International Design Standards Research Articles

Reluctance of Students to Utilize Virtual Educational Environments in Public Schools: Real World Experiences

This study aimed to explore the perspectives of public-school students who were hesitant to use the Darsak Educational Platform (DEP) during the COVID-19 pandemic in order to understand their real-life experiences. To achieve the aim of the study, the researchers employed a qualitative approach in its phenomenological form. The study sample consisted of 12 male and female students from various public schools in Jordan. The participants were chosen using an intentional method. Semi-structured interviews were used to collect the data. The study’s findings revealed a variety of causes that contributed to students’ resistance to using DEP. These causes include the students’ lack of readiness to learn through DEP, the DEP’s failure to comply with international design standards, the inadequate physical and technical teaching environment, and the limited digital competencies of teachers needed in the virtual learning environment. Given the findings of this research, the researchers advise that additional consideration should be given to the design of DEP. They also advise providing students with appropriate guidance in the usage of educational platforms.

Topology optimisation of offshore wind turbine jacket foundation for fatigue life and mass reduction

Offshore wind turbines are frequently regarded as a pricey source of electricity, and efforts are being made to lower both capital and operational costs by developing lighter and more robust structures. This paper presents a topology optimisation method to obtain a novel jacket foundation design by finding the optimum load path on the structure. The OC4 jacket model was computationally simulated considering the Aero-Hydro-Servo-Elastic loads, and the topology optimisation method was used to obtain a series of new designs. The structural optimisation is performed based on the dynamic response of the jacket, whilst restrained by relevant international design standards. In particular, time-domain fatigue simulations were performed to assess the structural integrity of the topology-optimised jacket for the first time. As a result, a range of optimised models with various thickness and diameter options are presented, which are shown to be rational and verify the optimisation procedure. The structural performance of the optimised geometry demonstrates the original jacket foundation is conservative, and the selection of optimised geometry achieved a mass reduction of 35.2% and simultaneously realised a 37.2% better fatigue life. The overall optimisation procedure and results provide useful practicalities for the design of offshore wind turbine foundations and potentially facilitate the structural integrity and cost reduction of the relevant industry.

Analytical and experimental shear evaluation of GFRP-reinforced concrete beams

Reinforced Concrete (RC) technology is advancing towards new frontiers enhancing its sustainability and durability through innovative materials. In particular, the application of Glass Fiber Reinforced Polymer (GFRP) bars, in lieu of steel reinforcement, shows excellent performance, especially in aggressive environments. Nevertheless, current international design guidelines and standards tend to be rather conservative, especially concerning shear reinforcement. This element hinders the technology’s competitiveness, not only in terms of material consumption but also in construction efficiency. This research aims to conduct an analytical comparison and experimental validation of the formulations found in some international standards pertaining to shear capacity in a specific case. The focus is on scenarios involving reduced shear reinforcement and cases where the number of stirrups falls below the minimum recommended by these standards. In the sample beam tests, two distinct flexural GFRP reinforcement ratios were employed to evaluate their influence on shear capacity, leading to diverse failure mechanisms: rupture of longitudinal GFRP bars and concrete crushing. The experimental results were used to compare the North American ACI, French AFGC, and Italian CNR shear capacity design approaches in the case of reduced transversal reinforced ratio. Analytical capacity expressions of the standards above are discussed with some remarks aiming at structural optimization.

Stakeholders’ Perspective on the Quality of Virtual Learning Material in Google Classroom

The COVID-19 pandemic stimulated education system worldwide to employ online learning to support learning despite difficult times. To respond to this challenge and to promote Sustainable Development Goal (SDG) 4, advocating quality education, a virtual learning material (VLM) for Biology was articulated in Google Classroom. Accordingly, this study aimed to evaluate its acceptability and conformity to the international standards for online courses using the Open SUNY Course Quality Review (OSCQR) rubric as the questionnaire. Respondents (N=40) involved four stakeholders: Senior High School Students, Pre-service Science Teachers, High School Teachers, and Science Instructors/Professors, with n=10 representatives each group. Their perspectives of the VLM acceptability in terms of Overview and Information, Technology and Tool, Design and Layout, Content and Activities, Interaction, and Assessment and Feedback were obtained through a Google Form by rating the 50-item questionnaire on a 4-point Likert scale together with two open-ended questions. With a grand mean of 3.81(SD=0.40), the findings revealed highly acceptable results. The qualitative responses also substantiated this result. Significant differences in the responses are also discussed, while the Cronbach alpha reliability test is high (α=0.923). Significantly, the VLM conforms with the international standards for online course design, suggesting it can be implemented among target students.

