RESIST-2020.pptx

SEISMIC REHABILITATION OF
OLD MASONRY-CONCRETE
BUILDINGS
Eng. Armando Demaj
PROJECT RESIST-
2020

OUTLINE
Introduction
Methodology
Experimental Campaign
Numerical Modelling
Conclusion
2022
SEISMIC REHABILITATION OF OLD MASONRY-CONCRETE
BUILDINGS
2

INTRODUCTION
Due to their architectural and heritage values, and sustainability concerns,
old buildings are preserved and rehabilitated rather than demolished and
reconstructed.
Seismic assessment and retrofitting of URM buildings is crucial for their
safety given that:
- no seismic provisions were considered during the design stage;
- vulnerable to seismic actions;
- still in use;
- Degradation with time;
- significant structural modifications occurred through years
2022 SEISMIC REHABILITATION OF OLD MASONRY-CONCRETE BUILDINGS 3

INTRODUCTION
- buildings built before 1755;
- “Pombalino” buildings (1755–1880);
- “Gaioleiro” buildings (1880–1930);
- Masonry – concrete buildings (1930–1960);
- Reinforced concrete buildings (after 1960).

EVOLUTION OF BUILT ENVIRONMENT IN PORTUGAL
Gomes et. al., 2021 (Source: INE, Censos 2011)

INTRODUCTION
The project RESIST-2020 aimed at broadening the knowledge on the
behavior of the load-bearing clay masonry walls of old buildings and
developing a strengthening solution to increase the shear strength and/or the
ductility.
Subject to study:
Old masonry-concrete buildings (a.k.a. “placa” buildings)
The “placa” buildings were built in mainland Portugal between 1930s and
1960s, and currently represent around 40% of the building stock. The
quarters of Alvalade, Arco do Cego, Alameda D. Afonso Henriques, Areeiro,
Encarnação, Boavista and Serafina are the main neighbourhoods of Lisbon
where these buildings are mainly located (Sotto-Mayor M. L. 2006).
The façade of a “placa”
building in Lisbon

METHODOLOGY
The methodology implemented in this study is based on:
- Experimental tests for the determination of the mechanical properties
of the constituent materials of the walls, mortars and bricks;
- Experimental tests on unreinforced and reinforced masonry wallettes
for the determination of the shear strength through diagonal
compression tests;
- Experimental tests on unreinforced wallettes for the determination of
the compressive strength through axial compression tests;

METHODOLOGY
- Experimental tests on unreinforced and reinforced triplets for the
determination of the in-plane shear strength of the bed joints of the
assemblages through triplets tests;
- Experimental tests on unreinforced and reinforced full-scale walls to
determine their behavior and the effect of the reinforcement through
cyclic shear tests;
- Numerical modelling for the simulation of all experimental tests and
their calibration using experimentally obtained data.

STRENGTHENING
TECHNIQUES
- The structural behavior of old buildings depends on
the behavior of its load-bearing walls.
- Recent earthquakes have shown that masonry walls
are vulnerable to earthquakes (Gölcük-Turkey,
1999; L’Àqualia-Italy, 2009; Mamurras, Albania,
2019; Izmir-Turkey, 2020)

STRENGTHENING
TECHNIQUES
The most common strengthening techniques obtained
from the literature review are:
- Grout Injection;
- Replacement of degraded elements;
- Reinforced plasters;
- Jacketing;
- Anchoring systems;
- Joint repointing;
- Reinforcement with FRP;
- Post-tensioning;
- NSM steel reinforcement.

