Www World Housing Net Whereport1view Php ID=100099

7/30/2019 Www World Housing Net Whereport1view Php ID=100099

1/21

World Housing Encyclopediaan Encyclopedia of Housing Construction in

Seismically Active Areas of the World

an initiative o fEarthquake Engineer ing Research Institute (EERI) and

International Association for Earthquake Engineering (IAEE)

HOUSING REPORTHistoric, braced frame timber buildings with masonry infill ('Pombalino'

buildings)

Report # 92

Report Date 08-05-2003

Country PORTUGAL

Author(s) Rafaela Cardoso, Mario Lo pes, Ri ta Bento, Dina D'Ayala

Reviewer(s) Paulo B. Lourenco

ImportantThis encyclopedia contains information contributed by various earthquake engineering professio nals around the world. All opinions, findings , conclusions &reco mmendations expressed herein are those of the various participants, and do not necessarily reflect the views o f the Earthquake Engineeri ng Researc hInstitute, the International Association fo r Earthquake Engineering, the Engineering Information Foundation, John A. Martin & Asso ciates, Inc. o r the participants'organizations.

Summary

Pombalino buildings (see Fig ures 1, 2, 3 and 4) are historic masonry buildings that can be identified by the presence of a three-dimensional timberstructure (named "gaiola pombalina"), which is enclosed in internal masonry walls above the first floor. The roofs are built with timber trusses cladwith ceramic tiles and the floor s are made of timber boards laid on timber jois ts. Gro und floor walls are ro ughly dressed stone masonry supporting asystem of vaults made of clay tiles, wi th stone arches. Foundations are made of short and small-diameter timber piles co nnected by a timber g rid.

PDFmyURL.com
http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://pdfmyurl.com/?otsrc=watermark&otclc=0.01


2/21

These buildings were built after the 1755 earthquake when fear of new earthquakes led to the enforcement of anti-seismic provisio ns, such asestablishing a maximum number of storie s and introducing an interio r timber structure called "gaiola." The buildings orig inally were mixed-use wi thcommercial enterprises on the gr ound floor and res idences on the upper floors. During the 20th century, most Pombalino buildings underwentsubstantial refurbishment when they we re co nverted and occupied entirely by banks and companies. For the building s that have maintained theirorig inal uses, the main problems result from poor maintenance.The expected collapse mechanisms due to earthquake actions are the overturning offacades (out-of-plane) o r shear failure at the plane of the walls at g round floor level (g lobal shear mechanism), leading to a g lobal collapse mechanism.Typical seismic strengthening of these buildings includes the introduction of a concrete/steel ring beam at the level of the roof eaves. Theintroduction of steel elements/pre-stresse d cables or of anchors co nnecting parallel masonry walls is also co mmon. Steel elements are also used toconnect detached timber elements from the floors and gaiola to the masonry. New techniques applying new materials like Fibre Reinforced Polymers(FRP) are also used to increase the strength of the connections of timber elements that compose the gaiola.

1. General Information

Buildings of this construction type can be found in downtown Lisbon, in the area near the Tag us River known as Baixa. This type of building can be fo und elsewhere inLisbon and in other urban areas in Portugal also destroyed in 1755, such as the Vila Real de Santo Ant nio in Algarve (in the southern part of Portugal). Beca use of its

historical relevance, the building example described in this work is from Baixa . This type o f ho using co nstruction is co mmon ly found in urban a reas .

Pombalino buildings were built mainly in the urban areas of regio ns that experienced the g reatest destruction fo llowing the 1755 earthquake.

This co nstructio n type has be en in pract ice fo r more tha n 200 years.

Currently, this type of construction is not being built. As time has passed , co nstruction practice s have cha ng ed and t imber elements have prog ressively falle n into d isuse in thethree-dimensional structure. Experience sho ws that masonry building s built between 1755 and 188 0 included a complete three-dimensional timber structure (gaio la) abo ve the

g round floo r. Most likely during the 1880' s, the practice of g aiola co nstruction was co mpletely abandoned. This time boundary, however, is not very precise because it ispossible to find many buildings with inco mplete g aiola structures built before 18 80 .

PDFmyURL.com


3/21

Figure 1: Typical Building (Santo s, 2000 )Fig ure 2: Typical build ing fro m a blo ck o f build ing s Fig ure 3: Typica l build ing fro m a blo ck o f building s

PDFmyURL.com
http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://www.world-housing.net/uploads/101417_092_03.jpghttp://www.world-housing.net/uploads/101416_092_02.jpghttp://www.world-housing.net/uploads/101415_092_01.jpg


4/21

Figure 4: Perspective drawing showing key load-bearing elements (adapted fromMascarenhas, 1994)

2. Architectural Aspects

2.1 SitingThese b uilding s are typically fo und in flat te rrain . They share co mmon wa lls with adja cent buildin g s . Pombalino buildings belong to a block of buildings (see Figures 2and 3) and they have co mmon walls with adjacent buildings. Common walls are perpendicular to the facades o f both buildings. The distance between blo cks of buildings

varies fro m 10 meters to 5 meters, co rrespon ding to a stree t's transverse d imension. S treet width d epen ds on it s importance (a main street is larg er than a se co ndary on e)