ANALYSIS OF DOMESTIC AND WORLD STANDARDS REGARDING THE CRITERIA OF THE BOUNDARY STATES FOR THE STEEL SILOS FOUNDATIONS

In the process of operation the structures of steel silos undergo various failures associated with natural and climatic loads and influences, the insufficient study of engineering and geological conditions, as well as some errors during operation. Damage to the above-ground structures of steel silos is mainly caused by roof structures and silo shells failures. Whilst operating silos, various types of raw material flow are distinguished during unloading. Possible scenarios of the operating technology violations can lead to deviations from the approved flow regime during unloading and they quite often become factors of an emergency situation. The conditions of loading and operation of silos have been compared pursuant to their presentation in the domestic and the foreign regulatory documents. A significant number of industrial accidents are associated with operation failures of reinforced concrete foundations, their insufficient load-bearing capacity and their deformability. It should be noted that the construction of the foundation affects its "flexibility", which may cause uneven settlement of the foundations and their base. Sometimes this leads to extra-design loads on the upper structure of the silo. In the domestic practice of increased diameters silos construction, the foundations with an underground gallery are the most common. For the construction areas having a high level of groundwater, the foundations with an above-ground under-silo storey are used. For the silos with an above-ground discharge funnel, the type of outflow influences the load pattern of the foundation. Whilst operating normally, the loads are uniform, and when the storage material hangs on the walls, the loads are uneven, which can lead to the destruction of the above-ground structure or a foundation tilting. The type of funnel significantly determines the shape of the outflow, which affects the distribution of internal forces in the silo and the load on the foundation. In this work, a brief analysis of the failure factors of steel silos has been carried out, and a comparative analysis of modern domestic and international design standards has been suggested concerning the criteria for the occurrence of boundary states of steel silos foundations during designing. There has also been analyzed the special operational features taking into account specific technological loads on silo shells and foundations, the certain features of engineering and geological conditions of construction sites. Conclusions have been made that the main criteria for foundations designing and calculating are the deformation criteria for limiting settlement and tilting. It should be noted that the foreign regulations place the issue of limiting maximum settlements within the scope of a designer's competence. Keywords: reinforced concrete foundation, steel silo, failure, boundary state, design norms.

Dynamic response analysis of a monopile-supported offshore wind turbine under the combined effect of sea ice impact and wind load

The existence of drifting ice is a key challenge for structural design of offshore wind turbines (OWTs) in cold regions. To better understand the structural behavior of OWT under combined sea ice impact and wind load effects, this paper investigates the dynamic response of a monopile-supported OWT using the nonlinear finite element method. The interaction between the OWT and ice impact, wind loads and soil contact are addressed in the developed numerical models in LS-DYNA. The coupling between the main program and the aerodynamic damping model is achieved by a user-defined load subroutine. To calibrate and verify the ice material model and the simulation technique, model test data are used of ice impacts with a nearly vertical monopile foundation. In the case study, numerical simulations of the interaction between a typical 5-MW monopile-supported OWT and an ice sheet are performed under various combined load scenarios. The dynamic response characteristics are presented and the effects of ice drifting speed and mean wind speed are elucidated by statistical methods. Finally, insights into the ice loads are obtained by comparing the simulation results against two international design standards. The present study contributes to an improved understanding of load effects of monopile OWTs in cold regions.

