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Proc. of Sixth International Conference On Advances in Civil, Structural and Mechanical Engineering -ACSM 2017Copyright Institute of Research Engineers and Doctors, USA .All rights reserved.ISBN: 978-1-63248-118-4 doi: 10.15224/ 978-1-63248-118-4-62Comparative Analysis on Seismic Provisions of the National Structural Codesof the Philippines (NSCP) 1992 and 2010as Applied to the Design of Reinforced Concrete Public School Building1Resurreccion Villa Garrote2Rizalyn C. Ilumin1Dean-College of Engineering and ArchitecturePangasinan State University, Urdaneta CityPangasinan, Philippinesthe Three- Storey Reinforced Concrete School Buildinghave resulted higher values of Design Base Shear V than inNSCP 1992 thus it implied that NSCP 2010 were moreconservative and cautious in terms of the safety andstructural integrity of the school building during seismicevents. The higher values of elastic response parametersand the larger sizes of structural elements and higherreinforcement index in NSCP 2010 enhance the structuralsafety of the Three-Storey Reinforced Concrete SchoolBuilding against severe earthquake , and its structural safetywere given due consideration under the seismic provisions ofNSCP 2010 wherein it should not collapse but with minimalnon-structural damage only during a severe earthquakewhile NSCP 1992 provide more emphasis on the economicaspect of design but with greater possibility of structuraldamage and even collapse during the occurrence of thesame earthquake.2Faculty-Department of Civil EngineeringPangasinan State University, Urdaneta CityPangasinan, PhilippinesAbstract—The main target of this research work isto show the differences of the National Structural Codes ofthe Philippines (NSCP) Seismic provisions of the 2 codes-NSCP 1992 and the new one, NSCP 2010. In order to workout for the main differences of the Design Base Shear (V),the Linear Static Analysis (LSA), which is considered as theStatic Lateral Force Procedure and the Response SpectrumAnalysis (RSA), another method specified in the NSCPcodes under the Dynamic Lateral Force Procedure werecarried out to analyze a Three Storey Reinforced ConcretePublic School Building. In the Dynamic Analysis, themaximum ground motion intensity, such as the peak groundacceleration (Amax) of the earthquake is considered.The outcome of this research work is anindispensable tool for Structural Designers who will assessthe seismic hazard of existing buildings designed under theNSCP 1992 in terms of their structural integrity. While thestructural designers’ liability is not limited to design flaws, itis their utmost concern to determine if there are deficienciesin their Seismic design criteria based from the NationalStructural Code of the Philippines. It is hoped that thisresearch work will guide the Structural Designer inrecommending structural strengthening and retrofitting ofexisting buildings which were designed under NSCP1992.This is to enhance structural integrity of buildingsthus, life threatening seismic hazard not only in SchoolBuildings but all existing buildings as well can be minimizedif not eliminated. The major findings of the research studyare the effects of the Seismic Provisions of NSCP 2010 onthe value of Design Base Shear which is greater than theeffects of NSCP 1992 Seismic Provisions, the ElasticResponse Parameters of Structural elements have resultedhigher values in NSCP 2010 than in NSCP 1992 SeismicProvisions and eventually resulted to bigger sections andhigher reinforcement index of structural elements in NSCP2010 than in NSCP 1992.In the light of these findings and conclusions ofthis research, the NSCP 2010 seismic provisions imposed onKeywords—BaseSpectrum, SeismicShear,Elastic,ResponseINTRODUCTIONThe Philippines is located within the PacificRing of Fire and belongs to the most earthquake proneregion in the world making it to be very vulnerable toseismic hazards. The poor performance of concretebuildings has been demonstrated dramatically in theJuly 1990 Luzon earthquake especially in the cities ofBaguio and Dagupan. These two (2) cities suffered themost devastation and many seismic hazards likecollapsed buildings and bridges, landslide andliquefaction were observed. With these devastations, theloss of life & limb and loss to properties attributed tothe collapse of structures specially buildings, theAssociation of Structural Engineers of the Philippinesreassessed and revised the National Structural Code ofthe Philippines (NSCP) 1987 3rd edition which is theexisting design code before the occurrence of the 1990Luzon earthquake. Thus, after 2 years, the NSCP 19924th edition were published.The July 1990 Luzon earthquake exacted aheavy toll in the human, economic, and social resources62

