common stipulation
    According to the appraisal conclusion and the client’s request, if the concrete structure need be strengthened by reliability qualification test, make sure that the reinforcement plan should be designed by the qualified professional according to the request of the criterion. Sometimes the whole building or some part of it need be strengthened, sometimes just the specified structure, members or joints. You should consider that if it is economical in technology, and avoid the unnecessary backout and replace.
    The reinforcement design of the concrete structure should be combined close with the working technic. You should take effective measure to guarantee that the added member join firm with existing structure member, the added section bond hard to the existing section, and working together. Besides, you should not to have an bad impact foundation. To the damage of the old structure caused by the high temperature and wet, low temperature, frozen and thaw, chemical corrosion, vibration, temperature stress, differential settlement of the base and so on, you should produce an effective countermeasure to strengthen according to the order in reinforcement design. To the concrete structure which be likely to incline, failure, distort largely, or collapse, you should produce corresponding temporary measure and the construction company should be required to administer strictly.
    After be strengthened, the safety degree of the concrete structure should be measured together from the factual condition by the client and the designer according to the ponderance of damage, importance of the structure and the life expectancy of reinforce design. In a general way, it is 30 years. To the structure or component which is reinforced with adhesive, you should inspect termly. The design company should determine when to inspect, but the first inspect should be finished in 10 years. You can not change the use and the environment if you are not allowed or not by technical test.

design principle
    The analyse method in the concrete structure strengthening design should accord with the fundamental in concrete structure design criterion (GB 50010), which is the actual national standard. In a general way, use the linear-elastic analyse method to calculate the load effect. You should have the credible experiment gist if you adopt the plastic internal force redistribution method except the structure member strengthening with R.C.
    When strengthening the concrete structures, you should design under the bearing ultimate state and calculate under the serviceability limited state. The structural calculating diagram must accord with its actual structure. The load effect combination, the combinatorial coefficient and the load subentry coefficient should be measured according to the actual national standard, Lode code for the design of building structures (GB50009), also should consider the additional stress caused by eccentric load, deformation of structure or temperature effect. The size of the existing structures or members should be measured by meterage. The size of the adding members should be measured by design documents. To the existing structures or members, adopt the standard value of the concrete strength and tensile strength of the stressed steel bars. If the old design documents is effective all the same and the structure did not degenerated, you also can adopt the standard value in the old design documents. If the structure should be detected again by appraisal of reliability, you should adopt the standard value in detect conclusion. The performance and quality of the reinforcement material also should be estimated by test. The design value should be adopted according to the interrelated formulation.
    When calculating the bearing capacity of the structures or members, you should consider the actual stressed condition, namely the stress excess of the old members, stress lag of the strengthened members, the condition of the old member and the strengthened member working together. After strengthened, if the load transfer path is changed or the structure weight is increased, you should calculate the stress of the corresponding structures, members and base. When strengthening the structures or members in earthquake zone, except the bearing capacity, you should also calculate its seismic capacity. Make sure that there is not any unsubstantial place caused by local reinforcement or abrupt change of rigidity. At the same time, you should also consider the earthquake action effect accretion caused by structural stiffness accretion. In order to prevent the collapse caused by the reinforced members failure, the old structures or members should bear the ultimate load of the structure. When calculating, the old structures or members should bear 1.5 fold of the standard value of the dead load.