Overcoming tunnelling challenges on the Mumbai Coastal Road project in India

Completed in January 2022, the 2.1 km long 12.2 m dia. twin-bore Mumbai Coastal Road tunnel is the country’s largest ever constructed using a tunnel boring machine. It is also India’s first undersea tunnel embracing all current international design and operational standards. This paper describes Mumbai’s unique hydrogeological conditions and its impact on the choice of tunnelling machine. It then discusses the logistics of transporting the huge machine through one of the world’s most congested cities; the decisions made in its assembly, lowering and relaunch; and how overall tunnelling challenges were overcome.

Bond prediction of stainless-steel reinforcement using artificial neural networks

Stainless-steel reinforcement has become increasingly popular in the construction industry in recent years, mainly due to its distinctive characteristics and excellent mechanical properties. There is a real need to develop a fundamental understanding of the bond behaviour of stainless-steel-reinforced concrete (RC). This paper investigates the bond behaviour of stainless-steel-RC using the advancement of artificial neural networks (ANNs) and compares the performance with experimental data available in the literature with reference to existing bond design rules according to international design standards. Accordingly, a new bond design formula is proposed to predict the bond strength capacity of stainless-steel reinforcement. The results show an excellent agreement between the experimental results and the predictions of the ANN model. Both Eurocode 2 and model code 2010 are shown to be extremely conservative compared with ANN predictions. The proposed ANN-based formula provides an excellent basis for engineers to specify bond strength of stainless-steel reinforcement in RC members in an efficient and sustainable manner, with minimal wastage of materials.

Microzonation of Sejong City Area Based on Site Amplification Generated by Pohang-Type Seismic Waves

When an earthquake occurs, the behavior of the ground is significantly influenced by the seismic wave characteristics (waveform) and soil layer conditions. In local and international seismic design standards, it is recommended that the input seismic wave should correspond to the design response spectrum and reflect the fault characteristics. In this study, ground response analysis was performed to satisfy the seismic design standards using modified design seismic waves generated by the Pohang seismic waves measured at the bedrock location. The peak ground acceleration, ground amplification ratio, and natural period of Sejong-si for Pohang-type seismic waves were determined using the Sejong-si 120 site exploration results. From a plotted risk map, a map of floors that could experience relatively large seismic loads during an earthquake was determined. Based on the risk map plotted in this study, it is possible to prepare for earthquake damage in advance by identifying the degree of seismic damage to a structure when an earthquake occurs and selecting the building inspection or seismic reinforcement priority.

Direct Design of Stainless Steel Frames: Recommendations and Case Studies

AbstractAcknowledging the potential of system‐based design approaches, most international design standards for steel structures include preliminary versions of such alternative design methods. The Direct Design Method (DDM) is one of these approaches, which allows designing steel structures directly using advanced numerical analyses without requiring further member checks. This paper presents the DDM design (and verification) procedure and summarizes the key aspects of the advanced finite element model necessary for the determination of the system strength, with an emphasis on cold‐formed stainless steel portal frames. Through the design of two frames, the DDM design procedure is illustrated and the resulting cross‐sections are compared with those derived using the traditional two‐step design approach in the Eurocode and ASCE design frameworks. The results demonstrate that the DDM verification process is simpler and more direct, and that lighter structures are obtained when designing using the DDM for strength considerations. Finally, this paper also highlights that allowing larger deformations in the ultimate limit state design for the DDM does not have additional negative effects on the serviceability requirements if compared to the traditional two‐step design approach.

Mechanical properties of macro synthetic fiber reinforced concrete at elevated temperatures: A systematic review and meta‐analysis

AbstractThe current infrastructure boom combined with the latest outcomes from 26th UN Climate Change Conference of the Parties (COP 26) seeking a carbon neutral society by 2050 have driven the increasing need for sustainable alternatives to be considered in construction. One such alternative is macro synthetic fibers, which have been gaining acceptance on major infrastructure projects. However, only limited uptake has occurred in permanent structures, due to a lack of knowledge around the behavior of macro synthetic fiber reinforced concrete (MSFRC) when exposed to elevated temperatures. Existing Australian and international design standards do not take into account the loss of strength for MSFRC after exposure to elevated temperatures. Hence, this systematic review sets out to combine all the existing knowledge on the mechanical properties of MSFRC and lay the groundwork for determining acceptable relationships between relative strengths and elevated temperatures. This study proposes relationships between temperature and compressive strength, splitting tensile strength, elastic modulus, flexural strength and residual flexural, and tensile strengths of MSFRC. These are compared to existing relationships determined for plain concrete and steel fiber reinforced concrete to position MSFRC within the context of existing and accepted knowledge.

