Module 3-Specialized 413a-Earthquake Engineering PDF

DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph...

DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] SPECIALIZED 413a – Earthquake Engineering Module 3: SEISMIC DESIGN CRITERIA ( NSCP 2015) Module 3 – Seismic Design Criteria is taking into account the seismic zoning, site conditions, occupancy, size, structural structure and height of the building in the procedures for structural design in compliance with design standards of the NSCP 2015. Objectives: 1. Understand the preliminary aspects of the Earthquake Engineering. 2. Be able to determine the basis for the seismic design by adopting the latest edition of the National Structural Code of the Philippines (NSCP), Volume I. Outline: 1. Criteria Selection 2. Earthquake Load Analysis- NSCP 2015 3. Earthquake Load Combination 4. Horizontal and Vertical Irregularities Content: EARTHQUAKE LOADS—NSCP 2015 SECTION 208 SECTION 208.1.1 PURPOSE The purpose of the earthquake provisions is primarily to design seismic-resistant structures to safeguard against major structural damage that may lead to loss of life and property. These provisions though are not intended to assure zero-damage to structures nor maintain their functionality after a severe earthquake. SECTION 208.1.2 Minimum Seismic Design Structures and portions thereof shall, as a minimum, be designed and constructed to resist the effects of seismic ground motions as provided in this section. NSCP SECTION 208.2—DEFINITIONS The following are the definition of terms and nomenclatures that will be used in the analysis and design of seismic forces. Base - the level at which the earthquake motions are considered to be imparted to the structure or the level at which the structure, as a dynamic vibrator, is supported. Base Shear, V - the total designed lateral force or shear at the base of a structure. Bearing Wall System - structural system without a complete vertical load carrying space frame (See Sec. 208.4.6.1). Boundary Element -an element at edges of opening or at perimeters of shear walls or diaphragms. Braced Frame - an essentially vertical truss system of the concentric or eccentric type, which is provided to resist lateral forces. 1 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] Building Frame System - an essentially complete space frame that provides supports for gravity loads (See Sec. 208.4.6.2). Cantilevered Column Effect – column element in a lateral-force-resisting system that cantilevers from a fixed base and has minimal moment capacity at the top, with lateral forces applied essentially at the top. Collector - a member or an element provided to transfer lateral forces from a portion of a structure to vertical elements of the lateral force resisting system. Component – a part or element of an architectural, electrical, mechanical or structural system. Component, Equipment – mechanical or electrical component or element that is part of a mechanical or electrical system. Component, Flexible – component, including its attachments, having a fundamental period greater than 0.06 second. Component, Rigid - component, including its attachments, having a fundamental period less than or equal to 0/06 second. Concentric Braced Frame - a braced frame in which the members are subjected primarily to axial forces. Design Basis Ground Motion – ground motion that has 10% chance of being exceeded in 50 years as determined by a site-specific hazard analysis or may be determined from a hazard map. A suite of ground motion time histories with dynamic properties shall be used to represent this ground motion. The dynamic effects of this motion may be represented by the Dynamic Response Spectrum. See Section 208.6.2. Design Response Spectrum – elastic response spectrum for 5% equivalent viscous damping used to represent the dynamic effects of the Design Basis Ground Motion for the design of structures in accordance with Sections 208.5 and 208.6. This response spectrum may be either a site-specific spectrum based on geologic, tectonic, seismological and soil characteristics associated with a specific site or may be a spectrum constructed in accordance with the spectral shape in Figure208-3 using site-specific values of Caand Cv and multiplied by the acceleration of gravity, 9.815 m/sec2. See Section 208.6.2. Design Seismic Force – minimum total strength design base shears, factored and distributed in accordance with Section 208.5. Diaphragm - a horizontal or nearly horizontal system acting to transmit lateral forces to the vertical resisting elements. The term "diaphragm" includes horizontal bracing systems. Diaphragm or Shear Wall Chord - the boundary element of a diaphragm or a shear wall, which is assumed to take axial stresses analogous to the flanges of a beam. Diaphragm Strut (drag strut, tie, collector) - the element of a diaphragm parallel to the applied load that collects and transfers diaphragm shear to vertical resisting elements or distributes loads within the diaphragm. Such members may take axial tension or compression. Drift - see story drift. Dual System -a combination of a Special or Intermediate Moment Resisting Space Frame and Shear Walls or Braced Frames designed in accordance with the criteria of Section. 208.4.6.4. Eccentric Braced Frame (EBF) -a steel braced frame designed in conformance with Section 515.9. Elastic Response Parameters – forces and deformations determined from an elastic dynamic analysis using an unreduced ground motion representation, in accordance with Section 208.5. Essential Facilities - structures that are necessary for emergency operations subsequent to a natural disaster. 