Comparison Of Elastic Design And Performance Based Plastic .
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012Comparison of Elastic Design and Performance BasedPlastic Design Method Based on the Inelastic ResponseAnalysis using SAP2000Sejal P DalalS A VasanwalaA K DesaiAssistant ProfessorCivil Engineering DeptSVIT,Vasad,IndiaAssociate ProfessorApplies Mechanics DeptSVNIT,SuratAssociate ProfessorApplies Mechanics DeptSVNIT,SuratGujarat,IndiaABSTRACTPresented in this paper is the comparison of a steel momentresisting frame designed by the Performance based Plasticdesign method and conventional elastic design method basedon the seismic evaluation done by both nonlinear static (Pushover Analysis) and nonlinear dynamic analysis (Time historyanalysis) under different ground motions using the SAP2000software. The Performance based Plastic design is adisplacement based method which uses pre-selected targetdrift and yield mechanisms as design criteria whereas theelastic design method is based on the conventional forcebased limit state method. The nonlinear static pushoveranalysis shows formation of hinges in columns of the framedesigned using elastic design approach leading to collapse.Whereas in the Performance based Plastic design method,formation of hinges is seen in the beams and bottom of basecolumns. Although the ground motions caused largedisplacements in the Performance based Plastic design frameas it was seen from the acceleration and displacementresponses obtained from the nonlinear time history analysis,the structure did not lose stability. Study of hysteretic energydissipation results reveals that the Performance based Plasticdesign method is superior to the elastic design method interms of the optimum capacity utilization.KeywordsPerformance based Plastic Design, Nonlinear Static PushoverAnalysis, Nonlinear Time History Analysis, Inelasticresponse, SAP2000.1. INTRODUCTIONPerformance based Plastic design method is a rapidly growingdesign methodology based on the probable performance of thebuilding under different ground motions. The structuresdesigned by current codes undergo large inelasticdeformations during major earthquakes. The current seismicdesign approach is generally based on elastic analysis andaccounts for inelastic behavior in a somewhat indirectmanner. The inelastic activity, which may include severeyielding and buckling of structural members and connections,can be unevenly and widely distributed in the structure. Thismay result in a rather undesirable and unpredictable response,sometimes total collapse, or difficult and costly repair work atbest (Dalal ,[1]).It should be noted that in this design approach, the designerselects the target drifts consistent with acceptable ductility anddamage, and a yield mechanism for desirable response andease of post earthquake damage reparability. The method hasbeen successfully applied to a variety of common steelframing systems like Steel Moment Resisting Frame (Lee andGoel, [2]), buckling restrained braced frame, EccentricallyBraced Frame (Chao and Goel, [3]), concentric bracedframes(Chao and Goel , [4]) Special Truss Moment Frame(Chao and Goel , [5]), composite buckling restrained bracedframe (Dasgupta et al, [6]) and, more recently, to ReinforcedConcrete (RC) moment frames. Results of extensive inelasticstatic and dynamic analyses showed that the frames developeddesired strong column-sway mechanisms, and the storey driftsand ductility demands were well within the target values, thusmeeting the desired performance objectives. Comparisons ofresponses with corresponding baseline frames designed bycurrent practice have consistently shown superiority of theproposed methodology in terms of achieving the desiredbehavior.2. THE SEISMIC EVALUATION OFSTRUCTURES DESIGNED USING PBPDMETHODThe seismic evaluation of structures designed using the PBPDmethod can be done either by nonlinear static (Pushover)analysis or nonlinear dynamic (Time History) analysis. Itmust be emphasized that the pushover analysis is approximatein nature and is based on static loading. As such it cannotrepresent dynamic phenomena with a large degree ofaccuracy. It may not detect some important deformationmodes that may occur in a structure subjected to severeearthquakes, and it may exaggerate others. Inelastic dynamicresponse may differ significantly from predictions based oninvariant or adaptive static load patterns, particularly if highermode effects become important. Thus, performance ofpushover analysis primarily depends upon choice of materialmodels included in the study.The time history analysis is an actual dynamic analysis thatcan be done for both linear and nonlinear systems. It is foundthat this analysis incorporates the real time earthquake groundmotions and gives the true picture of the possible deformationand collapse mechanism in a structure. But, at the same time,it is a very tedious and complex analysis having a lot ofmathematical calculations. Although non-linear dynamicanalysis is generally considered to be the most accurate of theavailable analysis methods, it is cumbersome for design. Also,mathematically, nonlinear static analysis does not alwaysguarantee a unique solution. Small changes in properties orloading can cause large changes in nonlinear response. Andhence it is advisable to perform these sophisticated analyseson software. Today, various softwares are available for these1
