• Title/Summary/Keyword: P-frames

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Iterative-R: A reliability-based calibration framework of response modification factor for steel frames

  • Soleimani-Babakamali, Mohammad Hesam;Nasrollahzadeh, Kourosh;Moghadam, Amin
    • Steel and Composite Structures
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    • v.42 no.1
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    • pp.59-74
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    • 2022
  • This study introduces a general reliability-based, performance-based design framework to design frames regarding their uncertainties and user-defined design goals. The Iterative-R method extracted from the main framework can designate a proper R (i.e., response modification factor) satisfying the design goal regarding target reliability index and pre-defined probability of collapse. The proposed methodology is based on FEMA P-695 and can be used for all systems that FEMA P-695 applies. To exemplify the method, multiple three-dimensional, four-story steel special moment-resisting frames are considered. Closed-form relationships are fitted between frames' responses and the modeling parameters. Those fits are used to construct limit state functions to apply reliability analysis methods for design safety assessment and the selection of proper R. The frameworks' unique feature is to consider arbitrarily defined probability density functions of frames' modeling parameters with an insignificant analysis burden. This characteristic enables the alteration in those parameters' distributions to meet the design goal. Furthermore, with sensitivity analysis, the most impactful parameters are identifiable for possible improvements to meet the design goal. In the studied examples, it is revealed that a proper R for frames with different levels of uncertainties could be significantly different from suggested values in design codes, alarming the importance of considering the stochastic behavior of elements' nonlinear behavior.

Encryption Scheme for MPEG-4 Media Transmission Exploiting Frame Dropping

  • Shin, Dong-Kyoo;Shin, Dong-Il;Shin, Jae-Wan;Kim, Soo-Han;Kim, Seung-Dong
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.4 no.5
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    • pp.925-938
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    • 2010
  • Depending on network conditions, a communication network could be overloaded when media are transmitted. Research has been carried out to lessen network overloading, such as by filtering, load distribution, frame dropping, and other methods. Among these methods, one of the most effective is frame dropping, which reduces specified video frames for bandwidth diminution. In frame dropping, B-frames are dropped and then I- and P-frames are dropped, based on the dependency among the frames. This paper proposes a scheme for protecting copyrights by encryption, when frame dropping is applied to reduce the bandwidth of media based on the MPEG-4 file format. We designed two kinds of frame dropping: the first stores and then sends the dropped files and the other drops frames in real time when transmitting. We designed three kinds of encryption methods using the DES algorithm to encrypt MPEG-4 data: macro block encryption in I-VOP, macro block and motion vector encryption in P-VOP, and macro block and motion vector encryption in I-, P-VOP. Based on these three methods, we implemented a digital rights management solution for MPEG-4 data streaming. We compared the results of dropping, encryption, decryption, and the quality of the video sequences to select an optimal method, and found that there was no noticeable difference between the video sequences recovered after frame dropping and the ones recovered without frame dropping. The best performance in the encryption and decryption of frames was obtained when we applied the macro block and motion vector encryption in I-, P-VOP.

Adaptive Video Watermarking using the Bitrate and the Motion Vector (비트율과 움직임 벡터를 이용한 적응적 동영상 워터마킹)

  • Ahn, I.Y.
    • 전자공학회논문지 IE
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    • v.43 no.4
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    • pp.37-42
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    • 2006
  • This paper proposes a adaptive video watermarking algorithm according to bitrate and motion vector size in MPEG2 system. The watermark strength in the I-frames is adapted for quantization step size and the strength in the P-B-frames is adapted for quantization step size and motion vector of macroblock to make the watermark more robust against the accompanying degradation due to aggressively compression. A realtime watermark extraction is done directly in the DCT domain during MPEG decoding without full decoding of MPEG video. The experimental simulations show that the video quality results almost invisible difference between the watermarked frames and the original frames and the watermark is resistant to frame dropping, MPEG compression, GoP conversion and low pass filter attacks.

