RCD Manuscripts.pdf

Palawan State University College of Engineering, Architecture, and Technology Bachelor of Science in Civil Engineering CE PC 4 Reinforced Concrete Design LESSON 2: GRAVITY LOADS ON STRUCTU...

Palawan State University College of Engineering, Architecture, and Technology Bachelor of Science in Civil Engineering CE PC 4 Reinforced Concrete Design LESSON 2: GRAVITY LOADS ON STRUCTURE REPORTERS: Xavier Levi C. Ong Deo Angelo M. Siruno Edgrado M. Zabala III INTRODUCTION Classification of Loads Loads can be classified based on:  The direction of the load,  Duration of the load,  Spatial distribution of the load, and  Source of the loading. Direction of the Load Based on their direction in which they act on a structure, loads are classified into two major categories. They are:  Gravity Loads (Vertical Loads)  Lateral Loads (Horizontal Loads) GRAVITY LOADS Forces delivered perpendicular to the roof or floor system are known as vertical loads or gravity loads. These loads can also be categorized as:  Dead load - is the combined weight of all the finishes that give the structure its appearance and the structural parts that make up the structure.  Live loads - are the weights placed on a structure by its occupants and the items they choose to assemble inside (furniture, storage, etc.).  Snow loads - The weight of ice and snow accumulation on a building's roof causes a force known as the snow load. If there is more snow than the building can support, either the roof or the entire structure may collapse. The height of the building, the size and shape of the roof, whether the building is located on a slope or not, how often snow falls, and other factors all affect how much snow falls. DEAD LOADS These are permanent loads that are carried by the structure throughout its lifetime. Dead loads are often referred to as stationary loads. Simply it is the weight of all the materials, and elements incorporated into the building or other horizontal and vertical structures. These include:  walls  built-in partitions  beam  cladding  floor  cranes  roofs  architectural items  ceiling  other fixed service items  machines  etc.  stairways NOTE!  Weight of Materials and Construction o When computing dead loads the engineer should utilize the actual weight of the materials, or equipment used in the structure for design. o Tables 204-1 and 204-2 can be used as a basis if there is an absence of information about the weight of the material.  Partition Loads and Access Floor System o Office and other types of buildings except residential, may have partition locations. These require an addition of a uniformly distributed load of 1 kPa to all other loads. o Meanwhile a uniformly distributed load of not less than 0.5 kPa shall be added to support an AFS. TABLE 204-1 Minimum Densities for Design Loads from Materials (kN/m3) TABLE 204-2 Minimum Design Loads (kPa) Live Loads  Live loads are also called imposed loads, and they are either moving loads, or movable loads, that do not have any impact or acceleration. All these loads are part of what an occupant brings into the building. These items are normally furniture and movable partitions.  Live loads shall be the maximum loads expected by the intended use or occupancy but in no case shall be less than the loads required. 1. Floor Live Loads  Floors shall be designed for the unit live loads as set forth in Table 205-1. These loads shall be taken as the minimum live loads of horizontal projection to be used in the design of buildings for the occupancies. 1.1 Distribution of Uniform Floor Loads  Where uniform loads are involved, consideration may be limited to full dead load on all spans in combination with full live load on adjacent spans and alternate spans. 1.2 Concentrated Floor Loads  Floors shall be designed to support safely the uniformly distributed live loads prescribed or the concentrated load given in Table 205-1 whichever produces the greatest load effects.  Otherwise specified the indicated concentration shall be assumed to be uniformly distributed over an area of 750-mm square and shall be located so as to produce the maximum load effects in the structural member.  Vehicles are used or stored for concentrated loads.  Each load shall be 40% of the gross weight of the maximum size vehicle to be accommodated. Consisting of two or more loads spaced 1.5m nominally on center without uniform live loads.  Parking garages for storage with no repair of refueling shall have a floor system designed for a concentrated load of not less than 9 kN acting on an area of 0.015 m² without uniform live loads. 