Shear capacity prediction of slender reinforced concrete structures with steel fibers using machine learning

Shear failure in reinforced concrete beams poses a critical safety issue since it may occur without any prior signs of damage in some cases. Many of the existing shear design equations for steel fiber reinforced concrete (SFRC) beams include significant uncertainty due to failure in reflecting the phenomenology of shear resistance accurately. Given these, adequate reliability evaluation of shear design provisions for SFRC beam is of high significance, and increased accuracy and minimisation of variability in the predictive model is essential. This contribution proposes machine learning (ML) based methods - Gaussian Process regression (GPR) and the Random Forest (RF) techniques - to predict the ultimate shear resistance of SFRC slender beams without stirrups. The models were developed using a database of 326 experimental SFRC slender beams obtained from previous studies, utilising 75% for model training and the remainder for testing. The performance of the proposed models was assessed by statistical comparison to experimental results and to that of the state-of-practice existing shear design models (fib Model Code 2010, German guideline, Bernat et al. model). The proposed ML-based models are in close alignment with the experimentally observed shear strength and the existing predictive models, but provide more accurate and unbiased predictions. Furthermore, the model uncertainty of the various resistance models was characterised and investigated. The ML-based models displayed the lowest bias and variability, with no significant trend with input parameters. The inconsistencies observed in the predictions by the existing shear design formulations at the variation of shear span to effective depth ratio is a major cause for concern; reliability analysis is required. Finally, partial resistance safety factors were proposed for the model uncertainty associated with the existing shear design equations

Reinforced concrete deterioration caused by contaminated construction water: an overview

Over the years, there were cases of building failures in most developing countries of the world that have led to the loss of lives and property. Yet, most investigations conducted on the causes of building failures have suggested poor design, inadequate supervision, and the use of inferior materials as the factors responsible for the failures. However, not so much emphasis has been placed on concrete mixing water as a contributing factor to the failures. Therefore, this review summarizes the effect of the type and composition of mixing water on the properties of concrete. Different sources of water that can be used to mix concrete were explored, alongside with the effect on fresh and hardened properties of concrete. The fresh properties of concrete, such as setting time and slump, were examined, while the hardened properties focused on the strength and durability of the concrete. A brief statement on the available regulation and standards for mixing water was also reported. This review shows the viability of using water from different sources, such as wastewater, to mix concrete successfully. However, the treatment of some types of water might be required to ensure that excellent strength and durability properties are achieved while preventing any threat to human life and the environment. Area for future research was also suggested, which, among other procedures, could help proffer solutions to the challenge of building failures in developing countries

DEVELOPMENT OF A COMPUTER PROGRAM FOR THE DESIGN OF LATERALLY UNRESTRAINED STEEL BEAMS

This study presents the design results of a C-sharp based computer program developed for the design of laterally unrestrained I-section steel beams. The program was developed based on the stipulations of BS 5950 and Eurocode 3 (EC3) design standards. Several sets of steel beam models having the same cross-sectional dimensions but different laterally unrestrained span lengths were designed using the developed program, and the results were validated using an established software, Staad Pro. The design results obtained were found similar to the results obtained using Staad Pro. For a specific beam section with constant loadings, as the span length of the laterally unrestrained compression flange increases the buckling capacity reduces, thus the longer the beam, the more it is susceptible to lateral torsional buckling. Comparison of the results obtained using BS 5950 to those of EC 3 at different laterally unrestrained span lengths revealed that the areas of design sections obtained for BS 5950 are 21.5%, on the average, higher than those of EC3. Thus, beams with laterally unrestrained compression flange designed according to the requirements of EC 3 are more economical. The difference in results is because of the differences in the principles of design and measures used between the two standards

Reinforced concrete deterioration caused by contaminated construction water: An overview

Over the years, there were cases of building failures in most developing countries of the world that have led to the loss of lives and property. Yet, most investigations conducted on the causes of building failures have suggested poor design, inadequate supervision, and the use of inferior materials as the factors responsible for the failures. However, not so much emphasis has been placed on concrete mixing water as a contributing factor to the failures. Therefore, this review summarizes the effect of the type and composition of mixing water on the properties of concrete. Different sources of water that can be used to mix concrete were explored, alongside with the effect on fresh and hardened properties of concrete. The fresh properties of concrete, such as setting time and slump, were examined, while the hardened properties focused on the strength and durability of the concrete. A brief statement on the available regulation and standards for mixing water was also reported. This review shows the viability of using water from different sources, such as wastewater, to mix concrete successfully. However, the treatment of some types of water might be required to ensure that excellent strength and durability properties are achieved while preventing any threat to human life and the environment. Area for future research was also suggested, which, among other procedures, could help proffer solutions to the challenge of building failures in developing countries