Modified Meyerhof approach for forecasting reliable ultimate capacity of the large diameter bored piles

The static loading test is undoubtedly the most reliable method for forecasting the ultimate capacity of the large diameter bored piles (LDBP). However, in-situ loading of this class of piles until reaching failure is practically seldom due to the large amount of settlement required for shaft and base mobilization. Therefore, many international design standards recommend either capacity-based or settlement-based methods to estimate the LDBP ultimate capacity in case of the impossibility of performing loading tests during the design phase. However, those methods are invariably associated with various degrees of uncertainty resulting from several factors, as evidenced in several comparative analyses available in the literature. For instance, the settlement-based method of the Egyptian code of practice (ECP 202/4) usually underestimates the ultimate capacity of LDBP. In contrast, Meyerhof's capacity-based method often overestimates the LDBP’s ultimate capacity. In this paper, a modified approach has been proposed to forecast the ultimate capacity of the LDBP. This approach was modified from Meyerhof’s classical formula (1976) through three fundamental stages. First, an assessment study was performed to evaluate the reliability of the estimated LDBP ultimate capacity using Meyerhof’s classical method. For this purpose, results of full scale loaded to failure loading LDBP test and related twenty-eight parametric numerical models with various pile geometrical and soil geotechnical parameters have been used. Based on the assessment study findings, the essential modifications were suggested in the second stage to adapt Meyerhof’s classic method. In the third stage, the results of several numerical models and in-situ loading tests were employed to assess the accuracy of the developed modified method. This study showed that Meyerhof's classical method overestimated the ultimate capacity of LDBP with an error percentage ranging from 14 to 46%. On the other side, the proposed modified approach has succeeded in estimating the ultimate capacity of loaded to failure in-situ LDBP test and twenty numerical LDBP models with error percentages ranging from 0.267 to 7.75%.

Composite overwrap repair of pipelines-reliability based design framework

Considering the ages and need for repairment of the gas and oil transmission pipes in the world, in the past years, lab and field experiments were performed on fiber reinforced polymer (FRP) wrapping to steel pipes. Although this technology has widely been employed for decades, further improvement on the design guidelines is still needed. In this context, this study proposes a reliability structural design framework for the repairment of corroded pipelines using FRP composite wrapping. To be consistent with international structural design standards, reliability-based design framework is to be proposed within a semi-probabilistic approach by calibrating safety factors to account for the associated uncertainties in capacity and load effects to best meet the cost-safety balance in design. Currently, the repair design practice for corroded pipelines is based on a deterministic approach, and it cannot ensure the proper consideration of uncertainties and meeting a consistent level of target reliability in design. This study involves comprehensive experiments of FRP materials under two different environmental conditions for onshore and offshore pipes, which were used to propose the best-fit statistical models to the design parameters to realistically represent the random variables in the proposed safety factor based structural design framework. Through extensive reliability analyses, the values for the safety factors for composite and steel have been proposed according to the target reliability indices and the corrosion rate. The proposed design framework for corroded steel pipes with FRP overwrap repairment is expected to improve the current design practice and optimize the cost and safety by meeting the target reliability level.