2. Special Loads  Provision shall be made for the special vertical and lateral loads as set forth in Table 205-2. 3. Roof Live Loads  The live loads shall be assumed to act vertically upon the area projected on a horizontal plane.  3.1 Distribution of Loads  For those light-gage metal preformed structural sheets serve as the support and finish of roofs, roof structural members arranged to create continuity shall be considered adequate.  If designed for full dead loads on all spans in combination with the most critical one of the following superimposed loads: o The uniform roof live load, set forth in Table 205-3 on all spans. o A concentrated gravity load of 9 kN placed on any span supporting a tributary area greater than 18 m² to creat maximum stress in the member. Otherwise, the concentrated load shall be placed on the member over a length of 0.75 m along the span. o Water accumulation as prescribed in Section 206.7. 3.2 Unbalanced Loading  Unbalanced loads shall be used where such loading will result in larger members or connections. Trusses and arches shall be designed to resist the stresses caused by unit live loads on one-half of the span or greater in any portion than the stresses produced on the entire span.  For roofs whose structures are composed of a stressed shell, framed or solid wherein stresses in any point loading are distributed, the requirements for unbalanced unit live load design may be reduced to 50%. 3.3 Special Roof Loads  For special purposes shall be designed for appropriate loads as approved by the building official. Greenhouse roof bars, purlins and rafters shall be designed to carry a 0.45 kN concentrated load. 3.4 Reduction of Live Loads  For roofs may be reduced on any member supporting more than 15 m², including flat slabs, except for floors in places of public assembly and for live loads greater than 4.8 kPa. R = r(A-15) Where: R = reduction in percentage r = rate of reduction equal to 0.08 for floors. A = area of floor or roof supported by the member, m²  The reduction shall not exceed 40% for members receiving load from one level only, 60% for other members. R = 23.1(1+ D/L) Where: R = reduction in percentage D = dead load per m² of area supported by the member, kPa L = unit live load per m² of area supported by the member, kPa  For storage loads exceeding 4.8 kPa, no reduction shall be made, except that design live loads on columns may be reduced to 20%.  The live load reduction shall not exceed 40% in garages for the storage of private pleasure cars having a capacity of not more than nine passengers per vehicle. 3.5 Alternate Floor Live Load Reduction  Unit live loads set forth in Table 205-1 may be reduced in any member, including flat slabs, having an influence area of 40m² 1 𝐿 = 𝐿0 [0.25 + 4.57 ( )] √𝐴1 Where: 𝐴1 = influence area, m² 𝐿 = reduced design live load per m² of area supported by the member 𝐿0 =unreduced design live load per m² of area supported by the member Table 205-1 Table 205-2 Table 205-3 OTHER MINIMUM LOADS 206.1 General In addition to the other design loads specified in this chapter, structures shall be designed to resist the loads specified in this section and the special loads set forth in. Table 205-2. See Section 207 for design wind loads and Section 208 for design earthquake loads. 206.2 Other Loads Buildings and other structures and portions thereof shall be designed to resist all loads due to applicable fluid pressures. F, lateral soil pressures, H, ponding loads, P, and self-straining forces, T. See Section 206.7 for ponding loads for roofs. 206.3 Impact Loads. The live loads specified in Sections 205.3 shall be assumed to include allowance for ordinary impact conditions. Provisions shall be made in the structural design for uses and loads that involve unusual vibration and impact forces. See Section 206.9.3 for impact loads for cranes, and Section 206.10 for heliport and helistop landing areas. 206.3.1 Elevators All elevator loads shall be increased by 100% for impact 206.3.2 Machinery For the purpose of design, the weight of machinery and moving loads shall be increased as follows to allow for impact:  Elevator machinery 100%  Light machinery, shaft- or motor-driven 20%  Reciprocating machinery or power-driven units 50%  Hangers for floors and balconies 33%  All percentages shall be increased where specified by the manufacturer. 