Response modification and seismic design factors of RCS moment frames based on the FEMA P695 methodology

  • Mohammad H. Habashizadeh;Nima Talebian;Dane Miller;Martin Skitmore;Hassan Karampour
    • Steel and Composite Structures
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    • v.49 no.1
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    • pp.47-64
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    • 2023
  • Due to their efficient use of materials, hybrid reinforced concrete-steel (RCS) systems provide more practical and economic advantages than traditional steel and concrete moment frames. This study evaluated the seismic design factors and response modification factor 'R' of RCS composite moment frames composed of reinforced concrete (RC) columns and steel (S) beams. The current International Building Code (IBC) and ASCE/SEI 7-05 classify RCS systems as special moment frames and provide an R factor of 8 for these systems. In this study, seismic design parameters were initially quantified for this structural system using an R factor of 8 based on the global methodology provided in FEMA P695. For analyses, multi-story (3, 5, 10, and 15) and multi-span (3 and 5) archetypes were used to conduct nonlinear static pushover analysis and incremental dynamic analysis (IDA) under near-field and far-field ground motions. The analyses were performed using the OpenSees software. The procedure was reiterated with a larger R factor of 9. Results of the performance evaluation of the investigated archetypes demonstrated that an R factor of 9 achieved the safety margin against collapse outlined by FEMA P695 and can be used for the design of RCS systems.

Nonlinear P-Δ analysis of steel frames with semi-rigid connections

  • Valipour, Hamid R.;Bradford, Mark A.
    • Steel and Composite Structures
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    • v.14 no.1
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    • pp.1-20
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    • 2013
  • This paper presents the formulation for a novel force-based 1-D compound-element that captures both material and second order P-${\Delta}$ nonlinearities in steel frames. At the nodal points, the element is attached to nonlinear rotational and a translational springs which represent the flexural and axial stiffness of the connections respectively. By decomposing the total strain in the material as well as the generalised displacements of the flexible connections to their elastic and inelastic components, a secant solution strategy based on a direct iterative scheme is introduced and the corresponding solution strategy is outlined. The strain and slope of the deformed element are assumed to be small; however the equilibrium equations are satisfied for the deformed element taking account of P-${\Delta}$ effects. The formulation accuracy and efficiency is verified by some numerical examples on the nonlinear static, cyclic and dynamic analysis of steel frames.

Effect of Tourmaline-added Eyeglass Frames on Normalization of Intraocular Pressure (토르말린이 첨가된 안경테가 안압 정상화에 미치는 영향)

  • Park, Sang-Chul;Jeong, Hye-Ri;Kwon, Jong-Moon;Lee, Gyu-Bin
    • The Korean Journal of Vision Science
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    • v.20 no.4
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    • pp.461-468
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    • 2018
  • Purpose : Tourmaline, a natural ore material, was applied to the entire eyeglasses to observe changes in intraocular pressure (IOP), one of the factors related to human ocular metabolism. Methods : After making eyeglass frames by mixing TR-90, which is the main material of eyeglass frames and 7wt% of tourmaline, The changes of intraocular pressure before and after wearing of tourmaline spectacle frames were divided into low, middle and high groups according to the intraocular pressure in 90 normal subjects (46 men and 44 women) in their 20s. Results : Total intraocular pressure was a significantly decreased to -4.14% (p<0.000) in the right eye after wearing tourmaline frames, and significantly decreased to -6.39 % (p<0.000) and -4.64 % (p<0.017) in the High and Middle groups, respectively. Total intraocular pressure was a significantly decreased to -2.74 % (p<0.004) in the left eye, and -4.58 % (p<0.000) in the High group only showed statically significant value. Conclusion : In this study, the spectacle frame containing 7wt% tourmaline was used and it was confirmed that the intraocular pressure was significantly decreased after wearing the spectacle frame, and it became close to the average value of the normal intraocular pressure range. The results of this study showed that tourmaline, which has the effect of promoting the metabolism and blood circulation of the body, has an effect on the normalization of the intraocular pressure by attaching it to the spectacle frame.

