Papers by Mohammadreza Vafaei
Smart Structures and Systems, 2018
Tuned Liquid Dampers (TLDs) have gained wide acceptance as a system for structural control and en... more Tuned Liquid Dampers (TLDs) have gained wide acceptance as a system for structural control and energy dissipation. However, they face limitation caused by low damping in deep water, which affects their efficiency. Another problem with deep water TLDs is that not all water depth participates in energy dissipation. This paper investigated the effect of upper mounted baffles on the effectiveness of TLDs. The Vertical Blockage Ratio (VBR) of baffles ranged from 10% -90%. The TLD (with and without baffle), structure, and combined structure with TLD (with and without baffles) were subjected to free and harmonic forced vibrations. Results indicated that baffles could significantly enhance the energy dissipation of TLDs, thus reducing structural responses more than structures equipped with ordinary TLDs. It was found that, there was an optimum valueof VBR in which the TLD's efficiency was maximized. When TLD had an appropriate VBR, the structural acceleration and displacement responses were suppressed significantly up to 51% and 56%, respectively
Malaysia’s strategic location has spared it from major seismic activities. Nevertheless, plethora... more Malaysia’s strategic location has spared it from major seismic activities. Nevertheless, plethora of far field tremors resulting from earthquakes in neighboring countries can be felt locally despite the fact that the epicenters of these earthquakes are mostly hundreds of kilometers away. With increasing frequency and intensity of late, this scenario has raised a major concern pertaining to the ability of the existing buildings and sensitive structures in the country to withstand earthquakes events in the future. Considering that no specific study has been contemplated with particular regards to the effect of earthquakes to telecommunications facilities in Malaysia, it is requisitely of prime significance to commence this study. The main objective of the study is to determine the seismic behavior and then evaluate the structural integrity of the existing telecommunication tower structures considering earthquake effects in Malaysia. The study covers the analysis of the four (4) legged...
Computer-aided civil and infrastructure engineering, Mar 11, 2024
International journal of applied engineering research, 2017
Unlike the conventional carbon steel that has been used widely as reinforcement bars, the usage o... more Unlike the conventional carbon steel that has been used widely as reinforcement bars, the usage of Inoxydable steel (Inox) is still limited despite their superior properties in strength and ductility. Hence, limited study has been conducted to determine the structural behavior of Inox including the constitutive law and material model when it is used as reinforcement bars in concrete element. In this study, tension stiffening model is specifically developed for Inox to determine their interaction properties with the surrounding concrete. This study uses constitutive laws developed for Inox from Austenitic type. An inverse method based on combination of results from experimental works and the one obtained from nonlinear numerical analysis (NNA) is applied to determine the parameters involved in the tension stiffening model. The tension stiffening model developed for inoxydable steel is then compared with the conventional carbon steel. Results from this study shows that the inverse method is able to develop tension stiffening model for concrete beam reinforced with inoxydable steel. When compared with carbon steel, tension stiffening for inoxydable steel is 50 percent higher during the cracking phase. Findings from this study; tension stiffening model parameters for inoxydable steel are very useful for modeling works which uses Inox as reinforcing steel bars.
Journal of Constructional Steel Research, Nov 1, 2020
Abstract Built-up battened columns are lightweight and have a larger moment of inertia when compa... more Abstract Built-up battened columns are lightweight and have a larger moment of inertia when compared with columns made by a single profile. However, these columns have shown poor seismic performance during past earthquakes. In this study, experimental and numerical investigations were focused on the seismic performance of these columns. A full-scale built-up battened column was subjected to quasi-static cyclic loading and its response was recorded. Furthermore, 81 built-up battened columns were simulated in ABAQUS software. The effects of batten spacing, batten thickness, chord distance, and axial force on the cyclic response of simulated columns were investigated. The obtained results indicated that the bulging of chord webs together with the local buckling of chord flanges were the main reason for the failure of columns. Besides, in all columns, the maximum stress in chords was almost twice larger than the maximum stress in battens. Furthermore, an increase in the batten thickness or a decrease in the batten spacing slightly increased the ultimate load of columns. Columns with a thicker batten exhibited a slightly smaller plastic deformation. The displacement ductility ratios of the built-up battened columns were all less than two even when they were subjected to an axial compression ratio smaller than 0.2. It was also observed that, in all columns, the ratio of ultimate load to the effective yield strength was less than 1.4.
