1 General Provisions
1.0.1 This code was formulated with a view to achieving reliable technology, safety and usability, economy and rationality and guaranteed quality for strengthening of masonry structures.
1.0.2 This code is applicable to strengthening design of buildings and general masonry structures.
1.0.3 Before strengthening of masonry structures, reliability appraisal shall be carried out, on basis of building types, respectively according to the relevant requirements of the current national standards "Standard for Appraisal of Reliability of Industrial Buildings and Structures"(GB 50144) and "Standard for Appraiser of Reliability of Civil Buildings" (GB 50292). Where it is carried out in combination with the seismic strengthening, seismic capacity appraisal also shall be carried out according to the relevant requirements of the current national standard "Standard for Seismic Appraisal of Buildings" (GB 50023).
1.0.4 Strengthening design of masonry structures shall meet not only those specified in this code, but also the requirements of relevant current national standards.
2 Terms and Symbols
2.1 Terms
2.1.1 Strengthening of masonry structures
Measures such as strengthening, partial replacement or internal force adjustment are taken for masonry structures with insufficient reliability or whose reliability is required to be improved by the Owner as well as the structure member and the relevant parts so as to make them have safety, durability and applicability specified in the current codes for design and required by the Owner.
2.1.2 Existing structure member
The original member before strengthening.
2.1.3 Important structure member
The structure member whose failure will affect or endanger the safe operation of the bearing structure system.
2.1.4 General structure member
Structure members beyond the important structure members.
2.1.5 Composite cement mortar
The mortar with cement and high-performance mineral admixture as main components and mixed with additive and short fine fiber.
2.1.6 Polymer modified cement mortar
The high-strength cement mortar mixed with modified epoxy emulsion or other modified copolymer emulsion. The polymer modified cement mortar for the bearing structure shall be able to significantly imporove the capacity of its substrates such as anchored reinforcement, bonded concrete and masonry.
2.1.7 Steel reinforcement mesh
The mesh welded with ordinary hot-rolled ribbed bar or cold-rolled ribbed bars.
2.1.8 Fiber reinforced poloymer
A kind of composite material with fiber reinforcement effect that are arrayed with high-strength continuous fiber according to certain rules and formed after dipping, bonding and curing with adhesives, which is generally referred to as the fiber reinforced poloymer.
2.1.9 Strength utilization factor of material
The calculation factor introduced considering that the strength of strengthening materials fails to be fully utilized under secondary load conditions.
2.1.10 External layer strengthening
A ind of strengthening method that the bearing capacity and rigidity of the existing structure member are improved through external reinforced concrete layer or steel reinforcement mesh mortar layer.
2.1.11 Sectional steel strengthening
A kind of strengthening method that the section steel limb and batten plate are welded into a structure for the masonry column enclosure and the external force is districuted according to their respecitive rigidity ratios, which is also referred to as dry-externally bonded steel.
2.1.12 External prestressed strut strengthening
A kind of strengthening method that precompression is applied to two diagonal steel struts with cut and bending through tightening the transverse screw rod device so as to discharge the load of the masonry columns to the strut.
2.1.13 Counterfort masonry column strengthening
A kind of strengthening method that partial wall is thickened at some distance along the length direction of the masonry wall to form stiffening wall with buttress.
2.1.14 Masonry crack repairing
A kind of repairing method adopted with a view to sealing the masonry crack or recovering the integrity of the cracked masonry.
2.2 Symbols
2.2.1 Material performance
Em - the elastic modulus of the existing structure member masonry;
Ea - the elastic modulus of the new section steel;
Ef - the elastic modulus of the new fiber reinforced poloymer;
fm0, f - the design values for the compression strength of the existing masonry and new masonry respectively;
fc - the design value for the axial compressive strength of the new concrete;
fy, - the design values for tensile and compression strength of the new reinforcement;
ff - the design value for the tensile strength of the new fiber reinforced poloymer.
2.2.2 Action effect and bearing capacity
N - the design value for axial compression after strengthening of structure member;
M - the design value for the bending moment after strengthening of structure member;
V - the design value for the shear force after strengthening of structure member;
δs - the tensile stress of the reinforcement.