2.2 Building ConfigurationA Pombalino building 's g eo metry is very regular bec ause the se building s were the result o f urban plann ing in Lisbo n afte r 1755. The ne ed fo r a quick recon struction o f thecity and the fear of a new earthquake led to the enfo rcement of new construction rules. These rules included not o nly anti-seismic provisions but also facade a rchitecture,building plan and ge ometry. A Pombalino building's plan is compact with a rectang ular or nearly rectangular shape with symmetrical config uration (see fig ure 6). There areno iso lated buildings as they are part of an urban block which is also symmetrical and with a rectang ular plan shape (see Fig ure 7). A typical block has 7 to 8 buildings, usuallya building at each c orner and one o n each side. Each blo ck has a size of 70x25 m while the streets have width rang ing f rom 5 to 20 m. The interior of each bloc k includes a

very small co urtyard accesse d on ly by the doo rs of the ba ck fa ade . In a typical building (see Fig ure 5), doors serve as the ground flo or opening s. First floo r openings areall of the same type (either doors with balconies o r windows), depending o n the importance of the street onto which the facade o pens. Windows comprise the opening s ofthe other floo rs. The eaves of the roof also include opening s and these might be do ors or small windows. The original plan called for the same dimensions and ho rizontalspacing of the opening s for all Pombalino building s. Main facades present a regular opening g rid with clearly identified masonry piers and spandrels. The number ofopenings in each building o r on each floo r varies from 3 to 6 and depends on the area of the building plan. If the main facade of an original building has 6 openings,approximately 26% of the overall area is for windows and 38 % o f the overall wall surface a rea is utilized for doo rs, measured at the floo r above g round level. At the g roundfloo r level of the same original building, the overall doo r area is 50% of the overall wall surface area. To prevent fire propag ation between buildings, which was one o f the

main causes of death in the 1755 earthquake, the masonry walls between adjoining building s have no opening s and extend beyond the roofs .

2.3 Functional PlanningThe main functio n of this building typolo g y is mixed use (bo th co mmercial an d residen tial use) . This was the main func tion a t the time of co nstruction . Since th en,commerce and o ffices have taken o ver large r areas and residential use has decreased. In a typical building of this type, there are no elevators and 1-2 fire-protected e xitstaircases. Each shop at the ground floor has at least one exit, corresponding to previously mentioned doors at this level, leading outside the building. Access to floorsabove is acco mplished by means of one do or and a single set of stairs. Shop extensio n to the upper floors usually introduces another staircase to the floo r above, and

sometimes elevators. The internal courtyards of the blocks have no a ccess from the outside so they canno t be used as escape route.

2.4 Modification to BuildingThe most co mmon mod ifica tion o f Po mbalino buildin s is the add ition o f bathro oms. If the flo ors ab ove round are use d fo r residence s, t icall the kitche n has be en

PDFmyURL.com
http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://www.world-housing.net/uploads/101418_092_04.jpg


5/21

. ,altered to provide fo r running water. It is also co mmon to observe the insertion o f larger shop windo ws on the g round floo r, which sometimes demolishes all verticalmasonry elements in the faca des. Behind the buildings, the area at the g round floo r level, once used as internal courtyards and free space, has been taken over by shops fo rtheir expansion needs. The most common adaptation of the old buildings for their new function is the introduction of elevators and new stairs and the demolition of

interior walls (at ground floo r and at floors above). The introduction o f at least one floo r at the top o f the building is also common .

Fi g ur e 5: P la n o f th e fa ca de s o f a typ ic al bl o ck o f bu il di ng s ( S an to s , 2 00 0 ) F ig ur e 6: P la n o f a typ ic al b ui ld in g ( S an to s , 2 00 0 )Figure 7 : Aeria l v iew of Lisbon Downtown showing simi la r blocks of 'Pombal ino'

bui ld ings

3. Structural Details

3.1 Structural System

Material Type of Load-Bearing Structure # Subtypes Most appropriate type

Masonry

Stone MasonryWalls

1Rubble stone (field stone) in mud/limemo rtar or without mortar (usually with

t imber roof)

2Dressed stone masonry (inlime/cement mortar)

Ado be/ Ear then Walls

3 Mu d w al ls

4 Mud wal ls wi th horizonta l wood e lements

5 A do b e b lo c k wa ll s

6 Rammed earth/Pise construct ion

Unreinforced maso nrywal ls

7Brick masonry in mud/limemortar

8Brick masonry in mud/limemo rtar with vertical posts

9Brick masonry in lime/cementmortar

PDFmyURL.com


6/21

10Conc ret e b l oc m a sonry i ncement mortar

Confined masonry

11Clay brick/tile maso nry, withwo o de n p o sts a nd be am s

12Clay brick maso nry, withconc rete posts/tie columnsand beams

13Concrete blocks, tie columnsand beams

Reinforced masonry

14Stone masonry in cementmortar

15Clay brick masonry in cementmortar

16Concrete block masonry incement mortar

Structural concrete

Moment resistingframe

17 Flat slab structure

18Designed for gravity loadson ly, with URM infill wall s

19Designed for seismic effects,with URM infil l wa lls

20Designed for seismic effects,with struc tura l in fill wal ls

21Dual system Frame withshear wall

Structural wall

22Moment frame with in-situshear walls

23Moment frame with precastshear walls

Precast concrete

24 Moment frame

25Prestressed moment framewith she ar wal ls

26 Large panel precast wa l l s

27 Shear wall structure withwall s c ast-i n-si tu

28Shear wall structure withprecast wall pan el structure

Steel

Moment-resistingframe

29 With brick masonry part i t ions

30With cas t in -situ co ncr etewall s

31 With l ightweight part i tions

Braced frame

32Concentric connect ions in a l lpanels

33Eccentric connect ions in afew panels

Structural wall34 Bol ted pla te

35 Welded pla te

Tim berLoad-bearing t imberframe

3 6 T ha tch

37Walls with bam bo o /ree d m esh

and po st (Wattle and Daub)

38Masonry with horizontalbeams/planks at intermediatelevels

39Post and beam frame (nospecia l connect ions)

40Woo d fr am e ( with spe cia lconnect ions)

41Stud-wall frame withplywoo d/gypsum boardsheathing

42 Woo den panel wa l l s

OtherSeismic pro tection systems

43 Building protected with base-isolatio n systems

44Building protected withseismic dampers

PDFmyURL.com


7/21

Hybrid system s 45 o ther (described belo w)

The structural system can be divide d into t he g round f loo r system (masonry walls and va ults) and the g aio la system (woo den inte rior walls) o f the flo ors abo ve the first flo or,described as follo ws: The ground to f irst floor level is comprised of stone masonry columns supporting stone arches and clay brickwork vaults (see Figure 11). Interior wallsabove the f irst floor are part of the g aiola. Ma sonry infill can be stone or clay bricks like those used at the g round floo r vaults. It is usual to find both types of masonry ininternal walls (see Fig ure 10). For the first building s built after the earthquake, there are reasons to believe that the masonry used was rubble recycled from destroyed buildings.Other internal partitions are the wo oden panels without structural function. Exterior walls (facades and walls between adjacent buildings) are sto ne masonry in lime mortar.