Proc. of Sixth International Conference On Advances in Civil, Structural and Mechanical Engineering -ACSM 2017Copyright Institute of Research Engineers and Doctors, USA .All rights reserved.ISBN: 978-1-63248-118-4 doi: 10.15224/ 978-1-63248-118-4-62of the Philippines at a time when she was struggling foreconomic development (F. Yamazaki, et. al p.6031). Bythen, there were periodic revisions of the NSCPespecially on its Seismic provisions, the NSCP 1992,NSCP 2001, and the most recent is the NSCP 2010.According to A. Oreta (2006),”Although our presentstructural design codes may have incorporated specialprovisions for the earthquake resistant design of newbuildings, there is still a danger of possible collapse orlife threatening damage in existing buildings speciallythe old ones” (p.186-187).Hospital and school buildingswhich were considered essential structures under thesaid codes, needed urgent evaluations on their expectedperformance against major earthquake. This is to avertmore devastations and loss of life and properties. Pastseismic hazard studies for the Philippines, based onhistorical earthquakes, were made by Molas &Yamazaki (1994). Torregosa et al. (2001) used bothhistorical earthquakes and active faults as basis forseismic hazard assessment in the Philippines, but nopublished report yet regarding the assessment of thedifferent NSCP codes seismic provisions. Goel andChopra (1991) have their Evaluation of the US SeismicProvisions for Asymmetric-Plan Systems. With thatstudy, it is the intent of US seismic codes that buildingssuffer no damage during some usually unspecified levelof moderate ground shaking. The reduction factorR 1.0 implies that the design base shear V of thecorresponding symmetric-plan system is just sufficientfor it to remain elastic during excitation. A parallelresearch work were done by Luca Ongaro (May, 2007)in her dissertation entitled “Comparing Italian SeismicCodes for Design of RC frame buildings. “The resultsof her study, comparing D.M. 16.01.1996-NormeTechniche per le Costruzioni in Zone Sismichi andOPCM 20.03.2003-Ordinanza del Presidente delConsiglio del Ministri—the DM code, advises orpartially applies the seismic concepts, but it does notforce the designer to understand the importance of theseperformance requirements. On the other hand, thedesign guidelines in OPCM code force the designer toaccount for good structural performance in order toproduce structures which are feasible from economicalpoint of view.” (Ongaro, 2007 p.144)the Design of Three-storey Reinforced Concrete PublicSchool Building.The main concern of the structural designer isto design buildings or any structure that will becomeearthquake resistant in seismically active areas based onexisting codes. Different design codes have beenexplored and prepared in our society’s quest to producestructures that will be safe during an earthquake. Thestructural analysis and design procedure can beorganized according to their basis as generally relatingto forces, moments and displacements which werereferred to under the NSCP codes as Elastic ResponseParameters (ERP) of the structures.The new Structural Code which is the NSCP2010, with emphasis on the seismic design provisionsset a more realistic value of Design Base Shear (V)which is the total lateral force or shear at the base of thestructure. The Design Seismic Force as provided for inthe two codes is the minimum total strength design baseshear (V). The new code integrated additionalparameters to be used in determining such function asthe design base shear.This function is considered to be the mostcritical in Seismic Analysis and Design. Under the newcode, upper and lower limits of V were considered,while it was not considered under the provisions ofNSCP 1992. This code adopted the Uniform BuildingCode (UBC) 1988 in which case the V is to bedetermined by only one empirical formula while inNSCP 2010, the same V will be determined by four (4)empirical formula in Seismic Zone 4 and threeempirical formula in Seismic Zone 2. This new codeadopted its seismic provisions from UBC 1997 wheremaximum moment magnitude (M) of an earthquakewas considered while in NSCP 1992, the said provisionwas not considered. The parameters that were givendue consideration in NSCP 1992 were limited toseismic zone, importance factor of the structure,numerical coefficient of building frame system, sitecoefficient for soil characteristics and fundamentalperiod of vibration of structure. Although, in the NSCP2010, the aforementioned parameters were alsoconsidered, but there are additional factors that weretaken into account, like seismic coefficients, Ca & Cv,near source factors, Na & Nv and moment magnitudeM.The main target of this research work is toshow the differences on the seismic design provisionsof the National Structural Codes of the Philippines byproposing a comparative analysis of the 2 codes, theNSCP 1992 and the new one, NSCP 2010 as applied to63