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012complicated analyses to make our task easier and faster.SAP2000 (CSI, [8]) is one of the most sophisticated and userfriendly software which performs the non- linear static (PushOver) and non- linear Time history analysis in a very simpleway.3. NON-LINEAR STATIC ANALYSIS(PUSH OVER ANALYSIS)The static pushover analysis is becoming a popular tool forseismic performance evaluation of existing and newstructures. The expectation is that the pushover analysis willprovide adequate information on seismic demands imposed bythe design ground motion on the structural system and itscomponents. A pushover analysis is performed by subjectinga structure to a monotonically increasing pattern of lateralforces, representing the inertial forces which would beexperienced by the structure when subjected to groundshacking. Under incrementally increasing loads variousstructural elements yield sequentially. Consequently, at eachevent, the structure experiences a loss in stiffness. Using apushover analysis, a characteristic nonlinear forcedisplacement relationship can be determined. Typically thefirst pushover load case is used to apply gravity load and thensubsequent lateral pushover load cases are specified to startfrom the final conditions of the gravity.4. INELASTIC NON-LINEARHISTORY ANALYSISUniversities For Research In Earthquake Engineering(CUREE) Steel Moment Frame (also known as SAC steelmoment frame) using SAP2000 is presented in this section.The frame was designed by the PBPD method its responsesunder static pushover and dynamic time-history analyses dueto selected set of ground motions were studied. The framingplan of the structure is shown in Figure 1. Since the originalSAC frame was designed according to the Uniform BuildingCode (UBC) (1994), same loading and other designparameters were used for the redesigning of the frame byPBPD method. The storey heights are 18 ft for the first storeyand 13 ft for all others.According to the UBC (1994), the elastic design spectralacceleration, Sa ZIC, where Z is the seismic zone factor, I isthe occupancy importance factor and C is the seismiccoefficient.With S 1·2 for S2 soil type, Z 0·4, I 1·0 and estimated T 2·299 s, C 0.9 , the value of Sa turned out to be equal to0·36.The design base shear was determined for a 2% maximumstorey drift ratio (θu) for ground motion hazard with a 10%probability of exceedance in 50 years (10/50 or 2/3 maximumconsidered earthquake (MCE)); A yield drift ratio (θy) of1·0% was used, which is typical for steel moment frames. Thecalculated values of significant design parameters are listed inTable 1.TIMENon-linear structural analysis is becoming more important inearthquake resistant design, particularly with the developmentof performance based earthquake engineering, which requiresmore information about the drifts, displacements and inelasticdeformations of a structure than traditional design procedures.Inelastic time history analysis is dynamic analysis, whichconsiders material nonlinearity of a structure. Considering theefficiency of the analysis, nonlinear elements are used torepresent important parts of the structure, and the remainder isassumed to behave elastically. Nonlinear elements are largelyclassified into Element Type and Force Type.The Element Type directly considers nonlinear properties bychanging the element stiffness. SAP2000 programs use theNewton-Raphson iteration method for nonlinear elements ofthe Element Type to arrive at convergence. Direct integrationmust be used for inelastic time history analysis of a structure,which contains nonlinear elements of the Element Type.The Force Type indirectly considers nonlinear properties byreplacing the nodal member forces with loads withoutchanging the element stiffness. For nonlinear elements of theForce Type, convergence is induced through repeatedlychanging the loads. If a structure contains nonlinear elementsof the Force Type only, much faster analysis can beperformed through modal superposition. Iterative analysis bythe Newton-Raphson method is carried out in each time stepin the process of obtaining the displacement increment untilthe unbalanced force between the member force and externalforce is diminished.The unbalanced force is resulted from the change of stiffnessin nonlinear elements of the Element Type and the change ofmember forces in nonlinear elements of the Force Type. Theanalysis of a 20 storied steel moment resisting frame is doneusing both the methods discussed above and is described inthe next section.Moment frames are very common for steel as well as RCbuilding structures. The Seismic Evaluation of a 20-StoreyStructural Engineers Association Of California (SEAOC), TheApplied Technology Council (ATC), And Consortium Of2