206.4 Anchorage of Concrete and Masonry Walls Concrete and masonry walls shall be anchored as required. by Section 104.3.3. Such anchorage shall be capable of resisting the load combinations of Section 203.3 or 203.4 using the greater of the wind or earthquake loads required by this chapter or a minimum horizontal force of 4 kN/m of wall, substituted for E. 206.5 Interior Wall Loads Interior walls, permanent partitions and temporary partitions that exceed 1.8 m in height shall be designed to resist all loads to which they are subjected but not less than a load, L, of 0.25 kPa applied perpendicular to the walls. The 0.25 kPa load need not be applied simultaneously with wind or seismic loads. The deflection of such walls under a load of 0.25 kPa shall not exceed 1/240 of the span for walls with brittle finishes and 1/120 of the span for walls with flexible finishes. See Table 208-13 for earthquake design requirements where such requirements are more restrictive.  Exception: Flexible, folding or portable partitions are not required to meet the loud and deflection criteria but must be anchored to the supporting structure to meet the provisions of this code Retaining walls shall be designed to resist loads due to the lateral pressure of retained material in accordance with accepted engineering practice. Walls retaining drained soil, where the surface of the retained soil is level, shall be designed for a load, H, equivalent to that exerted by a fluid weighing not less than 4.7 kPa per meter of depth and having a depth equal to that of the retained soil. Any surcharge shall be in addition to the equivalent fluid pressure. Retaining walls shall be designed to resist sliding by at least 1.5 times the lateral force and overturning by at least 1.5 times the overturning moment, using allowable stress design loads. 206.7 Water Accumulation All roofs shall be designed with sufficient slope or camber to ensure adequate drainage after the long-term deflection from dead load or shall be designed to resist ponding load P, combined in accordance with Section 203.3 or 203.4. Ponding load shall include water accumulation from any source due to deflection. 206.8 Uplift on Floors and Foundations In the design of basement floors and similar approximately horizontal elements below grade, the upward pressure of water, where applicable, shall be taken as the full hydrostatic pressure applied over the entire area. The hydrostatic load shall be measured from the underside of the construction. Any other upward loads shall be included in the design. Where expansive soils are present under foundations or slabs-on-ground, the foundations, slabs, and other components shall be designed to tolerate the movement or resist the upward loads caused by the expansive soils, or the expansive soil shall be removed or stabilized around and beneath the structure. 206.9 Crane Loads 206.9.1 General The crane load shall be the rated capacity of the crane. Design loads for the runway beams, including connections and support brackets of moving bridge cranes and monorail cranes shall include the maximum wheel loads of the crane and the vertical impact, lateral, and longitudinal forces induced by the moving crane. 206.9.2 Maximum Wheel Load The maximum wheel loads shall be the wheel loads produced by the weight of the bridge, as applicable, plus the sum of the rated capacity and the weight of the trolley with the trolley positioned on its runway where the resulting load effect is maximum.  206.9.3 Vertical Impact Force The maximum wheel loads of the crane shall be increased by the percentages shown below to determine the induced vertical impact or vibration force:  Monorail cranes (powered) - 25%  Cab-operated or remotely operated bridge cranes (powered) - 25%  Pendant-operated bridge cranes (powered) - 10%  Bridge cranes or monorail cranes with hand-geared ridge, trolley and hoist - 0% 206.9.4 Lateral Force The lateral force on crane runway beams with electrically powered trolleys shall be calculated as 20% of the sum of the rated capacity of the crane and the weight of the hoist and trolley. The lateral force shall be assumed to act horizontally at the traction surface of a runway beam, in either direction perpendicular to the beam, and shall be distributed with due regard to the lateral stiffness of the runway beam and supporting structure, 206.9.5 Longitudinal Forces The longitudinal force on crane runway beams, except for bridge cranes with hand- geared bridges, shall be calculated as 10% of the maximum wheel loads of the crane. The longitudinal force shall be assumed to act horizontally at the traction surface of a runway beam, in either direction parallel to the beam. 206.10 Heliport and Helistop Landing Areas In addition to other design requirements of this chapter, heliport and helistop landing or touchdown areas shall be designed for the following loads, combined in accordance with Section 203.3 or 203.4:  Dead load plus actual weight of the helicopter.  