NATIONAL STRUCTURAL CODE OF THE PHILIPPINES VOLUME I
BUILDINGS, TOWERS AND
OTHER VERTICAL STRUCTURES SIXTH EDITION
Association of Structural Engineers of the Philippines
Suite 713, Future Point Plaza Condominium 1 112 Panay Avenue, Quezon City, Philippines 1100
Tel. No : (+632) 410-0483 Fax No.: (+632) 411-8606 Email: [email protected]
Website: http://www.aseponline.org
Table of Contents
SECTION 401 - GENERAL ... 7
401.1 Notation ... 7
401.2 Scope ... 7
SECTION 402 - DEFINITIONS ... 8
SECTION 403 - SPECIFICATIONS FOR TESTS AND MATERIALS ... 13
403.1 Notation ... 13
403.2 Tests of Materials ... 13
403.3 Cement ... 13
403.4 Aggregates ... 13
403.5 Water ... 13
403.6 Steel Reinforcement ... 14
403.7 Admixtures ... 15
403.8 Storage of Materials ... 16
403.9 Standards Cited in this Chapter ... 16
SECTION 404 - DURABILITY REQUIREMENTS ... 18
404.1 Notation ... 18
404.2 Definitions ... 18
404.3 General ... 19
404.4 Exposure Categories and Classes ... 19
404.5 Special Exposure Conditions ... 19
404.6 Requirements for Concrete Mixtures ... 19
404.7 Alternative Cementitious Materials for Sulphate Exposure ... 19
404.8 Water-Cementitious Materials Ratio ... 19
404.9 Corrosion Protection of Reinforcement ... 19
SECTION 405 - CONCRETE QUALITY, MIXING AND PLACING ... 21
405.1 Notations ... 21
405.2 General ... 21
405.3 Selection of Concrete Proportions ... 21
405.4 Proportioning on the Basis of Field Experience and Trial Mixtures, or Both ... 22
405.5 Proportioning without Field Experience or Trial Mixtures ... 23
405.6 Average Strength Reduction ... 23
405.7 Evaluation and Acceptance of Concrete ... 23
405.8 Preparation of Equipment and Place of Deposit ... 25
405.9 Mixing ... 25
405.10 Conveying ... 25
405.11 Depositing ... 26
405.12 Curing ... 26
405.13 Hot Weather Requirements ... 26
SECTION 406 - FORMWORK, EMBEDDED PIPES AND CONSTRUCTION JOINTS ... 26
406.1 Design of Formwork ... 27
406.2 Removal of Forms, Shores and Reshoring ... 27
406.3 Conduits and Pipes Embedded in Concrete ... 27
406.4 Construction Joints ... 28
SECTION 407 - DETAILS OF REINFORCEMENT ... 28
407.1 Notations ... 29
407.2 Standard Hooks ... 29
407.3 Minimum Bend Diameters ... 29
407.4 Bending of Reinforcement ... 29
407.5 Surface Conditions of Reinforcement ... 29
407.6 Placing Reinforcement ... 29
407.7 Spacing Limits for Reinforcement ... 30
407.8 Concrete Protection for Reinforcement ... 31
407.9 Special Reinforcement Details for Columns ... 32
407.10 Connections ... 33
407.11 Lateral Reinforcement for Compression Members ... 33
407.12 Lateral Reinforcement for Flexural Members ... 34
407.13 Shrinkage and Temperature Reinforcement ... 34
407.14 Requirements for Structural Integrity ... 35
SECTION 408 - ANALYSIS AND DESIGN-GENERAL CONSIDERATIONS ... 38
408.1 Notations ... 38
408.2 Design Methods ... 38
408.3 Loading ... 38
408.4 Methods of Analysis ... 38
408.5 Redistribution of Negative Moments in Continuous Nonprestressed Flexural Members ... 39
408.6 Modulus of Elasticity ... 39
408.7 Lightweight Concrete ... 39
408.8 Stiffness ... 39
408.9 Effective Stiffness to Determine Lateral Deflections ... 40
408.10 Span Length ... 40
