Settlement of pier – clay soil, tensile and shear craks

Masonry Structure Vertical load – bearing structure

Declination of pier in

footing bottom - incorect

drainage and effects of

traffic – damages in

masonry of bay

raised humidity and

damage of surface layer of

pier

Damage of piers of structure – after ultimate limit state

Exterior part of pier – formwork from stone

block, interior part – filler from stone + mortar

Failures of head and

socle (base) of pier

Static securing of

overloading

(overstressing) piers

Local load of masonry under

binding beam

Deterioration (failure) of

thin masonry pier -

ultimate limit state

Cracks in facade – deformation

of steel beam overhead outlay

Part result of experimental works Brick P15 and P30

The influence of moisture on modul of elasticity and strength

abso

rpti

on

Str

ength

,

modul

of

elas

tici

ty

Brick

Brick

Brick

Brick

Brick

Brick

Sand stone – hard and soft spongilite stone

The influence of moisture on modul of elasticity and strength Part result of experimental works

Sand stone – hard Sand stone – soft

E

R

Abso

rpti

on

(%) A

bso

rpti

on

(%)

hard

soft

Mutual cooperation of brick and mortar in bed joint

Mortar with high strength

cohesion between brick and mortar – high

rigidity (small strain of mortar) - cracks in bed

joints

Mortar with small strength

Cohesion between brick and mortar – cracks

in bricks

tension

pressure tension

pressure

Mortar with high strength

cohesion between brick and mortar –

high rigidity (small strain of mortar)

- cracks in bed joints

Mortar with small strength

Cohesion between brick and mortar –

cracks in bricks

Isoline of principal stress σ1

Failure of masonry pier by cracks

Separate cracks Grave failure Emergency conditions

idealized work diagram

Deformation on

proportional limit

Formation

of

continuous

cracks –

plasticity of

mortar,

masonry

failure

ultimate deformation of masonry

Critical load Nt and ultimate load Nobs of

masonry depend on:

Compressive and tensile strength of mortar nad

brick (stone)

Dimensions, at first on depth of structurarl

matrials

Depth a quality of bed joints

Quality of mortar

Cohesion and workability of mortar

Brick bond

First cracks Expansion of

cracks Failures brick

pier - ultimate

limit state

deformation

pre

ssure

load

N

Failure of masonry pier load by normal force

first cracks load elastic zone Zone of cracking

creating continuous tension cracks

development and dissemination of tensile cracks

course of pressure trajectories Damage of pier in weaking zone

Zone of rise

of normal

strain – zone

of rise oblique

tensile cracks

Tensile cracks

Parting of pier into pole –

decrease of stability

trajectories of principal stresses Isoline of normal stress σx Isoline of normal stress σy

Failure of brick pillars

after reaching the ultimate load

Hmotnostní vlhkost (%) 1,5% 3,5% 14 % 16%

Mezní únosnost (kN) 630,9975 626,8 481,2 380,2

Mezní svislé poměrné přetvoření 0,00059 0,00080 0,00185 0,002065

Mezní příčné poměrné přetvoření -0,00589 -0,00719 -0,00377 -0,01962

Influence of moisture on load bearing capacity and vertical and horizintal

deformations of compression masonry piers – experimetal work

(bed joint 15mm, brick P15, lime mortar MV1)

CIX

12,312,88

13,76

11,56

13,0214,16 14,06

12,37

12,4

16,1614,97

14,78

150

150

11,56

12,37

14,7812,4

13,02

12,3

Mass moisture

Destruction of building – cause flood

Limit of rate vertical deformation

Limit of load capacity

Limit of rate horizontall deformation

Moisture – horizontal and

vertival section

631,0kN

101%626,8kN

100%

481,2kN

76%

380,2kN

60%

0,0kN

100,0kN

200,0kN

300,0kN

400,0kN

500,0kN

600,0kN

700,0kN

1,36% 3,56% 14,26% 15,81%

Vlhkost (%)

Za

tíže

ní

(kN

)

Comparation of limit load bearing capacity –

depending on the moisture

relativní únosnost podle ČSN 731101 a ČSN 730038, (e=0) relativní únosnost stanovená z pevností cihel v tlaku /2/ experimentálně stanovená relativní únosnost zděných pilířů

vlhkost (%)

rela

tivní ún

osnost (%

)1)

