NED UNIVERSITY OF ENGINEERING & TECHNOLOGY SEISMIC BUILDING CODE OF PAKISTAN

CHAPTER 3 SITE CONSIDERATIONS

Site Considerations Chapter 3 highlights different types of soil hazards that can damage a structure, in case of an earthquake. In conjunction some outlines are provided in order to select a site as to avoid maximum damage from these hazards. These hazards are listed as ; Fault rupture hazard Liquefaction Landslide and Slope instability Sensitive clays

CHAPTER 4 SOILS AND FOUNDATIONS

Soils and Foundations Chapter 4 emphasizes on the component where the SSI (Soil- Structure-Interaction) takes place. Sections 4.1 – 4.3 define the different terminologies and terms used in the Chapter. However, the core information is divided into the rest of the sections which forms the backbone of the chapter. 4.4 – Soil Profiles 4.5 – Requirements for Foundation 4.6 – Seismic Soil Pressures and Soil Retaining Structures

4.4 – Soil Profiles Soil profile development procedures are identified here. Vs Method (Average shear wave velocity method) N Method (Average field penetration resistance method) Su Method (Average undrained shear strength method)

4.5 - Requirements for Foundation Foundation requirements in different conditions are presented here, as to make certain that the underlying soil does not impose significant damage on the superstructure. Rules given in this Chapter for foundations are applicable to the foundations of reinforced concrete, structural steel, timber and masonry buildings. Some of the topics discussed are: Foundation Construction in Areas in Seismic Zones 2, 3, 4 Superstructure-to-Foundation Connection Piles, Caps and Caissons Foundation Tie Beams Wall Foundations of Masonry and Timber Buildings Footings on or adjacent to Slopes

4.6 – Seismic Soil Pressures and Soil Retaining Structures This section presents different soil pressure coefficients (and distribution) at rest and incase of an earthquake, on retaining structures for design and analysis purposes. Such as: Total Active and Passive Pressure Coefficients Dynamic Active and Passive Soil Pressures Dynamic Soil Pressures in Layered Soils In addition to soil pressure, stability requirements for retaining walls are also provided. Such as: Factor of safety against sliding (F.S. = 1.1) Factor of safety against over-turning (F.S. = 1.3) Reduction factor to convert the dynamic internal forces applicable for section design of RCC (R ZA = 1.5) and Steel sheet piles (R ZA = 2.5).

CHAPTER 5 STRUCTURAL DESIGN REQUIREMENTS

Structural Design Requirements Chapter 5 is divided into five sub divisions Division I – General Design Requirements Division II – Snow Loads Division III – Wind Design Division IV – Earthquake Design Division V – Soil Profile Types

Division I – General Design Requirements This division provides the general design requirements applicable to all structures. Sections 5.1 to 5.4 present a general description of the terminologies used in the division. Section 5.5 presents the requirements to achieve a stable structure, discussing issues such as; complete load path, overturning, distribution of horizontal shear force, anchorage, etc. Section 5.6 defines the partition loads on buildings and access floor system as 21 psf & 10.5 psf, respectively. Section 5.7 defines the live loads and their distribution on the floors according to different occupancies, enlisted in Table 5-A. Along side it also discusses the cases for live load reduction as given by the following equation:

USE OR OCCUPANCY UNIFORM LOAD 1 CONCENTR ATED LOAD Category Description kN/m 2 psfkNlbs 1.Access floor system Office use ,002 2 Computer use , Armories Assembly areas 3 and auditoriums and balconies therewith Fixed seating areas Movable seating and other areas Stage areas and enclosed platforms Cornices and marquees Exit facilities Garages General storage and/or repair Private or pleasure-type motor vehicle storage Hospitals Wards and rooms , Libraries Reading rooms ,000 2 Stack room , Manufacturing Light ,000 2 Heavy , Offices , Printing plants Press rooms ,500 2 Composing and linotype rooms , Residential 8 Basic floor area Exterior balconies Decks Storage Restrooms 9 14.Reviewing stands, grandstands, bleachers, and folding and telescoping seating Roof decks Same as area served or for the type of occupancy accommodated 16.Schools Classrooms , Sidewalks and driveways Public access Storage Light Heavy Stores , Pedestrian bridges and walkways TABLE 5-A – UNIFORM AND CONCENTRATED LOADS