408.11 Columns ... 40
408.12 Arrangement of Live Load ... 40
408.13 T-beam Construction ... 40
408.14 Joist Construction ... 41
408.15 Separate Floor Finish ... 41
SECTION 409 - STRENGTH AND SERVICEABILITY REQUIREMENTS... 42
409.1 Notations ... 42
409.2 General ... 42
409.3 Required Strength ... 43
409.4 Design Strength ... 43
409.5 Design Strength for Reinforcement ... 44
409.6 Control of Deflections ... 44
SECTION 410 - FLEXURE AND AXIAL LOADS ... 47
410.1 Notations ... 47
410.2 Scope ... 48
410.3 Design Assumptions ... 48
410.4 General Principles and Requirements ... 49
410.5 Distance between Lateral Supports of Flexural Members ... 49
410.6 Minimum Reinforcement of Flexural Members ... 50
410.7 Distribution of Flexural Reinforcement in Beams and One-way Slabs ... 50
410.8 Deep Beams ... 50
410.9 Design Dimensions for Compression Members ... 51
410.10 Limits for Reinforcement of Compression Members ... 51
410.11 Slenderness Effects in Compression Members ... 51
410.12 Magnified Moments ... 52
410.13 Moment Magnification Procedure - Nonsway ... 53
410.14 Moment Magnification Procedure - Sway ... 53
410.15 Axially Loaded Members Supporting Slab System ... 54
410.16 Transmission of Column Loads through Floor System ... 54
410.17 Composite Compression Members ... 54
410.18 Bearing Strength ... 55
SECTION 411 - SHEAR AND TORSION ... 56
411.1 Notations ... 56
411.2 Shear Strength ... 57
411.3 Lightweight Concrete ... 58
411.4 Shear Strength Provided by Concrete for Nonprestressed Members ... 58
411.5 Shear Strength Provided by Concrete for Prestressed Members ... 59
411.6 Shear Strength Provided by Shear Reinforcement ... 60
411.7 Design for Torsion ... 61
411.8 Shear - Friction ... 64
411.9 Deep Beams ... 65
411.10 Provisions for Brackets and Corbels ... 65
411.11 Provisions for Walls ... 66
411.12 Transfer of Moments to Columns ... 67
411.13 Provisions for Slabs and Footings... 67
SECTION 412 - DEVELOPMENT AND SPLICES OF REINFORCEMENT ... 70
412.1 Notations ... 70
412.2 Development of Reinforcement - General ... 71
412.3 Development of Deformed Bars and Deformed Wire in Tension ... 71
412.4 Development of Deformed Bars in Compression ... 72
412.5 Development of Bundled Bars ... 72
412.6 Development of Standard Hooks in Tension ... 72
412.7 Development of Headed and Mechanically Anchored Deformed Bars in Tension ... 73
412.8 Development of Welded Deformed Wire Reinforcement in Tension ... 73
412.9 Development of Welded Plain Wire Reinforcement in Tension ... 73
412.10 Development of Prestressing Strand ... 74
412.11 Development of flexural Reinforcement - General ... 74
412.12 Development of Positive Moment Reinforcement ... 74
412.13 Development of Negative Moment Reinforcement ... 75
412.14 Development of Web Reinforcement ... 75
412.15 Splices of Reinforcement - General ... 76
412.16 Splices of Deformed Bars and Deformed Wire in Tension ... 76
412.17 Splices of Deformed Bars in Compression ... 77
412.18 Special Splices Requirements for Columns ... 77
412.19 Splices of Welded Deformed Wire Reinforcement in Tension ... 77
412.20 Splices of Welded Plain Wire Reinforcement in Tension ... 78