Dead load plus a single concentrated impact load, L. covering 0.10 m² of 0.75 times the fully loaded weight of the helicopter if it is equipped with hydraulic-type shock absorbers, or 1.5 times the fully loaded weight of the helicopter if it is equipped with a rigid or skid- type landing gear.  The dead load plus a uniform live load, L, of 4.8 kPa. The required live load may be reduced in accordance with Section 205.5 or 205.6.  Palawan State University College of Engineering, Architecture, and Technology Bachelor of Science in Civil Engineering CE PC 4 Reinforced Concrete Design | Lesson 3 LATERAL LOADS ON STRUCTURE I. NSCP C101 II. Wind Loads III. Earthquake Loads IV. Other Lateral Loads Group 2: MILO, RACHELL KAYE ANN R. OMAPAS, DAN ANDRO P. REVILLAS, ALYSSA FE L.  LATERAL LOADS ON STRUCTURE I. CODE PROVISIONS - NSCP C101 Lateral Loads - Lateral loads are live loads that are applied horizontally, or parallel to the ground, acting on a structure. This includes wind, seismic and earth loads. Lateral loads on a building are usually resisted by walls and bracing. Section 207 - Wind Loads Section 208 - Earthquake Loads Section 209 - Soil Lateral Loads Section 207A Provides the basic wind design parameters that are applicable to the various wind load determination methodologies outlined in Sections 207B through 207F. Items covered in Section 207A include definitions, basic wind speed, exposure categories, internal pressures, enclosure classification, gust-effects, and topographic factors, among others. Section 207B Discusses about Directional Procedure for Enclosed, Partially Enclosed, and Open Buildings of All Heights: The procedure is the former "buildings of all heights method" in NSCP 2010 (ASCE 7-05), Method 2. A simplified procedure, based on the Directional Procedure, is provided for buildings up to 48m in height. Section 207C Discusses about Envelope Procedure for Enclosed and Partially Enclosed Low-Rise Buildings: This procedure is the former "low-rise buildings method" in NSCP 2010 (ASCE 7-05) Method 2. This section also incorporates NSCP 2010 (ASCE 7-05) Method 1 for MWFRS applicable to the MWFRS of enclosed simple diaphragm buildings less than 18 m in height. Section 207D Discusses Other Structures and Building Appurtenances: A single section is dedicated to determining wind loads on non-building structures such as signs, rooftop structures, and towers. Section 207E Discusses about Components and Cladding. This code addresses the determination of component and cladding loads in a single section. Analytical and simplified methods are provided based on the building height. Provisions for open buildings and building appurtenances are also addressed. Section 207F Discusses about Wind Tunnel Procedure. II. Wind Loads Wind load refers to the force exerted by the wind on structures such as buildings, bridges, towers, and other infrastructure. Main Wind-Force Resisting System (MWFRS) - elements of a building or structure that are specifically designed to resist and transfer wind loads safely to the foundation Section 207B. Directional procedure for buildings of all heights Section 207C. Envelope procedure for low-rise buildings Section 207D. Directional procedure for buildings appurtenances Section 207F. Wind tunnel procedure for any buidling or other structure Components and Cladding (C&C) - elements of a building's exterior that are not part of the primary structural system but are still essential for enclosing the building and protecting it from the elements Section 207E. Envelope Procedure, etc. Section 207F. Wind tunnel procedure for any buidling or other structure Main Wind-Force Resisting System (MWFRS) Section 207B. Directional procedure for buildings of all heights 1. Determine risk category of building or other structure (refer to Table 103-1 of NSCP) 2. Determine the basic wind speed, V, for the applicable risk category 3. Determine the six wind load parameters. 3.1 Wind directionality factor 𝐾𝑑 - The wind directionality factor accounts for the reduced likelihood that the maximum wind speed will impact all sides of a structure simultaneously. 