Lateral capacity and seismic characteristic of hybrid cold formed and hot rolled steel systems

This thesis addresses the application of hybrid cold-formed steel (CFS) - Hot-Rolled Steel (HRS) structures, as a new lateral force resisting system for light weight steel framed buildings in seismic regions. The study considers hysteretic behaviour, as well as maximum lateral load resisting capacity through comprehensive testing and advanced numerical analyses. The study identifies the advantages and disadvantages of the proposed hybrid system and provides in depth knowledge about performance characteristics of this innovative structural system, in order to facilitate the use of this system in earthquake-prone regions. The project is divided into three main parts: experimental, numerical and analytical studies. A comprehensive literature review is performed as a part of this study, in order to discover the existing gaps in the current knowledge regarding the structural performance of CFS structures and the methods for lateral performance enhancement. The literature review suggests that although CFS walls are not new, and have been used as non-structural components for many years, their application as main load-bearing structural frames is relatively new. That is, appropriate guidelines that address the seismic design of CFS structures have not yet been fully developed in the literature. In addition, the lateral design of these systems is not adequately detailed in the available standards of practice. There have been several attempts to improve the seismic performance of such structural system by different bracing or sheathing configurations. However, there is minimal background information available on hybrid systems such as hot rolled-cold formed structures. In this study, a series of CFS-HRS hybrid shear walls are constructed in order to investigate the lateral behaviour of the walls with different configurations to obtain the optimum combination of HRS and CFS. Different configurations are considered to provide the most efficient load transfer pattern from cold formed steel part of the wall to the Hot Rolled section, which is responsible for withstanding the lateral loads. The CFS part is aimed to transfer lateral loads to HRS part without any internal local failure. The ideal failure condition is the HRS yielding. Therefore, the optimum rigidity of the HRS part is of great importance to prevent any local failure happening prior to reaching the maximum lateral capacity of the HRS. For each experimental specimen, the hysteretic envelope curve is plotted, and different characteristics are evaluated. Since the failure mode of such systems is very complicated, the test results will provide the possible failure modes to be utilised for any further investigation or any optimisation analysis in numerical and analytical studies. In addition, Non-linear finite element (FE) analysis is employed using the ABAQUS software [1], in order to investigate the seismic performance of the proposed hybrid shear walls in multi-storey light steel frames. The nonlinear analysis accounts for different structural characteristics, including material non-linearity, geometric imperfection and residual stresses. The numerical models are verified based on experimental test results. The principal objective of this part of the study is aseismic optimisation of the proposed hybrid system and finding the corresponding dimensions and configurations to improve the strength and stiffness to achieve the objective. Using the hybrid wall panel system, a 4-storey building in an earthquake prone region is designed as per the relevant codes of practice. For the designed 4-storey building, the CFS part of the panel only bears the gravity loads, while a hot rolled steel collector transfers the lateral load to the HRS part acting as the main lateral load resisting system. Finally, the building is designed using different lateral load resisting systems and the results are compared with those from the proposed hybrid system in terms of cost. Furthermore, based on the real failure mode shapes obtained from test specimens, a Finite Strip Method program is developed to evaluate the elastic buckling mode shapes of a single stud with an arbitrary section detail. The code is helpful for design of CFS studs as explained in Chapters 3 and 5

A Mathematical Approach for Predicting Sufficient Separation Gap between Adjacent Buildings to Avoid Earthquake-Induced Pounding

Studies on earthquake-related damage underscore that buildings are vulnerable to significant harm or even collapse during moderate to strong ground motions. Of particular concern is seismic-induced pounding, observed in numerous past and recent earthquakes, often resulting from inadequate separation gaps between neighboring structures. This study conducted an experimental and numerical investigation to develop a mathematical equation to calculate a sufficient separation gap in order to avoid the collision between adjacent mid-rise steel-frame buildings during seismic excitation. In this study, the coupled configuration of 15-storey & 10-storey, 15-storey & 5-storey, and 10-storey & 5-storey steel frame structures was considered in the investigation. The investigation concluded with a large number of data outputs. The outputs were used to predict structural behavior during earthquakes. The obtained data were categorized into three main categories according to the earthquake's Peak Ground Acceleration (PGA) levels. Also, the derived equations were divided into three different equations to estimate the required seismic gap between neighboring buildings accordingly. The derived equations are distilled to empower engineers to rigorously evaluate non-irregular mid-rise steel frame buildings. Doi: 10.28991/CEJ-2023-09-10-02 Full Text: PD