Stone masonry walls (ground flo or)and woo den frame with masonry infill (floors above the first floo r).

3.2 Gravity Load-Resisting System

The vertical lo ad-resisting system is stone maso nry walls . Sing le leaf, irregular block, stone masonry walls. Masonry vaults at the ground f loo r, with ceramic regular blocksand stone arches (see Fig ure 11). Usually, the wall thickness of the Pombalino buildings varies from 1.0 to 1.2 meters and is the same for all flo ors. The Pombalino buildingsbuilt towards the end of the nineteenth century may present two or three different wall thicknesses. The usual changes a re observed between the g round floo r (1.0 to 1.2m)

and the first floo r (0.8 to 1.0m), and between the upper two floo rs. The thickness of the top flo or may vary between 0.5 and 0.8m.

3.3 Lateral Load-Resisting SystemThe late ral loa d-resisting system is stone maso nry walls . Maso nry walls and a three-dimensional wo od frame structure (gaiola) abo ve the first floor, double braced withdiag onal timber elements (see Fig ures 8, 9 and 10), f orm the lateral load-resisting system. The timber elements are no tched tog ether or con nected by iron o r metal ties,acco rding to histo rical information abo ut the construction techniques. The results of experimental tests performed on Po mbalino pane ls, and of tests performed on masonrypanels without diago nal bracing (Alvarez, 2000 and Lope s, 1986) showed that the g aiola exhibits ductile behavior and allows some energy dissipation. Connectionsbetween the timber elements, which sometimes include metallic (iron) elements, probably co ntribute to the o bserved ductile behavior. These results may be extrapolated to theperformance of the entire structure. According to the co nstruction proc ess (first the entire gaio la was built, then the masonry infill and the exterior walls), there are reasons tobelieve that interior timber frames are co nnected to floo r elements but these con nections must be better characterized. The co nnections o f interior timber frames between

stories must also be better characterized.

3.4 Building DimensionsThe typica l plan dimensio ns o f these b uilding s are: leng ths betwe en 8 an d 16 meters, and w idths betw een 1 0 and 1 2 meters. The building has 4 to 5 storey(s). The typicalspan of the roofing /floo ring system is 3.3 meters. Typical P lan Dimensio ns: The ab ove dimensio ns were measured in a buildin g w ith 6 o penin g s per flo or at the mainfacade . The horizontal spacing o f opening s is approximately 1.5 meters and the width of opening s (doors and windows at a floor above gro und floor) is approximately 1.2meters. Typical Number of Stories: Due to the co nstruction reg ulations of the time, the first Pombalino building s had a maximum of 4 stories including g round floo r, plus anhabitable attic under the roo f. The restriction o n the number of stories was lifted at the request of the developers soo n after the reconstruction process started, so that mostPombalino buildings have 5 stories. Typical Story Height: Ground floo r height is g reater than other floo rs: 4.5 meters. Typical Span: The distance among lo ad bearing

structures is from 2.88 to 3.70 meters . The typica l storey heig ht in such building s is 3.5-4.0 meters . The typica l structural wall density is more than 20 % . 6% - 24% Typicalwall den sity is 24% (bo th g round f loo r and flo ors ab ove). D irectio n parallel to fac ades : 14% (g round f loo r) and 18% (oth er flo ors ) Direc tion p erpend icular to f aca des:10% (ground flo or) and 6% (o ther floors) All values relate to the plan area o f the floo r. Measurements were made co nsidering o nly masonry and g aiola walls. Wall interiordoo rs are included. The stone arches and masonry vaults at ground flo or level support the interior walls of the floo rs above and therefore the wall density at ground flo or

level is smaller than at other flo ors.

3.5 Floor and Roof System

Material Description of floor/roof system Most appropriate floor Most appropriate roof

Masonry

Vaulted

Compo si te system o f concrete joi sts andmasonry panels

Structural concrete

Solid slabs (cast-in-place)

Waffle sl abs (c ast-in -pla ce)

Flat slabs (cast-in-place)

Precast jo ist system

Hol low core slab (precast)

PDFmyURL.com


8/21

Solid slabs (precast)

Beams and planks (precast) with concretetopping (cast-in-situ)

Slabs (post-tensioned)

SteelCom posite steel deck with concrete slab(cast-in-situ)

Tim ber

Rammed earth with ballast and concrete orplaster finishing

Woo d p lan ks o r b eam s wi th b all ast and co nc rete o r p las ter fini shi ng

Tha tche d r o o f su ppo rted o n w o o d p urli ns

Woo d s hin gl e r o o f

Woo d p lan ks o r b eam s th at su pp o rt c lay tile s

Woo d p lan ks o r b eam s sup po rtin g natu ralstones slates

Woo d p lan ks o r b eam s th at su pp o rt sl ate ,metal, asbestos-cement or plastic corrugatedsheets or tiles

Woo d p lan k, pl ywo o d o r m anu factur ed wo o dpanels on jo ists supported by beams or wa l l s

Other Described belo w

Woo d flo ors ca n be co nsidered a s a flexib le diaph rag m. The roo f timber structure depe nds o n the to p flo or o f the building beca use it may include win do ws op ening s withinthe timber frame. The number of pitches of the roof depends o n the kind of window, which is associated with construction practices at the time the building was built.Connection s between timber elements and masonry walls may have metallic elements like ancho rs. In the absence o f these elements, connectio n fo rces are transmitted only

by friction effect. The characteristics of the conne ction must be analyzed case by case.