1) vztaženo k únosnoti při w < 5% (100%)

Lo

ad

Moisture

Rat

e of

Lo

ad

Moisture

Load capacity – Czech standard

Load capacity – exprimental work – brick and mortar

Load capacity – experimental work – masonry pier

Damage of masonries with different

moduls of deformation

cement

mortar lime mortar lime mortar

Maintenance of masonry structure with cracks

a) surface failures structure – removal of plaster and failure parts of masonry – removal of mortar from joint (to depth 30 –

50 mm) depth of cemented joint loading and liaison activated fine-grained cement mortar made new lime or cement plaster

b) Considerable failures pieces of building materials – greatly disturbed unit building material should be replaced by new,

contact gap between the original block and stone seals can be covered with steel or brass buckles anchored with epoxy resin

d) Masonry piers with vertical tensile cracks – bracing and switch clamping (securing before transverse tensile strain and

transverse prestress strain raising load press capacity of pier)

c) Local failures of masonry structure – at first securing of bearing structure, removal of failure part of masonry, filling

from pieces building materials (similar properties as original materials), anchor by bond or steel elemets, joint between new

and old part overlay by reinforce

Bracing failures mortar piers

Prestress by steel plate

Spiral wrap by wire

or rod

Prestress wire or rod

steel profile

Prestress of masonry pier

by wire or rod – without

continouse crackcs

Bracing of pier by

angel iron and pin Bracing of pier by steel plate and

pin

pin Angel iron

Weld steel plate

e) Local craks (active, passive) tensile and sheare – „stitching“ by steel rod 14 mm - 25 mm with fixing in load

bearing part of masonry (masonry without failures), steel element should be protected with a layer of cement mortar backing

and then covered with plaster and networks against corrosion

Schema of using steel buckle

distance

Cement

mortar

Groove in

masonry

Steel

buckl

e

Schema of using buckle by failure corner

anch

or

pla

te

fill a crack by cement mortar

fill a hole

Schema of using steel

buckle

Crossection a-a´

view

ground plan

fixing

buckle

Scheme of using steel rod

(buckle)

distance

Cement

mortar

Groove in

masonry

Steel

rod

Scheme of using rod (buckle) by failure

corner

anch

or

pla

te

fill a crack by cement mortar

fill a hole

Scheme of using steel

rod (buckle)

Crossection a-a´

view

ground plan

fixing

buckle

large distance

between the

clamps

„stitching“

e) Group of active cracks – switch clamping with sealing and injecting of cracks (cement, epoxide resin, polyester resin,

cement mortar and resin)

steel net

anchor

cement plaster

cracks

cracks

High sterngth steel bars (HELI bars) in grove

Spínání narušených zdí – Bracing of failure walls

Bracin of masonry structure by steel tie or prestress cabels (for prestress use steel wedge, screw or special elements), for

statics is better symetric design of tie by both side of wall

Groove in masonry

Front wall view

cross-section

cross-section cross-section cross-section

steel tie

pin

cross-section

cross-section cross-section

steel tie

pin

closing the outer ring

of reinforced concrete Temporary bracing

Strengthening and maintenance of mortar piers and walls

a) Sterngthening by brick wall – good qaulity bricks, connection between origin and new structure by wall pocket or

steel anchor, fine grain mortar, inserting reinforcement bars into every 3rd and 6th horizontal mortal joints and bonding with

high strenthmortar

b) Strengthening by concrete – at least concrete C12/15, thickness 60 – 120 mm, reduce shrinkage – reiforced net +

concrete grouting, grunite concrete

Strengthening by

concrete

stirrup

stirrup

concrete

maso

nry

concrete

Bore hole

Wall (thickness 440 mm) + concrete monierka (layer)

