Search results

Damage to reinforced concrete (RC) structural elements is inevitable. Such damage can be the result of several factors, including aggressive environmental conditions, overloading, inadequate design, poor work execution, fire, storm, earthquakes etc. Therefore, repairing and strengthening is one way to improve damaged structures, so that they can be reutilized. In this research, the use of an ultra high-performance fibre-reinforced concrete (UHPFRC) layer is proposed as a strengthening material to rehabilitate damaged-RC beams. Different strengthening schemes pertaining to the structural performance of the retrofitted RC beams due to the flexural load were investigated.

A total of 13 normal RC beams were prepared. All the beams were subjected to a four-point flexural test. One beam was selected as the control beam and tested to failure, whereas the remaining beams were tested under a load of up to 50% of the ultimate load capacity of the control beam. The damaged beams were then strengthened using a UHPFRC layer with two different schemes; strip-shape and U-shape schemes, before all the beams were tested to failure.

Based on the test results, the control beam and all strengthened beams failed in the flexural mode. Compared to the control beam, the damaged-RC beams strengthened using the strip-shape scheme provided an increase in the ultimate load capacity ranging from 14.50% to 43.48% (or an increase of 1.1450 to 1.4348 times), whereas for the U-shape scheme beams ranged from 48.70% to 149.37% (or an increase of 1.4870–2.4937 times). The U-shape scheme was more effective in rehabilitating the damaged-RC beams. The UHPFRC mixtures are workable, as well easy to place and cast into the formworks. Furthermore, the damaged-RC beams strengthened using strip-shape scheme and U-shape scheme generated ductility factors of greater than 4 and 3, respectively. According to Eurocode8, these values are suitable for seismically active regions. Therefore, the strengthened damaged-RC beams under this study can quite feasibly be used in such regions.

Observations of crack patterns were not accompanied by measurements of crack widths due to the unavailability of a microcrack meter in the laboratory. The cost of the strengthening system application were not evaluated in this study, so the users should consider wisely related to the application of this method on the constructions.

Rehabilitation of the damaged-RC beams exhibited an adequate structural performance, where all strengthened RC beams fail in the flexural mode, as well as having increment in the failure load capacity and ductility. So, the used strengthening system in this study can be applied for the building construction in the seismic regions.

Aside from equipment, application of this strengthening system need also the labours.

The use of sand blasting on the surfaces of the damaged-RC beams, as well as the application of UHPFRC layers of different thicknesses and shapes to strengthen the damaged-RC beams, provides a novel innovation in the strengthening of damaged-RC beams, which can be applicable to either bridge or building constructions.

Scholars of disaster have discussed how place attachment affects the disaster landscape. The rupture of self from home, of familiar into strange and disconnected is explored through this lens. I propose in this paper that it is possible that what we are seeing is not a sudden disruption of place attachment, but an ongoing process of alienation.

In this paper I discuss the concepts of both place attachment and alienation. In particular I explore Marx’s concept of alienation. I then look at examples from disaster research and identify instances and concepts that can be better interpreted as an ongoing process of alienation.

I find that, when using Marx’s framework of alienation, we can take examples from disaster studies that might appear as a sudden disruption of place attachment and critically examine them as cases of alienation.

This exploration of disaster theory offers a new framework for bringing together urban theory, in particular critical urban theory, with disaster research.

This study aims to facilitate access to vascular disease screening for low-income individuals living in remote and conflict areas based on the results of a pilot trial in Colombia. Also, to increase the amount of diagnosis training of vascular surgery (VS) in civilians.

The operation method includes five stages: strategy development and adjustment; translation of the strategy into a real-world setting; operation logistics planning; strategy analysis and adoption. The operation plan worked efficiently in this study’s sample. It demonstrated high sensibility, efficiency and safety in a real-world setting.

The authors developed and implemented a flow model operating plan for screening vascular pathologies in low-income patients pro bono without proper access to vascular health care. A total of 140 patients from rural areas in Colombia were recruited to a controlled screening session where they underwent serial noninvasive ultrasound assessments conducted by health professionals of different training stages in VS.

The plan was designed to be implemented in remote, conflict areas with limited access to VS care. Vascular injuries are critically important and common among civilians and military forces in regions with active armed conflicts. As this strategy can be modified and adapted to different medical specialties and geographic areas, the authors recommend checking the related legislation and legal aspects of the intended areas where we will implement this tool.