µECM process investigation and sustainability assessment

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonMicro electro chemical machining (µECM) as an alternative machining process gains more attraction in micro and nano industries and gradually finds its place among other non-conventional manufacturing methods. µECM same as ECM aimed at electrically conductive materials; µECM process is based on anodic dissolution of the materials at atomic level. Current progress in µECM has presented valuable improvement in the process control and monitoring, shaping accuracy, simplifying the tool design and the process stability. This makes the µECM an outstanding alternative technology to produce accurate and complex 3-dimensional micro components. However, there is still a gap in application of µECM at research level and industrial level; development and commercialisation of the µECM require huge industrial investment which still needs justification to be attractive for investors. Despite worldwide attempts to investigate and demonstrate the µECM process in full details and develop the µECM technology for the industrial applications, there is still a need for further investigation and research due to the complex and multidisciplinary nature of this process. Currently, this process is very much dependent on operator experience and trial and error approach. The lack of trained knowledgeable operators in addition to the lack of a comprehensive database (combination of materials, electrolytes and machining parameters) have increased the time and the cost of the commercialised development of this technology. A comprehensive analytical literature review highlighted three areas of knowledge gap which can be further investigated and developed. One of the main challenges in current state of this technology is initial set up for machining parameters. Current records show that the initial parameters have been set up using trial and error approach or simulation data; and there is still ongoing effort to find a better solution to set up the initial parameters. The electrode-electrolyte interface was recognised as one of the main effective parameters on µECM machining performance. The complex nature of the reaction which happens at this interface, in addition to the electrode-electrolyte structure need further investigation and analysis in order to improve the µECM machining performance. Finally, the ever increasing demand to optimise all manufacturing processes and products, has increased the need to assess the sustainability of the machining process including new developed technologies; but there is very little information available in the area of micro and nano machining sustainability assessment including µECM. Therefore, in this research it has been tried to address these three knowledge gaps and to suggest new methodologies to overcome them using a new practice consisting of laboratory experiments, mathematical analysis and simulation to investigate the initial machining parameters’ values, explore the electrode-electrolyte interface structure for stainless steel workpiece and tungsten and nickel tool electrodes. Also, to introduce a series of indicators and measures to assess the sustainability of the µECM process to justify its initial high cost in comparison with any other machining process. Laboratory experiments carried out using potentiostat (iviumstat) and mathematical analysis and simulation took place using Matlab and Simulink; and a few experiments carried out using in house built µECM machine to examine the obtained results through the laboratory and simulation works. The results suggested that combination of 6.5 to 7.5 volts, electrolyte concentration between 0.4 and 0.7 mole/L and inter-electrode gap between 22 and 27 µm generates optimum process results. Additionally, electrode-electrolyte interface structure is a useful parameter to set up the pulse on time. Finally, introduced sustainability assessment indicators and measures provides the opportunity to assess the µECM process for further optimisation. As a result, µECM is a valuable process and in claim for current manufacturing industries especially in micro and nano products which demand higher accuracy and quality, better production life cycle and lower cost. So, it is very worthy to invest for further development to bring this technology to the industrial level

Pushover analysis for estimating seismic demand of elliptic braced moment resisting frames

U ovom se radu vrednuje seizmički odziv inovativnog čeličnog veznog sustava: okvir s eliptičnim vezovima (elliptic braced moment resisting frames - ELBRF). ELBRF ima bolje konstrukcijsko ponašanje u odnosu na druge vezne sustave te arhitektonsku prednost koja smanjuje smetnje pri umetanju otvora u zidove. Seizmičko ponašanje ELBRF-a procjenjuje se pomoću različitih obrazaca opterećenja primjenom konvencionalne metode postupnog guranja konstrukcije. Rezultati analize potvrđuju se pomoću nelinearne analize primjenom vremenskog zapisa (nonlinear time history analysis - NTHA) ELBRF okvira na 3, 5, 7 i 10 katova na tlu 2. tipa pogođenih potresima magnitude do 10 i uspoređuju se s posebnim okvirima (special moment resisting frames - SMRF) i okvirima s križnim i obrnutim V centričnim vezovima. Vrednuju se međukatni pomaci, pomaci te katni posmici. Postiže se proporcionalno točno vrednovanje pomoću metoda postupnog guranja konstrukcije u usporedbi s NTHA-om. Modalna metoda postupnog guranja konstrukcije (MPA) omogućuje procjenu seizmičkih zahtjeva s ciljem prevladavanja nedostataka raspoređivanja opterećenja prema FEMA-i kada se radi o učincima viših modova. Poboljšano je seizmičko ponašanje protupotresnog sustava ELBRF, oštećenja se prenose na gornje katove, a povećava se i faktor modifikacije odziva kod ELBRF-ova.In this paper, an innovative steel bracing system, known as the seismic response of elliptic braced moment resisting frame (ELBRF), is evaluated. ELBRF has a better structural behavior comparing to the other bracing systems and it has an architectural advantage allowing to place openings in walls with less interference. The demand for seismic performance of ELBRF is estimated through different loading patterns by adopting the conventional pushover methods. The pushover results are verified through nonlinear time history analysis (NTHAs) of 3, 5, 7, and 10-story ELBRF frames, which are on type II soil and are affected by 10 scaled earthquake records. These results are also with special moment resisting frames (SMRF) and X-Braced CBF and Inverted V-Braced CBF concentrically braced frames. Story drifts, displacements, and story shears are evaluated. A proportionally accurate estimation is observed through the pushover methods in comparison with NTHAs. Modal Pushover Analysis (MPA) can estimate the seismic demands by overcoming the shortcomings of FEMA load distributions when the higher mode effects are of concern. The seismic performance of the ELBRF system against earthquakes has improved, failure is transmitted to the upper stories, and the response modification factor is increased in ELBRF