2.2.3 Geometric parameters
Am0 - the sectional area of the existing structure member masonry;
Ac - the sectional area of the new concrete;
1 General Provisions
2 Terms and Symbols
2.1 Terms
2.2 Symbols
3 Basic Requirements
3.1 General Requirements
3.2 Principles for Calculation of Design
3.3 Strengthening Methods and Technology
4 Materials
4.1 Masonry Materials
4.2 Concrete Materials
4.3 Steel and Welding Materials
4.4 Wire Ropes
4.5 Fiber Reinforced Polymer
4.6 Structural Adhesives
4.7 Polymer Modified Cement Mortar
4.8 Materials for Masonry Crack Repairing
4.9 Short Fiber for Anticracking
5 Reinforced Concrete Layer Strengthening
5.1 General Requirements
5.2 Masonry Compression Strengthening
5.3 Masonry Shear Strengthing
5.4 Masonry Seismic Strengthening
5.5 Construction Requirements
6 Steel Rinforcement Mesh Mortar Layer Strengthening
6.1 General Requirements
6.2 Masonry Compression Strengthening
6.3 Masonry Shear Strengthing
6.4 Masonry Seismic Strengthening
6.5 Construction Requirements
7 Sectional Steel Strengthening
7.1 General Requirements
7.2 Calculation Methods
7.3 Construction Requirements
8 External Prestressed Strut Strengthening
8.1 General Requirements
8.2 Calculation Methods
8.3 Construction Requirements
9 Bonded Fiber Reinforced Ploymer Strengthening
9.1 General Requirements
9.2 Masonry Shear Strengthing
9.3 Masonry Seismic Strengthening
9.4 Construction Requirements
10 Wire Rope Mesh-Polymer Modified Cement Mortar Layer Strengthening
10.1 General Requirements
10.2 Masonry Shear Strengthing
10.3 Masonry Seismic Strengthening
10.4 Construction Requirements
11 Strengthening with Adding Masonry Counterfort Column
11.1 Calculation Methods
11.2 Construction Requirements
12 Construction Strengthening of Masonry Structures
12.1 Strengthening with Adding Ring Beam
12.2 Strengthening with Adding Constructional Column
12.3 Strengthening with Adding Concrete Padstone
12.4 Disassemblying and Bonding Partial Masonry
13 Masonry Crack Repairing
13.1 General Requirements
13.2 Masonry Crack Repairing by Filler
13.3 Masonry Crack Repairing by Grout
13.4 Masonry Crack Repairing by External Mesh
13.5 Masonry Crack Repairing by Replacement
Appendix A Determination for Load Characteristic Value of Existing Structures
Appendix B Specifications for Test and Evaluation of Bonding Tensile Strength between Strenthening Materials and Substrate
Explanation of wording in This standard
List of Quoted Standards
1 General Provisions
1.0.1 This code was formulated with a view to achieving reliable technology, safety and usability, economy and rationality and guaranteed quality for strengthening of masonry structures.
1.0.2 This code is applicable to strengthening design of buildings and general masonry structures.
1.0.3 Before strengthening of masonry structures, reliability appraisal shall be carried out, on basis of building types, respectively according to the relevant requirements of the current national standards "Standard for Appraisal of Reliability of Industrial Buildings and Structures"(GB 50144) and "Standard for Appraiser of Reliability of Civil Buildings" (GB 50292). Where it is carried out in combination with the seismic strengthening, seismic capacity appraisal also shall be carried out according to the relevant requirements of the current national standard "Standard for Seismic Appraisal of Buildings" (GB 50023).
1.0.4 Strengthening design of masonry structures shall meet not only those specified in this code, but also the requirements of relevant current national standards.
2 Terms and Symbols
2.1 Terms
2.1.1 Strengthening of masonry structures
Measures such as strengthening, partial replacement or internal force adjustment are taken for masonry structures with insufficient reliability or whose reliability is required to be improved by the Owner as well as the structure member and the relevant parts so as to make them have safety, durability and applicability specified in the current codes for design and required by the Owner.
2.1.2 Existing structure member
The original member before strengthening.
2.1.3 Important structure member
The structure member whose failure will affect or endanger the safe operation of the bearing structure system.
2.1.4 General structure member
Structure members beyond the important structure members.
2.1.5 Composite cement mortar
The mortar with cement and high-performance mineral admixture as main components and mixed with additive and short fine fiber.
2.1.6 Polymer modified cement mortar
The high-strength cement mortar mixed with modified epoxy emulsion or other modified copolymer emulsion. The polymer modified cement mortar for the bearing structure shall be able to significantly imporove the capacity of its substrates such as anchored reinforcement, bonded concrete and masonry.
2.1.7 Steel reinforcement mesh
The mesh welded with ordinary hot-rolled ribbed bar or cold-rolled ribbed bars.
2.1.8 Fiber reinforced poloymer
A kind of composite material with fiber reinforcement effect that are arrayed with high-strength continuous fiber according to certain rules and formed after dipping, bonding and curing with adhesives, which is generally referred to as the fiber reinforced poloymer.
