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- 저자 : Mati Ullah (검색결과 3 건)
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Mati Ullah Shah,Muhammad Usman,In-Ho Kim,Sania Dawood 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.5
Passive vibration control devices like tuned liquid column dampers (TLCD) not only significantly reduce buildings’ vibrations but also can serve as a water storage facility. The recently introduced modified form of TLCD known as tuned liquid column ball damper (TLCBD) suppressed external vibration efficiently compared to traditional TLCD. For excellent performance, the mass ratio of TLCBD should be in the range of 5% to 7%, which does not include the mass of the ball. This additional mass of the ball increases the overall structure mass. Therefore, in this paper, an effort is made to reduce the mass of TLCBD. For this purpose, a new modified version of TLCBD known as tuned liquid column hollow ball damper (TLCHBD) is proposed. The existing mathematical modeling of TLCBD is used for this new damper by updating the numerical values of the mass and mass moment of the ball. Analytically the optimal design parameters are obtained. Numerically the TLCHBD is investigated with a single degree of freedom structure under harmonic and seismic loadings. It is found that TLCHBD performance is similar to TLCBD in both loadings’ cases. To validate the numerical results, an experimental study is conducted. The mass of the ball of TLCHBD is reduced by 50% compared to the ball of TLCBD. Both the arrangements are studied with a multi-degree of freedom structure under harmonic and seismic loadings using a shake table. The results of the experimental study confirm the numerical findings. It is found that the performance behavior of both the dampers is almost similar under harmonic and seismic loadings. In short, the TLCHBD is lighter in weight than TLCBD but has a similar vibration suppression ability.
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Fathi Etaher Elbakoush,Qudrat Ullah Khan,Mati Ullah,Arif Ullah,Afaq Ullah Khan,Javed Khan,Asra Iftikhar 한국전기전자재료학회 2021 Transactions on Electrical and Electronic Material Vol.22 No.6
The carbonization performance of the iron-containing carbon film resulting from polyimide was examined, Polyimide/Fe composite films were prepared from Iron (III) 2,4-pentanedionate (Fe(acac)) and poly(amic acid) (PAA) based on ODA and PMDA via a solution process in DMAC, followed by carbonization the polyimide film at a temperature range of 600–1600 °C. The organized polyimide/Fe combined fi lms were characterized using a scanning electron microscope (SEM), and thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Raman. The formation of Fe particles and the synthesis of polyimide (PMDA/ODA) in the polyimide matrix is confirmed by FTIR results. Meantime, in the polyimide matrix, Fe particles were well spread which were showed by the SEM images. Kinetic parameters and thermal stability of the degradation methods for the organized polyimide/Fe combined films were examined in N 2 environment by TGA. The results have shown that the values of the calculated activation energies and thermal stability increased of the (Fe (acac)) the activation energy and loading also different with the weight-loss rate for all compositions.
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Muhammad Usman,Sania Dawood,Mati Ullah Shah,Muhammad Rizwan 국제구조공학회 2023 Smart Structures and Systems, An International Jou Vol.31 No.5
Base isolation is one of the most widely implemented and well-known technique to reduce structural vibration and damages during an earthquake. However, while the base-isolated structure reduces storey drift significantly, it also increases the base drifts causing many practical problems. This study proposes the use of Shape Memory Alloys (SMA) wires for the reduction in base drift while controlling the overall structure vibrations. A multi-degree-of-freedom (MDOF) structure along with base isolators and Shape-Memory-Alloys (SMA) wires in diagonal is tested experimentally and analytically. The isolation bearing considered in this study consists of laminates of steel and silicon rubber. The performance of the proposed structure is evaluated and studied under different loadings including harmonic loading and seismic excitation. To assess the seismic performance of the proposed structure, shake table tests are conducted on base-isolated MDOF frame structure incorporating SMA wires, which is subjected to incremental harmonic and historic seismic loadings. Root mean square acceleration, displacement and drift are analyzed and discussed in detail for each story. To better understand the structure response, the percentage reduction of displacement is also determined for each story. The result shows that the reduction in the response of the proposed structure is much better than conventional base-isolated structure.
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