Analytical asssessment of the structural behavior of a specific composite floor system at elevated temperatures using a newly developed hybrid intelligence method

The aim of this paper is to study the performance of a composite floor system at different heat stages using artificial intelligence to derive a sustainable design and to select the most critical factors for a sustainable floor system at elevated temperatures. In a composite floor system, load bearing is due to composite action between steel and concrete materials which is achieved by using shear connectors. Although shear connectors play an important role in the performance of a composite floor system by transferring shear force from the concrete to the steel profile, if the composite floor system is exposed to high temperature conditions excessive deformations may reduce the shear-bearing capacity of the composite floor system. Therefore, in this paper, the slip response of angle shear connectors is evaluated by using artificial intelligence techniques to determine the performance of a composite floor system during high temperatures. Accordingly, authenticated experimental data on monotonic loading of a composite steel-concrete floor system in different heat stages were employed for analytical assessment. Moreover, an artificial neural network was developed with a fuzzy system (ANFIS) optimized by using a genetic algorithm (GA) and particle swarm optimization (PSO), namely the ANFIS-PSO-GA (ANPG) method. In addition, the results of the ANPG method were compared with those of an extreme learning machine (ELM) method and a radial basis function network (RBFN) method. The mechanical and geometrical properties of the shear connectors and the temperatures were included in the dataset. Based on the results, although the behavior of the composite floor system was accurately predicted by the three methods, the RBFN and ANPG methods represented the most accurate values for split-tensile load and slip prediction, respectively. Based on the numerical results, since the slip response had a rational relationship with the load and geometrical parameters, it was dramatically predictable. In addition, slip response and temperature were determined as the most critical factors affecting the shear-bearing capacity of the composite floor system at elevated temperatures

A Scientometric Study of Oral Medicine Articles from Iran Published in PubMed-Indexed Journals

Objectives This study aimed to scientometrically assess the oral medicine articles from Iran published in PubMed-indexed journals.Methods In this descriptive cross-sectional study, the author information section of PubMed database was electronically searched for oral medicine articles published from the beginning of 2006 to the beginning of 2016 with at least one author from Iran using the keywords “oral medicine”, “oral and maxillofacial medicine”, “stomatology”, “stomatologist”, and “Iran”. The results were reported as frequency, and trend analysis was performed.Results A total of 280 oral medicine articles published from the beginning of 2006 to the beginning of 2016 were found to have at least one author from Iran, which comprised 2.9% of the entire articles in this field. The majority of published articles were original articles (77%) followed by case reports (15%), review articles (5%), short communications (2%) and letter to editors (1%). The majority of articles had been published in J Dent Res Dent Clin Dent Prospects (18%), followed by J Dent (Tehran) (6.7%), and J Contemp Dent Pract (5.5%). The trend of publication of articles was ascending during this time period except for the year 2011. The frequency of articles had a significantly ascending trend during the aforementioned time period (P=0.004).Conclusion From the beginning of 2006 to the beginning of 2016, Iran’s share of oral medicine articles published in PubMed-indexed journals was around 3% and had an ascending tren

Assessing satisfaction rate of freshman students regarding online registration at Qazvin University of Medical Sciences in the academic year 92-93

Background: Nowadays, satisfaction is a significant concept in the majority of organizations. Managing the traditional registration system of students is time consuming process for both students and administrative staff inside universities that include preparing and assessing the required documents on the day of registration. Therefore, facilitating the mentioned tasks not only may lead to increasing students' satisfaction but also may greatly improve the speed of educational tasks. Objective: The aim of the current research is to determine satisfaction rate of the newly arrived students regarding online registration system at Qazvin University of Medical Sciences in the academic year 2013-2014. Methods: The descriptive epidemiologic method was used for the present study with data collection method using a questionnaire in 2013. The questionnaires were distributed among 500 newly arrived students, and 366 questionnaires (73.2%) were collected. Data analysis was performed with SPSS software version 13. Findings: In this study, 275 female (75.1%) and 91 male (24.9%) were participated. The satisfaction rate was very high in of 65 participants (17.8%), high in 116 participants (35.5%), moderate in 130 participants (35.5%), low in 13 participants (3.5%), and very low in 42 participants (11.5%). The results demonstrated that as the rate of students' satisfaction rises in various fields of study and academic levels, they may develop and improve further in the academic processes. Conclusion: Based on the results, majority of the students have good satisfaction from the online registration. Moreover, they have suggested some points for enhancement of the process including change in the information announcement method, improvement in presenting the required announcement, and instructions plus adding some pictorial guidelines and finally sending some clear and accurate notes for students with shortage in their documents. In fact, by applying the mentioned solutions the online registration process will be facilitated and accelerated. Key words: Online registration, satisfaction, freshman student