3.6 Foundation

Type Description Most appropriate type

Sha l low foundat ion

Wall o r c o lum n e mb edd ed insoil, without foo ting

Rubble stone, fieldstoneisola ted foot ing

Rubble stone, fieldstone stripfoot ing

Reinforced-conc rete isolatedfoot ing

Reinforced-concrete stripfoot ing

Mat foundatio n

No foundat ion

Deep foundatio n

Reinforced-concrete bearingpiles

Reinforced-concrete skin

friction piles

Steel bearing pi les

Steel skin friction piles

Woo d p ile s

Cast-in-place concrete piers

Caissons

Other Described belo w

It consists of wood piles. Maso nry placed over a g rid of conne cted timber piles (see Fig ure 12). Timber piles are very short (g enerally less than 5 meters), and mobilize o nlylateral resistance bec ause soil with g oo d strength ca pacity is usually found at a de pth of 15 meters or more. Pile diameter is small (25 cm) and piles fo rm a reg ular mesh. Piles

were co m letel under wate r but the current water level is bec omin lowe r and some iles are de raded. The re is no evide nce o f fo undatio n soil inst abilit and so me authors

PDFmyURL.com


9/21

.maintain that pile deg radation is no lo ng er important to fo undation strength capa city because the timber mesh acted as so il reinforcement at the time of construction. Baixa

was rebuilt o ver rubble from colla psed buildin g s during th e 1755 earthqua ke and the timber g rid of piles wo uld be a g oo d measure to pro vide co mpactio n. Ho wever, this is

still an object of discussion and controversy.

Figure 8: Woo d braced frame of 'gaio la' after the remo val of cover maso nry (Museum of BCP, 2000)

4. Socio-Economic Aspects

4.1 Number of Housing Units and InhabitantsEach building typically has 5-10 ho using unit(s). 3 to 4 housing units in each building, o r 6 to 8 ho using units in each building. There are 1 or 2 units per floo r on abo veg round floo rs. The number of units may depend on the area of the building plan: there is only one unit per floo r if the number of windows is less than 4; if the number of

windo ws is more than 4, th ere can b e two un its per flo or. The number of inhab itants in a buildin g during th e day o r business ho urs is more tha n 20 . The number ofinhabitants during the evening and night is less than 5. S ome buildings belo ng to companies and banks and all floors have been adapted to new functions. In such cases, thenumber of inhabitants varies from a high number during business ho urs (40 to 50 workers and clients/costumers), to a small number of inhabitants (mainly security people,

less than 5) at night. If buildings were converted into commercial outlets, occupancy might be as high as 200 peo ple depending on time of day and the season.

4.2 Patterns of OccupancyOne family occupies one housing unit

.

4.3 Economic Level of Inhabitants

Income class Most appropriate type

a) very low-income class (very poor)

b) low-income class (poo r)

c) middle-income class

d) high-income class ( r ich)

Most of the residential occu ants are ver oor old eo le who have lived in the same house their entire life. When the last resident dies the buildin ma be abandoned or

PDFmyURL.com
http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://www.world-housing.net/uploads/101422_092_08.jpg


10/21


11/21

Long-term lease

other (expla in below)

Buildings adapted fo r banks and fo r other organizations that o ccupy entire buildings are owned by a group or poo l. Ground floo r shops are usually held by long-termlease. Commercial functions at the g round floo r sometimes oc cupy the first floor. The flo ors abo ve are residential units or small service o ffices (do ctors, lawyers, specialized

shops, etc), rented o r owned individually.

5. Seismic Vulnerability

5.1 Structural and Architectural FeaturesStructural/ArchitecturalFeature

StatementMost appropriate type

Yes No N/A

Lateral loadpath

The struc ture co ntai ns a c o mp lete lo ad pa th fo r se ism icforce effects from any horizo ntal direction that servesto transfer inertial forc es from the building to thefoundat ion.

BuildingConf igura t ion

The bui ldi ng is r eg ular with reg ard s to bo th th e p lanand the elevation.

Roof construction

The ro o f d iap hra gm is c o nsi de red to be rig id and it i sexpected that the roo f structure will maintain itsintegrity, i .e. shape and form, during an earthquake ofintensity expected in this area.

F l oorconstruction

The flo o r d iap hra gm (s) are co nsi der ed to be rig id an d i tis expected that the floo r structure(s) will maintain itsintegrity during an earthquake of intensity expected inthis area.

Foundat ionperformance

The re is n o evid en ce o f e xce ssive fo und atio n m o vem ent

(e.g. settlement) that would affect the integrity orperformance of the structure in an earthquake.

Wall a ndframestructures-redundancy

The num ber o f l ine s o f wa lls o r fra me s i n e ach pri nc ipa ldirection is greater than or equal to 2.

Wallproport ions

Height-to-thickness ratio o f the shear walls at each floo r level is:

Less than 25 (concrete walls);

Less than 30 (reinfor ced maso nry walls);

Less than 13 (unreinforced maso nry walls);

Foundat ion-wallconnect ion

Vertic al lo ad -bea rin g ele me nts (co lum ns, wal ls)are attached to the foundation s; concretecolumns and wa l l s a re doweled into thefoundat ion.