Proc. of Sixth International Conference On Advances in Civil, Structural and Mechanical Engineering -ACSM 2017Copyright Institute of Research Engineers and Doctors, USA .All rights reserved.ISBN: 978-1-63248-118-4 doi: 10.15224/ 978-1-63248-118-4-62were used to determine the values of the ElasticResponse Parameters (ERP) as well as the requiredcross sections and reinforcements of the most criticalstructural elements.OBJECTIVES OF THE STUDYThe main target of this research work is toshow the differences of the provisions of seismicanalysis and design of structures under the NationalStructural Codes of the Philippines (NSCP) bypreparing a comparative evaluation of the 2 codes—NSCP 1992 and the new one, NSCP 2010 in applyingto the Design of Multi-Story Public School Building.The values of design base shear V weredetermined from the formula as provided for in the twoCodes. Different data were derived from the analyticalprocedure which were carried out in the SeismicAnalysis of a Three Storey Reinforced Concrete SchoolBuilding as proposed in this study. The two methodsdescribed in the two NSCP codes Seismic Provisionsare the Linear Static Analysis (LSA) and ResponseSpectrum Analysis (RSA). Values of ERP of thedifferent structural elements in the two orthogonalframes which were considered to be the most criticalframes were compared and presented in tabular form.The analysis of gravity load, the Structural Analysis andDesign Program STAAD.Pro software was used whichis an additional loading requirement for the design ofsome critical elements of the aforementioned building.In the structural design of the said building, the ultimatestrength design (USD) principles under the AmericanConcrete Institute (ACI) was considered. The saidSeismic Analysis and Design was prepared to conformwith NSCP 1992 and a similar Analysis and Design wasprepared to conform with NSCP 2010.A comparativeanalysis of the design output of the most critical beams,girders and column sections was presented in tabularform.RESEARCH DESIGN ANDMETHODOLOGYIn order to work out for the main differencesof the Design Base Shear (V), the Linear StaticAnalysis (LSA), which is considered as the StaticLateral Force Procedure and the Response SpectrumAnalysis (RSA), another method specified in the NSCPcodes under the Dynamic Lateral Force Procedure werecarried out to analyze a Three Storey ReinforcedConcrete Public School Building. In the DynamicAnalysis, the maximum ground motion intensity, suchas the peak ground acceleration (Amax) of theearthquake among other parameters were considered.The structural design application for somecritical structural elements were carried out also usingUltimate Strength Design principles conforming toAmerican Concrete Institute (ACI) codes as adopted byNSCP. This is integrated in the analysis and designoutput using Structural Analysis and Design Program(STAAD.Pro) software. The main target of theaforementioned design applications is to point outdifferences between the seismic performance of publicschool buildings designed under NSCP 1992 and NSCP2010. Also the balance between a good seismicperformance and economy in the structure is also takeninto account. The NSCP 1992—Section 2.2 “LateralForces” and NSCP 2010 Section 208 “ EarthquakeLoads ” are also described in this research work tohighlight its similarities and differences.The difference in values of the design baseshear V as determined under the two codes wasanalyzed using the tests of significance of a differenceas the statistical tool. The different values of elasticresponse parameters and cross sections of the mostcritical structural elements as determined under the twocodes were compared and analyzed if their differencesare significant using the arithmetic average or mean andtests of significance of a difference as statistical tool.STRUCTURAL MODELING ANDANALYSIS PROCEDURESThe descriptive-comparative method waschosen to suit the required methodology. This is themost appropriate method in this study which seeks toestablish the differences of the effects of SeismicProvisions between NSCP 1992 and NSCP 2010structural codes as applied to the analysis and design ofa Three Storey Reinforced Concrete School Building.The analytical procedures using STAAD.Pro softwareAnalysis procedures. Both NSCP 1992 andNSCP 2010 provided two seismic analysis options forthe design of buildings namely: the static lateral forceprocedure and the dynamic lateral force procedure, bothwith specific conditions as indicated in its provisions,Sections 208.4.8.2 and 208.4.8.3.64