Division I – General Design Requirements Section 5.11 (Other Minimum Loads) provides description of other loads and some other guidelines, such as; Impact loads Interior wall loads Retaining walls Water accumulation Heliport and heli-stop landings 5.12 – Load Combinations; load combinations for ultimate and allowable conditions are provided. The major design combinations being: 1.4 D (5.12-1) 1.2 D L (L r or S) (5.12-2) 1.2 D (L r or S) + (f 1 L or 0.8 W) (5.12-3) 1.2 D W + f 1 L (L r or S) (5.12-4) 1.2 D E + (f 1 L + f 2 S) (5.12-5) 0.9 D ± (1.0 E or 1.3 W) (5.12-6)

Division I – General Design Requirements The allowable design combinations being; D (5.12-7) D + L + (L r r or S) (5.12-8) D + (W or E / 1.4) (5.12-9) 0.9 D ± E / 1.4 ( ) D [L+ (L r or S) + (W or E / 1.4)] ( ) provides load combinations for special seismic conditions; 1.2 D + f 1 L+ 1.0 E m ( ) 0.9 D ± 1.0 E m ( ) 5.13 Limits the deflection of structural members, which shall not exceed the values set forth in Table 5-D, based on the factors set forth in Table 5-E.

Division II – Snow Loads UBC-97 is referred for calculating the minimum design load: P f = C e I P g (40-1-1) Where: Ce = snow exposure factor (see Table A-16-A). I = importance factor (see Table A-16-B). P g =basic ground snow load, psf (N/m 2 ) – (For 50-year mean recurrence interval maps) Snow loads in excess of 1.0 kN/m 2 (20.88 psf) may be reduced for each degree of pitch over 20 degrees by R s as determined by the formula: R s = S/ For FPS: (5.14-1) R s = S/40-1/2 Where: R s = snow load reduction in kilo-Newton per square meter (lb/ft 2 ) per degree of pitch over 20 degrees. S = total snow load in kilo-Newton per square meter (lb/ft 2 ).

Division II – Snow Loads

Division III – Wind Design 5.20 defines the wind pressure on a surface as: P = C e C q q s I w (5.20-1) Where C e = combined height, exposure and gust factor coefficient as given in Table 5-G. C q = pressure coefficient for the structure or portion of structure under consideration as given in Table 5-H. I w = importance factor as set forth in Table 5-K. P = design wind pressure. q s = wind stagnation pressure at the standard height of 10 meters (33 feet) as set forth in Table 5-F. Unless detailed wind data is available; All the structures inland shall be designed to resist a wind velocity of not less than 144 km per hour (90 mph) at a height of 10 meters (33 ft) All the structures along the coast shall be designed to resist a wind velocity of not less than 180 km per hour (109 mph) at a height of 10 meters (33 ft). 5.21: The primary frames or load-resisting system of every structure shall be designed for the pressures calculated using Formula (5.20-1) and the pressure coefficient, C q, of either Method 1 (Normal Force Method) or Method 2 (Projected Area Method)

Division III – Wind Design Table 5-G Table 5-H Table 5-K Table 5-F

Division IV – Earthquake Design Sections 5.26 to 5.28 provide some basic definitions and notations used in the chapter. Some of them being: Design Basis Ground Motion is that ground motion that has a 10 percent chance of being exceeded in 50 years as determined by a site-specific hazard analysis or may be determined from a hazard map. Design Response Spectrum is an elastic response spectrum for 5 percent equivalent viscous damping used to represent the dynamic effects of the Design Basis Ground Motion for the design of structures in accordance with Sections 5.30 and Soft Storey is one in which the lateral stiffness is less than 70 percent of the stiffness of the storey above. Weak Storey is one in which the storey strength is less than 80 percent of the storey above.