Wall-ro o fconnect ions

Exterior walls are anchored for out-of-plane seismiceffects at each diaphragm level with metal ancho rs orstraps

Wall o pen ing s

The to tal wid th o f d o o r a nd win do w o pen ing s in a w allis:

For brick mason ry construction in cement mortar : lessthan of the distance between the adjacent crosswall s;

For ado be masonry, stone masonry and brick masonryin mud mo rtar: less than 1/3 of the distance betweenthe adjacent crosswall s;

For pre cast concr ete wall structures: less than 3/4 ofthe length of a perimeter wall.

Quality ofbuildingmaterials

Quality of building m aterials is con sidered to beadequate per the requirements of national codes andstandards (an estimate).

PDFmyURL.com


12/21

Quality ofwo rkm ans hip

Quality of workma nship (based on visual inspection offew typica l bui ld ings) i s considered to be goo d (perlocal construction standards).

MaintenanceBuildings of this type are generally well maintained and thereare no v isible s igns of deteriora t ion o f bui ld ingelements (concrete, steel, timber)

Add itio nalComments

The o rig ina l c o nce ptio n o f th e g aio la was to res ist s eis mi c a ctio ns and this supp o rts the pre dic tio n o f a go o d r esp o nse for this type o f b uild ing . Vertic al tran sitio n fr o m th e g ro undfloor (m asonr y walls) to the first floo r (gaio la woo d frame walls) may be a specific deficiency for the seismic behavior o f these buildings due to a step change in stiffness and theuni la tera l behavior of connect ions. The presence and performance of meta l l ic ( i ron) e lements a t the connect ions between t imber e lements and masonry wa l l s in the roo f and f loo rsare not entirely clear. In fact, som e cases were found where the connectio n between timber elements and maso nry depended o nly on the length o f the joist seat inside the maso nry. Inthat case, the strength of the conn ection dep ends only o n the friction between the materials and wo uld be smaller if there was a metallic element. The uneven quality of the origin almason ry or the construction o f different walls at various times also led to po or strength and stiffness prop erties. Construction practices were not the same for buildings built in thesame perio d, which might indicate that the quality of workman ship was not the same. As an example, it is possible to find different geo metries of g aiola in the same building and thereare several gaps in the connections between timber elements, which may or may not have nails. The quality of workmanship also decreased over time, as the first Pombalino buildingsshow better quality then those built in the nineteenth century. Like all masonry buildings, the presence o f large o pening s reduces the lateral stiffness and load ca pacity of facades.Ano ther sig nific an t unc erta inty is h o w im po rtan t a ro le the struc tural inte rve ntio ns had o n b uild ing s b ec ause the exte rio r m ay l o o k o rig ina l b ut th e i nte rio r c an be co mp lete ly m o difi ed.Removal of internal gaio la walls greatly increases the seismic vulnerability of Pombalin o building s.

5.2 Seismic FeaturesStructuralElement

Seismic Deficiency Earthquake Resilient Features Earthquake Damage Patterns

Wall Low resistance to out-of-plane seismic effects (overturning o f facades) and collapse o f the roof; Low resistance ofcon nections between facades and perpe ndicular maso nry walls due to bad quality of maso nry at corners, that can beassociated to co nstruction of co nnected walls at different times; possibility of formatio n of a glo bal collapsemechanism due to masonry low shear strength; Large openings reduce lateral capacity of facades. Connectionsbetween 'gaiola ' walls and maso nry walls may have low strength connectio ns if there are no me tallic elements; timber

decay due to water ingress.

Thr ee-d im ens io nal bra ced struc turethat reduces out-of-plane ho rizontaldisplacements of facades,contributing to reduced seismicvuln era bil ity o f Po mb ali no buil din gs ;it displays ductile behavio r.

Some crack openings andfall of external p laster. Nodetailed informationavailable. In poorlyconnected facades, out-of-

plane mechanism expected .Frame(Columns,

beams)

Roof andf loors

Low strength conn ections between timber elements of ro of and floo r and mason ry walls; timber decay due to water

ingress.A g o o d c o nn ecti o n b etwe enroof/floor t imber e lements andmaso nry walls may reduce seismicvuln era bil ity b eca use they cancontribute to reduced out of planehorizo ntal displacemen ts.

Mainly fall o f chim neys. Nodetailed information

available.

Foundat ionsTim be r p ile da ma ge due to wate r l eve l c han ge s m ay c ause buil din g settl em en ts. No informat ion ava i lable .

Some buildings may have metallic elements connecting timber elements (roof , floo r and 'ga iola') to the facades that are no t visible from the outside because the wallthickness covers them. Each building must be evaluated individually or integ rated in a block of buildings. It is important to co nsider block behavior in case of relevantstiffness differences between the buildings o f the same block (see Ramos and Loureno, 2003 and Silva et al., 2001). Past earthquakes (see Section 6) caused o nly light

damage to buildings in Baixa. The damage levels were so small (Baixa was far from epicentre) that the information was no t worth recording.

5.3 Overall Seismic Vulnerability Rating

The o verall rating of the seis mic vulnerability o f the ho using type is B: MEDIUM-HIGH VULNERABILITY (i.e., poo r seismic performance), the lower bo und (i.e., the worstpossible) is A: H IGH VULNERABILITY (i.e., very poor seismic performance), and the upper bound (i.e., the best po ssible) is C: MEDIUM VULNERABILITY (i.e., moderateseismic performance).