SECTION 413 - TWO-WAY SLAB SYSTEMS ... 78
413.1 Notations ... 78
413.2 Scope ... 79
413.3 Definitions ... 79
413.4 Slab Reinforcement ... 79
413.5 Openings in Slab Systems ... 81
413.6 Design Procedures ... 82
413.7 Direct Design Method ... 82
413.8 Equivalent Frame Method ... 85
SECTION 414 - WALLS ... 86
414.1 Notations ... 87
414.2 Scope ... 87
414.3 General ... 87
414.4 Minimum Reinforcement ... 87
414.5 Walls Design as Compression Members ... 88
414.6 Empirical Design Method ... 88
414.7 Non-Bearing Walls ... 88
414.8 Walls as Grade Beams ... 89
414.9 Alternate Design of Slender Walls ... 89
SECTION 415 - FOOTINGS ... 89
415.1 Notations ... 90
415.2 Scope ... 90
415.3 Loads and Reactions ... 90
415.4 Footings Supporting Circular or Regular Polygon-Shaped Columns or Pedestals ... 90
415.5 Moment in Footings ... 90
415.6 Shear in Footings ... 90
415.7 Development of Reinforcement in Footings ... 91
415.8 Minimum Footing Depth ... 91
415.9 Transfer of Force at Base of Column, Wall or Reinforcement Pedestal ... 91
415.10 Sloped or Stepped Footings ... 92
415.11 Combined Footings and Mats ... 92
415.12 Plain Concrete Pedestals and Footings... 92
SECTION 416 – PRECAST CONCRETE ... 92
416.1 Notations ... 92
416.2 Scope ... 92
416.3 General ... 92
416.4 Distribution of Forces among Members ... 92
416.5 Member Design ... 93
416.6 Structural Integrity ... 93
416.7 Connection and Bearing Design... 93
416.8 Items Embedded After Concrete Placement ... 94
416.9 Marking and Identification ... 94
416.10 Handling ... 94
416.11 Strength Evaluation of Precast Construction ... 94
SECTION 417 - COMPOSITE CONCRETE FLEXURAL MEMBERS ... 95
417.1 Notations ... 95
417.2 Scope ... 95
417.3 General ... 95
417.4 Shoring ... 95
417.5 Vertical Shear Strength ... 95
417.6 Horizontal Shear Strength ... 95
417.7 Ties for Horizontal Shear ... 96
SECTION 418 – PRESTRESSED CONCRETE ... 97
418.1 Notations ... 97
418.2 Scope ... 97
418.3 General ... 97
418.4 Design Assumptions ... 98
418.5 Permissible Stresses in Concrete – Flexural Members ... 98
418.6 Permissible Stress in Prestressing Tendons ... 99
418.7 Loss of Prestress ... 99
418.7.2 Friction Loss in Post-Tensioning Tendons ... 99
418.8 Flexural Strength ... 100
418.9 Limits for Reinforcement of Flexural Members ... 100
418.10 Minimum Bonded Reinforcement ... 100
418.11 Statically Indeterminate Structures ... 101
418.12 Compression Members – Combined Flexural and Axial Loads ... 101
418.13 Slab Systems: ... 102
418.14 Post-Tensioned Tendon Anchorage Zones ... 103
418.15 Design of Anchorage Zones for Monostrand or Single 16 mm Diameter Bar Tendons ... 104
418.16 Design of Anchorage Zones for Multistrannd Tendons ... 104
418.17 Corrosion Protection for Unbonded Prestressing Tendons ... 105
418.18 Post-Tensioning Ducts ... 105
418.19 Grout for Bonded Prestressing Tendons ... 105
418.20 Protection for Prestressing Steel ... 105
418.21 Application and Measurement of Prestressing Force ... 105
418.22 Post-Tensioning Anchorages and Couplers ... 106
418.23 External Post- Tensioning ... 109
SECTION 419 - SHELLS AND FOLDED PLATE MEMBERS ... 109
419.1 Notations ... 109