FAILURE MECHANISMS
The strength and stability of the structure are
dependent on its three-dimensional frame locking,
which is related to the interconnection of orthogonal
walls.
Basic components of a
masonry building
Box behavior of
connected walls
Failure due to lack of
connections
Reference: CVR Murthy, 2003

FAILURE MECHANISMS
The main in-plane failure mechanisms of masonry
walls when subjected to seismic actions are:
- Rocking;
- Shear cracking;
- Sliding failure
(a) rocking, (b) sliding, (c) diagonal shear (Pasticier et. al., 2008)

REINFORCEMENT
TECHNIQUE
The reinforcement solution is a NSM technique using
stainless steel twisted steel bars (TSB) and
traditional reinforced concrete reinforcement bars
(SB):
- opening slots of 25mm x 25mm
- applying a layer of premixed grout
- insert the reinforcement bar
- cover up until the surface with premixed grout

EXPERIMENTAL
CAMPAIGN
The experimental campaign included two types of masonry walls:
- Cement-mortar walls (strong walls)
Solid clay bricks
Mortar ratio by volume: 1 : 5 (cement : sand)
- Cement-hydrated lime mortar walls (weak walls)
Solid clay bricks
Mortar ratio by volume: 1 : 3 : 12 (cement : hydrated lime : sand)

TESTS ON MATERIALS -
BRICKS
Compressive strength on bricks
Cement mortar masonry specimens:
Original old bricks from demolition works of a building in the Duque
de Loulé avenue, in Lisbon, Portugal were used.
Dimensions: 244x116x68 mm3
Tests performed:
Compressive strength (N/mm2): 25.3 (2.49, 0.10)
Compressive strength test on old solid clay
brick

TESTS ON MATERIALS - BRICKS
Compressive strength on bricks
Cement-lime mortar masonry specimens:
Newly produced bricks with similar properties
Dimensions: 253x120x60 mm3
Tests performed:
Compressive strength (N/mm2): 26.5 (1.99, 0.08)
Compressive strength test on
newly produced solid clay brick

BRICKS
Static modulus of elasticity of bricks
Determination of static modulus of elasticity
Mean E = 4416 N/mm2 (583, 0.13)

MORTAR
Bedding mortar – “strong” walls
1 : 5 (cement : sand)
Cement: CEM II B-L 32.5 MAESTRO by SECIL
Sand: 1/3 was sandpit sand and 2/3 were river sand from the river Tagus
Bedding mortar – “weak” walls
1 : 4 : 15 (cement : hydrated lime : sand)
1 : 3 : 12 --//--
1: 3 : 8 --//--
Cement: CEM II B-L 32.5 MAESTRO by SECIL
Lime: Calicitic hydrated lime CL 90 by Lusical
Sand: river sand from the river Tagus

MORTAR
Mortar samples were collected, and specimens
were moulded to be tested for the following:
- Determination of dynamic modulus of
elasticity through ultrasonic pulse
velocity;
- Determination of dynamic modulus of
elasticity through resonance frequency;
- Determination of flexural strength;
- Determination of compressive strength;

TESTS ON MATERIALS – MORTAR
1 : 5 (CEMENT MORTAR)
Dynamic modulus of elasticity (N/mm2) Flexural strength (N/mm2)
Compressive strength (N/mm2)

TESTS ON MATERIALS – MORTAR
CEMENT-LIME MORTARS
Dynamic modulus of elasticity (N/mm2)
Compressive
strength (N/mm2)
Flexural
strength(N/mm2)

TESTS ON MATERIALS – PREMIXED GROUT
The reinforcing solution consists in embedding reinforcing bars in
pre-cut slots using a premixed grout.
- High performance, injectable
- Cementitious non-shrink grout
- Liquid + powder component
- Contains Portland Cement

TESTS ON MATERIALS – PREMIXED GROUT
Dynamic modulus of elasticity (N/mm2) Flexural strength (N/mm2) Compressive strength (N/mm2)

TESTS ON MATERIALS – REINFORCEMENT BARS
The reinforcement of the masonry assemblages was
carried out using two types of reinforcement bars:
SBΦ12
TSB Φ12 TSB Φ6
Close view of TSB Φ12
Material:
Austenitic stainless
steel Grade 304
Available diameters (mm): 4.5, 6, 8, 10 and 12
Tensile strength (6 mm Helibar): 10 kN
0.2% proof stress (N/mm2) 900 N/mm2

TESTS ON MATERIALS – REINFORCEMENT BARS
Tensile strength test
Bar type
Nominal
diameter
[mm]
Maximum
force Fm
[kN]
TSB Φ6 6 11.4
TSB Φ12 12 31.9
SB12 12 74.3