Vulnerab ility high medium-high medium medium-lo w low very low

very po or po or m o derate g o od very g o od excellent

Vulne rab ili tyClass

A B C D E F

5.4 History of Past Earthquakes

PDFmyURL.com


13/21

Date Epicenter, region Magnitude Max. Intensity

1856 37.10 -10.50 (Atlantic Ocean, Southwest of Portugal) 6

1909 38.95 -8.82 (Benavente (Centre of Portugal) 7 MMI IX (at epicenter)

1969 35.99 -10.81 (Atlantic Ocean, Southwest of Portugal) 7.5

The 19 09 e arthquake wa s felt in Lisb on a nd cause d lig ht damag e to b uilding s in Baixa , mainly crack open ing s and the f all of chimneys and ext ernal plast er. The intensit yshown in the table fo r this earthquake is the epicentral one, in Benavente, some 40 km from Lisbon. On the basis of damage o bserved in Pombalino buildings and inordinary masonry structures, it is not po ssible to co nclude whether the Pombalino buildings pe rformed better because all the observable damag e was lig ht. For the o therearthquakes shown in the table, with epicentres either in continental Po rtug al or in the Azores Islands, there is no record of significa nt damage to building s in Lisbon, due to

the long distance from the epicentre.

PDFmyURL.com


14/21

F ig u re 9: T im b e r s tr uc tu re e n cl o s ed in in te ri o r m a so n r y w al l F ig u re 10 : T im b er s tr uc tu re e n cl o se d i n i n te r io r ma so n r y w al l ( d et ai l)Figure 11: Masonry vaults at ground floo r

PDFmyURL.com


15/21

Figure 12: Woo d pile foundations (Santo s, 2000)

Figure 13: Reinforcement of the con nections between roo f and mason ry walls by acon crete beam (Co sta et al, 2001)

6. Construction

6.1 Building Materials

Structural element Building material Characteristic strength Mixpropo rtions/dimen sions Comments

WallsIrregular blocks of calcareo us masonry set in limemortar

Low tensile and shear strength characteristics, values not knownprecisely

Not known(see Cardoso et a l . ,2001)

Fo undatio n Sho rt and sm all d iameter tim ber piles (pine) S treng th va lues no t kno wn (see Alvarez, 20 0 0 )

Frames (beams &columns)

Tim be r-br ace d fr am e ( pin e a nd o ak) ga io la Str en gth value s n o t kn o wn pre cis ely No t kno wn(see Cardoso et a l . ,2001)

Ro of and flo or(s) Tim ber elem ents ( pine and o ak) S treng th va lues no t kno wn

6.2 BuilderOriginally built by developers. None se lf built .

PDFmyURL.com
http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://www.world-housing.net/uploads/101427_092_13.jpghttp://www.world-housing.net/uploads/101426_092_12.jpg


16/21

6.3 Constr uction Process, Problems and PhasingDue to time constraints, the co nstruction proc ess was hig hly organized. The g aiola and the entire woo d structure were built first, then the masonry infill was placed at thesame time as the exterior masonry walls were co nstructed. Finally, windows and d oo rs stones were placed with the f inishing wo rk. This sequence allo wed different specialists

(carpenters and masonry workers) to do their jobs without interference. The co nstructio n of this type o f ho using takes pla ce inc rementally over time. Typically, thebuilding is originally not designe d for its final constructed size. The reco nstructio n of Lisbo n afte r the 1755 earthquake wa s slow due to fina ncial an d eco no micconstraints, and it is likely that buildings in the same urban block might have been built in different years. The time g ap in the co nstruction o f individual buildings may explainsome of the observed architecto nic variances, as seen in the roof structure and lighting f or the stair wells, for example. Very often an extra flo or was built at the same time as

the rest of the building.

6.4 Design and Construction ExpertiseThe idea of using timber frames for the g aio la and f or the c onn ectio ns betwe en timber elements was insp ired by ship co nstructio n, in which th e Po rtugues e had g reatexpertise. Enginee rs and architects had a very important role in planning the reconstruction of the city. The plans included not only the new urban layout but also functiona land architectural aspects. Structural features were also examined and seismic considerations were a main concern as the introduction of the g aiola in these buildings sho ws.

6.5 Building Codes and StandardsThis co nstructio n type is addres sed by the co des/st anda rds of the co untry. A written do cument has neve r been fo und but co nstruction rules were practic ed and tran smittedbetween carpenters and masonry workers so it is assumed that there was a code of practice. The year the f irst code /stand ard address ing this type o f co nstructio n issued was1755-1758. N/A. The most rece nt co de/sta ndard ad dressing this co nstructio n type issued wa s There is no mention o f reg ulatio ns fo r this type of co nstructio n in modernbuilding codes or seismic codes. Title o f the co de o r standard: A written do cument has neve r been fo und but co nstructio n rules were practic ed and transmitted betwe encarpenters and masonry workers so it is assumed that there was a co de of practice. Year the first code/standard addressing this type o f construction issued: 1755-1758National building co de, material codes and seismic codes/standards: N/A When was the most recent co de/standard addressing this co nstruction type issued? There is no

mention of regulations fo r this type of construction in modern building co des or seismic codes .

Beg inning in 1758 and during the M arqus de Pombal's governance, the penalty for failing to f ollow co nstruction rules was the demolition o f the building by order of the

king.

6.6 Building Permits and Development Control RulesThis type o f co nstructio n is an eng ineered , and autho rized as pe r develo pment con trol rules .

Historical information indicates that the owners of the buildings which co llapsed during the 1755 earthquake contracted builders, who supervised the con struction. They had

to respect all rules imposed by the Marqus de Po mbal. Eng ineers and architects established these rules, as mentioned in section 7.6. Building pe rmits are required to buildthis housing type.

6.7 Building MaintenanceTypically, the building of this ho using type is maintained b y Owner(s), Tenant(s ) , No on e and o thers

.When buildin g own ers canno t aff ord the maintenanc e of the building

(low rents, etc.), they may require financial support fro m the City Council. The City Council has a special spending prog ram that was developed to allow improvements in o ld

masonry buildings. In most cases, these improvements do not include streng thening buildings.

