Figure 1
Typical damaged masonry structures. (a) Damage of masonry structure after long-term service. (b) Damage of masonry structure after earthquake.
Figure 2
Retrofitting strategies for URM structures.
Table 1
Design for specimens tested.
| Specimen | Strengthen method | Thickness of overlay (mm) | Steel mesh |
|---|---|---|---|
| S1 | Unstrengthen | — | — |
| S2 | Steel mesh-ECC layer (both double-sides) | 30 + 30 |
 6@200 |
| S3 | Steel mesh-mortar layer (both double-sides) | 30 + 30 |
 6@200 |
Figure 3
Dimension and configuration of the specimen (unit: mm). (a) Reinforcing mesh arrangement diagram. (b) Side view of reinforced specimen. (c) Top beam reinforcement diagram. (d) Floor beam reinforcement diagram.
Figure 4
Raw materials used for mixing ECC. (a) Cement. (b) Fly ash. (c) Silica fume. (d) Quartz sand. (e) Fiber. (f) Water reducer.
Figure 5
Masonry wall construction process. (a) Brick wall construction. (b) Loading beam formwork and concrete pouring.
Table 2
Properties of fibers.
| Fiber type | Length/mm | Diameter/μm | Elastic modulus/GPa | Elongation/% | Tensile strength/(N/mm2) | Density/(g/cm3) |
|---|---|---|---|---|---|---|
| PVA | 12 | 40 | 41 | 6.5 | 1,560 | 1.3 |
Table 3
Chemical properties of cement and mineral admixtures (unit: %).
| Material | SiO2 | Al2O3 | CaO | MgO | Fe2O3 | Na2O | TiO2 | SO3 | K2O |
|---|---|---|---|---|---|---|---|---|---|
| Cement | 19.06 | 4.71 | 66.17 | — | 3.49 | — | — | 2.40 | 0.46 |
| Fly ash | 54.76 | 24.56 | 4.85 | 0.10 | 6.54 | — | 1.85 | — | — |
| Silica fume | 96.74 | 0.32 | 0.11 | 0.10 | 0.08 | 0.09 | — | — | — |
Table 4
Mix proportions of the matrix (per m³).
| Materials | Quartz sand | Fly ash | Silica fume | Cement | Water |
|---|---|---|---|---|---|
| Mass ratio | 0.36 | 3.00 | 1.00 | 1.00 | 0.30 |
| Quantity (kg/m3) | 115 | 954 | 318 | 318 | 95 |
Figure 6
Strengthening of masonry walls. (a) Embed tie bars. (b) Steel mesh and strain gauges. (c) Surface layer ECC spraying. (d) ECC surface layer plastering.
Figure 7
Compressive strength test of a single brick. (a) Brick specimens. (b) Testing apparatus.
Table 5
Compressive strength of fried common bricks.
| Specimen | Loaded area dimensions (mm) | Ultimate load (kN) | Compressive strength (MPa) | (MPa) | S (MPa) | F k (MPa) |
|---|---|---|---|---|---|---|
| Z1 | 108 × 113 | 124.55 | 10.21 | 12.29 | 1.54 | 9.47 |
| Z2 | 109 × 112 | 126.45 | 10.36 | |||
| Z3 | 106 × 113 | 159.29 | 13.30 | |||
| Z4 | 107 × 115 | 165.89 | 13.48 | |||
| Z5 | 107 × 114 | 160.37 | 13.15 | |||
| Z6 | 108 × 115 | 170.39 | 13.72 | |||
| Z7 | 109 × 115 | 175.09 | 13.97 | |||
| Z8 | 109 × 113 | 130.13 | 10.57 | |||
| Z9 | 106 × 114 | 158.91 | 13.15 | |||
| Z10 | 107 × 115 | 135.62 | 11.02 |
Figure 8
Specimens and testing apparatus.