5 Bays at 20’ eachInternational Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012N6 Bays at 20’ eachFig. 1 : Plan and Elevation of the steel moment resisting frame3
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012Table 1 : The design parameters of the Steel MomentResisting FrameMaterialsStructural steel withfy 50 ksiFloor Seismic Weight for Roof645 kipsFloor Seismic Weight for Floor2Floor Seismic Weight for Floor3-20Seismic zone factor, Z622 kipsImportance factor, ISpectral Acceleration SaTime Period Tperformed on this 20 storied frame by assigning the hinges at6 inches from the column face as shown in figure 2a.608 kips0.410.36 g2.99 secYield drift ratio θy1%Target drift ratio θu2%Inelastic drift ratio θp θu- θy1%Ductility factor μs θu/ θy2.0Reduction Factor due toDuctility RμEnergy Modification Factor γ2.00.75Total Seismic Load W12191 kipsDesign Base shear Vy1146 kipsVy/W0.094Α0.942(a)Nonlinear static (pushover) and dynamic (time-history)analyses were carried out for the steel moment resisting framedesigned by both elastic design approach as well as PBPDmethod by using SAP2000 software. The analysis results areshown in the next section.5. INELASTIC RESPONSE ANALYSISOF THE STEEL MOMENT RESISTINGFRAME DESIGNED USING ELASTICDESIGN APPROACHThe steel moment resisting frame was first designed by theelastic design approach pertaining to the current UBC94 codesusing the SAP2000 software. The frame was then analyzed bythe nonlinear static Pushover analysis in SAP2000. Innonlinear static pushover analysis, the entire frame is carriedout up to the target drift by using design lateral forcedistribution. Nonlinear static push over analysis wasThe failure mechanism of this frame obtained by SAP2000 isshown in figure 2b. The results show formation of plastichinges in some columns of floors which may result into totalcollapse of the entire frame. The nonlinear Time historyanalysis of the frame when subjected to six different ground(b)Fig. 2 : (a) Hinges assigned in beams for applying the staticPushover Force. (b) Formation of Plastic hinges in theframe designed using elastic design approach.motions (Santa Monica, Petrolia, Lacco North 90 degrees ,Lacco North 0 degrees , Corralotos, and Altedena Earthquakeground motions as shown in figure 3) was also carried outusing the software. The acceleration and displacementresponse of this frame to these ground motions is shown in4
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012figures 4 and 5 and the hysteretic Energy dissipation curvesare shown in figure 6. It could be seen in the acceleration anddisplacement responses of this frame that the peak values areobtained in synchronization with the ground motion. Thehysteretic energy loops show that the structure remains in theelastic zone and fails before fully utilizing the capacity lyingin the inelastic zone. The reason is that the columns fail firstleading to the premature collapse of the structure as observedfrom the push over analysis.Fig. 3: The Santa Monica, Petrolia, Lacco N 90, Lacco N 0,Corralotos and Altedena Ground Motions5
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012Fig. 4: The acceleration response of the frame designed using elastic design approach when subjected to different groundmotions.6
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012Fig. 5: The displacement response of the frame designed using elastic design approach when subjected to different groundmotions.7
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012Fig. 6: The hysteretic energy dissipation of the frame designed using elastic design approach when subjected to differentground motions.8
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 20126. INELASTIC RESPONSE ANALYSISOF THE STEEL MOMENT DESIGN APPROACHIn order to achieve the main goal of performance based designi.e. a desirable and predictable structural response, it isnecessary to account for inelastic behavior of structuresdirectly in the design process. Figure 7 shows the target andyield mechanism chosen for the frame while designing itusing the performance based plastic design method. Thehinges are to be formed at the bottom of the base column andin beams only. The beams are modeled to behaveinelastically, while the columns are modeled (or „forced‟) tobehave elastically. P-Delta effect is captured by applying thefloor gravity loads on „gravity columns‟ (columns not part ofthe lateral force resisting frame), which can be lumped intoone.Fig. 7 : Target Yield mechanism for moment framedesigned using PBPD approach.Source: Goel et al [2]Unlike the force distribution in the current codes, the designlateral force distribution used in the PBPD method is based onmaximum story shears as observed in nonlinear Time historyanalysis results (Chao,2007). The design lateral force andshear distribution in the PBPD method are calculated fromequationsVi story shear force at level iVn story shear force at roof level ( nth level)wj seismic weight at level jhj height of level j from basewn seismic weight at the top levelhj height of roof level from baseT fundamental time periodThis formula of force distribution has been found suitable forMoment Frames, Eccentrically Braced Frames, ConcentricallyBraced Frames and Special Truss Moment Frames.