3.2 Exposure category - The exposure category characterizes the surrounding terrain's effect on wind speed and, consequently, the wind pressure on a structure. - 3.3 Topographic factor, 𝐾𝑧𝑡 - The topographic factor considers the effect of local topography on wind speed-up over hills, ridges, or escarpments.  - If site condition and location do not all the conditions specified in Section 207.8.1, Kzt = 1.00. 3.4 Gust effect factor, G - The gust effect factor adjusts for the dynamic response of a structure to wind gusts, which are short-duration increases in wind speed. - The gust effect factor for a rigid building or other structure is permitted to be taken as 0.85. 3.5 Enclosure classification - Enclosure classification refers to the categorization of a building based on the degree of openness of its external envelope, which affects internal wind pressure. 1. Partially Enclosed Building: The total area of openings in a wall that receives positive external pressure exceeds the sum of the areas of openings in the balance of the building envelope (walls and roof) by more than 10%. The total area of openings in a wall that receives positive external pressure exceeds 0.37 sq.m. 1% of the area of that wall, whichever is smaller, and the percentage of openings in the balance of the building envelope does not exceed 20%. 2. Open Building – each wall at least 80% open. 3. Enclosed Building - building that does not satisfy the conditions for partially enclosed or open building. 3.6 Internal pressure coefficient - The internal pressure coefficient accounts for the pressure differences inside a building caused by wind entering through openings and cracks. 4. Determine velocity pressure exposure coefficient, 𝐾𝑧 or 𝐾ℎ (refer to Table 207B.3-1) The velocity pressure coefficient adjusts the wind pressure based on the height of the structure above ground and the exposure category. 5. Determine velocity pressure 𝑞𝑧 or 𝑞ℎ using Eq. 207B.3-1 of NSCP Velocity pressure is the pressure exerted by the wind on a structure, calculated as a function of wind speed. 𝒒𝒛 = 𝟎. 𝟔𝟏𝟑𝒌𝒛 𝒌𝒛𝒕 𝒌𝒅 𝑽𝟐 Kz = velocity pressure exposure coefficient Kzt = Topographic factor Kd = wind directionality factor V = basic wind speed, m/s 6. Determine external pressure coefficient, 𝐶𝑝 or 𝐶𝑛 based Fig. 207B.4-1 to 7.  7. Calculate wind pressure, p, on each building surface using Eq. 207B.4-1 to 3. 𝒑 = 𝒒𝑮𝑪𝒑 − 𝒒𝒊(𝑮𝑪𝒑𝒊) q = velocity pressure exposure coefficient G = Topographic factor Cp = wind directionality factor qi = basic wind speed, m/s GCpi = – internal pressure coefficient (refer to Table 207A.11-1) SAMPLE PROBLEM: A 3- story educational building has the following parameters: Roof mean height = 9 m Total height abouve the ground = 12 m Exposure Category : B Location: Daet, Camarines Norte Plan Dimension = 8 m x 9 m Gable roof with 15 degrees slope Total area of opening in every wall that receives positive external pressure is 0.20 m Wind direction parallel with the least dimension of the building Determine the design wind load on the structure. Solution: Step 1: Risk category of building Category III - Special Occupancy Structures Step 2: Determine the basic wind speed, V Based on Fig. 207A.5-1A, V = 290 kph Note that V must be in meter per second. V = 290 km/h = 80.56 m/s Step 3. Determine the six wind load parameters. 3.1 Wind directionality factor 𝐾𝑑 = 0.85 3.2 Exposure category: B 3.3 Topographic factor  𝐾𝑧𝑡 = 1.0 (since it is not located along hills or escarpment) 3.4 Gust effect factor G = 0.85 3.5 Enclosure classification Enclosed Building since the opening does not exceed 0.37 sq.m. 3.6 Internal pressure coefficient 𝐺𝐶𝑝𝑖 = ±0.18 Step 4: Determine velocity pressure exposure coefficient, 𝐾𝑧 or 𝐾ℎ 𝐾𝑧 (windward) Using the values z = 12m and Exposure B 𝐾𝑧 = 0.76 𝐾ℎ (leeward wall and sidewall) Using the values h = 9m and Exposure B 𝐾ℎ = 0.70 Step 5: Determine velocity pressure 𝑞𝑧 or 𝑞ℎ using Eq. 207B.3-1 of NSCP windward wall 𝒒𝒛 = 𝟎. 𝟔𝟏𝟑𝑲𝒛𝑲𝒛𝒕𝑲𝒅𝑽 𝑞𝑧 = 0.613(0.76) (1) (0.85) (80.562) 𝑞𝑧 = 2,569.71 𝑁 𝑚2 = 𝟐. 𝟓𝟕 𝒌𝑷𝒂 leeward wall and side wall 𝒒𝒉 = 𝟎. 𝟔𝟏𝟑𝑲𝒉𝑲𝒛𝒕𝑲𝒅𝑽 𝑞ℎ = 0.613(0.70) (1) (0.85) (80.562) 𝑞ℎ = 2,367.01 𝑁 𝑚2 = 𝟐. 𝟑𝟕 𝒌𝑷a Step 6: Determine external pressure coefficient, 𝐶𝑝 or 𝐶𝑛 based Fig. 207B.4-1 to 7. windward wall, Cp = 0.8 leeward, Cp = -0.5 sidewall, Cp = -0.7 Roof, windward, Cp = 1.3 leeward, Cp = -0.6 Step 7: Calculate wind pressure, p, on each building surface using Eq. 207B.4-1 to 3. 𝒑 = 𝒒𝑮𝑪𝒑 − 𝒒𝒊(𝑮𝑪𝒑𝒊) Windward, where 𝑞 = 𝑞𝑧, 𝑞𝑖= 𝑞ℎ 𝑝 = (2.57) (0.85) (0.8) − (2.37) (0.18) 𝒑 = 𝟎. 