reinforcement technology in common use and corresponding material
choice
    Concrete structure reinforcement methods include direct reinforcement and indirect reinforcement. When designing, you should choose the suitable reinforcement method and the corresponding technology according to the factual condition and the use request. The methods which are adopted in direct reinforcement include: structure member strengthening with R.C, structure member strengthening with externally bonded steel frame, structure member strengthening with externally bonded steel board, structure member strengthening with fiber composite material, compression member confined by reinforcing wire. The methods which are adopted in indirect reinforcement include: structure member strengthening with externally applied prestressing, structure member strengthening with added fulcrum. The technic which be used together with the structurereinforcement methods include: crack repairing, post-installed fastenings and so on. Each method has its characteristic, and there is difference between different strengthening material and working technic. You should choose to use rationally according to the factual condition of the engineering.
1. structure member strengthening with R.C
    This method is suitable for strengthening of beam, board, column, wall and generic buildings. Its working technic is easy, has high adaptability and long-term use experience. Its disadvantages are: there is moisture work during construction, need to limit the load during the concrete curing time, and the structure weight is increased and the architectural space is minished. The main corresponding material are: GMA Admixture for Non-shrinkage Self Consolidating Concrete, JN-J Interface Treating Agent for Concrete, JN-Z Rebar Setting Injection and so on.
2. structure member strengthening with new concrete instead
    This method is suitable for partial strengthening of the diversified structure members. Its advantages are: the structure members can be resumed after strengthening, not change the existing architectural space. Its disadvantages are: the workload of eliminate the old concrete is large, it is easy to damage the steel bar, and there is moisture work. The main corresponding material are: HPG Cementitious Grouting Material or GMA Admixture for Non-shrinkage Self Consolidating Concrete, JN-J Interface Treating Agent for Concrete, JN-Z Rebar Setting Injection and so on.
3. structure member strengthening with externally bonded steel frame
    This method is suitable for strengthening of beam, column, wall, truss generic buildings. Its advantages are: the force is credible, this method can enlarge the bearing capacity of structure or members, does not minish the existing architectural space, it is simple andconvenient to work and there is not moisture work. Its disadvantages are: it must limit the temperature of using environment, and the strengthening expenses is higher than other method. The main corresponding material are: JN-M Structural Adhesive, JN-F Sealant, JN-S Chemical Anchor or JN-Z Rebar Setting Injection.
4. structure member strengthening with externally bonded steel board
    This method is suitable for strengthening of bending members and tensile members. Its advantages are: the construction period is short, and this method does not change the outline of structure and the existing architectural space. Its disadvantages are: it must limit the temperature of using environment, it is not easy to affix the steel board to the structure members with curvilinear surface, and the steel board need to do antirust treatment. You should use the draw-off method to plaster thinner steel board (2-5mm) externally, the main corresponding material are: JN architectural structural adhesive, JN-S chemical anchor. You should use the pouring method to plaster thicker ?steel board (＞5mm) externally, the main corresponding material are: JN-M Structural Adhesive, JN-F Sealant, JN-S Chemical Anchor or JN-Z Rebar Setting Injection.
5. structure member strengthening with fiber composite material
    This method is suitable for the strengthening when the bearing capacity of the tensile members and bending members is deficient. It also can be used to strengthen the compressed members when making use of restriction effect of the voluble fiber composite material. The fiber composite material is light and high-strength, it can conform to the requirements when plastering it on the curvilinear surface, it has high corrosion resistance and high water resistance, and it is convenient to construct. Its disadvantages are: it must limit the temperature of using environment, and you should do special defend treatment. If not, it can be damaged easily by fire or people. The main corresponding material are: JN-C Carbon Fiber Strengthening System (include JN-C carbon fiber fabric, JN-CS primer, JN-CE putty fillers and JN-C3P saturating resin).
6. compression member confined by reinforcing wire
    This method is suitable for enhancing the displacement ductility of concrete members. It increases the member weight little, and dose not change the outline of the member largely. It can not enhance the bearing capacity of the concrete members with rectangle section markedly, so limit its application. The main corresponding material are: JN-J Interface Treating Agent for Concrete or GMA Admixture for Non-shrinkage Self Consolidating Concrete
7. structure member strengthening with externally applied prestressing
    This method is suitable for the strengthening of long span structures and large-sized structures under the high stress and high strain. It can decrease the stress degree of the existing structure members, eliminate the stress lagging of the adding members, and change the use. Its disadvantage is that it is difficult to do defending treatment when there is heat sources and the surface temperature of the structure members is higher than 60℃ frequently, and it is costly to do it.
8. structure member strengthening with added fulcrum
    This method is suitable for the strengthening position where it is not strict for using condition and outline, and for the temporary support structure of the emergency project. It force definitely, and it is easy and convenient to construct, also it is easy to disassembly. But it minish the existing architectural space.
9. crack repairing technology
    There is two types: the first type is called obturate surface method or fill and obdurate method which aim to protect the steel bar from erosion (The main corresponding material are: JN-XF concrete crack sealant or JN-F sealant). The another type is called pressure-grouting method or injection method which not only aim to protect the steel bar from erosion, but also to resume the strength of concrete partially with injected reinforcing agent (The main corresponding material are: JN-L Low-viscosity Structural Adhesive or JN-M Structural Adhesive, JN-F Sealant). You should choose the suitable method according to the crack character, size and the repair request in the concrete structure reinforcement engineering.
10. post-installed fastenings technology
    The post-installed fastenings technology include rebar setting technology and anchor technology. The former is suitable for buildings structural strengthening, connecting or extending members in reconstruct, and remedy when the steel bar deviate the designing position or lacking steel bar. The latter is suitable for bonding the metal member (steel members, curtain wall keels) to the concrete structure, and also suitable for anchoring the other reinforcement material (steel board, fiber composite material) on the concrete surface. It can position accurately, and it is convenient to construct. Its disadvantage is that it increase the cost of the reinforcement engineering. The main corresponding material are: JN-Z Rebar Setting Injection, JN-S Chemical Anchor.