Experimental investigation on the flexural behaviour of stainless steel reinforced concrete beams

The durability of reinforced concrete (RC) structures and infrastructure has been the subject of significant attention from the engineering research community in recent years, mainly owing to the deterioration of RC elements due to corrosion of the embedded steel reinforcement. In this context, stainless steel reinforcement can provide an efficient solution to enhance the expected lifetime of concrete structures, reducing the damage due to corrosion of the reinforcement and carbonation and deterioration of the concrete. However, current international design standards for reinforced concrete structures do not include appropriate guidance for stainless steel reinforced concrete (SSRC). In order to investigate the behaviour of stainless steel RC beams, a series of six beam tests was conducted and is discussed herein. The key performance measures for RC beams such as load-deflection response, cracking behaviour and deflections at service load are assessed. The validity and applicability of existing design rules, which were developed for carbon steel RC, are also examined for stainless steel reinforced concrete members. Other recently developed design procedures, based on the Continuous Strength Method and including an accurate material model for the stainless steel bars, are also examined.

Conformity of the performance of calcium sulfoaluminate cement based concretes to empirical models in current international design standards

Construction industries often rely on empirical models in design standards to estimate concrete parameters and carry out accurate assessment of concrete structures. As the demand for alternative low carbon cements grows in the industries, however, the question arises whether the existing models, which are typically established for ordinary Portland cement concretes, can adequately predict the characteristics of newer alternative concretes. Calcium sulfoaluminate cement (CSAC) based concretes are amongst the most promising options due to their inherent high early-strength, rapid-hardening, expansive, low carbon footprint and low energy intensity properties. This study describes a series of mechanical and durability experiments on optimally proportioned CSAC based concretes to investigate whether their unique performance attributes cohere to the guidelines and empirical models stipulated by prominent design standards in the European, American, Japanese and Australian market. The study revealed that, indeed, some models were able to predict the relationship between tensile and compressive strengths, as well as the compressive and tensile strength development patterns of the CSAC concretes to an acceptable degree. However, with regards to the evolution of the drying shrinkage strain with time, the respective models produced significantly overestimated values, as they do not account for the expansive nature of the ettringite in the CSAC system, which consequently reduces the shrinkage. Similarly, well-accepted models for the progress of the carbonation depth with time poorly underestimated the experimental outputs, most likely because the reduced alkalinity in the CSAC system, that in fact aggravates the carbonation of ettringite, is not considered in the models. Overall, the outcomes of this research can serve as preliminary guidance for practitioners to confidently identify the specific models currently available in international standards that are readily admissible to CSAC concretes, and more importantly those models that need further attention, without which certain structural design risks may be exposed.

Fatigue performance of butt-welded austenitic stainless-steel joints evaluated by peak-stress method

In this study, the fatigue performance of butt-welded austenitic stainless-steel joints is investigated by fatigue test, nominal-stress method and peak-stress method. Welding profiles and misalignment were analyzed, residual stresses were measured, and fatigue tests were conducted. The experimental fatigue data are regressed to the stress range versus life-to-failure (S–N) curve of the nominal stress method, and the factor affected dispersion is analyzed by using the peak-stress method. The following conclusion can be drawn: (1) The fatigue strength is 155 MPa in nominal stress method, which is higher than that of structural steel (80 MPa) in the international fatigue design standards. (2) The influence of the welding misalignment and distortion can be accurately estimated by the combing the reference S-N curve and stress magnification factor formulae from the international fatigue design standards.

Behaviour of cold-formed steel built-up I-sections with perforated web under localized forces

This research focused on the web crippling behaviour of cold-formed steel (CFS) built-up I-sections with perforated web. The built-up I-sections were made up of two equal-sized unlipped channels fastened back-to-back in the web. The web hole was situated at the middle height of the web and directly under the bearing plate. Firstly, an experimental program consisting of 13 specimens without web holes and 38 specimens with perforated web is described. The built-up I-section members were tested under four different loading cases, including End-Two-Flange (ETF), Interior-Two-Flange (ITF), End loading (EL) and Interior loading (IL). Numerical simulation was conducted after the tests. The experimental results were utilized in the development and validation of nonlinear finite element (FE) models. Then the verified FE models were utilized to perform a parametric investigation of 318 built-up I-sections. The numerical and experimental strengths for specimens without web holes were compared to the design predictions from the existing design standards. The findings show that the strengths calculated from the existing standards are either conservative or unconservative. It should be mentioned that the existing international design standards do not have explicit design formula to predict the strengths of CFS built-up I-sections with perforated web undergoing web crippling. As a result, the test and FE capacities of specimens with perforated web were compared to the capacities predicted from the strength reduction factor formulas derived in this study. It is shown that the newly developed formulas can accurately calculate the web crippling capacities of CFS built-up I-sections with perforated web.