2.1.9 Strength utilization factor of material
The calculation factor introduced considering that the strength of strengthening materials fails to be fully utilized under secondary load conditions.
2.1.10 External layer strengthening
A ind of strengthening method that the bearing capacity and rigidity of the existing structure member are improved through external reinforced concrete layer or steel reinforcement mesh mortar layer.
2.1.11 Sectional steel strengthening
A kind of strengthening method that the section steel limb and batten plate are welded into a structure for the masonry column enclosure and the external force is districuted according to their respecitive rigidity ratios, which is also referred to as dry-externally bonded steel.
2.1.12 External prestressed strut strengthening
A kind of strengthening method that precompression is applied to two diagonal steel struts with cut and bending through tightening the transverse screw rod device so as to discharge the load of the masonry columns to the strut.
2.1.13 Counterfort masonry column strengthening
A kind of strengthening method that partial wall is thickened at some distance along the length direction of the masonry wall to form stiffening wall with buttress.
2.1.14 Masonry crack repairing
A kind of repairing method adopted with a view to sealing the masonry crack or recovering the integrity of the cracked masonry.
2.2 Symbols
2.2.1 Material performance
Em - the elastic modulus of the existing structure member masonry;
Ea - the elastic modulus of the new section steel;
Ef - the elastic modulus of the new fiber reinforced poloymer;
fm0, f - the design values for the compression strength of the existing masonry and new masonry respectively;
fc - the design value for the axial compressive strength of the new concrete;
fy, - the design values for tensile and compression strength of the new reinforcement;
ff - the design value for the tensile strength of the new fiber reinforced poloymer.
2.2.2 Action effect and bearing capacity
N - the design value for axial compression after strengthening of structure member;
M - the design value for the bending moment after strengthening of structure member;
V - the design value for the shear force after strengthening of structure member;
δs - the tensile stress of the reinforcement.
2.2.3 Geometric parameters
Am0 - the sectional area of the existing structure member masonry;
Ac - the sectional area of the new concrete;
Contents of GB 50702-2011
1 General Provisions
2 Terms and Symbols
2.1 Terms
2.2 Symbols
3 Basic Requirements
3.1 General Requirements
3.2 Principles for Calculation of Design
3.3 Strengthening Methods and Technology
4 Materials
4.1 Masonry Materials
4.2 Concrete Materials
4.3 Steel and Welding Materials
4.4 Wire Ropes
4.5 Fiber Reinforced Polymer
4.6 Structural Adhesives
4.7 Polymer Modified Cement Mortar
4.8 Materials for Masonry Crack Repairing
4.9 Short Fiber for Anticracking
5 Reinforced Concrete Layer Strengthening
5.1 General Requirements
5.2 Masonry Compression Strengthening
5.3 Masonry Shear Strengthing
5.4 Masonry Seismic Strengthening
5.5 Construction Requirements
6 Steel Rinforcement Mesh Mortar Layer Strengthening
6.1 General Requirements
6.2 Masonry Compression Strengthening
6.3 Masonry Shear Strengthing
6.4 Masonry Seismic Strengthening
6.5 Construction Requirements
7 Sectional Steel Strengthening
7.1 General Requirements
7.2 Calculation Methods
7.3 Construction Requirements
8 External Prestressed Strut Strengthening
8.1 General Requirements
8.2 Calculation Methods
8.3 Construction Requirements
9 Bonded Fiber Reinforced Ploymer Strengthening
9.1 General Requirements
9.2 Masonry Shear Strengthing
9.3 Masonry Seismic Strengthening
9.4 Construction Requirements
10 Wire Rope Mesh-Polymer Modified Cement Mortar Layer Strengthening
10.1 General Requirements
10.2 Masonry Shear Strengthing
10.3 Masonry Seismic Strengthening
10.4 Construction Requirements
11 Strengthening with Adding Masonry Counterfort Column
11.1 Calculation Methods
11.2 Construction Requirements
12 Construction Strengthening of Masonry Structures
12.1 Strengthening with Adding Ring Beam
12.2 Strengthening with Adding Constructional Column
12.3 Strengthening with Adding Concrete Padstone
12.4 Disassemblying and Bonding Partial Masonry
13 Masonry Crack Repairing
13.1 General Requirements
13.2 Masonry Crack Repairing by Filler
13.3 Masonry Crack Repairing by Grout
13.4 Masonry Crack Repairing by External Mesh
13.5 Masonry Crack Repairing by Replacement
Appendix A Determination for Load Characteristic Value of Existing Structures
Appendix B Specifications for Test and Evaluation of Bonding Tensile Strength between Strenthening Materials and Substrate
Explanation of wording in This standard
List of Quoted Standards
