometric descriptors (thickness, area, second moments of area, and radii of gyration) together with experimentally derived joint properties (rotational stiffness and ultimate joint moment). Among the evaluated regressors, the gradient boosting model provides the best predictive performance (cross-validated R2 and lowest root mean square error [RMSE]/mean absolute error [MAE]), showing close agreement with experimental outcomes and numerical trends. Results indicate axial capacity reductions of up to similar to 30% after joint degradation and a tendency toward coupled distortional and torsional-flexural (TF) instability. The findings highlight the engineering need to account for joint stiffness degradation in residual capacity checks and support rapid, data-informed decisions for inspection and retrofit of rack uprights. The study provides a practical predictive framework for postdamage capacity evaluation in industrial rack systems.

The development of a reliable analytical model for industrial steel pallet rack connections has long been a goal for researchers, as practitioners still rely primarily on costly and time-consuming experimental testing to assess structural behavior. The present study addresses this gap by developing an analytical framework that enables the prediction of moment-rotation behavior without extensive testing. The framework is calibrated for a specific upright profile within defined parameter ranges and is intended as a configuration-specific predictive tool to reduce reliance on testing within the validated geometric space. Eighteen specimens with varying connection configurations commonly used in practice were tested under monotonic loading in accordance with EN 15512. Major failure modes and the influence of configuration on behavior, particularly in terms of strength and stiffness, were identified. A four-parameter Richard Abbott analytical model was successfully calibrated using experimental data, achieving exceptional predictive accuracy, with R-2 > 0.94 across all configurations. Parametric equations expressing model parameters as functions of beam depth and tab count were developed, enabling direct prediction of behavior. A local parametric sensitivity analysis identified initial stiffness and reference moment as the most influential parameters, with average sensitivities of 16.3% and 18.7%. The validated model significantly outperforms previous approaches, offering a reliable design tool that removes the need for configuration-specific testing.

The study examined the impact of incorporating pumice and rubber obtained from waste tires as aggregate in specific ratios on geopolymer concrete (GPC). For this aim, various combinations and replacement percentages of pumice and waste tire rubber (WTR) were tested in GPC. Pumice was replaced with coarse aggregate in varying proportions of 0%, 5%, 10%, and 15% and WTR was added into mixture with same proportions. A total of 144 GPC specimens were cast and tested. Tests were performed to measure the compressive strength (CS), splitting tensile strength (STS), flexural strength (FS) and dynamic drop-weight tests. Evaluations of the setting time and workability were also conducted. When natural coarse aggregate was substituted with pumice in concrete, the strength of the resulting mixtures fell. The second research varied the percentage of WTR in the concrete mixture from 0%, 5%, 10%, and 15% while keeping the pumice percentage stable. The study showed that when the pumice ratio was set as constant, there was a steady loss of strength as the percentage of WTR increased. The experimental results demonstrated that partial replacement of coarse aggregate with pumice (up to 15%) led to a progressive reduction in both CS (up to 18.17%) and STS (up to 37.13%) of GPC. This decline in strength became more pronounced with the concomitant utilization of WTR. The findings demonstrated that as the WTR content elevated from 0 to 15%, there was a consistent decline in FS across all levels of pumice replacement, with reductions ranging approximately between 20 and 26%. Additionally, the study created an empirical formula related to STS and CS and compared with the formulas previously developed by various researchers. Scanning electron microscopy (SEM), Energy dispersive x-ray (EDX), and thermal gravimetric analysis (TGA) are also conducted. According to the data gathered from the impact tests, adding pumice to concrete has a negative impact on its impact behavior; on the other hand, adding 10% WTR has a favorable impact.

As concrete is one of the most commonly used construction materials, there is a massive production of cement, which causes cement manufacturing to be an energy-intensive industry. A significant amount of the cost of cement production, ranging from 20% to 25%, is attributed to thermal energy. In addition, the action of mining and burning fossil fuels results in the unfavorable emission of hazardous compounds into the environment. Therefore, the switch from conventional fossil fuels to alternative fuels (AFs) in the cement manufacturing business has attracted attention due to environmental and financial concerns. In this paper, four commonly used AFs are discussed, which are waste tires, municipal solid waste, meat and bone meal, and sewage sludge. It is found that each AF has a unique calorific value and properties, attributed to its source, treatment, and technology. Furthermore, the availability of AF is important as the amount varies depending on the location. In addition, their effects on gaseous emissions from the cement plant and the quality of clinker are found to be inconsistent. Thus, there will not be a single best type of AF option to be used in the cement industry. A good AF should be able to provide sufficient thermal energy while reducing the environmental impacts and costs. A careful analysis and multicriteria decision-making approach are always vital when employing AFs in order to prevent environmental problems, cost increases, as well as clinker quality degradation.

Conventional concrete significantly affects the environment due to high CO 2 emission into the atmosphere during the production process. In order to improve concrete performance and arrest the incidence of global warming, the use of additive materials for cement replacement has been promoted worldwide. This study was designed to investigate the mechanical properties of high-performance fiber-reinforced concrete (HFRC) produced using rice husk ash (RHA) and hybrid fiber (HF) in accordance with the densified mixture design algorithm (DMDA) mix design method. Samples were produced using RHA as a direct replacement for cement at 10%, 20%, and 30%. HF, comprising steel and polypropylene fibers, was added (by volume) to the 20% RHA group mixture to improve the HFRC sample properties. Based on the experimental results, higher RHA contents had a generally negative effect on the fresh properties of the HFRC mixtures. Compressive strength values ranged from 53 to 72 MPa with various RHA and HF content. RHA replacement levels up to 20% had an insignificant effect on the strength development and dynamic modulus of the HFRC samples. However, the addition of HF improved splitting tensile strength, flexural strength, and dynamic modulus remarkably at all curing ages. Furthermore, the 91-day drying shrinkage was in the ranges of 0.032%–0.039% and 0.023%–0.034% using different RHA and HF levels, respectively. Increasing both RHA and HF contents significantly reduced drying shrinkage in the samples. Multivariable regression was also performed, clarifying that all tested results were consistent and had good correlations. The results of this study also provide a potentially effective use for abundantly available industrial waste products such as fly ash (FA) and RHA to promote the production of greener and more sustainable concrete.