419.2 Scope And Definitions ... 109
419.3 Analysis and Design ... 110
419.4 Design strength of Materials ... 110
419.5 Shell Reinforcement ... 110
419.6 Construction ... 111
SECTION 420 - STRENGTH EVALUATION OF EXISTING STRUCTURES ... 112
420.1 Notations ... 112
420.2 Strength Evaluation-General ... 112
420.3 Determination of Required Dimensions and Material Properties ... 112
420.4 Load Test Procedure ... 112
420.5 Loading Criteria ... 113
420.6 Acceptance Criteria ... 113
420.7 Provisions for Lower Load Rating ... 113
420.8 Safety ... 113
SECTION 421 – EARTHQUAKE RESISTANT STRUCTURES ... 113
421.1 Notations ... 114
421.2 Definitions ... 115
421.3 General Requirements ... 116
421.3.6 Mechanical Splices in Special Moment Frames and Special Structural Walls ... 117
421.4 Intermediate Precast Structural Walls ... 118
421.5 Flexural Members of Special Moment Frames ... 118
421.6 Special Moment Frame Subjected to Bending and Axial Load ... 119
421.7 Joints of Special Moment Frames ... 121
421.8 Special Reinforced Concrete Structural Walls and Coupling Beams ... 122
421.9 Structural Diaphragms and Trusses ... 125
421.10 Foundations ... 127
421.11 Members not Designated as Part of the Seismic-Force-Resisting System ... 128
421.12 Requirements for Intermediate Moment Frames, Seismic Zone 2 ... 129
421.13 Special Moment Frames Using Precast Concrete ... 130
421.14 Ordinary Moment Frames ... 131
421.15 Special Structural Walls Constructed Using Precast Concrete ... 131
SECTION 422 - STRUCTURAL PLAIN CONCRETE ... 132
422.1 Notations ... 132
422.2 Scope ... 132
422.3 Limitations ... 132
422.4 Joints ... 132
422.5 Design Method ... 133
422.6 Strength Design ... 133
422. 7 Walls ... 134
422.8 Footing ... 134
422.9 Pedestals ... 135
422.10 Precast Members ... 135
422.11 Plain Concrete in Earthquake-Resisting Structures ... 135
SECTION 423 - ANCHORAGE TO CONCRETE ... 136
423.1 Definitions ... 136
423.2 Scope ... 137
423.3 General Requirements ... 137
423.4 General Requirements for Strength of Anchors ... 138
423.5 Design Requirements for Tensile Loading ... 139
426.6 Desing Requirements for Shear Loading ... 141
423.7 Interaction of Tensile and Shear Forces ... 143
423.8 Required Edge Distances, Spacings, and Thickness to Preclude Splitting Failure ... 143
423.9 Installation of Anchors ... 144
SECTION 424 - ALTERNATE DESIGN METHOD ... 144
424.1 Notations ... 144
424.2 Scope ... 145
424.3 General ... 145
424.4 Permissible Service Load Stresses ... 145
424.5 Development and Splices of Reinforcement ... 145
424.7 Compression Members With or Without Flexure ... 146
424.8 Shear and Torsion ... 146
SECTION 425 – ALTERNATIVE PROVISIONS FOR REINFORCED AND PRESTRESSED CONCRETE FLEXURAL AND COMPRESSION MEMBERS ... 148
425.1 Scope ... 149
425.2 Redistribution of Negative Moments in Continuous Non-Prestressed Flexural Members ... 149
SECTION 426 - ALTERNATIVE LOAD AND STRENGTH REDUCTION FACTORS ... 150
SECTION 427 STRUT AND TIE MODELS ... 152
427.1 Definitions ... 152
427.2 Strut-andTie Model Design Procedure ... 157
427.3 Strength of Struts ... 157
427.4 Strength of Ties ... 158
427.5 Strength of Nodal Zones ... 159