characteristic and principle of reinforce with adhesive

characteristic of reinforce with adhesive
    Sticking technology is an old and young technology. With the development of the science technology, not only the adhesive, but also the object, scale and adhesive technology developed well. The structural adhesive is used widely in navigation, shipbuilding, automobile and national defence industry. With the rapid development of the international chemical industry and the macromolecule material, the structural adhesive also be used in civil engineering. Not only the kind, performance, technology, but also the price are changed largely. It satisfies the needs in civil engineering commendably. Especially, the structural adhesive developed rapidly in civil engineering in past 10 years.
Comparing with traditional methods, using architectural structural adhesive to bond, repair and reinforce the old or new structure members In building engineering has many advantage, for example:
(1). The structural adhesive can bond the different material together. It is the unique advantage of bonding that the traditional methods can not compare with.
(2). The structural adhesive has high bonding strength. The strength of itself is exceed the concrete strength largely. It has nicer water resistance, medium resistance and high mechanical performance so that it can satisfies diversified use.
(3). Comparing with the riveted members or the welded members, the stress in joint of
the structure members strengthened with the synthetic resin is symmetrical. It will not generate stress concentration, and has high fatigue-crack resistance and good integrity.
(4). The construction technology is easy and convenient. It is a very technology with rapid working speed, 1high efficiency, short working period, low cost and good effect.
(5). The curing time of the structural adhesive is short. The bonded members can be loaded after 2-3 days. Especially, it is used to repair and reinforce in he emergency project. And the adding weight in bonding is little, the adding section of the reinforced members also is little. It does not minish the existing architectural space and change the outline of the members.
    In different reinforcement methods and different construction technologies, the corresponding adhesives and their performance are also different. JN series adhesive has many varieties, which can widely used in structure member strengthening with bonded steel plates, structure member strengthening with bonded carbon fiber laminate, concrete crack strengthening with injected adhesive, wet-enclosing steel reinforcement, drill holes and set steel bars (anchor) in concrete, repairing the exterior and interior bugs of concrete, interface treatment in new-old concrete, concrete surface protection with adhesive and so on.
    Compared to build a new construction, repairing and strengthening the construction is more complicated and more difficult. The complexity and difficulty are presented in every step of the strengthening construction, not only the investigation, detection, appraisal of the existing building, but also the strengthening design and the building of it. The bonding scheme should be measured by necessary investigation, detection, appraisal and design, but remember, the perfect bond depends on the joint, adhesive and construction technology.

design joint
    The design of the joint is an crucial aspect of perfect bonding. The joint which is made of many parts is the discontinuous part of structure, and its stress state is complicated. We simplify the stress state to the shearing force and the tensile force, and the tensile force has three types: uniform tensile force, non-uniform tensile force and peeling force.
The tensile strength, compressed strength and shearing strength is higher, but the?? peeling strength and bending strength is lower. So considering the mechanical performance, you should comply with the next following principle:
①. The stress direction of the adhesive should at the direction which has the highest bonding strength.
② Try to get the largest adhesive section to enhance the bearing capacity of the joint.
③ Avoid the stress concentration, reduce the failure which is caused by peel, cleave or bend.
④ Make sure the adhesive layer is thin, continuous and symmetrical, avoid lacking adhesive.
Besides, you should take some other factors into consideration. For example: adhesive technology, quality control, working procedure and cost check.

choose adhesive
    Comparing with the generic adhesive, building adhesive should have the following characteristics:
(1). After the adhesive cured, it should has nicer mechanical performance and nicer durability.
(2). It is convenient for use. It can harden rapidly under the room temperature or low temperature.
(3). No need to do surface treatment carefully. In some special condition, it can used to bonding on the moist or oil surface.
(4). It is nontoxic, non-stimulating and non-infectant.
(5). It must be suitable for construction.
(6). It is requested that the material is plentiful, the cost is low.
    Compared with other adhesives, the epoxy resin adhesive has perfect durability, bonds well with the generic engineering material, shrinks little during the curing process, has high mechanical performance. Furthermore, it is easy to meet the use request, and the price is lower. At present, the epoxy resin adhesive leads in the building adhesive (especially the architectural structural adhesive). JN series building adhesive also is the epoxy resin adhesive which has perfect durability mechanical performance. Its perfect durability mechanical performance is come from its particular chemical structure.
    JN series building adhesive has many kinds. Before use, you should know well the performance of the adhesive, purpose for use, design scheme and construction plan. Choose the suited adhesive according to the factual condition. To the special request in engineering (for example: fast curing, bond the moist surface, curing under low temperature), choose the corresponding improved products of JN series. JN series building adhesive can meet the request in repairing, rebuilding and strengthening in civil engineering.

construction technic
    The quality of repairing, reconstructing and strengthening in civil engineering has something to do with design and material. Besides, the quality also depend on the construction technology and construction quality. Material, design and construct not only connect but also restrict each other. Only the three aspects unite together, it can lead to satisfactory effect.
    Because of its particularity, not only you should comply with common request in civil engineering construction, but also should pay attention to the following points:
(1). You should do the surface treatment carefully because it is the most pivotal working procedure in bonding construct.
(2). You should know the performance and the characteristic of the adhesive amply? before construct.
(3). The mixed proportion should be exact (Each component should be churned up adequately and weight exactly before mixing. Then mix well).
(4). Make sure that the adhesive layer is symmetrical and full.
(5). Curing temperature and curing time should be exact.
(6). It must be constructed by the professional builder.