6.8 Constr uction EconomicsSince this is a construction method that is no long er practiced, values for co nstruction co sts are not available. The actual commercial value of Pombalino buildings varies anddepends on whethe r they have been abando ned or upon how diff icult it would be to ge t authorization to perform structural/functional chang es: if the building stillmaintains its original structure and use, the approximate co st may be from 400 to 450 euro/m2 depending o n the level of deterioration. If the building has been refurbished,the value depends o n its current use. For residential use, values rang ing from 1000 to 2500 e uro/m2 are usually quoted. Co mmercial values are not related to co nstruction

values. In f act, B aixa is lo cate d in the most ce ntral part o f Lisbo n and this justif ies the hig h prices quo ted . This info rmatio n is no t available .

PDFmyURL.com


17/21

7. Insurance

Earthquake insurance for this construction type is typically unavailable . For seismically strengthened e xisting buildings o r new buildings inco rporating seismically resilientfeatures, an insurance premium discount o r more co mplete co verage is unavailable. Until 2001, ea rthquake insurance was available. Now co mpanies avoid this type ofinsurance, but this may be a temporary situation ca used by the redefinition of policy in this sector . It is part of a g roup of risks related to housing that optio nally maycover damage ca used by earthquakes. Insurance co st depends on seismic zone, ag e, and the number of stories in a building.

8. Strengthening

8.1 Description of Seismic Strengthening Provisions

Strengthening of Existing Construction :

Seismic Deficiency Description of Seismic Strengthening provisions used

Low resistance to o ut-of-plane seismic effects (o verturning offacades) and ro of co l lapse ; low resi stance o f connect ions betweenfacades and perpendicular m asonry walls due to the bad quality of

the masonry at the connectio ns.

Introduction of a co ncrete or steel beam at the top of the building, con necting the roo f to walls (see Figures 13 and 14) andconfining masonry. The beam is executed along the whole perimeter of the building. Sometimes, these beams are executed at theskirting board level of all floo rs above gro und floor. Introduction of steel elements or ties (pre-stressed or no t), cables, or

anchors, connect ing para l le l masonry wa l l s .Masonry low shear streng th may be critical to shear failure of the

bui ld ing due to the format ion o f a g lo ba l col lapse mechanism.Introduction o f steel mesh, confining maso nry structural elements of facades (see Figure 15).

Settlement due to foundation failure Micro piles

Low strength connection between timber elements Use of steel rods and traditional techniq ues for strengthen ing timber elem ent conne ctions, such as the nails and bo lts. Use ofFRP in the strengthening o f timber reinforced m asonry loa d-bearing walls (see [Cruz et al., 2001]).

Low strength connect ion between t imber e lements and masonry

wal lsIntroduction o f steel elements, such as ties, which con nect timber elements to maso nry (see Figure 16).

Tim be r d am ag e d ue to wate r i ng res s, cr ea ting favo rab le co ndi tio ns

for fungi and insect attack.Substi tut ion or repa i r of bro ken t i l es and measures to waterproof the ro of . Somet imes, connect ions between roo f and facadesare also reinforce d during repair. Damaged timber elemen ts are removed and replaced with new timber elements of the same

geometry.

The most co mmon c on struction materials a re steel, co ncrete a nd pine . Mo rtar mixes and p ropo rtions must be co mpatible with o rigin al materials. Bes ides the c ost, e ffic iency,and durability of the strengthening solution, the feasibility of removing it from the structure without destruction must also be co nsidered. The complexity level of anyintervention is high be cause demolition is not desirable due to the historical importance o f these buildings. Mo st interventions must be performed in occ upied buildings, thus

increasing the exec ution time and co mplexity. There is little information available abo ut the expected effec tiveness of the seismic strengthening provisions listed above.

8.2 Seismic Strengthening Adopted

Has seismic strengthening described in the above table been performed in design and co nstruction practice, and if so, to what extent?The usual seismic streng thening techn ique utilized in d esig n practice is to improve the c on nectio ns betwe en the timber elements an d the maso nry walls beca use this is easie r toperform and is cheaper than the other interventions mentioned. Anothe r common strengthe ning technique is the introduction of ties which connect the facade s and prevent

out-of-plane displacements.

Was the wo rk done a s a mitigatio n eff ort o n an unda mage d building , or as repa ir follo wing an ea rthquake?The o bjective o f most rehabilita tion w ork is to a dapt o ld building s to ne w uses or to repair damag e due to ag e. When in terven tion is g oin g t o be d on e, seismic mitigatio n

should be a conce rn but seismic strengthening is not the current practice because of the added co st and lack of awareness on the part of owners to seismic risk.

PDFmyURL.com


18/21

8.3 Construction and Perfor mance of Seismic Strengthening

Was the co nstructio n inspec ted in the sa me manne r as the new c on struction ?Inspection techniques fo r old masonry buildings are diff erent from the techniques used in new buildings beca use the materials and co nstruction techniques a re not the same.Inspection o f new co nstruction to evaluate seismic vulnerability follows cod e provisions, whereas inspection of older buildings relies much more on the e xpertise of

individuals and on prof essional advice.

Who perfo rmed the con struction se ismic retrofit measures: a co ntracto r, or owne r/user? Was an arch itect o r eng ineer invo lved?At the time of the co nstructio n of Po mbalino buildin g s, co ntracto rs perfo rmed co nstructio n acc ording to c urrent earthquake te chnic al provisio ns. At the prese nt time,contracto rs, following eng ineering advice, usually include some seismic strengthening in the construction. Generally, architects are involved when co nstruction includes not

only repair but also modification, which happe ns in most cases.