Alkali-activated materials: advances on accelerated and long-term durability assessment and methodologies—a short review

Developments in material testing have brought about the invention of some durability assessment methodologies for alkali-activated materials. This study reported advances in accelerated and long-term durability assessment and methodologies for alkali-activated composites (AAC). For both alkali-activated materials (AAM) and ordinary Portland cement (OPC)-based composites, the common methods such as increased acid concentration, standard non-accelerated test, wetting and drying cycling, brushing were assessed. The study assessed common methods: increased acid concentration, standard non-accelerated test, wetting and drying cycling, and brushing. The discussion also identified the limitations associated with the accelerated and long-term durability assessment in AAM composite. Some limitations include concrete pore solution concentration, precursor type, and admixture. In AAMs, pore size is within ranges > 1 μm and < 20 nm, which is an indication of insignificant porosity. Also, the compressive strength coefficient of AAM mortars was better than the cement mortar after 75 cycles. Finally, the study revealed the most appropriate mechanism for measuring the durability of AAM composite, which could be well utilized in the construction field

Modelling the edge breakout shear capacity of single anchors using gene expression programming

The use of soft computing techniques is becoming more common in providing solutions to complex engineering problems such as the concrete breakout strength of anchor. Available techniques include semi-empirical equations that are known to over or underpredict and some soft computing techniques that is incapable of generating predictive equations. This study proposes a gene expression programming (GEP)-based mathematical model to predict the concrete edge breakout capacity of single anchors loaded in shear. In doing so, an experimental database compiled by the American Concrete Institute (ACI) Committee 355, containing 366 samples, was used for the model training and testing. The independent variables considered in the model development are the edge distance, anchor diameter, embedment depth and concrete strength. Moreover, the predictive performance of the developed model was compared to that of the existing models proposed in ACI 318 and the Eurocode 2 (EC2) design standards. The assessment showed that the proposed GEP-based model provided a much more uniform and accurate prediction of the actual strength than the models in the existing design standards. The proposed mathematical model is simple and robust and is expected to be very useful for evaluating the concrete breakout shear capacity of single anchors in pre-planning and pre-design phases; that is, towards inclusions in design standards

Fresh and hardened properties of concrete incorporating binary blend of metakaolin and ground granulated blast furnace slag as supplementary cementitious material

The growing demand for cement has created a significant impact on the environment. Cement production requires huge energy consumptions; however, Pakistan is currently facing a severe energy crisis. Researchers are therefore engaged with the introduction of agricultural/industrial waste materials with cementitious properties to reduce not only cement production but also energy consumption, as well as helping protect the environment. +is research aims to investigate the influence of binary cementitious material (BCM) on fresh and hardened concrete mixes prepared with metakaolin (MK) and ground granulated blast furnace slag (GGBFS) as a partial replacement of cement. +e replacement proportions of BCM used were 0%, 5%, 10%, 15%, and 20% by weight of cement. A total of five mixes were prepared with 1 :1.5 : 3 mix proportion at 0.54 water-cement ratios. A total of 255 concrete specimens were prepared to investigate the compressive, tensile, and flexural strength of concrete after 7, 28, and 56 days, respectively. It was perceived that the workability of concrete mixes decreased with an increasing percentage of MK and GGBFS. Also, the density and permeability of concrete decreased with an increasing quantity of BCM after 28 days. Conversely, the compressive, tensile, and flexural strength of concrete were enhanced by 12.28%, 9.33%, and 9.93%, respectively, at 10% of BCM after 28 days. +e carbonation depth reduced with a rise in content of BCM (up to 10%) and then later improved after 28, 90, and 180 days. Moreover, the effect of chloride attack in concrete is reduced with the inclusion of BCM after 28 and 90 days. Similarly, the drying shrinkage of concrete decreased with an increase in the content of BCM after 40 days