EXPERIMENTAL TESTS ON WALLETTE SPECIMENS
Unreinforced 1:5 mortar masonry wallettes
Type
Wallette
Designation
Dimensions
[cm3]
Experimental test
Type 1
WA-01
76x76x25 Axial compression
WA-02
WA-03
Type 2
UR-01
86x86x25 Diagonal Compression
UR-02
UR-03
Type 1
Type 2

Unreinforced 1 : 3 : 12 mortar masonry wallettes
No.
Wallette
designation
Dimensions
[mm3]
Experimental test
1 WAF-01
760x760x250
Axial compression
2 WAF-02
3 WAF-03
4 URF-01
Diagonal compression
5 URF-02
6 URF-03

Axial compression test
Instrumentation
LOAD CELL
LOADING CAP
BASE PLATE
LOAD CELL
LOADING CAP
BASE PLATE
WEST FACE EAST FACE
LOAD CELL
LOADING CAP
BASE PLATE
TRANSVERSE
LVDT 1 LVDT 4
LVDT 2
LVDT 3
LVDT 5
LVDT 6
LVDT 7 LVDT 8

Axial compression test on 1 : 5 mortar URM masonry
wallettes
Crack patterns

Axial compression test on 1 : 3 : 12 mortar URM masonry wallettes

Diagonal compression test
Instrumentation
LOAD CELL
LOADING CAP
BASE PLATE
LOAD CELL
LOADING CAP
BASE PLATE
WEST FACE EAST FACE
LOAD CELL
LOADING CAP
BASE PLATE
TRANSVERSE
LVDT W LVDT E
LVDT WV
LVDT WH
LVDT EV
LVDT EH

Diagonal compression test on 1 : 5 mortar URM masonry wallettes
Crack patterns

Diagonal compression test on 1 : 3 : 12 mortar URM masonry
wallettes
Crack patterns

URM wallettes summary
Wallettes with mortar 1:5
Compressive strength [N/mm2]
Wallettes with mortar 1:3:12
Compressive strength [N/mm2]
WAC-1 WAC-2 WAC-3
Averag
e
WBC-1 WBC-2 WBC-3
Averag
e
12.8 11.9 11.8 12.2 6.2 6.2 6.3 6.2
Wallettes with mortar 1:5
Shear strength [N/mm2]
Wallettes with mortar 1:3:12
Shear strength [N/mm2]
WAS-1 WAS-2 WAS-3 Averag
e
WBS-1 WBS-2 WBS-3 Averag
e
1.47 1.40 1.00 1.29 0.29 0.20 0.13 0.21

Reinforced wallettes - 1 : 5 mortar
2 HV 1 TSBΦ
6
sides
orient. # bars
mat.
1V1-
TSBΦ6
1H2-TSBΦ6
2H1-TSBΦ6
2HV1-TSBΦ6
Reinforcement using TSB Φ6 mm

2 HV 1 TSBΦ
6
sides
orient. # bars
mat.
2H1-
SBΦ12
2HV1-
SBΦ12
2DD1-SBΦ12
Reinforcement using SB Φ12 mm

2HV1-01
Damage patterns TSB Φ6 mm
1H2-01 2H1-01 1V1-01

Results TSB Φ6 mm
Energy Absorption at 20% Degradation of
Ultimate Load [× 10−3 N.mm/mm3]
Shear Strength [N/mm2]

2H1
Damage patterns SB Φ12 mm
2HV1 2DD1

Results SB Φ12 mm

Reinforced wallettes - 1 : 12 : 3 mortar
2 HV 1 TSBΦ
6
sides
orient. # bars
mat.
2V1_F - TSB Φ12 2H1_F - TSB Φ12 2HV1_F - TSB Φ12
Reinforcement using TSB Φ12 mm