Proc. of Sixth International Conference On Advances in Civil, Structural and Mechanical Engineering -ACSM 2017Copyright Institute of Research Engineers and Doctors, USA .All rights reserved.ISBN: 978-1-63248-118-4 doi: 10.15224/ 978-1-63248-118-4-62(Static Lateral Force Procedure or LinearStatic Analysis (LSA)The structure is modelled as linearly elasticwith secant stiffness through the yield point. It isperformed under a set of lateral static forces applied atfloor levels separately in two orthogonal horizontaldirections. The intent is to simulate through theseforces the peak inertia loads due to the horizontalcomponent of the seismic action in two horizontaldirections. The magnitude of the loads is intended toresult in the deformation demands which would becaused by design seismic force. This design seismicforce is defined as the minimum total strength designbase shear, factored and distributed in accordancewith the codes. Fundamental assumption in thismethod is that the structural components possessinfinite inelastic deformation capacity. The factormethod is one method in seismic analysis under thestatic force procedure will be used. It is applicable tothose structures that have a response not significantlyinfluenced by higher modes of vibrations, and thisusually happens when the structure is regular in planand elevation. Regular structures have no significantphysical discontinuities in plan or verticalconfiguration or in their lateral-force-resistingsystems as defined both in NSCP 1992 and 2010.Inthe LSA, the forces are linearly distributed along theheight and it is assumed a linear deformed shape ofthe structure. Under seismic loading, the structureshows global cantilever behaviour with a predominantflexural or shear shape depending on the relativestiffness of the vertical or horizontal elementsrespectively.The Design Base Shear V is computed usingthe formulas as given in Section 2.2.5.2.1 of NSCP1992 and in Section 208.5.2.1 of NSCP 2010.)RESULTS AND DISCUSSIONSThe seismic provisions of NSCP 1992 & 2010which contained the requirements for seismic analysisof structures varies in some parameters includingempirical coefficient.Table 1 shows some deviations and amendments inthe formula for the Design Base ShearTable 1 Comparison on the Provisions of SeismicAnalysis and Design Parameters:NSCP 1992 and NSCP 2010SeismicAnalysis &DesignParametersNSCP 1992NSCP 20101.DesignBase Shear(V )ZIC/ Rw (W)CvI/RT(W)2.5CaI/R(W) Upper Limit0.11CaIWLower Limit0.80ZNvIW/R Lower Limit2.NumericalCoefficientof structuralmaterial (Ct)0.085 for Steel MRSF0.075 for ReinforcedConcrete MRSF &Steel EBF0.050 for all otherstructure0.0853 for Steel MRSF0.0731 for Concrete MRSF &Steel EBF0.0488 for all other buildingsC 1.25S/ T2/3Ca , Cv & Na , Nv tables 208-7 &208-8School as StandardOccupancy 1.0School as Essential ancyImportanceFactor(I)5.NumericalCoefficientof structuralsystem (Rw,R) for RCBldgs.6.SeismicZone FactorThe total force shall be distributed over theheight of the structure in conformance with thefollowing equations as provided for in both NSCPcodes.108.50Zone 2,Zone 3, Zone 4Zone 2 & Zone 4Table 2 COMPARISON OF DESIGN BASE SHEAR(V)(LSA and RSA Methods)V Ft Fi , Ft 0.07TV, Ft need not exceed0.25V and equals zero if T 0.70 seconds or less.CriticalOrthogonalDirection3/4T Ct H , Ct are values depending on thestructural type H is the total height of the building.Linear StaticAnalysis (LSA)65NSCP1992V(KN)NSCP2010V (KN)%Difference

Proc. of Sixth International Conference On Advances in Civil, Structural and Mechanical Engineering -ACSM 2017Copyright Institute of Research Engineers and Doctors, USA .All rights reserved.ISBN: 978-1-63248-118-4 doi: 10.15224/ 978-1-63248-118-4-62Longitudinal FrameTransverse FrameResponse SpectrumAnalysis (RSA)187.30162.00Longitudinal Frame562.60Transverse he effects of the Seismic Provisions of NSCP2010 on the value of Design Base Shear is greater thanthe effects of NSCP 1992 Seismic Provisions.77.26%The Elastic Response Parameters of Structuralelements have higher values in NSCP 2010 than inNSCP 1992 Seismic Provisions.71.23%The resulting sections and reinforcements ofstructural elements are higher in NSCP 2010 than inNSCP 1992.Table 3 MAXIMUM DEFLECTION AT CRITICALBEAMS(STAADPRo Results)BEAM420382402481242449NSCP 1992 NSCP 2010Critical 537.4872.55219.52012.6037.993CONCLUSION and RECOMMENDATIONS% DIFFERENCENSCP 2010 seismic provisions imposed on theThree- Storey Reinforced Concrete School Buildinghave higher values of Design Base Shear (V) than inNSCP 1992.This indicated that NSCP 2010 were moreconservative and cautious in terms of the safety andstructural integrity of the school building.82.54%82.50%81.16%82.30%86.90%66.84%The higher values of Elastic ResponseParameter (ERP) and the larger sizes of structuralelements and its reinforcement in NSCP 2010 enhancedthe structural safety of the Three-Storey ReinforcedConcrete School Building against severe earthquake.Table 4 CRITICAL VALUE OF DESIGNULTIMATE MOMENTS for the most critical beam.