Application of generative design for structural optimization at the conceptual design phase

Optimization of structural components leads to higher performing designs, by reducing unnecessary cost and increasing the efficient use of material. The structural optimization process is a rigorous iterative time-consuming process. Developments within algorithmic aided design (AAD) tools have made it easier for structural engineers to achieve automation of optimization routines. Generative design (GD) provides optimization routines which can aid in the pursuit of optimal solutions, given a set of criteria. The use of GD in combination with finite element analysis (FEA), to optimize structural design, has yet to see noticeable adoption within the structural engineering community. This paper discusses two illustrative cases to demonstrate how GD tools have been applied to optimize structures at the conceptual phase. The results have been validated using FEM-design software. A workflow has been proposed, based on the lessons learnt from the cases. This workflow inherits characteristics that, when followed, yielded consistent and reliable results.publishedVersio

Utilization of Industrial By-Products/Waste to Manufacture Geopolymer Cement/Concrete

There has been a significant movement in the past decades to develop alternative sustainable building material such as geopolymer cement/concrete to control CO2 emission. Industrial waste contains pozzolanic minerals that fulfil requirements to develop the sustainable material such as alumino-silicate based geopolymer. For example, industrial waste such as red mud, fly ash, GBFS/GGBS (granulated blast furnace slag/ground granulated blast furnace slag), rice husk ash (RHA), and bagasse ash consist of minerals that contribute to the manufacturing of geopolymer cement/concrete. A literature review was carried out to study the different industrial waste/by-products and their chemical composition, which is vital for producing geopolymer cement, and to discuss the mechanical properties of geopolymer cement/concrete manufactured using different industrial waste/by-products. The durability, financial benefits and sustainability aspects of geopolymer cement/concrete have been highlighted. As per the experimental results from the literature, the cited industrial waste has been successfully utilized for the synthesis of dry or wet geopolymers. The review revealed that that the use of fly ash, GBFS/GGBS and RHA in geopolymer concrete resulted high compressive strength (i.e., 50 MPa–70 MPa). For high strength (>70 MPa) achievement, most of the slag and ash-based geopolymer cement/concrete in synergy with nano processed waste have shown good mechanical properties and environmental resistant. The alkali-activated geopolymer slag, red mud and fly ash based geopolymer binders give a better durability performance compared with other industrial waste. Based on the sustainability indicators, most of the geopolymers developed using the industrial waste have a positive impact on the environment, society and economy.publishedVersio

Effect of Organic Retarders on Fluid-State and Strength Development of Rock-Based Geopolymer

Granite waste is rich in aluminum and silicate has the potential of turning to geopolymer material after mixing with an alkali solution. One of the challenges in developing a geopolymer is to select a suitable retarder to adjust the target pumpability while maintaining workability and followed by a proper strength development rate. In this study, the effect of five selected organic retarders on workability, viscosity, and compressive strength has been examined. Sucrose, a calcium chelator, gluconic acid, sodium lignosulphonate, and ionic liquid were selected as candidate retarders. The experiments were carried out at room temperature according to American Petroleum Institute (API) standards for testing well cement. The tested retarders indicated a secondary effect on fluid-state properties. The reasons for the secondary effect are due to either the change in the pH of slurries or the interaction between ions released from the retarder and the geopolymer precursor. Gluconic acid and sucrose provided a longer setting time, while they significantly lowered the strength development in the short-term. Lignosulfonate had less impact on workability. However, it reduced viscosity and yield stress. All retarders influenced the strength development rate, but the sodium lignosulfonate, chelator, and ionic liquid had a negligible impact on final strength after 14 days of curing.acceptedVersio