2HV1_F-1
2HV1_F-2 2HV1_F-3

Results TSB Φ12 mm

2V1_F-1
2V1_F-2 2V1_F-3

Results TSB Φ12 mm

2H1_F-1
2H1_F-2 2H1_F-3

Results TSB Φ12 mm

EXPERIMENTAL TESTS ON TRIPLET SPECIMENS
1:5 mortar specimens

EXPERIMENTAL TESTS ON TRIPLET SPECIMENS
1:3:12 mortar specimens

EXPERIMENTAL TESTS ON FULL-SCALE WALLS
1:3:12 mortar

1:3:12 mortar

NUMERICAL MODELLING
FE models of wallettes:
• Unreinforced and reinforced – 1:5 mortar
• Discrete model (UR)
• Homogeneous model (UR)
• Homogeneous model+rebars (reinforced)
• Unreinforced and reinforced – 1:3:12 mortar
• Homogeneous model (UR)
• Homogeneous model+rebars (reinforced)
FE models of full-scale walls:
◉ homogeneous model+rebars of cyclic tests
○ Unreinforced wall
○ Reinforced wall

NUMERICAL MODELLING
Inelastic compressive stress-strain behavior for discrete FE model of mortar (left) and brick
(right)
Inelastic tension stress-strain behavior for discrete FE model of mortar (left) and brick (right)
Discrete model meshing in ABAQUS
Discrete model tension damage
0
1
2
3
4
0 0.002 0.004 0.006
Compressive
stress
[MPa]
Inelastic strain [-]
0
2
4
6
8
10
12
14
16
18
0 0.002 0.004 0.006 0.008
Compressive
stress
[MPa]
Inelastic strain [-]
Discrete modelling - ABAQUS
Unreinforced – 1:5 mortar
Concrete Damaged Plasticity Constitutive model - ABAQUS

NUMERICAL MODELLING
Inelastic compressive stress-strain behavior for homogeneous FE
model in compression (left) and tension (right)
Homogeneous model meshing in ABAQUS
Homogeneous model tension
damage
Homogeneous modelling
Unreinforced and reinforced – 1:5 mortar

NUMERICAL MODELLING
Inelastic compressive stress-strain behavior for homogeneous FE
model in compression (left) and tension (right)
Homogeneous model meshing in ABAQUS
Homogeneous model tension
damage
Homogeneous modelling
Unreinforced and reinforced – 1:3:12 mortar

NUMERICAL MODELLING
Discrete modelling - WALLETTES
Unreinforced – 1:5 mortar

NUMERICAL MODELLING
Homogeneous modelling - WALLETTES
Unreinforced and reinforced – 1:5 mortar
UR 2V1
1H2 2H1
1V1 2HV1-SBΦ12
2H1-SBΦ12 2DD1-SBΦ12

NUMERICAL MODELLING
Homogeneous modelling - WALLETTES

NUMERICAL MODELLING
Homogeneous modelling – FULL SCALE WALLS

NUMERICAL MODELLING
68
Homogeneous modelling – FULL SCALE WALLS

CONCLUSIONS
CEMENT-LIME
MORTARS
 The strengthening solution showed to be
effective contributing to an increased
shear strength and ductility
 In diagonal compressive tests shear
strength increased by 50%
 In diagonal compressive tests dissipated
energy at 20% degradation of the max.
force became 19 times higher.
 In full-scale wall tests drift capacity
doubled
 In full-scale wall tests the dissipated
energy was 75% higher
CEMENT MORTARS
20XX PRESENTATION TITLE 69
 The intended effect on masonry
assemblages is not provided
 The 45-degree orientation of reinforcement
shows improved strength, ductility, and
energy dissipation. However, it is
impractical.

The authors acknowledges FCT - Fundação para a Ciência e a Tecnologia by
the financial support to the work presented herein through the project
"RESIST-2020" - Seismic Rehabilitation of Old Masonry-Concrete Buildings”
ref. PTDC/ECI-EGC/30567/2017"
2022 PRESENTATION TITLE 70

THANK YOU
Armando Demaj
Epoka University, Tirana, Albania
ademaj@epoka.edu.al
Coordinated by:
Prof. João Gomes Ferreira, Prof. António
Sousa Gago, professors of the Department
of Civil Engineering Architecture and
Georesources of the Instituto Superior
Técnico and Doctor Ana Isabel Marques,
researcher of the Laboratório Nacional de
Engenharia Civil

RESIST-2020.pptx

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