The Experimental Studu on the P-Δ Influence of Weak Beam Unbraced Frames (보항복형 비가새 골조의 PΔ 영향에 관한 실험적 연구)

  • Kim, Hee Dong;Park, Sang Chul;Lee, Myung Jae
    • Journal of Korean Society of Steel Construction
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    • v.13 no.4
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    • pp.363-372
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    • 2001
  • The objective of this study is to evaluate the $P-{\Delta}$ effect in the case of weak beam unbraced frames by experimental approach. To evaluate $P-{\Delta}$ effect, four specimens were tested under monotonic loading condition. The parameters of tests are the stiffness of column and the axial load ratio. The results show that the value of axial load affects frame stability because $P-{\Delta}$ effects promote the yielding of beam. The maximum lateral load increases in proportion to the increment of column stiffness and rotational stiffness of supports, The collapse mechanism of weak beam unbraced frames is stably formed in the condition of low axial load ratio. The $B_2$ factor of limit state design code does not properly consider the $P-{\Delta}$ effect in inelastic region.

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Stability and P-Δ Analysis of Generalized Frames with Movable Semi-Rigid Joints (일반화된 부분강절을 갖는 뼈대구조물의 안정성 및 P-Δ 해석)

  • Min, Byoung Cheol
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.2
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    • pp.409-422
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    • 2013
  • For stability design and P-${\Delta}$ analysis of steel frames with semi-rigid connections, the explicit form of the exact tangential stiffness matrix of a generalized semi-rigid frame element having rotational and translational connections is firstly derived using the stability functions. And its elastic and geometric stiffness matrix is consistently obtained by Taylor series expansion. Next depending on connection types of semi-rigidity, the corresponding tangential stiffness matrices are degenerated based on penalty method and static condensation technique. And then numerical procedures for determination of effective buckling lengths of generalized semi-rigid frames members and P-${\Delta}$ and shortly addressed. Finally three numerical examples are presented to demonstrate the validity and accuracy of the proposed method. Particularly the minimum braced frames and coupled buckling modes of the corresponding frames are investigated.

Stability of Steel Frames with Weak Column-Strong Beam Considering P-Δ effect (P-Δ 효과를 고려한 기둥항복형 강구조 골조의 안정성)

  • Kim, Hee Dong;Lee, Myung Jae
    • Journal of Korean Society of Steel Construction
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    • v.15 no.4 s.65
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    • pp.457-466
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    • 2003
  • This study aimed to evaluate the stability of steel frames with weak column-strong beam and consider P-effect using the experimental approach. Towards this end, three specimens were tested under monotonic loading condition. Parameters of tests includes the stiffness of the column and the axial load ratio. Result showed that reduction in column stiffness promoted P- effect, which considerably influenced the frame's stability.

A Study on the Flexibility of Semi-Rigid Steel Frames under Lateral Loadings( II ) (횡하중을 받는 반강접 철골 골조의 유연도에 관한 연구( II ) -골조 해석모형을 중심으로-)

  • Kang, Cheol Kyu;Han, Young Cheol;Lee, Gab Jo
    • Journal of Korean Society of Steel Construction
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    • v.8 no.4 s.29
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    • pp.121-131
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    • 1996
  • Semi-rigid frames are frames for whcih the connections joining the beam and column are neither fully rigid nor perfectly pinned. In reality, all steel frames are semi-rigid in nature as all connections exhibit a certain degree of flexibility under loads. For semi-rigid frmaed structures, it is tended to reduce more rigidity of the member for the nonlinear behavior of connections and the P-delta effects of framed structure. To predict the actual behavior of semi-rigid steel frames, a more realistic analysis methods which explicitly takes into account the effect of connection flexibility should be used. In this research, the effect of connection flexibility in the semi-rigid structure has been investigated. To predict the response of flexibility connected frames, the algorithm of semi-rigid steel frame is developed using connection model having nonlinear spring on end of beam.

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