Improvements for the workflow interoperability between BIM and FEM tools

Transferring models, developed using Building Information Modelling (BIM), to Finite Element Method (FEM) tools is an important task in the integration of structural engineering into the open BIM workflow. Such integration saves the time spent by a structural engineer modelling a structure from scratch. There are various problems that can arise while transferring from BIM to FEM tools. A common problem in transferring the geometry and data from the BIM model into an FEM tool is the question of where to place nodes. Each column, beam or slab is defined as a volume in the BIM model and must be interpreted as lines and areas in the FEM analysis. This can be problematic, as transfer of forces must happen at a singular point in the FEM analysis, while the BIM model may be ambiguous regarding where these points are to be placed. This paper discusses the problems that occur when transferring a model from BIM to FEM tools and how to reduce some common mistakes by improving the existing workflow. Based on the needs of local Norwegian industries, the study mainly focuses on the transference of analytical models from Revit software to FEM tools such as Focus Konstruksjon, Robot Structural Analysis and SOFiSTiK. Then, improvements for the existing workflow are proposed for the aforementioned interoperability between BIM and FEM tools and verified using a case study.publishedVersio

Corrosion propagation phase and bond strength degradation of reinforced concrete structures: state of the art

Corrosion causes damage to reinforcing steel in concrete structures and governs the service life of the structures. Currently, researchers are paying attention to modelling the behaviour of the bond between the concrete and steel interface of corroded reinforcement. The main objective of this paper is to study the recent research relevant to the bond behaviour at the interface between corroded ribbed bars and concrete and to identify the future research focus. Initially, the paper presents the mechanisms of corrosion damage of reinforced concrete by discussing corrosive agents, causes and effects. Then mechanisms of corrosion prorogation, mechanical properties of corroded reinforcing steel and effects of corrosion on bond degradation of reinforced concrete are discussed in details. Thereafter, recent experimental researches on bond degradation between reinforcement and concrete are reviewed. Previous studies have proposed formulae, which depend on cover, reinforcing bar diameter, concrete strength and corrosion level, to predict the ultimate bond strength. Effect of other parameters (i.e. type of the bars, bar spacing, crack size, aggregate size, type of loading, stress state and etc.) on bond strength have not been properly studied in literature. Bond strength against biaxial bending or combined load action has not been investigated. Finally, the paper concludes with the significance of testing naturally corroded test specimens, compared to the artificially corroded specimens, as well as discussing loading situations.publishedVersio

Risk-Based Approach for Improving Concrete Bridges‘ Inspection Planning

Visual inspection forms the basis of the inspection planning process for concrete bridges. The authority responsible for bridge inspection maintains a database to record past inspection results, in order to plan future inspections. It is a challenge to recognize and classify bridges that it is essential to inspect based on inherent requirements. This is further exacerbated by the limited budget available. This manuscript describes a methodology for classifying bridges based on risk of potential failure and distributing the annual inspection budget for carrying out inspections on bridges accordingly. The absence of such a methodology allocation of resources for bridge inspection without real need. For example, on some occasions it is not necessary to inspect certain bridges on a time basis. Hence, this study focuses on developing an inspection-planning approach based on the actual and predicted condition (i.e. based on the database of past inspection data). It enables the bridges to be classified into different categories, based on the risk of potential failures. This enables the effective distribution of annual budgets among the bridges, avoiding unnecessary inspection that incurs pointless inspection costs

Experimental investigation of crack width variation along the concrete cover depth in reinforced concrete specimens with ribbed bars and smooth bars

Crack width variation along the concrete cover depth has been studied from the past for better understanding of the cracking phenomenon in reinforced concrete (RC) structures. Previous studies have highlighted important cracking behaviors like internal cracks. The behavior of ‘slip’ between the reinforcement and concrete and the formation of a nonuniform crack face along the concrete cover depth are still not very clearly understood. An experimental program has been conducted to study the crack width variation along the cover depth in concrete prisms reinforced with a central ribbed bar and smooth bar, by varying the concrete cover depths. Both in specimens with smooth bars (SS) and specimens with ribbed bars (SR), crack width is larger on the concrete surface than at the steel bar surface. The crack width at the reinforcement is considerably larger in the SS than in the SR. In the SR, the crack width increases from the reinforcement along the cover depth bi-linearly, while, in the SS, it increases linearly. For the SR, the aforementioned behavior is due to the occurrence of internal cracks. In the SS, significant slip has been identified at the reinforcement and concrete interface, whereas negligible slip has been observed in the SR. A surface crack width calculation model has been developed, considering both the strain difference and the effect of the nonuniform crack face along the concrete cover depth. Its predictions showed good agreement with the experimental surface crack widths from the conducted study and with the results from the experiments in literature.publishedVersio