Table 6
Test data for the mortar compressive strength.
| Compressive strength (MPa) | Average compressive strength (MPa) | |||
|---|---|---|---|---|
| Q-1 | 5.36 | 5.20 | 5.08 | 5.21 |
| Q-2 | 5.53 | 5.39 | 5.31 | 5.41 |
| Q-3 | 5.33 | 5.49 | 5.35 | 5.39 |
| M-1 | 10.16 | 10.23 | 10.19 | 10.19 |
Table 7
Mechanical properties of rebar.
| Reinforcing rebar | Rebar diameter (mm) | Yield strength (MPa) | Average (MPa) | Ultimate strength (MPa) | Average (MPa) | Elastic modulus (GPa) | Average (GPa) |
|---|---|---|---|---|---|---|---|
| HRB400 | 6 | 454.33 | 454.18 | 603.47 | 605.87 | 201.74 | 201.43 |
| 453.46 | 609.62 | 203.32 | |||||
| 454.75 | 604.52 | 199.24 |
Figure 9
Specimens and testing apparatus.
Figure 10
Loading scheme. (a) Loading device. (b) Loading system.
Figure 11
Schematic layout of measure points. (a) Schematic diagram of strain gauges attached on the reinforcing mesh. (b) Schematic diagram of strain and displacement gauges attached on the strengthened surface layer.
Figure 12
DIC measurement process. (a) DIC measurement area. (b) Diagram of the DIC data acquisition system.
Figure 13
Main instruments. (a) TDS-540 static resistance strain acquisition system. (b) Extension unit. (c) Displacement gauges. (d) DIC device.
Figure 14
Failure pattern of specimen S1. (a) The south side of the specimen. (b) The north side of the specimen.
Figure 15
Failure pattern of specimen S2. (a) The south side. (b) The west side. (c) The north side. (d) The east side.
Figure 16
Failure pattern of specimen S3. (a) Cracking at the bottom of the mortar layer. (b) Cracking at the bottom of the sidewall.
Figure 17
Comparison of hysteresis curves. (a) Specimen S1. (b) Specimen S2. (c) Specimen S3.
Figure 18
Skeleton curves. (a) Specimen S1. (b) Specimen S2. (c) Specimen S3. (d) Comparison of skeleton curves.
Figure 19
Strain distribution on the strengthening layer of specimen S2. (a) E-1∼E-7. (b) E-8∼E-15.
Figure 20
Strain distribution on the reinforcement of specimen S2. (a) Transverse reinforcement strain. (b) Vertical reinforcement strain.
Figure 21
Strain distribution on the strengthening layer of specimen S3. (a) M-1∼M-7. (b) M-8∼M-15.
Figure 22
Strain distribution on the reinforcement of specimen S3. (a) Transverse reinforcement strain. (b) Vertical reinforcement strain.
Figure 23
Strain contours and strain data obtained through DIC. (a) Strain contour map of specimen S2. (b) Strain distribution of specimen S2. (c) Strain contour map of specimen S3. (d) Strain distribution of specimen S3.
Figure 24
Comparison of stiffness degradation.
Figure 25
Energy equivalent method.
Table 9
Comparison of characteristic load, displacement, and ductility.
| Specimen | Loading direction | σ s/kN | Δ y/mm | σ p/kN | Δ p/mm | σ u/kN | Δ u/mm | μ |
|---|---|---|---|---|---|---|---|---|
| S1 | Forward | 88.43 | 2.09 | 97.32 | 2.39 | 82.79 | 3.14 | 1.51 |
| Downward | −74.46 | −2.16 | −82.39 | −2.38 | −70.01 | −3.25 | 1.50 | |
| Averages | 81.45 | 2.13 | 89.86 | 2.39 | 76.40 | 3.19 | 1.51 | |
| S2 | Forward | 115.06 | 3.01 | 145.18 | 5.14 | 123.40 | 6.79 | 2.26 |
| Downward | −116.81 | −3.05 | −142.63 | −5.16 | 121.23 | −6.77 | 2.22 | |
| Averages | 115.94 | 3.04 | 143.93 | 5.15 | 122.32 | 6.78 | 2.24 | |
| S3 | Forward | 109.81 | 2.65 | 117.51 | 3.22 | 111.52 | 4.80 | 1.81 |
| Downward | −89.29 | −2.34 | −107.83 | −3.19 | −105.32 | −4.79 | 2.04 | |
| Averages | 99.55 | 2.50 | 112.67 | 3.21 | 108.42 | 4.80 | 1.93 |
Figure 26
Schematic diagram of equivalent viscous damping factor calculation.
Figure 27
Comparison of energy dissipation capacity. (a) Equivalent viscous damping coefficient. (b) Cumulative energy dissipation. (c) Cumulative total energy dissipation.