(From LSA & MDM).CRITICALORTHOGONALDIRECTIONSEISMIC MOMENTS(DL LL)FACTOREDMOMENTSCOMBINED Mu% 19922010BEAM 262NSCP NSCP19922010BEAM 39.72421.6624.10The structural safety of the Three-StoreyReinforced Concrete Building designed under theseismic provisions of NSCP 2010 were given dueconsideration wherein it should not collapse but withminimal non-structural damage only during a severeearthquake while NSCP 1992 give more emphasis onthe economic aspect of design but with the possibilityof structural damage and even collapse during theoccurrence of the same earthquake.300.20 429.0042.90In relation with the findings and conclusionsof this research, the recommendations are:Table 3 shows that the maximum deflections at criticalbeams element are higher by 80.37% (average) underNSCP 2010 than those under NSCP 1992. The DesignBase Shear is higher by 57% and 77% under NSCP2010 using LSA and RSA respectively than those underNSCP 1992 as shown in Table 2. The Ultimate DesignMoments, (Mu) in tension for the most critical beam ishigher by 86.9% in NSCP 2010 than in NSCP 1992.Seismic structural assessment of existingReinforced Concrete Public School buildings in thePhilippines designed under NSCP 1992 located in areaswith high seismicity shall be done to avert furtherdamage, loss of life and properties during theoccurrence of an earthquake.The major findings of the research study are:Structural strengthening and retrofitting ofexisting public school building that were designedunder NSCP 1992 seismic provisions shall be66

Proc. of Sixth International Conference On Advances in Civil, Structural and Mechanical Engineering -ACSM 2017Copyright Institute of Research Engineers and Doctors, USA .All rights reserved.ISBN: 978-1-63248-118-4 doi: 10.15224/ 978-1-63248-118-4-62undertaken to improve its worthiness during severeearthquake.[4] Ongaro, L (2007) Comparing Italian SeismicCodes for the Design of Reinforced FrameBuilding, (pp.12-42 and p.144) MasteralThesis, Instituto Universitario di StudiSuperiori and Universita degli Studi di Pavia,Pavia, Italy.Theselectionofregularbuildingconfigurations and the application of sound detailingprinciples are more likely to provide the required levelof securing the building against collapse during anearthquake than detailed refinement of the analysistechniques, thereby the specific rules for a conceptualdesign for earthquake resistant buildings must strictlybe followed[5] Oreta, W (2006) Basic Structural PerformanceIndex of Earthquake Damaged RC Buildings:Technical Proceedings of Asia- PacificConference on Earthquake Engineering 2006(pp.186-187) Manila, Philippines.[6] Torregosa,R., Sugito, M., & Nojima,N.,(2001)Strong Motion Simulation for the Philippinesbased on Seismic Hazard Assessment, Journalon Natural Disaster Science, Vol.23 No.1,2001 pp.1889-1902[7] Yamazaki, F., & Molas G., (1992) SeismicHazard Analysis using Earthquake OccurrenceData, Earthquake Engineering Tenth WorldConference 1992, Balkema, RotterdamREFERENCES[1] Chopra, Anil K.(1995). Dynamics ofStructures, (pp.474-530) International Edition,New Jersey, USA: Prentice Hall2.Chopra,Anil K & Goel Rakesh K. (1991)Evaluation of US Seismic Code Provisions 7 (12),(pp3762-3782)[8] National Structural Code of the Philippines(NSCP) 1992 4th edition, Association ofStructural Engineers of the Philippines(ASEP), Manila, Phils.[3] Mahaylov,B.(2006)AnalysisofCodeProcedures for Seismic Assessment of ExistingBuilding,.Ph.D. Dissertation, European Schoolof Advanced Studies in Reduction of SeismicRisk. Rose School, Universita degli Studi diPavia, Pavia, Italy[10] American Concrete Institute (ACI 318-08),ACI Committee 318[9] National Structural Code of the Philippines(NSCP) 2010 6th edition, (ASEP), Manila,Phils.[11] STAADPro Version 2005, Bldg. 1001 US,Proprietary Program Research EngineersInternational,UserID(LZO LND)67

Static Lateral Force Procedure and the Response Spectrum Analysis (RSA), another method specified in the NSCP codes under the Dynamic Lateral Force Procedure were carried out to analyze a Three Storey Reinforced Concrete Public School Building. In the Dynamic Analysis, the maximum ground motion intensity, such as the peak ground