Different sub-specialties can implement the described method to be translated into significant areas of medicine, as the authors can adjust the deployment and execution for the assessment in peripheral areas, conflict zones and other public health crises that require a faster response. This is necessary, as the amount of training to which VS trainees are exposed is low. A simulated exercise offers a novel opportunity to enhance their current diagnostic skills using ultrasound in a controlled environment.

Evaluating and assessing patients with limited access to vascular medicine and other specialties can decrease the burden of vascular disease and related complications and increase the number of treatments available for remote communities.

It is essential to assess the most significant number of patients and treat them according to their triage designation. This management is similar to assessment in remote areas without access to a proper VS consult. The authors were able to determine, classify and redirect to therapeutic interventions the patients with positive findings in remote areas with a fast deployment methodology in VS.

Access to health care is limited due to multiple barriers and the assessment and response, especially in peripheral areas that require a highly skilled team of medical professionals and related equipment. The authors tested a novel mobile assessment tool for remote and conflict areas in a rural zone of Colombia.

Near-fault pulse-like ground motions have distinct and very severe effects on reinforced concrete (RC) structures. However, there is a paucity of recorded data from Near-Fault Ground Motions (NFGMs), and thus forecasting the dynamic seismic response of structures, using conventional techniques, under such intense ground motions has remained a challenge.

The present study utilizes a 2D finite element model of an RC structure subjected to near-fault pulse-like ground motions with a focus on the storey drift ratio (SDR) as the key demand parameter. Five machine learning classifiers (MLCs), namely decision tree, k-nearest neighbor, random forest, support vector machine and Naïve Bayes classifier , were evaluated to classify the damage states of the RC structure.

The results such as confusion matrix, accuracy and mean square error indicate that the Naïve Bayes classifier model outperforms other MLCs with 80.0% accuracy. Furthermore, three MLC models with accuracy greater than 75% were trained using a voting classifier to enhance the performance score of the models. Finally, a sensitivity analysis was performed to evaluate the model's resilience and dependability.

The objective of the current study is to predict the nonlinear storey drift demand for low-rise RC structures using machine learning techniques, instead of labor-intensive nonlinear dynamic analysis.

This study aims to investigate the individual electrochemical transients arising from local anodic events on stainless steel, to uncover the potential mechanisms producing different types of transients and to derive appropriate parameters indicative of the corrosion severity of such transient events.

An equivalent circuit model was used for the transient analysis, which was performed using a local current allocation rule based on the relative instant cathodic resistance of the coupled electrodes, as well as the kinetic parameters derived from the electrochemical polarization measurement.

The shape and size of the electrochemical current transients arising from SS 316 L were influenced by the film stability, local anodic dissolution kinetics and the symmetry of the cathodic kinetics between the coupled electrodes, where the ultralong transient might correspond to the propagation of film damage with a slow anodic dissolution rate. The dynamic cathodic resistance during the final stage of transient current growth can serve as a characteristic parameter that reflects the loss of passive film protection.

Estimation of the local anodic current trace opens a new way for individual electrochemical transient analysis associated with the charges involved, local current densities and changes in film resistance throughout localized corrosion processes.

Existing deterministic models that predict the capacity of corroded reinforced concrete (RC) beams have limited applicability because they were based on accelerated tests that induce general corrosion. This research gap was addressed by performing a combined numerical and statistical analysis on RC beams, subjected to natural corrosion, to achieve a much better forecast.

Data of 42 naturally corroded beams were collected from the literature and analyzed numerically. Four constitutive models and their combinations were considered: the elastic-semi-plastic and elastic-perfectly-plastic models for steel, and two tensile models for concrete with and without the post-cracking stresses. Meanwhile, Popovics’ model was used to describe the behavior of concrete under compression. Corrosion coefficients were developed as functions of corrosion degree and beam parameters through linear regression analysis to fit the theoretical moment capacities with test data. The performance of the coefficients derived from different combinations of constitutive laws was then compared and validated.

The results showed that the highest accuracy (R² = 0.90) was achieved when the tensile response of concrete was modeled without the residual stresses after cracking and the steel was analyzed as an elastic-perfectly-plastic material. The proposed procedure and regression model also showed reasonable agreement with experimental data, even performing better than the current models derived from accelerated tests and traditional procedures.

This study presents a simple but reliable approach for quantifying the capacity of RC beams under more realistic conditions than previously reported. This method is simple and requires only a few variables to be employed. Civil engineers can use it to obtain a quick and rough estimate of the structural condition of corroding RC beams.

The primary objective of this paper is to explore how space organizations can incorporate children and imagination in their accountability-based accounting and decision-making processes.

This study centers on stakeholder engagement with children, specifically examining the drawing competition associated with the CHaracterising ExOPlanet Satellite (CHEOPS) space exploration mission. We employ a multidimensional research design consisting of both an interpretive approach to the 2,748 space-related drawings submitted by children across Europe to the CHEOPS drawing competition in 2015 and a content analysis of 46 media releases published by ESA and the University of Bern, the key partners of the CHEOPS mission.

Our analysis of the children’s drawings and the CHEOPS media releases indicates that the related organizations account for some of the children’s visions and imaginations, but shortcomings exist in addressing the ethical and space environmental concerns related to space exploration. We explore implications for the space accounting agenda by applying the critical dialogic accountability framework proposed by Dillard and Vinnari (2019), which allows for a discussion on an outline for action by incorporating intergenerational equity (Thomson et al., 2018) and moral imagination (Werhane, 1999).

This study offers a novel exploration of a largely overlooked yet crucial stakeholder group: children. By focusing on their unique perspectives and imaginative capabilities, the paper brings forth the voices of those who will inherit the future of space exploration. Employing children’s drawings as a medium of symbolic communication, this research study offers fresh insights into their perceptions, particularly relevant to space accounting. This innovative approach not only enriches the literature on stakeholder engagement and accountability but also provides space organizations with valuable guidance on fostering inclusivity and ensuring that the interests of future generations are considered in decision-making processes.

Durability of concrete can be enhanced by reducing the pore size/volume of pores or by entrapping the pores. This can be achieved by adding concrete admixtures that have particle size finer than cement. In this study, GNP, having particle size much smaller than cement, has been introduced/added to concrete mix to control the pore size in concrete to tape out the contribution of GNP in the durability enhancement of concrete.

Different concrete mixes, at various water–cement ratios and amounts of graphene, have been manufactured to produce concrete containing three different %ages of GNP, i.e. 0%, 0.05% and 0.1%. To demonstrate the effect on durability of the concrete through the addition of GNP, these concrete samples have been subjected to repeated Freeze-Thaw cycles. Followed by testing after 28 days of curing, including weight loss, water absorption and strength, which are directly related to the durability aspect of concrete.

It has been observed that the addition of GNP to concrete mixes reduces the weight loss and pore size distribution and enhances tensile and compressive strength of concrete, thereby increasing the durability of concrete in unfavorable circumstances like freeze-thaw i.e. alternate hot and cold weather conditions.

This investigation presents original piece of experimental work conducted on modified concrete (GNP-based concrete). The aim is to construct the civil infrastructure in deep-cold region with increased life span and better performance.

This paper draws on African anti-colonial thought and Black consciousness to propose critical conscious leadership (CCL) as a decolonising leadership approach appropriate for pursuing emancipation, social justice and innovation in a new African university.

I utilised the method of critical discourse analysis to study Ihron Rensburg’s language as he reflected on his leadership at the University of Johannesburg (UJ). The study engaged with Rensburg’s writings and texts on his account of leading the merger and transformation of UJ. The primary text draws from his book “Serving Higher Purposes” (2020).

Through the construction of CCL, the paper proposes alternative tenets for leading transformation towards a new African university. CCL grounds a decolonised and pluriversal new African university’s character premised on a consciously revitalised alternative thinking that will carry the communitarian spirit of Africa in knowledge production, dissemination and consumption in humanising all and serving the greater good. And it operates within the dialectical tensions of the social and economic purpose of higher education (HE), African and global relevance, African and Western paradigms, excellent performance and attainment of social justice.

The proposed CCL offers an alternative leadership approach that responds to the call to “Dethrone the Empire” by centring Blackness in HE leadership, which is crucial for authentic transformation and decolonisation.

The literature on communication in change processes, although fundamental, appears to still be very fragmented. The purpose of this study is to provide an explanatory and integrated framework for the communication process in organizational change processes.

The authors conducted 22 semi-structured interviews with employees from 21 companies and 13 different sectors in Germany. The four-step Gioia inductive coding approach was adopted as the methodological approach of the current study.

A final research model reveals that the organizational change communication (OCC) process is marked by specific change-restraining forces associated with the fear of the unknown, habits and convenience. Results also suggest the importance of communication timing and factors that help shape the OCC process, namely the scope, contents and channels of the communication process. Finally, the current research highlights contextual variables of the OCC process, such as credibility or the level of honesty.

The importance of OCC, in particular the understanding of the scope, contents of the message and the channels of communication adopted in the change management process, are important variables in the complexity of change. The paper illustrates the intricacy of communication in change and reinforces the internal and external variables that help shape the OCC process, with implications for change agents and scholars.