A review of the engineering properties of metakaolin based concrete: towards combatting chloride attack in coastal/ marine structures

Changing human lifestyle and increasing urbanisation are contributory factors to the high demand for concrete construction materials across the globe. With the imminent developments in the unpopulated marine/coastal zones, higher installation of concrete facilities is still expected. However, poor design and construction procedures coupled with inadequate materials selection and exposure to aggressive environmental conditions, such as chloride laden environments, often result in the reduced aesthetic and structural performance of concrete. Deterioration of reinforced concrete structures located in a coastal/marine setting can influence the safety, economic, and sustainability aspects of society. Hence, there is an increased need for alternate binder systems with the ability to reduce the effects of chloride attack in concrete. 1is paper presents a critical review of the engineering properties of metakaolin (MK) based concrete exposed to chloride attack. 1e key advantages and limitations of using MK for concrete production purposes were outlined and evaluated. Areas for future research were also highlighted in this paper. Based on the favourable 28-day compressive strength (73–84 MPa) and durability performance documented across the numerous past year studies that were reviewed, it can be concluded that MK is a viable alternate binder material for combatting chloride attack in coastal/marine concrete structures. 1is, in conjunction with its lack of chemical CO2 emissions, proves that MK can be used to improve the serviceability and sustainability states of marine structures. 1e viewpoint of this review will guide concrete constructors and researchers on a possible framework for the utilisation of metakaolin for enhancing durability concrete in aggressive environments

Engineering performance of metakaolin based concrete

The sustainable development goal (SDG) 14 of the 2030 Agenda for Sustainable Development aims at protection, conservation, and management of coastal ecosystems and resources, including by strengthening their resilience, to avoid significant adverse impacts. Coastal/marine structures are exposed to aggressive environmental con- ditions, such as chloride laden environment. Deterioration of reinforced concrete structures located in a coastal/ marine setting can influence the safety, economic and sustainability aspects of the society. Hence, there is an increased need for sustainable materials with the ability to reduce the effects of chloride attack in concrete. This experimental study aims to investigate the engineering properties of metakaolin (MK) based concrete exposed to chloride attack. The investigation was conducted for different w/b ratios of 0.54–0.61. The MK, utilised as cementitious material, was varied from 0 to 20% with an increment of 5% and ages of concrete from 7 to 56 days were considered. The effects of the above-mentioned parameters on the various properties of concrete such as workability, compressive and flexural strength, durability, resistance to chloride attack and microstructure properties of the concrete samples were investigated. From the favourable strength and durability results that were observed during the experimental study (optimum compressive strength of 49.8 MPa for 10% MK and optimum flexural strength of 8.35 MPa for 5% MK), it can be concluded that MK is a feasible supplementary cementitious material for combatting chloride attack in coastal/marine concrete structures. The obtained results, in combination with the lack of carbon dioxide CO2 released during the MK manufacturing process, further highlights the positive influence of MK on improving the serviceability and sustainability states of coastal/marine structures

Mechanical and durability properties of recycled aggregate concrete with ternary binder system and optimized mix proportion

tThis study aimed to investigate the mechanical and durability properties of recycled aggre-gate concrete with a ternary binder system and optimized mix proportion. Two concretebatches were developed using a densified mix design approach (DMDA) to evaluate therequired mix proportions. Batch I have GGBS content varied at 0%, 10%, 20%, 30%, 40% and50% at constant w/b ratio of 0.45, while batch II concrete mix have varied water/binder ratios:0.3, 0.35, 0.4, 0.45 and 0.5 at constant GGBS replacement level of 30%. The fine aggregate(river sand) of the two batches was blended with fly ash at optimum loose packing density(FA + Sand) and superplasticizer (SP) was incorporated in the mix at a constant level of 1.4%.A control mix comprising of natural aggregate was also developed. The results obtainedshowcased the feasibility of producing structural concrete with recycled aggregates usingGGBS and fly ash. The mechanical and durability properties were best at 30% GGBS content and 0.35 water/binder ratio. The DMDA for mix proportion adopted for RAC contributed sig-nificantly to improving its properties when compared to NAC, especially at the optimumobserved RAC mix with compressive strength of 52 MPa. Also, the mix demonstrated goodpermeability resistance in terms of chloride-ion ingress and capillary water absorption