International Journal of Integrated Engineering, Dec 15, 2022
Response modification factor (R-factor) which is also referred to as behavior factor in Eurocode ... more Response modification factor (R-factor) which is also referred to as behavior factor in Eurocode 8, overstrength factor (Ω-factor), and deflection amplification factor (Cd-factor) are referred to as seismic design modification factors (SDMFs). Majority of existing seismic design codes use these parameters to estimate the intensity of seismic force and inelastic lateral displacement of structures when a linear analysis is conducted. The R-factor is an indication for the ability of a structural system to resist seismic forces, the Ω-factor is a measure for the reserve strength in the structural system and Cd-factor is a coefficient which is used to estimate the inelastic lateral displacements of a structural system through the calculated elastic lateral displacement. Seismic design codes often determine the values of these factors empirically based on engineering judgment and observed damage during past earthquakes [1]. Since seismic design codes have not proposed the value of these factors for all types of structural systems, many researchers have estimated them through numerical simulations. For example, Vafaei & Alih [2] assessed the SDMFs of air traffic control tower and showed that an increase in the height of towers decreased the R-factor significantly. Asgarian & Shokrgozar [3] investigated the R-factor of buckling restrained braced frames and proposed 8.35 and 12, respectively, as their R-factor for the ultimate and allowable stress design methods. In another study, Aliakbari & Shariatmadar [4] estimated these factors for steel slit panel-frames through pushover and nonlinear incremental dynamic analysis. They proposed an overstrength factor of 4.16 and a R-factor of 8.11 for the studied frames. Mahmoudi & Zaree [5] worked on the R-factor of concentrically braced steel frames. They reported that concentrically braced steel frames had a smaller R-factor than buckling restrained braced frames.
IOP conference series, May 1, 2022
In early 2017, Malaysia’s national annex for the seismic design of structures was published and l... more In early 2017, Malaysia’s national annex for the seismic design of structures was published and led to some concerns regarding the increase in the construction cost of buildings. This study investigated the change in the reinforcement weights of beams and columns due to seismic design based on Malaysia’s national annex. For this purpose, buildings with different numbers of stories (i.e., 3- and 6-storey), ductility classes (i.e., low and medium), and soil types (i.e., stiff and soft soil) were designed through two different methods. The first method followed the conventional design practice in Malaysia, in which the BS 8110 code was used to design structural elements only for gravity loads. However, the second design method was based on Malaysia’s national annex and Eurocode 2, and buildings were designed for gravity loads and seismic actions. The results showed that buildings with low ductility class constructed on the soft soil had the largest increase in the reinforcement weights compared to the conventional design. On the other hand, the buildings with medium ductility class constructed on stiff soil had lesser reinforcement weights than the conventional design.
Scientific Reports
Plastic sand paver blocks provide a sustainable alternative by using plastic waste and reducing t... more Plastic sand paver blocks provide a sustainable alternative by using plastic waste and reducing the need for cement. This innovative approach leads to a more sustainable construction sector by promoting environmental preservation. No model or Equation has been devised that can predict the compressive strength of these blocks. This study utilized gene expression programming (GEP) and multi-expression programming (MEP) to develop empirical models to forecast the compressive strength of plastic sand paver blocks (PSPB) comprised of plastic, sand, and fibre in an effort to advance the field. The database contains 135 results for compressive strength with seven input parameters. The R2 values of 0.87 for GEP and 0.91 for MEP for compressive strength reveal a relatively significant relationship between predicted and actual values. MEP outperformed GEP by displaying a higher R2 and lower values for statistical evaluations. In addition, a sensitivity analysis was conducted, which revealed t...
IOP Conference Series: Earth and Environmental Science, 2021
Malaysia national annex to Eurocode 8 was released in 2017 and now buildings in Malaysia should b... more Malaysia national annex to Eurocode 8 was released in 2017 and now buildings in Malaysia should be designed in accordance with specifications given in this annex. Unlike Eurocode 8 in which the inter-story drift control is compulsory for all types of structures, the drift control in the Malaysia national annex has been limited to very important buildings. This study was carried out to investigate to what extent limiting the inter-story drifts to the given values by the code will affect the seismic response of reinforced concrete (RC) structures. For this purpose, 4, 7 and 10-storey low-ductile RC buildings constructed on soft and stiff soils were designed for seismic actions. In the seismic design of buildings two different conditions were considered. First group of buildings were designed considering the limitation of interstory drift as suggested by the Eurocode 8. However, in the design of the second group of buildings the limitations of the inter-story drifts were not included. ...