2 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] Flexible Element or system - one whose deformations under lateral load is significantly larger than adjoining parts of the system. Limiting ratios for defining specific flexible elements are set forth in Sections 208.5.6. Horizontal Bracing System - a horizontal truss system that serves the same function as a diaphragm. Intermediate Moment Resisting Space Frame (IMRSF) - a concrete space frame designed in conformance with Section 421.10. Lateral Force Resisting System - that part of the structural system assigned to resist the design seismic forces. Moment Resisting Space System - a space frame in which the members and joints are capable of resisting forces primarily by flexure. Moment Resisting Wall Frame (MRWF) – a masonry wall frame especially detailed to provide ductile behavior and designed in conformance with Section 708.2.6. Ordinary Braced Frame (OBF) – steel-braced framed designed in accordance with the provisions of Section 515.7 and 516.5 or concrete-braced frame designed in accordance with Section 421. Ordinary Moment Resisting Space Frame (OMRSF) - a moment resisting space frame not meeting special detailing requirements for ductile behavior. Orthogonal Effects - the effects on the structure due to earthquake motions acting in directions other than parallel to the direction of resistance under consideration. Overstrength – a characteristic of structures where the actual strength is larger than the design strength. The degree of overstrength is material and system dependent. PEffect -the secondary effect on shears and moments of frame members induced by the vertical loads acting on the laterally displaced building frame. Shear Wall - a wall designed to resist lateral forces parallel to the plane of the wall (sometimes referred to as a vertical diaphragm or a structural wall). Shear Wall Frame Interactive System – uses combinations of shear walls and frames designed to resist lateral forces in proportion to the relative rigidities, considering interaction between shear walls and frames on all levels. Soft Story- one in which the lateral stiffness is less than 70% of the stiffness of the story above. See Table 208.9. Space Frame- a three-dimensional structural system without bearing walls composed of members interconnected so as to function as a complete self-contained unit with or without the aid of horizontal diaphragms or floor bracing systems. Special Concentrically Braced Frame (SCBF) – steel-braced frame designed in conformance with Section 515.8. Special Moment Resisting Space Frame (SMRSF) -a moment resisting space frame specially detailed to provide ductile behavior and complying withthe requirements given in Chapter 4 or 5. Special Truss Moment Frame (STMF) – moment-resisting space frame especially detailed to provide ductile behavior and comply with the provision of Section 515.10. Story - the space between levels. Story x is the story below level x. Story Drift - the displacement of one level relative to the level above or below. 3 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] Story Drift Ratio - the story drift divided by the story height. Story Shear, Vx - the summation of design lateral forces above the story under consideration. Strength - the capacity of a structure or a member to resist factored loads as specified in Chapters 2, 3, 4, 5 and 7. Structure - an assemblage of framing members designed to support gravity loads and resist lateral forces. Structures may be categorized as building structures or non-building structures. Subdiaphragm – a portion of a larger wood diaphragm designed to anchor and transfer local forces to primary diaphragm struts and the main diaphragm. Vertical Load Carrying Frame - a space frame designed to carry all vertical (gravity) loads. Wall Anchorage System – system of elements anchoring the wall to the diaphragm and those elements within the diaphragm required to develop the anchorage forces, including diaphragms and continuous ties, as specified in Section 208.8.2.7 and 208.8.2.8. Weak Story – one in which the story strength is less than 80% of that story above. See Table 208.9. BASIS FOR DESIGN The basis for the seismic design shall be stated on the structural drawings. The statement shall include:  The governing edition of the building code.  The total base shear coefficient used for seismic design.  A description of the lateral force resisting system. NSCP SECTION 208.4—CRITERIA SELECTION 208.4.1 Basis for Design. The procedures and limitations shall be determined considering the following:  Seismic zoning  Site characteristics  Occupancy  Configuration  Structural system  Height in accordance with this code Structures shall be designed with adequate strength to withstand the lateral displacements induced by the Design Basis Ground Motion, considering the inelastic response of the structure and the inherent redundancy, over-strength and ductility of lateral force-resisting frame. The minimum design strength shall be based on the Design Seismic Forces determined in accordance with the static lateral force procedure of Section 208.5. 208.4.2 OCCUPANCY CATEGORIES (TABLE 103-1, TABLE 208-1) For purposes of earthquake resistant design, each structure shall be placed in one of the occupancy categories in Table 103-1. Table 208-1 lists importance factors, I and Ip and structural observation requirements for each category. 4 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] 208.4.3 Site Geology & Soil Characteristics (Table 208-2) Each site shall be assigned a soil profile type based on properly substantiated geotechnical data using the site categorization procedure set forth in Section 208.4.3.1.1 and Table 208-2. 208.4.3.1. SOIL PROFILE TYPE SOIL Profile Types SA , SB , SC , SD , and SE are defined in Table 208-2 and Soil Profile Type SF is defined as soils requiring site-specific evaluation as follows: 5 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] 1. Soils vulnerable to potential failure or collapse under seismic loading, such as liquefiable soils, quick and highly sensitive clays, and collapsible weakly cemented soils. 2. Peats and/or highly organic clays, where the thickness of peat or highly organic clay exceeds 3.0 meters. 3. Very high plasticity clays with plasticity index, PI > 75, where the depth of clay exceeds 7.5 meters. 4. Very thick soft/medium stiff clays, where the depth of clay exceeds 35 meters. 5. The criteria set forth in the definition for Soil Profile Type SF requiring sitespecific evaluation shall be considered. If the site corresponds to these criteria, the site shall be classified as Soli Profile Type SF and a site-specific evaluation shall be conducted. Exception: When the soil properties are not known in sufficient detail to determine the soil profile type, Type SD shall be used. Soil Profile Type SE or SF need not be assumed unless the building official determines that Type SE or SF may be present at the site or in the event that Type SE or SF is established by geotechnical data. 208.4.4 SITE SEISMIC HAZARD CHARACTERISTICS Seismic hazard characteristics for the site shall be established based on the seismic zone and proximity of the site to active seismic sources, site soil profile characteristics and the structure’s importance factor. 208.4.4.1 Seismic Zone (Table 208-3) The Philippine archipelago is divided into two seismic zones only: Zone 2 – covers the provinces of Palawan (except Busuanga), Sulu and Tawi-Tawi Zone 4 – the rest of the country (shown in Figure 208-1) Each structure shall be assigned a seismic zone factor Z, in accordance with Table 208-3. 6 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] 208.4.4.2 Seismic Source Types (Table 208-4 to 8) Table 208-4 defines the types of seismic sources. The location and type of seismic sources to be used for design shall be established based on approved geological data; see Figure 208-2A. Type A sources shall be determined from Figure 208-2B, 2C, 2D, 2E or the most recent mapping of active faults by the Philippine Institute of Volcanology and Seismology (PHIVOLCS). 208.4.4.3 Seismic Zone 4 Near Source Factor In Seismic Zone 4, each site shall be assigned near-source factors in accordance with Tables 208-5 and 208-6 based on the Seismic Source Type as set forth in Section 208.4.4.2. 7 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] For high rise structures and essential facilities within 2.0 km of a major fault, a site specific seismic elastic design response spectrum is recommended to be obtained for the specific area. The value of Na used to determine Ca need not exceed 1.1 for structures complying with all the following conditions: 1. The soil profile type is SA , SB , SC or SD. 2. ρ = 1.0 3. Except in single-storey structures, residential building accommodating 10 or fewer persons, private garages, carports, sheds and agricultural buildings, moment frame systems designated as part of the lateral-force-resisting system shall be special moment-resisting frames. 4. The exceptions to Section 515.6.5 shall not apply, except for columns in one-storey or columns at the top storey of multi-storey buildings. 5. None of the following structural irregularities is present Type 1, 4 or 5 of Table 208-9, and Type 1or 4 of Table 208-10. 208.4.4.4 Seismic Response Coefficients Each structure shall be assigned a seismic coefficient, Ca, in accordance with Table 208-7 and a seismic coefficient, Cv, in accordance with Table 208-8. 8 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] 208.4.5. Configuration Requirements Each structure shall be designed as being structurally regular or irregular in accordance with Sections 208.4.5.1 and 208.4.5.2. 208.4.5.1 Regular Structures Regular structures have no significant physical discontinuities in plan or vertical configuration or in their lateral force resisting systems such as the irregular structures described in Section 208.4.5.2. 208.4.5.1 Irregular Structures 1. Irregular structures have significant physical discontinuities in configuration or in their lateral force resisting systems. Irregular features include, but are not limited to; those described in Tables 208-9 and 208-10. All structures in occupancy categories 4 and 5 in Zone 2 need to be elevated for vertical irregularities of Type 5 (Table 208-9) and horizontal irregularities of Type 1 (Table 208-10). 2. Irregular structures. Structures having any of the features listed in Table 208-9 shall be designated as having a vertical irregularity. EXCEPTION: Where no story drift ratio under design lateral load is greater 1.3 times the story drift ratio of the story above, the structure may be deemed to not have irregularities of Types 1 or 2 in Table 208-9. The drift ratio relationship for the top two stories need not be considered. The story drifts for this determination may be calculated neglecting torsional effects. 3. Plan Irregularity. Structures having one or more features listed in Table 208-10 shall be designated as having a plan irregularity. 9 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] Table 208-10 Horizontal Structural Irregularities Irregularity Type and Definition Reference Section 1. Torsional Irregularities –To Be Considered When Diaphragm Are Not Flexible Torsional irregularity shall be considered to exist when the 208.7.2.7 maximum storey drift, computed including accidental Item 6 torsion, at one end of the structure transverse to an axis more than 1.2 times the average of the storey drifts of the two ends of the structure. 2. Re-Entrant Corner Irregularity Plan configurations of a structure and its lateral- forceresisting system contain re-entrant corners, where 208.7.2.7 both projections of the structure beyond a re-entrant Items 6 and 7 corner are greater than 15.% of the plan dimension of the structure in any given direction. 3. Diaphragm Discontinuity Irregularity 208.7.2.7 Diaphragms with abrupt discontinuities or variations in Item 6 stiffness, including those having cutout or open areas 10 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] greater than 50% of the gross enclosed area of the diaphragm, or changes in effective diaphragm stiffness of more than 50% from one storey to the next 4. Out Of-Plane Offsets Irregularity 208.5.8.1.5 1 Discontinuities in a lateral force path, such as out-ofplane 208.7.2.7 offsets of the vertical. Item 6 5. Non-parallel Systems Irregularity The vertical lateral-load –resisting elements are not parallel 208.7.1 to or symmetric about the major orthogonal axes of the lateral force-resisting system. 208.4.6 Structural Systems Structural systems shall be classified as one of the types listed in Table 208-11 and defined below. Bearing Wall System. A structural system without complete vertical load carrying space frame. Bearing walls or bracing systems provide support for gravity loads. Resistance to lateral load is provided by shear walls or braced frames. Building Frame System. A structural system with essentially complete space frame providing support for gravity loads. Resistance to lateral load is provided by shear wall or braced frames. Moment Resisting Frame System. A structural system with an essentially complete space frame providing support for gravity load. Moment resisting space frames provide resistance to lateral load primarily by flexural action of members. Dual System. A structural system with the following features: 1. An essentially complete space frame providing support for gravity loads. 2. Resistance to lateral load is provided by Resistance to lateral load is provided by shear walls or braced frames and moment-resisting frames(SMRF, IMRF, MMRF or steel OMRF0. The moment- resisting frames shall be designed to independently resist at least 23 percent of the design base shear. 3. The two systems shall be designed to resist the total design base shear in proportion to their relative rigidities considering the interaction of the dual system at all levels. Cantilevered Column System. A structural system relying on cantilevered column elements for lateral resistance. Undefined Structural System. A structural system not listed in Table 208-11. Non-Building Structural System. A structural system conforming to Section 208.8. 208.4.7 Height Limits Height limits for the various structural systems in Seismic Zone 4 are given in Table 208.11. EXCEPTION: Regular structures may exceed these limits by not more than 50% for unoccupied structures, which are not accessible to the general public. SYSTEM LIMITATIONS Limits are placed on the use of so structural systems in accordance with the following requirements Structures with discontinuity in capacity, vertical irregularity Type 5 as defined in Table 208.9, shall not be permitted over two stories or 9 m in height where the weak story has a calculated strength of less than 65% of the story above. 11 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] EXCEPTION: Where the weak story is capable of resisting a total late seismic force of o times the design force prescribed in Section 208.5. Undefined structural systems shall be shown by technical and test data which establish the dynamic characteristics and demonstrate the lateral force resistance and energy absorption capacity to be equivalent to systems listed in Table 208-11 for equivalent values. See Section 208.4.9.2. All structures having irregular features described in Table 208-9 or 208-10 shall be designed to meet the additional requirements of the sections referenced in the tables. 12 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] 13 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] Soil Profiles Soil profile types are defined in accordance with Table 208-2 and NSCP Section 208.10.2. When the soil properties are not known in sufficient detail to determine the soil profile type, Type SD shall be used. Soil Profile Type SE must not be assumed unless the geotechnical engineer determines so with the presence of established geotechnical data. Rock Profile Types SA and SB shall be measured using the shear wave velocity test. It shall not be used if there is more than 3 meters of soil between the rock surface and the bottom of the spread footing or mat foundation. Highly weathered or fractured rock shall be measure on site or classified as Soil Profile Type SC. The hard rock, Soil Profile type SA shall be supported by the shear wave velocity measurement either onsite or profiles of the same rock type in the same formation with an equal or greater degree of weathering and fracturing. Where hard rock conditions are known to be continuous to a depth of 30 meters, surficial shear wave velocity measurements may be extrapolated to assess its value. Soil Profile Types SC, SD, SE shall be classified using any of the four tests: 1. Shear Wave Velocity, vs—for the top 30 meters. 2. Standard Penetration Resistance, N—for the top 30 meters. 3. Standard Penetration Resistance for Cohesionless Soil, NCH—PI  20 at the top 30 meters. 4. Undrained Shear Strength, su—PI  20 at the top 30 meters. Soft Clay Profile Type SE has an existence of soft clay of more than 3 meters. It shall be investigated where a soft clay layer is defined by the following su 25 kPa MC 40% PI  20 Profiles containing distinctly different soil layers shall be subdivided into those layers designated by a number from 1 to n at the bottom, where there are a total of n distinct layers in the upper 30 meters. Soil Profile type SF must require site-specific evaluation. Average Shear Wave Velocity Test The average shear wave velocity, vs shall be determined by the following ∑𝑛𝑖=1 𝑑𝑖 𝑣𝑠 = 𝑑 ∑𝑛𝑖=1( 𝑖 ) 𝑣𝑠𝑖 14 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] Where: di = thickness of layer i, meters. vsi = shear wave velocity in layer i, m/sec. Average Field Standard Penetration Resistance and Average Standard Penetration Resitance for Cohesionless Layers Tests The average field standard penetration resistance, N shall be determined with the following: ∑𝑛 𝑖=1 𝑑𝑖 𝑁= 𝑑𝑖 ∑𝑛 𝑖=1( ) 𝑁𝑖 The average standard penetration resistance for cohesionless layers, NCH shall be determined with the following ∑𝑛𝑖=1 𝑑𝑠 𝑁𝐶𝐻 = 𝑑 ∑𝑛𝑖=1( 𝑖 ) 𝑁 𝑖 where di = thickness of layer i, mm. ds = total thickness of cohesionless soil layers at the top 30 meters, mm. Ni = standard penetration resistance of a soil layer in accordance with an approved standard, blows/300 mm. Average Undrained Shear Strength Test The average undrained shear strength, su shall be determined with the following ∑𝑛𝑖=1 𝑑𝑐 𝑠𝑢 = 𝑑 ∑𝑛𝑖=1( 𝑖 ) 𝑠𝑢𝑖 where dc = thickness of cohesive soil at the top 30 meters, mm. dc = 30 - ds sui = undrained shear strength in accordance with an approved standard, kPa. 15 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] NSCP Section 208.4: CRITERIA SELECTION Exercises: 1. A structure has to be constructed in Agoo, La Union. The geographical coordinates were taken as 16o20’ N Latitude, 120o26’ E Longitude.  The near-source factor, Na should have been a. 1.00 b. 1.20 c. 1.08 d. 1.12  The near-source factor, Nv should have been a. 1.20 b. 1.36 c. 1.00 d. 1.60 2. A stratified soil profile is shown in the figure with the given thickness d, shear wave velocity vs, standard penetration test blows N, and undrained shear strength Su. N 1 = 11 d 1 = 6.00m v s1 = 167 m/s N 2 = 37 v s2 = 222 m/s d 2 = 9.25m d = 30.00 m N 3 = 69 v s3 = 378 m/s d 3 = 10.50m N 4 = 82 v s4 = 455 m/s d 4 = 4.25m S u1 = 32 kPa S u2 = 61 kPa S u3 = 112 kPa S u4 = 133 kPa  The average shear wave velocity of the profile in m/s is nearest to a. 287 b. 262 c. 356 d. 188  What should be the soil profile type if the average shear wave velocity test will be used? a. rock b. Stiff soil c. very dense soil d. hard rock  The average standard penetration resistance test per 300 mm is nearest to a. 30 b. 32 c. 35 d. 37  The average standard penetration resistance test per 300 mm when there is 7.50 m of sand and gravel soil at the from the bottom of the layer is nearest to a. 6.55 b. 8.75 c. 7.50 d. 3.55  What should be the soil profile type if the average standard penetration test will be used? a. SA b. SD c. SE d. SB  The average undrained shear strength in kPa is nearest to a. 55 b. 34 c. 65 d. 49  What should be the soil profile type if the average undrained shear strength test will be used? a. SE b. SD c. SB d. SC  At the layer of the cohesive soil, a soil sample weighing 750 g was taken to the laboratory for geotechnical tests. The test had shown that its liquid limit is 37.26%, and the plastic limit is 18.77%. The weight of the sample after oven-drying is 577.60 g.  The plasticity index of the soil is nearest to a. 19% b. 27% c. 15% d. 24%  The water content of the soil is nearest to. a. 9% b. 29% c. 35% d. 22%  Will the cohesive soil be classified as soft clay? a. yes b. no c. maybe d. it does not matter 16 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] 3. A six-storey reinforced concrete structure of a special moment-resisting frame type is shown below. The lateral forces have been applied so as to attain the corresponding floor displacements Si.The weights of each floor were carefully calculated. Floor level displacements can be taken from computer software. Determine whether there is a stiffness irregularity soft-storey (Type 1 vertical irregularity) in the first storey. To compare displacements rather than stiffness, it is necessary to use the reciprocal of the limiting ratios of 70% and 80% as they apply to storey stiffness, or reverse their applicability to the storey(s) above). The storey stiffness ratio is the storey height, hidivided by the storey drift (Si + 1 – S1). The storey drift ratio is the reciprocal of the stiffness ratio.  Determine whether a vertical weight (mass) irregularity (Type 2) exists. 4. The four-storey special moment frame building below has 7.50 m setback at the third and fourth storeys. It is supported by shear walls at the first and third bays. 4 @ 7.50 m = 30.00 m Roof Deck Shear Wall Shear Wall  Determine whether a vertical geometric irregularity (Type 3) exists.  Determine whether an in-plane discontinuity in the vertical lateral force-resisting element (Type4) exists. 17 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] 5. A concrete bearing wall building has typical transverse wall configuration shown below. All walls in this direction are identical, and the individual piers have shear contributions. Vnis the nominal shear strength calculated in accordance with NSCP Section 421.7.4 and Vm is the shear corresponding to the development of the nominal flexure strength as calculated in accordance with NSCP Section421.7.5. Pier Vn, kN Vm, kN 1 20 30 2 30 40 3 15 10 4 20 15 5 80 120 6 15 10 7 20 15 In calculating the storey strengths, use the smaller values of Vn and Vm given for each pier.  Determine if a discontinuity in capacity-weak storey condition (Type 5) exists. Roof Deck 5 6 7 1 2 3 4 6. A four-storey moment resisting frame building has rigid floor diaphragms. Under seismic forces, including the effects of accidental torsion, the following were the calculated displacements at Levels 2 and 3 Roof Deck Level 3 R,3 L,3 Level 2 R,2 L,2 L,3= 33.00 mm R,3 = 48.50 mm L,2= 25.00 mm R,2 = 30.50 mm  Determine whether a torsional plan irregularity (Type 1) exists in the second storey.  Compute the torsional amplification factor Ax for Level 3 as given in NSCP Section 205.5.7. a. 0.98 b. 0.88 c. 0.67 d. 0.75 18 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] 7. The plan of a ten-storey special moment frame is shown below. Determine if there is a plan re-entrant corner irregularity (Type 2). 8. A multi-storey reinforced concrete building has a bearing wall system located around the perimeter of the building. The bearing walls acting as shear walls the floor plan of the second floor that are shown below resists lateral forces. The symmetrically placed open area in the diaphragm is for an atrium, and has dimensions 12.00 m * 23.0 m. All diaphragms above the second floor have no significant openings. 38.00 m 23.00 m 12.00 m 24.00 m  Determine if a plan diaphragm discontinuity (Type 3) exists at the second floor. 9. A four-storey building has a concrete shear wall lateral force-resisting system in a building frame configuration. The plan configuration of the shear walls is shown below. Determine if there is a plan out- of-plane offset irregularity (Type 4) between the first and second floors. 4 @ 7.50 m = 30.00 m 1 2 @ 7.50 m = 15.00 m 2 3 First (Ground) Floor Plan 1 2 3 Typical (Upper) Floor Plan A B C D E 19 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] 10. A ten-storey building has the floor plan shown at all levels. Special moment-resisting frames are located at the perimeter of the building lines 1, 4, A, and F. 4 @ 7.50 m = 30.00 m F A B C D E 1 2 m 3 @ 6.00 = 18.00 m 3 4  Determine whether a non-parallel irregularity(Type 5) exists. Solutions and Answers to Criteria Selection: 1. Nearest fault to Agoo, La Union with geographical coordinates were taken as 16 o20’ N Latitude, 120o26’ E Longitude: PFZ: Tubao Fault which is 8 km from the given site. Tubao Fault is Type A seismic source. Using Table 208 – 4 to solve for Na: 5 km 1.2 8 km Na 10 km 1.0 8−5 𝑁 −1.2 𝑎 10−5 = 1.0−1.2 ; 𝑁𝑎 = 1.08 Using Table 208 – 7 to solve for Ca: Z = 0.4, Soil profile type: SD 𝐶𝑎 = 0.44𝑁𝑎 𝐶𝑎 = 0.44(1.08) = 0.4752 Using Table 208 – 5 to solve for Nv: 5 km 1.6 8 km Nv 10 km 1.2 8−5 𝑁𝑣 − 1.6 = ; 𝑁𝑣 = 1.36 10 − 5 1.2 − 1.6 Using Table 208 – 8 to solve for Cv: 𝐶𝑣 = 0.64𝑁𝑣 𝐶𝑣 = 0.64(1.36) = 0.8704 20  DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] 2.  Average shear wave velocity, vs: ∑𝑛𝑖=0 𝑑𝑖 6 + 9.25 + 10.5 + 4.25 𝑣𝑠 = 𝑑𝑖 = 6 9.25 10.5 4.25 = 261.52 𝑚/𝑠 𝑛 ∑𝑖=0 167 + 222 + 378 + 455 𝑣𝑠𝑖  Soil profile type using vs: SD – stiff soil profile (vs is between 180 to 360 m/s)  Average standard penetration resistance test per 300 mm, N: ∑𝑛𝑖=0 𝑑𝑖 6 + 9.25 + 10.5 + 4.25 𝑁= 𝑑𝑖 = 6 9.25 10.5 4.25 = 30.02 𝑛 ∑𝑖=0 + + + 𝑁𝑖 11 37 69 82  Average standard penetration resistance test per 300 mm when there is 7.50 m of sand and gravel soil , NCH: 𝑑𝑠 7.5 𝑁𝐶𝐻 = 𝑑𝑖 = 6 9.25 10.5 4.25 = 7.504 𝑛 ∑𝑖=0 11 + 37 + 69 + 82 𝑁𝑖  Soil profile type using N: SD – stiff soil profile (N is between 15 to 50)  Average undrained shear strength, Su: 𝑑𝑐 30 − 7.5 𝑣𝑠 = 𝑑𝑖 = 6 9.25 10.5 4.25 = 48.4 𝑘𝑃𝑎 𝑛 ∑𝑖=0 32 + 61 + 112 + 133 𝑆𝑢𝑖  Soil profile type using Su: SE – soft soil profile (Su< 50 kPa)  Plasticity index of the soil, PI: 𝑃𝐼 = 𝐿𝐿 − 𝑃𝐿 𝑃𝐼 = 37.26 − 18.77 = 18.49 % 𝑊𝑤 750−577.6  Water content of the soil, w: 𝑤 = = 𝑥 100 = 29.85% 𝑊𝑠 577.6  No. Soft clay layer, SE is defined by Su< 24 kPa, wmc ≥ 40% and PI > 20. 3. Stiffness Irregularity Soft Storey (Type 1 Vertical Irregularity)  Determine whether there is a stiffness irregularity soft-storey (Type 1 vertical irregularity) in the first storey. Level Storey Storey Drift Storey Storey Drift 0.70*Sx 0.80*Sx Savg of the Soft SDx = Dx-Dx- Next 3 x Displacement 1 Height Ratio Storeys Storey Dx (mm) hx (mm) Sx = SDx/hx Status 6 57.24 5.93 3,000.00 0.00198 0.001384 0.001581 - FALSE No 5 51.31 6.86 3,000.00 0.00229 0.001601 0.001829 - FALSE No 4 44.45 7.62 3,000.00 0.00254 0.001778 0.002032 - FALSE No 3 36.83 9.40 3,000.00 0.00313 0.002193 0.002507 0.00227 False Yes 2 27.43 9.40 3,000.00 0.00313 0.002193 0.002507 0.00265 FALSE No 1 18.03 18.03 3,500.00 0.00515 0.003606 0.004121 0.00294 False Yes 21 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected]  Determine whether a vertical weight (mass) irregularity (Type 2) exists. Upper Level Weight Lower Level Weight Level Weight 1.50 * X Wx (kN) 1.50 * Wx-1 Irregularity Wx+1 Irregularity Status Status 6 350.00 750.00 No - No 5 500.00 750.00 No 525.00 No 4 500.00 675.00 No 750.00 No 3 450.00 1,200.00 No 750.00 No 2 800.00 600.00 Yes 675.00 Yes 1 400.00 - - 1,200.00 No 4. Vertical Irregularity Type 3  Determine whether a vertical geometric irregularity (Type 3) exists. A vertical geometric irregularity is considered to exist where the horizontal dimension of the lateral force- resisting system in any storey is more than 130 percent of that in the adjacent storey. Level Width Upper Level Width Ratio Geometric X Lx (m) Width Lx/Lx+1 Irregularity Lx+1 (m) (%) Status RD 22.50 - Yes 4 22.50 22.50 100.00 No 3 30.00 22.50 133.33 Yes 2 30.00 30.00 100.00 No 1 30.00 30.00 100.00 No  Determine whether an in-plane discontinuity in the vertical lateral force-resisting element (Type4) exists. A type 4 vertical irregularity exists where there is an in-plane offset of the lateral load resisting elements greater than the length of those elements. In this example, the left side of the upper shear wall (between lines A and B) is offset 15 m from the left side of the lower shear wall (between lines C and D). This 15 m offset is greater than the 7.5 m length of the shear wall elements. 5. Vertical Irregularity Type 5 Level Storey Upper Level 0.80* of Upper Weak X Strength, kN Storey Level Storey Storey Strength, kN Strength, kN Status 2 105.00 #VALUE! #VALUE! 1 75.00 105.00 84.00 Yes 22 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] INTRODUCTION TO PLAN IRREGULARITIES Types of Plan Irregularities 1. Torsional Irregularity – to be considered when diaphragms are not flexible 2. Re-entrant corners 3. Diaphragm discontinuity 4. Out-of plane offsets 5. Nonparallel systems 6. Plan Irregularity Type 1  Determine whether a torsional plan irregularity (Type 1) exists in the second storey. A Type 1 torsional plan irregularity is considered to exist when the maximum storey drift, including accidental torsion effects, at one end of the structure transverse to an axis is more than 1.2 times the average of the storey drifts of the two ends of the structure. Referring to the above figure showing the displacements 𝛿 due to the prescribed lateral forces , this irregularity check is defined in terms of storey drift ∆𝛿𝑥 = (𝛿𝑥 − 𝛿𝑥−1 ) at ends R (right) and L (left) of the structure. Torsional irregularity exists at level x when 1.2(∆𝛿𝑅,𝑥 +∆𝛿𝐿,𝑥 ) ∆𝛿𝑚𝑎𝑥 = ∆𝛿𝑅,𝑥 > 2 = 1.2(∆𝛿𝑎𝑣𝑔 ) Where: ∆𝛿𝐿,2 = 𝛿𝐿,2 − 𝛿𝐿,1 ∆𝛿𝑅,2 = 𝛿𝑅,2 − 𝛿𝑅,1 ∆𝛿𝑚𝑎𝑥 = ∆𝛿𝑅,𝑥 , ∆𝛿𝑎𝑣𝑔 ∆𝛿𝐿,𝑥 +∆𝛿𝑅,𝑥 = 2 Determining storey drifts at level 3 ∆𝛿𝐿,2 = 33 − 25 = 8𝑚𝑚 ∆𝛿𝑅,2 = 48.5 − 30.5 = 18𝑚𝑚 8+18 ∆𝛿𝑎𝑣𝑔 = 2 = 13 𝑚𝑚 Checking 1.2 criteria ∆𝛿𝑚𝑎𝑥 ∆𝛿 18 ∆𝛿𝑎𝑣𝑔 = ∆𝛿 𝑅,2 = 13 = 1.4 > 1.2 𝑎𝑣𝑔 ∴ 𝑇𝑜𝑟𝑠𝑖𝑜𝑛𝑎𝑙 𝑖𝑟𝑟𝑒𝑔𝑢𝑙𝑎𝑟𝑖𝑡𝑦 𝑒𝑥𝑖𝑠𝑡𝑠  Compute the torsional amplification factor Ax for Level 3 as given in NSCP Section 205.5.7. When torsional irregularity exists at a levelx, the accidental eccentricity, equal to 5 percent of the building dimension, must be increased by an amplication factor Ax. This must be done for each level, and each may have a different Ax value. In this example, Ax is computed for level 2. 𝟐 𝜹 𝒎𝒂𝒙 𝑨𝒙 = (𝟏.𝟐𝜹 ) 𝒂𝒗𝒈 𝛿𝑚𝑎𝑥 = 𝛿𝑅,3 = 48.5 𝑚𝑚 𝛿𝐿,2 + 𝛿𝑅,2 𝛿𝑎𝑣𝑔 = 2 33 + 48.5 𝛿𝑎𝑣𝑔 = = 40.75 𝑚𝑚 2 2 48.5 𝐴2 = [ ] 1.2(40.75) = 0.98 < 1.0 ∴ 𝑢𝑠𝑒 𝐴𝑥 = 1.0 23 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] 7. Plan Irregularity Type 2 A Type 2 re-entrant corner plan irregularity exists when the plan configuration of a structure and its lateral force-resisting system contain re-entrant corners, where both projections of the structure beyond a re- entrant corner are greater than 15% of the plan dimension of the structure in the direction considered. The plan configuration of this building, and its lateral force resisting system, have identical re-entrant corner dimensions. For the sides on Lines 1 and 5, the projection beyond the re-entrant corner is 30 𝑚 − 22.5 𝑚 = 7.5 𝑚 7.5 This is 30 𝑜𝑟 25 % 𝑜𝑓 𝑡ℎ𝑒 30 𝑚 𝑝𝑙𝑎𝑛 𝑑𝑖𝑚𝑒𝑛𝑠𝑖𝑜𝑛. For the sides on Lines A and F, the projection is 24 – 18 m = 6m 6 This is 𝑜𝑟 25 % 𝑜𝑓 𝑡ℎ𝑒 24 𝑚 𝑝𝑙𝑎𝑛 𝑑𝑖𝑚𝑒𝑛𝑠𝑖𝑜𝑛. 24 Since both projections exceed 15%, there is a re-entrant corner irregularity. ∴ 𝑅𝑒 − 𝑒𝑛𝑡𝑟𝑎𝑛𝑡 𝑐𝑜𝑟𝑛𝑒𝑟 𝑖𝑟𝑟𝑒𝑔𝑢𝑙𝑎𝑟𝑖𝑡𝑦 𝑒𝑥𝑖𝑠𝑡𝑠 8. Plan Irregularity Type 3  Determine if a plan diaphragm discontinuity (Type 3) exists at the second floor. A Type 3 diaphragm discontinuity irregularity exists when diaphragms have abrupt discontinuities or variations in stiffness, including cut out or open areas greater than 50 % of the gross enclosed area of the diaphragm, or changes in effective diaphragm stiffness of more than 50 % from one storey to the next. Gross enclosed area of the diaphragm is 24 m x 38 m = 912 m2 Area of opening is 12m x 23m = 276 m2 50% of gross area = 0.5 (912) = 456 m2 276 < 456 m2 ∴ 𝑁𝑜 𝑑𝑖𝑎𝑝ℎ𝑟𝑎𝑔𝑚 𝑑𝑖𝑠𝑐𝑜𝑛𝑡𝑖𝑛𝑢𝑖𝑡𝑦 𝑖𝑟𝑟𝑒𝑔𝑢𝑙𝑎𝑟𝑖𝑡𝑦 𝑒𝑥𝑖𝑠𝑡 9. Plan Irregularity Type 4  Determine if there is a plan out-of-plane offset irregularity (Type 4) between the first and second floors. An out-of-plane irregularity exists when there are discontinuities in a lateral force path, for example: out-of- plane offsets of vertical resisting elements such as shear walls. The first storey shear wall on Line D has 7.5 m out-of-plane offset to the shear wall on Line E at the second storey and above. This constitutes an out-of – plane offset irregularity. ∴ 𝑂𝑓𝑓𝑠𝑒𝑡 𝑖𝑟𝑟𝑒𝑔𝑢𝑙𝑎𝑟𝑖𝑡𝑦 𝑒𝑥𝑖𝑠𝑡𝑠. 10. Plan Irregularity Type 5  Determine whether a non-parallel irregularity(Type 5) exists. A type 5 nonparallel system irregularity is considered to exist when the lateral load resisting elements are not parallel to or symmetric about major orthogonal axes of the building’s lateral force-resisting system. The vertical lateral force-resisting frame elements located on Line F are not parallel to the major orthogonal axes of the building (i.e. Lines 4 and A). Therefore, a nonparallel system irregularity exists. ∴ 𝐴 𝑛𝑜𝑛 𝑝𝑎𝑟𝑎𝑙𝑙𝑒𝑙 𝑠𝑦𝑠𝑡𝑒𝑚 𝑖𝑟𝑟𝑒𝑔𝑢𝑙𝑎𝑟𝑖𝑡𝑦 𝑒𝑥𝑖𝑠𝑡𝑠 24 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] NSCP Section 208.5: MINIMUM DESIGN LATERAL FORCES AND RELATED EFFECTS NSCP SECTION 208.5.1—EARTHQUAKE LOADS AND MODELING REQUIREMENTS Section 208.5.1.1—Earthquake Loads. Structures shall be designed for ground motion producing structural response to two bays with moment-resisting connections on opposite and seismic forces in any horizontal direction. The following earthquake loads shall be used in the load combinations set forth in Section 203: E = Eh + Ev Em =  o Eh where: E = the earthquake load on an element of a structure resulting from the combination of the horizontal component, Ehand the vertical component, Ev. Eh = the earthquake load due to the base shear, V as set forth in Section 208.5.2 or the design lateral force, Fp as set forth in Section 208.7. Em= the estimated maximum earthquake force that can be developed in the structure as set forth in Section 205.5.1.1, and used in the design of specific elements of the structure, as specifically identified in the NSCP. Ev= the load effect resulting from the vertical component of the earthquake ground motion. = 0.50Ca I D for Strength Design. = 0.00 for Allowable Stress Design. o = the seismic amplification factor that is requires to account for structural over-strength, as set forth in Section 208.5.3.1.  = Reliability/Redundancy Factor.  = 2 – (6.10/rmaxAB). 1.0  1.50. 1.25, for special moment-resisting frames, except when used in dual systems. The number of bays of special moment-resisting frames shall be increased to reduce r, such that  shall not exceed 1.25.  0.80 ri, for dual systems.  = 1.00, when drift is calculated or when the structure is located in Zone 2. rmax = the maximum element-storey shear ratio. For a given direction of loading, the element-storey ratio is the ratio of the design story shear in the most heavily loaded single element divided by the total design storey shear. = the largest element-storey shear ratio, riin any storey level at or below two-thirds height level of the building ri = the element-storey shear ratio for any given storey level, i. = for braced frames, the maximum horizontal force in a single brace element divided by the total storey shear. = for moment frames, the maximum of the sum of the shears in any two adjacent columns in a moment frame bay divided by the storey shear. = for columns common to two bays with moment-resisting connections on opposite sides at level I in the direction under consideration, 70% of the shear in that column may be used in the column shear summation. = for shear walls, the maximum value of the product of the wall shear multiplied by 3.0/lwand divided by the total storey shear, where lw is the length of the wall, in meters. = for dual systems, the maximum value of rias defined considering all lateral-load resisting elements. The lateral loads shall be distributed to elements based on relative rigidities considering the interaction of the dual system. 25 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] AB = the ground floor area of the structure, m2. = may be taken as the average floor area in the upper setback portion of the building where a larger base area exists in the ground floor. Dead, live and wind loads shall be in accordance with the applicable provisions of for gravity loads of the NSCPSection 204 and 205.Section 208.5.1.1 states that seismic dead load W, also known, as earthquake load is the total dead load and applicable portions of other loads listed below. 1. In storage and warehouse occupancies, a minimum of 25 percent of the floor live load shall be applicable. 2. Where an allowance for partition load is included in the floor design, the applicable portion of the load shall be not less than 0.50 KPa. 3. Total weight of permanent equipment shall be included. The ground motion producing lateral response and design seismic forces may be assumed to act non- concurrently in the direction of each principal axis of structure, except as required by Section 208.8.1 Section 208.5.1.2—Modelling Requirements. The mathematical model of the physical structure shall include all elements of the lateral-resisting system. The model shall also include the stiffness and strength of the elements, which are significant to the distribution of forces, and shall represent the spatial distribution of the mass and stiffness of the structure. of the structure. In addition, model shall comply with the following: 1. Stiffness properties of reinforced concrete an masonry elements shall consider the effects of the cracked section. 2. For steel moment frame systems, the contribution of the panel zone deformations to storey drift shall be included. Section 208.5.1.3—P Effects.The resulting member forces and moments and the storey drifts induced by P effects shall be considered in the evaluation of the overall structural stability and shall be evaluated using the forces producing the displacements s.  Pneed not be considered when the stability coefficient (ratio of the secondary moment to the primary moment) does not exceed 0.10.  The stability coefficient,imay be evaluated for any storey as the product of the total dead load, and the floor live loads, Pi as required in Section 203, above the storey times the seismic drift in that storey, I divided by the product of the seismic shear in that storey, Vi times the height in that storey, hi. 𝑷𝒊 ∆𝒊 𝜽𝒊 = 𝑽𝒊 𝒉𝒊  In Seismic Zone 4, P need not be considered when the storey drift ratio does not exceed 0.02/R. ∆𝑠 ≤ 0.02/𝑅 ℎ𝑠 26 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] Problems: 1. A reinforced concrete building intended for the College of Engineering of AUF that is to house about 1,500 students was to be designed for earthquake. The structure must be a special moment-resisting frame as shown below.  = 1.10 and f1 = 0.50 Roof Deck Floor Level A B C h4 D Base Level Beam A-B and column C-D are elements of the frame. Structural analysis has provided the following data: Dead Load, D Live Load, L Lateral Seismic Load, Eh Beam Moment at A 135 kNm 65 kNm 165 kNm Column Axial Load at C-D 400 kN 180 kN 490 kN Column Moment at C 55 kNm 30 kNm 220 kNm  The strength design moment at beam end A in kN-m should have been a. 406 or –90 b. 505 or –65 c. 316 or –47 d. 356 or –23  The strength design axial load at column C-D in kN should have been a. 987 or –96 b. 1197 or –75 c. 1197 or –26 d. 1356 or –63  The strength design moment at column end C in kNm should have been a. 304 or –205 b. 605 or –85 c. 335 or –205 d. 335 or –53 2. For the same building as shown in Exercise No. 1, determine whether the Peffects must be considered for the first storey if the following data were gathered: D = 38,556 kN L = 17,125 kN W = 38,452 kN (total weight of the structure) V1= 0.042 W h1 = 6.00 m (height of the first storey) 1 = 0.003 h1 (storey drift) SOLUTION: 1. Strength design moment at beam end A a. Determine earthquake load E: E =Eh + Ev Ev = 0.5CaID = 05(0.44)(1.0)(135) = 29.7 kN-m Eh = 165 kN-m E = 1.1(165) + 29.7 27 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] = 211 kN-m b. Apply earthquake load combinations MA = 1.2MD + 1.0ME + f1ML = 1.2(135) + 1.0(211)+0.5(65) = 406 kN-m MA = 0.9MD ± 1.0ME = 0.9(135) ± 1.0(211) = 333 kN-m or – 90 kN-m ∴MA = 406 kN-m or – 90 kN-m 1.4D =189 kN-m 1.2D +1.6 L = 266 kN-m 1.2D + f1L = 194.5 kN-m 2. Strength design axial load at column C - D a. Determine earthquake load E: E =Eh + Ev Ev = 0.5CaID = 05(0.44)(1.0)(400) = 88 kN Eh = 490 kN E = 1.1(490) + 88 = 627 kN b. Apply earthquake load combinations PC = 1.2D+ 1.0E + f1L = 1.2(400) + 1.0(627)+0.5(180) = 1197kN PC = 0.9D± 1.0E = 0.9(400) ± 1.0(627) = 987 kN or – 267 kN ∴ PC = 1197 kN or – 267 kN 1.4D =560 kN 1.2D +1.6 L = 768 kN 1.2D + f1L = 570 kN 3. Strength design moment at column top C a. Determine earthquake load E: E =Eh + Ev Ev = 0.5CaID = 05(0.44)(1.0)(55) = 12.1 kN-m Eh = 220 kN-m E = 1.1(220) + 12.1 = 254 kN-m b. Apply earthquake load combinations MC = 1.2MD + 1.0ME + f1ML = 1.2(55) + 1.0(254)+0.5(30) = 335 kN-m MC = 0.9MD ± 1.0ME = 0.9(55) ± 1.0(254) = 304 kN-m or – 205 kN-m 28 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] ∴MC = 335 kN-m or – 205 kN-m 1.4D =77 kN-m 1.2D +1.6 L = 114 kN-m 1.2D + f1L = 81 kN-m Note that the column section capacity must be designed for the interaction of P C = 1197 kN compression and MC = 335 kN-m (for dead, live and earthquake), and the interaction of PC = 267 kN tension and MC = - 205 kN-m (for dead and earthquake) Using allowable stress design: 1. E = Eh + Ev; Ev = 0 E = 1.1(165) + 0 = 181.5 kN-m D + E/1.4 = 135+ 181.5/1.4 = 264.64 kN-m 0.90D + E/1.4 = 0.90(135) + 181.5/1.4 = 251.14 kN-m 0.90D – E/1.4 = 0.90(135) – 181.5/1.4 = - 8.14 kN-m D + 0.75[L + E/1.4] = 135+ 0.75[65 + 181.5/1.4] = 329.64 kN-m ∴MA = 329.64 kN-m or – 8.14 kN-m 2. E = Eh + Ev; Ev = 0 E = 1.1(490) + 0 = 539 kN D + E/1.4 = 400 + 539/1.4 = 785 kN 0.90D + E/1.4 = 0.90(400) + 539/1.4 = 745 kN 0.90D – E/1.4 = 0.90(400) – 539/1.4 = - 25 kN D + 0.75[L + E/1.4] = 400 + 0.75[180 + 539/1.4] = 823.75 kN ∴PC = 823.75 kN or – 25 kN 3. E = Eh + Ev; Ev = 0 E = 1.1(220) + 0 = 242 kN-m D + E/1.4 = 55+ 242/1.4 = 227.86 kN-m 0.90D + E/1.4 = 0.90(55) + 242/1.4 = 222.36 kN-m 0.90D – E/1.4 = 0.90(55) – 242/1.4 = - 123.36 kN-m D + 0.75[L + E/1.4] = 55 + 0.75[30 + 242/1.4 = 207.14 kN-m ∴MC = 227.86 kN-m or – 123.36 kN-m 29 DON HONORIO VENTURA STATE UNIVERSITY COLLEGE OF ENGINEERING AND Cabambangan, Villa de Bacolor 2001, Pampanga, Philippines ARCHITECTURE Tel. No. (6345) 458 0021; Fax (6345) 458 0021 Local 211 URL: http://dhvsu.edu.ph DHVSU Main Campus, Villa de Bacolor, Pampanga E-Mail Address: [email protected] References: 1. AslamKassimali, UNDERSTANDING STRUCTURAL ANALYSIS 2. R.C. Hibbeler, STRUCTURAL ANALYSIS (7th Edition) 3. Encyc. Brit. – Encyclopedia Britannica 4. Jack C. McCormac and James K. Nelson Jr. – Structural Analysis (A Classical and Matrix Approach), Second Edition, 1997 5. C. H. Norris, J. B. Wilbur & S. Utku– Elementary Structural Analysis, Fourth Edition;1991 6. National Structural Code of the Philippines - 2015 30