5.29 – Criteria Selection The procedures and the limitations for the design of structures are described here considering seismic zoning, site characteristics, occupancy, configuration, structural system and height Structural systems Bearing wall system. A structural system without a complete vertical load- carrying space frame. Building frame system. A structural system with an essentially complete space frame providing support for gravity loads. Resistance to lateral load is provided by shear walls or braced frames. Moment-resisting frame system. A structural system with an essentially complete space frame providing support for gravity loads. Moment-resisting frames provide resistance to lateral load primarily by flexural action of members. Dual system. Resistance to lateral load is provided by shear walls or braced frames and moment resisting frames (SMRF, IMRF, MMRWF or steel OMRF). The moment-resisting frames shall be designed to independently resist at least 25 percent of the design base shear.

5.29 – Criteria Selection Section provides the criteria to choose the procedure of lateral force analysis. Simplified Static : Buildings of any occupancy (including single-family dwellings) not more than three storeys in height excluding basements that use light-frame construction. And other buildings not more than two storeys in height excluding basements. Static: All structures, regular or irregular, in Seismic Zone 1 and in Occupancy Categories 4 and 5 in Seismic Zone 2. Regular structures under 73.0 meters (240 feet) in height with lateral force resistance provided by systems listed in Table 5-N. And irregular structures not more than five storeys or 20 meters (65 feet) in height. Structures having a flexible upper portion supported on a rigid lower portion where both portions of the structure considered separately can be classified as being regular. Dynamic: The dynamic lateral-force procedure of Section 5.31 shall be used for all other structures.

– Static Force Procedure Design Base Shear – (Equation ) (Design Base Shear) (The total Seismic Dead Load) (Section )Section (Importance factor, depending on the use of the building)(Table 5-K)Table 5-K (Seismic Coefficient, depending on seismic zone and soil profile type)(Table 5-R)Table 5-R (Elastic fundamental Time Period of the structure) To be calculated as stated in Section Section (Response modification factor, representing Over Strength and global ductility capacity of lateral force-resisting systems)(Table 5-N)Table 5-N ≤ ≤ NEXT

– Structure Period Structure Period: The fundamental time period T shall be determined from equation or from equation Method A (5.30-8) Method B (5.30-9) PREV

Table 5-Q & R – Seismic Coefficient C a & C v PREV

Table 5-K – Occupancy Category PREV

– Seismic Dead Load Seismic dead load, W, 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 a partition load is used in the floor design, a load of not less than 0.48 kN/m 2 (10 psf) shall be included. 3. Design snow loads of 1.44 kN/m 2 (30 psf) or less need not be included. Where design snow loads exceed 1.44 kN/m 2 (30 psf), the design snow load shall be included, but may be reduced up to 75 percent where consideration of siting, configuration and load duration warrant when approved by the building official. 4. Total weight of permanent equipment shall be included. PREV

Table 5-N – Structural Systems PREV

Distribution of Lateral forces – Vertical distribution of force: Where F t is the concentrated force at the top: F t = 0.07 TV There fore the force at a level x is: ( ) – Horizontal distribution of force: The design storey shear, Vx, shall be distributed to the various elements of the vertical lateral-force-resisting system in proportion to their rigidities

Drift and Drift Limitations The maximum inelastic drift is to be calculated by: ∆ M = 0.7 R ∆ S ( ) Where ∆ S is the drift computed from the elastic analysis of the frame, using load combinations in section 5.12 Calculated storey drift using ∆ M shall not exceed times the storey height for structures having a fundamental period of less than 0.7 second. For structures having a fundamental period of 0.7 second or greater, the calculated storey drift shall not exceed times the storey height.

Vertical Structural Irregularities

Plan Structural Irregularities

5.31 – Dynamic Analysis Ground Motions: The ground motion representation shall be one having a 10-percent probability of being exceeded in 50 years, shall not be reduced by the quantity R and may be one of the following: An elastic design response spectrum constructed using the values of C a and C v consistent with the specific site. A site-specific elastic design response spectrum based on the geologic, tectonic, seismologic and soil characteristics associated with the specific site. (for a damping ratio of 0.05) Ground motion time histories developed for the specific site shall be representative of actual earthquake motions. The vertical component of ground motion may be defined by scaling corresponding horizontal accelerations by a factor of two-thirds.

Division V – Soil Profile Types The basic soil profile types are the same as defined in section Average shear wave velocity may be computed as: (5.36-1)

Division V – Soil Profile Types Average Field Penetration resistance may be computed as: Average Un-drained Shear Strength may be computed as: