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TCVN 9386:2012 is converted from TCXDVN 375:2006 into National Standard according to provisions at Clause 1, Article 69 of the Law on Standards and Technical Regulations and Point b, Clause 2, Article 7 of Decree No. 1272007NDCP of August 01, 2007, issued by Government, dated August 01, 2007, detailing the implementation of a number of articles of the Law on Standards and Technical Regulations. TCVN 9386:2012 is compiled by the Institute for Building Science and Technology Ministry of Construction, requested by Ministr of Construction, authenticated by the Directorate for Standards, Metrology and Quality, and announced by Ministry of Science and Technology. VIETNAM STANDARD TCVN 9386:2012 1st Publish DESIGN OF STRUCTURES FOR EARTHQUAKE RESISTANCES PART 1: GENERAL RULES, SEISMIC ACTIONS AND RULES FOR BUILDINGS PART 2: FOUNDATIONS, RETAINING STRUCTURES AND GEOTECHNICAL ASPECTS Hanoi - 2012 Contents Foreword Introduction GENERAL 1.1 Scope 1.2 Cited documents 1.3 Assumptions 1.4 Distinction between Principles and Application Rules 1.5 Terms and definitions 1.6 Symbols 1.7 S.I Units Performance requirements and compliance criteria 2.1 Fundamental requirements 2.2 Compliance Criteria Ground conditions and seismic action 3.1 Ground conditions 3.2 Seismic action Design of buildings 4.1 General 4.2 Characteristics of earthquake resistant buildings 4.3 Structural analysis 4.4 Safety verifications Specific rules for concrete buildings 5.1 General 5.2 Design concepts 5.3 Design to EN 1992-1-1 5.4 Design for DCM 5.5 Design for DCH 5.6 Provisions for anchorages and splices 5.7 Design and detailing of secondary seismic elements 5.8 Concrete foundation elements 5.9 Local effects due to masonry or concrete infills 5.10 Provisions for concrete diaphragms 5.11 Precast concrete structures Specific rules for steel buildings 6.1 General 6.2 Materials 6.3 Structural types and behaviour factors 6.4 Structural analysis 6.5 Design criteria and detailing rules for dissipative structural behaviour common to all structural types 6.6 Design and detailing rules for moment resisting frames 6.7 Design and detailing rules for frames with concentric bracings 6.8 Design and detailing rules for frames with eccentric bracings 6.9 Design rules for inverted pendulum structures 6.10 Design rules for steel structures with concrete cores or concrete walls and for moment resisting frames combined with concentric bracings or infills 6.11 Control of design and construction Specific rules for composite steel–concrete buildings 7.1 General 7.2 Materials 7.3 Structural types and behaviour factors 7.4 Structural analysis 7.5 Design criteria and detailing rules for dissipative structural behaviour common to all structural types 7.6 Rules for members 7.7 Design and detailing rules for moment frames 7.8 Design and detailing rules for composite concentrically braced frames 7.9 Design and detailing rules for composite eccentrically braced frames 7.10 Design and detailing rules for structural systems made of reinforced concrete shear walls composite with structural steel elements 7.11 Design and detailing rules for composite steel plate shear walls Specific rules for timber buildings 8.1 General 8.2 Materials and properties of dissipative zones 8.3 Ductility classes and behaviour factors 8.4 Structural analysis 8.5 Detailing rules 8.6 Safety verifications 8.7 Control of design and construction Specific rules for masonry buildings 9.1 Scope 9.2 Materials and bonding patterns 9.3 Types of construction and behaviour factors 9.4 Structural analysis 9.5 Design criteria and construction rules 9.6 Safety verification 9.7 Rules for “simple masonry buildings” 10 Base isolation 10.1 Scope 10.2 Definitions 10.3 Fundamental requirements 10.4 Compliance criteria 10.5 General design provisions 10.6 Seismic action 10.7 Behaviour factor 10.8 Properties of the isolation system 10.9 Structural analysis 10.10 Safety verifications at Ultimate Limit State Appendix A (informative): Elastic displacement response spectrum Appendix B (informative): Determination of the target displacement for nonlinear static (pushover) analysis Appendix C (normative): Design of the slab of steel-concrete composite beams at beamcolumn joints in moment resisting frames Appendix D (Reference): Symbols Appendix E (Regulation): Degree and importance factor Appendix F: Grading and classification of construction works Appendix G (Regulation): Ground acceleration zone map of Vietnam Appendix H (Regulation): Table of ground acceleration of administrative locations Appendix I (Reference): Table I.1 – Table of converting peak ground acceleration into earthquake level Part 2: Foundations, retaining structures and geotechnical aspects General 1.1 Field of application 1.2 Further reference documents for this regulation 1.3 Assumptions 1.4 Distinguish between principles and prescripts 1.5 Terms and definitions 1.6 Symbols 1.7 International system of units (SI) Earthquake effect 2.1 Definition of earthquake effect 2.2 Histogram Properties of ground soil 3.1 Strength parameters 3.2 Stiffness parameters and resistance parameters Requirements in choosing building location and ground soil 4.1 Choosing building location 4.2 Surveillance and study about ground Foundation system 5.1 General requirements 5.3 Designed effect 5.4 Criteria in testing and size determination Interaction between earth and structure Retaining wall structure 7.1 General requirements 7.2 Choice of structures and notes about designing 7.3 Analysis methods 7.4 Strength and stability test Appendix A (reference): Relief amplification factor Appendix B (compulsory): Experimental graphs used to analyzing simplified liquefaction Appendix C (compulsory): Pile head’s static stiffness Appendix D (reference): Structure-soil interaction (ssi): general effects and importance Appendix E (compulsory): Simplified analyzing method for retaining wall structure Appendix F (reference): Earthquake load bearing capacity of shallow foundation Foreword TCVN 9386:2012 is converted from TCXDVN 375:2006 into National Standard according to provisions at Clause 1, Article 69 of the Law on Standards and Technical Regulations and Point b, Clause 2, Article of Decree No 127/2007/ND-CP of August 01, 2007, issued by Government, dated August 01, 2007, detailing the implementation of a number of articles of the Law on Standards and Technical Regulations TCVN 9386:2012 is compiled by the Institute for Building Science and Technology Ministry of Construction, requested by Ministr of Construction, authenticated by the Directorate for Standards, Metrology and Quality, and announced by Ministry of Science and Technology Introduction TCVN 9386:2012: Design of structures for earthquake resistances is compiled based on the accepted Eurocode 8: Design of structures for earthquake resistance, with additions or substitutes to comply with typical characteristics of Vietnam Eurocode includes parts: EN1998 - 1: General provisions, seismic impacts and regulations for building structure; EN1998 - 2: Specific provisions relevant to bridges; EN1998 - 3: Provisions for the seismic assessment and retrofitting of existing buildings EN1998 - 4: Specific provisions relevant to silos, tanks and pipelines; EN1998 - 5: Specific provisions relevant to foundations, retaining structures and geotechnical aspects; EN1998 - 6: Specific provisions relevant to towers, masts and chimneys This new issued document mentions terms and provisions for buildings, with content corresponding to the following parts of Eurocode Part corresponds to EN1998 - 1; Phần corresponds to EN1998 - 5; Additional or substitute parts for contents of Part Appendix E: Degree and importance factor Appendix F: Grading and classification of construction works Appendix G: Ground acceleration zone map of Vietnam Appendix H: Table of ground acceleration of administrative locations Appendix I: Table of converting peak ground acceleration into earthquake level The common reference standards cited in Article 1.2.1 has not been replaced by the current standards of Vietnam, because of the need to ensure the standard uniformity with European standards system Vietnam standard system approaches to European standards system to release the cited standard as follows Ground acceleration zone map of Vietnam is the result of an independent project of State level: "Research on earthquake forecasting and ground oscillations in Vietnam, implemented by the Institute of Geophysics, and accepted by the Scientific Council of State level in 2005 The map used in this document has the reliability and legal value which is equivalent to a specific version of a map with the same name which has been revised based on recommendations in an evaluation report of the State’s Acceptance Council In Vietnam’s ground acceleration zone map, reference peak ground acceleration agR is expressed by isolines Value agR between two isolines is determined by the principle of linear interpolation In regions of dispute ground acceleration, value agR is determined by the Investor Peak ground acceleration agR can be converted into earthquake level by MSK-64 scale, MM scale or other scales when applying different seismic resistant design standards According to the value of the design ground acceleration ag = γI x agR , earthquakes are classified into types: - Strong earthquake ag ≥ 0,08g, seismic resistance must be calculated; - Weak earthquake 0,04g ≤ ag < 0,08g, mitigated seismic resistance methods are applied; - Very weak earthquake ag < 0,04g, seismic resistance design is not required In Eurocode 8, two types of spectral curves are recommended The spectral curve type is used for region with seismic magnitude Ms ≥ 5,5 ; the spectral curve type is used for region with seismic magnitude Ms < 5,5 In this document, the spectral curve type is used because most of regions of earthquake occurance in Vietnam have seismic magnitude Ms ≥ 5,5 For different construction works, different seismic resistance are designed Depending on the importance of the construction work, appropriate importance factor γI shall be selected In case of having dispute over importance factor, value γI shall be determined by the Investor DESIGN OF STRUCTURES FOR EARTHQUAKE RESISTANCES PART 1: GENERAL RULES, SEISMIC ACTIONS AND RULES FOR BUILDINGS GENERAL 1.1 Scope 1.1.1 Applicable scope of the document: Design of structures for earthquake resistances (1)P This document applies to the design and construction of buildings and civil engineering works in seismic regions Its purpose is to ensure that in the event of earthquakes: - Human lives are protected; - Damage is limited; and - Structures important for civil protection remain operational NOTE: The random nature of the seismic events and the limited resources available to counter their effects are such as to make the attainment of these goals only partially possible and only measurable in probabilistic terms The extent of the protection that can be provided to different categories of buildings, which is only measurable in probabilistic terms, is a matter of optimal allocation of resources and is therefore expected to vary from country to country, depending on the relative importance of the seismic risk with respect to risks of other origin and on the global economic resources (2)P Special structures, such as nuclear power plants, offshore structures and large dams, are beyond the scope of this document (3)P This document contains only those provisions that, in addition to the provisions of the other relevant standard documents, must be observed for the design of structures in seismic regions It complements in thisrespect the other standard documents 1.1.2 Scope of Part (1) This document applies to the design of buildings and civil engineering works in seismic regions It is subdivided in 10 Sections, some of which are specifically devoted to the design of buildings (2) Section contains the basic performance requirements and compliance criteria applicable to buildings and civil engineering works in seismic regions (3) Section gives the rules for the representation of seismic actions and for their combination with other actions (4) Section contains general design rules relevant specifically to buildings (5) Sections to contain specific rules for various structural materials and elements, relevant specifically to buildings as follows: - Section 5: Specific rules for concrete buildings; - Section 6: Specific rules for steel buildings; NOTE: Safety coefficient’s value is obtained through applying 7.2(6)P within the framework of simplified method in 7.3.2 Table 7.1 – Values of coefficient r used to calculate horizontal earthquake coefficient Retaining wall type r Gravitational wall with free wall head, capable of enduring maximum displacement dr = 300α.S (mm) Gravitational wall with free wall head, capable of enduring maximum displacement dr = 200α.S (mm) 1,5 Bending reinforced concrete wall, anchored or supported wall, reinforced concrete wall on vertical piles, displacement- restricted basement wall and abutment (6) With retaining wall higher than 10m and supplement information for coefficient r, refer to E.2 for more information (7) Except gravitational wall, vertical effect of acceleration may be neglected in retaining walls 7.3.2.3 Designed pressure of soil and water (1)P Total designed force acting on wall in case of earthquake must be calculated while taking into account the model’s limit equilibrium condition described in 7.3.2.1 (2) This force can be evaluated following Appendix E (3) The designed force mentioned in (1)P must be considered as the resultant of soil static and dynamic pressures (4)P In case there’s no detail study about relative stiffness, displacement form and relative mass of retention wall, the application point of the force caused by soil dynamic pressure resides at the wall’s midpoint (5) If a wall is capable of rotating freely around its base, application point of dynamic and static force can be considered to superpose each other (6)P Pressure force direction distributing on the wall together with wall normal forms an angle less than or equal to (2/3) Φ' in active state and equal to in passive state (7)P With soil lying beneath underground water level, one must distinguish between seepage prone status (in which water can move freely in soil skeleton) when dynamic load is present and waterproof status (in which practically no water drainage takes place under earthquake effect) (8) Under most normal prescripts and with soil having seepage coefficient less than 5.10 -4 m/s, pore water does not move freely in ground framework, earthquake effect happens practically without drainage and soil can be considered to be monophase environment (9)P Without hydrodynamic seepage, one must apply all the above prescripts while adjusting properly the volumetric soil mass and horizontal earthquake coefficient (10) Adjustment in case of no hydrodynamic seepage can be conducted following E.7 and E.7 (11)P With hydrodynamic seepage, effects caused by earthquake in soil and that in water must be viewed as independent effects (12) Hence, hydrostatic and hydrodynamic water pressure should be added up according to E.7 The application point of the former force can be assumed to lie at the distance of 60 % of the saturated layer’s depth 7.3.2.4 Hydrodynamic pressure acting on outside surface of wall (1)P Variation (decrease or increase) of pressure with respect to current hydrostatic pressure (caused by water oscillation on wall’s exposed surface) must be taken into account (2) This kind of pressure can be evaluated following E.8 7.4 Strength and stability test 7.4.1 Stability of ground soil (1)P The following test must be carried out: - Test of overall stability; - Test of soil local failure (2)P Test of overall stability must be carried out following rules in 4.1.3.4 (3)P The ultimate efficiency of ground soil must be tested both about sliding failure and about load bearing capacity fading (see 5.4.1.1) 7.4.2 Anchor (1)P Parts of anchors (including free cable section, anchor support, anchor head, lock constitution) must both meet: length standard and strength standard (to ensure the equilibrium of soil block in case of earthquake (see 7.3.2.1)), and the sufficient capability of bearing ground soil’s deformation caused by earthquake (2)P Anchor’s strength must meet standards in EN 1997-1:2004, corresponding to dynamic and long term foreseen limit (3)P Soil in which anchor lies must be ensured to maintain its strength to last during the foreseen earthquake period Insurance supply must also be enough to prevent liquefaction (4)P Distance Le between the anchor and the wall must surpass Ls calculated for nonearthquake load (5) Under prescripts in which soil containing anchor shoes has properties similar to that of soil behind wall and some prescripts about ground surface elevation, distance Le between anchor shoes in soil can be calculated via the following formula: Le = Ls (1 + 1,5α.S) 7.4.3 Structural strength (7.4) (1)P It is necessary to prove that, under the combination effect of earthquake and other likely generated loads, equilibrium state can be achieved without exceeding design strength of wall and other support structural elements (2)P In order to achieve such goal, one needs to consider proper limit state of structural failure in 8.5, EN 1997-1:2004 (3)P All structure elements must be examined to ensure that they satisfy the following condition: Rd > Ed (7.5) Where Rd : Element’s designed strength value, which is evaluated by ways similar to that in nonearthquake situations; Ed : Effects’ designed value, which are obtained from analyzing results represented in 7.3 APPENDIX A (Reference) RELIEF AMPLIFICATION FACTOR A.1 This appendix introduces some relief amplification coefficients which is simplified for earthquake effect and is used to examine earth’s slope stability These coefficients, symbolized by ST, are initial approximate values and considered independently with fundamental vibration period, hence they are multiplied as an invariant ratio coefficient by coordinates of designed elastic response spectrum given in Part of this building regulation These amplification coefficients must be priorly applied for slopes which have abnormal relief variance with respect to directions, such as lengthened top and lengthened partition higher than 30m A.2 With angle of slope smaller than 15° , relief effects may be neglected, whereas if local relief changes too abnormally, specific study is required With higher angles, apply the followings: a) Independent partitions and slopes: use ST ≥ 1,2 for positions near the top b) Tops whose width is much smaller than foot’s width It is recommended to use ST ≥ 1,4 near slope’s top whose average slope angle is greater than 30° and to use ST ≥ 1,2 for smaller slope angle; c) Existence of non-cohesive soil layers on the surface If there are noncohesive soil layers on the surface, minimum value ST given in a) and b) should be increased at least 20%; d) Amplification coefficient’s variance with respect to space Value of ST may be assumed to decrease in linear manner from partition or top, and take value at slope foot A.3 In general, in the range of slope top, earthquake amplification attenuates rapidly with respect to depth Therefore, relief’s effects taken into account with analysis of stability are maximums and are almost only on the surface along top’s edge, and are much more smaller on deep sliding surface where failure surface come across top foot In second case, if static analysis is applied, the relief effects could be neglected APPENDIX B (Compulsory) EXPERIMENTAL GRAPHS USED TO ANALYZING SIMPLIFIED LIQUEFACTION B.1 General Experimental graphs are utilized to analyze simplified liquefaction to study correlation between in situ test and repetitive shear stresses which is known to be the liquefaction cause during past earthquakes On horizontal axis is a kind of soil property measured on site, such as normalized penetration resistance or shear wave velocity νs , on the vertical axis is repetitive shear stress due to earthquake, usually normalized with effective soil’s own pressureσ'vo Limit curve of repetitive resistance is displayed in all graphs, divides the graphs into zones including non-liquefaction zone (on the right) and likely liquefaction zone (on the left and the top of the curve) Sometimes more than one curve are represented, for example curves corresponding to fine-grained soil or soil with different earthquake intensities Except static penetration resistance, it is not recommended to use experimental liquefaction standards when liquefaction occurs in soil layers or soil beds thinner than tens of cm When gravel content is rather high but observational data is not sufficient to establish a reliable liquefaction graph, possibility of liquefaction can not be excluded B.2 Graphs basing on SPT index The graph in Figure B.1 is one of the many graphs that are being most widely used for pure sand and silt sand SPT index is normalized with soil self pressure and with energy ratio N1 (60) following the way described in 4.1.4 Liquefaction seems to occur at values higher than certain threshold of τe, because soil‘s response is elastic and there’s no accumulation of pore water pressure Therefore, limit curve may not be extrapolated toward origin of coordinates If one wish to apply this criterion for earthquake with intensity different from Ms = 7,5, where Ms is surface wave intensity, then coordinates of the curve in Figure B.1 should be multiplied by coefficient CM given in Table B.1 Table B.1 – Values of coefficients CM Ms CM 5,5 2,86 6,0 2,20 6,5 1,69 7,0 1,30 8,0 0,67 B.3 Graphs basing on static penetration resistance CPT Basing on many studies about correlation between static penetration resistance and soil’s resistance against liquefaction, graphs having the form similar to that in Figure B.1 have been established Such direct correlations should be used prior to indirect correlations using relation between SPT index and static penetration resistance CPT B.4 Graphs basing on shear wave velocity νs This characteristic is considered to be a promising standard to estimate liquefaction possibility in soil type which is hard to sample (for example silt sand or sand) or hard to penetrate (for example gravel) Recently there have been significant advance in measuring νs on site However, correlation between νs and soil’s liquefaction resistance is still being studied and should not be used without consultancy from specialists KEY: τe/σ'vo - Repetitive stress ratio Curve 1: 35 % fine grains A - Pure sand Curve 2: 15 % fine grains B - Silt sand Curve 3: < % fine grains FIGURE B.1 - Relation between stress ratios causing liquefaction and N1(60) for pure sand and silt sand with earthquake Ms = 7,5 APPENDIX C (Compulsory) PILE HEAD’S STATIC STIFFNESS C.1 Pile’s stiffness is defined as force (moment) put on pile’s head to create unit displacement (rotation) along the same direction (displacement/rotation angle along other directions equals to zero), and is symbolized as KHH (horizontal stiffness), KMM (bending stiffness) and KHM = KMH (bending-horizontal displacement stiffness) Symbols used in Table C.1: E earth elastic modulus, equals to 3G; EP pile material’s elastic modulus; Es earth’s elastic modulus at the depth which equals to pile diameter; d pile diameter; z depth of pile sinking Table C.1 – Expressions of static stiffness of soft pile sunk into types of soil Type of soil K HH dE s K MM d 3Es K HM d 2E s E = Es.z/d Ep 0,60 Es 0,35 Ep 0,14 Es 0,80 Ep − 0,17 Es E = Es z d Ep 0,79 Es 0,28 Ep 0,15 Es 0,77 Ep − 0,24 Es 0,53 E = Es Ep 1,08 Es 0,21 Ep 0,16 Es 0,75 Ep − 0,22 Es 0,50 0,60 APPENDIX D (Reference) STRUCTURE-SOIL INTERACTION (SSI): GENERAL EFFECTS AND IMPORTANCE D.1 Due to structure-soil interaction, earthquake reaction of structure on soft pillow, such as structure on deformable ground, will differ from reaction of the same structure but on hard ground (clamped at its foot) subjected to an equivalent free field excitation, because of the following reasons: a) Displacement of foundation system on soft pillow differs from that of free field and may include a very important vibrating component of structure clamped at its foot; b) Fundamental vibration period of the structure on soft pillow is longer than that of structure clamped at its foot; c) Natural vibration periods, vibration modes and partial pattern coefficients of structure on soft pillow differ from those of structure clamped at its foot; d) Total damping rate of structure on soft pillow includes both internal and external damping rates occurring at the contact surface between soil and foundation, in addition to damping rate of upper structure D.2 With most of public buildings, interactions between soil and structure are advantageous because they decrease bending moments and shear forces in different elements in the upper structure With structures listed in chapter 6, on the contrary, the interaction effects between soil and structure may be disadvantageous APPENDIX E (Compulsory) SIMPLIFIED ANALYZING METHOD FOR RETAINING WALL STRUCTURE E.1 Theoretically, coefficient r is defined as ratio between acceleration value causing irreversible displacement corresponding to existing connection and acceleration value corresponding to equilibrium limit state (displacement starts to occur) Hence with wall allowing greater displacement coefficient r takes greater value E.2 With retaining wall structure higher than 10m, one may consider the problem is in one dimension with free field wave propagating vertically, and value α may take the mean value of horizontal maximum acceleration along the structure’s height for more accuracy to use in expression (8) E.3 Total designed force acting on retaining wall at its back, Ed , is given by the following formula: Ed = γ * (1 ± kv ).K H + Ews + Ewd (E.1) Where H : Wall’s height Ews : Static water force; Ewd : Dynamic water force; γ* : Soil’s unit weight; K : Earth pressure coefficient (static and dynamic); kv : Vertical earthquake coefficient (refer to expressions (9) and (10)) E.4 Earth pressure coefficient may be calculated following Mononobe and Okabe formulas: With active states: If β ≤ φ'd - θ K= sin (ψ + φ'd −θ) sin(φ'd + δ d ) sin(φ'd −β − θ) cos θ sin ψ sin(ψ − φ − δ d ).1 + sin(ψ − φ − δ d ) sin(ψ + β) 2 (E.2) If β > φ'd - θ K = sin2 (ψ + φ − θ ) cos θ sin2 ψ sin(ψ − φ − δ d ) With passive states (without regard to friction between earth and wall): (E.3) K= sin (ψ + φ'd −θ) sin φ'd sin(φ'd +β − θ) cos θ sin ψ sin(ψ + φ).1 − sin(ψ + β) sin(ψ + θ) (E.4) The following symbols are used in the expressions above: −1 tgφ ' Φ'd : Soil’s designed shear strength angle value, which means φ 'd = tg γ ; φ' ψ and β : Tilt angle of wall back and fill soil surface with respect to horizontal direction as shown in Figure E.1; −1 tgδ δd : Designed friction angle between soil and wall, which means: δ d = tg γ φ' θ : Angle which is defined from E.5 to E.7 below The expression for passive state should be used priorly for vertical wall surface (ψ = 90°) E.5 Underground water level beneath retaining wall Earth pressure coefficient Here the following parameters are employed: γ* : Volume weight of soil (E.5) tgθ = kh 1mkv Ewd = (E.6) (E.7) where kh : Horizontal earthquake coefficient (refer to expression (8)) On the other hand, one may use tables and graphs applied in static condition (only gravitational loads exist), with the following supplements: tgθ A = kh + kv (E.8) tgθ B = kh − kv (E.9) and The whole system of wall-soil rotates by the corresponding angle θA or θB The gravitational acceleration is replaced by the following value: gA = or g(1 + k v ) cos θ A (E.10) gB = g(1 − k v ) cos θ B (E.11) E.6 Impermeable soil bearing dynamic load lying beneath underground water level – Earth pressure coefficient Here the following parameters are employed: γ* = γ - γw tgθ = (E.12) γ k h γ − γ w 1µk v (E.13) Ewd = (E.14) Where γ : Saturated unit weight of soil; γw : Unit weight of water E.7 Permeable soil bearing dynamic load lying (high permeability) beneath underground water level – Earth pressure coefficient Here the following parameters are employed: γ* = γ - γw (E.15) tgθ = γd k h γ − γ w 1µk v (E.16) Ewd = k h γ w (H ' ) 12 (E.17) Where: γd : Dry unit weight of soil; H' : Height of underground water level, measured from wall base E.8 Hydrodynamic pressure on outside surface of wall This pressure q(z) may be calculated following the steps below: q( z ) = ± k hγ w h.z Where kh : Horizontal earthquake coefficient, r = (refer to expression (8)); h : Free water level height; z : Vertical coordinate with the coordinate origin placed at water surface E.9 Force which is caused by earth pressure acts on stiff structure (E.18) For stiff, clamped structure, active state can not develop in the soil, and with vertical wall and horizontal fill soil, dynamic force due to earth pressure increment may take: ∆Pd = α S γ H2 (E.19) Where H : Wall’s height Application of force may be assumed to be midpoint of wall’s height Active Passive Figure E.1 – Convention for angles in formula used to calculate earth pressure coefficient APPENDIX F (Reference) EARTHQUAKE LOAD BEARING CAPACITY OF SHALLOW FOUNDATION F.1 General expression Endurance against failure of a shallow band-shaped foundation’s load bearing capacity placed on a homogeneous surface may be examined by the following expression relating earth strength, designed effects (NEd , VEd , MEd) at altitude of foundation placing, to inertia forces in earth: (1 − e.F )CT ( β V )CT ( ) k' k N 1 − m.F − N a b + (1 − ƒ.F )CM (γ M )C M ( ) k' k N 1 − m.F − N c d −1≤ (F.1) where N= γ Rd NEd γ V γ M , V = Rd Ed , M = Rd Ed Nmax Nmax B.Nmax (F.2) Nmax : Foundation’s maximum force bearing capacity under effect of centrally applied load, which is defined in F.2 and F.3; B : Foundation’s with; F : Soil’s dimensionless inertia force, defined in F.2 and F.3; γRd : Model‘s coefficient (these coefficient are given in F.6) a, b, c, d, e, f, m, k, k', CT, CM, C’M, β, γ : Parameters’ values which depend on soil type, and are defined in F.4 F.2 Pure cohesive soil With Pure cohesive soil or water- saturated noncohesive soi, maximum force bearing capacity under vertical load effect centrally applied N max is determined by the following formula: Nmax = (π + 2) c B γM (F.3) Where : Soil’s undrained shear strength cu for cohesive soil, or soil’s undrained shear strength for non-cohesive soil subjected to cyclic load τcy,u ; c γM : Specific coefficient of material property Dimensionless inertia force of soil, F , is determined by the formula: F = ρ.ag S.B c Where ρ : Volume weight of soil; ag : Designed acceleration of A type ground (ag = γ1agR); (F.4) agR : Maximum reference acceleration of A type ground; γ1 : Operational importance factor; S : Soil coefficient defined in 3.2.2.2, Part of this building regulation The following restraint is applied in the expression of total force bearing capacity: < N ≤ 1, V ≤ (F.5) F.3 Pure non-cohesive soil With dry soil and saturated non-cohesive soil but not generating significant pore water pressure, maximum load bearing capacity of foundation under vertical centrally applied load N max is calculated by the formula below: Nmax = a ρ.g 1 ± v g .B Nγ (F.6) Where g : Gravitational acceleration; av : Vertical acceleration of ground, may take the expression 0,5 x ag x S; and Nγ : Load bearing capacity coefficient, which is a function of designed shear strength angle Φ'd (Φ'd consists of specific coefficient of material property γM of 3.1(3), refer to E.4) Dimensionless inertia force, F , in earth is calculated by the formula: F = ag (F.7) g tan φ ' d The following restraint is applied in the general expression: < N ≤ (1 − m.F )k ' (F.8) F.4 Parameter’s values Table F.1 contains parameter’s values in the general expression representing soil’s load bearing capacity of various types in F.2 and F.3 Table F.1 – Parameter’s value used in expression (F.1) Pure cohesive soil Pure non-cohesive soil a 0,70 0,92 b 1,29 1,25 c 2,14 0,92 d 1,81 1,25 e 0,21 0,41 f 0,44 0,32 m 0,21 0,96 k 1,22 1,00 k' 1,00 0,39 CT 2,00 1,14 CM 2,00 1,01 C'M 1,00 1,01 β 2,57 2,90 y 1,85 2,80 F.5 In most of normal prescripts it is allowable to take F as with cohesive soil With non-cohesive soil it is allowed to neglect F if agS < 0,1g (which means agS < 0,98 m/s2) F.6 Model coefficient γRd takes the values listed in Table F.2 Table F.2 – Values of model coefficient γ Rd From fairly compact to very compact sand Dry, noncohesive sand Saturated, non-cohesive sand Unsusceptible clay Susceptible clay 1,00 1,15 1,50 1,00 1,15 ... structure Appendix F (reference): Earthquake load bearing capacity of shallow foundation Foreword TCVN 9386:2012 is converted from TCXDVN 375:2006 into National Standard according to provisions... detailing the implementation of a number of articles of the Law on Standards and Technical Regulations TCVN 9386:2012 is compiled by the Institute for Building Science and Technology Ministry of Construction,... Standards, Metrology and Quality, and announced by Ministry of Science and Technology Introduction TCVN 9386:2012: Design of structures for earthquake resistances is compiled based on the accepted
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