(Chao,[8]).The current design codes obtain these lateral forces on theassumption that the structure behaves elastically and primarilyin the first mode of Vibration. However, building structuresdesigned according to these procedures undergo largedeformation in the inelastic range when subjected to majorearthquakes. The steel frame under this study was designedusing this lateral force distribution for the PBPD method andthen nonlinear static and time history analyses was carriedout. In nonlinear static pushover analysis, the entire frame iscarried out up to the target drift by using design lateral forcedistribution and thus the failure caused is shown in figure 8.Fig. 8: Formation of Plastic hinges in the frame designedusing PBPD approach.It could be clearly seen in figure 8 that hinges are formed inbeams only and the bottom of base columns which convertsthe whole structure into a mechanism and avoids the totalcollapse.andWhereβi Shear distribution factor at level iThe nonlinear time history analysis of the PBPD frame showsa considerable increase in the acceleration and displacementresponses as shown in figure 9 and 10 as compared to theframe designed using elastic design approach which leads to ahigher hysteretic energy dissipation. The increased hystereticenergy dissipation of the frame indicates that the structureutilizes its capacity lying in the inelastic zone. The reason is9
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012that the PBPD method is based on the “strong column weakbeam” concept and the beams fail first. As the structure turnsinto a mechanism due to formation in hinges in beams (2 ineach beam) and bottom of the base columns, it undergoeslarge deformation before failure.Fig. 9: The acceleration response of the frame designed using PBPD approach when subjected to different ground motions.10
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012Fig. 10: The displacement response of the frame designed using PBPD approach when subjected to different ground motions.11
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012Fig. 11: The hysteretic energy dissipation of the frame designed using PBPD approach when subjected to different groundmotions.7. RESULTS AND CONCLUSIONInelastic static and dynamic analyses of the steel frame whendesigned using elastic design methodology and performancebased plastic design methodology were carried out for sixdifferent ground motions using SAP2000 software. Theresults showed very good behavior of the PBPD frame understatic pushover loads. No unexpected plastic hinging wasobserved in the columns of the PBPD frame. The hinges are12
International Journal of Computer Applications (0975 – 8887)Volume 45– No.9, May 2012formed in beams only and the bottom of base columns whichconverts the whole structure into a mechanism and avoids thetotal collapse. Although these ground motions caused largedisplacements in the PBPD frame, the structure did not losestability. Also, the increased hysteretic energy dissipation ofthe frame indicates that the structure utilizes its capacity lyingin the inelastic zone. It can be thus concluded that the PBPDmethod is superior to the elastic design method in terms of theoptimum capacity utilization.Figure 10List of Abbreviations[1]Dalal S P , Vasanwala S V , Desai A K :2011 :“Performance based seismic design of Structures: AReview” International Journal Of Civil and structuralEngineering ISSN No. 0976-4399 Volume 1 No. 4 –2011 pp 795-803.[2]Lee SS, Goel SC. 2001. “Performance-Based design ofsteel moment frames using target drift and yieldmechanism.” Research Report no. UMCEE 01-17, Dept.of Civil and Environmental Engineering, University ofMichigan, Ann Arbor, MI.[3]Chao SH, Goel SC. 2006a. Performance-based designof eccentrically braced frames using target drift and yieldmechanism. AISC Engineering Journal Third quarter:173–200.[4]Chao SH, Goel SC. 2006b. A seismic design method forsteel concentric braced frames (CBF) for enhancedperformance. In Proceedings of Fourth InternationalConference on Earthquake Engineering, Taipei, Taiwan,12–13 October, Paper No. 227[5]Chao SH, Goel SC. 2008. Performance-based plasticdesign of seismic resistant special truss moment frames.AISC Engineering Journal Second quarter: 127–150.