Engineering properties and microstructure of a sustainable roof tile manufactured with waste rice husk ash and ceramic sludge addition

Clay replacement with waste rice husk ash (RHA) and ceramic sludge (CS), helps to reduce the consumption of natural clay and solves the ecological issues created by waste disposal. In this study, properties of waste RHA and CS added fired clay tile were investigated, focusing on structural, durability, thermal performance as well as the water quality of the harvested run-off from fired clay roof tiles manufactured in an industrial scale plant. Tiles were cast by clay replacement with waste RHA and CS in four mixtures: 10 %RHA and 0 % CS, 10 % RHA and 10 % CS, 10 % RHA and 15 % CS, and 10 % RHA and 20 % CS (by weight). For 10 %RHA and 10 %CS tiles, dry mass was reduced by 4.9 %, compared with conventional roof tiles, promising a light weight roof tile. Roof tiles with 10 % RHA and 10 %CS showed a transverse breaking load of 1519 N, whereas that of 20 %CS tiles showed 1427 N, indicating that a further 6.5 % strength improvement can be achieved with clay replacement with a combination of two waste materials. Clay replacement with 10 % RHA and 10 % CS resulted in water absorption of 15.25 %. When increasing the clay replacement with combined waste from 10% (10 %RHA and 0%CS) to 30 % (10%RHA and 20 %CS), weight gain due to acid and alkaline attacks reduced from 3.5% to 3.0%, and from 2.2 % to 1.6 %, respectively, indicating enhanced durability performance by incorporating combined waste. High porosity, also confirmed by SEM, contributed to enhanced thermal performance: tile with 10 % RHA and 10 % CS achieved 4.4 °C temperature reduction, compared to the conventional tile. pH value and total solid concentration of run-off water were in the range of recommended values of water for agricultural purposes, ensuring that the collected run-off can be utilized as an alternative water source for potable activities.publishedVersio

Thin-Walled Cylindrical Shell Storage Tank under Blast Impacts: Finite Element Analysis

Thin-walled cylindrical shell storage tanks are pressure vessels in which the walls of the vessel have a thickness that is much smaller than the overall size of the vessel. These types of structures have global applications in various industries, including oil refineries and petrochemical plants. However, these storage tanks are vulnerable to fire and explosions. Therefore, a parametric study using numerical simulation was carried out, considering the internal liquid level, wall thickness, material yield strength, constraint conditions, and blast intensity, with a diameter of 100 m and height of 22.5 m under different blast loads using the finite element analysis method. The thickness of the tank wall is varied as 10 mm, 20 mm, 30 mm, and 40 mm, while the fill level of internal fluid is varied as 25, 50, 75, and 100%. The blast simulation was conducted using LS-DYNA software. The numerical results are then compared with analytical results. The effects of blast intensity, standoff distance, wall thickness, and fill level of internal fluid on the structural behaviour of the storage tank were investigated and discussed.publishedVersio

Finite Element Analysis of Steel Plates with Rectangular Openings Subjected to Axial Stress

Steel plates with openings are among the important ship structural components used in the ship’s hull to withstand the hydrostatic forces of the ocean, which cause sagging and hogging moments at the ship’s bottom. The existence of openings on plates can cause structural rupture, stress concentration and a decrease in ultimate strength. This research is aimed at investigating the influence of selected parameters on the ultimate capacity of steel plates with rectangular holes subjected to axial stress, using ANSYS finite element analysis (FEA) under its non-linear static structural programme. The main parameters investigated in this paper are the plate thickness, opening aspect ratio, number of openings, position of openings, and the boundary condition of the plate. The influence of these parameters on the stress of plates and their deformation was evaluated. The comparison of the numerical simulation with the well-established analytical method using the Navier solution and Roark’s Formulas showed a good agreement.Finite Element Analysis of Steel Plates with Rectangular Openings Subjected to Axial StresspublishedVersio