𝟏𝟒 𝒌𝑷𝒂 𝑝 = (2.57) (0.85) (0.8) − (2.37) (−0.18) 𝒑 = 𝟐. 𝟏𝟕 𝒌𝑷a Leeward, where 𝑞 = 𝑞ℎ, 𝑞𝑖= 𝑞ℎ 𝑝 = (2.37) (0.85) (−0.5) − (2.37) (0.18) 𝒑 = −𝟏. 𝟒𝟑 𝒌𝑷𝒂 𝑝 = (2.37) (0.85) (−0.5) − (2.37) (−0.18) 𝒑 = −𝟎. 𝟓𝟖 𝒌𝑷a Sidewall, where 𝑞 = 𝑞ℎ, 𝑞𝑖= 𝑞ℎ 𝑝 = (2.37) (0.85) (−0.7) − (2.37) (0.18) 𝒑 = −𝟏. 𝟖𝟒 𝒌𝑷𝒂 𝑝 = (2.37) (0.85) (0.8) − (2.37) (−0.18) 𝒑 = −𝟎. 𝟗𝟖 𝒌𝑷a Roof For windward side, 𝑞 = 𝑞𝑧 , 𝑞𝑖= 𝑞ℎ 𝑝 = (2.57) (0.85) (−1.3) − (2.37) (0.18) 𝒑 = −𝟑. 𝟐𝟕 𝒌𝑷𝒂 𝑝 = (2.57) (0.85) (−1.3) − (2.37) (−0.18) 𝒑 = −𝟐. 𝟒𝟏 𝒌𝑷𝒂 For leeward side, 𝑞 = 𝑞ℎ, 𝑞𝑖= 𝑞ℎ 𝑝 = (2.37) (0.85) (−0.6) − (2.37) (0.18) 𝒑 = −𝟏. 𝟔𝟒 𝒌𝑷𝒂 𝑝 = (2.37) (0.85) (−0.6) − (2.37) (−0.18) 𝒑 = −𝟎. 𝟕𝟖 𝒌𝑷a III. EARTHQUAKE LOADS GENERAL PURPOSE The purpose of the succeeding 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 are not intended to assure zero-damage to structures nor maintain their functionality after a severe earthquake. MINIMUM SEISMIC DESIGN Structures and portions thereof shall, as a minimum, be designed and constructed to resists the effects of seismic ground motions as provided in this section. SEISMIC AND WIND DESIGN When the code-prescribed wind design produces greater effects, the wind design shall govern, but detailing requirements and limitations prescribed in this section and referenced sections shall be made to govern. BASIS FOR DESIGN OCCUPANCY CATEGORIES For purposes of earthquake-resistant design, each structure shall be placed in one of the occupancy categories listed in Table 103-1. Table 208-1 assigns important factors, I and Ip, and structural observation requirements for each category. 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 sourced, site soil profile characteristics and the struture’s importance factor. SEISMIC ZONE 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. 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 0 0 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).  Figure 208-1 Referenced Seismic Map of the Philippines 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. For high rise structures and essential facilities within 2. 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 used to determine need not exceed 1.1 for Na Ca structures complying with all the following conditions: 1. The soil profile type is SA, SB, SC, SD, or SE. 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 multistorey buildings. 5. None of the following structural irregularities is present Type 1, 4 or 5 of Table 208-9, and Type 1 or 4 of Table 208-10. SEISMIC RESPONSE COEFFICIENTS Each structure shall be assigned a seismic coefficient Ca, accordance with Table 208-7 and a seismic coefficient Cv, in accordance with Table 208-8. CONFIGURATION REQUIREMENTS Each structure shall be designated as being structurally regular or irregular in accordance with Sections 208.4.5.1 and 208.4.5.2. 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 features described in Section 208.4.5.2. 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 Seismic Zone 2 need to be evaluated only for vertical irregularities of Type 5 (Table 208-9) and horizontal irregularities of Type 1 (Table 208-10). 2. Structures having any of the features listed in Table 208-9 shall be designated as if having a vertical irregularity. 3. Structures having any of the features listed in Table 208-10 shall be designated as having a plan irregularity. EARTHQUAKE LOADS AND MODELING REQUIREMENTS Earthquake Loads Structures shall be designed for ground motion producing structural response and seismic forces in any horizontal direction. The following earthquake loads shall be used in the load combinations set forth in Section 203: IV. OTHER LATERAL LOAD: Soil Lateral Loads - is the lateral pressure exerted by the soil on a shoring system. It depends on the type of soil and how it interacts or moves with the retaining structure. 3 Most Common Type of Lateral Soil Load: At Rest State - When the wall is stationary and backfill soil has no tendency to move. Under the rest condition the retaining wall is stationary therefore lateral stress will be zero. Active Pressure - is developed when the wall moves away from the back fill. The active earth pressure is less than pressure at rest because the internal resistance is mobilized in the soil of backfill when the wall moves away from the back fill. Passive Pressure - the wall is pushed towards the back fill. The passive earth pressure is greater than earth pressure at rest because shearing resistance is built up between two surfaces of soil mass.