[6]Dasgupta P, Goel SC, Parra-Montesinos G. 2004.Performance-based seismic design and behavior of acomposite buckling restrained braced frame (BRBF). InProceedings of Thirteenth World Conference onEarthquakeEngineering, Vancouver, Canada, 1–6 August2004, Paper No. 497.[7]Computer and Structures (2000). SAP2000 NonlinearVersion 8, Berkeley, USA.[8]Chao SH, Goel SC, Lee S-S. 2007. A seismic designlateral force distribution based on inelastic state ofstructures.Earthquake Spectra 23: 3, 547–569.FEMAPBPDSEAOCUBCFederal Emergency Management AgencyPerformance Based Plastic DesignStructural Engineers Association of CaliforniaUniform Building CodeFigure 118.REFERENCESList of FiguresFigure 1Figure 2(a)Figure 2(b)Figure 3Figure 4Figure 5Figure 6Figure 7Figure 8Figure 9Plan and Elevation of the steel momentresisting frame.Hinges assigned in beams for applying thestatic Pushover Force.Formation of Plastic hinges in the framedesigned using elastic design approach.The Santa Monica, Petrolia, Lacco N 90,Lacco N 0,Corralotos and AltedenaGround MotionsThe acceleration response of the framedesigned using elastic design approachwhen subjected to different groundmotions.The displacement response of the framedesigned using elastic design approachwhen subjected to different groundmotions.The hysteretic energy dissipation of theframe designed using elastic designapproach when subjected to differentground motions.Target Yield mechanism for momentframe designed using PBPD approach.Formation of Plastic hinges in the framedesigned using PBPD approach.The acceleration response of the framedesigned using PBPD approach whensubjected to different ground motions.The displacement response of the framedesigned using PBPD approach whensubjected to different ground motions.The hysteretic energy dissipation of theframe designed using PBPD approachwhen subjected to different groundmotions.13
Pushover Force. (b) Formation of Plastic hinges in the frame designed using elastic design approach. The failure mechanism of this frame obtained by SAP2000 is shown in figure 2b. The results show formation of plastic hinges in some columns of floors which may result into total collapse of the entire frame. The nonlinear Time history
Magic Quadrant Vendor Strengths and Cautions Elastic Elastic is a Niche Pla yer in this Magic Quadrant. Elastic is based in Mountain View, California, U.S., the Netherlands and Singapor e. It has customers worldwide. Its SIEM platform is Elastic Security, which offers endpoint security, following Elastic 's acquisition of Endgame in 2019. Its .
Elastic stack best practices . Kibana best practices Q&A *What's not included: architecture design. Fair warning: We're going to move FAST! Introduction to Elastic. 3k employees in 40 countries Public company on NYSE. Elastic is a search company. . SaaS Managed Self-Managed Orchestrated Self-Managed Downloadable. Speed Scale Relevance
Figure 1. Oracle Exalogic Elastic Cloud consists of hardware and software engineered together. Oracle Exalogic Elastic Cloud Hardware Exalogic hardware is pre-assembled and delivered in standard 19‖ 42U rack configurations. Each Exalogic configuration is a unit of elastic cloud capacity balanced for compute-intensive workloads.
Made of titanium 2 elastic nails six areas of contact meant to provide constant pressure and stabilization for . No rotational fixation Diameter of elastic nails 2.5 - 4 mm[5] Titanium/Stainless Steel Elastic Nail System. For elastic stable intramedullary nailing (ESIN). Technique Guide 0X6.000.207_AB 07.04.10 13:01 Seite Cvr1 .
Apr 16, 2021 · ANSYS ANSYS Chemkin-Pro 2019 R3 2019 R2 2019 R1 19.2 19.1 19.0 ANSYS Elastic Units, BYOL ANSYS ANSYS Discovery Live (Floating License) 2020 R1 19.2 ANSYS Elastic Units, BYOL ANSYS ANSYS EnSight 10.2.3 ANSYS Elastic Units, BYOL ANSYS ANSYS EnSight GUI 10.2.7a, 10.2 ANSYS Elastic Units, BYOL A
Nomenclature Symbol Description C p specific heat D width of deposit DEP elastic-plastic stiffness matrix DE elastic stiffness matrix d secondary dendrite arm spacing de total strain increment deE elastic strain increment deP plastic strain increment deTh thermal strain increment deV volumetric strain increment E elastic modulus E v volumetric heat input f distribution factor
Twilio Elastic SIP Trunking FreePBX Configuration Guide, Version 1.0.1, 6.12.2018 1 Twilio Elastic SIP Trunking - FreePBXâ Configuration Guide This configuration guide is intended to help you provision your Twilio Elastic SIP Trunk to communicate with FreePBX, an open source communication server.
Elastic Wave Class Note 1, ECE471, U. of Illinois W. C. Chew Fall, 1991 Derivation of the Elastic Wave Equation (optional read-ing) The elastic eave equation governs the propagation of the waves in solids. We shall illustrate its derivation as follows: the waves in a solid cause perturbation of the particles in the solid.