Dependance of load bearing capacity of pier

with strengthening by concrete – diferent

thickness of concrete layers (a), rate of

transvers reinforcement (b)

brick pillar dimensions 450 mm x 450 mm,

height of 3.3 m of brick mortar P10 MVC 2.5

Cement plaster

Comparation of load bearing capacity

strengthening by concrete strengthening by brick wall

brick pillar dimensions 450 mm x 450 mm, height of 3.3

m of brick mortar P10 MVC 2.5

60 mm thick of concrete, strengthening by brick wall –

brick CP20, mortar MVC 5

c) strengthening by reinforced plaster – transversal reinforcement prevets development of tension cracks

reinforce net

Plaster

masonry

stirrup

strengthening by reinforced

plaster

strengthening by

additing steel stirrup

d) strengthening by additing steel stirrup on every or every 2nd bed joint + cement mortar

Pier 450 mm x 450 mm (brick P10, mortar MVC 2,5)

Change of transversal reinforcement

Comparasion of load bearing capacity of masonry pier - strengthening by reinforced plaster (25

mm thick)

design as

concreting

e) strengthening by steel jacketing – contact between original masonry and steel angle – cement mortar

Strap before welding preheating from 500 till 700 °C,

After cooling on normal temperature – steel structure prestress masonry

masonry

strap

Masonry pier 450 mm x 450 mm (brick P10, mortar

MVC 2,5) depending on the size (dimension) of

vertical steel angles (a) and horizontal steel bands (b)

Comparasion of load bearing capacity of

masonry pier - strengthening by steel

jacketing

Bands 35/5 Bands 40/5 Bands 45/5

Strengthening with carbon (CFR) or glass

(GFR) materials and wire

wire strap

Attention –

Use epoxi resin - low melting temperature

(80°C)

(concreting tl. 80mm, B20, reinforcement

Ø 6mm á 100mm) experimetal work

Parts results of experimetal works

Comparison of experimentally determined ulitimate loads of pressure

reinforced

plaster steel

stirrup

Sterngtheni

ng by

concrete

Steel

jacketing

Steel

jacketing

without

strengthe

ning

ult

imat

e lo

ad

f) strengthening by steel structure (thin – walled profile) – no reological changes, continualy load transfer, no

requirements of foundation strengthening

thin-walled steel profiles

Load bearing capacity of

thin-walled steel profiles

distributing angle

mas

onry

wal

l

Cement bed Steel plate

tensioning screw

Cement mortar

Replacement of

column

New

foundation

Lifting by

hydraulic

press

temporary

security

column

pulled

down the

pillars

temporary

masonry piers

Setting

new

steel

column Concrete middle

part of fundation

Masonry Structure Sterngthening by brick wall

good qaulity bricks,

connection between origin and new structure by wall pocket or steel anchor,

fine grain mortar,

inserting reinforcement bars into every 3rd and 6th horizontal mortal joints and bonding with high

strengthmortar

Sterngthening by concrete

at least concrete B15,

thickness 60 – 120 mm,

reduce shrinkage – reiforced net + concrete grouting, gunite concrete

strengthening by reinforced plaster

transversal reinrorcement prevets development of tension cracks

strengthening by additing steel stirrup

on every or every 2nd bed joint + cement mortar

strengthening by steel jacketing

contact between original masonry and steel angle – cement mortar, preheating strip

strengthening by steel structure (thin – walled profile)

no reological changes, continualy load transfer, no requirements of foundation strengthening

strengthening by bracing

without continouse crackcs in pirer

Masonry Structure Cracks: passive, active

a) sewing (perpendicular)

b) grouting (from bottom up)

c) switch clamp (tie, activation! – tension can caused buckling

d) bonding

Cause of failure of stress mortar piers and wall are lateral tension

Principal stress 1 in masory compression pier (thickness 450 mm) – influence of rate of moduls of elasticity

Ec : Em and thickness of bed joint

bed joint bed joint bed joint

Principal stress 2 in masory compression pier (thickness 450 mm) – influence of rate of moduls of elasticity

Ec : Em and thickness of bed joint

bed joint bed joint bed joint

Typical failures of wall bay

windows and masonry in areas of

concentrated stress

Tensile cracks

shear cracks

exfoliation

of surface

layer

shear stress compressive normal stress

Schema of deformation and failure of bay masonry course of shear force in

reinforced concrete load bearing structure

cantilever

beam Backing masonry

reinforced concrete

beam

Deformation of

Cantilever beam

wall,

pier

compressive normal stress

wall,

pier

beam, girder

shear forces

areas of concentrated stress