What wa s the perf ormance o f retrof itted building s of this type in subseq uent ea rthquakes?There is no info rmatio n availab le abo ut seismic perfo rmance of retrof itted building s of this type sinc e stron g e arthquake s have no t hit Lisbo n since 1 755. Some retrofitsolutions are being submitted to a homolo g ation process so pe rformance evaluation through labo ratory testing is being done. These techniques are recent and there hasbeen no o pportunity to co nfirm their effectiveness. Most of them were developed after observation o f damage due to recent earthquakes, such as the 1998 earthquake in

Azo res, Portug al, and th e 199 7 earthquake in Umbria, Italy. The results of numerical models o f masonry building s also p rovided in fo rmatio n related to their expec ted co llapse

mechanism and they inspired the desig n of some reinforcement solutions (see Croci, 1988 ).

PDFmyURL.com


19/21

Figure 14: Reinforcement of the con nections between ro of and maso nry walls by aconcrete beam (Appleton and Em

Figure 15: Shear reinforcement of masonry structural elements using steel elements(Silva, 2002)

Figure 16: Reinforcement of the co nnect ions of wo od f loors to m asonry wa l l s bysteel elements (Silva, 2002)

Reference(s)

1. Pombaline Downtown, Synthesis of a investigation work on several disciplines, since geo physical prospec ting to soc iolog ic prospective, with urban planning asobjective, Lisbon City Hall, Lisboa, 2000 (in Portuguese)Alvar ez,M.L.

2. Structural Reinforcement of a Ho using Building o f XVII Century, Inge nium (in Portuguese)

App leto n,J., and Em

3. Seismic Evaluation of Old Maso nry BuildingsCardo so,R., Lop es,M., and Bento,R.

Proceedings of 12th European Conference on Earthquake Engineering, Art n 2002

4. Anti-Seismic Construction - Small Buildings (in Po rtug uese)Carvalho,E.C., and Oliveira,C.S.

ICT, Technical Informatio n - S tructures LNEC, DIT 13, Lisbon 1997

5. The conservation and Structural Restoration of Architectural HeritageCroci,G.

Com putational Mechanics Publications 1988

6. Reinfo rcement Techniques of traditional constructions damag ed by 9/7/98 earthquake at Faial Island, Azores (in Portuguese)Co sta,A., Ar

Proceedings of S 2001

7. The Use of FRP in the Strengthening of Timber Reinforced Mason ry Load -bearing WallsCruz,H., Mour a,J.P., and Macha do ,J.S.

Proceed ings of Historical Constructions, Possibilities of Numerical and Experimental Techniques, Guimar 2001

8. Pombaline Lisbon and Illuminism (in Portuguese)Fran

Bertrand Boo kshop 1987

9. Pombaline Downtown, Some Technical Innovations, 2

PDFmyURL.com


20/21

Mascarenhas,J.

LNEC, Lisbon 1994

10. Promotional bulletin of Museum Building at Archaeo log ical Nuclei of Correeiros Street # BCP FoundationMuseum B CP

11. Evaluation of Se ismic Performance of an Old Masonry Building in LisbonLopes,M.

Proceed ings of the 11th World Co nference on Earthquake Engineerin g, Art n 1996

12. Portuguese Mo nog raph about Innovatio n at Building Rehabilitation (1987) (in Portug uese)LNEC

Buildings - LNEC Technical Report 123/88 1988

13. Lisbon Downto wn of Po mbal, Past and FutureSan tos,M.H.R.

Livros Horizonte 2000

14. Technical Viability of 'National Prog ram for the Seismic Vulnerability Reduction of Building Sto ck' (in Portug uese)Silva,V.C.

Publish at Seismic Vulnerability Reduction of Building , SPES - Portuguese So ciety of Seismic Engine ering and GECo RPA - Association for the Co nservation and Rehabilitation o f the

Arch itec to nic Patri mo ny 20 00

15. Accounting f or the 'Block Effect' in Structural Interventions in Lisbon's Old 'Pombaline' Downtown Building sSilva ,V.C., Lour en

Hystorical Co nstructions, Eds Louren 2003

16. Seismic Analyses of the Old Town Buildings in Baixa Pombalina, Lisbon PortugalRamos,L.F., and Lo uren

Proc. of the 9th North American Masonry Conference p.908-919 2003

Author(s)1. Rafaela Cardoso

Civil Engineer, Dept. of Civil Engineer ing, Instituto Superio r Tecnico

Av Rovi sco Pai s 1, L isb o a & nb sp10 49-0 01, PORT UGAL

Emai l:rafaela @civil.ist.utl.pt FAX: 3.51218E+11

2. Mario LopesProfessor, Dept. of Civil Engineer ing, Instituto Superio r T

Av. Ro visc o Pais 1, Lis bo a & nb sp10 49-0 01, PORTUGAL

Emai l:mlo pes@c ivil.ist.utl.pt FAX: 3.51218E+11

3. Rita BentoProfessor, Dept. of Civil Engineer ing, Instituto Superio r T

Av Rovi sco Pai s 1, L isb o a & nb sp10 49-0 01, PORT UGAL

Emai l:rben to@c ivil.ist.utl.pt FAX: 3.51218E+11

4. Dina D'AyalaDirector o f Postgra duate Studies, Department o f Architecture & Civil Eng ineering , University of Bath, Bath &nbspBA2 7AY, UNITED KINGDOM

Emai l:D.F.D'Ayala@ba th.ac.uk FAX: 00 44 1225 386691

Reviewer(s)1. Paulo B. Lourenco

PDFmyURL.com


21/21

Asso ciate P rofe sso r of Structural Eng ineeringDept. of Civil Engineering, University of Minho AzuremGuimaraes 4 800-058, PORTUGALEmail:pbl@c ivil.uminho.pt FAX: 351 253 51021 7

Save page as

PDFmyURL.com
http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://void%28location.href%3D%27http//html-pdf-converter.com/en/convert?u=%27+escape(location.href))

Documents

Www World Housing Net Whereport1view Php ID=100099