IOP Conference Series: Materials Science and Engineering, 2020
Seismic design modification factors that include the response modification factor (R), the overst... more Seismic design modification factors that include the response modification factor (R), the overstrength factor (Ω), and the displacement amplification factor (Cd) play a significant role in the seismic design of structures. The recommended values for these factors in seismic design codes are empirical and do not account for the differences in the intensity of the design live load in structures. This study investigates the change in the value of these factors as a result of the change in the intensity of the design live load. For this purpose, eighteen reinforced concrete frames with the different number of stories and ductility classes were designed and analyzed. Nonlinear static analysis was used to calculate the capacity curve of frames and their seismic response modification factors. Results indicated that the values of Ω and Cd for both low and high-ductile reinforced concrete frames decreased slightly as the intensity of design live load increased. An increase in the intensity of the design live load increased the R-factor in the high-ductile RC frames.
Advances in Engineering Technology Research
Liquid storage tank is an irreplaceable and extremely important vessel structure used to store li... more Liquid storage tank is an irreplaceable and extremely important vessel structure used to store liquid medium. In earthquake disaster, the liquid storage tank will not only be seriously damaged directly, but also cause serious secondary disasters, such as fire, explosion, poisoning, nuclear radiation, etc. The peak liquid sloshing wave height is an important reference index to judge whether the seismic design of the liquid storage tank is reasonable or not. The ratio of peak ground acceleration to peak ground velocity of the earthquake records (shown by A/V ratio) can well represent the characteristics of frequency content of earthquake records. In this paper, the finite element numerical simulation method is used to analyze the seismic response of six rectangular concrete tanks with different liquid heights, and their respective peak liquid sloshing wave heights are calculated. Nine seismic records with different A/V ratios are used, which are low frequency category, medium frequenc...
Journal of Vibration Engineering & Technologies
Journal of Materials Research and Technology
Physics and Chemistry of the Earth, Parts A/B/C
IOP Conference Series: Earth and Environmental Science, 2021
In this study, numerical analysis was used to derive seismic fragility curves for 3-, 6- and 9-st... more In this study, numerical analysis was used to derive seismic fragility curves for 3-, 6- and 9-story reinforced concrete (RC) frame with inadequate lap splice length and ground soft-story condition. The structural models were subjected to 15 far-field natural earthquake records. The peak ground acceleration (PGA) of the selected records was scaled in the range of 0.05g to 0.50g with an increment of 0.05g. Incremental dynamic analysis was employed to determine their inter-story drift demand and capacities. The obtained results indicated that the probability of severe damage to the RC frames increased as the number of stories decreased. It was also observed that the RC frames with inadequate lap splice length exhibited significantly higher probability of collapse when compared with RC frames with adequate lap splice length.
Infill panels can increase seismic performance of reinforced concrete, RC frames if it is uniform... more Infill panels can increase seismic performance of reinforced concrete, RC frames if it is uniformly distributed in plan and along the height of the structures. This study investigates the effect of infill panels in seismic vulnerability of low-ductile RC frames which is commonly constructed in low-to-medium seismicity countries like Malaysia. This type of structures is seismically vulnerable since it has insufficient strength and ductility to resist earthquake loads. Fragility curves are used in this study to assess the vulnerability level of fully infilled RC frames under different intensity and characteristic of earthquake loads. RC frames with three, six, and nine stories designed for gravity and lateral loads based on the common practices in Malaysia were modeled and analyzed using incremental dynamic analysis (IDA). 45 earthquake records were used and divided into three groups based on their peak ground acceleration (PGA) to peak ground velocity (PGV) ratios. Three structural p...
Structures with multiple degrees of freedom (MDOF) such as high-rise buildings and multi-span bri... more Structures with multiple degrees of freedom (MDOF) such as high-rise buildings and multi-span bridges are susceptible to multiple modes of vibration other than that of the first major mode, as other higher modes can become more significant. Extensive research has been carried out for improving damping devices in vibrational control, but is lacking towards specifically controlling other such significant modes. This research proposes a modified Tuned Liquid Damper (TLD) for the viability of multiple vibrational mode control. The objective of this research is to design a damping device that combines the TLD and Tuned Mass Damper (TMD) into a single Hybrid Damper (HD), and observe its performance in reducing dynamic response of a structural system. Another objective is to compare the HD performance to the performance of a damped structural system with conventional TLD. Three HD structural systems were constructed, varying only with successive increase in TMD mass ratio to a decrease in ...
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Papers by Mohammadreza Vafaei