Lightweight steel systems: Proposal and validation of seismic design rules for second generation of Eurocode 8

The current edition of Eurocode 8 (EN 1998 (CEN (2004))) does not explicitly cover the earthquake-resistant design of the Lightweight steel (LWS) buildings made with cold-formed steel (CFS) frame. Extensive research has been carried out in the past decade on this topic that provides a solid background for an update of the current provisions and the development of a new edition of the code. As part of the revision process of Eurocode 8, several activities are currently under development. Within this framework, this paper presents a set of design rules for the seismic design of LWS buildings based on background studies carried out at the University of Naples “Federico II”. A critical review of the provisions given by international design standards for the seismic design of LWS systems is also presented. The proposed design rules include a set of provisions for achieving the dissipative behaviour of Lateral Force Resisting System (LFRS) and predicting their design strength, together with behaviour factor values and geometrical and mechanical limitations. Different types of LFRS are analysed, namely CFS strap-braced walls and CFS shear walls with steel sheets, wood, or gypsum sheathing. Worked examples are also presented to show the applicability of the proposed design rules on a set of building archetypes. Validation numerical study is performed using both nonlinear static and incremental dynamic analysis approaches. Finally, the collapse performance of the archetypes is assessed following the seismic performance evaluation protocol of FEMA P695.

Experimental study on cyclic shear performance of steel plate shear wall with different buckling restraints

The buckling-restrained cold-formed steel plate shear wall (SPSW) is a new type of shear wall that integrates building and structural functions. It consists of an embedded steel plate, hat-section steel strips, two thermal and sound insulation layers, two oriented strand board (OSB) plates. In order to study the cyclic shear performance of SPSW with different buckling restraints, six SPSW specimens with different buckling restraints and one SPSW specimen without buckling restraints were tested with hinged frame. The test results showed that the hat-section steel strips (i.e. stiffeners) can significantly decrease the outward buckling deformation of the embedded steel plate, thus preventing the formation of tension field on the diagonal direction of SPSW and improving the energy dissipation capacity, ductility and bearing capacity of the SPSW. Among all the specimens, the cross-shaped buckling restraints has the highest efficiency in improving the bearing capacity of the SPSW, followed by the X-shaped. In addition, as the number of steel strips increases, the restraint effect of steel strips, the energy dissipation capacity and the plastic deformation performance of specimens are also gradually improved. Finally, the shear capacities of all SPSW specimens are calculated by according to existing international design standards. As can be seen from the results, the design rule in AISC is the most conservative, while the design method of Eurocode 8 is most accurate.

In-plane and out-of-plane structural performance of fully grouted reinforced masonry walls with varying reinforcement ratio – A numerical study

Most international masonry design standards include the contribution of reinforcements to enhance the capacity of reinforced masonry walls subject to seismic loading. As masonry is brittle, it can potentially fail before the reinforcing bars yield, especially in closely spaced reinforced masonry walls. The assumption that these bars yield at the ultimate load could, therefore, result in an unrealistic over-prediction of the flexural and shear capacities of the walls. This paper presents a detailed investigation of several fully grouted reinforced masonry (FGRM) walls subject to in-plane and out-of-plane loading that is independent of each other. The analyses include the level of pre-compression and a wide range of reinforcement ratios. The assessment has been carried out through an explicit finite element (FE) model. Validation of the FE model is briefly presented and the structural performance, i.e., load capacity, lateral drift index, displacement ductility and stiffness of the FGRM walls are discussed in detail. The influence of reinforcement ratio on the yielding of reinforcing bars in the FGRM walls under in-plane and out-of-plane loading is also shown. It is found that the increase in reinforcement ratio beyond a critical limit degraded the structural performance of the FGRM walls and a suitable reinforcement ratio range is proposed.